A comparative assessment of the forces and moments generated with various maxillary incisor intrusion biomechanics

The aim of this study was to comparatively evaluate the intrusive forces and buccolingual torquing moments generated during anterior maxillary intrusion using different maxillary incisor intrusion mechanics. Five wire specimens were used for each of the following intrusive arches: blue Elgiloy utility arch 0.016 x 0.016 inch, TMA utility arch 0.017 x 0.025 inch, Burstone TMA intrusion arch 0.017 x 0.025 inch, and reverse curve of Spee NiTi 0.016 x 0.022 inch. The wires were inserted on bracketed dental arches constructed on maxillary Frasaco models, segmented mesially to the maxillary canines. Simulated intrusion from 0.0 to 3 mm was performed using the orthodontic measurement and simulation system (OMSS), and forces and moments were recorded in the sagittal plane at 0.1 mm vertical displacement increments. All measurements were repeated five times for each specimen and values recorded at 1.5 mm for all wires were used for statistical evaluations. The results were analysed with one-way analysis of variance with forces and moments serving as the dependent variables and wire type as the independent variable. Post hoc multiple comparisons were performed using the Tukey test (0.05 error rate). Comparison of the two major intrusion techniques for the maxillary anterior teeth, segmented and bioprogressive, revealed that the Burstone TMA 0.017 x 0.025 inch intrusion arch exerted the lowest force on the incisors (0.99 N), followed by the TMA utility 0.017 x 0.025 inch (1.33 N) and the blue Elgiloy 0.016 x 0.016 inch utility (1.43 N). The highest force was recorded for the reverse curve of Spee NiTi and exceeded the value of 9 N. The lowest buccolingual moments were recorded with the Burstone intrusion arch (2.47 Nmm), whereas the highest was registered for the utility arch constructed with a 0.017 x 0.025 inch TMA wire (7.31 Nmm).