[in Japanese]

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[in Japanese]

View full abstract

[in Japanese]

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Purpose: Treatment policies for shortened dental arch (SDA) with the loss of few posterior teeth are divided into two contrary options: positive prosthetic treatment and no treatment. In this study, the effect of chewing with a simulated SDA on masticatory muscle activity was investigated in order to evaluate functional features of SDA during chewing.
Materials: Eight healthy dentate subjects participated in this study. An acrylic resin occlusal splint covering the lower full dental arch was fabricated for each subject and then the posterior region of the splint was removed consecutively to simulate SDA without bilateral second molars and that without bilateral first and second molars. Activity of the masseter and temporal muscles from the onset of chewing to the completion of swallowing was measured when the subject was instructed to eat rice or beef jerky while wearing one of three types of splint. The muscle activity and number of chewing cycles were compared among the three types of splint.
Results: The total muscle activity and number of chewing cycles increased as the splint was shortened. The effect of simulated SDA on muscle activity was larger when using the splint without bilateral first and second molar regions than that without bilateral second molar regions. However, the mean muscle activity required for one chewing cycle was almost constant irrespective of the type of splint.
Conclusions: It is suggested that positive prosthetic treatment is effective for SDA in cases which have lost all occlusal support in the molar region.

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Purpose: Life-threatening choking or severe aspiration pneumonia due to unnoticed dislodging of dentures and provisional restoration materials (PRM) can develop in those who have poor swallowing or coughing function, such as frail elderly people or patients managed under anesthesia or sedation with or without an artificial airway. Dentists and healthcare workers are increasingly criticized for incidents associated with unnoticed dental dislodging. While dentists in general should make every effort to prevent unnoticed dislodging of PRM, dental anesthesiologists should pay special attention to prevent the development of life-threatening conditions. It is therefore imperative to develop measures to add radiopaqueness to PRM.
Materials and Methods: We tried mixing various proportions of nano zirconia powder with self-cured acrylic resins and tested their physical and dental material properties including radiopaqueness, anti-bending strength, initial polymerizing times and Vickers hardness.
Results: Nano zirconia containing self-cured acrylic resin showed radiopaqueness in a dose-dependent manner, however, durability tended to decrease and initial polymerizing time tended to increase.
Conclusions: It was concluded that 30-40 wt% of nano zirconia containing self-cured acrylic resin produces appropriate radiopaqueness with little compromise of the dental material properties required of PRM, and further development for its clinical application is warranted.

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Patient: The patient was a 67-year-old woman who visited our clinic with the chief complaint of poor esthetic appearance of the lower front teeth. On examination, she had severe attrition of the mandibular anterior teeth and was dissatisfied with their appearance. After regaining proper vertical dimension with an occlusal splint, a maxillomandibular prosthesis was provided.
Discussion: After regaining adequate vertical dimension using the occlusal splint, the masticatory function was evaluated by electromyography (EMG), which confirmed improvement in masticatory function.
Conclusion: Prosthetic treatment to regain proper vertical dimension in patients with a decreased vertical height due to severe attrition resulted in improvement in esthetics and mastication, thus improving satisfaction of the patient over time.

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Patient: A 65-year-old female visited and complained of painful mastication, mobility of the maxillary bridges and poor esthetic appearance. She had non-vertical stop occlusion, which caused impairment of mastication and appearance. Treatment dentures were used to reconstruct the occlusal relationship. Definitive dentures with stud attachment and cast clasp were fabricated in consideration of the mandibular position of treatment dentures.
Discussion: The Oral Health Impact Profile (OHIP-J) indicated a decrease of the score from 127 at the initial visit to 17 at the recall visit 3 years after placement of definitive dentures. During a 3-year follow-up, the prognosis has been excellent.
Conclusion: The use of new dentures improved the occlusal relationship and esthetics. Furthermore, this rehabilitation improved the patient’s oral health-related quality of life.

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Patient: A 55-year-old female complained of restricted mouth opening and noise of the left-side TMJ. Treatment was initiated with lifestyle intervention and occlusal splint therapy. By the treatment for TMD with the occlusal splint, TMD symptoms were alleviated and an abnormality of occlusal contact became clear. Occlusal contact was improved by prosthodontic treatment, and TMD symptoms did not recur for the next six years.
Discussion: The treatment with the occlusal splint relieved the TMD symptoms and clarified the need for prosthodontic treatment in this case.
Conclusion: This case suggests that although reversible methods are recommended in the treatment of TMD, prosthodontic treatment needs to be carried out immediately when there is a clear association with occlusal factors.

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Patient: A 64-year-old woman came to our hospital with the chief complaint of inflammatory pain in the marginal gingiva of the maxillary molars and mastication disorder due to ill-fitting mandibular dentures. Ill-fitting margin of the prosthetic device and imbalance of the crown-root ratio were observed. In order to improve the crown-root ratio and oral hygiene, a treatment denture was placed. The magnetic attachment overdenture was selected as the final prosthesis in consideration of a design that would less affect the occlusal relationship in the future.
Discussion: It is considered that the stability of the denture when functioning can be achieved by dispersing the occlusal force and improving the crown-root ratio.
Conclusion: A long-lasting good outcome was obtained by applying the magnetic attachment overdenture for the treatment of cross bite.

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Patient: The patient was a 78-year-old woman who presented with a masticatory disorder owing to unsteadiness of dentures and mobility of abutment teeth. The patient had non-vertical stop occlusion and severe alveolar ridge resorption. After extraction of hopeless abutment teeth, masticatory function was improved by applying an overdenture using magnetic attachments.
Discussion: Introducing a magnetic attachment system decreased occlusal load on the abutment teeth and the overdenture improved the occlusal plane. These treatments resulted in good postoperative progress.
Conclusion: Introducing a magnetic attachment system resulted in a positive outcome for a case with severe alveolar ridge resorption.

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Patient: A 66-year-old man presented with the chief complaint of masticatory disturbance caused by multiple missing teeth. His occlusal status was Eichner class C1, with no removal partial dentures (RPDs). Temporary RPDs were fabricated to restore chewing function, and were adjusted until the occlusion stabilized, then crown prostheses and RPDs were made.
Discussion: For patients without vertical stop in occlusion, it is important to reduce the difference in support ability between edentulous and non-edentulous areas. In this case, the remaining teeth were stabilized by connecting them to fixed prostheses, and RPDs were designed to distribute occlusal forces over the teeth and the edentulous alveolar ridge. The metal frames of the RPDs provided enough resistance against bending forces.
Conclusion: This case with non-vertical stop occlusion was successfully rehabilitated using RPDs to provide occlusal support.

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Patient: The patient was a 70-year-old man with loss of maxillary molars and a habit of bruxism. The diagnosis was infraocclusion caused by loss of molar occlusal support and attrition of teeth.
Discussion: The loss of occlusal support increased bruxism and caused infraocclusion. Occlusal reconstruction with bite raising was chosen to preserve the remaining teeth and restore masticatory function and esthetics.
Conclusion: Bite raising increased the occlusal vertical dimension and stopped the collapse of remaining teeth. Oral function and esthetics were recovered by occlusal reconstruction and good results were obtained for this patient with infraocclusion due to attrition.

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Patient: A 74-year-old woman visited our hospital with a complaint of progressive residual ridge resorption and chewing difficulty. Improvement of masticatory function and determination of suitable mandibular position were carried out using a treatment denture. A hollow complete denture was adopted as the definitive denture of her upper jaw.
Discussion: Maxillary complete dentures for patients with severe ridge resorption have a tendency to be large in volume and mass, which may decrease retention of the dentures. In this case, retention was increased by hollowing out the anterior part of the denture base and decreasing its mass. Three years after receiving the final prosthesis, the patient is highly satisfied with the esthetics and sensation.
Conclusion: This case report demonstrates that a favorable outcome can be obtained in a case of severe maxillary ridge resorption by insertion of a weight-saving complete denture.

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Patient: The patient was a 69-year-old male who first visited with the chief complaint of mastication disorder due to instability of conventional mandibular full dentures. The mandibular ridge was found to be resorbed severely. We fabricated a two-implant-supported overdenture.
Discussion: This case suggested that the implant-supported overdenture with Rocator abutment whose retentive force can be adjusted by replacing the retention disk is helpful for improving the stability of dentures and improving QoL, especially for patients with severe ridge resorption of the mandible causing instability of dentures.
Conclusion: We treated an edentulous patient with severe ridge resorption of the mandible using implant-supported overdenture with a good outcome.

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