Three-dimensional assessment of teeth first-, second- and third-order position in Caucasian and African subjects with ideal occlusion

Lombardo et al. Progress in Orthodontics (2015) 16:11

DOI 10.1186/s40510-015-0086-9

RESEARCH Open Access

Three-dimensional assessment of teethfirst-, second- and third-order position in Caucasian and African subjects with ideal occlusion

Luca Lombardo*, Alessandro Perri, Angela Arreghini, Michele Latini and Giuseppe Siciliani

Abstract

Background: The aim of this study was to provide an updated version of Andrews seminal study by exploiting 3D software to analyse the tip, torque and in-out values of two groups of different racial and ethnic background.

Methods: The analysis was conducted on one Caucasian group (30 individuals) and one of African origin (29). All subjects were adult, in normal occlusion and had no previous history of orthodontic treatment. Rhinoceros 3D modelling software was used to identify anatomical reference points, planes and axes and to make the appropriate measurements.

Results: Compared to Andrews measurements, we found more positive coronal tip values in both African and Caucasian subjects, while the torque values we measured tended to be less negative in the posterior sectors than those reported by Andrews. We measured greater tip values in the lower jaw of Caucasian with respect to African subjects, particularly in the middle sectors.

Conclusions: Race and ethnicity have a strong influence on values of tip, torque and in-out. This is translated as a more positive tip in Caucasian subjects and a more positive torque in those of African descent (greater proclination of the incisors). Finally, with respect to the values reported by Andrews, we found a tendency to more positive mean tip (except for at the upper second molars and lower incisors) and less negative torque in the posterior sectors.

Keywords: Tip; Torque; In-out; Straight-wire prescription; Andrews

Background

Andrews was the first to put forward the hypothesis that the ideal occlusion of untreated patients could serve as the target of orthodontic treatment [1]. However, despite Andrews undeniable influence on orthodontics as we know it today, several authors [16] have identified sources of bias in this seminal study, in both the method Andrews adopted for making his measurementsascribable to the instruments he usedand the sample he selectedNorth American subjects of Caucasian origin. Nevertheless, only Sebata [2], Watanabe [3], Currim [4] and Doodamani[5] have since replicated Andrews study using different samples (Japanese in the first two, Indians in the latter...