|Year : 2022 | Volume
| Issue : 2 | Page : 123-129
Clinicoradiographic comparison of sagittal condylar guidance angle determined by dynamic and radiographic methods
R Vijaya Kumar, Mahesh Eraiah Gowda, MP Shashidhar
Commandant, Command Military Dental Centre (SWC), Jaipur, Rajasthan, India
|Date of Submission||11-May-2021|
|Date of Decision||09-Jan-2022|
|Date of Acceptance||14-Jul-2022|
|Date of Web Publication||21-Dec-2022|
Mahesh Eraiah Gowda
Command Military Dental Centre (SWC), Jaipur, Rajasthan
Source of Support: None, Conflict of Interest: None
Aim: This in vivo study was conducted to compare sagittal condylar guidance angle measured (SCGA) using cone-beam computed tomography (CBCT) panoramic-section and CBCT cross-section and extraoral Gothic arch tracing method (EGTM) in completely edentulous patients.
Materials and Methods: Based on the inclusion and exclusion criteria, 30 completely edentulous individuals were evaluated. Radiologically, two modalities of CBCT imaging were used to record SCGA, i.e., CBCT panoramic section view and CBCT cross-sectional view. After recording, the CBCT of the patient SCGA was measured using the Frankfort horizontal reference line and mean curvature line. The most superior and most inferior points of the curvature were identified to determine the mean curvature line. SCGA was measured in the clinical method using EGTM with Hight tracers for the same patients. Data obtained using three methods were subjected to statistical analysis.
Results: The mean right and left SCGA using CBCT panoramic view was 29.33 and 29.52, respectively. The mean right and left SCGA using CBCT cross-sectional view was 31.24 and 31.63, respectively. The mean right and left SCGA using extraoral Gothic arch method was 26.67 and 27, respectively. The SCGA differed significantly among the groups.
Conclusion: There was a significant difference in values of SCGA when evaluated using the three techniques. The radiographic methods (CBCT panoramic section view and CBCT cross-sectional view) were comparable but varied significantly from extraoral Gothic arch tracing technique.
Keywords: Cone-beam computed tomography cross-section, cone-beam computed tomography panoramic section, cone-beam computed tomography, extra oral Gothic arch tracing, sagittal condylar guidance angle
|How to cite this article:|
Kumar R V, Gowda ME, Shashidhar M P. Clinicoradiographic comparison of sagittal condylar guidance angle determined by dynamic and radiographic methods. J Dent Def Sect. 2022;16:123-9
|How to cite this URL:|
Kumar R V, Gowda ME, Shashidhar M P. Clinicoradiographic comparison of sagittal condylar guidance angle determined by dynamic and radiographic methods. J Dent Def Sect. [serial online] 2022 [cited 2023 Jan 31];16:123-9. Available from: http://www.journaldds.org/text.asp?2022/16/2/123/364516
| Introduction|| |
Every prosthodontist's effort while rehabilitation of completely edentulous patients is to provide a complete denture prosthesis, i.e., in physiologically and functionally harmonious relation with the adjoining stomathognathic system. Recording of maxillomandibular relation is one of the important steps in the successful rehabilitation with complete denture prosthesis. Determining and recording of sagittal condylar guidance angle (SCGA) has been well debated in the prosthodontic and orthodontic literature and numerous methods have been advocated by various authors/researchers.
The “Condylar Guidance” is defined as the “mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossa and the articular eminence” (GPT 9). Intraoral or positional wax methods, graphic records such as gothic arch tracing method, functional recordings, and cephalometrics are some of the methods that are used to record the centric and eccentric relation of the mandible. The condylar guidance inclination in the semi-adjustable articulator is set using records from one of the above-mentioned methods. The extraoral Gothic arch tracing method (EGTM) is advocated and still used in academic institutions as “gold standard” for setting of SCGA. A protrusive record of 6-mm distance is obtained and used for programming of the semi-adjustable articulator based on which the condylar guidance is set. This technique-sensitive method is prone for errors which can be due to various factors related to patient, operator or equipment/material. Some of reasons for these errors are, neuromuscular control of the patient, stability of record bases, quality of the recording media, and variation in the properties of the material.,,,,
With the advent of newer radiological technologies, the temporomandibular joint (TMJ) and condylar guidance could be better analyzed and recorded using other approach., Researchers and authors have been advocating various radiographic methods such as lateral cephalograms, oral pantographs, and tomograms for recording the condylar guidance. The main drawbacks of widespread usage of radiographic methods are additional costly equipment, radiation exposure to the patient. However, there is still a scarcity of evidence in literature to support the use of radiographic techniques over the conventional clinical methods for recording of condylar guidance.,,
The growing popularity of cone-beam computed tomography (CBCT) has resulted in an easier, more accurate, lesser radiation exposure, easily available, cost-effective imaging modality for diagnosis and treatment planning in dentistry. Various researchers have suggested the SCGA values obtained from radiographic methods such as orthopantomagram, lateral cephalogram, transcranial projections, linear tomography, and magnetic resonance imaging, can be directly used in the programming of semi-adjustable articulator.,, This would save time and avoid performing some of the patient-sensitive procedures. This study was taken up to compare the SCGA values obtained using CBCT panoramic section view and CBCT cross-section view with that of values obtained using EGTM.
| Materials and Methods|| |
This study was conducted involving 30 patients aged between 50 and 70 years with completely edentulous arches. The patients were selected from a post graduate teaching institution based on inclusion and exclusion criteria. The inclusion criteria were class I inter-ridge relation with well-healed and rounded ridges. Exclusion criteria were any patients with deteriorating general health, poor neuromuscular control, temporomandibular disorders, inadequate inter-ridge space, and bone disorders. A written consent was obtained from each of the patient before performing radiographic imaging procedure. Proper radiographic protocols adhering to “As low as reasonably achievable” principles were adhered to. An ethical clearance certificate was obtained from the institutional ethical committee of the institute.
Extraoral gothic arch tracing method (dynamic method)
Conventional steps in the fabrication of complete dentures were carried out till the recording of tentative maxillomandibular relation with split cast mounting of the maxillary and mandibular casts on Hanau Wide Vue semi-adjustable articulator (Whipmix Corporation, USA). Hight tracers were attached to occlusal rims with the stylus part attached to maxillary rim and recording plate to the mandibular rim. The patient was guided about various movements that needed to be performed and after adequate training, the patients were able to give a definitive arrow point tracing with acceptable sharp apex. The arrow point tracing was secured by attaching transparent film of the same size on the recording plate. The transparent film was perforated 6 mm from the apex of centric point and the patient was guided to hold the stylus in this protrusion point. Type II dental plaster with anti-expansion solution was mixed and was placed in-between the rims and protrusive records were obtained. This protrusive record was used to program the articulator. The centric locknuts of the Hanau Wide Vue semi-adjustable articulator were released, incisal guide pin raised approximately half inch from the guide table. The protrusive record was placed and right and left side calibrations of horizontal condylar assembly were adjusted till the complete seating of the protrusive record without any gaps between the notches on the cast and split cast mounting. After tightening the locknuts the SCGA was recorded on the right and left sides.
Cone-beam computed tomography section views (radiographic technique)
CBCT scan of the subjects was performed using NewTom Giano HR hybrid CBCT with high resolution following low dose exposure protocols. Using the Auto adaptive picture treatments (ApT) filter software the CBCT images were rendered into panoramic section and cross-section images. The ApT-based software allowed us to render both the panoramic section and cross-section images for measuring SCGA. On these two CBCT sectional images, the orbitale and porion were marked and joined to obtain Frankfort horizontal plane. The most superior and most inferior points of the curvature were identified to determine the mean curvature line [Figure 1]. The angulation at the intersection of mean curvature line and the Frankfort horizontal line in both the panoramic and cross-sectional were measured to obtain the right and left side SCGAs [Figure 2] and [Figure 3]. All the images were performed and measured by the same operator. The data obtained were collated and subject to statistical analysis.
|Figure 1: Schematic representation of measurement of SCGA in a radiographic tracing. (a) FH plane, (b) Line from most superior to the most inferior point of the curvature of glenoid fossa, (c) Sagittal condylar guidance angle; angle made by the intersection of line a and b. SCGA: Sagittal condylar guidance angle measured|
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|Figure 2: Measurement of SCGA in CBCT panoramic view. (a) Condyle on left side, (b) Condyle on right side. (a: FH plane, b-Line from most superior to the most inferior point of the curvature of the glenoid fossa, c: Sagittal condylar guidance angle; angle made by intersection of line a and b). SCGA: Sagittal condylar guidance angle measured, CBCT: Cone-beam computed tomography|
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|Figure 3: Measurement of SCGA in CBCT cross-sectional view. (a) Condyle on the right side, (b) Condyle on the left side. (a: FH plane, b: Line from most superior to most inferior point of the curvature of glenoid fossa, c: Sagittal condylar guidance angle; angle made by intersection of line a and b). SCGA: Sagittal condylar guidance angle measured, CBCT: Cone-beam computed tomography|
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| Results|| |
The data on categorical variables are shown as n (% of cases) and the data on continuous variables are presented as mean and standard deviation (SD). The inter-group statistical comparison of means of continuous variables was done using ANOVA. The inter-group statistical significance of multiple group comparisons of means of continuous variables was done using ANOVA with Bonferroni's post hoc test. The intra-group statistical comparison of means of continuous variables is done using “paired t-test.” The underlying normality (null hypothesis) assumption was tested before subjecting the study variables to t-test and ANOVA. In the entire study, the P < 0.05 is considered to be statistically significant. All the hypotheses were formulated using two-tailed alternatives against each null hypothesis (hypothesis of no difference). The entire data were statistically analyzed using Statistical Package for Social Sciences (SPSS ver. 22.0, IBM Corporation, USA) for MS Windows.
Of 30 cases studied, 10 (33.3%) had age between 55 and 59 years, 13 (43.3%) had age between 60 and 64 years, and 7 (23.3%) had age between 65 and 69 years [Table 1]. The mean ± SD of age of cases studied was 62.07 ± 3.62 years and the minimum–maximum age range was 55 and 69 years [Graph 1]. Of 30 cases studied, 17 (56.7%) were male and 13 (43.3%) were female. The male-to-female sex ratio was 1.31:1.00 [Table 2] and [Graph 2].
Distribution of mean right-sided SCGA differs significantly across three methods of measurement (P < 0.001). The distribution of mean left-sided SCGA differs significantly across three methods of measurement (P < 0.001). The distribution of mean (mean of right and left) SCGA differs significantly across three methods of measurement (P < 0.001). The distribution of mean right-sided SCGA did not differ significantly compared to left-sided SCGA in all the three groups studied. The details of mean sagittal condylar guidance obtained from extraoral gothic arch tracing and CBCT images are given in [Table 3] and [Graph 3]. The differences in mean sagittal condylar guidance between right and left side with both the methods of measurement are given in [Table 4] and [Graph 4]. Differences in the sagittal condylar guidance values between EGTMs and CBCT images are given in [Table 5].
|Table 3: Distribution of mean sagittal condylar guidance angles (degrees) across three methods of measurements namely extraoral Gothic arch tracing method, cone-beam computed tomography panoramic section and cone-beam computed tomography cross-section on the right and left sides|
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|Table 4: Distribution of mean sagittal condylar guidance angles (degrees) according to side of measurement by extraoral Gothic arch tracing method, cone-beam computed tomography panoramic section, and cone-beam computed tomography cross-section|
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|Table 5: Distribution of mean difference in sagittal condylar guidance angles between by extraoral Gothic arch tracing method, cone-beam computed tomography panoramic section, and cone-beam computed tomography cross-section|
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The distribution of mean difference in SCGA was significant between the methods EGTM and CBCT panoramic section view and CBCT cross-section view (P < 0.05). Distribution of mean difference in SCGA was significantly higher between by EGTM method when compared to both CBCT views. Distribution of mean difference in SCGA was significantly lower in the CBCT panoramic section view when compared to CBCT cross-section view [Table 5] and [Graph 5].
| Discussion|| |
The mandibular movements involve complex series of coordinated three-dimensional movements in various planes. Condylar guidance is an important factor which needs to be accurately recorded in patients for prosthodontic rehabilitation. The clinical implications of correct recording of SCGA are reduced chair side adjustments during delivery of prosthesis to patients. Hence, it is very important to record the SCGA accurately to avoid occlusal interferences. During complete denture fabrication the EGTM is used to validate the tentative centric relation and also to obtain the protrusive record for calibrating the SCGA on the articulator. This method is being routinely followed in academic institutions. Accurate recording of SCGA with this method still remains difficult because of problems like not all types of semi-adjustable articulators are calibrated to accept lateral records, many of manufacturers have set the SCGA in increments of 5°. The gothic arch tracing cannot be performed in many patients because it needs stable record bases with adequate interarch space, also, it is a time-consuming procedure which requires patients with good neuromuscular control who are able to perform all the movements as directed by the dentist.,,
The CBCT scan provides the clinician with a comprehensive view of the entire maxillomandibular region, providing accurate images of maxilla and mandible with adjoining structures. It is the most accurate and noninvasive method of measuring the curvature of the glenoid fossa. In this study, we used the CBCT ApT-based software to render both the CBCT panoramic sectional views and the CBCT cross-sectional views of the TMJ region for measuring the SCGA. A literature search found that there were few studies available using CBCT panoramic views and CBCT cross-sectional views for the determination of SCGA. We intended to evaluate which CBCT view is better and closer to the routinely suggested method of EGTM. Studies by Schmitter, Shrestha, Prasad Thakur and Linsen found that SCGA measurement using graphic method had lower reproducibility, which the authors attributed to variations among instruments, operators, etc. Prasad and Mawani reported that SCGAs obtained radiographically are higher than those obtained from graphic records methods, our study showed similar results. Kwon et al. compared SCGA measured using panoramic technique and two CBCT sectional views. They observed that SCGA differed significantly among the three methods which are in accordance with our study data. They also found a correlation between SCGA obtained using CBCT sectional views and protrusive occlusal record which is in agreement with our data obtained from this study. However, the mean SCGA found by CBCT panoramic section and CBCT cross-section views are were not in agreement with our study. In this study, the mean right and left SCGA by EGTM technique was 26.67, by CBCT panoramic view was 29.33 and CBCT cross-sectional view was 31.24.
Based on previous studies,,,, it was inferred that radiographic techniques gave a higher value of SCGA by 2°–10° when compared to clinical methods. In this study, the mean right and left EGTM method was 26.67 and 27.00. The mean right and left SCGA by CBCT, the panoramic view was 29.33 and 29.52, respectively, and the mean right and left SCGA by CBCT cross-section view was 31.24 and 31.23, respectively. The values show that the graphic method gave lower SCGA compared to CBCT sectional views which is similar to studies conducted by Kwon et al. We also found results with strong correlation between clinical and graphic methods. However, if a correlation between the graphic method and CBCT methods of measuring SCGAs could be ascertained, a clinically acceptable SCGA can be derived by adjusting the values obtained using CBCT method. In our study, we found a consistent correlation in the SCGAs measured using CBCT and EGTM methods suggesting that CBCT can be used as an alternative method for measuring SCGA. In this study, it was found that age and gender have no influence on the SCGA, similar results were obtained by Thakur and Linsen.
SCGA measurements obtained by both CBCT panoramic sectional view and CBCT cross-sectional view were found to be comparable in our study. The SCGA was 2°–5° higher in CBCT panoramic sectional view compared to EGTM and SCGA were 2°-7° higher in CBCT cross-sectional views compared to EGTM. Therefore, it can be opined that subtracting the excess variation in the degrees and obtaining the SCGA with CBCT can be a practically acceptable method for clinical applications. However, further studies with larger samples are needed to confirm the present results.
The condylar guidance in edentulous subjects is influenced by various age-related factors. In general, it could be inferred from the present study that neither CBCT panoramic view or CBCT cross-section view were found to give SCGA values similar to the clinical method of extraoral Gothic arch technique. Since the distribution of mean difference in SCGA in CBCT panoramic section group is narrow when compared to CBCT cross-section group and mean of the panoramic group are closer to the mean of EGTM group [Graph 5]. Hence, CBCT panoramic view seems to provide more accurate SCGA when compared to CBCT cross-sectional view.
Given the trend toward digitization in prosthodontics, modern-day techniques like CBCT will be more commonly involved in the clinical workflow. However, till reliable correlation can be arrived using CBCT-based modalities to measure SCGA, the clinical methods like graphic methods which are more practical and consistent in results should be preferred. The patient-centric treatment approach will decide the choice of technique which needs to be simple and convenient. Further studies to arrive at correlation between radiographic techniques of measuring SCGA to other clinical-based modalities for measuring SCGA are required to substantiate the results of this study.
| Conclusion|| |
The present study compared the SCGA values obtained by CBCT panoramic section view and CBCT cross-section view with that of values obtained using extraoral Gothic arch tracing method using a protrusive record of 6 mm. A significant difference between the SCGA values between the three groups was observed. However, no statistically significant difference was found between the right and left sides within the group. No statistically significant difference was seen in the SCGA values between the age and gender groups, neither in the graphic tracing method groups nor with the CBCT methods. Within the limitations of the study, it is concluded that CBCT may be a viable alternative to the conventional method of recording SCGA using extraoral Gothic arch tracing.
The authors would like to express their gratitude to Dr. Pushkar Andhare, Division of Orthodontics, Department of Dental Surgery, AFMC, Pune, for collating and assisting in measuring the SCGA in CBCT views.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]