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Purpose: To examine the effect of tightening and loosening the dental implant screw on implant osseointegration in an elderly rat model.Materials and Methods: Titanium dental implants were inserted in the bilateral tibiae of 34 elderly Wistar rats (1 year and 3 months old). Rats were randomly divided into five groups: control (no loading); immediate loading (IL) (vertical load [3 Hz for 15 minutes/day] immediately after implantation); early loading (EL) (load started on postoperative day 7); five times abutment removal (R5) (tightening and loosening of the abutment screw once per day for 5 days each week); and two times abutment screw removal (R2) (tightening and loosening of the abutment screw once per day for 2 days each week). After 4 weeks, the rats were euthanized, and the bone structure surrounding the dental implants was evaluated using microcomputed tomography analysis.Results: Osseointegration failed more frequently in the EL, R2, and R5 groups than in the control and IL groups (P = .06). The EL, R2, and R5 groups also tended to have lower relative gray values than the control and IL groups.Conclusion: Tightening and loosening the abutment screw might negatively affect dental implant osseointegration in the early healing stage in older adults. [ABSTRACT FROM AUTHOR]

Purpose: To apply finite element analysis (FEA) to investigate the stress distribution in a 4-mm-high ultrashort implant when supporting crowns of different heights in order to test the possibility of using this implant unitarily in the posterior edentulous mandible.Materials and Methods: Three models of atrophic mandibles were created (M1, M2, and M3). Each model contained a 4-mm-length implant of a titanium-zirconium alloy, screw-type with internal connection, supporting nonsplinted screwed-in crowns of 10, 12.5, and 15 mm in height. Axial and oblique loads were simulated in the three model crowns.Results: In an oblique load, the stress tended to be concentrated in the lingual region. In the qualitative results of the axial load, peaks of tension occurred in the lower angle between the inner groove and the inner conical portion of the implant. Regarding the differences in crown height, the 15-mm height produced a higher stress peak due to the lever effect of the crown under an oblique load.Conclusion: Within the limits of this study, the results suggest the possibility of using single crowns of proposed heights with unitary ultrashort implants installed in the posterior edentulous mandible, so long as there is no oblique load on the crown. [ABSTRACT FROM AUTHOR]

Purpose: To assess the influence of a screw access hole (SAH) and mechanical cycling on the fracture load of implant-supported crowns (ISCs) manufactured with screw-retained (s) or cement-retained (c) abutments with either metal (M) or zirconia (Z) infrastructure.Materials and Methods: Six groups of restorations were made based on type of infrastructure (M or Z), fixation (s or c), and whether they underwent aging (a) with mechanical cycling: Zc, Zs, Zsa, Mc, Ms, and Msa. All ISCs were porcelain veneered and tested for compression to failure in distilled water (37°C) using a universal testing machine. ISCs from groups Zsa and Msa were mechanically cycled (106 cycles; 2 Hz, 100 N) in distilled water before compressive testing. Fractographic principles were followed to assess the fracture surfaces. The fracture load data were statistically analyzed using one-way analysis of variance and Tukey test (α = .05). The relationships between experimental group and failure mode were analyzed using chi-square test (α = .05).Results: Regardless of the infrastructure material, cement-retained ISCs (Zc and Mc) showed higher fracture load values than screw-retained ISCs (Zs, Zsa, Ms, and Msa) (P < .001), which were statistically similar to each other (P > .05). Aging had no effect on the fracture load of ISCs. There was a significant relationship between failure mode and experimental group (P < .001). Catastrophic fractures were found only in Zc and Zs. All metal-based ISCs failed from chipping reaching the metal infrastructure.Conclusion: Cement-retained ISCs showed higher fracture resistance than screw-retained prostheses. No catastrophic failures were found for metal-based ISCs. Aging did not affect the fracture load, but did affect the failure mode of ISCs. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to describe and analyze the restoration profiles of 5,491 implant-supported single crowns, fixed partial dentures (FPDs), and splinted restorations prescribed between January 2005 and December 2009.Materials and Methods: Dental clinicians qualified in or before December 2004, registered in Victoria, and placing and/or restoring implants in private practice were invited to participate in the study. Data was extracted by two trained and calibrated research assistants from dental records. Cross tabulation was carried out in SPSS (IBM) to provide descriptive statistics on clinician profiles, patient demographics, and restoration information.Results: A total of 34 practitioners participated in the study: 25 general dentists and 9 specialists. Clinicians that graduated between 1970 and 1989 (16 to 40 years of experience) prescribed most of the prostheses (82.0%). Female patients were present in higher numbers across most age and restoration groups. Of the implant-supported prostheses, 5,491 fit the criteria for simple basic restorations and were included in this report. The majority of the prostheses (86.7%) were single-tooth restorations. Metal-ceramic was the material of choice for the majority of the restorations (3,382/5,491). The use of single implant-supported crowns in the anterior mandible was rare. More than 65% of the implant-supported restorations in this study were screw retained directly to the implant. The specialist clinicians in this study largely used the screw-retained method to retain single implant-supported crowns (82.0%). General dentists provided 1,066% more cement-retained single implant-supported crowns compared with other practitioners.Conclusion: This report showed that during the period of January 2005 to December 2009, private practice clinicians in Victoria, Australia favored porcelain-fused-to-metal material over all-ceramic for implant restorations. Most implant restorations were single crowns. More female patients received implant-supported restorations in the posterior region of the mouth. The clinicians included in this study, particularly the specialists, generally favored a retrievable design in choosing the retention method for the prostheses. [ABSTRACT FROM AUTHOR]

Purpose: To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex.Materials and Methods: In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm.Results: Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component.Conclusion: These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the stability of titanium screws in implant-abutment connections by measuring the force necessary to induce unscrewing.Materials and Methods: A total of 60 implant-abutment couplings were assigned to two groups (n = 30 each). The sequence 10-20-32 Ncm was tested in Group 1; the sequence 10-20-32-32-32 Ncm was tested in Group 2. The force necessary to unscrew each abutment-implant sample was recorded and statistically analyzed. The significance level was set at P < .05.Results: Significant differences were found between the two sequences. Group 2 required higher forces than Group 1 to unscrew.Conclusion: The stability of the implant-abutment joint may be improved by tightening with the sequence 10-20-32-32-32 Ncm. [ABSTRACT FROM AUTHOR]

Nonrotational capability is recommended for multiple-implant-supported prostheses, as well as single-tooth restorations. Interlocking interfaces facilitate the fabrication of custom re-angulated abuments when required, provides built-in troubleshooting redundancy in the event of implant loss, and helps reduce torque on retaining screws. The path of insertion can be established in the laboratory with a verification jig and any interferences adjusted or reangulated, or a standard gold cylinder substituted with compatible armamentarium. Brånemark nonrotational abutments can be used in place of standard abutments for all multiple-implant-supported prostheses, regardless of position or orientation. When required, a standard gold cylinder can be used with the Brånemark nonrotational abutment. Specialized abutments, such as the Estheticone, can also utilize nonrotational conical cylinders to reduce torque on the gold retaining screws. [ABSTRACT FROM AUTHOR]

The article offers information on solving problems related to dental abutment loosening, final fixation screw loosening and maintenance occurring with implant-supported restorations. The problem of abutment loosening can be fixed by using a cone-to-screw configuration in the design of the abutment. The dentist may choose either a screw-retained or cemented restoration for stabilizing abutment connection of the final restoration. A stable abutment connection and a cemented restoration can reduce treatment costs. Having a 45-degree shoulder in the ITI Dental Implant System offers a very stable and accurate foundation for a cemented restoration.

The article presents information on the design of superstructures to be placed in dental implants. It is stated that prosthetics dentistry involves fixed prostheses rigidly cemented to teeth or removable prostheses that anchor to teeth, but, both of them have risks and limitations. It is mentioned that in the design of the superstructure to be placed over the implant, the access opening for the connecting screw should guide the prosthetic framework to a defined position on the implant. It is stated that the site of the screw access opening is affected by the implant placement and inclination. The article describes several treatments for the screw access opening by using the Branemark implant.

The posterior design of the implant superstructure (the ceramometal crown) was classified into four categories: a ceramometal crown with an access hole on top; a cemented ceramometal crown; a ceramometal crown retained with a lingual screw; and a telescopic ceramometal crown. Cemented ceramometal crowns and telescopic ceramometal crowns are considered simpler, more esthetic, and more resistant to fracture among the four models. [ABSTRACT FROM AUTHOR]

This laboratory study used a photoelastic-coating technique to investigate the relationship between the magnitude and location of discrepancies of fit and the amount and distribution of surface stresses on an implant superstructure. For the test superstructure involving four abutments and a single fit discrepancy, maximum surface stress was found over the intermediate abutment, regardless of the location of the fit error. The results show a positive relationship between the size of the fit discrepancy and the magnitude of stress on the superstructure for gaps of up to 104 μm at an end abutment and 55 μm at an intermediate abutment, when the gold screws were tightened at 10-Ncm torque. [ABSTRACT FROM AUTHOR]

Two commercially available, screw-retained attachments and an experimental attachment were modeled and analyzed by computerized finite element method. Mechanical test specimens were then developed. Cast rectangular bars were fabricated with the attachments or were joined by soldering at midspan as a control. These bars were subjected to three-point loading. The soldered connector was stronger than the three attachment designs, and the experimental attachment was stronger than the two commercial products. There was general agreement between the mechanical and finite element testing. The use of computer-aided technology to design dental devices with improved mechanical properties was demonstrated by this study. [ABSTRACT FROM AUTHOR]

The finite element method was used to model a 4.0 × 13.0-mm IMZ implant restored with a cast gold crown to examine the relationship between deflection of the prosthetic superstructure and stress concentrations in the retaining screw using both the polyoxymethylene intramobile element and the analogous titanium element under various loading conditions. A strong correlation was observed between the peak stresses in the screw and the deflection of the superstructure. Deflections and stress concentrations generally increased with increases of either the load magnitude or the load angle. Greater deflection and stress concentrations within the coronal retaining screw were predicted with the use of the resin IME than with the titanium element. [ABSTRACT FROM AUTHOR]

There has been an increasing interest in the use of implants for partially edentulous patients. This introduces other biomechanical situations than those experienced in completely edentulous patients. In a prospective multi-center study, 521 implants in 154 patients were loaded with 197 free-standing prostheses. The patients have been followed for 3 years. The cumulative success rate for the prostheses was 94.8% and for the implants it was 93.9%. Most of the lost prostheses were only supported by two implants. A frequent technical complication was fracture and loosening of gold screws, which was more frequent in prostheses supported by only two implants. [ABSTRACT FROM AUTHOR]

The various clinical and laboratory procedures for use of auxiliary prefabricated metal screw retention, castable plastic telescopic, and custom laboratory-fabricated systems are presented as adjuncts to implant-supported restorative procedures. These devices aid in the fabrication of predictable and retrievable screw-retained, fixed-detachable implant-supported prostheses for various conditions and combinations of support. Ancillary screw systems are also useful in solving cosmetic problems when implant placement compromises this goal. [ABSTRACT FROM AUTHOR]

The first 50 edentulous arches treated with osseointegrated fixed partial dentures at the Postgraduate Dental Education Center, Örebro, Sweden, were studied retrospectively with concern for complications and time used for supplementary treatment and maintenance. The longest observation period was 9 years, the shortest 3 years, and the mean 5.2 years. Twenty-two percent of the patients experienced fractures of artificial teeth and/or the acrylic resin superstructure. The most severe technical complications were fractured or bent abutment screws (three) and fracture of the framework (one). The average time for supplementary treatment and maintenance was as follows: for surgery, 0.16 hours per prosthesis and year; for prosthodontics, 0.64 hours per prosthesis and year; and for dental laboratory procedures, 1.0 hour per prosthesis and year. [ABSTRACT FROM AUTHOR]

The article examines the retention and stress-distributing characteristics of three Brasseler/Vlock endodontic posts. These posts include threads of moderate pitch over their entire length and a conical fin arrangement occlusally. The stresses associated with the installation and simulated functional loading of the posts were observed photoelastically. Stress-free channels were made in photoelastic sheets on a miniature lathe. Zinc phosphate cement was placed in the channels and the posts were screwed in place. The retention potential of the posts was found by measuring the force needed to remove them from extracted human teeth.

The article focuses on the development of orthodontic screws for removable appliances. It states that an important step in the process of creating the expansion screw type of appliance was the application of the Coffin spring. It describes how various modifications in removable appliances were designed for the arch and tooth repositioning in transverse, sagittal and vertical directions. It offers information on the modifications in the expansion screws of the second generation, as well as the third generation of standard and special screws, created through the technical advances in materials and the construction of precision mechanics. It also offers information on the universal V 2A steel alloy expansion screw, developed to overcome disadvantages of the chrome- and nickel-plated screws.

The article presents a discussion on the possibilities and limits of treatment with endosseous implants. Several issues that creep into implant procedures include the reduced amount of force transferred to the implant bed and dampening of the stresses tips due to the use of polyoxymethylene screws in the implant cylinder. As to the techniques used in the procedure, a low sped handpiece is preferred, to avoid thermal insults when the deep bed is prepared in bone. It is concluded that there is no universally applicable implant or implant procedure and they normally depend on case to case basis.

Several photographs are presented depicting coronal build-up for the devitalized tooth including one which shows fabrication of temporary restoration, temporary precision crowns and a dental model with plastic posts and pins.

The article focuses on the procedures of incorporating a crown in a removable partial prosthesis. It states that lengthening the usability of prosthesis and the tooth are possible if the abutment is repaired with a new crown. It cites the case of an old woman that has a broken prosthetic tooth, wherein it caused her partial denture. After evaluating the case of the old woman's damaged prosthesis, it was considered that her present prosthesis should be retained, a pin should be built to prolong the amalgam core and install a new crown to secure the denture's grasp.

Abutment screw loosening (ASL) is a fairly common problem that adversely affects the longterm success of a dental implant restoration. Dental laboratory error can play a role in the etiology of ASL. This article presents three cases that demonstrate how laboratory errors in the fabrication of implant restorations and mismanagement of abutment surfaces can result in ASL. It describes a method for examination of the abutment surface. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of different screw-tightening sequences and torque applications on stresses in implant-supported fixed complete dentures supported by five abutments.Materials and Methods: Strain gauges fixed to the abutments were used to test the sequences 2-4-3-1-5; 1-2-3-4-5; 3-2-4-1-5; and 2-5-4-1-3 with direct 10-Ncm torque or progressive torque (5 + 10 Ncm). Data were analyzed using analysis of variance and standardized effect size.Results: No effects of tightening sequence or torque application were found except for the sequence 3-2-4-1-5 and some small to moderate effect sizes.Conclusion: Screw-tightening sequences and torque application modes have only a marginal effect on residual stresses. [ABSTRACT FROM AUTHOR]

In Class I malocclusions, when the only complaint is the localized crossbite of a premolar, resulting from a mild shortage of space, correction can be simply undertaken. Adams clasps and an expansion screw are incorporated into a simple removable appliance designed to provide space to align the malpositioned tooth, which is then guided into the line of the arch by a piece of elastomeric thread stretched between the Adams clasps. [ABSTRACT FROM AUTHOR]

Many clinicians expect complete healing after the removal of temporary anchorage devices, but clinical examination may reveal scar-like tissue. This report presents the typical features of scarring detected after the removal of miniscrews, and the clinical outcome of scar revision along with its pathologic features. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the microleakage at the implant-abutment (I-A) interface of Morse tapered implants inoculated with different volumes of bacterial suspension. Methods: Morse tapered IA sets were selected and divided in two groups depending on the type of abutment: passing screw (PS) and solid (S), and then subdivided into four subgroups (n=6) according to the suspension volume: PS1: 0.1 µL; PS3: 0.3 µL; PS5: 0.5 µL; PS7: 0.7 µL; S1: 0.1 µL; S3: 0.3 µL; S5: 0.5 µL and S7: 0.7 µL. A control test was performed to verify the presence of external contamination during the inoculation and the implants were incubated for microbiological analysis. The microleakage was evaluated every 24 h for 7 days by the clarity of solution. After this period, the implants were disassembled for confirmation of bacterial viability. Results: All the specimens with 0.7 µL and one sample of S5 presented turbidity in the control test indicating external contamination, and were excluded from the study. After 7 days of observation, none of the specimens presented positive results for microleakage and the bacterial viability was confirmed in all specimens. The 0.1 µL and 0.3 µL volumes did not present bacterial microleakage, meaning that these volumes may be inadequate for analysis. Conclusions: None of the sets evaluated showed bacterial microleakage at the I-A interface and the volume of 0.7 µL exceeded the internal capacity of the implants. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to compare the treatment duration and dentoskeletal changes between two different anchorage systems used to treat maxillary dentoalveolar protrusion and to examine the effectiveness of en-masse retraction using two miniscrews placed in the midpalatal suture. Methods: Fifty-seven patients (9 men, 48 women), who had undergone level anchorage system treatment at Aichi-Gakuin University Dental Hospital (Nagoya, Japan) were divided into two groups according to the method of maxillary posterior anchorage reinforcement: midpalatal miniscrews (25 patients, mean age 22 years) and conventional anchorage (32 patients, mean age 19 years). The en-masse retraction period, overall treatment duration, pre-treatment effective ANB angle, and change in the effective ANB angle were compared with an independent-samples t-test. Results: Compared to the headgear group, the duration of en-masse retraction was longer by approximately 4 months in the miniscrew group (p < 0.001). However, we found no significant difference in the total treatment duration between the groups. Moreover, a greater change in the effective ANB angle was observed in patients treated with miniscrews than in those treated with the conventional method (p < 0.05). Conclusions: The level anchorage system treatment using miniscrews placed in the midpalatal area will allow orthodontists more time to control the anterior teeth during en-masse retraction, without increasing the total treatment duration. Furthermore, it achieves better dentoskeletal control than does the conventional anchorage method, thereby improving the quality of the treatment results. [ABSTRACT FROM AUTHOR]

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Objectives: This study aimed to validate the Quality of Life with Implant-Prostheses (QoLIP-10) questionnaire for assessing the impact of screwed implant-supported rehabilitations on oral health-related quality of life (OHRQoL). Methods: 131 patients wearing screw-retained implant restorations were assigned to the following groups: Group 1 (HP; n = 50): fixed-detachable hybrid prostheses (control), Group 2 (S-PD; n = 43): metal-ceramic screwed partial dentures, and Group 3 (S-CD; n = 38): metalceramic screwed complete dentures. Impacts on OHRQoL were evaluated using the QoLIP- 10 and Oral Health Impact Profile (OHIP-14sp) scales. Data on global oral satisfaction, sociodemographics, health-behaviours, and prosthetics were gathered. Reliability and validity of the QoLIP-10 were investigated for screwed prosthesis wearers. The Spearman's rank test was applied to determine the correlation between both indices. Descriptive and nonparametric probes were run to evaluate the influence of the study variables on OHRQoL. Results: The QoLIP-10 confirmed its psychometric capacity for screwed prosthesis wearers. Both tests were inversely correlated. HP wearers reported the worst dental-facial aesthetics, performance, and functional limitation outcomes. Gender, education level, complaints about the mouth, perception of treatment needs, and prosthetic status modulated the OHRQoL. Conclusions: Screwed implants restorations provide better OHRQoL than do fixed-detachable hybrid prostheses. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to compare the success rates of the manual and motor-driven mini-screw insertion methods according to age, gender, length of mini-screws, and insertion sites. Methods: We retrospectively reviewed 429 orthodontic mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods. Results: The motor-driven method was used for 228 mini-screws and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used. Conclusions: Taken together, the motor-driven insertion method can be helpful to get a higher success rate of orthodontic mini-screw placement. [ABSTRACT FROM AUTHOR]

In order to apply high, short-term forces during rapid maxillary expansion (RME) to the sutures of the maxilla with minimum loss of force and without causing unwanted side-effects (dentoalveolar tipping, etc.), the appliance should be as rigid as possible. The retention arms of the RME screws, representing a particularly vulnerable and stressed weak point of RME appliances, were the focus of this laboratory technical study. Retention arms of 16 types of RME screws comprising four arms and one with eight arms were examined using a three-point bending test. According to their ability to absorb the applied bending loads, the screws were classified in product groups from 1 (highest) to 6 (lowest).Fifteen of the tested retention arms (stainless steel), despite having the same diameter (1.48–1.49 mm), differed up to 69.81 per cent between the highest (288.0 N) and lowest (169.6 N) maximum force parameters and up to 66.40 per cent between the highest (3325.9 N/mm2) and lowest (1998.7 N/mm2) maximum bending stress parameters. Due to optimum formability, though reduced rigidity, a titanium screw for nickel-sensitive patients (group 6) displayed the lowest force and bending tension values. The stainless steel double arms of the eight-arm screw device welded on both ends displayed the highest force data. The mean ductilities of the groups with the most and least rigid single steel arms differed by 22.77 per cent. Statistical analysis using the Pearson correlation coefficient revealed a significant indirect correlation between ductility and both maximum force (r = −0.780, P < 0.001) and maximum bending stress (r = −0.778, P < 0.001). The SUPERscrews, the Tiger Dental four-arm screw (group 1), and the eight-arm screw displayed the highest capacity to absorb an applied bending load. The screws in groups 3–6 appear acceptable for RME during the pre-pubertal period, whereas in the pubertal and post-pubertal period, groups 1 and 2 are sufficient. In early adulthood only the screws in group 1 and especially the eight-arm screw seem advisable, as mechanical demands increase with age. [ABSTRACT FROM PUBLISHER]

PURPOSE: To compare the prosthetic outcome of screw- and cement-retained implant-supported restorations of the fixed bridges. METHODS: A total of 185 Straumann implants were placed in the alveolar bone of 68 partially edentulous patients from Jan. 2006 to Dec. 2007. All of them were 2 to 6 units of combination crowns with Straumann system. Then they were followed up for 3 years. In each group, the retention, influence on hard and soft tissues, passive fitting and rupture strength of the ceramic layer were evaluated. The data was analyzed with SPSS 12.0 software package. RESULTS: There were more advantages of retention and the rupture strength of the ceramic layer in the cement-retained group, while there was less influence on the hard and soft tissues, and more facility of maintenance and reparation in the screwed-retained group. The difference between the two groups was statistically not significant (P>0.05). CONCLUSIONS: The clinical outcomes of implant restorations are satisfactory, either screw-retained or cement-retained. Cement retention is used in 2 to 3 unit combination crowns, while screw retention is more suitable for complicated cases. [ABSTRACT FROM AUTHOR]