Tensile bond strength of Er,Cr:YSGG laser-irradiated human dentin and analysis of dentin–resin interface

Lee, Bor-Shiunn; Lin, Po-Yen; Chen, Min-Huey; Hsieh, Tseng-Ting; Lin, Chun-Pin; Lai, Juin-Yih; Lan, Wan-Hong

doi:10.1016/j.dental.2006.03.016

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Volume 23, Issue 5 , Pages 570-578, May 2007

Tensile bond strength of Er,Cr:YSGG laser-irradiated human dentin and analysis of dentin–resin interface

Bor-Shiunn Lee
- Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan
Po-Yen Lin
- Dental Department, Taiwan Adventist Hospital, Taipei, Taiwan
Min-Huey Chen
- Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan
Tseng-Ting Hsieh
- Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan
Chun-Pin Lin
- Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan
Juin-Yih Lai
- R&D Center for Membrane Technology, Department of Chemical Engineering, Chung Yuan University, Chung Li 32023, Taiwan
Wan-Hong Lan
- Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan
- Corresponding author. Tel.: +886 2 23123456x6851; fax: +886 2 23821212.

Received 5 July 2005; received in revised form 6 March 2006; accepted 9 March 2006.

Abstract

Objectives

As the bond strength of composite resin to Er,Cr:YSGG laser-irradiated dentin has not yet been evaluated, the objectives of this study were to investigate the tensile bond strength and to analyze the resin–dentin interface among bur-cut/acid-etched, Er,Cr:YSGG laser-ablated/acid-etched and Er,Cr:YSGG laser-ablated human dentin.

Methods

Crown dentin disks prepared from extracted human third permanent molars were used for the observation of surface morphological changes by scanning electron microscope (SEM). The laser energy parameters were 3.5W and 20Hz with water spray (air pressure level, 80%; water pressure level, maximum level). Another group of crown dentin disks were prepared for composite resin restoration and observation of resin–dentin bond interface after demineralization in 6N hydrochloric acid (HCl) for 1min and deproteinization in 1% sodium hypochlorite solution (NaOCl) for 10min. The tensile bond strengths of the three groups were measured by a universal testing machine at a crosshead speed of 0.5mm/min. Fracture types at the dentin–resin interface were analyzed using the digital stereoscopic microscope and fractured surfaces of the debonded specimens were examined by SEM.

Results

All three groups showed that the treated surfaces were free of dentin debris and smear layer. The peritubular dentin protruded from the surrounding intertubular dentin after laser irradiation. The dentin–resin interface treated with Er,Cr:YSGG laser irradiation and acid etching demonstrated numerous resin tags converging into a bulge and then diverging again. The length of resin tags was greater than 100μm. The tensile bond strengths of bur-cut/acid-etched, aser-ablated/acid-etched and laser-ablated human dentin were 5.37±1.51, 5.17±1.41 and 3.29±0.86MPa, respectively. No statistical significance was found between the bur-cut/acid-etched and laser-ablated/acid-etched groups. The predominant fracture modes of bur-cut/acid-etched, laser-ablated/acid-etched and laser-ablated human dentin were Type 1 (50%), Type 2 (70%) and Type 1 (70%), respectively.

Significance

Er,Cr:YSGG laser irradiation affects adversely adhesion of resin to dentin but acid etching following laser irradiation could increase the tensile bond strength as high as that of bur-cut/acid-etched human dentin.

Keywords: Er,Cr:YSGG laser, Acid etching, Dentin, Scanning electron microscopy, Adhesion, Hybrid layer