Byron W. Benson

Variations in adult cortical bone mass as measured by a panoramic mandibular index

This study defines a new radiomorphometric index of mandibular cortical bone mass, the panoramic mandibular index (PMI). Differences in the index in a population of 353 adult subjects, equally divided by sex, age (30 through 79 years), and racial group (black, Hispanic, white), were evaluated. The data were analyzed with respect to side, racial group, sex, age, and combinations of these variables. Blacks were found to have a greater mean PMI than Hispanics or whites, who were statistically similar. Age-related changes comparing younger and older age groups within each sex and racial group indicated a significant decrease in mean PMI with increasing age in black and Hispanic women. The mean PMI in white men increased with advancing age.

Comparison of titanium and cobalt-chromium removable partial denture clasps

STATEMENT OF PROBLEM The use of titanium alloys for removable partial dentures is an increasingly popular application. While the flexibility of titanium would allow for cast clasps to be placed in deeper undercuts than advisable with cobalt-chromium, it is possible that the retentive forces of the titanium clasp might not maintain sufficient retention after repeated flexing of the clasp arm during insertion and removal of the partial denture. PURPOSE This study assessed the characteristics of cast clasps made of titanium and titanium alloys to determine whether these materials are suitable alternatives for removable partial denture applications. MATERIAL AND METHODS Removable partial denture clasps at two undercut depths were fabricated from commercially pure titanium, titanium alloy (Ti-6A1-4V), and cobalt-chromium. Loss of retention force was measured as the clasps underwent 3 years of simulated clinical use. The data were subjected to ANOVA and Scheffés tests to determine differences. Evidence of casting defects and porosity was evaluated by radiographic examination and nonparametric statistics. SEM microscopy was used to observe surface characteristics that were described qualitatively. RESULTS For the 0.75 mm undercut specimens, there was less loss of retention for clasps made from pure titanium and titanium alloy than for cobalt-chromium clasps. Porosity was more apparent in the pure titanium and titanium alloy clasps than in those made from cobalt-chromium, but the amount of porosity did not correspond to evidence of fractures or permanent deformation. CONCLUSIONS The long-term retentive resiliency of the pure titanium and titanium alloy clasps suggests that these materials are suitable for removable partial dentures.

Inclusion of tobacco exposure as a predictive factor for decreased bone mineral content.

Tobacco exposure has been implicated as a risk factor for decreased bone density, which might result in osteoporosis. Cotinine, a metabolite of nicotine, is commonly used as a marker for tobacco exposure (active or passive). The objective of the present study was to compare tobacco exposure with other predictive factors for low bone mineral content (BMC), as determined by dual photon bone absorptiometry (DXA) in a national U.S. sample. Publicly available interview and clinical examination data from the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES-III) were used. Our data included 14,060 subjects from 19,528 randomly selected representative U.S. households. Clinical laboratory data included serum values for calcium and cotinine. BMC was assessed radiologically by DXA at five proximal femur sites. BMC values were adjusted for age, as well as height, weight, and bone area to correct for bone and body size. We used t tests to compare continuous variables and chi-square tests to explore associations between categorical variables. Multivariate regression models were developed for each gender with appropriate covariates. Intertrochanter BMC explained the most variation (highest R 2 ) and was selected as the basis of the comparison. Serum cotinine had a significant inverse relationship to BMC in both males (p = .0069) and females (p = .0063). Serum cotinine, as a marker for tobacco exposure, is a statistically significant risk factor for decreased BMC in both genders and should be included in multivariate regression models to predict low BMC.

Endodontic working length assessment: Comparison of storage phosphor digital imaging and radiographic film

OBJECTIVE This study compared the difference in interpretation of the position of endodontic file tips between two imaging systems: photostimulable storage phosphor luminescence imaging versus radiographic film. STUDY DESIGN Thirteen patients were selected at random. Preoperative and trial file length radiographs were made with a dual image receptor composed of a Digora Digital Imaging Plate and a piece of Ektaspeed Plus film. Exposure techniques for E-speed film were used. Root length and file length measurements were made from digital images with the Digora systems measuring tools. Measurements were also made on radiographic film with a 7 x measuring magnifier. Root length, file length, and their difference were compared for both film and digital images. RESULTS Differences were found to be less in digital than in film images. Photostimulable storage phosphor luminescence imaging performed similarly to Ektaspeed Plus film for measuring root lengths, but file tip positions (especially of small file sizes) were difficult to visualize with E-speed film. CONCLUSIONS The smaller difference between file tip and root apex found with digital imaging suggests that this technique is more accurate to assess trial file length. This imaging modality for assessing file positions during root canal treatment may be beneficial to the practitioner.

Reconstruction of Canine Mandibular Bone Defects Using a Bone Transport Reconstruction Plate

Objectives:Reconstruction of mandibular segmental bone defects is a challenging task. This study tests a new device used for reconstructing mandibular defects based on the principle of bone transport distraction osteogenesis. Methods:Thirteen beagle dogs were divided into control and experimental groups. In all animals, a 3-cm defect was created on one side of the mandible. In 8 control animals, the defect was stabilized with a reconstruction plate without further reconstruction and the animals were killed 2 to 3 months after surgery. The remaining 5 animals were reconstructed with a bone transport reconstruction plate, comprising a reconstruction plate with attached intraoral transport unit, and were killed after 1 month of consolidation. Results:Clinical evaluation, cone-beam CT densitometry, three-dimensional histomorphometry, and docking site histology revealed significant new bone formation within the defect in the distracted group. Conclusion:The physical dimensions and architectural parameters of the new bone were comparable to the contralateral normal bone. Bone union at the docking site remains a problem.

Effective dose and risk assessment from detailed narrow beam radiography

Studies of the effectiveness of commonly used imaging techniques have shown that they are less than optimal in revealing oral disease. The diagnostic accuracy of detailed narrow beam radiography (scanography) has been reported to be significantly better than intraoral periapical radiography for the observation of periodontal pathoses and at least as good as periapical radiography for detecting periapical lesions. The purpose of this study was to calculate and compare the effective doses and risk estimates from the use of detailed narrow beam radiography and intraoral radiography. With the use of a tissue equivalent human phantom and thermoluminescent dosimetry, the effective dose from detailed narrow beam radiography was found to vary from 5 to 35 microSv depending on the anatomic location of the image layer and intraoral radiography from 9 to 150 microSv depending on the type of survey. Effective doses of these magnitudes represent 0.6 to 18.8 days of equivalent natural radiation exposure and a probability for stochastic effects on the order of 0.37 to 10.95 x 10(-6).

The assessment of impacted maxillary canine position with panoramic radiography and cone beam CT

OBJECTIVE The aim of this study was to correlate the position of impacted maxillary canines on panoramic radiography with cone beam CT (CBCT) and analyse the labiopalatal position of canines and root resorption of permanent incisors in CBCT according to the mesiodistal position of canines on panoramic radiographs. METHODS This study was a retrospective radiographic review of 63 patients with 73 impacted maxillary canines. The mesiodistal position of the canine cusp tip was classified by sector location and analysed on 73 impacted canines from 63 panoramic radiographs. The labiopalatal position of the impacted canines and root resorption of permanent incisors were evaluated with CBCT. The sector location on panoramic radiographs was compared with the labiopalatal position of impacted maxillary canines on CBCT. The statistical correlation between panoramic and CBCT findings was examined using the χ(2) test and the Fishers exact test. RESULTS Labially impacted canines in CBCT were more frequent in Panoramic Sectors 1, 2 and 3, mid-alveolus impacted canines were more frequent in Sector 4 and palatally impacted canines were more frequent in Sector 5. There was a statistically significant association between the panoramic sectors of the impacted canines and the labiopalatal position of the canines (p < 0.001). Root resorption of permanent incisors showed a significant difference according to sector location (p < 0.001) and was observed in Sectors 3, 4 and 5. CONCLUSIONS This study suggests that the labiopalatal position of impacted canines and resorption of permanent incisors might be predicted using sector location on panoramic radiography.

Analysis of the Size and Position of the Mental Foramen Using the CS 9000 Cone-beam Computed Tomographic Unit

INTRODUCTION The mental foramen (MF) houses vital neurovascular structures, thus making it an anatomic landmark of great importance for many dental procedures. Because the size and position of the MF can vary, proper planning is necessary beforehand to prepare the strategy of treatment. The purpose of this retrospective observational study was to determine and compare the size and position of the MF using the CS 9000 CBCT unit (Carestream Dental, Rochester, NY) to the findings from similar studies. METHODS Tangential, axial, and coronal CBCT images of 106 patients were retrospectively evaluated to determine the size and position of the MF with respect to the mandibular second premolar apex and the cementoenamel junction. Distinguishing characteristics of sex, age, and race were evaluated. RESULTS Regarding location, 53.7% of the MFs were located mesial, 45.3% distal, and 1% coincident to the apex of the mandibular second premolar. Males had a significantly greater coronal height and tangential height measurement than females. Black patients had a significantly greater distal horizontal distance from the cementoenamel junction than white patients. The mean width of the MF was 4.08 mm (axial) or 4.12 mm (tangential), whereas the mean height was 3.54 mm (tangential) or 3.55 mm (coronal). CONCLUSIONS The present study shows that the size and position of the MF can be reliably measured using limited field of view CBCT technology. The findings are similar to previous studies when considering the averages and ranges of the measurements.

Effect of the geometry of the intraoral position-indicating device on effective dose

OBJECTIVE The objective of this study was to calculate and compare the effective dose and to estimate risk from the use of intraoral position-indicating devices of differing geometries. STUDY DESIGN Thermoluminescent dosimeters were placed at selected sites in the upper portion of a tissue-equivalent human phantom to record the equivalent dose to weighted tissues and organs. The phantom was exposed to simulated complete mouth surveys with either a long (29.8 cm) or short (19.6 cm) round open-end position-indicating device, a long (35.3 cm) or short (23.3 cm) rectangular open-end position-indicating device, or a pointed (29.6 cm) closed-end position-indicating device. RESULTS The effective dose was calculated as the sum of the equivalent doses to each organ or tissue multiplied by that organ or tissues weighting factor. The salivary glands were included as part of the remainder. The effective dose ranged from 362 micro Sv for the pointed position-indicating device, to 63 micro Sv for both the long and the short rectangular position-indicating devices. CONCLUSIONS These effective doses were calculated to represent a probability for stochastic effects that range in magnitude from 26 x 10(-6) to 4.6 x 10(-6).

Grid versus air gap: A comparison of cephalometric techniques

This study compares two cephalometric radiography techniques: one that uses a grid, the other an air gap, both of which increase image contrast by reduction of scatter radiation to the film. A 12.0 cm water phantom was used with a modified cephalometric radiography unit operating at 71 kVp. Air gaps (patient-to-film distances) of 0.0, 7.5, 12.5, 17.5, 25.5 cm were compared with a 10:1 ratio stationary focused grid at 0.0 cm. Comparisons were made from the measured patient surface exposure, the calculated contrast improvement factor, nominal magnification, and image resolution at each distance. Radiation exposure to the patient was 2.52 times greater with the grid than without. Using regression formulas, the contrast improvement factor of the grid was calculated to equate to an air gap of 9.5 cm. The 9.5 cm air gap would reduce patient exposure by 59.6% with similar image contrast and resolution as compared with the grid. Overall magnification was increased by 6.6% with the 9.5 cm air gap.