Clinical Study On The Effect Of Different Curing Methods Cements On The Color Stability Of Porcelain Restoration

As the improvement of people's living standards and aesthetic awareness,patients' aesthetic demands for oral restoration increase as well.In order to meet people's requirements,oral restoration materials are also developed constantly.Porcelain material becomes the best one in anterior teeth restoration because of its excellent bio-compatibility and optical properties which are similar to natural teeth.In anterior teeth restoration,what doctors and patients care most is the color and shape of the restorations.However,the final color of the porcelain restoration is influenced by many factors,such as the color of the material itself,the color of the abutment and the color of the cements.With the physical-chemical reactions in patients' oral cavity,the color change of the cements may be displayed through the ceramic layer,and it has an important effect on the final color of the restorations.At present,the researches on the influence of the cements on the color stability of porcelain materials are mainly done in vitro.That is to say,scholars accelerate the aging process of cements and porcelain in a simulative oral cavity and then analyse the color change of cements and porcelain materials.However,the oral cavity is a complex environment,and the experiments in vitro in some ways can not completely simulate the real oral environment.So we design the clinical trials in order to confirm the in vitro experiments to provide the basis for the choice of clinical ceramic cements in anterior teeth restoration.The study is divided into three parts.In each part,20 cases of anterior teeth with all ceramic crowns were collected,10 of which were repaired with zirconia crowns and 10 with IPS.e max crowns.The ceramic crowns in the three-part was adhered to the prepared abutment by GC FujiCEM(self-cure),RelyX Unicem(dual-cure)and RelyX Veneer(light-cure).The color values of the incisal,middle and cervical of each restoration were measured by shadepilot immediately,1 week,1 month,3months,6months,9months and 12 months after bonding.And then the law of color variation and influences of three cements on the color stability of porcelain restoration were analysed.The results are showed as below:1.After being bonded by FujiCEM,the L* values decreased but the a*b*?E values increased as time went on.After 9 months,the ?E at cervical of e.max crowns was 1.53,beyond the critical value that can be recognized by eyes.At the same measurement time,?E at cervical was the largest,followed by the middle,and the incisal was minimum.The ?E at the incisal and middle of zirconia crowns has no difference(P>0.05).The ?E at the incisal,middle and cervical of the e.max crowns has significant differences(P<0.05).The ?E of zirconia and e.max crowns has significant differences(P<0.05).2.After being bonded by Unicem,the L* values decreased but the a*b*?E values increased as time went on.After 12 months,the largest ?E of zirconia and e.max crowns were 0.76 and 1.14,which were below the critical value that can be recognized by eyes.And the ?E in different measurement time has significant differences(P<0.05).At the same measurement time,?E at cervical was the largest,followed by the middle,and the incisal was minimum.And the ?E at different parts has significant differences(P<0.05);the ?E of zirconia and e.max crowns has significant differences(P<0.05).3.After being bonded by Veneer,the L* a*b*?E values changed as time went on.After 12 months,the largest ?E of zirconia and e.max crowns was 0.63 and 0.89.And the ?E in different measurement time has significant differences(P<0.05).At the same measurement time,The ?E at the incisal,middle and cervical of the zirconia crowns has no differences(P>0.05),but of e.max crowns,the ?E at different parts has significant differences(P<0.05);The ?E of zirconia and e.max crowns has significant differences(P<0.05).4.After being bonded by GC FujiCEM,RelyX Unicem and RelyX Veneer,the largest ?E of zirconia crowns was 0.97,0.76,0.63 after 12 months.And of e.max crowns,it was 1.57,1.14,0.89.The ?E of restorations between different cements has significant differences(P<0.05).Conclusions:1.As time went on,all the cements had a certain effect on the color stability of the two kinds of all-ceramic restorations.The restorations became dark and the color tended to be red and yellow,and the color difference increased.The effect of the adhesives on the color of the restorations can not be visually recognized within 12 months after bonding,except the color change of e.max crowns after 9 months bonded by GC FujiCEM.2.The same cement has different effects on the color stability of the incisal,middle and cervical of the porcelain restorations.Among them,the color stability of the cervical of the restoration of the greatest impact,followed by the middle and the incisal of the smallest impact.3.The same cement has different effects on the color stability of the same parts of the zirconia crowns and e.max crowns,and the color stability of e.max restorations is more susceptible to the effects of adhesives.4.The effect of different curing methods cements on the color stability of porcelain restorations is different.The chemical curing cement GC FujiCEM has the greatest influence on the color stability of the porcelain restorations,and the double curing adhesive RelyX Unicem takes the second place.The light curing adhesive RelyX Veneer has the least effect on the color stability of the restorations.And the effects of different curing methods cements on the color stability of porcelain restorations was statistically different.