DETERMINATION OF GROWTH PATTERN USING OPG A NEW APPROACH IN ORTHODONTIC DIAGNOSIS

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1 Case Report DETERMINATION OF GROWTH PATTERN USING OPG A NEW APPROACH IN ORTHODONTIC DIAGNOSIS Authors : Bhavya Trivedi*, Aatman Joshipura**, A.F. Bhatia***, Krishnamurthy****, Nirav Patel***** ABSTRACT The aim of the study was to explore the possibility of using 'OPG' for estimating measure of "gonial angle, mandibular plane angle and ratio between the lower third anterior facial height to posterior facial height and it's comparison with that of cephalometric findings. Digital lateral cephalograms and digital OPGs of 30 males and 30 females were collected randomly from the records section of the department of orthodontics and dentofacial orthopedics, KM Shah dental college and hospital. From OPG and cephalogram required data were collected and subjected to statistical analysis for the purpose of comparison and concluding the results.after the statistical analysis of the data it was concluded that: - There is no statistically significant difference between the GA, MPA and LPFH on the right and left side in males, females and overall samples. There is a very high correlation and no statistically significant difference between GA, MPA and ratio of LPFH to LAFH on OPG and lateral cephalogram in males, females and overall samples. Hence when OPG is available there is no need for taking an additional lateral cephalogram for estimation of above parameters and thus the mandibular morphology. Introduction: When initially introduced, Panoramic radiographs (OPGs) were used as a substitute for the full mouth intraoral periapical radiographs to examine the dental conditions of the person during the diagnosis 1 and treatment planning. In orthodontic practice it was used to provide important information about the teeth, their axial inclinations and surrounding 2-4 tissues. Various investigators explored its usefulness in collecting information about the morphology of the skeletal structures in the lower 5-16 third of face. Gonial angle, mandibular plane angle and ratio of LTPFH to LTAFH are the important measurements Address of corresspondance DR. Aatman Joshipura, 16, shardanagar society, Near shreyas crossing, Paldi, Ahmedabad 7 that are usually evaluated during the orthodontic diagnosis. They give us an idea about the growth direction of mandible and face. An increased gonial angle and mandibular plane angle with reduced ratio of LTPFH to LTAFH indicates a vertical growth pattern, while reduced gonial angle and mandibular plane angle with increased ratio of LTPFH to LTAFH 1 indicates a horizontal growth pattern. For this purpose lateral cephalogram is generally required. As the OPG radiographs are invariably taken for the routine dental diagnostic procedures, one can take advantage of it in understanding the morphology and growth direction of mandible. Moreover the disadvantage of superimposition of the right and left side images in lateral cephalogram can be 10 overcome in OPG. This study was carried out to clarify the possible application of panoramic radiograph as an adjuvant **, *****Senior lecturer, *Professor, ****Reader Department of orthodontics, Ahmedabad dental college and hospital, Rancharda, Ahmedabad ***Prof and HOD, Department of orthodontics, K M Shah dental college and hospital, Piparia, Vadodara 63

2 tool to lateral cephalogram for the assessment of dento-facial skeletal pattern in the lower third of face. Materials And Method Source of the sample was the pretreatment case records of the patients visiting the Department of Orthodontics; K. M. Shah Dental College & Hospital, Piparia, Vadodara. Ethical committee approval of the university for taken. Sample size was a total of 30 males and 30 females and the Radiographs used were Orthopantomogram (OPG) and Lateral cephalograms. In the inclusion criteria following points were t o b e c o n s i d e r e d w h i l e s e l e c t i n g radiographs:- Good quality digital radiographs Showing all the permanent teeth fully erupted, at least up to 2nd molars No previous history of orthodontic treatment No previous history of trauma particularly birth injury to mandibular condyle The samples for this study consist of good quality pre-treatment lateral cephalograms and OPGs of patients of good quality in the Compact Disc from the Department of Orthodontics & Dentofacial Orthopedics, K. M. Shah Dental College & Hospital, piparia, Vadodara. The radiographs selected are of the subjects fulfilling required criteria. To avoid distortion and magnification of images, we were careful to obtain the radiograph from same machine with standard exposure and to ensure proper patient position. All the tracings are done personally using dolphin imaging software.(version 10.5) Digital software as a tool in cephalometric tracing has been proved very 23, 24 well. The dolphin imaging software has many advantages including the fact that it has an accuracy of 0.1 mm linear measurement and 0.1 degree angular measurements. All the required parameters are obtained in such a way that they have the similar anatomical landmarks visible in both OPGs and lateral cephalogram. The points required to be plotted on lateral cephalogram and OPG are as under. Points plotted are: 1. ANS: (anterior nasal spine) The anterior tip of the sharp bony process of the maxilla at the lower margin of anterior nasal spine. 2. Me: (Menton)The lowest point on the symphyseal shadow of the mandible seen on lateral cephalogram. 3. Co: (condylion)the most superior midpoint on the condyle of the mandible. 4. Go: (Gonion) A point on the curvature of the angle of the mandible located by bisecting the angle formed by bisecting the angle formed by lines tangent to the posterior ramus and inferior border of the mandible. 5. Po: (porion) The most superiorly positioned point of the external auditory meatus. 6. Or: (Orbitale) The lowest point on the inferior rim of the orbit. 7. Anterior facial height: linear distance from Anterior nasal spine (ANS) to Menton (Me) 8. Posterior facial height: linear distance from Condylion (Co) to Gonion (Go) 9. Gonial angle: angle between tangent to lower border of mandible and ramus 10. Mandibular plane angle: angle between mandibular plane (tangent to lower border of mandible) and horizontal plane (Co to Or) From each Lateral Cephalogram the following parameters were measured using Dolphin Imaging software Gonial angle Mandibular plane angle Posterior and anterior facial heights in lower third of face and their ratios 64

3 Figure A: landmarks and planes used in lateral cephalogram (Figure C: The landmarks and planes used in OPG) [The above figure is just a representation and understanding of the landmarks and planes used. The data for study was collected by using dolphin imaging software only] [The above figure is just a representation and understanding of the landmarks and planes used. The data for study was collected by using dolphin imaging software only] Thus from OPG and cephalogram required data were collected and subjected to statistical analysis for the purpose of comparison and concluding the results. The various statistical analysis used are T- test and Pearson's correlation test From each OPG, following data is obtained using same software. Right Gonial Angle Left Gonial Angle Right Mandibular plane angle Left Mandibular plane angle Right lower posterior facial height Left lower posterior facial height Lower Anterior facial height Ratio of lower anterior facial height to mean lower posterior facial height Figure B: screen shot of measurements on OPG 65

4 Discussion During orthodontic diagnostic procedures, an orthodontist is interested in estimating the gonial angle of the mandible, the slope/orientation of the mandibular plane as well as the ratio between the lower third posterior facial heights to the lower third anterior facial heights, as all these are important in assessment of the direction of growth of the mandible. Usually for this purpose, lateral cephalogram is used and help of certain related established cephalometric parameters is taken. This is particularly of great importance while handling a young child. In present day clinical practice, the OPG radiographs are routinely taken to provide important information about the erupted and unerupted teeth and assessment of health of surrounding bone and 2-4 supporting tissues. The OPG radiograph thus taken for routine dental investigations like status of extent of dental caries present in the teeth, the periodontal conditions including level of bone support and presence or absence of any periapical pathology, can be used as a substitute to assess the mandibular morphology and facial growth direction to avoid additional exposure of x-rays to the child. This is possible provided we confirm that the values of the important established cephalometric parameters related to the morphology of the mandible remains unaltered between the OPG and the lateral cephalogram; thus extending the use of OPG which is an essential diagnostic record. Moreover the disadvantage of superimposition of the right and left side images in lateral cephalogram 10 can be overcome in OPG. Use of digital radiographic systems is gaining popularity and offers several advantages over conventional cephalograms; measurements can be performed quickly, treatment plans can be determined easily, chemical and associated environmental hazards are eliminated, the images are easy to store, and communication between providers is facilitated. In addition, rapid superimposition of serial radiographs and cost- 24 efficient duplication of radiographs are possible. 66

5 For the present study, the digital lateral cephalograms and digital OPGs of 30 males and 30 females were collected randomly from the records section of the department of orthodontics and dentofacial orthopaedics, KMSDCH. To study the morphology of the angle of mandible, orientation of mandibular plane and assessment of the direction of growth of craniofacial skeleton on the lower third of face, on each OPG total seven measurements and on corresponding lateral cephalogram of the same patient total four measurements were taken. On an OPG, paired readings for bilaterally situated gonial angle, orientation of the mandibular plane and the lower third posterior facial height were recorded and compared for males, females and total samples. The ratio of lower third posterior facial height to lower third anterior facial height was also estimated and recorded from OPG. Corresponding similar parameters were recorded from lateral cephalogram of the same individuals for the purpose of comparisons. According to Turp JC, Vach 9 W, Harbich K, Alt KW and Sturb JR the linear measurements of OPG and lateral cephalogram can't be compare reliably, hence in the present study their ratio is taken. Table 1 and table 3 shows the mean and standard deviation values of various angular and linear measurements of different parameters and % ratio between LPFH to LAFH for the overall total sample of sixty subjects in OPG and lateral cephalogram respectively. Chart 1 and chart 3 represents the same graphically. Table 2 shows the mean and standard deviation values of bilateral situated paired readings for gonial angle, mandibular plane angle and LPFH. When statistically compared by the T-test and the correlation co-efficient these three bilaterally situated landmarks having paired readings do not show significant difference between the measurement on the right and left side for overall sixty subjects. Similar comparison was done separately for males and females respectively, which also confirmed no significant difference in the measurements recorded on right side and left side. In the support of the findings of the present study, 13 Ongkosuwito EM et al and Larheim TA, Svanaes 12 DB also concluded that there is no statistically significant differences between the reproducibility of the right and left sides Thus, it is concluded that using measurement from any one side of an OPG for parameters gonial angle, mandibular plane angle and lower posterior facial height side serves the required diagnostic purpose without any chance of making error. In the present study therefore, the mean value for bilaterally situated landmarks in OPG was used further for comparison with corresponding landmarks on lateral cephalogram. The established value of GA according to Bjork- Jaraback analysis is and MPA according to Tweed analysis is 25 which is almost similar to the present study - GA (122.1 ±7.25) and MPA (27.4 ±5.34) (Table 3 and chart 3). Table 4 gives the comparison for GA, MPA and ratio as measured in cephalogram and OPG. No statistical difference is found at any level during this comparison. Chart 4 graphically represents comparison of various parameters on OPG and lateral cephalogram. Table 5 shows values for correlation coefficient estimated for the parameters GA, MPA and ratio when measured on an OPG and lateral cephalogram. Chart 5, 6 and 7 graphically represents the correlation for each parameter between the two diagnostic tools viz. OPG and lateral cephalogram. The value of 'r' is highly significant for each correlation at p= Abu elhaija in 2005 compared the GA between panoramic radiographs and cephalometric radiographs with the mean values 127.2±6.2 and 125.7±6.5 respectively and the correlation value 'r' was In the present study the mean for GA was 122.3±7.6 and 122.1±7.25 for OPG and lateral cephalogram respectively and the correlation value 'r' is All these proves that the gonial angle, the slope/orientation of the mandibular plane and the ratio between the lower third posterior facial height to the lower third anterior facial height are similar in both OPG and lateral cephalogram. Hence when OPG 67

6 is available there is no need for taking an additional lateral cephalogram for estimation of above parameters and thus the mandibular morphology. Conclusion For the present study, the digital lateral cephalograms and digital OPGs of 30 males and 30 females were collected randomly from the records section of the department of orthodontics and dentofacial orthopaedics, KMSDCH. The aim of the study was to explore the possibility of using 'OPG' for estimating measure of "gonial angle, mandibular plane angle and ratio between the lower third anterior facial height to posterior facial height and it's comparison with that of cephalometric findings. After doing required statistical analysis it was concluded that:? There is no statistically significant difference between the GA, MPA and LPFH on the right and left side in males, females and overall samples.? There is a very high correlation and no statistically significant difference between GA, MPA and ratio of LPFH to LAFH on OPG and lateral cephalogram in males, females and overall samples. Bibilography 1) Frency R. karjodkar Textbook of dental and maxillofacial radiology ; ) Graber TM, Brainerd FS. Current orthodontic concepts and techniques ) Friedland B.Clinical radiological issues in orthodontic practice Semin Orthod 1998; 4 : ) Bruks A, Enberg K, Nordqvist I, Hanson AS, Jansson L. Radiographic examinations as an aid to orthodontic diagnosis and treatment planning 5) Paulsen HU. Morphological changes of the TMJ condyles of 100 patients treated with the Herbst appliance in the period of puberty to adulthood: a long term radiographic study. Eur J Orthodontics 1997; 19 : ) Peltola JS, Kononen M, Nystrom M. A followup study of radiographic findings in the mandibular condyles of orthodontically treated patients and associations with TMD. J Dent Reseach 1995; 74; ) Mattila K, Altonen M, Haavikko K. Determination of the gonial angle from the orthopantomogram.angle Orthod 47: , ) Akcam M0, Altiok T, Ozdiler E. Panoramic radiographs: a tool for investigating skeletal pattern. Am J Orthgd Dentofacial Ortho 123: , ) Turp JC, Vach W, Harbich K, Alt KW, Sturb JR. Determining mandibular condyle and ramus h e i g h t w i t h t h e h e l p o f a n orthopantomogram- a valid method? J Oral Rehab 23: , ) E l h a m S. l A b u A l h a i j a, Pa n o ra m i c radiographs: determination of mandibular steepness; The Journal of Clinical Pediatric Dentistry; Volume 29, Number 2; ) Fischer-Brandies H, Fischer-Brandies E, Dielert E The mandibular angle in the orthopantomogram Radiologe Dec;24(12): ) Larheim TA, Svanaes DB, Reproducibility of ro t a t i o n a l p a n o ra m i c ra d i o g ra p hy : Mandibular linear dimensions and angles; American Journal of Orthodontics and Dentofacial Orthopedics Volume 90, Issue 1, July 1986, Pages ) Ongkosuwito EM Dieleman MM, Kuijpers- Jagtman AM, Mulder PG, van Neck JW,2009 L i n e a r m a n d i b u l a r m e a s u re m e n t s : comparison between orthopantomograms and lateral cephalograms; Cleft Palate Craniofac J Mar;46(2): Epub 2008 Jun 3. 14) Mostafa shahab, barat-ali and nima mokhber L i n e a r m a n d i b u l a r m e a s u re m e n t s : comparison between orthopantomograms and lateral cephalograms. The Cleft palate craniofacial journal official publication of the 68

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