| With the rapid development of modern digital technology,the chair-side CAD/CAM system is widely used in the field of dental restoration.The chair-side CAD/CAM system has several advantages in that it is easy to be manipulated,precise to acquire the impression,and is immediately to produce restoration.Only once treatment by chair-side system could save much time,which is developed to be the preferred way for doctors and patients.Since 2012 when Cerec AC chair-side system was applied in clinics,its optical scanner could more precisely return the oral situation,color reduction realistically,and the three-dimensional reconstruction could be extended to the whole dentition.The strength of matched new generation of machinable Lithium Disilicate Glass-ceramic(LDGC)IPS e.max CAD is higher up to 360 Mpa,which is much higher than feldspathic ceramic and leucite reinforced glass ceramic.Moreover,the application of new generation of zirconia ceramic(ZC)inCoris in the Cerec AC has enlarge the restoration types using chair-side system.However,there is still few research on evaluating the clinical performance of Cerec AC system and new material restoration.In this study,we used follow-up study on the LDGC and ZC restorations at3 rd,6th,12 th,24th months after treatment respectively,analyzes the reasons of failure and further investigated the impact of restoration type,tooth position and cement on the restoration survival rate.These results may provide the valuable information for using the chair-side system in clinics.Objective:The study aimed to evaluate the clinical performance of LDGC and ZC restorations produced using Cerec AC system,to analyze failure reasons,and to investigate the type,tooth region,and cement on the effect of the restorations’ survival rate which may providing more valuable information for chair-side system’ clinical application.Materials and methods:This experiment adopts follow-up method to investigate the LDGC restorations and ZC restorations made by Cerec AC system,at 3rd,6th,12 th,24thmonths after treatment respectively.Following the standards of CDA,we evaluate their clinical performance,calculate survival rate of two kinds of restorations by Kaplan-Meier surial analysis,and explore effect of the type,tooth position and cement on survival rate of restoration by Log-Rank test.Result:1、The 24 months follow up study of 450 pieces of LDGC restoration in clinics showed outstanding performance at marginal fit,shape matching,secondary caries,gingival and postoperative sensitive.The grade A is above 99%;Color matching grade A94.9%.In observation period,18 pieces of restorations were suffered from chipping,5pieces of restorations were uncemented and 1 was suffered from bad adjacency;Among the failing restorations,1 occurred on anterior teeth,1 occurred on premolar and 22 occurred on molars;15 pieces of restorations failured during first 1-3 months after permanent cementation,6 failured in 4-6 months after permanent cementation,2 failured in 7-12 months after permanent cementation and 1 failured in 13-24 months after permanent cementation(chi square test,P < 0.001).2、CSR of LDGC restorations was 94.2% at 24 months.CSR of full crowns was94.6%,of inlays was 92.5%,of onlays was 95.8%,of veneers was 94.4%(Log-Rank test,P=0.952).CSR of anterior restorations was 97.6%,of the premolars was 98.5%,of the molars was 92.3%(Log-Rank test,P=0.043).CSR of restorations using total-etch adhesive was 92.9%,of restorations using self-etch adhesive was 93.8%,of restorations using self-bonding adhesive was 95.5%,of restorations using resinforced glass innomer cement was 95.5%(Log-Rank test,P=0.746).3、The 24 months follow up study of 182 pieces of ZC restoration in clinics showed excellent performance at marginal fit,secondary caries,postoperative sensitive.The gradeA is up to 100%;Gingival grade A 99.5%;Color matching grade A 91.2%.In observation period,2 pieces of restorations were suffered from chipping,2 pieces of restorations were suffered from color mismatching and 1 was suffered from bad adjacency;Among the failing restorations,1 occurred on premolar teeth and 4 occurred on the molars.5 pieces of restorations failured during first 1-12 months after permanent cementation,no failure in13-24 months(chi square test,P=0.033).3 pieces of restorations failured during 1-3months,1 failured in 4-6 months and 1 failured in 7-12 months.4、CSR of ZC restorations was 97.1% at 24 months.CSR of full crowns was 96.3%,of consecutive crowns was 100%,of integrated abutment crowns was 98.2%(Log-Rank test,P=0.716).CSR of anterior restorations was 100%,of the premolars was 96.3%,of the molars was 97.0%(Log-Rank test,P=0.777).CSR of restorations using glass innomer cement was 97.7%,of restorations using reinforced glass innomer cement was 95.5%,of restorations using composite resin adhesive was 100%(Log-Rank test,P=0.748).Conclusion:1.Chair-side Cerec AC LDGC and ZC restorations showed outstanding performance at marginal fit,secondary caries,postoperative sensitivity,shape matching and gingival,the grade A is up to 99%.Survival rate is higher in the short term.The 24 months CSR are much high,which were 94.2% and 97.1%.The clinical performance is satisfactory.2.The effect of restoration type and cement have few effect on the survival rate of LDGC and ZC restorations.The effect of tooth position has few effect on the survival rate of ZC restorations but has statistical effect on the LDGC restorations.The failure happening on the molars is much higher than on premolar and anterior area,which indicated that we should pay attention to the choice of clinical indication,when using LDGC restorations on molar position.Thus,prosthodontists must ensure that there are no occlusal interferences with the restoration when providing an occlusal adjustment and must provide enough space for the restorations.3.For both LDGC and ZC restorations,the failure happen almost within 3 month after permanent cementation,which indicated that prosthodontists should carefully make an occlusal adjustment,introduce the beginner on the restoration use and regularexamination.4.The ceramic chipping is the major reason of failure restorations,prosthodontists should pay more attention to it. |
