Study On Clinical Application Materials And Methods Of Carapse And Pit Closure And The Effect Of Caries Prevention

As one of the most common disease in oral cavity, caries always brings the experience of pain, problems with eating, chewing, smiling and communication due to missing, discolored or damaged teeth have a major impact on people’s daily lives and well-being. According to current researches, placement of sealants on the permanent molars of children and adolescents is effective for caries reduction. There is evidence shown that sealed permanent molars are less likely to receive restorative treatment, that the time between receiving sealants and restorative treatment is greater, and that the restorations were less extensive than those in permanent molars that were unsealed.Pits and fissures in teeth surfaces sealed with an adhesive material, either composite resin or glass-ionomer. Two new glass-ionomer-based materials with potentially improved properties:glass-carbomer and a high-viscosity glass-ionomer (KMEM), have been introduced to market when present research started. In this study, the retention rate and caries preventive effect of these two materials for use in sealants will be compared with that of composite resin. Additionally, there is a new applying technique for ART glass ionomer which adds light curing after sealing material is applied and before it is set. The result of present study may reveal which material is more suitable for application in schools and communities without rotary instrument and a regular recall system in China.Meanwhile, it is will help to improve the properties if we can make it clear which variables can influence the retention and the caries preventive effect. For clinicians, they may use materials of which the performance in vivo are predictable. As one of the most challenging properties of dental materials, wear-resistance is important for its lasting periods in oral. To test whether resin or glass-ionomer has a higher wear resistance, a chewing model was designed to simulate the process of mastication and abrasive wear of the sealant materials on extracted tooth surfaces was assessed the in vitro with abrasive medium which we think may have a positive effect on the abrasion of sealants. To measure the vertical loss and volume loss of the sealants before and after the mimicry of mastication, profilometer are used to scan the occlusal surface of sealed teeth and calculate the material loss.Part I Sealant study of two new materials and applying technique. Study1:Sealant retention after4yearsObjectives:The hypotheses tested were:the cumulative survival rate of fully and partially retained high viscosity glass ionomer and glass carbomer sealant are both higher that composite resin after4years; the cumulative survival rate of fully and partially retained high viscosity glass ionomer sealant with heat supplied is higher than that of high viscosity glass ionomer sealant without heat supplied after4years.Methods:The randomized controlled clinical trial covered405children (mean age8-years). Three dentists placed sealants in pits and fissures of high caries-risk children. Evaluation by two independent evaluators was conducted after0.5,1,2,3,4years. The Kaplan-Meier survival method, ANOVA and t-test were used in data analyses.Results:1304first permanent molars were sealed.12.3%of children and15.4%of sealants dropped out. According to both traditional and modified categorization, the survival rate of completely and partial retained resin-composite and sealant in occlusal and in smooth tooth surfaces was statistically higher and those of glass carbomer was lower than those of sealants of the other three groups. The survival rate of completely and partial retained high viscosity glass ionomer with and without LED light curing in occlusal and in smooth tooth surfaces was not statistically significantly different.Conclusion:The retention performance glass carbomer sealant was the poorest. And the LED light curing will not contribute to the retention rate to high viscosity glass ionomer sealant.Study2:Caries preventive effect of sealant after4yearsObjectives:The hypotheses tested were:the cumulative survival rates of dentine caries lesion-free pits and fissures of ART conventional high-viscosity glass-ionomer sealants with light-curing (high-intensity LED) and glass-carbomer sealants are higher than those of conventional ART sealants and resin-composite sealants after4years.Methods:The randomized controlled clinical trial covered405children (mean age8-years). Three dentists placed sealants in pits and fissures of high caries-risk children. Evaluation by two independent evaluators was conducted after0.5,1,2,3,4years. The Kaplan-Meier survival method, ANOVA and t-test were used in data analyses.Results:1304first permanent molars were sealed.12.3%of children and15.4%of sealants dropped out.46re-exposed pits and fissures,39(occlusal)7(free smooth surfaces), in42children developed a dentine carious lesion. The cumulative survival of dentine caries lesion-free occlusal pits and fissures in ART plus LED group (98%) was statistically significantly higher than in the resin-composite group (96.4%) and in the glass-carbomer group (94.5%). The cumulative survival of dentine caries lesion-free occlusal pits and fissures in the glass-carbomer group was statistically significantly lower than that in the conventional ART group (97.3%). For the free smooth surfaces, there was no statistically significantly difference among the four sealant groups.Significance:Light-cured ART conventional high-viscosity glass-ionomer sealants prevented the occurrence of dentine cavities best.Part II:In-vitro surface wear of a high-viscosity glass-ionomer with resin coat used as a sealantObjectives:To test the surface wear of a glass-ionomer sealant material that uses a resin coat meant to protect the surface in comparison to a conventional glass-ionomer and a resin sealant material.Methods:The occlusal surface of48extracted human third molars were sealed with a resin (Clinpro), conventional high-viscosity glass-ionomer (KMEM) and a high-viscosity glass-ionomer with resin coat (Equia system). The Rub&Roll wear simulation device and ACTA wear abrasive slurry was used to mimic clinical wear. The mean height loss of the sealants and that of enamel was measured twice after120,000cycles using a profilometer. Paired t-test and ANOVA were used to analyse the data.Results:The reproducibility test of measuring surface wear did not show a statistical significant difference (p=0.303). The mean height loss was 29.88μm (Clinpro),36.85μm (KMEM) and35.26μm (Equia system) which differences were not statistically significant (p=0.108).Conclusions:Surface wear of the newly developed high-viscosity glass-ionomer with resin coat was not different from the conventional high-viscosity glass-ionomer and resin sealant materials.