Feasibility of CBCT in Diagnosing Otosclerosis by Measuring CBCT Bone Density: A Preliminary Study.

The aim of this study was to measure cone beam computed tomography (CBCT) derived bone density of 6 anatomic points around the otic capsule in preoperative assessment of patients with clinically suspected otosclerosis, and to compare these densities with control group. CBCT images of 21 patients (34 ears, the otosclerosis group) with surgically confirmed otosclerosis and 26 patients (52 normal ears, the control group) were evaluated in this prospective study. Six regions of interest (ROI) were set manually around the otic capsule with the slice thickness of 0.3 mm. The mean CBCT bone density these regions were measured and compared in the case and control groups. In the case group, the mean CBCT bone density at the fissula ante fenestram (FAF) was significantly lower than the control group. Moreover, at the 4 points of the other ROIs (3-6) CBCT bone densities were significantly lower in the case group compared to the control group (p < 0.01). In this group, among 13 bilateral otosclerosis, 22 ears had conductive hearing loss (CHL), 4 ears had mixed hearing loss (MHL) and among 8 unilateral otosclerosis, 5 ears had CHL, 3 ears had MHL. Our study showed the mean CBCT bone density of ROIs 1 and 6 were correlated with the average air-bone gap in the bilateral and unilateral otosclerosis group, respectively. Quantitative evaluation of CBCT with a slice thickness of 0.3 mm can be used as a suitable tool for diagnosis and follow-up of otosclerosis in temporal bone.

A Radio-Odontometric Analysis of Sexual Dimorphism in First Molars Using Cone-Beam Computed Tomography.

OBJECTIVE: Different techniques for sex prediction are developed and used in the forensic medicine field. One of these methods is based on the teeth morphometry. The aim of the present study was to evaluate the degree of sex determination of the maxillary and mandibular first molar teeth in cone beam computed tomography images. METHOD AND MATERIALS: This study was carried out on cone beam computed tomography images of 100 men and 100 women with a mean age of 21.28 ± 2.47 years. The roof, floor and height of pulp chamber, as well as marginal enamel thickness and dentin thickness at the height of contour, tooth width, and crown length were measured. Student t test and discriminant analysis were applied to assess the differences in the measured parameters between men and women. RESULTS: According to the present study, the maxillary first molar was more dimorphic than the mandibular teeth. The accuracy of sex identification of mandibular and maxillary first molar tooth was 84% and 77%, respectively. The mesiodistal measured variables were more accurate in sexual differentiation than the buccolingual ones. For sex differentiation, the most dominant variables for maxillary and mandibular first molar teeth were crown height and dentin thickness, respectively. CONCLUSIONS: The first molar tooth showed an acceptable level of sex determination accuracy based on the odontometric measurements.

Evaluation of the Prevalence of Atherosclerosis Within the Course of Internal Carotid Artery in Cone Beam Computed Tomography Images.

The aim of the present study was to retrospectively evaluate the gender-related and age-related prevalence and severity of calcifications within the segments of the internal carotid artery in cone beam computed tomography (CBCT). By using a documented visual scale, out of 400 CBCT examinations a total of 304 CBCT scans of adult patients over 40 years old were evaluated as to the prevalence and severity of intracranial calcifications within the segments of the internal carotid artery. Calcifications were found in 117 CBCT scans. These calcifications were detected along the extracranial (C1: 53%), petrous (C2: 22.2%), Lacerum (C3:27%), cavernous (C4: 94%), and ophthalmic-clinoid (C5/C6: 65%) segments. The Friedman test showed significant differences in the severity of calcifications among the internal carotid artery segments. The McNemar test showed no significant differences between calcifications on the right or left side segments. The Chi square test showed no significant differences in the prevalence of calcifications between men and women; it also showed that the prevalence of calcifications increased with increase in age (P < 0.05). In this study, the frequency and severity of calcifications decreased throughout the C4, C5/C6, and C1 segments in a descending order; moreover, an increased incidence of calcifications by increase in age was documented irrespective of gender.

Designing and Fabricating Nano-structured and Micro-structured Radiation Shields for Protection against CBCT Exposure.

Researchers have always been interested in finding new and effective materials for protection against radiation. This experimental study aimed to design and fabricate new types of nano-material and micro-material based shields against the ionizing effect of cone beam computed tomography (CBCT) X-rays. To fabricate a flexible prototype, we added dioctyl phthalate (DOP) oil to emulsion polyvinyl chloride (PVC) powder. The paste was mixed and dispersed. Then, nano- and micro-powders of WO3 and Bi2O3 were added to the paste, with the weight ratio of 20% PVC, 20% DOP, and 60% nano- and micro-metals. Using an ultrasonic mixer, the polymer matrix and metals were mixed and a paste with a thick texture was developed. The resultant paste was poured into glass molds and the molds were then heated in an oven. After cooling, the resultant sheets were selected for further experiments. A CBCT unit and dosimeter were used to evaluate the characterization and X-ray shielding properties of the fabricated prototypes. The half-value layers (HVL) for nano-WO3, micro-WO3, nano-Bi2O3, and micro-Bi2O3 were 0.0390, 0.0524, 0.0351, and 0.0374 cm, respectively. In addition, the linear attenuation coefficient (µ) for these materials were 17.77, 13.20, 19.71, and 18.5 cm-1, respectively. The findings indicate that nano-structured samples are more effective in the attenuation of X-ray energy. The nano-structured WO3 prototype was nearly 34% more efficient in attenuating radiation compared to the micro-structured WO3 prototype. This difference in nano- and micro-structured Bi2O3 prototypes was 6.5%.

Difficulty of palatal impacted canine treatment in different sagittal and vertical skeletal malocclusions: A retrospective 3D evaluation.

OBJECTIVE: To evaluate the difficulty of impacted canine treatment in different kinds of sagittal and vertical malocclusion using the KPG index, a novel 3D classification system for canine impaction. MATERIALS AND METHODS: In this cross-sectional study, 74 cone-beam computed tomography (CBCT) images of subjects with palatally impacted canines were collected from one dental radiographic clinic. Impacted canines were assessed and KPG index of difficulty of treatment was calculated for each tooth. Lateral cephalograms corresponding with each CBCT were also traced and analysed. To assess the relationship between the level of treatment difficulty and type of malocclusion, the Chi2 test was used. The Kruskal-Wallis H test was used to assess the difficulty score between the three classes of malocclusion. RESULTS: There was no correlation between different sagittal skeletal measurements and treatment difficulty of impacted teeth (P>0.05). A positive correlation was shown between KPG index and linear measurements of A to Pn and facial angle (FH-N Pog) (P<0.05). Difficulty of treatment did not differ among various patterns of vertical growth. CONCLUSION: Treatment of impacted canines is more difficult in patients with maxillary prognathism and it is recommended that these patients be more meticulously evaluated prior to treatment.

Comparison of Dental Panoramic Radiography and CBCT for Measuring Vertical Bone Height in Different Horizontal Locations of Posterior Mandibular Alveolar Process.

STATEMENT OF THE PROBLEM: Accurate measurement of the available bone height is an essential step in the pre-surgical phase of dental implantation. Panoramic radiography is a unique technique in the pre-surgical phase of dental implantations because of its low cost, relatively low-dose, and availability. PURPOSE: This article aimed to assess the reliability of dental panoramic radiographs in the accurate measurement of the vertical bone height with respect to the horizontal location of the alveolar crest. MATERIALS AND METHOD: 132 cone-beam computed tomography (CBCT) of the edentulous mandibular molar area and dental panoramic radiograph of 508 patients were selected. Exclusion criteria were bone abnormalities and detectable ideal information on each modality. The alveolar ridge morphology was categorized into 7 types according to the relative horizontal location of the alveolar crest to the mandibular canal based on CBCT findings. The available bone height (ABH) was defined as the distance between the upper border of the mandibular canal and alveolar crest. One oral radiologist and one oral surgeon measured the available bone height twice on each modality with a 7-dayinterval. RESULTS: We found a significant correlation between dental panoramic radiographs and cone-beam computed tomography values (ICC=0.992, p< 0.001). A positive correlation between the horizontal distance of the alveolar crest to the mandibular canal and measured differences between two radiographic modalities had been found (r=0.755, p< 0.001). For each single unit of increase in the horizontal distance of the alveolar crest to the mandibular canal, dental panoramic radiographs showed 0.87 unit of overestimation (p< 0.001). CONCLUSION: Dental panoramic radiographs can be employed safely in the pre-surgical phase of dental implantation in posterior alveolus of mandible, especially in routine and simple cases.

Comparison of the Bony Changes of TMJ in Patients With and Without TMD Complaints Using CBCT.

STATEMENT OF THE PROBLEM: Temporomandibular joint disorders (TMD) may show a poor correlation between their clinical findings and radiological characteristics. PURPOSE: The aim of this study was to assess the osseous alterations of temporomandibular joint (TMJ) in symptomatic and asymptomatic subjects by employing cone beam computed tomography (CBCT) images. MATERIALS AND METHOD: In this study, CBCT images of 120 temporomandibular joints in 30 patients with TMJ disorder and 30 age- and sex-matched individuals without TMJ complaints were evaluated. Osteoarticular derangements of the joint were assessed by two experienced examiners. Data was statistically analyzed with SPSS software using chi-square test (p <0.05). RESULTS: Out of 120 CBCT images (60 in each group), at least one osseous change was observed in 90% and 86.7% joints in symptomatic and asymptomatic subjects, respectively. There were no significant differences between symptomatic and asymptomatic subjects regarding frequency of osteoarticular changes including flattening (73.3% vs. 75%), irregularity (36.7% vs. 48.3%), sclerosis (20% vs. 8.3%), cyst (3.3% vs. 3.3%), erosion (13.3% vs. 21.7%), hypoplasia (3.3% vs. 5%), ankylosis (1.7% vs. Zero), osteophyte (43.3% vs. 40%), decrease joint space (3.3% vs. 3.3%), and increase joint space (5% vs. 5%). (p> 0.05). CONCLUSION: By employing CBCT as a modern diagnostic imaging tool, findings of this study revealed that the frequency of various temporomandibular joint alterations on CBCT images is comparable in patients with and without TMD complaints, suggesting that some people with TMJ structural damage may not display clinical manifestations. Moreover, CBCT imaging might not be necessary for TMD patients and more attention should be given to clinical examination.

Cone Beam CT Study of Temporal Crest Canal.

STATEMENT OF THE PROBLEM: It is crucial for clinicians to be certain about the location of mandibular canal and determine any anatomical variants relevant to it. The temporal crest canal (TCC) is a rare anatomical variant of mandibular canal that lack of awareness about its presence can complicate surgical procedures. PURPOSE: This study investigated the anatomical characteristics and prevalence of the TCC using CBCT. MATERIALS AND METHOD: This descriptive cross-section study evaluated 327 CBCTs (654 sides) from all the patients with various problems. TCC on sagittal and axial plans were identified and then classified into two types based on their configuration. The prevalence of TCC was calculated amongst men and women. RESULTS: Six TCC (0.91%) were observed in 654 sides. We observed all 6 TCCs in females. One case (0.30%) was bilateral TCC, and the remaining four (1.22%) cases were unilateral TCC (two on the left and two on the right side). Considering the classification of TCC, five sides had presentation of type I and one case was type II based on Kawai et al. study. CONCLUSION: Three-dimensional images of CBCT data are useful in confirming the presence of TCC. TCC is considered as a clinically significant structure; therefore, this variation should be carefully investigated using reconstructed CBCT images.

Cone Beam Computed Tomographic Evaluation of Mandibular Asymmetry in Patients with Cleft Lip and Palate.

OBJECTIVE: The purpose of the present study was to compare mandibular vertical asymmetry in patients with unilateral and bilateral cleft lip and palate and subjects with normal occlusion. MATERIALS AND METHODS: Cone beam computed tomography scans of three groups consisting of 20 patients with unilateral cleft lip and palate, 20 patients affected by bilateral cleft lip and palate, and a control group of 20 subjects with normal occlusion were analyzed for this study. Condylar, ramal, and condylar plus ramal asymmetry indices were measured for all subjects using the method of Habets et al. Kruskal-Wallis and Mann-Whitney tests were used to determine any significant differences between the groups for all indices at the 95% level of confidence. RESULTS: There were no significant differences regarding sex for all mandibular asymmetry indices in all three groups. All Asymmetry indices (condylar, ramal, and condylar plus ramal asymmetry) were significantly higher in the unilateral cleft group compared with the other two groups. CONCLUSION: Cone beam computed tomography images showed that patients with cleft lip and palate suffered from mandibular asymmetry. Subjects with unilateral cleft lip and palate had a more asymmetric mandible compared with the bilateral cleft lip and palate and control groups. Therefore, the mandible appears to be the leading factor in facial asymmetry in subjects with unilateral cleft lip and palate.

Association between condylar position and vertical skeletal craniofacial morphology: A cone beam computed tomography study.

OBJECTIVE: Condylar position may play an important role in the establishment of different craniofacial morphologies. The aim of the present study was to determine the possible association between condylar position and vertical skeletal craniofacial morphology in subjects with normal sagittal skeletal pattern using CBCT. METHOD AND MATERIAL: The CBCT images of 45 patients with Class I sagittal skeletal pattern were classified into three balanced groups on the basis of SN-MP angle. Each group contained 15 subjects: low angle, normal angle and high angle. The condylar position was determined for the left and right joints. Chi square test was applied to assess the association between condylar position and vertical skeletal growth pattern. RESULTS: The condyles were more anteriorly-positioned in patients with high angle vertical pattern than in those with normal and low angle vertical pattern. No significant differences were found in condylar position between low angle and normal angle subjects. CONCLUSION: A significant correlation between condylar position and vertical skeletal pattern was found in the present study. This relationship can be considered for predicting and establishing a proper treatment plan for temporomandibular diseases during orthodontic treatment.

Comparison of the Effects of Transcutaneous Electrical Nerve Stimulation and Low-Level Laser Therapy on Drug-Resistant Temporomandibular Disorders.

STATEMENT OF THE PROBLEM: Temporomandibular disorder (TMD) is a clinical term used for clinical signs and symptoms that affect the temporomandibular joints, masticatory muscles, and associated structures. Surgical and non-surgical treatments can be used for management of TMD. Non-surgical route is the main part of the treatment, since clinicians prefer non-aggressive treatment for TMD such as pharmacological and physical therapy. Low-level laser therapy (LLLT) and transcutaneous electrical nerve stimulation (TENS) are the main procedures in physical therapy. PURPOSE: The aim of this study was to evaluate the effectiveness of TENS and LLLT in treatment of TMD patients who did not respond to pharmacological therapy. MATERIALS AND METHOD: This clinical trial was performed on 45 patients who randomly received either TENS or LLLT for 8 sessions. LLLT was applied with diode laser (Ga-Al-As, 980nm, dose 5j/cm2) and TENS by using two carbon electrodes with 75 Hz frequency (0.75 msec pulse width). Helkimo index and visual analogue scale (VAS) were measured during the treatment period and throughout the follow-up sessions. RESULTS: Significant reduction in the VAS and Helkimo index was observed in both TENS and LLLT group. There was no significant difference between the two methods during the treatment; however, TENS was more effective in pain reduction in follow-ups. CONCLUSION: This study justified the use of TENS therapy as well as LLLT in drug-resistant TMD. Both were useful in relieving the pain and muscles tenderness, although, TENS was more effective than LLLT.

Influence of Head Position on the CBCT Accuracy in Assessment of the Proximity of the Root Apices to the Inferior Alveolar Canal.

STATEMENT OF THE PROBLEM: The most important risk factor for inferior alveolar nerve (IAN) damage is the proximity of the mandibular root apices to the alveolar canal. Failure to position the patient's head at standardized orientation during cone beam computed tomography (CBCT) scans might adversely affect the relative position of the alveolar canal and mandibular root apices with subsequent treatment failure. PURPOSE: The purpose of the present study was to investigate the influence of the orientations of the skull during the scanning procedure on the accuracy of CBCT images in determining the positional relationship of the mandibular tooth apices to the alveolar canal. MATERIALS AND METHOD: CBCT scans of 7 human dry skulls were obtained by using NewTom VGi CBCT in standard, tilt, flexion, extension and rotation positions of the head. The shortest radiographic distance between the mandibular tooth apices and the IAN canal of 20 points were measured on cross sectional images of CBCT in all position scans. A sample t-test was used to compare the measurements at different head position with the standard position values. RESULTS: Significant differences were found in the measurements of normal and tilt orientations. However, there was no statistically significant difference between the measurements in standard position and other deviated positions. The mean errors in all head positions were less than 0.5mm. CONCLUSION: Alteration of patient head positioning during CBCT scanning does not affect the relative position of the IAN and the apices of posterior teeth.

A cone beam computed tomographic evaluation of the size of the sella turcica in patients with cleft lip and palate.

OBJECTIVE: Changes in the size of the sella turcica are frequently related to pathologies and syndromes. The aim of this was to compare the sella turcica dimensions in patients with unilateral and bilateral cleft lip and palate and non-cleft subjects. METHODS: Cone beam computed tomography (CBCT) images of three groups consisted of 20 patients with unilateral cleft lip and palate; 20 patients with bilateral cleft lip and palate and a control group consisting of 20 non-cleft subjects were the research population in this pilot study. The sella turcica linear dimensions in terms of length, depth and diameter were measured for all subjects. One-way ANOVA test was used to determine any significant differences among the three groups for the measured parameters. RESULTS: The length, depth and diameter of sella turcica were found to be significantly smaller in the unilateral and bilateral groups compared with the normal age and gender matched group. No significant differences were found in the measured variables between the unilateral and bilateral cleft patients. CONCLUSION: CBCT images showed a greater likelihood of abnormal sella turcica dimensions in patients with unilateral and bilateral cleft lip and palate. Therefore, the sella turcica dimensions may have an intrinsic relationship to the cleft condition.

Cone Beam Computed Tomographic Analysis of the Course and Position of Mandibular Canal.

PURPOSE: Estimation of the relative position of infra alveolar nerve (IAN) canal and its relation to the mandibular anatomical landmarks can be clinically useful in minimizing the risk of surgery complications such as neurosensory disturbances that may occur after invasive mandibular surgical procedures. The purpose of the present study was to investigate the anatomic location and radiographic course of the mandibular canal compared to anatomic landmarks on CBCT and to discuss its clinical significance and also to determine the possible correlations between the mandibular position and the age of the patients. METHODS: This cross sectional study was conducted on 242 CBCT of patients (99 males and 143 females). The location of canal was evaluated in 4 different regions. The first section in trans-axial view after mental foramen, in which the loop of mandibular canal is formed, was selected as point 1 for measurement and intervals of 10 mm, respectively, points 2, 3, 4 were selected for measurement. On these sections, the shortest linear distances (mm) from the most buccal and lingual aspects of the canal to the corresponding cortical plates of the mandible and also the minimum linear distance between the inferior aspect of canal and inferior border of mandible in these regions were calculated. RESULTS: There was statistically significant correlation between the anatomic course of the canal and the patients' gender. The mean vertical position of the canal, as measured from the lower border of the IAN canal to the inferior border of the mandible, was 8.50 mm, ranging from 4.80 to 14.50 mm. On average, the mandibular canal was situated more lingually at all sites to the point it reached the mental foramen. However, at the mental foramen region (Point 1), it was located closer to the buccal cortical plate. CONCLUSION: Assessment of the exact course of the IAN preoperatively along the body of the mandible by using CBCT might contribute to efficient and accurate surgical planning and therefore positively influence the surgical results. The results of this study confirm the necessity of using CBCT before invasive surgical procedures to determine the variations in the relative position and course of IAN canal.

Sexual Dimorphism of Maxillary Sinus Dimensions Using Cone-Beam Computed Tomography.

Sex determination of unknown persons plays an important role in forensic medicine. Cone-beam computed tomography (CBCT) is an excellent imaging modality for accurate measurement of maxillary sinus dimensions. This study aimed to evaluate whether maxillary sinus measurements on CBCT scans can be applied for sex determination. The width, length, and height of maxillary sinuses in CBCT images of 100 patients (50 males and 50 females) were measured. Student's t-test and discriminant function analysis were used to compare differences in the measured parameters between males and females. The correct predictive accuracy rate of sex determination was 78% in females and 74% in males with overall accuracy of 76%. Based on discriminant analysis, the most pronounced variable in differentiation of sex groups was maxillary sinus height. This study suggests that maxillary sinus measurements can be valuable for sex determination in forensic investigation, especially for cases in which other traditional methods are not applicable.

Evaluation of Condylar Position after Orthognathic Surgery for Treatment of Class II Vertical Maxillary Excess and Mandibular Deficiency by Using Cone-Beam Computed Tomography.

STATEMENT OF THE PROBLEM: In orthognathic surgeries, proper condylar position is one of the most important factors in postoperative stability. Knowing the condylar movement after orthognathic surgery can help preventing postoperative instabilities. PURPOSE: The aim of this study was to evaluate the condylar positional changes after Le Fort I maxillary superior repositioning along with mandibular advancement by using cone beam computed tomography (CBCT). MATERIALS AND METHOD: This cross-sectional study was conducted on 22 subjects who had class II skeletal malocclusion along with vertical maxillary excess. Subjects underwent maxillary superior repositioning (Le Fort I osteotomy) along with mandibular advancement. The CBCT images were taken a couple of days before the surgery (T0), and one month (T1) and 9 months (T2) after the surgery. The condyles positions were determined from the most superior point of the condyle to three distances including the deepest point of the glenoid fossa, the most anterior-inferior point of the articular eminence, and the most superior point of the external auditory meatus in the sagittal plane. RESULTS: The mean mandibular advancement was 4.33±2.1 mm and the mean maxillary superior repositioning was 4.66±0.3 mm. The condyles displaced inferiorly, anteriorly, and laterally between T0 and T1. They were repositioned approximately in the initial position in T2. No correlation was observed between the mandibular and maxillary movement and the condylar positions. CONCLUSION: The condyles displaced in the inferior-anterior-lateral position one month after the bilateral sagittal split osteotomy for mandibular advancement in combination with the maxillary Le Fort I superior repositioning. It seems that the condyles adapted approximately in their initial position nine months after the surgeries.

Comparison of the Pharyngeal Airway Volume between Non-Syndromic Unilateral Cleft Palate and Normal Individuals Using Cone Beam Computed Tomography.

STATEMENT OF THE PROBLEM: Individuals with cleft lip and cleft palate mostly have airway problems. Introduction of cone beam computed tomography (CBCT) and imaging software has provided the opportunity for a more precisely evaluating 3D volume of the airway. PURPOSE: The purpose of this study was to analyze and compare 3D the pharyngeal airway volumes of cleft palate patients with normal individuals using CBCT. MATERIALS AND METHOD: 30 complete cleft palate patients were selected from the Department of Orthodontics; Dental University (Shiraz, Iran) who had CBCT scans of the head. The control group included 30 individuals with Class I angle occlusion who were matched for age and gender with the experimental group. ITK-SNAP 2.4.0 PC software was used to build 3D models of the airways for the subjects and measuring airway volumes. The statistical analyses were performed using SPSS software (version 19). Mann-Whitney test was adopted with p< 0.05 as statistical significance. RESULTS: The average volume of the pharyngeal airway of cleft group was 18.6 cm3, with mean volumes of 6.8 cm3 for the superior component and 11.3 cm3 for the inferior component. The total and superior airway volume of cleft group were significantly lower than non-cleft groups (p= 0.008, p= 0.00, respectively) but the inferior airway volumes were not significantly different between the cleft and non-cleft groups. There was a significant and positive correlation between superior airway volume and inferior airway volume in cleft palate patients (r=+0.786, p< 0.001) and control group (r=+0.575, p= 0.001). CONCLUSION: 3D analysis showed that the nasal and total airway was restricted in individuals with cleft palate but the inferior airway was not compromised in these individuals. This would be a crucial data to be considered for surgeons during surgical planning.

Correlation between condylar position and different sagittal skeletal facial types.

OBJECTIVE: Condylar position may play a key role in the stability of orthodontic treatment of patients presenting with different skeletal patterns. The aim of the present study was to assess via cone beam computed tomography (CBCT) correlations between condylar position and sagittal skeletal relationship. PATIENTS AND METHODS: Condylar positions in CBCT images of 20 patients presenting with a Class I skeletal pattern, 20 with a Class II skeletal pattern, and 20 with a Class III skeletal pattern were evaluated retrospectively. The χ (2) test was used to assess the correlation between condylar position and sagittal skeletal relationships. RESULTS: The condyles were anteriorly positioned in patients with Class II skeletal pattern in comparison with those with Class I and III skeletal patterns. No significant differences in condylar position between Class I and Class III subjects were detected. CONCLUSION: A significant correlation between condylar position and sagittal skeletal patterns was observed in the present study. This relationship should be considered when planning and carrying out the appropriate orthodontic treatment for temporomandibular anomalies.

Effect of radiofrequency radiation from Wi-Fi devices on mercury release from amalgam restorations.

BACKGROUND: Dental amalgam is composed of approximately 50% elemental mercury. Despite concerns over the toxicity of mercury, amalgam is still the most widely used restorative material. Wi-Fi is a rapidly using local area wireless computer networking technology. To the best of our knowledge, this is the first study that evaluates the effect of exposure to Wi-Fi signals on mercury release from amalgam restorations. METHODS: Standard class V cavities were prepared on the buccal surfaces of 20 non-carious extracted human premolars. The teeth were randomly divided into 2 groups (n = 10). The control group was stored in non-environment. The specimens in the experimental groups were exposed to a radiofrequency radiation emitted from standard Wi Fi devices at 2.4 GHz for 20 min. The distance between the Wi-Fi router and samples was 30 cm and the router was exchanging data with a laptop computer that was placed 20 m away from the router. The concentration of mercury in the artificial saliva in the groups was evaluated by using a cold-vapor atomic absorption Mercury Analyzer System. The independent t test was used to evaluate any significant differences in mercury release between the two groups. RESULTS: The mean (±SD) concentration of mercury in the artificial saliva of the Wi-Fi exposed teeth samples was 0.056 ± .025 mg/L, while it was only 0.026 ± .008 mg/L in the non-exposed control samples. This difference was statistically significant (P =0.009). CONCLUSION: Exposure of patients with amalgam restorations to radiofrequency radiation emitted from conventional Wi-Fi devices can increase mercury release from amalgam restorations.