Fit of single tooth zirconia copings: comparison between various manufacturing processes.

STATEMENT OF PROBLEM: Various CAD/CAM processes are commercially available to manufacture zirconia copings. Comparative data on their performance in terms of fit are needed. PURPOSE: The purpose of this in vitro study was to compare the internal and marginal fit of single tooth zirconia copings manufactured with a CAD/CAM process (Procera; Nobel Biocare) and a mechanized manufacturing process (Ceramill; Amann Girrbach). MATERIAL AND METHODS: Abutments (n=20) prepared in vivo for ceramic crowns served as a template for manufacturing both Procera and Ceramill zirconia copings. Copings were manufactured and cemented (Clearfil Esthetic Cement; Kuraray) on epoxy replicas of stone cast abutments. Specimens were sectioned. Nine measurements were performed for each coping. Over- and under-extended margins were evaluated. Comparisons between the 2 processes were performed with a generalized linear mixed model (α=.05). RESULTS: Internal gap values between Procera and Ceramill groups were not significantly different (P=.13). The mean marginal gap (SD) for Procera copings (51(50) µm) was significantly smaller than for Ceramill (81(66) µm) (P<.005). The percentages of over- and under-extended margins were 43% and 57% for Procera respectively, and 71% and 29% for Ceramill. CONCLUSIONS: Within the limitations of this in vitro study, the marginal fit of Procera copings was significantly better than that of Ceramill copings. Furthermore, Procera copings showed a smaller percentage of over-extended margins than did Ceramill copings.

A comparison of acrylic and multilithic teeth bond strengths to acrylic denture base material.

AIM: Debonding of denture teeth from the denture base can be frustrating for both the clinician as well as his or her patients. The wear resistance of composite denture teeth has been well investigated since their introduction, but there have been few studies about the bonding of these teeth to acrylic denture base resins. The aim of this study was to compare the bond strengths of two brands of acrylic and one brand of multilithic denture teeth to acrylic denture base material. METHODS AND MATERIALS: In this experimental-laboratory study, three types of denture teeth--Yaghoot, Super Brilian, and Major--were used. After grinding the glossy ridge lap surfaces, the teeth were mounted on two sides of triangular-shaped wax models. Then the wax elimination and resin processing laboratory procedures were carried out as is done with the fabrication of a complete denture. Each of the specimens was tested using a universal testing machine with a cross head speed of 5 mm/min at an angle of 130 degrees to the long axis of the teeth. The data were analyzed using one-way ANOVA and Chi-square tests. RESULTS: The mean bond strength in the Yaghoot group was 717.43+/-293.59 N while in the Super Brilian group it was 578.40+/-395.38 and in the Major group, 547.95+/-296.75N. However, there was no significant difference between the three groups (p=0.194). CONCLUSION: Although the mean bond strength in the multilithic group was higher than in the other groups, no significant difference was found between the three groups. There was no significant difference between the three groups with regard to the prevalence and type of fracture site. CLINICAL SIGNIFICANCE: The bonding strength of multilithic denture teeth to denture base resins was found to be comparable to, and even slightly higher than, acrylic conventional denture teeth, making them a promising choice for clinicians in the fabrication of removable dentures.

Adhesion of Streptococcus mutans NCTC 10449 to artificial teeth: an in vitro study.

STATEMENT OF PROBLEM: Plaque on dentures may foster the occurrence of denture stomatitis and periodontal diseases in gingival tissues adjacent to partial dentures. Thus, it is beneficial for dental materials to have a low susceptibility to plaque adhesion. PURPOSE: The purpose of this study was to evaluate the susceptibility of commonly used artificial teeth to adhesion of the oral bacterium Streptococcus mutans. MATERIAL AND METHODS: Fifteen specimens each of 12 different artificial teeth were prepared by cutting standardized slabs from the buccal tooth surfaces. After normalizing size (round specimens, diameter of 5 mm, 2 mm thick), polishing (grinding paper, grain 1000 and 4000; universal polishing paste), and assessing surface roughness with a profilometric contact surface measurement device, specimens were incubated with Streptococcus mutans NCTC 10449 suspension for 2.5 hours at 37 degrees C. A veneering composite resin (Sinfony) was used as a control. Adherent bacteria were quantified using a fluorometric assay (Resazurin reduction); relative fluorescence intensity correlates linearly with the number of adherent bacteria. Medians and 25%/75% percentiles were calculated, and statistical analysis was performed using the Kruskal-Wallis test and the Bonferroni-adjusted Mann-Whitney U test. RESULTS: The highest values, indicating high adhesion of streptococci, were observed for filler-supplemented teeth with median relative fluorescence values ranging from 6356 to 18,770. Similar values were recorded for a double cross-linked resin tooth (6444). Significantly lowest values, ranging from 1173 to 3974, were found for unfilled PMMA acrylic resin teeth and acrylic resin teeth with an interpenetrating network (1436). CONCLUSIONS: Within the limitations of this study, it can be concluded that the adhesion of Streptococcus mutans to unfilled PMMA teeth and teeth with an interpenetrating network is lower than adhesion to artificial teeth supplemented with fillers or double cross-linked acrylic resin teeth.

Determinaçäo da largura dos dentes ântero-superiores na seleçäo de dentes artificiais / Determination of the upper anterior teeth width in artificial teeth selection

Estudou-se em 120 indivíduos, metade dentados e os demais portadores de dentaduras completas, entre outras características, a largura do nariz em repouso e sua correlaçäo com a distância intercaninos, medida de cúspide a cúspide, em linha reta. Uma técnica de projeçäo da largura nasal (PANC) foi comparada com a técnica de projeçäo das comissuras labiais, para escolha da largura dos dentes. Analisou-se ainda a regiäo de incidência da linha intercuspídea canina sobre a papila incisiva, nos dentados. Finalmente, foram analisadas duas tabelas de modelos de dentes artificiais encontradas no comércio. Com base nos resultados, dentro das condiçöes estabelecidas, concluiu-se o seguinte: näo é adequado se estabelecer correlaçäo entre a largura do nariz em repouso e a distância intercaninos, medida de cúspide a cúspide, em linha reta; confirmou-s e o método PANC como mais adequado que o de projeçäo das comissuras labiais; existem dentados nos quais a largura dos seis dentes ântero-superiores é maior que a medida máxima dos artificiais disponíveis no mercado; a linha intercuspídea canina superior incidiu sobre a papila incisiva, no seu terço posterior, em 63,666 por cento dos dentados; há forte evidência de que, nas próteses totais superiores, os dentes foram escolhidos com largura menor que o adequado, para o sexo masculino