| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 99 === Objectives: The stress around implants has been considered to affect the prognosis of implant therapy. The purpose of this study was to evaluate the effects of platform switching on the peri-implant bone strain in dental implants with external and internal connections, with strain gauge technique, under three different loads: the central vertical load, the lingual vertical load, the horizontal load. The other purpose was to evaluate whether increasing the degree of horizontal offset resulted in decreasing the peri-implant bone strain.
Methods: Four types of implant：external hex connection and internal hex connection platform implant（OSSEOTITE® Parallel Walled Implants, BIOMET 3i, Palm Beach Gardens,USA）, length 13㎜ with different diameter 5.0 ㎜, 6.0 ㎜, were embedded in a 20 x 22 x 70 mm (width x height x length) epoxy resin block. Four strain gauges (EA-00-031CE-350) were bonded on resin surface adjacent to the buccal, mesial , lingual , and distal side of the implant platform. A CAD-CAM 10 x 10 x 11.5 ㎜ (width x length x height) tetragonal column customized abutments was fabricated. Three types of load were applied (vertical loads at two locations:the central vertical load, the lingual vertical load, and a horizontal load) with three different intensities (10N, 30 N and 50N). Each load was repeated 10 times and the data from the strain gauge were recorded and analyzed.
Results: 1. Under the central vertical load, the platform switching design did not change peri-implant bone strain tendancy significantly. 2. Under the lingual vertical load, there was a tendency that the platform switching design decreased peri-implant bone strain. The greater amount of horizontal shifting, the smaller the peri-implant bone strain. When the applied load was larger, the tendency of reduced bone strain became more statistically significant. 3. Under the horizontal load, the trend was similar to that under lingual vertical load. 4. There was a difference between external hex connection and internal hex connection groups. Under the off-axis load, the reduction percentage of peri-implant bone strain in platform switching group of the internal hex connection group was not as large as that of the external hex connection.
Conclusions: The data suggested that under off-axis load, there was a trend that the platform switching design decreased peri-implant bone strain in both external and internal connection groups. The greater amount of horizontal shifting, the smaller the peri-implant bone strain. When the applied load was larger, the tendency become more statistically significant. However, the reduction percentage in peri-implant bone strain in platform switching group of the internal hex connection group was not as large as that of the external hex connection under the off-axis force application.
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