Effect of vertical implant position on marginal bone loss: a randomized clinical trial.

OBJECTIVES: One of the most important factors that has influence on dental implants success rate is marginal bone loss. The purpose of this study is to investigate the effect of the implant's vertical position and the soft tissue's thickness on the rate of marginal bone loss of the dental implant. MATERIALS AND METHODS: In this single-blind randomized clinical trial study, 56 implants placed in the posterior region of mandible of 33 patients (19 women, 14 men) were divided into two groups. The group of crestal (28 implants) and subcrestal (28 implants) implants, each group was divided into two sub-groups with soft tissue thickness of 2 mm and less than 2 mm (14 implants) and more than 2 mm (14 implants). The amount of marginal bone loss was measured by Scanora 5.2 program with radiographs Digital parallelism based on the effect of the vertical position of the implant, soft tissue thickness, three months after placement, and three months after loading implants (six months after implant placement). RESULTS: The results showed that marginal bone loss in subcrestal implants is significantly more than crestal implants (p-value = 0.001), and also marginal bone loss in the soft tissue thickness group of 2 mm and less is significantly more than the group of soft tissue thickness more than 2 mm (p-value < 0.001). The amount of marginal bone loss three months after implant loading was significantly higher than three months after implant placement (p-value < 0.001). CONCLUSION: The implant's vertical position and the soft tissue's thickness around the implant are effective factors in the amount of marginal bone loss. Marginal bone loss is more in subcrestal implants and in cases with less soft tissue thickness. The time factor significantly affects the amount of marginal bone loss. TRIAL REGISTRATION: this clinical trial was registered at Iranian Registry of Clinical Trials, registration number IRCT20120215009014N415, registration date 20,220,110, (https//en.irct.ir/trial/60,991).

Effect of photobiomodulation therapy with different wavelengths on bone mineral density in osteoporotic rats.

Osteoporosis is associated with severe pain, bone deformity, fracture, and bone loss. It is important to find strategies to prevent bone resorption and treat osteoporosis. This study sought to assess the effect of photobiomodulation therapy (PBMT) with different wavelengths on bone mineral density (BMD) in osteoporotic rats. This animal study evaluated 63 adult female rats. The rats underwent ovariectomy to induce osteoporosis. Ovariectomized rats were randomly divided into 9 groups of control (OC), treatment with zoledronic acid alone (0.02 mg/kg), and treatment with 660 nm, 810 nm, and 940 nm PBMT alone (3 times a week for 6 weeks, energy density of 4 J/cm2), and combined with zoledronic acid. The healthy control group (HC) only underwent sham surgery. The rats underwent cone-beam computed tomography (CBCT) 52 days after the first treatment session to measure their BMD according to the gray value (GV) of images. To assess the biomechanical properties of bone, the resected bones were subjected to 3-point bending test (3-PBT). The experimental groups had significant differences with the OC group regarding radiographic and biomechanical properties of bone (P < 0.05), indicating a healing course. No significant difference was noted between the experimental groups treated with different laser wavelengths and those treated with zoledronic acid (P > 0.05). In the condition of this study, it was found that PBMT at a constant energy density of 4 J/cm2 with 660-, 810-, and 940-nm wavelengths is effective for enhancement of bone mineral density and biomechanical properties. No significant difference was noted between different wavelengths of diode laser regarding radiographic and biomechanical properties of bone.

Cone-beam computed tomography assessment of the root canal morphology of primary molars.

BACKGROUND: This study aimed to assess the root canal morphology of primary molars using cone-beam computed tomography (CBCT). METHODS: This cross-sectional study evaluated 60 maxillary and mandibular primary first and second molars on CBCT scans of patients retrieved from the archives of Hamadan School of Dentistry between 2018-2020. The teeth were evaluated regarding the number of roots and canals, canal type according to the Vertucci's classification, and root surface concavities. Data were analyzed descriptively and by independent t-test. RESULTS: The most frequent number of canals and roots in the maxillary right and left first molars was 3 canals (60%) and 3 roots (80%). These values were 4 canals (80%) and 5 canals (50%) with 3 roots in the maxillary right and left second molars, respectively, 4 canals (100%) and 2 roots (50%), and 3 canals (60%) and 2 roots (50%) in mandibular right and left first molars, respectively, and 4 canals (92.3%) and 3 roots (61.5%) in mandibular right and left second molars. Vertucci's type IV was the most common canal type in mesial and distal canals, type I was the most common in mesiobuccal, mesiolingual, distobuccal, and distolingual, and types I and II were the most common in the palatal canal. The maximum and minimum concavities were noted in the buccal (26.7%) and mesial (8.3%) surfaces, respectively. CONCLUSIONS: A wide variation exists in the number of roots and canals of maxillary and mandibular primary molars, which calls for further attention in treatment of such teeth.

Association of root morphology of mandibular second molars on panoramic-like and axial views of cone-beam computed tomography.

BACKGROUND: Knowledge about the anatomy and morphology of the root canal system is essential for successful surgical and non-surgical root canal treatments. However, precise assessment of the root morphology and anatomy is not often possible on two-dimensional radiographs. This study aimed to investigate the association of root morphology of mandibular second molars on panoramic-like and axial views of cone-beam computed tomography (CBCT). METHODS: This cross-sectional study evaluated 1,231 CBCT scans of mandibular second molars obtained between October 2018 and February 2022 that were retrieved from the archives of a private radiology clinic. Panoramic-like images were reconstructed from the CBCT scans. The root morphology of mandibular second molars was classified on panoramic-like images as type 1, 2, 3, 4, or 5. The root pattern on axial CBCT images was classified into three types of single, double and C-shaped. The association of root morphology on panoramic-like and axial CBCT views was analyzed by the Chi-square test and Fisher's exact test at 0.05 level of significance. RESULTS: Of all, 62.7% of mandibular second molars were type 1; out of which, 97.3% had a double-root pattern on axial CBCT images. Also, 28.6% of them were type 2; of which, 92.6% had a double-root pattern. Moreover, 3.9% were type 3; of which, 47.9% had a C-shaped pattern; 0.9% were type 4, and 45.5% of them showed a single-root pattern; 3.8% were type 5 with 76.6% of them showing a single-root pattern. The prevalence of C-shaped canals was higher in females, and most C-shaped canals had a C3 pattern. CONCLUSION: Root morphology on panoramic-like CBCT views had a strong association with the root canal pattern on axial CBCT views. According to the results, mandibular second molars with a type 3 morphology on panoramic-like CBCT images are highly probable to have a C-shaped canal.

Comparison of the amount of artifacts induced by zirconium and titanium implants in cone-beam computed tomography images.

BACKGROUND: This study aimed to compare the amount of artifacts induced by the titanium and zirconium implants on cone-beam computed tomography (CBCT) and assess the effect of different exposure settings on the image quality for both materials. METHODS: In this experimental study, 30 zirconium and 30 titanium implants were placed in bovine rib bone blocks. CBCT images were taken in two different fields of view (FOV: 4 × 6 cm2 and 6 × 8 cm2) and at two resolutions (133 µ and 200 µ voxel size). Subsequently, two observers assessed the images and detected the amount of artifacts around the implants through gray values. Data were analyzed by paired t test and independent t test using SPSS 21 and the 0.05 significance level. RESULTS: The results showed that titanium implants caused lower amounts of artifacts than zirconium implants, which was statistically significant (P < 0.001). The larger FOV (6 × 8 cm2) resulted in a lower amount of artifacts in both groups, although the results were only statistically significant in the zirconium group (P < 0.001). The amount of artifacts was increased when using the 133 µ voxel size in both groups, which was only significant in the zirconium group (P < 0.001). CONCLUSION: Our results suggest that zirconium implants induce higher amounts of artifacts than titanium ones. We also concluded that the artifacts could be minimized using the larger FOV and voxel size.

Complementarity of surgical therapy, photobiomodulation, A-PRF and L-PRF for management of medication-related osteonecrosis of the jaw (MRONJ): an animal study.

BACKGROUND: This study aimed to evaluate the complementarity of surgical therapy, photobiomodulation (PBM), advanced platelet-rich fibrin (A-PRF), and Leukocyte and platelet-rich fibrin (L-PRF) for the management of medication-related osteonecrosis of the jaw (MRONJ). METHODS: Sixty rats underwent injection of zoledronate followed by left mandibular first and second molar extractions to induce MRONJ lesions. All rats were examined for the signs of MRONJ 8 weeks post-dental extraction. Forty-nine rats with positive signs of MRONJ were appointed to seven different groups as follows: control (Ctrl); surgery alone (Surg); surgery and PBM (Surg + PBM); surgery and A-PRF insertion (Surg + APRF); surgery and L-PRF insertion (Surg + LPRF); surgery, A-PRF insertion, and PBM (Surg + APRF + PBM); surgery, L-PRF insertion, and PBM (Surg + LPRF + PBM). Euthanasia was carried out 30 days after the last treatment session. The lesions' healing was evaluated clinically, histologically, and radiographically. Data were analyzed using STATA software version 14, and the statistical significance level was set at 5% for all cases. RESULTS: According to the present study, A-PRF and L-PRF treatment resulted in significant improvements in clinical, histological, and radiographical parameters compared to the Ctrl group (P < 0.05). The PBM also decreased wound dimensions and the number of empty lacunae compared to the Ctrl group (P < 0.05). Surg + APRF + PBM and Surg + LPRF + PBM were the only groups that presented a significantly higher mean number of osteocytes (P < 0.05). No significant differences were observed between A-PRF and L-PRF treatment groups (P > 0.05). CONCLUSIONS: Surgical resection followed by applying A-PRF or L-PRF reinforced by PBM showed optimal wound healing and bone regeneration in MRONJ lesions.

Upper Airway Changes Following Different Orthognathic Surgeries, Evaluated by Cone Beam Computed Tomography: A Systematic Review and Meta-analysis.

PURPOSE: This study sought to assess the upper airway changes following different orthognathic surgeries using cone-beam computed tomography. METHODS: An electronic search of the literature was conducted in major electronic databases including Medline (PubMed), Web of Science, Scopus, and Open Grey for articles published up to January 20, 2018. Human studies that evaluated the changes in the volume and minimum cross-sectional area of the upper airway or its subdivisions in patients who had undergone orthognathic surgery by use of cone-beam computed tomography were included. Manual search of the bibliographies of the included articles was also conducted. The included studies underwent risk of bias assessment. RESULTS: A total of 1330 articles were retrieved. After excluding the duplicates and irrelevant articles, 41 studies fulfilled the eligibility criteria for this systematic review; out of which, 30 entered the meta-analysis. The majority of studies had a medium risk of bias. Mandibular setback, and maxillary advancement + mandibular setback decreased the volume of the upper airway (-6042.87 mm3 and -1498.78 mm3, respectively) and all its subdivisions in long-term (>3 months), except for the nasopharynx, the volume of which increased following maxillary advancement + mandibular setback. Mandibular advancement and maxillomandibular advancement both increased the upper airway volume in long-term (7559.38 mm3 and 7967.06 mm3, respectively); however, only the changes after the former procedure were significant. The minimum cross-sectional area increased after maxillomandibular advancement (161.43 mm2), and decreased following maxillary advancement + mandibular setback (-23.79 mm2) in long-term. CONCLUSION: There is moderate evidence to suggest that mandibular advancement is the only orthognathic movement that provides a statistically significant change in long-term upper airway volume.

Comparison of Biofeedback and Combined Interventions on Athlete's Performance.

The aim of this study was the comparison of neurofeedback and biofeedback as a combination, against biofeedback intervention alone on athletic performance. 45 novice basketball players were allocated into three groups and assigned accordingly, two experimental and one control group. The experimental group 1 received 24 biofeedback sessions only, experimental group 2 received 24 biofeedback and neurofeedback sessions combined, whereas the control group didn't receive any form of intervention. Athletic performance scales were used before and after each intervention and multivariate analysis of covariance was used to compare the two groups. Results showed that in comparison to the control group, the athletic performance scales scores in both experimental groups were significantly increased. Furthermore, in experimental group 2 (combined method), we noticed a significantly greater improvement in performance levels than experimental group 1. We concluded that neurofeedback and biofeedback interventions combined, can be used as an effective method to enhance athletic performance.

Cone-beam computed tomographic analysis of apical transportation and centering ratio of ProTaper and XP-endo Shaper NiTi rotary systems in curved canals: an in vitro study.

BACKGROUND: Cleaning and shaping of the root canal system is an important step of endodontic treatment. Canal transportation is a common procedural error in preparation of curved canals. This study aimed to compare the canal transportation and centering ratio of two rotary files in curved canals using cone-beam computed tomography (CBCT). METHODS: Forty-four extracted human mandibular first molars with mature apices and 10° to 30° apical curvature were selected. The samples were randomly divided into two groups (n = 22) with similar curvature. The canals were prepared with ProTaper and XP-endo Shaper file systems according to the manufacturers' instructions. The CBCT images were obtained using Cranex 3D CBCT scanner before and after root canal preparation, and canal transportation and centering ratio of the files at 3, 4 and 5 mm levels from the apex were calculated. Data were compared between the two groups using independent t-test at 0.05 level of significance. RESULTS: The ProTaper Universal caused greater canal transportation and had lower centering ratio than XP-endo Shaper in both mesiodistal and buccolingual directions at all levels from the apex. The difference between the two groups regarding canal transportation was significant at all levels from the apex in buccolingual direction (P < 0.05) except for 3 mm from the apex (P > 0.05). The difference between the two groups regarding centering ratio was not significant (P > 0.05) in mesiodistal direction at all levels except for 4 mm from the apex (P < 0.05). CONCLUSION: The ProTaper Universal causes greater canal transportation in both buccolingual and mesiodistal directions than XP-endo Shaper.

Effect of exposure parameters of cone beam computed tomography on metal artifact reduction around the dental implants in various bone densities.

BACKGROUND: This study aimed to assess the effect of exposure parameters such as milliampere (mA) and field of view (FOV) of cone beam computed tomography (CBCT) on a metal artifact of dental implants placed in different bone densities. METHODS: A total of 27 bone blocks with different densities (nine were type 1, nine were types 2 and 3, and nine were type 4) were used in this in vitro, experimental study. These blocks were placed in mandibular wax models. The blocks were scanned after drilling (hole preparation) and after implant placement using Cranex3D imaging system with a 4 × 6 cm2and 6 × 8 cm2 FOV and 4 and 10 mA. Gray value of the bone blocks was recorded before and after placement of implants. RESULTS: In general, irrespective of bone density, the amount of artifacts was lower in small FOV compared to large FOV (P < 0.05). Change of mA had no effect on metal artifacts (P > 0.05). Artifacts in type 4 bone were greater than in other bone types (P < 0.05). Difference between type 1 and types 2 and 3 was not significant (P > 0.05). CONCLUSION: According to the results of this study, Peri-implant artifacts were seen in all bone types; the amount of artifacts in type 4 bone was higher than that in other types. Size of FOV and bone density affect the metal artifacts around dental implants; so that a smaller FOV can be used to decrease metal artifacts.

Cone Beam Computed Tomography Findings of Desmoplastic Ameloblastoma of Maxilla.

Desmoplastic ameloblastoma (DA) is one of 6 subtypes and also a rare variant of ameloblastoma. It is not recognized perfectly up to now. Although most of the conventional ameloblastomas can be diagnosed in posterior of the mandible, DA more transpires in anterior of the jaws. Our patient was a 57-year-old man with swelling in the right side of the anterior maxilla. In the medical examination bone expansion was detected with a normal covering mucosa and no discoloration. This paper provides more information about cone beam computed tomography image features of DA.

Cherubism: An Unusual Study With Long-Term Follow-Up.

Cherubism is an uncommon hereditary benign fibro-osseous disorder characterized by bilateral enlargement of the mandible and the maxilla that presents with varying degrees of involvement and a tendency toward spontaneous remission.The first visit was in 2002. A 16-year-old female was referred to an orthodontist for correction of her dental crowding. In the radiographic examination that was taken for her treatment the first time in 2002, a jaw bone lesion was discovered accidentally. X-ray panoramic imaging revealed well-defined multilocular radiolucencies involving the posterior body of the mandible and ascending rami with displaced teeth. This lesion had no effect on inferior alveolar canal and maxilla.There was no significant past medical history, and there was no family history suggestive of a similar complaint. On extraoral examination, there was no swelling in both rami of the mandible and face. Histopathological examination of the biopsy specimen showed proliferating fibrous connective tissue interspersed by multinucleated giant cells. It was diagnosed as a case nonfamilial cherubism. An extensive long-term follow-up till 12 years was maintained. In 2014, after 12-years follow-up for this lesion, panoramic imaging examination showed progress of this lesion in mandible and maxilla.

Cone-Beam Computed Tomography Study Of Crown Dilaceration With a Talon Cusp in an Unerupted Permanent Maxillary Tooth.

This article describes a rare case of crown dilaceration with a talon cusp in an unerupted permanent maxillary central incisor. Our patient was a 7-year-old boy with a history of trauma to his primary maxillary teeth (#51 and 52), at 3 years of age complaining of failure of eruption of tooth #11. Periapical radiography showed incomplete formation of tooth root #11 and more superior position of tooth bud #11 relative to tooth bud #12. A cone-beam computed tomography was ordered, which revealed crown dilaceration with a talon cusp in tooth bud #11. The patient was scheduled for follow-up at 6 months.

Effect of Field of View on Detection of Condyle Bone Defects Using Cone Beam Computed Tomography.

In maxillofacial imaging, cone beam computed tomography (CBCT) is currently the modality of choice for assessment of bony structures of the temporomandibular joint (TMJ). Factors affecting the quality of CBCT images can change its diagnostic accuracy. This study aimed to assess the effect of field of view (FOV) and defect size on the accuracy of CBCT scans for detection of bone defects of the TMJs. This study was conducted on 12 sound TMJs of 6 human dry skulls. Erosions and osteophytes were artificially induced in 0.5, 1, and 1.5-mm sizes on the anterior-superior part of the condyle; CBCT scans were obtained with 6, 9, and 12-inch FOVs by NewTom 3G CBCT system. Two maxillofacial radiologists evaluated the presence/absence and type of defects on CBCT scans. The Cohen kappa was calculated to assess intra- and interobserver reliability. The Mann-Whitney U test was applied to compare the diagnostic accuracy of different FOVs.In comparison of 6- and 12-inch, 9- and 12-inch FOVs in detection of different sizes of erosive lesions, difference was significant (P <0.05), whereas difference between 6- and 9 inch just in 0.5-mm erosive lesion was significant (P = 0.04). In comparison of 6- and 12-inch FOVs in detection of different sizes of osteophyte lesion, difference was significant (P < 0.05), whereas between 6- and 9-inch FOVs statistically significant difference was not observed (P > 0.05). The highest and the lowest diagnostic accuracy of CBCT scans for condyle defects were obtained with 6-inch and 12-inch FOVs, respectively. Diagnostic accuracy of CBCT scans increased with an increase in size of bone defects.

Comparative Sensitivity Assessment of Cone Beam Computed Tomography and Digital Radiography for detecting Foreign Bodies.

AIM: Foreign body detection and determining whether it is adjacent to critical organs has a significant role in its removal. Various imaging techniques have been used to locate foreign bodies. This study aimed to compare cone beam computed tomography (CBCT) and digital radiography for detecting foreign bodies in an in vitro model. MATERIALS AND METHODS: Foreign bodies composed of normal glass, barium glass, wood, and stone with two sizes were placed into three different locations of two sheep heads. Digital radiography [lateral cephalometric, submentovertex (SMV)] and CBCT were compared to investigate their sensitivity for detecting foreign bodies. RESULTS: Diagnostic sensitivity of digital radiography in lateral cephalometric view, SMV view, and CBCT for detecting all types of foreign bodies was 67.2, 32.3, and 76.6% respectively. None of these techniques were successful in detecting wood satisfactory. Stone was detected relatively higher than other foreign bodies (82.6%). Diagnostic sensitivity of CBCT in detecting foreign bodies was 100%, except for wood. Accuracy of imaging techniques in detecting foreign bodies according to locations in descending order was lip, mandibular angle, and maxillary sinus. CONCLUSION: It can be concluded that appropriate amount of radiopacity is enough for CBCT to exactly detect foreign body, regardless of its location or size. CLINICAL SIGNIFICANCE: In maxillofacial traumatic patients, CBCT seems to be a better and cost-effective technique for detecting hidden foreign bodies than other routine techniques.

In vitro comparison of the effect of different slice thicknesses on the accuracy of linear measurements on cone beam computed tomography images in implant sites.

BACKGROUND AND AIMS: Use of dental implants in edentulous patients has become a common treatment modality. Treatment of such implants requires radiographic evaluation, and in most cases, several different imaging techniques are necessary to evaluate the height, width, and structure of the bone at the implant site. In the current study, an attempt was made to evaluate the accuracy of measurements on cone beam computed tomography (CBCT) images with different slice thicknesses so that accurate data can be collected for proper clinical applications. MATERIALS AND METHODS: In the present in vitro study, 11 human dry mandibles were used. The width and height of bone at the central, canine, and molar teeth areas were measured on the left and right sides by using digital calipers (as gold standard) and on CBCT images with 0.5-, 1-, 2-, 3-, 5-, and 10-mm slice thicknesses. Data were analyzed with SPSS 16, using paired t-test, Tukey test, and inter class correlation. RESULTS: Data were collected by evaluation of 11 skulls and 63 samples on the whole. There were no significant differences in bone width in any area (P > 0.05). There were significant differences in bone height in the central and molar teeth areas (P = 0.02). The measurements were not significant only at 4-mm slice thickness option and 5-mm slice thickness option for height compared with the gold standard (P = 0.513 and 0.173, respectively). The results did not show any significant differences between the observers (P = 0.329). CONCLUSION: The highest measurement accuracy of CBCT software program was observed at 4-mm slices for bone width and 5-mm slice thickness for bone height.

Influence of Head Orientation in Linear Measurement for Implant Planning in Cone Beam Computed Tomography.

AIM: Use of dental implants in edentulous patients has become a common treatment modality. Treatment of such implants requires radiographic evaluation, and in most cases several different imaging techniques are necessary in order to evaluate the height, width and the structure of bone at implant site. The aim of this study was to evaluate the influence of head orientation in linear measurement for implant planning in cone beam computed tomography (CBCT). MATERIALS AND METHODS: In the present in vitro study, 11 human dry mandibles were used. The width and height of bone at the central, canine and molar teeth areas were measured on the left and right sides by using digital calipers (as gold standard) and on CBCT images with Reaxis option and no Reaxis. Data were analyzed with Statistical package for the social sciences (SPSS) 18, using pair t-test, Tukey test and intraclass correlation (ICC). RESULTS: Data were collected by evaluation of 11 skulls and 66 samples on the whole. There were no significant differences in bone width in any area in both Reaxis and no Reaxis option (p > 0.05). There were significant differences in bone height in the central (p = 0.005) and molar teeth areas (p = 0.010). The results did not show any significant differences between the observers (p = 0.329). CONCLUSION: Using the Reaxis option does not affect the measurement of bone width, while use of this option can make a significant difference for height measurements.

Evaluation of the accuracy of linear measurements on lateral cephalograms obtained from cone-beam computed tomography scans with digital lateral cephalometric radiography: an in vitro study.

OBJECTIVES: A cephalometric analysis especially designed for the patient who requires maxillofacial surgery was developed to use landmarks and measurements that can be altered by common surgical procedures. Identification of landmarks in cephalometry is very important and useful for orthognathic surgery. The aim of this study was to evaluate the accuracy of linear measurement based on digital lateral cephalograms (DLC) and on lateral cephalograms obtained from cone-beam computed tomography (CBCT) scans. MATERIALS AND METHODS: The linear distances between anatomic landmarks on 6 dry human skulls were measured by 2 observers using digital calipers for sella-nasion (S-N), menton-nasion (M-N), anterior nasal spine-nasion (ANS-N), anterior nasal spine-posterior nasal spine (ANS-PNS), and pogonion-gonion (Pog-Go). Then, images were obtained by using DLCs and in lateral cephalograms obtained from CBCT scans. The measurement errors were calculated for each modality, compared with each other, and analyzed via SPSS software version 18. RESULTS: For all lines (S-N, M-N, ANS-N, Pog-Go, and ANS-PNS), CBCT-derived values did not differ from actual dry skull dimensions (gold standard) (P > 0.05). In DLC, for S-N, M-N, ANS-N, and Pog-Go lines, measurements were significantly higher than actual measurements (P ≤ 0.05), but ANS-PNS values did not differ from actual measurements (P > 0.05). CONCLUSIONS: The results showed that the values obtained in CBCT imaging compared with calculated values of the digital lateral cephalometry much closer to the actual distance are more accurate indicators of this type of imaging and that CBCT permits oral surgeons to visualize the position and surgical anatomy of the tooth as it will be seen in the operating theater and allows orthodontists to plan directional traction.

Evaluation of the mandibular canal visibility on cone-beam computed tomography images of the mandible.

BACKGROUND: The mandibular canal (MC) is an important and necessary landmark that should be considered before any surgery in the posterior region of the mandible. This study is aimed to evaluate the visibility and position of the MC in an Iranian population using cone-beam computed tomography. METHODS: In this cross-sectional study, cone-beam computed tomography images of 69 patients, which were available as soft copies in the archives of the databases in the Department of Oral Radiology at Hamadan University of Medical Sciences (Hamadan, Iran), were analyzed. The visibility, corticalization, and position of the MC were assessed by 2 expert oral radiologists independently. The χ2 test, unpaired t test, and 1-way analysis of variance were used for analysis. RESULTS: The right and left MCs were clearly visible in 89.6% and 84.7% of the cases, respectively. Among 87.5% of cases, the MC was observed simultaneously in 2 sides. Position of the MC in relation to surrounding structures showed lowest asymmetry at the second premolar area. There were no statistically significant difference between sex and the evaluated parameters. CONCLUSIONS: Cone-beam computed tomography was successful in most cases in displaying the MC. The areas with most MC visibility in the right and left sides were the second and third molar regions, respectively. This visibility declined forwardly in both sides.

Impact of rare earth element added filters on the X-ray beam spectra: a Monte Carlo approach.

The effectiveness of added filters including conventional and rare earth materials for dental radiography tasks was investigated using a simulation approach. Current study focuses on the combination of a range of various filters to investigate the reduction of radiation absorbed dose and improving the quality of a radiography image. To simulate the X-ray beam spectrum, a MCNP5 code was applied. Relative intensity, beam quality, and mean energy were investigated for a typical dental radiography machine. The impact of different rare-earth materials with different thicknesses and tube voltages on the X-ray spectrum was investigated. For Aluminum as a conventional filter, the modeled X-ray spectra and HVL values were in a good agreement with those reported by IPEM. The results showed that for a 70 kVp voltage, with an increase of the thickness and atomic number of a given added filters, an increase of HVL values were observed. However, with the increase of the attenuator thickness, X-ray beam intensity decreases. For mean energy, different results were observed. It was also found that rare earth made filters reduce high energy X-ray radiation due to k-edge absorption. This leads to an ideal beam for intra-oral radiography tasks. However, as a disadvantage of rare earth added filters, the reduction of the tube output levels should also be considered.