Yoshikazu Kobayashi

Abstract Background The COVID-19 pandemic led to concerns about the potential airborne transmission of the virus during dental procedures, but evidence of actual transmission in clinical settings was lacking. This study aimed to observe the behavior of dental sprays generated from dental rotary handpieces and to evaluate the effectiveness of high-volume evacuators (HVEs) using laser light sheets and water-sensitive papers. Methods A dental manikin and jaw model were mounted in a dental treatment unit. Mock cutting procedures were performed on an artificial tooth on the maxillary left central incisor using an air turbine, a contra-angle electric micromotor (EM), and a 1:5 speed-up contra-angle EM (×5EM). Intraoral vacuum and extraoral vacuum (EOV) were used to verify the effectiveness of the HVEs. The dynamics and dispersal range of the dental sprays were visualized using a laser light sheet. In addition, environmental surface pollution was monitored three-dimensionally using water-sensitive papers. Results Although the HVEs were effective in both the tests, the use of EOV alone increased vertical dispersal and pollution. Conclusions The use of various types of HVEs to reduce the exposure of operators and assistants to dental sprays when using dental rotary cutting instruments is beneficial. The study findings will be helpful in the event of a future pandemic caused by an emerging or re-emerging infectious disease.

OBJECTIVE: Quantitative analyses of gamma-ray accumulation in single-photon emission computed tomography (SPECT), and the evaluation of antiresorptive agent-related osteonecrosis of the jaw (ARONJ) have been reported recently. However, the relationship between the quantitative parameters calculated from SPECT and the detailed morphological changes observed in computed tomography (CT) remains unclear. This study aimed to investigate patients' characteristics and morphological changes observed on CT, and their effects on the quantitative values in SPECT. METHODS: From April 2017 to March 2019, patients diagnosed with ARONJ at our hospital were enrolled. The data obtained before September 2017 were reviewed retrospectively, and other data were collected prospectively. CT scans were evaluated for internal texture, sequestrum formation, periosteal reaction, cortical perforation, bone expansion, and pathological fracture. For quantitative assessment, the ratio of the maximum standardized uptake value (SUV) to the mean SUV in the temporal bone (rSUVmax) was calculated from SPECT images. The factors affecting rSUVmax were investigated by multiple regression analysis. The statistical significance level was set at α = 0.05. RESULTS: Overall, 55 lesions of 42 patients (median age and interquartile range, 75 [67-80 years], 27 female) were evaluated. Male sex (p = 0.007) and bilateral location (p < 0.0001) were selected as variables in the multivariate analysis. Adjusted coefficient of determination R2 was 0.59 (p < 0.0001). CONCLUSION: Sex and horizontal progression of the disease may affect individually calibrated SUVs in SPECT for patients with ARONJ.

<sec><title>Objective:</title> Some patients with cleft palate (CP) need secondary surgery to improve functionality. Although 4-dimensional assessment of velopharyngeal closure function (VPF) in patients with CP using computed tomography (CT) has been existed, the knowledge about quantitative evaluation and radiation exposure dose is limited. We performed a qualitative and quantitative assessment of VPF using CT and estimated the exposure doses. </sec><sec><title>Design:</title> Cross-sectional. </sec><sec><title>Setting:</title> Computed tomography images from 5 preoperative patients with submucous CP (SMCP) and 10 postoperative patients with a history of CP (8 boys and 7 girls, aged 4-7 years) were evaluated. </sec><sec><title>Patients:</title> Five patients had undergone primary surgery for SMCP; 10 received secondary surgery for hypernasality. </sec><sec><title>Main Outcome Measures:</title> The presence of velopharyngeal insufficiency (VPI), patterns of velopharyngeal closure (VPC), and cross-sectional area (CSA) of VPI was evaluated via CT findings. Organ-absorbed radiation doses were estimated in 5 of 15 patients. The differences between cleft type and VPI, VPC patterns, and CSA of VPI were evaluated. </sec><sec><title>Results:</title> All patients had VPI. The VPC patterns (SMCP/CP) were evaluated as coronal (1/4), sagittal (0/1), circular (1/2), and circular with Passavant’s ridge (2/2); 2 patients (1/1) were unevaluable because of poor VPF. The CSA of VPI was statistically larger in the SMCP group ( P = .0027). The organ-absorbed radiation doses were relatively lower than those previously reported. </sec><sec><title>Conclusions:</title> Four-dimensional CT can provide the detailed findings of VPF that are not possible with conventional CT, and the exposure dose was considered medically acceptable. </sec>

The aim of this study was to investigate the relationship of quantitative parameters between the two-dimensional region of interest (ROI) and the three-dimensional volume of interest (VOI) for accumulation of radiopharmaceutical. Single-photon emission computed tomography combined with computed tomography (SPECT/CT) images of the NEMA/IEC phantom were acquired. The ROIs and VOIs were automatically set to the sphere and background in the phantom. We defined as two-dimensional analysis (2D analysis) that which used ROIs set on the center section of the sphere, and as three-dimensional analysis (3D analysis) that which used VOIs set on the center of gravity of the sphere. Dose linearity (DL), the recovery coefficient (RC), the contrast-to-noise ratio (CNR), and standardized uptake value (SUV) were evaluated. Each index value was compared between both analyses. DL was almost 1 under both conditions. RC showed a similar tendency with 2D and 3D analyses. The CNR for 3D analysis was smaller than for 2D analysis. The maximum SUV was almost equal with both analyses. The mean SUV with 3D analysis was underestimated by 4.83% on average compared with 2D analysis. For the same accumulation, a difference may occur in the quantitative index between 2 and 3D analyses. In particular, the quantitative parameters based on the average value tends to be smaller with 3D analysis than 2D analysis. The quantitative parameters in 2D analysis showed dependence upon the cross section used for setting the ROI, whereas 3D analysis showed less dependence on the position of the VOI.

In recent years, some research on postoperative computed tomography evaluations of secondary bone grafting into the alveolar cleft have been reported. Here we report a study on volumetric evaluation and the prognostic factors of bone bridge formation after secondary bone grafting into the alveolar cleft using computed tomography. For 60 patients with unilateral cleft lip and palate patients (30 with unilateral cleft lip and alveolar: UCLA, 30 with unilateral cleft lip, alveolar, and palate: UCLP), we performed computed tomography scanning pre- and post-operatively. We calculate bone bridging ratio from bone defect volume and evaluated the prognostic factors of it. The median of bone bridge ratio was 83.6% and 66.3% in UCLA and UCLP, respectively. Both from uni- and multi-variate analysis, the existence of cleft palate and preoperative bone defect volume were selected as statistically significant prognostic factors. The type of tooth inducted into alveolar cleft or its state of eruption were not related with prognosis.

BACKGROUND: Nasopharyngoscopy is a common method to evaluate velopharyngeal closure in patients with cleft palate. However, insertion of a fiberoptic nasopharyngoscope causes discomfort in patients. The aim of this study was to estimate the reliability of short-time exposure images obtained using 320-row area detector computed tomography (320-ADCT) as a novel evaluation method for the assessment of velopharyngeal function. METHODS: We evaluated five healthy adult volunteers and five postoperative adult patients with cleft palate. During a 3.3-s imaging exposure, the participants were asked to perform two tasks: nasal inspiration and subsequent oral expiration through a catheter into a water-filled cup. The movement of the velopharyngeal structures was recorded during each examination, and the presence of velopharyngeal insufficiency (VPI) and velopharyngeal closure (VPC) patterns were estimated. If VPI was detected, the cross-sectional area was also calculated. Cohen's kappa and weighted kappa coefficients were used to evaluate the concordance of nasopharyngoscopy and 320-ADCT evaluation. RESULTS: Speech pathology evaluation did not reveal hypernasality in any study participant. Micro-VPI was detected by nasopharyngoscopy in one healthy volunteer and two patients. 320-ADCT detected micro-VPI in two more patients. The cross-sectional area of the VPI in these subjects ranged from 2.53 to 16.28 mm2. Nasopharyngoscopy and 320-ADCT were concordant in detecting VPI in eight participants (κ = 0.6) and in assessing VPC patterns in nine (κ = 0.82). Moreover, images obtained using 320-ADCT allowed for reduced dead angle and, thus, easy detection of micro-VPI and Passavant's ridges. CONCLUSION: Although the radiation exposure cannot be ignored, our novel evaluation method using 320-ADCT enables more detailed evaluation of VPC than nasopharyngoscopy. Future studies should investigate the relationship between 320-ADCT findings and speech pathology evaluations.

Objective The usefulness of computed tomography (CT) for measuring bone defect volume in the alveolar cleft has attracted considerable attention in recent years. Moreover, 320-row area detector CT (320-ADCT) is currently widely utilized. This technology helps to acquire smooth three-dimensional images, with a reduced exposure dose and improved image resolution, similar to those of dental cone-beam CT (CBCT). We compared the exposure dose of 320-ADCT with that of dental CBCT, and analyzed the reliability of a volumetric method for measuring bone defects in the alveolar cleft using 320-ADCT, both experimentally and clinically. Methods We performed thermoluminescent dosimeter measurements using an anthropomorphic RANDO phantom. Additionally, we evaluated the reproducibility of the volumetric measurement method for the bone defective volume using CT images of simulated bone defects in pigs. In addition, we evaluated the inter-rater reliability of the volumetrically measured values of bone defects in 20 patients with a unilateral cleft. Results The exposure doses of 320-row area detector CT and CBCT were similar. The errors of volumetric values between calculated and actual bone defects created in pigs were up to 7.6%. Inter-rater reliability of the calculated volumes of bone defect was evaluated as high, according to Bland–Altman analysis. Conclusions CT examination with a low exposure dose and precise analysis is feasible without the use of highly specialized dental CBCT.

In recent years, some reports on postoperative computed tomography evaluations of secondary bone grafting into the alveolar cleft have been published. Here, we report a retrospective study on the prognostic factors of bone bridge formation after secondary bone grafting into the alveolar cleft, evaluated with computed tomography.<br>In 13 cases, we evaluated the bone bridge formations at a total of 9 points: each of the 3 points of the buccal, central, and palatal sites in 3 different height slices of the central incisor in the cleft side (root tip, middle, and alveolar crest).<br>The frequencies of bone bridge formations were as follows: all cases in middle/buccal, 9 (69.2%) in middle/central, 8 (61.5%) each in root tip/buccal and alveolar crest/central, 6 (46.2%) in alveolar crest/buccal, 5 (38.5%) in middle/palatal, 4 (30.8%) in alveolar crest/palatal, and 3 (23.1%) each in root tip/central and root tip/palatal. Moreover, a univariate logistic regression analysis clearly showed that the preoperative width of the alveolar cleft could be a predictive factor of postoperative bone bridge formation in the central and palatal regions at the middle height of the tooth root.