Evaluation of the bending strength of rigid internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy: in vitro study

Fixation methods in sagittal split ramus osteotomy: a systematic review on in vitro biomechanical assessments

The aim of this systematic review was to assess the stability of rigid internal fixation (RIF) techniques in sagittal split ramus osteotomy (SSRO) based on in vitro biomechanical assessments, with particular interest in large mandibular advancements. In general, RIF methods can be divided into three groups: bicortical screws, miniplates, and a combination of the two. An electronic search of the PubMed, CINAHL, and Embase databases was performed, and studies published between January 2003 and March 2018 were screened for inclusion. Comparative studies with an in vitro experimental design, using biomechanical assessments to measure the stability of RIF methods in SSRO, were included. Of 104 unique studies identified in the initial search, 24 were included. Twenty-two of these 24 studies analyzed an advancement of the mandible of 7mm or less. The use of a single four-hole or six-hole miniplate was less stable than the use of bicortical screws, hybrid techniques, double miniplates, or grid plates. Two studies analyzed advancements of 10mm, for which two miniplates placed in parallel and a grid plate showed most stability. Although there was agreement between studies with regard to results, more biomechanical studies are required to quantify the stability of fixation methods in larger mandibular advancements.

Comparison of the Stability of Mandibular Sagittal Osteotomy Fixation between Two Types of Titanium Miniplates: A Biomechanical Study in Sheep Mandibles

This study aimed to compare the biomechanical stability of the fixation of mandibular sagittal split osteotomy of the ramus by two types of titanium miniplates in sheep mandibles. Seven preserved sheep mandibles with similar weight and size were selected, dissected with complete removal of soft-tissue structures, and sectioned in their midline. After performing sagittal split osteotomy, 5 mm of advancement was standardized and samples were divided into two groups according to the type of titanium miniplate (GI = seven hemimandibles were fixed with straight titanium miniplate, GII = seven hemimandibles were fixed with L-shaped titanium miniplates), and then subjected to compressive load. The means (standard deviation) of the compressive load and extension values were 70.68 N (22.26) and 63.36 mm (15.60) to straight miniplates, and 78.80 N (32.54) and 70.55 mm (5.42) to L-shaped miniplates. After comparison and statistical analysis, the results showed no significant difference between the two types of titanium miniplates.

Assessment of Root Perforation within Simulated Internal Resorption Cavities Using Cone-beam Computed Tomography

INTRODUCTION

Internal root resorption lesions may perforate external root surfaces, which may not be detectable on conventional radiographic images. The purpose of this study was to evaluate the accuracy of cone-beam computed tomographic (CBCT) imaging in the detection of small perforations within simulated internal resorption cavities.

METHODS

Artificial internal root resorption cavities with minimal (0.1-0.2 mm) wall thickness were prepared at 64 sites on buccal and lingual halves of 32 single-rooted mandibular teeth that had been split mesiodistally. Perforations with 0.5-mm diameters were produced using a #40 K-file in half of the specimens. All teeth were placed in dry sheep mandibles and imaged using a NewTomVGi CBCT scanner (6 × 6 cm field of view, 0.1-mm resolution; NewTomQR srl, Verona, Italy). Two observers evaluated the images. Interexaminer and intraexaminer agreement were assessed using the kappa statistic. Sensitivity, specificity, and predictive values were used to assess diagnostic accuracy.

RESULTS

Intra- and interobserver agreement on perforation detection were high. The sensitivity and specificity of CBCT-based detection of perforation in internal root resorption were 81.3% and 84.4%, respectively.

CONCLUSIONS

CBCT imaging is useful for perforation detection in internal root resorption defects.

Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: a study in sheep mandibles

Among the osteotomies performed in orthognathic surgery, the sagittal osteotomy of the mandibular ramus (SOMR) is the most common, allowing a great range of movements and stable internal fixation (SIF), therefore eliminating the need of maxillomandibular block in the postoperative period.

OBJECTIVES

The purpose of this study was to evaluate the biomechanical resistance of three national systems used for SIF in SOMR in sheep mandibles.

MATERIAL AND METHODS

The study was performed in 30 sheep hemi-mandibles randomly divided into 3 experimental groups, each containing 10 hemi-mandibles. The samples were measured to avoid discrepancies and then subjected to SOMR with 5-mm advancement. In group I, 2.0x12 mm screws were used for fixation, inserted in an inverted "L" pattern (inverted "L" group). In group II, fixation was performed with two 2.0x12 mm screws, positioned in a linear pattern and a 4-hole straight miniplate and four 2.0x6.0 mm monocortical screws (hybrid group). In group III, fixation was performed with two 4-hole straight miniplates and eight 2.0x6.0 mm monocortical screws (mini plate group). All materials used for SIF were supplied by Osteosin - SIN. The hemimandibles were subjected to vertical linear load test by Kratos K2000MP mechanical testing unit for loading registration and displacement.

RESULTS

All groups showed similar resistance during mechanical test for loading and displacement, with no statistically significant differences between groups according to analysis of variance.

CONCLUSION

These results indicate that the three techniques of fixation are equally effective for clinical fixation of SOMR.

In vitro comparison of biomechanical characteristics of sagittal split osteotomy fixation techniques

The aim of the present study was to compare the biomechanical stability of 10 different fixation methods used in sagittal split osteotomy. Twenty-five fresh sheep mandibles were stripped of all soft tissues and sectioned at the midline. A sagittal split osteotomy with 5mm advancement was performed on each hemimandible. The hemimandibles were randomly divided into 10 groups of 5, and then fixed with 5 different bicortical screws, 4 different miniplates with or without bicortical screws, and 1 resorbable screw configuration. All specimens were mounted on a specially designed 3-point biomechanical test model and compression loads were applied using the Lloyd LRX testing machine until 3mm displacement was reached. Load/displacement data were gathered and compared using the Mann-Whitney U-test with Bonferroni correction (P<0.01). The 3 bicortical screws in an inverted backward-L pattern provided the most biomechanical stability of the screw patterns tested. The miniplate fixed obliquely with 2 bicortical screws in the proximal segment provided the most biomechanical stability of the miniplate groups.