PubMed · 9442732
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J I Haring. 1997. Case #3. Hypercementosis.. https://pubmed.ncbi.nlm.nih.gov/9442732/
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The aim of this study was to evaluate in vivo the cariostatic potential of the resin-reinforced glass-ionomer (Vitremer core build-up restorative; 3M Dental Product Division) when used as a bonding agent for orthodontic brackets. The mineral distribution and topography of the enamel surface adjacent to the bracket base was determined by quantitative microradiography (TMR) and confocal laser scanning microscopy (CLSM). The study was designed in split-mouth technique using 9 pairs of premolars to be extracted for orthodontic reasons. One tooth of each pair was bonded with the resin-reinforced glass-ionomer, and the control contralateral premolar with the non-fluoridated composite (Concise, 3M Dental Products Division). After 4 weeks all teeth were extracted and stored until analysis. The lesion depths and mineral loss values in enamel adjacent to brackets bonded with Vitremer were significantly lower than in teeth bonded with the composite, indicating that the resin-reinforced glass-ionomers significantly reduced caries lesion development in vivo. CLSM images show a severe cariogenic challenge around orthodontic brackets and support TMR measurements.
It is conventionally taught that the carious lesion in dentin undermines the enamel due to lateral spread of the lesion at the enamel-dentin junction (EDJ). The aim of the present study was to challenge this hypothesis by testing an alternative hypothesis, that lateral spread is related to advanced lesions where the dentin is infected. Selected points in the groove-fossa system of 100 unrestored occlusal surfaces were examined and the teeth divided into five groups (scores 0-4) depending on the clinical appearance of the lesion. Teeth were sectioned through these sites and texture of the dentin was assessed by probing. Colour slides of the section face with the more extensive changes in the dentin were projected and the dimensions of the lesions at the EDJ were assessed by three examiners on two separate occasions. Inter- and intra-examiner reproducibility was assessed and found acceptable. Results showed that in 47 teeth demineralisation had not reached the EDJ. In the remaining teeth the presence or absence of lateral spread of the lesion at the EDJ was related to the clinical features of the lesion. Lateral spread was rarely found in lesions with an apparently intact enamel surface (scores 0-2). However, 32% of sites with microcavitation (score 3) and 63% of sites with obvious cavitation (score 4) showed lateral spread. Of those 31 sections which were judged to have soft dentin, 80% had lateral spread. In conclusion, the phenomenon of lateral spread of caries at the FDJ is related to advanced lesions with cavity formation where the dentin is soft and infected.
Teeth are subjected to stress during normal function. The manner in which the resulting strain is distributed within the tooth is related to its structure. The Moiré fringe technique was used to map the in-plane strain distribution in slices from human tooth crowns under compression. The strain inside enamel is much less than in dentin, and there is a roughly 200 microm thick zone in dentin beneath the dentin enamel junction which undergoes larger strain than the central coronal dentin. This zone is softer and less mineralized than the bulk of the dentin. The strain distribution in this zone along the dentin-enamel junction shows localized maxima on both the lingual and the labial sides. This study is consistent with the hypothesis that within the dentin there are structural adaptations for transferring and minimizing stress.