The value of orthodontic study models for treatment planning

Abstract

Introduction. In order to establish an accurate diagnosis and proper therapy planning in orthodontics, it is necessary to perform the analysis of dental records. The only non-invasive three-dimensional record that provides important information in orthodontics is the study cast. The present study was conducted to determine the Linder Harth, Korkhaus and Bolton analyses on dental casts before and after treatment, in two different cases with different approaches to treatment plan. Aim of the study. The aim of the present study is to determine the contribution of study casts in orthodontic treatment planning. Material and methods. Dental records of two patients were selected, one case treated with extraction of upper first premolars and with non-extraction therapy in another one. These cases were selected randomly, without malocclusion restriction, from the Chair of Pediatric Oromaxillo- facial surgery, Pedodontics and Orthodontics, SUMPh Nicolae Testemitanu. Two sets of dental casts with permanent dentition were examined in the transverse and sagittal plane. Manual measurements were done with a digital caliper directly on the dental casts, and the obtained values were compared to those defined by the formula. Results. For the first case (with extraction of upper first premolars) in the pre-treatment stage, for the maxillary arch, Linder Harth analysis showed that in the premolar arch the width is 3,6 mm less than the expected value and in the molar one 3,2mm less. Korkhaus analysis established for the upper arch in the anterior segment a deficiency of 3mm and 5,5mm in the posterior one. The Bolton's anterior ratio was 76% and the overall ratio 88%; this indicates maxillary tooth material excess. For the second case (non-extraction case) in the pretreatment stage, for the maxillary arch, Linder Harth analysis showed that in the premolar arch the width is 1,25mm less than the expected value, but for the molar one with 4,1mm more. Korkhaus analysis established for the upper maxillary, only in the anterior segment (-1,5mm) a relative narrow dental arch, but for the posterior segment the values are within the normal range. The anterior ratio of Bolton is 80%, and indicates mandibular anterior excess. Conclusions. The data collected and analyzed from these study casts in order to evaluate the differences in pre-treatment and post-treatment stages, established the value and the contribution of study casts in determination of best approach in treatment planning. Orthodontic treatment planning is more than just deciding on extraction or non-extraction case. It requires an individual approach, despite the great importance of biometric standards.