|Year : 2019 | Volume
| Issue : 4 | Page : 169-175
Comparative study to correlate between two different radiographically determined condylar inclination with different facial forms in completely edentulous patients
Athi Rai A1, Muthu Kumar B2, Brintha J. Jei MDS 2
1 Department of Prosthodontics, Vinayaka Missions Sankarachariyar Dental College, Salem, Tamil Nadu, India
2 Department of Prosthodontics, SRM Dental College, Chennai, Tamil Nadu, India
|Date of Submission||06-Aug-2019|
|Date of Acceptance||27-Aug-2019|
|Date of Web Publication||28-Feb-2020|
Brintha J. Jei
Department of Prosthodontics, SRM Dental College, Chennai 600 078, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Many studies have determined condylar inclination (CI) by various clinical and radiography methods. But there was no previous study to find the correlation between facial forms and CI. So, this study made an effort to find any relation that exists between facial forms and CI in completely edentulous patients.
This study determined the relation of CI of completely edentulous patients in square, square tapering, tapering, and ovoid facial forms using two different radiographic methods.
Materials and methods
CI was recorded for 20 individuals, five for each group. For each individual CI was recorded by cone beam computed tomography (CBCT) and digital cephalogram with the occlusal rims in centric position. The CI was measured by the angle formed between the Frankfort horizontal plane and line joining the deepest point in the glenoid fossa (point A) and articular eminence (point B). Clinically, the facial forms were recorded by digital photographic records and were analyzed using the image analyzing software.
The data obtained were statistically analyzed using the Kruskal–Wallis test and Mann–Whitney test with Bonferroni correction for multiple pairwise comparison and facial forms were analyzed with digital cephalogram and CBCT. It had shown significant values for group III and group IV.
The obtained values for all the four facial forms were clinically relevant and can be used to program the semiadjustable articulator. CBCT was the better imaging technique to record CI and can be employed.
Keywords: condylar inclination, cone beam computed tomography, digital cephalogram, digital photography, facial form
|How to cite this article:|
AthiR, MuthuK, Jei BJ. Comparative study to correlate between two different radiographically determined condylar inclination with different facial forms in completely edentulous patients. Tanta Dent J 2019;16:169-75
|How to cite this URL:|
AthiR, MuthuK, Jei BJ. Comparative study to correlate between two different radiographically determined condylar inclination with different facial forms in completely edentulous patients. Tanta Dent J [serial online] 2019 [cited 2020 Mar 28];16:169-75. Available from: http://www.tmj.eg.net/text.asp?2019/16/4/169/279730
| Introduction|| |
Rehabilitation of the edentulous patient is one of the most mystifying challenges in dentistry as providing harmony among the occlusal surfaces of the artificial teeth. Condylar inclination (CI) plays a key role in both function and preservation of the surrounding structures. Among the five factors governing the articulation which was given by Hanau, CI is the most important and essential factor for obtaining balanced occlusion,. According to the glossary of prosthodontic terms CI is defined as 'mandibular guidance generated by the condyle and articular disk traversing the contour of the glenoid fossae.' The condyle descends along the posterior slope of the articular eminence of the mandibular fossa when it moves out of centric relation position [3–6]. The amount of inferior movement of the condyle when the mandible is protruded is based on the steepness of articular eminence.
Clinically, condylar guidance is measured by interocclusal records; it forms an equivalent angle of 30.4° with the horizontal reference plane approximating the anatomic limits of the TMJ and can vary from steep to shallow in different patients,. Several studies have shown the unreliability of recording and replicating condylar guidance using these methods [10–13]. With this uncertainty, recent studies have proved the liability of radiographs as a valuable aid to determine CI. So, to record CI accurately radiographic methods can be used as they use stable bony landmarks. Gilbao et al. determined the radiographic outline of the glenoid fossa and articular eminence in a radiographic image which represents the equivalent outlines of the condylar path in the skull and determines CI which can be studied without altering the function of the participant.
The temporal constituent is S-shaped in adults, consisting of a prominent articular eminence on which the condylar process slides during mandibular movements and a concave mandibular fossa. The clinical significance of the condyle–fossa relationship affects the morphology of the face and the position of the mandible,. The face was divided into simple ratios by the famous artist Leonardo Da Vinci in the 15th century for an esthetic evaluation of proportions. Later Leon Williams classified facial forms in the frontal plane as square, tapering, and ovoid which influenced the selection of anterior teeth in edentulous patients. Heartwell further divided facial forms into four types. Salzmann and Sassouni grouped facial forms into square, square tapering, tapering, and ovoid using the bony landmarks euryon, zygion, and gonion [18–21]. Various studies had found the relationship of articular eminence morphology with different skeletal groups but there were no previous study to find the relation between facial forms and CI.
Therefore, this study aims to find out the CI of completely edentulous patients determined using two radiographic imaging techniques and the determined CI was correlated with four different facial forms in the frontal plane.
| Materials and Methods|| |
The protocol of the study and the informed consent were approved by the Institutional Ethics Committee (SRMU/M and HS/SRMDC/2012/M.D.S-PG Student/201) before the start of the study. The study comprised a total of 20 completely edentulous patients of either gender, in the age group of between 40 and 70 years. All patients were informed about the aim of this research and written consents were signed from them to participate in this research.
Inclusion criteria included patients with class 1 ridge relationship, adequate inter-ridge distance, well-rounded ridges, no TMJ disorders, first-time denture wearers, and edentulous for a period of 3–8 months. Exclusion criteria were poor neuromuscular coordination, flabby, uneven or atrophic ridges, with TMJ disorders, history of systemic diseases, and repeated complete denture wearers. The patients were divided into four groups of five in each group [Table 1] based on facial forms.
Facial form determination
Photographs of completely edentulous patients were captured using a photographic setup consisting of digital single-lens reflex camera EOS 550D Canon with 50 mm lens EF-S1 and an effective focal length of 9 AF points (×0.87 magnification) with the maximum resolution of 18.0 megapixel with CMOS sensor. To standardize the procedure, images were made with the help of a tripod (positioned in front and at the eye level of the patients to avoid blurry edges and instability). A nonreflective light gray background was used to obtain well-defined images.
The patients were positioned 120 cm in front of the background and all the pictures were made in the aperture priority mode of camera with built-in flashlight for uniform and constant illumination and shutter speed of 1/125 per se cond and the opening diaphragm f/5.6 cross-type center.
To assure standardized image, heads were positioned at the center of the image using the focus point in the camera. The eyes and ears were parallel to the transverse plane and the floor, with the patient looking forward and facial median line perpendicular to the floor in the sagittal plane. The camera lens was kept 5 feet away from the participant. Patients were positioned on a line marked on the floor and framed alongside a vertical metallic centimeter scale, allowing calibration of measurements at life-size (1:1).
The patient's forehead, neck, and ears were clearly visible during the recording with their lips relaxed and looking into their eyes in the vertical mirror on the opposite side, ∼110 cm from the patient. To standardize the images in natural head position, the patients were asked to walk few steps, stand at rest position facing the camera, and was positioned near the scale, look into their eyes in the mirror, placing their arms at their side and their lips were compatible. Eyewear, if any, was removed and the operator ensured that the patient's forehead, neck, and ears were clearly made visible during the recording procedure. The digital photographic records were analyzed using the image analyzing software – Adobe Photoshop Creative Suite 53. Images were changed to gray scale by Adobe Photoshop version 5 (Adobe Systems Complex, San Jose, California, USA), and saved in the JPEG format for digitization. The freeform pen of the software tool was used to draw precise paths, connecting the cephalometric landmarks like euryon (E), zygion (Z), and gonion (G) on one side of the face and the other joining the points euryon (E'), zygion (Z'), and gonion (G') on the contralateral side of the face on each photograph to determine the facial form of each individual.
Prior to imaging procedure
In order to make the digital cephalogram and cone beam computed tomography (CBCT) radiographic images of the patients in centric relation, primary and final impressions of maxillary and mandibular arch of each patient were made with routine standardized procedures. Master casts were prepared using type III dental stone. To standardize the procedure, temporary record bases were fabricated on the master cast with thermoplastic vinyl sheets of 1.5 mm thickness using vacuum press machine4 and finished. Wax occlusal rims were fabricated for maxillary and mandibular ridges. Tentative jaw relation was performed using Niswonger's method. Face bow transfer was done5 and mounted on Hanau wide-Vue articulator using the split cast technique. High gothic arch tracers were attached to the occlusal rims to train the patient for achieving centric relation. Then the radiographic images were made in all the patients with occlusal rims in centric position.
Digital cephalometric radiography
All participants were positioned in the cephalostat by means of ear rods, forehead clamp with the sagittal plane at right angle to the central beam, the Frankfort horizontal (FH) plane parallel to the floor, occlusal rims in centric relation, and the lips in repose with the right side facing the film. To standardize the procedure, images for all the patients were taken by a single operator. The digital cephalometric images were produced by Kodak 8000 C Digital Panoramic and Cephalometric Machine. The Hard copy of the Kodak digital image, with a resolution of 228 dpi, was produced with a printer on a photo paper at 1:1 ratio. Manual tracing was performed using a 0.5 mm tipped 4H mechanical lead pencil on fine-grain 0.003-inch transparent acetate matte tracing papers taped to the digital hard copy cephalogram. The tracing process was performed by the same operator in a dark room withtransilluminated light using a screen viewing box. The FH plane was traced by identifying orbital [Or] point and porion [Po] point and the AE line traced by identifying points marked A and B using a millimeter ruler. Angular measurements were made using a protractor [Figure 5]. The CI angulation values obtained for the patients of four groups were tabulated and statistically analyzed.
Cone beam computed tomography
The CBCT scan of midfacial region for all the individuals in full skull view, extending from the superior aspect of the supraorbital rim to the mandibular body, was performed using a KODAK 9500 Cone Beam 3D system. The patients were made to stand in erect position with their FH plane perpendicular to the table and floor and within the circular gantry housing of the radiography tube to obtain a constant orientation of sagittal images. The patients were told to bite the occlusal rim in centric. The images were made by a single operator to standardize the procedure. The CS-3 dimension imaging software system was used for analyzing the image obtained on the selected axial image. A line along the posterior slope of the AE was drawn, extending from the deepest point on the roof of the glenoid fossa (point A) to the most convex point on the apex of the AE (point B). Similarly, the FH plane was drawn joining the two points – Po and Or. The angle made between FH plane and AE line was premeditated to obtain CI angle [Figure 5]. The data obtained were tabulated and then statistically analyzed.
| Results|| |
The obtained values were tabulated and analyzed using Kruskal–Wallis tests and Mann–Whitney tests with Bonferroni correction for multiple pairwise comparison.
[Table 2] shows the comparison between the groups using Kruskal–Wallis test. Significance value P was less than 0.05 and showed significant CI values in CBCT with a value of 0.043.
|Table 2: Kruskal-Wallis test to compare between facial forms in cone beam computed tomography|
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In [Table 3], overall comparison for each groups was made between digital cephalogram and CBCT using the Wilcoxon signed-rank test. The results were significant for group I, group III, and group IV.
|Table 3: Wilcoxon signed ranks test to compare between cone beam computed tomography and digital cephalogram (overall)|
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[Table 4] shows the comparison between groups and the P value level of significance was less than 0.005. In group I the mean was 16.20, group II it was 14.20, group III it was 5.50, and group IV it was 6.10.
[Table 5] shows the descriptive statistics for the difference between digital cephalogram and CBCT of the CI for all the groups. The mean, SD, and median values were obtained for each group. The mean ± SD values for each group were group I = 1.14 ± 1.06, group II = 0.46 ± 0.74, group III=−1.24 ± 1.09, and group IV=−1.02 ± 0.78. The median ( first quartile, third quartile) values for each group are group I − 0.70 (0.60, 1.30), group II = 0.90 (0.30.1.00), group III=−0.90 (−1.20, −0.90), and group IV - 0.70 (−1.40, −0.50).
|Table 5: Descriptive statistics for difference in condylar inclination of group I, group II, group III, and group IV between cone beam computed tomography and digital cephalogram|
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In [Table 6], the comparison was made between the groups for the difference values in CI obtained between CBCT and digital cephalogram by using Mann–Whitney test with Bonferroni correction for this multiple pairwise comparison. It showed significance for group I vs group III.
|Table 6: Mann-Whitney test with Bonferroni correction for multiple pairwise comparison|
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In the graph scatter plot diagram showed the cumulation of CI for digital cephalogram and CBCT between 39° and 41° [Figure 6]. CI differences with digital cephalogram and CBCT between the four groups are graphically shown as box plot. The CI values of groups I and II were positive while CI of groups III and IV were negative [Figure 7].
|Figure 6: Box plot diagram of comparison between cone beam computed tomography and digital cephalogram.|
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|Figure 7: Box Plot diagram for comparison between condylar inclination and groups I, II, III, and IV.|
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The comparison between the differences of CI using digital cephalogram and CBCT of the four groups showed that the CI values for groups III and IV were statistically significant in both the imaging technique – digital cephalogram and CBCT.
| Discussion|| |
According to Fenn, the slope of condylar path is a fixed quotient and is peculiar to each patient. Condylar path is traversed by the condyle in relation to the AE when the mandible moves from centric relation and forms the CI. Katsavrias and Nickel stated that during growth, the AE is flat in early years and becomes steeper when teeth erupts and occludes while Moffet contradicted it.
This study coincided with Ingervall who stated that there is a marked inclination of the condylar path and marked height of the AE associated with the rectangular facial form as they had smaller inclination of face and the articular tubercle height was prominent. In this study, the CI values obtained for square facial form were comparatively higher among the other groups in Digital Cephalogram. But the mean CI obtained for square facial form with CBCT was in contradiction to the results given by Ingervall in 1974. Zamacona et al. noted that a distinction should be made when using different methods that measure the horizontal CI relative to different planes as different planes produce different outcomes. FH plane significantly correlated with the true horizontal and the natural head position than other hinge axis–orbital planes. The other axis planes such as Camper's plane and occlusal plane were not considered as it deviated from the true horizontal and natural head position to about 6° and 10°, respectively. So in this study, FH plane was used for determining the facial forms through photographs and CI using the radiographic techniques.
For the diagnosis and treatment in craniofacial skeletal development and orthognathic surgeries two-dimensional cephalometric radiography has been used widely. The lines and angles on the image can be analyzed by using this image. Though it is somewhat difficult to discriminate the overlapping structures, these imaging techniques are commonly used to compare the measured values from this image with the general known value to find the asymmetry. The study was conducted with the Digital Cephalogram as images recorded can be manipulated and alter its visual appearance to facilitate landmark identification. Although conventional radiographic film is quite stable and can retain its evidence for many years, it is not always a trustworthy archive medium due to film deterioration. On the other hand, the Digital Cephalogram reduces radiation exposure and allows all the benefits of the older digitized forms of radiology eliminating the need for film or the associated chemicals necessary for the development. According to Thurzo et al. tracing on paper using hand instruments was comparable to the digitized radiographic tracings and the outcomes of studies using manual methods could be considered perfectly valid. Manual tracing was found to yield more reproducible angular measurements than linear measurements when constructed on a tracing. The results of the study of the four groups with the digital cephalogram were 4–6° higher than the mean CI values applied for programming the articulator based on Hanau's formula.
When the various angles and distances were analyzed and compared between CBCT and conventional lateral cephalogram Van Vlijmen et al. concluded that there was no difference in many parts. Being the most acceptable imaging technique for TMJ view, CBCT as the three-dimensional imaging technique was used to measure the CI of different facial forms in this study. Ingervall stated that there is a marked inclination of the condylar path and marked height of the AE associated with the rectangular facial form. In this study, CI values obtained for group I were comparatively higher among the other groups in Digital Cephalogram. This result coincides with the study conducted by Ingervall. The mean CI obtained for group I with CBCT was in contradiction to the results given by Ingervall in 1974. This study showed that facial form does correlate with the CI of the individuals while the time span of the edentulous state in the individuals also influences the CI,,,,,,.
The CI values for tapering and ovoid facial forms were comparatively similar in both the Digital Cephalogram and CBCT imaging techniques. So, the values obtained using the Digital Cephalogram can be applied to program the semi-adjustable articulator for any individual. The mean CI values obtained were group I – 39.00, group II – 38.00, group III – 41.20, and group IV – 41.00 which can be used to program the articulator.
Limitations of the study
The study was conducted with limited number of patients for each facial form, with uneven distribution of the genders influencing the results. Only digital photographs were used in this study and if any other facial analysis technique were followed it may influence the study results.
Further scope of the study
The possible limitations of the present study could be overcome with new clinical trials, required in the same context for future prosthodontic application.
| Conclusion|| |
- The CI values obtained with CBCT were more significant than the values obtained with the Digital cephalogram for all facial forms
- The mean CI values obtained with CBCT for square facial form – 39.00, square tapering facial form – 38.00, tapering facial form – 41.20, and ovoid facial form – 41.00. So, these CI values could be used to program the semi-adjustable articulator.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]