I was looking at articles relating on how lasers effect bond strength and I found these. I had always thought that lasers increase bond strength, but these articles seem to state otherwise. Anyone’s thoughts?

: J Clin Laser Med Surg. 2003 Apr;21(2):105-8. Links

Influence of the frequency of Er:YAG laser on the bond strength of dental enamel.

Goncalves M, Corona SA, Pecora JD, Dibb RG.

School of Dentistry of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil.

OBJECTIVE: The present study had the aim of evaluating the influence of different frequencies of the Er:YAG laser on adhesive resistance of enamel and one restorative system. Background Data: There have been no reports of studies assessing the influence of the pulse frequency variation of the Er:YAG laser on adhesive resistance of the enamel/resin interface. MATERIALS AND METHODS: Fifty surfaces of enamel from extracted human third molars were planed and divided into five groups at random. Enamel surface treatment was realized by the Er:YAG laser at 80-mJ power and 1-, 2-, 3-, and 4-Hz pulse frequencies, followed by etching. For the control group, only acid conditioning with 37% phosphoric acid for 15 sec was used. The Single Bond/Filtek Z250 system was chosen for the fabrication of the specimens, which were stored in 100% relative humidity for 24 h, at 37 degrees C. The specimens were submitted to tensile resistance tests using a Universal Testing Machine (50 Kgf and 0.5 mm/min). RESULTS: The mean values in MPa were 1 Hz, 25.58 (+/-6.16); 2 Hz, 25.58 (+/-3.79); 3 Hz, 21.34 (+/-3.78); 4 Hz, 21.17 (+/-3.13); and phosphoric acid only, 22.44 (+/-7.0). Data were submitted to statistical analysis using ANOVA, and there was no significant difference in tensile resistance between the studied groups.
CONCLUSION: The results suggest that the Er:YAG laser, with 80-mJ power associated with acid conditioning at 1-, 2-, 3-, and 4-Hz frequencies, did not present significant improvement in tensile bonding of enamel, as compared to acid conditioning only.

J Dent. 2003 Feb;31(2):127-135. Related Articles, Links

SEM evaluation of the interaction pattern between dentin and resin after cavity preparation using ER:YAG laser.

Schein MT, Bocangel JS, Nogueira GE, Schein PA.

Abdon Batista 121, sala 904 Centro, 89201-010, SC, Joinville, Brazil

Objective. The aim of this study was to describe the interaction pattern formed between dentin and resin on cavities prepared with an erbium laser (Er:YAG). The morphological aspect of the irradiated dentin after acid etching was also observed.Methods. Ten dentin disks were obtained from fresh extracted third molars. Each disk received two cavities, one prepared with a conventional high-speed drill, while the other cavity was obtained by the use of an Er:YAG laser (KaVo KEY Laser, KaVo Co.). The laser treatment was performed with 250mJ/pulse, 4Hz, non contact mode, focused beam, and a fine water mist was used. Five disks were prepared for morphological analysis of the acid etched dentin. The other five disks had their cavities restored with Single Bond (3M) followed by Z100 resin (3M). The specimens were observed under scanning electron microscopy after dentin-resin interface demineralization and deproteinization.
Results and conclusions. It was observed that the morphological characteristics of the acid-etched irradiated dentin were not favorable to the diffussion of monomers through the collagen network. The dentin-resin interfacial aspect of irradiated dentin, after acid etching, showed thin tags and scarce hybridization zones, which agreed with the morphology of the irradiated and acid-etched dentin substrate observed.

Eur J Oral Sci. 2002 Aug;110(4):322-9. Related Articles, Links

Micro-tensile bond strength of two adhesives to Erbium:YAG-lased vs. bur-cut enamel and dentin.

De Munck J, Van Meerbeek B, Yudhira R, Lambrechts P, Vanherle G.

Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Belgium.

The purpose of the study was to assess the hypotheses that laser irradiation is equally effective for bonding as traditional acid-etch procedures, and that tooth substrate prepared either by Erbium:YAG laser or diamond bur is equally receptive to adhesive procedures. Buccal/oral enamel and mid-coronal dentin were laser-irradiated using an Erbium:YAG laser. A total-etch adhesive (OptiBond FL) applied with and without prior acid-etching and a self-etch adhesive (Clearfil SE Bond) were employed to bond the composite. The micro-tensile bond strength (microTBS) was determined after 24 h of storage in water. Failure patterns were analysed using a stereo-microscope, and samples were processed for Field-emission Scanning Electron Microscopy (Fe-SEM) evaluation. Unbonded, lased enamel and dentin surfaces were evaluated using Fe-SEM as well. The total-etch adhesive bonded significantly less effectively to lased than to bur-cut enamel/dentin. Laser ‘conditioning’ was clearly less effective than acid-etching. Moreover, acid etching lased enamel and dentin significantly improved the microTBS of OptiBond FL. The self-etch adhesive performed equally to lased as to bur-cut enamel, but significantly less effectively to lased than to bur-cut dentin.
It is concluded that cavities prepared by laser appear less receptive to adhesive procedures than conventional bur-cut cavities.