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Purpose: To compare teeth prepared to receive a metallic versus a metal-ceramic crown with respect to (1) in vitro dentin permeability before and after using a desensitizing agent and (2) pulpal eugenol concentration after sealing a temporary crown with a zinc oxide-eugenol based cement. Materials and Methods: The roots of 20 human mandibular molars were separated and the crowns were prepared to receive a metallic crown. The hydraulic conductance was recorded before and after using Protect dentin desensitizer. The crowns were then further reduced to receive a metal-ceramic crown and the hydraulic conductance was recorded under the same conditions, on deeper dentin, before and after using the desensitizing agent. Twenty additional teeth were prepared: 10 to receive a metallic crown and 10 teeth to receive a metal-ceramic crown. A tube filled with 1 mL phosphate buffered saline (PBS) was sealed to the cementoenamel junction. A temporary crown was sealed onto the preparation with Temp Bond. The amount of eugeno] that diffused across dentin into PBS was spectrofluorimetrically measured at Day 1 and Day 7. The crown preparations were vertically sectioned and the dentin remaining thickness was recorded. Results: The hydraulic conductance of teeth prepared for a metal-ceramic crown was twice as high as teeth prepared for a metallic crown (P<0.001). The desensitizing agent reduced the hydraulic conductance in both groups (P< 0.001). The two groups showed the same hydraulic conductance after using Protect (ns). No significant difference was found in the amount of eugenol diffusion between the two groups of teeth although eugenol diffusion decreased with time (P< 001). No correlation was found between eugenol diffusion and remaining dentin thickness. [ABSTRACT FROM AUTHOR]

Purpose: To compare in vitro the efficacy of five resin-based desensitizing agents at reducing human dentin permeability and to compare their cytotoxicity. The tested hypothesis was that their different curing techniques cause variations in efficiency and cytotoxicity. Materials and Methods: Dentin slices (0.5 ± 0.05 mm thick) were prepared from human third molars (10 per group) and their hydraulic conductance was recorded before and after application of one of the desensitizing agents with a Fludec device. Six desensitizing agents were studied: one light curing agent (Seal and Protect); one self-curing agent (Pain Free); three resin-based agents without any polymerization initiator (Health-Dent, Gluma Desensirizer, Isodan); one oxalate-based agent served as a control (Protect). A MTT assay on L 929 fibroblasts was performed to measure the cytotoxicity of the six desensitizing agents applied onto additional dentin slices (10 per group). Results: All the desensitizing agents resulted in a large decrease in dentin permeability. The best results were obtained with Gluma Desensitizer, Isodan, Pain Free and Protect. A statistically significant difference was found among the materials (P= 0.001). All the materials were non-cytotoxic. Cell viability ranged from 88% for Seal and Protect to 100% for Isodan. No difference was found among their cytotoxicity. [ABSTRACT FROM AUTHOR]

Purpose: To investigate pulpal injury by measuring odontoblast numbers, and pulp dentin repair activity by measuring reactionary dentin area, in relation to the remaining dentin thickness (RDT) of cavity preparations in 217 human teeth. Materials and Methods: Cavities were restored with adhesive bonded composite, resin-modified glass-ionomer cement, zinc oxide-eugenol or calcium hydroxide materials. The teeth were extracted for orthodontic reasons between 20-381 days post-operatively, and odontoblast numbers and reactionary dentin area were analyzed histomorphometrically, and statistically using ANOVA. Results: Reactionary dentin deposition was observed beneath cavities with a RDT above 0.5 mm as well as beneath cavities with a RDT below 0.25 mm; however maximal reactionary dentin appeared to be beneath cavities with an a RDT between 0.5-0.25 mm (P= 0.0001). The area of reactionary repair was also influenced by the choice of restoration material (P= 0.0385) bam greatest to least; calcium hydroxide, composite, resin-modified glass-ionomer cement and zinc oxide-eugenol. Odontoblast numbers were maintained beneath cavities with a RDT above 0.25 mm, cavities placed closer to the pulp appeared to injure underlying odontoblasts, reducing their numbers (P= 0.0001). The choice of cavity restoration material also influenced the survival of underlying odontoblasts (P= 0.0061). [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the influence of dentin etching with phosphoric acid on hydrogen peroxide diffusion through human dentin in internal bleaching. Methods: 46 human premolars were extracted for orthodontic reasons from adolescents. The teeth were endodontically treated and a flat defect was created at the enamel-cementum junction. The teeth were divided into two groups: the access cavity was etched for 30 seconds with 35% H3P04 in the first group and left intact in the second group. The teeth were filled with 20μL of 35% hydrogen peroxide gel. The receiving medium on the other side was renewed at Day 1, Day 2 and Day 7 to quantify the diffusing hydrogen peroxide. An analysis of variance was performed to compare the diffusion between the two groups. Results: This work demonstrated a higher hydrogen peroxide diffusion when the access cavity was etched (P< 0.01). [ABSTRACT FROM AUTHOR]

Purpose: To assess the influence of in-office whitening gel pH on whitening efficiency., Methods: Hydrogen peroxide diffusion and color changes on bovine teeth were assessed. Three gels with close hydrogen peroxide concentrations but with various pH levels were tested: Zoom 2 (Discus Dental), Opalescence Endo and Opalescence Boost (Ultradent). The pH levels were respectively: 3.0, 5.0 and 7.0. Thirty enamel slices and tooth crowns were used for both studies (n = 10 per group per study). Hydrogen peroxide diffusion through the enamel slices and the tooth crowns was spectrophotometrically recorded every 10 minutes for 1 hour to calculate the diffusion coefficients. Color changes were spectrophotometrically recorded every 10 minutes for 1 hour and quantified in term of CIE-Lab., Results: The hydrogen peroxide diffusion coefficient through enamel ranged from 5.12 +/- 0.82 x 10(-9) cm2 s(-1) for pH 3 to 5.19 +/- 0.92 x 10(-9) cm2 S(-1) for pH 7. Through tooth crowns it ranged from 4.80 +/- 1.75 x 10(-10) cm2 s(-1) for pH 5 to 4.85 +/- 1.82 x 10(-10) cm2 s(-1) for pH 3. After 1 hour, the deltaE varied from 5.6 +/- 4.0 for pH 7 to 7.0 +/- 5.0 for pH 3 on enamel slices and from 3.9 +/- 2.5 for pH 5 to 4.9 +/- 3.5 for pH 7 on tooth crowns. There was no statistically significant difference between groups for both parameters.