Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 19 1 2025 03 31 Comparison of dental effects of traditional and clear twin block: A randomized clinical trial 57 60 10.34172/joddd.025.41445 EN Ahmad Behroozian https://orcid.org/0000-0001-9987-4098 Anahita Pourahmad https://orcid.org/0009-0005-5282-2481 Mahsa Zali https://orcid.org/0000-0003-4564-9770 Amir Zandesh https://orcid.org/0009-0008-8742-5058 Journal Article 10.34172/joddd.025.41445 2024 06 22 2024 10 20 Background. Growth modification is a strategy for the treatment of skeletal Cl II patients. Clear twin block (CTB) is a modification of traditional twin block (TTB), which is made from thermoplastic sheets instead of acrylic resin and wire. This study compared the dental effects of the clear and TTBs. Methods. In this randomized clinical trial, 60 growing skeletal Cl II patients with dental Cl II div 1 malocclusion were selected and randomly divided into two groups: TTB and CTB. Cephalometric radiography and stone models were taken before treatment (T1 ) and six months (T2 ) after appliance insertion. Data were analyzed using independent t-test and paired t-test at the 0.05 significance level. Results. There was a significant difference between CTB and TTB in IMPA at T2 (P<0.05). Intragroup comparisons showed no significant change from T1 to T2 in the CTB group and for U1-SN and U1-Pal amounts in the TTB group. T1-T2 comparison showed a significant change in IMPA in the TTB group (P<0.05). Conclusion. TTB showed more protrusion of lower incisors compared to CTB.