Effect of a laboratory surfactant on compatibility of type IV dental stones with addition-cured silicone impression materials.

This study compared the effect of a surfactant on surface detail reproduction between combinations of addition-cured silicone impression materials and type IV stones. Six hundred impressions were made of a ruled test block using; Examix-NDS, Doric-Es Flo-Light, Panasil Contact Plus, Extrude Wash and President Plus Jet. Half of the impressions were treated with a surfactant (Aurofilm). Impressions were poured with type IV dental stones; Silky Rock, Fuji Rock, Suprastone and Vel-Mix and the 20 mu line was scored. A laboratory surfactant (Aurofilm) significantly reduced (P<0.01) compatibility with; (i) Examix-NDS and Suprastone, (ii) Examix-NDS and Velmix, (iii) Extrude Wash and Fuji Rock.

Hydrogen peroxide tooth-whitening (bleaching): review of safety in relation to possible carcinogenesis.

Hydrogen peroxide in the form of carbamide peroxide is widely used in professionally and self-administered products for tooth whitening. Hydrogen peroxide is a highly reactive substance that can damage oral soft and hard tissues when present in high concentrations and with exposures of prolonged duration. This review examines the issue of oral mucosal damage and possible carcinogenicity relating to the use of hydrogen peroxide in the mouth for tooth whitening, with an emphasis on safety with prolonged exposure to low concentrations of peroxide products.

Type IV gypsum compatibility with five addition-reaction silicone impression materials.

STATEMENT OF PROBLEM: The compatibility of current addition-reaction silicone impression materials and Type IV gypsum products is not completely understood. PURPOSE: The purpose of this study was to compare surface detail reproduction between various combinations of contemporary addition-reaction silicone impression materials and Type IV gypsum products. MATERIAL AND METHODS: Under standardized conditions, 300 impressions were made of a ruled stainless steel die (ADA specification 19), using 5 addition-reaction silicones (Examix-NDS, Doric-ES Flo-Light, Panasil Contact Plus, Extrude Wash, and President Plus Jet). Fifteen impressions of each material were poured with each Type IV gypsum product (Silky-Rock, Fuji Rock, Suprastone, or Vel-Mix). Using x12 magnification, 2 independent examiners scored the reproducibility of a 20-microm line in both the impression and the resultant casts. Statistical analysis was performed using 2-way analysis of variance and post hoc Bonferroni testing (alpha = .05). RESULTS: All impression materials tested fully reproduced the 20-microm line. Different impression materials showed different compatibility with different Type IV gypsum products. Only 25% of the Type IV gypsum casts completely reproduced the resultant 20-microm line with fine margins, and 88% of the completely reproduced casts were made from Suprastone. CONCLUSION: Not all combinations of impression material and Type IV gypsum products used exhibited similar compatibility.

Influence of flowable liner and margin location on microleakage of conventional and packable class II resin composites.

This in vitro study evaluated gingival wall microleakage in packable and microhybrid conventional composite restorations with and without a flowable composite liner. Each group was evaluated with gingival margins situated in both enamel and cementum/dentin. Two hundred and forty Class II cavities were prepared in extracted third molars, half with gingival margins in enamel and half with margins in dentin/cementum. In groups of 30, restoration was undertaken with packable alone (3M Filtek P60), conventional alone (3M Z250), packable plus flowable liner (3M Filtek Flow) and conventional plus flowable liner. All used 37% phosphoric acid etch and Scotchbond 1 (3M) as the bonding system. After restoration, the teeth were thermocycled (between 5 degrees C, 37 degrees C and 60 degrees C) 1,500 times, soaked in 0.1% methylene blue, sectioned and microleakage from the gingival margin scored. Statistical analysis was performed using Kruskal Wallis and Mann-Whitney U tests. There was no significant difference between systems in terms of leakage scores when gingival margins were situated in enamel (p=0.70). All restorations with margins in cementum/dentin leaked significantly more than those with margins in enamel (p<0.001). There was no significant difference between leakage scores of 3M Z250 and Filtek P60 with cementum/dentin gingival margins (p=0.68). Use of a flowable composite liner (3M Filtek Flow) against cementum/dentin was associated with increased microleakage (p<0.001). In this study, leakage scores suggest that gingival margins should be placed in enamel. The conventional and packable resin composites tested were not associated with differences in microleakage. Leakage data do not support the use of flowable resin composite linings in Class II resin composite restorations.

Effect of screw hole filling on retention of implant crowns.

The screw access channels of 15 degrees angled Esthetic Abutments (Brånemark System) were either (a) completely filled with a vinyl polysiloxane impression material (Memosil), (b) partially filled with Memosil or (c) had lower portion filled with Memosil and the remainder with composite resin. The force required to remove a temporarily cemented restoration was measured. The removal force was significantly reduced with the channel completely filled with Memosil compared to those partially filled with Memosil (p<0.01) or with composite resin placed over Memosil (p<0.01). The method selected to fill the screw access channel of an implant abutment can be a significant factor affecting retention of a cemented restoration.