Thickness of the Buccal and Alveolar Bones Overlying Central Incisors: A Radiographic Iraqi Study

Background Initial bone thickness has a substantial impact on the success of dental implant treatments. The objective of the current study was to analyze the thickness of the buccal and alveolar bone at the central incisors using CBCT in relation to gender and side to determine the anatomical features and choose the best implant treatment option for minimizing the surgical complications. Methods One hundred CBCT images were investigated (50 females and 50 males, aged 20 to 50 years old). The buccal bone thickness and alveolar bone thickness were evaluated for right and left sides of each subject at three sites; C: crest (3 mm); M: middle (6 mm); A: apical (9 mm) from the cementoenamel junction. Results The mean thickness of buccal bone was less than 2 mm on the incisors according to side and gender. Buccal bone thickness revealed a statistically significant difference between right and left sides at the apical point in both females and males with p values of (p ≤ 0.001) and (0.001), respectively. The buccal bone thickness displayed statistically significant differences between genders at all sites. The alveolar thickness demonstrated similar significant differences between genders except for the crest site. Conclusions Iraqi participants had about 1 mm buccal bone thickness at 3 mm apical from the CEJ in right and left central incisors with a progressive rise in bone thickness to be less than 2 mm at the apex. Alveolar bone also showed the same increase in bone thickness from crest to apex. Bone thickness was greater in males than females. The present study provided valuable CBCT data on bone thickness of the esthetic maxillary region as a preoperative analysis for establishing an immediate implant treatment plan with aesthetically pleasing long-term outcomes.


Introduction
Missing teeth are commonly treated with dental implants. e initial stability of dental implants and their survival rates are directly associated with patients' osseointegration ability [1]. e patients usually desire that their missing anterior teeth be replaced as soon as possible, so that they can resume their normal lives without the psychological problem of being edentulous and so that their appointments are reduced. erefore, immediate implants placed between 0 and 7 days after tooth extraction came into existence to overcome this problem [2]. Devorah Schwartz-Arad concluded in their literature review article that immediate dental implants have a high survival rate when placed into fresh extraction sockets, and when inserted 3-5 mm beyond the apex and close to the crest of the alveolar bone [3]. e morphology, width, height, and density of the alveolar bone must be determined to choose the right size of the implant and the placement angle [4].
Bone thickness of the alveolar bone anteriorly is critical for dental implant therapy in terms of the esthetic outcomes. After tooth extraction, there will be a significant reduction in the buccolingual and apical-coronal extent of the alveolar region, which may affect the placement of implant-supported crown in the esthetic zone [5].
Moreover, sufficient buccal bone thickness in the anterior maxillary region is crucial for proper implant positioning. e thickness of the labial plate of the maxilla especially of the central incisors was reported to be very thin, necessitating extreme caution when inserting an implant [6,7]. Next to upper central tooth extraction and immediate implant placement, the facial bone that covers the roots of the tooth is prone to resorption more than the palatal plate, leading to the center of the ridge to move to the palatal direction [8]. e amount of resorption is really affected by the original bone thickness. e thinner bone will contribute to a greater bone loss, dehiscence, fenestration, and recession of the soft tissue, risking the aesthetics and success of the implant [9,10].
As studies have shown variances in bone patterns in various people, it is extremely crucial to pick a site for the installation of dental implants before the treatment and to thoroughly evaluate the oral anatomy and the width of both the ridge and the alveolar crest [11].
Cone beam computed tomography (CBCT) is extremely important for evaluating the advantages of the bony components surrounding the teeth as compared to older techniques.
is technology has the advantages of high resolution, being noninvasive, low radiation dosage, and being cost efficient [12]. CBCT images are the most used means of measuring buccal bone thickness (BBT) in comparison of gender, age, and tooth differences across different patients and among other factors [13,14]. Vera et al. [15] stated that CBCT scans can identify the BBT and its condition in the concerned area as an indicator for prolonged success of the implant.
A number of researches have employed CT to investigate maxillary alveolar bone thickness in the skull, but it may be inefficient as only two-dimensional data are available [16]. Few investigations have been conducted on CBCT, practically in the Iraqi population. Moreover, the anterior maxilla is esthetically sensitive for immediate dental implants position because of its particular anatomy. e objective of the current study was to analyze the thickness of the buccal and alveolar bone at the central incisors using CBCT in relation to gender and side of an Iraqi sample to determine the anatomical features and choose the best implant treatment option for minimizing the surgical complications.

Materials and Methods
One hundred CBCT images were investigated (50 females and 50 males, aged 20 to 50 years old), who were referred from different departments needing CBCTfor various dental treatments. For all research participants, the ethical principles established in the Helsinki Declaration of 1964 were implemented. e local ethical approval by the Scientific Committee of Oral Medicine Department was obtained (protocol 16; November 2020). Following their approval, all participants provided consent forms. e minimum sample size was estimated to be 45 patients in each group using G * Power 3.1.9.7 software and data generated through our pilot study. e CBCT scanning was done by Myray, Italy, FOV 8 × 8 cm, voxel size 0.3 mm, exposure time 9.34 s, kVp 75, mA 5. e CBCT scans clearly showed the front maxilla and central incisors. Teeth having a root canal, periapical lesion, periodontal disease, malformation, or treatment such as fillings, crowns, or bruising were eliminated from the research. e evaluation of the central incisors was done by CBCT. e data was collected and repeated by the same radiologist after one week. e two readings were almost the same, though to assess the intraobserver reliability, a paired t-test was conducted for 10 random CBCT scans showing no significant difference. e mean of each 2 measurements was utilized in the statistics. e buccal bone thickness (BBT) and alveolar bone thickness (ABT) were evaluated at three sites, which are C: crest (3 mm); M: middle (6 mm); A: apical (9 mm) from the cementoenamel junction (CEJ), and vertical to the long axis of the tooth at each point. e right and left sides were evaluated for all subjects [17], Figure 1.

Statistical Analysis.
Data analysis was conducted with SPSS software version 21. Shapiro-Wilk and Levene's tests were used to investigate the data's normality and homogeneity of variance respectively. e independent t-test was used to compare thickness data between genders. A p value ≤0.05 was considered statistically significant.

Results
e study involved 100 CBCT images (200 teeth), divided equally into male and female groups. e means of buccal bone thickness (BBT) at the crest, middle, and apical sites of females on the left side were (0.92 ± 0.22), (1.17 ± 0.16), and (1.19 ± 0.25), respectively. And they were (0.90 ± 0.25), (1.17 ± 0.20), and (1.47 ± 0.32) for the right side, respectively. For males, the means of BBT at the three sites were (1.00 ± 0.09), (1.20 ± 0.08), and (1.35 ± 0.21) for the left side, respectively. Likewise, they were (1.02 ± 0.08), (1.21 ± 0.06), and (1.48 ± 0.27) for the right side, respectively. Regarding the sides, the left BBT showed statistically significant difference across genders on two points (C and A), in spite of the right side showing statistically significant difference at one point only (C). e male groups had higher bone thickness than female groups at these points (Table 1).

Discussion
In dentistry, implant surgery is now the most prevalent therapy for lost teeth. Related research has shown that a     e Scientific World Journal 3 positive bone state leads to greater osseointegration and an increased lifespan of dental implants; hence, a preoperative examination of the jawbone health is required [18,19]. e current work applied CBCT to investigate bone thickness in the implantation sites as a presurgical assessment for the outer boney layer and the alveolar bone, which has proved to be useful for the patients in relevant studies using the same technology [20,21]. CBCT has become the standard option for implant position planning, especially in esthetic zone. For example, augmentation surgical procedure may be required to enhance the bone around the dental implant if alveolar bone atrophy determined by CBCT was severe [9]. Compared to the palatal bone, the labial cortical plate at the anterior maxillary region is thinner, and resorption occurs more easily after teeth extraction [8]. e mid-buccal bone recession was about 0.5 mm after the first year of dental implantation according to a prospective study of single immediate implant placement at the maxillary anterior region [22]. In addition to that, excessive force applied to a thin buccal plate by implant insertion might cause microfractures and crestal bone loss. erefore, it is critical to guarantee the existence of hard tissues to perform the implantation process without serious complications by using the right implant site and angling in the alveolar bone.
Moreover, the prevalence and rate of peri-implant soft tissue marginal recession that happens in the labial and interproximal sites after implant placement should be a major concern for clinicians from the dental implant aesthetics perspective. e mean free gingival recession around a single-tooth implant was found to be 0.5-1 mm [23]. Patients with thin scalloped gingiva were shown to be more prone to recession, whereas the thick-flat biotype was found to be a significant determining factor in achieving a satisfying esthetic outcome in implant restorations [24]. Further, certain periodontists have observed that thin alveolar contours are covered by thin gingival forms, suggesting that gingival contours are associated with underlying bone anatomy. As a result, soft tissue aesthetics surrounding implants are primarily influenced by bone anatomy [25].
With a number of modern studies [26,27], the current work conducted on data to evaluate the thickness surrounding natural dentition. e soundness of determining BBT over natural teeth by CBCT has been approved and applied by many studies to find the length between CEJ and crest of the bone plus BBT of anterior teeth [28]. When assessing the thickness of the labial walls, choosing a reference point appears to be crucial. In the present study, CEJ was used as a reference point in accordance with previous studies using 3 mm distance [17,29]. Measurements of bone thickness were also performed at 1 to 5 mm apical to the labial bone crest [13].
Clinicians have a public opinion that 2 mm is the smallest required thickness of the buccal wall to preserve the length of the alveolar crest and to calculate the quantity of crest resorption vertically after extraction [30]. us, due to the esthetic effect and long-term repercussions, the BBT must be carefully considered prior to tooth extraction and implant insertion. According to a one-year follow-up study, labial plate of 1-2 mm was suggested for better esthetic outcomes in immediate implant treatment, because enormous gingival recession and bone resorption were found in patients with a thickness of less than 0.5 mm [31]. us, in cases with thin buccal bone walls, dentists must consider the use of bone augmentation or graft material in immediate implant treatment plan [32]. In the current work, the mean of BBT on the left side was increased from 0.92 mm at the crest to 1.19 mm at the apex in females, while it was 0.90 mm coronally and 1.47 mm apically on the right side. According to males, it was 1.00 mm at the crest and increased to 1.35 mm at the apex of the left side. As for the right side, it was 1.02 mm coronally and 1.48 mm apically.
Januário et al. and other authors [13,33] observed that BBT was slim and rarely >2 mm at different distances from CEJ during their studies by CBCT, which was compatible with the current outcome. Another study looked at BBT for 73 individuals without recording results exceeding 2 mm in bone thickness [30]. However, the finding was in disagreement with dos Santos et al. [34] who noticed that BBT was <1 mm in the majority of patients through examination of 202 CBCT (1463 teeth), while, in another prior study using 50 CBCT scan of maxilla, less than 10% of buccal bone sites had more than 2 mm thickness and in 14.4% of the central incisor buccal bone sites were ≥2 mm [35].
is variation in BBT results may be related to the difference in sample sizes, age, and gender. e present work revealed a progressive rise in the thickness of the buccal and alveolar bone from the crest towards the apex. Koç et al. [36] and authors of other studies [37,38] concluded a coinciding view with the present finding, indicating a steady increase in thickness in an apical direction.
e finding was also consistent with that of Deguchi et al. [39], who discovered that the thickness of cortical bone increases with height and decreases with depth. For central incisors, the BBT was thicker at the apex and  [40]. Another publication mentioned that the alveolar width of the central incisor diminished from the apical to crest direction [29], which is in line with the current work. In contrast, AlTarawneh et al. [41] reported that the mean measure of labial plates decreased towards the apical portion. is discrepancy might be attributed to the characteristics of the included cases as well as the different measuring depth used. e absence of significance in the current study among BBT on the left and right sides was observed for the first two points (Table 3) since only the apical point was significant. Lee et al. [29] found no significant difference between the left and right BBT through a study of twenty participants. e present study described the statistically significant difference of the left BBT between genders on two points (C and A), in spite of the right BBT being statistically significant at one point only (C). Fuentes et al. [35] noted that the BBT of the right central did not vary by gender, in contrast to the left central that showed a significant difference by this factor, and proposed that gender is not an indicator for thickness since this exhibited a different impact by gender. e current finding indicated that males possess larger BBT than females at various root levels regardless of sides. e result is supported by specific past study groups [26,29,42]. Additionally, Adiguzel et al. [43] concluded that gender was significantly related to the BBT in the maxilla. According to the Cassetta et al. [44] study on 48 computed tomography scans, men had thicker alveolar cortical bone than women, and the alveolar crest thickens as it approaches the apex. Age could also be a deciding factor according to the literature. It has been noted that the thickness of the labial bone at the cervical part decreases with age [45], and that postmenopausal women have much thinner labial bone [37].
is study concluded gender differences in thickness of the alveolar ridge that women had smaller thickness than men except for the crest site. Men had stronger muscles for mastication than women to apply higher biting force [46]. Uner et al. [17] conducted a study on 160 CBCT (320 teeth) at 3, 6, and 9 mm depths below the crest with ages ranging from 21 to 53 and suggested a gender difference. Males had wider alveolar ridges than females in every location studied, which approximated current work except for the crest, which was statistically nonsignificant. Likewise, Lim et al. [47] asserted that women had a smaller ridge width than men during CBCT study of 32 subjects (13 men; 19 women).
Resorption of the buccal plate is more likely to impact the anterior regions than the posterior ones because the resorption is extra serious when the walls are first thinner. CBCT is the optimal method for preventing compromises in esthetic reconstruction [48]. It enables multiple measures at several sites and the existent bone property [49]. e research had certain limitations, which included the age impact. Second, the study only covered Iraqi patients. Several outcomes may not apply to other ethnicities. Finally, when the bone plate is exceedingly thin, CBCT readings may produce substantial inaccuracies and overestimations.

Conclusions
e present study presents valuable information regarding the thickness of buccal walls in the esthetic maxillary central incisor region in an Iraqi population as a preoperative analysis for establishing immediate implant treatment plan for aesthetically pleasing long-term outcomes.
Iraqi participants had about 1 mm buccal bone thickness at 3 mm apical from the CEJ in right and left central incisors sites with a progressive rise in the thickness to be less than 2 mm at the apex. In the esthetic maxillary region, there is a significant preponderance of thin BBT, which should be considered when performing dental procedures, such as tooth extractions or immediate implants. Alveolar bone also showed the same increase in bone thickness from crest to apex. Bone thickness was greater in males than females.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declared that there were no conflicts of interest.

Authors' Contributions
Nuhad A. Hassan conceptualized the study, conducted investigation, wrote the original draft of the manuscript, critically reviewed intellectual contents, and approved the final version to be published. Aseel S. Khazaal Al-Jaboori formulated the methodology, reviewed and edited the manuscript, visualization, and supervision, critically reviewed intellectual contents, and approved the final version to be published.