Sensory and motor feedback is an important component of the masticatory process. The palate is a key part of this feedback, being one of the most densely innervated parts of the oral cavity and an important organ in oral functions such as mastication, swallowing and speech. Maxillary defects therefore cause difficulties in both sensation and functionality, but these can be recovered by supplying maxillary obturator prostheses.
Oral stereognostic ability （OSA） is one of these sensations and is dependent on an interaction between the palate and tongue. This clinical study investigated the influence of maxillary defects on OSA, and the effects of maxillary obturator prostheses in the OSA of post-maxillectomy patients.
OSA in post-maxillectomy patients with remaining maxillary defects was compared with that in healthy subjects. These comparisons reveal that maxillary defects cause OSA to decline, whereas the maxillary obturator prosthesis recovers OSA to normal levels. This suggests that maxillary obturator prostheses improve not only oral functionality but also oral stereognostic ability.

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In cases with maxillary defects, there are complicated undercut areas that may also contain sensitive tissue. For such cases, we developed a novel impression method using an addition-curing silicone rubber impression material mixed with Vaseline for secure and precise impression. The new impression material had the same degree of permanent strain and dimensional stability as traditional addition-curing silicone rubber impression material. However, it had problems including a difficult procedure and rough surface of the plaster model. Therefore, we developed a second new impression material that has the same degree of surface roughness as traditional addition-curing silicone rubber impression material and an easy procedure for maxillary defects.

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The purpose of this study was to describe a long-term observation of abutment teeth in patients with maxillary defects and rehabilitated with obturator prostheses. Forty-eight patients participated in this study. Maxillary defect classification, history of irradiation therapy and flap reconstruction, types of obturator design and weight, types of direct retainers and duration, and periodontal conditions were investigated retrospectively. The results showed that the majority of obturator wearers had a maxillary midline defect or unilateral defect in which their prosthesis used a wire clasp or magnetic attachment as a direct retainer near the defect side. The average duration of abutment teeth was five years and ten months, and periodontal conditions were favorable with a probing depth of less than 3 mm in most of the cases. While nine percent of the abutment teeth were extracted, in most of the cases the teeth spontaneously dropped out due to excessive loading over long-term usage and deteriorated periodontal conditions. The probing depth and weight of the obturator showed a significant positive relation. Alveolar bone around the abutment teeth was significantly highly absorbed in midline resection cases. This study suggested typical designs of obturator prostheses and prognosis for direct retainers. Further study is needed for indirect retainers and functional assessments.

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Facial implants installed in the auricular portion show a high survival rate, but shorter longevity in the orbital portion was reported in some papers. On the other hand, the outer plate of the cortical bone of the temporal bone is thicker than that of the bone around the orbital portion. The objective of this study was to examine the effect of the outer plate thickness on the stress distribution around facial implants using 3D finite element analysis.
Two kinds of 3D finite element models consisting of a cylindrical bone portion and the facial implants with abutments were constructed. The thickness of the outer plate of the cortical bone was 3.6 mm in model T, and 2.0 mm in model O. A static load of 10 N was applied on the upper surface of the abutment.
Maximum values of von Mises stress increased as the load direction inclined, and those in model O were larger than those in model T under the same loading conditions. These results suggest that flange implants should be installed in the bone with a thick outer plate of cortical bone, and the load on the implants should be as parallel to the long axis of the implant as possible.

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The purpose of this study was to investigate the effects of loading positions on the stress distributions in the bone portion around two connected craniofacial osseointegrated implants （COIs）.
A three-dimensional finite element model of two COIs with abutments inserted in the bone portion was created. The abutments were connected by the superstructure, and an extension bar was added. A static load （10N） was applied on the top surface of the superstructure at the midpoint between the COIs （load position ①）, the center of a COI （load position ②）, the midpoint of the extension beam （load position ③） or the end point of the extension beam （load position ④） in the direction of 0°, 30°, 60° or 90° to the long axis of COIs, respectively.
The maximum von Mises stress in the bone portion increased when the load position shifted from ① to ④, and when the load direction tilted to the long axis of the COIs. These results suggested that the load should be applied between the connected COIs, and as parallel to the long axis of COIs as possible.

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Skin grafts are occasionally used to repair mucosal defects in oral surgery. The stability of dento-maxillary prostheses can be acquired through the use of skin grafts. We report our method for skin grafting and summarize the results obtained in nine patients who received maxillofacial prosthetics. The procedure involves the following steps: 1） skin incision, 2） taking a split-thickness skin graft, 3） dermal layer excision, and 4） reefing of skin. This method was developed to simplify postoperative management and minimize scarring. Skin grafts obtained with a scalpel can easily be engrafted to the site of defects. The wound at the donor site can then be closed by suturing. Our technique was used in nine patients （3 men, 6 women） 33 to 79 years of age. Seven patients had squamous cell carcinoma, and the other two had verrucous carcinoma. Donor sites were the inguinal region （n＝5）, supraclavicular region （n＝3）, and axillary skin （n＝1）. Excellent postoperative outcomes were obtained in all patients. These results suggest that our method for skin grafting may facilitate postoperative management and shorten the hospital stay.

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The masticator space is occasionally included as part of the excised tissue in maxillectomy in cases when a maxillary tumor extends posteriorly. However, excision of this area without any tissue covering causes postoperative trismus and a fallen cheek in most cases. In this study, the subject group included maxillectomy patients in whom the masticator space was covered by a free vascularized flap and the control group included those who did not receive any flap. Both the groups were provided with dento-maxillary prostheses to close the defect between the oral and nasal cavities. For both groups, measurements of the range of mouth opening, a questionnaire survey regarding masticatory situation, a gum-chewing test, and a blowing test were performed. The results showed that the subject group （2 patients） had better outcomes than the control group. Therefore, our results suggest that combining a free vascularized flap with a dento-maxillary prosthesis is useful in patients undergoing maxillectomy involving excision of the masticator space.

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For successful facial prosthetic treatment, it is necessary to obtain a facial impression though this is stressful for the patient and causes inaccuracy owing to its weight and body posture. Recently, 3D data acquisition systems have been developed that can acquire the 3D data without any contact with the object. In this study, the effect of body posture on the displacement of facial surface was evaluated using a 3D scanner.
Five subjects participated in this study. Digital facial data were obtained by 3D scanner （RexcanⅢ, Solutionix） in five positions: 0 degree （upright position）, 30 degrees, 45 degrees, 60 degrees and 90 degrees （horizontal position）. These data were then evaluated using 3D digital analysis software （Geomagic Qualify, Geomagic）. The amounts of discrepancy between the upright position and the four reclining positions were calculated after data superimposition.
As a result, the amounts of discrepancy increased between the upright position and each reclining position as the inclination increased. Especially, a larger discrepancy was observed on the cheek under the zygomatic bone.

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