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Table of Contents   
ORIGINAL RESEARCH  
Year : 2012  |  Volume : 23  |  Issue : 1  |  Page : 49-52
Quantitative assessment of palatal bone thickness in an ethnic Indian population: A computed tomography study


Department of Orthodontics, Ragas Dental College and Hospital, Chennai, India

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Date of Submission23-Mar-2011
Date of Decision09-Jun-2011
Date of Acceptance21-Jan-2012
Date of Web Publication26-Jul-2012
 

   Abstract 

Context: Variations in palatal bone thickness (PBT) at various locations have caused considerable problems when using these sites for anchorage purposes.
Aims: To find the comparative thickness of the palatal bone at different locations and to validate its morphology for anchorage purposes using mini-implants (MI).
Settings and Design: This investigation was undertaken to compare the mean PBT and level of significance of differences between male and female subjects and between two different age-groups.
Materials and Methods: The computed tomography (CT) data for 60 patients (30 males and 30 females) in two different age-groups (group A: 15-24 years; group B: 25-35 years) were imported into CAD-based medical software, (MIMICS® ; Materialise, Belgium) for multiplanar reconstruction. The measurements were made in two planes- transverse and sagittal-and at different positions in each of the planes.
Statistical Analysis: The mean and standard deviations of the PBT at different points were calculated. The Student's t-test and Mann-Whitney U test were used for comparisons between the groups.
Results: Significant variations were observed in the thickness of the palatal bone for both groups tested, with the anterior region at 4 mm behind the incisive papilla showing the maximum thickness.
Conclusions: Despite the palatal bone being thickest in the mid-palatal suture (MPS) region, this is not the ideal site for anchorage purposes due to inadequate calcification and interposition of connective tissue, especially in young growing children. So, the alternate optimum position is the paramedian region, 3 mm lateral to the MPS and 4 mm from the incisive foramen (IF).

Keywords: Anchorage, computed tomography, palatal bone thickness

How to cite this article:
Jayakumar G, Rajkumar, Biju T, George M A, Krishnaswamy N R. Quantitative assessment of palatal bone thickness in an ethnic Indian population: A computed tomography study. Indian J Dent Res 2012;23:49-52

How to cite this URL:
Jayakumar G, Rajkumar, Biju T, George M A, Krishnaswamy N R. Quantitative assessment of palatal bone thickness in an ethnic Indian population: A computed tomography study. Indian J Dent Res [serial online] 2012 [cited 2021 Apr 20];23:49-52. Available from: https://www.ijdr.in/text.asp?2012/23/1/49/99038
Variations in palatal bone thickness (PBT) at various locations have caused considerable problems when using these sites for anchorage purposes. Numerous studies conducted worldwide have shown considerable variations in PBT, even between adjacent sites, which makes clinical applications such as placing mini-implants (MI) less predictable. [1]

The ethnic background of the patient has also been shown to be associated with PBT. Anthropometric studies document differences in body characteristics, including craniofacial features, between different races. [2] Direct measurements on conventional radiographs have shown that there are differences between racial groups in craniofacial anatomy, and these differences have been documented for a variety of structures in the head and neck. [2],[3],[4] It is also important to assess if there are any predictable differences between different age-groups and between male and female subjects within a particular ethnic population.

It has been documented that the mid-palatal suture (MPS) region is the center of maxillary growth and development. [5],[6],[7],[8] For children and adolescents implant placement is preferred in the lateral region of the palate instead of the median suture region as implant placement in the latter may affect maxillary growth and development. The anatomy of the palatine bone differs between individuals and between different sites in the same individual. [9],[10] Thus, it is necessary to measure the bone height of the palatal implant sites prior to placement. Bone quality and the age of the patient are other factors that decide the success rate of the placement. In view of the above mentioned variations, it is important to have an idea of the PBT at various locations in order to determine the optimum site for MI placement. [11] This study was therefore undertaken to evaluate the various anatomic characteristics, using CT scan, and to provide fundamental guidelines for MI placement.

The CT data set was subjected to three-dimensional (3D) reconstruction to produce a 3D virtual object; this allows measurement of any area in the scanned volume with better accuracy and avoids the projection or superimposition errors encountered in conventional two-dimensional (2D) techniques. Further, the development of modern medical imaging computer technology allows manufacturing of a physical model of the scanned data by rapid prototyping. In this study, 2D slice images were first obtained through CT scanning and 3D image data fields were reconstructed using this. [12]

Aims and objectives

  • To evaluate the 3D mean PBT in order to determine which location would provide the best anchorage for MI
  • To compare the differences between the mean PBT in male and female subjects in group A (15-24 years) and group B (25-35 years) separately
  • To compare the mean PBT between group A and group B subjects in males and females separately.



   Materials and Methods Top


Sample selection

CT images of the skulls of 60 subjects were collected from the KGS Advanced MRI and CT Scan Center, Madurai, India. CT images of patients with a history of trauma to the maxilla or any other dental or skeletal anomalies were eliminated. The sample was divided into two groups according to age. Group A consisted of 30 subjects (15 male and 15 female) with ages ranging from 15 years to 24 years, and group B consisted of 30 subjects (15 male and 15 female) with ages ranging from 25 years to 35 years.

Image acquisition

The CT images were recorded using a 3D volume computed tomography scanner (Siemens SOMATOM Sensation® 64-slice) under uniform conditions using high-resolution bone algorithm (slice thickness: 0.60 mm; 120 kV; and 225 and 250 mAs) as shown in [Figure 1]. The CT images were saved in standard DICOM format.
Figure 1: Patient positioned in the 3D volume scanner

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Three-dimensional reconstruction

The CT data were imported into CAD-based medical software, (Mimics® ; Materialise, Belgium) for multiplanar reconstruction. The bone was segmented by thresholding and a 3D object of the maxilla was reconstructed for further evaluation. Automatic segmentation of the maxilla was done and reconstructed. The 2D data was converted into 3D data for accurate measurement of the landmarks, which would have otherwise been cumbersome in the DICOM format. The 3D software reconstruction helps to improve the observation skill and image quality of the object. The CT scan was done in a bone window with the Hounsfield units range between 850 and 1450. [13],[14],[15],[16] Hence, the regular patient data like soft tissue and restorations were not taken into consideration.

The incisive foramen (IF) was identified in the 3D reconstructed object of the maxilla for each patient and a point was selected in the most inferior border of the IF; all the measurements were made from this point. [17],[18],[19] The same point also reflects in the other reconstructed axial, coronal, and sagittal planes in 2D images. [20],[21],[22]

Measurement approach

The measurement points were made in the anterior region of the palate at 4, 8, and 12 mm and, in the posterior region of the palate, at 24 mm and 28 mm from the most inferior border of the IF at the midline in the coronal view. Also, lateral to the midline, the measurements of the PBT were made only on the right side of each patient at 0, 3, and 6 mm as shown in [Figure 2]. Earlier studies by Gracco et al. have reported that there are no differences in the PBT between the right and left sides. [23] A total of 900 measurements (15 for each of the 60 patients) were recorded and each measurement was entered into an MS Excel® worksheet. The minimum and maximum of the measurements were noted and the mean and standard deviation (SD) were calculated.
Figure 2:

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Statistical analysis

The results of the present study was subjected to statistical analysis to calculate the mean and SD of every measurement for each paracoronal view to find out the thickest point of the palatal bone and to interpret the differences between the thicknesses of the palatal bone values in each of the two groups and also between the groups. Student's t-test and the Mann-Whitney U test were used for statistical analysis. Parametric and nonparametric methods were used to calculate the P value. For the palatal thickness value, the mean, SD, and the minimum and maximum values were calculated.


   Results Top


The study group comprised 60 patients in all, with 30 patients each in groups A and B. The mean age in group A was 18.56 ± 2.59 years, and the mean age in group B was 30.23 ± 3.55 years.

The mean value, SD, and the minimum and maximum values of PBT were calculated for groups A and B separately from 4, 8, 12, 24, and 28 mm from the IF at 0, 3, and 6 mm on the right side of the MPS [Table 1].
Table 1: PBT from the mid-palatal suture to various distances from IF in group A and group B

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The PBT did not vary significantly between the genders at 0 mm (P=.601) and at 6 mm (P=.164) in group A. The difference between males (8.03 ± 3.32 mm) and females (5.42 ± 1.96) was significant at 3 mm distance from midline, 4 mm from the IF (P=.014). In contrast, in group B, highly significant difference was observed between the genders at 0 mm (P=.000), 3 mm (P=.000), and 6 mm (P=.001) [Figure 3].
Figure 3: Graph of PBT at various distances from the MPS in group B between genders

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   Discussion Top


The MPS is a high-density bone structure with sufficient bone height up to the crista nasalis, making it a good location for orthodontic MI placement. [24] As for the type of screws to be used in this area, Wehrbein et al.[25] have recommended small-diameter (3.3 mm) to medium-diameter (4-6 mm) MIs and studied the maximum bone height at the MPS area that can be used to place orthodontic MIs without perforating the nasal cavity. These studies also showed that the MPS is a solid anatomical structure that can be reliably used to place orthodontic MIs, with at least 2 mm of additional bone height from the estimate made from lateral cephalograms. However, all these studies were conducted on different ethnic populations and the results need not be applicable to Indian patients. Also, different malocclusion types pose biomechanical challenges that necessitate the placement of MI at various locations in the palate. It is well documented that the palatal bone has varied thickness and this study was therefore done to find out the safe zones for MI placement.

The definitive length of the MI should also be taken into account apart from the thickness of the mucosa, because of the variations in the soft tissue measurements. [26]

During the growth phase, females tend to have more skeletal maturity than males of the same age. In group A, females had greater PBT than males at a site 3 mm lateral to the MPS, and this difference was statistically significant (P=.014). This probably indicates that the rapid bone remodeling along the MPS (0 mm) and alveolar bone region (6 mm) does not exhibit significant difference in PBT between genders in the growing age group. After growth cessation, as indicated in [Figure 3], males exhibit more PBT than females at all levels. This finding is of profound interest to the clinician for determining the length of the MI according to the age and sex of the patient. The thickest portion was 4 mm posterior to the incisive papilla at the midline and that the thickness remained consistent in both the age groups. Despite the level of the suture being the thickest spot in various sections of the palate, it is not suitable for MI placement in all clinical situations because of incomplete ossification and the possibility of interposition of connective tissue between the MI and bone, especially in young growing children. Hence, the paramedian region nearest to the suture is the most suitable area for positioning of the MI, and the best point is 3 mm lateral to the MPS in the anterior part of the palate, 4 mm from the IF.

The lowest PBT in this ethnic Indian population was determined to be 28 mm from the IF and 6 mm lateral to the MPS in both the groups. The thickness tends to decrease posteriorly and laterally. Risky regions, with less than 4 mm of bone thickness, are predominantly seen in the lateral regions, away from the mid-palatal region. The above results can be useful to the clinician when selecting the suitable length of the MI depending on the thickness of the vertical bone at various locations in the palate. In most patients, the stability of the MI might be compromised and the nasal cavity may be perforated in the paramedian area if the selected site is far away from the MPS. In such situations it is recommended that the clinician take a preoperative CT to ascertain the exact bone thickness to reduce the risk of perforation.


   Conclusions Top


The results of this study clearly prove that there are significant variations in the thickness of the palatal bone at different sites, at different ages, and between genders. This means that the clinician needs to take into consideration all these factors when determining the appropriate site for placement of MI. However, as our findings show, in terms of pure anatomic considerations, the site of choice is 4 mm posterior to the IF in the paramedian region.

This study involved only ethnic Indian subjects and the results cannot be generalized to other ethnic groups. Research needs to be carried out to determine universally acceptable norms.

 
   References Top

1.Deguchi T, Nasu M, Murakami K, Yabuuchi T, Kamioka H, Takano-Yamamoto T. Quantitative evaluation of cortical bone thickness with computed tomographic scanning for orthodontic implants. Am J Orthod Dentofacial Orthop 2006;129:721e.7-12.  Back to cited text no. 1
    
2.Farkas LG, Katic MJ, Forrest CR, Alt KW, Bagic I, Baltadjiev G, et al. International anthropometric study of facial morphology in various ethnic groups/races. J Craniofac Surg 2005;16:615-46.  Back to cited text no. 2
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3.Harris JE, Kowalski CJ, LeVasseur FA, Nasjleti CE, Walker GF. Age and race as factors in craniofacial growth and development. J Dent Res 1977;56:266-74.  Back to cited text no. 3
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5.Bernhart T, Vollgruber A, Gahleitner A, Dörtbudak O, Haas R. Alternative to the median region of the palate for placement of an orthodontic implant. Clin Oral Implants Res 2000;11:595-601.  Back to cited text no. 5
    
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11.Hoste S, Vercruyssen M, Quirynen M, Willems G. Risk factors and indications of orthodontic temporary anchorage devices: A literature review. Aust Orthod J 2008;24:140-8.  Back to cited text no. 11
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13.Moon SH, Park SH, Lim WH, Chun YS. Palatal Bone Density in Adult Subjects: Implications for Mini-Implant Placement. Angle Orthod 2010;80:137-44.  Back to cited text no. 13
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14.Henriksen B, Bavitz B, Kelly B, Harn SD. Evaluation of bone thickness in the anterior hard palate relative to midsagittal orthodontic implants. Int J Oral Maxillofac Implants 2003;18:578-81.  Back to cited text no. 14
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15.Kang S, Lee SJ, Ahn SJ, Heo MS, Kim TW. Bone thickness of the palate for orthodontic mini-implant anchorage in adults. Am J Orthod Dentofacial Orthop 2007;131: S74-81.  Back to cited text no. 15
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16.Park YC, Lee JS, Kim DH. Anatomical characteristics of the midpalatal suture area for miniscrew implantation using CT image. Korean J Orthod 2005;35:35-42.  Back to cited text no. 16
    
17.Keith King. Paramedian palate morphology in the adolescent: A cone beam computed tomography study. Am J Orthod Dentofacial Orthop 2005;128:262.  Back to cited text no. 17
    
18.Keith S, King A, Ernest W, Faulkner G. Vertical bone volume in the paramedian palate of adolescents: A computed tomography study. Am J Orthod Dentofac Orthop 2007;132:783-8.  Back to cited text no. 18
    
19.King KS, Lam EW, Faulkner MG, Heo G, Major PW, Predictive factors of vertical bone depth in the paramedian palate of adolescents. Angle Orthod 2006;76:745-51.  Back to cited text no. 19
    
20.King KS, Lam EW, Faulkner MG, Heo G, Major PW. Vertical bone volume in the paramedian palate of adolescents: A computed tomography study. Am J Orthod Dentofacial Orthop 2007;132:783-8.  Back to cited text no. 20
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21.Kyung SH, Lim JK, Park YC. A study on the bone thickness of midpalatal suture area for miniscrew insertion. Korean J Orthod 2004;34:63-70.  Back to cited text no. 21
    
22.Lee JS, Kim DH, Park YC, Kyung SH, Kim TK. The Efficient Use of Midpalatal Miniscrew Implants. Angle Orthod 2004;74:711-4.  Back to cited text no. 22
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23.Gracco A, Lombardo L, Cozzani M, Siciliani G. Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement. Am J Orthod Dentofacial Orthop 2008;134:361-9.  Back to cited text no. 23
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25.Wehrbein H. Bone quality in the midpalate for temporary anchorage devices. Clin Oral Implants Res 2009;20:45-9.  Back to cited text no. 25
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26.Park YC, Lee JS, Kim DH. Anatomical characteristics of the midpalatal suture area for miniscrew implantation using CT image. Korean J Orthod 2005;35:35-42.  Back to cited text no. 26
    

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Correspondence Address:
Ganesan Jayakumar
Department of Orthodontics, Ragas Dental College and Hospital, Chennai
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.99038

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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

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