Background. Dental arch length, width, and perimeter was important keys for Diagnosis and treatment of orthodontic cases. Cone beam computed tomography (CBCT) can provide precise measurements of arch width and tooth dimension. Aim of our study is to find the reliability of Paulino et al's and Vaishnav et al's regression equations and to investigate the arch length prediction from inter-canine arch width in samples of Egyptian population based on CBCT software measurements in both upper and lower arch and in both genders . Material and Methods: The study was carried out on 60 patients who visited the department of oral and maxillofacial radiology department, Fayoum University for dental treatments. The study sample were grouped into two groups, group A and group B aged between 18-25 years old. CBCT examination was performed for all patients. Upper and lower arches were selected for linear measurements using CBCT and a regression equation was used to predict the arch length based on ICW measurements and correlate it to actual linear measured arch length from CBCT samples of male and female groups
Results: There was a highly significant difference at p-value (0.01) between Male, and Female for ICW,and AL in both mandible and maxilla, for the benefit of the male sample. There was statistically significant difference of predicted Al using two regression equations formula
Conclusion: The regression equation formulae was not reliable to predict arch lengths ,so we developed a new regression equation for Egyptian population in maxillary and mandibular arch for male and female.