Brief overview of Dental Implants and Discusses about the Biomechanics and Treatment Planning of Implants

1. IMPLANTS : AN OVERVIEW,
BIOMECHANICS AND
TREATMENT PLANING
By Dibya Falgoon Sarkar
(North Bengal Dental College & Hospital)

2. OVERVIEW OF IMPLANTS
• Implantation: The process
of grafting/ inserting a
material such as an inert
foreign body (alloplast) or
tissue within the body
• Endosteal Implants: A
device placed into the
alveolar bone and/or basal
bone of mandible/ maxilla
that transects only one
cortical plate. (Anusavice)

3. TYPES OF IMPLANTS

4. COMPONENTS OF AN IMPLANT
An endosteal implant has
mainly three parts :
1. Implant Body (fixture) :
It can be further divided into-
apex, crest module , body. It
can have different surfaces.
Generally made of titanium
alloys.
2. Transmucosal Abutment
3. Implant Prosthesis

5. ADVANTAGES OF IMPLANTS:
1. Improved maintainence of bone at edentulous site
2. Improved esthetics
3. Improved stability and retention for cases of implant
supported prostheses
4. Psychological advantage
DISADVANTAGES OF IMPLANTS:
1. Implants are highly expensive
2. Technique sensitive and time consuming
3. Cannot be done in patients who do not recover
quickly

6. BRIEF OVERVIEW OF
PLACEMENT OF IMPLANTS
Most common method used for implant placement is
the TWO-STAGE SURGICAL PROCESS :
1. First stage involves the surgical part, where
implant is placed within the bone. It is left within
the bone until initial bone healing has occurred.
2. A second stage surgery is then done where the soft
tissue is reflected and the implant is uncovered to
attach the permucosal abutment.
3. The restorative phase then follows wherein a
crown, a partial denture, or a removable
overdenture is constructed .

7. OSSEOINTEGRATION
Theories of Implant to tissue integration :
1. Wiess’ theory of fibro-osseous integration :
• Proposed by Dr.Charles Wiess
• Complete encapsulation of the implant with soft tissues
• Soft tissue interface could resemble the highly vascular
periodontal fibers of natural dentition
2. Branemark’s theory of osseointegration :
• Osseointegration is characterized by direct contact between
bone and the surface of a functional implant
• It have also been achieved by the use of bioactive materials
that stimulate formation of bone

8. BRIEF OVERVIEW OF MECHANISM
OF OSSEOINTEGRATION
• It includes a process wherein
bone producing cells migrate
along the implant surface through
the connective tissue scaffolding
that forms adjacent to the
implant interface.
• At first woven bone forms which is
converted to lamellar bone under
load stimulation
• Implant’s surface topography
influences the strength of
attachment to the bone

9. STRESS TREATMENT THEOREM
FOR IMPLANT DENTISTRY
• The most common implant
related complications are
biomechanical problems that
occur after implant is loaded
• Thus the overall treatment
plan should
1. Assess the greatest force
factors in the system
2. Establish mechanisms to
protect the overall implant-
bone prosthetic system

10. TREATMENT PLANNING FOR
IMPLANT DENTISTRY
Carl E. Misch developed a treatment plan sequence to decrease
the risk of biomechanical overload, consisting of the following:
1. Prosthesis Design
2. Patient force factors
3. Bone density in edentulous sites
4. Key implant position and number
5. Implant size
6. Available bone in the edentulous sites
7. Implant design

11. PROSTHETIC OPTIONS IN
IMPLANT DENTISTRY
• According to stress treatment
theorem by Misch, the final
restoration is planned, similar to the
architect designing a building before
making the foundation
• Only after this the abutments
necessary to support the specific
predetermined restoration can be
designed
• An axiom for implant treatment is to
provide the most predictable and cost-
effective treatment that will satisfy
the patient’s anatomical need sand
personal desires

13. MISCH PROPOSED FIVE PROSTHETIC
OPTIONS FOR IMPLANT DENTISRY

14. REMOVABLE PROSTHESES :
TWO TYPES BASED ON SUPPORT
RP-4 RP -5

15. PATIENT FORCE FACTORS
RELATED TO PATIENT CONDITIONS
1. PARAFUNCTIONS – BRUXISM,
CLENCHING, TONGUE THRUSTING
2. CROWN HEIGHT SPACE
3. MASTICATORY DYNAMICS
4. ARCH POSITION
5. NATURE OF OPPOSING TEETH

16. PARAFUNCTIONS
• These forces are most damaging
to the implant
• Bruxism –Primarily concerns
horizontal, non-functional
grinding of teeth. Presents with
wear facets on teeth
• Clenching – A habit that
generates a constant force
exerted from one occlusal
surface to other without any
lateral movement. Donot
present wear facets but cause
fatigue fractures in implants
• Tongue Thrusting Habit

17. TREATMENT PLANNING FOR
PARAFUNCTION PATIENTS
• Bruxism – Treatment plan is modified primarily in two ways when
implants are inserted in posterior regions:
1. Additional implants that are wider in diameter
2. The anterior teeth may be modified to recreate the proper incisal
guidance and avoid posterior interferences during excursions.
• Clenching – Additional implants are indicated with greater diameter,
narrow posterior occlusal tables, and mutually protected occlusion are
inicated

18. CROWN HEIGHT SPACE
• It is measured from the crest of
the bone to the plane of
occlusion in the posterior region
and incisal edge of the arch in
question in the anterior region
• Ideal CHS for fixed implants is
8-12mm
• Removable prosthesis often
require > 12mm CHS
• Excessive CHS can cause
increased stress accumulation
leading to crestal bone loss (e.g
– atrophied bone)

20. TREATMENT PLANNING FOR
EXCESSIVE CROWN HEIGHT SPACE
• Because CHS is a considerable force
magnifier various methods are
adopted to decrease the stress:
1. Shorten the cantilever length
2. Minimize offset loads to the buccal and
lingual
3. Increase the no. of implants
4. Increase diameters of implants
5. Fabricate removable restoration which are
less retentive & incorporate soft tissue
support
6. For >15mm CHS eliminated all occlusal
contacts in centric relation in most
posterior parts

21. TREATMENT PLANNING BASED ON
NATURE OF OPPOSING TEETH
• Highest forces are created by
implant prostheses because
proprioception is lost .
• Case 1- When opposing arch
has a fixed implant
prosthesis or natural teeth
Thus, length of cantilever
should be reduced and no. of
implants are increased
• Case 2 –When opposing arch
have a removable denture
the bite force is minimum

22. BONE DENSITY: A KEY DETERMINANT
IN TREATMENT PLANNING
• There is an indisputable influence
of bone density on clinical success
• Wolff in 1892 told that “every
change in form & function of bone
is followed by certain definite
changes in the internal
architecture and equally definite
alteration in external
confirmation, in accordance with
mathematical laws
• Bone density decreases in jaws
after tooth loss due to less loading
• Bone density change is greatest
after tooth loss in posterior
maxilla and least in anterior
mandible

24. TREATMENT PLANNING BASED
ON BONE DENSITY
• As the bone density decreases the
strength of the bone decreases.
• To decrease the incidence of
microfracture of the bone we must
reduce the stress/ the biomechanical
load on the implants by:
1. Shorten the cantilever length
2. Overlying prostheses should have
narrow occlusal tables
3. Removable prostheses like RP-4
types are preferred so that they
can be removed at night.
This reduces the effects from
nocturnal parafunctions
4. For soft bone types we can go for
bone augmentation

25. TREATMENT PLANS RELATED TO
KEY IMPLANT POSITIONS AND
IMPLANT NUMBER
Misch proposed 4 guidelines for key implant positions
1. Cantilevers should be reduced or preferably eliminated
from the prostheses.
Terminal abutments acts as key positions
2. Three adjacent pontics should not be designed
3. Canine & molar sites are key positions when adjacent teeth
are missing
4. Arch dynamics where he divided each arch into five
segments
Distance of an implant from adjacent natural tooth =1.5mm
and adjacent implant =3mm {Misch}

26. No Cantilevers
• Cantilevers in prostheses acts
as force magnifiers to the
implants
• Ideal treatment plan should
eliminate cantilevers
• Howevers in cases where
where bone height is not
available in posterior mandible
we give cantilever pontics
• Cantilevers act as class 1 levers
No Three Adjacent
Pontics
• Three adjacents pontics are avoided
in prostheses as it leads to flexure
of implant abutments on loading

27. CANINE & FIRST MOLAR SITES
AND KEY ARCH POSITIONS
• When multiple teeth are missing
and the canine edentulous site is
a pier abutment position, the
canine position is a key implant
position which helps disocclude
the posterior teeth during
excursions
• First molar is also a key implant
site
• Misch said that when multiple
missing teeth extend beyond one
of the open pentagon segments, a
key implant position needs to be
situated in each segment
• Patient with missing teeth
from first molar to first
molar

28. IMPLANT BODY SIZE
• The initial treatment plan
should include the ideal
implant size based primarily
on biomechanic and esthetic
considerations
• The size of an implant used to
be determined primarily by
the existing bone volume
height, width, and length
• Ideal implant length under
normal conditions is 12mm
and upto 15mm for softer bone
types
• 4mm diameter implant is
used in most situations

29. RATIONALE FOR SHORTER IMPLANTS
• When the existing bone is
short, as in posterior maxilla
we have to use shorter
implants (<12mm)
Implant Diameter

30. IMPLANT DESIGN BASED ON ESTHETICS
Anterior Tooth
Replacement
• The implant body should be
of lesser width than the
natural tooth crowns.
This helps in mimicking the
emergence profile of a natural
tooth as the implant emerges.
• For multiple anterior implants
each implant should be at a
distance of 3mm from each
other
Posterior Tooth
Replacement

31. CASES WITH INSUFFICIENT
BONE IN THE EDENTULOUS SITE
• Available bone can be adjudged
as compromised when :
1. Ridge width is less than
2.5mm
2. Ridge height is less than
12mm
3. Angulation of Occlusal Load
>30degrees
4. Crown Height Space
>15mm
• Treatment Modifications :
1. Osteoplasty
2. Subperiosteal implants
3. Ridge Augmentation
4. Transosteal Implants
5. Ramus frame implants

32. DIAGNOSTIC TOOLS USED FOR
TREATMENT PLANNING

33. REFERENCES
• Contemporary Implant Dentistry ----
Carl E. Misch
• Phillip’s Science of Dental Materials ---
- Anusavice