Open-mouth Position Research Articles

Generation of virtual models for planning orthognathic surgery using a modified multimodal image fusion technique

Streak artefacts caused by dental metals deteriorate the quality of computed tomography (CT) images. We developed and evaluated a method for generating three-dimensional virtual models to plan orthognathic surgery in patients with multiple dental materials, to avoid the adverse effects of metal artefacts in image fusion. The method basically consists of four procedures: (1) fabrication of a splint in the open-mouth position with fiducial markers, (2) reconstruction of a virtual skull model in the open-mouth position from CT scanning, (3) reconstruction of two virtual dental models in the open-mouth position and either the intercuspal position (ICP) or centric relation (CR) from surface scanning, and (4) three serial steps of image registration and subsequent repositioning of the mandible to the ICP or CR. This method allows for the registration of skull and dental models under artefact-free conditions. To validate the method, CT and dental cast data from 30 patients were used. The registration accuracy was 0.080mm for the initial registration, 0.033mm for the second registration, and 0.028mm for the third registration. The present method can be used to determine the occlusal relationships and craniofacial morphology of patients with dental metals and can be applied to computer-assisted diagnosis and surgery.

Mechanical loading leads to osteoarthritis-like changes in the hypofunctional temporomandibular joint in rats

ObjectivesTemporomandibular joint (TMJ) hypofunction secondary to feeding a liquid diet in the growing period leads to morphological hypoplasia. However, few studies have evaluated the results of mechanical loading on the hypoplastic TMJ. This study investigated whether TMJ hypofunction in rats causes osteoarthritis (OA)-like changes when exposed to mechanical loading. DesignMale 21-day-old Wistar rats were divided into four groups. The first group (C) served as the control. In the second group (W), mechanical loading was applied to the TMJ by continuous steady mouth opening (3h/day for 5 days) from 63 days of age. A jaw-opening device was used to hold the mandible open in the maximal mouth-opening position with a cobalt–chromium (Co–Cr) wire (φ: 0.9mm). Groups C and W both received a normal hard diet. The third group (L) and fourth group (LW) were fed a liquid diet and group LW were subjected to the same loading as group W. We evaluated the TMJ using micro-CT, toluidine blue staining and immunohistochemistry of matrix metalloproteinase (MMP)-13. ResultsIn group LW in the superior and posterior regions of the condyle, bone volume fraction, trabecular thickness and trabecular number were significantly decreased and trabecular spacing was significantly increased. The ratio of MMP-13 immunopositive cells was significantly higher than in the other groups. OA-like changes were also observed, including reduced thickness of the cartilage, irregularities in the chondrocytic layer, and cell-free areas. ConclusionsTMJ hypofunction in rats is likely to lead to OA-like changes when exposed to mechanical loading.

Magnetic resonance imaging of the temporomandibular joint acquired using different parameters

Abstract Introduction: Magnetic resonance imaging (MRI) is considered the examination of choice for the diagnosis of abnormalities in the TMJ. Considering the difficulty in defining and standardizing the diagnostic criteria, and the need for more accurate and reliable diagnosis of conditions in the TMJ, the aim of the present study was to compare three different MRI parameters: Tl-weighted, T2-weighted and proton density-weighted in the diagnosis of changes in the temporomandibular joint. Materials and Methods: Fifty magnetic resonance imaging examinations of the temporomandibular joint (100 temporomandibular joints) were conducted according to a protocol that evaluates disc position, disc function and bone abnormalities. The images were obtained bilaterally in parasagittal sections in closed and open mouth positions in the three studied parameters Three trained oral radiologists assessed all the images. Reliability of the intra- and inter-examiner response was analyzed using the concordance test (Fleiss' kappa; α = 0.05). Results: The reliability of the response patterns between observers for different protocols varied from very good to good. Observers were less constant in their response patterns when assessing proton density-weighted images. There was very good agreement for disc morphology, cortical bone and bone structures/functions; however, there was wide variation for medullary bone marrow signs. Conclusion: T2-weighted imaging was found to be the best examination to assess the medullary bone. For evaluating of disc morphology, cortical bone and bone structures/functions, any protocol is indicated once the protocol does not interfere with the analysis.

Influence of oral stabilization appliances in intra-articular pressure of the temporomandibular joint

Aims:This study analyzed the intra-articular pressure in the upper compartment of the temporomandibular joint (TMJ) under different functional conditions. The influence of stabilization appliances on intra-articular pressure was studied.Methodology:Seventy-four joints from 64 patients (55 women and 9 men; mean age: 43·2±11·86 years; range: 19–61 years) with TMJ disorders were examined. Only 50 joints passed the inclusion criteria. Intra-articular pressure was measured using a 21G needle inserted into the joint and connected to a pressure transducer. Pressure was measured with the jaw in the following positions: at rest, maximal mouth opening, clenching in maximal intercuspal position, and clenching with an oral interoclusal appliance.Results:Fifty joints were included in the study (without blood reflux), mean pressure at rest was negative (–6·06±4·55 mmHg); when the mouth was opened to its maximal position the pressure was lower (−26·09±6·42 mmHg). Mean intra-articular pressure was higher in the maximal intercuspal position (58·56±24·90 mmHg). When an interoclusal appliance device was fitted, mean intra-articular pressure reduced its value by 31·24%, which reached a mean value of 40·56±18·84 mmHg (P<0·001). There were no significant differences in sex. The group over 45 years old had higher pressure values in maximal open mouth position than the group of patients under 45 years old (P<0·02).Conclusions:Interoclusal appliances can reduce pressure in the upper compartment of the TMJ and improve functional status of the joint.

Assessment of lingual frenulum lengths in skeletal malocclusion.

The orofacial musculature plays a pivotal role in maintaining a balance in positioning of the teeth and any imbalance which occurs in this , results in malocclusion. Lingual frenum is a soft tissue structure which tethers the ventral surface of the tongue to the floor of the mouth. This study was performed to analyze the lingual frenal lengths in skeletal class I, class II and Class III malocclusion and to correlate relationship between both. This study comprised of 30 subjects, with 10 in each group and an impression was made with the maximum mouth opening position and the tip of tongue touching the incisive papilla. The length of the lingual frenum was then measured from the casts. The maximum mouth opening position was also determined by measuring the interincisal distance with the maximum mouth opening position. Statistical analysis was done to analyze the relationship between both. The lingual frenum was found to be longest in class III malocclusion, with a statistical significant value of p<0.01. The class II and class I malocclusion did not show much difference. The maximum mouth opening position was also increased in class III malocclusion, followed by class II and class I malocclusion, in a descending order. The lingual frenum exerts erratic forces and a long lingual frenum pushes the mandibular anteriors forwards, resulting in malocclusion. Hence, a relationship between the lingual frenum and malocclusion is essential, so that the erratic forces can be eliminated and excellent results can be achieved, following the correction of malocclusion.

Median mandibular flexure at different mouth opening and its relation to different facial types: A prospective clinical study

Objective:To measure the arch width and Median mandibular flexure (MMF) values at relative rest and maximum jaw opening in young adults with Dolichofacial, Mesofacial, and Brachyfacial types and tested whether the variation in the facial pattern is related to the MMF values in South Indian population.Materials and Methods:This Prospective clinical study consisted of sample of 60 young adults. The subjects were grouped into 3 groups: Group 1: Brachyfacial, Group 2: Mesofacial and types, Group 3: Dolichofacial. Impressions were taken for all the 60 subjects and the casts were scanned and digitized. The intermolar width was measured for Dolichofacial, Mesofacial, and Brachyfacial subjects at relative rest (R) and maximum opening (O).Results:The statistical analysis of the observations included Descriptive and Inferential statistics. The statistical analysis was executed by means of Sigma graph pad prism software, USA Version-4. Kruskal wallis (ANOVA) followed by Dunns post hoc test was performed. Mann Whitney U-test was performed to assess the difference in MMF values between Males and Females of the three groups. The Mean (SD) Mandibular flexure in individuals with Brachyfacial type was 1.12 (0.09), Mesofacial type was 0.69 (0.21), and Dolichofacial type was 0.39 (0.08).Conclusions:The Mean intermolar width was maximum in Brachyfacial type and minimum in Dolichofacial type. MMF was maximum at the maximum mouth opening position and was maximum in individuals with Brachyfacial type.

Magnetic resonance imaging evaluation of discal attachment of superior head of lateral pterygoid muscle in individuals with symptomatic temporomandibular joint

There has been much speculation on the role of the lateral pterygoid muscle (LPM) in temporomandibular joint (TMJ) internal derangement. As a result, this muscle has been the focus of many reports attempting to understand its possible role in TMJ internal derangement. Magnetic resonance (MR) imaging exams of 108 TMJ disorder patients were assessed for types of morphologic insertion of the superior head of LPM to the condyle-disc complex and possible correlation with disc position. The investigation was made on the sagittal T1-weighted MR images in closed- and open-mouth positions. There was a lack of correlation between attachment pattern of the superior head of LPM and presence or absence of anterior disc displacement. The explanation of anterior disc displacement based on the attachment type of the superior head of LPM is unlikely; the type of muscular insertion does not appear to have a predictive or prognostic value for TMJ internal derangement.

Ultrasonography has an acceptable diagnostic efficacy for temporomandibular disc displacement

Medline, Embase and the Chinese Biomedical Literature databases were searched with no language restrictions. Studies evaluating the diagnostic efficacy of ultrasonography in detecting TMJ disc displacement in participants with any symptoms or clinical signs related to temporomandibular disorders (TMD), with use of MRI as the gold standard, were included. Study selection, data abstraction and risk of bias assessment were carried out independently by two reviewers. A meta-analysis was conducted. Fifteen studies (14 cohort studies and one case control) were included in this review; six studies had a low risk of bias, six studies an unclear risk and three studies a high risk. Meta-regression indicated that the detected results were not influenced by the types of ultrasonography, image dimensions, types of transducer and ultrasonic image of the disc (P= .05). The Q* values (the point where sensitivity equals specificity on the summary reviewer operator characteristics curve) of ultrasonography for the closed- and open-mouth positions were 0.79 and 0.91, respectively. The diagnostic efficacy of disc displacement with reduction had a sensitivity of 0.76, a specificity of 0.82, a positive likelihood ratio of 3.80, a negative likelihood ratio of 0.36, a diagnostic odds ratio of 10.95, an area under the curve of 0.83 and a Q* of 0.76. The diagnostic efficacy of disc displacement without reduction had a sensitivity of 0.79, a specificity of 0.91, a positive likelihood ratio of 80.5, a negative likelihood ratio of 0.25, diagnostic odds ratio of 36.80, an area under the curve of 0.97 and a Q* of 0.92. The diagnostic efficacy of ultrasonography is acceptable and can be used as a rapid preliminary diagnostic method to exclude some clinical suspicions. However, positive ultrasonographic findings should be confirmed by magnetic resonance imaging. Also, the ability of ultrasonography to detect lateral and posterior displacements is still unclear.

Effects of open mouth and rubber dam on upper airway patency and breathing

Rubber dams increase the quality and safety of dental treatment. However, the condition of a rubber dam over an open mouth may also obstruct the route for respiration. We tested whether an open mouth with or without a rubber dam would affect upper airway patency and breathing pattern. Twenty young healthy volunteers were imaged with a magnetic resonance (MR) system under three conditions: mouth closed, mouth open, and rubber dam with mouth open. Respiration was concurrently monitored with plethysmography. MRI slices of the upper airway were obtained at 5-mm thicknesses, and the size of the cross-sectional area of the upper airway was measured by image analysis software. Respiratory cycle duration and tidal volume were also measured with digital signal analysis software. The volume of the upper airway became significantly decreased with the mouth open. Analysis of each cross-sectional area of the upper airway revealed that while the oropharyngeal area was significantly narrower with an open mouth, the retropalatal and hypopharyngeal areas were not affected. Placing a rubber dam had no additional influence on upper airway patency but was seen to significantly shorten mean respiratory duration and decrease tidal volume. Open mouth position plays the largest role in decreased upper airway patency, and open mouth position with a rubber dam may further disrupt breathing pattern. Breathing pattern may become deteriorated by airway obstruction during dental treatments requiring a rubber dam.

Web-based calibration of observers using MRI of the temporomandibular joint

Research diagnostic criteria for temporomandibular disorders (RDC/TMDs) were proposed in 1992 with the aim of standardizing and testing methods for diagnosing TMDs. RDC/TMDs have so far been lacking standardized methods for imaging and criteria for imaging diagnosis of disorders of the temporomandibular joint (TMJ). Criteria for disorders of the TMJ have recently been proposed for MRI. The aim of this study was to publish MR images of the TMJ on the web and to test the agreement of five observers using the criteria. 20 cases of MRI of the TMJ were published on the web together with the criteria. The MR images were taken in closed and open mouth positions, and sagittal and coronal views. Five observers diagnosed disc position, disc shape, joint effusion and loose calcified bodies in the TMJ. In all cases except one, three or more observers agreed upon the diagnosis. All agreed on whether a loose calcified body was present or not. The second best agreement was obtained for disc position in the sagittal view, where all observers agreed in 16 of the 20 cases. For disc position in the coronal view and the evaluation of the disc shape, observer agreement was lower. Criteria were useful in order to standardize and simplify evaluation and thereby probably increase the diagnostic outcome among different observers for MRI of the TMJ. We recommend that the criteria be used internationally to facilitate comparisons between different studies.

Transformation of temporomandibular joint disc configuration in internal derangement patients using magnetic resonance imaging

PurposeThe normal disc configuration is biconcave; however, the deformed disc can be found in internal derangement (ID) of the temporomandibular joint (TMJ). The purpose of this study was to evaluate the relationship between the transformation patterns of TMJ disc configuration during mouth opening and disc displacement status, disc reduction ability and TMJ clinical symptoms. MethodsTMJ MR images from volunteers and ID patients were analyzed for closed and open mouth positions. MR images of ID patients were classified into 4 groups: symptomatic joint with anterior disc displacement with or without reduction (ADW or ADWo) and asymptomatic joint with ADW or ADWo. The disc configurations in both positions were categorized as biconcave, biplanar, convex or folded; then the patterns of transformation were observed. ResultsFor the ADW group, the most common disc configuration for closed and open mouth positions were biplanar (66.7%) and biconcave (86.3%). The transformation pattern was significantly related to disc reduction ability (p<0.05). ConclusionsThe transformation patterns of disc configuration during opening were related to anterior disc displacement and disc reduction ability.

Ultrasonography for Detection of Disc Displacement of Temporomandibular Joint: A Systematic Review and Meta-Analysis

To assess the diagnostic efficacy of ultrasonography in detecting disc displacement of the temporomandibular joint. MEDLINE (using OVID, 1950 to April 2011), EMBASE (1980 to April 2011), and the Chinese Biomedical Literature Database (1978 to April 2011) were searched electronically. In addition, relevant journals and reference lists of the included studies were manually searched for any eligible studies on diagnostic accuracy. Two authors performed the study inclusion, data extraction, and risk of bias assessment in duplicate. Meta-analysis was performed with MetaDisc 1.4. Fifteen studies were included in this meta-analysis; 6 studies had a low risk of bias, 6 studies an unclear risk, and 3 studies a high risk. Meta-regression indicated that the detected results were not influenced by the types of ultrasonography, image dimensions, types of transducer, and ultrasonic image of the disc (P > .05). The Q* values of ultrasonography for the closed- and open-mouth positions were 0.79 and 0.91, respectively. The diagnostic efficacy of disc displacement with reduction had a sensitivity of 0.76, a specificity of 0.82, a positive likelihood ratio of 3.80, a negative likelihood ratio of 0.36, a diagnostic odds ratio of 10.95, an area under the curve of 0.83, and a Q* of 0.76. The diagnostic efficacy of disc displacement without reduction had a sensitivity of 0.79, a specificity of 0.91, a positive likelihood ratio of 80.5, a negative likelihood ratio of 0.25, diagnostic odds ratio of 36.80, an area under the curve of 0.97, and a Q* of 0.92. The diagnostic efficacy of ultrasonography is acceptable and can be used as a rapid preliminary diagnostic method to exclude some clinical suspicions. However, positive ultrasonographic findings should be confirmed by magnetic resonance imaging. Also, the ability of ultrasonography to detect lateral and posterior displacements is still unclear. More high-quality studies are needed to assess the diagnostic efficacies of some specific ultrasonographic methods. Standards and criteria for ultrasonographic techniques in the diagnosis of disc displacement should be established in the future.

Magnetic resonance imaging findings of true bifid mandibular condyle with duplicated mandibular fossa

Bifid mandibular condyle (BMC) is a rare asymptomatic morphological alteration with no predilection for age group or gender. Its morphology varies from a shallow groove to two condylar heads with separate necks, oriented mediolaterally or anteroposteriorly. This report describes an unusual case of anteroposterior bifid condyle in a 39-year-old female patient with the main complaint of mouth-opening limitation and a deviation of the mandible to the left side. Magnetic resonance imaging (MRI) findings revealed a bifid condyle on the left side and duplicated mandibular fossa, with the articular disc over the anterior head. The MRI images in the open-mouth position revealed minimal movement of the condyle. Despite the increased number of mediolateral bifid mandibular condyle cases described in the literature, none of previously reported cases of BMC included an anteroposterior bifid condyle case with two distinct mandibular fossa.

Indirect measurement of the temporomandibular joint disc elasticity with magnetic resonance imaging.

The radiological evaluation of the temporomandibular joint (TMJ) consists of demonstrating the morphological features of the disc and the condyle in closed and open mouth positions using MRI. We aimed to determine elasticity of the disc by measuring the amount of elongation during mouth opening. The study population included 49 patients. Coronal T(1) and multiplane oblique T(2) weighted gradient recalled echo sequences were acquired in open and closed mouth positions. Biconcave TMJ disc lengths were measured on sagittal oblique images in both positions. Elongation ratio (ER) was calculated for each patient. According to the findings, TMJs are classified into subgroups: normal (N), dislocated with reduction (DWR), pure DWR (p-DWR), DWR with additional findings (DWR-a) and dislocated without reduction (DWOR). Statistical analysis was performed using the χ(2) test and receiver operating characteristic analysis. Out of 98 discs, 22 of them were evaluated as N, 60 as DWR (28 p-DWR, 32 DWR-a) and 16 as DWOR. There was no significant difference among the disc lengths in three subgroups at the closed mouth position (P = 0.15), whereas there was significant difference in the open mouth position (P = 0.0001). There was significant difference among subgroups as far as ER is concerned (P < 0.05). ER is a strong indicator of elasticity. Compared with the N group, elasticity of the disc was not significantly different in the p-DWR group but the disc elasticity was very degraded in DWR-a and in DWOR. A negative conversion or one smaller than 1.4 mm means a compromised disc, although sometimes it will possess normal anatomical configurations or signal characteristics.

Treatment of dens fracture with cannulated screw fixation under locational guidance

Objective To evaluate the clinical effect of the cannulated screw fixation in treatment of the dens fracture under locational guidance. Methods The study involved 27 patients treated with the cannulated screw fixation under locational guidance from January 2005 to January 2009.There were 19 patients with type II fracture and eight with type light m fracture.The lateral and open mouth position X-ray examination of the cervical ventebrae was done to observe the fracture healing. Results The operation lasted for a range of 40 minutes to 1.3 hour (average 1.0 hour),which showed no any complications.The patients were followed up for average 6.5 months(3-12 months),which showed sound fracture healing in 26 patients but nonhealing in one. Conclusion The cannulated screw fixation for treatment of the dens fracture under locational guidance is characterized by easy operation,minor trauma and satisfactory outcome. Key words: Spinal fractures; Dentate gyrus; Fracture fixation,internal; Navigation

Mandibular coronoid process hyperplasia causing restricted mouth opening

A 52-year-old Caucasian woman underwent pre-anaesthetic evaluation before myomectomy for uterine fibroids. She had limited mouth opening of 10 mm (intra-incisal) and her lateral excursive movements were poor. There was no history of trauma or known temporomandibular dysfunction. The patient had not previously undergone surgery under general anaesthesia. She was not concerned about her limited mouth opening and had not sought medical help for it. Orthopantomogram (Figure 1) and unenhanced computed tomography of the mandible in the closed (Figure 2a) and open mouth (Figure 2b) positions were performed. The orthopantomogram and computed tomography showed bilateral mandibular coronoid process hyperplasia. In the open mouth position, the elongated coronoid processes impinge on the zygomatic arch, limiting the mouth opening. The patient underwent bilateral mandibular coronoidectomy (Figure 3). Intra-incisal opening improved to 28 mm following surgery and she subsequently underwent myomectomy.

Quantification of disc displacement in internal derangement of the temporomandibular joint using magnetic resonance imaging

Many measures have been developed to determine the extent of disc displacement in internal derangements of the temporomandibular joint (TMJ) using magnetic resonance imaging. The purpose of this study was to develop a quantitative method of analyzing disc position and to evaluate the positions of the disc in internal derangements of the TMJ (group 1, with reduction; group 2, without reduction). Magnetic resonance images of 150 TMJs in 20 healthy volunteers and 55 patients with internal derangements were evaluated. The anatomical points of interest of the TMJ, including the anterior (DA) and posterior (DP) points of the disc, were marked on parasagittal magnetic resonance images of the TMJ disc taken in both the closed- and the open-mouth positions. All points were recorded using an x-y coordinate system, with reference to a referral line. In the closed-mouth position, the DP in patients in group 1 was situated in a more-anterior direction than the DP in volunteers. The DP in group 2 was located further anterior and inferior than the DP in group 1. However, the position of the DA did not differ between group 1 and group 2. In the open-mouth position, the DP was displaced anteroinferiorly to a greater extent in group 2 than in group 1 (one-way ANOVA, followed by Scheffe's test; P < 0.0001). The distance between the disc points in the closed- and open-mouth positions was also evaluated. Comparison of the disc point position in the closed- and open-mouth positions in symptomatic and asymptomatic displaced TMJ discs revealed no significant difference. In conclusion, most of our results quantitatively support previously reported findings in imaging, surgical, and histopathological studies of TMJ internal derangement. We suggest that our measure of disc position of the TMJ would be useful to assess the status and response to treatment of internal derangements of the TMJ.

Assessment of diagnostic accuracy of high-resolution ultrasonography in determination of temporomandibular joint internal derangement

The aim of this study was to determine the value of dynamic high-resolution ultrasonography (HR-US) in the evaluation of internal derangements of a temporomandibular joint (TMJ) in the open and closed mouth position. The study designed to collect the sample from the Outpatient Department of Oral Medicine and Radiology at GDC, Bangalore. Patients with pain, clicking, deviation, and tenderness were included in the study as a symptomatic group. The asymptomatic group was free of any symptoms. Maximum mandibular range of motion (Open and Closed) was performed during HR-US of TMJ in 100 consecutive patients, (50 symptomatic and 50 asymptomatic cases, a total of 400 joints, with 200 joints in the right and left closed and open mouth position;36 males and 64 females; age range, 16-50 years; mean age 27.56 years). Subsequently, the entire group, after clinical diagnosis, went for HR-US. Sonography confirmed the diagnosis by showing internal derangement in 34 (68%) of the symptomatic group and the remaining 16 (32%) patients failed to show any derangement. In the asymptomatic group 40 patients did not show any pathology associated with TMJ, whereas, 10 patients showed internal derangement. The data obtained was analyzed statistically. HR-US performed during the maximal range of motion (Open and Closed) helped to detect 34 instances (68 joints) of internal derangement, which were true positive cases, whereas, 16 patients (32 joints) showed a false positive finding for internal derangement (ID). The results obtained showed a sensitivity of 64%, specificity of 88%, positive predictive value of 84%, and a negative predictive value of 71%, with an accuracy of 76%. Dynamic HR-US being non-invasive can provide valuable information about internal derangement of the TMJ in mandibular closed mouth than open mouth position.

Temporomandibular joint evaluation with magnetic resonance imaging in children with functional unilateral posterior crossbite, treated with rapid maxillary expansion

The purpose of this prospective study was to evaluate qualitatively articular disc position and configuration of the temporomandibular joint (TMJ) with magnetic resonance imaging (MRI) in children with functional unilateral posterior crossbite (FUPXB) treated with Haas-type orthopedic appliances. The sample included 30 Brazilian children (60 TMJs) of both sexes (8 boys, 22 girls), aged 6.8 to 14.2 years (mean, 10.5 years; SD, 2.1 years). The MRIs were acquired in closed-mouth (CM), maximum-intercuspal (MI), and open-mouth (OM) positions in 3 stages of treatment: initial (T1), at the beginning of treatment; intermediate (T2), immediately after the removal of the expander, and final (T3), 9 months later, at the end of the observation period. No changes were found in articular disc positions of 96.6% of the TMJs in the CM and MI positions, and in 95% in the OM position at T1, T2, and T3. For the articular disc configuration, no changes were observed in 96.66% of the TMJs in the CM and MI positions, and in all TMJs in the OM position, at T1, T2, and T3. On average, this treatment method did not change articular disc positions and configurations.

Influence of scanning and reconstruction parameters on quality of three-dimensional surface models of the dental arches from cone beam computed tomography

The study aim is to investigate the influence of scan field, mouth opening, voxel size, and segmentation threshold selections on the quality of the three-dimensional (3D) surface models of the dental arches from cone beam computed tomography (CBCT). 3D models of 25 patients scanned with one image intensifier CBCT system (NewTom 3G, QR SLR, Verona, Italy) using three field sizes in open- and closed-mouth positions were created at different voxel size resolutions. Two observers assessed the quality of the models independently on a five-point scale using specified criteria. The results indicate that large-field selection reduced the visibility of the teeth and the interproximal space. Also, large voxel size reduced the visibility of the occlusal surfaces and bone in the anterior region in both maxilla and mandible. Segmentation threshold was more variable in the maxilla than in the mandible. Closed-mouth scan complicated separating the jaws and reduced teeth surfaces visibility. The preliminary results from this image-intensifier system indicate that the use of medium or small scan fields in an open-mouth position with a small voxel is recommended to optimize quality of the 3D surface model reconstructions of the dental arches from CBCT. More research is needed to validate the results with other flat-panel detector-based CBCT systems.