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 (
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 (
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 (
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 (
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.
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.