The aim of this investigation was to evaluate the use of resonance frequency measurements in the clinical measurement of implant stability. Resonance frequency measurements are undertaken by measuring the response of a small transducer attached to an implant fixture or abutment. Two groups of patients were selected for study. Group A comprised 9 patients who had a total of 56 implants placed. Resonance frequency measurements were made at fixture installation and repeated 8 months later at abutment connection. The resonance frequency of the implant/transducer system increased for 50 out of the 56 implants from a mean value of 7473 Hz +/- 127 Hz (P < 0.05) to a mean of 7915 Hz +/- 112 Hz (P < 0.05). Two implants had failed to integrate and the resonance frequency of these had fallen. Group B comprised 9 patients who had been provided with fixed prostheses and had a total of 52 implants placed. They were examined 5 years after fixture placement and the prostheses removed. All implants were judged clinically to be osseointegrated. The level of the marginal bone around each implant was calculated by measuring the number of exposed threads on intraoral periapical radiographs and added to the length of each abutment to give a value termed the effective implant length (EIL). Measurements indicated a correlation (R = -0.78, P < 0.01) between EIL and resonance frequency. The results support the hypothesis that the resonance frequency of an implant/transducer system is related to the height of the implant not surrounded by bone and the stability of the implant/tissue interface as determined by the absence of clinical mobility.
A photogrammetric technique was tested to measure the topography of the mucosa around implants, placed in edentulous upper jaws. Photographs were taken of casts from 6 patients, who all had used a removable overdenture for one year. Another series of photographs was taken on new casts after the use of a fixed prosthesis for a second year. The 6 pairs of photographs were measured and compared in an analytical stereo plotter for surface contour and implant positions. The results from the measurements indicated a trend of general recession of the mucosa after one year with fixed prosthesis, both on the buccal as well as on the palatal side. The mean volume of recession was 222.4 mm3, corresponding to an average of 0.4 mm3/mm2 of mucosa. More recession was generally observed on the palatal side, but obvious variations between the patients were present. In conclusion, the photogrammetric technique was considered to be well suited for analysing tissue contours in various dental situations.
The objective of the present study was to assess possible adaptive functional changes in the masticatory system after insertion of fixed prostheses supported by osseointegrated implants in the edentulous mandible. Registrations of mandibular movement characteristics and maximal biteforce were performed at insertion and after 1 week, 3 months and 1 year after connection. The duration of the opening and closing phase decreased and maximal biteforce increased significantly (p < or = 0.05-0.001) from connection of the prostheses to the annual check-up. However, the process of functional adaptation implied 2 identified stages. An immediate phase that occurred within the 1st week, probably due to altered impact from mechano-sensitive receptors and a later more time-dependent phase, based on learning and new cortical engrams. Accordingly, the process of adaptation will continue over a long period of time.
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