Abstract: The sample attachment level (M) of each tooth is measured in a plurality of tooth samples taken per tooth type from a plurality of teeth extracted as unconservable teeth. A lost periodontal membrane area (SL) is calculated based on the sample attachment level (M) and a total periodontal membrane area (S). A bite force coefficient (B) different according only to each tooth type, which reflects the bite force of each tooth, is found. The relation between the bite force coefficient (B) and a lost periodontal membrane area (SLB) at the time of loss of each tooth is statistically processed for each tooth type, and a linear equation showing the relation between the bite force coefficient (B) and the lost periodontal membrane area (SLB) at the time of loss of each tooth is prepared by use of the presence of a linear relation between both parameters.

Abstract: The invention provides a mold for injection-molding a golf ball, which mold has a cavity inner wall with a vertical diameter connecting both poles in a vertical direction thereof that is longer than a horizontal diameter connecting both poles in a horizontal direction thereof. A method of manufacturing golf balls using such a mold is also provided. The use of this mold eliminates molding problems that arise when molding the outermost cover layer of a golf ball, enabling the cover to be stably molded and also making it possible to easily and reliably obtain golf balls of high symmetry in which a cover of uniform thickness has been formed.

Abstract: The sample attachment level (M) of each tooth is measured in a plurality of tooth samples taken per tooth type from a plurality of teeth extracted as unconservable teeth. A lost periodontal membrane area (SL) is calculated based on the sample attachment level (M) and a total periodontal membrane area (S). A bite force coefficient (B) different according only to each tooth type, which reflects the bite force of each tooth, is found. The relation between the bite force coefficient (B) and a lost periodontal membrane area (SLB) at the time of loss of each tooth is statistically processed for each tooth type, and a linear equation showing the relation between the bite force coefficient (B) and the lost periodontal membrane area (SLB) at the time of loss of each tooth is prepared by use of the presence of a linear relation between both parameters.

Abstract: The invention provides a mold for injection-molding a golf ball, which mold has a cavity inner wall with a vertical diameter connecting both poles in a vertical direction thereof that is longer than a horizontal diameter connecting both poles in a horizontal direction thereof. A method of manufacturing golf balls using such a mold is also provided. The use of this mold eliminates molding problems that arise when molding the outermost cover layer of a golf ball, enabling the cover to be stably molded and also making it possible to easily and reliably obtain golf balls of high symmetry in which a cover of uniform thickness has been formed.