Ultrasonic cavity preparation: Effect on the immature dentition

Abstract

T HE GROWTH OF THE REALIZATION that clinical dental treatment is founded on a basic scientific rationale has received powerful impetus by the introduction of the ultrasonic dental tool. Histopathologic evaluation of the new device, an analysis of potential tissue effects resulting from clinical use, was soon recognized by the profession as a necessity for thorough appraisal. Early report& 2, 3 attested to the mechanical effectiveness of the ultrasonic tool in removing tooth substance; manipulative advantages to the operator, technical advantages in the smoothness and precision of the preparations, and human advantages in terms of lessened stress to the patient were outlined and evaluated. The new modality of energy application to the tooth heightened the need for a biologic assay of tissue response in comparison with tissue effects produced by rotary instrument cavity preparation. Preliminary papers4-* were devoted to pulp studies of adult, erupted teeth in both humans and animals. Reactions were generally mild and judged reversible. A study9 of heat flow within the pulp and at the apex of the tooth, induced by cavity preparation, indicated no thermogenesis beyond 14” F. with any device, including ultrasonics, when water coolant was used. Safe limits prevailed. One report, however, by Hansen and Nielseni focused attention in a new direction ; on the possible effect of ultrasonic preparation on extremely labile, growing dental structures. Their findings disclosed a dysplastic response, inducing distortion of amelogenesis and disruption of dentinogenesis in the continuously erupting guinea pig incisor subjected to ultrasonic cavity preparation. Though no direct homologue exists in higher animal orders, this report on a tooth of continuous growth bore implications of potential effects on the immature dentitions of children. This article is an attempt to evaluate the ultrasonic device as used in the preparation of cavities in deciduous and immature permanent teeth. It is aimed as a histologic bio-assay of ultrasonic effect on the deciduous tooth being shed, the underlying permanent tooth and its developing membranes, and the young permanent tooth with incomplete root, together with supporting and surrounding structures.