COMPARATIVE CEPHALOMETRIC AND 3D CONE BEAM COMPUTED TOMOGRAPHY ANALISIS OF ALVEOLAR BONE DESTRUCTION FOR TEETH IN ANTERIOR CROSSBITE

Purpose: To assess the degree of bone destruction for teeth in anterior crossbite by means of 3D cone beam computed tomography and lateral cephalometry. Material/methods: 20 patients with anterior crossbite underwent 3D cone beam computed tomography and lateral cephalometry of the anterior segments of the maxilla and mandible. The destruction of the bone in the anterior segments of the maxilla and mandible was measured (vestibularly and lingually)– the distance from the cemento-enamel junction to the top of the alveolar bone. The parameters of bone resorption for teeth 21 and 31 on cephalogramsand 3D computed tomography images were compared. For both incisors, the mean value registered by means of cephalometry was slightly higher than that registered with 3D. Results: The total mean value of bone destruction for anterior teeth was significantly higher vestibularly compared to lingually, both for the maxilla (p = 0.030) and mandible (p = 0.030). Significantly higher mean values of bone destruction were found in the mandible compared to the maxilla. For both incisors (21 and 31), the mean value of resorption recorded by cephalometry was slightly higher than that recorded by 3D cone beam computed tomography, but without statistical significance. Conclusion: We found significantly higher values of vestibular bone destruction compared to lingual bone destruction. Bone destruction in the mandible reached a significantly higher level than that in the maxilla. No statistically significant difference was found between the mean values of bone destruction measured by means of cepha-lometry and 3D cone beam computed tomography.


INTRODUCTION:
Anterior crossbite of single teeth or a group of teeth is a common masticatory trauma, leading to changes in the dental complex as a result of occlusal forces. Adequate tissue capacity is exceeded which results in bone destruction.[1, 2, 3, 4] The aim of the present study is to assess the degree of bone destruction for teeth in anterior crossbite in patients with completed growth by means of 3D cone beam computed tomography and lateral cephalometry.

AIM:
To assess the degree of bone destruction for teeth in anterior crossbite in patients with completed growth by means of 3D cone beam computed tomography and lateral cephalometry.

MATERIALS AND METHODS:
The study involved 20 patients withwith anterior crossbite of single teeth or group of teeth, of whom 16 (80%) men and 4 (20%) women, with a mean age 25.70±5.95 years. The patients' age ranged between 18 and 37 years. (Table 1) The number of teeth in crossbite varied between 2 and 12 for the individual patients, with a mean number of teeth in crossbite 8.0±3.0 teeth. The patients were admitted for consultation and treatment in the Department of Periodontology and Oral Diseases and the Department of Orthodontics in the Faculty of Dental Medicine-Plovdiv. Subjects underwent 3D cone beam computed tomography of the anterior segments of the maxilla and mandible and lateral cephalometry. They were informed about the nature and purpose of the study. They signed a Declaration of informed consent for participation and a Patient Information Form about the risks and expected benefits of the study. The study was approved by the institutional Ethics in Human Research Committee (protocol No.2106 /2020).
The data was analyzed through the following statistical programs: IBM SPSS, version 26 (2019); Med Calc, version 19.0.7 (2020); and Minitab, version 19, 2020. The parameters of bone destruction, were measured on continuous scales and normally distributed according to the Kolmogorov-Smirnov test (Kolmogorov-Smirnov p >0.05 for all dimensions). The dimensions of bone destruction were presented as mean values and standard deviations. Bone destruction was analyzed for all target teeth separately and in total for each of the two jaws. The vestibular and lingual dimensions were compared through a paired-samplest-test. Bland-Altman's plot was used to establish the level of agreement between measurements based on lateral cephalogram and 3D cone-beam computed tomography. The mean value of the difference between the two methods was compared to zero through a one-sample t-test. Statistical significance was graded against the value of p as follows: * p > 0.05 -significant, ** p < 0.01 -very significant, *** p < 0.001 -highly significant.
Bone resorption between the maxilla and mandible showed significantly higher values in the mandible (Fig.  4). The average vestibular bone resorption was 3.68±0.69 mm in the mandible versus 3.13±0.64 mm in the maxilla,   The Bland-Altman plots (Fig. 4) illustrate the high level of agreement between lateral cephalogram and 3D cone-beam computed tomography in the measurement of bone resorption at incisor 21 (panel A) and incisor 31 (panel B). 4.34±4.20 + = The mean of lateral cephalogram is higher than the mean of 3D; -= The mean of lateral cephalogram is smaller than the mean of 3D.

DISCUSSION:
The morphology of the alveolar bone is indicative of the occurrence of its destruction when there are negative influencing factors. Han JY and Jung GU (2011) assessed the vestibular bone thickness of t he frontal teeth. According to them the thickness of the vestibular plate is thinnest in the area of the alveolar ridge (0.78 mm-1.17 mm; 3 mm-6 mm apically from theridge) and mostly in the area of the lower lateral incisor. [5] Even seemingly minor dental discrepancies highly overload theperiodontal tissues. [6] The masticatory forces change their normal direction in the case of incorrect occlusion of the incisors. A horizontal component of these forces occurs during biting off which exceeds the compensatory potential of the tissues. Teeth incross bite are subjected to excessive load-ing during their function.
[3] When the masticatory forces exceed the compensatory potential of the tissues, the result is tissue damage, expressed in structural and functional changes in the periodontal tissues. The direction of the applied force is also important.They are usually oriented along the vertical axis of the teeth and are transferred to the alveolar bone, which reacts with destruction. When the masticatory forces with changed direction are present frequently and for long periods of time, the adjacent alveolar bone reacts with destruction.
[2] In crossbite of the entire frontal area in class III malocclusion the lower incisors are often inclined lingually as a compensatory mechanism to reach intercuspation. Lingually inclined mandibular incisors (less than 85° of IMPA) are more susceptible to vestibular recessions and loss of alveolar bone. Our results showed a small positive bias, which was not significantly different from zero on lateral cephalogram and 3D cone-beam computed tomography . Kapila SD and Nervina JM in their review of clinical examination, CBCT and conventional radiological methods report that CBCT continues to gain popularity, its use currently is recommended in cases in which clinical examination supplemented with conventional radiography cannot supply satisfactory diagnostic information. [10] Patients with an anterior crossbite, combined with sagittal changes in the posterior part of the dentition and with complete jaw growth exhibit an increased angle of the mandibular plane (hyperdivergent). They have a narrower symphysis and a thinner alveolar bone supporting the frontal mandibular teeth. [8] The long and narrow symphysis predisposes towards progressive loss of both vestibular and lingual mandibular alveolar bone due to thinner alveolar bone support.
[9] Our data correspond to the studies and conclusions of the cited authors.

CONCLUSION:
We found significantly higher values of vestibular bone destruction compared to lingual bone destruction. Bone destruction in the mandible (vestibular and lingual) reached a significantly higher level than that in the maxilla. Although cephalometric methods are to a certain extent similar to the 3D cone-beam computed tomography, when measuring bone resorption, they are quite limited. The former is informative about the condition of the alveolar bone only in the area of the central incisors. In order to obtain a more precise and comprehensive picture of the level of vestibular and lingual destruction of the entire frontal segment, 3D cone-beam computed tomography is required. Although there is no statistical difference between the two methods, we recommend the CBCT study because there the resolution is greater and a section can be made for any are, that we want to observe. Lateralcephalogram has limitations, as it can examines only the most protruding tooth.