Since the introduction of osseointegration, replacement of missing teeth by
1.
BRIEF
OF
1.1
RESUME means of implants has become a predictable treatment modality for both
THE completely and partially edentulous patients. Challenging aspect of implant
INTENDED WORK
therapy is placement and subsequent restoration in the aesthetic zone; because
NEED FOR STUDY
the levels of crestal bone and soft tissue dimensions are critical factors in the
aesthetic outcome.1
The observed changes in crestal bone height following implant restoration can
be attributed to various theories which states that:

Crestal bone levels are dependent on the location of implant-abutment
junction following implant placement.

If the implant-abutment is positioned deeper within the bone, it will
eventually lead to increased bone loss.

Crestal bone resorption is related to overload and damage of
supporting interfacial bone.
The long term preservation of peri-implant tissues is of primary importance, as
it affects aesthetic and functional outcome of the restoration.
Following implant insertion and loading, crestal bone usually undergoes
remodeling and resorption during the first year.
The crestal bone loss generally coincides with the level of the first thread of
the implants, resulting in a crown that appears longer than desired, therefore
affecting the aesthetic outcome of the restoration.
Radiographic observations have shown that, diminished bone dimensions both
horizontally and vertically at the facial aspect of the implant.
Numerous techniques for hard and soft tissue management to achieve an ideal
aesthetic result are reported in literature.
It has been reported that platform switching reduces the post restoration crestal
bone loss.
This concept of platform switching was presented by LAZZARA and
PORTER in the year 1991.
Many studies in the literature have shown that platform switching is associated
with:

Reduced inflammatory cell infiltrate at the implant abutment interface.

Reduced stresses on peri-implant bone area,
in comparison with conventional implant-abutment connection.2
However, there are no studies that compare stresses induced in peri-implant
bone when using straight and angulated abutments associated with
conventional and platform switching.
Therefore, the purpose of the current study was to measure and compare stress
distribution on peri-implant bone when two different implant abutment
connections are placed in the anterior maxilla using:
1. Two different abutments.
2. Two different loading conditions.
1.2
REVIEW
LITERATURE
OF 1) Four mathematical models of an implant-supported central incisor were
created with varying abutment angulations: straight abutment (S1 and S2) and
angulated abutment at 15 degrees (A1 and A2), submitted to 2 loading
conditions (100 N): S1 and A1—oblique loading (45 degrees) and S2 and
A2—axial loading, parallel to the long axis of the implant. Maximum (σmax)
and minimum (σmin) principal stress values were obtained for cortical and
trabecular bone.
Implants with straight abutments generated the highest stress values in bone.
In addition, this effect was potentiated when the load was applied obliquely 1.
2) A study was conducted where a three-dimensional finite element analysis
(3D FEA) models were created to replicate an external hexagonal implant
system with peri-implant bone tissue in which three different implantabutment configurations were represented. In the regular platform (RP) group,
a regular 4.1-mm-diameter
abutment (UCLA) was connected to regular 4.1-mm-diameter implant. The
platform-switching (PS) group was simulated by the connection of a wide
implant (5.0 mm diameter) to a regular 4.1-mm diameter UCLA abutment. In
the wide-platform (WP) group, a 5.0-mm-diameter UCLA abutment was
connected to a 5.0-mm-diameter implant. An occlusal load of 100 N was
applied either axially or obliquely on the models using ANSYS software.
Platform switching led to improved
biomechanical stress distribution in peri-implant bone tissue. 2
3) A review of literature was done to discuss the biomechanical effects of
platform switching in two different implant systems. Six 3D finite element
models were created to replicate two different implant systems with periimplant bone tissue, in which six different implant abutment
configurations were represented: model XiVE-a: 3.8-mm-diameter implant
and
3.8-mm-diameter abutment; model XiVE-b (platform-switching model): 4.5mm-diameter implant and 3.8-mm-diameter abutment; model XiVE-c: 4.5mm-diameter implant and 4.5-mm-diameter abutment; model 3i-a: 4.0-mmdiameter implant and 4.1-mm-diameter abutment; model 3i-b (platformswitching model): 5.0-mm-diameter implant and 4.1-mm diameter.; model 3ic: 5.0-mm-diameter implant and 5.0-mm-diameter abutment vertical and
oblique loads of 100 were applied to all models.
However in both implant systems, platform switching design reduced the
stress concentration in the crestal bone and shifted it towards the area of
implant-abutment interface.3
4) A review of literature to assess radiographic marginal bone-level changes
and the survival of platform-switched implants compared to conventional
platform-matched implants was done. The review and meta-analysis show that
platform switching may preserve inter implant bone height and soft tissue
levels. The degree of marginal bone resorption is inversely related to the
extent of the implant-abutment mismatch. Further long-term, well-conducted,
randomized controlled studies are needed to confirm the validity of this
concept.4
1.3
OBJECTIVES
THE STUDY
OF 1) To analyze the stresses in straight abutments with two different implant
abutment connections
2) To analyze the stresses in angulated abutments with two different implant
abutment connections.
3) To analyze and compare stress distribution between straight and angulated
abutments with two different implant abutment connections.
2.
MATERIALS AND CT scan images of anterior maxilla will be acquired at small slice intervals.
2.1
METHODS
The slices will be assembled and a three-dimensional model will be
SOURCE OF DATA constructed using ANSYS software. The model representing maxilla will be
restored with straight and angulated abutments in conventional and platform
switching.
To assess stress distribution in the peri-implant bone tissue, the implants and
prosthetic components, loading will be simulated by applying loads to
prosthetic crown.
The stress distributions will be plotted with the color maps to enable
comparisons of the two implant systems.
Statistical analysis will be performed to interpret the peak equivalent stress in
bone tissue, implant, abutment screw and prosthesis.
2.2
METHOD
OF Cortical bone of various thicknesses will be defined around the cancellous
COLLECTION
core. A three-dimensional model of a dental implant will be created. Straight
OF DATA
and angulated abutments will be used and Abutment will be angulated at
15degree.
Young’s modulus of elasticity and Poisson’s ratio of the following elements
will be used in the cases of stress analysis
1) Cortical bone
2) Cancellous bone
3) Titanium alloy
A masticatory load of 100N will be applied under two different loading
conditions

Axial

Oblique
Finite element analysis will reveal stresses and deformation at every node in
the model. Results will be generally displayed as stress contours overlaid on
the original model. This type of display permits the detection of maximal
stresses and stress concentrations for the entire model.
2.3
DOES THE STUDY Not applicable
REQUIRE
ANY
INVESTIGATION
OR
INTERVENTIONS
TO
BE
CONDUCTED ON
PATIENTS
OR
OTHER HUMANS
OR ANIMALS?
IF
SO,
DESCRIBE
PLEASE
BRIEFLY.
2.4
HAS
ETHICAL Not applicable
CLEARANCE
BEEN OBTAINED
FROM
YOUR
INSTITUTION?
1) Martini AP et al. Straight and Angulated Abutments in Platform Switching:
3.
LIST
REFERENCE
OF Influence of Loading on Bone Stress by Three-Dimensional Finite Element
Analysis. The Journal of Craniofacial Surgery 2012;23:415-418.
2)Tabata LF et al. Platform Switching: Biomechanical Evaluation Using
3-Dimensional Finite Element Analysis. Int J Oral Maxillofacial Implants
2011;26:482–491.
3)Sahabi M et al. Biomechanical Effects of Platform Switching in Two
Different Implant Systems: A 3 –Dimensional Finite Element Analysis. The
Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
2013;10.
4) Atieh MA et al. Platform Switching for Marginal Bone Preservation
Around
Dental Implants: A Systematic Review and Meta-Analysis. J Periodontal
2010;81:1350-1366.
5) Çimen H et al. Analyzing the Effects of the Platform-Switching procedure
on stresses in the bone and implant-abutment complex by 3-Dimensional FEM
analysis. Journal of Oral Implantology 2012;38:21-25.