Fragment reattachment or direct restoration? An in vitro study.

BACKGROUND/AIM: The fracture resistance of teeth subjected to fragment reattachment may improve when the technique is performed using intermediate materials. The aim of this study was to evaluate the influence of different bonding materials, including pre-heated composite resin, on the fracture resistance of teeth subjected to the reattachment technique compared with a direct composite resin restoration. MATERIALS AND METHODS: After simulating a tooth fracture, each specimen was reattached by using one of the following intermediate materials (n = 15): G0, negative control (sound teeth); G1, Z100; G2, pre-heated Z100; G3, Filtek Z350 XT; G4, pre-heated Filtek Z350 XT; G5, Filtek Z350 XT Flow; and G6, RelyX Veneer. In G7, direct class IV restorations were performed using Filtek Z350 XT composite resin. The fracture resistance was evaluated using a universal testing machine under a compressive load of 1 mm/min. One-way analysis of variance (ANOVA) and the post hoc Tukey test (5%) were conducted. RESULTS: G0 showed the highest fracture resistance, and this was statistically different from the other experimental groups (p < .05) except for G2 and G4, in which the fragments were bonded using pre-heated resins. A statistically significant difference was found between groups G1 and G6 (one-way ANOVA, p = .04). For G1 and G2, a significant difference was found between bonding with and without pre-heating (p < .05). This difference was not observed in G3 and G4 (p > .05). No statistically significant difference was found between the reattached and directly restored groups (t-test, p = .53). CONCLUSIONS: The tooth reattachment technique using pre-heated composite resin showed fracture resistance values similar to those of the sound tooth group. No difference was found between the fragment reattachment and direct composite resin techniques.

Preload evaluation of different screws in external hexagon joint.

PURPOSE: This study compared the maintenance of tightening torque in different retention screw types of implant-supported crowns. MATERIALS AND METHODS: Twelve metallic crowns in UCLA abutments cast with cobalt-chromium alloy were attached to external hexagon osseointegrated implants with different retention screws: group A: titanium alloy retention screw; group B: gold alloy retention screw with gold coating; group C: titanium alloy retention screw with diamond-like carbon film coating; and group D: titanium alloy retention screw with aluminum titanium nitride coating. Three detorque measurements were obtained after torque insertion in each replica. Data were evaluated by analysis of variance (ANOVA), Tukey's test (P < 0.05), and t test (P < 0.05). RESULTS: Detorque value reduced in all groups (P < 0.05). Group A retained the highest percentage of torque in comparison with the other groups (P < 0.05). Groups B and D retained the lowest percentage of torque without statistically significant difference between them (P > 0.05). CONCLUSIONS: All screw types exhibited reduction in the detorque value. The titanium screw maintained the highest percentage of torque whereas the gold-coated screw and the titanium screw with aluminum titanium nitride coating retained the lowest percentage.

Simplified prosthetic rehabilitation of a patient with partial finger amputation after a firearm injury.

OBJECTIVE: This study reports a clinical case of rehabilitation of a patient who had her left little finger amputated at the mesial phalanx because of a gunshot wound. The finger prosthesis was custom- made using a silicone. CASE DESCRIPTION: This study presents a clinical case of a female patient who had her left little finger amputated at the mesial phalanx because of a gunshot wound in 2016. The patient was attended at a reference center in maxillofacial rehabilitation in the city of Brasilia, Distrito Federal, Brazil, for the manufacture of a finger prosthesis. After molding, a finger waxing was obtained using the right little finger as a template. The waxing was later adjusted on the plaster model of the affected stump. The prosthesis was manufactured with silicone and intrinsically stained with a makeup powder. A water-based adhesive and a ring were used to generate a slight compression so that the prosthesis was retained on the stump. OUTCOMES: The rehabilitation showed satisfactory levels of stability, retention, and aesthetics, and it was usable and clinically acceptable, as observed in a follow-up appointment in February 2020. CONCLUSIONS: The complete or partial reestablishment of functions performed by important structures, such as the fingers, is essential to increase the quality of life of individuals, improving their performance of daily activities. In addition, reporting on this public health problem allows scientific advancement in the area.

Implant platform switching: biomechanical approach using two-dimensional finite element analysis.

In implant therapy, a peri-implant bone resorption has been noticed mainly in the first year after prosthesis insertion. This bone remodeling can sometimes jeopardize the outcome of the treatment, especially in areas in which short implants are used and also in aesthetic cases. To avoid this occurrence, the use of platform switching (PS) has been used. This study aimed to evaluate the biomechanical concept of PS with relation to stress distribution using two-dimensional finite element analysis. A regular matching diameter connection of abutment-implant (regular platform group [RPG]) and a PS connection (PS group [PSG]) were simulated by 2 two-dimensional finite element models that reproduced a 2-piece implant system with peri-implant bone tissue. A regular implant (prosthetic platform of 4.1 mm) and a wide implant (prosthetic platform of 5.0 mm) were used to represent the RPG and PSG, respectively, in which a regular prosthetic component of 4.1 mm was connected to represent the crown. A load of 100 N was applied on the models using ANSYS software. The RPG spreads the stress over a wider area in the peri-implant bone tissue (159 MPa) and the implant (1610 MPa), whereas the PSG seems to diminish the stress distribution on bone tissue (34 MPa) and implant (649 MPa). Within the limitation of the study, the PS presented better biomechanical behavior in relation to stress distribution on the implant but especially in the bone tissue (80% less). However, in the crown and retention screw, an increase in stress concentration was observed.

An implant-transfer technique without impression material.

Different transfer impression techniques for implant-supported prostheses have been suggested to obtain a working cast. This article describes and illustrates clinical and laboratory prosthodontic procedures to transfer implant positions with splinted transfer copings and without impression material to form a laboratory analog transfer template. With this technique, a preliminary cast is modified to place the analogs according to a corrected position and obtain the master cast. Although this technique does not record adjacent tissues, it is a simple procedure, less time consuming, and easily performed.

Effect of superstructure materials and misfit on stress distribution in a single implant-supported prosthesis: a finite element analysis.

This finite element analysis study evaluated the optimal material combination for the superstructure of single implant-supported prosthesis with different fit patterns. Two models of a two-dimensional finite element analysis were constructed: group A (control), prosthesis presenting precise fit to implant; and group B, prostheses with unilateral angular misfit of 100 microm. Each group was divided into 5 subgroups according to different materials for framework (gold alloy, titanium, and zirconia) and veneering (porcelain and modified composite resin). Evaluation was performed on ANSYS software with 133-N load applied at the opposite side of misfit on the model. The load was applied with a 30-degree angulation and 2-mm off-axis. The presence of unilateral angular misfit (group B) increased the von Mises stresses in the implant (40%) and retention screw (7%) in comparison to group A. The combination of porcelain/titanium and porcelain/zirconia displayed more favorable stress distribution. When gold alloy was used as a framework material, there was no difference in stress values for both veneering materials in all groups. The use of stiffer and softer superstructures materials did not affect the stress distribution and stress values in the supporting tissue. According to the biomechanical point of view, materials with high elasticity modulus are more suitable for the superstructure of implant-supported prosthesis.

Comparison of single-standing or connected implants on stress distribution in bone of mandibular overdentures: a two-dimensional finite element analysis.

This study aimed to compare the influence of single-standing or connected implants on stress distribution in bone of mandibular overdentures by means of two-dimensional finite element analysis. Two finite element models were designed using software (ANSYS) for 2 situations: bar-clip (BC) group-model of an edentulous mandible supporting an overdenture over 2 connected implants with BC system, and o'ring (OR) group-model of an edentulous mandible supporting an overdenture over 2 single-standing implants with OR abutments. Axial loads (100 N) were applied on either central (L1) or lateral (L2) regions of the models. Stress distribution was concentrated mostly in the cortical bone surrounding the implants. When comparing the groups, BC (L1, 52.0 MPa and L2, 74.2 MPa) showed lower first principal stress values on supporting tissue than OR (L1, 78.4 MPa and L2, 76.7 MPa). Connected implants with BC attachment were more favorable on stress distribution over peri-implant-supporting tissue for both loading conditions.

A comparison of patient satisfaction between treatment with conventional complete dentures and overdentures in the elderly: a literature review.

BACKGROUND: It has been stated that mandibular overdentures are more satisfactory than conventional dentures, but problems relating to the use of retrospective ratings, lack of control group and sequential provision of treatment may compromise the findings. OBJECTIVE: To establish a comparison between treatment with conventional complete dentures and implant-retained overdentures in elderly patients by conducting a literature review. MATERIALS AND METHODS: A search of English language peer-review literature was completed using Medline up to 2008 focusing on evidence-based research. Randomised clinical trials (RCTs) and longitudinal prospective studies were favoured in the review, using a general hierarchical classification. Articles that did not focus exclusively on the comparison of patient satisfaction between complete dentures and overdentures were excluded from further evaluation. The last search was conducted in February 2008. Key terms included quality of life, patient satisfaction, edentulism, complete denture and overdenture. RESULTS: Among the 90 articles found in the initial search, 27 met the inclusion criteria. This included 18 RCTs and eight prospective and one cohort study. Most of the articles stated superiority of the mandibular implant-retained overdenture therapy over the conventional complete denture regarding patient satisfaction and quality of life. CONCLUSION: Even with implant treatment presenting higher patient satisfaction and improvement of quality of life, it was not possible to establish a direct comparison between the studies due to differences in adopted methodologies.

Prevalence of symptoms of temporomandibular disorders, oral behaviors, anxiety, and depression in Dentistry students during the period of social isolation due to COVID-19.

OBJECTIVE: Temporomandibular dysfunction (TMD), anxiety, and depression are disorders that, due to the current lifestyle, are affecting an increasing portion of the population. Investigating the prevalence of the symptoms of these disorders during the quarantine due to the coronavirus 2019 pandemic (COVID-19) is important to outline clinical strategies for patient care. This study assessed the prevalence of TMD symptoms, anxiety, depression, and oral behaviors and their associations during the social isolation due to COVID-19. METHODOLOGY: Questionnaires were used to assess TMD symptoms in accordance with the Diagnostic Criteria for Temporomandibular Disorders: clinical protocol and assessment instruments, a questionnaire to verify oral behaviors and Hospital Anxiety and Depression Scale to assess symptoms of anxiety and depression in students of dentistry at the Faculty of Health Sciences of the University of Brasília in May 2020. Qualitative data were subjected to descriptive statistics and chi-squared analysis (p<0.05). The relationship between quantitative and qualitative data was evaluated using Spearman's rho correlation (p<0.05). RESULTS: There was a high prevalence of TMD symptoms, anxiety, and depression in the participants, resulting in association between gender and anxiety symptoms (p=0.029). There was a positive correlation between oral behaviors and TMD symptoms (r=0.364; p<0.001), between oral behaviors and anxiety symptoms (r=0.312; p=0.001), and between oral behaviors and symptoms of depression (r=0.216; p=0.021). CONCLUSION: Social isolation due to the COVID-19 pandemic has an impact on the prevalence of TMD symptoms, anxiety, and depression.

Biomechanics studies in dentistry: bioengineering applied in oral implantology.

The application of engineering knowledge in dentistry has helped the understanding of biomechanics aspects related to osseointegrated implants. Several techniques have been used to evaluate the biomechanical load on implants comprising the use of photoelastic stress analysis, finite element stress analysis, and strain-gauge analysis. Therefore, the purpose of this study was to describe engineering methods used in dentistry to evaluate the biomechanical behavior of osseointegrated implants. Photoelasticity provides good qualitative information on the overall location and concentration of stresses but produces limited quantitative information. The method serves as an important tool for determining the critical stress points in a material and is often used for determining stress concentration factors in irregular geometries. The application of strain-gauge method on dental implants is based on the use of electrical resistance strain gauges and its associated equipment and provides both in vitro and vivo measurements strains under static and dynamic loads. However, strain-gauge method provides only the data regarding strain at the gauge. Finite element analysis can simulate stress using a computer-created model to calculate stress, strain, and displacement. Such analysis has the advantage of allowing several conditions to be changed easily and allows measurement of stress distribution around implants at optional points that are difficult to examine clinically. All the 3 methodologies can be useful to evaluate biomechanical implant behavior close to the clinical condition but the researcher should have enough knowledge in model fabrication (experimental delineation) and results analysis.

Effect of passive fit absence in the prosthesis/implant/retaining screw system: a two-dimensional finite element analysis.

The misfit between prostheses and implants is a clinical reality, but the level that can be accepted without causing mechanical or biologic problem is not well defined. This study investigates the effect of different levels of unilateral angular misfit prostheses in the prosthesis/implant/retaining screw system and in the surrounding bone using finite element analysis. Four models of a two-dimensional finite element were constructed: group 1 (control), prosthesis that fit the implant; groups 2 to 4, prostheses with unilateral angular misfit of 50, 100, and 200 mum, respectively. A load of 133 N was applied with a 30-degree angulation and off-axis at 2 mm from the long axis of the implant at the opposite direction of misfit on the models. Taking into account the increase of the angular misfit, the stress maps showed a gradual increase of prosthesis stress and uniform stress in the implant and trabecular bone. Concerning the displacement, an inclination of the system due to loading and misfit was observed. The decrease of the unilateral contact between prosthesis and implant leads to the displacement of the entire system, and distribution and magnitude alterations of the stress also occurred.

Finite element analysis to compare complete denture and implant-retained overdentures with different attachment systems.

This finite element analysis compared stress distribution on complete dentures and implant-retained overdentures with different attachment systems. Four models of edentulous mandible were constructed: group A (control), complete denture; group B, overdenture retained by 2 splinted implants with bar-clip system; group C, overdenture retained by 2 unsplinted implants with o'ring system; and group D, overdenture retained by 2 splinted implants with bar-clip and 2 distally placed o'ring system. Evaluation was performed on Ansys software, with 100-N vertical load applied on central incisive teeth. The lowest maximum general stress value (in megapascal) was observed in group A (64.305) followed by groups C (119.006), D (258.650), and B (349.873). The same trend occurred in supporting tissues with the highest stress value for cortical bone. Unsplinted implants associated with the o'ring attachment system showed the lowest maximum stress values among all overdenture groups. Furthermore, o'ring system also improved stress distribution when associated with bar-clip system.

Comparison between complete denture and implant-retained overdenture: effect of different mucosa thickness and resiliency on stress distribution.

BACKGROUND: The effect of different mucosa characteristics on stress distribution of complete dentures and overdentures remains unknown. OBJECTIVE: The aim of this study was to evaluate the effect of different mucosa thickness and resiliency on the stress distribution of complete dentures and implant-retained overdentures using a two-dimensional finite element analysis. MATERIAL AND METHODS: Representative models of the edentulous mandible were constructed on AutoCAD software according to the groups' characteristics. In group CD, a model of the edentulous mandible supporting a complete denture was obtained while in group IO, a model of edentulous mandible supporting an overdenture over two unsplinted implants with an o' ring system was constructed. In each group, mucosa assumed three characteristics of thickness (1, 3 and 5 mm) corresponding to the resiliencies hard, resilient and soft respectively. Evaluation was performed on Ansys software with 100N vertical load applied on central incisor teeth. The principal stress was used as analysis criteria. RESULTS: Group IO showed higher stress values than group CD regardless of mucosal thickness and resiliency. Stress decreased at the supporting tissues in both groups as the thickness and resiliency of mucosa increased. In relation to the supporting tissues, cortical bone showed the highest stress values. CONCLUSION: It was concluded that the use of an attachment system increases stress values and the thickness and resiliency of mucosa influence more on these values.

A comparison of profilometer and AutoCAD software techniques in evaluation of implant angulation in vitro.

PURPOSE: The aim of this study was to compare 2 different methods of assessment of implants at different inclinations (90 degrees and 65 degrees)--with a profilometer and AutoCAD software. MATERIALS AND METHODS: Impressions (n = 5) of a metal matrix containing 2 implants, 1 at 90 degrees to the surface and 1 at 65 degrees to the surface, were obtained with square impression copings joined together with dental floss splinting covered with autopolymerizing acrylic resin, an open custom tray, and vinyl polysiloxane impression material. Measurement of the angles (in degrees) of the implant analogs were assessed by the same blinded operator with a profilometer and through analysis of digitized images by AutoCAD software. For each implant analog, 3 readings were performed with each method. The results were subjected to a nonparametric Kruskal-Wallis test, with P < or = .05 considered significant. RESULTS: For implants perpendicular to the horizontal surface of the specimen (90 degrees), there were no significant differences between the mean measurements obtained with the profilometer (90.04 degrees) and AutoCAD (89.95 degrees; P = .9142). In the analyses of the angled implants at 65 degrees in relation to the horizontal surface of the specimen, significant differences were observed (P = .0472) between the mean readings with the profilometer (65.73 degrees) and AutoCAD (66.25 degrees). CONCLUSIONS: The degrees of accuracy of implant angulation recording vary among the techniques available and may vary depending on the angle of the implant. Further investigation is needed to determine the best test conditions and the best measuring technique for determination of the angle of the implant in vitro.

Effect of different mucosa thickness and resiliency on stress distribution of implant-retained overdentures-2D FEA.

The study aimed to evaluate the effect of different mucosa thickness and resiliency on stress distribution of implant-retained overdentures using a two-dimensional finite element analysis. Models were used in order to simulate two situations. In group A, model represented an edentulous mandible supporting an overdenture retained by two-splinted-implants connected with bar-clip system while in group B, model simulated an edentulous mandible supporting an overdenture retained by two-splinted-implants connected with bar-clip system associated with two-distally placed o'ring system. In each group, mucosa assumed three characteristics of thickness (1, 3 and 5 mm) in the resiliencies: hard, resilient and soft, respectively. Evaluation was performed on Ansys software. Group A showed higher stress values regardless of the mucosa characteristics. Overall, stress decreased at the supporting tissues as mucosa thickness and resiliency increased. Regarding supporting tissues, cortical bone showed the highest stress values. The use of bar-clip attachment system with distally placed o'ring attachment design optimized the stress distribution.

Prosthetic transfer impression accuracy evaluation for osseointegrated implants.

PURPOSE: : The objective of this study was to evaluate and compare 3 impression techniques for osseointegrated implant transfer procedures. MATERIALS AND METHODS: : (1) Group Splinted with Acrylic Resin (SAR), impression with square copings splinted with prefabricated autopolymerizing acrylic resin bar; (2) Group Splinted with Light-Curing Resin (SLR), impression with square copings splinted with prefabricated light-curing composite resin bar; (3). Group Independent Air-abraded (IAA), impression with independent square coping aluminum oxide air-abraded. Impression procedures were performed with polyether material, and the data obtained was compared with a control group. These were characterized by metal matrix (MM) measurement values of the implants inclination positions at 90 and 65 degrees in relation to the matrix surface. Readings of analogs and implant inclinations were assessed randomly through graphic computation AutoCAD software. Experimental groups angular deviation with MM were submitted to analysis of variance and means were compared through Tukey's test (P < 0.05). RESULTS: : There was no statistical significant difference between SAR and SLR experimental groups and MM for vertical and angulated implants. Group IAA presented a statistically significant difference for angulated implants. CONCLUSION: : It was concluded within the limitations of this study, that SAR and SLR produced more accurate casts than IAA technique, which presented inferior results.

Accuracy of impression techniques for implants. Part 1--Influence of transfer copings surface abrasion.

PURPOSE: This study evaluated the influence of surface abrasion of transfer copings to obtain a precise master cast for a partially edentulous restoration with different inclinations. MATERIALS AND METHODS: Replicas (N = 30) of a metal matrix (control group) containing two implants at 90 degrees and 65 degrees in relation to the benchtop were obtained using a polyether impression material and three impression techniques: square impression copings splint with dental floss and autopolymerizing acrylic resin (TRS), square impression copings abraded with aluminum oxide (TA), and square impression copings abraded with aluminum oxide and adhesive-coated (TAA). The replicas obtained in type V stone were digitalized, and the images were exported to AutoCAD software to perform the readings of possible degree alterations in implant inclinations. The results were submitted to analysis of variance (ANOVA) and Tukey test (alpha < 0.05). RESULTS: Comparing the techniques with regard to the 90 degrees implant inclination, no statistical difference was observed between the three techniques and the control group. Analyzing the three techniques with regard to the 65 degrees implant inclination, no significant difference was seen between technique TA and the control group. CONCLUSIONS: Technique TA presented more accurate master casts than TRS and TAA techniques. The angulated implant (65 degrees ) tended to generate more imprecise master casts than implants perpendicular to the surface.

Abordagem multidisciplinar no tratamento de incisivo lateral com fratura oblíqua e lesão periapical: relato de caso clínico / Multidisciplinary approach in the treatment of lateral incisor with oblique fracture and periapical injury: clinical case report

Casos de fraturas dentárias oblíquas muitas vezes possuem um prognóstico desfavorável, geralmente com indicação da extração do elemento dental. O presente artigo visou relatar o tratamento do caso clínico de um paciente do sexo masculino, 12 anos, que compareceu à Unidade de Saúde Bucal do Hospital Universitário de Brasília com encaminhamento de extração do dente 12, apresentando fratura oblíqua que se estendia subgengivalmente na face vestibular. O trauma havia ocorrido há três anos e o paciente havia sido submetido a diversas intervenções endodônticas, apresentando no momento da consulta inicial por nossa equipe uma lesão periapical extensa. Após a realização da anamnese, exame clínico e radiográfico, foi adotada uma abordagem multidisciplinar conservadora com a manutenção do dente e a realização da enucleação da lesão periapical por meio de intervenção cirúrgica e posterior reabilitação. Em uma mesma sessão, foi realizada a obturação do conduto com cone de guta percha e cimento sealer 26 e a cirurgia parendodôntica juntamente com a apicoplastia. Uma semana após a intervenção cirúrgica foi realizada restauração classe IV com resina composta baseada no enceramento dos modelos de diagnóstico montados em articulador. Com base em uma avaliação criteriosa e multidisciplinar, foi possível adotar uma abordagem conservadora no caso em questão, com a manutenção e reabilitação de um dente permanente em um paciente jovem, evitando a indicação de exodontia(AU)

Cases of oblique dental fractures often have an unfavorable prognosis, usually with the indication of extraction of the dental element. The present article aimed to report the treatment of the clinical case of a 12-year-old male patient, who attended the Oral Health Unit of the Hospital Universitário de Brasília with a referral for extraction of tooth 7, presenting an oblique fracture that extended subgingivally on the labial surface. The trauma had occurred three years ago and the patient had undergone several endodontic interventions, presenting an extensive periapical lesion at the time of the initial consultation by our team. After anamnesis, clinical and radiographic examination, a conservative multidisciplinar approach was adopted with the maintenance of the tooth and the enucleation of the periapical lesion through surgical intervention and subsequente rehabilitation. In the same session, the conduit was filled with gutta-percha cone and sealer cement 26 and parendodontic surgery was performed together with apicoplasty. One week after the surgical intervention, class IV restoration was performed with composite resin based on the waxing of the diagnostic models mounted on an articulator. Based on a careful and multidisciplinary evaluation, it was possible to adopt a conservative approach in the case in question, with the maintenance and rehabilitation of a permanent tooth in a young patient, avoiding the indication of extraction(AU)

Tratamiento de caries relacionada a radiación: una revisión de literatura

Resumen Caries relacionada a radiación es una complicación tardía frecuente de la radioterapia de cáncer de cabeza y cuello, ocasionada por efectos directos e indirectos de la radioterapia. El objetivo del presente trabajo es realizar una revisión y analizar literatura sobre el manejo de caries relacionada a radiación, materiales usados, fallas en el tratamiento y protocolo con mejores resultados; tres revisores independientes realizaron una búsqueda en diferentes bases de datos: PubMed, Lilacs y Web Of Science, determinando criterios de inclusión y exclusión para la selección. Estudios clínicos y revisiones indicaron que los materiales más usados son cemento ionómero de vidrio convencional, cemento ionómero de vidrio modificado con resina y resina compuesta con aplicaciones de flúor. Son necesarios más estudios para definir el mejor tratamiento que incluya técnica de preparación de la cavidad y material restaurador con mejores resultados. Se recomienda realizar estudios comparando diferentes sistemas adhesivos, concentraciones de flúor y restauraciones en dentina radicular.

Resumo Cárie relacionada à radiação é uma complicação tardia frequente da radioterapia de câncer de cabeça e pescoço, ocasionada por efeitos diretos e indiretos da radioterapia. O objetivo do presente trabalho é realizar uma revisão e analisar literatura sobre o tratamento de cárie relacionada à radiação, materiais usados, falhas no tratamento e manejo com melhores resultados; foi realizada uma busca em diferentes bases de dados: PubMed, Lilacs e Web Of Science, por três revisores independentes, usando critérios de inclusão e exclusão. Estudos clínicos e revisões de literatura indicam que os materiais mais usados são cimento de ionômero de vidro convencional, cimento de ionômero de vidro modificado com resina e resina composta com aplicações de flúor. Mais estudos são necessários para definir o melhor tratamento que inclua a técnica de preparo cavitário e material restaurador com melhores resultados. Recomenda-se a realização de estudos comparando diferentes sistemas adesivos, concentrações de flúor e restaurações em dentina radicular.

Abstract Radiation-related caries are a frequent late complication caused by the direct and indirect effects of head and neck cancer radiotherapy. This study aimed to review and analyze the literature on managing radiation-related caries, restorative materials, treatment failures, and treatment protocols. A search was conducted in Pubmed, Lilacs, and Web of Science by three independent reviewers, and inclusion and exclusion criteria were used for paper selection. According to clinical studies and literature reviews, the most used materials are conventional glass-ionomer cement, resin-modified glass-ionomer cement, and composite resin with fluoride applications. More studies are needed to determine the best treatment, including cavity preparation technique and restorative material with better results. We suggest conducting studies comparing various adhesive systems, fluoride concentrations, and root dentin restorations.

Platform switching: biomechanical evaluation using three-dimensional finite element analysis.

PURPOSE: The objective of this study was to evaluate, using three-dimensional finite element analysis (3D FEA), the stress distribution in peri-implant bone tissue, implants, and prosthetic components of implant-supported single crowns with the use of the platform-switching concept. MATERIALS AND METHODS: Three 3D finite element models were created to replicate an external-hexagonal implant system with peri-implant bone tissue in which three different implant-abutment configurations were represented. In the regular platform (RP) group, a regular 4.1-mm-diameter abutment (UCLA) was connected to regular 4.1-mm-diameter implant. The platform-switching (PS) group was simulated by the connection of a wide implant (5.0 mm diameter) to a regular 4.1-mm-diameter UCLA abutment. In the wide-platform (WP) group, a 5.0-mm-diameter UCLA abutment was connected to a 5.0-mm-diameter implant. An occlusal load of 100 N was applied either axially or obliquely on the models using ANSYS software. RESULTS: Both the increase in implant diameter and the use of platform switching played roles in stress reduction. The PS group presented lower stress values than the RP and WP groups for bone and implant. In the peri-implant area, cortical bone exhibited a higher stress concentration than the trabecular bone in all models and both loading situations. Under oblique loading, higher intensity and greater distribution of stress were observed than under axial loading. Platform switching reduced von Mises (17.5% and 9.3% for axial and oblique loads, respectively), minimum (compressive) (19.4% for axial load and 21.9% for oblique load), and maximum (tensile) principal stress values (46.6% for axial load and 26.7% for oblique load) in the peri-implant bone tissue. CONCLUSION: Platform switching led to improved biomechanical stress distribution in peri-implant bone tissue. Oblique loads resulted in higher stress concentrations than axial loads for all models. Wide-diameter implants had a large influence in reducing stress values in the implant system.