ABSTRACT
OBJECTIVE: The aim of this study was to compare the craniomaxillofacial changes when using high-pull J-hook headgear (HPJH) and mini-implants (MIs) as maxillary anchorage in adolescents. STUDY DESIGN: 40 female adolescents with dentoalvolar protrusion were divided into 2 groups; the HPJH group (n=20) and the MI group (n=20). Lateral cephalograms taken before treatment (T0) and after anterior tooth retraction (T1) were superimposed on the stable structures and then craniomaxillofacial changes were evaluated. RESULTS: The cranial base angle, SNB, and facial angle decreased in the HPJH group but increased in the MI group. ANB decreased more in the MI group than in the HPJH group. Mandibular plane angle increased in the HPJH group but decreased in the MI group. Facial height index increased in the MI group while it showed no change in the HPJH group. Mandibular true rotation occurred clockwise in the HPJH group and counterclockwise in the MI group. Maxillary central incisors were intruded and retracted more in the MI group than in the HPJH group. Maxillary first molars were extruded in the HPJH group and were intruded in the MI group. Maxillary first molars were protracted more in the HPJH group than in the MI group. Mandibular central incisors were retracted more in the HPJH group than the MI group. Mandibular first molars were extruded more in the MI group than in the HPJH group. CONCLUSION: More favorable craniomaxillofacial changes occurred in the MI group than in the HPJH group.
Subject(s)
Malocclusion, Angle Class II , Orthodontic Anchorage Procedures , Adolescent , Cephalometry , Extraoral Traction Appliances , Female , Humans , Mandible , Maxilla , Tooth Movement TechniquesABSTRACT
OBJECTIVE: The aim of this finite element study was to clarify the mechanics of tooth movement in palatal en-masse retraction of segmented maxillary anterior teeth by using anchor screws and lever arms. METHODS: A three-dimensional finite element method was used to simulate overall orthodontic tooth movements. The line of action of the force was varied by changing both the lever arm height and anchor screw position. RESULTS: When the line of action of the force passed through the center of resistance (CR), the anterior teeth showed translation. However, when the line of action was not perpendicular to the long axis of the anterior teeth, the anterior teeth moved bodily with an unexpected intrusion even though the force was transmitted horizontally. To move the anterior teeth bodily without intrusion and extrusion, a downward force passing through the CR was necessary. When the line of action of the force passed apical to the CR, the anterior teeth tipped counterclockwise during retraction, and when the line of action of the force passed coronal to the CR, the anterior teeth tipped clockwise during retraction. CONCLUSIONS: The movement pattern of the anterior teeth changed depending on the combination of lever arm height and anchor screw position. However, this pattern may be unpredictable in clinical settings because the movement direction is not always equal to the force direction.