Abstract
Aim To assess changes in the craniocervical structure and in hyoid bone position in skeletal Class II subjects with and without temporomandibular disorders (TMD). Materials and Methods The cephalometric analysis of 59 subjects with skeletal Class II was evaluated and compared. The measurements considered were ANB as a parameter of Class II and C0-C1 distance, C1-C2 distance, craniocervical angle, and hyoid bone position for the cervical spine analysis. Patients were divided into patients with TMD (group A) and patients without TMD (group B). TMD were evaluated with Diagnostic Criteria for TMD (DC/TMD). Descriptive statistics and Pearson's and Spearman's correlation analysis, with p value <0,005, were performed. Results C0-C1 and C1-C2 distance values and hyoid bone position resulted within the normal range in the majority of patients examined. Craniocervical angle was altered in 33 patients. The reduction of this angle with the increase of the ANB value resulted to be statistically significant in group A, according to Pearson's correlation index. No other data were statistically significant. Conclusions The significant relationship between skeletal Class II and cervical spine cannot be highlighted. The alteration of craniocervical angle seems to be mildly present, with backward counterclockwise rotation of the head upon the neck in the sample (groups A and B). The presence of TMD as a key factor of changes in neck posture could explain the different result between the two groups about the relationship between ANB and craniocervical angle. This result should be further analyzed in order to better understand if cervical spine changes could be related to mandibular postural ones in the craniocervical space or to temporomandibular joint retropositioning, more recognizable in Class II with TMD, which could determine functional changes in other structures of this unit; neck posture could be the result of a compensatory/antalgic mechanism in response to TMD.
Highlights
The stomatognathic system is composed of several structures which, acting in synergy, provide the complex functions of swallowing, sucking, chewing, speech, and breathing. Functionality of these components has a cybernetic and integrated control, and it depends on the specific individual adaptability and response to perturbing factors. This system correlates with the cervical spine and hyoid bone, forming a functional craniocervical mandibular unit
Correlation indexes were always very close to zero, and these proved that distributions were independent of the previous associations. This is not in line with the results obtained in some publications of the scientific literature, which support a correlation between skeletal class II and morphologic and postural cervical spine alterations [6, 9, 19]
Festa [6] found the relationship between cervical lordosis and cranial base and mandibular length
Summary
The stomatognathic system is composed of several structures which, acting in synergy, provide the complex functions of swallowing, sucking, chewing, speech, and breathing. Functionality of these components has a cybernetic and integrated control, and it depends on the specific individual adaptability and response to perturbing factors. This system correlates with the cervical spine and hyoid bone, forming a functional craniocervical mandibular unit. Many studies found support for anatomical [1, 2] and functional [3, 4] relationship between the cranial region, the temporomandibular joint, the cervical spine, and the hyoid bone. There is presence of suggestive results in these studies, the mechanism of this relationship is still unclear
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