Effects Of Self-etching And Total-etching Systems On Pulp Tissue

The developments in dentine adhesives has changed the design of cavity preparations, replacing the extensive removal of tooth structure with more conservative preparations. Recently, although many commercial adhesive systems are available, there are two major simplified approaches to adequate bonds according to the way interacting with the dentin smear layer. The first is the total-etching (TE) technique which use 30 to 40 percent phosphoric acid to etch detine and enamel before the clinician applies the adhesive to the preparation. Etching detine removes the smear layer and opens up the dentinal tubules. The second approach is the self-etching (SE) technique, which are been used increasingly, do not require a separate acid-etch step, and do not remove the smear layer. The SE technique simultaneously conditions both enamel and dentin using an acidic primer. They rely on their acidic functional monomers to dissolve hydroxyapatite and to yield a resin-infiltrated zone with minerals incorporated. Most of studies have demonstrated there were no significant differences in bond strength, ability of obturation and durable ability between them. However, Few studies were majored on the postoperative sensitivity of dentin bonding adhesives. The effect of dentin adhesive systems on pulp was one of resons on postoperative sensitivity of resin composite filling. The objectives of our research were to study the effects of adhesive systems on pulp tissue in fields of histology, micromorphology and clinical evaluation and to discuss the relationship between dentin adhesive systems and postoperative sensitivity of resin composite filling from different angles and to provide clinical advices for using adhesives during the resin composite filling. Three parts were included in this study: 1. The response of Mini pigs pulp to Total-etching versus Self-etching system Establishing the model of experiment animal in the mini pig. Deep class V cavities were prepared on the buccal surface of 147 premolars and molars on 7 mini pigs. To evaluate the response of the pulpo-dentin complex following application of six common adhesive and filling glass inomer cement in cavities according to the manufacturer' instructions. Blank control group did not use any adhesive and filling glass inomer cement directly. The results showed that cavity preparation induced pulp pathology reactions of pulp area undersurface cavity including vascular dilatation, odontoblastic morphology change and odontoblasts arranging in disorder. During following adhesive restoration process, the stimulus on pulp was mild in SE groups that did not delay pulp repair. TE group which showed vacuolar degeneration of odontoblastic layer had more stimulus on pulp. 2. Interfacial micromorphology of Total-etching vers. Self-etching system created in dentin. Extracted human molars were bonded with all kinds of adhesives according to the manufacturers' instructions,and a thin layer of 3M Z100 composite applied. The teeth were sectioned parallel to the bonded surface to obtain a bonded dentin disc. All the ultrastructures of dentin bonding interface were observed with SEM . The result showed that all teeth showed hybrid layer formation. However, the thickness varied depending on the adhesive systems and the total-etching(Prime & Bond NT) showed the thick hybrid layer whereas SE bonded to dentin exhibitedthe thiner hybrid layer. Moreover, in the teeth which were used total-etching, the composite did not penetrate to the depth of the zone of demineralized dentin, leaving a substantial area of exposed dentin matrix at the dentin/cement interface. In contrast, there was substantial composite diffusion throughout the demineralized dentin when the self-etching primer was used without acid etching pretreatment. 3. Effect on postoperative Sensitivity:Total-etching versus Self-etching systems. Patients were selected on the basis of requiring Class I and II restorations in molars and premolars. The authors placed 20 restorations with each SE material and TE ( Prime & Bond NT ). The restored teeth were...