Histological preparation of teeth and tooth growth

Background: Traditional techniques for preparation of teeth for histological analysis include: 1) Ground section of non-decalcified tooth and view by polarized light. 2) Decalcify the tooth and then section and stain as per soft tissue. 3) Cryomicrotomy -non-decalcified tooth is immersed rapidly in liquid nitrogen and sectioned with a cryostat using a heavy-duty freezing microtome. Objectives: This study introduces a petrographic technique for histological preparation of teeth, so that thin sections of teeth can be viewed under the microscope without decalcification. In addition the article discusses the use of tetracycline to measure tooth growth in rats. Methods: Six Wistar rats were given tetracycline as a marker of tooth growth. An incisor tooth from each sacrificed animal was imbedded in an epoxy resin and ground down to achieve a tooth slice, 30 μm thick. Results: The petrographic preparation technique for teeth for histological analysis clearly demonstrated that thin sections of teeth can be viewed under the microscope with both calcified and soft tissues present in one view. In addition, the mean growth of teeth was 0.010 mm/day during the period of tetracycline administration and 0.016 mm/day when no tetracycline was being administered. Conclusion: This technique, although a petrographic preparation technique that has been used for more than forty years, is new to dental research and allowed detailed analysis of teeth with all calcified and non-decalcified tissues present in one section. This study also showed that the presence of tetracycline caused a reduction in tooth growth and this finding needs to be taken into consideration when interpreting the results of other studies when tetracycline is used as a histological marker of tooth growth.