Arch length (AL), intercanine width (ICW), and intermolar width (IMW) are essential for diagnosis and treatment planning and are closely related factors in orthodontics. The aim of the present study was to determine correlations between these measurements and to predict some of these measurements based on others. The dental casts of 197 Spanish patients (119 females and 78 males) with a mean age of 18 years (11-26 years) in the permanent dentition attending the Orthodontic Department of the University of Valencia, Spain, were selected. ICW, IMW, and AL on each dental cast were measured using a previously tested digital method. Correlation between variables was determined using Pearson's correlation coefficient. Linear regression analysis was applied and the 95 per cent confidence intervals (CIs) for slope and intercept were determined. The data showed very high correlations between ICW and AL, both for the upper and lower arches and for males and females, r = 0.925. This coefficient was very close to 1, indicating a linear relationship. The regression equation for AL and ICW was AL = 1.36 ICW + 29.39 for both arches. There was very high correlations between AL and ICW for the upper and lower arches and a regression equation between both magnitudes was established indicating that the size of one factor can be predicted by knowing the other. For an increase of 1 mm in ICW, the AL increases approximately 1.36 mm with a 95 per cent CI (1.30-1.42).

Objectives: The aims of this work were: firstly, to draw up tables of percentile tooth sizes similar to those of Sanin and Savara for three age groups of a Spanish population; secondly, to describe changes in tooth size between those groups over time, as well as observing any sexual dimorphism and, finally, to compare both the Spanish and Sanin and Savara's American population samples. Material and methods: The sample included 359 patients and was divided into three age groups: adolescents, young adults and adults, of both genders. After dental cast digitalization, mesiodistal tooth-size was measured on each dental cast using a digital method. Dental size tables organized by percentiles for each group of age and gender were drawn up. Percentiles under 30 were considered as small, between 30 and 70 as average, and above 70 as large. As symmetry was found between contralateral teeth, the mean between the teeth of the two semi-arches was considered. Results: The mesiodistal tooth sizes of adolescents did not present statistically significant differences between genders, in contrast to the two other age groups. Conclusions: Mesiodistal tooth diameters tended to diminish with age, especially in women, in the Spanish population. The values obtained for our dental tables, organized by percentiles, were slightly higher than those found by Sanin and Savara in an American population, especially for women.

Objectives: Given the controversy in the literature about the variations in intercanine and intermolar distances and arch perimeter once the eruption of permanent teeth is completed, the aims of this study were to assess the changes of these measures with age, analyzing its sexual dimorphism and variability in a Spanish population. Study Design: 188 Spanish individuals distributed in three age groups were selected: 63 adolescents (mean age: 14.15 years), 62 young adults (mean age: 21.9 years) and 63 adults (mean age: 40 years). The intercanine and intermolar distances and arch perimeter were measured in each dental cast from each individual of the sample using a digital method. The results were compared between sex and age groups, the sexual dimorphism percentage (%) of each measure and its variability coefficient (VC%) were calculated. Results: The results depend on sex and age and, therefore, these two factors will be analyzed jointly for each of them with the variation coefficient of the measurement. Intercanine and intermolar distances and arch perimeter were greater in men than in women, especially in the young adult and adult groups. Conclusions: The intercanine distance and arch perimeter tended to decrease with age particularly in the female sex, whilst the intermolar distance didn't undergo significant changes. The intercanine distance is the dimension that presented the greatest variability, whereas the intermolar distance presented the least. The changes occur in the transition from adolescence (14 years of age) to adulthood (22 years of age) and the subsequent alterations are not relevant.

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