STUDY AND CHARACTERIZATION OF

THE CREST MODULE DESIGN:

A 3D FINITE ELEMENT ANALYSIS

Cristiana Costa, MS,a Nuno Peixinho, PhD,b João Pedro Silva, PhD,c and Sandra Carvalho, PhDd

THE JOURNAL OF PROSTHETIC DENTISTRY 2015;113:541-547

CONTENTS

•INTRODUCTION

•MATERIALS AND METHODS

•RESULTS

•DISCUSSION

•CRITICAL ANALYSIS

•CONCLUSION

INTRODUCTION

•Osseointegration

•Stress management

•Microbial protection

•Surgical insertion method

• The crest module is a region of highly concentrated mechanical stress, where bone reabsorption usually occurs due to overload, absence of stimulation, or microbial contamination, all factors that lead to treatment failure.

MATERIAL AND METHODS1. Seven (3D) solid models of a

mandibular section and a dental implant were built with 3D computer-aided design software (SolidWorks 2013; Dassault Systèmes SA)

2. Before undergoing numerical finite element (FE) stress analysis with software (Ansys Workbench 15.0; Ansys Inc)

3. Each 3D solid mandibular models included 2 layers of bone

1. M1, cylindrical

2. M2, divergent with a maximum diameter equal to the implant body diameter

3. M3, cup shaped

4. M4, convergent

Nobel Biocare (Brånemark Mk III, Mk IV, NobelActive; M6, M2, M4) Astra Tech Implant System (OsseoSpeed TX;M1, M5).

5. M5, extended divergent; 6. M6, divergent with a

maximum diameter superior to the implant body diameter;

7. M7, divergent, similar to M5, but with a greater thread length.

• In the FE models, isotropic, homogeneous, and linear elastic materials were used.

• Regarding the mandibular cross section used in FE models, the bone properties were defined as being of type 2 according to the Lekholm and Zarb classification.

The top surface of the implant models was subjected to a 30-degree oblique force of

250 N, which represents the average value of maximum occlusal load.

Sahin S, Cehreli MC, Yalçin E. The influence of functional forces on the biomechanics of implant-supported prostheses-a review.

J Dent 2002;30: 271-82.

• The mesh elements of the FE models were tetrahedrons, with 10 nodes each, refined in the BIC regions

• From the convergence study carried out during the validation test of the FE models, the mesh refinement parameters were defined.

• Regarding the global mesh controls, a minimum and a maximum size of 0.1 and 0.5 mm were set, while in the crest module at the bone-implant interface a 0.3 mm mesh was applied

According to these validation tests, osseointegrated dental implants under a buccolingual force of 20 N experienced lateral displacements of 15.49 mm as reported by Sekine et al.

They measured the buccolingual mobility of osseointegrated dental implants with elastic strain meters, endosteal implant movement ranged from 12 to 66 mm in the buccolingual direction.

Sekine H, Komiyama Y, Hotta H, Yoshida K. Mobility characteristics and tactile sensitivity of osseointegrated fixture-supporting systems.

Tissue integration in oral and maxillofacial reconstruction. Amsterdam: Elsevier; 1986.

RESULTS

After the validation tests of FE models:

• Maximum principal elastic strain,

• Minimum principal elastic strain,

• Maximum shear elastic strain were evaluated .

•The highest values of maximum principal stress and strain obtained were 49.22 mpa and 2850 microstrain in M4

• The lowest were 23.85 mpa and 1499.6 microstrain in M5

DISCUSSION

The intent in applying a 30-degree oblique force of 250 N was to bring the FE models as close as possible to the actual occlusal loading conditions and combined stress

effect in the cortical bone crest.

• The crest module design parameters of surface area and platform diameter are important geometric indicators in predicting the level of success of dental implant treatments based on primary stability, osseointegration potential, and microbial protection capacity.

• M2 showed the highest peak values of minimum principal stress/strain and maximum shear stress/strain because of its great divergent angle (14 degrees) compared to other divergent designs.

• M4, with its convergent crest module design, produced higher values of minimum principal stress/strain than the cup shape (M3) or the divergent design (M7), which were expected to have higher levels.

• M5 and M7 also showed better shear stress distribution .

• Therefore, as a result of the strain peaks and their distribution in the cortical bone region of models M5 and M7, it is expected that they would show less bone loss in the first years after treatment compared to the other tested specimens.

• With its high platform diameter and its coronal divergent design, M5 is capable of compressing the cortical bone crest by improving its initial stability, sealing the socket bone area, and providing a barrier for the attack of microbial organisms

CRITICAL ANALYSIS

•Study is limited to type 2 bone.

CONCLUSION

•This study demonstrates that crest module design influences the distribution and concentration levels of stress and strain along the adjacent cortical bone.

•Extended divergent collar designs were found to be the most advantageous, especially in the reduction of cortical bone critical stresses, of tensile and shear.

•Geometrical shape of the extended divergent collar design promotes the reshaping and strengthening of the cortical bone crest.

REFERENCES

•Flemming I. Loss of osseointegration caused by occlusal load of oral implants. A clinical and radiographic study in monkeys. Clin Oral Implants Res 1996;7: 143-52.

•Bozkaya D, Muftu S, Muftu A. Evaluation of load transfer characteristics of five different implants in compact bone at different load levels by finite elements analysis. J Prosthet Dent 2004;92:523-30.

•Boldt J, Knapp W, Proff P, Rottner K, Richter EJ. Measurement of tooth and implant mobility under physiological loading conditions. Ann Anat 2012;194: 185-9.

•Sekine H, Komiyama Y, Hotta H, Yoshida K. Mobility characteristics and tactile sensitivity of osseointegrated fixture-supporting systems. Elsevier; 1986.