Fourier analysis of the dental arch form.

概要

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Rectangular coordinate values of the position of the teeth on the dental arch were measured from standardized photographs of Japanese dentitions. Data were obtained from 281 dental casts consisting of 217 males (upper jaw: 116, lower jaw: 101) and 64 females (upper jaw: 28, lower jaw: 36) ranging in age from 16 to 22 years. These data were transformed into polar coordinate values which served a quantitative description of the size and shape of the dental arches using Fourier analysis. Fourier analysis facilitates a morphological study of the dental arch using two separation components which are recognizable as the size and the shape. The shape of dental arch were described accurately by only two or three harmonics in the Fourier series. This meant that the amount of information of raw data (a total of 28 x and y coordinate values) were reduced to minimal significant variables. The constant values of Fourier series that represented the size of dental arch were highly correlatable with the mesiodistal diameter of tooth crown in both the upper and lower jaws, espcially those of both the canine and first molar. This facts indicated that the size of the canine and first molar among the teeth in each jaw might have some important role in determining the size of the dental arch. The amplitudes, when synthesized the sine and cosine wave in the same harmonic, represented the feature of dental arch shape. Moreover, when the constant value was standardized, the effects of size can be removed. The amplitude of first harmonic, which removed the size effects, represented the approximate shape which showed the ratio between dental arch length and width. This is confirmed by the results obtained from a principal component analysis of dental arch. The principal compnents were obtained from the correlation matrix of 13 measurements, which consisted of 7 widths and 6 lengths of dental arch which was calculated from the rectangular coordinate values as standardized as the dental arch area. Approximately fifty percent of the information was centered in the first component in each jaw, and this was regarded as a ratio between the dental arch length and width. The first composite score was highly correlatable with the amplitude of first harmonic. The amplitude of the second harmonic represented both the inclination of the posterior teeth and squareness of the anterior teeth in their alignment. It was notable that the second amplitude corresponded to the second and third principal component factors. The shape of the dental arch was classified by cluster analysis using the first and second amplitudes into 7 clusters. When the typical arch shape of each cluster was compared with each other, the first and second amplitude demonstrated the variation of dental arch shape. The constant values, first and scond amplitudes in upper jaw were highly correlatable with those in lower jaw. This fact indicated that the morphology of dental arch was in harmony between the upper and lower jaws. These correlation coefficients were larger in males than in females. This fact suggested that similarity between the upper and lower dental arch shapes was higher in males than in females, which might be related to the fact that the dental crowding and arthrosis of temporomandibular joint were more frequently found in females than in males. No clear correlation was found between teeth size and first or second amplitudes. This fact indicates that dental arch shape was independent from each tooth size. It seems that dental arch shape is strongly influenced by the morphology of the maxillary and mandibular bones and the functional effects of jaw movements during mastication.
歯科基礎医学会の論文

Fourier analysis of the dental arch form.

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概要

歯科基礎医学会 | 論文

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