Effect of different impression methods and ceramic materials on adaptation of inlays / Efeito de diferentes métodos de moldagem e materiais cerâmicos na adaptação de inlays

Objective: The aim of this study was to evaluate the internal and marginal adaptation of inlays fabricated from different types of impressions (conventional and digital) and different ceramics (feldspathic and lithium disilicate). Material and Methods: Forty premolars were prepared for all-ceramic inlay restoration and assigned to 4 groups (n=10), according to the impression method (conventional with addition silicone and digital impression) and ceramic type (lithium disilicate and feldspathic ceramic blocks). For each type of impression, 10 inlays were milled from lithium disilicate blocks and the other 10 from feldspathic ceramic blocks in a CAD-CAM facility. The internal adaptation was analyzed by the replica technique. The marginal fit was analyzed under a stereo microscope by directly measuring the gap formed between the inlay and the tooth in the proximal and occlusal regions. Results: The marginal or internal adaptations were not affected by type of impression (conventional = digital impression), irrespective of the ceramic type. Only the internal adaptation was affected by the material type, i.e., feldspathic ceramic had lower values than lithium dissilicate ceramic, when considering the digital impression. Conclusion: The conventional and digital impressions promoted similar marginal and internal adaptation for feldspathic and disilicate ceramic inlays. For the digital impression the feldspathic inlays showed better internal adaptation than lithium dissilicate inlays. (AU)

Objetivo: O objetivo deste estudo foi avaliar a adaptação interna e marginal de inlays confeccionadas a partir de diferentes tipos de moldagens (convencional e digital) e diferentes materiais cerâmicos (feldspática e dissilicato de lítio). Materiais e Métodos: Quarenta pré-molares foram preparados para inlay totalmente cerâmica e distribuídos em 4 grupos (n = 10) segundo o método de moldagem (convencional com silicone de adição e moldagem digital) e tipo cerâmica (dissilicato de lítio e blocos de cerâmica feldspática). Para cada tipo de moldagem, 10 inlays foram confeccionadas a partir de pastilhas de dissilicato de lítio e as outras 10 de blocos de cerâmica feldspática, por meio do sistema CAD-CAM. A adaptação interna foi analisada pela técnica da réplica. O ajuste marginal foi analisado com estéreo microscópio medindo diretamente o espaço entre a inlay e o dente nas regiões proximal e oclusal. Resultados: As adaptações marginais e internas não foram afetadas pelo tipo de moldagem (convencional = impressão digital), independentemente do tipo de cerâmica. Somente a adaptação interna foi afetada pelo material, sendo que a cerâmica feldspática apresentou menores valores que a cerâmica de dissilicato, considerando a moldagem digital. Conclusão: As moldagens convencional e digital promoveram adaptação marginal e interna semelhante de inlays de cerâmica feldspática e dissilicato testadas. Para moldagem digital, a cerâmica feldspática mostrou melhor adaptação interna do que a dissilicato de lítio (AU)

The Impact of Conical and Nonconical Abutments on Bacterial Infiltration at the Implant-Abutment Interface.

This study evaluated the in vitro bacterial microleakage at the implant-abutment interface of three prosthetic connections: external (EH) and internal hexagon (IH) and taper connection (TC: solid [ST], taper with internal hexagon [IT], and short taper [OT]). Escherichia coli (E coli) and Streptococcus sanguinis (S sanguinus) were inoculated in the apical portion of the abutment screw, which was immersed in sterile brain-heart infusion broth for 14 days. There were no differences between the percentages of bacterial infiltration for IH (9.09%), ST (21.74%), IT (22.73%), and OT (11.11%). EH did not present viable bacteria. There were no significant differences in the counts of connections inoculated and not infiltrated by E coli or S sanguinis nor in those infiltrated by both bacteria (one-way analysis of variance, P < .05). Except for EH, all implant designs and abutments showed bacteria that were capable of surviving and causing infiltration.

Morphology and bacterial colonisation of tooth/ceramic restoration interface after different cement excess removal techniques.

OBJECTIVES: To evaluate the influence of different protocols for resin cement removal during cementation on biofilm formation. METHODS: Twenty-eight ceramic blocks, which were injected under pressure, were placed over enamel blocks obtained from freshly extracted bovine incisors. The ceramic blocks were cemented to the enamel blocks using a dual-cured resin cement and the excess resin was removed according to the experimental group: TS: Teflon spatula; BR: brush; BR+: brush and polishing; SB+: scalpel blade and polishing. After autoclaving, the samples were colonised by incubation in a sucrose broth suspension standardised with Streptococcus mutans in microaerophilic stove. Specimens were quantitatively analysed for bacterial adherence at the adhesive interface using confocal laser scanning microscopy and counting the colony forming units, and qualitatively analysed using SEM. The roughness (Ra/Rz/RSm) was also analysed. Data were analysed by 1-way ANOVA and Tukey's test (5%). RESULTS: The roughness values ranged from 0.96 to 1.69 µm for Ra (p>0.05), from 11.59 to 22.80 µm for Rz (p=0.02<0.05) and from 293.2 to 534.3 µm for RSm (p=0.00). Bacterial adhesion varied between 1,974,000 and 2,814,000 CFU/ml (p=0.00). Biofilm mean thickness ranged from 0.477 and 0.556 µm (p>0.05), whilst the biovolume values were between 0.388 and 0.547 µm(3)/µm(2) (p=0.04). Lower values for roughness, bacterial adhesion, biofilm thickness and biovolume were found with BR, whilst TS presented the highest values for most of the parameters. SEM images confirmed the quantitative values. CONCLUSIONS: The restoration margin morphology and interface roughness affects bacterial accumulation. The brush technique promoted less bacterial colonisation at the adhesive interface than did the other removal methods. CLINICAL SIGNIFICANCE: The brush technique seems to be a good option for removing the excess resin cement after adhesive cementation in clinical practice, as indicated by its better results with lower bacterial colonisation.