Effect of prophylactic polishing protocols on the surface roughness of esthetic restorative materials.

Many polishing protocols have been evaluated in vitro for their effect on the surface roughness of restorative materials. These results have been useful in establishing protocols for in vivo application. However, limited research has focused on the subsequent care and maintenance of esthetic restorations following their placement. This investigation evaluated the effect of five polishing protocols that could be implemented at recall on the surface roughness of five direct esthetic restorative materials. Specimens (n=25) measuring 8 mm diameter x 3 mm thick were fabricated in an acrylic mold using five light-cured resin-based materials (hybrid composite, microfilled composite, packable composite, compomer and resin-modified glass ionomer). After photopolymerization, all specimens were polished with Sof-Lex Disks to produce an initial (baseline) surface finish. All specimens were then polished with one of five prophylactic protocols (Butler medium paste, Butler coarse paste, OneGloss, SuperBuff or OneGloss & SuperBuff). The average surface roughness of each treated specimen was determined from three measurements with a profilometer (Surface 1). Next, all specimens were brushed 60,000 times at 1.5 Hz using a brush-head force of 2 N on a Manly V-8 cross-brushing machine in a 50:50 (w/w) slurry of toothpaste and water. The surface roughness of each specimen was measured after brushing (Surface 2) followed by re-polishing with one of five protocols, then final surface roughness values were determined (Surface 3). The data were analyzed using repeated measures ANOVA. Significant differences (p=0.05) in surface roughness were observed among restorative materials and polishing protocols. The microfilled and hybrid resin composite yielded significantly rougher surfaces than the other three materials following tooth brushing. Prophylactic polishing protocols can be used to restore a smooth surface on resin-based esthetic restorative materials following simulated tooth brushing.

An in-vitro investigation of variables influencing mercury vapor release from dental amalgam.

Controversy regarding patient exposure to mercury from dental amalgam is more than 150 years old. Researchers continue to investigate the amount of mercury vapor released from amalgam both in vivo and in vitro. In this investigation, an in vitro testing method previously described in the literature was used to quantify the effect of operator-controlled variables on mercury release from dental amalgam. The variables tested were alloy morphology (spherical, admixed or atomized irregular particle), operator skill (inexperienced, novice and expert), operator technique (overfill and evenly fill) and cavity design (standard Class I, double volume and double surface area). Preparations fabricated in sections of acrylic rod were filled with dental amalgam, placed in 25 mL glass bottles and sealed. Mercury vapor concentrations were measured using a Jerome M-411 at specified times. Standardized mean concentrations for each time and total mercury released over time were calculated and analyzed with ANOVA and Tukey HSD. Statistically significant differences ((alpha = 0.05) were identified for all variables tested. Total mercury vapor release was consistently found to be greater for admixed as compared to spherical amalgam. Amalgam restorations prepared by an inexperienced operator demonstrated statistically less mercury vapor than a novice or experienced clinician for both spherical and admixed morphologies. A statistically significant difference in mercury vapor using different condensation and carving techniques was found for the spherical amalgam but not for the admixed material. Restoration design demonstrated significant differences in total mercury vapor dependent on volume and exposed surface area of the amalgam restoration. In this in vitro investigation, mercury vapor release from amalgam was dependent on alloy morphology, operator experience, operator technique and restoration design.

Evaluation of dental adhesive systems with amalgam and resin composite restorations: comparison of microleakage and bond strength results.

A variety of laboratory tests have been developed to assist in predicting the clinical performance of dental restorative materials. Additionally, more than one methodology is in use for many types of tests performed in vitro. This project assessed and compared results derived from two specific laboratory testing methods, one for bond strength and one for microleakage. Seven multi-purpose dental adhesives were tested with the two methodologies in both amalgam and resin composite restorations. Bond strength was determined with a punch-out method in sections of human molar dentin. Microleakage was analyzed with a digital imaging system (Image-Pro Plus, Version 1.3) to determine the extent of dye penetration in Class V preparations centered at the CEJ on both the buccal and lingual surfaces of human molar teeth. There were 32 treatment groups (n = 10); seven experimental (dental adhesives) and one control (copal varnish, 37% phosphoric acid) followed by restoration with either amalgam or resin composite. Specimens were thermocycled 500 times in 5 degrees and 55 degrees C water with a one-minute dwell time. Bond strength and microleakage values were determined for each group. ANOVA and Student-Newman-Keuls tests demonstrated an interaction between restorative material and adhesive system with a significant difference among adhesives (p < 0.05). Using a multi-purpose adhesive system resulted in both a statistically significant increase in bond strength and a statistically significant decrease in extent of microleakage (p < 0.05). The effect of the adhesive upon both microleakage and bond strength was greater in the resin composite restorations than in the amalgam restorations. Bond strength testing was more discriminating than microleakage evaluation in identifying differences among materials.

Investigation of two mercury vapor collection techniques.

OBJECTIVES: The purpose of this investigation was to develop and test two in vitro mercury vapor collection techniques: a closed bottle technique (CB) and an intraoral flow (IOF) technique. METHODS: Amalgam samples were prepared in acrylic first molars (#30) with standardized Class I preparations. In the CB technique, samples were placed in either a 25, 100 or 500 ml bottle (n = 5). Vapor was analyzed with the Jerome M-411 using a syringe method over a 7 day period. In the IOF technique an impression of the lower right quadrant of a Typodont was taken with PVS impression material leaving a 5 mm space over #30. Samples were analyzed with the Jerome M-411 connected to the impression tray via tygon tubing at the buccal surface. Average mercury vapor release rates and standard deviations were calculated for each method. Data were analyzed by two-way ANOVA followed by Tukey HSD pairwise analysis for significant findings (alpha = 0.05). RESULTS: Both techniques indicated mercury vapor release was dependent on volume. The largest bottle, 500 ml, yielded a significantly greater (p < or = 0.00) amount of mercury vapor within the CB systems. In the IOF technique, the addition of air flow over the restoration demonstrated a significant increase (p < or = 0.05) in mercury vapor released compared to the sealed IOF technique. SIGNIFICANCE: A method for mercury vapor analysis was developed for possible intraoral application. The IOF method with direct air flow removes possible saturation effects found in a CB system, while limiting external variables, which may contribute to errors associated with in vivo measurements.

Effects of palladium addition on emission of mercury vapor from dental amalgam.

OBJECTIVES: The purpose of this investigation was to test the hypothesis that palladium causes a reduction in mercury emission when added to dental amalgam during condensation. METHODS: Mercury vapor release was measured in a closed bottle system and an Intraoral Flow device(IOF). Conventional amalgam restorations were modified by addition of various palladium pellets. 1.57 mm diameter palladium pellets with different porosities were fabricated. These pellets were then placed in amalgam restoration using typical condensation and carving procedures. The samples were stored in a closed bottle and mercury measurements were taken from the bottles at 30 min, 1, 3, 5, 24 and 48 h and 7 days after trituration using a Jerome 411 Mercury Vapor Analyzer (Arizona Instrument Corp., Jerome, AZ). The palladium pellets identified as the most effective in mercury vapor reduction were further tested in an IOF device. Data were analyzed by two-way ANOVA followed by Tukey HSD pairwise analysis for significant findings (alpha = 0.05). RESULTS: The palladium containing amalgams when tested in the closed bottle system yielded significantly lower (p < 0.05) mercury vapor release than the controls. Pellets fabricated with the highest porosity yielded the greatest reduction in overall mercury vapor release. In the IOF device the overall amount of mercury vapor released from the palladium containing amalgams was also significantly less than the control (p < 0.05). SIGNIFICANCE: Mercury vapor emission from dental amalgam was greatly reduced by adding palladium pellets to amalgam during condensation. These techniques require only slight modifications of the standard operative procedures.