The general prognosis of luxational tooth injury and recommendations for treatment are described based on the guideline for management of acute dental trauma which was established by the Japan Association for Dental Traumatology in 2012. The most important points for dentists when starting to consider prosthodontic treatment for a tooth affected by luxational injury are healing of damaged periodontal tissues and prevention and/or treatment of external root resorption. It is not difficult to optimize healing of periodontal tissues. However, the condition and timing at which to start considering prosthodontic treatment for the affected tooth with luxational injury such as intrusion or avulsion are not clear because the pathogenesis of external root resorption has not been elucidated yet. Therefore, prosthodontic treatment can be considered based on informed choice of the patient after he/she is informed of the risk to the outer root resorption of the tooth affected by luxational injury.

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Traumatized teeth may concurrently suffer damage to the hard tissue, periodontal tissue and pulp. Recent statistics from several countries show that 15-23% of 12-year-olds have suffered trauma to the permanent dentition.
Long-term clinical investigations as well as experimental studies on various aspects of dental traumatology have been instrumental to the revision of the guideline on treating traumatic dental injuries. The complications peculiar to dental injuries are circulatory disturbance, tooth crack (incomplete fracture), pulp canal obliteration, internal resorption, and external root resorption. Follow-up and mouth guards are effective for maintaining the long-term functions of traumatized teeth.

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In this study we discussed the treatment options and their outcomes for traumatized teeth according to the treatment guideline suggested by the Japan Association for Dental Traumatology in 2012. With conventional prosthodontic principles, traumatized teeth are usually treated with pulp extraction followed by core build-up and preparation for crowns. In addition, fixed partial dentures and dental implants are applied after extraction, which provide immediate outcomes.
Treatments for those teeth should be carried out with a step by step interdisciplinary approach combining pulp-capping, adhesion, extrusion as well as replantation according to the basic concept of the guideline, by preserving existing tissues and utilizing the healing capability as much as possible.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Purpose: Although a relationship between masticatory function and higher brain function has been reported, its mechanism has not been revealed. Higher brain function, which includes the development of neural circuits and their functional expression after the differentiation and maturation of neurons, the ramification of dendrites and the formation of synapses, involves the synthesis of cholesterol by brain-derived neurotrophic factor. In this study, we evaluated whether solid feed, which requires mastication, is more conducive than liquid feed to the expression of brain-derived neurotrophic factor and its synthesis of cholesterol in rats.
Methods: After rats were raised on solid or liquid feed for eight weeks, the brain tissue was divided into the cerebellum, medulla oblongata, hypothalamus, mesencephalon - hippocampus - corpus striatum, and cerebral cortex. The expression of brain-derived neurotrophic factor was measured by real-time RT-PCR, the receptors for brain-derived neurotrophic factor were immunostained and the total amount of cholesterol was measured.
Results: Rats raised on solid feed had significantly greater expression of brain-derived neurotrophic factor and more receptors for it as well as a greater total amount of cholesterol in cerebral cortex.
Conclusions: This study suggests that mastication affects the synthesis of cholesterol via brain-derived neurotrophic factor involved in learning and memory function.

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Patients: A 69-year-old male patient visited our dental office with the chief complaint of discomfort caused by his complete dentures. Intraoral examination revealed that both mandibular and maxillary ridges appeared to be good and to retain the dentures although he had a habit of tongue-thrusting. The existing dentures were duplicated and used as treatment dentures in this case. New complete dentures were fabricated by referring to the duplicated dentures.
Discussion: The duplicate dentures method, in which dentures can be reversed after modification, enabled the duplicated dentures to be actively modified to reduce the patient’s sense of resistance to the new dentures.
Conclusion: The application of duplicate dentures appeared to be useful in the process of replacing the existing dentures with new dentures.

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Patient: The patient was a 60-year-old woman with chronic periodontitis who had strong esthetic requirements. Originally, we recommended overdentures to the patient as she was unwilling to undergo bone grafting. However, the patient refused to wear removable partial dentures. This led us to perform occlusal reconstruction with a professional retrievable implant-supported prosthesis.
Discussion: As the tight fit of an electroformed inner-outer cap without cementing gave stability to this prosthesis, the patient was satisfied with the similarity of the prosthesis to the fixed ones when wearing it. In addition, this type of prosthesis is easily removed with an instrument such as a crown-remover for maintenance or solving problems.
Conclusion: A professional retrievable prosthesis consisting of three units was effective in restoring masticatory function and esthetics for a patient with strong esthetic requirements.

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Patient: An edentulous patient with masticatory dysfunction experienced an ill-fitting complete mandibular denture and its recurrent fracture. Several attempts to reinforce the denture were unsuccessful.
Discussion: It was hypothesized that the recurrent fractures were attributable not only to the structure of the denture, but also to the dispersion and uneven distribution of functional force through the denture. Therefore, correct tooth alignment, proper contours of the polished surfaces, and centric and lingualized bilateral balanced occlusion were ensured to establish a neutral zone before fabricating a new complete denture. The patient’s masticatory function was restored, and no signs of fracture have since been observed.
Conclusion: This case highlights the importance of functional factors (e.g., the centric relation of the mandible, a neutral zone, and balanced occlusion) in addition to structural factors (e.g., denture thickness) as potential causes of mandibular denture fracture.

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Patient: The patient was a 76-year-old male with the complaints of denture base fracture and pain of the masseter muscle. A diagnosis of infraocclusion, caused by loss of molar occlusal support and attrition of teeth, was made. The occlusal vertical dimension was increased by treatment dentures. Finally, metal-structured dentures were inserted.
Discussion: The metal-structured dentures were effective for treating the loss of molar occlusal support and attrition of teeth. The occlusal vertical dimension was increased and pain of the masseter muscle was cured.
Conclusion: The treatment dentures were applied to this patient with myalgic pain caused by infraocclusion in order to improve the occlusal vertical dimension. Subsequent application of the final prosthesis resulted in a positive outcome.

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Patient: The patient was a 59-year-old female with the chief complaint of chewing difficulty due to instability of removable partial dentures. The partially edentulous arches with non-vertical stop occlusion lacking all tooth contacts (Eichner C1) after extraction of unsalvageable teeth were restored with a mandibular conical crown-retained partial denture and a maxillary clasp-retained removable partial denture.
Discussion: Chewing ability was improved and high patient satisfaction was achieved after the prosthetic treatments using a conical crown-retained partial denture for the mandible in which a traditional clasp-retained removable partial denture would not provide sufficient denture stability. Occlusal position and denture stability were maintained at 3 years after treatment.
Conclusion: A combination of a mandibular conical crown-retained partial denture and a maxillary clasp-retained partial denture is effective for prosthetic restoration in patients with non-vertical stop occlusion.

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Patient: The patient was a 30-year-old woman, who presented with a chief complaint of cosmetic disturbance by diastema and discolored upper front teeth. The patient was diagnosed as having grinding-type sleep bruxism (SB) after clinical examinations. She was treated with porcelain laminate veneers (PLV) for the upper front teeth and also provided with a full-coverage maxillary occlusal splint for SB, which resulted in a favorable prognosis.
Discussion: PLVs are generally contraindicated for patients with SB. Application of an occlusal splint can allow a favorable prognosis even after PLV restoration.
Conclusion: Accurate diagnosis and appropriate management of SB are essential in order to secure a favorable prognosis for prosthodontic treatment, especially in the case of all-ceramic restorations such as PLVs.

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Patient: An 82-year-old woman presented in our clinic with a masticatory disorder caused by an unstable complete mandibular denture. Her maxillary teeth consisted of a fixed prosthesis. The mandible was edentulous with severe bone resorption in the molar region. After consultation, prosthetic treatment was recommended only for the edentulous mandible. Four implants were placed in the anterior part of the mandible, and an overdenture was set using a bar attachment.
Discussion: A comparison of Yamamoto’s masticatory efficacy before and after treatment indicated that the prosthetic treatment using an implant overdenture resulted in an improvement of masticatory efficacy.
Conclusion: Implant overdentures are effective and bring favorable long-term outcomes for patients with mandibular single denture with severe residual ridge resorption.

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Patient: A 73-year-old male presented with the chief complaints of repeated denture fracture and pain in the maxillary anterior gingiva. Because the left molar region exhibited scissor bite, eccentric tooth movement was not possible and the mandibular anterior teeth impinged on the palatal gingiva. Old dentures were used to elevate the occlusion and the tooth crown axis was repaired to achieve left occlusal support, following which the dentures were placed.
Discussion: Improvement of scissor bite was enhanced with occlusal elevation while simultaneously creating space for dentures. This resulted in long-term, stable esthetic appearance and achieved functionality.
Conclusion: The patient’s chief complaints were resolved with occlusal support for the molar region, resulting in high patient satisfaction.

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Patient: The patient was a 78-year-old female who visited our hospital with the chief complaint of masticatory disturbance. The lower alveolar ridge had been severely adsorbed, for which a new denture was prepared in consideration of the piezography to determine the morphology of the polished surface of the denture and the buccolingual arrangement of the artificial teeth, and the occlusion pattern - lingualized occlusion.
Discussion: Using a functional impression method, piezography was used to locate the lower artificial teeth and lingualized occlusion to make occlusal force lingualized worked the denture stabilized.
Conclusions: Piezography was effective in stabilizing the denture for the patient with severe adsorption of the alveolar ridge. When preparing a complete denture, it is important to select an appropriate occlusal pattern in consideration of the condition of the alveolar ridge and the patient’s dietary preference.

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Patient: The patient was a 51-year-old female whose chief complaint was esthetic dissatisfaction caused by multiple dental caries and metal prostheses. After extraction of the teeth that could not be saved, the occlusal support in the molar area disappeared. During the treatment, the patient refused to use removable partial dentures. The patient’s satisfaction in esthetics and masticatory function, periodontal tissues, occlusion, and stomatognathic function were evaluated during the period of provisional restorations in the shortened dental arch manner, then final restorations were provided to the patient.
Discussion: As a result of proper diagnosis and meticulous maintenance, a favorable condition has been maintained for 7 years.
Conclusion: The shortened dental arch concept might be acceptable provided that a detailed diagnosis and adequate maintenance by both the patient and dental professionals are performed.

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