Assessment of the Inferior Alveolar Nerve Canal Course Among Saudis by Cone Beam Computed Tomography (Pilot Study)

Feasibility of implant placement in healed mandibular molar sites: A retrospective cone beam computed tomography study

STATEMENT OF PROBLEM

Implant placement in the mandibular molar sites plays a crucial role in the restoration of edentulous mandibles. However, the evaluation of bone quantity before implant surgery using cone beam computed tomography (CBCT) is lacking.

PURPOSE

The purpose of this clinical study was to evaluate CBCT images of edentulous patients to analyze the feasibility of implant placement in healed mandibular molar sites.

MATERIAL AND METHODS

The CBCT data of 138 patients were analyzed in the sagittal plane for measurements of mandibular bone height (MBH), superior bone height (SBH), inferior bone height (IBH), buccal bone width (BBW), lingual bone width (LBW), and alveolar bone widths (ABWs). The edentulous sites were categorized according to the bone quantity and complexity of the implant surgery. Multivariate analysis of variance (MANOVA) was used to analyze the site, sex, and age-related variations. An independent t test was used to compare the difference of bone dimension in different sites and between sexes. One-way ANOVA followed by post hoc tests were used to analyze the difference between different age groups. Categorical variables were presented as number of events and percentages. The chi-squared test was used to compare categorical variables (α=.05).

RESULTS

A total of 534 sites of interest were recorded, including 274 hemimandibles. A significant difference in BBW was found between the first and second molar sites. Men had higher MBH, SBH, IBH, and BBW than women. The distribution of implant surgical complexity in the conventional group was 63.5%, while the buccolingual tilted implant group accounted for 17.0%, and the complicated group accounted for 19.5%. Of the 274 hemimandibles, an implant could be placed directly at molar sites in 88% of situations.

CONCLUSIONS

The BBW at the mandibular second molar site was greater than that at the first molar site. The amount of available bone in the SBH and BBW was greater in men than in women at the healed molar sites. Age did not significantly affect the complexity of the implant surgery. Implants can be placed directly in healed mandibular molar sites in most patients who require a complete arch mandibular implant-supported restoration.

Identification of the inferior alveolar canal using cone-beam computed tomography vs. panoramic radiography: a retrospective comparative study

BACKGROUND

This study aims at evaluating the visibility levels of the inferior alveolar canal (IAC) at different mandibular sites using panoramic (conventional & CBCT reformatted) and CBCT coronal views in a sample of a Palestinian population.

METHODS

The panoramic (conventional [CP] & CBCT reformatted [CRP]) and CBCT coronal views (CCV) of 103 patients (206 records, right and left sides) were analyzed. The visibility of IAC at five sites extending from the first premolar to the third mandibular molar region was evaluated visually (and compared among the radiographic views) as clearly visible, probably visible, invisible/poorly visible, or not present at the examined site. On CCV, the maximum dimension of the IAC (MD), the vertical distance (VD) between the mandibular cortex and IAC, and the horizontal position (HP) of the IAC were noted. Statistical significance in the differences and relationships of the variables was tested using several statistical tests.

RESULTS

There was a statistically significant relationship between the radiography modality (CP, CRP, CCV) and the visibility level of IAC (assessed in scores) at the five mandibular sites. When assessed on CP, CRP, and CCV, the IAC was clearly visible at all sites in 40.4%, 30.9%, and 39.6%, respectively, while being invisible/poorly visible in 27.5%, 38.9%, and 7.2% for the same views, respectively. The mean values of MD and VD were 3.61 mm and 8.48 mm, respectively.

CONCLUSION

Different radiographic modalities would characterize the IAC's structure in different qualities. Superior visibility levels were obtained interchangeably using CBCT cross-sectional views and conventional panorama at different sites compared to CBCT reformatted panorama. The IACs visibility was noted to improve at their distal aspects irrespective of the radiographic modality used. Gender -but not age- was a significant factor in the visibility level of IAC at only two mandibular sites.

Assessment of the Proximity of the Inferior Alveolar Canal with the Mandibular Root Apices and Cortical Plates-A Retrospective Cone Beam Computed Tomographic Analysis

Various endodontic interventions often lead to iatrogenic damage to the inferior alveolar nerve present in the inferior alveolar canal (IAC). The purpose of the present study was to analyze the relationships of IAC with the root apices of mandibular teeth and with the mandibular cortical plates.

MATERIALS

116 cone beam computed tomography (CBCT) scans were examined and the shortest distance of IAC with the root apices of mandibular canines, premolars and molars, and with cortical plates was analyzed. The data were statistically analyzed using SPSS.

RESULTS

The shortest mean distance between IAC and lingual cortical plate (LCP) was found in the third molar area, and between IAC and buccal cortical plate (BCP) in the second premolar area. A high incidence of 60% direct communication (DC) was present in mandibular second molars; 38% in mandibular third molars; 13% in mandibular second premolars; 12% in mandibular first molars; and 1% in mandibular first premolars.

CONCLUSION

Anteriorly, IAC was found to be significantly present in close approximation to the roots of mandibular canines. Posteriorly, IAC was found to be in significant proximity to the distal roots of mandibular second molars.

Inferior alveolar nerve topography and its bifurcation features: a cone beam computed tomography evaluation

BACKGROUND

Mandibular canal (MC) is the most important vital structure in mandible to prevent from complications such as bleeding and paresthesia. The aims of the present study were to inform the features (diameter, distances to the mandibular borders, and distance to tooth apex) of the MC for each posterior tooth region, and to present the bifurcation features of the MC.

METHODS

Four-hundreds-eighteen MC images of 209 patients were evaluated. The parameters were recorded from right and left hemi-mandibles for each posterior teeth region: 1) MC diameter; 2) MC and mandibular basis distance; 3) MC and crest distance; 4) MC and tooth apex distance; 5) MC and buccal plate distance; 6) MC and lingual plate distance; and 7) possible implant length (the distance between 2 mm coronal of the MC and 1 mm apical of the crest). Additionally, MC bifurcation type and bifid mandibular canal length were noted for right and left sides.

RESULTS

While higher MC diameter values were recorded at molars, MC diameter in first premolars bilaterally were the lowest. In premolars, MC and mandibular basis distance showed higher values than molars. There was a trend of decrease in MC and crest distance from molars to premolars. The highest MC and tooth apex distance was measured in second molar; however, the lowest was in the first premolar. Additionally, MC and buccal plate distances were higher in molars, while MC and lingual plate distances were higher in premolars. Possible implant length in first premolar was the lowest, when it was the highest in second molars.

CONCLUSIONS

For simulating overall MC topography, it extended bucco-coronally from molars to premolars. Due to this topography, possible implant length increased from premolars to molars.

Analysis of the mandibular canal course using unsupervised machine learning algorithm

Objectives

Anatomical structure classification is necessary task in medical field, but the inevitable variability of interpretation among experts makes reliable classification difficult. This study aims to introduce cluster analysis, unsupervised machine learning method, for classification of three-dimensional (3D) mandibular canal (MC) courses, and to visualize standard MC courses derived from cluster analysis in the Korean population.

Materials and methods

A total of 429 cone-beam computed tomography images were used. Four sites in the mandible were selected for the measurement of the MC course and four parameters, two vertical and two horizontal parameters were measured per site. Cluster analysis was carried out as follows: parameter measurement, parameter normalization, cluster tendency evaluation, optimal number of clusters determination, and k-means cluster analysis. The 3D MC courses were classified into three types with statistically significant mean differences by cluster analysis.

Results

Cluster 1 showed a smooth line running towards the lingual side in the axial view and a steep slope in the sagittal view. Cluster 2 ran in an almost straight line closest to the lingual and inferior border of mandible. Cluster 3 showed the pathway with a bent buccally in the axial view and an increasing slope in the sagittal view in the posterior area. Cluster 2 showed the highest distribution (42.1%), and males were more widely distributed (57.1%) than the females (42.9%). Cluster 3 comprised similar ratio of male and female cases and accounted for 31.9% of the total distribution. Cluster 1 had the least distribution (26.0%) Distributions of the right and left sides did not show a statistically significant difference.

Conclusion

The MC courses were automatically classified as three types through cluster analysis. Cluster analysis enables the unbiased classification of the anatomical structures by reducing observer variability and can present representative standard information for each classified group.

A CBCT Based Three-Dimensional Assessment of Mandibular Posterior Region for Evaluating the Possibility of Bypassing the Inferior Alveolar Nerve While Placing Dental Implants

A high rate of nerve injury and related consequences are seen during implant placement in the posterior mandibular arch. An approach has been proposed to avoid nerve injury by dodging the inferior alveolar nerve (IAN) while placing an implant. A prospective study with a total of 240 CBCT (cone beam computed tomography) images of patients with three dentate statuses, namely, edentulous (group I), partially edentulous (group II) and dentate (group III) were included in the study. The nerve path tracing was done on CBCT images with On-demand 3D software. The three dimensions, i.e., the linear distance from the outer buccal cortical plate to the inferior alveolar nerve (BCPN), linear distance from the outer lingual cortical plate to the inferior alveolar nerve (LCPN) and linear distance from the midpoint of the alveolar crest to the inferior alveolar nerve (ACN) were assessed. The data were presented and analyzed between variables using one-way ANOVA and independent t-test in SPSS version 21.LCPN of the right 1st premolar region (p < 0.05) was significantly different among the groups with edentulous subjects recorded with the minimum value (6.50 ± 1.20 mm). Females were found to have significantly (p < 0.05) less available bone (6.03 ± 1.46 mm) on the right side of the mandibular jaw compared to males in edentulous group of patients. On comparing age groups for partially edentulous subjects, LCPN of the right 1st premolar region had significantly (p < 0.05) less available bone (6.03 ± 0.38 mm) in subjects with age ≥54 years. The IAN follows a lingual course in the molar region and later flips to the buccal side in the premolar region. The LCPN dimension in the 1st and 2nd premolar region was found to be more than 6 mm irrespective of age, gender and side of the jaw. Thus, it can be considered as a suitable site for placing implants while bypassing the IAN with CBCT assessment remaining as the mainstay in the pre-surgical phase.

Effect of CBCT dose reduction on the mandibular canal visibility: ex vivo comparative study

OBJECTIVES

To compare the difference in mandibular canal (MC) visibility using three different cone beam computed tomography (CBCT) acquisition protocols: high resolution (HR), standard resolution (ST) and Quick scan+ (QS+).

METHODS

Twenty-five human dry mandibles were scanned by one CBCT machine; i-CAT FLX (Imaging Sciences International, Hatfield, PA, USA), using three different acquisition protocols: high-resolution (HR), standard (ST) and Quick scan+ (QS+). DICOM data were transferred to a third party software Ondemand 3D (Cybermed Co., Seoul, Korea). The fusion module was used to superimpose images derived from different acquisition protocols to standardize the areas to compare the MC visibility. Comparison was performed at nine selected cross sections extending from an area distal to the third molar posteriorly to the first premolar anteriorly. Two expert radiologists evaluated the degree of MC visibility using five-scale scoring system.

RESULTS

There was a statistically significant difference between the three acquisition protocols (HR, ST, QS+) at all investigated areas regardless of dentition status (p value < 0.001-0.034) except at the MR1M area where there was no statistically significant difference (p value = 0.094). HR protocol showed the highest prevalence of fully and partially corticated MC at almost all investigated areas while QS+ protocol showed the highest prevalence of invisible MC and clear and unclear non-corticated MC at almost all investigated areas.

CONCLUSIONS

QS+ protocol of i-CAT FLX CBCT machine is a recommended low-dose CBCT acquisition protocol for MC visibility at dentulous posterior mandibular regions while ST protocol is recommended at edentulous areas.