Annexure II proforma for registration of subjects for dissertation



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RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES

BANGALORE, KARNATAKA

ANNEXURE II




PROFORMA FOR REGISTRATION OF SUBJECTS FOR DISSERTATION



1.

Name of the Candidate

And


Permanent Address:

(BLOCK LETTERS)



DR.NAMRATHA.N

NO. 30,” MARUTHI PRASANNA”,

NANDAGOKULA LAYOUT, SHAMPUR

ARABIC COLLEGE POST,

BANGALORE-560045


Local Address:

(BLOCK LETTERS)




DEPARTMENT OF PROSTHODONTICS

M.S.RAMAIAH DENTAL COLLEGE & HOSPITAL,

M.S.R.NAGAR, M.S.R.I.T. POST,

BANGALORE – 560054








Address for correspondence

M.D.S STUDENT,

DEPARTMENT OF PROSTHODONTICS,

M.S.RAMAIAH DENTAL COLLEGE,

BANGALORE-54



2.

Name of the Institution

M.S.RAMAIAH DENTAL COLLEGE AND HOSPITAL, BANGALORE.


3.

Course of Study and Subject

MASTER OF DENTAL SURGERY,

PROSTHODONTICS.




4.

Date of Admission to the Course

28/05/2009.


5.

Title of the Topic



Comparison of stress patterns around implants placed in All On Four and Nordic Bridge Concept for a full arch implant supported fixed restoration in Maxilla- A FINITE ELEMENT ANALYSIS.


6. BRIEF RESUME OF THE INTENDED WORK


INTRODUCTION:

The therapeutic regimen for treating patients with missing teeth has been significantly expanded by modern implant techniques. However, a prerequisite for successful oral implants is the presence of sufficient bone height and width. In using dental implants for edentulous patients in maxilla, clinicians frequently are confronted with anatomic variations of the premolar and molar areas. The maxillary sinus and its position are one of the reasons for this variation.

Thus, implant placement in the maxilla can be difficult for many reasons, including inadequate posterior alveolus, increased pneumatization of maxillary sinus, and close approximation of sinus to crestal bone. The thickness of bone beneath the maxillary sinus correlates with the degree of pneumatization. Sinus pneumatization may minimize or completely eliminate the amount of vertical bone available. In addition to the problem of a compromised alveolar ridge, the maxillary sinus can vary in size and shape, making implant placement impossible without surgical modification.

The solution can include complex surgical techniques, such as maxillary sinus lift and bone grafting procedures. In case of bone grafting procedures, patient discomfort, sensitivity, and pain can result in the donor site in addition to the prolonged treatment time. Another problem with this approach is the generally lower success rate associated with implants placed in augmented bone. Further considerations are the issues of additional cost, high degree of difficulty requiring surgical expertise, and inability of some patients, such as elderly patients, patients with specific health problems, or fearful patients, to accept this type of rehabilitation. In an effort to avoid this anatomic structure, distal implants may be tilted anteriorly by an axial angle. As a result implant supported prosthesis can be extended further distally and cantilever length could be reduced.


NEED FOR THE STUDY:

The principle of Implant therapy is that occlusal forces are absorbed by the peri implant bone. The magnitude and direction of forces can vary and is dependent on the mechanical and biologic load bearing ability of the peri implant bone. Exceeding the threshold level of this load bearing ability will result in mechanical or biologic failure. Strain is a natural consequence of stress and the amount of strain is directly correlated to the stress applied to the bone and the stiffness of the bone. The critical aspect here is the quantum of strain occurring in the bone causing fatigue fracture more than the amount of stress.

Vertical and transverse loads from mastication induce axial forces and bending moments and result in stress gradients in the implant as well as in the bone. A key factor for the success or failure of a dental implant is the manner in which stresses are transferred to the surrounding bone. Load transfer from implants to surrounding bone depends on the type of loading, the bone–implant interface, the length and diameter of the implants, the angulation of implants, the shape and characteristics of the implant surface, the prosthesis type, and the quantity and quality of the surrounding bone. In the past 2 decades, finite element analysis (FEA) has become an increasingly useful tool for the prediction of the effects of stress on the implant and its surrounding bone. FEA allows researchers to predict stress distribution in the contact area of the implants.

Finite Element Analysis (FEA) is a technique for obtaining a solution to a complex mechanical problem by dividing the problem domain into a collection of much smaller and simpler domains in which the field variables can be interpolated with the use of shape functions. Finite element analysis is a useful evaluation method where accurate results can be obtained with incorporation of appropriate data.


REVIEW OF LITERATURE:

1. A photo elastic study was done on “all on four concept” in edentulous mandible with distal implants tilted by 15 degrees, 30 degrees and 45 degrees. At 45 degree angle there was a high isochromatic fringe concentration around the implant indicating higher stress around the implant in apical region with a force of 147.09 N load.1


2. A study was done on tilted and non tilted implants in edentulous maxilla through finite element analysis and it was found that implant tilting can allow for decrease in inter implant distance and shortening of cantilever length so that a better load distribution is achieved. 2
3. A 1 year retrospective clinical study including 32 patients where all on four concept was done on 128 immediately loaded implants showed that there was a 1 year cumulative survival rate of 97.6%.3
4. A finite element analysis was conducted to determine the magnitude of stress in supporting bone when implants were arranged in either straight line or offset configuration. In addition, the effects of axial and non axial loading and changes in prosthesis height were also assessed. Least stress was found on vertical implant with 6mm prostheses versus 12 mm prostheses and more stress was found in the supporting bone when the angle of force application was increased by 15 degrees. Creating an offset did not compensate for the increased stress.4
5. Finite element analysis is a useful tool in assessing the effects of stress on the implant and surrounding bone. Load transfer from implant to the surrounding bone depends on type of loading, length, diameter and the angulations of implant placed, the type of prosthesis and the type of surrounding bone. FEA allows researchers to predict stress distribution in and around implants.5
6.A study was done on 16 edentulous mandibles where early functional loading of inserted Branemark system implants was performed using permanent fixed constructions, nicknamed “ the Nordic Bridge”,. In the 18 month follow up study done no implant was lost and for next five years further follow up of the patients showed that no implant had failed.6

AIM OF THE STUDY:


  1. To study the stress distribution in ALL ON FOUR concept in maxilla.




  1. To study the stress distribution in the NORDIC BRIDGE CONCEPT.

.

  1. To compare the stress pattern of the new concept of ALL ON FOUR against the traditional Nordic bridge concept.

MATERIALS AND METHOD:

3D finite element model of maxilla is fabricated by using CT scan through Mimic software. This processed data is converted to surface data which is then taken into Hyper mesh software to create a finite element model.

Two finite element models are created in the computer. In the first model an all on six concept is simulated in which 6 implants are placed vertically and parallel to each other.

In the second model an all on four concept is simulated in which two implants are vertically placed in anterior region and the other two distal implants are placed which are tilted anteriorly.

A force of 100 Newton static axial and 50 Newton static nonaxial loads will be applied on the implants on both the models and strain on the peri implant area will be analyzed.

Each model will be evaluated separately for the strain pattern around the implants and the analysis will be done using ANSYS software.




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

No.




    1. Has ethical clearance been obtained from your institution in case of above?

Yes.



8. LIST OF REFERENCES
1. Stress pattern around distal angled implants in all on four concept configuration.

Tasneem begg, Greta A. V. M Geerts, Jasson Gryzagoridis,

Int J Oral and Maxillofac Implants 2009; 24:663-671
2. A finite element analysis of tilted versus non tilted implant configurations in edentulous maxilla. Chiara M Bellini, Davide Romeo, Fabio Galbusera, Enrico Agliardi, RiccardoPietrabissa, AntoniosZampelis, Francetti, Int J Prosthodont 2009;22:155-157.
3. All-on-4 Immediate - Function Concept with Branemark system Implants for completely edentulous Maxillae: A 1 Year Retrospective Clinical Study.

Paulo Malo, ;Bo Rangert, Miguel Nobre, RDH.

Clinical Implant Dentistry and Related Research, Volume 7,Supplement 1,2005.
4. Finite element analysis of effect of prosthesis height, angle of force application, and implant offset on supporing bone.

Murat sutpideler, Steven E Eckert Mark Zobitz, Kai Nan An,. Int J Oral and Maxillofac Implants,2004; 19:819-825


5. Application of finite element analysis in implant dentistry:A review of the literature

Jian-Ping Geng, ,a Keson B. C. Tan, and Gui-Rong Liu, Faculty of Dentistry and Faculty of Engineering, National University of Singapore, Singapore ;J Prosthet Dent 2001;85:585-982


6. Immediate / early loading of oral implants in compromised patients ;Ulf Lekholm. Periodontology ;2000, vol 33, 2003, 194-203.





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