Evaluation of standardized methods for registration of time-dependent orthodontic tooth movements

An in vitro study was conducted to compare reproducibility of repeated recordings obtained from devices constructed for standardized registrations. An existing radiographic method and a new photographic technique were employed. On five in vitro models, half of the maxilla from dry skulls, special designed splints with a Troll-biten film holder were constructed. A stiff metal bar attached to the splints and to either an X-ray apparatus or a standard photographic camera made it possible to obtain standardized registrations. For each model 10 radiographs and photographs were taken before and after the canine was moved. Subtracting the values from well defined points for these pictures, 10 pairs of coordinates were available for each of the models with both methods. The findings showed very similar reproducibility for the two methods with 95 per cent of the discrepancies within a magnitude of 0.12 mm for the radiographic method and 0.14 mm for the photographic method. When evaluating the canine movements, similar results were observed. No significant difference could be detected in the five in vitro models. In addition, the results showed that a splint can be used as a stable reference for registration of tooth movements. Because of ethical objections to unnecessary radiation, the photographic registration technique might substitute the radiographs in future investigations where standardized periodic records are necessary for the description of tooth movement.