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EVALUATION OF THE ASYMMETRY OF THE MANDIBLE IN HEALTHY CHILDREN
AGED 6- 18-YEARS-OLD
VESELA STOICHKOVA
Chief Assistant Professor, Department of Orthodontics, Faculty of Dental Medicine,
Medical University-Sofia, Bulgaria
Abstract: 422 healthy Bulgarian patients have been examined. All patients had orthodontic treatment needs and had no orthodontic treatment in the past. It was interesting to investigate whether there is difference in the left and right part of the mandibular body, ramus and coronoid process. The difference between the two genders and according to the age of the patients has been studies as well.
Key words: mandible, asymmetry, children, orthopantomogram
In growing patients it is of great importance to find on time the presence of asymmetry in the facial region because after the pubertal spur the growth slowly reduces and any discrepancies during the active growth of the young boys and girls can leave a trace on their social-emotional health. Thepattern of function of the muscles in the orofacial region, such as one-side chewing can lead to hyper- or hypotonus respectively of the masticatory muscles and thus create asymmetry of the mandible [1]. Due to different reasons - functional, anatomical or both, there might be laterodeviation or laterognatia with deviation of the midline of the lower jaw [2] According to Lin et al. the mandibular codyle determines the presence or absence of mandibula deviation.[3] The authors prove that the occlusal contacts influence the bone density and the shape of the condyle. Another scientific team from Korea emphazises the role of both size and shape of the mandibular body and the mandibular condyle in the formation of the asymmetry, with predominant role of the condyle [4]. Dr Lee and al. found correlation between the transversal asymmetry of the dental arches and the asymmetry of the face. They have measured the distance form the canine and the molar to the midline of the jaw [5]. All structures of the body are in close relationship to each other, starting from the body posture and ending with the skeleton and the glenoid fossa. [6] Sometimes in our daily orthodontic practice we may see different occlusal relationships on left and right side of the dentition and therefore for example the patient may have Class I on one side and Class II on the other side. It was interesting to investigate if this dental asymmetry correlates with the skeletal asymmetry. We dicided to study the orthopantomogram, lateral cephalogram and dental casts of our patients. So, the aim of the study was to investigate the asymmetry in the mandible in healthy Bulgarian children according to gender and age.
The materials and methods included 422 healthy Bulgarian patients with orthodontic treatment needs and no orthodontic treatment in the past from a private dental clinic in Sofia have been examined. The requirements of the study fulfilled only the following records: 103 panoramic X-rays, 100 lateral cephalograms and 87 pairs of dental casts. The age of the patients was from 6 to 18 years old, from them 52 were female and 51 - male. 1819 measurements have been performed.
The skeletal Class was evaluated on the lateral cephalogram. From all patients, with Skeletal Class I were 64 patients, with Class II - 30 patients and with Class III - 6 patients. The dental class was determined on the dental casts both for the left and for the right side.
The patients were divided into groups according to their gender and according to their age. The patients were divided as follows: the boys into two groups (6-12-years-old and 13-15-years-old) and the girls into two groups (6-9-years-old and 10-13-yers-old), expecting to find also difference in the parameters due to the pubertal spur.
The following linear and angular parameters have been measured from left and right side of the mandible: Co_SnP, SnP_Ag, Par_6, Co_Go, Go_M, Co_M, Com_Agm, < Co_Go_M. (Picture 1)
2. Picture 1. Evaluation of the parameters on orthopantomogram. The methods of the statistics that have been used in the research include: Kruskal Wallis Test, Descriptive statistics, ANOVA, Independent Samples Test, Levence's Test, t-test for Equality of Means, Group Statistics.
Results: The statistical analysis has shown no asymmetry in the mandible in healthy Bulgarian children in none of the groups. This means that the left and right sides of the mandible and the parameters, evaluated on the panoramic X-rays, have no statistical difference. The only statistically significant difference found in the research was in the linear parameters between the group of the 6-12-years-old boys and the 13-15-years-old boys where the linear parameters had statistically significant higher values. This confirms that in boys the maximum mandible growth occurs during the pubertal spur in the age from 13 to 15 years old. (Table 1). Table 1. Comparison between left and right side of the mandible on OPG according to gender
Ranks
Mean Sum of
Gender N Rank Ranks
Co SnP difference Male 52 53,24 2768,50
Female 52 51,76 2691,50
Total 104
SnP Ag difference Male 52 49,07 2551,50
Female 52 55,93 2908,50
Total 104
Par 6 difference Male 52 55,16 2868,50
Female 52 49,84 2591,50
Total 104
Co Go M Male 52 51,94 2701,00
difference Female 52 53,06 2759,00
Total 104
Co Go difference Male 52 50,80 2641,50
Female 52 54,20 2818,50
Total 104
Go M difference Male 52 51,26 2665,50
Female 52 53,74 2794,50
Total 104
Co M difference Male 52 52,28 2718,50
s
Female Total 52 104 52,72 2741,50
Com agm Male 52 50,91 2647,50
difference Female 52 54,09 2812,50
Total 104
Test Statistics3
Co SnP SnP Ag Par 6 Co Go M Co Go Go M Co M Com agm
differenc differenc differenc differenc differenc differenc differenc differenc
e e e e e e e e
Mann- 1313,500 1173,500 1213,500 1323,000 1263,500 1287,500 1340,500 1269,500
Whitney
U
Wilcoxo 2691,500 2551,500 2591,500 2701,000 2641,500 2665,500 2718,500 2647,500
n W
Z -,252 -1,167 -,917 -,189 -,578 -,420 -,075 -,536
Asymp. ,801 ,243 ,359 ,850 ,563 ,674 ,940 ,592
Sig. (2-
tailed)
a. Grouping Variable: Gender
Group Statistics
Std. Std. Error
Gender N Mean Deviation Mean
Co SnP difference Male 52 ,5769 25,15937 3,48898
Female 52 -1,7308 33,17932 4,60114
SnP Ag difference Male 52 -2,1154 36,53290 5,06620
Female 52 5,1923 31,65317 4,38950
Par 6 difference Male 52 8,0769 17,71655 2,45684
Female 52 3,2692 16,17565 2,24316
Co Go M Male 52 -2,2500 4,33352 ,60095
difference Female 52 -2,2500 4,32446 ,59970
Co Go difference Male 52 -12,5000 36,77568 5,09987
Female 52 -7,6923 35,89830 4,97820
Go M difference Male 52 -11,3269 124,02794 17,19958
Female 52 21,9231 142,45795 19,75536
Co M difference Male 52 -16,5769 62,45229 8,66057
Female 52 -19,0385 53,40411 7,40582
Com agm Male 52 -,0290 ,11144 ,01545
difference Female 52 -,0156 ,14888 ,02065
Conclusion: In healthy Bulgarian children who have referred for orthodontic treatment in a private dental clinic in Sofia no mandibular asymmetry was found neither in the group of boys, nor in the group of the girls. There was no difference in the length of the ramus and the body of the mandible, and in the coronoid process between boys and girls before the pubertal spur. The ramus and the body of the mandible, as well as the size of the coronoid process, in boys aged 13-15-years-old were statistically bigger than in the group of 6-12-years-old ones. Further investigations are needed to evaluate the correlation between the skeletal class, the dental class and the asymmetry.
LIST OF USED SOURCES:
1. Персин Л.С. Ортодонтия. Диагностика, виды зубочелюстных аномалий, «Ортодент-Инфо», 1999, 137 стр.
2. Vasconcelos BC, Gon9alves F, Andrade A, Guillen M, Landim F. Mandibular asymmetry: literature review and case report. Braz J Otorhinolaryngol. 2012 Jul-Aug;78(4):137. doi: 10.1590/S1808-86942012000400028. PMID: 22936154; PMCID: PMC9446356.
3. Lin, H., Zhu, P., Lin, Y. et al. Mandibular asymmetry: a three-dimensional quantification of bilateral condyles. Head Face Med 9, 42 (2013). https://doi .org/10.1186/1746-160X-9-42
4. You KH, Lee KJ, Lee SH, Baik HS. Three-dimensional computed tomography analysis of mandibular morphology in patients with facial asymmetry and mandibular prognathism. Am J Orthod Dentofacial Orthop. 2010 Nov;138(5):540.e1-8; discussion 540-1. doi: 10.1016/j.ajodo.2010.04.025. PMID: 21055584.
5. Lee JY, Han SH, Ryu HS, Lee HM, Kim SC. Cone-beam computed tomography analysis of transverse dental compensation in patients with skeletal Class III malocclusion and facial asymmetry. Korean J Orthod. 2018; 48(6):357-366.
6. Tun Oo L, Miyamoto JJ, Takada JI, Moriyama K. Correlation between the position of the glenoid fossa and condylar translational movement in skeletal Class III mandibular asymmetry patients. Eur J Orthod. 2022; 44(3):294-302.
