Ultrastructural preservation of rat embryonic dental tissues after rapid fixation and dehydration under microwave irradiation

Adequate preservation of the cells and matrix of mineralising tissues remai ns difficult, as organic components and initial mineral deposits may be los t during conventional processing for electron microscopy. In this study, we have reduced significantly the processing time using microwave irradiation . Rat molar tooth germs were fixed in 4% glutaraldehyde +4% formaldehyde wi th 0.1 M sodium cacodylate in a laboratory microwave oven for two periods o f 20 s with a maximal temperature of 37 degrees C. After conventional washi ng and post-fixation. specimens were dehydrated in graded ethanols under mi crowave irradiation for a total of 7 min 20 s. For comparison, some specime ns were processed by conventional methods. After embedding, ultrathin secti ons were examined by electron microscopy. In differentiating ameloblasts an d odontoblasts, plasma membranes, mitochondria, rough endoplasmic reticulum , the Golgi complex, together with all other cytoplasmic organelles exhibit ed excellent preservation. Microtubules, microfilaments and coated vesicles were particularly evident. Crystal-like mineral deposits were conspicuousl y present in relation to dentine matrix vesicles and collagen fibrils as we ll as in enamel matrix. The matrix of forming enamel had a globular electro n-lucent appearance. It is concluded that this is a rapid method which prov ides a preserved or even improved morphology.