Clinical and laboratory evaluation of two different types of the post system in restoring obstructed primary anterior teeth

The aim of the present study was to evaluate the clinical and laboratory behaviors of carbon fiber cone posts versus ceramic posts in primary anterior teeth. Clinical follow-up showed that there were no differences between the two groups, concerning the stability and retention. Radiographic follow-up showed that there was no evidence of post or root fracture at the follow-up periods. Laboratory evaluation showed that there were no statistically significant differences in the mean retentive and compressive values of the two tested post systems. Visual examination of the mode of fracture of the specimens showed that in each of the two groups, there were two types of failure Cohesive failure and Adhesive failure. From the present study, it can be concluded that the prefabricated non-metallic posts can be successfully used in restoring badly destructed primary anterior teeth under normal occlusion. The technique of application was easy but time consuming for the two types of posts, also the ceramic posts gave satisfactory esthetic results contrary to the carbon fiber posts

Laboratory evaluation of new shock absorbent material for mouth guards

This study evaluated the physicomechanical properties of photopolymerized urethane diacrylate "Lite Line" as a new mouth guard material compared with heat cured silicone rubber "Molloplast-B" as a commercial product used to fabricate mouth guards. The tests chosen were those that measured tensile strength, elongation percent modulus of elasticity, energy absorption, tear strength, surface hardness and abrasion resistance of both materials as they were considered the properties of greatest importance to the function of a mouth protector. The appropriate standardized test procedures, which were established by the American Society for Testing and Materials [ASTM] were followed in this study. From the results of this study it was concluded that, the photopolymerized urethane diacrylate Lite Line showed higher mean value of tensile strength, elastic modulus and surface hardness with the lowest percent of elongation. Lite Line had better shock absorbing properties compared to Molloplast-B, so maximum protection can be achieved by the use of Lite Line for fabrication of mouth guards. There were no significant differences between the Lite Line and Molloplast-B in the tear strength values. Surface roughness mean values showed significant differences between the two tested materials before and after abrasion resistance test. Molloplast-B appeared with smoother surface than Lite Line following abrasion test as shown in SEM photomicrographs. In general, the physicomechanical properties of the tested materials were within the accepted range of variation for a mouth guard material

Effect of a gypsum hardener on the surface quality of stones casts obtained from alginate and silicone rubber base impression materials

This article was conducted to study the effect of Epoxy resin [Araldite] as a hardening agent on the surface quality of commonly used dental stone die material [Moldano] as regards compatibility, reproduction of fine details, surface hardness and surface morphology of stone casts obtained from alginate [CA 37] and silicone rubber base [xantopren and Optosil] impression materials. Twenty stone casts were prepared against each type of I. M. These casts were classified as following: Group I: [Control group] consisted of 5 casts were prepared according to manufacturers instructions without additive. w/p ratio 0.3.- Group II[a] :Consisted of 5 casts which were constructed by adding 2.5% by weight epoxy resin to the mixing water just before mixing with powder. Group II[b]: 5 casts were prepared by adding 5% by weight epoxy resin to the mixing water. Group II[c]: 5 casts were prepared by adding 10% by weight epoxy resin to the mixing water. Multifactorial experiments were carried out on the different groups and evaluated according to the A.D.A. specification No. 25 for gypsum products

study of compressive strength and fluoride release from light-cured and auto-cured glass ionomer cement liners

This study attempted to evaluate one type of light-cured glass ionomer cement liner [Vitra-bond] compared with conventional auto-cured type [Ketac-bond] through the study of compressive strength at different periods of time [1 hour, 24 hours, and 1 week following mixing] and the measurement of fluoride released from them in artificial saliva every 24 hours for 30 days were investigated. From the present study, it is concluded that the compressive strength values for both light and auto-cured glass ionomer liners tested increased with time. There was no significant differences between them in the 1 hour compressive strength values, while highly significant differences were noted after 24 hours and 1 week. In general, the strength of Vitra-bond was greater than that of Ketac-bond at the different periods of measurements. Fluoride release patterns were similar for all glass-ionomer cements tested, i.e. a large initial release was followed by a rapid decline in the amount released with some fluctuation within the observation period [30 days]. Vitra-bond showed the highest mean values of fluoride release, while Ketac-bond showed the lowest values over the test period

Effect of thermocycling on some properties of conventional and high impact strength denture base materials

This article was conducted to examine and compare the effect of thermocycling on some important properties of two types of denture base materials, which were conventional and high impact strength resins. High impact strength resin was prepared by dissolving different proportion of butadiene-styrene rubber [BSR] in MMA monomer, the prepared monomer was then polymerized with ordinary PMMA by conventional means. So, graft copolymers were obtained. Three groups were prepared according to the concentration of BSR in MMA, i.e. 10%, 20% and 30% by weight. The test specimens of each group were classified into three subgroups depending on the degree of thermocycling, i.e. 500, 1000 and 1500 thermal cycles, respectively, between 60C and 5C, with immersion time 30 seconds per cycle. In addition, one group of uncycled samples was tested [control group]. Multifactorial experiments were carried out on the different groups and evaluated with respect to impact strength, flexural strength, young's modulus and tensile tooth-base bond strength. From the results obtained, it could be concluded that both impact and flexural strength of high impact strength resin are superior to the conventional heat-cured acrylic resin, while the young's modulus values for the two types are considered within the clinical and technical limits of use as denture base materials. Thermocycling used in this study did not affect the impact, transverse, young's modulus and tensile tooth-base bond strength values of high impact strength resin, while a significant effect was reported for conventional heat- cured acrylic resin. The tooth-base bond strength of high impact strength resin is inferior to heat-cured resin. Further investigations are required to increase the bond strength by mechanical or chemical means of retention

effect of heat used as a secondary cure upon the physico-mechanical properties of inlay composite resin

The purpose of this study was to evaluate one type of commercially available photocured composite resin inlay [Estilux posterior CVS] through the study of some important physicomechanical properties. These properties, including compressive strength, diametral tensile strength, surface hardness, surface roughness and degree of cure, were measured for the tested material both with and without heat treatment

Laboratory evaluation of molloplast-B used for resilient layer dentures

The application of [Molloplast-B] which is a heat-cured silicone base material used for resilient layer dentures was evaluated. Its bond strength to both heat and cold cured polymethyl methacrylate resins was tested through tensile and shear bond strength tests. The effect of water immersion on this bond strength after two days, one month and three months was studied, also SEM study for the nature of surface interface between the material and both heat and cold PMMA resins at different stages of measurements was carried on. The results of this investigation showed both clinical and technical satisfactory bond strength between the material and the different dentures bases used in the study, while dramatic reduction of bond strength values was observed especially after three months immersion in water due to absorption of water by the resilient material resulting in "adhesive failure". The absorbed water had its effect through: direct percolation into the bond site and through changing the viscoelastic properties of the [Molloplast-B] itself. These findings were supported by the results obtained from the scanning electron microscopic study