RESUMEN
Background: Many diseases and conditions weaken the strength of tooth making it to fracture. Many cavity designsand materials are used to restore the tooth to bring about the normal function. The present study was done to determine which one of the three class II cavity design offer the best fracture resistance to the teeth when used with different restorative materials. Methods: 165 molars (150 intact and 15 carious) were collected and preserved in hydrogen peroxide. These teeth were divided into five groups and restored with silver amalgam, compomer (Dyract AP) and metal modified ionomer cement (Miracle mix). The restored teeth were subjected to a compressive load using Universal Testing Machine by flat and metallic die. Results: Conventional designs with amalgam restoration seemed to withstand more load when it was imparted through a flat surface (741 kg ±158 SD) compared to the box or slot designs. However, when the load was imparted through a metallic die, the slot design with compomer restoration gave the maximum value (SD) of 472 (±88) kg. When analyzed statistically on the difference in the fracture resistance among the different restoration materials and the different cavity designs, statistically significant values were found between certain combinations. Conclusion: The study concluded that in the case of silver amalgam material, the test conducted by flat surface gives the best strength for the conventional design which is 3% and 23% better than that of box type and slot type respectively. However, when tested with a metallic die, slot type takes 8.3% more load than the conventional type. Among the various restoration materials tested for, amalgam provides more strength followed by compomer and miracle mix.
RESUMEN
Background: Gypsum products are being used for construction of dental prosthesis. Most of the researches done sofar on gypsum materials are on its use as fixed and removable prosthodontics. And although many studies have looked at a multitude of means for altering its properties, relatively less has been explored on examining the abrasion resistance of the gypsum product itself. Objectives: The current study was done to determine the abrasion resistance of three commercially available type IV gypsum products on application of three die-hardeners when abraded with 20gm and 50gm load stylus. Methods:An experimental in vitro study was done in the Dept. of Prosthodontics, UP Dental College & Research Center and the Dept. of Pharmacy, BBD National Institute of Technology & Management, Lucknow. A standardized machined die was fabricated so that the die consisted of 27 vertical ridges of 1mm depth. Three type IV gypsum products viz., Kalrock, Elite Rock and Denstone Plus and three die-hardeners viz., Hartebad die-hardener, Handae die-hardener and Maarc die-hardener were included in the study. 40 samples were prepared from each of the die-stones by pouring into impressions made by using the putty-wash technique. Resultantly, 120 samples were prepared which were let to mature. These 120 samples were divided into 24 groups, each group consisting of 5 samples. They were grouped as uncoated, coated with Hartebad die-hardener, coated with Handae die-hardener and coated with Maarc die-hardener. They were sub-grouped further for abrading under 20gm and 50gm loads by using an abrasion-testing machine. After 10 oscillations, the loss of mass was measured using analytical electronic machine. The different findings were compared by using appropriate statistical analytic tests. Results: The abrasion resistance of type IV gypsum products increased with the application of surface-hardeners irrespective of the load and Elite Rock showed better abrasive resistance while Denstone Plus showed lesser abrasion resistance among all the type IV gypsum products tested. Conclusion: Elite Rock when coated with Hartebad die-hardener showed maximum abrasion resistance irrespective of the load applied.