The Research On Effect Of Wedge-shaped Defect Restored By Flowable Composites

Noncarious Cervical Lesions ( NCCLs ) is an abrasion that caused by long-term abrasing in tooth cervical. Being of its wedge shape, it also called wedge-shaped defect. It's well known to be prevalent in oral. Now filling is the best therapy way and being used commonly. But the ways of filling are often limited by materials' performance. The key point of success is to select a good one. As a new material, flowable composites has its' own characteristics. For example, low elastic modulus, well fluidity, and so on. It is reported that flowable composites is more adapted to fill wedge-shaped defect. In this research, we compared flowable composites and two dental materials that were usually being used in clinical. In order to give a reference to clinical application, we evaluate the microleakage of restorations and bond strength in vitro and the clinical assessment for three kinds of restorations of cervical wedge-shaped defect. The study has three parts as follows:Part Ⅰ: Experimental Research1 In vitro evaluation of microleakage of a flowable composite inwedge-shaped class V restorationsMaterials and Methods: V-shaped non-retentive cavities were prepared on buccal cervical surface of 24 fresh extracted maxillary premolars at the CEJ Level. Teeth were randomly assigned to 3 groups with 8 teeth in each group: (A) Aeliete flo; (B) Dyract AP; (C) GIC TYPE II. Each material was used according to manufacturer's directions. After load cycling and thermal cycling, all teethwere then immersed in 2% methylene blue solution for 24 hours. Each samplewas then longitudinally sectioned to obtain 4 pieces from buccolingual direction.These were examined under ×40 magnification; the degree of microleakage wasassessed as the ratio of the extent of dye penetration at the tooth-restorationinterface to the length of the wall. Then they were analyzed by scanningelectronic microscope ( SEM) under ×1000 magnification.Result: Statistical analysis revealed a significant difference (P < 0.001) inmicroleakage among three materials. Aeliete flo showed less microleakage onboth margins compared to the others (0.80±0.14) .Conclusion: It can be concluded that flowable composites (i.e. Aeliete flo)may be recommended to improve the marginal seal of a restoration.2 Comparative of the bond strength of flowable composites and two materialsMaterials and Methods: Eighteen third molars of human had their occlusal enamel removed in order to expose a flat dentinal surface. After polishing by 600-grit wet sand paper on it, the adhesive procedures were carried out. The teeth were divided at random into three groups of 6 specimens, according to the employed adhesive system and composite resin or other materials: A (Aeliete flo), B ( Dyract AP), C ( GIC TYPE Ⅱ). After 24 h in distilled water at 25℃, the teeth were longitudinally sectioned in two perpendicular directions in order to obtain parallelogram-shaped specimens with a cross-sectional area of 0.8mm~2 on the average. The test specimens were submitted to MTT. Then the results were compared.Result: The Tyrian/One-Step Plus (Aeliete flo) bonding system produced significantly higher bond strength ( 28.45±10.79 MPa) than all other systems evaluated. The others bond strengths were 14.75±7.41 MPa (Dyract AP), 2.63±1.72 MPa (GIC TYPE Ⅱ), Statistical analysis revealed a significant difference ( P < 0.05 ) among them.Conclusion: It can be concluded that the bond strength of Aeliete flo ( Tyrian/One-Step Plus ) has a comparable high value using microtensile test.Part II: Clinical Study Clinical evaluation of a flowable composite in wedge-shaped defectsMaterials and Methods: 136 cervical wedge-shaped defects from 37 patients were randomly assigned to four groups according to using either flowable composites ( Aelite flo) or compomer (Dract AP) and with or without preparing cavity. The restorations were clinically evaluated at 6 months and 12 months with modified USPHS criteria for seven categories. Statistical analysis was completed with the Fisher's exact test.Result: No statistical...