The purpose of this investigation was to observe radiographically the periodontal tissue changes caused by occlusal trauma and to recognize the factors related to film viewing in diagnosis.
Full cast crowns were designed on the fourth mandibular premolar in adult dogs, in order to produce injurious forces from three directions: distal, buccal and longitudinal occlusal forces.
As a preliminary to this study, the most effective exposure factors for the periodontal tissue changes were determined.
The standardized serial radiographs were taken at the same experimental site during 0-120 days period after cementing the full crown, and individual photograms were analyzed by the indirect radiographic image magnification and the microphotography as well as clinical observation.
Results
1. The most effective exposure factors to observe the periodontal tissue changes were as follows: 50 kilovoltage peak in case 15 milliamperage and 2 second exposure.
2. The error seen in the standardized radiographic images was 0.6%.
3. Clinical changes attributed to occlusal trauma include accumlation of dental plaque, redness and swelling of the gingiva, gingival bleeding and tooth mobility. The depth of the periodontal pocket was also increased.
4. The direction of pathological migration depends upon the one of occlusal trauma.
5. Radiographic changes of the periodontal tissue were as follows:
increase or decrease of the width of the periodontal space, thickening or disappearance of the lamina dura, condensation or radiolucense of the bone trabeculae, and root resorption. Especially, observed in all cases, widening of the periodontal space is good objective to diagnose a occlusal trauma.
6. It took about 7 to 20 days untill these radiographic evidences appear.
7. The radiographic changes caused by traumatic occlusion flom three directions were characteristic respectively.
The most common sites were mesio-distal cervical portion and furcation area.
As above mentioned, the standardized radiographs with the most effective factors are necessary for the observation of the injurious effect upon the periodontal tissue.
In addition, analysis of these radiagrams by the indirect radiographic image magnification and the microphotography is very effective.
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