Maxillomandibular relationship record methods for computer-engineered complete dentures: a scoping review.

OBJECTIVES: The purpose of this scoping review was to identify different methods employed for recording the maxillomandibular relationship (MMR) for computer-aided designed and manufactured (CAD-CAM) complete dentures (CDs). MATERIALS AND METHODS: This scoping review followed the PRISMA-ScR guidelines and was developed according to Arksey and O'Malley and The Joanna Briggs Institute protocol. The methods were registered on the Open Science Framework (< osf.io/rf4xm> ). The focus question was: "What are the different techniques for recording the maxillomandibular relationship in the digital workflow used in CECDs?" Two investigators searched 3 online databases [MEDLINE (PubMed), Scopus, and Science Direct] independently. The inclusion criteria were clinical studies and reviews that assessed techniques for recording MMR using digital workflow for manufacturing of CECDs. A descriptive analysis was performed considering the study design, manufacturing system, clinical steps, and tools for the determination of MMR, and the difficulty level of procedures. RESULTS: 4779 articles were identified in the electronic search and 10 studies were included for data analysis. The review identified 4 commercially available CAD-CAM denture systems and 3 innovative methods suitable for abbreviating the number of appointments (2 to 4 visits). The trial denture is inherent to the procedure for the Baltic System and 3 innovative techniques. Three techniques (2 innovative and WholeYouNexteeth) demonstrated lower difficulty levels for performing the clinical procedures, regardless of the professional skills. CONCLUSIONS: The commercially available and innovative techniques for the recording of MMR may provide predictability of the treatment. The techniques are effective, however, rely on the learning curve and the patient's clinical condition. CLINICAL RELEVANCE: Recording of the maxillomandibular relationship is paramount for the manufacturing and functionality of complete dentures. Clinicians should be aware of the different tools and techniques described for registering the jaw relationship.

Evaluation of Masticatory Function, Satisfaction, and Quality of Life Among Users of Complete Dentures Relined with Resilient Materials: A Systematic Review.

PURPOSE: To evaluate whether complete dentures (CDs) relined with long-term resilient liners (LTRLs) favor better masticatory function, satisfaction, and quality of life among completely edentulous patients compared to conventional CDs. MATERIALS AND METHODS: This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist and was registered in PROSPERO (the International Prospective Register of Systematic Reviews; CRD42021258700). The population, intervention, comparison, and outcome (PICO) purpose was to determine whether CDs relined with LTRLs favor better masticatory function, satisfaction, and quality of life among completely edentulous patients when compared to CDs. Searches were performed in the PubMed/MEDLINE, Embase, Scopus, Lilacs, BBO, and OpenGrey databases. Manual searches were also performed to identify additional primary studies. RESULTS: Overall, 3,953 articles were found. After removing duplicates, reading the articles, and applying the inclusion and exclusion criteria, 15 articles were selected for qualitative analysis, totaling 422 patients with follow-up periods ranging from 1 week to 3 years. Among these, 8 studies assessed masticatory function using different methods, 2 assessed satisfaction, 1 assessed quality of life, and 4 assessed more than one outcome. Through qualitative analysis, LTRLs showed satisfactory results in most studies when compared to CDs in relation to masticatory function, satisfaction, and quality of life. CONCLUSIONS: LTRLs favor better masticatory function, satisfaction, and quality of life among completely edentulous patients compared to CDs.

Complete denture rehabilitation for a patient with Parkinson's disease using clinical strategies: A case report.

OBJECTIVE: To present clinical strategies for prosthetic rehabilitation with complete dentures (CDs) of a Parkinson's disease patient. CASE REPORT: An 82-year-old patient sought the Department of Dentistry at UFRN, reporting retention dissatisfaction and hamper to the mandibular CD adaptation. Patient-reported a dry mouth sensation, and exhibited disordered mandibular movements, tremors, and resorbed mandibular ridge. Aiming retention and stability, double molding with zinc enolic oxide impression paste, neutral zone technique, and non-anatomic teeth were proposed as clinical strategies. At delivery, identification and relief in the supercompression areas were performed to facilitate the acceptance and use of the new dentures. CONCLUSION: The strategies promoted patient satisfaction regarding retention, stability, and comfort. This treatment may be considered for the rehabilitation of Parkinson's disease patients, favoring the adaptation process.

Use of impression technique to identify areas of super compression before installation of new complete dentures: a randomized double-blind trial.

OBJECTIVE: To identify pressure areas using an impression technique and to evaluate whether adjustment of dentures prior to installation can decrease ulcer frequency, number of adjustments, and improve satisfaction with treatment. MATERIALS AND METHODS: Fifty complete denture users were selected and randomly divided into two groups. Pressure areas were identified in 25 subjects using the impression technique with fluid silicone, and the denture base in these areas was adjusted before installation. A total of 25 subjects received new complete dentures without adjustments before installation. The number of ulcers observed was registered at 1, 7, 15, and 30 days after installation. Patient satisfaction was collected before and 1 month after the installation. The number of necessary post-installation adjustments was considered. Comparisons between the groups with respect to the number of ulcers, adjustments, and patient satisfaction were performed using the Mann-Whitney test. RESULTS: Identification of pressure areas reduced the number of ulcers after installation of the new prostheses. These results were observed in the 1- (p = 0.004) and 7-day (p = 0.002) adjustments for the maxilla and in all the adjustments for the mandible. The technique improved patient satisfaction (p = 0.031) and reduced the number of post-installation adjustments (p ≤ 0.001). CONCLUSION: A reduction in the incidence of ulcers, number of adjustments and improvement in patient satisfaction could be observed with the use of the technique.

Factors associated with the non-adaptation to new mandibular complete dentures: a scoping review.

PURPOSE: To identify and map the scientific evidence regarding the factors that may influence the adaptation of complete edentulous to the mandibular complete denture. MATERIALS AND METHODS: An electronic search strategy in the PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library, and Virtual Health Library databases from 1945 to 2021, was conducted, according to the criteria established by PRISMA-ScR. Studies that addressed factors that influenced adaptation and acceptance to mandibular complete denture were included, such as socio-demographic and psychological aspects and patient-centered condition, and denturer-elated factors. RESULTS: The search yielded 9264 studies, of which 87 articles were considered eligible for full-text screening. Of this total, 23 were included for data extraction. Sociodemographic factors do not interfere with adaptation to a mandibular complete denture. Reports of complaints regarding pain and discomfort negatively impact the acceptance of complete dentures. Patients with a neuroticism personality have more difficulty accepting the complete dentures, being more predisposed to abandon them. CONCLUSION: The psychological condition interferes with the predictability of treatment. Older and female patients, using first mandibular dentures, with resorbed ridges, and poor technical quality had more difficulty adapting to the complete dentures. However, these data must be interpreted with caution due to the variability of methodologies of the studies included in this review. Int J Prosthodont 2023. doi: 10.11607/ijp.7774.

Mechanical properties and accuracy of removable partial denture frameworks fabricated by digital and conventional techniques: A systematic review.

STATEMENT OF PROBLEM: Providing a removable partial denture (RPD) can be a complex, time-consuming, and error-prone procedure. Computer-aided design and computer-aided manufacturing (CAD-CAM) techniques have shown promising clinical outcomes; however, the influence of manufacturing techniques on the properties of RPD components is unclear. PURPOSE: The purpose of this systematic review was to determine the accuracy and mechanical properties of RPD components fabricated with conventional and digital methods. MATERIAL AND METHODS: This study followed the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) and was registered on the international prospective register of systematic reviews (PROSPERO) database (CRD42022353993). An electronic search was conducted on PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library in August 2022. Only in vitro studies comparing the digital with the lost-wax casting technique were included. The quality of the studies was assessed by using the methodological index for nonrandomized studies (MINORS) scale. RESULTS: Of the 17 selected studies, 5 evaluated the accuracy of RPD components as well as the mechanical properties, 5 studies evaluated only the component accuracy, and another 7 evaluated only the mechanical properties. The accuracy was similar regardless of the technique, with discrepancies within clinically acceptable values (50 to 426.3 µm). The surface roughness was higher for 3D-printed clasps and lower for milled clasps (P<.05). The metal alloy significantly influenced the porosity, with the highest number of pores obtained by casting for Ti clasps and by rapid prototyping for Co-Cr clasps. CONCLUSIONS: In vitro studies showed that the digital technique provided similar accuracy to that of the conventional technique within a clinically acceptable range. The manufacturing technique influenced the mechanical properties of RPD components.

Patient-reported outcome measures and prosthetic events in implant-supported mandibular overdenture patients after immediate versus delayed loading: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Immediately loaded mandibular overdentures are clinically acceptable treatment options that have gained popularity because their use shortens the treatment duration. However, whether the immediate loading of dental implants can match the prosthetic events, satisfaction, and quality of life of delayed loading is still unclear. PURPOSE: The purpose of this systematic review and meta-analysis was to compare the prosthetic events, satisfaction, and quality of life of immediate versus delayed loading implants in patients rehabilitated with mandibular overdentures. MATERIAL AND METHODS: This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered at The International Prospective Register of Systematic Reviews (PROSPERO) (CRD42021258187). Electronic searches were carried out by 2 independent reviewers in the PubMed/MEDLINE, Cochrane Library, and Web of Science databases up to May 2021. Only randomized clinical trials and prospective studies with at least 10 participants that compared immediate versus delayed loading were selected. A meta-analysis was performed by using the RevMan 5 software program for complications and maintenance outcomes. RESULTS: Seven articles were included in the qualitative analysis, and 4 were included in the quantitative analysis. The meta-analysis demonstrated no significant difference between immediate and delayed loading for prosthetic complications (RR=1.71; 95% CI=0.67-4.37; I2=85%, P=.27) or maintenance (RR=1.92, 95% CI=0.44-8.28; I2=94%, P=.38). CONCLUSIONS: Although the prosthetic complications and maintenance were more likely to favor the delayed loading group, available evidence showed no statistical difference for prosthetic complications and maintenance between immediate loading and delayed loading in mandibular overdentures.

Surface roughness of acrylic resins used for denture base after chemical disinfection: A systematic review and meta-analysis.

OBJECTIVE: This study aimed to systematically review the literature regarding the surface roughness of polymethylmethacrylate (PMMA) for denture bases, disinfected with different chemical agents and analyse the outcomes of the included studies. BACKGROUND: Various chemical disinfection protocols to clean the removable dental prosthesis are reported in the literature, however systematic reviews analysing the outcomes in the surface roughness of the PMMA are lacking. METHODS: The Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) checklist was used to structure this systematic review. The inclusion criteria were as follows: clinical trials, in vitro studies, studies in English and studies comparing the effects of chemical disinfection products on the surface roughness of PMMA. An electronic search was performed in the following databases: PubMed/MEDLINE, Scopus and Web of Science.; we also conducted a manual search for articles published in specific journals of dental prostheses and dental materials. RESULTS: Thirteen in vitro studies in this systematic review and meta-analysis. According to the meta-analysis, the effects of 0.5% (P = .32; MD: 0.06; CI: -0.05 to 0.17; heterogeneity: P < .00001; I2  = 92%) and 1% NaOCl solutions (P = .27; MD: 0.01; CI: -0.01. to 0.03; heterogeneity: P = .03; I2  = 55%) did not statistically differ between the groups studied. Effects of alkaline peroxide were statistically significant (P = .0009; MD: 0.01; CI: 0.01-0.02; heterogeneity: P = .004; I2  = 65%), suggesting that it promotes deterioration of the PMMA surface. CONCLUSION: The alkaline peroxide, when used as a disinfectant, generated changes on the surface roughness of PMMA and should be used with caution; however, NaOCl, even at different concentrations, caused fewer changes on the surface of the denture base.

Pterygomaxillary Disjunction and its Influence on the Result of Surgically Assisted Maxillary Expansion: A Systematic Review and Meta-analysis.

AIM: The aim of this study was to evaluate the available evidence to identify the influence of pterygomaxillary disjunction on the result of surgically assisted maxillary expansion. BACKGROUND: LeFort I type osteotomy with disjunction of the pterygomaxillary suture is a procedure widely used in maxillofacial surgery. However, the need for its performance during surgically assisted maxillary expansions has been discussed in literature, since serious complications can be caused during this stage. REVIEW RESULTS: Systematic review of articles was performed using three databases (PubMed, Web of Science, and Cochrane) published until May 2019. After applying the selection criteria, five articles were included in the systematic review, with a total of 141 patients. Meta-analysis showed the absence of significant difference between intervention and control groups in the preoperative period (standardized mean difference = -0.28; confidence interval, CI 95% = -0.81, 0.26; p = 0.31) and postoperative period (standardized mean difference = -0.12; 95% CI = -0.65, 0.42; p = 0.66). In general, the heterogeneity of statistical estimates was low (I2 = 0%). CONCLUSION: No statistically significant difference was observed between control group (without pterygomaxillary disjunction) and intervention group (with pterygomaxillary disjunction). CLINICAL SIGNIFICANCE: Based on the data analyzed in this systematic review, it could be concluded that pterygomaxillary disjunction is not a mandatory step to achieve satisfactory maxillary expansion. Thus, not performing pterygomaxillary disjunction can prevent complications and reduce surgical time.

Comparison of three anesthetic techniques for the removal of posterior mandibular teeth with 2% lidocaine: a systematic review.

OBJECTIVES: The present systematic review aimed to evaluate whether the IANB (conventional inferior alveolar nerve block) technique is superior to the VA (Vazirani-Akinosi) or GG (Gow-Gates) techniques for anesthesia in the removal of posterior mandibular teeth. MATERIALS AND METHODS: This systematic review was structured according to the PICO strategy, adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) checklist, and was recorded on the international prospective register of systematic reviews (PROSPERO-CRD42020153130). Studies were included based on the eligibility criteria and data from the included studies were collected by one author, while another reviewed the compilation. RESULTS: Eight studies were included, all of which were randomized controlled trials. Three studies tested the techniques by exclusively performing lower third molar removal; the others covered other posterior lower teeth. All studies used the same local anesthetic and the same vasoconstrictor: lidocaine 2% with epinephrine/adrenaline. A total of 1056 patients were evaluated. CONCLUSIONS: Some differences were observed between the techniques. Because of the heterogeneity between studies, clinical trials with more specific methodologies, such as comparisons of GG and VA with IANB for mandibular tooth removal, and the same clinical homogeneity will be worthwhile. CLINICAL RELEVANCE: A systematic review of which anesthetic technique is most effective for mandibular teeth removal may positively impact the population's life. There are no systematic reviews which approach this theme in a well-structured perspective.

Influence of Diabetes on the Survival Rate and Marginal Bone Loss of Dental Implants: An Overview of Systematic Reviews.

We aimed to conduct an analysis of the systematic reviews (SRs) in literature about the implant survival rate (ISR) and marginal bone loss (MBL) in diabetic and nondiabetic patients. This work was registered in The International Prospective Register of Systematic Reviews (CRD42018095314) and was developed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the Cochrane Library Handbook. A search was performed on PubMed, Cochrane, Scopus, Embase, and LILACS. The PICO (problem/patient/population, intervention/indicator, comparison, outcome) question was "Do the survival rates of dental implants and marginal bone loss differ between diabetic and nondiabetic patients?" A total of 130 articles were retrieved. After eliminating repetitions, 118 were reviewed. Finally, 6 SRs were included. All the reviews indicated that there is no effect of diabetes on the ISR; however, a negative effect of the disease can be observed in MBL. Analysis of the quality of the studies was performed using the assessment of SRs in dentistry (Glenny Scale) and Assessing the Methodological Quality of Systematic Reviews (AMSTAR 2). Glenny Scale showed a moderate to high quality of the included studies. In contrast, AMSTAR 2 pointed out a critically low level for 4 studies, with no study fulfilling the criteria for high quality. It may be concluded that there is no effect of diabetes on the ISR; however, a negative effect of the disease can be observed on MBL.

Clinical performance of bulk-fill and conventional resin composite restorations in posterior teeth: a systematic review and meta-analysis.

OBJECTIVES: The purpose of this systematic review was to compare the clinical performance of bulk-fill resin composites with conventional resin composites used for direct restorations of posterior teeth. METHODS: This review followed the PRISMA statement. This review was registered at PROSPERO (registration number CRD42016053436). A search of the scientific literature was performed by two independent reviewers using the PubMed/MEDLINE, Embase, The Cochrane Library, and Web of Science databases from commencement until January 2018. The research question was "Do bulk-fill resin composites have a clinical performance comparable to conventional resin composites in posterior restorations?" Only studies evaluating class I and II direct restorations in permanent teeth with a follow-up period of at least 1 year were included. The RevMan 5 program was used for meta-analysis, calculating the relative risk (RR) and 95% confidence interval (CI) of the dichotomous outcome (restoration failure or success). RESULTS: Ten articles were selected, comprising 941 analyzed restorations. The mean follow-up period was 33.6 months (12-72 months). No statistically significant differences in the failure rate were observed between conventional and base/flowable bulk-fill resin composites (p = 0.31; RR 1.49; 95% CI 0.69-3.25) or full-body/sculptable bulk-fill resin composites (p = 0.12; RR 1.89; 95% CI 0.84-4.24). CONCLUSIONS: The present systematic review and meta-analysis indicate similar clinical performances of bulk-fill and conventional resin composites over a follow-up period of 12 to 72 months. CLINICAL SIGNIFICANCE: Based on the results of this study, the bulk-fill resin composites could be an alternative for direct restorations in posterior teeth. However, clinical trials of longer duration are required.

Surgical versus non-surgical treatment of actinic cheilitis: A systematic review and meta-analysis.

OBJECTIVE: The aim of this systematic review was to compare outcomes between surgical and non-surgical treatment of actinic cheilitis (AC). MATERIALS AND METHODS: A systematic review and meta-analysis based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses guideline were performed. A search of PubMed/MEDLINE, Web of Science, and Cochrane Library databases was conducted. Articles were selected based on the inclusion criteria: randomized clinical trials, prospective/retrospective studies, and case series with at least 10 patients, with a minimum follow-up period of 6 months. A weighted remission rate (RER) and recurrence rate (RR) with a 95% confidence interval was performed. Data analysis was performed using a comprehensive meta-analysis software. RESULTS: A total of 283 ACs in 10 studies were included. About 2.5% surgically treated cases underwent malignant transformation. The weighted remission rate was higher for surgical (92.8%) compared to non-surgical treatment (65.9%). The recurrence rate was lower for surgical (8.4%) compared to non-surgical treatment (19.2%). CONCLUSION: In this systematic review, the surgical treatment was more favorable than non-surgical for AC. Meanwhile, further studies are needed that should maximize methodological standardization and have greater rigor of the data collection process.

Optimal number of implants for complete-arch implant-supported prostheses with a follow-up of at least 5 years: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Consensus is lacking regarding the optimal number of implants for supporting complete-arch prostheses with good survival rates and lower prosthetic complications and marginal bone loss. PURPOSE: The purpose of this systematic review was to evaluate the influence of the number of implants used for complete-arch prostheses with at least 5 years of follow-up. MATERIAL AND METHODS: A search was performed in the PubMed/MEDLINE, Scopus, and Cochrane Library databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria and was registered in The International Prospective Register of Systematic Reviews (CRD42016048468). The following was the population, intervention, comparison, outcome (PICO) question: Does the number of implants influence the longevity of complete-arch prostheses? RESULTS: Nineteen studies including 1006 patients with a mean age of 61.44 years were selected for evaluation. The number of implants per jaw ranged between 2 and 9 in the maxilla, mandible, or both jaws. For implant survival rate in complete-arch prostheses with fewer than 5 implants per jaw, the pooled weighted event rate was 1.4% (I2=25.26%; P=.211) and 4.2% (I2=81.35%; P<.001) for complete arches with more than 4 implants per jaw. For the prosthesis survival rate, the pooled weighted event rate for a complete-arch with fewer than 5 implants per jaw was 1.5% (I2=0%; P=.677) and 9% (I2=17.33%; P=.304) for complete arches with more than 4 implants per jaw. For prosthesis complications for complete arches with fewer than 5 implants per jaw, the pooled weighted event rate was 19.9% (I2=93.5%; P<.001) and 24.5% (I2=88.89; P<.001) for complete arches with more than 4 implants per jaw. The mean marginal bone loss for complete arches with fewer than 5 implants per jaw was 1.22 ±0.49 mm (I2=99.46; P<.001) and 1.46 ±0.46 mm (I2=99.6; P <.001) for more than 4 implants per jaw. CONCLUSIONS: The current systematic review indicated no relationship of the number of implants used to support a complete-arch prosthesis with implant survival rate, prosthesis survival rate, prosthesis complications, or marginal bone loss in studies with follow-up periods of between 5 and 15 years.

Influence of the implant diameter with different sizes of hexagon: analysis by 3-dimensional finite element method.

The aim of this study was to evaluate the stress distribution in implants of regular platforms and of wide diameter with different sizes of hexagon by the 3-dimensional finite element method. We used simulated 3-dimensional models with the aid of Solidworks 2006 and Rhinoceros 4.0 software for the design of the implant and abutment and the InVesalius software for the design of the bone. Each model represented a block of bone from the mandibular molar region with an implant 10 mm in length and different diameters. Model A was an implant 3.75 mm/regular hexagon, model B was an implant 5.00 mm/regular hexagon, and model C was an implant 5.00 mm/expanded hexagon. A load of 200 N was applied in the axial, lateral, and oblique directions. At implant, applying the load (axial, lateral, and oblique), the 3 models presented stress concentration at the threads in the cervical and middle regions, and the stress was higher for model A. At the abutment, models A and B showed a similar stress distribution, concentrated at the cervical and middle third; model C showed the highest stresses. On the cortical bone, the stress was concentrated at the cervical region for the 3 models and was higher for model A. In the trabecular bone, the stresses were less intense and concentrated around the implant body, and were more intense for model A. Among the models of wide diameter (models B and C), model B (implant 5.00 mm/regular hexagon) was more favorable with regard to distribution of stresses. Model A (implant 3.75 mm/regular hexagon) showed the largest areas and the most intense stress, and model B (implant 5.00 mm/regular hexagon) showed a more favorable stress distribution. The highest stresses were observed in the application of lateral load.

A 3-D finite element study of the influence of crown-implant ratio on stress distribution.

The purpose of this study was to assess the influence of the crown height of external hexagon implants on the displacement and distribution of stress to the implant/bone system, using the three-dimensional finite element method. The InVesalius and Rhinoceros 4.0 softwares were used to generate the bone model by computed tomography. Each model was composed of a bone block with one implant (3.75 x 10.0 mm) with external hexagon connections and crowns with 10 mm, 12.5 mm and 15 mm in height. A 200 N axial and a 100 N oblique (45°) load were applied. The models were solved by the NeiNastran 9.0 and Femap 10.0 softwares to obtain the results that were visualized by maps of displacement, von Mises stress (crown/implant) and maximum principal stress (bone). The crown height under axial load did not influence the stress displacement and concentration, while the oblique loading increased these factors. The highest stress was observed in the neck of the implant screw on the side opposite to the loading. This stress was also transferred to the crown/platform/bone interface. The results of this study suggest that the increase in crown height enhanced stress concentration at the implant/bone tissue and increased displacement in the bone tissue, mainly under oblique loading.

Stress analysis in platform-switching implants: a 3-dimensional finite element study.

The aim of this study was to evaluate the influence of the platform-switching technique on stress distribution in implant, abutment, and peri-implant tissues, through a 3-dimensional finite element study. Three 3-dimensional mandibular models were fabricated using the SolidWorks 2006 and InVesalius software. Each model was composed of a bone block with one implant 10 mm long and of different diameters (3.75 and 5.00 mm). The UCLA abutments also ranged in diameter from 5.00 mm to 4.1 mm. After obtaining the geometries, the models were transferred to the software FEMAP 10.0 for pre- and postprocessing of finite elements to generate the mesh, loading, and boundary conditions. A total load of 200 N was applied in axial (0°), oblique (45°), and lateral (90°) directions. The models were solved by the software NeiNastran 9.0 and transferred to the software FEMAP 10.0 to obtain the results that were visualized through von Mises and maximum principal stress maps. Model A (implants with 3.75 mm/abutment with 4.1 mm) exhibited the highest area of stress concentration with all loadings (axial, oblique, and lateral) for the implant and the abutment. All models presented the stress areas at the abutment level and at the implant/abutment interface. Models B (implant with 5.0 mm/abutment with 5.0 mm) and C (implant with 5.0 mm/abutment with 4.1 mm) presented minor areas of stress concentration and similar distribution pattern. For the cortical bone, low stress concentration was observed in the peri-implant region for models B and C in comparison to model A. The trabecular bone exhibited low stress that was well distributed in models B and C. Model A presented the highest stress concentration. Model B exhibited better stress distribution. There was no significant difference between the large-diameter implants (models B and C).

Influence of implant inclination associated with mandibular class I removable partial denture.

The aim of this study was to use two-dimensional finite element method to evaluate the displacement and stress distribution transmitted by a distal extension removable partial denture (DERPD) associated with an implant placed at different inclinations (0, 5, 15, and 30 degrees) in the second molar region of the edentulous mandible ridge. Six hemimandibular models were created: model A, only with the presence of the natural tooth 33; model B, similar to model A, with the presence of a conventional DERPD replacing the missing teeth; model C, similar to the previous model, with a straight implant (0 degrees) in the distal region of the ridge, under the denture base; model D, similar to model C, with the implant angled at 5 degrees in the mesial direction; model E, similar to model C, with the implant angled at 15 degrees in the mesial direction; and model F, similar to ME, with the implant angled at 30 degrees in the mesial direction. The models were created with the use of the AutoCAD 2000 program (Autodesk, Inc, San Rafael, CA) and processed for finite element analysis by the ANSYS 8.0 program (Swanson Analysis Systems, Houston, PA). The force applied was vertical of 50 N on each cusp tip. The results showed that the introduction of the RPD overloaded the supporting structures of the RPD and that the introduction of the implant helped to relieve the stresses of the mucosa alveolar, cortical bone, and trabecular bone. The best stress distribution occurred in model D with the implant angled at 5 degrees. The use of an implant as a support decreased the displacement of alveolar mucosa for all inclinations simulated. The stress distribution transmitted by the DERPD to the supporting structures was improved by the use of straight or slightly inclined implants. According to the displacement analysis and von Mises stress, it could be expected that straight or slightly inclined implants do not represent biomechanical risks to use.

Photoelastic analysis of the influence of platform switching on stress distribution in implants.

The aim of this study was to evaluate the stress distribution of platform switching implants using a photoelastic method. Three models were constructed of the photoelastic resin PL-2, with a single implant and a screw-retained implant-supported prosthesis. These models were Model A, platform 5.0 mm/abutment 4.1 mm; Model B, platform 4.1 mm/abutment 4.1 mm; and Model C, platform 5.00 mm/abutment 5.00 mm. Axial and oblique (45°) loads of 100 N were applied using a Universal Testing Machine (EMIC DL 3000). Images were photographed with a digital camera and visualized with software (AdobePhotoshop) to facilitate the qualitative analysis. The highest stress concentrations were observed at the apical third of the 3 models. With the oblique load, the highest stress concentrations were located at the implant apex, opposite the load application. Stress concentrations decreased in the cervical region of Model A (platform switching), and Models A (platform switching) and C (conventional/wide-diameter) displayed similar stress magnitudes. Finally, Model B (conventional/regular diameter) displayed the highest stress concentrations of the models tested.