CONFOCAL MICROSCOPIC OBSERVATION OF STRUCTURAL-CHANGES IN GLASS-IONOMER CEMENTS AND TOOTH INTERFACES

This study aimed to develop techniques to allow dynamic imaging of a c avity before, during and after placement of glass-ionomer restorative materials. Cavities were cut in recently extracted third molars and th e teeth longitudinally sectioned. Each hemisected tooth surface was pl aced in green modelling compound at 90 degrees to the optical axis of the microscope. The cavity surface was imaged using a video rate confo cal microscope in conjunction with an internally focusable microscope objective. The sample on the stage was pushed up to the objective lens which 'clamped' the cover glass onto it. Water, glycerine or oil was placed below the coverglass, with oil above. Internal tooth structures : were imaged by changing the internal focus of the objective. The res torative material was then placed into the cavity. Video images were s tored either onto video tape or digitally, using a frame grabber, comp uter and mass memory storage. Software controls produced time-lapse re cordings of the interface over time. Preliminary experiments have exam ined the placement and early maturation of conventional glass-ionomer cements and a syringeable resin-modified glass-ionomer cement. Initial contact of the cement matrix and glass particles was visible as the p lastic material rolled past the enamel and dentine: before making a bo nd Evidence fnr water movement from the dentine into the cement has al so been seen. After curing the early dimensional changes in the cement s due to water flux were apparent using the time-lapse facility. This new technique enables examination of developing tooth/restoration inte rfaces and the tracking of movement in materials. (C) 1998 Published b y Elsevier Science Ltd. All rights reserved.