## 4 Discussion
This conclusion suggests the existence of a complex relationship between meso-distal coronary dimensions, variations in the size of dental arches, and primary dental crowding, therefore, generalizations could not be made, and each arch must be assessed and treated individually. A cross-sectional study conducted on a sample of 312 dental casts of Sudanese subjects aged 16-26 years (three subgroups of 104 casts with normal, crowded, and spaced dental arches) showed that subjects with dental crowding were more likely to have smaller dental arch measurements and increased tooth material than subjects with a normal arch [36]. In addition to variations of meso-distal teeth dimensions, in the present study group, the bucco-lingual dimensions of upper incisors were smaller in maxillary crowded arches than in non-crowded and spaced arches (central incisors in female patients, lateral incisors in all patients), the bucco-lingual dimensions of lower central incisors were larger in severely mandibular crowded arches in male patients, the bucco-lingual dimensions of lower first permanent molars were larger in mandibular severely crowded arches than in normal and spaced ones in all patients. These results partially agree with the assumption of [PERSON] et al., who concluded that the bucco-lingual diameters of the central mandibular incisor, the mandibular and maxillary canine, and the maxillary premolars are the only bucco-lingual teeth diameters that can influence dental crowding [34]. The cited study concluded that the coronary proportions of the maxillary central incisors, the meso-distal diameter of the maxillary lateral incisors, and the bucco-lingual dimension of mandibular central incisors seem to be largely responsible for variations in dental crowding. Regarding crown proportions, expressed as the ratio between meso-distal and bucco-lingual diameters, our study showed that upper incisors and lower lateral incisors presented statistically significantly larger crown proportions (due to increased meso-distal diameter and/or decreased bucco-lingual diameter) in arches with crowding than in normal and spaced arches. The crown proportions of upper and lower first permanent molars were larger in patients with spaced arches than in those with normal arches. These findings do not support the conclusions of [PERSON] et al., who analyzed a group of 50 untreated white subjects (25 men and 25 women) with varying degrees of crowding and found that mandibular incisor crown shape was no predictor of lower incisor crowding [37]. Our results are similar to the previous assumption of [PERSON], who included tooth shape among the determining factors in mandibular anterior crowding (persons with ideal incisor alignment were shown to have incisors with smaller meso-distal and larger bucco-lingual dimensions than persons with incisor crowding) [38]. Analyzing the synthesis of the statistically significant results presented in Table 10, we can appreciate that the study results are consistent regarding crown size variations of upper incisors and lower lateral incisors in crowded dentitions. A statistically significant increase of meso-distal diameter (for upper central incisors and lower lateral incisors) and a statistically significant decrease of bucco-lingual diameter (for upper incisors) were encountered, and both correlated with a statistically significant increase of crown proportions for each of these teeth. Related to lower central incisors and lower first permanent molars, their bucco-lingual diameter was statistically significantly larger in patients with crowded arches. Exploring possible data correlations with Pearson test, low negative correlations were depicted for meso-distal diameters of maxillary central incisors, lower lateral incisors, and lower permanent first molars and the values of arch length discrepancies.