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Excess cement around cement-retained implant crowns is associated with a higher incidence of peri-implantitis, but there are limited data to indicate which cement application technique minimizes excess cement. The purpose of this in vitro study was to evaluate the amount of excess cement that resulted from different cement application techniques. Fifty identical titanium custom abutments and monolithic zirconia crowns were digitally designed and milled in the shape of a maxillary first molar. Ten crowns were cemented by applying temporary cement only to the intaglio coronal surface of the crown; these specimens were used as a control group to determine the amount of cement to be used in all other groups. Four different cement application methods were evaluated (n = 10): wall layer technique, in which cement was brushed on the intaglio axial walls of the crown; precementation technique, in which cement was applied to the intaglio coronal aspect of the crown, and the crown was precemented on an abutment replica, quickly removed, and then repositioned on the milled abutment; rim application, in which cement was applied to the cervical marginal rim of the crown; and increased cement space, in which the cement space was increased to 60 μm (compared with 40 μm in other groups) and cement was brushed on the intaglio coronal surface. Digital photographs of the cemented crowns were taken, and image editing software was used to measure the displacement of excess cement, that is, the distance that it traveled below the finish line on the mesial, distal, buccal, and lingual surfaces. Excess cement was then removed from each specimen and weighed. An analysis of variance test was used to evaluate the difference among groups, and each pair of groups was compared with the t test. Compared with all of the other experimental groups, specimens cemented with the wall layer technique showed a significantly smaller amount of cement excess in terms of both the distance traveled and weight (P < 0.05). Based on the findings, the wall layer cementation technique, in which cement is brushed on the intaglio walls of the crown, is recommended to reduce excess cement around implant crowns., Competing Interests: No conflicts of interest reported.

Objectives: To digitally evaluate the trueness and fit of additively and subtractively manufactured fixed complete dentures in materials intended for definitive use., Methods: An edentulous maxillary model with implants at the left first molar, left canine, right canine, and right first molar site was digitized and a fixed complete denture was designed. This design was used to fabricate fixed dentures in an additively manufactured resin for definitive use (AM), a high-impact polymer composite (SM-CR), and a strength gradient zirconia (SM-ZR) (n = 10). Each fixed denture was digitized and the surface (overall, occlusal, except occlusal, and abutments), linear, and interimplant distance deviations were analyzed. The fit was assessed with the triple-scan protocol. Data were analyzed with Welch analysis of variance and Games-Howell tests (α = 0.05)., Results: SM-ZR led to lower overall deviations than AM, which had the highest occlusal and the lowest abutments deviations (P ≤ 0.007). SM-ZR had the lowest occlusal and SM-CR had the highest except occlusal deviations (P ≤ 0.002). AM mostly had higher linear and SM-CR mostly had higher interimplant distance deviations (P ≤ 0.043). AM led to the highest marginal gap at the left canine site, while SM-CR had the highest and SM-ZR had the lowest gaps at the right canine site (P ≤ 0.022)., Conclusions: SM-ZR dentures mostly had trueness and marginal fit similar to or better than the other groups. Tested fixed complete dentures were mostly smaller than the design file in terms of interimplant distances., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Statement of Problem: Several additively and subtractively manufactured resin-based materials indicated for interim and definitive fixed dental prostheses have been launched. However, knowledge of the bond strength of these materials to different implant abutment materials is limited., Purpose: The purpose of this in vitro study was to evaluate the shear bond strength (SBS) of additively and subtractively manufactured resin-based materials to different implant abutment materials., Material and Methods: One hundred and ten disk-shaped specimens (Ø3×3 mm) were fabricated either additively from 2 resins indicated for definitive use (Crowntec; AM&#95;CT and VarseoSmile Crown Plus; AM&#95;VS) and 1 resin indicated for interim use (FREEPRINT temp; AM&#95;FP) or subtractively from a nanographene-reinforced polymethyl methacrylate (G-CAM; SM&#95;GC) and a high-impact polymer composite (breCAM.HIPC; SM&#95;BC). After allocating 2 specimens from each group for scanning electron microscope evaluation, the specimens were divided according to the abutment material (CopraPeek; polyetheretherketone, PEEK and Dentium Superline Pre-Milled Abutment; titanium, Ti) (n=10). All specimens were airborne-particle abraded with 50-µm aluminum oxide. After applying a resin primer (Visio.link) to PEEK and an adhesive primer (Clearfil Ceramic Primer Plus) to Ti specimens, a self-adhesive resin cement (PANAVIA SA Cement Universal) was used for cementation. All specimens were stored in distilled water (24 hours, 37 °C), and a universal testing device was used for the SBS test. SBS data were analyzed with 2-way analysis of variance and Tukey honestly significant difference tests, while the chi-squared test was used to evaluate the difference among the abutment-resin pairs in terms of failure modes (α=.05)., Results: The interaction between the material type and the abutment type and the main factor of material type affected the SBS (P<.001). SM&#95;BC-PEEK and SM&#95;GC had the lowest SBS followed by SM&#95;BC-Ti, whereas AM&#95;VS-PEEK had the highest SBS (P≤.001). AM&#95;CT-Ti had higher SBS than AM&#95;FP-PEEK (P=.026). SM&#95;GC had the lowest and AM&#95;VS had the highest SBS, while AM&#95;CT and AM&#95;FP had higher SBS than SM&#95;BC (P≤.004). The distribution of failure modes was significantly different among tested material-abutment pairs, and only for AM&#95;CT among tested materials (P≤.025). Most of the material-abutment pairs had a minimum of 80% adhesive failures., Conclusions: Regardless of the abutment material, additively manufactured specimens had higher bond strength and one of the subtractively manufactured materials (SM&#95;GC) mostly had lower bond strength. The abutment material had a small effect on the bond strength. Adhesive failures were observed most frequently., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: Recent studies indicate that reusing healing abutments (HAs) may pose a risk of biomaterial cross contamination among patients. The intent is to investigate whether postgraduate periodontics residency programs in the United States are reusing dental implant HAs and determine if there is a standardization in the decontamination and sterilization protocol of used HAs., Methods: An electronic survey consisting of-seven multiple choice and/or short answer questions pertaining to the re-use of HAs among postdoctoral periodontics programs was sent to program directors of 57 accredited dental schools in the United States via an online survey system (Qualtrics). Three follow-up remainder emails were sent to programs that did not respond after over a 6-month period. Data were analyzed using descriptive statistics., Results: Of the 57 postdoctoral periodontics program directors contacted, only 14 responded with three programs (3/14, 21%) reported reusing HAs. Approximately, 46% stated their residents place dental implants in two stages, while ∼54% stated they used a one-stage protocol indicating varied time exposure of HA to the oral cavity. Even in a two-stage protocol, the extended time HA remained in situ varied from 4 weeks to 6 months. Each program reusing HAs employed a distinct decontamination approach highlighting a notable lack of standardization in practices., Conclusion: The findings from our study suggest that a minority of residency programs in the United States are reusing HAs. However, the limited number of responses leaves uncertainty regarding whether our findings underestimate the prevalence of this practice and accurately reflect the reality. Among those re-using HAs, there seems to be a lack of standardization in their decontamination, potentially leading to cross-contamination of residual biomaterial among patients., (© 2024 The Author(s). Journal of Dental Education published by Wiley Periodicals LLC on behalf of American Dental Education Association.)

Purpose: To assess how well torque-limiting devices (TLDs) are known and used by European dentists, and their adherence to screw tightening protocols and screw loosening occurrence through a survey, including the correlation between the dental specialty-of-interest and the recognition, the tightening protocol used, and between the calibration and the occurrence of screw loosening., Materials and Methods: A 10-question survey was distributed to dentists to collect data on their specialty-of-interest, TLD usage, knowledge on TLDs, calibration, the term "preload," tightening speed, tightening protocols used, and occurrence of screw loosening. Pearson test was used for correlation analysis between the specialty-of-interest and the recognition-based questions, the tightening protocol used, and between the calibration and the frequency of screw loosening., Results: Of 422 respondents, 24% calibrated their TLDs, 27% knew the term "preload," 76% selected the correct location to read on TLDs, and 6% was aware of the effect of tightening speed. The correlation between the specialty-of-interest and the recognition-based questions was nonsignificant (p < .05) but was significant for used tightening protocol (p < .001). The correlation between the calibration and the occurrence of screw loosening was nonsignificant (p = 0.16). Tightening protocols' effect on screw loosening was similar, which was mostly observed less than once a year (p < .001)., Conclusions: A lack in dentists' knowledge was found on calibration, the term preload, and the effect of tightening speed, which were not impacted by the dentists' specialty-of-interest, which affected the preferred tightening protocol. The tightening protocol and calibration did not impact the occurrence of screw loosening, which was mostly observed less than once a year., (© 2024 The Author(s). Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

Several protocols have been used with computer-aided design and computer-aided manufacture (CAD-CAM) prostheses after image-guided implant surgery based on a prosthetically driven surgical plan. For delayed approaches, a CAD-CAM custom healing abutment can be manufactured before the surgery and installed immediately after implant placement. However, information on the use of emergence profile segmentation on which to base the digital design and on the use of low-cost 3-dimensional printers to produce custom healing abutments are lacking. The purpose of this article was to present a fully digital workflow to digitally design and 3-dimensionally print custom healing abutments with a biocompatible light-polymerizing resin based on the natural emergence profile of the tooth to be replaced., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Tightly sealed peri-implant gingival tissue provides a barrier against oral bacterial invasion, protecting the alveolar bone and maintaining long-term implant survival. To investigate if zinc can enhance the integration between peri-implant gingival tissue and abutment surface, we herein present novel zinc/chitosan/gelatin (Zn/CS/Gel) coatings prepared using the electrophoretic deposition (EPD) technique. The effect of these coatings on human gingival fibroblasts (hGFs) was investigated by culturing these cells on top of the EPD coatings. Surface characterization demonstrated that Zn 2+ were released in a sustained and pH-responsive manner. The preclinical cell culture evaluation of these coatings indicated that the zinc-containing coatings enhanced cell migration, adhesion and collagen secretion of hGFs. Moreover, the zinc-containing coatings exhibited antibacterial efficacy by inhibiting the growth of Porphyromonas gingivalis and reducing attachment of Staphylococcus aureus. Notably, zinc-free CS/Gel coatings prevented attachment of P. gingivalis as well. The coatings were also shown to be cytocompatible with epithelial cells and osteoblasts, which are other relevant cell types which surround dental implants after clinical placement. Based on our findings, it can be concluded that Zn-containing coatings hold promise to enhance the adhesion of gingival tissue to the implant surface, which may potentially contribute to the formation of a robust peri-implant soft sealing counteracting bacterial invasion., (© 2024 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Statement of Problem: Zirconia abutments have become popular as they provide favorable esthetic outcomes. However, studies investigating how abutment material affects abutment screw torque performance and implant conical surface morphological changes in internal conical connection systems are scarce., Purpose: The purpose of this in vitro study was to investigate the influence of abutment material on abutment removal torque and implant conical surface morphological changes in internal conical connection implant-abutment assemblies of 2 diameters after simulated long-term oral use., Material and Methods: Thirty abutments of 3 materials (1-piece titanium, 1-piece zirconia, zirconia with alloy base) and 2 diameters (regular, narrow) made by the original manufacturer were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading with parameters corresponding to anterior and posterior mastication scenarios simulating long-term oral use. An abutment removal torque test was done before and after aging. Morphological changes in the implant conical contact surface were observed with a scanning electron microscope (SEM). Initial and after-aging torque loss values were calculated and analyzed separately with 1-way ANOVA and Tukey HSD post hoc tests (α=.05)., Results: All specimens survived artificial aging. For initial and after-aging torque loss, the 1-piece zirconia groups showed significantly greater values (P<.001) for both diameters. In the SEM observation, the 1-piece zirconia groups showed distinct widespread surface damage while the other groups exhibited only minor damages., Conclusions: Regardless of diameter, 1-piece zirconia abutments tend to induce more abutment removal torque loss and implant conical surface morphological changes than those with metal connections, both initially and after simulated long-term oral use. Zirconia abutments with an alloy base performed similarly to 1-piece titanium abutments., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Studies on the biomechanics of obturators in the currently used designs of Aramany class I defect are lacking. Also, modifications of the designs presently used in unilateral palatal defects are needed to produce a prosthesis with more retention and less stress on the abutments., Purpose: The purpose of part I of this study was to differentiate among Aramany class I obturators of 4 designs regarding retention and associated stress using numerical and experimental methods., Material and Methods: Four finite element models and 36 different base obturators were fabricated and divided into 9 acrylic resin bases retained with Adams clasps and 9 linear, 9 tripodal, and 9 fully tripodal design obturators from casts obtained from a scanned skull. After modification, the prostheses were fabricated on the casts obtained from a 3-dimensionally printed cast. The retention was evaluated, and the data were collected and analyzed using a statistical software program (α=.05). The displacement and associated stress in the assorted casts were compared by using 5-N displacing force at 3 points using finite element analysis. The quantitative assessment was made by measuring the displacement and von Mises stress distribution on the prostheses and their supporting structures. The qualitative analysis was done by using a visual color mapping to depict stress location and intensity., Results: No significant differences were found between fully tripodal (4.478 ±2.303 MPa) and tripodal obturators (4.478 ±2.286 MPa; P=.153), although fully tripodal showed more resistance to anterior displacement (4.522 ±0.979 and 3.553 ±1.58 MPa for fully tripodal and tripodal designs, respectively; P=.007), and tripodal obturators produced more resistance to middle displacement (5.441 ±1.778 and 2.784 ±0.432 MPa for tripodal and fully tripodal design respectively; P=.001). The fully tripodal obturator showed more retention (3.736 ±1.182 MPa) than the linear one (2.493 ±1.052 MPa; P=.001). The maxillary central incisor was the most stressed abutment, followed by the lateral incisor, while the second molar was the least., Conclusions: Regarding retention, the fully tripodal obturator produces retention comparable with the tripodal and significantly more than the linear. Acrylic resin prostheses retained with Adams clasps may be similar to metal-based prostheses regarding retention and stress distribution on the supporting structures., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Abutment screw fracture is a mechanical complication associated with the failure of dental implant-supported restorations. Retrieval of fractured abutment screws without damaging the internal surface of implants is challenging and can be time-consuming. Microtube extraction devices are used to remove separated endodontic instruments. This article presents a conservative method of retrieving a fractured implant abutment screw using a microtube device., (Copyright © 2022 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: To evaluate clasp-retained removable partial dentures (C-RPDs) with a metal framework for survival, maintenance requirements, and biologic implications., Method and Materials: C-RPDs were retrospectively analyzed based on patient records. Treatment failure was defined as fracture of a framework component (metal base or connector) or loss of an abutment tooth. Other outcome variables included factors that might conceivably impact C-RPD survival (maxilla vs mandible, Kennedy classes, opposing dentitions, treatment by students vs certified dental practitioners), mobility and caries of abutment teeth (in relation to clasp designs), and maintenance requirements (relining, clasp or resin fractures). Differences were evaluated by appropriate statistical tests at the P ≤ .05 level., Results: A total of 612 patients (339 men, 273 women) 60.0 ± 11.5 years old at delivery were included, covering 842 C-RPDs and a mean observation period of 42.1 ± 33.2 months. Kaplan-Meier C-RPD survival was 76.2% after 5 years and 49.5% after 10 years. Biologic complications (ie, loss of abutment teeth) accounted for the vast majority (95.6%) of C-RPD failures, and Kaplan-Meier C-RPD survival was significantly better in the mandible (P = .015). Some clasp designs contributed significantly to caries and removal of abutment teeth (both P .05). No other significant differences were noted., Conclusion: Tooth loss both emerges as the main cause of C-RPD failure and might be amenable to careful selection of clasp designs. Overall, better C-RPD survival should be expected in the mandible. A noncontributory role of Kennedy classes and opposing dentitions is tentatively suggested based on numerically heterogenous subgroups.

This retrospective study examined factors influencing labial bone resorption in the anterior maxilla 6 months after implant insertion with simultaneous guided bone regeneration. Involving 79 patients (118 implants), the study measured labial horizontal bone width and vertical dimensions using cone beam computed tomography scans taken immediately after surgery and at 6 months. A generalized linear mixed model analyzed potential influencing factors: age, sex, implant site, timing of placement, buccal bone width at the implant platform level post-surgery, implant connection, and bone defect morphology. Significant bone resorption was noted at 6 months. The statistical analysis revealed that buccal bone width at the implant platform, implant connection, and bone defect morphology significantly impacted labial bone resorption, while patient age, sex, timing of placement, and implant site did not. Implants with a buccal bone width ≥2 mm showed significantly less labial horizontal and vertical bone resorption (horizontal P < 0.001, vertical P = 0.001), and healing abutments reduced resorption compared to cover screws (horizontal P = 0.002, vertical P = 0.034). More significant vertical resorption occurred in non-contained bone defects after guided bone regeneration (P = 0.040)., Competing Interests: Competing interests None., (Copyright © 2024 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: This study aimed to investigate whether the presence of a mesial cantilever influences the biomechanical behavior and screw loosening in fixed partial dentures (FPDs) with a distally tilted implant in the atrophic posterior maxilla and where to best place the distal implant., Methods: Two configurations of implant-supported four-unit FPDs were modelled using finite element analysis. Five interabutment distances were considered. The stress and strain distributions in the implants, abutments, and prosthetic screws were verified under occlusal loading. The development of the axial force on the abutments and screws was also examined. Two-sample t-tests were used to identify differences (P < 0.05)., Results: The von Mises stress distributions of the components in the two configurations were similar, as were the maximum plastic strains of the distal prosthetic screws, distal implants, and 30° abutments. The difference in the maximum plastic strains of the straight abutments was statistically significant. The preload of the 30° abutment screws was significantly reduced after the initial loading. In the absence of a mesial cantilever, the axial force on the straight abutments increased. However, when a mesial cantilever was used, the preload of the straight abutments was maintained, and the axial force on the prosthetic screws fluctuated less. The axial force fluctuation of the abutments gradually decreased as the interabutment distance increased., Conclusions: Mesial cantilever usage had minimal effect on stress or strain distribution in FPD implants, abutments, or prostheses. However, it helped resist screw loosening. The distal screw access hole was preferably positioned close to the prosthetic end.

Purpose: This in vitro study investigated the influence of material selection, crown morphology, and vertical crown height on the biomechanical behavior of screw-retained monolithic hybrid abutment crowns (HACs)., Methods: Ninety implants were embedded in accordance with ISO standard 14801; ninety HACs were mounted (N=90). Monolithic crowns with varying group-specific designs were luted using titanium bases. HACs were fabricated from monolithic lithium disilicate ceramic (LD) or zirconia-reinforced lithium silicate ceramic (ZLS). The crown morphology was either maxillary premolar (LD&#95;PM, ZLS&#95;PM) or molar (LD&#95;MO). The three groups were further divided into three subgroups of ten specimens, each designed with a small (7.5 mm), middle (10.5 mm), and high (13.5 mm) configuration of crown heights (N=10). A load-to-failure test at 30° off-axis was conducted using a universal testing machine until failure. For statistical analysis, Kolmogorov-Smirnov and Mann-Whitney U tests were conducted (P < 0.05)., Results: All LD&#95;MO groups presented the highest failure values (808.7 to 947.9 N), followed by the LD&#95;PM (525.8 to 722.8 N) and ZLS&#95;PM groups (312.6 to 478.8N). A comparison between LD and ZLS materials (P < 0.001) as well as the crown morphology (P < 0.001) showed significant differences in failure values. The values in the subgroups of ZLS&#95;PM (low, middle, high) decreased as the crown height increased. The fracture modes showed no consistent patterns across the test groups., Conclusions: Material selection, crown morphology, and vertical crown height appear to be important factors that may influence the clinical failure values and patterns of screw-retained single implant crowns.

Purpose: This study aimed to determine the usefulness of machine learning techniques, specifically supervised and unsupervised learning, for assessing the cementation condition between a fixed partial denture (FPD) and its abutment using a resonance frequency analysis (RFA) system., Methods: An in vitro mandibular model was used with a single crown and three-unit bridge made of a high-gold alloy. Two cementation conditions for the single crown and its abutment were set: cemented and uncemented. Four cementation conditions were set for the bridge and abutments: both crowns were firmly cemented, only the premolar crown was cemented, only the molar crown was cemented, and both crowns were uncemented. For RFA under cementation conditions, 16 impulsive forces were directly applied to the buccal side of the tested tooth at a frequency of 4 Hz using a Periotest device. Frequency responses were measured using a 3D accelerometer mounted on the occlusal surface of the tested tooth. Both supervised and unsupervised learning methods were used to analyze the datasets., Results: Using supervised learning, the fully cemented condition had the highest feature importance scores at approximately 3000 Hz; the partially cemented condition had the highest scores between 1000 and 2000 Hz; and the highest scores for the uncemented condition were observed between 0 and 500 Hz. Using unsupervised learning, the uncemented and partially cemented conditions exhibited the highest anomaly scores., Conclusions: Machine learning combined with RFA exhibits good potential to assess the cementation condition of an FPD and hence facilitate the early diagnosis of FPD retention loss.

Purpose: To investigate the esthetic outcomes based on the color differences in zirconia (Zr) of varying thickness, resin cement color, and types of titanium (Ti) implant surface treatments., Materials and Methods: Overall, 28 high-translucency monolithic zirconia (HTMZ) specimens were arranged into four groups based on Zr thickness: 1.0, 1.5, 2.0, and 2.5 mm (n &#61; 7 per thickness). Each group was tested using two resin cement colors (clear and opaque) in combination with six surface-treated Ti groups (n &#61; 7), including untreated titanium (UT), anodization (AN), 50-μm alumina airborne-particle abrasion followed by AN (SBAN), AN followed by 50-μm alumina airborne-particle abrasion (ANSB), 9.5% hydrofluoric acid followed by AN (HFAN), and AN followed by 9.5% hydrofluoric acid (ANHF). This created a total of 48 experimental groups, including the use of composite resin (n &#61; 7, shade A2D) for four control groups. All specimens were measured using a spectrophotometer and subsequently compared with composite resin (control) with the corresponding Zr thickness to establish color differences. A color difference of < 2.7 was considered clinically acceptable. The data obtained were statistically analyzed using ANOVA and post hoc test (P &#61; .05)., Results: Zr thickness, resin cement color, and type of Ti implant surface treatment significantly affected the observed color differences (P < .05). When using 2.5-mm HTMZ with clear resin cement on AN, UT, SBAN, HFAN, and ANSB, the mean color differences were below the clinically acceptable values, and the 95% CIs of color differences were below the clinically acceptable values for AN, UT, and SBAN groups., Conclusions: HTMZ with a minimum thickness of 2.5 mm and clear resin cement on AN, UT, and SBAN groups potentially result in acceptable color matching with 95% CIs.

Aim: The objective of the present study was to determine the 3-year clinical and dimensional soft tissue change following implant placement in healed sites before and after loading with either customized or conventional healing abutments., Materials and Methods: Premolar/molar implants were immediately loaded with either provisional and customized abutments without finishing lines according to the principles of the biologically oriented preparation technique (BOPT; test group) or conventional healing abutments (control group). Three months later, the definitive crowns were fabricated. Primary outcomes (soft tissue changes) and secondary outcomes (adverse events) were registered., Results: A total of 50 of the 87 subjects who were originally included were finally selected for the present retrospective analysis: 23 in the test group and 27 in the control group. During the first days after surgery, two adverse events of mucositis occurred, one in each group. A few technical complications were recorded such as the unscrewing of four screw-retained crowns. A significant increase in the alveolar width was observed in both groups (test: &#43;2.5 ± 0.5 mm; control: &#43;1.0 ± 0.9 mm). The widths appeared unchanged from 3 months to 3 years in both groups. There were no significant differences regarding the width of the keratinized mucosa measured at baseline and after follow-up. The Jemt papilla index showed a higher increase in the test group compared with the control group., Conclusions: Within the 3-year follow-up period, the peri-implant soft tissue outcomes of single, immediately loaded implants with customized healing abutments showed better results in terms of thickness and width compared with those of the conventional group. The number of side effects (mucositis and dehiscence) appeared to be very similar for both groups. In addition, customized healing abutments led to significant augmentation of the alveolar width, which was more than twice of that registered in the conventional group.

Aim: The objective of the present study was to investigate the effect of using different materials for the fabrication of implant abutments and crowns on the mechanical behavior of implant-supported single crowns after artificial aging. The materials were tested in different combinations to reveal whether using stiff or resilient materials as an abutment or a crown material might influence the fracture strength of the whole structure., Materials and Methods: A total of 40 implants (blueSKY) were restored with identical custom-made CAD/CAM abutments milled out of lithium disilicate or ceramic-reinforced polyetheretherketone (PEEK) and divided into five test groups (n &#61; 8). Forty crowns made of three different materials (zirconia, lithium disilicate, and ceramic-reinforced PEEK) were used to restore the abutments. Specimens were subjected to mechanical loading up to 1,200,000 cycles in a chewing simulator (Kausimulator) with additional thermal cycling. The surviving specimens were subjected to quasi-static loading using a universal testing machine (Z010)., Results: The PEEK abutments with zirconia crowns showed the highest median failure load (3890.5 N) while the PEEK abutments with lithium disilicate crowns exhibited the lowest (1920 N). Fracture and deformation occurred in both the crowns and abutments., Conclusion: The failure load of the restorations was influenced by the material of the abutment and crown. Restoring PEEK abutments with zirconia crowns showed a high failure load and no screw loosening.

Background: In edentulous jaws, factors such as the number of implants, cross-arch distribution, and the angle among implants may affect the accuracy of the implant impression. This study explored factors influencing the accuracy of implant abutment-level digital impressions using stereophotogrammetry in edentulous jaws., Methods: Two standard all-on-4 and all-on-6 models of edentulous jaws were constructed in vitro. In the stereophotogrammetry group (PG), the implant digital impression was made using stereophotogrammetry and saved as an STL file. In the conventional group (CNV), the impression was made using the open-tray splint impression technique. An electronic and optical 3D measuring instrument was used to scan the standard model and the conventional plaster model to obtain STL files. Using 3D data processing software (GOM Inspect Pro, Zeiss), the distance and angle between the abutments in the CNV impression and the PG impression were measured and compared with the data from the standard model., Results: The distance deviation in the PG and the CNV was 145 ± 196 μm and 96 ± 150 μm, respectively, with a significant difference (P < 0.001). The angle deviation in the PG and the CNV was 0.82 ± 0.88° and 0.74 ± 0.62°, respectively, with no significant difference (P = 0.267). In the PG, the distance deviation was negatively correlated with the distance between implants (r = -0.145, P = 0.028) and positively correlated with the angle of implants (r = 0.205, P = 0.002). The angle deviation was negatively correlated with the distance between implants (r = -0.198, P = 0.003) and positively correlated with the angle of implants (r = 0.172, P = 0.009). In the CNV, the effect of inter-implant distance on impression accuracy was also shown by Spearman correlation analysis: r = 0.347 (P < 0.001) for distance deviation and r = -0.012 (P = 0.859) for angle deviation. The effect of inter-implant angulation on impression accuracy deviation was r = -0.026 (P = 0.698) for distance deviation and r = 0.056 (P = 0.399) for angle deviation., Conclusions: The CNV method is closer to the real value of the original model. The distance between implants and the distribution angle had a weak correlation with the accuracy of digital impressions but no significant correlation with the accuracy of traditional impressions., (© 2024. The Author(s).)

Objective: This study assessed the effect of the anodization of titanium abutments on the color parameters and color difference of lithium disilicate (LDS) all-ceramic crowns., Materials and Methods: In this study, 19 straight abutments were divided into two groups: anodized (n = 9) and non-anodized control (n = 9), with one hybrid zirconia abutment as a reference. Anodization was achieved by applying 63 V energy using seven 9 V flat batteries in series, with an electrolyte solution comprising 1 g trisodium phosphate in 250 mL distilled water for 5 s, resulting in a gold-yellow color. Abutments were then scanned, and full-contour monolithic IPS e.max maxillary central incisor crowns were fabricated with 2 mm thickness and glazed. Reflectance was measured using a spectroradiometer, and color coordinates (L*, a*, b*, h*, and C*) were calculated using CS-10W software. Color differences of the crowns in both groups were quantified using the CIEDE2000 (ΔE 00 ) color difference formula and analyzed by t-test (α = 0.05) compared to the standard sample., Results: The L*, a*, b*, and c* parameters in anodized abutments were significantly higher than those in non-anodized abutments, while the h* parameter in anodized abutments was significantly lower than that in non-anodized abutments (p < 0.001 for all). There was a significant difference in ΔE 00 of the two groups (p = 0.043)., Conclusion: Anodization of titanium abutments improved the color parameters of LDS all-ceramic crowns and significantly decreased their ΔE compared with non-anodized abutments., (© 2024 The Author(s). Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Broken screw removal from the implant connection is a common but challenging process. Several proposed methods and technical solutions may result in unsuccessful removal; thus, a novel, more conservative, risk-free method is proposed as a first attempt. The proposal is to use a silicon restoration holder to be twisted counterclockwise on the dried surface of the broken fragment inside the implant connection. This method, within the limitations of a minimal case series, yielded 100% results; however, despite previous attempts with less conservative techniques, this approach showed no efficacy. This article aims to promote the use of silicon restoration holders as a minimally invasive first attempt at broken screw retrieval treatment before considering other options.

Objective: To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation., Material and Methods: Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05)., Results: Mean values (μm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups., Conclusions: Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objectives: This study aimed to evaluate the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM)-assisted templates (CCAT), guiding rod templates (GRT), and freehand (FH) preparation of guide planes., Methods: Forty-five identical maxillary resin casts were divided into three groups, in which the guide planes of the two abutment teeth were prepared using a CCAT (n=15), GRT (n=15), and FH (n=15). The CCAT and GRT were digitally designed on a digital cast of virtually prepared guide planes and fabricated using three-dimensional printing (3DP) technology. To assess the 3D trueness, the prepared guide planes were digitally scanned and compared to the virtually designed guide planes. The angle deviation was measured to assess the trueness of the direction of the guide plane preparation. Shapiro-Wilk and Levene's tests were used to check the normality and equivalence of the variance of the data. The data were compared by using the Kruskal‒Wallis H test (α=0.05)., Results: The CCAT group exhibited significantly better 3D trueness (78.5±19.8 μm) than the GRT group (211.3±42.4 μm, p<0.05) and the FH group (198.9±44.3 μm, p<0.05). Additionally, the CCAT group (1.31±0.50°) showed significantly smaller direction trueness compared to the GRT (4.65±0.72°, p<0.05) and FH (5.64±0.70°, p<0.05) groups., Conclusions: The novel CAD-CAM-assisted template significantly improved the quality of the guide planes compared with the GRT and FH procedures. This enhancement suggests that removable partial dentures can be predictably inserted immediately after guide plane preparation., Clinical Significance: CAD-CAM-assisted templates improve the quality of guide plane preparation., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The purpose of this study was to investigate the vertical marginal discrepancy (VMD) and residual excess cement (REC) of cementable and screwmentable monolithic zirconia crowns cemented with different types of cement. Abutments were attached to 40 implant analogues. Crowns were created using computer-aided design/computer-aided manufacturing technology from monolithic zirconia blocks, either with or without a screw access hole (SAC). Crowns created both ways were split into two groups and cemented with resin and zinc polycarboxylate cement under a 5-kg weight. VMD and REC values were evaluated using an X20 zoom stereomicroscope. Data were analysed using two-way ANOVA and the Bonferroni test. According to the two-way ANOVA results, REC measurements differed significantly in the crown design and cement groups. However, whilst VMD values were significantly different in both crown design groups, there was no significant difference in the cement groups. According to the Bonferroni test results, the highest REC (157.241 ± 44.29 µm) and VMD (68.052 ± 16.19 µm) values were found in the crowns without SAC and cemented with zinc polycarboxylate. Screwmentable crowns are more effective than cementable crowns in reducing REC and VMD. Whilst polycarboxylate cement reduces VMD in screwmentable crowns, resin cement is more suitable for cementable crowns., (© 2024. The Author(s), under exclusive licence to The Society of The Nippon Dental University.)

Purpose: The optimal configuration of a customized implant abutment plays a crucial role in promoting bone remodeling and maintaining the peri-implant gingival contour. However, the biomechanical effects of abutment configuration on bone remodeling and peri-implant tissue remain unclear. This study aimed to evaluate the influence of abutment taper configurations on bone remodeling and peri-implant tissue., Materials and Methods: Five models with different abutment taper configurations (10°, 20°, 30°, 40°, and 50°) were analyzed using finite element analysis (FEA) to evaluate the biomechanical responses in peri-implant bone and the hydrostatic pressure in peri-implant tissue., Results: The results demonstrated that the rate of increase in bone density was similar in all models. On the other hand, the hydrostatic pressure in peri-implant gingiva revealed significantly different results. Model 10° showed the highest maximum and volume-averaged hydrostatic pressures (69.31 and 4.5 mmHg), whereas Model 30° demonstrated the lowest values (57.83 and 3.88 mmHg) with the lowest excessive pressure area. The area of excessive hydrostatic pressure decreased in all models as the degree of abutment taper increased from 10° to 30°. In contrast, Models 40° and 50° exhibited greater hydrostatic pressure concentration at the cervical region., Conclusion: In conclusion, the abutment taper configuration had a slight effect on bone remodeling but exerted a significant effect on the peri-implant gingiva above the implant platform via hydrostatic pressure. Significant decreases in greatest and average hydrostatic pressures were observed in the peri-implant tissues of Model 30°. However, the results indicate that implant abutment tapering wider than 40° could result in a larger area of excessive hydrostatic pressure in peri-implant tissue, which could induce gingival recession., (© 2023 by the American College of Prosthodontists.)

Objectives: This study compared the accuracy of seven intraoral scanners (IOS) by the virtual-fit method., Methods: Four maxillary arches with tooth abutments were scanned with an industrial reference scanner (n=1) and by Aoralscan3, EmeraldS, Helios600, Lumina, Mediti700, Primescan, and Trios5 IOSs (each n=12). Two complete-arch fixed frameworks were designed on each IOS scan with a 70 µm (group 70) and a 90 µm internal cement space (group 70+20, additional 20 µm at the margin). The virtual-fit method was comprised of superimposing the framework designs onto the reference scan using a non-penetrating algorithm simulating the clinical try-in. Internal and marginal gaps were measured. Precision was estimated by the mean absolute errors (MAE)., Results: In group 70, Mediti700 (43 µm), Primescan (42 µm), and EmeraldS were in the best homogenous subset for the marginal gap, followed by the Lumina (67 µm), Aoralscan3 (70 µm), and Trios5 (70 µm), whereas Helios600 (118 µm) was in the third subset. Based on the MAE at the margin, Mediti700, Trios5, and EmeraldS were in the first-best homogenous subset, followed by Primescan. Lumina and Helios600 were in the third subset, and Aoralscan3 was in the fourth subset. In group 70+20, the marginal gap was significantly decreased for Lumina and Aoralscan3, whereas MAE significantly decreased for EmeraldS and Aoralscan3. The rank of IOSs was similar for the internal gap., Conclusion: EmeraldS, Mediti700, Primescan, and Trios5 meet the marginal and internal fit criteria for fixed tooth-borne complete arch restorations. Increasing the cement space during design could enhance restoration fit., Clinical Significance: The virtual-fit alignment method can effectively evaluate the accuracy of different intraoral scanners, offering valuable clinical guidance for distinguishing among them. Recent software and hardware versions of long-standing IOS manufacturers are suitable for fabricating complete arch restoration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Statement of Problem: The use of a scannable healing abutment is a convenient option for fabricating implant-supported restorations (ISRs) with a digital workflow; however, clinical studies evaluating prosthetic efficacy are lacking., Purpose: The purpose of this randomized controlled trial was to investigate the prosthetic efficacy of definitive posterior single ISRs fabricated after scanning using a scannable healing abutment-scan peg (SHA-SP) in comparison with a conventional scan body (CSB). The time for data acquisition, quality of proximal and occlusal contacts, and relative occlusal force of ISRs were measured., Material and Methods: Twenty-four participants eligible for single ISRs to replace the mandibular first molar with adjacent and antagonist teeth present were randomly allocated to either a study group (n=12) receiving ISRs after intraoral scanning using an SHA-SP or a control group (n=12) receiving ISRs after intraoral scanning using CSB. During the surgical procedure, a prefabricated contoured scannable healing abutment was screwed to the implant in the SHA-SP group, while a custom-made healing abutment was used in the CSB group. After a healing period of 3 months, an intraoral scan was made, and the duration of data acquisition was recorded. The ISRs were milled from zirconia and evaluated for the quality of proximal and occlusal contacts using dental floss and shim stock, respectively. The relative occlusal forces of the ISRs and their contralateral natural teeth were measured using a digital occlusal analyzer. Statistical analysis was done using an independent sample t test for quantitative variables and a Pearson chi-squared test for qualitative variables between the tested groups (α=.05)., Results: The direct digital workflow using SHA-SP was statistically less time consuming than the CSB (P<.001). The 2 groups were statistically similar regarding the quality of the proximal contacts (P=.281) or occlusal contacts (P=.307) and the relative occlusal forces of ISRs (P=.315). The relative occlusal forces of the ISRs in both groups were significantly lower than those of their contralateral natural teeth (P<.001)., Conclusions: Direct digital workflow using SHA-SP was more rapid, saving clinical chairside time, and produced proximal and occlusal contacts of comparable quality with those obtained with CSB. The relative occlusal forces of ISRs in both workflows were lower than their contralateral natural teeth., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: To assess radiographic, clinical and patient-reported outcomes of single zirconia implant-supported crowns on titanium base abutments (TBA) over a 7.5-year period., Methods: Twenty-four patients received bone-level titanium implants and screw-retained zirconia implant crowns utilising TBA. Marginal bone level (MBL), clinical parameters (probing depth-PD, bleeding on probing-BoP, plaque control record-PCR), technical complications (USPHS criteria) and patient satisfaction were assessed at crown delivery (baseline), 1 year (FU-1) and at 7.5 years (FU-7.5) of follow-up., Results: Eighteen patients were available for re-examination at 7.5 years. The mean MBL at FU-7.5 (0.35 ± 0.20mm) did not significantly change compared to baseline (0.54 ± 0.39, p=.352) and to FU-1 (0.54 ± 0.45mm, p=0.524). From baseline to 7.5 years, the mean PD increased significantly, from 3.0 ± 0.6mm to 3.7 ± 0.8mm (p=0.005). However, BoP and PCR did not significantly change; (BOP: from 27.1 ± 20.7% to 25.0 ± 20.0%, p=0.498; PCR: from 11.1 ± 21.2% to 25.0 ± 25.1%, p=0.100). Nine patients presented with more than one bleeding site. This denoted a peri-implant mucositis prevalence of 50%, whilst none of the implants presented peri-implantitis. One incidence of minor and major ceramic chipping were reported on 2 out of the 18 crowns, resulting in a prosthetic survival rate of 94.4%. Seventeen patients were highly satisfied with their result., Conclusion: Single implant-supported zirconia crowns on TBA displayed: (i) minor number of technical complications, (ii) high prosthetic survival rate, (iii) stable marginal bone level and (iv) high patient satisfaction at 7.5 years., Clinical Implications: Titanium base abutments despite their high use in clinical practice, lacked medium- and long-term studies. The presented findings highlight their clinical performance at 7.5 years as they display satisfying radiographic, clinical and patient-related outcomes. TBA appear to be a suitable abutment choice for medium-term implant-supported restorations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Statement of Problem: Unscrewing the healing abutment can affect the soft tissue integration and apical migration of the biological width, which may compromise the integrity of peri-implant soft tissue., Purpose: The purpose of this clinical study was to determine the level of glycosaminoglycan (GAG) detected in the peri-implant crevicular fluid (PICF) between the test group (1-time abutment) and control group (healing abutment) for implant-retained mandibular overdentures., Material and Methods: Two dental implants were installed in the canine regions of the mandibular ridge of 18 healthy completely edentulous participants using 2-stage surgery and a delayed loading protocol. At the second stage surgery, the implant on the right side was exposed, and a healing abutment was screwed onto the implant (control group), while on the left side the definitive ball abutment was screwed onto the implant (test group). After 10 days, the healing abutment in the control group was unscrewed and replaced with the definitive ball abutment. For both groups, the ball attachment was directly picked up to incorporate the attachment house to the mandibular denture. PICF samples were collected from the participants at 7 days, 3 months, and 6 months after overdenture use. Statistical analysis was done with an independent samples t test (α=.05)., Results: A significant difference was found in the volume of PICF and the level of GAG between the test and control groups at the 7-day evaluation period (P=.008, P=.002, respectively), while the volumes of PICF and the levels of GAG were not significantly different (P>.05) at the other evaluation periods., Conclusions: The 1-time abutment protocol offers biochemical and economic advantages compared with the conventional method of using the healing abutment before placement of the definitive attachment for an implant-retained overdenture with single attachments., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: To evaluate the effect of the deterioration of computer aided design/computer aided manufacturing (CAD/CAM) burs during zirconia milling, on surface roughness, contact angle, and fibroblast viability., Materials and Methods: Ceramic blocks were milled and 75 ceramic disks (8 × 1.5 mm) made and allocated into three groups (n = 25): G1-brand new 2L and 1L burs, G2-2L bur at the end of lifetime and brand new 1L bur and G3-both burs at the end of their lifetimes. Roughness (Ra, Rq, and Rz) was evaluated using a 3D optical profilometer, the contact angle by the sessile drop method and the cell viability of the mouse NIH/3T3 fibroblast, using the Alamar Blue assay at intervals of 24, 48, and 72 h (ISO 10993-5). Data were analyzed by one-way ANOVA and Kruskal-Wallis tests (p ≤ 0.05)., Results: Roughness increased as the burs deteriorated and G3 (0.27 ± 0.04) presented a higher value for Ra (p < 0.001). The highest contact angle was observed in G3 (86.2 ± 2.66) when compared with G1 (63.7 ± 12.49) and G2 (75.3 ± 6.36) (p < 0.001). Alamar Blue indicated an increase in cell proliferation, with no significant differences among the groups at 24 and 72 h (p > 0.05)., Conclusions: The deterioration of the burs increased the surface roughness and decreased the wettability, but did not interfere in cell viability and proliferation., Clinical Significance: The use of custom zirconia abutments represents an effective strategy for single crowns restorations. Our findings suggest that these abutments can be efficiently milled using CAD/CAM burs within their recommended lifetime., (© 2024 Wiley Periodicals LLC.)

Objective: The aim of this investigation was to evaluate the effect on clinical and radiological outcomes of the one-abutment, one-time protocol (test) versus placing the definitive abutment on the day of functional loading after having disconnected and connected three times the healing abutment during the prosthetic phase (control)., Materials and Methods: Forty patients with 80 implants were randomly allocated to either the test or the control group. Changes in the radiographic marginal bone levels (MBLs), clinical outcomes, prosthetic-related outcomes, and patient-reported outcomes measures (PROMs) were assessed and compared 6 and 12 months after functional loading., Results: Thirty-seven patients with 74 implants were followed at 12 months. A statistically significant bone remodeling was observed in both groups following implant placement. MBLs were significantly greater in the control group at the 6- (-0.13 mm vs. -0.61 mm) and 12-month visits (-0.01 mm vs. -0.53 mm). Bone loss was significantly greater in the control group from surgery to 6 and 12 months and from loading to 6 and 12 months. The abutment height was significantly greater in the test group, however, there were no significant differences in the restorative angle. Similarly, there were no statistically significant differences between groups for the measured clinical variables (probing depth, plaque, and bleeding index) and PROMs., Conclusions: Disconnecting and reconnecting the healing abutment was associated with significantly higher bone loss after 12 months, as compared to the placement of the definitive abutment at implant installation., (© 2024 The Author(s). Clinical Implant Dentistry and Related Research published by Wiley Periodicals LLC.)

Objectives: To evaluate the fracture resistance (FR) of polyetheretherketone (PEEK) abutments produced by additive and subtractive methods compared to milled zirconia abutments., Methods: Custom abutments were designed on Ti-base abutments and produced from three different materials, namely additively manufactured PEEK (PEEK-AM), subtractively manufactured PEEK (PEEK-SM), and zirconia (N = 60). PEEK-AM abutments were printed using PEEK filaments (VESTAKEEP®i4 3DF-T, Evonik Industries AG) on a M150 Medical 3D Printer (ORION AM) by fused filament fabrication (FFF). All surface treatments were carried out according to the manufacturer's instructions. All abutments were cemented on Ti-bases with hybrid abutment cement and then restored with milled zirconia crowns. Each subgroup was divided into non-aged and aged subgroups (n = 10). The aged groups were subjected to thermomechanical aging (49 N, 5-55 °C, 1.2 million cycles). FR tests were performed by using an universal testing machine. Data were statistically analyzed with one-way and two-way ANOVA and t-test., Results: The survival rate of the specimens after aging was determined as 100%. It was found that both the material and aging had a significant effect on the FR (p<.001). There was a statistical difference among the fracture values of the groups (p<.001). In both the aged and non-aged groups, PEEK-AM showed the statistically lowest FR, while the highest FR was seen in the zirconia group, which was significantly higher than the PEEK-SM (p<.001)., Conclusion: Hybrid abutments were successfully manufactured, and extrusion-based processed PEEK seems to be a good alternative to subtractive processed PEEK. However, since subtractive manufacturing still appears to be superior, further developments in additive manufacturing are needed to further improve the quality of 3D-printed PEEK parts, especially in terms of accuracy and bonding between adjacent layers., Clinical Significance: Additively manufactured PEEK abutments have the potential to be an alternative for implant-supported restorations in the posterior region., Competing Interests: Declaration of competing interest All other authors have no conflicts of interest to declare. The authors do not have any financial interest in the companies whose materials are included in this article., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the effect of different cement types on the incidence of failure and loss of retention of zirconia and metal-ceramic single crowns (SCs) cemented on implant abutments., Methods: We placed 567 implant-supported SCs in 358 patients and retrospectively evaluated long-term retention for up to 12.8 years. The frameworks were made from metal alloy (n = 307) or zirconia (n = 260). SCs were cemented with permanent (glass-ionomer cement; n = 376) or semipermanent cement (zinc oxide non-eugenol cement; n = 191) on standardized (n = 446) or customized (n = 121) abutments. Kaplan-Meier curves were used to calculate the incidence of decementation. Differences between survival curves were assessed with log-rank tests. Cox-regression analysis was performed to evaluate multiple risk factors., Results: Of the 567 SCs, 22 failed because of technical complications and four because of implant loss. Loss of retention was observed in 50 SCs. Analysis revealed a 7% probability of loss of retention for zirconia and 16% for metal-ceramic SCs after 10 years (p = .011). After 5 years, loss of retention was higher for standardized abutments than for customized abutments (p = .014). The probability of loss of retention was higher with semipermanent than with permanent cement (p = .001). Cox-regression analysis revealed semipermanent cement as the only significant risk factor for SC failure (p = .026)., Conclusions: In contrast to semipermanent cement, permanent cement provides acceptable long-term retention of cemented implant-supported SCs. These possible positive effects of customized abutments have to be controlled with larger sample sizes., (© 2024 The Author(s). Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

This study evaluated fracture resistance of monolithic fixed dental prostheses (FDPs) fabricated using different placement strategies of various connector designs in multilayered zirconia disc. Monolithic FDPs were placed in translucent and dentin layers of multilayered zirconia disc and fabricated with V-shaped and U-shaped connector designs gained by sharp and blunt millings. The FDPs were cemented on abutment models made of polymer material, underwent thermal cycles, and loaded to fracture using the universal testing machine. Fracture loads and modes were analyzed using two-way ANOVA, Tukey's post hoc test, and Fisher exact test (p≤0.05). The chosen placement strategy and connector designs gained by different milling procedures in computer-aided design/computer-aided manufacturing technology affect fracture resistance of monolithic FDPs made of multilayered zirconia materials. Placing the connector in translucent layer rather than dentin layer of multilayered zirconia disc and using sharp milling significantly reduces fracture resistance of monolithic multilayered zirconia FDPs.

Background: Failure to restore missing teeth in time can easily lead to the mesial tilting of the distal abutment teeth. However, a fixed partial denture (FPD) can improve stress conduction and distribution and prevent periodontal injuries. In these more complex cases, it is necessary to consider various factors comprehensively to improve conventional treatment planning and achieve better results., Methods: We selected a patient with a missing first molar and a mesial inclination of the second molar, leaving inadequate space or bone mass for implant denture restoration, necessitating an FPD for restoration. Three-dimensional finite element analysis (3D-FEA) combined with photoelastic analysis were used to explore how the inclination angle (0 ‒ 30°) and different dental restoration materials (zirconia, lithium disilicate, polymer-infiltrated ceramic network, and resin composite) affect the biomechanical behaviour of FPD‒abutments‒periodontal tissue complex., Results: The stress was easily concentrated in the FPD connectors, enamel shoulder collar, periapical area, and root bifurcation. The stress on FPD and the periodontal ligament (PDL) of the second premolar increased with an increase in the elastic modulus of FPD, with an opposite trend in the abutments, the alveolar bone, and the PDL of the second molar. The stress on the FPD and alveolar bone increased with increased inclination angle of the distal abutment. The stress on two abutments and their PDL were positively correlated with the inclination angle in two stages; however, when the inclination angle > 12°, the second premolar and its PDL showed a negative correlation., Conclusions: FPDs can be used for restoration within 24° of distal abutment inclination, but protecting the abutments (< 12° especially) and the periodontal tissue (> 12° especially) must be taken seriously. For this purpose, an FPD material with higher strength is recommended., (© 2024. The Author(s).)

Purpose: To evaluate the influence of abutment material, cement thickness, and crown type on the esthetics of implant supported restorations., Material and Methods: In total, 60 specimens were prepared to represent six abutment groups: Group PA &#61; pink-anodized Ti; Group GA &#61; gold-anodized Ti; Group T &#61; nonanodized Ti; Group H &#61; hybrid (Ti &#43; zirconia); Group P &#61; PEEK (Ti &#43; PEEK); and Group C &#61; composite resin (control). Crown specimens (n &#61; 120) were obtained from Vita Enamic (VE) and Vita Suprinity (VS). Two cement thicknesses (0.1 and 0.2 mm) were used. The color values of crown configura:ons were measured and ΔE00* values were calculated. Statistical analyses included were Shapiro Wilk, three-way ANOVA, and Tukey HSD tests (P ≤ .05)., Results: Abutment (P < .001) and crown materials (P &#61; .001) had a significant effect on ΔE00* values, while cement thickness did not. Groups PA and H resulted in significantly lower mean ΔE00* values than other abutments, whereas Group T revealed the highest. Unlike VS, cement thicknesses created a significant difference on the ΔE00* values for VE (P ≤.05)., Conclusions: Pink-anodized Ti or hybrid abutments for VE and pink- or goldanodized Ti for VS seem to be better options, in terms of color change. Cement thickness of 0.1 mm resulted in higher ΔE00* value than 0.2 mm for VE (P ≤ .05).

Purpose: To evaluate the behavior of hybrid abutment crowns fabricated from monolithic lithium disilicate ceramic (LDC) and to compare the influence of different in vitro artificial aging protocols., Materials and Methods: A total of 32 monolithic hybrid abutment crowns of monolithic LDC were fabricated. Of these, 24 were artificially aged using three different protocols up to a 20 year simulation (1.2 × 106, 2.4 × 106, 4.8 × 106 chewing cycles, thermocycling), a control group underwent no artificial aging (n &#61; 8, N &#61; 32). Load-to-failure tests were conducted for all specimens, and failure values were compared (P < .05)., Results: All specimens passed in vitro aging. Mean failure load values between 532.6 and 562.8 N were found but did neither differ significantly among the test groups nor from the control group., Conclusions: Within the limitations of this in vitro pilot study, hybrid abutment crowns manufactured from monolithic LDC seem to offer appropriate long-lasting mechanical stability over a simulation period up to 20 years. The failure values and complication pattern seem to be independent of several aging protocols in this test set-up.

Background: Advancements in digital dentistry helped in custom-milling screw-channels in implant-supported restorations; however, the fit of these restorations is still unclear especially for contemporary computer aided designing/computer aided manufacturing (CAD/CAM) materials. This study aimed to compare the internal and marginal fit of Ultra translucent multilayered zirconia versus lithium disilicate implant-supported hybrid abutment crowns (HACs) constructed with custom-milled screw-channels on Titanium-base., Materials and Methods: A total of 24 HACs with custom-milled screw-channels were constructed from lithium disilicate (Group LDS) and Ultra translucent multilayered zirconia (Group UT) using digital workflow (n = 12). The internal and marginal gaps of HACs on their corresponding Titanium-bases were assessed using replica technique and stereomicroscope, respectively. After testing for normality, quantitative data were expressed as mean and standard deviation and compared using independent t-test at a level of significance (P ≤ 0.05)., Results: There was no statistically significant difference between Group LDS and Group UT in terms of marginal and internal fit. The internal and marginal gaps in both groups were within the accepted values reported in literature., Conclusions: UT and LDS HACs with custom-milled screw-channels demonstrated comparable and acceptable internal fit and marginal adaptations to Ti-base, which lied within the range reported in literature., (© 2024. The Author(s).)

Background: The purpose of this in vitro study was to investigate the effect of polishing post-treatment process on the torque loss ratio and microgap of Selective Laser Melting (SLM) abutments before and after mechanical cycling test through improving the surface roughness of the implant-abutment interface., Materials and Methods: Forty SLM abutments were fabricated, with 20 underwent minor back-cutting, designated as polishing, in the implant-abutment interface. The abutments were divided into three groups: SLM abutments (group A), original abutments (group B), and polished SLM abutments (group C), each containing 20 abutments. Surface roughness was evaluated using a laser microscope. Implant-abutment specimens were subjected to mechanical cycling test, and disassembly torque values were measured before and after. Scanning electron microscope (SEM) was used to measure microgap after longitudinal sectioning of specimens. Correlation between surface roughness, torque loss ratio, and microgap were evaluated. LSD's test and Tamhane's T2 comparison were used to analyze the data (α = 0.05)., Results: The Sz value of polished SLM abutments (6.86 ± 0.64 μm) demonstrated a significant reduction compared to SLM abutments (26.52 ± 7.12 μm). The torque loss ratio of polished SLM abutments (24.16%) was significantly lower than SLM abutments (58.26%), while no statistically significant difference that original abutments (18.23%). The implant-abutment microgap of polished SLM abutments (2.38 ± 1.39 μm) was significantly lower than SLM abutments (8.69 ± 5.30 μm), and this difference was not statistically significant with original abutments (1.87 ± 0.81 μm). A significant positive correlation was identified between Sz values and the ratio of torque loss after cycling test (r = 0.903, P < 0.01), as well as Sz values and the microgap for all specimens in SLM abutments and polished SLM abutments (r = 0.800, P < 0.01)., Conclusion: The findings of this study indicated that the polishing step of minor back-cutting can lead to a notable improvement in the roughness of SLM abutments interface, which subsequently optimized the implant-abutment fit. It can be seen that the application of minor back-cutting method has advanced the clinical use of SLM abutments., (© 2024. The Author(s).)

Background and Objectives : This study uses finite element analysis to evaluate the impact of abutment angulation, types, and framework materials on the stress distribution and fatigue performance of dental implant systems. Materials and Methods : Three-dimensional models of maxillary three-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Two different framework materials were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The distribution of stress and fatigue performance were then assessed, considering the types of restoration frameworks used and the angles of the abutments in three distinct locations. The simulation aspect of the research was carried out utilizing Abaqus Software (ABAQUS 2020, Dassault Systems Simulation Corp., Johnston, RT, USA). Results : In all models, fatigue strengths in the premolar region were higher than in the molar region. Maximum stress levels were seen in models with angled implants. In almost all models with the zirconia framework, fatigue performance was slightly lower. Conclusions : According to the findings of this study, it was concluded that the use of metal-framework multi-unit restorations with minimum angulation has significant positive effects on the biomechanics and long-term success of implant treatments.

In recent years, a wide variety of materials have been used in dental implant treatment. In selecting the superstructures and abutments to be used it is important to consider their potential effect on the stability and durability of the planned implant. Excessive force applied to an implant during maintenance commonly results in complications, such as fracture of the superstructure or abutment, and loosening or fracture of the screws. This report describes a case of implant treatment for a 23-year-old man with esthetic disturbance due to trauma to the maxillary anterior teeth. The left maxillary central incisor could not be conserved due to this trauma, which had been caused by a traffic accident. After extraction, the tooth was restored with an anterior bridge. The crown of the left maxillary lateral incisor was fractured at the crown margin and, at the patient's request, implant treatment was selected as the restorative treatment for the missing tooth. A thorough preoperative examination was performed using placement simulation software. One titanium screw-type implant was placed in the maxillary left central incisor under local anesthesia. An all-ceramic crown with a zirconia frame was placed as a screw-fixed direct superstructure. At one year postoperatively, however, the superstructure and abutment became detached due to trauma. The fractured zirconia abutment was removed and replaced with a remanufactured abutment and superstructure. The patient has reported no subsequent dental complaint over the last 11 years. In this case, a surface analysis of the fractured zirconia abutment was performed. The scanned images revealed a difference in the fracture surfaces between the tensile and compressive sides, and electron probe microanalysis demonstrated the presence of titanium on the fracture surface. It was inferred that the hard zirconia abutment had scraped the titanium from the internal surface of the implant.

Objective: The objective of this study is to evaluate the changes at marginal bone level at implants restored with screw-retained prosthesis connected directly to the implants or with an intermediate abutment, after 3-year follow-up., Material and Methods: Thirty-six partially edentulous patients received 72 implants. Each patient received 2 implants and a 2-4-unit screw-retained implant-prosthesis. The test group implants received a screw-retained prosthesis connected directly to the implant shoulder, the control group prosthesis were connected through a 3-mm standardised intermediate abutment. Clinical and radiological data were recorded at baseline and at 6-, 12-, and 36-month follow-up., Results: At 36 months, the mean marginal bone loss was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 for the test group, with no significant differences between groups (p > .05). Clinical variables (Probing Pocket Depth, Bleeding on Probing and Plaque Index) at 36 months also showed no significant difference between groups. Minor complications frequency was 6.7% in the control group and 5.3% in test group. None of the groups suffered from mayor complications. Patient Reported Outcomes (PROs) showed a General Satisfaction mean score in the control group of 9.40 (SD 0.82) and 9.37 (SD 1.06) in the test group with no significant differences between groups., Conclusions: Bone-level implants restored with screw-retained partial prostheses with or without intermediate abutments showed similar radiographic and clinical outcomes after 3 years., (© 2024 The Author(s). Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

Objective: To evaluate the mechanical performance of patient-specific prefabricated temporary shell versus laboratory-fabricated CAD/CAM provisional restorations on titanium temporary abutments, with and without thermo-mechanical ageing., Materials and Methods: Implants with a conical connection were divided into four groups (n = 24) and restored with temporary shell or laboratory-fabricated central or lateral incisor PMMA restorations that were relined or bonded on titanium temporary abutments. The diameter of the central and lateral incisor groups' implants was regular (ϕ 4.3 mm) or narrow (ϕ 3.5 mm), respectively. Half of each group's specimens were subjected to ageing, simultaneous thermocycling (5-55°C) and chewing simulation (120,000 cycles, 50 N, 1.7 Hz) resulting in eight groups in total (n = 12). The aged specimens were evaluated with optical microscopy, and survival and complication rates were determined according to modified USPHS criteria. The non-aged specimens and those that had survived ageing were loaded until failure, whereupon bending moments were calculated., Results: Survival rates after ageing were 100% for all groups. Apart from wear facets (ϕ 2-3 mm) on the palatal restoration surface, no complications were observed. The mean fracture load and bending moments ranged between 597.6-847.1 N and 433.3-550.6 Ncm, respectively, with no significant differences between the eight groups (p = .25; p = .20)., Conclusions: As patient-specific temporary shell central and lateral incisor provisional implant-supported restorations are mechanically stable enough to withstand clinical bite forces, even after thermo-mechanical ageing, they may serve as an alternative to laboratory-fabricated provisional restorations., (© 2024 The Author(s). Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

Objectives: Tooth preparation is complicated because it requires the preparation of an abutment while simultaneously predicting the ideal shape of the tooth. This study aimed to develop and evaluate a system using augmented reality (AR) head-mounted displays (HMDs) that provide dynamic navigation capabilities for tooth preparation., Methods: The proposed system utilizes optical see-through HMDs to overlay digital information onto the real world and enrich the user's environment. By integrating tracking algorithms and three-dimensional modeling, the system provides real-time visualization and navigation capabilities during tooth preparation by using two different visualization techniques. The experimental setup involved a comprehensive analysis of the distance to the surface and cross-sectional angles between the ideal and prepared teeth using three scenarios: traditional (without AR), overlay (AR-assisted visualization of the ideal prepared tooth), and cross-sectional (AR-assisted visualization with cross-sectional views and angular displays)., Results: A user study (N = 24) revealed that the cross-sectional approach was more effective for angle adjustment and reduced the occurrence of over-reduction. Additional questionnaires revealed that the AR-assisted approaches were perceived as less difficult, with the cross-sectional approach excelling in terms of performance., Conclusions: Visualization and navigation using cross-sectional approaches have the potential to support safer tooth preparation with less overreduction than traditional and overlay approaches do. The angular displays provided by the cross-sectional approach are considered helpful for tooth preparation., Clinical Significance: The AR navigation system can assist dentists during tooth preparation and has the potential to enhance the accuracy and safety of prosthodontic treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Statement of Problem: Various options are available to allow angle correction for screw-retained restorations for malaligned implants, including angled abutments, angled screw channel abutments, and angled implants. However, the effect these angle correction components have on prosthetic screw loosening is unclear., Purpose: The purpose of this systematic review was to assess the effect of angled abutments, angled screw channel abutments, and angled implants on prosthetic screw loosening., Material and Methods: This manuscript followed the Preferred Reporting Items for the Systematic Review and Meta-Analyses (PRISMA) statement. Searches were performed through 31 December 2021 in PubMed/MEDLINE, EMBASE, and Web of Science with no year limit targeting in vitro studies evaluating the effect of angulation correction components on screw loosening., Results: A total of 460 articles were identified. After removing duplicates, 306 titles were screened. Nine of the remaining 36 articles selected for full-text analysis met the selection criteria. The qualitative analysis used data from 394 implants. All studies featured straight abutments as the control group, and, in 8 studies, the angle correction component was included on the level of the abutment. Only in 1 study was the angle correction component at the level of the implant. The angle correction of the prosthetic component varied from 0 degrees in all studies up to a maximum correction of 30 degrees. Statistically significant increases in screw loosening with increasing abutment angle correction were reported by multiple authors (P<.05). However, other articles reported nonsignificant differences in screw loosening because of angulation after cyclic loading (P>.05). The only study investigating angle correction at the implant level found significantly less screw loosening (P<.05) in the angled implant group compared with the nonangled implant group., Conclusions: Several options are available to correct discrepancies between the surgical axis and the ideal prosthetic axis for rehabilitations supported by dental implants. The current evidence does not clearly indicate the superiority of any single solution for minimizing screw loosening., (Copyright © 2022 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to investigate the influence of undercut depths on abutment teeth regarding the retentive force of clasps fabricated through selective laser melting (SLM), and to compare them with conventional cast clasps., Methods: Akers clasps made of cobalt chromium alloy were fabricated using the SLM method (SLM), and the retentive forces were compared with clasps made with the conventional cast method (Cast). Three undercut amounts (0.25 mm, 0.15 mm, and 0 mm) were applied on the abutment tooth. The specimens were subjected to 10,000 repetitive insertion/removal cycles., Results: SLM-0.15 showed slightly lower initial retentive force than the Cast specimens, it remained within an acceptable range. During insertion/removal test, the SLM-0.15 specimen showed a significant difference between the initial retentive force and the retentive force after 5,000 cycles, indicating that SLM-0.15 was the least likely to change in retentive force within the parameters established in this study. The inner clasp surface on the SLM groups had higher surface roughness before testing compared to the Cast specimen., Conclusions: Akers clasps fabricated by SLM demonstrated optimal initial retentive forces with smaller undercuts than conventional Cast clasps, and the retentive forces changed less with repetitive insertion/removal., (Copyright© 2024 Dennis Barber Ltd.)

Purpose: This study aimed to assess the effect of abutment variation and creep on dental implant restorations., Materials and Methods: Three finite element analysis (FEA) models of implant restorations were created, which were restored by conventional one-piece abutment (CA), hybrid abutment crown (HAC), and multi-unit abutment (MUA). The contacts were considered intimate (no friction), except for implant/abutment, abutment/screw, and abutment/screw/crown (HAC) attachments. The related mechanical parameters were used to improve the authenticity of the study. Instantaneous loads and constant loads (100 s) of 130 N were applied at a 30° angle to the palatal portion of the crown. Results were qualitatively and quantitatively evaluated using the equivalent von Mises stress, micro-gap distance of the implant-abutment interface (IAI), preload changes, and safety index., Results: The stress state of each component differed depending on the restoration type, from CA and HAC to MUA. Implants and screws were the structures that suffered the most stress under instantaneous loads. Each metal structure exhibited a substantial decrease in stress during a constant loading period. The screws of the MUA abutment showed more preload loss (62.1 N) after constant loads for 100 s. MUA base produced less micro-gap (0.72 μm) at the IAI when it was compared with the CA group (0.93 μm) and HAC group (3.29 μm)., Conclusions: The abutment type influences the mechanical properties and performance of implant restorations. The creep effect decreases the maximum stress level and increases the safety factors of each structure, indicating that stress-related mechanical complications may not occur more easily., (© 2023 by the American College of Prosthodontists.)

Statement of Problem: Early tightening torque at the implant-healing abutment interface is a recognized concern in implant treatment. However, little is known regarding the effects of toothbrushing methods on the interface established between the implant and healing abutments of different heights., Purpose: The purpose of this in vitro study was to evaluate the effect of different toothbrushing methods on tightening torque for healing abutments of different heights., Material and Methods: A total of 60 implants (Bilimplant; Proimtech) were embedded in epoxy resin blocks. The following 6 test groups were established: healing abutments with manual toothbrush group (Oral B Pro Expert All in one; Oral B) and 4 mm height (MTB-4, (which served as the control); 6 mm height (MTB-6, which served as the control); sonic toothbrush group (Philips Sonicare 3100 Series; Philips Oral Healthcare) and 4 mm height (S-4); 6 mm height (S-6); oscillating/rotating toothbrush group (Oral B Smart 6 6000N; Oral B) and 4 mm height (OR-4) and 6 mm height (OR-6). Each specimen was tightened to 15 Ncm and brushed. The digital torque meter (Cap Torque Tester Series TT01; Mark10) was used to calculate the reverse torque values., Results: The highest torque loss value in the average torque losses in the test groups was 1.3 (OR-6); the lowest was 0.3 (S-4). While a significant difference was found between groups S-4 and S-6 (P=.018), no statistically significant difference was found among the other groups (P>.05)., Conclusions: Torque loss was greater in the healing abutment with a height of 6 mm and with the oscillatory and rotational brushing method., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: To evaluate structural damage and loosening of abutments placed on narrow diameter implants after cyclic fatigue., Methods: Sixty Morse taper narrow diameter implants (Neodent, Brazil) received two types of abutments (1PA- one-piece abutment or 2PA- two-piece abutment), which were randomly divided into 3 fatigue experiments (n = 10). The implants were placed into a customized supporting holder and a software-assisted digital torque wrench secured the manufacturer recommended torque for each abutment. Cone beam computed tomography (CBCT) scans were acquired, before and after fatigue, and post-processed (software e-Vol DX) to assess damage and abutment displacement. The boundary fatigue method was adapted to use 2 × 10 6 cycles, 2 Hz of frequency and constant peak load of 80 N (first experiment) that varied according to the failure rate of previous specimens (second and third experiments). Failure was evaluated using CBCT scans and removal torque values. Data were used to estimate long-term torque degradation, probability of failure and Weibull modulus (software ALTA PRO9)., Results: All 2PA specimens became loosen independently of the applied fatigue load, and structural bending was observed in 14 abutments. Eight 1PA got loosen during the fatigue experiment. The Weibull analysis showed a lower modulus (m = 1.0; 0.7, 1.4) for 1PA than for 2PA (m = 2.6; 2, 3.4) resulting in longer predicted lifetimes and slower torque degradation for 1PA than for 2PA specimens., Significance: 1PA showed greater long-term survival probability than 2PA. Predicting the lifetime and mechanical behavior of implant-abutment systems are useful information to clinicians during the decision-making process of oral rehabilitations., (Copyright © 2024 Elsevier Inc. All rights reserved.)

A digital approach is described for fabricating a splinted framework and custom open tray for the impression of multiple implants based on a virtually created implant cast with the digital prediction of the future impression coping positions. In this technique, impression copings to be used in the definitive impression-making process were digitally scanned and aligned to a preliminary cast using installed protective caps of screw-retained abutments as references, which resulted in a virtual cast that offers information both about the impression coping positions and their surrounding tissues and could allow a splinted framework and custom open tray to be digitally designed and fabricated. Creation of a virtual cast through digital technologies eliminates the traditional manual splinted framework and custom tray fabrication procedures. Additionally, only one set of impression copings and analogs is needed in this technique, thereby reducing treatment time and cost. It also offers a splinted framework and custom open tray with consistent quality., (© 2023 by the American College of Prosthodontists.)