Brent E. Larson

Dosimetry of a cone-beam computed tomography machine compared with a digital x-ray machine in orthodontic imaging

INTRODUCTION Cone-beam computed tomography (CBCT) has become a routine imaging modality for many orthodontic clinics. However, questions remain about the amount of radiation patients are exposed to during the scans. This study determined the amounts of radiation potentially absorbed by a patient during orthodontic imaging with a CBCT machine with various scan settings compared with a conventional 2-dimensional digital x-ray machine. METHODS The radiation exposures delivered by a next generation i-CAT CBCT machine (Imaging Sciences International, Hatfield, Pa) at various scan settings and orthopantomograph OP100/OC100 digital x-ray machine (Instrumentarium Dental, Tuusula, Finland) during panoramic and cephalometric radiography were recorded using thermoluminescent dosimeters placed inside a head and neck phantom. The manufacturer-recommended settings for an average adult male were used for both types of machines. Effective doses were calculated using the tissue-weighting factors recommended by the 2007 International Commission on Radiological Protection. RESULTS The effective doses at various voxel sizes and field of view settings ranged from 64.7 to 69.2 μSv for standard resolution CBCT scans (scan time 8.9 s) and 127.3 to 131.3 μSv for high resolution full field of view scans (scan time 17.8 s), and measured 134.2 μSv for a high-resolution landscape scan with a voxel size as would be used for SureSmile (OraMetrix, Richardson, Tex) therapy (scan time 26.9 s). The effective doses for digital panoramic and lateral cephalometric radiographs measured 21.5 and 4.5 μSv, respectively. CONCLUSIONS CBCT, although providing additional diagnostic and therapeutic benefits, also exposes patients to higher levels of radiation than conventional digital radiography.

Accuracy and precision of a 3D anthropometric facial analysis with and without landmark labeling before image acquisition

OBJECTIVE To determine the influence of landmark labeling on the accuracy and precision of an indirect facial anthropometric technique. MATERIALS AND METHODS Eighteen standard linear craniofacial measurements were obtained from 10 adults using the 3dMDface system, with landmarks labeled (Labeled_3D) and without landmarks labeled (Unlabeled_3D) before image acquisition, and these were compared with direct anthropometry (Caliper). Images were acquired twice in two different sessions 1 week apart (T1 and T2). Accuracy and precision were determined by comparing mean measurement values and absolute differences between the three methods. RESULTS Mean measurements derived from three-dimensional (3D) images and direct anthropologic measurements were mostly similar. However, statistically significant differences (P < .01) were noted for seven measurements in Labeled_3D and six measurements in Unlabeled_3D. The magnitudes of these differences were clinically insignificant (<2 mm). In terms of precision, results demonstrated good reproducibility for both methods, with a tendency toward more precise values in Labeled_3D, when compared with the other two techniques (P < .05). We found that Labeled_3D provided the most precise values, Unlabeled_3D produced less precise measurements, and Caliper was the least capable of generating precise values. CONCLUSIONS Overall, soft tissue facial measurement with the 3dMDface system demonstrated similar accuracy and precision with traditional anthropometry, regardless of landmarking before image acquisition. Larger disagreements were found regarding measurements involving ears and soft tissue landmarks without distinct edges. The 3dMDface system demonstrated a high level of precision, especially when facial landmarks were labeled.

Cone-beam computed tomography is the imaging technique of choice for comprehensive orthodontic assessment

It is interesting to observe the adoption of new technology in dentistry and orthodontics. Of particular interest is the use of cone-beam computed tomography (CBCT) as the imaging protocol of choice for comprehensive orthodontic treatment. A concise review of the diffusion of innovation in dentistry was published by Parashos and Messer, who concluded that the adoption of technology is affected by factors that “include a complex interplay of perceived benefits and advantages, and psychosocial and behavioral factors, in decision-making.” Lateral and posteroanterior cephalograms were introduced to orthodontics in the early 1930s by Broadbent; yet, adoption of this technology, which is an accepted standard today, was still being resisted when Steiner wrote in 1953 about the use of cephalogram films: “It has been claimed by many that it is a tool of the research laboratory and that the difficulties and expense of its use in clinical practice are not justified. Many have argued that the information gained from cephalometric films, when used with present methods of assessment, do not contribute sufficient information to change, or influence, their plans of treatment.” Steiner’s statement could easily be applied to the use of CBCT today. A recent review suggested that CBCT should be used as an adjunct imaging technique in orthodontics. I propose that, although we still have much to learn about how to best use CBCT imaging to improve the outcomes of orthodontic treatment, we know enough about its application to consider it the imaging of choice for comprehensive orthodontic treatment. BENEFITS OF CBCT FOR ORTHODONTIC ASSESSMENT

Technique Comparison for Efficient Orthodontic Tooth Measurements Using Digital Models

OBJECTIVE To determine the best technique for measuring mesial-distal tooth widths on digital models. METHODS The individual mesial-distal tooth widths were measured (first molar to first molar, maxillary and mandibular) on 32 stone casts and corresponding digital models (emodels, GeoDigm, Chanhassen, Minn). The digital models were measured using five different techniques: occlusal aspect, occlusal aspect zooming in on each individual tooth, facial aspect rotating as needed, facial aspect from three standard positions (R buccal, facial, and L buccal), and qualitatively rotating the model in any position deemed necessary. Measurements were repeated three times at least 1 week apart. The operator time needed to complete each set of measurements was recorded. RESULTS Four of five digital measurement techniques (except for the facial aspect from three standard positions) showed a slight positive bias (overestimation in measured width) compared with stone cast measurements. Measuring from the occlusal aspect resulted in the greatest Pearson correlation (98.509%), the least Altman-Bland standard deviation of differences value (1.881 mm), and the second fastest measuring time (2 minutes 3 seconds). Qualitatively rotating the model had similar Pearson correlation and Altman-Bland values to the Occlusal technique but took the longest time to measure (7 minutes 1 second). CONCLUSIONS The Occlusal measurement technique for digital models was the best combination of accuracy, repeatability, and speed of measurement.

Effect of alendronate on orthodontic tooth movement in rats

INTRODUCTION Osteoclastic activity is required for orthodontic force to move teeth through alveolar bone. Bisphosphonates are drugs that inhibit osteoclast maturation, function, and survival. The aim of this study was to assess orthodontic tooth movement in rats receiving bisphosphonate treatment. METHODS Two groups of Sprague-Dawley rats were used. The rats in the treatment group received 7 mg per kilogram of body weight per week of alendronate sodium, and those in the control group received no drugs. A coil spring exerting a constant 50-g force was activated across the span from the central incisors to the first molar. As the first molar tipped mesially, a diastema between the first and second molars was created. Vinyl polysiloxane impressions were poured in die stone, and the diastema was measured indirectly with a charged-couple device microscope camera and Optimas software (Media Cybernetics, Newburyport, Mass). RESULTS Statistical analysis with repeated-measures analysis of variance showed less orthodontic tooth movement in the alendronate group compared with control group (0.06 vs 0.24 mm at 2 weeks, and 0.45 vs 1.06 mm at 4 weeks; P = 0.0004 for the alendronate vs control main effect). CONCLUSIONS This study demonstrated an inhibitory effect of alendronate administration on orthodontic tooth movement in a rat model.

Treatment of white spot lesions with ACP paste and microabrasion.

OBJECTIVE To examine the effects of application of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) paste and microabrasion treatment on the regression of white spot lesions (WSLs). MATERIALS AND METHODS Artificially-induced WSLs in bovine enamel were randomly assigned to one of four treatment groups: CPP-ACP paste only, microabrasion only, microabrasion and CPP-ACP, and a control. Samples were treated with each regimen twice daily for 2 weeks and stored in remineralizing solution between the treatments. Quantitative light-induced fluorescence was used to measure changes in fluorescence, which indicate changes in mineral content of WSLs immediately before (T1) and 2 weeks after treatment (T2). A two-within-subject factor analysis of variance was used to analyze the significance of any changes in mineral content of the lesions from T1 to T2. RESULTS There was a statistically significant (P < .05) gain in fluorescence associated with the microabrasion only, as well as the microabrasion and CPP-ACP treatments. The changes in fluorescence for the CPP-ACP treatment alone were not statistically significant (P  =  .40). CONCLUSIONS CPP-ACP paste alone does not significantly improve the fluorescence value (ie, the mineral content) of WSLs. Within the limitations of this in vitro study, microabrasion treatment with or without CPP-ACP improved the fluorescence and thus reduced WSLs.

Asymmetry assessment using cone-beam CT: a class I and class II patient comparison

OBJECTIVE To estimate possible differences in skeletal asymmetry between patients with skeletal Class I and skeletal Class II relationships. MATERIALS AND METHODS Cone beam computed tomography (CBCT) images were examined from 70 consecutive patients who presented for orthodontic care and fit the inclusion criteria. Asymmetry was quantified using an asymmetry index developed by Katsumata et al. Anatomic landmarks were defined and reference planes were established to determine the asymmetry of the landmarks using a constructed coordinate plane system. Thirty randomly selected patients were reanalyzed to assess the reliability of the method. RESULTS Statistical analysis did not find any significant relationship between asymmetry and A-P skeletal relationship for any of the landmarks. Asymmetry index scores were reproducible within a certain range of agreement for each landmark. CONCLUSIONS Based on this study, the discrepant jaw growth resulting in a Class II skeletal pattern results in no more skeletal asymmetry than Class I skeletal patterns.

Accuracy, reproducibility, and time efficiency of dental measurements using different technologies

INTRODUCTION Historically, orthodontists have taken dental measurements on plaster models. Technological advances now allow orthodontists to take these measurements on digital models. In this study, we aimed to assess the accuracy, reproducibility, and time efficiency of dental measurements taken on 3 types of digital models. METHODS emodels (GeoDigm, Falcon Heights, Minn), SureSmile models (OraMetrix, Richardson, Tex), and AnatoModels (Anatomage, San Jose, Calif) were made for 30 patients. Mesiodistal tooth-width measurements taken on these digital models were timed and compared with those on the corresponding plaster models, which were used as the gold standard. Accuracy and reproducibility were assessed using the Bland-Altman method. Differences in time efficiency were tested for statistical significance with 1-way analysis of variance. RESULTS Measurements on SureSmile models were the most accurate, followed by those on emodels and AnatoModels. Measurements taken on SureSmile models were also the most reproducible. Measurements taken on SureSmile models and emodels were significantly faster than those taken on AnatoModels and plaster models. CONCLUSIONS Tooth-width measurements on digital models can be as accurate as, and might be more reproducible and significantly faster than, those taken on plaster models. Of the models studied, the SureSmile models provided the best combination of accuracy, reproducibility, and time efficiency of measurement.

Effectiveness of computer-assisted orthodontic treatment technology to achieve predicted outcomes.

OBJECTIVE To evaluate the effectiveness of computer-assisted orthodontic treatment technology to produce the tooth position prescribed by the virtual treatment plan. MATERIALS AND METHODS Posttreatment models of 23 patients treated with SureSmile were digitally superimposed on their corresponding virtual treatment plan models utilizing best-fit surface-based registration. Individual tooth-position discrepancies between virtual treatment plan and actual outcome were computed. Discrepancies less than 0.5 mm in mesial-distal, facial-lingual, and vertical dimensions, and less than 2° for crown torque, tip, and rotation were considered clinically ideal. One-sided test of equivalence was performed on each discrepancy measurement, with P < .05 considered statistically significant. RESULTS Mesial-distal tooth position was clinically ideal for all teeth with the exception of maxillary lateral incisors and second molars. Facial-lingual tooth position was clinically ideal for all teeth except maxillary central incisors, premolars, and molars, and mandibular incisors and second molars. Vertical tooth position was clinically ideal for all teeth except mandibular second molars. For crown torque, tip, and rotation, discrepancy exceeded the limits considered clinically ideal for all teeth except for crown torque on mandibular second premolars and crown tip on mandibular second premolars and first molars. CONCLUSIONS The effectiveness of computer-assisted orthodontic treatment technology to achieve predicted tooth position varies with tooth type and dimension of movement.

Craniofacial and intraoral phenotype of Robinow syndrome forms

Beiraghi S, Leon‐Salazar V, Larson BE, John MT, Cunningham ML, Petryk A, Lohr JL. Craniofacial and intraoral phenotype of Robinow syndrome forms.