RESUMEN
<p><b>OBJECTIVE</b>To study the methods of decalcification for making united slices of tooth and affiliated periodontic tissues.</p><p><b>METHODS</b>Twenty-one samples containing dog molars and affiliated periodontic tissues were divided into seven mean groups. The pH value of solution, time of decalcification, weight and volume of samples, and content of decalcified calcium were detected. The slices were observed by HE, specific, and immunohistochemical stain.</p><p><b>RESULTS</b>The velocity of decalcification increased with decrease of solution pH. The weight of samples lightened by 37.61%, the volume reduced by 25.97% on average, and calcium decalcified was 174.49 mg per gram humid samples. The EDTA decalcification was slowest, but it was best. Decalcification was fast in Plank-Rycho solution while the section was worst, and faster in the formyl solution containing aluminium chloride than in EDTA, and the section was better.</p><p><b>CONCLUSIONS</b>The 50% formyl solution containing aluminium chloride is an ideal decalcifying solution.</p>