A new method for accurate dental measurement

Using digital dividers (analogue-digital transformer, Brandt-Hermanussen device), it has become possible to measure distances between human teeth with a technical error of 0.04 mm. The technique implies a small preparation (trough) into the respective teeth. The ball-shaped metal probes of the instrument fit into these troughs and enable the determination of this distance directly in the patient. It does not require the use of casts. The present method was compared with two conventional and popular techniques of tooth arch determination, using the natural retentions of the deepest points of the central fossa of the respective teeth without the preparation of an artificial trough (manual caliper rule with nonius, digital caliper rule). The technical error of these techniques ranged between 0.46 mm and 0.52 mm. In order to investigate whether the preparation of an artificial trough could be avoided, the digital measuring dividers were modified and equipped with sharp probes for the determination of the natural distance between the deepest points of the central fossa, in analogy to the conventional techniques. Under these circumstances however, the technical error increased up to 0.27 mm (observer 1), and 0.21 mm (observer 2). It is concluded that dental marking is necessary for accurate dental measurement.