Synthetic Mandibles Research Articles

A review of biomechanical studies for mandibular angle fracture internal fixation

Mandible fractures correspond to 19-40% of all facial fractures. Among all mandible fractures, 12-30% are fractures of the mandibular angle. These fractures are mainly caused by sports activities, interpersonal violence and car accidents. The presence of the third molar and the thin transverse bone area seem to be responsible for the frequent involvement of the mandibular angle in facial fractures. Before the advent of antibiotics, a high frequency of infection was always associated after an open reduction in mandibular angle fractures. Wired osteosynthesis and maxillomandibular fixation (MMF) were traditional methods for fixing mandibular angle fractures. The limitation of both methods has influenced the development of new approaches for the treatment of mandibular angle fractures. Currently, osteosynthesis of mandibular angle fractures with plates and screws has become an effective treatment option. Several forms are described in the literature as: fixation of bone segments with a miniplate on the upper edge of the mandible, fixation with two miniplates, lag screw or by a single rigid plate on the lower edge of the mandible. The purpose of this study was to summarize the main characteristics of biomechanical studies such as the type of mandible source used, the plating techniques employed, the plate material, and the loading protocols used to evaluate the stability of the fixation methods. The Medline (PubMed) database was searched combining relevant terms and pertinent articles in English were included. Articles had to meet the following inclusion criteria: be in vitro biomechanical studies evaluating fixation methods for mandibular angle fractures. A total of 27 articles fulfilled the inclusion criteria. Synthetic mandibles (n=12), animal mandibles (n=9), and human cadaveric mandibles (n=5) were used as the sample source to perform the biomechanical analysis. One article used both synthetic and human cadaveric mandibles. Also, a variety of fixation techniques was described such as mini-plates, lag-screws, reconstruction plates, and three-dimensional plates. The materials of the bone plates used were: stainless steel, commercially pure titanium, titanium alloy or bioresorbable. However, there was inconsistency in reporting the materials and not all studies clearly stated the material of the bone plates. For the biomechanical analysis, there was a high variation among all studies regarding the loading protocols used. The same side of fixation, the anterior part of the mandible (central incisors) or the contralateral side were reported as the dentate regions in which the force was applied. For more than 2 decades, in vitro biomechanical studies have been used to help researchers and clinicians in the field of Oral and Maxillofacial Surgery to properly evaluate and compare the different devices and techniques available for the treatment of mandibular angle fractures. Also, biomechanical studies are important to answer questions on fatigue performance and fracture strength on the gross level.

Assessment of biomechanical properties of specially-designed miniplate patterns in a mandibular subcondylar fracture model with finite element analysis and a servohydraulic testing unit.

The aim of our study was to compare the biomechanical stability of three different systems used to fix mandibular condylar fractures on synthetic polyurethane mandibles using a servohydraulic testing unit and finite element analysis (FEA). We measured the resistance to displacement loads causing 1.75 and 3.5mm displacements of the fragments, and the maximum resistance values before failure of the fixation system in 30 condylar necks of 15 polyurethane mandible models. The three subgroups investigated were arranged as a triangular plate (n=10), a quadrangular plate (n=10), and a straight miniplate (n=10). The most successful fixation pattern was achieved with two straight four-hole miniplates. However, the triangular plate can easily be applied as a second option by an endoscopic approach. The rectangular plates showed no success in mandibular condylar fractures.

A Robust Model to Test the Accuracy of Cone Beam Computed Tomography Linear Measurements

In planning for placement of dental implants in edentulous mandibles, the accuracy of the linear measurements of the cone beam computed tomography (CBCT) has been questioned. This study used a digital caliper as the gold standard to which linear measurements taken from CBCT were compared. Customized aluminum screws, 2.8 mm in diameter and 11-12 mm in length, were used as dental implant analogues in the canine, premolar, and molar regions in completely edentulous synthetic polyurethane mandibles. A 2 mm aluminum wire was used as the mandibular canal. A total of 240 readings by the digital caliper and the CBCT were recorded for the screws length and diameter, mandibular canal wire diameter, and the distance from the apices of the screws to the superior border of the mandibular canal wire. The statistical analysis was performed using the paired sample T test, with a p value of .05 considered statistically significant. Statistically significant differences between the digital caliper readings and those of the CBCT were recorded in the canine, premolar and molar regions where all the over-and under-estimations did not exceed half a millimeter. The statistically significant discrepancies found in the linear measurements of the CBCT were less than 1 mm, and therefore did not exclude the CBCT from being a beneficial tool in the planning for dental implant placement. However, it is important to note that the results of this study and cannot be generalized to all CBCT machines as they are not created equal by different manufacturers.

In vitro study of a modified sagittal split osteotomy fixation technique of the mandible: a mechanical test

This study was performed to evaluate the compressive mechanical strength of rigid internal fixation (RIF) using 1.5-mm L-shaped plates fixed with monocortical screws in sagittal split osteotomy (SSO). Thirty synthetic hemimandibles, which had all undergone a 5-mm advancement, were divided into three groups: three 12-mm bicortical titanium screws were placed in an inverted L pattern in group A; one straight 2.0-mm system spaced titanium plate fixed with four 5-mm monocortical screws was used in group B; two 1.5-mm system L-shaped titanium plates, each fixed with four 5-mm monocortical screws, were used in group C. The models were subjected to compressive and progressive mechanical tests with forces applied in the area between the second premolar and first molar to verify resistance in Newtons (N). A displacement speed of 1mm/min was applied, with a maximum 10mm displacement of the distal segment or until disruption of the fixation. The deformity and/or eventual rupture of the plates were evaluated, and consequently their technical stability was determined. The results showed that the modified fixation technique tested in this study on synthetic mandibles resulted in adequate stability and superior mechanical behaviour compared to simulated osteosynthesis with the use of a straight 2.0-mm titanium plate.

Impairment of an atrophic mandible by preparation of the implant cavity: a biomechanical study

An important complication during insertion of implants in atrophic mandibles is the fracture that can be induced by preparation of the cavity. We designed this study to identify which configuration of cavities in the interforaminal region was the least likely to fracture. An electromechanical testing machine was used to measure breaking loads of specifically-designed synthetic models of atrophic mandibles. The implant cavities correlated with the common clinical patterns. Intact atrophied synthetic mandibles broke at a mean (SD) load of 729.48 (59.94) N (control group). Models with four different configurations of cavities fractured as follows: two short, wide cavities (8 x 4.2mm) at a mean (SD) load of 569.17 (67.7) N; two long, thin cavities (15 x2.8mm) at a load of 563.40 (62.0) N; four short, wide cavities (8 x 4.2mm) at a load of 667.01 (71.89) N; and four long, thin cavities (15 x 2.8mm) at a load of 409.50 (43.61) N. Biomechanical findings showed that there was a greater risk of fracture of atrophic mandibular models in long, thin implant cavities with more preparation sites. Each cavity prepared for an implant increased the risk of fracture in an atrophic mandible. The risk of fracture is greatest with long, thin cavities.

Biomechanical Evaluation of a Mandibular Spanning Plate Technique Compared to Standard Plating Techniques to Treat Mandibular Symphyseal Fractures.

Purpose. The purpose of this study is to compare the biomechanical behavior of the spanning reconstruction plate compared to standard plating techniques for mandibular symphyseal fractures. Materials and Methods. Twenty-five human mandible replicas were used. Five unaltered synthetic mandibles were used as controls. Four experimental groups of different reconstruction techniques with five in each group were tested. Each synthetic mandible was subjected to a splaying force applied to the mandibular angle by a mechanical testing unit until the construct failed. Peak load and stiffness were recorded. The peak load and stiffness were analyzed using ANOVA and the Tukey test at a confidence level of 95% (P < 0.05). Results. The two parallel plates' group showed statistically significant lower values for peak load and stiffness compared to all other groups. No statistically significant difference was found for peak load and stiffness between the control (C) group, lag screw (LS) group, and the spanning plate (SP1) group. Conclusions. The spanning reconstruction plate technique for fixation of mandibular symphyseal fractures showed similar mechanical behavior to the lag screw technique when subjected to splaying forces between the mandibular gonial angles and may be considered as an alternative technique when increased reconstructive strength is needed.

Which kind of frontal mandibulotomy is the smartest? A biomechanical study

PurposeRetrospective clinical evaluation and biomechanical tests were performed to compare the primary stability and the rate of pseudarthrosis formation after irradiation for two types of mandibular split osteotomies: the stairstep osteotomy (SSO) and the straight-line osteotomy (SLO). MethodsThe postoperative occurrence of pseudarthrosis was retrospectively analysed in 46 non-consecutive clinical cases of SSO and SLO between 2003 and 2013.Biomechanical tests were performed on 12 standardised synthetic mandibles (Synbone) to compare the SSO and SLO approaches. Two 2.0 mm monocortical miniplates (Medartis) were used for osteosynthesis. The artificial mandible specimens were loaded to 300 N on the Mandibulator test bench while interfragmentary motion was measured using the PONTOS optical measurement device. ResultsThe retrospective clinical analysis showed a rate of pseudarthrosis of 19% in the SLO group versus only 5% in the SSO group (p = 0.17).In the biomechanical investigation, the average interfragmentary movement was 14.3 ± 7.70 for the SLO group and 4.57 ± 2.33 for the SSO group under a maximum load of 300 N, resulting in a statistically significant difference between the two approaches (p = 0.014). ConclusionTo minimise the rate of postoperative pseudarthrosis formation, SSO is superior to SLO for mandibular split procedures, because SSO provides greater resistance to vertical loads and allows less interfragmentary movement. Level of evidence2C (Outcomes research).

In vitro comparison of 1.5 mm vs. 2.0 mm screws for fixation in the sagittal split osteotomy

Purpose Numerous “ in vitro” investigations have been conducted to evaluate the role of screw size and pattern in determining optimal resistance to deformation, often these have been controversial. The aim of this study was to evaluate the effect of screw size and insertion technique on the stability of sagittal split osteotomies. Materials and methods This study used twenty polyurethane replicas of human hemimandibles with a prefabricated sagittal split ramus osteotomy (SSRO). The hemimandibles were stabilized with 1.5 mm and 2.0 mm titanium screws inserted in an inverted L configuration. All specimens were tested to determine the strength and stability of the fixation. Results In all cases there was failure of the synthetic bone before there was any evidence of screw failure. There were no significant differences in the load necessary to make the construct fail between the 1.5 or 2.0 mm screw sizes. Conclusion There was no statistically significant difference between the strengths achieved with screws of 1.5 and 2.0 mm diameters for fixation of SSRO performed in synthetic mandibles. There was no fracture of the 1.5 mm or 2.0 mm diameter screws in any of the tests. 1.5 mm diameter screws in an inverted L pattern have as much stability and mechanical resistance as a 2.0 mm screw, may be safely used for this procedure.

Validation d’un protocole de mise en charge des modèles mandibulaires fragilisés

The purpose of this study was to validate an experimental model of weakened synthetic mandible loaded in a device simulating masticatory forces by studying the reproducibility of the fracture threshold. Both sides of five synthetic mandibles were weakened by progressive synthetic bone resection. The synthetic mandibles were submitted, after each resection, to static chewing exercises in the simulator. The threshold fracture was recorded. The fracture threshold mean resection height was 19.33 mm with a percentage of error of 6.72%. The low percentage of error allowed us to validate this experimental model. A comparison with other experimental or finite element models confirmed our protocol and results. We plan to apply this protocol to fresh weakened mandibles.

Three-dimensional accuracy of measurements made with software on cone-beam computed tomography images

The purpose of this article was to evaluate the accuracy of measurements made on 9- and 12-in cone-beam computed tomography (CBCT) images compared with measurements made on a coordinate measuring machine (CMM), which is the gold standard. Ten markers were placed on a synthetic mandible, and landmark coordinates and linear and angular measurements were determined with the CMM. Three-dimensional CBCT images, measuring 9 and 12 in, were taken of the mandible with a CBCT machine (NewTom 3G, Aperio Services, Verona, Italy), and landmark coordinates and linear and angular measurements were obtained with AMIRA (Mercury Computer Systems, Berlin, Germany) software. The coordinate intrareliability correlation coefficient was almost perfect between the 3-dimensional CBCT images and the CMM measurements. With the Student t test, we found no significant statistical difference between linear and angular measurements from the CMM and the NewTom 3G images, which differed less than 1 mm and 1 degrees , respectively. The NewTom 3G produces a 1-to-1 image-to-reality ratio.

An Experimental Method for Stereolithic Mandible Fabrication and Image Preparation

Reproduction of anatomical structures by rapid prototyping has proven to be a valid adjunct for craniofacial surgery, providing alternative methods to produce prostheses and development of surgical guides. The aim of this study was to introduce a methodology to fabricate asymmetric human mandibles by rapid prototyping to be used in future studies for evaluating mandibular symmetries. Stereolithic models of human mandibles were produced with varying amounts of asymmetry in the condylar neck, ramus and body of the mandible by means of rapid prototyping. A method for production of the synthetic mandibles was defined. Model preparation, landmark description and development of the experimental model were described. A series of synthetic mandibles ranging in asymmetry were accurately produced from a scanned human mandible. A method for creating the asymmetries, fabricating, coating and landmarking the synthetic mandibles was formulated. A description for designing a reproducible experimental model for image acquisition was also outlined. Production of synthetic mandibles by stereolithic modeling is a viable method for creating skeletal experimental models with known amounts of asymmetry.

Biomechanical Testing of Different Osteosynthesis Systems for Segmental Resection of the Mandible

This investigation assessed the mechanical behavior of 3 different locking and nonlocking reconstruction systems-Unilock 2.4, Reconstruction 2.4, and Reconstruction 2.7-with regard to plate and screw fracture. Five different plate/screw configurations (Unilock 2.4-locking screws, Unilock 2.4 -conventional screws, Reconstruction 2.4-conventional screws, Reconstruction 2.7-conventional screws, and Unilock 2.4-locking screws with a 1-mm gap; Synthes, Umkirch, Germany) were tested on synthetic mandibles. All mandibles were resected on the left side between the canine and third molar, reconstructed, and loaded cyclically between 30 and 300 N up to 250,000 cycles or until screw or plate failure occurred. No screw fractures were observed. All plates fractured close to the distal fragment. The Unilock plates fixed with locking screws withstood significantly more cycles until failure than the Reconstruction plates 2.4 fixed with conventional MF-Cortex screws. No significant differences were found in the other groups. Only 2 of the 34 plates tested, both of the Reconstruction 2.7 system, reached the runout limit. Unilock plates fixed with locking screws have a higher long-term stability than the Reconstruction 2.4 system. A 1-mm gap between the plate and mandible does not lead to early screw failure in the Unilock 2.4 system with locking screws. The Reconstruction 2.7 system seems superior if well contoured, because 2 of those plates reached the runout limit; however, this system is not as easy to handle as the 2.4 systems, and good contouring is difficult to achieve. Therefore, we consider the Unilock 2.4 system with locking screws the best choice.

Biomechanical Evaluation of Different Types of Rigid Internal Fixation Techniques for Subcondylar Fractures

The aim of this study was to evaluate the biomechanical stability of various internal fixation systems for subcondylar fractures. Eighteen identical synthetic mandibles were used. Left condylar processes were cut to mimic perpendicular subcondylar fracture and right sides were mimicked oblique subcondylar fracture. The fixation systems used included single 4-hole mini adaptation plate, double fixation with the same plates, single 4-hole mini dynamic compression plate (DCP), Eckelt lag screw system, Wurzburg lag screw plate system and double 4-hole biodegradable miniplates made of poly L-lactide (PLLA). In oblique fractures, one of the screws fixing plates was used bicortically through bone fragments. The loading vector simulated physiologic forces to the condyle on biting with servohydraulic testing machine until failure was reached. Load-displacement curve, maximum load for failure, and stiffness were measured. In perpendicular fracture, double adaptation plate showed the highest level of tolerance load followed by Eckelt lag and double PLLA plate. In stiffness, double adaptation plate and Eckelt lag screw showed higher level of stiffness, whereas double PLLA was almost at the same level of single DCP. In oblique fracture, double adaptation plate showed the highest strength. In this laboratory setting, double adaptation plates fixation proved to have superior biomechanical stability in both fracture conditions. Eckelt lag screw showed good stability in the perpendicular fracture, however, it was weak in the oblique fracture.

An In Vitro Comparison of an Adjustable Bone Fixation System

The purpose of this study was to biomechanically compare an adjustable plating system and several variations with an inverted-L pattern of 3 bicortical screws to fix a bilateral sagittal split osteotomy. Sixty polyurethane mandible replicas (Synbone, Laudquart, Switzerland) were used in this study. Ten uncut mandibular replicas served as control models. Fifty experimental synthetic mandibles had bilateral sagittal split osteotomies created with a 7-mm advancement. Fixation modalities included 3 bicortical screws in an inverted-L pattern, a 4-hole sagittal split plate with adjustable slider (slide 0), an adjustable plate with an additional bicortical screw (slide 1), an adjustable plate with 2 additional bicortical screws (slide 2), and an adjustable plate with 3 additional bicortical screws (slide 3). The alloplastic mandibles were secured in a custom fabricated jig and subjected to vertical loads at the incisal edge and torsional loading at the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0- to 900-N range were recorded. Yield load, yield displacement, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second-order best-fit polynomials were created for the experimental data curves. For incisal edge loading, the control was significantly greater for yield load than the experimental models. No significant difference was noted between slide 0, slide 1, and slide 2, but significant differences were seen with slide 3 and the inverted-L. There were no significant differences between slide 1, slide 2, slide 3, and inverted-L. For molar load, the control was significantly different than the experimental models. However, there was no significant difference between the experimental models. Mandibular advancements of 7 mm in a synthetic mandible fixed with a 4-hole sagittal split plate with adjustable slider alone is resistant to torsional forces and comparable to that seen with 3 bicortical screws placed in an inverted-L fashion. However, when loading at the incisal edge, additional bicortical screws are necessary to achieve the similar resistance to vertical load as that seen with 3 bicortical screws.

Biomechanical Evaluation of Fixation Techniques for Bridging Segmental Mandibular Defects

To compare biomechanical properties of currently available plating systems used to reconstruct segmental mandibular defects. Controlled in vitro investigation. Academic medical center laboratory. Thirty-two polyurethane mandibles were equally divided among 4 groups: mandibles with a 4-cm lateral segmental defect that was bridged with a (1) 3.0-mm locking-screw reconstruction plate, (2) 2.4-mm low-profile reconstruction plate, or (3) 2.4-mm reconstruction plate and (4) uncut (control) mandibles. All plates were contoured and secured to the synthetic mandibles with 4 bicortical screws on either side of the defect. Three constructs from each group were subjected to contralateral-molar single-load-to-failure testing. Mean yield displacement, yield load, and bending stiffness were quantified and compared among the 4 groups. The single-load-to-failure data were used to establish conditions for fatigue testing; such testing was then performed on the remaining 5 samples in each group. Mean cycles to failure were measured and compared among the 4 groups. Mean yield displacement, yield load, and bending stiffness were comparable among the plated groups. Both the 3.0-mm locking-screw and 2.4-mm low-profile reconstruction plate designs withstood 1580 and 1124 times more cycles to failure, respectively (P = .005), than did the control group. The other reconstruction plate was also superior to the unplated controls, offering an 865-fold improvement. All 3 mandibular fixation device systems tested produce comparable levels of single load to failure biomechanical integrity; however, the higher-profile plating system design offered slightly superior fatigue performance. No differences in performance were observed between the locking and nonlocking designs; neither failed at the screw-substrate interface.

Do position and soft tissue affect distraction vector? An in vitro investigation

Objectives: The purpose of this investigation was to provide an in vitro evaluation of the effects of soft tissue and position on vector during distraction. Materials and Methods: A polyurethane skull and mandible replica (Synbone, Landquart, Switzerland) was used in this study along with an internal distraction device (Synthes Maxillofacial, Paoli, PA). The first portion of the investigation evaluated the effects of distractor position (inferior body, midbody, and superior body) on distraction vector. The second portion of the investigation used polyethylene straps to simulate the suprahyoid muscles and muscles of mastication, and polysulfide to simulate periosteum and mucosa. A laser light source attached to the synthetic mandible was projected on a grid 7.1 m from the construct to measure deflection from the starting point. The distractor was advanced 8.0 mm for each trial. Five trials each for inferior, middle, and superior, with and without simulated soft tissues (N = 30) were performed. Vertical and horizontal deflection along with absolute distance were measured and recorded. Means and standard deviations were derived for groups, and compared for statistical significance (P <.05) with a 1-way analysis of variance for the effects of position with and without simulated soft tissue, and with a paired t-test for the effects of simulated soft tissue within groups of similar distractor position. Results: Statistically significant differences (P <.05) for distractors without simulated soft tissues were only noted for vertical deflection between the inferior and superior distractor groups. Statistically significant differences were noted for all measures, for all distractor positions with simulated soft tissues. Statistically significant differences were noted for all measures between similar distractor positions with and without simulated soft tissues. Distractors without simulated soft tissues were deflected lateral to the y-axis and above the x-axis. Distractors with simulated soft tissues were deflected lateral to the y-axis, but below the x-axis. For distractors with simulated soft tissues, the closer to the inferior border, the less the deflection from the x-axis. Conclusion: Position alone had minimal effects on distraction vector. Simulated soft tissues affected the vector of distraction. The combination of position and simulated soft tissues affected distraction vector. © 2002 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 60:149-155, 2002

An in vitro evaluation of distractors used for osteogenesis

Objective. The objective of this investigation was to evaluate and compare the mechanical behaviors of distractors used for osteogenesis under various conditions by means of common engineering standards. Study design. Five groups of 5 synthetic mandibles were used in this study (N = 25). The first portion of the investigation compared mandibles without intervention (group A [controls]; n = 5), mandibles that had uniform osteotomies stabilized with an external distractor (group B; n = 5), and mandibles that had simulated sagittal osteotomies rigidly fixated with 3 positional screws (group C; n = 5). The second portion of the investigation compared uniform osteotomies (group B; n = 5) and uniform corticotomies (group D; n = 5) that were stabilized with the same external distractor. The last portion of the investigation compared osteotomies stabilized with an external distractor (group B; n = 5) and osteotomies stabilized with an internal distractor (group E; n = 5). Each construct was subjected to vertical loads on a mechanical testing unit. Common engineering standards, including yield load, yield displacement, maximum load, displacement at maximum load, and stiffness, were measured, recorded, and compared by means of a 1-way analysis of variance and a Scheffé multiple comparison test or independent-samples t test. The means between groups were considered significant for P < .05. A polynomial best-fit curve was calculated for the load/displacement data for each group. Results. During the first portion of the investigation, no significant differences were noted between the control, rigidly fixated sagittal osteotomy, and external distractor with osteotomy groups for displacement at maximum load ( P = .19). Significant differences were noted between groups for yield displacement ( P = .009), yield load ( P < .001), maximum load ( P < .001), and stiffness ( P < .007). Failures occurred in the control and rigidly fixated groups with fractures of the synthetic mandibles. Failures occurred in the external distractor group with permanent deformation or torsion of the pins. During the second portion of the experiment, no statistically significant differences were noted between the corticotomy and osteotomy groups in stiffness ( P = .363), maximum load ( P = .207), or yield displacement ( P = .940). Statistically significant differences were noted between groups for yield load ( P = .036) and displacement at maximum load ( P = .010). Failures occurred in both groups with permanent deformation or torsion of the pins. During the last portion of the investigation, statistically significant differences were noted between the external distractor and internal distractor groups in yield load ( P < .001), yield displacement ( P < .001), maximum load ( P = .001), and displacement at maximum load ( P = .01); no significant differences were noted in stiffness ( P = .71). Failures occurred in the external distractor group with permanent deformation or torsion of the pins. Failures occurred in the internal distractor group with fracture of the model or displacement beyond 30.0 mm. Conclusions. Different patterns of mechanical behavior were found between the control and rigidly fixated sagittal osteotomy groups and the external distractor group, between the corticotomy and osteotomy groups, and between the internal and external distractor groups.

Wurzburg lag screw plate versus four-hole miniplate for the treatment of condylar process fractures

Purpose : The purpose of this study was to compare the biomechanical stability of rigidly fixed condylar neck fractures using either a conventional four-hole miniplate system or the Wurzburg lag screw plate system. Materials and Methods : Ten identical synthetic mandibles were used for this study. Simulated bilateral condylar neck fractures were fixed with the lag screw plate system on one side and the miniplate system on the other. The mandibles were loaded with an MTS servohydraulic testing machine at a rate of 1 cm/min until failure was reached. Data for resistance to motion and ultimate strength for each fixation device were compared by paired Student t-tests. Results : The mean resistance to motion for the four-hole miniplate was 64.0 kg/mm (SD = 10.1; range = 52–94) and for the lag screw system was 80.2 kg/mm (SD = 24.0; range = 55 to 126). The mean failure strength was 4.0 kg (SD = 0.9) (range = 2.6 to 5.5) for the miniplate system and 5.0 kg (SD = 2.5; range = 3.4 to 7.2) for the lag screw system. The lag screw system was significantly ( P < .05) better than the miniplate for both parameters measured. Conclusion : In laboratory testing using synthetic mandibles, the Wurzburg lag screw-plate fixation system proved superior to a four-hole miniplate system in regard to resistance to motion and failure strength. Clinical trials are necessary to substantiate these laboratory data and determine whether the system can be effectively applied by the surgeon.