Scanning electron microscopic study of air abrasion effects on human dentine

Mechanical Surface Micro-Abrasion (MSM) is a technique of cavity preparation and surface treatment. By means of a precise air-powder jet it cleans and widens pits and fissures before sealing, in order to create micro-retention on tooth surface and to prepare small therapeutic cavities. It is particularly indicated in children's therapy. The aim of this study is to verify (by SEM) the existence of a relationship between working time and distance and both macroscopic and ultrastructural aspects of the treated surfaces following cavity preparation by MSM.

This experimental study was carried out in vitro using a Micro- Abrasion system on 60 human third mandibular molars. Before SEM observation the surfaces were divided in five groups, each with a different working time and distance. All specimens were observed by SEM at several magnifications.

After a treatment of 5 sec at a distance of 2 mm a small preparation could be noticed with a circular section of 0.5 mm of diameter. With a working time of 15 sec, and a working distance of 2 mm, a cavity preparation on dentinal tissue was obtained. With a working distance of 15 mm, even for a relatively long time of treatment, such as 30 sec, no preparation was noticed but only a sandblasted surface of a circular section with a diameter of 3.5 mm. With different time of application the authors noticed different microscopic aspects.

The authors realised that the macroscopic size and shape of cavities is connected to working distance, while working time is important to determine the depth of preparation and ultrastructural aspect. SEM analysis of dentin surface shows how different parameters determine macroscopic and ultrastructural aspects. It can help to standardise a protocol to follow according to the desired treatment.