Laboratory and Clinical Investigations Into the Diagnosis and Management of Fissure Caries Using Fissure Sealant, Glass Ionomer (Polyalkenoate) Cement and Composite Resin

This thesis comprises a series inter-related studies designed to elucidate aspects of the diagnosis and management of fissure caries using "sealant restorations". In a preliminary study, the use of the probe in addition to visual inspection did not improve the validity of the decisions to leave untreated, fissure seal or investigate fissures in a group of extracted teeth. A group of Community Dental Officers participated in a large survey/field trial in which they recorded details of 569 investigative cavities prepared in fissures. They were asked to predict the size of the lesion. As the size of the lesion increased, the accuracy of the prediction reduced and was not improved in operators using the probe. Caries lesions were most frequently underestimated in right mandibular first molars and both mandibular second molar teeth. The restorations in the field trial were assessed after 6 months, 1 year and 2 years. Sealant restorations were placed predominantly in first permanent molar teeth. The figures for complete retention of fissure sealant after 6, 12 and 24 months were: 56, 42 and 34% for therapeutic fissure sealants; 25, 17 and 9% for intra-enamel composite sealant restoration; 21, 12 and 13.8% for glass ionomer sealant restorations and 28, 19 and 18% for laminate sealant restorations. It was estimated that at the end of the two year field trial over 85% of restorations would survive a further one to two years and 37% would survive for more than two years. Eighty-seven to ninety-two percent of restorations required either no treatment of minimal additions of further fissure sealant. Improved retention of sealant was found with increasing age of patient at the time of restoration placement and with reduced size of restoration surface. Loss of fissure sealant from the surface of the restorative materials was noted more frequently than from the adjacent fissures of the occlusal surfaces of molar teeth. In vitro studies designed to investigate means of optimising shear bond strength of fissure sealant to restorative materials showed that when the base resin systems in the composite and fissure sealant are different, the mean shear bond strengths are significantly reduced. A significant increase in shear bond strength was noted, with both light and self cured fissure sealant, when Scotchbond Dual Cure was applied to the glass ionomer cement surface. A hospital based clinical trial with strict protocols was carried out to demonstrate the optimum performance of 150 sealant restorations. No restorations were lost and in the small type 2 restorations (n=15), 100% retention of fissure sealant was noted. In the larger type 4 restorations, complete fissure sealant retention was observed in 67% of teeth (n=97). The presence of small composite restorations did not adversely affect fissure sealant retention. Fissure sealant retention to glass ionomer cement restorations was significantly less (P