The aim of this research was to compare the condylar morphology of patients with unilateral condylar hyperplasia (UCH) and patients with a class III skeletal relationship using cone beam computed tomography (CBCT). A prospective study was conducted on patients with facial asymmetry attending the division of oral and maxillofacial surgery of the study university in Chile. Fifteen patients with UCH and 15 with a class III skeletal relationship were selected. Linear measurements of the condylar processes were obtained at a scale of 1:1 using the software Ez3D Viewer Plus. Analysis of variance (ANOVA) and the paired t -test were used, considering P < 0.05. Patients with UCH presented statistical differences between the hyperplastic condyle and non-hyperplastic condyle for anteroposterior and mediolateral diameters, condylar neck length, and ramus height. Patients with a class III skeletal relationship showed no differences between the right and left sides; the morphology of their condyles was similar to the condyles with hyperplasia and presented statistical differences when compared with the non-hyperplastic condyles (one-way ANOVA, P < 0.05). The condylar morphology of UCH patients could be related to the development of a class III skeletal relationship. These findings provide an insight into the possibility of some class III patients presenting bilateral condylar hyperplasia.
Unilateral mandibular condylar hyperplasia (UCH) is a complex deformity of the condyle and the mandible that causes facial asymmetry. UCH is diagnosed through the clinical findings of facial asymmetry; occlusal changes should be demonstrated clinically and radiographically, with active hyperplasia being confirmed by bone scan performed at the initial diagnosis and repeated at least 6 months later. Condylar growth activity has traditionally been assessed by planar scintigraphy with technetium methylene diphosphonate (99m-Tc-MDP); however this method lacks anatomical precision. MDP-SPECT (single photon emission computed tomography) has the capability of three-dimensional (3D) reconstruction and subsequent thin-sectioning. The information is typically presented as cross-sectional slices through the patient, but can be freely reformatted or manipulated as required.
Classically, condylar hyperplasia has been described as a unilateral pathology and this could be related to the facility of identifying the facial asymmetry produced by differences in the sizes of the condyles. Another factor is the difficulty in establishing the abnormal size when both condyles present hyperplasia, given that a certain asymmetry is normal to all human body structures. Moreover, the diagnostic tools to assess condylar growth are based on the percentage differences in isotope uptake, which is higher in the condyle with hyperplasia. Finally, the comparison between the hyperplastic condyle and non-hyperplastic condyle is one the most important factors for obtaining a final diagnosis of UCH.
Thus the use of SPECT and scintigraphy has no value in cases of bilateral condylar hyperplasia. In contrast to most studies in the literature, there is a hypothesis that some patients with a class III occlusal and skeletal relationship present a bilateral condylar hyperplasia, called CH type 1A, as the primary cause. From a biological point of view, it is possible; the concept of hyperplasia is an abnormal growth of cells, and hypothetically this could affect both sides.
The purpose of this study was to compare the temporomandibular joint (TMJ) morphology of patients with UCH and patients with a class III skeletal relationship using cone beam computed tomography (CBCT).
Materials and methods
This prospective study was conducted at the Division of Oral and Maxillofacial Surgery of the Universidad de La Frontera (Chile). A total of 30 patients, 15 consecutive patients with facial asymmetry related to UCH and 15 consecutive patients with a class III facial deformity, aged between 15 and 30 years, were assessed between January 2011 and June 2014. These patients had presented for the surgical correction of a mandibular or facial deformity. The study was conducted according to the recommendations for research involving human beings and was approved by the Ethics Committee in Research of the Universidad de La Frontera.
The inclusion criteria for patients with a class III facial deformity ( Fig. 1 , CH type 1A of Wolford’s classification ) were: (1) overjet less than 0 mm with a class III dental occlusion and no missing teeth, (2) sella–nasion–B-point (SNB) angle of more than 84° with an established prognathism of the mandible, with or without hypoplasia of the maxilla, (3) A-point–nasion–B-point (ANB) angle ≤0°, and (4) mandibular midline deviation of less than 4 mm.
The inclusion criteria for patients in the UCH group ( Fig. 2 , CH type 1B of Wolford’s classification ) were (1) mandibular deviation from the midline more than 5 mm (evaluated on the chin in relation to the facial midline considering glabella, pronasale point, and superior labial philtrum), (2) dental occlusion with a unilateral crossbite, (3) lower dental midline deviated more than 4 mm, (4) patient’s perception of active mandible deviation in the last year, (5) class I or class III dental occlusion with no absent teeth, (6) assessment by 99m-Tc-MDP SPECT showing a final difference in condyle absorption equal to or greater than 10%; the SPECT was done according to routine protocols and the result was assessed by a medical specialist in nuclear medicine.
The following data were collected: gender, age, and cephalometric parameters. All patients underwent standardized CBCT imaging (Pax Zenith 2011; Vatech, Yongin, Korea), with settings of 90 kV and 120 mA, voxel size 0.12 mm, and 1 mm cuts in a 90 mm × 240 mm window, which recorded the condition and morphology of the bilateral TMJ. The computed tomography images were obtained with the patients in maximum dental intercuspation and the head positioned with the Frankfort plane parallel to the floor.
Linear measurements of the condylar processes were obtained on a scale of 1:1 using the software Ez3D Viewer Plus (Vatech). The measurements were taken using a previously reported method. The measurements are described in Table 1 and shown in Figs 3–5 . Two further images were obtained for each measurement, immediately before and immediately after (1 mm cuts) the middle area, calculated in the 3D reconstruction (the middle point was obtained in the sagittal, coronal, and axial views). A final number was obtained from the average of the three measurements.
|Anteroposterior diameter of the condyle||This was measured on the sagittal view. A longitudinal line was drawn at the widest point of the condyle. This line started at the point on the most anterior cortical bone and ended at the point on the most posterior cortical bone. The middle point was obtained from the 3D reconstruction and applied.|
|Mediolateral diameter of the condyle||This was measured on the coronal view. A longitudinal line was drawn at the widest point of the condyle. This line was perpendicular to the axial axis of the condyle, starting and ending at the closest points of the most medial and lateral cortical bone ( Fig. 3 ).|
|Condylar neck length||This was measured on the sagittal view. A longitudinal line was drawn that started at the uppermost cortical point of the condylar head and ended at a point of contact with the second line started in the sigmoid notch (the line was drawn starting at the sigmoid notch, perpendicular to the posterior border of the ramus).|
|Height of the mandibular ramus||This was measured on the sagittal view. The greatest dimension from the most superior aspect of the condyle to the line parallel to the inferior border of mandible. The line is parallel to the posterior border of the ramus ( Fig. 4 ).|
|Depth of the mandibular condylar fossa||This was measured on the sagittal view. A line from the upper point of the mandibular fossa was drawn, perpendicular to another line from the most inferior point of the mandibular eminence. The measurement was taken from the upper point of the mandible fossa to the intersection between these two lines ( Fig. 5 ).|
The data were analyzed using descriptive and correlational statistics in SPSS v. 18.0 for Windows software (SPSS Inc., Chicago, IL, USA). The paired Student’s t -test was used for each measurement, to evaluate the average of the differences between the sides for each element of the sample. The Shapiro–Wilk test was performed and the sample was shown to be normally distributed. Levene’s test was applied and showed homogeneity between the variances. The intra-class correlation coefficient (ICC) was used to assess method error. Every measurement was performed by one operator and repeated twice at an interval of 1 week. The correlation coefficient between the measurements of the first and second tracings was 0.99 and had a P -value of 0.001. One-way analysis of variance (ANOVA) and Tukey’s post hoc test were used to compare the measurements of patients with condylar hyperplasia and class III facial deformity, with results being significant at P < 0.05.
Thirty patients were included in this study, 15 with a class III skeletal relationship and 15 with UCH. Most of the patients in both groups were women (UCH 53.3%, class III 66.7%) ( Table 2 ). The mean age of those in the UCH group ( Table 3 ) was 19.26 ± 3.59 years, and the UCH occurred mainly on the right side (53.3%). The patients with a class III skeletal relationship were older, with a mean age of 26.0 ± 3.61 years. No difference was observed between the groups regarding gender ( P = 0.46).
|ID||Age, years||Sex||Overjet (mm)||ANB angle||SNB angle|
|ID||Age, years||Sex||Hyperplastic condyle side||Chin deviation, mm|