Effect Of Air Abrasion On Adhesive Performance Of Mottled Enamel

The typical clinical manifestation of mottled enamel is the chalky or fuscescentplaque, even worse complicating parenchymatous defect, all of which can show asevere adverse effect on patients'beautiful outlook. Veneer is a relatively idealtreatment which is used prosthetic materials overlaying on the tooth surface withbonding technique in order to improve the color of mottled enamel. However, theprosthetic restorations are more easily to fall off than normal tooth because of thespecific structure of mottled enamel. The technique of air abrasion is applied on thecurrent adhesive prosthesis of composite resin. The enamel and dentin can get a moreeffective bonding to composite resin by using that technique. At present, air abrasionhas been used to remove caries,prepare cavity and repair composite materials. In thisstudy, the bonding effect of mottled enamel by using air abrasion will be evaluatedbefore the adhesive of porcelain laminate veneer. With the final purpose to inspectwhether air abrasion technique can be used to pretreatment the mottled enamel beforebonding veneer in clinic.PartⅠThe Study of Air Abrasion on Shear Strength of MottledEnamel-Porcelain Bonding Objective:To evaluate the effects of air abrasion, acid etching and the combinationof both procedures on shear strength of mottled enamel-porcelain in vitro.Methods:Thirty extracted teeth with moderate fluorosis were prepared using theDean′s index (DI) and divided into 3 groups(n=10), group A (the enamel wasprepared with acid-etching)；group B (the enamel was prepared with air abrasion)；group C(the enamel was prepared with air abrasion and acid-etching)；then all thegroups were bonded with porcelain disc. The shear bond strength was examined andcompared by analysis of variance. Debonded surface was examined withstereomicroscope. SEM was used to observe the mottled enamel after pretreatment.Results:The shear bond strength of group A was (15.25±2.82)MPa,group B was(11.75±2.26)MPa,group C was (18.77±3.90)MPa. A significant difference in shearbond strength was found between group A and group C (P＜0.05),and there was alsosignificant difference between group A and group B (P＜0.05).Conclusion:The adhesive strength of mottled enamel to porcelain could beimproved with using air abrading and acid etching as a pretreatment method offluorosis enamel.PartⅡThe Effect of Air Abrasion on Microleakage between Mottledenamel–Composite Resin Cement–PorcelainObjective:To evaluate the effects of air abrasion, acid etching and the combinationof both procedures on the microleakage between mottled enamel–composite resincement–porcelain .Methods:Eighteen bicuspid extracted teeth with fluorosis from patients needingorthodontic force were prepared and divided into 3 groups(n=6), group A:theenamel was prepared with acid-etched；group B:the enamel was prepared with airabraded；group C:the enamel was prepared with air abraded and acid-etched；then all the groups were bonded with porcelain disc using composite resin cement. All ofthe samples was thermalcycled for 500 times, then put into 1% methylenumsolution soaking for 24 hours. The samples were cut off along the odontal long axis,microleakage of the samples was observed and taken photographs under40×stereomicroscope, the immersed distance of enamel-composite resin cement andcomposite resin cement-porcelain was both measured by the analytical software.The values of microleakage were examined and compared by analysis of variance.Results:The microleakage value of group A was (0.98±0.30)mm,group B was(1.39±0.33)mm,group C was (0.48±0.24)mm. A significant difference ofmicroleakage was found between group A and group C (P＜0.05),and there wasalso significant difference between group A and group B (P＜0.05). There were nodifferences of composite resin cement-porcelain among three groups.Conclusion:The microleakage between mottled enamel and composite resincement can be reduced by using air abrading and acid etching as a pretreatmentmethod of fluorosis enamel which could increase the marginal adaptation betweenmottled enamel and composite resin cement.