Dental Hypotheses

ORIGINAL RESEARCH
Year
: 2017  |  Volume : 8  |  Issue : 1  |  Page : 8--16

Craniofacial and airway growth in 9–11 years old normal dental occlusion in Iranian adolescents: A longitudinal cephalometric study


Homa Fathi1, Elham Mohammad-Rabei2, Sattar Kabiri3, Alireza A Baghban4, Sepideh Soheilifar5, Mahtab Nouri6,  
1 Dentist, Tehran, Iran
2 School of Dentistry, Arak University of Medical Sciences, Arak, Tehran, Iran
3 Orthodontist, Tehran, Iran
4 Proteomic Research Center, Department of Basic Sciences, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran
5 Department of Orthodontics, Dental Research Center, Hamadan Medical Sciences, Hamadan, Iran
6 Dentofacial Deformities Research Center, Research Institute of Dental Sciences and Orthodontic School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Correspondence Address:
Sepideh Soheilifar
Shahid Fahmideh Street, Hamadan
Iran

Abstract

Introduction: The present study was aimed to assess the amount and direction of growth in cranial base, jaws, and soft tissue of airway structures by cephalometric analysis in 9–11-years-old Iranian girls and boys. Materials and Methods: Thirty-four Iranian children with normal occlusion and class I molar relationships were recruited, and 2 lateral cephalograms were obtained from 9 and 11-year-old children Cephalometric variables included variables defining cranial base length and angle, maxillomandibular length and height, dental relationship, head and cervical position, soft palate and tongue, vallecula and hyoid position, and pharyngeal dimension. Normal distribution was confirmed by Kolmogorov–Smirnov analysis (P>0.05). Paired t-test was used for assessing growth changes. P value was set at 0.05. Results: Anterior, posterior, and total cranial base length were increased significantly. The increase in total and upper anterior, total and lower posterior facial heights, ramus height, and palatal inclination were statistically significant. Maxillomandibular length increased significantly with insignificant change in their position. Dental relationship and head and cervical posture were stable. Oropharyngeal and nasopharyngeal anteroposterior dimension did not change. However, hypopharynx sagittal length increased significantly. Nasopharyngeal vertical dimension increased and hyoid moved anteriorly and inferiorly. Conclusion: The results of the present study showed that cranial base and jaws grow anteriorly and inferiorly while maintaining dental occlusion and head posture. Most of the airway structures grow simultaneously with craniofacial components.



How to cite this article:
Fathi H, Mohammad-Rabei E, Kabiri S, Baghban AA, Soheilifar S, Nouri M. Craniofacial and airway growth in 9–11 years old normal dental occlusion in Iranian adolescents: A longitudinal cephalometric study.Dent Hypotheses 2017;8:8-16


How to cite this URL:
Fathi H, Mohammad-Rabei E, Kabiri S, Baghban AA, Soheilifar S, Nouri M. Craniofacial and airway growth in 9–11 years old normal dental occlusion in Iranian adolescents: A longitudinal cephalometric study. Dent Hypotheses [serial online] 2017 [cited 2017 Mar 23 ];8:8-16
Available from: http://www.dentalhypotheses.com/text.asp?2017/8/1/8/202025


Full Text

 Introduction



Comprehensive understanding of the normal growth of craniofacial structures facilitates realization of significant variations in the growth and development, which is an important part of diagnosis and treatment planning. This helps to predict direction and magnitude of facial growth, which in turn facilitates treatment planning.[1] In addition, post treatment growth in craniofacial and jaw structures would change orthodontic treatment results. Facial growth usually varies with uneven direction and amount. It is claimed that there is a relationship between facial growth and occlusion. This relationship is not necessarily constant and shows considerable interindividual and intraindividual diversity.[2]

Many studies have shown a relationship between craniofacial anomalies and “respiration obstruction syndrome.”[3],[4],[5],[6],[7],[8] This term has been used to describe the various conditions associated with chronic obstruction of upper airway in growing children.[8]

Soft tissue morphology of the upper airway that can be related to respiration obstruction includes large adenoids, tonsils and soft palates, and narrowed pharyngeal airway.[9],[10],[11] Other facial features that are associated with airway obstruction are excessive anterior facial height, incompetent lip posture, protruding maxillary dentition, increased mandibular angle, and posterior dental crossbite.[7],[12],[13] Moreover, if left untreated, it may adversely affect the quality of life such as learning disabilities in school and inadequate sleep.[14],[15]

There are some expensive or unavailable techniques for airway assessment such as computed tomography,[16] fluoroscopy,[17] acoustic reflection,[18] fibrotic pharyngoscopy,[19] and magnetic resonance imaging.[20]

Lateral cephalometric image is a less expensive and available method, which is a useful screening tool for assessing upper airway structures.[21] Although providing two-dimensional view of a three-dimensional (3D) complex, many studies have confirmed the liability of lateral cephalometric measurements for upper airway space, and it has been shown that the measurements were highly correlated with 3D techniques such as computed tomography (CT) and magnetic resonance imaging (MRI).[22],[23],[24],[25]

Some studies have provided reference values for upper airway for adult and children in some races.[9],[26],[27] However, no cephalometric norms for upper airway of Iranian children have been established, which makes the present study a novel one. In the present study, normal occlusion children who do not have respiratory problems were selected precisely. Various soft and hard tissue variables were assessed by a computer software. The objective of this retrospective study was to obtain upper airway norms for normal Iranian children and assessing growth changes in craniofacial and airway structures in them.

 Materials and Methods



Participants

This retrospective cross-sectional study was conducted among 34 participants. The inclusion criteria consisted of children with normal occlusion and class I molar relationship, normal overjet and overbite, without a history of previous orthodontic treatment or mouth breathing. Research and ethics committee of Shahid Beheshti University of Medical Sciences approved this study. Two cephalograms were obtained in a period of 2 years for 9 and 11-year-old children during 1996–1998 in Qazvin city. Biologic age was assessed by cervical vertebral maturation (CVM) method and was evaluated to be CV2 in all included patients. One X-ray machine (PLANMECA PM 2002 CC PROLINE, Helsinki, Finland) was used to obtain all lateral cephalograms.

Lateral cephalometric radiographs were obtained using a standardized technique, with the jaw in centric relation and the teeth in occlusion, the lips relaxed, and the head in the natural head position.

The landmarks and reference lines used in the analysis are shown in the [Table 1],[Table 2],[Table 3],[Table 4]. The variables for upper airway measurements included 43 linear, 34 angular and 1 area measurements. Cephalometric analysis was carried out using Orthosurger X software. The accuracy of this software has been confirmed in previous studies.[28],[29]{Table 1}{Table 2}{Table 3}{Table 4}

All lateral cephalometric radiographs were scanned by a radiographic scanner (Microtech Scan Maker 48 bit color, i800). The digitization and measurements were performed separately by two investigators. Intraclass correlation coefficient (ICC) was assessed to be 0.77. The magnification factor was taken into account for each cephalometric radiograph.

Statistical analysis

Mean and standard deviation (SD) was calculated for each measurement. Data distribution was analyzed with the Kolmogorov–Smirnov tests. All the cephalometric variables were normally distributed (P=0.05). For comparison of statistical changes, paired t-test was used. The data were analyzed using SPSS 20 (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.) with a 5% level of significance (P<0.05).

 Result



A total of 34 patients were recruited, from which 2 were lost to follow up. The results of paired t-test on cephalometric variables are shown in [Table 5] and [Table 6].{Table 5}{Table 6}

 Discussion



In the present study, craniofacial and airway growth of 9–11-year-old patients were assessed via cephalometric analysis. It has been proposed that early orthodontic treatment can improve skeletal, muscular, and dentoalveolar abnormalities.[30] Orthodontists usually monitor patients before the onset of adolescence. Therefore, it would be important to determine normal growth of craniofacial structures during this critical period. Therefore, this age range was chosen.

Cranial base length shows significant changes as anterior, posterior, and total cranial base length were increased from 9-year-old to 11-year-old. This result is in agreement with previous studies. A recent systematic review has shown that anterior cranial base is not a stable structure and its length increases up to adulthood.[31] Remodeling of sella turcica in the backward and downward direction and bone apposition in frontal bone and increase in the size of frontal sinus play a role in this phenomenon.[32],[33] Spheno-occipital synchondrosis grows up to late ages, and posterior cranial base length increases in a backward and downward direction.[34],[35] However, this increase is not reflected in the sella-articular length. Despite the fact that sella point position is somewhat stable in the horizontal plan in this age,[32] sella-basion length increases because of the dorsal displacement of the basion point, where as articular point which is dependent on mandibular position and morphology shows more variation than basion point.[36] Lewis et al. found that cranial base length undergoes growth spurt in both genders.[37],[38] It has been shown that their growth is almost complete approximately in 11–13 years old in females and 15 years old in males.[39] In contrast, some studies have shown that cranial base would not grow after 7 years old.[40] Differences in study design (longitudinal versus cross sectional), landmarks, and sample population may justify these differences. Anterior and posterior cranial base increased in similar increments. Cranial base angle (Ba-S-N and Ar-S-N) was not changed during the study period. Wilhelm et al. reported that cranial base angle decreases significantly from 1 month to 2 years old, however, remained unchanged afterwards.[41]

Sella-ptm length showed insignificant increase during the 2-year follow-up. This is in agreement with the results of previous studies where ptm showed insignificant drift during the treatment.[32]

Vertical analysis showed that total anterior facial height (Na-Gn) and upper anterior facial height (N-ANS) underwent significant increase where as lower anterior facial height increase was insignificant. Moss et al. demonstrated that from 6 to 14 years, the upper anterior facial height increments were larger than lower anterior facial height.[42] In addition, in Snodell et al. study, from 6 to 8 years old, lower anterior facial height was more mature than upper anterior facial height, gaining 75–84% of its length versus 71–82% up to 6 years old.[43] In addition, ramus height (Ar-Go) and posterior facial height (S-Go) increased significantly. Lux et al. stated that ramus height increase is more than mandibular length and mandibular width between 7 and 15 years old.[44] Yavus et al. found that from 10 to 14 years old ramus height increases significantly.[45] Posterior facial height increased significantly in Yoon et al. study.[1] In the present study, anterior facial height increased more than posterior facial height whereas ramus height growth was more than lower anterior facial height.

Palatal plane angle (NSL-NL) increased significantly. This can be attributed to significant increase in upper anterior facial height. This finding is in contrast to the results of previous studies.[46],[47],[48] However, in the study by Nanda et al., the palatal plane inclination increased from 6 to 11 years and then decreased from 17 to 23 years old with overall insignificant changes.[48] It appears that palatal plane inclination shows fluctuation during growth, increasing in a period while decreasing in another, causing diversity in results of different studies. Mandibular plane angle decreased insignificantly. This finding reflects the significant increase in ramus height and insignificant increase in anterior facial height. Previous studies have shown that mandibular plane angle decreases significantly.[2],[49] In the study by Sinclair et al., the decrease in the angle was small in both sexes from 9 to 13 years old and was only significant in males.[2] The difference can be attributed to differences in age ranges (9–11 versus 9–13) and the mixed nature of our participants.

Maxillary length (ANS-ptm and ss-ptm), mandibular total length (con-prognathion), mandibular body length (pog-go) increased significantly. This is in agreement with the results of previous studies.[1],[44] As expected, total mandibular length increased more than body length and maxillary length, reflecting the 3-dimensional mandibular growth.

Maxillomandibular position relative to cranial base did not change from 9 to 11 years. This can be attributed to forward drift of the nasion point, which is accompanied by forward growth of jaws.[50] In addition anterior portion of the mandible and maxilla are resorptive and anterior nasal spine and A point drift inferiorly and posteriorly, which causes insignificant changes in landmarks associated with mandibular and maxillary position.[47],[51],[52] Similarly, Bhatia et al. had stated that S-N-Pog remains in almost the same level from 4 to 17 years old.[53] Some studies have shown that maxillomandibular position (indicated by SNA and SNB) to cranial base increases with time.[2],[49] In the study by Chung et al., the participants were followed from 9 to 18 years old. However, in the present study, the follow-up period was assigned to be from 9 to 11 years old. The difference in findings may be attributed to the longer follow-up period.[49] In addition, in the study by Sinclair et al., SNA and SNB angles showed small but statistically significant increase from 9 to 13 years old, whereas these variables changed insignificantly in females. ANB angle was not changed significantly. In our study, both males and females were included and it was not possible to analyze the results separately. This fact may create the difference between findings.[2]

Incisor angulation and anteroposterior position did not change significantly, and consequently, overjet and overbite remained unchanged. Sinclair et al. had shown that from 9–13 years, incisor position remained reasonably stable, except the proclination of lower incisors relative to mandibular plane in males. Others had stated that changes in tooth position is correlated to the amount and direction of craniofacial growth. However, incisor angular positioned remained unchanged, perhaps due to functional stabilization, reflecting the stable position of jaws in present study.[47]

The craniocervical inclination (reflected in CVT-FH, CVT-NL, CVT-NSL, OPT-FH, OPT-NL, OPT-NSL) and cervical inclination to horizontal plan (reflected in CVT-Ho, OPT-Ho) did not change significantly. The results of other studies are the same as ours.[54]

Craniovertical angulation (indicated by NSL-VER, FH-VER, NL, VER) was stable from 9 to 11 years old and this result has been shown in other studies as well.[54] Palatal plane to soft palate angle decreased insignificantly, and this result is similar to those of Akcam et al. in normal population.[55] Thickness of pharyngeal space at the palatal level (pm-UPW) and uvula level (u-MPW) increased insignificantly during the observational period. However, Akcam et al. had stated that the former increases significantly, whereas the later undergoes insignificant changes. Taylor et al. had demonstrated that measurements that include posterior pharyngeal wall show little change from 9–12 years. This is similar to our results and can be attributed to the involution of adenoids in this period.[56] The hypopharynx underwent a significant increase. This can be attributed to the fact that this area lacks adenoids which show involution.

Hyoid bone moved inferiorly and slightly anteriorly. These movements can be attributed to forward displacement of the mandible and vertical growth of cervical vertebrae, respectively.[56] The results of a study has shown that hyoid position is dependent on age and facial type and is independent of obesity.[57] In addition, vallecula moved inferiorly. Kollias et al. found a similar phenomenon in adults aged 22 to 42 years old.[58] This can be attributed to caudally extended tongue mass which in turn can increase tongue length from vallecula to tongue tip, as observed in the present study. Tongue height was increased significantly,which was similar to results of Chavanavesh et al.[59] Vertical growth along with elongation and consequent changes in orientation of vallecula-tongue tip length can explain this change.

The distance between posterior portion of maxilla to the anterior arch of Atlas (lower bony nasopharynx) and Basion (upper bony nasopharynx) showed insignificant decrease which can be attributed to continued elongation of maxillary and palatal length along with forward growth of anterior arch of atlas which compensates spheno-occipital synchondrosis growth. This is in agreement with significant increase in the palatal length observed in present study. Taylor et al. found similar results from 12 to 18 years old.[56] King et al. had proposed that sagittal length of nasopharynx is established in early infancy.[60],[61] Nasopharyngeal height increased significantly, whereas nasopharyngeal depth showed insignificant change.

Finally, it should be mentioned that assessing growth changes in lateral cephalometry poses some shortcoming including 2-dimensional view and difficulty in defining landmarks.[50] In addition, airway evaluation is even more difficult because it is not possible to precisely monitor the respiratory cycle, which may directly affect the airway morphology and size.[62] However, lateral cephalometry is an inexpensive method which provides good assessment of airway elements.[58] Prospective and functional analysis of airway tract is proposed for future studies.

 Conclusion



The present study concludes that among 9–11 years old:

Cranial base length, maxillomandibular length, and anterior and posterior facial height increased.

Airway analysis revealed an increase in nasopharyngeal height, hypopharyngeal depth, tongue length, and height. Hyoid bone drifted anteriorly and inferiorly.

No changes in head posture was observed.

Dental relationship was stable.

Financial support and sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.

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