The interaction of tooth-coloured dental restorative materials (a conventional glass-ionomer, two resin-modified glass-ionomers and two compomers) with acidic beverages has been studied with the aim of investigating how long-term contact affects solution pH and specimen surface hardness. For each material (ChemFil Superior, ChemFlex, Vitremer Core Build-Up/Restorative, Fuji II LC, Dyract AP and F2000) disc-shaped specimens were prepared and stored in sets of six in the following storage media: 0.9% NaCl (control), Coca-Cola, apple juice and orange juice. After time intervals of 1 day, 1 week, 1 month, 3 months, 4 months, 6 months and 1 year, solution pH and Vickers Hardness Number were determined for each individual specimen. Differences were analysed by anova followed by Student-Newman-Keuls post hoc analysis. All materials were found to reduce the pH of the 0.9% NaCl, but to increase the pH of the acidic beverages. The conventional glass-ionomers dissolved completely in apple juice and orange juice, but survived in Coca-Cola, albeit with a significantly reduced hardness after 1 year. The other materials survived in apple juice and orange juice, but showed greater reductions in surface hardness in these beverages than in Coca-Cola. Fruit juices were thus shown to pose a greater erosive threat to tooth coloured materials than Coca-Cola, a finding which is similar to those concerning dentine and enamel towards these drinks.

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The pulpal response to orthodontic force is thought to involve cell damage, inflammation, and wound healing. These situations are likely to be associated with the release of angiogenic growth factors. We therefore investigated human dental pulps to determine if angiogenic changes could be detected after orthodontic force application. Fifteen premolar teeth were treated with straight-wire fixed orthodontic appliances for two weeks, and comparisons were made with 15 untreated control premolar teeth from the same subjects. The teeth were extracted and sectioned. The pulps were removed, divided into 1-mm sections, embedded in collagen, and cultured in growth media for up to four weeks. Cultures were examined daily, by light microscopy, for growth and number of microvessels. Apparent microvessels were observed within five days. Confirmation of microvessel identification was by electron microscopy for endothelial cell morphology. There were significantly greater numbers of microvessels at day five and day ten of culture in the pulp explants from orthodontically treated teeth compared with those from the pulps of control teeth. These results are consistent with the hypothesis that there is an increase in angiogenic growth factors in the pulp of orthodontically moved teeth.

SUMMARYIn man, parotid flow has been recorded bilaterally using modified Lashley cups in response to mechanical stimulation of the teeth. The stimulus was defined and controlled by monitoring the rectified and integrated masseter electromyographic activity (e.m.g.) during repeated clenching on closely fitting bite-blocks placed between the molar teeth. Unilateral clenching on a bite-block resulted in a greater flow from the ipsilateral than the contralateral gland, and both exceeded the control values. There was also a positive correlation between the masseter e.m.g. activity and ipsilateral parotid flow. Parotid flow was also recorded before and during local anaesthesia of various intra-oral branches of the trigeminal nerve. Anaesthesia of two to three inputs always produced significant reductions in ipsilateral flow, but anaesthesia of a single input was not always effective. These results provide evidence in support of the hypothesis that intra-oral mechanoreceptors, particularly periodontal mechanoreceptors, are involved in the masticatory-salivary reflex.