Evaluating the effect of different combination of impression and pouring materials on marginal and internal adaptation of zirconia crowns / Evaluación del efecto de diferentes combinaciones de materiales de impresión y vertido en la adaptación marginal e interna de las coronas de circonio

Purpose: Two important factors in dental prosthesis are making an accurate impression and producing a suitable cast which represents the exact relationship between prepared tooth and oral structures. This study, aimed to investigate the effects of different combinations of impression and pouring materials on marginal and internal adaptation of premolar zirconia crowns. Material and Methods: Forty maxillary premolars were prepared considering round shoulder finish line. The impressions were made either by additional (Panasil) or condensation (Speedex) silicon, and poured by two different types of gypsum materials (Siladent or GC gypsum) (N=10). Zirconia crowns were fabricated using a CAD-CAM system. The crowns were cemented, and the samples were cut in bucco-lingual direction. Marginal and internal gaps were measured by stereomicroscope (×25). Results: The mean marginal gaps for Pansil-Siladent, Panasil-GC, Speedex-Siladent, and Speedex-GC were 141 µm, 143 µm, 131 µm, and 137 µm respectively. The internal gaps were 334 µm, 292 µm, 278 µm, and 257 µm respectively. The independent T-Student test showed no significant differences in average marginal or internal gap among various impression and gypsum materials or their interactions (p>0.05). Two-way ANOVA test showed no significant differences in maximum marginal or internal gap among various impression and gypsum materials and their interactions (p>0.05). Conclusion: The present study revealed no statistically significant difference in marginal/internal gap among crowns prepared using different combinations of impression-pouring materials evaluated.

Introducción: Dos factores importantes en la prótesis dental son hacer una impresión precisa y la producción de un modelo adecuado que represente la relación exacta entre el diente preparado y las estructuras orales. Este estudio, tuvo como objetivo investigar los efectos de diferentes combinaciones de materiales de impresión y vertido sobre la adaptación marginal e interna de coronas de zirconio premolar. Material y Métodos: Se prepararon cuarenta premolares maxilares considerando la línea de meta del hombro redondo. Las impresiones se realizaron con silicio adicional (Panasil) o de condensación (Speedex) y se vertieron con dos tipos diferentes de materiales de yeso (yeso Siladent o GC) (N = 10). Las coronas de zirconio se fabricaron utilizando el sistema CAD-CAM. Las coronas se cementaron y las muestras se cortaron en dirección buco-lingual. La brecha marginal e interna se midió con estereomicroscopio (×25). Resultados: Las brechas marginales medias para Pansil-Siladent, Panasil-GC, Speedex-Siladent y Speedex-GC fueron de 141µm, 143µm, 131µm y 137µm, respectivamente. Las brechas internas fueron 334µm, 292µm, 278µm y 257µm, respectivamente. La prueba de T-Student independiente no mostró diferencias significativas en la brecha marginal o interna promedio entre varios materiales de impresión y yeso o sus interacciones (p>0.05). La prueba ANOVA bidireccional no mostró diferencias significativas en el espacio marginal o interno máximo entre varios materiales de yeso y de impresión y sus interacciones (p>0.05). Conclusión: El presente estudio no reveló diferencias estadísticamente significativas en la brecha marginal/interna entre las coronas preparadas con diferentes combinaciones de materiales de impresión y vertido evaluados.

Inflammatory response of canine gingiva to a chemical retraction agent placed at different time intervals.

BACKGROUND: Exposure of the gingival sulcus while controlling hemorrhage is prerequisites for maximizing treatment outcomes of cervical carious lesions and for obtaining quality impressions for the fabrication of indirect restorations with cervical finish lines. Gingival retraction cords saturated with different chemical agents are widely used for this purpose. The aim of this study was to investigate and compare the inflammatory potential of 15.5%ferric sulfate on connective tissue when placed at different times. MATERIALS AND METHODS: All procedures were performed on three dogs under general anesthesia. Retraction cords saturated with a 15.5% ferric sulfate solution were placed into the gingival sulcus and evaluated after 3 min and 10 min of exposure to the chemical agent. Excisional biopsies of the exposed gingival tissue were then obtained at intervals of 1 h, 24 h, and 7 days. For all specimens, histology evaluation was performed using light microscopy. Data collected from the microscopic images of all tissue specimens were analyzed by using the Wilcoxon Signed Rank and Kruskal-Wallis Tests. P value less than 0.05 was considered as significant. RESULTS: Histopathologic examination of the biopsied gingival tissue revealed that the ferric sulfate solution caused significant tissue changes at the beginning of both the 3-min and 10-min gingival exposure time (P > 0.05). However, the tissue returned to a normal histological appearance by the end of day 7 in all cases (P > 0.05). CONCLUSION: The results of this study revealed that the biologic effects of 15.5% ferric sulfate solution are clinically acceptable and reliable when gingival exposure times of 3 min and 10 min are used for gingival retraction.