Anthropometric Analysis of the Mandibular Anterior Buccal and Lingual Bone in Iranian Adult Population by CBCT

AUTHORS

Soosan Sadeghian 1 , Farzad Yahyapour 1 , * , Roshanak Ghafari 1 , Sina Jafari 1

1 Department of Orthodontics, School of Dentistry, Islamic Azad University, Isfahan (Khorasgan) Branch, Isfahan, Iran

How to Cite: Sadeghian S, Yahyapour F, Ghafari R, Jafari S. Anthropometric Analysis of the Mandibular Anterior Buccal and Lingual Bone in Iranian Adult Population by CBCT, Iran J Ortho. 2017 ; 12(2):e7591. doi: 10.5812/ijo.7591.

ARTICLE INFORMATION

Iranian Journal of Orthodontics: 12 (2); e7591
Published Online: November 13, 2016
Article Type: Original Article
Received: June 19, 2016
Accepted: September 20, 2016
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Abstract

Background: Because of the special anatomy and esthetic considerations, orthodontic and implant treatments are somehow fine and difficult in mandibular anterior zone. The aim of this study was to evaluate anthropometric analysis of the buccal and lingual bone thickness of mandibular anterior zone using CBCT.

Methods: In this descriptive- analytic study CBCT images of 20 (18 - 40 years old) patients (10 men, 10 women) were obtained. Four reference lines were designed for every anterior tooth of mandible. 3D program were used for measuring.

Results: Mean thickness of buccal alveolar plate was 1.44 ± 0.34 mm for central incisor, 1.35 ± 0.25 mm for lateral incisor, 1.46 ± 0.25 mm for canine. Mean thickness of lingual alveolar plate was 1.61 ± 0.33 mm for central incisor, 1.73 ± 0.43 mm for lateral incisor, 1.99 ± 0.48 mm for canine. Buccal bony curvature angle below root apex was 151.1 ± 7.7° at central incisor, 145.14 ± 6.71° at lateral incisor, 155.08±8.16° at canine. Distance between root apex and the deepest point of buccal bony curvature was 2.2 ± 0.54 mm for central incisor, 2.31 ± 0.62 mm for lateral incisor, 2.55 ± 0.59 for canine. However; the comparison of all findings between men and women did not show significant difference (P > 0.05).

Conclusions: The thickness of lingual bony plate of mandibular anterior zone in Iranian adult is more than the thickness of labial plate; also the labial bony plate thickness will increase from coronal to apical zone of the teeth. The labial bony curvature below root apex of mandibular central incisor was higher than that of lateral incisor and canine and it seems that the labial bony plate below root apex of central incisor is most curved.

Keywords

Buccal Alveolar Bone Thickness Cone-Beam CT Mandibular Anterior Teeth

Copyright © 2016, Iranian Journal of Orthodontics. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

1. Background

Orthodontic treatment in mandibular anterior region due to specific anatomy and the esthetic of this region is considered difficult and delicate. The root is always covered with a thin and sensitive labial bony plate that may be damaged during different treatments such as orthodontics, implantation, extraction or in trauma and pathologic lesions (1).

As a result of this damage, deformity of the area and thinning over of the bony plates occurs that increases the need for bone graft in the area before orthodontic treatment, especially installing mini screw (2, 3). Oral anatomy, ridge width, and the width of the alveolar crest should be carefully checked before treatment. Because the studies showed differences in the pattern of bone in different people, selection of place for installing mini-implants and preparing the place is very important (2).

Considering that in non-extraction orthodontic treatments and labial movement of the teeth in anterior region of mandible, awareness about the thickness of bone in these areas is critical to prevent problems such as dehiscence (4). Surgical intervention for increasing ridge width is inevitable prior to orthodontic treatment in areas with bony defect, especially when mini screw installation is needed (3, 5-7).

Several studies have examined maxillary cortical bone thickness of the skull by medical and spiral CT (1), but few researches has been done in mandible. Cone beam computed tomography compared with previous techniques is very valuable in assessing the benefits of the bony structures around the teeth. The advantages of this technique include: non-invasive, high-resolution, low radiation dose, economical and (8).

Vera et al. (5) studied 43 patients with implants, by use of CBCT measured buccal bone thickness of maxillary first premolar. Lee and colleagues studied Korean people aged 20 to 39 years and by use of CBCT examined maxillary buccal bone thickness (1).

Huynh-Ba et al. (6) reviewed extraction site of 93 anterior maxillary teeth and evaluated the buccal and palatal bone thickness. In this study, researchers found that the majority of buccal and palatal bone thickness around the extraction site is thin (about one mm or less). While the minimum required thickness of the buccal bone in the anterior maxillary for implant treatment, inserting screw for orthodontics is about 2 mm and this amount of bone only were seen in a limited number of maxillary anterior extraction sites, indicating the need for bone grafts in these areas for orthodontic treatment and implant insertion.

Baumgartel and Hans (2) studied 30 human skulls by CBCT, and evaluated buccal bone thickness in all areas between the teeth (2). They concluded that the mandibular buccal cortical bone is thicker than maxillary buccal cortical bone; also found that in both jaws as going away from the head of the alveolar crest, the buccal cortical thickness increases. Park & Chu (3) evaluated buccal thickness between roots of 60 adult patients via three-dimensional images.

2. Objectives

The aim of the current study was to evaluate the thickness of the buccal and lingual cortical bone in the lower jaw as well as the curvature of the buccal cortex, in Iranian adult population by use of CBCT that can guide the choice of treatment and if need to use screw or the implant fixtures, to select the appropriate type, size and dimensions.

3. Methods

This study was performed by CBCT of 20 patients (10 men and 10 women) from age 18 to 40 that referred to the Oral and Maxillofacial Radiology Center of Isfahan Azad University, school of dentistry. Patients with mandibular anterior teeth (canine to canine) with a healthy periodontium. So, a total of 120 teeth composed of 40 for each central, lateral and canines.

The CBCT images by Scanera 3D unit Soredex, Tuusulu, Finland and Flat Panel CMOS sensor with high resolution and 0.25 mm voxel size software were taken.

The images evaluated through on Demand 3D (Version 1) software, measurements has been done by the orthodontists and maxillofacial radiologist to the hundredth of millimeter of accuracy were recorded which included:

1) The average thickness of the buccal and lingual alveolar plate in 4 reference lines which were perpendicular to the long axis of each tooth, on the cross-sectional image.

“A line” 3mm below the CEJ, “B line” 4.5 mm below the CEJ, “C line” at the midpoint between the CEJ and root apex and the “D line” were drawn at the apex of the root. Then calculation of the average thickness of the buccal and lingual alveolar bone plate was performed on the reference lines (Figure 1).

Reference Lines, Buccal Plate Thickness and Lingual Plate Thickness
Figure 1. Reference Lines, Buccal Plate Thickness and Lingual Plate Thickness

2) Angle of curvature of the buccal bone below the apex of the root. Three reference points R, Q, and P, were used here. “Point P” in the upper part of the upper-anterior buccal plate, “Point R” in buccal plate at the confluence of the D reference line, “Point Q” on the deepest point of the buccal bone between R, P were determined and the angle formed between the points was calculated (Figure 2A).

3) The distance between the apexes of the root to the deepest point of the curvature of the buccal bone (Q) The vertical distance between the reference lines D to point Q was calculated (Figure 2B). All seven measurements were done on 120 anterior teeth.

The data entered in the software SPSS by ANOVA one-sided and t-tests done for statistical analysis. As archival images were used, there was no moral problem.

(A) Root Apex Angle of Curvature of the Buccal Bone (PQR∠) (left), (B) The Distance Between the Apex of the Root to the Deepest Point of the Curvature of the Buccal Bone
Figure 2. (A) Root Apex Angle of Curvature of the Buccal Bone (PQR∠) (left), (B) The Distance Between the Apex of the Root to the Deepest Point of the Curvature of the Buccal Bone

4. Results

In this study it was found that in the anterior region of mandible the overall average thickness of lingual alveolar plate is greater than the buccal alveolar plate (Table 1).

Table 1. Overall Average Index in Mandibular Anterior Region (mm)a
TotalFemaleMaleIndex Study
1.58 ± 1.281.56 ± 0.431.60 ± 0.42distance between CEJ and buccal alveolar crest
1.41 ± 0/341.37 ± 0.271.46 ± 0.41thickness of the buccal alveolar plate
1.77 ± 0.461.77 ± 0.451.78 ± 0.48thickness of the lingual alveolar plate
6.03 ± 0.656.03 ± 0.626.04 ± 0.69The buccolingual root width
3.45 ± 0/83.4 ± 0.783.51 0.82The mesiodistal root width
155.16 ± 8.67154.61 ± 8.56125.26 ± 8.78The mean angle of curvature of the buccal bone beneath apex of mandibular anterior teeth
2.35 ± 0/642.4 ± 0.592.31 ± 0.69The average distance between the apex of the tooth root to the deepest point of the curvature of buccal

aValues are expressed as Mean ± SD.

Table 1 shows that in mandibular central incisor region, curvature below the apex of the labial bone is smaller than other anterior teeth; as a result, maximum curvature of the buccal bone in anterior region is located in the central area.

Table 2 shows that overall thickness of the buccal plate of central incisors, lateral incisors and canines in the reference lines A and B are very thin. The difference between Incisors and canines at point D is statistically significant (ANOVA one-way test).

Table 2. Comparison of the Buccal Plate Thickness of Mandibular Anterior Teeth in the Reference Line (mm)a
CanineMean ± SDNo. of SamplesReference Line
LateralCentral
0.54 ± 0.250.59 ± 0.220.64 ± 0.2640A
0.65 ± 0.20.63 ± 0.220.6 ± 0.2540B
1.23 ± 0.520.88 ± 0.271.09 ± 0.3940C
3.6 ± 0.673.35 ± 0.92.92 ± 0.8540D

aP < 0.05 (The difference is significant).

It was observed in Table 3 that the average thickness difference of the lingual plate of mandibular anterior teeth at points A, B and C, between the central incisors and canines according to ANOVA is statistically significant. The buccal alveolar plate thickness (Table 2) and lingual plate (Table 3) from reference line A to line D has increased.

Table 3. Comparison of the Lingual Plate Thickness of Mandibular Anterior Teeth in the Reference Line (mm)
CanineMean ± SDNo. SamplesReference Line
LateralCentral
1.02 ± 0.620.78 ± 0.31a0.55 ± 0.240A
1.18 ± 0.741.05 ± 0.46a0.75 ± 0.2940B
1.91 ± 0.981.6 ± 0.69a1.19 ± 0.3340C
3.97 ± 1.033.78 ± 0.933.83 ± 1.2840D

aP < 0.05 (The difference is significant).

Table 4. Comparison of the Angle of Curvature of the Buccal Bone Below the Apex of the Anterior Mandibular Teeth in Degreesa
P ValueMean ± SD (Degree)GenderTooth
0.53156.26 ± 8.6MaleCanine
153.9 ± 7.96Female
155.08 ± 8.16Total
0.23152.31 ± 6.57MaleLateral
155.96 ± 6.67Female
154.14 ± 6.71Total
0.95148.22 ± 7.84MaleCentral
153.98 ± 6.74Female
151.1 ± 7.7Total

aP < 0.05 (The difference is significant).

As shown in Table 4, the lowest angle of curvature of the buccal bone of the incisors was in central incisor (7.7 ± 1.151 degree) which shows the most curvature of the buccal bone in this tooth.

Table 5. Comparison Between Root Apexes of Mandibular Anterior Teeth to the Deepest Point of the Curvature of the Buccal Bone (mm)a
P ValueMean ± SD (Degree)GenderTooth
0.722.5 ± 0.69MaleCanine
2.6 ± 0.5Female
2.55 ± 0.59Total
0.542.4 ± 0.73MaleLateral
2.23 ± 0.51Female
2.31 ± 0.62Total
0.172.04 ± 0.59MaleCentral
2.37 ± 0.45Female
2.2 ± 0.54Total

aP < 0.05 (The difference is significant).

According to Table 5, the highest finding is in canine (2.55 ± 0.59 mm), which has statistically significant difference with lateral and central incisors (ANOVA test one way).

5. Discussion

Three factors are involved for success in implants and bone anchorage cases: bone quality, implant design and type and placement techniques of implant in bone. In terms of bone quality , the most important factor in determining the initial stabilization is the cortical bone, specially more than 1 mm cortical bone thickness is more valuable (3).

The aim of this study was to determine buccal and lingual bone thickness of mandibular anterior region anthropometrically in Iranian adult population by CBCT and compare them in both males and females to be used in orthodontic treatment, installing mini screw for bone anchorage and implants. Due to the importance of the anterior mandibular orthodontic treatment and lack of calculated indices in this area in previous studies, this study decided to examine these indices in the anterior mandible by CBCT.

The indices measured in the anterior mandible in Iranian adult on CBCT images included determining the average distance between the CEJ and buccal bone crest, the average thickness of the buccal and lingual alveolar plate, to determine the angle of buccal bone curvature below the apex of the anterior teeth and the distance between the apex of the tooth root to the deepest point of the curvature of the buccal bone in the lower jaw.

Mini- screw and implant placement in a correct three-dimensional position, regardless of the implant system, is the key to a beauty, appropriate and safe treatment. Facial bone width and length can guarantee long-term success of dental implants, gingival margins around implants and adjacent teeth (1).In general, the buccal bone crest below the CEJ in the anterior maxillary was 3 mm and in anterior mandibular about 2 mm (1).

According to the present study, the average thickness of the buccal plate in areas of mandibular central, lateral and canine in Iranian adult population in points A, B (3 and 4.5 mm below the CEJ) was less than 1 mm and at points C and D, more than 1 mm, but generally buccal plate had less thickness than the lingual plate in these areas. So in the lower jaw, orthodontic movements towards labial should be done with more caution. Also placement of the implant must be such that the implant axis oriented exactly at the top of the ridge or even slightly toward lingual to prevent buccal plate perforation or dehiscence.

Lok Lee and colleagues (1) in determining the average thickness of the buccal plate in the anterior maxilla of Korean adults found that the average thickness of the buccal plate in all parts is less than 1 mm and the average thickness of the palatal plate is greater than the thickness of the buccal plate.

Vera and colleagues found that a small number of anterior maxillary teeth show buccal bone thickness more than 1 mm. However, in this study, the overall thickness of the buccal plate in the lower jaw was greater than 1 mm (5).

With this result, Baumgaertel and his colleagues (2) in their study on buccal plate thickness of anterior mandibular teeth reached to this conclusion that mandibular buccal plate thickness is thicker than the maxillary buccal bone cortex.

Park and colleagues (3) also showed that the mandibular buccal cortical thickness is over 1 mm and thicker than the maxillary buccal cortex, because the thin maxillary buccal cortex compensated by an increase in cancellous bone trabeculae (9).

Results of the present study about buccal and lingual plate thickness are in agree with the results of Baumgaertel and Hans (2) and Park and Cho (3) which showed that the thickness of the anterior mandibular buccal plates is less than the anterior mandibular lingual plate and thickness of mandibular buccal cortex is more than 1 mm. The primary stability of the implant is provided with cortical bone thickness of 1 mm and the success rate is increased by increasing bone thickness (3).

Primary implant stability with a thickness of 4 to 5 mm of bone around the apex of fresh extracted tooth socket will reach the ideal and causing bone drilling with minimal damage. Although thicker cortical bone is resistant to resorption, but in some patients who have a thinner cortex, bone graft is done to prevent potential resorption after the implantation (1).

The final diameter of implant is determined according to the bone thickness and length of the missing tooth. The minimum possible distance between the implant and the adjacent tooth is 2 mm based on marginal bone will come to its lowest resorption level (1). Therefore, the use of implants with a big neck and massive scale in anterior mandibular region is not recommended and generally suggest 3.3 to 3.8 mm diameter for mandibular central 1 (1).

Placing implants, orthodontic correction and inserting mini screw in anterior mandibular region should be undertaken with caution, and more attention to the buccal and lingual cortical bone thickness and screw type and size of implant used should be paid. In this study, the angle of curvature of the buccal bone (PQR) below the apex of the teeth were measured 155.08 ± 8.16, 154.14 ± 6.71 and 151.1 ± 7.7 for canine, lateral and central incisor respectively (Table 4). The lowest angle of curvature of the buccal bone was in the mandibular central incisors, which specifies that the buccal bone in this area has the greatest curvature.

Lok Lee and colleagues (1) in the maxillary anterior teeth reached the same conclusion. These findings suggest that the central axis of the implant drill in the drilling area should be quite parallel to the buccal alveolar plate to prevent perforation, also tapered implants are recommended in this area (1).

In case of immediate implantation after tooth extraction, implants should have the greatest possible height in order to achieve the ideal and sufficient primary stability (1).

In this study, the mean distance between the apex of the mandibular tooth root to the deepest point of the buccal bone curvature in Iranian adults was calculated and showed 2.2 ± 0.54 mm in central, 2.31 ± 0.62 mm in lateral, 2.55 ± 0.59 mm in canine region (Table 5). These results can be used as a guide to choose the appropriate height of implant.

Considering the fact that in this study for the first time in Iranian adult population indices studied in male and female were in the anterior mandible and statistical analysis showed no significant difference in bone thickness buccal, lingual, and buccal curvature angle in both sexes, so the need for different treatment of the two sexes is not felt.

5.1. Conclusion

According to the results obtained in this study, no significant differences was observed between the two sexes in terms of the average distance between the CEJ and buccal bone crest. And the same for the average thickness of the buccal alveolar plate, thickness of lingual alveolar plates, width of roots in anterior region of lower jaw mesiodistaly and buccolingually, the angle of curvature of the buccal bone at the apex of the tooth and the distance between the apex of the tooth root to the deepest point of the curvature of the buccal bone in the lower jaw.

It was also found that the thickness of the buccal plate of the mandibular anterior teeth in Iranian adult population is more than 1 mm and generally anterior mandibular lingual plate thickness is greater than its buccal plate.

In addition, it was found that the greatest curvature of the bone in mandibular anterior teeth is in the central area of buccal plate.

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