Panorametry: suggestion of a method for mandibular measurements on panoramic radiographs

Reproducibility of 2D and 3D Ramus Height Measurements in Facial Asymmetry

In our clinic, the current preferred primary treatment regime for unilateral condylar hyperactivity is a proportional condylectomy in order to prevent secondary orthognathic surgery. Until recently, to determine the indicated size of reduction during surgery, we used a ‘panorex-free-hand’ method to measure the difference between left and right ramus heights. The problem encountered with this method was that our TMJ surgeons measured differences in the amount to resect during surgery. Other 2D and 3D method comparisons were unavailable. The aim of this study was to determine the most reproducible ramus height measuring method. Differences in left/right ramus height were measured in 32 patients using three methods: one 3D and two 2D. The inter- and intra-observer reliabilities were determined for each method. All methods showed excellent intra-observer reliability (ICC > 0.9). Excellent inter-observer reliability was also attained with the panorex-bisection method (ICC > 0.9), while the CBCT and panorex-free-hand gave good results (0.75 < ICC < 0.9). However, the lower boundary of the 95% CI (0.06−0.97) of the inter-observer reliability regarding the panorex-free-hand was poor. Therefore, we discourage the use of the panorex-free-hand method to measure ramus height differences in clinical practice. The panorex-bisection method was the most reproducible method. When planning a proportional condylectomy, we advise applying the panorex-bisection method or using an optimized 3D-measuring method.

Relationship between Physiological Resorption of Primary Molars with Its Permanent Successors, Dental Age and Chronological Age

The aim of the present study was to analyse root resorption of the primary mandibular molars and their relationship with their permanent successors and the age of the patient. Methods: The sample consisted of 408 digital panoramic radiographs. The mesial and distal crown-to-root ratios (CRR) of #74 and #75 were calculated by dividing the measures of the length of each root by its coronal height. The Demirjian formation stage of the premolar was established, and dental age was determined. A descriptive and statistical analysis was performed using SPSS to determine the correlation between the variables (Pearson’s correlation coefficient) and to identify the differences between them (Student’s t-test), with a confidence level of 95%. Results: 723 molars were measured, and tables of CRR depending on dental and chronological age were obtained. The CRR decreased with increasing dental and chronological age, but not uniformly. The CRR of #74 and #75 decreased slightly when the successor premolar was in the initial stages of formation. Gender differences were obtained with respect to chronological age, mainly in girls, because the root resorption of #74 was always more advanced, and the formation of the #34 more advanced. Conclusions: Root resorption of the molar is slight and progressive when the successor premolar begins formation until stage D, and becomes higher starting at stage E. It is possible to determine the state of the child’s maturation and the CRR according to dental and chronological age.

Periimplant Bone Resorption at the Level of Tilted Implants in SKY Fast & Fixed Restorations

Implant-prosthetic rehabilitation registers multiple variants, but their short- and long-term evolution has been a frequent concern. This study aimed to evaluate the peri-implant bone resorption at the level of the tilted implants in the SKY fast & fixed restorations, with reference to clinical and treatment parameters. An observational study was conducted on a convenience sample of patients with implant-prosthetic rehabilitation in one or both jaws, according to the SKY fast & fixed protocol (Bredent, Germany). Bone resorption was assessed on panoramic radiography. Other data were collected from the patient’s medical records. Thirty tilted implants were analyzed, 12 of which were in the maxilla and 18 in the mandible. After the follow-up period, both bone resorption (maximum 7 mm) and bone apposition (maximum 8 mm) were observed. There was a tendency for the resorption to be more pronounced in the mandible, in patients where tooth loss was due to periodontal disease, and when implants with length less than 16 mm were used. Resorption was statistically significantly lower when bone addition materials and membranes were used at the extraction socket, and when SKY fast & fixed rehabilitation was performed in both jaws. SKY fast & fixed implant-prosthetic technique, which involves applying a small number of implants, and a fixed prosthesis corresponding to a shortened dental arch, is a viable method of treatment that outcomes the need for complex and expensive surgical interventions, and proves to be beneficial in maintaining the optimal parameters of bone support.

Influence of the intergonial distance on image distortion in panoramic radiographs

OBJECTIVES

The aim of this study was to evaluate the influence of the intergonial distance during the formation of panoramic radiographic images by means of horizontal and vertical measurements.

METHODS

30 macerated mandibles were categorized into 3 different groups (n = 10) according to their intergonial distances as follows: G1, mean distance 8.2 cm, G2, mean distance 9.0 cm and G3, mean distance 9.6 cm. Three metal spheres 0.198 cm in diameter and placed at an incline using an isosceles triangle were separately placed over the internal and external surfaces of the mandibles before radiographic exposure for the purpose of taking the horizontal and vertical measurements. The occlusal planes of the mandibles were horizontally placed on the chin rest of the panoramic machine Orthopantomograph® OP 100 (Instrumentarium Imaging, Tuusula, Finland) and were then radiographed. In the panoramic radiographs, an expert radiologist measured the distances between the metal spheres in the horizontal and vertical directions using a digital caliper. The data were tabled and statistically analysed by Student's t-test and analysis of variance with Tukey post-test (α = 0.05).

RESULTS

In all three groups magnification of the distances between spheres was observed when compared with the real distance in both horizontal and vertical measurements (p < 0.05). Differences in both horizontal and vertical measurements were observed between the different regions (p < 0.05), however there were no differences between groups in the same region (p > 0.05). Differences between horizontal and vertical measurements were observed in different regions in all evaluated groups (p < 0.05).

CONCLUSION

The intergonial distance is a factor that had no influence on image formation in the panoramic radiograph.