The "8020" goal of retaining 20 or more teeth after the age of 80 necessitates investigating oral health status in people below the age of 80. The purpose of this study was to determine similarities and differences between people in their sixties attending college and achievers of the 8020 goal. The results of oral examination and occlusal force measurement in 46 students enrolled at a college for the elderly in Chiba City with an average age of 66.9 years (22 men, 24 women) were compared with data from previous surveys of fifty-two 8020 achievers (28 men, 24 women). Occlusal force was measured and evaluated using Dental Prescale (Fuji Photo Film Co., Tokyo). The average number of present teeth was 25.8, and no subjects showed anterior crossbite, comparable with findings in 8020 achievers. Average occlusal force was ‫1.044ע9.249‬ N ‫9.545ע6.920,1(‬ N for men, ‫1.503ע4.368‬ N for women), not significantly different from that in 8020 achievers. The results of multiple regression analysis suggest that occlusal force is unaffected by aging if many teeth are present.

Few studies have investigated the morphologic characteristics of teeth, dental arches and occlusion in elderly persons with many remaining teeth. The purpose of this study was to establish a method of measurement using 3-D imaging to investigate tooth angulation in the elderly from the orthodontic point of view. The dental casts of 20 elderly persons with many remaining teeth were digitized with a 3-D laser scanner (VMS-100F, UNISN INC., Osaka, Japan) to construct 3-D images. The mesio-distal angulation of each tooth was then measured with analytical software (SURFLACER, UNISN INC. and IMAGEWARE 12, UGS PLM Solutions, MO, USA). The occlusal plane formed by the incisal edge of the central incisor and distal buccal cusp tip of the first molar on either side was used as a reference plane for measurements. Mesio-distal tooth angulation (indicated in degrees) of maxillary teeth in this subjects averaged 1.26 for central incisors, 5.46 for lateral incisors, 7.84 for canines, 6.59 for first premolars, 5.78 for second premolars, 1.64 for first molars and ‫71.4מ‬ for second molars. Average values for mandibular teeth were 0.91 for central incisors, 2.35 for lateral incisors, 7.04 for canines, 8.76 for first premolars, 10.44 for second premolars, 7.33 for first molars and 12.67 for second molars. There was no statistical difference between the data in man and women except maxillary second molar (pϽ0.05). Mesial angulation in the mandibular arch showed a progressive increase from the anterior to the posterior. However, this tendency was not observed in the maxillary arch.

Tooth inclination has been discussed many times in terms of esthetics and functionality, but reports related to aging are extremely rare. The purpose of this study was to evaluate tooth inclination in the elderly from the orthodontic point of view. The dental casts of twenty elderly persons with many remaining teeth were digitized with a 3-D laser scanner (VMS-100F,UNISN INC., Osaka, Japan) for reconstruction into 3-D images. Inclination of each tooth was then measured with an analytical software (SURFLACER, UNISN INC. and IMAGEWARE 12, UGS PLM Solutions, MO, USA). The occlusal plane formed by the incisal edge of the central incisor and distal buccal cusp tip of the first molar on either side was used as a reference plane to measure tooth inclination, and the complementary angle as tooth inclination was measured. The average tooth inclinations (degrees) of the maxillary teeth were 8.08 for central incisors, 8.10 for lateral incisors, 4.85 for canines, ‫86.6מ‬ for first premolars, ‫85.5מ‬ for second premolars, ‫51.5מ‬ for first molars, and ‫14.5מ‬ for second molars. The corresponding values for the mandibular teeth were 6.78 for central incisors, 4.87 for lateral incisors, ‫37.5מ‬ for canines, ‫47.31מ‬ for first premolars, ‫12.91מ‬ for second premolars, ‫67.32מ‬ for first molars, and ‫36.82מ‬ for second molars. There was no statistical difference between men and women, except for in the maxillary lateral incisors (pϽ0.05). Tooth inclination showed a progressive decrease from anterior to posterior. The decrease in the mandibular teeth was more regular than that of the maxillary teeth.

The purpose of this study was to clarify the effect of aging on the dentition by quantifying the dimensions of the dental arches in elderly persons aged over 80 years with 20 or more remaining teeth (8020 achievers). The study included twenty 8020 achievers (10 males and 10 females, with an average age of 82.3 years and an average of 28.3 present teeth). Their dental casts were digitized with a 3-dimensional (3-D) laser scanner, reconstructed into 3-D images, and measured with IMAGEWARE. The anterior and posterior widths of the upper and lower coronal arches and their anterior and posterior lengths together with the anterior and posterior widths of the maxillary and mandibular basal arches and their anterior and posterior lengths were measured. An unpaired t-test was performed using statistical analysis software. Dental models of 31 people with normal occlusion (16 males and 15 females, with an average age of 23.3 years) were measured with digital calipers and compared with the measurements obtained from the 8020 achievers. Several common items with significant differences were observed in the mandibular measurements. Each comparison indicated a tendency toward a decrease in size in the 8020 group: Coronal Arch P-length (p<0.05 in Male group, p<0.01 in Female group), Basal Arch A-width (p<0.05 in Male group, p<0.001 in Female group), Basal Arch A-length (p<0.001 in both group), and Basal Arch P-length (p<0.001 in both group). From these results, 3-D dental model analysis in twenty 8020 achievers revealed narrowing of the mandibular intercanine width and shortening of the mandibular anterior and posterior lengths.