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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 2  |  Page : 91-95

Proximity of the mandibular anterior root apices to the buccal bone surface: A cone-beam computed tomographic study


1 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
2 Department of Oral Medicine and Radiology, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
3 Department of Oral Pathology and Microbiology, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
4 Department of Periodontology, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India

Date of Submission28-Sep-2021
Date of Decision24-Nov-2021
Date of Acceptance17-Jan-2022
Date of Web Publication01-Jul-2022

Correspondence Address:
Dr. Neeta Shetty
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore. Affiliated to Manipal Academy of Higher Education, Manipal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_183_21

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  Abstract 


Aim: The aim of this study is to evaluate the distance from the buccal cortical bone surface to the root apex in the anterior mandibular teeth using cone-beam computed tomography (CBCT) and to correlate it to various associated factors (tooth type, gender, and age).
Materials and Methods: CBCT images of mandibular anterior teeth from 120 patient records with a sample size of 360 teeth were analyzed. The distance from the buccal bone surface to root apex and 3 mm above the root apex in the sagittal view was reconstructed using the Romexis software version 3.2.1.
Results: Distances from the buccal cortical bone surface to the apices of the root and 3 mm from the apex of the root were greater at the mandibular canine region than the central and lateral incisor (P < 0.001). The buccal bone was significantly thicker corresponding to the apices of the teeth compared to the region 3 mm from the apex (P < 0.001) The mean distance value from the cortical buccal bone surface to the lateral incisor apex (4.03 mm) was significant more among females (P = 0.006). Furthermore, the measured distance at the root apex and 3 mm above the of the root apex of the mandibular anterior roots were significantly more in patients below the age of 40 years (P < 0.05).
Conclusion: The distance from the buccal bone's surface to the apex and 3 mm from the apex in the mandibular anterior region is significantly affected by the tooth type and patients' age. CBCT is a reliable tool for presurgical evaluation for both these parameters during endodontic surgeries and implant placement.

Keywords: Apical, computed tomography, implants, mandibular, peripical surgery


How to cite this article:
Gupta I, Shetty N, Ahmed J, Mala K, Natarajan S, Shetty NJ. Proximity of the mandibular anterior root apices to the buccal bone surface: A cone-beam computed tomographic study. Endodontology 2022;34:91-5

How to cite this URL:
Gupta I, Shetty N, Ahmed J, Mala K, Natarajan S, Shetty NJ. Proximity of the mandibular anterior root apices to the buccal bone surface: A cone-beam computed tomographic study. Endodontology [serial online] 2022 [cited 2022 Aug 8];34:91-5. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/2/91/349567




  Introduction Top


Cone-beam computed tomography (CBCT) scans have gained widespread acceptance and popularity due to their versatile application in dental imaging. It gives a precise three-dimensional (3D) image of the region of interest, with the radiation dose being relatively low.[1] Alqerban et al. considered CBCT scans (3D) to be more detailed for identifying dental structures and locating initial resorption sites than conventional 2D X-ray imaging.[2] The mesiodistal and the gingivoinsical height of the oral structures can be obtained through conventional radiology; however, the buccolingual dimension cannot be assessed. Hence, CBCT is considered a crucial tool for the measurement of buccolingual dimensions specific to the region of interest. Therefore, the use CBCT as a tool for these measurements becomes indispensable in field of endodontics and implantology.[3]

Dental implants are one of the treatment options in patients having missing teeth or wish for replacement immediately after extraction. The assessment of bone thickness, quality and quantity with CBCT, is easier because of the image's 3D nature. These images have proven to be constructive in the examination of cortical bone thickness and measuring the distance from crucial anatomical structures, especially during immediate implant placement.[4]

Knowledge of anatomical structures and meticulous preoperative radiological evaluation can limit operative and postsurgical complications. Since variations exist in every patient, CBCT helps determine the boundaries of safe areas for surgery or implant placement.[5] Vital information and visualization of anatomical structures are essential for favorable outcome and prognosis in an endodontic surgery since it provides better understanding and approach to the surgical field. The concerns for a dentist during apical surgery in the mandibular anterior region are the root apex position, the buccal bone plate thickness, and distance from the outer surface of the buccal cortical plate to the root.[6] However, studies evaluating the thickness of the anterior mandibular buccal cortical bone are quite limited. According to Baumgaertel and Hans, mandibular bone is thicker than maxillary cortical bone.[7] At present, calipers and CBCT scans are used to measure the buccal bone thickness and compare variations according to gender, age, and tooth type.[8],[9],[10],[11],[12]

During planning an endodontic surgery, 3D information of root configuration and jawbones obtained by CBCT imaging is desirable. Such imaging provides specific information of the anatomical relationship of the root apices to the adjacent vital structures in various directions.[13],[14],[15] At present, there is a lack of data on the distance of the root apex from the buccal bone surface correlated to multiple factors such as age, sex, adjacent teeth, and root configuration for mandibular anterior teeth. Hence, this study was conducted to evaluate the distance from the buccal bone surface to the root apices of the mandibular anterior teeth by utilizing CBCT images and assessing the differences in gender and age.


  Materials and Methods Top


Ethical clearance

“Ethical approval for this study (Protocol reference no. 17018), was provided by the Institutional Ethics Committee of Manipal College of Dental Sciences, Mangalore, on March 13, 2017.” After obtaining ethical clearance, the sample size calculated. Assuming the mean as 3 and SD as 1 for the present study, at a 95% confidence interval and 90% power with the precision error of 0.7, the following formula had applied to calculate the sample size of 360.

n = (Zα/2 + Zβ) 2 × 2 × σ2/d2

CBCT patient records were retrieved from the archives in the department of oral medicine and radiology. Out of the 200 scan records, 60 scans of males and another 60 females, with the age group ranging between 20 and 70 years who fulfilled the inclusion criteria were selected. In total, 360 teeth were evaluated. Scans with those having all the anterior mandibular teeth in either left or right mandibular quadrant with fully developed root apices and no evidence of any apparent periapical pathology were considered in the inclusion criteria. The exclusion criteria included the presence of any periapical pathosis, root resorption, nonidentificable root apices, and dilacerated or excessive root curvature and any missing mandibular anterior teeth in the CBCT image.

The CBCT images had been captured using a Planmeca Promax 3D Mid unit (Planmeca Oy, Helsinki, Finland). (15 bit resolution, flat panel sensor, maximum FOV of 20 cm × 18 cm). The images were constructed by taking a series of 0.2–0.4 mm thick cross-sectional images in both small and medium field of views at 8 mA and 90 KVp with a 12 s exposure time. The scans were taken using the standard patient protocols that included positioning patients with the FH plane parallel to the floor, using patient stabilizing tools, and minimizing patient movements. Romexis software version 3.2.1 (Helsinki, Finland) was used to reconstruct the images.

Radiographic measurements

The distances were measured from the outer surface of the buccal cortical bone to the outer surface of the root at the apex in a buccolingual direction in the sagittal plane in the region of the mandibular anterior tooth. After measuring the buccolingual distance at the apex for each tooth, namely the mandibular central incisor, lateral incisor and mandibular canine, a line was drawn, 3 mm vertically and superiorly to the root apex. The distance was then measured again from the root surface to the outer surface of the buccal cortical plate at this level. Furthermore, the distance was measured in the cross-sectional plane in millimeters using the Romexis software [Figure 1]a, [Figure 1]b, [Figure 1]c.
Figure 1: (a) Distance measured from the outer surface of the buccal cortical bone to the outer surface of the root apex. (b) 3 mm line drawn vertically and superiorly to the apex. (c) Distance measured from the root surface to the outer surface of the buccal cortical plate

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Statistical analysis

Paired t-test was applied to calculate the difference between the two observations for each pair of types of teeth and independent Student's t-test was used to determine whether there is a statistically significant difference with the associated factors (gender and age). The significance level was set at P < 0.05. SPSS software program version 16.0 (IBM Corp, Somers, NY) was used to perform all the statistical analyses.


  Results Top


On comparison of the mean values of the thickness of bone over the apices and at 3 mm from the apices of the central incisor, lateral incisor and canine, it was found to be significantly thicker (P < 0.001) at the canine region. The thickness of the mandibular buccal cortical bone in anterior teeth region was greater at the apex than at the 3 mm level (P < 0.001) [Table 1]. The mean values of the buccal bone thickness at the apical region were higher in canine (4.01 mm) compared to both central incisor (3.62 mm) and lateral incisor (3.71 mm) and were statistically significant.(P < 0.001) [Table 1].
Table 1: Comparative mean and standard deviation values of the thickness of bone over the apices and at 3 mm from the apices of the mandibular anterior teeth

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The values of the mean distance at 3 mm from the apex was significantly greater at the canine region (1.20 mm) when compared to the central incisor (0.89 mm) and the lateral incisor (0.75 mm) (P < 0.001). Also, the central incisor compared to the lateral incisor had a significantly higher mean value of the distance at 3 mm from the apex vertically to the outer surface of the buccal cortical bone (P = 0.012) [Table 1].

Independent t-test was applied to compare the buccal cortical bone thickness between males and females. A significant difference in the thickness of buccal cortical bone at the apical region was not observed among males and females except at the apex of the lateral incisors wherein increased thickness was observed in the female group (P < 0.006) [Table 2]. When comparing the thickness from the buccal bone surface at the apex and 3 mm from the apex, it showed significantly thicker buccal cortical bone in patients <40 years (P < 0.001) [Table 3].
Table 2: Comparison of the thickness of the buccal cortical bone between males and females

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Table 3: Comparison of the thickness of the buccal cortical bone among patients below 40 years and above 40 years

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  Discussion Top


CBCT images can pinpoint peril-apical or peri-implant bone defects in all three planes, true to scale, and without distortions revealed by histological correlation.[16] Mandible usually has more cortical density than maxilla, and their cortical thickness generally increases anteriorly.[17] Prediction of the outcome of an endodontic surgery or primary implant stability is more accurate by evaluating the bone structure. Thus, CBCT can prognosticate the amount of bone to be removed during a periapical surgery and the time needed for the osseointegration of implants. It can also predict a suitable interval between implant insertion and prosthetic loading.

Surgical endodontics is a preferred treatment modality for treating apical pathology in the case of repeated failed root canal therapy. To access the root end, it necessitates the preparation of a bony window by drilling through the cortical bone. Apical surgery demands an accurate and exact osteotomy approach to obtain the operating field right at the apex. Thus, knowledge about the buccal cortical bone thickness becomes a critical factor for precise endodontic surgery.

The present study results revealed that the thickness of the bone at the root apices from the buccal cortical bone surface ranges between 3.62 mm and 4.01 mm. Also, from the buccal bone surface to the root surface at 3 mm level from the root apex was within the range of 0.89 mm to 1.20 mm, signifying a gradual thinning of the buccal cortical bone. Since the thickness of the buccal cortical bone is thinner at this area, precautions must be taken not to damage the tooth surface during access to the surgical site. Moreover, according to clinical guidelines, 1–2 mm is the minimum buccal alveolar bone thickness is required during implant placement.[18] The mandibular canine, both at the apex and 3 mm had the highest distance measured from the buccal cortical plate which implies that the maximum amount of bone that needs to be removed during apical surgery is in this region. According to Gupta et al., the average thickness of the crustal cortical bone in the anterior mandible region is about 1.08 ± 0.30. Site-related factors such as quality and quantity of bone and implant position in jaw play a vital role in implants' success.

Morphological studies have revealed that the apical 3 mm of the root is a potential problem area for the existence of canal irregularities, such as accessory or lateral canals.[19] Studies have also demonstrated that root resection of the apical 3 mm at a zero-degree bevel angle helps remove the majority of anatomical entities, which can be potential causes of failure in the future.[20],[21] Hence, data regarding the distance between the buccal bone surface and the apical 3 mm level of the root in the present study provides valuable clinical information for surgical endodontics.

A significant difference in buccal bone thickness concerning gender was not noted. Apart from the thickness of the bone at the region of the lateral incisor apex, which was found to be greater in the females. However, there are no supporting evidence in the literature. Therefore, recommending or planning different apical surgery protocols based on this factor seems to be of no clinical relevance. Age, on the other hand, has a significant influence on the thickness of the buccal cortical bone. The distance from the root apex to the buccal bone surface was significantly lesser in patients above 40. This decrease in dimension could be explained by age-related bone loss in women and men which is mostly influenced by gonadal steroid deficiency and secondary physiological hyperparathyroidism that occurs later in life.[22] Other influencing factors include vitamin D deficiency, intrinsic defects in osteoblast function, impairment of the growth hormone/insulin-like growth factor level, reduced peak bone mass, age-associated sarcopenia, and various sporadic secondary causes.[23] However, the limited number of the sample size in the present study is a shortcoming and more investigations may be essential to generalize this finding of reduced dimension in patients older than 40. Hence, based on the current findings, it can be postulated that more surgical removal of bone is required in younger patients during apical surgeries. López-Jarana et al. suggested that since mandibular central incisors, lateral incisors, and canines are the critical sites with <2 mm buccal bone thickness additional regenerative strategies can be considered at the surgical sites.[24]

Some amount of discrepancies in CBCT measurements may exist between the values calculated on the CBCT images and the actual values of the subjects. In a previous study, the mean absolute errors between CBCT and direct measurements were insignificant (0.30 mm and 0.13 mm for buccal bone height and buccal bone thickness, respectively), and the values obtained from the different analyses were not significantly varied.[25] Although CBCT measurements are not exactly similar to the actual measurements, the CBCT values are acceptable during the planning of surgical cases since the difference in values is minimal and hence insignificant. Limitations of our study include the sample size and also investigations across different ethnicities would probably have given a more varied picture in terms of measurement values. Variations in root morphology and effect of periapical infections and systemic conditions have not been taken into account while measuring the buccal bone thickness.

The significance of this study was to help us gain knowledge about the exact thickness of the buccal cortical plate that is available for surgical removal during endodontic surgery, thereby preventing any damage to the adjacent structures and avoiding any unnecessary bone removal which shall help us to achieve a more precise and favorable prognosis in patients undergoing endodontic surgical procedures. Furthermore, CBCT analyses help to ensure the most appropriate dental implant treatment approach.


  Conclusion Top


It can be concluded that there was a difference in thickness of the buccal cortical bone at the root apices and at 3 mm level superior. The thickness of buccal wall in the anterior mandibular region is <2 mm. Among the three sites, the canines have thicker bone labial compared to incisors and the distance from the root apex to the buccal bone surface was reduced in patients older than age 40. The female group demonstrated thicker bone at the apex of lateral incisor. The current study results suggest that most of the assessed areas in the mandibular anterior region could require additional tissue regenerative procedures to preserve both hard and soft tissue volumes. These results also provide the basis for the placement of implants or apical surgery in the mandibular anterior region.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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