Color stability of composite, ceromer, and ormocer after accelerated aging

The aim of this study was to determine the color stability of 3 modern esthetic restorative materials after accelerated aging. The materials studied were TPH spectrum [Hybrid composite], Tetric cream [ceromer], and Definite [ormocer]. Four common shades of [B2, A2, A3, and A4] of each material were selected. Five specimens of 10 mm diameter and 1.5 mm thickness of each shade were mode by condensing the material into a Teflan mold. Pre-cure color values, L[x],a[x],b[x], were measured with a spectrophotometer. The material was light polymerized and post-cure color parameters were obtained. Specimens were then immersed in distilled water at 60°C. After 4 and 8 weeks, the color values were remeasured and the color differences [deltaE[x] ab] were calculated. Although all materials underwent color changes during light polymerization, the magnitude of the differences were slight. After accelerated aging, the materials were significantly darker and lighter shades showed smaller discoloration compared to darker ones. However, non of the tested materials exhibited a visually perceptible color change [deltaE[x] ab > 3.3] after 8 weeks of accelerated testing. The low discoloration observed with modern materials is probably related to the high inorganic filler contents and to the direct grafting of the resin to the filler particles. The nature of the resin may also account for the color stability of the restorative materials

Abrasive wear of packable posterior composites

This study was conducted to measure the abrasive wear of packable posterior composites, and to compare the wear resistance of the materials with that of universal composites and dental amalgam. Surface hardness was also measured to determine the relationship between hardness and volume loss due to wear. Two packable composites and two universal composites were used. Samples of a high-capper amalgam were used as reference material. Specimens of each material were prepared and subjected to toothbrush-dentifrice abrasion using 100,000 strokes of brushing. The amount of volume change of each material was calculated, and the Vickers hardness of test materials was also measured. Data were analyzed by one-way ANOVA, followed by the Duncan multiple range test and the Pearson correlation co-efficient at a level of P<0.05. Results indicated that packable composites exhibited significantly higher abrasion resistance than universal composites. Dental amalgam showed the lowest wear among the all tested materials. Significant relationship was observed between pooled data of volume loss and hardness. For individual material, however, non-significant association was noted. The improved wear resistance, and increased hardness of packable composites compared to universal composites may have been due to their improved chemical formulations

Influence of microabrasion on shear bond strength of composite resin to dentin

The purpose of this study was to determine the influence of microabrasion on shear bond strength of composite resin to dentin. Ninety noncarious recently extracted human molars were selected. The occlusal surface of teeth was ground, exposing flat dentin surface to accommodate bonded restorative material. The teeth were divided into nine groups of 10 teeth each. The dentin surfaces of the first group were conditioned with Total Etch for 10 seconds, then washed and dried to serve as control. Air abrasion conditioning of the remaining 8 groups was accomplished with "Micro Prep Director+" air abrasion device using 0.4mm nozzle tip perpendicular to sample surface and 1cm away from it. Surface abrasion was performed using a 27 micro m aluminum oxide particle stream at 60 psi for 10 seconds in two groups, and for 20 seconds in another two groups. Air pressure was then increased to 120 psi to abrade surfaces of another two groups for 10 seconds, and for 20 seconds in the remaining two groups. Additional conditioning with Total Etch was performed to the surfaces of the last four groups combined with air abrasion treatment. Three teeth from each of the nine groups were mounted in a profilometer and three Ra values were recorded for dentinal surface roughness before and after surface treatment. Remaining samples were prepared for bonded composite restorations, and shear bond strengths were determined using a testing machine. Results revealed significantly higher roughness of etched surface than air abraded dentin. Meanwhile acid etching created bond strengths to dentin that were almost twice as high as those achieved by air abrasion. It could be, thus, suggested that cavities prepared by air abrasion should also be acid etched to achieve adequate bonding with resinous materials

Class-lonomer cements: a critical review

Recently, there has been a considerable interest in the clinical application of glass-ionomer cements. Some of the inherent physical and chemical properties make the glass-ionomer cements excellent dental restorative materials in selected clinical situations. These include the slow release of fluoride, which may produce an anticariogenic action, physicochemical bonding to enamel and dentin, reducing the need for retentive cavity preparation and biocompatibility with pulpal tissue. The introduction of faster setting and metal-reinforced glass-ionomer has exp and ed their application in restorative dentistry

effect of carbamide-peroxide gel on microleakage of composite resin restorations

This study aimed to report the effect of home-use carbamide-peroxide gel on microleakage of composite filled class V cavities. Specimens were thermocycled and immersed in bleaching solution for one, three or six hours daily for one month. Then, the restored teeth were placed in methylene blue dye and sectioned. The extent of dye penetration along the tooth-restoration interface was compared. The results indicated that significantly more leakage was associated with prolonged bleaching. It may be advantageous to limit the use of home-bleaching agents when composite resin restorations are present