UNIVERSITI SAINS MALAYSIA 2016 Effect of Cortical thickness on Stress Distribution of Dental Implant: In Vivo Case Study   Maya Genisa Assoc. Prof. Solehuddin Bin Shuib, Assoc. Prof. Zainul Ahmad Rajion, Dr. Abdullah Pohchi and Assoc. Prof. Dasmawati Mohamad UNIVERSITI SAINS MALAYSIA 2016

Results and Discussion Outline Introduction Conclusion Material and Method Results and Discussion

Introduction Important of dental implant : To maintain bone after edentulous To improve facial aesthetics To improve function and performance of mastication. The success of dental implants for long lifetime depends on: Implant placement technique The strength of foundation of implant Generated stress and its distribution due to mastication especially in the early Osseo integration phases Stress distribution around implant is a main determinant for the success of osseointegration.

Factors Affecting the Stress Distribution The stress distribution as a response of external loading depends on the transferring of load and its propagation. Factors affecting the stress distribution: Type of loading Bone–implant interfacing Length and diameter of implant Shape and characteristics of implant surface Quantity and quality of the surrounding bone.

Biomechanical Assessment Biomechanical assessment on dental implant system during loading can help to understand the mechanism of osseo integration of dental implant. There is no available technique to measure stress distribution clinically Numerical method such Finite Element Analysis (FEA) can be use to predict stress distribution during loading. By knowing the stress distribution can help to understand a key factor for the success or failure of a dental implant.

Objective To investigate: The effect of bone quantity (cortical thickness) on the stress distribution by using Finite element analysis (FEA) method for certain loading type (vertical loading) to simulate the masticatory process.

Methodology Criteria of Sample FEA Pre CBCT Scanning Implant Surgery CBCT Scanning / Monitoring Segmentation and Model Building FEA

Sample Selection Selected Patient : Age : between 25-55 years old Race : Malay Sufficient oral hygiene No infection during treatment Treated with MEGA GEN implant to replace edentulous of molar on mandible

Implant Surgery Technique Implant surgery was conducted by dentist specialist in HUSM Following HUSM procedure Using delayed implant technique MEGA GEN dental Implant Normal position

CBCT scanning Pre scanning is conducted to evaluate the quality and quantity of available space for implant placement Post scanning is conducted to evaluate the position of implant Using Promax -Planmeca CBCT machine with exposure: 84 kVp, 8 mA, 320-μm voxel resolution, and FOV 16 cm Patient was positioned with standing position Data was recorded in DICOM format

Segmentation and Model Building Segmentations are performed using MIMICS software Version 17.0 Separation of each component are based on threshold HU. Component of dental implant model consist of neighbor teeth, implant body, crown, cortical and trabecular bone.

Segmentation & Model Building The Region of Interest (ROI) is cropped to get only an area around the implant and neighbour teeth only. On this bulk of ROI, every element that consist of two neighbour teeth, bone, implant and crown were segmented using Boolean operation technique. In the final stage, the morphology operation was performed to get the variation in the cortical thickness.

Results and Discussion Cortical thickness model are derived from CBCT image data using morphology operation after segmentation. Four different cortical thickness models ( 2.3 mm, 2.85 mm, 3.53 mm and 3.93 mm) Meshes are generated similarly to each other

FEA Simulation Density (gr/cc) Young Modulus, E (GPa) Poisson’s Ratio Material properties : Homogeneous ( Density, Young Modulus and Poisson’s ratio) Contact Surface : Implant-bone : frictional Teeth-bone : bound Crown – implant : bound Loading type : 200 N vertical Force directed on top of crown (Post- crown condition) Density (gr/cc) Young Modulus, E (GPa) Poisson’s Ratio Bone 2.17 13.7 0.3 Teeth 2.9 50 0.33 Implant 4.51 105 0.37 Porcelain Prosthesis 6.05 70 0.19

Stress Distribution The stress responses due to a 200 N vertical force Measured stress : Von Mises stress Stresses were propagated intensively in the area close to the implant body

Effect of Cortical Thickness Four different probe locations have been placed to measure generated stress on each model.

Conclusions Cortical thickness plays an importance role in the stress distribution. Generated stress due to vertical loading on model with thicker cortical, will be propagated easily into trabecular. In this case, trabecular will receive more stress compared with model with thinner cortical thickness. Continuous loading as resulted by mastication process during healing stage need to be taken into account to avoid overload on the new implant modelling/remodelling the bone, hence the long lifetime of dental implant can be achieved. 

Acknowledgment The authors are grateful to USM for funding this research with the grant number: PRGS: 1001/PPSG/8146004 Short term grant: 304/PPSG/61313004. 600-RMI/FRGS 5/3 (142/2014)

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