Retention of gold alloy crowns cemented with traditional and resin cements.

The aim of this study was to measure in vitro retention of cast gold crowns cemented with traditional and resin cements. Forty-eight human molars were prepared on a lathe to produce complete crown preparations with a consistent taper and split into six groups, eight crowns in each group. Crowns were cast in a high-gold alloy and then cemented. After 24 hours, the retention force (N) was recorded and mean values were analyzed by one-way analysis of variance and the Fisher post-hoc least significant difference (PLSD) multiple comparisons test (a = .05). Failure sites were examined under 3100 magnification and recorded. Mean values (SD) for each group in increasing order of retention force were: Harvard Cement: 43 N (27), TempoCem: 59 N (16), PermaCem Dual: 130 N (42), RelyX Luting Cement: 279 N (26), Contax and PermaCem Dual: 286 N (38), and TempoCem with Contax and PermaCem Dual: 340 N (14). The Fisher PLSD interval (P = .05) for comparing cements was 29 N. Zinc-phosphate cement and provisional resin cements had the lowest retention forces. Resin cement with a bonding agent and the hybrid-ionomer cement had similar retention forces. Resin cement with a bonding agent applied after use of a provisional resin cement had a significantly higher retention force than the other cements tested.

Effects of an antimicrobial additive to toothbrushes on residual periodontal pathogens.

OBJECTIVE: Previous studies have reported the link between residual microbial contamination of toothbrushes and periodontal diseases. The goal of this pilot study was to evaluate the effects of an antimicrobial additive (Microban) to toothbrushes on residual retention of periodontal pathogens. METHODOLOGY: Twenty patients had one side of their mouths brushed with a toothbrush containing the antimicrobial agent (experimental side), and the other side with a toothbrush containing no agent (control). Toothbrushes were air-dried (25 degrees C) for four or 24 hours. Toothbrush heads were vortexed and cultured for Prevotella species (Ps), Porphyromonas gingivalis (Pg), Actinobacillus actinomycetemcomitans (Aa), and non-specific colony-forming units (NS). The plates were incubated and counted. Means and standard deviations were calculated, and data were analyzed using a series of t-tests (paired and unpaired) and Wilcoxon matched-pairs signed-rank test. RESULTS: No significant inter- or intra-group differences in mean counts were found; however, when four-hour and 24-hour data for Aa, Pg, or NS were combined, experimental counts were lower than controls in 39/50 (78%) of the matched pairs (Wilcoxon signed-rank test p = 0.01). CONCLUSION: Toothbrushes containing the antimicrobial additive showed lower microbial counts than those without, but between-group means were not statistically significant.

Influence of enamel surface preparation on composite bond strength.

PURPOSE: To evaluate the influence of air-particle abrasion and treatments on in vitro tensile bond strength of resin composite bonded to human enamel was evaluated using a single-bottle adhesive. METHODS: Human teeth were divided into 12 groups of three treatments (none, 27-microm Al2O3 air-particle abrasion, 50-microm Al2O3 air-particle abrasion) and four conditioners [none, phosphoric acid (PA), NRC (no-rinse conditioner), and PA/NRC]. Bonding agent (Prime & Bond NT) and a resin composite (TPH Spectrum) were applied as inverted cones. Specimens were stored for 24 hours at 37 degrees C and debonded in tension using a testing machine at 0.5 mm/minute. RESULTS: Phosphoric acid treatment used with Prime & Bond NT produced the best bond strengths (24 MPa) to enamel for surfaces treated with 27-microm air-particle abrasion and for surfaces not treated with air-particle abrasion (control). With one exception, air-particle abraded surfaces resulted in bond strengths between 9 to 16 MPa. NRC with or without the use of phosphoric acid in general did not improve tensile bond strength to enamel when compared to surfaces not treated with NRC.