Comparison of oral hypofunction tests and determination of reference values for a subjective masticatory function test.

BACKGROUND: In Japan, oral hypofunction has been recognized as a disease since 2018. An alternative to occlusal force testing for assessing oral hypofunction is the evaluation of the number of natural teeth. Subjective masticatory function testing, which evaluates the ease or difficulty in chewing foods, is an effective alternative to occlusal force testing. However, no reference values have been established for this test. We determined the reference values of the subjective masticatory function test and evaluated its potential as a substitute for the number of natural teeth for assessing oral hypofunction. METHODS: The sample consisted of 184 older adults who visited the Department of Geriatric Dentistry, Showa University Dental Hospital, from July 2018 to January 2020. The subjective masticatory function test (table for evaluation of chewing function in complete denture wearers [Chewing Score 20]) was performed using 20 foods. The occlusal force test and a receiver operating characteristic curve were used to determine the reference values for Chewing Score 20. The sensitivity, specificity, and positive and negative predictive values were calculated and compared with the occlusal force test and the number of natural teeth. RESULTS: A significant correlation (r) was found between the occlusal force test and the Chewing Score 20 (r = 0.526, p < 0.001). The reference value for Chewing Score 20 was < 85. Although the Chewing Score 20 was less sensitive than the number of natural teeth, it demonstrated a higher specificity and a positive predictive value. CONCLUSION: Herein, a score of < 85 on the subjective masticatory function test was determined to be the optimal quantitative reference. The subjective masticatory function test may be used as an alternative for assessing oral hypofunction.

Occlusal status of implant superstructures at mandibular first molar immediately after setting.

BACKGROUND: Occlusal contact on the implant superstructures is important for successful treatment. The purpose of this study was to investigate the occlusal contact of single implant superstructures at the mandibular first molar immediately after seating from weak to strong clenching. METHODS: Subjects were nine patients who had just been fitted with an implant prosthesis in the mandibular first molar region, with no missing teeth other than in the implant region. First, while masseter muscle activity was monitored, maximum clenching strength (100 % maximum voluntary contraction (MVC)) was determined with an electromyogram. Next, occlusal load and occlusal contact area were measured three times at clenching intensities of 40, 60, 80, and 100 % MVC by the use of pressure-sensitive film for occlusal force diagnostic and Occluzer for occlusal force measurement. Finally, the occlusal contact area was measured once each at 20, 40, and 60 % MVC using a silicone testing material and BiteEye for occlusal contact measurement. A two-way analysis of variance (ANOVA) was used to determine occlusal loading and occlusal area as dependent variables, and clenching strength and presence or absence of implant as between-subject factors. A multiple comparison test was performed using the Bonferroni method. RESULTS: The occlusal contact area and occlusal load of the implant prosthesis increased with clenching strength, and the increases in occlusal contact area and occlusal load of the implant prosthesis were less than those of the contralateral tooth at high clenching strength. However, significant difference was not observed when compared with both sides of the molar region regardless of clenching strength. CONCLUSIONS: The occlusal contact area of the implant had a tendency to be adjusted smaller than the natural tooth by a dental technician and a dentist. On the other hand, despite the small tissue displaceability of the implant, occlusal load on the implant prosthesis was smaller than on the natural tooth at high clenching strength.