Mina Mahdian

Diagnostic accuracy of 2 cone-beam computed tomography protocols for detecting arthritic changes in temporomandibular joints.

INTRODUCTION The temporomandibular joint (TMJ) is a complex joint that often develops degenerative joint disease. Clinical examination alone cannot usually diagnose this accurately, and a radiographic examination complements and aids in diagnosis and treatment. The osseous components of the TMJ complex are best imaged using computed tomography. The evolution of cone-beam computed tomography (CBCT) offers a low radiation dose and a high spatial resolution alternative and is becoming the imaging modality of choice for the TMJ. To further reduce the dose and yet not compromise the diagnostic task at hand, some alternative rotation acquisition protocols are available but have not been adequately evaluated. The aim of this study was to evaluate the diagnostic efficacy of 2 CBCT acquisition protocols to detect degenerative changes associated with the TMJ complex. METHODS Thirty-four TMJs, from 17 dry human skulls, were obtained from the anatomy department at the School of Dental Medicine of the University of Connecticut. The sample consisted of complete dentate and partially dentate skulls with no identifiable markers such as age, sex, or ethnicity. Small and large lesions simulating early and established arthritic changes were created on the mandibular condyle. Each defect was randomly created on the medial pole, articulating surface, or lateral pole. After simulating the articular disc with rubber dam material, the condyle and the glenoid fossa were articulated and positioned in place by a rubber band. The skulls were scanned by using an Accuitomo CBCT scanner (J. Morita Corp, Kyoto, Japan) with 180° and 360° rotation protocols. Two operators scored the lesions and compared the results to the gold standard, which was the master list of where the lesions were made on the condyles. RESULTS On the 102 randomly selected sites, 39 large and 33 small lesions were made, and the rest of the sites had no lesions. The detection rates for areas with large lesions and areas with no lesions were 100% between the examiners. However, of the 33 small lesions, each examiner was able to identify 32 of them with the 360° scans: a 97.4% detection rate when compared with the gold standard. With the 180° scan, 94.9% of the small lesions were detected when compared with the gold standard, and 96.9% were detected with the 360° scan. The overall interexaminer reliability was over 90% for both imaging protocols (Cronbachs alpha, 92.4% for 180° and 97% for 360°). CONCLUSIONS Based on the results of this study, the 180° CBCT acquisition protocol can detect small and large arthritic lesions with high reliability and is comparable with the 360° spin acquisition.

Radiographic evaluation of the maxillary sinus prior to dental implant therapy: A comparison between two-dimensional and three-dimensional radiographic imaging

Purpose This study was performed to evaluate the diagnostic efficacy of panoramic radiography and cone-beam computed tomography (CBCT) in detecting sinus pathology. Materials and Methods This study was based on a retrospective evaluation of patients who had undergone both a panoramic radiograph and a CBCT exam. A total of 100 maxillary sinuses were evaluated. Four examiners with various levels of expertise evaluated the images using a five-point scoring system. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficacy of the two modalities. The image analysis was repeated twice, with at least two weeks between the evaluation sessions. Interobserver reliability was assessed using Cronbachs alpha, and intraobserver reliability was assessed using Cohens kappa. Results Maxillary sinus pathology was detected in 72% of the patients. High interobserver and intraobserver reliability were observed for both imaging modalities and among the four examiners. Statistical analyses using ROC curves demonstrated that the CBCT images had a larger area under the curve (0.940) than the panoramic radiographs (0.579). Conclusion Three-dimensional evaluation of the sinus with CBCT was significantly more reliable in detecting pathology than panoramic imaging.

The effect of He–Ne and Ga–Al–As lasers on the healing of oral mucosa in diabetic mice

Delayed wound healing is one of the complications of diabetes mellitus. Low-level laser therapy (LLLT) has been used to accelerate wound healing however the effect of LLLT on the hard palate wound healing in streptozotocin-induced diabetic (STZ-D) mice has not yet been characterized. This study aims to determine the effect of LLLT (He-Ne and Ga-Al-As laser) on the process of wound healing in the hard palate among diabetic and non-diabetic mice. 90 adult male mice were divided into six groups. Type 1 diabetes mellitus was induced in three groups by means of injection of STZ. Of these, one group was irradiated with He-Ne laser (DH group), one with Ga-Al-As laser (DG group) and one did not undergo any LLLT (DC group). The remaining groups were non-diabetic which were allotted to laser therapy with He-Ne laser (NH group) or with Ga-Al-As laser (NG group) or no LLLT (NC group). Five animals from each group were killed on the third, seventh, and fourteenth days after surgery, and biopsies were made for histological analysis. On the 3rd and 7th days after the surgery, the number of polymorphonuclear (PMN) cells in NH, DH, NG, and DG groups was significantly lower than that of the control groups. On the 3rd, 7th and 14th days, the fibroblasts and new blood vessel counts and collagen fibers in diabetic laser treated groups (DG and DH) were significantly higher compared to that of NC, DC, NH and NG groups. On the 7th and 14th days, the fibroblasts and new blood vessel counts and collagen fibers in NH, DH, NG, and DG groups were also significantly higher than that of the control groups, and the fibroblast and new blood vessel counts and collagen density fibers in NH and DH groups were higher than that of the NG and DG groups. LLLT with He-Ne laser compared to Ga-Al-As laser has a positive healing effect on hard palate gingival wounds in STZ-D mice.

Evaluation of linear measurements of implant sites based on head orientation during acquisition: An ex vivo study using cone-beam computed tomography.

Purpose This study evaluated the effect of various head orientations during cone-beam computed tomography (CBCT) image acquisition on linear measurements of potential implant sites. Materials and Methods Six dry human skulls with a total of 28 implant sites were evaluated for seven different head orientations. The scans were acquired using a Hitachi CB-MercuRay CBCT machine. The scanned volumes were reconstructed. Horizontal and vertical measurements were made and were compared to measurements made after simulating the head position to corrected head angulations. Data was analyzed using a two-way ANOVA test. Results Statistical analysis revealed a significant interaction between the mean errors in vertical measurements with a marked difference observed at the extension head position (P<0.05). Statistical analysis failed to yield any significant interaction between the mean errors in horizontal measurements at various head positions. Conclusion Head orientation could significantly affect the vertical measurements in CBCT scans. The main head position influencing the measurements is extension.

Evaluation of alveolar bone dimensions in unilateral palatally impacted canine: a cone-beam computed tomographic analyses.

INTRODUCTION The purpose of this study was to evaluate the alveolar bone dimensions and arch perimeter discrepancy in unilateral palatally impacted canines. METHODS This retrospective split-mouth study reviewed 207 cone-beam computed tomography (CBCT) scans of patients with unilateral or bilateral impacted canines referred for orthodontic treatment. Out of 207 CBCT scans, only 39 scans in which canines were unilaterally palatally impacted were approved for the study based on our inclusion and exclusion criteria. Two fiducial lines were used to orient the examiners and standardize the measurements. Arch perimeter, buccopalatal (BP) width, and alveolar height were measured both on the impacted and non-impacted side. Two different examiners measured all the parameters. A one-sample Kolmogorov-Smirnov test was used to examine normality of distribution of outcomes. Wilcoxon Signed Rank tests were used for comparing arch width and alveolar bone height between the impacted and non-impacted sides. For arch perimeter, the paired-sample t-test was used. RESULTS The arch perimeter, BP width, and alveolar bone height was significantly decreased on the impacted side (P < 0.05). The mean arch perimeter on the impacted side was 41.7 ± 2.5mm compared to 43.5 ± 2.37 on the non-impacted side. Similarly, BP width and alveolar bone height on the impacted side was 6.87 ± 1.08 mm and 18.12 ± 2.28 mm, respectively, whereas on the non-impacted side was 8.70 ± 1.13 mm and 19.49 ± 2.09 mm, respectively. CONCLUSION There was a significant decrease in the arch perimeter and alveolar bone dimensions (BP width and alveolar bone height) on the impacted side.

The reliability of tablet computers in depicting maxillofacial radiographic landmarks.

Purpose This study was performed to evaluate the reliability of the identification of anatomical landmarks in panoramic and lateral cephalometric radiographs on a standard medical grade picture archiving communication system (PACS) monitor and a tablet computer (iPad 5). Materials and Methods A total of 1000 radiographs, including 500 panoramic and 500 lateral cephalometric radiographs, were retrieved from the de-identified dataset of the archive of the Section of Oral and Maxillofacial Radiology of the University Of Connecticut School Of Dental Medicine. Major radiographic anatomical landmarks were independently reviewed by two examiners on both displays. The examiners initially reviewed ten panoramic and ten lateral cephalometric radiographs using each imaging system, in order to verify interoperator agreement in landmark identification. The images were scored on a four-point scale reflecting the diagnostic image quality and exposure level of the images. Results Statistical analysis showed no significant difference between the two displays regarding the visibility and clarity of the landmarks in either the panoramic or cephalometric radiographs. Conclusion Tablet computers can reliably show anatomical landmarks in panoramic and lateral cephalometric radiographs.

Calcification of the stylohyoid ligament in panoramic radiography and cone beam computed tomography among patients referred for dental implant treatment planning.

Background:Calcification of the stylohyoid ligament (SHL) is a common condition noted as an incidental finding in routine radiographic examination. Due to proximity with important neurovascular structures, elongation and calcification may sometimes lead to dysphagia and pain. The objective of this study was to evaluate the incidence of calcified SHL detected on cone beam computed tomography (CBCT) scans and panoramic radiographs (PR) in patients referred for dental implant therapy. Methods:Retrospective analysis of 30 patients referred for dental implants to the Department of Oral and Maxillofacial Radiology at the University of Connecticut School of Dental Medicine was done. Patients were imaged using Hitachi CB MercuRay CBCT machine, and PRs were obtained using Planmeca panoramic machine. CBCT reconstructions and panoramic images were evaluated for the incidence and pattern of SHL calcification. Results:Nineteen patients (63.3%) had calcified SHLs, 16 of whom were reported to have bilateral involvement. PR was unable to show complete calcification of the ligament in any of the cases, whereas CBCT showed evidence of complete calcification when present (14 cases). Conclusion:CBCT was more accurate in determining the pattern and extent of calcification of the SHL in patients undergoing implant treatment planning.

The Effect of Composite Thickness on the Stress Distribution Pattern of Restored Premolar Teeth with Cusp Reduction

PURPOSE Different thicknesses of restorative material can alter the stress distribution pattern in remaining tooth structure. The assumption is that a thicker composite restoration will induce a higher fracture resistance. Therefore, the present study evaluated the effect of composite thickness on stress distribution in a restored premolar with cusp reduction. MATERIALS AND METHODS A 3D solid model of a maxillary second premolar was prepared and meshed. MOD cavities were designed with different cusp reduction thicknesses (0, 0.5, 1, 1.5, 2.5 mm). Cavities were restored with Valux Plus composite. They were loaded with 200 N force on the occlusal surface in the direction of the long axis. Von Mises stresses were evaluated with Abaqus software. RESULTS Stress increased from occlusal to gingival and was maximum in the cervical region. The stressed area in the palatal cusp was more than that of the buccal cusp. Increasing the thickness of composite altered the shear stress to compressive stress in the occlusal area of the teeth. CONCLUSION The model with 2.5 mm cusp reduction exhibited the most even stress distribution.

Using hand-held dental x-ray devices: ensuring safety for patients and operators.

BACKGROUND Since the introduction of hand-held x-ray units in dentistry, a few inexpensive devices have emerged that lack the necessary safety measures and failed to meet U.S. Food and Drug Administration (FDA) standards. They are advertised actively and sold online in the United States. METHODS The authors present several safety issues associated with an imported hand-held x-ray device that has not been cleared by the FDA and compare the device with an FDA-cleared unit. RESULTS The authors found that the non-FDA-cleared device posed major safety hazards, including high radiation doses to patients and operators, lack of operator shielding, lower-than-acceptable kilovolt (peak) value, inadequate collimation, lack of an audible signal of x-ray generation and absence of a so-called dead-man switch. CONCLUSIONS AND PRACTICAL IMPLICATIONS Dental professionals must be aware of unsafe x-ray equipment and use only those devices that have been cleared by the FDA to protect themselves and their patients.

Light transmittance of CAD/CAM ceramics with different shades and thicknesses and microhardness of the underlying light-cured resin cement

Objectives The aim of this in vitro study was to evaluate the effects of the thickness and shade of 3 types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials. Materials and Methods A total of 120 specimens of 2 shades (A1 and A3) and 2 thicknesses (1 and 2 mm) were fabricated using VITA Mark II (VM; VITA Zahnfabrik), IPS e.max CAD (IE; IvoclarVivadent), and VITA Suprinity (VS; VITA Zahnfabrik) (n = 10 per subgroup). The amount of light transmission through the ceramic specimens was measured by a radiometer (Optilux, Kerr). Light-cured resin cement samples (Choice 2, Bisco) were fabricated in a Teflon mold and activated through the various ceramics with different shades and thicknesses using an LED unit (Bluephase, IvoclarVivadent). In the control group, the resin cement sample was directly light-cured without any ceramic. Vickers microhardness indentations were made on the resin surfaces (KoopaPazhoohesh) after 24 hours of dark storage in a 37°C incubator. Data were analyzed using analysis of variance followed by the Tukey post hoc test (α = 0.05). Results Ceramic thickness and shade had significant effects on light transmission and the microhardness of all specimens (p < 0.05). The mean values of light transmittance and microhardness of the resin cement in the VM group were significantly higher than those observed in the IE and VS groups. The lowest microhardness was observed in the VS group, due to the lowest level of light transmission (p < 0.05). Conclusion Greater thickness and darker shades of the 3 types of CAD/CAM ceramics significantly decreased the microhardness of the underlying resin cement.