The present studies aims to study the periodical change of the biting force after the insertion of a clasp and an attachment extension partial denture and deal with the studies on the periodical change of the biting force of an abutment tooth and an artificial tooth supporting these dentures a clasp and an attachment extension partial denture by adjusting a unilateral or a bilateral partial denture and inserting each into a missing mandibular unilateral and a bilateral molar.
The thirty-eight subjects aged 20 to 49 (m. 20, f. 18) in the present studies have a unilateral or a bilateral molar extracted because of dental caries more than three months ago, and are provided with the alveolar ridge suitable for dentureinserting, and have never had any plate dentures, and have normal remaining teeth. Partial dentures consist of clasp extension partial denture (Co-Cr metal framework denture) and attachment ones (ASC 52). To the same subject the author inserted and used a clasp extension partial denture for ten months, and after one more month the author measured each biting force by changing it into an attachment extension partial denture and inseting it.
The biting force was measured by the instrument for measuring the biting force with strain-guage (bite element) made by Showa Sokki Co. Ltd. and its record was kept by the multipurpose monitor recorder (RM-150) made by Nihon Kodensha Co. Ltd. The author measured the largest biting force of an abutment tooth, an artificial tooth and each natural tooth on the noninserted side by intercalating the bite element between upper teeth and a lower tooth, and having it bitten as hard as possible. That is, it was measured as follows: immediately before and after the insertion of the denture, two days, and one, two and three weeks, and one, two, three, four, six, eight and ten months after the insertion.
The results of the present studies are summarized as follows.
1. The biting force of an abutment tooth supporting a clasp and an attachment extension partial denture in both a unilateral and a bilateral denture is obviously larger immediately after than before the insertion, while it is the smallest in a longterm of periodical change.
2. Plenty of cases show that the biting force of the abutment teeth of unilateraldentures is smaller than that of the same tooth on non-inserted side in a clasp and an attachment extension partial denture.
3. In an increasing order of the biting force of abutment teeth are the caine, the first premolar, the second premolar and the first molar.
4. There is the least difference in the biting force between all abutment tooth supporting a unilateral and a bilateral denture. And there is also the least difference in the bitin force between each abutment tooth supporting a bilateral partial denture.
5. In a clasp and an attachment extension denture, the biting force of an artificial tooth is smaller than that of an abutment tooth, and the biting force of the second molar is clearly smaller than that of the first molar.
6. As shown in many cases of unilateral partial dentures in a clasp and an attachment extension partial denture, the biting force of an artificial tooth is on a great increase one monthafter the insertion and becomes the largest two or thsee months after.
The biting force of bilateral clasp extension partial dentures continue to increase three or four weeks after the insertion and becomes the largest two or three months after the insertion, while the biting force of bilateral attachment extension partial dentures continues to increase three or four weeks after the insertion and becomes the largest two months after the insertion. And each biting force in aunilateral and a bilateral denture often begins to decrease a little about six months after the insertion.

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