Preoperative application of limited cone beam computerized tomography as an assessment tool before minor oral surgery

CBCT in Dental Implantology: A Key Tool for Preventing Peri-Implantitis and Enhancing Patient Outcomes

(1) Introduction: Trust is a cornerstone of the patient-physician relationships. Unforeseen complications in the health care system could jeopardize patients' trust in their physicians. (2) Aim: This article presents a quantitative figure regarding foreseeing the necessity of a three-dimensional quantitative visualization of bone structure and concurrently preparing for an ancillary procedure by a dentist to successfully perform the surgery that could minimize unforeseen complications; (3) Materials and method: This retrospective study has been derived based on an analysis of 1134 patients who had received 4800 dental implants from January 2001 to August 2020, out of which 200 cases were randomly selected for this study. Each procedure during implant treatment was categorized as OPG (Orthopantomography) or OPG with CBCT as per all the procedures which included and were coded as follows, 1: Surgery & Restoration, 2: GBR (Guided Bone Regeneration), 3: GTR (Guided Tissue Regeneration), 4: Block Bone Graft, 5: Spreading, 6: Splitting, 7: Internal Sinus, 8: External Sinus, 9: PRF (Platelet Rich Fibrin). Any of the 200 cases in which implant placement could not have been performed for reasons related to a lack of CBCT were selected for this study. The surgery was aborted halfway through without implant placement in these cases due to a lack of bone quantity and/or lack of primary stability. These cases were registered for re-evaluation and statistical analysis; (4) Results: 7% of the cases that used OPG alone led the surgeon to unexpectedly abort in the middle of the surgery without implant placement. All (100%) of the patients who had CBCT during treatment planning were able to receive implants during the surgery. None of the patients left the surgery without receiving implants if CBCT was used (0%); (5) Discussion: Radiographic image quality is defined as the amount of information within the image that allows the radiologist to make a diagnostic decision with a particular level of certainty (Martin et al., 1999) and hence the importance of CBCT. The unexpected 7% of devastating situations for patients who started surgery but did not have implant placement led to [A] aborting the surgery, [B] procedural difficulties requiring an alternative treatment plan, [C] a negative impact on the patient's behavior, and [D] wanting to change doctor due to a lack of trust; (6) Conclusion: This study indicates that in implant dentistry patients' mistrust could be avoided by 7% if CBCT is obtained. It also shows the significance of cone-beam computed tomography as an adjunct to panoramic radiography during the diagnosis and treatment planning phase. The use of panoramic radiography alone can lead to a 7% likelihood of misdiagnosis. A lack of CBCT during treatment planning negatively affects the outcome of surgical procedures.

Relationship between Impacted Mandibular Third Molars and the Mandibular Canal on CBCT Scans

This study aimed to assess the relationship of impacted mandibular third molars with the mandibular canal on cone beam computed tomography (CBCT) scans. This cross-sectional study was conducted on CBCT scans of 137 patients with 204 impacted mandibular third molars. The relation of age, gender, class of impaction, anatomical position of canal relative to tooth (buccal, lingual, inferior, inter-radicular), tooth angulation (mesioangular, vertical, distoangular, horizontal), relationship of tooth with the mandibular canal (no contact, in contact, relation), relationship of tooth with the mandibular cortex, anatomical site of contact of tooth with the mandibular cortex (buccal, lingual, inferior), and the impression of canal (grooving, no effect) on impacted teeth were evaluated. Data were analyzed using one-way ANOVA, Chi-square test and Fisher's exact test. Class B of impaction (78.9%), inferior position of canal relative to the impacted tooth (53.9%) and mesioangular angulation (53.4%) had the highest frequency, respectively. The relationship of tooth with the mandibular canal was "relation" in most cases (53.4%) followed by no contact (26.9%) and in contact (19.6%). Significant associations were noted between depth of impaction (P < 0.001), tooth angulation (P = 0.024), anatomical position of canal relative to tooth (P < 0.001), relationship of tooth with the mandibular cortex (P = 0.032) and anatomical site of contact of tooth with the mandibular cortex (P = 0.013) with the impacted tooth-mandibular canal relationship. CBCT provides accurate information about the relationship of impacted third molars with the mandibular canal and can decrease the risk of traumatization of inferior alveolar nerve (IAN) during their surgical extraction.

Assessment of Accessory Canals and Foramina in the Mandibular Arch Using Cone-Beam Computed Tomography and a New Classification for Mandibular Accessory Canals

Objectives

The objectives of the study include the following: (i) to assess the presence of accessory canals and foramina in the body of the mandible using cone-beam computed tomography (CBCT), (ii) to evaluate the location, number, diameter, and length of accessory canals in the body of the mandible, and (iii) to propose a new classification for mandibular accessory canals based on the location.

Methods

A total of 50 (25 males and 25 females) CBCT scans were analyzed in three anatomical planes and three-dimensional (3D) reconstructions for the exact number, location, diameter, and accessory length canals and accessory foramina in the body of the mandible. The statistical analysis used was an independent t-test.

Results

Out of 50 CBCT scans, a total of 243 accessory canals and 245 accessory foramina were found. About 53% of accessory canals and foramina were found in males, while 47% were observed in females; 89% were evident in the anterior region, and only 11% were in the posterior region. The majority (64%) of the medial lingual canals had a diameter greater than or equal to 1 mm, while only 32% of accessory canals had a diameter of less than 1 mm (p < 0.05). The mean length of median lingual canals in females was 1.2910 ± 0.2582 mm and 2.6438 ± 0.5288 mm in male subjects. Mandibular accessory canals are classified broadly into anterior and posterior accessory canals, which have further subdivisions.

Conclusion

CBCT plays a dynamic role in determining the mandible location of various neurovascular structures, including accessory canals and foramina. Female subjects were observed with more accessory canals and foramina and more common in the anterior region than in the posterior region.

Flat-panel conebeam CT in the clinic: history and current state

Research into conebeam CT concepts began as soon as the first clinical single-slice CT scanner was conceived. Early implementations of conebeam CT in the 1980s focused on high-contrast applications where concurrent high resolution ( < 200    μ m ), for visualization of small contrast-filled vessels, bones, or teeth, was an imaging requirement that could not be met by the contemporaneous CT scanners. However, the use of nonlinear imagers, e.g., x-ray image intensifiers, limited the clinical utility of the earliest diagnostic conebeam CT systems. The development of consumer-electronics large-area displays provided a technical foundation that was leveraged in the 1990s to first produce large-area digital x-ray detectors for use in radiography and then compact flat panels suitable for high-resolution and high-frame-rate conebeam CT. In this review, we show the concurrent evolution of digital flat panel (DFP) technology and clinical conebeam CT. We give a brief summary of conebeam CT reconstruction, followed by a brief review of the correction approaches for DFP-specific artifacts. The historical development and current status of flat-panel conebeam CT in four clinical areas-breast, fixed C-arm, image-guided radiation therapy, and extremity/head-is presented. Advances in DFP technology over the past two decades have led to improved visualization of high-contrast, high-resolution clinical tasks, and image quality now approaches the soft-tissue contrast resolution that is the standard in clinical CT. Future technical developments in DFPs will enable an even broader range of clinical applications; research in the arena of flat-panel CT shows no signs of slowing down.

Unicystic Ameloblastoma in a Child Treated with a Combination of Conservative Surgery and Orthodontic Treatment: A Case Report

Unicystic ameloblastoma (UAM) is a variant of intraosseous ameloblastoma that occurs as a single cystic cavity. This report describes a case of UAM of the mandible in a seven-year-old girl. The lesion radiographically mimicked a dentigerous cyst. Under the primary diagnosis of a dentigerous cyst, marsupialization was performed to erupt the first molar involved in the cystic lesion and to obtain a definitive diagnosis. The biopsy specimen revealed ameloblastoma. During careful observation, orthodontic treatment, which was performed to upright and promote the eruption of the first molar involved in the tumor, maintained the space needed for enucleation of the tumor. Finally, the second primary molar was extracted, and the lesion was enucleated at 3 years and 4 months after marsupialization. The results of the histological examination revealed UAM. Conclusively, the treatment course not only avoids a resection of the mandible but also induces eruption of the teeth involved in the tumor. Thus, the combination of conservative surgery and orthodontic treatment was effective in the management of UAM that mimics a dentigerous cyst.

Citation Classics in Cone Beam Computed Tomography: The 100 Top-Cited Articles

Aim

The purpose of this study was to identify and characterize the 100 most cited articles on cone beam computed tomography (CBCT).

Materials and Methods

A comprehensive list of citation classics in CBCT was generated by searching the Scopus database without year or language restrictions. The top 100 articles were retrieved after reading abstracts or full texts. The following study variables were evaluated: number of citations, citation density, journal name, impact factor, category and quartile of journals, publication year, authors with their affiliations, article type, and topics covered.

Results

The citation number ranged from 86 to 624, with a mean of 161.9 citations per article. The top 100 articles were distributed in 29 journals, and the journal with the most articles was Dentomaxillofacial Radiology (n=16). The articles were published between 1998 and 2012, and eight authors published more than 3 papers. The USA produced the most papers (n=38), followed by the UK (n=12). King's college London Dental Institute led the list of classics, with 8 articles.

Conclusions

This is the first citation analysis to provide a detailed list of the most influential articles on CBCT and helps to recognize the quality of the works, discoveries, and trends steering the field.

Imaging Factors Impacting on Accuracy and Radiation Dose in 3D Printing

Objectives

To compare reconstructed area and surface roughness of 3D models acquired using nine image acquisition protocols. Radiation dose was also compared among acquisition protocols.

Methods

A dry craniofacial specimen was scanned using three CT devices (a cone beam CT, a 16-channel fan beam CT, and a 64-channel fan beam CT), with three different acquisition protocols each. Nine 3D models were manufactured using polylactic acid. Surface roughness and reconstructed area were determined for each 3D model. The radiation dose during acquisitions was measured using lithium crystals. ANOVA was used to compare the data among the 3D models. Linear function optimization techniques based on stochastic variables were applied to identify the most suitable protocol for use.

Results

For surface roughness, statistically significant differences were observed among all 3D models and the specimen. For reconstructed area, CBCT and one CT-16 channel protocols originated 3D models statistically significant different from the specimen. Higher radiation doses were observed with fan beam CT acquisitions.

Conclusions

All three CT devices were suitable for 3D printing when used at full resolution. The highest reconstruct area vs. radiation dose ratio was found for 64-channel CT devices.

Coronectomies: assessment and treatment planning

Coronectomy procedures are widely carried out in secondary care, involving the removal of the dental crown, while retaining the roots in situ. This paper defines and explains the rationale behind coronectomy. It also seeks to review the indications for referral of wisdom teeth, and how to identify high-risk wisdom teeth radiographically using two- and three-dimensional imaging. Using this information, this article aims to provide the practitioner with information on short- and long-term management of high-risk wisdom teeth and discusses coronectomy versus extraction. It also discusses the complications of coronectomy and the importance of adequate consent.

Comparing panoramic radiographs and cone beam computed tomography: Impact on radiographic features and differential diagnoses

OBJECTIVES

The aims of this study were to determine whether lesion features appear differently on panoramic radiography (PAN) and cone beam computed tomography (CBCT), and whether the use of CBCT affects diagnostic accuracy and observers' confidence in comparison with PAN.

STUDY DESIGN

Three oral and maxillofacial radiologists reviewed 33 sets of PAN images and CBCT volumes of biopsy-proven lesions. They described 12 different lesion features and provided up to 3 ranked differential diagnoses, as well as their confidence with respect to those diagnoses. Their confidence was weighted by the rank at which the correct diagnosis was provided.

RESULTS

Odds ratios (ORs) were statistically significant for border definition (OR = 5.45; P = .004), continuity of border cortication (OR = 0.34; P = .035), effect on neurovascular canals (OR = 6.38; P = .043), expansion (OR = 18.56; P < .001), cortical thinning (OR = 30.22; P < .001), and cortical destruction (OR = 9.80; P < .001). There was no association between the 2 modalities and the rank at which the correct differential diagnoses were made or the observers' weighted confidence.

CONCLUSIONS

Before acquiring a CBCT scan to aid in the diagnosis of an intraosseous lesion, clinicians should consider the diagnostic information that is expected to be gained. In this study, although there were differences between PAN and CBCT with respect to some lesion features, CBCT did not help improve diagnostic accuracy.

Evaluation of factors influencing the success rate of orthodontic microimplants using panoramic radiographs

Objective

The purpose of this study was to investigate factors influencing the success rate of orthodontic microimplants (OMIs) using panoramic radiographs (PRs).

Methods

We examined 160 OMIs inserted bilaterally in the maxillary buccal alveolar bone between the second premolars and first molars of 80 patients (51 women, 29 men; mean age, 18.0 ± 6.1 years) undergoing treatment for malocclusion. The angulation and position of OMIs, as well as other parameters, were measured on PRs. The correlation between each measurement and the OMI success rate was then evaluated.

Results

The overall success rate was 85.0% (136/160). Age was found to be a significant predictor of implant success (p < 0.05), while sex, side of placement, extraction, and position of the OMI tip were not significant predictors (p > 0.05). The highest success rate was observed for OMIs with tips positioned on the interradicular midline (IRML; central position). Univariate analyses revealed that the OMI success rate significantly increased with an increase in the OMI length and placement height of OMI (p = 0.001). However, in simultaneous analyses, only length remained significant (p = 0.027). Root proximity, distance between the OMI tip and IRML, interradicular distance, alveolar crest width, distance between the OMI head and IRML, and placement angle were not factors for success. Correlations between the placement angle and all other measurements except root proximity were statistically significant (p < 0.05).

Conclusions

Our findings suggest that OMIs positioned more apically with a lesser angulation, as observed on PRs, exhibit high success rates.

Analyses of anatomical relationship between mandibular third molar roots and variations in lingual undercut of mandible using cone-beam computed tomography

Background/purpose

Anatomical features of the lingual undercut region is a potential factor that might increase the risk of displacement of a tooth or fragment. The aim of this study was to report the normal anatomical relationship of impacted lower third molar roots to the lingual cortex and soft tissues of mandible and anatomical variations of lingual balcony in the impacted third molar region.

Materials and methods

One hundred impacted third molars (54 males, 46 females) from 65 (31 men, 34 women) patients were evaluated for this study using cone-beam computed tomography. Three measurements [bone thickness, angle (Ang) 1 and Ang 2] were recorded on the coronal section slices of cone-beam computed tomography images; in these images, the impacted third molar root was closest to the lingual soft tissues.

Results

The average distance between the tooth root and the lingual outer cortical bone layer (bone thickness) was 1.03 mm. The averages of Ang 1 and Ang 2 were 140.61° and 153.44°. Ang 1 and Ang 2 of female patients were larger than those of male patients.

Conclusion

The narrow angulation of the lingual balcony region and the relationship between roots and lingual soft tissues should be noted to avoid undesirable complication of displacement of a tooth or fragment into sublingual, submandibular, and pterygomandibular spaces. There was no relation in the floor of the mouth between the position of the impacted third molar roots and different lingual undercut angulation variations.

Cone Beam CT in Diagnosis and Surgical Planning of Dentigerous Cyst

Diagnosis and preoperative planning are critical in the execution of any surgical procedure. Panoramic radiography is a routine method used in dentistry to assist clinical diagnosis; however, with this technique 3D anatomical structures are compressed into 2D images, resulting in overlapping of structures which are of interest in the diagnosis. In this study we report the case of a patient who presented with a dentigerous cyst of expressive dimensions in the body of the mandible region. The surgery was planned and executed after observing the margins of the lesion by Cone Beam Computed Tomography (CBCT). We conclude that CBCT is a precise method to help diagnosis; it provides greater accuracy in surgical treatment planning through 3D image display, allowing more effective results.

Correlating the clinical assessment of impacted mandibular third molars with panoramic radiograph and intraoral periapical radiograph

Aims And Objectives:

This study was conducted to compare the clinical assessment of impacted third molars of mandible with panaromic radiograph (OPG) and intraoral periapical radiograph (IOPA) and to assess the efficacy of IOPA and. Moreover, we corroborated the OPG and IOPA findings of impacted mandiblar third molar root apex to inferior alveolar canal.

Materials and Methods:

A total of 200 patients with pericoronitis were examined who were indicated for surgical extraction, among which 50 patients were selected for the study. All the patients underwent a radiographic survey with a digital OPG and IOPA of impacted mandibular third molars, along with clinical survey for anatomic relationship, type of impaction, space available, position in relation to second molar, number of roots, root curvature, and proximity of nerve canal. The data was subjected to statistical analysis. The Statistical Package for Social Sciences version 4.0.1 software was used for analyzing the collected data.

Results:

The study revealed that IOPA was more accurate in determining a majority of the factors affecting the third molar surgery, including relationship of the external oblique ridge (IOPA vs OPG = 96%:90%), anteroposterior relation with ramus (IOPA vs OPG = 70%:66%), vertical depth of impaction (IOPA vs OPG = 72%:68%), number of roots (P = 0.013), morphology of roots (IOPA vs OPG = 96%:90%); however, OPG was found to be accurate in evaluating the type of impaction (IOPA vs OPG = 88%:94%), canal relation, along with root of impacted molar (IOPA vs OPG = 74%:86%).

Conclusion:

To conclude, although IOPA has a marginal angle over OPG in assessing various parameters, only the number of roots have a greater accuracy (P < 0.0013) in IOPA than with OPG. However, the OPG is the better choice to be considered when the patient is associated with trismus.

Comparison of Cone Beam Computed Tomography and Multi Slice Computed Tomography Image Quality of Human Dried Mandible using 10 Anatomical Landmarks

INTRODUCTION

Cone Beam Computed Tomography (CBCT) has gained a broad acceptance in dentomaxillofacial imaging. Computed Tomography (CT) is another imaging modality for diagnosis and preoperative assessments of the head and neck region.

AIM

Considering the increased radiation exposure and high cost of CT, this study sought to subjectively assess the image quality of CBCT and Multi Slice CT (MSCT).

MATERIALS AND METHODS

A dry human mandible was scanned by five CBCT systems (New Tom 3G, Scanora, CRANEX 3D, Promax and Galileos) and one MSCT system. Three independent oral and maxillofacial radiologists reviewed the CBCT and MSCT scans for the quality of 10 landmarks namely mental foramen, trabecular bone, Periodontal Ligament (PDL), dentin, incisive canal, mandibular canal, dental pulp, enamel, lamina dura and cortical bone using a five-point scale.

RESULTS

Significant differences were found between MSCT and CBCT and among the five CBCT systems (p<0.05) in visualization of different anatomical structures. A fine structure such as the incisive canal was significantly less visible and more variable among the systems in comparison with other anatomical landmarks such as the mental foramen, mandibular canal, cortical bone, dental pulp, enamel and dentin (p<0.05). The Cranex 3D and Promax systems were superior to MSCT and all other CBCT systems in visualizing anatomical structures.

CONCLUSION

The CBCT image quality was superior to that of MSCT even though some variability existed among different CBCT systems in visualizing fine structures. Considering the low radiation dose and high resolution, CBCT may be beneficial for dentomaxillofacial imaging.

The effect of milliamperage, number of basis images, and export slice thickness on contrast-to-noise ratio and detection of mandibular canal on cone beam computed tomography scans: an in vitro study

OBJECTIVES

The aim of this study was to evaluate the effect of milliamperage, number of basis images, and export slice thickness on contrast-to-noise ratio (CNR) and confidence in detecting mandibular canal.

STUDY DESIGN

Two phantoms were used. Each phantom consisted of a dry mandible with an epoxy resin bone tissue substitute block and a water-equivalent block, submerged in water. Each mandible was scanned with a Morita 3D Accuitomo cone beam computed tomography (CBCT) machine (Morita, Kyoto, Japan). Scans were made with 180-degree and 360-degree rotations, at 4, 6, and 8 mA. Each scan was exported in Digital Imaging and Communications in Medicine (DICOM) format at slice thicknesses of 0.125 mm, 0.25 mm, 0.75 mm, and 1.0 mm, resulting in 24 image sets for each phantom. The CNR was calculated. Variables were analyzed using factorial analysis of variance. The scans were also evaluated by five observers who were asked to state their confidence in detecting the mandibular canal on a four-point confidence scale.

RESULTS

Increasing the number of basis images, milliamperage, or export slice thickness significantly increased the CNR. Reducing the export slice thickness improved observers' confidence in detecting the mandibular canal.

CONCLUSIONS

The CBCT acquisition settings should be carefully chosen, depending on specific diagnostic tasks. The lowest slice thickness equal to the voxel size should always be used for exporting CBCT data despite the higher noise.

Noninvasive differential diagnosis of dental periapical lesions in cone-beam CT scans

PURPOSE

This paper proposes a novel application of computer-aided diagnosis (CAD) to an everyday clinical dental challenge: the noninvasive differential diagnosis of periapical lesions between periapical cysts and granulomas. A histological biopsy is the most reliable method currently available for this differential diagnosis; however, this invasive procedure prevents the lesions from healing noninvasively despite a report that they may heal without surgical treatment. A CAD using cone-beam computed tomography (CBCT) offers an alternative noninvasive diagnostic tool which helps to avoid potentially unnecessary surgery and to investigate the unknown healing process and rate for the lesions.

METHODS

The proposed semiautomatic solution combines graph-based random walks segmentation with machine learning-based boosted classifiers and offers a robust clinical tool with minimal user interaction. As part of this CAD framework, the authors provide two novel technical contributions: (1) probabilistic extension of the random walks segmentation with likelihood ratio test and (2) LDA-AdaBoost: a new integration of weighted linear discriminant analysis to AdaBoost.

RESULTS

A dataset of 28 CBCT scans is used to validate the approach and compare it with other popular segmentation and classification methods. The results show the effectiveness of the proposed method with 94.1% correct classification rate and an improvement of the performance by comparison with the Simon's state-of-the-art method by 17.6%. The authors also compare classification performances with two independent ground-truth sets from the histopathology and CBCT diagnoses provided by endodontic experts.

CONCLUSIONS

Experimental results of the authors show that the proposed CAD system behaves in clearer agreement with the CBCT ground-truth than with histopathology, supporting the Simon's conjecture that CBCT diagnosis can be as accurate as histopathology for differentiating the periapical lesions.

Comparative evaluation of mandibular canal visibility on cross-sectional cone-beam CT images: a retrospective study

OBJECTIVES

The purpose of this study was to determine the visibility of the mandibular canal (MC) in CBCT images and if the visibility of the MC is affected by gender, location and/or age.

METHODS

CBCT images were evaluated for the visibility of the MC by a board-certified oral and maxillofacial radiologist, a board-certified periodontist and a periodontics resident. Representative slices were examined for the first premolar (PM(1)), second premolar (PM(2)), first molar (M(1)) and second molar (M(2)) sites by all examiners. The visibility of the MC was registered as either present or absent.

RESULTS

360 total CBCT cross-sectional images were examined, with the MC identified in 204 sites (56%). Age had a significant effect on MC visibility, but it differed by location: for PM(1), age 47-56 had lower visibility than age 65+ (p = 0.0377). Gender also had a significant effect on canal visibility, where females had lower visibility than males overall (p = 0.0178) and had the most pronounced difference for PM(1) (p = 0.0054). Location had a significant effect on visibility, but it differed by age and by gender: for age 65+, M(2) had lower visibility than PM(1) (p = 0.0411) and PM(2) (p = 0.0180), while for females, PM(1) had lower visibility than M(1) (p = 0.0123) and M(2) (p = 0.0419).

CONCLUSIONS

The MC was visualized only in just over half of the CBCT images. Age, gender and location had significant effects on the visibility.

A retrospective radiographic evaluation of the anterior loop of the mental nerve: comparison between panoramic radiography and cone beam computerized tomography

Objectives: To compare the prevalence and the length of mental loop, measured with panoramic radiography (PR) and cone beam computerized tomography (CBCT). Material and Methods: PG and CBCT images where analyzed by a single calibrated examiner to determine the presence and the position of the mental foramen (MF), its distance to the lower mandible border, the anterior length of the mental loop (ML) and the bone quality in 82 PR and 82 CBCT. Results: ML was identified in 36.6 % of PR and 48.8 % of CBCT. PR showed a magnification of 1.87 when compared to CBCT. The mean of anterior extension of the inferior alveolar nerve and the distance to the inferior border of the mandible was higher for PR (2.8 mm, sd 0.91 mm on the PR , range 1.5 to 4.7 mm and 1.59, sd 0.9 on the CBCT ,range 0.4 to 4.0 mm) Conclusions: There is a magnification in PR images with respect to those of CBCT. The differences between CBCT and PR with regards to the identification and length of the ML are not statistically significant. Identification and accuracy measurements of ML did not depend on the bone quality. Considering that two dimensional imaging provides less accurate and reliable information regarding the anterior loop, a CBCT scan could be recommended when planning implant placement in the anterior region.

Key words:Mental loop, mental nerve, mental canal, preoperative implant planning, panoramic tomography, cone beam computerized tomography.

CBCT Evaluation of Bony Nasal Pyramid Dimensions in Iranian Population: A Comparative Study with Ethnic Groups

Background. The aim of the present study was to have normative data of nasal bone thickness for use before reconstructive surgery and nasal augmentation through radiography analysis. Methods and Materials. In this descriptive-analytical study, 74 patients were selected from people referred to Radiology Department of Isfahan University for CBCT examination in 2012. Patients with a history of nasal surgery or facial trauma and known congenital anomaly were excluded from the study. Height of nasal bone and width of pyriform aperture and nasal bone thickness in lateral and medial osteotomy line were measured. All these measurements were repeated by two radiologists; finally one sample t-test was performed. Results. The mean thickness of nasal bone on the lateral osteotomy line was 1.92 ± 0.29 mm in females and 1.73 ± 0.32 mm in males (P value = 0.39). The mean thickness of medial osteotomy line was 1.63 ± 0.47 mm in females and 1.94 ± 0.19 mm in males (P value = 0.31). The mean length of nasal bone was 23.5 ± 3.34 mm in females and 25.7 ± 2.96 mm in males (P value = 0.11). The mean width of pyriform aperture was 23.77 ± 2.58 mm in females and 25.67 ± 1.79 mm in males (P value = 0.25). Conclusions. The dimensions of nasal pyramid are known to be significant in choosing suitable osteotome size for reducing surgery side effect. Our results can be used for preoperative estimation of nasal bone dimension of people undergoing reconstructive surgery and augmentation.

Configuration of the inferior alveolar canal as detected by cone beam computed tomography

AIMS

The aim of this study is to evaluate the course of the inferior alveolar canal (IAC) including its frequently seen variations in relation to root apices and the cortices of the mandible at fixed pre-determined anatomic reference points using cone beam volumetric computed tomography (CBVCT).

MATERIAL AND METHODS

This retrospective study utilized CBVCT images from 44 patients to obtain quantifiable data to localize the IAC. Measurements to the IAC were made from the buccal and lingual cortical plates (BCP/LCP), inferior border of the mandible and the root apices of the mandibular posterior teeth and canine. Descriptive analysis was used to map out the course of the IAC.

RESULTS

IACs were noted to course superiorly toward the root apices from the second molar to the first premolar and closer to the buccal cortical plate anteriorly. The canal was closest to the LCP at the level of the second molar. In 32.95% of the cases, the canal was seen at the level of the canine.

CONCLUSIONS

This study indicates that caution needs to be exercised during endodontic surgical procedures in the mandible even at the level of the canine. CBVCT seems to provide an optimal, low-dose, 3D imaging modality to help address the complexities in canal configuration.

Remodeling of autogenous bone grafts after osteotome sinus floor elevation assessed by limited cone beam computed tomography

This study assessed the radiographic appearance of bone graft domes longitudinally after osteotome sinus floor elevation using cone beam computed tomography (CBCT). This study presents the radiological findings of a 6-month follow-up CBCT study in maxillary osteotome sinus floor elevation. We examined 52 patients with a crestal bone height of less than 8 mm in the posterior maxilla who required sinus augmentation. Implants (n = 91) were subsequently placed in regenerated bone following osteotome sinus floor elevation; autogenous bone was used as the augmentation material. In all cases, the grafted augmentation material tended to be absorbed, but at least 1 mm of grafted augmentation material was recognized around the implant fixtures on CBCT at the second implant operation. The border between the grafted augmentation material and the existing bone was indistinct. The grafted area apical to the implants undergoes shrinkage and remodeling. It was suggested that sufficient grafted autogenous bone changes into bone to support an implant.

Three-dimensional images contribute to the diagnosis of mucous retention cyst in maxillary sinus

OBJECTIVE

To evaluate the detection of mucous retention cyst of maxillary sinus (MRCMS) using panoramic radiography and cone beam computed tomography (CBCT).

STUDY DESIGN

A digital database with 6,000 panoramic radiographs was reviewed for MRCMS. Suggestive images of MRCMS were detected on 185 radiographs, and patients were located and invited to return for follow-up. Thirty patients returned, and control panoramic radiographs were obtained 6 to 46 months after the initial radiograph. When MRCMS was found on control radiographs, CBCT scans were obtained. Cysts were measured and compared on radiographs and scans. The Wilcoxon, Spearman and Kolmorogov-Smirnov tests were used for statistical analysis. The level of significance was set at 5%.

RESULTS

There were statistically significant differences between the two methods (p<0.05): 23 MRCMS detected on panoramic radiographs were confirmed by CBCT, but 5 MRCMS detected on CBCT images had not been identified by panoramic radiography. Eight MRCMS detected on control radiographs were not confirmed by CBCT. MRCMS size differences from initial to control panoramic radiographs and CBCT scans were not statistically significant (p= 0.617 and p= 0.626). The correlation between time and MRCMS size differences was not significant (r = -0.16, p = 0.381).

CONCLUSION

CBCT scanning detect MRCMS more accurately than panoramic radiography.

Identification of the mental neurovascular bundle: a comparative study of panoramic radiography and computer tomography

OBJECTIVES

To compare the images of the mental canal in panoramic radiography (PR) and computed tomography (CT) by analyzing the concordance with diagnostic tests and examiners.

MATERIAL AND METHODS

The position of the mental foramen (MF), distance to the lower mandibular border, anterior length of the mental loop (ML), agreement between examiners and diagnostic concordance were registered in 50PR and 50CT.

RESULTS

ML was identified (34.5/41%, PR/CT). PR magnification was 36.6% higher than in CT. The anterior extension and distance to the inferior border of the MF was higher for PR (2-6.2 mm). Inter-examiner agreement on CT was good (κ = 0.628) and very good on PR (κ = 0.845).

CONCLUSION

There is a magnification (36.6%) of the images in PR with respect to the CT. Identification of MF and ML is not related to the bone quality. Inter-examiner agreement is better on PR.

Accuracy of linear measurements of galileos cone beam computed tomography in normal and different head positions

Introduction. The aim of this study was to determine the accuracy of linear measurements in dry human skulls in ideal position and different deviated positions of the skull. Methods. 6 dry human skulls were included in the study. Opaque markers were attached to alveolar bone. Buccolingual and mesiodistal distances and heights were measured in 5 different regions of either jaws using a digital caliper. Radiographic distances were measured in ideal, rotation, tilt, flexion, and extension positions of the skulls. The physical and radiographic measurements were compared to estimate linear measurement accuracy. Results. The mean difference between physical measurements and radiographic measurements was 0.05 ± 0.45. There was a significant difference between physical measurements and radiographic measurements in ideal, rotation, tilt, and extension positions (P   value < 0.05). Conclusions. The accuracy of measurements in GALILEOUS CBCT machine varies when the position of the skull deviates from ideal; however, the differences are not clinically significant.

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

Purpose

The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them.

Materials and Methods

Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report.

Results

The effective dose was the highest for Somatom Sensation 10 (425.84 µSv), followed by AZ3000CT (332.4 µSv), Somatom Emotion 6 (199.38 µSv), and 3D eXaM (111.6 µSv); it was the lowest for Implagraphy (83.09 µSv). The CBCT showed significant variation in dose level with different device.

Conclusion

The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Antrum Approach Planning for Removal of Impacted Tooth Using Cone-Beam Computed Tomography

Due to the great number of structures in the maxillofacial region, cone-beam computed tomography (CBCT) is an important procedure in presurgical planning for removal of impacted teeth. Most of the information provided by this imaging technique cannot be visualized in conventional radiographs. In addition, CBCT reduces patient exposure to radiation in comparison with helical computed tomography and provides dental practitioners with easy access. We report the clinical case of a patient who underwent a surgical procedure for removal of an impacted maxillary premolar. CBCT-assisted presurgical treatment was used, enabling a more conservative surgical access, a less traumatic and less time consuming procedure than conventional surgical intervention.

Comparative study between conventional and cone beam CT-synthesized half and total skull cephalograms

OBJECTIVES

The aim of this study was to compare cephalometric measurements obtained from conventional cephalograms with total and half-skull synthesized cone beam CT (CBCT) cephalograms.

METHODS

Cephalometric analyses of 30 clinically symmetric patients were conducted by a calibrated examiner on conventional and CBCT-synthesized cephalograms (total, right and left). Reproducibility was investigated using the intraclass correlation coefficient (ICC). The Bland-Altman analysis was used to assess the agreement of the measurements from each factor obtained by conventional, total, right and left CBCT-synthesized cephalograms.

RESULTS

The ICC was above 0.9 for most of the 40 cephalometric factors analysed, revealing similar levels of reproducibility. When the measurements obtained from conventional and CBCT-synthesized cephalograms were compared, the Bland-Altman analysis showed a strong agreement between them.

CONCLUSIONS

Half-skull CBCT-synthesized cephalograms offer the same diagnostic performance and equivalent reproducibility in terms of cephalometric analysis as observed in conventional and total CBCT-synthesized cephalograms.

Accuracy of bone surface size and cortical layer thickness measurements using cone beam computerized tomography

OBJECTIVES

The purpose of this study was to determine the accuracy of Cone Beam Computerized Tomography (CBCT) reconstructions in displaying bone surface size and cortical layer thickness.

MATERIALS AND METHODS

Two fresh frozen cadaver heads were scanned using a CBCT (i-CAT(™) 3D Imaging System; Imaging Sciences International Inc.). The mandibles were sectioned and digitalized for histological evaluation. Dimensions as measured on these sections were compared with CBCT measurements of the same region with the use of 3D image-based planning software (Procera System NobelGuide(™); Nobel Biocare). To allow optimal comparison between histological and CBCT sections, reference markers were placed into the mandibles. The Student t-test was utilized to analyze the data. Differences with P-values <0.05 were considered significant.

RESULTS

The total height and width of the mandibular body, as measured on CBCT views, were larger compared with the histological values with a maximum difference of 0.33 mm (SD ± 0.34). Cortical thickness measurements were significantly thicker on CBCT sections (P < 0.006) with absolute differences ranging up to ±0.63 mm (SD ±0.28) and relative differences ranging up to 82.6%.

CONCLUSION

CBCT images (i-CAT 3D Imaging System), viewed on the planning software Procera System NobelGuide, tend to overestimate the anatomical truth in assessing both bone height and width; especially cortical thicknesses are depicted thicker than in reality. When using CBCT images for presurgical assessment, one should be aware of this phenomenon of exaggeration of dimensions.

Postoperative evaluation of grafted bone in alveolar cleft using three-dimensional computed tomography data

Objective : Postoperative evaluation of bone formation in the alveolar cleft by computed tomography imaging has been reported. We quantitatively evaluated bone grafts in the alveolar cleft preoperatively and postoperatively using three-dimensional data and superimposition of images. Subjects : A total of 12 patients with complete unilateral cleft lip and palate (six left-sided and six right-sided) were studied. Methods : Helical computed tomography scans were taken immediately before surgery and at 6 months after surgery and the DICOM files obtained were processed using Mimics and 3-matic software for three-dimensional data analysis. The preoperative and postoperative computed tomography data were superimposed, and the position and length of the unerupted canines and width of the alveolar cleft measured. Results : Strong and significant correlations were observed between bone formation in the alveolar cleft bone graft region and preoperative canine position (r  =  -.766, p < .01) and canine length (r  =  .681, p < .05). Stepwise multiple regression analysis demonstrated that only the preoperative canine position was independently and significantly correlated with bone formation in the alveolar cleft. Conclusion : These results indicate that the optimal timing for surgery is when the canine cusp is close to the alveolar plane.

Estimation of paediatric organ and effective doses from dental cone beam CT using anthropomorphic phantoms

OBJECTIVES

Cone beam CT (CBCT) is an emerging X-ray technology applied in dentomaxillofacial imaging. Previous published studies have estimated the effective dose and radiation risks using adult anthropomorphic phantoms for a wide range of CBCT units and imaging protocols.

METHODS

Measurements were made five dental CBCT units for a range of imaging protocols, using 10-year-old and adolescent phantoms and thermoluminescent dosimeters. The purpose of the study was to estimate paediatric organ and effective doses from dental CBCT.

RESULTS

The average effective doses to the 10-year-old and adolescent phantoms were 116 μSv and 79 μSv, respectively, which are similar to adult doses. The salivary glands received the highest organ dose and there was a fourfold increase in the thyroid dose of the 10-year-old relative to that of the adolescent because of its smaller size. The remainder tissues and salivary and thyroid glands contributed most significantly to the effective dose for a 10-year-old, whereas for an adolescent the remainder tissues and the salivary glands contributed the most significantly. It was found that the percentage attributable lifetime mortality risks were 0.002% and 0.001% for a 10-year-old and an adolescent patient, respectively, which are considerably higher than the risk to an adult having received the same doses.

CONCLUSION

It is therefore imperative that dental CBCT examinations on children should be fully justified over conventional X-ray imaging and that dose optimisation by field of view collimation is particularly important in young children.

The clinical relevance of bifid and trifid mandibular canals

Background

Bifid mandibular canals (BMC) and trifid mandibular canals (TMC) are variations on the normal anatomy with incidences ranging from 0.08% to 65.0%. Such aberrations have an important clinical impact. For example, an extra mandibular canal may explain inadequate anesthesia, especially when two mandibular foramina are involved. Furthermore, during mandibular surgery, a second, or even third, neurovascular bundle may be damaged causing paresthesia, neuroma development, or bleeding.

Case report

Two cases are presented in this article. One patient had a BMC on both sites, and the other patient had a TMC on one site and a BMC on the other site.

Discussion

Initial screening for the presence of a BMC or TMC can be executed by conventional panoramic radiography. BMCs or TMCs are diagnosed, before executing mandibular surgery; additional CBCT scanning is indicated.

Four curious cases of cone-beam computed tomography

Cone-beam computed tomography (CBCT) has become popular, and its many inherent advantages are indisputable. Nevertheless, CBCT is prescribed cautiously because the radiation dosage is higher than that of conventional radiography. When and to what extent should CBCT be prescribed for orthodontic patients? The purpose of this article is to present 4 curious cases in which a considerable discrepancy was found between the conventional panoramic radiograph and the CBCT view. Is it time to spare patients an unnecessary conventional panoramic radiograph and shift to CBCT for all patients?

Ability of two radiographic methods to identify the closeness between the mandibular third molar root and the inferior alveolar canal: a pilot study

OBJECTIVES

The aim was to compare the ability of two radiographic methods: the panoramic radiograph (PR) in combination with a 20-degree negative angle periapical radiograph (-20 degrees Pa) vs two periapical radiographs Pa + (-20 degrees Pa), in evaluating the closeness of the lower third molar root and the inferior alveolar canal.

METHODS

2 radiographic methods of 32 impacted third molars were used. Two untrained dental students evaluated the closeness of the association between the root tip of the lower third molar and the inferior alveolar canal, both when in contact and separated, using dental cone beam CT as the gold standard. The position of the inferior alveolar canal relative to the third molar root was also recorded. The sensitivities and specificities of these findings were evaluated. Kappa values were used to assess the intra- and interobserver reliability.

RESULTS

Of the 32 teeth, 23 (68.6%) showed contact between the root tip of the third molar and the inferior alveolar canal on dental cone beam CT, and 9 (31.4%) showed separation. The respective mean sensitivities of PR + (-20 degrees Pa) and Pa + (-20 degrees Pa) in detecting contact were 97.9% and 84.8% and the respective mean specificities in detecting separation were 16.7% and 44.4%. Intraobserver agreement in both techniques ranged from 0.69 to 0.94. The respective interobserver reliability was 0.88 in PR + (-20 degrees Pa) and 0.75 in Pa + (-20 degrees Pa).

CONCLUSIONS

Both the PR + (-20 degrees Pa) and the periapical vertical tube-shift technique Pa + (-20 degrees Pa) have high potential for detecting the closeness between the third molar root and the inferior alveolar canal.

Reproducibility of 3 different tracing methods based on cone beam computed tomography in determining the anatomical position of the mandibular canal

PURPOSE

To investigate the reproducibility of 3 different tracing methods to determine a reliable method to define the proper anatomical position of the mandibular canal based on cone beam computed tomography (CBCT) data.

MATERIALS AND METHODS

Five dentate and 5 edentate patients were selected at random from the CBCT database. Two independent observers traced both the left and the right mandibular canal using 3-dimensional image-based planning software (Procera System NobelGuide; Nobel Biocare, Göteborg, Sweden). All mandibular canals were traced using 3 different methods. Method I was based on coronal views, also known as cross-sections. Panorama-like reconstructions were the starting point for method II. The third method combined methods I and II.

RESULTS

With respect to interobserver reliability, no significant difference (P = .34) for the various methods was observed. The reproducibility was better in edentate than in dentate jaws (P = .0015). The difference between 2 tracings was the lowest for the combined method: within a range of 1.3 mm in 95% of the course of the canal. The most obvious deviations were mainly seen in the anterior part of the canal.

CONCLUSIONS

The best reproducible method for mandibular canal tracing is the combined method III. Between observers, still a mean 95th percentile deviation threshold of 1.3 mm (SD 0.384) is noted, indicating that a safety zone of 1.7 mm should be respected. When planning surgery on CBCT-based data, surgeons should be aware of the obvious deviations located in the region of the anterior loop of the canal.

Accuracy and precision of linear measurements in cone beam computed tomography Accuitomo tomograms obtained with different reconstruction techniques

OBJECTIVES

To assess the accuracy and precision of linear measurements, the influence of different object positions in cone beam CT (CBCT) images and the effect of different systems for reformatting and viewing the tomograms on measurement values.

METHODS

An object consisting of Plexiglas plates with metal spheres was radiographically examined in three positions using the CBCT unit Accuitomo. Tomograms were reformatted using the i-Dixel software and Sectra picture archiving and communication system (PACS) multiplanar reformatting (MPR). Two observers measured 20 linear distances in axial, frontal and sagittal planes. Physical measurements of actual distances by means of a digital caliper served as the gold standard.

RESULTS

For measurements performed on the Accuitomo and Sectra PACS workstations, the mean differences between repeated measurements were below 0.13 mm (standard deviation (SD) 0.13 mm) and 0.21 mm (SD 0.18 mm), respectively. Mean differences between the two observers were below 0.11 mm (SD 0.07 mm) and 0.15 mm (SD 0.09 mm). The mean difference between the gold standard and the basic position when using the Accuitomo workstation, was -0.08 mm (SD 0.21 mm) and for a deviated/rotated position -0.08 mm (SD 0.23 mm) and -0.09 mm (SD 0.20 mm). None was statistically significant (P > 0.05). For measurement performed on MPR tomograms using the Sectra PACS workstation, mean differences were -0.09 mm (SD 0.17 mm) for basic position, and -0.08 mm (SD 0.19 mm) and -0.13 mm (SD 0.15 mm) for deviated and rotated positions, respectively. The mean difference between gold standard and basic/rotated positions was statistically significant, with P = 0.032 and P = 0.002.

CONCLUSIONS

Our study confirms previous findings indicating that measurements in 3DX Accuitomo FPD (flat panel detector) tomograms show a high level of agreement with actual distances. Our findings suggest the possibility of minor distortion in tomograms reformatted by means of Sectra PACS MPR.