Marginal Mandibulectomy and Oral Rehabilitation of Xeroderma Pigmentosum Patient.

Xeroderma pigmentosum (XP) may cause tissue deformation in patients who have undergone oral cancer surgery requiring resection of any part of the mandible. Oral rehabilitation is a pivotal factor in the restoration of function and esthetics. The aim of this study was to report a clinical case of successful prosthetic rehabilitation of a 57-year-old woman who presented with marginal mandibulectomy and a significant reduction in maximal mouth opening after treatment for XP. With her reduced opening and considerable loss of structure and tissue, she had difficulty speaking, swallowing, and altered esthetics. The oral rehabilitation was performed with complete maxilla denture and mandible overdenture retained by 2 implants. This case demonstrates that the rehabilitation with mandible overdentures and complete maxilla dentures provide function and esthetic improvement in the mutilated area for XP patients with marginal mandibulectomies.

Preparation of ICD and overdenture in patients with Cushing's Syndrome: five-year follow-up / Preparo de PTI e overdenture em pacientes com Síndrome de Cushing: cinco anos de acompanhamento

The aim of this study is to report a clinical case of a patient with Cushing's syndrome, low self-esteem and need for oral rehabilitation. A 50-year-old female patient with hypercortisolism sought care at School of Dentistry of the Federal University of Minas Gerais. During anamnesis, the patient reported painful symptoms and mobility of the upper and lower teeth. On clinical examination, absence of many teeth were observed, periodontal disease and caries lesions. After discussion of the case, the planning involved the extraction of all teeth, and the preparation of Maxillary Immediate Complete Dentures (ICD's) and Immediate Mandibular Implant-retained Overdenture (IMIO). The treatment proposed allowed the restored aesthetics, phonetics and chewing(AU)

O objetivo desse estudo é relatar um caso clínico de uma paciente com síndrome de Cushing, baixa autoestima e necessidade de reabilitação oral. Paciente do sexo feminino, 50 anos de idade e com hipercortisolismo, procurou atendimento na Faculdade de Odontologia da Universidade Federal de Minas Gerais. Durante a anamnese, a paciente relatou sintomas dolorosos e mobilidade dos dentes superiores e inferiores. No exame clínico, foi observada a ausência de muitos dentes, doença periodontal e lesões cariosas. Após a discussão do caso, o planejamento envolveu a extração de todos os dentes, e o preparo de Prótese Total Imediata maxilar (PTI), e Overdenture Implantorretida Imediata mandibular. O tratamento proposto permitiu que restaurasse a estética, fonética e mastigação(AU)

Qualitative evaluation of immediate rehabilitation: a case report with 5 years of follow-up / Avaliação qualitativa de reabilitação imediata: relato de caso com 5 anos de acompanhamento

Próteses totais imediatas e overdentures mandibulares em carga imediata, são boas alternativas para restaurar a função e a estética. Além disso, proporcionam um fator psicológico positivo, eliminando as consequências emocionais e sociais da perda dos dentes. O objetivo deste estudo foi relatar um caso clínico, com cinco anos de acompanhamento, utilizando parâmetros clínicos e ferramentas qualitativas, para analisar o impacto na qualidade de vida do paciente e no sucesso do tratamento. Este caso clínico foi desenvolvido em um projeto assistencial da Faculdade de Odontologia da Universidade Federal de Minas Gerais, Brasil, que promove a reabilitação oral de pacientes de baixa renda com dentes severamente comprometidos. Paciente do sexo masculino, 57 anos, apresentou-se para tratamento com condição severa de saúde dental e periodontal. O plano de tratamento proposto foi a extração dos dentes remanescentes e confecção de prótese total imediata maxilar e overdenture mandibular, em carga imediata, sobre implantes. O paciente foi acompanhado periodicamente, a cada seis meses, para substituição do o´rings, conforme recomendação do fabricante. Após 5 anos, as próteses foram reembasadas com resina acrílica termopolimerizável e os componentes protéticos da overdenture foram substituídos. Em um acompanhamento qualitativo, a equipe utilizou uma entrevista narrativa, com foco nos impactos do tratamento na qualidade de vida desse paciente. Ele confirmou, em um relato em primeira pessoa, sua satisfação com o tratamento realizado e a melhora nas relações sociais, afetivas e no trabalho, mostrando como a reconquista do sorriso pode transformar a experiência pessoal do indivíduo(AU)

Immediate complete dentures and mandibular immediately loaded overdentures are good alternatives to restore function and aesthetics. Moreover, they provide positive psychological factor, eliminating the emotional and social consequences of tooth loss. The aim of this study was to report a clinical case, with five years of follow-up using clinical parameters and qualitative tools, to analyze the impact on quality of life and the success of treatment. This clinical case was developed in an assistance project of the Dental School of Federal University of Minas Gerais in Brazil, which promotes oral rehabilitation of low-income patients with severely damaged dentitions. A 57-yearold male patient presented for treatment with a severe dental and periodontal health condition. The proposed treatment plan was extraction of the remaining teeth and making maxillary immediate complete denture and mandibular immediately loaded implant-supported overdenture. The patient was monitored periodically, every six months, to replace the polymer ring ball attachment, according to the manufacturer's recommendation. After 5 years, the prostheses were relining with heat-polymerized acrylic resin and overdenture prosthetic components were replaced. In a qualitative follow-up, the team used a narrative interview, focusing on the impacts of treatment in the quality of life of this patient. He confirms, in a firstperson account, his satisfaction with the treatment performed and improvements in social and affective relations and in the work, showing how the reconquest of the smile can transform the personal experience of the individual(AU)

Oral Candidiasis and COVID-19 in Users of Removable Dentures: Is Special Oral Care Needed?

Elderly patients with systemic disorders and immunocompromised patients seem to have a higher risk of developing morbidity from COVID-19. Candida albicans (C. albicans) is a potentially dangerous pathogen for these patients, especially for denture wearers with prosthetic stomatitis who require mechanical ventilation. C. albicans infection, the main candidiasis infection associated with denture wear, can complicate COVID-19 and increase the associated morbidity and mortality. Therefore, early diagnosis of C. albicans infection in COVID-19 patients is important to establish more effective antifungal treatment methods and prophylaxis strategies. Hospitalized COVID-19 patients should undergo an oral examination to assess their oral health, and those with poor oral health should receive the appropriate care and monitoring.

Prótese e implante sobre enxerto alógeno: análise histológica e acompanhamento clínico: radiográfico por 8 anos / Prosthesis and implant on allogenic graft: histological analysis and clinical: radiographic follow-up for 8 years

Este relato de caso clínico tem como objetivo descrever a utilização de osso alógeno na reconstrução de maxila atrófica para posterior reabilitação com prótese fixa metalocerâmica sobre implantes, fazer uma análise histológica do tecido ósseo enxertado e descrever o acompanhamento clínico e radiográfico por 8 anos. Uma paciente de 54 anos, com edentulismo parcial e atrofia moderada-a-severa na maxila, apresentou-se para tratamento demonstrando muito interesse em receber prótese sobre implantes. Após exame clínico e radiográfico, foi realizada montagem dos modelos de estudo em ASA para enceramento diagnóstico e obtenção de um guia multifuncional (tomográfico/ cirúrgico). A tomografia indicou a necessidade de reconstrução óssea maxilar. Procedeuse então à aposição de blocos de osso alógeno para aumento horizontal nas regiões anterior e posterior da maxila. Um dos blocos foi triturado e utilizado para levantamento do assoalho do seio maxilar no lado esquerdo. Dez meses depois, uma nova tomografia foi solicitada, utilizando o mesmo guia inicial, e os implantes instalados, utilizando o guia multifuncional como guia cirúrgico. Neste momento, material ósseo foi coletado na interface osso enxertado/osso nativo com uma broca trefina. Os resultados histológicos demonstraram viabilidade das células ósseas no enxerto, além da presença de vasos sanguíneos. Após o tempo necessário para osseointegração, procedeu-se com tratamento protético. Nenhuma complicação foi relatada até oito anos de controle. A sequência de tratamento proposta forneceu bons resultados estéticos e funcionais. Concluiu-se, então, que o emprego de osso alógeno é uma alternativa viável para a reconstrução de rebordos alveolares severamente reabsorvidos(AU)

This clinical case report aims to describe the use of allogeneic bone in the atrophic maxilla reconstruction for subsequent rehabilitation with a fixed metal-ceramic prosthesis on implants; to perform a histological analysis of the grafted bone tissue; and to describe the clinical and radiographic monitoring for 8 years. A 54-year-old patient, with partial edentulism and moderate-to-severe atrophy in the maxilla showed great interest in receiving implant prostheses. After c linical and radiographic examination, the ASA study models were assembled for diagnostic waxing and a multifunctional guide (tomographic / surgical) was obtained. Tomography indicated the need for maxillary bone reconstruction. Allogeneic bone blocks were then placed for horizontal enlargement in the anterior and posterior regions of the maxilla. One of the blocks was crushed and used to lift the floor of the maxillary sinus on the left side. Ten months later, a new tomography was requested, using the same initial guide, and the implants installed, using the multifunctional guide as a surgical guide. At this time, bone material was collected at the grafted bone / native bone interface with a trephine drill. Histological results demonstrated viability of bone cells in the graft, besides the presence of blood vessels. After the necessary time for osseointegration, a prosthetic treatment was performed. No complications were reported up to eight years of control. The propose treatment sequence provided good aesthetic and functional results. It was concluded, then, that the use of allogeneic bone is a viable alternative for the reconstruction of severely reabsorbed alveolar edges(AU)

Dimensional precision of implant-supported frameworks fabricated by 3D printing.

STATEMENT OF PROBLEM: Selective laser melting (SLM) is a promising additive technology for clinical practice, but data on dimensional precision assessed by marginal fit combined with stress and strain investigations of implant-supported fixed partial dentures (FPDs) are lacking. PURPOSE: The purpose of this in vitro study was to verify whether the SLM additive manufacturing technology provides better dimensional precision for 3-unit FPD frameworks than subtractive manufacturing with soft metal block (SMB) milling and the standard casting technique. MATERIAL AND METHODS: Thirty 3-unit implant-supported FPDs with Co-Cr frameworks were made by the casting, SMB milling, and SLM methods (n=10). The marginal fit between the framework and the implant abutment was evaluated with photoelastic (PH) and strain gauge (SG) models. Stress and strain in the implant-supported system were measured by quantitative PH and SG analyses after prosthetic screw tightening. Data were subjected to the Kruskal-Wallis test, Mann-Whitney U test, and Spearman correlation test (α=.05). RESULTS: The framework manufacturing method affected the marginal fit (P<.001), stress, and strain values (P<.05). The SLM group showed the best mean ±standard deviation marginal fit (µm) (PH model: 8.4 ±3.2; SG model: 6.9 ±2.1) in comparison with SMB milling (PH model: 42.3 ±15.7; SG model: 41.3 ±15.3) and casting (PH model: 43.5 ±27.8; SG model: 41.3 ±24.6) (P<.05). SLM showed lower mean ±standard deviation stress and strain values (60.3 ±11.6 MPa; 91.4 ±11.1 µstrain) than casting (225.5 ±142.8 MPa; 226.95 ±55.4 µstrain) and SMB milling (218.6 ±101.7 MPa; 289.7 ±89.3 µstrain) (P<.05). A positive correlation was observed between fit and stress or strain for all groups (P<.05). CONCLUSIONS: Three-unit FPD frameworks made using the SLM technology showed better dimensional precision than those obtained with the casting or SMB milling methods.

The Influence of Post System Design and Material on the Biomechanical Behavior of Teeth with Little Remaining Coronal Structure.

PURPOSE: To evaluate the influence of different post systems on the biomechanical behavior of teeth with a severe loss of remaining coronal structure. MATERIALS AND METHODS: Fifty standardized bovine teeth (n = 10 per group) were restored with: cast post-and-core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP), or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure patterns (FP) were evaluated. Finite element models evaluated the stress distribution after the application of 100 N. RESULTS: All specimens survived TC. Similar FS was observed among post-containing groups. Groups P-FP and CC presented 100% repairable fractures. The von Mises analysis showed the maximum stresses into the root canal in groups restored with metallic posts. Glass-fiber posts and CC presented the maximum stresses at the load contact point. Glass-fiber groups showed lower stresses in the analysis of maximal contact pressure; CPC led to the highest values of contact pressure. The modified von Mises (mvM) stress in dentin did not show differences among groups. Moreover, mvM values did not reach the dentin fracture limit for any group. CONCLUSIONS: The type of intracanal post had a relevant influence on the biomechanical behavior of teeth with little remaining coronal structure.

Photoelastic and finite element stress analysis reliability for implant-supported system stress investigation

Aim: To compare the reliability between photoelastic and finite element (FE) analyses by evaluating the effect of different marginal misfit levels on the stresses generated on two different implant-supported systems using conventional and short implants. Methods: Two photoelastic models were obtained: model C with two conventional implants (4.1×11 mm); and model S with a conventional and a short implant (5×6 mm). Three-unit CoCr frameworks were fabricated simulating a superior first pre-molar (P) to first molar (M) fixed dental prosthesis. Different levels of misfit (µm) were selected based on the misfit average of 10 frameworks obtained by the single-screw test protocol: low (<20), medium (>20 and <40) and high (>40). Stress levels and distribution were measured by photoelastic analysis. A similar situation of the in vitro assay was designed and simulated by the in silico analysis. Maximum and minimum principal strain were recorded numerically and color-coded for the models. Von Mises Stress was obtained for the metallic components. Results: Photoelasticity and FE analyses showed similar tendency where the increase of misfit generates higher stress levels despite of the implant design. The short implant showed lower von Mises stress values; however, it presented stresses around its full length for the in vitro and in silico analysis. Also, model S showed higher µstrain values for all simulated misfit levels. The type of implant did not affect the stresses around pillar P. Conclusions: Photoelasticity and FEA are reliable methodologies presenting similarity for the investigation of the biomechanical behavior of implant-supported rehabilitations

Overdentures mandibulares sobre implantes imediatos não esplintados, em carga imediata: acompanhamento de 36 meses / Mandibular overdentures on implants immediately implanted, immediate load: 36 month follow-up

Objetivo: Relatar a taxa de sobrevivência de implantes imediatos suportando overdentures mandibulares, em carga imediata, e o índice de sucesso dos tratamentos acompanhados por 36 meses. Métodos: Os implantes foram instalados em um projeto de extensão universitária que se propõe a reabilitar pacientes de baixa renda, com dentição seriamente comprometida. Quarenta e dois pacientes foram selecionados para o estudo. Em três casos, não se alcançou travamento primário compatível com o procedimento de carga imediata sobre implantes. Nesses pacientes, as próteses foram capturadas de forma convencional, após o período de osseointegração. Trinta e nove pacientes receberam o tratamento proposto. Três deles sofreram perda precoce de um dos implantes, todos ainda no primeiro mês após os procedimentos. Os implantes perdidos foram, posteriormente, substituídos e recapturados após três meses. Trinta e seis pacientes completaram o período de osseointegração sem apresentar perdas. Os pacientes passaram, então, a ser avaliados semestralmente, sendo que 25 completaram o estudo. Onze pacientes não compareceram às consultas de reavaliação por motivos variados. Resultados: A taxa de sobrevivência, até o final do período de osseointegração foi de 96,15%, isso é, 3 implantes perdidos em 78 imediatamente carregados. O índice de sucesso dos tratamentos acompanhados por 36 meses foi de 100%, uma vez que não foi observada nenhuma perda adicional de implantes. Conclusão: A reabilitação oral de pacientes que perderam todos os seus dentes mandibulares, por meio de overdentures sobre implantes imediatos não esplintados, em carga imediata, utilizando-se o sistema bola, mostrou-se muito satisfatório, com alta taxa de sobrevivência dos implantes, e alto índice de sucesso dos tratamentos acompanhados por 36 meses. O projeto de extensão tem observado resultados clínicos, tanto estéticos quanto funcionais, altamente satisfatórios, proporcionando uma melhora acentuada na autoestima e na qualidade de vida da população assistida.

Aim:This study aimed to report the survival rate of immediate implants supporting mandibular overdentures, which have been immediately loaded, and the success rate of the treatments followed up for 36 months. Methods: The implants were installed in a university extension project that seeks to rehabilitate low-income patients with seriously compromised dentitions. Forty-two patients were selected for the study. In three cases, the primary stability proved to be incompatible with the immediate loading procedure on implants. Thus, in these cases prostheses were captured conventionally after the period of osseointegration. Thirtynine patients received the proposed treatment. Three of them suffered an early loss of one of the implants, all in the first month after the procedures. The lost implants were replaced and recaptured after three months. Thirty-six patients completed the period of osseointegration without implant loss. The patients were evaluated every six months, and twenty-five patients completed the study. Eleven patients did not take part in the follow-up sessions for various reasons. Results: The survival rate until the end of the period of osseointegration was 96.15%, in other words, within the 78 immediately loaded implants, three were lost. The success rate of treatments followed up for 36 months was 100%, without additional loss of implants. Conclusion: The oral rehabilitation of patients using overdentures on immediate implants with immediate loading, using the ball system, proved to be very satisfactory, with a high survival rate of the implants, and high success rates of treatments followed up for 36 months.

Marginal fit and photoelastic stress analysis of CAD-CAM and overcast 3-unit implant-supported frameworks.

STATEMENT OF PROBLEM: Several studies have shown the superiority of computer-assisted design and computer-assisted manufacturing (CAD-CAM) technology compared with conventional casting. However, an advanced technology exists for casting procedures (the overcasting technique), which may serve as an acceptable and affordable alternative to CAD-CAM technology for fabricating 3-unit implant-supported fixed dental prostheses (FDPs). PURPOSE: The purpose of this in vitro study was to evaluate, using quantitative photoelastic analysis, the effect of the prosthetic framework fabrication method (CAD-CAM and overcasting) on the marginal fit and stress transmitted to implants. The correlation between marginal fit and stress was also investigated. MATERIAL AND METHODS: Three-unit implant-supported FDP frameworks were made using the CAD-CAM (n=10) and overcasting (n=10) methods. The frameworks were waxed to simulate a mandibular first premolar (PM region) to first molar (M region) FDP using overcast mini-abutment cylinders. The wax patterns were overcast (overcast experimental group) or scanned to obtain the frameworks (CAD-CAM control group). All frameworks were fabricated from cobalt-chromium (CoCr) alloy. The marginal fit was analyzed according to the single-screw test protocol, obtaining an average value for each region (M and PM) and each framework. The frameworks were tightened for the photoelastic model with standardized 10-Ncm torque. Stress was measured by quantitative photoelastic analysis. The results were submitted to the Student t test, 2-way ANOVA, and Pearson correlation test (α=.05). RESULTS: The framework fabrication method (FM) and evaluation site (ES; M and PM regions) did not affect the marginal fit values (P=.559 for FM and P=.065 for ES) and stress (P=.685 for FM and P=.468 for ES) in the implant-supported system. Positive correlations between marginal fit and stress were observed (CAD-CAM: r=0.922; P<.001; overcast: r=0.908; P<.001). CONCLUSIONS: CAD-CAM and overcasting methods present similar marginal fit and stress values for 3-unit FDP frameworks. The decreased marginal fit of frameworks induces greater stress in the implant-supported system.

Comparison between all-on-four and all-on-six treatment concepts and framework material on stress distribution in atrophic maxilla: A prototyping guided 3D-FEA study.

We evaluated two treatment concepts for the rehabilitation of moderate atrophic maxilla with dental implants (all-on-four and all-on-six) and the effect of framework material on the stress distribution of implant-support system. A three-dimensional finite element model based on a prototype was built to simulate an entirely edentulous maxilla with moderate sinus pneumatization that was rehabilitated with a full-arch fixed dental prosthesis. Four standard implants were positioned according to the all-on-four concept and four standard implants and two short implants were placed according to the all-on-six concept. Three framework materials were evaluated: cobalt-chrome (CoCr), titanium (Ti) and zirconia (Zr), totalizing six groups. A unilateral oblique force of 150N was applied to the posterior teeth. The von Mises (σVM), maximum (σmax) and minimum (σmin) principal stress and displacements were obtained. All-on-six showed smaller σmin, σVM and σmax values on the cortical bone, implants and trabecular bone, respectively. All-on-four exhibited higher displacement levels. Ti presented the highest stress values on the cortical bone, implants, abutments, prosthetic screws and displacement levels. In conclusion, the all-on-six approach and framework stiffer materials showed the most favorable biomechanical behavior. However, the stress values did not exceed the bone resistance limits for both treatment concepts.

The effect of casting and masticatory simulation on strain and misfit of implant-supported metal frameworks.

The influence of casting and masticatory simulation on marginal misfit and strain in multiple implant-supported prostheses was evaluated. Three-unit screw retained fixed dental prosthesis (FDP) and screw retained full-arch fixed dental prosthesis (FAFDP) frameworks were made using calcinable or overcasted cylinders on conical dental implant abutment. Four groups were obtained according to the cylinder and prosthesis type (n=10). Frameworks were casted in CoCr alloy and subjected to strain gauge analyses and marginal misfit measurements before and after 10(6) mechanical cycles (2 Hz/280 N). Results were submitted to ANOVA, Tukey's HSD and Pearson correlation test (α=0.05). No difference was found on misfit among all groups and times (p>0.05). Overcasted frameworks showed higher strain than the calcinable ones (FDP - Initial p=0.0047; Final p=0.0004; FAFDP - Initial p=0.0476; Final p=0.0115). The masticatory simulation did not influence strain (p>0.05). No correlation was observed between strain and misfit (r=0.24; p>0.05). In conclusion, the marginal misfit value in the overcasted full-arch frameworks was higher than clinical acceptable data. It proved that overcasted method is not an ideal method for full-arch prosthesis. Overcasted frameworks generate higher strain upon the system. The masticatory simulation had no influence on misfit and strain of multiple prostheses.

Fit and Stability of Screw-Retained Implant-Supported Frameworks Under Masticatory Simulation: Influence of Cylinder Type.

PURPOSE: The aim of the study was to evaluate the effect of a prosthetic cylinder and casting on the misfit and loosening torque of screw-retained multiple-unit implant-supported dental prostheses under masticatory simulation. MATERIALS AND METHODS: Screw-retained, three-unit fixed dental prostheses (FDP) and screw-retained full-arch FDP frameworks were waxed using calcinable (plastic cylinders) or overcasted (premachined cast-on cylinders) on the dental implant abutments. The cylinders were cast in Co-Cr alloy to obtain four groups according to cylinder type and prosthesis type (n = 10). The screws were tightened with 20 N/cm (abutment) and 10 N/cm (prosthetic) torque according to the manufacturer's recommendation. After 24 hours, the initial loosening torque was analyzed. The initial misfit measurements were performed according to the Schiffleger test. The screws were retightened, and the specimens were submitted to 10(6) mechanical cycles (2 Hz/280 N). Loosening torque and misfit were reevaluated (final measurements), and data were submitted to ANOVA, Tukey's HSD, and Pearson's correlation tests (α = 0.05). RESULTS: The calcinable three-unit FDP demonstrated greater misfit (initial: 107.53 ± 40.36 µm; final: 99.00 ± 40.85 µm) than did the overcasted three-unit FDP frameworks (initial: 51.50 ± 22.98 µm; final: 44.33 ± 14.14 µm) (initial: p = 0.0005; final: p = 0.0007). No difference was noted between the calcinable and overcasted full-arch FDP frameworks (p > 0.05). Masticatory simulation did not affect the misfit (p > 0.05). The overcasted full-arch FDP presented a lower abutment screw loosening torque (12.05 ± 1.80 N/cm) than did the calcinable ones (14.75 ± 1.72 N/cm) in the final measurement (p = 0.0024). The calcinable groups presented a lower prosthetic screw loosening torque than did the overcasted groups in the final evaluation (p < 0.05). After masticatory simulation, the prosthetic screw loosening torque of the calcinable three-unit FDP decreased (initial: 5.49 ± 1.07 N/cm; final: 3.73 ± 1.15 N/cm; p = 0.0044). Correlation between misfit and loosening was observed only for the prosthetic screws (p < 0.05). CONCLUSIONS: The overcasted components provided a better fit in three-unit FDPs but did not influence the fit of full-arch FDPs. Prosthetic screws of overcasted frameworks presented higher stability, whereas masticatory simulation did not influence misfit but did reduce the prosthetic screw loosening torque of calcinable three-unit FDP frameworks.

Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating.

PURPOSE: The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. MATERIALS AND METHODS: Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 10(6) cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). RESULTS: The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). CONCLUSION: The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.

Influence of the casting technique and dynamic loading on screw detorque and misfit of single unit implant-supported prostheses.

OBJECTIVE: This study aimed to evaluate the influence of the casting procedure and cyclic loading of prosthetic frameworks on detorque of prosthetic screws and marginal misfit of single unit implant-supported prostheses. MATERIALS AND METHODS: Twenty specimens were obtained, each one consisting of a set of an implant (external hexagon 3.75 × 13 mm - Branemark type), a prosthetic abutment (entirely calcinable or overcasted UCLA) and a prosthetic screw. After the specimens were obtained, the prosthetic screws were tightened with 30 Ncm torque and released 24 h later in order to evaluate initial detorque. The screws were retightened and marginal gaps were assessed. All specimens were submitted to 10(6) loading cycles, performed with 2 Hz frequency and 130 N load. The specimens were re-evaluated for marginal misfit and detorque after the mechanical loading (final marginal misfit/final detorque). The results were submitted to analysis of variance for repeated measurements, followed by Tukey HSD test (α = 0.05). RESULTS: No statistically significant differences were found on detorque values of the prosthetics screws for all groups and intervals evaluated (p = 0.8922). The entirely calcinable abutments showed higher initial marginal misfit compared to the overcasted ones (p = 0.0438). There was no statistically significant difference on marginal misfit before and after mechanical loading for both groups (p > 0.05). CONCLUSIONS: It can be concluded that the overcasted abutments showed lower misfit values when compared to the entirely casted abutments. No difference was observed on detorque values of prosthetic screws. After mechanical loading there was no difference on marginal misfit and detorque between the groups.