Objective : Obstructive sleep apnea （OSA） is classified as a sleep disorder. Treatment is imperative because OSA increases the risk of developing hypertension, cardiovascular disease, cerebral apoplexy, and sudden death. Nasal continuous positive airway pressure and oral appliances （OA） are the most common treatments for OSA. Recent research has focused on the treatment effect of OA on positional-dependent OSA, in which the apnea hypopnea index （AHI） is significantly increased in the supine compared with that in the lateral sleeping position. The aim of the study was to investigate the treatment effect of OA for positional- and nonpositional-dependent OSA.
Methods : This study evaluated 73 patients who underwent OA treatment at the Department of Oral and Maxillofacial Surgery of Aichi Medical University Hospital. Patients underwent polysomnography in the presence and absence of OA and were classified as having either positional- or nonpositional-dependent OSA. The AHI changes were compared between the two groups for the presence and absence of OA. Additionally, changes in AHI were compared during the supine versus lateral sleeping position with OA treatment in both groups. Logistic regression analysis was performed to evaluate the effect of OA treatment.
Results : AHI decreased after treatment with OA in both positional- and nonpositional-dependent OSA. There was no difference in AHI decrease between the supine and non-supine sleeping positions. Positional- and nonpositional-dependent OSA was not found to be a predictor of OA treatment effect.
Conclusions : Positional- or nonpositional-dependent OSA was not selected as an independent predictor for the therapeutic effect of OA.

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Objectives : Obstructive sleep apnea （OSA） is classified as a sleep disorder. Oral appliance （OA） therapy and nasal continuous positive airway pressure （nCPAP） are the most common treatments for OSA, but their effectiveness is dependent on the patients’ compliance. After adjusting the mandibular position in consideration of side effects, patients undergoing OA therapy should participate in sleep tests with OA to evaluate the treatment efficacy. If the effect is low, the OA should be readjusted. Recent researches point out that sleep tests with OA have not been adequately conducted, and improvements are desired. The purpose of this study was to investigate the background of OA therapy, OA adherence and the implementation status of sleep tests with OA.
Methods : This study evaluated 780 patients who underwent OA therapy at the Department of Oral and Maxillofacial Surgery of Aichi Medical University Hospital. We examined the medical records of the subjects retrospectively. We investigated the implementation status of sleep tests with OA, what sleep test method was used and when OA therapy was interrupted. We compared the patients’ background in the groups with OA evaluation and without OA evaluation.
Results : There were 399 cases in the group with OA evaluation and 315 cases in the group without OA evaluation. The group with OA evaluation （age: 56.12±13.78） was significantly older than the group without OA evaluation （age: 52.69±15.10）. There was no gender difference between the groups with OA evaluation and without OA evaluation. The implementation status of polysomnography （PSG） and out-of-center sleep testing （OCST） performed at the time of OA evaluation differed between ages.
Conclusions : There were many cases in which OA adherence was low and the effect of treatment was not evaluated. It was considered that the social background due to age may have had an influence.

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Objectives: This study aimed to assess the efficacy of a digital manufacturing process including optical digitizing and 3-dimensional （3D） additive manufacturing for fabricating oral appliances （OAs） for obstructive sleep apnea. Fitness to dental arch and the retention force of OAs were compared between OAs manufactured using 3D printing with photopolymerizable resin and OAs manufactured using the conventional method with heat-polymerized acrylic resin.
Methods: Digitally manufactured OAs were made of photopolymerizable resin using a 3D printer （DWS DS 3000, DWS, Italy） based on the digital morphological data of the experimental dental cast （Nissin, Tokyo）, which were optically obtained by TRIOS （3Shape, Denmark）. As a control, OAs were manufactured using a heat-polymerized acrylic resin （Acron, GC, Tokyo） on a plaster dental cast made from the impression of the experimental dental cast （Nissin, Tokyo）. OAs of the upper and lower arches in both groups （digital and conventional） were manufactured separately, and their inner surface fitness and retention force to the experimental dental cast were evaluated. The fitness of the OA was evaluated by assessing coincidence of the optically scanned images of the inner surface of the OA and the dental cast. Retention force was measured using a tensile test, in which the OA was worn on the experimental dental cast. To evaluate the influence of combining the upper and lower arches, the upper and lower arches of OAs separately manufactured were attached with acrylic resin on the articulator in both groups. Additionally, one-piece OAs were manufactured by 3D printing to merge the upper and lower parts on the software. The fitness of the OAs to the dental arches on the cast was compared among the three groups.
Results: The fitness of digitally manufactured OAs was significantly lower than that of the conventionally manufactured OAs. The retention force of the digitally manufactured OAs was significantly higher than that of the conventionally manufactured OAs. The fitness of one-piece OAs tended to be lower than that of OAs manufactured separately.
Conclusion: The results show that OAs manufactured using digital technology did not fit as accurately as conventionally made OAs. This could be the result of the polymerization shrinkage of photopolymerizable resin. Further development of the manufacturing processes and materials for digital fabrication of OAs is required.

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Objective: Adverse events due to long-term use of night guards have not been sufficiently elucidated. We herein report a case of occlusal changes in a patient who underwent continuous regular observations for at least 14 years since starting to use a night guard and discuss the precautions in the management of night guard use.
Case: A 50-year-old female, with the chief complaints of clenching, tongue ache, abrupt awakening, etc.
Results: A night guard for the upper jaw was fabricated, and shrinkage of the interdental space in the maxillary anterior region and occlusal changes （open bite） were observed after 12 years and 6 months of its continuous intermittent use. A new night guard for the lower jaw was also fabricated because the patient wanted to continue using it even after the observation. The patient has been using these night guards without any major worsening.
Conclusion: Night guards intended to prevent tooth abrasion, root fracture, or tongue pain from sleep-related bruxism may lead to adverse events. As with oral appliances, the fabrication process requires adequate consideration as well as regular and quantitative management.

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