ACTA FAC MED NAISS 2009; 26 (4): 187-194

Original article

UDC 616.314-073.7

COMPARISON OF MEASUREMENTS MADE ON DIGITAL 2D MODELS AND STUDY CASTS

 

Dragan Mladenović1, Lidija Popović2, Branko Mihailović3, Aleksandar Janković4, Milan Stoiljković1, Dušan Živković3, Milan Miladinović3

1Faculty of Medicine in Niš, Clinic of Dentistry in Niš, Niš, Serbia
2Institute for Psychophysical Diorders and Speech Pathology Belgrade, Belgrade, Serbia
3Faculty of Medicine in Priština, Clinic of Dentistry in Priština, Priština, Serbia
4Faculty of Medicine in Niš, Dermatology Clinic, Niš, Serbia


SUMMARY

The caliper and Korkhaus grid may be used to make direct measurements on upper and lower study casts. The limitations of these direct measurements are: tool must be perfectly positioned on the cast, measuring is time-consuming, any accidental move of grid gives incorrect results. It is also hard to see through Korkhaus grid, as it tires one's eyes. Digital models solve all the aforesaid problems. The aim of the study was to compare the accuracy of measurements between the upper teeth and medial line of the palate, and lower teeth and medial line of the mandible on digital models (2D) and plaster study casts. The sample consisted of 17 randomly selected pairs of the study cast (34 objects for measuring, 242 individual teeth) from the model base of the Clinic of Dentistry in Niš. Dentitions of all models were permanent or mixed. Only permanent teeth were measured. The occlusal sides of the study casts were digitized into 2D. XPA3 Ortho software was used for taking measurements on digital objects (indirect measurements). Afterwards, the same measurements were performed directly on the study casts by means of Korkhaus hand measurement ruler and by digital calliper - “gold standard”. The obtained results show ANOVA significance of 0.570 and F=0.563 between groups. Duncan test does not identify any group, and Spearman rank test shows certain correlation in the general sense (p < 0.0001 and rho=0.947), which is more than sufficient. The measurements show statistical discrepancy. Further improvement of the software and the method of digitisation are necessary to overcome the existing problems, and finally substitute the current hand measurement by calliper or ruler by software measurements in two dimensions.

Key words: computerized dentistry, digital models, accuracy, plaster study casts, XPA3 Ortho