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The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio were measured at 70 μm from the deepest point of the removing groove. Furthermore, three other teeth samples were manually treated with the ADPJ at the three above mentioned voltages (one tooth each) for 1 min. The KHN and Ca/P mass ratio were measured at 70 μm from the surface of the residual dentin part. In both the KHN and Ca/P mass ratio, higher residual dentin depended on the applied voltage of ADPJ. The ADPJ enabled the removal of softened carious dentin in an applied voltage-dependent manner.

The higher sensitivity of the new-generation positron emission tomography/computed tomography (PET/CT) with silicon photomultiplier (SiPM) may increase false-positive rates in detecting metastatic lymph nodes (LNs). This study aimed to clarify the usefulness of the SiPM PET scanner in diagnosing LN metastasis of oral squamous cell carcinoma (SCC).We retrospectively reviewed consecutive F-18 fluorodeoxyglucose PET/CT images of 39 SCC patients using SiPM PET and 31 SCC patients using non-SiPM PET. We measured the maximum standardized uptake value (SUVThe sensitivity and specificity of SiPM PET were 86.2% and 95.6%, respectively (cut-off SUVSiPM PET had higher diagnostic accuracy for LN metastasis of oral SCC than non-SiPM PET, even for small LN metastasis without increasing false-positives.

Background/Aim: Idiopathic condylar resorption (ICR) is a morphological change of the condylar head that occurs following orthodontic treatment or orthognathic surgery. This complication is serious, as it can cause relapse after mandible treatment. The aim of this experimental study was to evaluate the mechanism of influence of condylar resorption on compressive mechanical stress in temporomandibular joint following a change in occlusal position by mandible advancement. Materials and Methods: An osteotomy procedure at the midline of mandible was performed in 15 rabbits, with the left side moved forward by 3.5 mm. Advancement of the left side of the mandible resulted in compressive mechanical stress on condylar head on the left side. Samples were subjected to micro-computed tomography, histological staining and immunohistochemistry. Results: The area and depth of anterior condylar resorption at two weeks were significantly different as compared to those at one week (p

BACKGROUND Skeletal mandibular protrusion would influence to the muscle fatigue of the masticatory muscles. Establishing a diagnostic procedures combining physiological and biochemical information is necessary for quantitative evaluation of masticatory muscle fatigue. OBJECTIVE The transverse relaxation time (T2 time) of muscle functional magnetic resonance imaging (mfMRI), and 31 P-magnetic resonance spectroscopy (MRS) were used to investigate the reliability as parameters for measuring the masseter muscle in patients with skeletal mandibular prognathism. METHOD The subjects were 19 patients diagnosed as skeletal mandibular protrusions and 19 healthy subjects as a control group. Transverse relaxation time (T2 value) determined by mfMRI along with creatine phosphate (PCr) and inorganic phosphorus (Pi) determined by 31 P-MRS before, during, and after clenching were used for molecular imaging of muscle fatigue. RESULTS The average T2 value of the patient group was significantly higher than that of the healthy control group at rest. Furthermore, the average T2 value transiently increased in both groups during experimental clenching. The PCr and Pi showed a tendency toward a transient decrease and increases, respectively. The pH in the masseter muscle showed a transient decrease in both groups prior to and following experimental clenching. The pH in the masseter muscle of the patient group was significantly lower than that in the healthy control group at rest and recovery. CONCLUSION We showed mfMRI and 31 P-MRS are useful for evaluating masseter fatigue during clenching, and the masseter muscle in the prognathic patients showed more severe fatigue than the healthy controls.

The most typical maxillofacial feature of patients with acromegaly is mandibular protrusion. This study aimed to determine differences in maxillofacial morphology between skeletal Class III patients with and without acromegaly using cephalometric analysis. Cephalograms of 37 patients with acromegaly (Acro), 37 age-matched non-acromegalic patients with skeletal Class III malocclusion (C-III), and 37 age-matched Class I malocclusion patients (C-I; control) were retrospectively collected. The skeletal and dental morphology of each group was analyzed using cephalometric analysis, which included linear and angular measurements and facial profilograms. In addition, we analyzed diagnostic performance and cutoff values for discriminating acromegaly from skeletal Class III malocclusion using receiver operating characteristic (ROC) curve analysis. The mandibular ramus height was larger in the Acro group than in the other groups. The increase in L1/MP in the Acro group, which represented labial inclination of the mandibular central incisors, was the most characteristic feature in this study. ROC curve analysis indicated that a cutoff value of 88.4° for L1/MP had the highest diagnostic performance in discriminating acromegaly from non-acromegalic Class III malocclusion. Acromegaly was characterized by a greater degree of bimaxillary prognathism than was non-acromegalic Class III malocclusion. Focusing on labial inclination of the mandibular central incisors would be the most useful way to differentiate acromegaly from non-acromegalic Class III malocclusion.

Understanding the variations in root canal morphology is important for successful endodontic treatment. Mandibular first premolars have a single root in 98% of cases, and multiple root canals are found in approximately 20% of cases. However, the details of these characteristic findings in panoramic radiography and their diagnostic accuracy are unknown. This study aimed to investigate the characteristic radiographic findings of mandibular first premolars possessing multiple root canals and determine the diagnostic accuracy using panoramic radiography. Four radiologists evaluated 347 mandibular first premolars in 186 patients who underwent panoramic radiography and dental cone beam computed tomography (CBCT). Two radiologists confirmed the existence of single or multiple root canals using CBCT. The remaining two radiologists evaluated the imaging findings of the root canal morphology and classified them into two patterns: gradual narrowing and sudden narrowing. In the case of the sudden narrowing pattern, the location of sudden narrowing was also evaluated. A gradual narrowing pattern was observed in 56% of teeth with a single root canal, and a sudden narrowing pattern was observed in 83% of teeth with multiple root canals. When sudden narrowing between the cervical and apical 1/4 of the root canal was used as the diagnostic criterion for multiple root canal teeth, the highest diagnostic performance was observed (sensitivity, 76.1%; specificity, 73.9%). The sudden narrowing between the cervical level and the apical 1/4 level of the root canal is a practical diagnostic criterion for mandibular first premolar with multiple root canals.

A perfusion defect (PD) in non-enlarged lymph nodes (LNs) of oral squamous cell carcinoma (OSCC) is the most reliable radiological criterion for the diagnosis of metastasis. However, conventional contrast-enhanced (CE) T1 weighted images using turbo spin echo (TSE) sequence is limited in detecting PD in non-enlarged LNs due to flow artifacts from cervical blood vessels. Vessel wall (VW) MR imaging with blood vessel flow suppression and high spatial resolution may provide new insights into the detection of PD. However, there are no reports in the literature on the usefulness of VW MR imaging for the diagnosis of LN metastasis. It is demonstrated that PD of non-enlarged LNs in CE VR MR imaging of OSCC patients is useful for the diagnosis of metastatic LNs. VW MR imaging was significantly more sensitive in detecting PD of non-enlarged metastatic LNs than conventional TSE imaging on visual evaluation. Furthermore, it was found that the image contrast between PD and surrounding intranodal tissue in CE VW MR images was higher than that in conventional CE TSE images. In the correlation between imaging and histopathological findings of metastatic LNs, all LNs that exhibited PD on CE VW MR images were at an advanced histopathological metastatic stage. The pathology of PD was necrotic tissue with keratinization. The results indicated that PD in CE VW imaging is useful in diagnosing non-enlarged LNs at an advanced metastasis stage. The addition of VW MR imaging to conventional MR examination achieves higher diagnostic performance for non-enlarged metastatic LNs.

Patient A 33-year-old man diagnosed with extranodal natural killer cell/T-cell lymphoma, nasal type (ENKTCL-NT) inducing palatal perforation was referred to the perioperative oral care support center of Tohoku University Hospital for dental care to support cancer treatment including chemotherapy and hematopoietic stem cell transplantation (HSCT). Dental review during chemotherapy revealed mucositis suspected to be caused by mucosal trauma from altered jaw function (chewing and speech) due to palatal perforation. Although the patient was already in the cleanroom, an oral appliance as well as conservative care as recommended in oral management guidelines for HSCT were used to prevent worsening of oral mucositis at subsequent HSCT including High-dose chemotherapy and total body irradiation. After HSCT, a prosthodontist fitted a palatal obturator made by a dental technician and an oral surgeon reviewed the necrotic bone and removed the sequestra according to the changes in the palate. This approach involving a multidisciplinary team including a hematologist improved the impaired oral function and minimized oral complications . Discussion ENKTCL-NT and its treatment have a significant impact on patients' oral status. Hence, it is important to provide customized dental care based on previously endorsed guidelines according to the type of disease, treatment requirements, and oral and systemic status. Conclusions This report indicated the importance of dental care with a customized plan before, during, and after HSCT for ENKTCL-NT with multidisciplinary supportive care for cancer patients to improve the impaired oral function and to minimize oral complications.

To ascertain the effects of exposure parameters (tube current and tube voltage) and the gutta-percha cone (GPC) size on root fracture-like artifacts obtained with cone-beam computed tomography (CBCT). Fracture-like artifacts appearing on CBCT images of nine extracted human mandibular premolars filled with GPCs of size #50 or #80 were analyzed using six exposure factors: two tube voltages (80 kV and 110 kV); and three tube currents (4 mA, 7 mA, and 10 mA). On axial images, the gray value (GV) was recorded at three points: the mesiobuccal portion (MBP) as the sound dentin, the mesial portion (MP) as the artifact line, and the water area (WA). The rate of decrease in the GV (RDGV) of the artifact line was calculated using the formula: RDGV (%) = (GV of MBP − GV of MP) × 100/(GV of MBP − GV of WA). Comparison of the #80 group and the #50 group with equal tube voltages and tube currents shows that artifact lines in the #80 group were more obvious than those in the #50 group. The artifact lines with 80 kV were markedly more visible than those with 110 kV for each tube current and GPC size. Tube current changes did not affect the artifact line for any tube voltage or GPC size. For the reduction of artifacts, we recommend selection of higher tube voltages and lower tube currents when taking CBCT images of teeth with each GPC size.

Effect of octacalcium phosphate/gelatin composite (OCP/Gel) on angiogenesis was studied by its implantation in rat calvaria critical-sized defect in relation to bone regeneration for 2 and 4 weeks. The implantation of OCP/Gel disks was analyzed by radiomorphometry using a radiopaque material perfusion (Microfil®) method and histomorphometry by hematoxylin and eosin-staining before and after the decalcification. Effect of the OCP dose in the range up to 4 mg per well on the capillary-like tube formation by human umbilical vein endothelial cells (HUVECs) was also examined in a transwell cell culture. The results showed that the blood vessels formation by OCP/Gel group was significantly higher at 2 weeks than other groups but decreased at 4 weeks during the advancement of new bone formation. The capillary-like tube formation was highest in an OCP dose of 1 mg per well while other OCP doses above or below 1 mg did not show such a stimulatory effect. The results established both in vivo and in vitro confirmed that OCP has a positive effect on angiogenesis during bone regeneration in a suitable dose ranges, suggesting that the angiogenesis stimulated by OCP could be involved in the OCP/Gel-enhanced bone regeneration. Statement of significance We have reported that octacalcium phosphate (OCP) materials display stimulatory capacities on the bone tissue-related cells. However, the effect of OCP on the angiogenesis and its relation to the OCP-enhanced bone regeneration is unknown. This study confirmed the capacity of OCP on angiogenesis before increasing the new bone mass after the implantation of a composite of OCP and gelatin (OCP/Gel). The blood vessels formation took place associated with the area beginning of the new bone formation, which finally decreased together with development of bone formation. Because OCP was ascertained stimulating the capillary-like tube formation in HUVEC culture with a certain OCP dose, the present study is the first report showing the capacity of OCP on angiogenesis during the OCP/Gel-enhanced bone regeneration.

Oral bacteria may contribute to postoperative infectious complications including postoperative pneumonia or surgical site infection. The aim of this study was to investigate the impact of preoperative dental care on postoperative outcomes among surgical patients under general anesthesia.Retrospective cohort study.We analyzed clinical records of major surgical patients at a university hospital between 2016 and 2018. Subjects were categorized into either the preoperative dental care group, those being referred to dentists by their surgeons based on an individual surgeon's judgment for dental care before surgery, or the control group.The primary outcome was postoperative infectious complications. Secondary outcomes were postoperative inflammation markers (C-reactive protein and fever), and economic outcomes (postoperative length of hospital stay and medical expenses). As the main analysis, the average treatment effects of the preoperative dental care were obtained from the augmented inverse-probability weighting (AIPW) method with consideration of demographics and perioperative risk factors to estimate causal effect of the intervention from the observational data. Then, stratified analyses by age and surgical sites were conducted with the inverse-probability weighting and linear regression methods, respectively.In the AIPW estimation, compared with the control group, the care group saw a significantly lower rate of postoperative infection (average treatment effect -3.02) and shorter fever duration (-2.79 days). The stratified analysis by age revealed significant positive impact of dental care in all age groups, including the highest treatment effects observed among patients younger than 60. Also, treatment effect was observed in wider surgical sites than previously known.This study indicates a significant impact of preoperative dental care on preventing postoperative infection and inflammation. Along with old age or certain types of surgeries in which advantages of dental referral have been already known, preoperative dental referral could be beneficial for broader types of patients.

Background While hand and ultrasonic scalers are the primary tools used for the removal of dental calculus in periodontal treatment, many studies have shown that they also damage the enamel surface. We have developed a novel actuator-driven pulsed water jet (ADPJ) system, which has the ability to selectively remove materials depending on their stiffness. Considering the different material properties between teeth and dental calculus, it might be possible to develop the ADPJ to remove dental calculus without damage to the tooth’s enamel surface using a suitable jet pressure. Therefore, the aim of this study was to assess the effectiveness of the ADPJ in removing dental calculus, and the surface features of the teeth after its use. Methods A total of 93 artificial teeth coated with artificial dental calculus were examined in this study. The weights of 90 teeth were measured before and after the use of ADPJ, which had an applied voltage setting of 150, 200, or 240 V. The three remaining teeth were instrumented with a conventional hand scaler, ultrasonic scaler, or ADPJ (set at 240 V). Damage to the artificial tooth surfaces was evaluated using 5% Evans blue dye under an optical microscope. Furthermore, apatite pellets, which are utilized as experimental substitutes for natural teeth, were assessed after the use of ADPJ and both conventional scalers. Results The ADPJ significantly reduced the amount of artificial calculus, and the removal rate was dependent on the applied voltage. No damage was observed on the surface of the artificial tooth and apatite pellet following the use of ADPJ, in contrast to the conventional scalers. Conclusions The results of this study demonstrate the in vitro effectiveness of ADPJ in the removal of dental calculus, without causing damage to tooth surfaces.

Background The impact of the jaw bone condition, such as bone quantity and quality in the implant placement site, affecting the accuracy of implant placement with computer-guided surgery (CGS) remains unclear. Therefore, this study aimed to evaluate the influence of bone condition, i.e., bone density, bone width, and cortical bone thickness at the crestal bone on the accuracy of implant placement with CGS. Methods A total of 47 tissue-level implants from 25 patients placed in the posterior mandibular area were studied. Implant placement position was planned on the simulation software, Simplant® Pro 16, by superimposing preoperative computed tomography images with stereolithography data of diagnostic wax-up on the dental cast. Implant placement surgery was performed using the surgical guide plate to reflect the planned implant position. The post-surgical dental cast was scanned to determine the position of the placed implant. Linear and vertical deviations between planned and placed implants were calculated. Deviations at both platform and apical of the implant were measured in the bucco-lingual and mesio-distal directions. Intra- and inter-observer variabilities were calculated to ensure measurement reliability. Multiple linear regression analysis was employed to investigate the effect of the bone condition, such as density, width, and cortical bone thickness at the implant site area, on the accuracy of implant placement (α = 0.05). Result Intra- and inter-observer variabilities of these measurements showed excellent agreement (intra class correlation coefficient ± 0.90). Bone condition significantly influenced the accuracy of implant placement using CGS (p < 0.05). Both bone density and width were found to be significant predictors. Conclusions Low bone density and/or narrow bucco-lingual width near the alveolar bone crest in the implant placement site might be a risk factor influencing the accuracy of implant placement with CGS.

Objective We assessed the aetiology of idiopathic condylar resorption by examining the effects of oestrogen and compressive mechanical stress under a low systemic oestrogen condition in temporomandibular joints (TMJ) caused by an ovariectomy. Materials and methods Female rabbits were divided into non-ovariectomy (non-OVX) and ovariectomy (OVX) groups. A cortical osteotomy was performed with a custom device that was increased in length by 0.25 mm every 12 hr for 1 week after the operation, during which the TMJs in the rabbits received compressive mechanical stress. Samples from both groups were examined with micro-computed tomography and histological staining. Results Area and depth of bone resorption were both greater in the OVX group. Furthermore, a significantly earlier and greater prevalence of sub-condylar bone resorption was noted in that group, while cells positive for tartrate-resistant acid phosphatase were increased in the OVX group. Conclusions The present findings suggest that oestrogen induced a much greater amount of bone resorption on the anterior surface of the condylar head at an earlier stage in the TMJs of the present model rabbits. Thereafter, restoration of TMJ function appeared to occur in a normal manner.

A simple bone cyst (SBC) is an intrabone cavity without epithelial lining, which occasionally occur with fibrous-osseous lesions. The imaging finding of the scalloped border and conserving the lamina dura, periodontal ligament spaces, or follicular spaces are considered radiographically pathognomonic of SBC. SBC has been reported to occur with fibrous-osseous lesions, including cemento-osseous dysplasia (COD). Computed tomography (CT) imaging findings are sparse, and there are no reports of magnetic resonance imaging (MRI) findings, including apparent diffusion coefficient (ADC) value calculated by diffusion-weighted MRI for the florid COD-associated SBC. We report a case of a 39-year-old woman who was referred to our hospital because a panoramic radiograph of her right mandible showed asymptomatic radiolucency in the apical molar area. CT images showed a low-density lesion in the periapical areas of the right mandible, which accompanied a well-defined, high-density lesion, and a mixed low/high-density lesion with an unusual marked irregular border in the left mandible. The MRI showed cyst-like extremely hyperintense signals on fat-suppressed T2-weighted images at the right mandibular low-density and the left mandibular mixed low/high-density areas. ADC map showed high values (over 2.5×10−3 mm2/s) at the cystic areas in the bilateral mandible. We performed incisional biopsies of the bilateral mandibular lesions and resections of the bilateral maxillary lesions. Surgical and histopathological findings established a diagnosis of florid COD in the bilateral mandible and maxilla, simultaneously complicated by multiple SBCs in the bilateral mandible. The ADC value of cystic component is useful for the diagnosis, if the COD-associated SBC exhibits solitary, nonspecific, or rare imaging findings.

Objective We analysed the correlation between magnetic resonance images of the parotid and submandibular glands and the salivary flow rate in patients with Sjogren's syndrome. Methods We retrospectively reviewed magnetic resonance images (heterogeneous signal-intensity distribution and gland volume on T1- and fat-suppressed T2-weighted images, and multiple high-signal-intensity spots on magnetic resonance sialograms in the parotid and submandibular glands) obtained from 66 patients who were diagnosed with Sjogren's syndrome. We evaluated the relationship between these imaging features and their salivary flow rates in stimulated and unstimulated conditions. Results We found that as the disease progressed, both the heterogeneous signal-intensity distribution and the volumes of the parotid and the submandibular glands were significantly related to the stimulated and the unstimulated salivary flow rate. These imaging features were more highly correlated in assessments of the submandibular gland than in those of the parotid gland for both stimulated and unstimulated salivary flow rates. Conclusions Magnetic resonance image features of heterogeneity and smaller volume in the submandibular gland are reliable for predicting hyposalivation related to the progression of Sjogren's syndrome.

Objective We experimentally compared the effects of compressive and tractional mechanical stress on the temporomandibular joint (TMJ) of rabbits to assess the etiology of progressive condylar resorption. Materials and methods We performed a cortical osteotomy using custom-made devices that were lengthened by 0.25 mm every 12 h for 1 week after surgery. During this time, the rabbit TMJ was under compressive or tractional mechanical stress. The samples in each group were examined using micro-computed tomography and histological staining. Results Scores for the area of bone resorption were higher in the compressive group than in the tractional group. Moreover, scores for the depth of bone resorption were higher in the compressive group than those in the tractional group. We observed a significantly higher prevalence of resorption in the subcondylar bone in the compressive group than in the tractional group. There were substantially more cells that were positive for tartrate-resistant acid phosphatase in the compressive group than in the control and tractional groups. Conclusions The outcomes here suggest that excessive mechanical stress, particularly compressive mechanical stress, may significantly affect morphological bone change findings in the TMJ.

The purpose of the present study was to investigate the efficacy of perioperative oral managements (POMs) on perioperative nutritional conditions in patients undergoing surgery with general anesthesia. Medical records were retrospectively reviewed and the effects of POMs were investigated based on a large number of cases using a multicenter analysis. The profile of serum albumin levels was assessed and compared between patients with and without POMs using the multivariate analysis. Seventeen Eleven thousand and one hundred sixty patients (4,873 males and 6,287 females) were reviewed. Of these, 2710 patients (24.3%) had undergone POMs. The results of a multivariate analysis revealed the significant positive effect of POMs on perioperative serum albumin level (change between at admission and discharge, (Estimate: 0.022, standard error: 0.012, P < .0001). Patient gender, age, surgical site, performance status, the American Society of Anesthesiologists (ASA) physical status classification, operation time, amount of blood loss, and serum albumin level at admission were also significant predictors. Adjusted multivariate analysis of the effects of POMs on perioperative change of serum albumin level in all subjects reveled the significance of POMs intervention (estimate: 0.022, standard error: 0.012, P < .0001). These results suggest that POMs exerts significant positive effects on perioperative serum albumin levels in patients underwent surgery under general anesthesia.

Objectives The aim of this study was to compare cone-beam computed tomography (CBCT) with intraoral radiography (parallel and bisecting techniques) for their detection capabilities of various horizontal angle root fractures in human teeth.

The purpose of this study was to clarify the diagnostic value of capsule-like rim enhancement (CLRE) on magnetic resonance imaging (MRI) for distinguishing malignant from benign tumours of the parotid gland. We retrospectively evaluated contrast-enhanced T1-weighted images of 100 patients with malignant and benign parotid tumours for the presence, completeness, and irregularity of CLRE and its maximum thickness. We investigated any correlation of imaging and histopathological findings for 51 cases showing CLRE with available histology. The presence and completeness of CLRE did not differ significantly between benign and malignant tumours. Malignant tumours had more irregular CLRE than benign tumours (P

Background Alveolar bone is often lost after tooth extraction. Few studies have assessed the longitudinal changes in bone volume that occur within these extraction sites. Purpose To investigate the longitudinal morphological changes in extraction sockets following sustained continuous subcutaneous infusion of human recombinant insulin-like growth factor I (IGF-I). Materials and Methods Fourteen rats were subjected to right mandibular first molar extraction. Experimental rats (n = 7) received a continuous subcutaneous infusion of human recombinant IGF-I (320 mg/day) for 3 weeks by osmotic minipump. Control animals were treated with saline via the same method (n = 7). All rats were then housed for an additional 3 weeks. Micro-CT scanning was performed immediately after tooth extraction and at 1, 2, 3, and 6 weeks after extraction. Results New bone formation was markedly higher in the IGF-I-treated group as compared with the control group. The loss in alveolar ridge height in the IGF-I group was significantly lower than that in the control group at each time point after extraction on the buccal side and at 2, 3, and 6 weeks on the lingual side. Conclusions IGF-I treatment increases the volume of newly formed bone and reduces the loss in alveolar ridge height following tooth extraction.

Introduction The purpose of this article was to test the theory that short miniscrews will decrease the possibility of damaging the root, but the failure rate will increase. Methods One hundred eighty-six miniscrews (diameter, 1.3 × 5 mm, n = 63; 6 mm, n = 62; 7 mm, n = 61) were placed in 105 consecutive patients. Multislice computed tomography and cone-beam computed tomography scans were taken before and after miniscrew placement. Insertion torque was measured at miniscrew placement. Results The success rate of the miniscrews in the maxilla (93.4%) was higher than that in the mandible (70.3%). A significantly lower success rate with 5-mm miniscrews was observed compared with 6-mm and 7-mm miniscrews in the mandible. Miniscrews placed in less than approximately 3.8 mm of bone and those within 1.4 mm of the root had significantly higher failure rates. Miniscrews placed with insertion torque greater than 10 Ncm had a tendency for a lower success rate. Conclusions The optimum lengths of miniscrews of a diameter of 1.3 mm are 5 mm in the maxilla and 6 mm in the mandible. They should be placed at a distance from the root with insertion torque less than 10 Ncm for safe orthodontic anchorage without failure.

There are a lot of diseases which show the abnormal elastic property. Although many medical doctors and dentists have noticed the change of tissue elasticity due to the disease, the diagnostic device to examine the tissue elastic property objectively has not well developed.

Objective To determine the optimal scan settings (scan mode and position of field of view [FOV]) for cone beam computed tomography to reduce root fracture-like artifacts that are often observed in teeth filled with gutta-percha cones (GPCs). Study Design Fracture-like artifacts that appeared on cone beam computed tomography images of 9 extracted human mandibular premolars filled with GPCs were analyzed using I-mode (FOV, 102 mm; voxel size, 0.2 mm) and D-mode (FOV, 51 mm; voxel size, 0.1 mm) settings. Results The artificial lines were more obvious in I-mode than in D-mode. Increased distance between the center of the FOV and the GPCs produced stronger artificial lines in both I-mode and D-mode. Conclusion To reduce fracture-like artifacts, it is critical to use a mode with small voxel size and to place the target tooth in the center of the FOV.

Objectives To evaluate the effects of artificially decreased occlusal vertical dimension on the fiber phenotypes of the masseter muscle in the rat. Materials and methods The experimental animals were divided into two groups: A decreased occlusal vertical dimension (DOVD) group and a sham-operated control group. Five rats from each group were sacrificed on days 0, 3, 7, and 14 after the operation. The extent of DOVD, the masseter muscle fiber composition, and fiber diameter were analyzed. Results The average decrease in the vertical dimension was 1.1 ± 0.5 mm. The masseter muscle fiber composition of Type IIA and Type IIB muscle fibers shifted significantly in favor of Type IIA fibers on day 3 in the DOVD group. Toward the end of the observation period, shifting occurred back to the original composition. A significant decrease in the diameter of muscle fibers was seen on day 3 in the DOVD group. Conclusion In this experiment, when the occlusal vertical dimension was artificially reduced, the masseter muscle atrophied and the muscle fiber type changed temporarily while adapting to the new position of the mandible.

The aim of this study was to assess the efficacy of magnetic resonance imaging (MRI) for the differential diagnosis of basal cell adenocarcinoma (BCAC) and basal cell adenoma (BCA) in the salivary gland. Magnetic resonance imaging findings and pathological correlations were studied retrospectively in three cases of pathologically verified BCA and one case of BCAC. The MRI findings from previously reported cases (16 cases of BCA, 1 case of BCAC) were reviewed. All three BCAs showed well-defined margins, a round or ovoid shape, homogeneous hypointense signal on T1-weighted imaging (T1WI), and moderate contrast enhancement on contrast-enhanced T1WI. T2-weighted imaging showed heterogeneous hyperintense signals in two cases and a hypointense signal in one. The BCAC displayed MRI findings similar to those of the BCAs, with histopathologically verified partial invasion into the surrounding tissue remaining undetected. Time-signal intensity curves on dynamic MRI displayed rapid enhancement followed by a low washout pattern in all BCA cases, and a gradual enhancement pattern in the BCAC case. Both of these patterns are nonspecific and are commonly seen in other salivary tumors. Both the BCAs and the BCAC showed nonspecific findings on MRI, making it difficult to distinguish between these entities, even with dynamic MRI.

Objective The accuracies of intraoral radiography (IOR), multidetector helical computerized tomography (MDHCT) at slice thicknesses 0.63 mm and 1.25 mm, and limited cone-beam computerized tomography (LCBCT) were compared for detection of horizontal tooth root fracture. Study design In 7 beagle dogs, 28 maxillary anterior teeth were used, of which 13 had artificially induced horizontal root fracture. The specimens were examined by the above-mentioned 4 modalities. Diagnosis of root fracture was based on direct visualization of radiolucent line in each image by 6 radiologists. Results Sensitivity, negative predictive value, and diagnostic accuracy (true positives + true negatives) for detecting fracture lines in LCBCT (0.96 ± 0.04, 0.97 ± 0.03, 0.93 ± 0.04, respectively) were significantly higher than MDHCT at 0.63 mm (0.76 ± 0.09, 0.8 ± 0.05, 0.8 ± 0.05, respectively), MDHCT at 1.25 mm (0.49 ± 0.09, 0.66 ± 0.04, 0.69 ± 0.05, respectively), and IOR (0.51 ± 0.18, 0.67 ± 0.08, 0.69 ± 0.08, respectively). Specificity and positive predictive value showed no significant intermethod difference among the 4 modalities. Conclusion Limited cone-beam CT is more useful than the other 3 radiographic modalities for diagnostic imaging of horizontal tooth root fracture.

Objective To investigate morphological changes in the dental arches of acromegaly-like rats recently developed by means of exogenous IGF-I administration. Design Human recombinant IGF-I (640 μg/day) was continuously administered subcutaneously for 4 weeks by osmotic mini-pumps to 10-week-old male rats ( n = 6). Control animals were injected with saline alone ( n = 6). After administration, all the rats were housed for 4 more weeks. Arch width ( W ), length ( L ) and angle ( θ ) in the mandible and maxilla were measured once a week during and after IGF-I administration. Results The concentration of circulating IGF-I, and W and θ in the mandible were significantly increased as compared with the control rats. Although the mandibular dental arch stopped expanding once administration ended, it did not return to the control size. Conclusions In our acromegaly-like rat model, mandibular dental arch growth is greater in the lateral than antero-posterior direction during and after IGF-I administration.

We report here a case of masticatory disturbance evoked by trigeminal schwannoma, in which we have evaluated the changes in occlusal force and masticatory sensation before and after treatment for the tumour. The patient was a 43-year-old woman and her chief complaint was a loss of masticatory sensation on her left side. MR imaging revealed an enhanced tumour in the left cavernous sinus/Meckel's cave. The left masseter muscle function and occlusal force showed remarkable decreases before treatment; however, the sensory thresholds of her facial skin and dental pulp were not significantly different from the control side, indicating that her loss of masticatory sensation was not due to sensory disturbance but to occlusal force weakness. Gamma-knife radiosurgery resulted in a significant improvement in masticatory sensation following an increase in occlusal force.

Objective We analyzed the diagnostic performance of the MR imaging findings of the parotid, submandibular, and sublingual glands to discriminate between patients with and without Sjogren's syndrome. Methods We retrospectively analyzed the correlation between the MR imaging and histopathological findings obtained from 69 patients with clinically suspected Sjogren's syndrome. We evaluated the heterogeneous signal intensity distribution on T1- and T2-weighted images, the multiple high-signal-intensity spots on MR sialograms, and the volume of the parotid, submandibular, and sublingual salivary glands. Results The multiple high-signal-intensity spots in the parotid gland showed the highest sensitivity and diagnostic accuracy (82% and 83%, respectively). In addition, the multiple high-signal-intensity spots and the heterogeneous signal intensity distribution in the submandibular gland showed high specificity (100% and 88%, respectively). The volume of the submandibular gland, but not that of the parotid or sublingual gland, was smaller in patients with Sjogren's syndrome. Conclusions The presence of multiple high-signal-intensity spots on an MR sialogram in the parotid gland should be considered the best diagnostic indicator for Sjogren's syndrome. The presence of spots, heterogeneity, and the change to smaller volumes in the submandibular gland were also helpful because of their high specificity, particularly in advanced cases. This article is protected by copyright. All rights reserved.

An acromegaly-like rat model recently developed by exogenous administration of insulin-like growth factor I (IGF-I) was used to investigate morphological and histopathological tongue changes and clarify whether the changes were reversible. Human recombinant IGF-I (640 microg/day) was continuously subcutaneously infused into ten-week-old male rats for four weeks (IGF-I group; n = 6). Control sham-operated animals were injected saline alone (control group; n = 6). Rats were sacrificed immediately on ending administration at the age of fourteen weeks. Another 12 rats (6 from each group) were housed for an additional four weeks after administration ended. Total IGF-I (human + rat) increased significantly during administration, returning to control levels afterwards. Tongue weights significantly increased with histopathological changes present (increases in the muscle-bundle width, spaces between muscle-bundles and epithelium thickness) in the IGF-I group compared to control rats. Tongue size returned to control levels after discontinuation of IGF-I administration. These findings suggest that the characteristic tongue enlargement was developed experimentally in our acromegaly-like rat model, and that such morphological and histopathological tongue changes are reversible on normalization of circulating IGF-I levels.