Kátia Rodrigues Reis

In vitro wear resistance of three types of polymethyl methacrylate denture teeth

The wear resistance of denture teeth is important to the longevity of removable prostheses of edentulous patients. The ability of denture teeth to maintain a stable occlusal relationship over time may be influenced by this property. The purpose of this in vitro study was to evaluate the wear resistance of polymethyl methacrylate (PMMA) denture teeth based on their chemical composition when opposed by a ceramic antagonist. The maxillary canines (n=10) of 3 PMMA denture teeth (Trubyte Biotone, cross-linked PMMA; Trilux, highly cross-linked IPN (interpenetrating polymer network)-PMMA; and Vivodent, highly cross-linked PMMA) were secured in an in vitro 2-body wear-testing apparatus that produced sliding contact of the specimens (4.5 cycles/s, sliding distance of 20 mm, under 37°C running water) against glazed or airborne particle abraded ceramic. Wear resistance was measured as height loss (mm) under 300 g (sliding force) after 100,000 cycles, using a digital measuring microscope. Mean values were analyzed by 2-way ANOVA and Tukeys test (α=0.05). The wear of Trubyte Biotone (0.93 ± 0.14 mm) was significantly higher than that of both other types of teeth tested against abraded ceramic (p<0.05). The Vivodent tooth (0.64 ± 0.17 mm) exhibited the best wear resistance among the denture teeth tested against airborne particle abraded ceramic. There were no statistically significant differences (p>0.05) in wear among the 3 denture teeth evaluated against glazed ceramic. Trilux and Vivodent teeth tested against either glazed or airborne particle abraded ceramic did not differ significantly from each other (p<0.05). All teeth showed significantly more wear against airborne particle abraded ceramic than against glazed ceramic (p<0.05). In conclusion, the three types of PMMA denture teeth presented significantly different wear resistance against the abraded ceramic. The high-strength PMMA denture teeth were more wear-resistant than the conventional PMMA denture tooth.

Influence of different catilever extensions and glass or polyamaramid reinforcement fibers on fracture strength of implant-supported temporary

In long-term oral rehabilitation treatments, resistance of provisional crowns is a very important factor, especially in cases of an extensive edentulous distal space. The aim of this laboratorial study was to evaluate an acrylic resin cantilever-type prosthesis regarding the flexural strength of its in-balance portion as a function of its extension variation and reinforcement by two types of fibers (glass and polyaramid), considering that literature is not conclusive on this subject. Each specimen was composed by 3 total crowns at its mesial portion, each one attached to an implant component (abutment), while the distal portion (cantilever) had two crowns. Each specimen was constructed by injecting acrylic resin into a two-part silicone matrix placed on a metallic base. In each specimen, the crowns were fabricated with either acrylic resin (control group) or acrylic resin reinforced by glass (Fibrante, Angelus) or polyaramide (Kevlar 49, Du Pont) fibers. Compression load was applied on the cantilever, in a point located 7, 14 or 21 mm from the distal surface of the nearest crown with abutment, to simulate different extensions. The specimen was fixed on the metallic base and the force was applied until fracture in a universal test machine. Each one of the 9 sub-groups was composed by 10 specimens. Flexural strength means (in kgf) for the distances of 7, 14 and 21 mm were, respectively, 28.07, 8.27 and 6.39 for control group, 31.89, 9.18 and 5.16 for Kevlar 49 and 30.90, 9.31 and 6.86 for Fibrante. Data analysis ANOVA showed statistically significant difference (p<0.05) only regarding cantilever extension. Tukeys test detected significantly higher flexural strength for the 7 mm-distance, followed by 14 and 21 mm. Fracture was complete only on specimens of non-reinforced groups.

Ressonância magnética nos desarranjos internos da ATM: sensibilidade e especificidade

OBJECTIVE: the aim of this paper is to review the literature concerning the reliability and applicability of magnetic resonance imaging (MRI) in the diagnosis of temporomandibular joint (TMJ) internal disorders. METHODS: articles that have used TMJ from cadavers to compare MRI findings with anatomic findings, as well as some papers that have compared clinical findings with MRI findings were evaluated. According to the findings identified on these articles, the MRI sensitivity and specificity properties for the TMJ internal disorders diagnosis were calculated. Then, the MRI reliability and applicability for the TMJ internal disorders diagnosis were discussed. RESULTS: 90% of sensitivity and 88% of specificity were found. CONCLUSION: the TMJ MRI presents good sensitivity and specificity for the TMJ internal disorders diagnosis. But dentists should beware and request this exam only in cases where MRI will be essential to the treatment planning.

Análise do método de Willis na determinação da dimensão vertical de oclusão

O presente trabalho avaliou o metodo de Willis na determinacao da dimensao vertical em 39 individuos dentados, com idade entre 19 e 45 anos. Uma forte correlacao foi observada entre o terco medio da face e a DVR (r = 0,73, p = 0,000), e entre o terco medio e a DVO (r = 0,74, p = 0,000). Nao houve diferenca significante entre o terco medio e a DVO (p = 0,11); contudo foram observadas diferencas entre o terco medio e a DVR (p = 0,000), e entre a DVO e a DVR (p = 0,000). A analise estatistica indicou que o metodo de Willis foi adequado na determinacao da dimensao vertical de oclusao.