Abstract:

Objective To evaluate the clinical effect of using a new cross buccal tube (XBT) to close the extraction gap of the maxillary second premolar and control the anchorage. Methods Fifteen adolescent patients with moderate to severe crowding, skeletal Class Ⅰ, missing maxillary second premolars or difficult to retain during clinical examination were selected. PASS orthodontic technique was used to reduce the number of maxillary second premolars to relieve crowding and retract the anterior teeth. Before and after treatment, head lateral images were taken and cephalometric measurements were taken. Changes of bone and dental indexes related to molar anchorage and anterior adduction were observed. Results After treatment, teeth of all patients were arranged neatly, the occlusion relationship was good and the profile was improved. Before and after treatment, there were no significant changes in bone indicators such as ∠SNA, ∠SNB and ∠ANB (P>0.05). There was no significant change in vertical height ∠MP-SN (P>0.05). The angle of the upper and lower central incisors, ∠U1-SN, ∠U1-NA, ∠ L1-MP and ∠L1-NB decreased significantly, while ∠U1-L1 increased significantly (P<0.05). The upper incisor margin point moving towards the distal (P<0.05), and there was no significant change in the position of the upper incisor root apex and first molar (P>0.05). Conclusion The application of the new cross buccal tube is beneficial for adolescent patients to control the occlusion of the extraction gap of the maxillary second premolar.

Key words: orthodontic anchorage procedures, adolescent, new cross buccal tube, second premolar extraction