The Treatment Effects of Sliding Mechanic System During En-Masse Retraction in Adult Maxillary Dental Protrusion Patients

Abstract

Introduction: Protrusion of maxillary anterior teeth is usually found in adult patients with exposed in maximal incisal display at rest. En-masse retraction of the anterior teeth with maximum anchorage control should be done without extrusion and excessive retroclination of the incisors. One interesting method to en-masse retract with achieving these treatment goals is using the asymmetrical V-bend for retraction of the six maxillary anterior teeth. Objectives: To investigate the effects of en masse retraction system with asymmetrical V-bend archwire in the dental changes of the incisor, canine, premolar, and molar Material and methods: The 17 adult subjects (mean age 20.44 ± 4.75 years) with protrusion of the maxillary anterior teeth who were planned with bilaterally extraction of the maxillary first premolars with maximum anchorage control and presented the residual extraction space at least 4 mm after correction of crowding were selected for this study. An 0.018x 0.022- inch stainless steel wire bent as asymmetrical V-bend was engaged on full-sized anterior brackets (0.018x0.025-inch slot) and oversized premolar brackets similar in the size with buccal tubes on the first molars (0.022x0.028-inch slot). Exerting 150 g of force were used bilaterally for the en masse retraction until 4 months period of observation, Lateral cephalograms and study models were taken at pre-retraction (T1) and after 4 months of retraction (T2) periods to evaluate the treatment effects. Wilcoxon signd-ranks test was used to analyze the data. Results: The data analysis showed statistically significant differences (p <0.05) in all dimension of tooth movement. The maxillary incisor was retracted 0.7 ± 0.3 mm, retroclined 3.00 ± 0.85 and intruded 0.24 ± 0.31 mm. The maxillary second premolar and the first molar were moved mesially 0.31 ± 0.31mm and 0.29 ± 0.27 mm, respectively. In the angulation changes, the premolar was tipped distally 3.25 ± 1.47° and the molar was tipped distally 3.25 + 1.47°. In vertical changes, the premolar was extruded 0.35 ± 0.33 mm while the molar was intruded 0.12 ± 0.65 mm. Rate of the en-masse retraction was 0.68 ± 0.12 mm/month; meanwhile rate of the anchorage loss was 0.08 ± 0.07 mm/month. Conclusion: With this en-masse retraction system consisting of asymmetrical V-bend archwire, the maxillary anterior teeth could be retracted generously with maximum anchorage control. Moreover, the system could control the incisor changes appropriately without excessive retroclination and no extrusion.