Comparisons of shear bond strengths between laser-treated dentin and bonding systems

• Main Authors: Chih-Kai , Hsu, 許智凱
• Other Authors: Shun-Te , Huang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/44875034456297182333

碩士 === 高雄醫學大學 === 牙醫學研究所 === 89 === 英文摘要 In the last few years, a number of studies have indicated that lasers can cause the obliteration of the dentinal tubules, enhancing the resistance to the acid and causing a rough surface on the dentin. The effects of the laser energy on the dentin ranged from no visible effects, to charring, cracking, cratering, and glazing. Nowadays, lasers are used more frequently in dental clinic. Dentin treated by Nd:YAG laser showed no remnants of infected layer of carious dentin. If laser-treated dentin could bond with the restorative material well, it will increase the motivation of using lasers. The objective of this study was to evalulate and compare the shear bond strength of the four different bonding systems {Scotchbond Multi-purpose ( ScBM ), Single Bond ( SgB ), Clearfil SE Bond ( SEB ), Prime & Bond NT / NRC ( PB ) } on control and lasers (Nd:YAG laser, CO2 laser) treated dentin between both the permanent and primary teeth , then observing their adhesion by the scanning electronic microscope. The samples of the permanent teeth were collected from the buccal and lingual surfaces and the samples of the primary teeth were collected from the labial surfaces.Cutting those samples into 4×4 mm2 dentinal discs , then polished with ＃320、＃600、＃800 sand papers and randomly divided into three groups : (1) control (2) Nd:YAG laser (3) CO2 laser. The parameters of the lasers were (1) Nd : YAG laser : 5 W , 50 pps ,spot size 0.6 mm, moving rate 10 mm /sec , energy density 83.33 J /cm2 . (2) CO2 laser : 2 W, continuous wave , spot size 0.3 mm , moving rate 8 mm / sec , energy density 83.33 J / cm2 . Each group then bonded with four dentin bonding systems individually. All bonded samples would have a shear bond strength test. The results of the shear bond strength test would have been analyzed by ANOVA test and t-test. The shear bond strength (MPa) of intermaterial permanent teeth group were as follows: (1) control group : SgB ( 22.75 ± 4.58 ) > ScBM ( 17.90 ± 3.73 ) > SEB ( 17.71 ± 1.89 ) > PB ( 13.43 ± 3.17 ). (2) Nd:YAG group : SEB ( 9.75 ± 1.33 ) > { SgB (7.40 ± 1.33 ) , ScBM ( 7.40 ± 1.86 ) } > PB ( 4.96 ± 1.14 ) . (3) CO2 group : no significant pairs. The shear bond strengths of the intermaterial comparison of the primary teeth group were as follows: (1) control group : SgB ( 15.24 ± 3.26 ) > {ScBM ( 11.42 ± 2.01 ) , SEB ( 9.67 ± 1.98 ) } > PB ( 8.04 ± 1.50 ) . (2) Nd:YAG group : SgB ( 4.37 ± 2.00 ) > ScBM ( 2.30 ± 0.94 ) ; SEB ( 9.67 ± 1.98 ) > ScBM ( 2.30 ± 0.94 ) . (3) CO2 group : ScBM ( 5.30 ± 1.84 ) > PB ( 1.96 ± 0.83 ) ; SEB ( 5.00 ± 1.65 ) > PB ( 1.96 ± 0.83 ) . In addition to ScBM group of the CO2 laser group, all shear bond strengths of the permanent teeth group were better than the primary teeth group. The results of observing the bond failure pattern were as follows : (1) Most of the control groups of both the permanent and primary group were adhesive failure pattern. (2) Most of the Nd:YAG and CO2 laser group of both the permanent and primary group were adhesive-cohesive (complex) failure pattern. The results of the observation by scanning electronic microscope were listed below: (1) Both the dentin surface of permanent and primary teeth groups after the application of 37% phosphoric acid showed the openings of the dentinal tubules, and no smear layer remained. (2) The dentin surface of both permanent and primary teeth group after application of NRC or the primer of Clearfil SE Bond didn’t remove the smear layer completely. Some of the openings of the dentinal tubules are still completely or partially occluded. (3) The surfaces after laser (Nd:YAG laser,CO2 laser) treatment of both permanent and primary group showed the appearance of the melting and recrystallization. (4) The resin tags distributed along the dentinal tubules in the most of all groups before and after shear bond strength test. (5) In the four different bonding systems, hybrid layer could be found in the most of the control groups of both permanent and primary teeth groups. In conclusion, (1) shear bond strengths obtained from the control group were higher than the Nd:YAG group and CO2 group of both permanent and primary group. (2) In addition to ScBM group of the CO2 laser group, shear bond strengths of four different bonding systems were higher in the permanent teeth group than those in the primary teeth groups. (3) The laser (Nd:YAG laser or CO2 laser)-treated surface showed the appearance of the melting and recrystallization. The smear layer on the laser- treated dentin surface became less. (4) The dentin surface etched with 37% phosphoric acid for 15 seconds produced better removal effect of smear layer than the dentin surface applied with the primer of Clearfil SE Bond or NRC for 20 seconds. (5) The formation of the hybrid layer in the control group are better than in the Nd:YAG and CO2 laser group of both permanent and primary group. (6) Most of the control group were adhesive failure pattern, but most of the laser (Nd:YAG laser,CO2 laser) groups were adhesive-cohesive (complex ) failure pattern.