In Vitro Biomechanical Evaluation of the Use of Conventional and Locking Miniplate/Screw Systems for Sagittal Split Ramus Osteotomy

• Published in: Journal of oral and maxillofacial surgery Vol. 68; no. 4; pp. 724 - 730
• Main Authors: Ribeiro-Junior, Paulo Domingos, MSD, PhD, Magro-Filho, Osvaldo, PhD, Shastri, Kalpakam A., DDS, FFDRCSI, Papageorge, Maria B., DMD, MS
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.04.2010; Elsevier
• Subjects: Analysis of Variance; Biological and medical sciences; Biomechanical Phenomena; Biomechanics. Biorheology; Bone Plates; Bone Screws; Compressive Strength; Dental Stress Analysis; Dentistry; Equipment Design; Fundamental and applied biological sciences. Psychology; Humans; Jaw Fixation Techniques - instrumentation; Mandible - surgery; Medical sciences; Models, Anatomic; Orthognathic Surgical Procedures - instrumentation; Orthopedic surgery; Osteotomy - instrumentation; Otorhinolaryngology. Stomatology; Random Allocation; Statistics, Nonparametric; Surgery; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Tissues, organs and organisms biophysics; Biomechanics; Treatment; Screw; Osteotomy; Stomatology; Surgery; In vitro; Locking
• ISSN: 0278-2391; 1531-5053
• DOI: 10.1016/j.joms.2009.07.018

Purpose The aim of this in vitro study was to assess the biomechanical stability of 9 different osteosynthesis methods after sagittal split ramus osteotomy by simulating the masticatory forces and using a 3-point biomechanical test method. Materials and Methods Forty-five polyurethane hemimandibles with bone-like consistency were randomly assigned to 9 groups (n = 5) and subjected to sagittal split ramus osteotomy. After 4-mm advancement of the distal segment, the bone segments were fixed by different osteosynthesis methods using 2.0-mm miniplate/screw systems: group A, one 4-hole conventional straight miniplate; group B, one 4-hole locking straight miniplate; group C, one 4-hole conventional miniplate and one bicortical screw; group D, one 4-hole locking miniplate and 1 bicortical screw; group E, one 6-hole conventional straight miniplate; group F, one 6-hole locking straight miniplate; group G: two 4-hole conventional straight miniplates; group H, two 4-hole locking straight miniplates; and group I, 3 bicortical screws in an inverted-L pattern. All models were mounted on a base especially constructed for this purpose. Using a 3-point biomechanical test model, the hemimandibles were loaded in compressive strength in an Instron machine (Norwood, MA) until a 3-mm displacement occurred between segments vertically or horizontally. Data were analyzed by analysis of variance and Tukey test (α = 1%). Results The multiparametric comparison of the groups showed a statistically significant difference ( P < .01) between groups that used 2 miniplates (groups G and H), 1 miniplate and 1 bicortical screw (groups C and D), and only bicortical screws (group I) compared with groups that used only 1 miniplate with 2 screws per segment (groups A and B) and 3 screws per segment (groups E and F). Conclusion The placement of 2.0-mm–diameter bicortical screws in the retromolar region, associated or not with conventional and locking miniplates with monocortical screws, promoted a better stabilization of bone segments. Locking miniplates presented a better performance in bone fixation in all groups.