Relationship between head posture and parameters of sagittal position and length of jaws/Povezanost polozaja glave i parametara sagitalnog polozaja i duzine vilica.
There are many studies in orthodontic literature that have examined the relationship between the head posture and craniofacial morphology [1-18]. The head position is estimated on the basis of the craniocervical angle, which is formed by the basic anterior cranial base (NS), and odontoid process tangent (OPT) which passes through the lower end last point on the body of the second cervical vertebra . The first study of the head position was published by Solow B. and A. Tallgren in 1976 , who analyzed variables defining craniofacial morphology and defining head posture, on the cephalometric radiographs of 120 subject between the ages of 20 and 30 years. The results have shown that the extension of the head in relation to the cervical spine, i.e. an increased craniocervical angle, is connected with a large anterior and small posterior facial height, reduced sagittal craniofacial dimensions, large inclination of the mandible compared to the anterior cranial base and nasal plane, facial retrognathism, large angle of the cranial base and reduced nasopharyngeal space. There is a reduced anterior and increased posterior facial height, increased sagittal craniofacial dimensions, reduced inclination of the mandible, facial prognathism, decreased angle of the cranial base and increased nasopharyngeal space in the flexion of the head (reduced craniocervical angle). By examining the head position in children with skeletal class I, II and III, whose average age was 9.5 years, D'Attilio M, et al.  found that children with skeletal class III showed a significantly lower angle of cervical lordosis than those with class I and II. A significantly higher extension of the head was found in children with skeletal class II compared to those with skeletal class I and III. There is a significant difference between these three classes in the inclination of the maxillary and mandibular plane compared to the cervical spine.
The size and position of the mandible are the characteristics that are strongly connected with the position of the head and neck . Solow B. and Siersbsek N.  found a reduced craniocervical angle in cases where a face grew with rotation forward and an increased one in cases where a face grew with rotation backwards.
Kim Phong et al.  have found a connection between the extension of the head in relation to the cervical spine, with an increased angle of the cranial base, increased vertical dimensions of the face and jaws retrognathism.
By examining the sagittal yaws position inpersons with skeletal class I authors found that the angle of maxillary prognathism (SNS) and angle of mandibulary prognathism (SNB) are significantly lower than the standard values, which indicates the posterior position of yaws and retrognathic facial type .
The aim of this study is to analyze the connection between head posture and parameters of the sagittal position and length of the jaws in people with different sagittal skeletal jaw relations.
Material and Methods
This study included 90 subjects between the ages of 8 and 14 years, who were examined at the Department of Dentistry, Faculty of Medicine in Novi Sad.
The selection of the test sample was carried out according to the following criteria:
--they had not been treated orthodontically previously;
--sagittal skeletal relation in class I, II and III;
--absence of congenital disorders of craniofacial complex, diseases of muscles and temporomandibular joint;
--absence of any upper airway obstruction;
The subjects were divided into three groups consisting of 30 subjects with I, II and III class of sagittal intermaxillary relations based on the values of angle ANB (indicator of sagittal jaws relations) assording to the following criteria:
--ANB = 2-4[degrees]--skeletal class I
--ANB > 4[degrees]-skeletal class II
--ANB < 2[degrees]--skeletal class III.
Lateral cephalometric radiograph was done for each subject according to the standard recording conditions and cephalometric analysis was done by means of the computer program "Onyx Ccph". The craniocervical angle (NS/OPT) was analyzed as an indicator of the head posture in relation to the cervical spine. The following parameters were analyzed as the indicators of the sagittal position and length of jaws: the angle of maxillary prognathism, the angle of mandibular prognathism, ANB angle as an indicator of sagittal jaw relations, maxillary length (Asnp), and the length of the mandible (Gn-Go). All the parameters are shown in Figure 1.
The values of the angles are expressed in degrees, and the values of jaw length in millimeters.
After completion of the analysis, the obtained data were statistically analyzed by means of methods taken from descriptive statistics methods: methods of data sorting (grouping and tabulation), arithmetic mean and standard deviation. Parametric tests for large and small independent samples (ANOVA and Student's t test) and non-parametric tests for large and small independent samples were used in this study and they were taken from differential statistical methods (Pearson [chi square] test, Mann-Whitney test and Kruskal Wallis test). In order to measure the form and degree of dependence, the correlation and regression analysis was used: linear regression, correlation coefficient and coefficient of determination.
The results obtained by the comparative analysis of the value of the angle NS/OPT in relation to the skeletal class are given in Table 1.
By testing the significance of differences based on ANOVA test, the difference in the value of the craniocervical angle between the analyzed groups was found to be statistically significant (F = 3.97; p <0.05), and their comparison showed that there was a statistically significant difference between the patients with class I and II (t = 2.48; p <0.05), and among those with class II and III (t = 2.29; p <0.05).
The results of the comparative analysis of the value of the angle of maxillary prognathism SNA and mandibular prognathism SNB are shown in Table 2. ANOVA test results show a statistically significant difference in average values of SNA angle (F = 9.88; p < 0.001) between the analyzed groups of patients, and their mutual comparison led to the conclusion that there is a statistically significant difference between the patients with class I and II (t = 4.15; p < 0.01), and between those with class II and III (t = 4.09; p < 0.01). After a statistically significant difference in the values of the angle SNB between skeletal class (F = 15.82; p < 0.001) had been established, their comparison showed a statistically significant difference in the value of the angle between the patients with I and III (t = -4.16; p < 0.01), as well as between those with class II and III (t = -4.90; p <0.01).
The results of correlation analysis between the craniocervical angle and parameters of the jaw position are shown in Table 3. A positive correlation between the angle of NS/OPT and SNA angle was found (r = 0.103; r = 0.112) in the patients with I and II class, however, the degree of this dependence was not statistically significant. In the class III a negative correlation was established, but it was not statistically significant either (r = -0.002). The coefficient of determination for all three classes was very low (less than 0.1) which indicates that the impact of variability NS/OPT angle on the value of SNA angle was a very small percentage. In the patients with class I and III a positive correlation between angles NS/OPT and SNB was found, which was not statistically significant (r = 0.044; r = 0.179 p > 0.05). In those with class II, a negative correlation was found, which was also statistically insignificant (r = -0.005; p > 0.05).
By analyzing the shape and degree of dependence of the ANB angle in relation to the angle of NS/OPT it was found that the forms of dependence were linear, and that the dependence degree was statistically significant (r = 0.311, p <0.05) in the patients with class I. The coefficient of determination was [R.sup.2] = 0.2018, which indicated that 20% of the variability of ANB angle could be explained by the variability of NS/OPT angle, and that 80% was attributed to other factors. The degree of dependence was not statistically significant in the patients with class II and III (r = 0.156; r = -0.075 p> 0.05), which means that the variability of craniocervical angle had little influence on the variability of ANB angle ([R.sup.2] less than 0.1 or 10%).
In the total sample consisting of the patients with I, II and III class, the angle NS/OPT was in positive correlation with the angles SNA and ANB, and in negative correlation with the angle of SNB. This would practically mean that the increase in the angle NS/OPT led to an increase in SNA angle and a decrease in the SNB angle, which led to an increase in ANB angle.
Table 4 shows the results of the descriptive analysis of the upper and lower jaw length values in all three groups of patients. There was a significant difference in the average values of the upper jaw length between the patients with class II and III (t = 2.84; p <0.05). The highest average value of the lower jaw length was observed in the patients with class III, and this value was significantly different from the average value of this parameter in those with class II (t = -2.83; p <0.01).
The results of correlation analysis between the craniocervical angle and the length of the upper and lower jaw are shown in Table 5. Craniocervical angle in the patients with class I was in positive correlation with the length of the upper jaw and in negative correlation with the length of the lower jaw, but this correlation had no statistical significance. In the patients with class II, we found a statistically significant positive correlation of craniocervical angle and the upper jaw length (r = 0.318; p <0.05), as well as a significant negative correlation of craniocervical angle and the lower jaw length (r = -0.220; p <0.05). In the patients with class III a negative correlation of craniocervical angle and length of the upper jaw was found, and a positive correlation of craniocervical angle and the lower jaw length.
The analysis of linear and angular parameters on the lateral cephalometric radiographs of patients with malocclusions class I, II and III revealed the difference in the value of the craniocervical angle between the groups, as well as the correlation between craniocervical angulation and parameters of the sagittal position and length of the jaws.
In the patients with class I malocclusion the average value of the craniocervical angle was 94.06 . which is in line with the results of previous study  which revealed that the value of the craniocervical angle was 94.6 in children between the ages of 7 and 13 years, without craniofacial anomalies, diseases of the muscles and joints and without obstruction of the upper airways. A statistically significant difference of the angle values was established between the patients with class I and II, and II and III.
The highest value of the craniocervical angle (100.8[degrees]) was observed in the patients with class II, while the values for class I and III were similar. This corresponds to the findings of DAttilio M. , who found that children 9.5 years old on average, with class II division showed significantly greater craniocervical angle compared with children of the same age who had class I and III. Capruso et al.  found a connection between skeletal class II and increased craniocervical angle. Arntsen and Sonnesen  also found an increased head extension in the patients with class II malocclusion. Gonzalez and Manns  and Festa et al.  found similar results. In contrast to this Hedayat et al.  found no significant difference in the head position between the patients with class I and II.
These results are opposed to the findings obtained by Hugare J. and Harkiness E.  who found that the distal occlusion was combined with flexion of the head, and did not agree with the results of Solow and Sonnesen  who found that subjects with mutual distal moral relationship had angles NS/OPT and cervical spine angulation (OPT/CVT), 3-4 less than the subjects without this malocclusion.
The correlation analysis showed that the sagittal position of the maxilla was in positive correlation with the craniocervical angle in the patients with class I and II, and the correlation was negative in the patients with class III. Although it is proved that this influence of craniocervical angle on the level of the maxillary prognathism is very small (less than 10%), such correlations may contribute to an increase in the angle of maxillary prognathism in class II and to its decrease in class III, and this leads to a deterioration of basic anomaly. In addition, Marcotte M.  found a high correlation between the sagittal position of the maxilla and the head position. When it comes to the angle of mandibular prognathism SNB, it is in positive correlation with the craniocervical angle in subjects with class I and III, but the correlation is negative in subjects with class II. This can also be a mechanism that can lead to a deterioration of basic anomaly by increasing the angle of mandibular prognathism in class III, and by its reduction in class II. Marcotte M.  found a negative correlation between the craniocervical angle and the angle of the mandibular prognathism.
The craniocervical angle has a much greater effect on ANB angle, rather than individually at angles whose difference is ANB angle. This is a result of various influences on the angles of the maxillary and mandibular prognathism. By the analysis of the total test sample, regardless of the class, we obtained the result that the angle ANB was in a positive correlation with the angle NS/OPT. This again means that an increase in the angle NS/OPT favors the formation of class II, which is characterized by an increased value in ANB angle.
A statistically significant positive correlation was found between the craniocervical angle and the length of the maxilla, which disagrees with the findings of the study published by the Festa et al.  and which brings into connection the maxillar length only with the length of the anterior cranial base.
The lowest average value of the mandibular length was found in the subjects with class II. Given that the largest craniocervical angle was found in this class of malocclusion, the finding which relates to the length of the mandible is in line with previous findings  which claim that the subjects with the extension of the head in relation to the cervical spine have reduced length of the mandible. In the subjects with class II a statistically significant positive correlation was found between the craniocervical angle and the upper jaw length, as well as a significant but negative correlation between the craniocervical angle and the lower jaw length.
The results of correlation analysis of craniocervical angle and the maxilla and mandible length in class II, as well as the previously established positive correlation between craniocervical angle and SNA angle, and the negative correlation between craniocervical angle and SNB angle indicate that an increased craniocervical angle may be one, but certainly not the only factor in the_mechanism of the occurrence of class II malocclusion. This is in line with the results obtained by Arntsen and Sonnesen  in their analysis, which are indicative of the correlation between the head position, the morphology of the cervical spine and craniofacial morphology in subjects with class II malocclusion.
Persons with class II malocclusion have the highest value of the craniocervical angle, i.e. the greatest head extension in relation to the cervical spine. High levels of craniocervical angle in persons with class II may be a contributing factor that deteriorates the basic anomaly of class II due to their acting in terms of increasing the maxillary prognathism angle and reducing the mandibular prognathism angle.
The positive correlation between the value of the craniocervical angle and the upper jaw length and a significant negative correlation between the value of the craniocervical angle and the lower jaw length can also contribute to the occurrence of class II malocclusion.
Abbreviations NS --anterior cranial base OPT --odontal process tangent ANB angle --an indication of sagittal jaws relations SNA --angle of maxillary prognathism SNB --angle of mandibulary prognathism NS/OPT --craniocervical angle
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Rad je primljen 23. V 2016.
Recenziran 17. VI 2016.
Prihvacen za stampu 5. VII 2016.
Vladanka VUKICEVIC (1) and Dorde PETROVIC (2)
University of Pristina, Faculty of Medicine
Department of Dentistry, Kosovska Mitrovica (1)
University of Novi Sad, Faculty of Medicine
Department of Dentistry of Vojvodina (2)
Corresponding Author: Doc. dr Vladanka Vukicevic, Medicinski fakulet, 38220 Kosovska Mitrovica, Anri Didana bb, E-mail: firstname.lastname@example.org
Caption: Figure 1. Points, lines and angles used to assess the craniocervical angulation, sagittal position and length of jaws: N--nasion; S--sella; A--subspinale; B--supramentale; Me--menton; Gn--gnathion; A'--projection of the point A on the base plane of the maxilla; snp--spina nasalis posterior; cv2ip--most inferior and posterior point on the second cervical vertebra corpus; OPTodontoid process tangent through cv2ip point; NS--the anterior cranial base plane; 1. NS/OPT--craniocervical angle; 2. SNA--angle of maxillary prognathism; 3. SNB --angle of mandibulary prognathism; 4. ANB angle--an indicator of sagittal jaws relations; A'-snp--length of maxilla; Gn-Go--length of mandible Slika 1. Tacke, linije i uglovi korisceni za procenu kraniocervikalne angiilacije, sagitalnog polozaja i duzine vilica: N--Nasion; S--Sella; A--subspinale; B--supramentale; Me--menton; Gn--gnathion; A'--projecija tacke A na osnovnu ravan maksile; snp--spina nasalis posterior; cv2ip--krajnja zadnja donja tacka na telu drugog vratnog prsljena; OPT-tangenta odontoidnog procesusa koja prolazi kroz tacku cv2ip; NS--osnovna ravan prednje kranijalne baze; 1. NS/OPT-kraniocervikalni ugao; 2. SNA--ugao maksilarnog prognatizma; 3. SNB--ugao mandibularnog prognatizma; 4. ANB ugao--pokazatelj sagitalnog odnosa vilica; A'-snp--duzina maksile; Gn-Go--duzina mandibule
Table 1. Craniocervical angle (NS/OPT) values as compared to skeletal class Tabela 1. Vrednosti kraniocervikalnog ugla (NS/OPT) u odnosu na skeletnu klasu Skeletal class/ Total/ Skeletna klasa Ukupno I II III Number of patients/ 30 30 30 90 Broj pacijenata Min 77 79.20 72.20 72.20 Max 115.20 126.30 120 126.30 Mean/Srednja vrednost 94.06 100.80 94.59 96.49 SD 1.81 11.10 1.80 10.64 ANOVA F = 3.97; p < 0.05 t-test (I i II) t = -2.48 p < 0.05 t-test (I i III) t = -0.21 p > 0.05 t-test (II i III) t = 2.29 p < 0.05 Table 2. SNA and SNB angle values as compared to skeletal class Tabela 2. Vrednosti ugla maksilarnog (SNA) i mandibularnog prognatizma (SNB) u odnosu na skeletnu klasu SNA SNB I II III I II III Number of patients/ 30 30 30 30 30 30 Broj pacijenata Min 74.50 78 67 71.90 73.10 71 Max 85.30 85.90 86 82 79 87 Mean/Srednja vrednost 78.96 82.70 78.38 75.98 75.87 79.56 SD 0.54 0.37 0.72 0.52 0.31 0.69 ANOVA F = 9.88; p < 0.001 F = 15.82; p < 0.001 t-test (I i II) t = -4.15 p < 0.001 t = 0.18 p > 0.05 t-test (I i III) t = 0.34 p > 0.05 t = -4.16 p < 0.001 t-test (II i III) t = 4.09 p < 0.001 t = -4.90 p < 0.001 Table 3. Craniocervical angle correlation--parameters of jaw position Tabela 3. Korelacija kraniocervikalni ugao (NS/OPT) parametri polozaja vilica Correlation (r)/ NS/OPT Korelacija (r) Probability (p)/ I II III Total/ Verovatnoca (p) Ukupno SNA r 0.103 0.112 -0.002 0.123 P n.s. n.s. n.s. n.s. SNB r 0.044 -0.005 0.179 -0.066 P n.s. n.s. n.s. n.s. ANB r 0.311 0.156 0.075 0.177 P 0.05 n.s. n.s. 0.05 n.s.--not significant/nije statisticki znacajno; ANB--pokazatelj sagitalnog odnosa vilica; SNB--ugao mandibularnog prognatizma, SNA--ugao maksilarnog prognatizma Table 4. Maxillary (A'-snp) and mandible length (Gn-Go) as compared to skeletal class Tabela 4. Duzine maksile (A'-snp) i mandibule (Gn-Go) u odnosu na skeletnu klasu A'--snp Gn-Go I II III I II III Number of patients/ 30 30 30 30 30 30 Broj pacijenata Min 36.40 35.80 32.90 53.90 58.20 60.30 Max 51.50 51.10 50.30 84.20 77 87.50 Mean/Srednja 43.75 46.67 42.86 67.57 65.08 70.14 vrednost SD 0.65 0.61 0.75 1.22 0.83 1.17 ANOVA F = 3.53; p> 0.05 F = 3.58; p< 0.05 t-test (I i II) t = 0.08 p > 0.05 t= 1.01 p > 0.05 t-test (I i III) t = 0.89 p > 0.05 t = -1.52 p > 0.05 t-test (II i III) t = 2.84 p < 0.05 t = -2.83 p < 0.01 Table 5. Craniocervical angle correlation-lengths of jaws Tabela 5. Korelacija kraniocervikalni ugao (NS/OPT) duzine vilica Correlation (r)/ NS/OPT Korelacija (r) Probability (p)/ I II III Total/Ukupno Verovatnoca (p) A'-snp r 0.028 0.318 -0.020 -0.057 p n.s. 0.05 n.s. n.s. Gn-Go r -0.107 -0.220 0.006 -0.105 p n.s. 0.05 n.s. n.s. A'-snp--duzina maksile; Gn-Go--duzina mandibule
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|Title Annotation:||Original study/Originalni naucni rad|
|Author:||Vukicevic, Vladanka; Petrovic, Dorde|
|Date:||Sep 1, 2016|
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