A brief resume of the intended work need for the study



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a) BRIEF RESUME OF THE INTENDED WORK

NEED FOR THE STUDY


The mandibular angle region is the second most frequent site for fracture. Various plating techniques and materials are available for fixation of fractures of the facial skeleton including the mandible. The different materials of plates and screws advocated for the fixation of mandibular angle fractures are the Titanium miniplates, the 3-D Titanium miniplates, locking titanium miniplates as well as the Bio-degradable (resorbable) plates.
As the mandibular angle region is under the constant forces from the muscles of mastication as well as forces from the occlusal loads it is inferred that the mandibular angle fractures are biomechanically complex as major stress bearing trajectories of the mandible are disrupted in this area.
It has been proved by various studies that fixation of the mandibular angle fracture is most stable when fixed at the upper border when compared with the other areas of the angle. Hence, this study is conducted to evaluate the stress distribution among titanium miniplates, 3-D titanium miniplates, locking titanium miniplates and resorbable plates used in the fixation of mandibular angle fractures, all four fixations being placed at the upper border, with the application of occlusal loads (bite forces) and muscle forces respectively.
Finite element analysis (FEA) has been used in Dentistry from the early 70’s to replace photo elasticity tests. In this study finite element models will be created for three dimensional analyses.

REVIEW OF LITERATURE

A three-dimensional study of loads across the fracture of different fracture sites of the mandible was done to describe and compare the value and direction of the loads across different positions in fractures of the mandible. In a three-dimensional model, bending and torsion moments and shear forces were compared for five mandibular fractures. The fractures were located in, respectively, the angle, posterior body, anterior body, canine and symphysis region. Positive bending movements were defined to give compression at the border, negative bending movements to give compression at the alveolar side of the mandible. The angle and posterior body fracture were noted to have high positive bending movements, small torsion movements and high shear forces with maximum values. The numbers of bite points with negative bending moments were found to be different for all fractures. These bite points were always located on the fractured side. It was concluded that the bending and torsion moments and shear forces vary over a large range for the angle, posterior body, anterior body, canine and symphysis fractures and that the angle fracture in specific, has the highest shear force (78% of the applied bite force).1


An In-vitro 3-Dimensional Finite Element analysis was done to evaluate mandibular biomechanics relative to aspects of load transfer, stress distribution and displacements and was concluded that the applied procedure of generating the FE model is a valid and accurate, non-invasive method to predict different parameters of the complex biomechanical behavior of human mandibles.2
A 3-dimensional finite-element analysis investigating the biomechanical behavior of the mandible and plate osteosynthesis in cases of fractures of the condylar process was conducted to analyze the incongruencies with respect to the complex biomechanical behavior of the mandible. The study recommended the use, whenever possible, of 2 plates for osteosynthesis of fractures of the condylar neck in combination with bicortically placed screws. The stiffness of a singular osteosynthesis plate made of titanium in a diametrical dimension of approximately 5.0 x 1.75 mm and was found to be equivalent to the physiological bone stiffness in the investigated fracture sites.3
A Finite element analysis study was done to compute the load on different osteosynthesis plates in a simplified model using finite element analysis, and to find out whether miniplates were sufficiently stable for application at the mandibular angle. It was concluded that a single mini-plate is sufficiently stable to withstand the reduced masticatory forces in most cases. Mini-plate osteosynthesis according to Champy and Lodde (1976) used for treating fractures of the mandibular angle seems to lead to few complications; this study confirmed this finding with the data obtained in the model analysis.4
A computer-based study used finite element analysis (FEA) to assess whether rigid fixation by resorbable polymer plates and screws can provide the required stiffness and strength for a typical mandibular angle fracture. The study results indicated that titanium fixation more rigidly fixes the 2 bone segments in a relative position. However, they also showed that resorbable polymers provide sufficient stiffness to meet the currently established norms for fracture immobility. Furthermore, the analyses showed that resorbable polymers are capable of withstanding the stresses generated by the bite loads of post-surgical patients. The results indicated that mandibles, fixed with either titanium or resorbable materials, showed nearly identical stress patterns.5
A three-dimensional finite element analysis was also used to compare the biomechanical stability of bilateral sagittal split ramus osteotomies fixed by lag screws with linear and triangular configuration and double or single six-hole miniplates with mono-cortical screws after a set-back operation. The study used computer models to compare the mechanical characteristics of the mandibular structure after bilateral sagittal split ramus osteotomy setback surgery with four different fixation techniques. It was concluded that either triangular lag screw configuration or double miniplates led to better stability and lower mechanical stresses near the osteotomy than the linear lag screws or single oblique miniplates.6
A Biomechanical Analysis was done to study the choice of optimal metallic biomaterials (Cr–Ni–Mo steel and titanium) for implants applied in maxillo-facial surgery. It was noted that the maximum stress values did not exceed the yield stress of the metallic biomaterials of the miniplates and that the bone fragment displacements did not exceed the given value of 1 mm, which is useful for initiating electromechanical effects and the generation of flow potentials, which contribute to the transportation of mineral components to the bones. These investigations have thus shown, that the two-miniplate stabilizing system ensures an appropriate stabilization of the bone fragments because the pressure of mandible fragments is useful for an appropriate osteosynthesis.7
A recent Three Dimensional Finite element analysis was conducted and analyzed by creating a 3-dimensional (3-D) finite element model (FEM) model of the human mandible with an angle fracture after reduction with miniplates of different design types, sizes, and locations. The main parameter chosen to compare stabilization alternatives is the fracture mobility. It was noted that when the miniplate was placed superiorly, the behavior and results became acceptable and the single miniplate and if used alone, must be placed as high as possible.8

OBJECTIVE OF THE STUDY


To evaluate

  1. The stresses in a Three-Dimensional Finite element model created, by mimicking muscular and occlusal loads in the area of the angle of the mandible, following treatment of mandibular angle fractures.

  2. The stress distribution along titanium plate and screws used for fixation.

  3. The Stress Distribution of 3-D titanium plate and screws used for fixation.

  4. The Stress distribution of titanium locking miniplate and screws used for fixation.

  5. The Stress Distribution of bio-degradable plate and screws used for fixation.

The above mentioned materials will be analyzed under maximum occlusal and muscle loads.

b) MATERIALS AND METHODS

3 Dimensional finite element models of a normal Human Mandibles are created with the aid of ANSYS Software, images being taken from a 2-Dimensional Computerized tomographic scans. The created models will have the average dimensions of the mandible along with the standard properties of cortical and cancellous bone, teeth in the arch as well as the properties of the materials that are utilized in the study.


The Physical models will include:

  1. Mandibular Bone

  2. Teeth in the alveolus

  3. Plates

    1. Titanium miniplate and screws

    2. 3-D titanium plate and screws

    3. Titanium Locking miniplate and screws

    4. Biodegradable plate and screws

SOURCE OF DATA


  1. 2-D CT scan obtained from a healthy 25 year old male patient

  2. All materials are considered to be homogenous, isotropic and linear elastic

  3. Properties of the materials used in this study are obtained from related authentic literature

  4. Commercial finite element analysis package – ANSYS for calculations and model processing

  5. Von Mises equivalent stresses in the plate, screws and angle of mandible region will be calculated.



MATERIALS

  1. 2D-CT Scan of Mandible

  2. ANSYS Software for FE Model Creation


  3. Specified Plates and screws(2.5mm titanium miniplates 4 holed with gap, 4 holed 3-D titanium plate, 2.5mm titanium locking miniplate 4 holed with gap and 6 holed resorbable plates with screw diameter of 2.5 x 6mm and 8mm for all the plates)



METHODOLOGY

Finite element models are prepared from a 2-D CT Scans obtained. The three-dimensional finite element models of the specified plates and screws will also be created. A fracture is simulated at the mandibular angle region. Each of the models will be fixed using the finite element models of 2.5mm titanium miniplates 4 holed with gap, 4 holed 3-D titanium plate, 2.5mm titanium locking miniplate 4 holed with gap and 6 holed resorbable plates with screw diameter of 2.5 x 6mm and 8mm, all of these being fixed at the upper border.

An occlusal load of 100 N will be applied and the first molar region and a load of 50 N applied at the canine region respectively. The stresses accumulated are calculated by the Von Mises equivalent stress patterns on the plate and screws. The muscular forces for the Temporalis, Medial Pterygoid and the Masseter muscles respectively, will be applied. A comparative analysis for the stress patterns over the 4 different fixation systems is hence obtained.


Inclusion Criteria

  1. A 25 year old healthy male patient

  2. Patient who had no genetic, endocrinic or any other systemic disease

  3. Patient with no gross skeletal defect and dental malocclusion

  4. Patient who had a full complement of dentition

  5. Patient who has not undergone any previous jaw surgeries

  6. Patient who has not undergone any surgical removal of impacted third molars

  7. Patient with no previous trauma to jaw


Exclusion criteria

  1. Patient with compromised medical status

  2. Patient with any genetic or developmental disorders

  3. Patient with severe malocclusion

  4. Patient with missing set of teeth in lower jaw

  5. Patient with previous history of trauma and surgery been done

  6. Patient with compromised bone due to surgical removal of impacted third molars



Does the study require any investigation or interventions to be conducted on the patient or other humans or animals? If so, please describe briefly.


Yes, a 2-Dimensional Computerized tomographic scan of a normal mandible is required for the study, to create the three-dimensional finite element models.

Has ethical clearance been obtained from your institution?

YES.

_________




c) LIST OF REFERENCES





  1. J. Tams et al: A three-dimensional study of loads across the fracture for different fracture sites of the mandible; British Journal of Oral and Maxillofacial Surgery; 1996; 34,400-405

  2. Dirk Vollmer et al: Experimental and Finite element study of a human mandible; Journal of Cranio-Maxillofacial Surgery 2000; 28, 91-96

  3. Arne Wagner et al: A 3-dimensional finite-element analysis investigating the biomechanical behavior of the mandible and plate osteosynthesis in cases of fractures of the condylar process; Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002; 94:678-86

  4. Kay-Uwe Feller et al: Analysis of complications in fractures of the mandibular angle – a study with finite element computation and evaluation of data of 277 patients: Journal of Cranio-Maxillofacial Surgery 2003; 31, 290-295

  5. Tyler Cox, Markell W. Kohn and Thomas Impelluso :Computerized Analysis of Resorbable Polymer Plates and Screws for the Rigid Fixation of Mandibular Angle Fractures; J Oral Maxillofac Surg 2003; 61:481-487

  6. Erkan Erkmen et al: Three-dimensional finite element analysis used to compare methods of fixation after sagittal split ramus osteotomy: setback surgery-posterior loading; British Journal of Oral and Maxillofacial Surgery 2005; 43, 97-104

  7. A Ziebowicz , J. Marciniak: The use of miniplates in mandibular fractures - biomechanical analysis; Journal of Materials Processing Technology 175 2006; 452-456

  8. Hasan Husnu Korkmaz : Evaluation of different miniplates in fixation of fractured human mandible with the finite element method; Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007; 103:e 1-e 13


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