Search

A cast-free approach is described to fabricate an implant-supported interim restoration by using the postoperative cone beam computed tomography (CBCT) scan to locate the placed implant. A postoperative intraoral scan was aligned to the postoperative CBCT scan through a dental implant planning software program. An attached interim abutment and implant analog complex was then scanned and superimposed on the placed implant in the postoperative CBCT scan. Once the best alignment was achieved, a virtual cast was generated, and an interim restoration with bilateral positioning wings was fabricated on the interim abutment and inserted during the second-stage surgery. This technique offers a cast-free approach to inserting an implant-supported interim restoration immediately after the second-stage surgery to guide the healing of the soft tissue that can minimize chairside time and optimize the clinical workflow.

Retrofitting a crown to an existing removable partial denture (RPD) is a complex process and requires additional clinical and laboratory procedures. Various methods have been described for retrofitting a new tooth-supported crown. However, if an abutment tooth has to be extracted, descriptions of techniques for restoring a new edentulous site with an implant-supported crown retrofitted to an existing RPD are lacking. Therefore, this technical report describes a straightforward approach to fabricating an implant-supported surveyed crown fitted to an existing RPD by using an acrylic resin template.

Statement of problem Residual cement in the peri-implant sulcus may cause peri-implant mucositis, which can lead to peri-implantitis. Clinical studies comparing the role of the collar height of the definitive restoration and the type of cement used for luting the prosthesis in the amount of residual cement are lacking. Purpose The purpose of this clinical study was to determine the volume of residual cement left undetected in the peri-implant sulcus by an implant prosthesis with 3 different collar heights and 3 luting cements. Material and methods Participants with single implants in the premolar region were divided into 3 groups of 10 according to the distance from the peri-implant soft tissue crest to the implant platform: group low collar (sulcus depth 4 mm). A metal-ceramic crown with an occlusal opening was fabricated on a straight titanium abutment, which facilitated removal of the crown along with the abutment after cementation. The implant luting cements used were composite resin cement (RelyX U200), Type I glass ionomer cement (GC Gold Label 1), and zinc oxide noneugenol interim luting cement (RelyX Temp NE). The modified crown was cemented with 1 cement each during the impression, bisque evaluation, and definitive crown cementation appointments. The crown was retrieved, and the residual cement collected during each appointment. The measurements obtained were statistically analyzed with general linear model analysis followed by post hoc testing using the Bonferroni test (α=.05). Results Mean volume of the residual excess cement (mm3) formed in group low collar was 0.33 ±0.17, 0.26 ±0.17, and 0.08 ±0.08 for subgroups Resin, GIC, and ZNE, respectively. In group medium collar, it was 1.18 ±0.31, 1.08 ±0.3, and 0.61 ±0.32; and in group high collar, it was 2.33 ±0.31, 2.1 ±0.74, and 1.31 ±0.56 for the same subgroup, respectively. There was a statistically significant difference in the formation of REC between the collar height groups (P .05). Conclusions The collar height of the definitive restoration and the type of luting cement play significant roles in the formation of residual cement in fixed implant-supported restorations.

To test the bond strength of one-piece zirconia implants with either standard or reduced height using different luting agents and pretreatments of the ceramic crowns' inner surfaces.Twenty monolithic CAD/CAM-fabricated zirconia single crowns were cemented onto 10 one-piece zirconia implants with either 5-mm or 4-mm abutment height (Z-Look3 Evo SLM, Z-Systems) using 13 different luting agents. After water storage, the crowns were removed using a specially developed test fixture in a universal testing machine (Z010, Zwick/Roell). The maximum force was recorded (N), and the force per area was calculated (MPa). The statistical evaluation was performed using univariate analysis of variance (SPSS version 25.0, IBM).A mean of 4.19 MPa (SD 2.90) at 5 mm and 3.89 MPa (SD 2.85) at 4 mm was obtained for all luting agents. The highest values were achieved for a resinmodified glass-ionomer cement, with 12.37 MPa (4 mm)/12.00 MPa (5mm). The lowest values were shown for a long-term temporary material, with 0.73 MPa (4 mm)/1.07 MPa (5 mm). Only a polycarboxylate cement (P.001) and a glass-ionomer cement (P = .006) showed statistically significant differences, in favor of the reduced abutment height. The latter did not significantly reduce bond strength for any of the materials examined.Implants with a reduced abutment height are clinically suitable. Pretreatment of the crowns' inner surfaces with ceramic primer showed to be advantageous.

The objective of this study was to determine the influence of height and thickness of the one wall remaining coronal tooth structure on the fracture resistance of an endodontically treated root with resin abutment build-up using resin composite and fiber-reinforced resin composite post. Static and dynamic fracture tests were performed by placing the remaining tooth wall on the tensile side and applying loads at an angle of 30° from the tooth axis. Superior static fracture resistance was observed when the wall remaining on the tooth had a height and thickness greater than 1.0 mm. The dynamic fatigue test showed high loading capacity or fracture resistance in specimens with large height and thickness. The dynamic fatigue test showed the influence of the remaining tooth structure on fracture resistance clearly. In conclusion, the static and dynamic fracture resistances increased with the height and thickness of the one wall remaining tooth structure.

Screw-retained implant-supported ceramic restorations have shown increased rates of technical complications compared with their cemented counterparts, including fracture and chipping of the ceramic structures. The present clinical report identified the causes leading to the catastrophic failure of a screw-retained lithium disilicate veneered crown cemented to a zirconia abutment with a titanium base by using a systematic fractographic approach. A combination of occlusal overloading, a deficient design and inadequate material selection was identified as being responsible for the fracture. These findings highlight the importance of a thorough analysis of the anatomic conditions and loading scenario of screw-retained implant-supported restorations.

Owing to the satisfactory esthetic and functional outcomes of implant surgery for the anterior teeth, some dentists consider it the gold standard treatment. However, the risk of developing peri-implantitis is positively associated with the long-term use of the implant. This necessitates the development of an implant design that reduces the risk of peri-implantitis, considering the long-term use of implants in young patients. This case report describes a new approach for an implant surgery using a two-stage implant in a 28-year-old woman. Her clinical course was satisfactory during the 4-year postoperative follow-up period; no inflammation was noted in the surrounding tissues. The two-stage implants allow for the removal of an implant body from an infected area and its replacement with a new abutment if peri-implantitis develops in the future. This article is protected by copyright. All rights reserved.

BackgroundThe All-on-four dental implant method is an implantology method designed to provide a comfortable prosthetic treatment option by avoiding advanced surgical procedures. This research aims to compare and evaluate the stress and tension values in conventional angled multiunit abutment-implant connection systems and monoblock dental implants used in the all-on-four procedure with finite element analysis.MethodsTwo master models were created by placing four implants connected to multiunit abutments (group A) in the interforaminal region of a completely edentulous mandible and four monoblock implants (group B) in the same region of another completely edentulous mandible. Group A implants were classified according to their diameter as follows: 3.5 mm (M1A), 4.0 mm (M2A), and 4.5 mm (M3A). Similarly, group B implants were classified as M1B, M2B, and M3B. In the six models rehabilitated with acrylic fixed prostheses, a 100 N force was applied to the anterior implant region, and a 250 N force was applied to the posterior cantilever in both axial and 30° oblique directions. Von Mises stresses were analyzed in the bone and implant regions of all models.ResultsM1A and M1B, M2A and M2B, and M3A and M3B were compared with each other under axial and oblique forces. The maximum Von Mises stresses in the bone around implants and the prosthesis screws, and the maximum and minimum principal stresses in the cortical and trabecular bone in group A models were significantly higher than those in group B models.ConclusionsIn monoblock implant systems under axial and oblique forces, higher stress is accumulated in the bone, prosthesis screw and implant compared to multiunit abutment-implant connection systems.

Objective To characterize the biomechanical performance of fiber-reinforced composite 5-unit implant-supported fixed dental prostheses (FDPs) receiving individually milled crowns by insilico and fatigue analyses. Methods Eighteen implant-supported five-unit fiber-reinforced composite frameworks with an individually prepared abutment design were fabricated, and ninety resin-matrix ceramic crowns were milled to fit each abutment. FDPs were subjected to step-stress accelerated-life testing with load delivered at the center of the pontic and at 2nd molar and 1st premolar until failure. The reliability of the prostheses combining all loaded data and of each loaded tooth was estimated for a mission of 50,000 cycles at 300, 600 and 900 N. Weibull parameters were calculated and plotted. Fractographic and finite element analysis were performed. Results Fatigue analysis demonstrated high probability of survival at 300 N, with no significant differences when the set load was increased to 600 and 900 N. 1st and 2nd molar dataset showed high reliability at 300 N, which remained high for the higher load missions; whereas 1st premolar dataset showed a significant decrease when the reliability at 300 N was compared to higher load missions. The characteristic-strength of the combined dataset was 1252 N, with 1st molar dataset presenting higher values relative to 2nd molar and 1st premolar, both significantly different. Failure modes comprised chiefly cohesive fracture within the crown material originated from cracks at the occlusal area, matching the maximum principal strain location. Significance Five-unit implant-supported FDP with crowns individually cemented in a fiber-reinforced composite framework presented a high survival probability. Crown fracture comprised the main failure mode.

PURPOSE To report on pilot tests for a planned study on single implant-supported crowns made from different restorative materials using finite element analysis (FEA) and in vitro load-to-failure testing. MATERIALS AND METHODS Within this pilot study, FEA was conducted using Ansys 2019 R2 to simulate stress and deformation for implant-supported crowns made of lithium disilicate ceramic (LiS2) and zirconia (3Y-TZP). Additionally, an in vitro load to failure test was conducted using two specimens per group to evaluate the failure mode and to confirm the findings from the FEA. RESULTS/CONCLUSION FEA revealed stress areas at the palatal cervical areas of the crowns. In the load to failure test, both hybrid abutment crowns made of LiS2 fractured (410 N and 510 N) before plastic deformation of the metal implant components occurred. The monolithic hybrid abutment crowns made of 3Y-TZP did not fracture until tests were interrupted at 646-N and 690-N occlusal force, when plastic deformation of the metal implant components was visually observed.

Objective: To evaluate the clinical outcomes of pediatric patients implanted a novel 4.5 mm wide laser ablated titanium bone anchored implant system and to evaluate the implant stability over the first 12-month period. Study Design: A prospective, single-subject, repeated measure, cohort study. Participants served as their own controls. Setting: Community and tertiary referral hospital pediatric assessment center. Patients: A total of 115 consecutive pediatric patients aged 4 to 15 years were implanted with 176 laser ablated titanium bone anchored implants from January 2016 to January 2019. Main Outcome Measure: Clinical outcomes, implant failure rates, and post implantation implant stability quotient (ISQ) scores were studied over the first 12-month period. Data were analyzed for statistical significance through mixed effect modeling, with the significance level p = 0.01. Results: A median 12-month survival of 96.6% was observed. Six implants (3.5%) were lost in total, one of these (0.6%) was lost due to trauma. Adverse skin reactions (Holgers grade 2–4) were observed in 4.4% of all postoperative visits, occurring in 22 individuals (19.1%). Neither the ISQ high (ISQH) nor ISQ low (ISQL) values increased significantly between the stage 1 and 2 surgeries. In contrast, the ISQ results, irrespective of abutment size, demonstrated an increasing trend from 49.1 to 57 over the 12 months review period. A statistically significant change was only demonstrated from the 3 months follow up onwards. Conclusion: The use of 4.5 mm wide laser-ablated titanium bone anchored hearing implants resulted in superior survival rates and excellent clinical outcomes compared with previous implant systems.

Background: Mobile tooth is a problem that often occurs and result in tooth loss. It caused by disease or periodontal tissue’s injury. Splint is a device that is made to stabilize or tighten mobile tooth due to a trauma or disease. It works by distribute the occlusion pressure to reduce tooth mobility. Removable partial denture frame is one treatment for missing teeth and permanent splints. Objective: The aim of this treatment is to explained effect of periodontal splints for edentulous patient. Case: First case: A woman complained mobile teeth on the incisors. Intraoral examination showed remaining teeth couldn’t be abutment. Second case: A woman complained mobile teeth on the incisors. Intraoral examination showed remaining teeth could be abutment. Case management: First case: Patient was given initial therapy and continued with rehabilitative therapy by removable partial denture metal frame. Second case: Patient was given initial therapy splinting using fiber reinforced composite. A week post treatment patient felt comfortable. Conclusion: It can be concluded periodontal splinting reduced teeth mobility and prevent further damage to the periodontal tissue og Edentulous patient.

Dental implants are fixtures that constitute for the replacements of the root of a missing natural tooth. Dental implant therapy has been widely used for the restoration of partially and fully edentulous patients. The implant literature emphasizes the importance of a passively fitting prosthesis to prevent prosthodontic complications or even loss of fixture integration. Failure to achieve a passively fitting prosthesis and force tightening of superstructure may result in complications such as abutment, framework, and gold screw loosening or fracture. Various materials that can be used for making an implant impression are polyether, polyvinylsiloxane, condensation silicone, polysulfide, irreversible hydrocolloid material, and various others. There are various studies in relation to the accuracy of these impression materials out of which various scientists concluded different results with most studies stating polyether with the maximum amount of dimensional accuracy in comparison to other materials. An accurate implant impression plays a significant role and serves as a starting point in the process of producing good working casts. Thus, the accuracy of impression techniques becomes a significant issue in consideration of passive fit. Reproduction of intraoral relationship of implants through impression procedures is the first step in achieving accurate fit prosthesis. This transference is still complicated by the number, angulation, depth, and position of implants. The advent of computer-aided design/computer-assisted manufacturing technology improved the framework fabrication procedures and has increased the precision of fit of implant prosthesis.

Purpose To assess the survival rate of 3 mol % yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) minimally invasive anterior and posterior single and double partial retainer fixed dental prostheses (PRFDPs). Materials and methods Twenty-three patients (18 women and 5 men, age range: 20 to 66 years) with single-tooth gaps received 28 3Y-TZP PRFDPs. Eight PRFDPs had two partial retainers and one pontic, two PRFDPs had two partial retainers and one pontic with a mesial cantilever, and 18 PRFDPs had one retainer and one cantilever. The abutment teeth were prepared following specific guidelines for all-ceramic restorations, considering existing direct restorations, carious processes, and occlusal conditions. The restorations were made of 3Y-TZP using CAD/CAM technology. Cementation was performed either conventionally, using resin-modified glass-ionomer (n = 6), or adhesively, using dual-polymerized resin cement (n = 22). Kaplan-Meier survival analysis was conducted. A P value of .05 was considered statistically significant. Results During the observation period (5.92 ± 1.74 years, minimum = 2 years, maximum = 10 years), three debondings occurred, all in the two-retainer group and the mandible. The survival rates for the two types of intervention were different, with 100% for a single retainer and 70% for a double retainer, but without a significant difference (log-rank test χ2(1) = 0.200, P = .655). Conclusion The 3Y-TZP PRFDPs presented in this study showed no failure when bonded and not conventionally cemented. Therefore, they can be used in cases where implant therapy is not possible or indicated.

Objectives The aim of this prospective case series was to assess the implant outcomes as well as hard and soft tissue dimensional changes of immediate implant placement in posterior sites using a custom-made sealing socket abutment (SSA) combined to peri-implant socket filling (PISF). Material and methods Twenty patients were considered for single extraction and immediate implant in upper or lower posterior regions. The remaining peri-implant sockets were filled with Deproteinized Bovine Bone Mineral. Based on intra-oral scans (IOS), custom-made SSAs were placed the same day. Implant survival rate, peri-implant bone changes, peri-implant health and pink esthetic score (PES) were recorded up to 1 year post implant placement. Moreover, CBCT and IOS were performed to monitor hard and soft tissue dimensional changes. Results One implant failed to osseointegrate leading to an implant survival rate of 95% after 1 year. Peri-implant bone changes yielded 0.19±0.31 mm and 84.2% of the implants displayed no or mild bleeding on probing. Horizontal bone remodeling was not significant from baseline to 1 year at any levels. Finally, soft tissue profile was stable in the most cervical area while minor changes occurred during the first 6 months below the gingival margin. Absence of mid-buccal recession (0.07 mm) and good PES were found after 1 year. Conclusion Despite its limitations, this study showed that immediate implants in the posterior region using the SSA + PISF protocol resulted in promising implant outcomes with limited hard and soft tissue dimensional changes while decreasing the overall treatment time.

Whether cone beam computed tomography (CBCT) scans can be used for the fabrication of computer-aided design and computer-aided manufacturing (CAD–CAM) fixed dental prostheses (FDPs) is not known. The purpose of the present study was to compare the marginal fit of 3-unit zirconia FDPs fabricated by using CBCT or 3-dimensional (3D) laboratory scanning. Extracted second premolar and molar teeth in a maxillary typodont model were prepared. The first molar was removed and the typodont model was scanned with a laboratory or a CBCT scanner to generate two virtual 3D cast groups (3DL and CBCT). Forty four 3-unit zirconia FDPs were designed on virtual casts and milled. The vertical marginal discrepancy (VMD) was measured by ×100-magnification microscopy at seven locations on each abutment. A total of 616 measurements were made at 14 fixed locations in two groups of 22 specimens. The VMD data for 3DL and CBCT groups were statistically analyzed using the Mann–Whitney U test (α = 0.05). The mean VMDs on premolar ranged between 44 and 55 µm (median: 43–55 µm) in 3DL, and 74 and 100 µm (median: 72–93 µm) in CBCT; and on the molar, between 47 and 114 µm (median: 46–114 µm) in 3DL, and 91 and 162 µm (median: 93–156 µm) in CBCT. There was a significant difference between the gaps in 3DL and CBCT groups (p

The aim of this study was to compare the screw removal torque of mini-conical prosthetic components and straight trunnion of indexed morse taper implants after mechanical cycling. The sample consisted of 40 implants and 20 mini-conical prosthetic components (MC group) and 20 straight trunnion components (ST group). Each group consisted of 10 specimens, with 2 implants in each, and cobalt–chromium metallic crowns were screwed into each sample. The components of the MC group received a torque of 20 N-cm with a digital torque wrench, and after 10 min were retightened with the same value as the initial torque. The components of the ST group received a torque of 30 N-cm, with a digital torque wrench, and after 10 min, they were retightened with the same value. The screws of the respective crowns of the two groups received a torque of 10 N-cm and after 10 min were retightened with the same value. Each group was subjected to the fatigue test in a mechanical cycler at 2,000,000 cycles, with a load of 250 N and frequency of 4 Hz. At the end of the fatigue test, the loosening torque of each screw of the specimens was measured through a digital torque wrench. The data were analyzed by two-way ANOVA and a Tukey test. In both groups, there were loss of torque. The results showed no statistic difference between MC and ST groups (p > 0.05).

the aim of clinical trial was to evaluate biologic and prosthetic complications with two versus four mini-implants supporting mandibular overdentures in patients with knife edge ridges. Twelve edentulous participants (6 men and 6 women, mean age =58.47 years) were randomly assigned into 2 groups; Group 1(control); included six participants who received four mini dental implants equally distributed in the interforaminal area of the mandible. Group 2 (study); included six participants who received two mini dental implants the canine area of the mandible. For both groups mandibular dentures were connected to the implants by O-ring attachments. The incidence biologic and prosthetic complications (related to the implants/attachments and to the overdentures) were measured from base line 12 months after overdenture insertion and compared between groups. Results: The implant survival rate, peri-implantitis, pocket depth >3mm, bone loss >1mm, separation of the metal housing from the denture base, teeth fracture, overdenture fracture, and denture relinings did not significantly differ between groups. The 4-implant group showed significant higher pain, edema, peri-implant mucositis, teeth wear, and denture border adjustments than the two implant group. The 2-implant group showed significant higher abutment bending /fracture, O/ring wear/ distortion, and O/ring damage/replacement than the 4-implant group 2 mini-implants may be a suitable alternative to 4-mini-implants when used to retain mandibular overdentures as it was associated with reduced pain, edema, peri-implant mucositis, teeth wear, and denture border adjustments. However, 2-mini-implants are associated with increased prosthetic complications related to attachments as abutment bending /fracture, O/ring wear/ distortion, and O/ring damage/replacement.

Impression techniques using digital technology seemed to be studied with the accuracy planning to initiate acceptable prosthetic results in implant dentistry. In order to overcome these misfit, digital impression by means of an intra-oral scanner may assist. The purpose of this study was conducted to assess the efficacy of using digital impression technique compared to conventional technique Material and Methods: 8 patients were examined with a total of 22 implants placed, each patient had undergone two impression techniques: a digital impression: intraoral scan body, and a conventional impression: open tray impression, the total deviation between the two impression techniques was measured. This was done by scanning the scan body in patient mouth in group I and digitalizing the conventional open tray impression by scanning the scan body on the cast produced by the open tray in group 2. The scan body was replaced on the software (Exocad software) with custom made abutment and the deviation between the two groups was measured using (Geomagic Control X; 3D systems) GOM inspection software Results: Total deviation between groups, the open tray conventional impression was compared to hypothesized reference digital impression and were calculated using GOM inspect software. The total deviation was statistically significantly different among the studied groups. Conclusions: In partially edentulous patients, intraoral oral scanning using intra oral scan bodies improves over all accuracy, than conventional open tray impression technique.

Akinori Tasaka,1 Takahiro Shimizu,1 Takeshi Hirabayashi,2 Shuichiro Yamashita1 1Department of Removable Partial Prosthodontics, Tokyo Dental College, Tokyo, Japan; 2Dental Laboratory of Suidobashi Hospital, Tokyo Dental College, Tokyo, JapanCorrespondence: Akinori TasakaDepartment of Removable Partial Prosthodontics, Tokyo Dental College, 2-9-18 Kandamisakicho Chiyoda-ku, Tokyo, 101-0061, JapanTel +81-3-6380-9167Fax +81-3-6380-9167Email atasaka@tdc.ac.jpAbstract: This clinical report describes a technique for fabricating a retrofit zirconia crown and clasp for an existing removable partial denture (RPD) using computer-aided design and computer-aided manufacturing (CAD/CAM). A 58-year-old patient developed acute pulpitis of a tooth, and the RPD clasp was broken on the tooth. A pre-preparation scan was captured using an intraoral scanner. The existing RPD was placed in the mouth, and scans of the post-preparation, antagonist arch, and interocclusal record were made. A zirconia crown was designed by superimposing the pre-preparation scan and the post-preparation scan of the abutment tooth. The design data were transferred to a 5-axis milling machine, and the crown was milled from zirconia. The crown was luted using resin cement. An intraoral scan of the crown with RPD was taken, and the RPD was removed to re-scan the proximal guide plane of the crown. The I-bar clasp was designed, and the casting pattern was built using a 3D printer. The pattern was used to cast the clasp. The clasp was set using autopolymerizing acrylic resin to the RPD. The main advantages of this efficient process are that patients can use their RPDs during fabrication of the crown of the abutment tooth. The limitations of using this technique include the cost of the intraoral scanner and the education for the dental clinicians and technicians. In this clinical report, CAD/CAM technology prevented human error, required no adjustment, and uninterrupted use of the RPD for fabricating a retrofit zirconia crown and clasp for an existing RPD.Keywords: removable partial denture, denture repair, CAD/CAM, zirconia crown, I bar clasp

A digital technique for designing and fabricating an individual tooth tray used for taking subgingival impression of complete crown preparation was described. The digital model of required dentition region was obtained before performing crown preparation. An individual tooth tray with retention attachments was designed and printed with plastic material. After conducting crown preparation, the individual tooth tray loaded with the final impression material was placed onto the abutment to deliver the impression material subgingivally. A final overall impression was made with full arch stock tray to pick up the individual tooth tray with the accurate impression of abutment.

INTRODUCTION The computer-aided design/computer-aided manufacturing (CAD/CAM) technology has revolutionised dentistry at present. An operator's skills can affect the overall clinical duration and marginal accuracy of the prosthesis fabricated through this workflow. The aim of this study was to assess the effect of CAD/CAM hands-on training compared with that of a self-instructional video on the performance of dental students in digital impression and fabrication of a CAD/CAM crown. METHODS In this cross-sectional study, 30 undergraduate dental students were shown a CEREC demonstration video. Each operator then captured a digital impression using the intra-oral scanner, and a crown was subsequently milled. All participants underwent a training course before repeating the process. Marginal discrepancy for each crown on its abutment tooth was measured before and after training using a stereomicroscope and was evaluated using Wilcoxon signed rank test. The duration taken for the process was recorded before and after training and evaluated using paired t-test. RESULTS The overall mean ±standard deviation marginal adaptation for the CEREC crowns was 78.15 ± 42.83 μm before training and 52.41 ± 17.12 μm after training. The Wilcoxon signed rank test found significant difference (p

The purpose of this study is to numerically analyze a 3D model of an implant under fatigue loads. A bone and a V shape implant were modeled using SolidWorks2008 software. In order to obtain an exact model, the bone was assumed as a linear orthotropic material. Mechanical loads were applied in terms of fastening torque to the abutment and mastication force applied at the top of the crown. The abutment was tightened into the implant by applying a 35 N.cm torque causing tensile stress within the abutment screw as a preload that is harmful not only for the fatigue life of the abutment, but also for the stability of the implant-abutment interface. A 700 N force at an angle of 30 degrees to the vertical direction was applied to the crown. The mechanical analysis results showed that the abutment is the critical component of the implant system in terms of fatigue failure. This is due to the fact that the tensile preloads originated from the fastening torque. The results were presented in terms of fatigue life in the abutment. Fatigue life of the abutment and implant were calculated based on the Goodman, Soderberg, Smith–Watson–Topper (SWT), and Marrow theories. According to the results of the fatigue life prediction, abutment screws may fail after about 3 × 105 cycles. The predicted results by the Goodman theory are at a very good accordance with the clinical data.

Purpose: The success of an artificial crown mainly depends on the biomechanical factors such as bonding capacity of cement between the crown and abutment tooth, and root strength of the abutment tooth. In this case series, we aim to provide insight on the potential use of the cast metal post and cost for patients with intellectual disabilities and severely compromised tooth structure. Material and Methods: The first patient was a 41-year old male with the chief complaint of a dislodged porcelain fused metal (PFM) crown of tooth #20 (mandibular left second bicuspid). The patient was informed about the advantages, disadvantages, and risks of each option. After further consideration and discussion with the parents and the patient, we decided to rebuild the coronal tooth structure with the cast metal post and core and prosthetic restoration with the same crown. Patient satisfaction was measured on the visual analog scale as 10/10. The second case involves a 26-year old female, who presented with a chief complaint of chronic lingering pain on tooth #9. The tooth structure was extensively damaged and un-supportive of the ferrule, therefore, it was decided to build a metal post and core instead of a fiber post. The prosthetic restoration was made with a monolithic zirconia crown and the patient was followed up twice in 6 months and graded the satisfaction as 10/10 on a visual analog scale. Results: The most common type of posts used in dentistry has been cast post and cores in the last decade which generally includes an additional laboratory stage where a custom post is prepared according to the impression taken from the prepared post space. Conclusions: Both the presented cases explain an interesting advantage of restoring a root canal treated tooth with a metal post and core system which implies that in a prefabricated post and core restored tooth failure, a metal post, and core can potentially be the treatment of choice instead of extracting the tooth.

Successful endodontic treatment depends upon the clinician’s precise knowledge and ability to manage complex internal anatomy in order to avoid failure during endodontic treatment. Mandibular canines normally have single root with centrally placed single canal and internal anatomy as simple as could be expected, but there are such canines with a single root with two canals, two roots or fused roots. The occurrence of two canal joining to one for a men may be a rare entity with 4-15% prevalence. Canine is the cornerstone of mouth due to its position and very important as abutment for any type of restoration, so long term success of the restorative depend directly on the quality of endodontic treatment. This article presents a case series of successful endodontic management of mandibular canine with two canals which merge into one canal with one foramina and mandibular canine with two roots and two canals. Keywords: Mandibular canine, One canal, Two canals, Bilateral, Endodontic treatment

Background The present review aimed to investigate the feasibility and clinical effectiveness of a direct bonded fixed partial denture (DBFPD) based on available literature. The efficiency of a DBFPD is mainly affected by the type of artificial denture tooth, the type of luting agent, and the adhesive preparation. Methods The parameters were reviewed based on the in vitro and in vivo studies conducted. An acrylic resin tooth or a composite resin tooth for removable dentures should be used as the artificial tooth for the pontic. Results Considering the luting agent, a methyl methacrylate-based resin luting agent, which has low mechanical strength but is capable of plastic deformation and could sustain for a long time, should be used. Appropriate pre-adhesive treatment should be performed on both the artificial and abutment teeth. The cases in which a DBFPD can be applied are limited to one missing anterior tooth, as long as it is not overstressed. Patient cooperation in cases of occlusion seems to be another prerequisite. Conclusion Knowledge and selection of the material and case indications are essential, and patient cooperation is pertinent in studying the long-term prognosis of a DBFPD.

Objective The purpose of this study was to evaluate the influence of the connector area on the chipping rate of the VM9 veneering ceramic in a 4-unit yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) framework, using a novel sonographic technique. Materials and Methods The framework was designed as a 4-unit fixed dental prostheses (FDP) with two abutment teeth at the first mandibular premolar and second mandibular molar. The cross-sectional area of the connector was 7.5, 8, or 9 mm2. The prepared teeth were scanned using CAD/CAM technology, and five frameworks were prepared for each design, making a total of 15. The frameworks were divided according to the veneering ceramics: Y-TZP FDPs using Vita VM9 (12 frameworks), and porcelain fused to metal (PFM) FDPs using Vita VM13 (3 frameworks). The specimens were statically loaded until failure. To capture the initiation of the failure within the specimens, a novel sonographic technique, designed for this research, combining acoustic emission and visual monitoring during live load bearing tests, was used to determine the failure load value. Failed frameworks were inspected using a microscope, and failure patterns were identified. One-way ANOVA and Tukey HSD tests were applied for statistical analysis of the results (p-value ≤ 0.05). Results Despite the fact that the chipping strength is proportional to the cross-sectional area of the connector, the effect of the cross-sectional area on chipping load revealed no statistically significant differences, while PFMs showed superior chipping strength relative to the zirconia frameworks regardless of the connector's size. A high rate of catastrophic fracture occurred while loading the specimens. Conclusion The effect of the cross-sectional area on chipping load revealed no statistically significant differences in Y-TZP frameworks. The novel sonographic technique may be a potential method to study the behavior of dental ceramics, including chipping and fracture.

Purpose To compare the precision of adaptation of cobalt-chromium (Co-Cr) three-unit fixed dental prostheses (FDPs) fabricated using different techniques. Materials and methods A master model was prepared to receive a three-unit FDP. This model was duplicated 60 times from a silicone mold. The dies (N = 60) were scanned and divided into three groups (n = 20 each) to receive the FDPs made of pre-sintered Co-Cr (CS), laser-sintered Co-Cr (LS), or cast Co-Cr (Gi). Frameworks were layered with ceramic, and each framework was seated on its specific model. The replica technique was used to measure the marginal and internal discrepancies in the mesiodistal and buccolingual planes. Prepared silicone samples were examined with scanning electron microscopy. Obtained data were analyzed using Levene test, t test, and analysis of variance (α = .05). Results When overall mean discrepancy values were compared, in mesiodistal planes, LS showed better adaptation than Gi (P = .025). Similar adaptation was found for CS and Gi, and for CS and LS (P = .169 and P = 1.000, respectively). In buccolingual planes, the difference in fit was not significant among the three tested groups (P > .05). In a pairwise comparison between materials, a net increase in values between points 1 and 5 was noted (P = .57). Difference in discrepancy values within points was significant. This was confirmed at abutment level on some measurement points. Within each material, at abutment level, differences were significant at several measurement locations in both the mesiodistal and buccolingual planes. Conclusion Within the limitations of this study, three-unit Co-Cr FDPs showed similar marginal and internal discrepancy values. Presintered and laser-sintered Co-Cr alloys can be considered for three-unit FDP fabrication.

Objective To compare the effect of temporary fixed restorations to final fixed restorations on gingival health of abutment tooth by evaluating the level of IL-1β in gingival crevicular fluid (GCF) as an inflammatory biomarker. Subjects and methods It was a nonrandomized prospective observational study. Samples of GCF were collected from 24 participants with provisional and permanent definitive full-coverage restorations with subgingival margin placements at three intervals for each participant: Interval 1, after preparation and immediately before cementation of temporary fixed restoration. Interval 2, after two weeks of temporization and before receiving the final fixed restoration. Interval 3, after two weeks of final fixed restorations. GCF were collected from gingival crevice of the abutment tooth by pre-prepared filter paper with dimensions of 2mmx13mm. They were prepared for IL-1β concentration assay by enzyme-linked immuno sorbent assay – analysis (ELIZA). Results Were analyzed by SAS® software, Descriptive means and medians were used and the repeated ANVOA test was applied (1st interval) showed the highest level of IL-β (13.587 ± 5.735). In 2nd interval the level of IL-β was significantly reduced (9.602 ± 3.279). While, in 3rd interval the level of IL-β was the lowest (6.293 ± 3.279). Conclusion The material and technique of fabrication of both temporary and final fixed restorations are critical for gingival health. PMMA CAD-CAM based temporary restorations showed to be compatible to gingival health by decreasing the level of IL-β level, but the zirconia as a final fixed restoration showed to have optimum compatible effect on gingival health.

Introduction Bone anchored hearing solutions are a well-known option for patients with a conductive, mixed conductive-sensorineural hearing loss and those with single-sided deafness. Objective The aim of the present study was to evaluate the Ponto bone-anchored hearing system in terms of behavioral performance and self-reported outcomes, by comparing unaided and aided performance (softband and abutment), as well as aided performance with the sound processor on softband (preoperatively) versus abutment (postoperatively). Methods Fourteen adult bone-anchored candidates, with either a bilateral (n = 12) or unilateral (n = 2) conductive or mixed hearing loss, participated in the present study. Sound-field hearing thresholds were evaluated unaided and aided (softband and abutment). A speech-in-noise test was also performed unaided and aided for two spatial configurations (S0N90; implanted side; S0N90; nonimplanted side). The Glasgow Health Status Inventory and the Speech, Spatial and Quality of sound questionnaires were administered pre- and postsurgery to compare quality of life and perceived unaided and aided performance. Skin reaction (Holgers scores) was evaluated at 15 days, 6 weeks, and 10 weeks after surgery. Results Significant improvements postoperatively relative to unaided were obtained for sound-field thresholds at all tested frequencies. Additionally, sound-field thresholds were significantly improved with the sound processor on abutment relative to the softband at frequencies > 1 kHz. Improved performance postoperatively relative to unaided was also obtained in the speech-in-noise test and in self-reported outcomes. Conclusions Improvements in behavioral performance and self-reported outcomes were obtained with the sound processor mounted on abutment.

Objectives This study aimed to determine whether distally angulating an implant is a successful strategy to avoid the maxillary sinus and the need for bone augmentation, while increasing the anterior-posterior (A-P) implant distribution in the edentulous maxilla. Materials and methods In 115 patients with edentulous maxillae, virtual implant planning was performed utilizing cone-beam computer tomographs. Axial (8 mm length) and tilted (12 mm length) dental implants with 30-degree and 45-degree angulation were virtually positioned to avoid entering the maxillary sinus, while maximizing A-P distribution. Measurements were made between the tilted and axial implants to assess the change in A-P distribution of implants at the implant and abutment levels. Results Forty-seven sites (20.4%) were not able to have either treatment modality with insufficient bone for implant placement. Axial implants were placed more distally than 45-degree and 30-degree tilted implants in 24% and 42% of sites, respectively. The average change in A-P spread measured at the implant level, for 30- and 45-degree tilted implants was -0.25 mm (95% CI -0.76, 0.26) and 1.9 mm (95% CI 1.4, 2.3), respectively. When measured from the center of each multi-unit abutment the average increase in A-P distances for tilted implants appears larger in the 30-degree and 45-degree groups by 0.97 mm and 1.74 mm, respectively compared to measurements at the implant level. Conclusions Angulating 12 mm implants provides a limited increase in A-P distribution of implants in edentulous rehabilitation in most situations. In certain patients, the use of 8mm axial implants may provide a greater A-P spread.

Introduction. Reducing the time of implant integration and the period of prosthetics is an important task of dentistry since this leads to improved quality of life and successful rehabilitation of the patient. Therefore, currently, there is an intensely increased interest in immediate or early loading of the implant, when certain parameters of primary implant stability in the bone tissue are achieved. Materials and Methods. The materials used to perform the procedure for placement of a customized provisional composite abutment were a provisional prefabricated abutment with a retention grip for the composite; aluminum oxide powder with a particle size of 27 μm for better adhesion of the composite, with which the retention grip of the provisional abutment is coated; 3M Single Bond Universal light-curing adhesive applied to the provisional abutment; and Filtek Bulk Fill 3M composite including a low-viscosity radiopaque nanocomponent and ytterbium trifluoride filler with a particle size of 0.01–3.5 nm. Methods used in this study were as follows: fabrication technique using the Cervico system for a customized provisional composite abutment; sandblasting of the provisional abutment using the apparatus RONDOFLEX (KERR); light polymerization of low-viscosity composite using Demi Ultra Kerr lamp (luminous flux power not less than 1100 mW/cm2); and radiographic control of the abutment fit in the implant. Results. The surgical and orthopedic treatment of 20 patients was performed using this technique. The control group consisted of 11 patients with similar pathology, in whose surgery the fabrication of a provisional prosthesis was used. As a result, it was possible to form a gingival profile, in comparison with the control group, to accelerate mucogingival and bone integration, as well as to quickly carry out orthopedic rehabilitation of the patient. The average value of the time required for the final formation of soft tissues for prosthetics in patients in the experimental group was significantly lower than those in the comparison group ( p = 0.007 and p = 0.028 , respectively). In most clinical cases, there is no need for surgery on soft tissues, which eliminates the possibility of additional traumas. Conclusions. The use of a promising technology for the fabrication of a crown on the implant and a customized provisional composite abutment significantly reduced the period of orthopedic rehabilitation of the patient. Immediate implantation with a customized provisional composite abutment completely forms the gingival profile, reduces the risk of microbial contamination in the area of bone formation, minimizes soft tissue ischemia, and accelerates the processes of mucogingival and bone integration around the implant.

Made available in DSpace on 2022-04-29T08:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Dental implants are widely used as a long-term treatment solution for missing teeth. A titanium implant is inserted into the jawbone, acting as a replacement for the lost tooth root and can then support a denture, crown or bridge. This allows discreet and high-quality aesthetic and functional improvement, boosting patient confidence. The use of implants also restores normal functions such as speech and mastication. Once an implant is placed, the surrounding bone will fuse to the titanium in a process known as osseointegration. The success of osseointegration is dependent on stress distribution within the surrounding bone and thus implant geometry plays an important role in it. Optimisation analyses are used to identify the geometry which results in the most favourable stress distribution, but the traditional methodology is inefficient, requiring analysis of numerous models and parameter combinations to identify the optimal solution. A proposed improvement to the traditional methodology includes the use of Design of Experiments (DOE) together with Response Surface Methodology (RSM). This would allow for a well-reasoned combination of parameters to be proposed. This study aims to use DOE, RSM and finite element models to develop a simplified optimisation analysis method for dental implant design. Drawing on data and results from previous studies, two-dimensional finite element models of a single Branemark implant, a multi-unit abutment, two prosthetic screws, a prosthetic crown and a region of mandibular bone were built. A small number of combinations of implant diameter and length were set based on the DOE method to analyse the influence of geometry on stress distribution at the bone-implant interface. The results agreed with previous studies and indicated that implant length is the critical parameter in reducing stress on cortical bone. The proposed method represents a more efficient analysis of multiple geometrical combinations with reduced time and computational cost, using fewer than a third of the models required by the traditional methods. Further work should include the application of this methodology to optimisation analyses using three-dimensional finite element models. Centre for Simulation in Bioengineering Biomechanics and Biomaterials (CS3B) Department of Mechanical Engineering Engineering College of Bauru (FEB) São Paulo State University (UNESP) Department of Mathematics Faculty of Science (FC) São Paulo State University, São Paulo State Centre for Simulation in Bioengineering Biomechanics and Biomaterials (CS3B) Department of Mechanical Engineering Engineering College of Bauru (FEB) São Paulo State University (UNESP) Department of Mathematics Faculty of Science (FC) São Paulo State University, São Paulo State

BACKGROUND Chlorhexidine (CHX) is a broad-spectrum antimicrobial agent commonly used in medicine. Application of (CHX) during abutment connection reduced the bacterial load at the implant-abutment interface. We hypothesize this treatment may consequently reduce peri-implant soft tissue inflammation and marginal bone loss. PURPOSE To evaluate the effect of a single application of CHX gel inside the dental implant internal hexagon on peri-implant tissue. METHODS Forty patients were recruited to this randomized, double-blinded, clinical trial. At the time of implant installation, a 4-mm healing abutment was connected to the implant. In the test group, chlorhexidine gel 1% was applied inside the implant hex, whereas control implants did not receive any gel. Clinical and radiographic measurements included soft tissue recession (REC), plaque index (PI), gingival index (GI), plaque index (PI), keratinized mucosa width (KM), probing depth (PD), and a peri-apical parallel x-ray. Peri-implant crevicular fluid (PICF) was collected for cytokine analysis. t-Test was used to compare changes from baseline to 3 months. Mann-Whitney U test and t test were used to compare test and control groups. RESULTS Twenty patients in the test group and 17 in the control group completed the study. One implant in the control group failed to osteointegrate. There were no significant differences between the control and test groups for REC changes, bone loss, and PD. GI was significantly lower in the test group after 1 week (1.79 ± 0.24 vs 0.75 ± 0.18, respectively) and 3 months (1.18 ± 0.21 vs 0.25 ± 0.12, respectively) although PI was equal. At 3 months, interleukin 1-β (IL1-β) was higher in the control group (p

AIM The aim of this study was to assess the effectiveness of different gingival displacement materials in the management of the width of the gingival sulcus. MATERIALS AND METHODS Totally, 60 participants who were aged 18 years and more were chosen for this study. The eligible participants were those who required fixed prosthesis with at least one abutment. A modified sectional tray was used to make impressions with elastomeric materials along with additional polysilicon using the double mix single impression technique. All participants were divided randomly into three experimental groups with each group having 20 participants as follows: group I-Expasyl, group II-Magic Foam Cord, and group III-Traxodent. Soon after retraction, impressions were made and assessed in a comparable manner to pre-retraction impressions. Image analysis software was used to measure the quantity of displacement of the gingiva, marked as the distance from the tooth to the gingival crest in the horizontal level under stereomicroscope. RESULTS The highest mean sulcular gingival width (0.644 ± 0.22) was found in Traxodent group followed by Expasyl group (0.590 ± 0.11) and Magic Foam Cord group (0.528 ± 0.01). A statistically significant difference (p

A common mistake of an orthopedic dentist when carrying out odontopreparation of teeth is nonobservance of the parameters of the permissible convergence of the axial walls of the teeth [1]. Analysis of the literature allows us to conclude that with the taper of the tooth walls at 15 degrees, the retention of the crowns is 70 % [2]. The aim of this work was the development of an improved method for coaxial odontopreparation of teeth. This article describes the method of odontopedication of teeth, which are a support for fixed orthopedic structures of an extended nature. The essence of the method is to create a bed on the abutment teeth using a thin fissure bur. The process of coaxial preparation of abutment teeth in the author's technique consists of several stages, which makes it possible to control the preparation accuracy and qualitatively reduce the likelihood of excessive grinding of tooth tissues.

The aim of this study was to develop a new method to evaluate the consistency of resin cements by modeling the operation of setting a crown. First, the weight of the resin cements and the inner surface area of the crown were measured to configure the conditions for consistency evaluation using a model abutment tooth and a model crown. As the evaluation method, a 200 mm2 contact surface area of a glass plate was placed on top of 30.0 mg of resin cement paste, and a pressure of 10.0 N was applied to the glass plate. When the paste was spread over the entire bottom surface of the glass plate, it was designated a "Pass". A "Pass" result was obtained for all resin cements tested and a "Fail" result for all resin composites, indicating the usefulness of the new method for assessing cement flowability when setting a crown.

The purpose of this article is to classify the types of telescopic prostheses that protect natural teeth as an alternative to traditional removable prostheses, and to explain their advantages, disadvantages, indications and clinical significance in order to minimize the problems of removable dentures. Telescopic prostheses consist of an inner (primary) crown permanently cemented to an abutment and an outer (secondary) crown attached to the prosthesis. Primary crowns protect the abutment from bruises and thermal irritation, and also provide retention and stabilization of the secondary crown. The secondary crown combines the primary crown with the prosthesis to form a telescopic unit, providing prosthetic retention and stability. Â

The aim of this systematic review with meta-analysis was to compare the survival rate of single crowns supported by extra-short implants (≤ 6 mm) to those supported by conventional implants, with or without previous maxillary sinus augmentation. The proportion of failures was described according to the type of complication and follow-up periods. Materials and methods: Randomized and prospective clinical trials were selected from six databases and gray literature. The risk of bias was evaluated by Joanna Briggs Institute Critical Appraisal Checklist, and the certainty of the evidence was analyzed with Grading of Recommendations Assessment, Development, and Evaluation. Meta-analyses were processed with RevMan and MedCalc Statistical Software. Results: Single crowns supported by extra-short implants had a similar risk of failure to those supported by conventional implants, regardless of previous maxillary sinus augmentation (P > .05). Overall failure proportion of extra-short implants was 5.19%, but it varied according to follow-up (1.18% before loading, 1.56% at 12 months, 1.20% at 24 months, 2.10% at 48 months). Biologic failure complications were 37.90% for bleeding on probing, 22.45% for peri-implantitis, and 11.29% for infection. Prosthodontics failure complications were 14.88% for abutment failures and 14.73% for prosthetic screw loosening. Considering the risk of bias, most studies were classified at moderate risk. Conclusion: The risk of failure of single crowns supported by extra-short implants is similar to those supported by conventional implants, regardless of previous maxillary sinus augmentation or follow-up period. The most frequent biologic and prosthetic complications were bleeding on probing and abutment failures, respectively.

Aim: The aim of this within-subject study was to evaluate and compare clinical denture base deformation with two types of denture base reinforcement for telescopic implant retained overdentures. Materials and methods: Six completely edentulous participants received two implants in the canine region of the mandible and the implants were connected to the overdentures with resilient telescopic attachments. Each patient received 2 types of denture reinforcement for the mandibular overdentures; 1) metal reinforced overdentures, 2) PEEK reinforced overdentures. Four strain-gauges were adhered to the lingual polished surface of each denture abutment top (C1 and C3), and 5 mm below abutment top (C2 and C4). Strain registrations were performed during maximum voluntary clenching. Results: The measured strains and implant positions C1 and C3 were tensile in nature and the measured strains at implant positions C2 and C4 were compressive in nature. The highest microstrain was noted at C3, followed by C1, then C2, and the lowest strain was noted was with C4 for both groups. There was no significant difference in recorded microstrains between C1 and C3 or between C2 and C4. For all strain gauge positions, PEEK reinforced overdentures recorded significantly higher microstrains than metal-reinforced overdentures. Conclusion: Within the limitation of this short term cross over trial, cobalt-chromium metal reinforcement for mandibular implant assisted overdentures is recommended than PEEK reinforcement as it reduced denture base strains and deformation during maximum voluntary clenching.

Background: Provisional dental restoration fabricated to enhance esthetic, stabilization of abutment teeth and maintain function for limited period of time after which it is to be replaced by definitive fixed restoration. The surface roughness of temporary crowns are considered crucial in achieving successful definite restorations. Most bacteria in the oral cavity can only survive on hard and rough surfaces. The objective of the present study is to evaluate and compare the surface roughness of two types of commercially available composite material (Harvard- temp and Charm- temp). The specimens were tested in dry conditions and after two weeks of storage in artificial saliva at 25⁰C. Material and Methods: A total of 32 specimens of dimensions 64mm×10mm×2.5mm were divided in two groups according to the type of material (Harvard-temp or Charm-temp). Each group of material has 16 specimens. These 16 specimens were divided in two groups: a control group (eight specimens) in dry conditions and an aging group (eight specimens) and stored in artificial saliva for two weeks. The TR 200 device was used to measure the surface roughness of specimens in micrometers (µm) before and after aging in artificial saliva. Results: After comparing the results, a significant difference was found in the surface roughness in dry and aging conditions of Harvard – temp (P 0.05). Conclusion: that in-vitro aging research might be an informative predictor of provisional materials’ properties before clinical application. Clinical significance: Both materials can perform adequately in the oral cavity for two weeks. However, the Charm temp mayperform more adequately and maintain good surface roughness.

Background/purpose With the advancement of an over aging society, the average number of remaining teeth has increased. However, these remaining teeth do not always have sufficient alveolar bone support, and sometimes fabricated connected crowns are applied. This study evaluated the influence of crown material, crown thickness, and alveolar bone resorption on the stress distribution within the abutment teeth of connected crowns. Materials and methods Using structural analysis software, a premolar crown model was fabricated. Three kinds of crown materials, two types of crown thickness, two types of post and core systems, and two levels of alveolar bone were assumed and evaluated for the stress distribution within the abutment teeth. Results The higher material properties crown was, the more stress was concentrated at the marginal area. The composite resin core showed larger stress values around the marginal area, and the metal core showed larger stress values at the tip of the post. Alveolar bone resorption progressed, the marginal area stress value increased. Conclusion The low elastic modulus crown material polyetheretherketone (PEEK) prevented stress concentrations at the marginal area of the crown and dentine, even with alveolar bone resorption. However, the amount of bone resorption has a great influence on the stress distribution around the tip of the post compared to the type of crown material.

Background/purpose: With the rise of digitalization in dentistry, intraoral scanners and digital impressions have recently been adopted by many clinicians. The aim of this study was to investigate surface topography of prepared teeth and the accuracy of digital impressions. Materials and methods: Twenty mandibular typodonts, containing left first premolar and left first molar abutment teeth manufactured by using CAD/CAM, were used in this study. An intraoral scanner was used to scan each typodont, and each STL file generated was exported in high resolution (Group H), moderate resolution (Group M), and low resolution (Group L). All 60 files were inspected in a 3-D mesh processing software. For each file, the number of triangulation points in the meshwork were obtained for both abutment teeth. Results: The measurements obtained from the 3-D mesh processing software revealed that the mean number of triangulation points on the 3-D surface of the abutment teeth (20 premolars + 20 M) were 790,625 ± 98,890 dots in Group H, 592,283 ± 74,881 dots in Group M, and 198,067 ± 19,328 dots in Group L. Significant differences were found between Group H and M (p

The purpose of this randomized clinical study was to evaluate the efficacy of platform-switching (PS) vs platform-matching (PM) implants when paired with a newly designed marginless abutment (MA) vs a conventional abutment (CA) in maintaining peri-implant tissue stability. Marginal bone level (MBL) and probing depth were measured up to 1 year postloading. Eighty implants were inserted in 42 patients and randomly assigned to one of four groups, each with a different implant/abutment configuration: Group 1 (PM+CA), Group 2 (PM+MA), Group 3 (PS+CA), and Group 4 (PS+MA). Data were collected at implant placement (T0), abutment placement (T1), final crown placement (T2), and 1 year postloading (T3). At the 1-year follow-up, MBL was more stable in Groups 3 and 4 compared to Groups 1 and 2. These results suggest that the role played by the implant-abutment connection (PS vs PM) is more important than the type of abutment preparation (MA vs CA).