Orthodontic treatment of a nine-year-old patient with hypophosphatemic rickets diagnosed since the age of two: A case report

Hypophosphatemic rickets (HR) is a genetic disorder with various types of inheritance. It results mainly from defects in factors that control mineral ion homeostasis such as 1,25(OH)₂D (Calcitriol) and FGF23 (Fibroblast Growth Factor 23). The existing bibliography regarding orthodontic treatment in patients with hypophosphatemic rickets is extremely limited. The aim of this case report is to describe the orthodontic treatment of a 9-year old Caucasian female patient suffering from HR. The patient presented a healthy late mixed dentition and periodontium. She suffered from a mild Class III maxillary skeletal pattern. There was a bilateral posterior crossbite, short lingual frenulum, a right maxillary mesioposition with a Class II subdivision on this side and a moderate space deficiency in the dental arches. The disorder was controlled by medication. In specific, patient was taking 1.5mL of phosphate four times per day, 0.3mL of calcitriol twice per day and 50,000 IU of Vitamin D3 on a weekly basis. Given the Class III skeletal pattern, the medical condition and the absence of relevant bibliography, it was decided to perform maxillary expansion, facemask traction and orthodontic treatment with fixed appliances. By the end of treatment, Class I canine and molar relationships were achieved, overjet and overbite were corrected and space deficiency was addressed in both arches. PAR index was 27 at the beginning of treatment and became 2 by the end of treatment (92.5% correction). The aesthetic component of IOTN was 4 and changed to 1, while the dental component used to be 5i and became 2g. With regards to retention, upper and lower fixed retainers from canine to canine and upper and lower vacuum formed appliances were used. In conclusion, a patient with controlled HR was orthodontically treated in a successful way. Orthodontic therapy was performed in a minimally invasive manner. Thus, HR does not constitute a contraindication for orthodontic treatment, when the disorder is kept under control.

Anterior teeth root inclination prediction derived from digital models: A comparative study of plaster study casts and CBCT images

BACKGROUND

To assess the accuracy of digital models generated using commercially available software to predict anterior teeth root inclination characteristics and compare the results to relevant data obtained from CBCT images.

MATERIAL AND METHODS

Following sample size calculation and after application of inclusion and exclusion criteria, pre-treatment maxillary and mandibular plaster models and the corresponding CBCT scans of 31 patients attending a private orthodontic clinic were selected. The subjects were 10 males and 21 females with age range 12 to 40 years. Plaster models were scanned using the high resolution mode of an Ortho Insight 3D scanner and CBCT scans were taken using a Kodak 9500 Cone Beam 3D System machine. The teeth on the digital scans were segmented and virtual roots were predicted and constructed by the Ortho Insight 3D software. The long axes of the predicted roots and the actual roots, as segmented from the CBCT images, were computed using best-fit lines. The inter-axis angle was used to assess error in root inclination prediction by the software. Mann-Whitney and Kruskal-Wallis tests were used. Intra-examiner error was evaluated using the Bland-Altman method.

RESULTS

The maximum disparity in angle between images derived from digital models and CBCT data was almost 40 degrees (upper left canine). The upper and lower canines produced the worst results, followed by the lower lateral incisors. The upper central incisors showed the best results, although the maximum angle of difference exceeded 20 degrees (with the median around 8 degrees).

CONCLUSIONS

Root morphology imaging prediction is not a primary function of this software and this study confirmed its limitation as a sole tool in routine clinical applications. At present these predictions cannot be considered accurate or reliable unless correlated clinically with a radiographic image. Key words:Digital models, CBCT, tooth root inclination prediction software.