Purpose: Dental arch length, width, and perimeter are considered to be important for the diagnosis and treatment of orthodontic cases. This study aimed to utilize dental arch width and length to create an equation for predicting dental arch perimeter. Materials and methods: Sixty-seven pairs of study models for patients with normal occlusion who received dental treatment were included in this study. Dental arch width at the level of the canines, first premolars, and first molars, in addition to dental arch length and perimeter, were measured using a digital vernier with 0.01mm accuracy. Data were subjected to step-wise regression analysis to determine the major predictors of arch perimeters and develop regression equations for both arches. The predicted arch perimeters were compared with the actual measured values using paired sample t-test. Results: For both arches, the perimeter showed a direct, moderate to strong, highly significant correlation with the length and width measurements. Findings from step-wise regression analysis indicated that there was a strong correlation between arch perimeter and the inter-canine width and arch length, which explained 67.7% of the variation in arch perimeter in the maxillary arch. In the mandibular arch, inter-molar width, inter-canine width, and arch length explained 55.1% of the variation in the dental arch perimeter. The arch perimeter values predicted from the developed equations were not significantly different from the actual values that were measured. Conclusion: New regression equations based on dental arch width and length at the level of the premolars, molars, and canines were developed to predict dental arch perimeters for both the mandibular and maxillary arches.
Resorption of permanent maxillary incisors is a common complication of ectopically positioned maxillary canines and when they occur they may drastically increasing both the cost and complexity of the orthodontic treatment, thus early diagnosis and corrective measures are imperative. This study aimed to investigate the association between the maxillary impacted canines labio-palatal and mesio-distal positions and the associated root resorption of adjacent maxillary incisors. Materials and Methods: The sample included 46 patients with an age ranged between 12 and 30 years referred to the CT scan image to detect unilaterally or bilaterally impacted maxillary canines. The mesio-distal position of the canine cusp tip, the labio-palatal position of the impacted canines, contact and root resorption of permanent incisors were evaluated with CT scan image. The association between the impacted canines position and root resorption of permanent incisors were analyzed using Chi square test.Results: Labially and mid-alveolus impacted canines were more common in sectors I and IV, while palatally impacted canines were most frequent in Sector IV. Lateral incisors were more often affected than central incisors by root resorption. Root resorption of permanent incisors showed a high significant association with sector location [p ≤ 0.001] and was observed in sectors III and IV.Conclusions: When canine impactions are suspected in sectors III or IV, CT scan must be considered to disclose suspected incisor resorption.
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