Rare finding of Eustachian tube calcifications with cone-beam computed tomography.

Soft tissue calcification is a pathological condition in which calcium and phosphate salts are deposited in the soft tissue organic matrix. This study presents an unusual calcification noted in the cartilaginous portion of the Eustachian tube. A 67-year-old woman presented for dental treatment, specifically for implant placement, and cone-beam computed tomography (CBCT) was performed. The CBCT scan was reviewed by a board-certified oral and maxillofacial radiologist and revealed incidental findings of 2 distinct calcifications in the cartilaginous portion of the Eustachian tube. To the authors' knowledge, no previous study has reported the diagnosis of Eustachian tube calcification using CBCT. This report describes an uncommon variant of Eustachian tube calcification, which has a significant didactic value because such cases are seldom illustrated either in textbooks or in the literature. This case once again underscores the importance of having CBCT scans evaluated by a board-certified oral and maxillofacial radiologist.

The marginal mandibular nerve in relation to the inferior border of the mandible.

PURPOSE: Injury to the marginal mandibular nerve (MMN) can occur in numerous surgeries involving incisions near the inferior border of the mandible. Injury to this nerve can cause considerable cosmetic and functional deformities. A thorough knowledge and understanding of the anatomic pathway of the MMN is important to avoid permanent nerve damage. The purpose of this study was to determine the position of the marginal mandibular nerve in relation to several key mandibular anatomic landmarks and to identify variations of the nerve as it approaches the inferior border of the mandible. MATERIALS AND METHODS: Human cadavers were dissected superficially from the parotid gland to the mental protuberance to expose the MMN. At complete exposure of the nerve, 5 anatomic landmarks on the inferior border of the mandible were identified and labeled. The distance between the MMN and these landmarks was recorded, and the average measurements were used to approximate the most common pathway of the MMN. RESULTS: It was found that the MMN runs, on average, 0.75 mm below the gonion, 0.08 mm superior to the posterior border of the antegonial notch, 0.06 mm superior to the arc of the antegonial notch, 1.29 mm superior to the anterior border of the antegonial notch, 3.6 mm superior to the point at which the facial artery reaches the inferior border of the mandible, and 10.9 mm superior to the vertical line that extends from the commissure of lip to the inferior border of the mandible. CONCLUSION: These data suggest 3 general pathways of the MMN in relation to the inferior border of the mandible.

Mandibular incisive canal: cone beam computed tomography.

PURPOSE: Panoramic radiography is often used to analyze the anatomical structure of the teeth, jaws, and temporomandibular joints. Cone beam computed tomography (CBCT) imaging allows multiple axial slices of the image to be obtained through these anatomical structures. The aim of this study was to assess CBCT compared with panoramic radiography to verify the presence, location, and dimensions of the mandibular incisive canal. MATERIALS AND METHODS: CBCT scan images and panoramic radiographs of 89 subjects were compared for the presence of the mandibular incisive canal, its location, size, and anterior-posterior length. The distance between the incisive canal and the buccal and lingual plate of the alveolar bone, and the distance from the canal to the inferior border of the mandible and the tooth apex were also measured. A paired t-test was used to calculate any significant difference between the two imaging techniques. RESULTS: Eighty-three percent of the CBCT scans showed the presence of the incisive canal, as did 11% of the panoramic radiographs. The range of the incisive canal diameter, as seen in the CBCT scans, was from 0.4 × 0.4 mm to 4.6 × 3.2 mm. The mean length of the canal was 7 ± 3.8 mm. The distance from the inferior border of the mandible to the canal was 10.2 ± 2.4 mm, and the mean distance to the buccal plate was 2.4 mm. The apex-canal distance (in dentate subjects) was 5.3 mm. CONCLUSION: The presence, location, and dimensions of the mandibular incisive canal are better determined by CBCT imaging than by panoramic radiography.

Utilization of the tympanomastoid fissure for intraoperative identification of the facial nerve: a cadaver study.

PURPOSE: Intraoperative identification of the facial nerve is an essential component of parotid gland surgery. Failure to visualize the facial nerve during the procedure can result in significant complications such as facial palsy. Several anatomic landmarks are used clinically to identify the facial nerve trunk; however, most of these structures have variable locations with respect to the nerve. The tympanomastoid fissure is the closest and least variable of the anatomic landmarks used in parotid gland surgery. The aim of this study was to evaluate the distance between the tympanomastoid fissure and the facial nerve trunk. MATERIALS AND METHODS: Thirty cadaver sides were dissected. A modified Blair incision exposed the facial nerve trunk, and the dissection was extended to the stylomastoid foramen and adjacent mastoid process. The distance between the most lateral aspect of the tympanomastoid fissure and facial nerve trunk was obtained using a digital caliper. RESULTS: The distance from the tympanomastoid fissure to the facial nerve trunk ranged from 3.3 to 9.2 mm with a mean of 4.9 mm. CONCLUSIONS: The results showed that the tympanomastoid fissure is a close and predictable anatomic landmark that can be used to identify the facial nerve trunk intraoperatively.

Image quality produced by different cone-beam computed tomography settings.

INTRODUCTION: The aim of this study was to evaluate image quality at different cone-beam computed tomography settings and 3 fields of view. METHODS: A Hitachi CB MercuRay (Hitachi Medical Systems, Tokyo, Japan) was modified to allow different setting combinations. The variables consisted of 4 milliampere settings (2, 5, 10, and 15 mA), 2 kilovolt (peak) settings (100 and 120 kV[p]), presence or absence of a copper filter, and 3 fields of view (6, 9, and 12 in). Thirty-two scans were taken on a cadaver head and 16 scans on a dry skull. The groups were divided by field of view, and the images were ranked by at least 30 judges. Diagnostic quality was addressed in a questionnaire. Descriptive statistics and rankings were calculated with Excel 2003 (Microsoft, Redmond, Wash) and the Friedman and Wilcoxon signed rank tests with SPSS software (version 14.0.1; SPSS, Chicago, Ill). RESULTS: The presence or absence of a filter showed significant differences (P <.006) in 2 pairs of the 9-in field of view. Variation in kilovolt (peak) settings showed significant differences (P <.006) in the 6-in 5-mA images with a filter. Altering the milliampere settings showed significant differences (P <.008) in the 6- and 12-in groups. The 9-in group showed significant differences between 2 mA and 10 and 15 mA. Overall, the 6-, 9-, and 12-in images had diagnostic quality 56%, 99%, and 99% of the time, respectively. CONCLUSIONS: Presence or absence of a filter and the kilovolt (peak) setting did not affect overall image quality. Images taken at lower milliampere settings showed good diagnostic quality.

An evaluation of two dental simulation systems: virtual reality versus contemporary non-computer-assisted.

Contemporary dental simulation systems were developed to improve dental students' transition from the preclinical laboratory to the clinic. The purpose of this study was to compare the efficacy of a virtual reality computer-assisted simulation system (VR) with a contemporary non-computer-assisted simulation system (CS). The objectives were to determine whether there were differences between the two systems in the quality of dental students' preparations and the amount of faculty instruction time. Students who completed their first year of dental school and had no previous experience preparing teeth were group matched according to their performance in the first-year Dental Anatomy laboratory course and assigned to VR (n=15) or CS (n=13). In the summer, they spent two weeks (approximately 3 hrs/day) executing amalgam and crown preparations on typodont teeth. Short presentations describing the preparations were given to both groups; however, preparation criteria were available on the computer for the VR group, while the CS group received handouts. Both groups could request feedback from faculty, although VR also obtained input from the computer. A log was kept of all student-faculty (S-F) interactions. Analysis of the data indicated significant differences between groups for the following variables: mean number of S-F interactions was sixteen for the VR group versus forty-two for the CS group; and mean time of S-F interactions was 1.9+/-2 minutes versus 4.0+/-3 minutes (p<0.001) for VR and CS, respectively. Faculty spent 44.3 hours "interacting" with twenty-eight students, averaging 0.5 hours per VR student and 2.8 hours per CS student. Thus, CS students received five times more instructional time from faculty than did VR students. There were no statistical differences in the quality of the preparations. While further study is needed to assess virtual reality technology, this decreased faculty time in instruction could impact the dental curriculum.