PubMed · 5290556
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A C McLundie. 1971. The scanning electron microscope.. https://pubmed.ncbi.nlm.nih.gov/5290556/
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STATEMENT OF PROBLEM: The proper choice of prosthetic materials for restoration of occlusal surfaces is important for the protection of the hard tissue of the opposing teeth and for regular functioning of the stomatognathic system. PURPOSE: This study evaluated the resistance to wear of gold, Palliag M, Dentacolor, Chromasit, and Stellon materials and the enamel and dentin of natural teeth during functional contacts in an artificial oral environment with and without an abrasion material (Al2 O3 ). MATERIAL AND METHODS: The 5 nonceramic prosthetic materials used in the restoration of occlusal surfaces of fixed partial dentures were examined in contact with enamel and dentin during a simulated masticatory process in 2 environments (with and without abrasion). Wear was evaluated by means of a special device designed for wear examination. RESULTS: The findings highlighted that the wear of nonceramic prosthetic materials in contact with enamel or dentin was similar. Dentin showed greater wear when in contact with these materials than with the enamel surface. CONCLUSION: Artificial environmental factors significantly influenced the wear of the hard tissue of teeth, especially when in contact with materials having low microhardness.
Treatment of periodontitis which involves the furcation area of molar teeth has always been a challenge. Sixty extracted human molar teeth were used for an anatomic study to clarify the possible morphologic factors which may affect the diagnosis, prognosis, and clinical management of periodontally involved teeth. Teeth were embedded in methylmethacrylate and cut in 70 microm cross sections from the cementoenamel junction to the apex. Cervical enamel projection, root and root trunk lengths, root proximities as well as depths of root concavities coronally, apically, and at the furcation roof were measured. Cervical enamel projections were observed in 30% of the teeth examined. The shortest root trunk was found at the buccal aspect of mandibular first molars, permitting furcation involvement at early stages of periodontal disease. The most apically located furcation was found at the distal site of maxillary first molars. Furcation roofs showed severe concavities and complex cementum morphology. Teeth exhibiting cervical enamel projection were found to have deeper root concavities compared to teeth without cervical enamel projection and mesial roots of mandibular molars possessed greater furcal concavities than distal roots. The presence of root concavities complicates the diagnosis of furcation involvement and restricts access of periodontal instruments, resulting in incomplete treatment. Furcation anatomy may also influence the long-term prognosis of the teeth by favoring the retention of bacterial deposits and making oral hygiene procedures almost impossible. The present study shows that knowledge of a tooth's unique anatomic characteristics is a prerequisite for effective periodontal therapy.