0452 Biomechanics of Invisalign® Splint and Modified Hawley Appliances
K. OCHIAI, University of California - Los Angeles, University of Southern California, USA, H. IKEDA, University of Southern California, UCLA, Los Angeles, USA, C. WARKOMSKI, University of Southern California, Los Angeles, USA, and A. CAPUTO, UCLA, School of Dentistry, Los Angeles, CA, USA

Introduction: Various removable appliances are used for minor tooth movement, and have residual space closure applications. The conventional Hawley retainer may be modified as an active appliance for space closure. The clear plastic sequential overlay technique (Invisalign®) has been utilized for active space closure. These sequential appliances utilize a proprietary computer-generated technique for fabrication. The purpose of this study was to photoelastically examine the stresses generated by a modified Hawley appliance design and an Invisalign® clear aligner in a simulated space closing condition. Methods: A photoelastic model of a dentulous adult maxilla was fabricated using different teeth and bone simulants. Polyvinyl siloxane impressions (PVS) were made of the simulated patient condition. Casts were fabricated for three modified Hawley appliance designs that utilized bilateral posterior elastics. The Hawley appliances were fabricated with wires of different diameters (0.028, 0.030, 0,032”). A PVS master impression was subsequently sent for image processing and proprietary splint fabrication. Diagnostic conditions were approved and prescription splint appliances were delivered and fitted for testing. Comparison to Hawley wire activated conditions with and without elastics were observed and photographed in a polariscope. Results: The Hawley appliances demonstrated increased stress transfer with increasing wire diameter. Application of elastics demonstrated both posterior molar and anterior space closure stresses. The application of the non-activated clear splint appliance demonstrated light pressures throughout. The activated clear splint appliance demonstrated pressure and stress distributions findings consistent with the predicted and prescribed anterior tooth movements. Conclusion: The modified Hawley appliances demonstrated anterior and posterior closing pressures. The clear splint appliance demonstrated controlled anterior closing pressures to the prescribed tooth areas. Clinical appliance selection may be determined by specific patient requirements.

Seq #33 - Orthodontic Treatment
1:00 PM-2:00 PM, Wednesday, 28 June 2006 Brisbane Convention & Exhibition Centre Exhibit Hall 1

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