Quintessence International, 09/1998

Objective: A 6-month, double-blind study was undertaken to assess the efficacy and safety of a 10% carbamide peroxide gel designed for at-home tooth bleaching. Method and materials: Sixty patients were randomized into two equal subgroups balanced by age, gender, and oral health status. Shade guide measurements, color transparency photographs, and colorimeter readings were taken and evaluated at baseline and 1, 2, 3, 6, 12, and 24 weeks. The active phase of treatment lasted 14 days. Results: At 22 weeks postbleaching (week 24 of the study), patients receiving the active agent had a 14.1 rank order difference in the shade guide from baseline, and 66% had a clinically observable color change as determined by photographic assessment. They also had a measurable, statistically significant color change from baseline to 6 months of AE* = 5.0. The tooth color of maxillary incisors stabilized at week 6 and maxillary canines at week 12. The mean color change lost from weeks 2 to 24 was 45% (in A E*). Transient tissue and tooth sensitivity, noted in some pat ients, resolved after treatment was completed. Conclusion: The product tested is an effective and safe tooth-whitening agent.

This article demonstrates a technique for correcting minor incisal defects in custom-fitted bleaching trays directly on patients without making new impressions.

Objective: The effect of salivary contamination of enamel and dentin on bonding efficacy of an experimental one-bottle resin adhesive was investigated. Method and materials: The adhesive was a light-curing urethane dimethacrylate/hydroxyethyl methacrylate/4-methacryl oxyethyl trimellitate and anhydride mixture dissolved in acetone. Evaluation parameters were shear bond strength and marginal gap width in a dental cavity. Apart from a control group without contamination (group 1), etched enamel and dentin were (2) contaminated with saliva and air dried; (3) contaminated, rinsed, and blot dried; (4) coated with adhesive, contaminated, rinsed, and blot dried; (5) coated with adhesive, light cured, contaminated, rinsed, and air dried; or (6) treated as in group 5, with additional adhesive application after air drying. Results: There was no negative effect in groups 3 and 4, compared with control Air drying after salivary contamination (group 2) resulted in low shear bond strengths and wide marginal gaps. Contamination of the cured adhesive layer (groups 5 and 6) had no adverse effect on enamel shear bond strengths, but resulted in 50% reduced dentin shear bond strengths and wide marginal gaps. Conclusion: The one-bottle adhesive system is relatively insensitive to salivary contamination, provided that the contamination occurs prior to light curing of the adhesive and is carefully rinsed and blot dried. Salivary contact after adhesive curing must be avoided.

Objective: Changes in the occlusal marginal adaptation of computer-machined inlay restorations were assessed over 3 years. Method and materials: Each of 21 patients received two Cerec 9Vita Mark II) two- or three-surface restorations, with margins entirely in enamel, placed using two of four luting agents: a homogeneous microfilled resin composite, a fine hybrid composite, a realtively coarse hybrid composite, and an encapsulated glass-ionomer cement. Replicas of the restorations were made at baseline 6 months or 1 year (93% of original restorations), 2 years (79%), and 3 years (83%). The percentage of continuous margin on the occlusal margin was evaluated for the enamel-luting agent and luting agent-porcelain interfaces using a scanning electron microscope. Results: Mean continuous margin values were high for all groups at the enamel-luting agent interface; there were no significant differences among the luting agents. For each luting agent, the percentage of continuous margin decreased significantly at the luting agent-porcelain interface over 3 years; differences among the luting agents at 3 years were not significant (Kruskal-Wallis test). After 3 years, the wear of the luting agents was significantly different. The least wear occurred with the microfilled resin composite; the coarse hybrid composite showed the most wear. Conclusion: The occlusal margins of Cerec inlays exhibited consistently high-quality adaptation at 3 years. The microfilled resin composite luting agent was more wear resistant than the hybrid composites and the glass-ionomer cement.

A case of unusual foreign body impaction of 6 years' duration is reported. The foreign body was retained in the right infraorbital region, extending to the ethmoid sinus. The importance of careful history taking and clinical examination and the problems encountered in evaluation of relatively radiolucent foreign bodies with magentic resonance imaging are discussed.

Objective: Acemannan, a complex mannose carbohydrate dervied from the aloe vera plant, has an inherent stickiness/viscosity. Prototype Acemannan denture adhesive for mulations were evaluated for pH changes, cytotoxicity to human gingival fibroblasts and adhesive strength in both dry and wet conditions. Method and materials: The denture adhesive formulations consisted of five combinations of Acemannan with varying concentrations of preservtives and two other formulations without preservatives. The pH of each formulation was measured over 24 hours. Assessment of cytotoxicity was accomplished using the in vitro, tetrazolium-based colorimetri c assay on cultures of human gingival fibroblasts after exposure to the adhesive formulations for up to 24 hours. The adhesive strength was evaluated with a universal testing machine under intial dry conditions and after immersion in a constant-temperature water bath for up to 20 minutes. Results: Formulations 1 and 2 acheived and maintained pH values above 6.0 (the critical pH for hydroxyapatite dissolution) approximately 6 hours into the study. None of the prototypes demonstrated an initial pH above the critical pH. Formulations 1, 2, 3, and 5 exhibited significant cytotoxicity to human gingival fibroblasts over 24 hours. Formulations 4, 20:1, and 150:1 demonstrated minimal cytotoxicity. Formulation 1 exhibited the poorest adhesive strength, while the most viscous formulation (prototype 150:1) was by far the best performer. Generally, adhesive bond strengths for all prototypes were quite high and relatively stable over time in a wet environment. Conclusion: To achieve the ideal adhesive in terms of strength, pH, and cytotoxicity. Acemannan formulation 150:1 should be adjusted to contain the preservative concentration of formulation 4 and have an initial pH value of 6.0 or higher.