The Shear Bond Strength of Acetone and Ethanol-based Bonding Agents to Bleached Teeth

Resident: Adam J. Bottrill
Date: 16FEB11
Region: Providence
Article title: The Shear Bond Strength of Acetone and Ethanol-based Bonding Agents to Bleached Teeth
Author(s): Montalvan, Ericka DMD
Journal: Pediatric Dentistry
Page #s: 531-536
Vol:No Date: 28:6 2006
Major topic: In-office bleaching, bonding agents
Minor topic(s): None
Type of Article: In vitro randomized study.

Main Purpose: The purpose of this in vitro study was to evaluate the: (1) shear bond strenth (SBS) of acetone and ethanol-based bonding agents to composite resin 24 hours after being bleached with 35% hydrogen peroxide; and (2) interface morphology and mode of fracture (IMMF) between composite resin and enamel.

Key points in the article discussion:

I. General

A. Mechanisms of action in hydrogen peroxide and carbomide peroxide bleaching agents are poorly understood.
1. It is thought that MAYBE the H2O2 moves through tooth denaturing proteins which may increase the movement of ions (and stain?) through the tooth.
B. The amount of whitening depends on the concentration and time of application of these substances.
C. Enamel has been described as showing increased porosity and increased formation of surface precipitate that may decrease the bond strength of composite to enamel after bleaching.
D. Some suggest that waiting a few weeks after bleaching MAY reduce the effects on bond strength.
E. The reduction of bond strength MAY also be due to the presence of residual oxygen on resin infiltration and polimerization.

II. Methods:

A. 40 extracted teeth randomely assigned to 4 groups
1. 35% H2O2+acetone
2. H2O2+ethanol
3. acetone
4. ethanol
B. All teeth acid etched, bonding agent, resin stub, stored in saline fof 24hrs.
C. SBS determined, SEM used for IMMF eval.

III. Results:

A. SBS significantly lower in bleached vs unbleached teeth.
B. SBS did not sig vary between acetone vs ethanol based.
C. Bleaching did not interfere with adhesive treatment.
D. IMMF showed continuous interface between resin and enamel of unbleached teeth.
E. IMMF showed "sparse" interface between the resin and enamel of bleached teeth.

IV. Conclusions:

A. Morphological changes in human tooth enamel, 24hr after bleaching, were associated with reduction in the SBS of adhesives.
B. Contrary to some suggestions ethanol produced no better results than acetone.
C. Should continue to study other methods of whitening (toothpaste etc...)



Assessment of article: Weaknesses were substantial: unknown history of extracted teeth, cannot readily generalize this in vitro study to clinical application (saline storage etc...). I haven't figured out whether I think the weaknesses of this study outweigh the benefits.