Janice S. Lee

Evaluation of the human airway using cone-beam computerized tomography

OBJECTIVE The goal of this project was to define and measure human airway space with radiographic volumetric 3-dimensional imaging and digital reconstruction of the pharynx using cone-beam computerized tomography. STUDY DESIGN This was a randomized retrospective study. Ten patient scans were selected randomly from a pool of 196 subjects seeking dental treatment at the University of California, San Francisco. Digital Imaging and Communications in Medicine-format volume images were captured using a low-radiation rapid-scanning cone-beam computerized tomography system (Hitachi MercuRay). RESULTS Detailed progressive rostrocaudal cross-sectional area histograms indicated that 8 of the 10 subjects demonstrated a region of maximum constriction near the oropharynx level. The most restricted cross-sectional area varied from 90 mm(2) to 360 mm(2). CONCLUSIONS The maximum constriction of the airway in 10 subjects quietly breathing for 10 seconds indicated variation in the level of the pharynx and the extent of the rostrocaudal zone of restriction.

Comparison of Pharyngeal Airway Changes on Plain Radiography and Cone-Beam Computed Tomography After Orthognathic Surgery

PURPOSE The purpose of the present prospective study was to develop a 3-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether changes in the airway before and after orthognathic surgery correlate on 2-dimensional lateral cephalogram and 3-dimensional CBCT images. MATERIALS AND METHODS Patients requiring orthognathic surgery during 2004 to 2005 were recruited for the present study. Lateral cephalograms and CBCT scans were obtained at 3 points: preoperatively, within 1 month postoperatively, and after 6 months postoperatively. The nasopharynx, oropharynx, and hypopharynx were segmented on both the radiograph and the CBCT scan for each patient in a repeatable manner at each point. For the lateral cephalogram, linear measurements in the middle of each of the 3 segments were obtained. For the CBCT, volumetric measurements of each of the 3 segments were obtained. The intrarater variability was assessed, and Pearsons correlation was used to compare the 2 imaging modalities. RESULTS A total of 20 patients scheduled for orthognathic surgery were recruited for the present study. Of the 20 patients, 13 were female and 7 were male. The mean age at surgery was 23.85 years (range 14 to 43). Of the 20 patients, 6 underwent maxillary advancement only, 8 underwent mandibular advancement with or without genioplasty, and 6 underwent 2-jaw surgery or mandibular setback. We examined the entire cohort without separation into procedure or examination point and found a weak, but statistically significant, correlation between the linear and volume measurements in the nasopharyngeal and oropharyngeal regions but not in the hypopharyngeal region (r = 0.43, P < .002; r = 0.49, P < .0002; r = 0.16, P = .26, respectively). The maxillary advancement group (n = 6) demonstrated a correlation between the linear and volume measurements in the nasopharyngeal region (r = 0.53, P = .03). The mandibular advancement with or without genioplasty group (n = 8) showed a correlation in the nasopharyngeal and oropharyngeal regions (r = 0.55, P < .02, and r = 0.46, P = .05, respectively). For the combination/setback procedures (n = 6), a correlation was found in the oropharyngeal region (r = 0.64, P < .01). All other comparisons between the linear and volume measurements did not correlate. Additionally, no correlations were found between the linear and volumetric change in airway size between 6 months postoperatively and preoperatively, except for the oropharyngeal region (r = 0.67, P < .01). CONCLUSION We present a method of measuring the airway that could be used for both 2-dimensional and 3-dimensional images. It includes segmentation of the pharyngeal airway into its nasopharyngeal, oropharyngeal, and hypopharyngeal components. Correlations were found between the linear and volumetric measurements of the segmented airway in patients who had undergone orthognathic surgery; however, the correlations were generally weak.

Anthropometric analysis of the human mandibular cortical bone as assessed by cone-beam computed tomography.

PURPOSE The purpose of this study is to assess cortical thickness, height, and width with cone-beam computed tomography (CBCT), and determine the relationship of these parameters with age. PATIENTS AND METHODS A total of 113 subjects from the University of California at San Francisco Orthodontic Clinic with a CBCT scan were enrolled. Subjects were stratified by age in decades. Thickness of buccal and lingual cortices and mandibular height and width were evaluated in 5 regions (13 sites). A single factorial ANOVA was used to compare the parameters among age groups. P less than or equal to .05 was statistically significant. RESULTS There were 44 (38.9%) males; 69 females. For all groups, the thickest to the least thick cortical plates were: base of the mandible, lower buccal one third, upper lingual one third, upper buccal one third, and lower lingual one third. In all groups, the mandible increased in height as the midline was approached, and the width of the upper third of the mandible decreased from the second molar to the symphysis whereas the reverse occurred in the lower third. Comparison of the age groups showed that subjects 10 to 19 years old had thinner cortical plates than other age groups (P <or= .05) with peak thickness in subjects 40 to 49 years old. The subjects 10 to 19 years old also had lower posterior mandibular height (P <or= .05). There was no statistical difference in width among the groups. CONCLUSIONS The mandibular cortical bone is thickest at the base, on the buccal side. Subjects who are 10 to 19 years old have thinner cortical bone and decreased mandibular height compared with all other age groups. The mandible continues to mature through 40 to 49 years of age and then decreases in thickness after this period.

Morphologic Evaluation and Classification of Facial Asymmetry Using 3-Dimensional Computed Tomography

PURPOSE A systematic classification is needed for the diagnosis and surgical treatment of facial asymmetry. The purposes of this study were to analyze the skeletal structures of patients with facial asymmetry and to objectively classify these patients into groups according to these structural characteristics. PATIENTS AND METHODS Patients with facial asymmetry and recent computed tomographic images from 2005 through 2009 were included in this study, which was approved by the institutional review board. Linear measurements, angles, and reference planes on 3-dimensional computed tomograms were obtained, including maxillary (upper midline deviation, maxilla canting, and arch form discrepancy) and mandibular (menton deviation, gonion to midsagittal plane, ramus height, and frontal ramus inclination) measurements. All measurements were analyzed using paired t tests with Bonferroni correction followed by K-means cluster analysis using SPSS 13.0 to determine an objective classification of facial asymmetry in the enrolled patients. Kruskal-Wallis test was performed to verify differences among clustered groups. P < .05 was considered statistically significant. RESULTS Forty-three patients (18 male, 25 female) were included in the study. They were classified into 4 groups based on cluster analysis. Their mean age was 24.3 ± 4.4 years. Group 1 included subjects (44% of patients) with asymmetry caused by a shift or lateralization of the mandibular body. Group 2 included subjects (39%) with a significant difference between the left and right ramus height with menton deviation to the short side. Group 3 included subjects (12%) with atypical asymmetry, including deviation of the menton to the short side, prominence of the angle/gonion on the larger side, and reverse maxillary canting. Group 4 included subjects (5%) with severe maxillary canting, ramus height differences, and menton deviation to the short side. CONCLUSION In this study, patients with asymmetry were classified into 4 statistically distinct groups according to their anatomic features. This diagnostic classification method will assist in treatment planning for patients with facial asymmetry and may be used to explore the etiology of these variants of facial asymmetry.

Comparison of methohexital and propofol use in ambulatory procedures in oral and maxillofacial surgery.

PURPOSE Short-acting anesthetic agents, such as propofol and methohexital, are commonly used for ambulatory procedures in the practices of oral and maxillofacial surgeons (OMS). This study compares the safety and anesthetic outcomes of propofol and methohexital. In addition, the study compares the safety and outcomes of these agents when administered either by an OMS who simultaneously provides anesthesia and performs the procedure (anesthetist/surgeon), or by a non-OMS provider of anesthesia (anesthesiologist or certified registered nurse anesthetist; CRNA) whose sole obligation is to provide anesthesia. MATERIALS AND METHODS This is a prospective study of anesthesia techniques used in an office-based ambulatory setting by OMS throughout the United States, in which either propofol or methohexital was used for sedation/anesthesia. The study variables included demographic information, anesthetic agent, adverse outcomes related to anesthesia, operative procedure, and provider of anesthesia. These variables were compared with the patient group that received a benzodiazepine/narcotics regimen for sedation (control group). Bivariate (contingency tables) and multivariate (logistic regression) analyses were conducted. P < or = .05 was considered statistically significant. RESULTS The study included 47,710 patients who met the inclusion criteria: 26,147 (54.8%) patients were in the propofol group, 15,859 (33.2%) were in the methohexital group, and 5,704 (12.0%) were in the benzodiazepine group. Among all study patients, 333 (0.7%) had an adverse event. The most common complication was nausea and vomiting without aspiration. Of the patients in the propofol group, methohexital group, or benzodiazepine group, 0.4%, 1.1%, and 0.8% had an adverse event, respectively. The higher number of complications among patients in the methohexital group compared with patients in the other 2 groups was statistically significant. Of 26,147 patients in the propofol group, 23,799 (91.0%) received anesthesia from an anesthetist/surgeon (OMS), and 2,368 (9.1%) from an anesthesiologist or nurse anesthetist (non-OMS). A total of 109 patients (0.4%) had an adverse event. The majority of patients who received anesthesia from a non-OMS were in the propofol group (2,368 of 2,404 patients; 98.5%). There was no statistically significant difference in the occurrence of adverse outcomes when comparing patients in the propofol group who received anesthesia from an OMS with those who received anesthesia from a non-OMS (P = .24, bivariate analysis; P = .33, multivariate analysis). CONCLUSIONS There is a statistically significant increase in adverse events related to methohexital compared with propofol or benzodiazepine/narcotics for anesthesia. Propofol appears to have the lowest risk for adverse events. There is no statistically significant difference in the number of adverse outcomes between the administration of propofol for ambulatory surgery by OMS as an anesthetist/surgeon and anesthesiologist/nurse anesthetist. It remains critical that our specialty maintains the highest standards, to provide safe anesthesia and to reduce adverse anesthetic events.

Cone-Beam Computed Tomographic Comparison of Surgically Assisted Rapid Palatal Expansion and Multipiece Le Fort I Osteotomy

PURPOSE To examine and compare the skeletal and dental effects of surgically assisted rapid palatal expansion (SARPE) and multipiece Le Fort osteotomy using cone-beam computed tomography (CBCT). MATERIALS AND METHODS This was a prospective cohort study. Patients underwent SARPE or multipiece Le Fort I osteotomy to address maxillary transverse deficiency. CBCT scans were taken preoperatively, immediately postoperatively or after retention, and at least 6 months postoperatively. Four landmark measurements and ratios of dental-to-skeletal change were used to follow skeletal and dental widths in the posterior and anterior maxillary regions. Wilcoxon signed-rank test and Wilcoxon 2-sample rank-sum test were used to compare the landmark measurements and the ratio of dental-to-skeletal change for the 2 surgeries. A P value less than .05 was statistically significant. RESULTS Thirteen patients (mean, 28.3 yr old; 7 women) were enrolled: 9 were treated by multipiece Le Fort I osteotomy and 4 were treated by SARPE. The ratios of dental-to-skeletal expansion in the posterior maxilla for the Le Fort procedure and SARPE were 0.70 ± 0.41 and 25.20 ± 15.8, respectively, and the dental-to-skeletal relapses were 1.17 ± 0.80 and -3.63 ± 3.70, respectively. The ratios of dental-to-skeletal expansion in the anterior maxilla for the Le Fort procedure and SARPE were 0.58 ± 0.38 and 31.80 ± 59.4, respectively, and the dental-to-skeletal relapses were 2.25 ± 3.41 and 4.86 ± 8.10, respectively. CONCLUSION There was greater correlation between dental and skeletal changes in the multipiece Le Fort procedure, indicating bodily separation of the segments, whereas the SARPE showed noteworthy dental and skeletal tipping. Dental relapse was greater than skeletal relapse for these 2 procedures.

Treatment of Arteriovenous Malformation of the Mandible With Resection and Immediate Reconstruction

Arteriovenous malformation (AVM) of the mandible is a rare entity but one that has significant potential for fatality due to massive hemorrhage. Current treatment has involved surgical resection of the mandible in conjunction with adjunctive endovascular embolization to help control hemorrhage. However, jaw resection is deforming and often leaves a significant defect requiring subsequent bone grafting and replacement of lost teeth. We report an endovascular and surgical technique to treat central AVMs of the mandible that permits resection and complete removal of the intraosseous lesion yet prevents facial deformity by preserving the mandibular bone contour and permitting reconstruction of the dentition and restoration of function.

Facial surface morphology predicts variation in internal skeletal shape

INTRODUCTION The regular collection of 3-dimensional (3D) imaging data is critical to the development and implementation of accurate predictive models of facial skeletal growth. However, repeated exposure to x-ray-based modalities such as cone-beam computed tomography has unknown risks that outweigh many potential benefits, especially in pediatric patients. One solution is to make inferences about the facial skeleton from external 3D surface morphology captured using safe nonionizing imaging modalities alone. However, the degree to which external 3D facial shape is an accurate proxy of skeletal morphology has not been previously quantified. As a first step in validating this approach, we tested the hypothesis that population-level variation in the 3D shape of the face and skeleton significantly covaries. METHODS We retrospectively analyzed 3D surface and skeletal morphology from a previously collected cross-sectional cone-beam computed tomography database of nonsurgical orthodontics patients and used geometric morphometrics and multivariate statistics to test the hypothesis that shape variation in external face and internal skeleton covaries. RESULTS External facial morphology is highly predictive of variation in internal skeletal shape ([Rv] = 0.56, P <0.0001; partial least squares [PLS] 1-13 = 98.7% covariance, P <0.001) and asymmetry (Rv = 0.34, P <0.0001; PLS 1-5 = 90.2% covariance, P <0.001), whereas age-related (r(2) = 0.84, P <0.001) and size-related (r(2) = 0.67, P <0.001) shape variation was also highly correlated. CONCLUSIONS Surface morphology is a reliable source of proxy data for the characterization of skeletal shape variation and thus is particularly valuable in research designs where reducing potential long-term risks associated with radiologic imaging methods is warranted. We propose that longitudinal surface morphology from early childhood through late adolescence can be a valuable source of data that will facilitate the development of personalized craniodental and treatment plans and reduce exposure levels to as low as reasonably achievable.

In Search of the Highest Quality: Levels of Evidence in Oral and Maxillofacial Surgery

and infrastructure required toconduct anRCT. 11 In oral and maxillofacial surgical journals, 1.3 to 3% of articles over a 3- and a 10-year period were RCTs. 5,10 This is comparable to similar journals in plastic surgery and otolaryngology. RCTs require randomization of treatment, blinding of subjects and providers, appropriate sample size based on power calculations, data on subjects excluded or lost to follow-up, and a detailed description of these components, all of which are intended toprovide unbiased data and results.However, there is variability in the quality of RCTs that can result from deficiencies in any of these features. In addition, in oral and maxillofacial surgical research, enrolling enough patients for adequate power may be difficult in 1 center or department. To improve the quantity and quality of RCTs in oral and maxillofacial surgical research, RCTs to compare therapies may be conducted by multicenter research teams or practice-based research networks. These 2 research strategies are encouraged by the American

Coronectomy in lower third molar removal

Hypothesis: That coronectomy is an acceptable technique for the management of selected impacted lower third molars in close relationship to the inferior alveolar nerve. Significance: Inferior alveolar nerve involvement with lower third molar removal remains a clinical problem with considerable morbidity. Materials and Methods: Thirty patients, needing lower third molar removal and with the tooth in critical relationship to the inferior alveolar nerve, were enrolled in this study. Evaluation was with Panorex radiograph with added CT scanning in selected cases. Surgically a buccal and lingual flap was raised, a lingual retractor was placed, and the crown of the lower third molar was removed at an angle of 45° from buccal to lingual. The crown was drilled off completely rather than only going through two thirds of the way and then cracking the crown off. The lingual retractor protected the lingual nerve during this procedure. Once the crown had been removed additional buccal root was removed until the whole remaining root fragment of the tooth was at least 3 mm below the crest of the bone. The socket was then irrigated and a watertight primary closure obtained. Results: Thirty patients had a total of 41 lower third molars treated by coronectomy. No cases of inferior alveolar or lingual nerve involvement were noted. There were no cases of wound breakdown. Follow-up radiographs taken at 6 months following the removals indicate that bone has formed over the residual roots. There have been no complications and no patients have required re-exploration. Follow-up varies from 3.1 years to 7 months, and to date there has been no sign of eruption of the residual roots. Discussion: Inferior alveolar nerve damage following third molar removal remains a significant problem in oral and maxillofacial surgery. The relationship of the nerve to the roots can be diagnosed in 3 dimensions with a combination of panoral radiograph and CT scanning, and where there is an intimate relationship and the tooth still needs to be removed, coronectomy appears to offer some advantages over conventional techniques. It can only be used for vertical or mesioangular impactions and is not suitable for horizontal impactions where the nerve may be damaged by sectioning the tooth. Conclusion: Coronectomy is a successful technique for dealing with impacted lower third molars where the roots are in intimate relationship to the inferior alveolar nerve.