Bulletin of Tokyo Dental College最新文献

Although the working environment may play a role in dental acid erosion, few studies have been conducted on this in Japanese workers in recent years. The purpose of this study was to investigate oral health status, including dental erosion, in workers who may have been exposed to an acidic environment. The study participants were recruited by an online research company. Oral examinations and questionnaire surveys were conducted on this cohort in January 2023. A total of 144 participants were finally included. Workers exposed to an acidic environment showed more use of protective equipment and underwent more dental examinations at the workplace (p<0.001). Possible dental erosion was observed in only 3 out of the total of 144 participants (2.1%), however. No significant difference was observed in the number of teeth, caries experience, or dental erosion according to the number of years of acid exposure in the workplace. The results of this study suggest that acid exposure exerts a relatively small effect on the oral health status of workers in Japan.

In recent years, a wide variety of materials have been used in dental implant treatment. In selecting the superstructures and abutments to be used it is important to consider their potential effect on the stability and durability of the planned implant. Excessive force applied to an implant during maintenance commonly results in complications, such as fracture of the superstructure or abutment, and loosening or fracture of the screws. This report describes a case of implant treatment for a 23-year-old man with esthetic disturbance due to trauma to the maxillary anterior teeth. The left maxillary central incisor could not be conserved due to this trauma, which had been caused by a traffic accident. After extraction, the tooth was restored with an anterior bridge. The crown of the left maxillary lateral incisor was fractured at the crown margin and, at the patient's request, implant treatment was selected as the restorative treatment for the missing tooth. A thorough preoperative examination was performed using placement simulation software. One titanium screw-type implant was placed in the maxillary left central incisor under local anesthesia. An all-ceramic crown with a zirconia frame was placed as a screw-fixed direct superstructure. At one year postoperatively, however, the superstructure and abutment became detached due to trauma. The fractured zirconia abutment was removed and replaced with a remanufactured abutment and superstructure. The patient has reported no subsequent dental complaint over the last 11 years. In this case, a surface analysis of the fractured zirconia abutment was performed. The scanned images revealed a difference in the fracture surfaces between the tensile and compressive sides, and electron probe microanalysis demonstrated the presence of titanium on the fracture surface. It was inferred that the hard zirconia abutment had scraped the titanium from the internal surface of the implant.

Cardiac ischemia, such as angina pectoris or myocardial infarction, is associated with pain in the oral cavity, lower jaw, head, or neck, or spanning from the left upper arm to the shoulder. When presenting to a dentist, however, appropriate treatment for such patients is often delayed, as dental problems are usually the first to be suspected when the chief complaint is orofacial pain. This report describes a case of a 70-year-old woman who was aware of pain and a burning sensation in the oral cavity upon exertion for a year prior to presenting at our clinic. She had been examined by her family physician, an otolaryngologist, and another dentist, none of whom found any abnormalities other than suspected periodontal disease and caries, for which she was treated. An examination at our clinic revealed no abnormal dental findings that would have been consistent with the mandibular pain, however. Although no chest symptoms were reported, pain was elicited on exertion, suggesting cardiogenic toothache. An immediate referral to a cardiologist was therefore made on the same day. The patient visited the cardiology department of the University Hospital of Tokyo Dental College 6 days later. The increased frequency of symptoms on exertion suggested unstable angina, and the patient was admitted to the emergency department on the same day. Emergency coronary angiography showed that right coronary artery #1 was 99% stenosed proximally (highly calcified plaque). The diagnosis was unstable angina pectoris, with the right coronary artery #1 as the responsible lesion, and percutaneous coronary angioplasty was performed on the same day. Subsequently, all the orofacial pain disappeared, confirming unstable angina as the cause. The pain characteristics in this case were consistent with pain associated with cardiac ischemia, which led to the immediate referral to the cardiology department. In cases of toothache associated with cardia ischemia, it is essential to seek cardiological care as soon as possible.

The present study investigated the cyclic fatigue properties of titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) as implant materials and compared their properties with those of commercially pure titanium. Ti-6Al-4V and Ti-6Al-7Nb cylinders with diameters of 3.0 mm were examined. The surfaces of the cylinders were roughened by sand blasting with alumina particles and acid etching. Static and cyclic tests were performed according to ISO 14801:2016. The yield force in the static test (YS) was measured in 5 specimens of each alloy using a universal testing machine. The yield force in a cyclic test (YC) was measured in 20 specimens of each alloy using the staircase method, which involved applying a cyclic load at a frequency of 10 Hz for 10⁶ cycles. After the cyclic loading tests, cross-sections of the specimens were examined under an optical microscope. The YS values for Ti-6Al-4V and Ti-6Al-7Nb were 1463 N±93 N and 1405 N±79 N, respectively, and the YC values were 870 N±58 N and 853 N±202 N, respectively. Microscopic observation revealed cracks on the tensile side of some of the specimens, including run outs and failures. The results of this study suggest that the YC values for Ti-6Al-4V and Ti-6Al-7Nb were 40% less than those for YS. The yield force of Grade-4 Cp-Ti significantly decreased after cyclic loading. The YC values for Ti-6Al-4V and Ti-6Al-7Nb were approximately 900 N, which was markedly greater than that for commercially pure, Grade-4 titanium (700 N).

This case report describes a 19-year-old woman with skeletal Class I crowding and an unsalvageable maxillary right central incisor. She visited our clinic with the chief complaint of mobility of the maxillary right central incisor due to a traffic accident. After extraction of the maxillary right central incisor, the space was closed orthodontically. All the maxillary right teeth were moved mesially with an elastic chain attached to a palatal lever arm which was connected to palatal temporary anchorage devices (TADs). After orthodontic treatment had been completed, the maxillary right lateral incisor and peg-shaped left lateral incisor were restored with a porcelain laminate veneer. The maxillary right canine was morphologically reshaped and built up with composite resin. Consequently, esthetically ideal occlusion and functional lateral guidance with uncontacted molars were obtained. These results show that mesial movement of the entire dental arch with TADs is a useful orthodontic treatment option in patients in whom the maxillary central incisor has been extracted.

The morphogenetic process of development of the circumference of the mandibular fossa during tooth eruption, which involves the replacement of deciduous teeth with permanent teeth, is strongly affected by occlusion. To the best of our knowledge, no studies have investigated the effect of occlusion on this process. This study investigated the morphogenetic process of development during tooth eruption using dried skulls harvested from Indian donors. The average distance between the ala-major-squamosa suture and the foramen ovale according to age group was as follows: 3.24 mm in the 8-month-old group and 8.92 mm in the adult group. The average distance between the ala-major-squamosa suture and the apex of the articular tubercle according to age groups was as follows: 10.38 mm in the 8-month-old group and 19.34 mm in the adult group. The average distance between the point of intersection of the petrosquamous fissure and petrotympanic fissure located on the perpendicular line drawn posteriorly from the shortest distance of the medio-lateral axis between the ala-major-squamosa suture and the apex of the articular tubercle according to age group was as follows: 9.68 mm in the 8-month-old group and 14.3 mm in the adult group. These results suggest that the mandibular fossa is strongly affected by load due to occlusion, unlike the growth of the neurocranium. This indicates that the effect of occlusion is a secondary element in the morphogenetic process of development of the circumference of the mandibular fossa.

The aim of this randomized crossover trial was to clarify the effects of chewing gummy jelly containing a compound of decanoic acid, oligonol, methyl cellulose, and citral (DOMAC) on mental stress and autonomic nervous activity in facemask wearers. A placebo gummy jelly was used in conjunction with DOMAC. Eight healthy adults with no tooth loss (mean age: 35±5 yr) were included. The participants were required to chew one DOMAC or placebo gummy jelly for 5 min after wearing a facemask for 20 min in the laboratory, then the other gummy jelly after a washout period. Rate of change in salivary immunoglobulin A (IgA) as a marker of stress was compared between before and after chewing. Additionally, sympathetic and parasympathetic activity was compared at both time points. A significant difference was observed in the percentage change in salivary IgA from that at before wearing a facemask: 127±34% (mean±standard deviation) while wearing a facemask; 46±20% while chewing DOMAC gummies; and 47±26% while chewing placebo gummies (p<0.05). Parasympathetic nervous system activity was 971.2±1040.7 ms² at 20 min after facemask wearing; 295.0±253.0 ms² after DOMAC gummy chewing; and 1956.1±2798.0 ms² after chewing a placebo gummy jelly; with significant differences only being found between 20 min after facemask wearing and after DOMAC gummy chewing (p<0.05). Sympathetic nervous system activity was 1.80±1.83 at 20 min after facemask wearing; 4.06±3.33 after DOMAC gummy chewing; and 4.95±7.02 after chewing a placebo gummy jelly; with significant differences only being found between 20 min after facemask wearing and after DOMAC gummy chewing. These results suggest that chewing gummy jellies containing DOMAC relieves stress caused by facemask wearing and activates sympathetic nervous system activity.

The aim of this study was to investigate the effects of combining mechanical (ultrasonic) and chemical cleaning (using denture cleaners) on the surface roughness of silicone or acrylic soft relining materials. The silicone soft relining material with the lowest Shore A hardness and a acrylic soft relining material routinely used in Japan were selected. Four groups were established based on type of treatment: immersion in water (W); ultrasonic cleaning in tap water (U); ultrasonic cleaning in a hypochlorous acid denture cleanser (HU); or ultrasonic cleaning in an acidic denture cleanser (AU). Following the tests, surface roughness was determined as the arithmetic mean height of the surface (Sa) and maximum height (Sz). Data were analyzed using the Kruskal-Wallis test followed by Bonferroni correction for a multiple comparison. No significant difference was observed in the Sa or Sz of the silicone soft relining material between the 4 groups. Significant differences were observed in the Sa of the acrylic soft relining material between Groups W and HU (p=0.008) and between Groups W and AU (p=0.008), but no significant differences in the Sz among the 4 groups. Combining U with AU or U with HU yielded no increase in the surface roughness of the silicon soft relining material. The surface roughness of the acrylic soft relining material showed an increase, however, with the combination treatments used.

This study investigated decline in oral function in healthy young adults and compared it with that observed in an earlier studies employing older adults. The participants comprised 130 young healthy adults (mean age 24.1±2.9 yr), all with complete dentition. All participants underwent the oral hypofunction test established by the Japanese Society of Gerodontology, which evaluates oral hygiene, oral dryness, occlusal force, tongue-lip motor function (oral diadochokinetic rate; ODK), tongue pressure, and masticatory and swallowing function. The average value for and rate of hypofunction of each parameter were calculated. In healthy young adults, the scores were 28.9±17.1% for oral hygiene; 28.8±2.2 for oral dryness; 959.9±499.8 N for occlusal force; 7.0±0.8 times/sec for ODK /pa/, 7.6±0.8 times/sec for /ta/, and 6.9±0.9 times/sec for /ka/; 41.8±8.4 kPa for tongue pressure; 249.8±94.1 mg/dl for masticatory function; and 0.2±0.7 for swallowing function. No sign or symptom of change in oral function was observed at a high rate in young adults. Occlusal force, tongue-lip motor function, and tongue pressure showed a large difference in the rate of hypofunction between younger and older adults, however.

This report describes a case of gingival recession in multiple teeth with severe dentin hypersensitivity (DH) in which treatment included periodontal plastic surgery. The patient was a 34-year-old woman presenting with the chief complaint of DH at gingivalrecession sites. The patient had undergone orthodontic treatment when she was 30 years old. An initial examination revealed that none of the sites showed a probing depth of ≥4 mm and 21% of sites bleeding on probing. The clinical diagnosis was plaque-induced gingivitis. Teeth #14, 16, 23, 25, 26, 34, 35, 45, and 46 showed gingival recession ranging from 1 to 4 mm. Gingival recession at #45 extended to the muco-gingival junction. No association with alveolar bone loss was observed in any of the interdental areas. Therefore, the sites presenting with gingival recession were classified as Miller Class I, except #45, which was classified as Class II. The periodontal phenotype was 'thin'. Based on the results of clinical examination and diagnosis, initial periodontal therapy (IP) consisting of oral hygiene instruction, supra-gingival scaling, application of a desensitizing agent, and composite resin restoration was performed. The Visual Analog Scale (VAS) score, which was used to assess degree of DH, showed only a minimal decrease, however, at post-IP. Subsequently, a modified coronally advanced tunnel (a modified technique for achieving a coronally advanced flap) using a connective tissue graft was performed in #14, 16, 23, 25, 26, 45, and 46. After re-evaluation, the patient was placed on maintenance care. The series of interventions resulted in a considerable improvement in the VAS and oral health-related quality of life scores. Furthermore, a change in the periodontal phenotype, from 'thin' to 'thick', was observed, which may contribute to the prevention of further gingival recession and DH. The present case suggests that periodontal plastic surgery is an effective treatment modality for the resolution of DH.