Ernest W.N. Lam

The Effect of Vertical and Horizontal Head Positioning in Panoramic Radiography on Mesiodistal Tooth Angulations

The purposes of this study were to examine the effect of potentially common patient positioning errors in panoramic radiography on imaged mesiodistal tooth angulations and to compare these results with the imaged mesiodistal tooth angulations present at an idealized head position. A human skull served as the matrix into which a constructed typodont testing device was fixed according to anteroposterior and vertical cephalometric normals. The skull was then repeatedly imaged and repositioned five times at each of the following five head positions: ideal head position, 5 degrees right, 5 degrees left, 5 degrees up, and 5 degrees down. The images were scanned and digitized with custom software to determine the image mesiodistal tooth angulations. Results revealed that the majority of image angles from the five head positions were statistically significantly different than image angles from the idealized head position. Maxillary teeth were more sensitive to 5 degrees up/down head rotation, with 5 degrees up causing mesial projection and 5 degrees down causing distal projection of maxillary roots. Mandibular anterior teeth were more sensitive to 5 degrees right/left head rotation, with the projected mesiodistal angular difference between 5 degrees right and 5 degrees left rotation ranging from 4.0 degrees to 22.3 degrees. Maxillary teeth were relatively unaffected by 5 degrees right/left head rotation, and mandibular teeth were relatively unaffected by 5 degrees up/down head rotation. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution with an understanding of the inherent image distortions that can be further complicated by the potential for aberrant head positioning.

Effect of buccolingual root angulation on the mesiodistal angulation shown on panoramic radiographs

INTRODUCTION The purpose of this study was to evaluate the effect of buccolingual root angulation on the perception of root parallelism in panoramic images. METHODS A skull-typodont device was constructed according to cephalometric norms. The bases of the typodont were partially sectioned so that the buccolingual orientation of 4 adjacent pairs of teeth could be easily modified. Three buccolingual angulations were used for each tooth. Nine image sequences were necessary to analyze all possible buccolingual orientation combinations between adjacent teeth. The true root parallelism angulations relative to an orthodontic archwire were compared with the angulations obtained from scanned panoramic films. RESULTS The largest root parallelism differences for adjacent teeth occurred between the maxillary canine and the first premolar. The second largest differences occurred in the mandibular canine-premolar area. No significant differences were found in the incisor area. CONCLUSIONS The root parallelism expression in the canine-premolar region can be modified by altering the buccolingual orientation. Buccolingual orientation changes do not seem to affect the incisor area. The clinical usefulness of panoramic radiography to assess root parallelism should be approached with caution, especially in premolar extraction sites.

Resolution of Maxillary Sinus Mucositis after Endodontic Treatment of Maxillary Teeth with Apical Periodontitis: A Cone-Beam Computed Tomography Pilot Study

INTRODUCTION Apical periodontitis (AP) is an inflammatory response that can affect the maxillary sinus. This study characterized maxillary sinus mucositis adjacent to teeth with AP and assessed its resolution after endodontic treatment. METHODS Thirty maxillary sinuses in subjects (n = 29) who had AP associated with maxillary posterior teeth were imaged with cone-beam computed tomography (CBCT). When mucositis was detected, its resolution was assessed with CBCT scanning 3 months after treatment, and periapical healing was assessed using the periapical index (PAI) after 6 months. RESULTS Excluding 5 sinuses obscured by sinusitis, mucositis was detected in 14 of 25 sinuses (56%). Nonsignificant inverse association was observed between the mucosal lining thickness and the distance from the sinus to root apices with AP. Four noncompliant subjects were discontinued. Three months after treatment, mucositis was fully resolved in 3 of 10 subjects (30%), partially resolved in 3 of 10 subjects (30%), unchanged in 3 of 10 subjects (30%), and worsened in 1 subject (10%). Six months after treatment, 6 of 10 subjects (60%) had reduced PAI scores classified as healed or healing. The subject with expanded mucositis at 3 months was not healing at 6 months. CONCLUSIONS Within the limited sample of this pilot study, CBCT imaging revealed a lower-than-expected prevalence of mucositis adjacent to teeth with AP. Fully resolved mucositis was not common 3 months after endodontic treatment, suggesting that in specific cases it might linger beyond 3 months after the elimination of the endodontic infection. Because of the low statistical power, the association between the resolution of mucositis and periapical healing could not be explored.

Cone-beam Computed Tomography for Detecting Vertical Root Fractures in Endodontically Treated Teeth: A Systematic Review

INTRODUCTION A vertical root fracture (VRF), commonly found in teeth with endodontic treatment, is challenging to diagnose and has poor treatment outcomes. Cone-beam computed tomography (CBCT) has become an increasingly popular imaging modality in endodontics, but image artifacts arising from root-filling materials may hinder VRF detection. The aim of this investigation was to conduct a systematic review to assess the diagnostic ability of CBCT for detecting VRFs in endodontically treated teeth. METHODS A systematic review of in vivo clinical diagnostic literature (initial search December 2014, updated August 2015) was conducted. Assessment of methodological quality was performed by using the modified Quality Assessment of Diagnostic Accuracy Studies tool. RESULTS Four studies with a total of 130 patients were included. The reported ranges of values were 40%-90% for VRF prevalence, 84% (0.64-0.95) to 100% (0.83-1.00) for sensitivity, 64% (0.35-0.87) to 100% (0.03-1.00) for specificity, 71% (0.51-0.87) to 100% (0.63-1.00) for positive predictive value, and 50% (0.01-0.99) to 100% (0.84-1.00) for negative predictive value. All 4 studies revealed multiple items at high risk or unclear risk of bias. CONCLUSIONS Because of the significant imprecision in the range of reported estimates and the biases observed in the included studies, there is currently insufficient evidence to suggest that CBCT is a reliable test in detecting VRFs in endodontically treated teeth.

Predictive factors of vertical bone depth in the paramedian palate of adolescents.

OBJECTIVE To determine whether a relationship exists between the vertical bone depth in the paramedian palate (PP) of growing patients and age, gender, and palatal morphology. Clinically detectable traits may decrease the need for further imaging prior to implant placement for orthodontic anchorage. MATERIALS AND METHODS Cone beam computed tomagraphic scans (Newtom-9000, Verona, Italy) were acquired in 183 orthodontic patients (10-19 years old). Vertical bone depth was measured at nine unilateral locations in the PP of each subject. Measurements were analyzed with univariate and multivariate statistical tests. RESULTS Significant variability in the bone thickness was found among locations and among subjects. Male subjects had significantly greater mean bone thickness in six of the nine locations measured, showing a mean of 1.22 mm more vertical bone than females showed at these locations. Age and palatal measurements did not demonstrate a clinically useful relationship with bone depth. CONCLUSIONS Age and palatal morphology are not valid predictors of bone height in the PP. Because of the large variability of bone thickness in this region, computed tomographic imaging remains valuable prior to paramedian implant placement in growing individuals. The paramedian palate presents a promising region for palatal implant placements when the midpalatal suture is to be avoided.

The effects of slice thickness and interslice interval on reconstructed cone beam computed tomographic images

OBJECTIVE The objective of this study was to compare the effects of varying 2 image-processing parameters, slice thickness and interslice interval, on the appearances of reconstructed cone beam CT (CBCT) images. STUDY DESIGN Bone height was used a metric for comparing images reconstructed with different slice thicknesses and interslice intervals. We examined 102 putative implant sites in 18 subjects who had treatment planned for dental implants and who were imaged with custom-fitted imaging stents with linear radiopaque markers. Image slice thickness and interslice interval were increased in millimetric increments from 1 to 5 mm, and bone height was used to determine if varying these parameters had a bearing on the resulting images. RESULTS Statistically significant differences were found between bone heights when slice thickness or interslice interval were varied by greater than 1 mm (P < .005). CONCLUSIONS Understanding the effects of slice thickness and interslice interval may be important in the portrayal of both normal anatomy and pathoses in CBCT images.

A retrospective analysis of referral patterns for oral radiologic consultation over 3 years in Ontario, Canada

OBJECTIVES To determine the types of practitioners who most commonly refer and the film type and diagnostic entities that are most frequently submitted for oral radiologic consultation in Ontario, Canada. STUDY DESIGN A total of 430 referral letters and responses from 2 Ontario oral radiologists from 2003 to 2005 were analyzed. Data collected included the specialty of the referring practitioner, the film type(s) submitted, the radiographic density of the entity of interest, and the interpretation by the radiologist. RESULTS General practitioners (58.9%) and oral surgeons (21.5%) were the most frequently referring practitioner types, representing 1.2% and 17.1% respectively of each group practicing in Ontario. Also, 18.2% of oral pathologists referred. Panoramic radiographs (79.5%) were included in referrals more often than intraoral radiographs (46.0%). Of the entities, 37.0% were radiopacities, 27.4% were radiolucencies, and 13.5% had mixed radiopaque-radiolucent density. The radiologists interpreted normal features (55.6%) most often. CONCLUSION Panoramic radiographs with normal findings were submitted to oral radiologists for consultation most frequently in Ontario.

Image distortion and magnification of 3 digital CCD cephalometric systems.

OBJECTIVE The magnification and distortion of images made from scanning and nonscanning CCD cephalometric systems was evaluated. STUDY DESIGN Acrylic box and dry human skull phantoms were imaged using a conventional cephalostat, the nonscanning Kodak 8000C, the horizontally scanning GE/Instrumentarium OC100D, and the vertically scanning Sirona OrthophosDS. True linear and angular measurements of the phantoms were made using a coordinate measuring system and the Hitachi MercuRay cone beam system. The accuracy of linear and angular measurements was assessed, as were magnification and distortion, where appropriate. RESULTS Statistically significant differences between linear and angular measurements were found for almost all measurements for both phantoms. In general, the conventional cephalostat and Sirona OrthophosDS systems produced the greatest magnification and distortion while the GE/Instrumentarium OC 100D and Kodak 8000C systems, the least. CONCLUSIONS Measurement differences related to the beam geometries of these systems could not be predicted a priori. Unaccounted for, these differences could result in clinically significant consequences.

High‐resolution cone‐beam computed tomography for assessment of bone invasion in oral cancer: Comparison with conventional computed tomography

Radiologic assessment of mandibular bone invasion is critical in evaluating the extent of bone resection required in patients with oral cancer. There are a few reports of improved sensitivity with cone‐beam CT (CBCT) over conventional CT.

Évaluation de l’angulation radiculaire mésio-distale pour les images panoramiques et l’impact de l’angulation radiculaire vestibulo-linguale

Resume Des images panoramiques ont ete realisees a partir d’un fantome anatomiquement correct avec trois angulations vestibulo-linguales pour chaque dent (originelle, 10° de torque radiculo-vestibulaire et 10° de torque radiculo-lingual). La vraie angulation vestibulaire de chaque dent a ete determinee a l’aide d’un appareil de mesure a coordonnees tridimensionnelles. Chaque dent avait au moins une valeur d’angulation qui etait statistiquement differente des autres angles mesio-distaux ayant des orientations vestibulo-linguales differentes. Les racines ayant des orientations vestibulaires ont ete projetees plus en distal que dans la realite ; les racines positionnees en lingual ont ete projetees plus mesialement. Les canines et les premolaires aux deux arcades etaient les dents les plus touchees ; ce phenomene etait plus prononce au maxillaire qu’a la mandibule. Les changements d’orientation vestibulo-linguale n’ont pas influence l’expression de l’angulation radiculaire dans la region des incisives.