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.