The effect of mechanical and chemo-mechanical temporary cement cleaning methods on shear bond strength with self-adhesive resin cement (an in-vitro study).

BACKGROUND: Adhesive tooth-colored restorations are strongly dependent on the substrate surface cleanliness to allow intimate contact between resin cement and dentin surface, so several methods were adopted for the total cleaning of temporary cement residues. This study aimed to assess the effect of mechanical and chemo-mechanical cleaning methods of temporary cement on the immediate shear bond strength of self-adhesive resin cement to dentin surface. METHODS: Forty freshly extracted lower first premolars were cut to expose a flat dentin surface. Discs of temporary crown composite resin material were constructed and cemented to the flat dentin surface using resin-based and non-eugenol temporary cement then stored at room temperature in distilled water. Dividing of samples into two groups according to the method of temporary cement cleaning. Group I (n = 20) mechanical cleaning using the rotary instrument, and group II (n = 20) chemo-mechanical cleaning using chlorhexidine-containing scrub. CAD/CAM reinforced Composite discs were bonded to the dentin surface using self-adhesive composite resin cement, then measurement of shear bond strength was done using a universal testing machine. Further analysis of failure mode after debonding was performed by Scanning electron microscope. RESULTS: No statistically significant difference was found between the mean shear bond strength of the two cleaning methods (P-value = 0.636). Regardless of the cleaning method, the group cemented with resin-based temporary cement showed statistically significantly higher mean shear bond strength than non-eugenol temporary cement (P-value = 0.048). CONCLUSION: Both cleaning methods (mechanical and chemo-mechanical) applied in this study were effective in cleaning temporary cement remnants from the dentin substrate surface with statistically significant differences between results of shear bond strength with significantly higher values recorded with resin-based temporary cement.

Fracture resistance of primary molars restored with endocrowns versus zirconia crowns (an in vitro study) / Resistência à fratura de molares decíduos restaurados com endocrowns versus coras de zircônia (um estudo in vitro)

Objective: This study aimed to assess the fracture resistance of primary molars restored with endocrowns compared to prefabricated zirconia crowns. Material and Methods: Twelve sound, defect-free primary second molars were selected and divided into two groups: group I included 6 molars restored with zirconia crowns, while group II included 6 teeth restored with endocrowns. For both groups access cavity was prepared for the teeth to open pulp chamber. Fracture resistance of both groups was tested using a universal testing machine. Results: Zirconia crown showed statistically significantly higher mean fracture resistance than Endocrown (P-value = 0.001, Effect size = 2.72). Conclusion: Pulpotomized primary molars restored with Zirconia crowns showed significantly higher mean fracture resistance compared to primary molars restored with endocrowns, meanwhile both restorations have shown higher mean fracture resistance than the maximum biting force in children. (AU)

Objetivo: Este estudo teve como objetivo avaliar a resistência à fratura de molares decíduos restaurados com endocrowns em comparação com coroas de zircônia pré-fabricadas. Material e Métodos: Doze segundos molares decíduos hígidos e livres de defeitos foram selecionados e divididos em dois grupos: o grupo l incluiu 6 molares restaurados com coroas de zircônia, enquanto o grupo ll incluiu 6 dentes restaurados com edocrowns. Para ambos os grupos, foi preparada uma cavidade de acesso à câmara pulpar. A resistência à fratura de ambos os grupos foi testada em uma máquina de ensaio universal. Resultados: A coroa de zircônia apresentou resistência média à fratura estatisticamente significativa maior do que endocrown (p=0,001, Tamanho do efeito = 2,72). Conclusão: Molares decíduos pulpotomizados restaurados com coroas de zircônia apresentam resistência média à fratura significativamente maior em comparação aos molares decíduos restaurados com endocrowns, entretanto, ambas as restaurações mostraram maior média à fratura do que a força máxima de mordida em crianças (AU)