Shear Strength of Composite Bonded to Er:YAG Laser-prepared Dentin

Abstract

An Er:YAG laser coupled with a cooling stream of water effectively removes dental hard tissues. However, before such a system can be deemed clinically viable, some safety and efficacy issues must be addressed. We compared the bonding of composite to dentin following the preparation of the dentinal surface with either an Er:YAG laser (lambda = 2.94 microns) or a standard dental bur and with and without a subsequent acid-etching treatment. The crowns of extracted human molars were removed, revealing the underlying dentin. We removed an additional thickness of material with either a dental handpiece or an Er:YAG laser (350 mJ/pulse at 6 Hz) by raster-scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were obtained. Several samples from each group received an acid-conditioning treatment. A cylinder of composite was bonded onto the prepared surfaces. The dentin-composite bond was then shear-stressed to failure on a universal testing apparatus. The results indicate that laser-irradiated samples had improved bond strengths compared with acid-etched and handpiece controls. SEM photographs of the surfaces show exposed tubules following the laser treatment: tubules could also be exposed with acid etching. We conclude that Er:YAG laser preparation of dentin leaves a suitable surface for strong bonding or an applied composite material.

An In Vitro Comparison of the Bond Strength of Composite to Superficial and Deep Dentin, Treated With Er:YAG Laser Irradiation or Acid-Etching

“…Lasers have been employed for tooth surface modification and improving restoration bonding. [11][12][13][14] Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser has the capacity to produce a micro-retentive pattern when applied on tooth surfaces. The effect of Er:YAG laser depends on parameters such as energy output, frequency, pulse mode, and irradiation time.…”

Temperature rise in cavities prepared by high and low torque handpieces and Er:YAG laser

“…Class I and class V cavity preparations with Er:YAG laser in enamel, cemen tum and carious tissue was carried out by Oelgiesser et al (2003), 18 at different irradiation energies (600-1000 mJ) and pulse frequencies (7)(8)(9)(10)(11)(12), with an air-water spray as a cooling system. The authors stated that the elevation meas ured in the pulp chamber during lasing with various energies and pulse rates was low and did not exceed the critical value of 5.5ºC.…”

“…9 Because the wavelength of the Er:YAG (Erbium:Yttrium-Aluminum-Garnet) laser can absolve water and hydroxyapa tite, 10 it can be indicated for the removal of caries and cavity preparations. 11,12 Some Er:YAG laser beams can penetrate to deeper areas than the ablated area; damage of the nerve fibres and terminals might be a mechanism of pain reduction in cavity ablation with Er:YAG laser. 1 The treatment with an Er:YAG laser needs to be performed with constant water cooling because macroscopic observations of the dentine irradiated without water cooling showed dark lesions, suggesting carbonisation of the tissue.…”

Evaluation of the Bond Strength of Resin Cements Used to Lute Ceramics on Laser-Etched Dentin

“…[6][7][8] Erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) and erbium: yttrium-aluminum-garnet (Er:YAG) lasers can ablate enamel and dentin effectively because of the high absorption by water and hydroxyapatite. 6 Surfaces irradiated by these lasers showed a characteristic rough surface, clean and without debris, open dentinal tubules, and microirregularities caused by the preferential removal of the intertubular dentin, suggesting that the resultant dentin surface is receptive to adhesive procedures.…”

“…11 In contrast, the results of this study are not in agreement with the findings of Visuri et al, in which it was determined that Er:YAG laser-irradiated dentin samples had improved bond strengths compared with handpiece treatments with or without a subsequent acid-conditioning step. 7 These differences may be related to the different type of laser used, duration of exposure, and energy applied to the surface.…”