Transverse maxillary constriction (TMC) is a malocclusion

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1 ORIGINAL ARTICLE Does a transverse maxillary deficit affect the cervical vertebrae? A pilot study Luca Di Vece, a Giacomo Faleri, a Maria Picciotti, a Lorenzini Guido, b and Roberto Giorgetti c Siena, Italy Introduction: The aim of this pilot study was to analyze the morphology of the cervical vertebrae of subjects with transverse maxillary constriction. Methods: The study population included 40 subjects (7-11 years of age) undergoing palatal expansion to correct transverse maxillary constriction, and a control group of 40 subjects (7-11 years of age) without transverse maxillary constriction. Two observers assessed cervical morphology on lateral cephalograms by means of templates showing cervical maturation sequences. Round angles and concave vertebral body edges were classified as vertebral anomalies that could not be associated with physiologic vertebral growth. Agreement between the data collected by the observers was assessed with the Cohen kappa test, and the data of the 2 groups were compared with the Fisher exact test (P \0.05). Results: The 2 observers agreed in their assessments (k.0.5). The greater percentage of vertebral defects in the study group was significant (P\0.05) according to both observers. Rounding of the anterosuperior angle of the vertebral body was the most common defect in the study group. Vertebral defects of the study group were mainly at vertebrae C4 and C5. Conclusions: A statistically significant correlation, worthy of further study, was found between transverse maxillary constriction and cervical vertebral defects. (Am J Orthod Dentofacial Orthop 2010;137:515-9) From the School of Dental Medicine, University of Siena, Siena, Italy. a Postgraduate student, Department of Orthodontics. b Assistant professor, School of Dental Medicine. c Professor and chair, Department of Orthodontics. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Luca Di Vece, Polyclinic Santa Maria Le Scotte, University of Siena, Department of Odontostomatological and Ophthalmological Sciences, Viale Bracci 1, Cap 53100, Siena, Italy; , lucadivece@hotmail.it. Submitted, February 2009; revised and accepted, August /$36.00 Copyright Ó 2010 by the American Association of Orthodontists. doi: /j.ajodo Transverse maxillary constriction (TMC) is a malocclusion characterized by narrow and high palatal vault, unilateral or bilateral crossbite, possible dental crowding because of contraction of the dental arches, and reduced volume of the nasal cavities. Reliable and objective techniques to assess the geometry of nasal cavities, such as acoustic rhinometry, rhinomanometry or 3-dimensional imaging, have allowed many authors to investigate the changes in the nasal cavities of patients undergoing correction of TMC. Among the findings of these investigations were reduction of nasal airway resistance, increased nasal minimum cross-sectional area, increased binasal cavity width, and increased total nasal volume after palatal expansion. 1-7 Although correction of TMC is associated with improved mechanical airflow through the nose, the effect of this procedure on the breathing pattern is still debatable. The transition from oral to nasal breathing after palatal expansion is not predictable in frequency and scale because of the variability of individual responses. 8 Tecco et al 9 studied changes in head posture in mouth-breathing girls after rapid maxillary expansion and found that it increased nasopharyngeal airway patency and significantly changed craniocervical angles. McGuinness and McDonald 10 observed a progressive decrease in extended head posture in adolescents with unilateral or bilateral crossbite undergoing rapid maxillary expansion. They attributed this phenomenon to the change from oral to nasal breathing. The literature also reports a correlation between craniocervical alterations, especially changes in normal cervical lordosis, in subjects with impaired nasal respiration. The authors supposed that these changes reflected an adaptation that restored the correct dimensions of the upper airways and ensured adequate ventilation These phenomena might be associated with altered balance of the muscles connecting the skull to the cervical spine and chest; these muscles maintain correct posture of the head and take part in respiratory movements Huggare and Kylamarkula 20 observed reduced thickness of the posterior arch of the atlas in subjects with altered respiratory function from enlarged adenoids. They believed that cranial extension induced by respiratory obstruction altered the soft tissues (functional matrix) around the atlas. Other authors found vertebral morphologic anomalies in subjects with dentofacial features typically associated 515

2 516 Di Vece et al American Journal of Orthodontics and Dentofacial Orthopedics April 2010 with oral respiration: Class II malocclusion, increased overjet, and open bite. 21,22 Cervical vertebrae are a biologic indicator for skeletal maturity. Lamparski 23 cited 6 stages corresponding to 6 maturational phases in the cervical vertebrae that can be identified during the pubertal period. The skeletal orthopedic effects of palatal expansion techniques vary according to the morphologic characteristics of the median suture palate, which are related to individual skeletal maturation. These studies suggested that the optimal age for orthopedic correction of TMC is before the pubertal peak (cervical vertebral maturation stage 1, 2, or 3) ,26 The aim of this preliminary study was to analyze the cervical vertebrae of subjects with TMC awaiting rapid maxillary expansion and compare them with the vertebrae of a control group without TMC. MATERIAL AND METHODS The study group included 40 subjects (20 boys, 20 girls; mean age, 8 years 7 months 6 1 year 2 months) awaiting rapid maxillary expansion to correct TMC. These patients were selected from the medical records of the dentistry department of Siena University, Siena, Italy, according to the following criteria: medical history and examination negative for congenital maxillofacial malformations and related syndromes, severe skeletal asymmetries, or dentofacial deformities requiring orthognathic surgery; clear pretreatment lateral cephalometric radiographs with good contrast including vertebrae from C2 to C6; and age between 7 and 11 years at the time of cephalometric films. The patients selected needed palatal expansion for correction of bilateral or unilateral crossbite, 27,28 or maxillary tooth size-arch length discrepancy when transpalatal width was less than 33 to 34 mm. 29,30 The control group consisted of 40 subjects (22 boys, 18 girls; mean age, 9 years 2 months 6 1 year 3 months) selected from the records of a dental office in Grosseto, Italy, inclusion criteria were the same as in the study group. No control subject had TMC. The profiles of vertebrae C2 through C6 were traced on lateral cephalograms. Two independent observers (L.D.V., G.F.) assessed cervical vertebrae morphology on the images of the 2 groups. They used templates with different magnifications on in acetate sheets showing Lamparski s cervical maturation sequence to establish the cervical vertebral maturation stage of each subject without confusing physiologic development and growth with morphologic anomalies. 23 To facilitate visual analysis of the cervical vertebrae, morphologic anomalies known as vertebral Table I. Vertebral defects found by observer 1 in the 2 groups Group Defects No defects Total Sample Control Total defects were classified as either round or concave (Fig 1, Fig 2). Round was noted when extensions of the upper or lower edges met the anterior or inferior edges of the vertebral body outside the radiographic profile of the vertebra. Round was divided into anterosuperior, posterosuperior, anteroinferior, and posteroinferior according to the angle of that vertebral body. Concave was noted when at least 1 mm separated the midpoint of the edge of the vertebra and the line joining the vertices of the vertebra. Concave was divided into anterior, superior, inferior, and posterior according to its location on the side of the vertebra. Normal maturation processes, such as absence of the C3 anterosuperior angle or concavity of the inferior edge of C2 characterizing Lamparski s cervical vertebral maturation stage 2, were excluded. 23 Statistical analysis The Cohen kappa test was used to measure the diagnostic concordance between the assessments of the 2 observers in the 2 groups. Detection of at least 1 vertebral defect in a patient by both observers was considered a concordant assessment. The Fisher exact test (P \0.05) was used to compare the percentages of vertebral defects in the 2 groups. The test was calculated for both observations. RESULTS Both observers found a higher percentage of vertebral defects in the TMC group (observer 1, 75%; observer 2, 83%) than in the controls (observer 1, 15%; observer 2, 15%). The Cohen kappa indicated good agreement between the 2 observers for the study group and was not calculated for the control group because of the congruence of the observations. The higher percentage of vertebral defects in the TMC patients scored by observer 1 was statistically significant with respect to those scored in the controls (P \0.05) (Table I). The same was true for observer 2 (P \0.05), as suggested by the high concordance of the observations. The types of defects in the study group were concavity of the posterior border and rounding of the anterosuperior, posterosuperior, and anteroinferior angles of the

3 American Journal of Orthodontics and Dentofacial Orthopedics Di Vece et al 517 Volume 137, Number 4 Table II. Vertebral defects in the sample and control groups Sample Control Observer 1 Observer 2 Observer 1 Observer 2 Type of defect Vertebra Number of defects Total Number of defects Total Vertebra Number of defects Total Number of defects Total Anterosuperior angle C C C C C4 C6 3 Anteroinferior angle C C3 2 C4 1 C5 C6 1 Posteroinferior edge C C4 4 7 C5 5 9 C6 4 4 Posterosuperior angle C3 2 2 Total vertebral body. In the control group, only rounding of the anterosuperior angle was found. The most common defect in the study group according to both observers (observer 1, 57%; observer 2, 63%) was rounding of the anterosuperior angle of the vertebral body. The vertebrae of the TMC patients with the most defects were C4 (observer 1, 34%; observer 2, 32%) and C5 (observer 1, 24%; observer 2, 42%). Both observers noted that the most common defect was rounding of the anterosuperior angle (observer 1, 46% in C4 and 29% in C5; observer 2, 35% in C4 and 45% in C5) (Table II). DISCUSSION Deviations from normal in the cervical spine area can be detected in lateral cephalograms: odontoid or atlas malformations, occipitalization of the atlas, basilar impression, spina bifida, ossification defects, and displacement of vertebral bodies. 31,32 Because respiratory disorders are usually multifactorial problems, it is difficult to define clearly the etiology of oral breathing. For nasal breathing to occur, functional and anatomic integrity of the airways is necessary. A simple mechanical obstruction blocking the air passage is enough for a person to change his breathing pattern to keep his vital functions; thus, oral breathing is considered supplemental or pathologic breathing. 33 Although there is significant evidence that poor nasal breathing will lead to mouth-nasal breathing, its impact on dental facial growth is still unclear. 34 The clinical effects of transversal maxillary deficiency on the breathing pattern are not predictable. The adaptation processes associated with oral breathing are a possible link between 2 apparently distant areas such as the maxilla and the cervical vertebrae. The increase in airway resistance in the nose could start compensation mechanisms (oral respiration) in predisposed subjects with a low adaptation threshold. Oral respiration can have repercussions on craniofacial and craniocervical morphology and functions. 35,36 According to the soft-tissue stretching hypothesis of Solow and Kreiborg, 37 respiratory obstruction starts neuromuscular feedback that can alter craniocervical posture. This leads to stretching of soft tissues that can increase the pressure they exert on skeletal tissues, modifying the direction of bone growth. The functional matrix theory of Moss 38 states that skeletal units, including cervical vertebrae, do not develop autonomously but respond to the protection and support requirements of the functional matrix, ie the requirements of the soft tissues that maintain correct functional spaces. Changes in craniocervical relationships induced by oral respiration in subjects with narrow palates can lead to changes in the muscle-tendon-ligament complex, which, according to Moss s theory, not only maintains cervical postural balance, but also guides skeletal development according to functional requirements. Structures close to vertebral bodies, such as the anterior longitudinal ligament and the long muscles of the neck, could modify the functional space in which the cervical vertebrae develop if forced to adapt to a new craniocervical posture. Many authors believe that external agents such as pressure, 39 body posture, 40 and facial components 41 can modify the height of vertebral bodies.

4 518 Di Vece et al American Journal of Orthodontics and Dentofacial Orthopedics April 2010 Fig 1. Vertebral defect. Fig 2. Highlighted vertebral defects. The cervical vertebrae of growing children are susceptible to modeling. Secondary ossification centers do not form until puberty, when they trigger mineralization of the epiphyses of the upper and lower edges of the vertebral bodies. 42 The cervical vertebrae of our study group were still maturing. Incomplete ossification can magnify the influence of alterations of the vertebral functional matrix during vertebral morphologic development. The vertebral defects of the patients in this study were mostly found on the upper and lower edges of the vertebral bodies. The epiphyses of the cervical vertebrae are disc-shaped in most mammals but not in humans, in whom they are ring shaped on the upper and lower perimeters of the vertebral bodies. 42 This feature might make the epiphyseal zone thinner and more readily deformed by the action of surrounding soft tissues. The point of maximum concavity of cervical lordosis is at C4 and C5, coinciding with the fulcrum of the movements of flexion and extension of the cervical spine. 43 These factors could play a role in the genesis of vertebral defects in specific parts of the cervical spine. The vertebral defects need to be evaluated in a larger population to explain the findings of the anomalies also in the control group. A longitudinal study into whether vertebral morphologic defects persist into adulthood is also necessary. Such an investigation could be conducted by observing our study group at the end of growth. The cervical vertebrae of members of the study group should also be reassessed after correction of TMC. This was a pilot study that needs further investigations to determine the possible influence on the clinical use of the cervical vertebral method. CONCLUSIONS These results highlight the possibility of a correlation between TMC and morphologic anomalies of the cervical vertebrae. REFERENCES 1. Hershey HG, Stewart BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion. Am J Orthod 1976;69: Hartgerink DV, Vig PS. The effect of rapid maxillary expansion on nasal airway resistance. Am J Orthod Dentofacial Orthop 1987;92:381-9.

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