Comparison Study On Total-etching And Self-etching Dentin Adhesive Systems

PART ONE The microtensile bond strengths of total-etching/self-etching adhesives to different dentinStudy 1 Objective To evaluate the microtensile bond strengths of 7 total-etching / self-etching dental adhesives to normal dentin. Methods 35 intact young human premolar teeth extracted for orthodontic reasons were used. Superficial occlusal flat dentin of these premolar teeth were exposed, finished with wet 600-grit silicon carbide paper. All teeth were randomly divided into 7 groups. Totally 7 dentin adhesive systems were selected, among which All Bond 2 (AB2). Single Bond( SB) and Prime & Bond NT (PB) were total-etching systems, Fluoro-Bond (FB), Clearfil SE Bond (SEB), XenoIII and iBond were self-etching systems. Each group bonded with one dentin adhesive system according to manufacturers' recommendations. Then 5-6mm thickness of composite (Spectrum TPH, TPH) was build up on it. Samples were tested in tension in a Microtensile tester at 1 mm/min. Each fractured specimen was examined by stereomicroscope. Results The microtensile bond strengths of each dentin adhesive systems were: AB2 (28.47±4.94) MPa; SB (26.33+5.02) MPa; PB (28.22±6.16) MPa; FB (24.42±4.19) MPa; SEB (32.18±9.78) MPa; XenoIII (32.49±7.96) MPa; iBond (32.70±8.55) MPa. There was no statistical difference among 7 dentin adhesive systems. Most of fracture mode were mixed failure. There was no significant difference among 4 fracture modes. Conclusion No significant difference between the total-etching adhesive system and self-etching adhesive system bonding to normal dentin. It was recommended that dentin adhesive agent should be used according to the clinical situation.Study 2 Objective To evaluate the microtensile bond strengths of 4total-etching / self-etching adhesives to caries-affected dentin. Methods Twenty extracted carious human molars were stained by SablerMSeek ( Ultradent Products, Inc. USA) and ground to expose flat surfaces where the caries lesion was surrounded by normal dentine. Surfaces were bonded with AB2, SB, SEB or Xeno III according to manufacturers' recommendations. Then 5-6mm thickness of composite (Spectrum TPH, TPH) was build up. Samples were tested in tension in a Microtensile tester at 1 mm/min. Each fractured specimen was examined by stereo microscope. Results Two-way ANOVA revealed a significant influence of both the type of dentin and the adhesive systems tested on microtensile bond strength values. However, the interaction of these two factors was not statistically significant. All adhesives attained higher strengths in normal dentin than in caries-affected dentin. Significantly lower results were obtained with SB. Most of fracture mode was mixed failure. There was no significant difference among 4 fracture modes. Conclusion It was recommended that dentin adhesive agent should be used according to the type of dentin and the clinical situation.Study 3 Objective To evaluate the microtensile bond strength of 4total-etching / self-etching adhesives to cervical sclerotic dentin. Methods The adhesive systems, two total-etch adhesives (AB2, SB)and two self-etch adhesives (SEB, XenoIII) were applied in both naturally-occurring, cervical sclerotic dentin and artificially prepared wedge-shaped lesions. Samples were tested in tension in a Microtensile tester at 1 mm/min. Each fractured specimen was examined by stereomicroscope. Results Three-way ANOVA revealed a significant influence of the type of dentin on microtensile bond strength values. Highest results were obtained with AB2, however, there was no significant difference among 4 adhesive systems. The major mode of failure was mixed failure. Conclusion It was recommended that dentin adhesive agent should be used according to the type of dentin and the clinical situation.PART TWO SEM and LSCM observation on the dentin-adhesive resininterface of total-etching / self-etching dental adhesive systemsStudy 4 Objecitve To observe the microstructure characteristic of thedentin-adhesive resin interface of total-etching adhesive system (PB) and self-etching adhesive system (XenoIII) under SEM and LSCM. Methods 6 intact young human premolar teeth extracted for orthodontic reasons were used. Superficial occlusal flat dentin of these premolar teeth were exposed, finished with wet 600-grit silicon carbide paper. All teeth were randomly divided into two groups in order to prepare SEM and LSCM specimens. Each tooth was divided into two nearly equal halves parallel to its long axis for accepting treatment of the two dentin adhesive systems respectively. For SEM group, a block of resin composite was bonded with two dentin adhesive systems according to the manufacturers' instructions. For LSCM group, a block of resin composite was bonded with the same two dentin adhesive systems that labeled with 0.1 % Rhodamine B according to the manufacturers' instructions. Results 4~6um thickness of resin-infiltrated zone (hybrid layer) of total-etching adhesive system PB could be observed by means of SEM and LSCM with well-formed cone shaped resin tags. Resin tags penetrated lateral branches of dentinal tubules were observed to form a micro-network of resin. SEM and LSCM examination showed that the thickness of hybrid layer of self-etching adhesive system XenoIII was 4~5um and the hybrid layer was more uniformly infused with resin. Resin tags were observed to traverse from the resin layer above into the undermineralized dentin below and less network were found. Conculsion The thickness of hybrid layer was similar between PB and XenoIII under SEM and LSCM observation. There was slight different on the penetration of the resin tags in the bonding interface. It was suggested that SEM, LSCM and other methods can be used together to evaluate the relationship between the bonding interfaces and bonding strength.PART THREE Biocompatiability Study on total-etching/self-etching adhesive systems in vitro & in vivo.Study 5 Objective To evaluate the cytotoxicity of different dentin adhesive systems to human pulp cells. Methods Four dentin adhesive systems (PB, SB, Xeno III and iBond) were diluted with the culture medium by a ratio of 1:1000, 1:2000 and l:4000(v/v), and the fifth generation pulp cells were exposed to culture medium containing different dentin adhesive systems dilutes for 12h, 24h, and 48h, then the morphological changes of pulp cells were observed with microscopy and cytotoxicity were analyzed with modified MTT assay. Results Either concentration of 4 systems was toxicity to pulp cell. There was significant difference between 4 dentin adhesive systems. Conclusion The working time and concentration of dentin bonding system have some effects on the cytotoxicy. Total-etching system was more cytotoxic than self-etching system, and SB was the strongest cytotoxic agent among these adhesive agents.Study 6 Objective To evaluate the response of pulpo-dentin complexfollowing application of two different dentin adhesive systems in deep dentinal surface performed in human teeth. Methods Deep class V cavities were prepared on the buccal surface of 38 premolars. In Group 1, the cavity walls (dentin and enamel) were conditioned with 36% phosphoric acid and the total-etching dentin adhesive system PB was applied. In Group 2, the self-etching dentin adhesive system XenoIII was applied to the cavities. In Group 3 and 4, before application of PB or XenoIII repectively, the cavity floor was lined with the calcium hydroxide cement. The cavites were restored with light-cured Spectrum TPH composite resin. Two teeth were used as intact contact group. The teeth were extracted between 7 and 20 days and prepared for microscopic assessment. Serial sections were stained with HE and Brown and Brenn techniques. Results In Group 1, the inflammatory response was more evident than in Group 2, 3 and 4. Diffusion of dental material components across dentinal tubules was observed in Group 1, in which the intensity of the pulpresponse increased as the remaining dentin thickness. In Group 3 and 4, all the teeth showed normal histological characteristics which were similar to the intact control group. Bacteria were not evidenced in these four groups. Conclusion Total acid etching followed by application of PB were not recommended when used in deep cavity. In this situation, the self-etching adhesive system XenoIII seems to be safe to the human pulp. And it was suggested that the cavity walls should be lined with calcium hydroxide cement before etching deep dentin and applying PB.