A New Proposal for Calibrated Gauges for Removable Partial Dentures: A Finite Element Analysis.

AIM: The aim of this study was to evaluate the stress distribution of a planned removable partial denture (RPD) using new proposals for calibrated gauges of 0.3 mm and 0.35 mm undercuts through the three-dimensional (3D) finite element methodology, and compare them with 0.25 mm and 0.5 mm gauges that are already existing in clinical practice. MATERIALS AND METHODS: Kennedy class-I edentulous 3D models and their respective RPDs (InVesalius software; Rhinoceros and SolidWorks CAD) were created and exported to the finite element program HyperMesh 2019 for mesh configuration. In the following steps, axial loading (0º) of 40 N per point was performed, with 3 points on the molars and 2 points on the premolars, totaling 280 N unilaterally. The model was processed by the OptiStruct 2019 software and imported into the HyperView 2019 software to obtain the stress maps (MPa). RESULTS: The use of 0.30 and 0.35 mm calibrated gauges presented tensions similar to those with the 0.25 mm gauge (gold standard) and caused no significant damage to biological structures. The use of a 0.5 mm undercut caused greater traction force in the periodontal ligament of the abutments. CONCLUSIONS: The 0.35 mm undercut seems promising as it presented more favorable results in this simulation, on the other hand, a 0.5 mm undercut is greater than that necessary for retainers made of CoCr. CLINICAL SIGNIFICANCE: This study aims to measure a new undercut gauge (0.35 mm) to increase the retention area in abutment teeth of removable partial dentures.

The effectiveness of microwave disinfection in treating Candida-associated denture stomatitis: a systematic review and metaanalysis.

OBJECTIVE: To evaluate the effectiveness of microwave disinfection in treating Candida-associated denture stomatitis (CADS). MATERIALS AND METHODS: The PubMed/MEDLINE, Embase, and Scopus databases were searched for reports on randomized clinical trials (RCTs) published in English until May 2020 (PROSPERO CRD42020192062) that evaluated the treatment of CADS by using microwave disinfection. The main outcomes were the improvement of clinical signs and/or the decrease in the residual yeast present on the dentures and palatal mucosa. The mean differences, standard deviations, risk ratio, and 95% confidence interval were calculated by using the random-effects model. Heterogeneity was assessed by using Cochran's Q test and I2 values. The level of significance was set at α = 0.05. RESULTS: Five RCTs with 245 participants were included. The descriptive investigations demonstrated that microwave disinfection was as effective (p > 0.05) as 0.2% chlorhexidine, 0.02% sodium hypochlorite, and topical nystatin (100.000 IU/mL), and was superior to topical miconazole in treating CADS. The metaanalysis did not show a statistical difference between microwave disinfection and nystatin (100.000 IU/mL) treatment in terms of mycological counts, cure, and recurrence rates (p > 0.05). CONCLUSION: Microwave disinfection showed comparable results with those of conventional therapies for treating CADS. In addition, treatment with 650 W for 3 min once a week for 14 days had better cost-effect results, indicating both the prevention and treatment of CADS. CLINICAL RELEVANCE: Our findings provide evidence regarding the treatment of CADS using microwave disinfection, and also indicating the best cost-effective option for this treatment modality.

Does Continuous Chemical Disinfection Affect Mechanical Properties of CAD/CAM PMMA?

PURPOSE: To analyze the effect of disinfectants on the roughness and mechanical properties of CAD/ CAM polymethylmethacrylate (PMMA) dentures. MATERIALS AND METHODS: Two groups of denture base resins were tested-heat-polymerized and milled blocks. For each resin, 120 specimens were produced for flexural strength (FS) and flexural modulus (FM) analyses (total: 240 specimens), and 40 were produced for microhardness and surface roughness evaluations (total: 80 specimens). They were categorized into the following groups based on immersion: control (deionized water); H1 (1% sodium hypochlorite); H05 (0.5% sodium hypochlorite); and C2 (2% chlorhexidine) groups. The immersion periods were 0 (T0), 130 (T1), and 260 (T2) cycles. Statistical analyses were performed for flexural properties using threeway ANOVA. Microhardness (KHN) and surface roughness (Ra) were analyzed using repeated-measures ANOVA. A significance level of 5% was set. RESULTS: CAD/CAM PMMA showed higher FS (P = .001) and FM (P < .001) than conventional PMMA. The KHN value was superior to the conventional PMMA (P < .001). The chemical solution affected the surface roughness of both resins (P = .007). The CAD/ CAM PMMA block showed increased Ra values when H1 was used. Cycling separately increased the FS of conventional PMMA (T1 vs baseline; P < .05). However, the FM of CAD/CAM PMMA was higher (T1 and T2 vs baseline; P < .05). The time factor increased the microhardness of both resins (T2 vs baseline; P < .05). CONCLUSIONS: The CAD/CAM resin showed higher values compared to conventional PMMA in all tests, regardless of the chemical solution used; however, the values obtained for both resins were clinically acceptable.

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).

The toxic effects of chloroquine and hydroxychloroquine on skeletal muscle: a systematic review and meta-analysis.

The aim of this systematic review was to perform qualitative and quantitative analysis on the toxic effects of chloroquine (CQ) and hydroxychloroquine (HCQ) on skeletal muscles. We designed the study according to PRISMA guidelines. Studies for qualitative and quantitative analyses were selected according to the following inclusion criteria: English language; size of sample (> 5 patients), adult (> age of 18) patients, treated with CQ/HCQ for inflammatory diseases, and presenting and not presenting with toxic effects on skeletal muscles. We collected data published from 1990 to April 2020 using PubMed, Cochrane Library, EMBASE, and SciELO. Risk of bias for observational studies was assessed regarding the ROBIN-I scale. Studies with less than five patients (case reports) were selected for an additional qualitative analysis. We used the software Comprehensive Meta-Analysis at the confidence level of 0.05. We identified 23 studies for qualitative analysis (17 case-reports), and five studies were eligible for quantitative analysis. From case reports, 21 patients presented muscle weakness and confirmatory biopsy for CQ/HCQ induced myopathy. From observational studies, 37 patients out of 1,367 patients from five studies presented muscle weakness related to the use of CQ/HCQ, and 252 patients presented elevated levels of muscle enzymes (aldolase, creatine phosphokinase, and lactate dehydrogenase). Four studies presented data on 34 patients with confirmatory biopsy for drug-induced myopathy. No study presented randomized samples. The chronic use of CQ/HCQ may be a risk for drug-induced myopathy. There is substantiated need for proper randomized trials and controlled prospective studies needed to assess the clinical and subclinical stages of CQ/HCQ -induced muscle myopathy.

Platelet-Rich Fibrin in Coverage of Gingival Recession: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis sought to evaluate the efficacy of platelet-rich fibrin (PRF) membranes versus subepithelial connective tissue grafts (SCTGs) in the coverage of Miller class I and II gingival recessions. After the inclusion and exclusion criteria were applied, the quality of seven articles (Cohen's Kappa = 0.9) was evaluated using the Jadad scale. The MEDLINE/PubMed, Cochrane, and Web of Science databases were consulted, and manual searches were performed in the most popular periodontics journals. The studies included considered a total of 122 patients, 203 surgical fields on which SCTGs were used, and 205 surgical fields on which PRF was used. The parameters analyzed were probing depth, clinical attachment level, gingival recession, and keratinized mucosa. The minimum follow-up period accepted was 6 months. A statistically significant difference between the SCTG and PRF groups was found only in the case of keratinized mucosa. However, gingival recession, clinical attachment level, and probing depth parameters in the PRF group were found to be statistically equal to those of the SCTG group (the gold standard) (p ≥0.05). PRF membranes were determined to be a promising alternative to autogenous gingival grafts in the treatment of Miller class I and II gingival recessions.

Analysis of vertical marginal discrepancy in feldspathic porcelain crowns manufactured with different CAD/CAM systems: Closed and open.

OBJECTIVE: The objective of this study is to compare the marginal adaptation of feldspathic porcelain crowns using two computer-aided design/computer-aided manufacturing systems, one of them is open and the other is closed. MATERIALS AND METHODS: Twenty identical titanium abutments were divided into two groups: open system (OS), where ceramic crowns were created using varied equipment and software, and closed system (CS), where ceramic crowns were created using the CEREC system. Through optical microscopy analysis, we assess the marginal adaptation of the prosthetic interfaces. The data were subjected to the distribution of normality and variance. The t-test was used for the analysis of the comparison factor between the groups, and the one-way ANOVA was used to compare the variance of crown analysis regions within the group. A significance level of 5% was considered for the analyses. RESULTS: There was a significant difference between the systems (P = 0.007), with the CS group having the higher mean (23.75 µm ± 3.05) of marginal discrepancy when compared to the open group (17.94 µm ± 4.77). Furthermore, there were no differences in marginal discrepancy between the different points between the groups (P ≥ 0.05). CONCLUSIONS: The studied groups presented results within the requirements set out in the literature. However, the OS used presented better results in marginal adaptation.

Complete overdentures retained by mini implants: A systematic review.

OBJECTIVE: The purpose of this systematic review was to evaluate the use of mini implants to retain complete overdentures in terms of survival rates of mini implants, marginal bone loss, satisfaction, and quality of life. DATA: This report followed the PRISMA Statement and PICO question. This review has been registered at PROSPERO under the number CRD42016036141. SOURCE: Two independent reviewers performed a comprehensive search of studies published until September 2016 and listed in the PubMed/MEDLINE, Embase, and The Cochrane Library databases. The focused question was: is the use of mini implants feasible for prosthodontic rehabilitation with complete overdentures? RESULTS: The 24 studies selected for review evaluated 1273 patients whose mean age was 65.93 years; these patients had received 2494 mini implants and 386 standard implants for retaining overdenture prosthesis. The mean follow-up time was 2.48 years (range: 1-7 years). There was a higher survival rate of mini implants (92.32%). More frequent failures for maxillary (31.71%) compared with mandibular arches (4.89%). The majority of studies revealed marginal bone loss values similar to those of standard implants (<1.5mm). All studies verified an increase in satisfaction and quality of life after rehabilitation treatment with mini dental implants. CONCLUSION: The present systematic review indicates that the use of mini implants for retaining overdenture prosthesis is considered an alternative treatment when standard treatment is not possible, since it presents high survival rates, acceptable marginal bone loss, and improvements in variables related to satisfaction and quality of life. CLINICAL SIGNIFICANCE: Based on the results of this study, the use of a minimum 4 and 6 mini implants can be considered a satisfactory treatment option for rehabilitation of the mandibular and maxillary arches respectively with a complete overdenture.

Root-supported overdentures associated with temporary immediate prostheses--a case-report.

Complete denture fabrication can be a treatment challenge for many dentists, especially when the patient has remaining teeth. So, planning for use of clinical alternatives to improve the treatment prognosis and to enable greater comfort to patient must be considered. This case report describes the use of remaining roots to aid in the stability, support and retention of root-supported overdentures. Thus, immediate prostheses were planned for temporary rehabilitation prior to definitive overdentures. The aim of this study was to demonstrate the planning of root-supported overdentures attached with a ball system for retention associated with immediate dentures between the periods of preparation to fabrication of the definitive overdentures. The proposed treatment met the patient's needs such as being able to carry on normal activities during the sequencing of procedures to be performed over a period of time. The treatment had longevity with patient's knowledge about the necessity of oral hygiene and periodic controls.

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 (3.75x10.0 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.

A proposta deste estudo foi avaliar a influência da altura da coroa de implantes de hexágono externo sobre o deslocamento e distribuição de tensões para o sistema implante/osso utilizando o método de elementos finitos. Os softwares InVesalius e Rhinoceros 4.0 foram usados para gerar o modelo de osso por meio de uma tomografia computadorizada. Cada modelo foi composto de um bloco ósseo com um implante (3.75 x 10.0 mm) com conexão de hexágono externo e coroas de 10 mm, 12.5mm e 15 mm em altura. Uma carga axial de 200 N e oblíqua (45°) de 100 N foram aplicadas. Os modelos foram resolvidos pelo software NeiNastram 9.0 e Femap 10.0 para obtenção dos resultados que foram visualizados por meio de mapas de deslocamento, de von Mises (coroa/implante) e tensão máxima principal (osso). A altura da coroa sob carga axial não influenciou o deslocamento e concentração de tensões, enquanto que a carga oblíqua aumentou a ação destes fatores. A maior concentração de tensões foi observada no pescoço do parafuso do implante no lado oposto à aplicação de carga. Esta tensão foi transferida para a interface coroa/plataforma/interface óssea. Os resultados deste estudo sugerem que o aumento da coroa amplia a concentração de tensões no tecido ósseo/implante, aumentando o deslocamento no tecido ósseo, principalmente sob carga oblíqua.

Implantes tipo plataforma modificada: revisión de literatura / Implants modified platform type: literature review

El propósito de esta revisión fue explorar el concepto de Plataforma modificada en Implantología y su desempeño clínico. La definición de plataforma modificada será considerada junto con una revisión de literatura pertinente, con la finalidad de proveer directrices basadas en evidencias científicas. Fueron utilizadas las siguientes bases de datos: Pubmed, Biblioteca Cochrane e ISI. Los criterios de inclusión fueron: artículos clínicos, de laboratorio y de revisión sobre el tema, en lengua inglesa. Fueron seleccionados 40 artículos, utilizando los descriptores "plataforma switching dental implants", "platform shifting and dental implants", "expanded platform dental implant". De acuerdo con esta revisión, los implantes plataforma modificada presentan una tasa de remodelación ósea ( media < 1mm) más favorable que los implantes convencionales. Este hecho parece ser resultante de un conjunto de factores biológicos y mecánicos. El concepto de plataforma modificada tiene importante relevancia en el área estética

The purpose of this revision was to explore the concept of Platform Switching in implantology and its acting in the clinical practice. The concept of platform switching will be considered together with a revision of pertinent literature, with the purpose of providing guidelines based on scientific evidences. The following databases were used: Pubmed, Library Cochrane and ISI in the last 17 years. The inclusion approaches were: clinical articles, laboratorials and of revision on the topic, in English language. 41 articles were selected, using the describers "platform switching dental implants", "platform shifting and dental implants", "expanded platform dental implant". In accordance with this revision, implant them platform switching they present a rate of more favorable bony remodeling that you implant them conventional. This fact seems to be resulting of a group of biological factors and mechanics. The concept of platform switching has important relevance in the aesthetic area