3D evaluation of the morphological and volumetric changes of the tongue and oral cavity before and after orthognathic surgery for mandibular prognathism: a preliminary study.

BACKGROUND: The volumetric ratio of the tongue to the oral cavity has been recognized to be one of the important factors for the maintenance of stable occlusion. Oral cavity capacity is changed after orthognathic surgery in patients with mandibular prognathism; however, the volumetric changes of the oral cavity including the tongue before and after surgery have not been analyzed. The purpose of this study was to evaluate the morphological and volumetric changes of the tongue and oral cavity following orthognathic surgery using a newly developed vinyl polysiloxane impression method. MATERIALS AND METHODS: The study was performed in fifteen subjects who underwent surgical orthognathic treatment. Impressions of the tongue together with the oral cavity were obtained before orthognathic surgery and 1, 3, and 6 months after orthognathic surgery. These impression patterns were scanned using cone-beam computed tomography (CT), and three-dimensional (3D) images of the oral cavity including the tongue, and the upper and lower dental arches were reconstructed. The morphological and volumetric changes in the oral cavity capacity and the tongue volume were examined. RESULTS: The volume of the tongue with the volume of the oral cavity decreased after orthognathic surgery. There was a correlation between the decrease in the oral cavity capacity and tongue volume. The volumetric ratio of the tongue to the oral cavity seems to be maintained before and after orthognathic surgery. CONCLUSION: VPS method, free from radiation exposure, may be useful for investigating the morphological and volumetric changes of the tongue and oral cavity, which may possibly influence the stability of the dental arch and occlusion during surgical orthodontic treatment.

Evaluation of tongue volume and oral cavity capacity using cone-beam computed tomography.

The aims of this study were to reveal the usefulness of a newly developed method for measuring tongue volume (TV) and oral cavity capacity (OCC) and to assess the relationship between them. The tongue was coated with a contrast agent, and the TV and OCC were determined using cone-beam computed tomography (CBCT). We enrolled 20 adults who were scheduled to undergo CBCT to evaluate the relationship of the third molar roots to the alveolar nerve before molar extraction. Each participant's tongue was coated with a contrast agent, and CBCT of the tongue and oral cavity was performed. Using computer software, we evaluated reconstructed 3D images of the TV, oral cavity proper volume (OCPV), and OCC. The mean TV was 47.07 ± 7.08 cm3. The mean OCPV and OCC were 4.40 ± 2.78 cm3 and 51.47 ± 6.46 cm3, respectively. There was a significant correlation between TV and OCC (r = 0.920; p < 0.01) but not between TV and OCPV. The mean TV/OCC ratio was 91 ± 5%. The proposed method produced CBCT images that enabled effective measurement of TV and OCC. This simple method of measuring TV and OCC will be useful in the diagnosis on the tongues with abnormal size.

Linear measurement accuracy of dental CT images obtained by 64-slice multidetector row CT: the effects of mandibular positioning and pitch factor at CT scanning.

PURPOSE: To evaluate whether the measurement accuracy of dental CT images is affected by the mandibular positioning and the pitch factor at CT scanning. MATERIALS AND METHODS: Three dry mandibles were scanned by 64-slice multidetector row CT (MDCT) and micro-CT. For MDCT scanning, 7 different mandibular positioning and 3 different pitch factors were applied. After reformatting dental CT images, the bone height was measured on these images. It was also measured on the corresponding micro-CT image, which was defined as the actual value. The difference of the measurement values between these 2 was defined as the measurement error. RESULTS: There was no significant difference in the measurement errors due to either the mandibular positioning or the pitch factor. CONCLUSION: The measurement accuracy of dental CT images obtained was not affected by either mandibular positioning or pitch factor at CT scanning.

Preoperative predictive model of cervical lymph node metastasis combining fluorine-18 fluorodeoxyglucose positron-emission tomography/computerized tomography findings and clinical factors in patients with oral or oropharyngeal squamous cell carcinoma.

OBJECTIVE: This study aimed to construct a preoperative predictive model of cervical lymph node metastasis using fluorine-18 fluorodeoxyglucose positron-emission tomography/computerized tomography ((18)F-FDG PET/CT) findings in patients with oral or oropharyngeal squamous cell carcinoma (SCC). STUDY DESIGN: Forty-nine such patients undergoing preoperative (18)F-FDG PET/CT and neck dissection or lymph node biopsy were enrolled. Retrospective comparisons with spatial correlation between PET/CT and the anatomical sites based on histopathological examinations of surgical specimens were performed. We calculated a logistic regression model, including the SUVmax-related variable. RESULTS: When using the optimal cutoff point criterion of probabilities calculated from the model that included either clinical factors and delayed-phase SUVmax ≥0.087 or clinical factors and maximum standardized uptake (SUV) increasing rate (SUV-IR) ≥ 0.100, it significantly increased the sensitivity, specificity, and accuracy (87.5%, 65.7%, and 75.2%, respectively). CONCLUSIONS: The use of predictive models that include clinical factors and delayed-phase SUVmax and SUV-IR improve preoperative nodal diagnosis.

Accuracy of orthodontic miniscrew implantation guided by stereolithographic surgical stent based on cone-beam CT-derived 3D images.

OBJECTIVE: To develop surgical stents for cone-beam computed tomography (CBCT) 3-dimensional (3D) image-based stent-guided orthodontic miniscrew implantation and to evaluate its accuracy. MATERIALS AND METHODS: Ten surgical stents were fabricated with stereolithographic appliances (SLAs) according to 3D CBCT image-based virtual implantation plans. Thirty self-drilling miniscrews were implanted at two to three positions on each side of the maxillary or mandibular posterior arches in three phantoms: 20 guided by 10 surgical stents in two phantoms (stent group) and 10 guided freehand in one phantom (freehand group). Six parameters (mesiodistal and vertical deviations at the corona and apex and mesiodistal and vertical angular deviations) were measured to compare variations between the groups. RESULTS: No root damage was found in the stent group, whereas four of 10 miniscrews contacted with roots in the freehand group. In the stent group, deviations in the mesiodistal and vertical directions were 0.15 ± 0.09 and 0.19 ± 0.19 mm at the corona, respectively, and 0.28 ± 0.23 and 0.33 ± 0.25 mm at the apex, respectively; angular deviations in the mesiodistal and vertical directions were 1.47° ± 0.92° and 2.13° ± 1.48°, respectively. In the freehand group, the corresponding results were 0.48 ± 0.46 mm and 0.94 ± 0.87 mm (corona), 0.81 ± 0.61 mm and 0.78 ± 0.49 mm (apex), and 7.49° ± 6.09° and 6.31° ± 3.82°. Significant differences were found in all six parameters between the two groups (Student's t-test, P < .05). CONCLUSIONS: 3D CBCT image-based SLA-fabricated surgical stents can provide a safe and accurate method for miniscrew implantation.

A membrane method for terahertz spectroscopy of amino acids.

We present here the results of applying a membrane method to terahertz (THz) transmittance spectroscopy of amino acids. Two kinds of amino acids dissolved in water or bovine serum were dropped and dried on polymer membranes. Absorbance spectra of the membranes were obtained with a GaP THz spectrometer. The frequency range was 0.6 - 6.0 THz and the line width was 3 GHz. Characteristic absorption peaks attributable to the amino acids were observed with membranes made of suitable materials.

Radiopacity of experimental composite resins containing radiopaque materials.

This study aimed to investigate the relationship between the radiopacity of an experimental light-cured composite resin and the amount and type of its radiopaque material: Ti, SrCO3, ZrO2, BaSO4, or Bi2O3. Radiopacity of each material was evaluated in terms of aluminum equivalent thickness using an aluminum step wedge. Then, the half-value layer thickness of the experimental composite resin, which had an aluminium equivalent thickness of 1 mm, was evaluated. It was found that the effects of elemental composition were not identical when evaluated in terms of aluminum equivalent thickness and by half-value layer. Nevertheless, both measurement methods indicated that radiopacity increased with increase in radiopaque material content as well as increase in atomic number of the element.

Imaging of epithelial cancer in sub-terahertz electromagnetic wave.

We used sub-terahertz (THz) imaging to exam two cross sections of epithelial cancer tissue embedded in paraffin using a 0.19 THz electromagnetic wave. The sub-THz imaging system was constructed with a tunnel injection transit time (TUNNETT) diode, a Schottky barrier diode detector and a X-Z stage. We examined the difference between a sub-THz wave absorption in melanoma and nevus tissue.