|Year : 2016 | Volume
| Issue : 1 | Page : 34-40
Calvarial thickness in relation to sagittal and vertical malrelations in Egyptians
Dina M Tawfik1, Eman M El Shourbagy2, Safaa A Ghobashy2
1 Orthodontic Department, Faculty of Dentistry, Tanta University; Ministry of Health, Tanta, Egypt
2 Orthodontic Department, Faculty of Dentistry, Tanta University, Tanta, Egypt
|Date of Submission||22-Feb-2016|
|Date of Acceptance||17-Mar-2016|
|Date of Web Publication||26-Jul-2016|
Dina M Tawfik
27, Toot Ankh Amoon St, Tanta
Source of Support: None, Conflict of Interest: None
The purpose of this study was to evaluate the relationship between skull thickness and different skeletal patterns in both sexes.
Materials and methods
A total of 120 pretreatment lateral cephalometric radiographs of adult patients seeking orthodontic treatment at the orthodontic clinic in the Faculty of Dentistry, University of Tanta, were evaluated. The patients' ages ranged between 18 and 25 years. All radiographs had been classified into two categories according to the anteroposterior and vertical relationships as follows: normodivergent facial pattern with an FH-MP angle between 22 and 28° and a normal sagittal pattern with an ANB angle between 2 and 4°. The thickness of the frontal, parietal, and occipital bones was measured on lateral radiographs of patients with skeletal class II and class III, both high-angle and low-angle cases, and compared with the control group.
Female patients with skeletal class II malocclusion had a significantly thicker frontal bone and thinner occipital bones compared with male patients.
The frontal bone and occipital bones are important key bones for understanding the calvarial phenotype and sexual dimorphism in different skeletal patterns.
Keywords: cranial vault, facial pattern, lateral cephalometry, skull thickness
|How to cite this article:|
Tawfik DM, El Shourbagy EM, Ghobashy SA. Calvarial thickness in relation to sagittal and vertical malrelations in Egyptians. Tanta Dent J 2016;13:34-40
|How to cite this URL:|
Tawfik DM, El Shourbagy EM, Ghobashy SA. Calvarial thickness in relation to sagittal and vertical malrelations in Egyptians. Tanta Dent J [serial online] 2016 [cited 2017 Dec 16];13:34-40. Available from: http://www.tmj.eg.net/text.asp?2016/13/1/34/186944
| Introduction|| |
In humans, the cranial vault is imperfectly composed in newborns to allow the large head to pass through the birth canal. During birth, the various bones are connected by cartilages and ligaments only. The open portion between the major bones of the upper part of the vault, called fontanelle, normally remains soft for up to 2 years after birth. As the fontanelles close, the vault loses some of its plasticity. The sutures between the bones remain until 13 or 14 years of age, allowing for growth of the brain. The cranial vault is directly proportional to the skull size and is developed early. The skull thickness is an essential part of the craniofacial morphology. Craniofacial morphology has been evaluated in the interest of orthodontics and maxillofacial and plastic surgery.
Calvarial bone is an important site of bone graft in reconstructive surgery. The knowledge of calvarial thickness is of importance in different fields such as forensic dentistry and physical anthropology, aiding in understanding the etiology of skeletal pattern and subsequently helping the orthodontist and maxillofacial and plastic surgeons in correct diagnosis and treatment plan, which will reflect in successful treatment outcome. However, limited data are available on skull thickness in relation to different skeletal patterns, although skull thickness has been measured and analyzed over the years in medical studies ,,,,,,. Relationships between thickness and sex, general body build, and ethnicities have been studied ,,,,,,,,,,. Among the pathological conditions demonstrating a general thickening of the skull compared with normal standards are chronic severe anemia , Camurati-Engelmann disease , hyperparathyroidism ,, hyperostosis frontalis interna , and hyperostosis cranii ex vacuo .
Fibrous dysplasia , osteoma ,, and clefts  are examples of pathological conditions with a local thickening of the skull.
The inter-relationship between thickness of the skull and skeletal malocclusions has not been published until very recently. Jacobsen et al.  measured the thickness of the skull in patients with skeletal deep bite and compared this with a control group including 18 profile radiographs. He found that patients with this vertical malocclusion have a general thickening of the skull. Arntsen et al.  measured the thickness of the frontal, parietal, and occipital bones on lateral radiographs of patients with skeletal class II and class III malocclusion. They found that in class I and class III there was no significant difference in skull thickness between men and women, whereas in class II the frontal bone was thicker and the occipital bone was thinner in women when compared to men.
Aim of the work
This study was performed to evaluate the relationship between skull thickness and different skeletal patterns in both sexes.
| Materials and Methods|| |
A total of 120 pretreatment lateral cephalometric radiographs of adult patients seeking orthodontic treatment at the orthodontic clinic in the Faculty of Dentistry, Tanta University, and private clinics in Tanta city were selected. All patients are informed about the purpose and steps of this research and using of their lateral cephalometric radiographs according to the ethics committee of Faculty of Dentistry Tanta University.
The potential study sample was determined according to these criteria: age 18-25 years, no history of orthodontic treatment, presence of all permanent teeth, no craniofacial anomalies or systemic disorders, and no history of previous skull fracture or open brain surgery. All radiographs chosen had been classified into two categories according to Egyptian norms  and each group was subdivided into three subgroups based on the anteroposterior or vertical relationships as follows: a normodivergent facial pattern (68 participants) and a normal sagittal pattern (70 participants).
The selection criterion for the normodivergent facial pattern group was an FH-MP angle between 22 and 28° (according to Alex analysis). This group was divided into three subgroups according to the ANB angle: subgroup 1, class I (ANB angle between 2 and 4°): it consisted of 25 lateral cephalometric radiographs (12 men and 13 women); subgroup 2, class II (ANB angle>4°): it consisted of 23 lateral cephalometric radiographs (12 men and 11 women); and subgroup 3, class III (ANB angle<2°): it consisted of 20 lateral cephalometric radiographs (nine men and 11 women).
The selection criterion for the normal sagittal pattern group was an ANB angle between 2 and 4° (according to Alex analysis). This group was divided into three subgroups according to the FH-MP angle: subgroup 1, normal angle (FH-MP angle between 22 and 28°): it consisted of 27 lateral cephalometric radiographs (12 men and 15 women); subgroup 2, high angle (FH-MP angle>28°): it consisted of 23 lateral cephalometric radiographs (11 men and 13 women); and subgroup 3, low angle (FH-MP angle<22°); it consisted of 20 lateral cephalometric radiographs (11 men and nine women).
Through this classification, the influence of vertical facial pattern was excluded in the normodivergent group to detect the effect of sagittal pattern on calvarial thickness, and the influence of sagittal skeletal pattern was also excluded in the normal sagittal group to detect the effect of vertical pattern on calvarial thickness.
The thickness of the frontal (f), parietal (p), and occipital (o) bones was calculated by measuring the distances from the points where the perpendicular bisectors of the cords nasion–bregma, bregma–lambda, and lambda–basion intersected the inner and outer contours of the respective bones  ([Figure 1]).
Linear measurements including anterior facial height, posterior facial height, AF-BF distance, frontal bone thickness, parietal bone thickness, and occipital bone thickness, and angular measurements including SNA, SNB, ANB, and FH-MP angles were measured ([Figure 2] and [Figure 3]).
|Figure 3: Linear measurements recorded. AF-BF distance, anterior facial height (N-M) and posterior facial height (S-Go).|
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| Statistical Analysis|| |
The χ2-test was applied to determine the differences in distribution between sexes. The mean and SD values of the calvarial bone thickness between the normodivergent and normal facial pattern groups were compared with one-way analysis of variance to determine whether there were any significant differences among the subgroups. Where significant F factors occurred, the Tukey's multiple comparison test was used to identify which group was different.
The unpaired t-test was performed to determine the mean sex differences in calvarial bone thickness. The level of significance was set at P- value less than 0.05. The Pearson correlation coefficient was calculated to ascertain the strength of the relationship between the cephalometric parameter and calvarial thickness in male and female patients.
These analyses were performed with the statistical package for the social science (SPSS) V 16 (Chicago, USA).
| Results|| |
The proportion of male and female patients in each group on the basis of sagittal relationship is presented in ([Table 1]).
The sample distribution according to vertical skeletal relationship is presented in [Table 2]. Sixty-eight percent of patients had a normal angle.
The results showed nonsignificant differences between the subgroups of the normodivergent facial pattern group in terms of parietal and occipital bone thickness, whereas there were significant differences in terms of frontal bone thickness between the subgroups, with significant increase in class III compared with class II ([Table 3]).
|Table 3: Comparison of frontal bone thickness among the subgroups of the normodivergent facial pattern|
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The results presented in [Table 4] and [Table 5] show nonsignificant differences in calvarial bone thickness among the subgroups of the normodivergent facial pattern group in both male and female patients.
|Table 4: Comparison of values of calvarial bone thickness among females with normodivergent facial pattern|
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|Table 5: Comparison of values of calvarial bone thickness among males with normodivergent facial pattern|
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The unpaired Student t-test showed no significant sex differences with respect to calvarial thickness of frontal, parietal, and occipital bones in skeletal class I and class III subgroups, whereas in the skeletal class II subgroup there was a significant sex difference (P < 0.05), with female patients having thicker frontal bone thickness compared with male patients and male patients having thicker occipital bone compared with female patients ([Table 6]).
|Table 6: Sex differences in normodivergent subgroups with skull thickness measurements|
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The results showed nonsignificant differences between the subgroups of the normal sagittal facial pattern group with respect to frontal, parietal, and occipital bones.
The results showed nonsignificant differences with respect to calvarial bone thickness among the subgroups of the normal sagittal facial pattern group in both male and female patients ([Table 7] and [Table 8]).
|Table 7: Comparison of values of calvarial bone thickness among females with normal sagittal facial pattern|
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|Table 8: Comparison of values of calvarial bone thickness among males with normal sagittal facial pattern|
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The unpaired Student t-test showed no significant sex difference regarding calvarial thickness of frontal, parietal, and occipital bones in skeletal normal and high-angle subgroups, whereas in the low-angle subgroup occipital bone thickness showed significant sex difference (P < 0.05), with male patients having a thicker occipital bone compared with female patients ([Table 9]).
|Table 9: Sex differences in normal sagittal facial pattern subgroups with skull thickness measurements using student|
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The results of the correlation coefficient analysis for total female cephalometric parameters showed significant positive correlation between SNA, ANB, FH-MP angle, and anterior facial height with frontal bone thickness ([Table 10]), whereas the total male cephalometric parameters showed negative correlation between occipital bone thicknesses and FH-MP angle ([Table 11]).
|Table 10: Correlation coefficients between total female cephalometric parameter and calvarial thickness|
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|Table 11: Correlation coefficients between total male cephalometric parameter and calvarial thickness|
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| Discussion|| |
The calvaria is an important site of bone graft harvest , and aids the orthodontist and maxillofacial and plastic surgeons in taking successful treatment decisions. Therefore, the aim of the current study was to evaluate the calvarial thickness parameters in different skeletal patterns and in both sexes ,.
The sample of this study consisted of 120 patients. Their ages ranged between 18 and 25 years to eliminate the effect of growth on the results of the study.
The radiographs were classified into two main groups based on Egyptian norms . The purpose of this classification was to investigate the relationship between the calvarial thickness of adult patients with vertical skeletal malocclusion in patients with only a normal sagittal facial pattern and to investigate the relationship between calvarial thickness in adult patients with sagittal skeletal malocclusions in patients with only a normodivergent facial pattern. In other words, the influence of a vertical facial pattern was excluded in the normodivergent group to detect the effects of a sagittal pattern on calvarial thickness and the influence of a sagittal skeletal pattern was excluded in the normal sagittal group to detect the effects of vertical patterns on calvarial thickness. Therefore, the interference of many interrelated and confounding variables was minimized, as the selection criteria were defined strictly.
Björk  reported that there was a connection between the thickness of the bone in general and the development of malocclusions and found that sturdy children responded better to orthodontic treatment and attributed it to greater growth activity. As skull thickness could be indicator of the thickness of bone in general, the hypothesis of the present study was that a difference in skull bone thickness might occur because of skeletal malocclusion. Arntsen et al.  and Jacobsen et al.  found that skull thickness was associated with severe malocclusion.
Differences in the mean thickness of the frontal, parietal, and occipital bone between the different craniofacial patterns and between sexes were then assessed by means of the unpaired t-test. The most important outcome of this test was that there were nonsignificant sex differences in the normodivergent subgroups with respect to calvarial thickness in skeletal class I and class III subgroups. This is in agreement with the studies of Lynnerup et al. , Gonzales et al. , and Arntsen et al. , and in disagreement with those of Ishida and Dodo  and Dostálová et al. . These conflicting results might be due to differences in age and race.
It has been observed that the frontal and occipital bone thickness was significantly different between sexes in skeletal class II (P ≤ 0.05), with female patients having thicker frontal bone compared with male patients, and male patients having thicker occipital bone than female patients. Thus, it can be concluded that a deviation in the theca cranii is related to class II malocclusion. This result was also confirmed by the positive correlation between frontal bone thickness and SNA angle, ANB angle, FH-MP angle, and anterior facial height. This can be explained by sexual dimorphism of frontal and occipital bones thickness between male and female patients with skeletal class II malocclusions. These results were compatible with those of Gonzales et al.  and Arntsen et al.  and not in agreement with those of Ishida and Dodo  and Dostálová et al. . Arntsen et al.  stated that the local thickening in the frontal bone in female patients with class II malocclusion might be due to the short nasal bone in this malocclusion and the local thinning of the occipital bone might be related to the attachment of the neck musculature to this occipital region, which may influence the head posture. In 2009, Arntsen et al.  added that this local thickening of the female frontal bones in patients with skeletal class II malocclusion is not easy to explain but that it may be due to excessive bone deposition in this region during and after adolescence,. Thus, no clear trends have emerged and the findings have been somewhat conflicting, which could probably be due to the differences in the sampling method.
Among the characteristics of facial morphology, facial type, such as average (normal angle), long (high), or short (low angle), is an important factor in orthodontic treatment, mainly because facial type influences the anchorage system, growth prediction of the maxillofacial structures, and goals of orthodontic treatment, along with bite forces and masticatory muscles . However, the relationship between skull thickness and facial type is not yet fully understood. Statistical calculations were performed in the normal sagittal pattern group to assess the mean differences between the three groups and the calvarial bone thickness in the pooled sample with analysis of variance test. The results revealed absence of significant differences between the vertical cephalometric values and cranial vault thickness. This finding is supported by the study of Ishida and Dodo . However, Jacobsen et al.  stated that patients with skeletal deep bite have a significantly thicker skull compared with patients with neutral occlusion and normal vertical craniofacial morphology. This contradictory finding may be related to the variance in the ages of the samples. However, the unpaired t-test to evaluate the sex differences in the normal sagittal facial pattern subgroups with cranial vault thickness revealed no significant sex differences in normal and high-angle facial pattern groups, whereas a significant relationship was seen between low-angle and short facial type and occipital bone thickness in male patients.
Ricketts et al.  described the long face pattern as being long and narrow with dental arches that are frequently crowded and have weak musculature and an obtuse mandibular gonial angle. In contrast, the short face pattern or low-angle case is short and wide, with a strong square mandible, broad dental arches, and consequently have a strong musculature. These findings are compatible with the present study in which patients with a low angle have a significantly thicker skull compared with patients with a normal vertical facial pattern.
Jaw-closing muscle activity is said to be greatest in cases with a large posterior facial height, a small anterior facial height, a long mandible, a flat mandibular plane, and a small gonial angle ,,. Tsunori et al.  added that these relationships are independent of overall size and their specificity argues for differences in the tension-generating capacities of muscle according to facial types.
The result of the present study also revealed a significant sex difference in the thickness of the occipital bone in male patients than in female patients; this may be due to the sex difference in the level of circulating hormones during the growth spurt, which subsequently can affect the growth rhythm of bones. This explanation is in accordance with those of Liebermann  and Motoc et al. .
Thus, it can be concluded that calvarial thickness could be used as a sex indicator especially for frontal and occipital bones. In contrast, the parietal bone showed no significant differences between total skeletal groups in male and female patients. This finding is hard to explain, but it may be attributed to a different growth rhythm for the parietal bone that was not dramatically affected by the circulating hormones, similar to the occurrence in frontal and occipital bones during the growth spurt.
Bone grafts are widely used in the reconstruction of osseous defects in the oral and maxillofacial region, and successful osseointegration of dental implants requires sufficient bone surrounding implant. Moreover, autologous bone is considered the gold standard with regard to quality, quantity, and an uneventful healing . It is hoped that the topographic map of the skull thickness presented in this study will assist the surgeons in choosing the safest area of cranial bone graft harvest, thus increasing the safety of the procedure.
| Conclusion|| |
On the basis of the results obtained after statistical analysis the following conclusions were found: with the pooled sample test, there were no significant differences in cranial vault thickness in both of the sagittal and vertical malrelations. There was a significant relationship in calvarial bone thickness between sex and facial growth pattern. Variations in skeletal thickness may be attributable to vertical skeletal malrelation, especially in male patients with a hypodivergent facial pattern. Among patients with skeletal class II malocclusion, female patients had thicker frontal bone compared with male patients, and male patients had thicker occipital bone compared with female patients. The frontal and occipital bones are important key bones for understanding the calvarial phenotypic and sexual dimorphism in different skeletal patterns.
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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], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11]