The role of welding techniques in the biomechanical behavior of implant-supported prostheses.

This in vitro study investigated the role of welding techniques of implant-supported prostheses in the 2D and 3D marginal misfits of prosthetic frameworks, strain induced on the mini abutment, and detorque of prosthetic screws. The correlations between the analyzed variables were also investigated. Frameworks were cast in commercially pure titanium (cp-Ti). A marginal misfit of 200µm was simulated in the working models (control group) (n=20). The 2D marginal misfit was analyzed according to the single-screw test protocol using a precision optical microscope. The 3D marginal misfit was performed by X-ray microtomography. Strain gauge analysis was performed to investigate the strain induced on the mini abutment. A digital torque meter was used for analysis of the detorque and the mean value was calculated for each framework. Afterwards, the frameworks were divided into two experimental groups (n=10): Laser (L) and TIG (T). The welding techniques were performed according to the following parameters: L (390V/9ms); T (36A/60ms). The L and T groups were reevaluated according to the marginal misfit, strain, and detorque. The results were submitted to one-way ANOVA followed by Tukey's HSD test and Person correlation analysis (α=0.05). Welding techniques statistically reduced the 2D and 3D marginal misfits of prosthetic frameworks (p<0.001), the strain induced on the mini abutment replicas (p=0.006), and improved the screw torque maintenance (p<0.001). Similar behavior was noted between L and T groups for all dependent variables (p>0.05). Positive correlations were observed between 2D and 3D marginal misfit reading methods (r=0.943, p<0.0001) and between misfit and strain (2D r=0.844, p<0.0001 and 3D r=0.864, p<0.0001). Negative correlation was observed between misfit and detorque (2D r=-0.823, p=0.003 and 3D r=-0.811, p=0.005). In conclusion, the welding techniques improved the biomechanical behavior of the implant-supported system. TIG can be an acceptable and affordable technique to reduce the misfit of 3-unit Ti frameworks.

Biofilm formation on complete denture liners

AIM: To clinically evaluate biofilm growth on 4 liners in complete denture base surfaces of 20 geriatric patients. MATERIAL AND METHODS: Patients received new complete maxillary dentures prepared with 4 chambers (10x10x2 mm) in the tissue surface of acrylic denture base. Each of the 4 chambers was randomly filled with the following denture liners: Eversoft (M1); Kooliner (M2); GC Reline Extra Soft (M3); Elite Soft Relining (M4). Patients were randomly separated into 2 treatment groups: T1- sanitization with soft brush and dentifrice; T2- similar to T1 with daily immersion in cleansing chemical solution (Ortoform). Patients had 8 follow-up sessions over a 3-month period. The internal denture surface was stained with a dental plaque dye at each of the follow-up visits. Standardized photographs were taken, and biofilm growth was scored. Data were tabulated and submitted to Analysis of Variance. Means were compared by Tukey (p<0.05) and T tests. RESULTS: Kooliner (M2) means were significantly different from the others for both groups T1 and T2. Treatment 1 promoted higher biofilm growth scores than treatment 2. The highest score after treatment 1 was Kooliner (M2) and the lowest was Elite Soft Relining (M4). As for treatment 2, Eversoft (M1) was statistically different from Elite Soft Relining (M4). Again, Kooliner (M2) presented the highest score and Elite Soft Relining (M4) the lowest. Kooliner (M2) was statistically different from both GC Reline Extra Soft (M3) and Elite Soft Relining (M4). CONCLUSION: Of the materials and treatments studied, the best clinical selection for lower biofilm growth scores would be Elite Soft Relining (M4) with treatment 2.

Influence of chemical and mechanical polishing on water sorption and solubility of denture base acrylic resins

Este estudo avaliou a influência dos métodos de polimento na absorção de água e solubilidade da resina acrílica para base de prótese. Foram confeccionadas 80 amostras, divididas nos seguintes grupos: Clássico (CL), e QC 20 (QC) — polimerização por banho de água aquecida; Acron MC (AC), e Onda Cryl (ON) — polimerização por microondas; e submetidas ao polimento mecânico (PM) — pasta de pedra pomes, branco de Espanha, escova macia e cone de feltro em torno de bancada; ou polimento químico (PQ) — monômero específico em polidora química. O primeiro processo de dessecação foi seguido de armazenagem em água destilada a 37 ± 1ºC por 1 h, 1 dia, 1, 2, 3 e 4 semanas. Ao término de cada período, foi realizada mensuração da absorção de água. Após a quarta semana, um segundo processo de dessecação foi realizado para o cálculo da solubilidade. Os resultados foram submetidos à análise de variância e teste de Tukey (p<0,05). As médias de absorção de água (%) e solubilidade (%), respectivamente, foram: CL-PM: 1,92 e 0,02; CL-PQ: 1,98 e 0,52; QC-PM: 2,31 e -0,05; QC-PQ: 2,32 e 0,25; AC-PM: 2,45 e -0,07; AC-PQ: 2,43 e 0,41; ON-PM: 2,32 e -0,06; ON-PQ: 2,34 e 0,27. O polimento mecânico promoveu menor solubilidade para as resinas acrílicas; inicialmente, os valores de absorção de água foram maiores para as amostras polidas quimicamente, entretanto, após 4 semanas todos os grupos apresentaram-se semelhantes entre si.

Influence of chemical and mechanical polishing on water sorption and solubility of denture base acrylic resins.

Influence of polishing methods on water sorption and solubility of denture base acrylic resins was studied. Eighty samples were divided into groups: Classico (CL), and QC 20 (QC) - hot water bath cured; Acron MC (AC), and Onda Cryl (ON) - microwave cured; and submitted to mechanical polishing (MP) - pumice slurry, chalk powder, soft brush and felt cone in a bench vise; or chemical polishing (CP) - heated monomer fluid in a chemical polisher. The first desiccation process was followed by storage in distilled water at 37 +/- 1 degrees C for 1 h, 1 day, 1, 2, 3 and 4 weeks. Concluding each period, water sorption was measured. After the fourth week, a second desiccation process was done to calculate solubility. Data were submitted to analysis of variance, followed by Tukey test (p

Processo de fundição do titânio e de suas ligas na área de reabilitação oral / Casting procedure of titanium and its alloys in oral rehabilitation area

O titânio e suas ligas tem despertado grande interesse na Odontologia e, em especial, na área de prótese dental, considerando suas propriedades favoráveis como alta resistência mecânica e baixo peso específico. A sua técnica de fundição é pouco disseminada e difere dos métodos convencionais. Assim, o objetivo desse trabalho é descrever o processo de fundição do titânio comercialmente puro e ligas dele derivadas, destacando as principais características físicas e mecânicas desse metal e sua perspectiva para aplicação em próteses convencionais (prótese parcial fixa e prótese parcial removível) e próteses sobre implantes

Fit of cast commercially pure titanium and Ti-6Al-4V alloy crowns before and after marginal refinement by electrical discharge machining.

STATEMENT OF PROBLEM: Titanium has been suggested as a replacement for alloys currently used in single-tooth restorations and fixed partial dentures. However, difficulties in casting have resulted in incomplete margins and discrepancies in marginal fit. PURPOSE: This study evaluated and compared the marginal fit of crowns fabricated from a commercially pure titanium (CP Ti) and from Ti-6Al-4V alloy with crowns fabricated from a Pd-Ag alloy that served as a control. Evaluations were performed before and after marginal refinement by electrical discharge machining (EDM). MATERIAL AND METHODS: Forty-five bovine teeth were prepared to receive complete cast crowns. Stone and copper-plated dies were obtained from impressions. Fifteen crowns were cast with each alloy (CP Ti, Ti-6Al-4V, and Pd-Ag). Marginal fit measurements (in micrometers) were recorded at 4 reference points on each casting with a traveling microscope. Marginal refinement with EDM was conducted on the titanium-based crowns, and measurements were repeated. Data were analyzed with the Kruskal-Wallis test, paired t test, and independent t test at a 1% probability level. RESULTS: The Kruskal-Wallis test showed significant differences among mean values of marginal fit for the as-cast CP Ti crowns (mean [SD], 83.9 [26.1] microm) and the other groups: Ti-6Al-4V (50.8 [17.2] microm) and Pd-Ag (45.2 [10.4] microm). After EDM marginal refinement, significant differences were detected among the Ti-6Al-4V crowns (24.5 [10.9] microm) and the other 2 groups: CP Ti (50.6 [20.0] microm) and Pd-Ag (not modified by EDM). Paired t test results indicated that marginal refinement with EDM effectively improved the fit of CP Ti crowns (from 83.9 to 50.6 microm) and Ti-6Al-4V crowns (from 50.8 to 24.5 microm). However, the difference in improvement between the two groups was not significant by t test. CONCLUSION: Within the limitations of this study, despite the superior results for Ti-6Al-4V, both groups of titanium-based crowns had clinically acceptable marginal fits. After EDM marginal refinement, the fit of cast CP Ti and Ti-6Al-4V crowns improved significantly.

Técnica de Nóbilo para o tratamento do bruxismo: caso clínico / Nóbilo's technique for bruxism treatment: a clinical case

A maior parte dos indivíduos realizam atividade de bruximo em alguma fase de suas vidas, em graus variados. Os tecidos do sistema mastigatório geralmente se adaptam a esse comportamento, com desgaste dental e remodelaçäo dos componentes articulares. A tendência de ranger e desgastar os dentes, em associaçäo com a raiva ou agressäo, tem sido reconhecida desde os tempos bíblicos, levando a inúmeros estudos, tanto em seres humanos como em animais. Muitos termos têm sido usados para designar o desgaste näo-funcional dos dentes, gerando interpretaçöes confusas quanto à etiologia, prevalência e formas de tratamentos. Embora tenha sido estudada extensivamente uma possível relaçäo causa e efeito, existem ainda espaços vazios no conhecimento atual. Entretanto, a agressäo reprimida, a tensäo emocional e a frustraçäo säo citados continuamente como os mais importantes na etiologia do bruxismo. Muito mais controvertido ainda é o papel da oclusäo na etiologia e tratamento do bruxismo. Desta forma podemos dizer que tanto o Bruxismo como as contraçöes isométricas da musculatura do Sistema Estomatognático, têm como causa primária os conflitos psiquicos oriundos das emoçöes reprimidas, que näo tiveram possibilidades de exteriorizar-se. Os autores apresentaram o procedimento clínico e laboratorial utilizando as Pistas Deslizantes de Nóbilo na terapia interceptadora dos pacientes com bruxismo acentuado