An In Vitro Evaluation of Rigid Internal Fixation Techniques for Sagittal Split Ramus Osteotomies: Advancement Surgery

Brasileiro, Bernardo Ferreira; Grempel, Rafael Grotta; Ambrosano, Glaucia Maria Bovi; Passeri, Luis Augusto

doi:10.1016/j.joms.2008.11.009

« Previous Next »Journal of Oral and Maxillofacial Surgery
Volume 67, Issue 4 , Pages 809-817, April 2009

An In Vitro Evaluation of Rigid Internal Fixation Techniques for Sagittal Split Ramus Osteotomies: Advancement Surgery

Bernardo Ferreira Brasileiro, DDS, MS, PhD
- Associate Professor, Division of Oral Diagnosis, Federal University of Sergipe, Department of Dentistry, Aracaju, Sergipe, Brazil
- Address correspondence and reprint requests to Dr Brasileiro: Hospital Universitário, Departamento de Odontologia, Universidade Federal de Sergipe, Rua Cláudio Batista, s/n, Bairro Sanatório, Aracaju, SE, Brazil 49060-100
Rafael Grotta Grempel, DDS, MS
- Third-Year Resident of Oral and Maxillofacial Surgery, Piracicaba Dental School, State University of Campinas, São Paulo, Brazil
Glaucia Maria Bovi Ambrosano, DDS, MS, PhD
- Professor, Division of Biostatistics, Piracicaba Dental School, State University of Campinas, São Paulo, Brazil
Luis Augusto Passeri, DDS, MS, PhD
- Professor, Division of Oral and Maxillofacial Surgery, Piracicaba Dental School, and Division of Plastic Surgery, Faculty of Medical Sciences, State University of Campinas, São Paulo, Brazil

Purpose

This in vitro investigation was developed with the purpose of comparing the biomechanical features of 3 different methods of rigid internal fixation for sagittal split ramus osteotomies for mandibular advancement.

Materials and Methods

Rigid internal fixation techniques included a 4-hole plate and 4 monocortical screws (miniplate group), a 4-hole plate and 4 monocortical screws with 1 additional bicortical positional screw (hybrid group), and 3 bicortical positional screws in a traditional inverted-L pattern (inverted-L group). Screws and miniplates were made of titanium and from a 2.0-mm system (MDT, Rio Claro, SP, Brazil). Sixty polyurethane replicas of human hemimandibles (Nacional, Jaú, SP, Brazil) were used as substrates, simulating a 5-mm advancement surgery by a sagittal split ramus osteotomy. They were adapted to a test support, and were submitted to lateral torsional forces on the buccal molar surface and vertical cantilever loading on the incisal edge by an Instron 4411 mechanical testing unit (Instron, Norwood, MA) for recording peak loading at 1 mm, 3 mm, 5 mm, and 10 mm of displacement. Each group was formed by 10 replicas, subjected to a linear noncyclical testing only once. Means and standard deviation were analyzed using analysis of variance and Tukey tests, with a 5% level of significance. Testing failures were also recorded.

Results

The miniplate group showed lowest load peak scores (P < .01) when compared with the other fixation techniques, irrespective of the direction of force. The inverted-L group showed higher resistance (P < .01) than the hybrid group when vertical forces were applied. For molar load, the hybrid and inverted-L groups showed no significant difference.

Conclusions

For mandibular advancement surgery of 5 mm, it was concluded that the rigid internal fixation technique for sagittal split ramus osteotomies based on 3 bicortical screws in the inverted-L pattern was the most stable in a laboratory environment. Furthermore, the results suggested that installation of a bicortical positional screw in the retromolar region may significantly optimize the resistance of the miniplate and monocortical screw fixation.