Accurate mandibular canal segmentation of dental CBCT using a two-stage 3D-UNet based segmentation framework.

OBJECTIVES: The objective of this study is to develop a deep learning (DL) model for fast and accurate mandibular canal (MC) segmentation on cone beam computed tomography (CBCT). METHODS: A total of 220 CBCT scans from dentate subjects needing oral surgery were used in this study. The segmentation ground truth is annotated and reviewed by two senior dentists. All patients were randomly splitted into a training dataset (n = 132), a validation dataset (n = 44) and a test dataset (n = 44). We proposed a two-stage 3D-UNet based segmentation framework for automated MC segmentation on CBCT. The Dice Similarity Coefficient (DSC) and 95% Hausdorff Distance (95% HD) were used as the evaluation metrics for the segmentation model. RESULTS: The two-stage 3D-UNet model successfully segmented the MC on CBCT images. In the test dataset, the mean DSC was 0.875 ± 0.045 and the mean 95% HD was 0.442 ± 0.379. CONCLUSIONS: This automatic DL method might aid in the detection of MC and assist dental practitioners to set up treatment plans for oral surgery evolved MC.

[Oral panorama reconstruction method based on pre-segmentation and Bezier function].

For patients with partial jaw defects, cysts and dental implants, doctors need to take panoramic X-ray films or manually draw dental arch lines to generate Panorama images in order to observe their complete dentition information during oral diagnosis. In order to solve the problems of additional burden for patients to take panoramic X-ray films and time-consuming issue for doctors to manually segment dental arch lines, this paper proposes an automatic panorama reconstruction method based on cone beam computerized tomography (CBCT). The V-network (VNet) is used to pre-segment the teeth and the background to generate the corresponding binary image, and then the Bezier curve is used to define the best dental arch curve to generate the oral panorama. In addition, this research also addressed the issues of mistakenly recognizing the teeth and jaws as dental arches, incomplete coverage of the dental arch area by the generated dental arch lines, and low robustness, providing intelligent methods for dental diagnosis and improve the work efficiency of doctors.

Prevalence of Favorable Anatomy for Palatal Emergence of an Immediate Implant in the Maxillary Central Incisor Post-Extraction Site.

The purpose of this study was to determine the prevalence of favorable anatomy for palatal emergence of an immediate flapless implant in the maxillary central incisor post-extraction site. Implants were virtually placed into maxillary central incisor sites using 3-dimensional implant planning software. Following a strict implant placement criterion to keep a safe distance to the buccal plate and other anatomical structures, sockets were assessed to determine their suitability for an implant emerging from the palatal aspect. From 321 patients included in this study, 62.3% presented a suitable socket anatomy for an immediate implant to be placed with an angulation suitable for a screw-retained crown. In 29% of the cases, the implants had to be labially tilted to maintain a minimum distance to the buccal plate; 8.7% were unsuitable for immediate implants due to anatomic limitations. The position and angulation for an immediate implant in the maxillary central incisor socket should be carefully assessed preoperatively with 3-dimensional images, as many sites will not be candidates for a palatal emergence and thus a screw-retained restoration.

New Method for Analysis of the Temporomandibular Joint Using Cone Beam Computed Tomography.

Modern dentistry commonly uses a variety of imaging methods to support diagnosis and treatment. Among them, cone beam computed tomography (CBCT) is particularly useful in presenting head structures, such as the temporomandibular joint (TMJ). The determination of the morphology of the joint is an important part of the diagnosis as well as the monitoring of the treatment results. It can be accomplished by measurement of the TMJ gap width at three selected places, taken at a specific cross-section. This study presents a new approach to these measurements. First, the CBCT images are denoised using curvilinear methods, and the volume of interest is determined. Then, the orientation of the vertical cross-section plane is computed based on segmented axial sections of the TMJ head. Finally, the cross-section plane is used to determine the standardized locations, at which the width of the gap between condyle and fossa is measured. The elaborated method was tested on selected TMJ CBCT scans with satisfactory results. The proposed solution lays the basis for the development of an autonomous method of TMJ index identification.

Can Implant-Retained Fixed Prostheses Trigger Bone Response in the Posterior Region of Edentulous Mandibles? A 32-Month Cone-Beam Computerized Tomography Study Analyzing Bone Height and Density.

Research has shown that the presence of implants can revert bone resorption and thus contribute to a greater preservation of the residual bone ridge, especially in edentulous mandibles. Bone remodeling has yet to be extensively studied in the context of prosthetic options for edentulous arches. This study aims to evaluate the long-term behavior of bone tissue in the posterior region of edentulous mandibles rehabilitated with implant-retained fixed prostheses using cone-beam computerized tomography (CBCT). Selected individuals were rehabilitated with 5 external hexagon platform implants and an implant-retained fixed prosthesis. The CBCT scans were performed immediately after surgery and after 8, 22, and 32 months (T0, T8, T22, and T32, respectively). Implants were installed between the mental foramen. Subsequently, bone crest height and density were measured in the posterior region of the mandible on the images in 3 distinct areas at 5, 10, and 15 mm from the center of the distal implant axis. Analysis of variance and the Bonferroni post hoc test were used for multiple analyses. The results indicate a statistically significant difference in bone height between T0 and all subsequent times; the bone height at T32 was 8.85% higher than at T0 (P = .05). There was a difference in bone height between all analyzed regions. The bone growth difference between the 5-mm and 15-mm positions was 28.42% after 32 months (P = .00). A significant increase of 5.76% in bone density was observed between T0 and T22 (P = .03). Within the limitations of this study (sample size, follow-up duration), it was demonstrated that the use of implant-retained fixed prostheses in the mandible resulted in qualitative and quantitative bone growth (bone preservation) in the posterior region of the mandible. Further research is needed to identify the validity of our findings for other populations and to determine the duration of the bone-remodeling process in rehabilitated edentulous mandibles.

Evaluation of facial and palatal alveolar bone thickness and sagittal root position of maxillary anterior teeth on cone beam computerized tomograms.

BACKGROUND: Amount of bone covering the facial and palatal surface of the root and the sagittal root position are important parameters while considering an immediate implant placement. AIMS: This study measures the distance from cement-enamel junction (CEJ) to alveolar crest and thickness of alveolar bone of maxillary anterior teeth facially and palatally at 5 different points. MATERIALS AND METHODS: CBCT scans of 79 systemically healthy patients were evaluated by two calibrated and independent examiners. Measurements like: 1) distance from CEJ to Crest. 2) Thickness of facial and palatal alveolar bone at five different points a) Crest, b) 2 mm from the crest, c) mid root level, d) apical 3rd, e) apex. 3) Sagittal root position. 4) Labiopalatal distance at the apex. 5) Length of the bone from apex to the nasal floor for incisors. 6) Presence of fenestrations and dehiscences were assessed. RESULTS: Healthy maxillary anteriors were evaluated and less than 2 mm bone was seen at all five points, 0.5 to 1 mm bone is seen in all anteriors at crest, 2 mm from crest, midroot, apical 3rd level. 1 to 2 mm is seen at apex. Labiopalatal width at apex ranged from 3 mm to 13 mm with a mean of 7.45 ± 2.24 mm for centrals, 7.69 ± 2.14 mm for lateral incisors, and 6.76 ± 2.42 mm for canines. CONCLUSION: The present study supports the finding of very thin facial bone over maxillary anteriors and frequent occurrence of fenestrations and dehiscences. Pre-treatment evaluation of alveolar bone surrounding the maxillary anteriors is important to avoid complications during implant placement.

Diagnostic Potential of Panoramic Radiography and CBCT in Detecting Implant-Related Ex Vivo Injuries of the Inferior Alveolar Canal Border.

The aim of this ex vivo study was to compare the diagnostic performances of panoramic radiography and cone beam computerized tomography (CBCT) in detecting implant-related injuries of the inferior alveolar canal. Monocortical bone windows were created in 60 fresh sheep hemimandibles, the inferior alveolar canals were revealed and 120 dental implants were inserted. Three types of injuries, described as pilot drill damage (PDRILL), collapsing of the superior border of the canal (COLL), penetration of the implant tip into the canal (PENET) and one control group, were simulated. Standard (PANO) and dentition mode panoramic (PANO-DENT) images as well as CBCT data presented as multiplanar reconstruction (MPR) and cross-sectional (CROSS) views were evaluated by 6 observers who had also expressed their level of confidence to their final diagnosis. Intra- and interobserver agreement scores were rated good. The area under the curve (AUC) values and the confidence scores for CROSS and multiplanar reformation (MPR) views were both significantly higher than those of PANO and PANO-DENT (P < .05 for each) in PDRILL group. In COLL group, observers showed less confidence to PANO and PANO-DENT compared to CROSS and MPR techniques (P < .05 for each). No other significant differences were found. Within the limits of this experimental study, it can be suggested that the standard and dentition modes of panoramic radiography can be as effective as CBCT in the detection of penetrating and collapsing injuries, but multiplanar and cross-sectional views of the CBCT are more accurate than panoramic radiography in the detection of pilot drill injuries in sheep mandible.

Three-dimensional evaluation of skeletal and dental changes in patients with skeletal class III malocclusion and facial asymmetry after surgical-orthodontic treatment.

OBJECTIVE: To evaluate skeletal and dental changes in patients with skeletal Class III malocclusion and facial asymmetry after surgical-orthodontic treatment using cone-beam computerized tomography (CBCT). METHODS: This study included forty adult patients diagnosed with skeletal Class III malocclusion and asymmetry who underwent either isolated mandibular surgery or bimaxillary surgery. CBCT scans were taken before treatment (T0), at the completion of presurgical orthodontic treatment (T1) and after treatment (T2). Mimics 17.0 and 3-Matics 7.0 were used to measure skeletal and dental parameters. Skeletal and dental changes within each group from pretreatment to posttreatment were assessed, and Pearson correlation analysis was used to analyze the correlations among skeletal changes. RESULTS: The three-dimensional changes in condylar position were insignificant after surgical-orthodontic treatment in either group (P > 0.05). However, in the one-jaw surgery group, there were significant backward rotations of the condyle and ramus on the nondeviated side (P < 0.05), and the condyle on the deviated side rotated inward and forward significantly in the two-jaw surgery group (P < 0.05) at T2. There were no significant differences in the changes in the total alveolar bone thickness of bilateral first molars during dental decompensation (P > 0.05). The ratio between the buccal and the total bone thickness around the maxillary first molar on the deviated side decreased significantly at T1, as did those around the mandibular first molar on the nondeviated side (P < 0.05). CONCLUSIONS: Condylar angulations were less stable after treatment (7 to 9 months after surgery) in both the one-jaw and the two-jaw surgery groups, while condylar displacements were insignificant. In addition, orthodontists should keep a watchful eye to the relative position of the root in the alveolar bone during tooth decompensation.

Dental implant location via surface scanner: a pilot study.

PURPOSE: Implant location is performed after placement to verify that the safety of neighboring anatomic structure and the realizability of prosthetic plan. Routine postoperative location is based on radiological scanning and raises the concerns on radiation exposure and inconveniency in practice. In the present study a location method based on surface scanning was introduced and the accuracy of this method was assessed in vitro. MATERIAL AND METHODS: A total of 40 implants were placed in 10 resin mandible models. The models were scanned with intraoral scanner (IS group) and extraoral scanner (ES group). The implant position was located with fusing the images of surface scanning and cone beam computerized tomography (CBCT) after implant placement. Deviations were measured between positions located by surface scanner and postoperative CBCT with the parameters: central deviation at apex (cda), central deviation at hex (cdh), horizontal deviation at apex (hda), horizontal deviation at hex (hdh), vertical deviation at apex (vda), vertical deviation at hex (vdh) and angular deviation (ad). RESULTS: In IS group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.27 mm, 0.23 mm, 0.12 mm, 0.10 mm, 0.21 mm, 0.19 mm and 0.72°, respectively. In ES group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.28 mm, 0.25 mm 0.14 mm, 0.11 mm, 0.22 mm, 0.20 mm and 0.68°, respectively. The implant deviations in IS and ES groups were of no significant difference for any of the measurements. CONCLUSIONS: Dental implant can be located via surface scanner with acceptable accuracy for postoperative verification. Further clinical investigation is needed to assess the feasibility of the method.

CT texture analysis in the differentiation of major renal cell carcinoma subtypes and correlation with Fuhrman grade.

OBJECTIVE: CT texture analysis (CTTA) using filtration-histogram-based parameters has been associated with tumor biologic correlates such as glucose metabolism, hypoxia, and tumor angiogenesis. We investigated the utility of these parameters for differentiation of clear cell from papillary renal cancers and prediction of Fuhrman grade. METHODS: A retrospective study was performed by applying CTTA to pretreatment contrast-enhanced CT scans in 290 patients with 298 histopathologically confirmed renal cell cancers of clear cell and papillary types. The largest cross section of the tumor on portal venous phase axial CT was chosen to draw a region of interest. CTTA comprised of an initial filtration step to extract features of different sizes (fine, medium, coarse spatial scales) followed by texture quantification using histogram analysis. RESULTS: A significant increase in entropy with fine and medium spatial filters was demonstrated in clear cell RCC (p = 0.047 and 0.033, respectively). Area under the ROC curve of entropy at fine and medium spatial filters was 0.804 and 0.841, respectively. An increased entropy value at coarse filter correlated with high Fuhrman grade tumors (p = 0.01). The other texture parameters were not found to be useful. CONCLUSION: Entropy, which is a quantitative measure of heterogeneity, is increased in clear cell renal cancers. High entropy is also associated with high-grade renal cancers. This parameter may be considered as a supplementary marker when determining aggressiveness of therapy. KEY POINTS: • CT texture analysis is easy to perform on contrast-enhanced CT. • CT texture analysis may help to separate different types of renal cancers. • CT texture analysis may enhance individualized treatment of renal cancers.

Novel parotid sialo-cone-beam computerized tomography features in patients with suspected Sjogren's syndrome.

OBJECTIVE: Sjogren's syndrome (SjS) causes salivary gland impairment leading to oral dryness. Parotid sialo-cone-beam computerized tomography (sialo-CBCT) demonstrates ductal architecture and to a lesser extent gland activity. This study characterizes radiographic features of patients suspected for SjS and looks for a possible correlation with the diagnosis of SjS. METHODS: The clinical and radiographic data of suspected SjS/dry mouth patients referred for sialo-CBCT in 2011-2014 were reviewed retrospectively. Two observers studied the scans for various radiographic features including duct morphology, level of branching, ductopenia and sialectasia. These features were analysed taking the specific clinical data and two sets of SjS criteria: The 2002 American-European Consensus Group (AECG) and the 2012 American College of Rheumatology (ACR) Group. RESULTS: Sialo-CBCT scans of 67-referred patients suffering from dry mouth (115 parotid glands) were included. Intraradiographic association was found between ductopenia and all other radiographic parameters. Minimal, yet important, radiographic differences were found between left and right parotid glands. AECG-confirmed-SjS patients showed strong correlation with radiographic features, whereas ACR 2012-confirmed-SjS patients did not. CONCLUSION: Sialo-CBCT demonstrates novel radiographic features which may clarify the diagnosis of SjS. Further studies are needed to determine the role of sialo-CBCT in diagnosis of SjS.

Evaluation of video compression methods for cone-beam computerized tomography.

PURPOSE: Cone-beam computerized tomography (CBCT) is routinely performed for verification of patient position in radiotherapy. It produced a large amount of data which require a method to compress them for efficient storage. In this study three video compression algorithms were introduced and their performance was evaluated based on real patient data. MATERIALS AND METHODS: At first CBCT images in multiple sets of a patient were transferred from reconstruction workstation or exported from treatment planning system. Then CBCT images were sorted according to imaging time (time-prioritized sequence) or imaging location (location-prioritized sequence). Next, this sequence was processed by a video compression algorithm and resulted in a movie. Three representative video compression algorithms (Motion JPEG 2000, Motion JPEG AVI, and MPEG-4) were employed and their compression performance was evaluated based on the CBCT data of 30 patients. RESULTS: Among three video compression algorithms, Motion JPEG 2000 has the least compression ratio since it is a lossless compression algorithm. Motion JPEG AVI and MPEG-4 have higher compression ratios than Motion JPEG 2000 but come with certain image losses. For MPEG-4, location-prioritized sequences show higher compression ratio than time-prioritized sequences. Based on the results achieved on the clinical target verification application, the registration accuracy of CBCT after decompression was comparable to that of the original CBCT. CONCLUSIONS: Video compression algorithms could provide a higher compression ratio comparing to static image compression algorithm. Although the loss of CBCT image due to compression its impact on registration accuracy of patient positioning is almost negligible. Video compression method is an effective way to substantially reduce the size of CBCT images for storage.

A morphometric analysis of developmental instability in children born with unilateral cleft lip and palate.

Unilateral cleft lip and palate (UCLP) is a congenital deformity that occurs due to inadequate merging of the nasal and maxillary prominences during fetal development. Randomly distributed bilateral asymmetries known as fluctuating asymmetry (FA) occur in normally symmetric organisms when evolved mechanisms of developmental stability or equilibrium are disturbed by genetic, environmental, or unknown factors. Here, we hypothesize that facial skeleton FA will be increased in a sample of individuals born with UCLP (n = 24) relative to sex- and age-matched controls (n = 24). To test this hypothesis, 23 anatomical landmarks were measured on individual anonymized cone-beam computerized tomography (CBCT) images in children and adolescents (7-17 years). For each individual, 81 pairs of linear distances were used to estimate FAs across the face. To explore sample variation and statistical differences, a principal components analysis and Euclidean Distance Matrix Analysis multivariate bootstrap approach were carried out. Samples show some separation in multivariate space with 44.44% of FA differences being significantly different. The magnitude of FA was larger in the UCLP sample for every significant measurement. The magnitude of significant FA is highest near regions derived from the maxillary and nasal prominences, such as the nasal aperture. These results are useful for medical and dental practitioners when developing treatment options for children and adolescents with UCLP. Clin. Anat. 32:206-211, 2019. © 2018 Wiley Periodicals, Inc.

Assessing the Accuracy of Low-cost Surgical Guides Generated Using Ridge Mapping by Means of Cone Beam Computerized Tomography.

AIM: Assessing the accuracy of surgical guides generated with the help of a simple chair side ridge mapping technique by comparing the planned implant position with the achieved implant position on post-op computerized tomography scans. MATERIALS AND METHODS: In this study, 20 implant sites in patients were selected. Ridge mapping was done through a vacuum press template at three buccal (B1, B2, B3), three lingual (L1, L2, L3), and one crestal (C) points for each implant site. Readings were transferred onto the cast, and surgical guides were fabricated for implant placement. Postoperative cone beam computerized tomography (CBCT) was done to assess planned and achieved implant position. Comparison was done between soft tissue depths and implant distance from the crest of alveolar bone determined by the ridge mapping technique with measurements done on CBCT. The points used for ridge mapping were used as the reference for measurements. The data were analyzed using paired t test. p < 0.05 was considered to be statistically significant. RESULTS: On comparing the mean values of soft tissue depths from the ridge mapping and CBCT data, insignificant differences were found at B1, B2, L1, L2, L3, and C, but significant differences were found at B3. On comparing the implant distances from alveolar bone from both the data, insignificant differences were found at B, B2, B3, L1, L2, and L3 and significant difference was found at the crest in the mean values. CONCLUSION: Under the limitations of the above study, it can be concluded that a simple chairside procedure like ridge mapping can be used as an effective way for guided implant placement in sufficient available alveolar bone.

Disruption of symmetry: A quantitative assessment of facial skeleton anatomy in children born with unilateral cleft lip and palate.

Unilateral cleft lip and palate (UCLP) is a craniofacial deformity characterized by lip and palate clefting on one side of the face. UCLP originates from failures in neural crest migration and differentiation during embryological development, impairing facial primordia fusion (medial nasal, maxillary, and lateral processes) resulting in clefting. Persons with UCLP experience issues in nasal breathing, speaking, and mastication. Facial directional asymmetry (DA), consisting of left-right side differences biased toward one particular side, can arise from environmental or hereditary factors. This retrospective, cross-sectional study, quantifies DA in the facial skeleton of children with surgically repaired UCLP. We tested the hypothesis that DA is significantly increased in persons with UCLP. Twenty-three anatomical landmark coordinates were measured from cone beam computed tomography images of two age- and sex-matched samples: (1) persons with UCLP post-surgery (n = 26, 7-17 years); (2) typical children (n = 26, 7-17 years). From these coordinates, 81 bilateral paired measurements were calculated and statistically assessed for DA differences using Principal Components Analysis and Euclidean Distance Matrix Analysis. Samples separate in high-dimensional space and 35.8% of bilateral measures are statistically significant. Patterns of significant DA differences between samples were explored based on magnitude. Compared with the control group, in all but five cases, significant DA was greater in persons with UCLP. Regions derived from the maxillary and nasal prominences demonstrated the most DA. These results are important for medical practitioners for identifying the extent to which patients with UCLP deviate from the norm. Clin. Anat. 31:1129-1136, 2018. © 2018 Wiley Periodicals, Inc.

A 10-Year Cone Beam Computerized Tomography Observation of the Buccal Bony Wall of an Immediately Placed Implant at the Anterior Maxilla: A Case Report.

Since the introduction of immediate implant placements, the buccal bony wall has been a major consideration for success due to its correlation with soft tissue contour and color. This report presents the stability of the buccal wall thickness of an immediately placed implant at the anterior maxilla over 10 years. Although the width of the buccal wall decreased at the 2-year post-op follow-up, it remained stable afterward according to cone beam computerized tomography (CBCT) scans. Hence, this report suggests that ensuring adequate bony wall thickness with bone augmentation and fixture position may promise the longevity of the buccal bony wall and surrounding soft tissue in an immediate implant placement.

Health of periodontal tissues and resorption status after orthodontic treatment of impacted maxillary canines.

OBJECTIVE: The aim of the present study was to evaluate the changes of incisor root resorption associated with impacted maxillary canines and health of periodontal tissues around maxillary canines erupted with orthodontic treatment. MATERIALS AND METHODS: Twenty patients with a unilateral palatally impacted maxillary canine were included in the study. Cone-beam computed tomography images taken before and after orthodontic treatment were compared with the contralateral canines serving as control teeth. RESULTS: Root resorption was present in 10% of central and 40% of lateral incisors before treatment. After treatment, the incidence of resorption decreased. The thickness of the buccal bone surrounding the impacted canines was similar to that surrounding the contralateral canines, except in the apical area. Periodontal pocket depth and alveolar bone loss were greater for the impacted canine teeth than for the contralateral canines. CONCLUSIONS: Incisor root resorption associated with impacted canine teeth showed signs of repair after orthodontic treatment. Slight differences related to periodontal health were found between the previously impacted teeth and contralateral canine teeth.

Cone beam computerized tomography evaluation of incisive canal and anterior maxillary bone thickness for placement of immediate implants.

PURPOSE: Variation of dimensions of the nasopalatine canal and anterior maxillary bone thickness vary in relation to age, gender, edentulism, and ethnicity; thorough knowledge with regard to these landmarks is of vital importance prior to surgical procedures such as implant placement and local anesthesia in the anterior maxilla. Cone beam computerized tomography (CBCT) aids in accurate treatment planning in such situations. SUBJECTS AND METHODS: A total of 300 participants were selected by the inclusion and exclusion criteria. CBCT was performed with Hyperion X9 CBCT Scanner. Images were reconstructed from the CBCT data using NNT image reconstruction software and visualized using multi-planar resolution screen. The dimensions of the nasopalatine foramen (NPF), the incisive canal (IC) and foramen, and anterior maxillary bone thickness were measured. RESULTS: The mean diameter of NPF was found to be 3.27 mm, incisive foramen (IF) was 3.62 mm, IC was 2.12 mm. The average length of the IC was 10.66 mm. The IF was located at a mean distance of 13.81 mm away from the most anteroinferior point of the cortical plate of the labial bone of the maxilla. The anterior maxillary bone was the thickest at the nasal spine level (10.94 mm), and was the narrowest at lower labial alveolus (7.16 mm). The average anterior maxillary bone thickness was found to be 8.36 mm. CONCLUSION: Within the limitations of the study, it was found that found that gender and age are important factors that affected the characteristics of the IC and the amount of bone anterior to it.

Digital implant impressions by cone-beam computerized tomography: a pilot study.

OBJECTIVES: To evaluate the adjustment of structures designed from a digital impression of implants obtained by cone-beam computerized tomography (CBCT). MATERIALS AND METHODS: Thirty implants were placed in five edentulous mandibles of fresh cadaver heads, six per mandible. Special scan bodies were screwed in the implants and a CBCT was taken. DICOM images were converted to STL and digitally processed to obtain a digital model of the implants. A Cr-Co structure was designed and milled for each mandible, and the adjustment was assessed as in a real clinical situation: passivity while screwing, radiographic fitting, optical fitting, and probing. RESULTS: Good adjustment was found in three of the structures, and only slight discrepancies were found in the other two. CONCLUSION: Cone-beam computerized tomography might be a valid impression-taking method in full-mouth rehabilitations with implants. Further evaluations are needed with more implant and CBCT systems. The radiation dose might be considered when deciding to use this impression system. The types of patients appropriate for this treatment option should also be determined to fulfill the principles of the ALARA law.

Evaluation of root canal morphology of human primary molars by using CBCT and comprehensive review of the literature.

OBJECTIVE: Knowledge of primary tooth morphology is essential for clinical dentistry, especially for root canal treatment and dental traumatology. However, this has not been well documented to date with a large sample. This study was carried out to investigate the variation in number and morphology of the root canals of the primary molars, to study the applicability of cone beam computerized tomography (CBCT) in assessing the same and to provide a comprehensive review of the literature. MATERIALS AND METHODS: A total of 343 primary molars, without any root resorption, were divided into four main groups including the maxillary first molars, maxillary second molars, mandibular first molars and mandibular second molars. All of them were analysed in CBCT images in the axial, sagittal and coronal planes. Various parameters such as the number of roots, number of canals, the root canal type, diameter of root and root canal and root canal curvature were studied. RESULTS: Primary molars in all four groups showed variability in the number of roots and root canals. As far as length of the roots was concerned, the palatal root of the maxillary molar was found to be longest, while the distobuccal root was shortest. In mandibular molars, the mesial root was longer than the distal root. The length of distobuccal root canal of the maxillary molars and the distolingual canal of the mandibular molars was found to be shortest. The number of roots and root canals varied from two to four and three to four, respectively. The maxillary molars exhibited more one-canal than two-canal roots. CONCLUSION: The present study provides comprehensive information to the existing literature concerning the variation in root canal morphology of the maxillary and mandibular primary molar teeth. These data may help clinicians in the root canal treatment of these teeth.