Biological aspects of implants /certified fixed orthodontic courses by Indian dental academy

Biological Aspects of Implants

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.com

Overview

Introduction
Definitions
History
Classification
Implant Materials, Surfaces, And Forms
Surface modifications
Response Of Bone To Implants
Osseointegration
Events After Implant Placement
Factors influencing Osseointegration
References


Introduction

Over years different clinical skills
have been tried to help patients
with the effects of partial or
complete edentulism. Dental
problems that were historically
the most difficult can be solved
today with assistance of dental
implants


Definition

A dental implant is a device of biocompatible material(s) placed
within / against the mandibular / maxillary bone to provide
additional / enhanced support for prosthesis / tooth

The Glossary of Prosthodontic Terms (GPT) defines an implant
as “a prosthetic device or alloplastic material implanted into
the oral tissues beneath the mucosal and/or periosteal layer,
and /or within the bone to provide retention and support for a
fixed or removable prosthesis.”


History

The Mayan civilization has been shown earliest known examples to
have used endosseous implant, dating back over 1,350yrs before
Per Branemark started with titanium
Archeologists found a fragment of mandible dating about 600AD.
which is considered to be that of a woman in her 20s had three
tooth shaped pieces of shell placed into sockets of three missing
lower incisor.
• The tooth-shaped shell implants and the jaw were examined
radiographically and it was determined that compact bone had
formed around 2 of the implants and the bone was radio
graphically similar to that which forms around blade implants. This
may be the earliest example of any endosseous implant.


Classification

Based on relation to bone form
Endosteal
Subperiosteal
Transosseous

Based on shape
Blade form
Root form

Based on material used
Metallic
Ceramic

Subperiosteal Implants (Eposteal implants):

It is a framework specially fabricated to fit on top of supporting
areas in the mandible or maxilla under the mucoperiosteum with
perimucosal extension for support and attachment of a prosthesis.

Indications:
In cases of advanced alveolar resorption in which volume of
residual bone is insufficient for insertion of endosteal implant.
Used in atrophied bone and where jaw structure is limited



Types:
Interdental subperiosteal implants
Total subperiosteal implants
Circumferential subperiosteal implants
Advantages:
light weight
individually designed metal framework fits over remaining
bone


Subperiosteal Implants :(Eposteal implants)

The subperiosteal implant
is retained by periosteal
integration in which the
outer layer of periosteum
provides dense fibrous
envelope & anchors the
implant to bone through
sharpeys` fibers



Preoperative

Postoperative



Used only in the anterior mandible
in the very atrophic mandible

Due to the complex nature of the
surgical approach this implant is
not used frequently.


Endosteal Implants

They are surgically placed within alveolar and basal bone and are
subdivided into
• Root form
implants include those that approximate the shape and
dimensions of tooth roots (called root form implants)

• Blade form
those that are plates of metal (called blade implants)

• Ramus form
those that are metal frameworks where only a portion of the
metal is implanted into bone (ramus frame implants).

Root Form

Alvin Strock placed first successful
root form implant in 1938 in the
University of Harvard

Placed directly into bone, like
natural tooth forms
Designed to resemble the shape
of natural tooth
Can be placed anywhere in
mandible / maxilla where there is
sufficient available bone


Root Form

Cylindrical in shape

Can be threaded, smooth, stepped,
parallel/threaded, with /without
coating, with /without grooves /
vent
3 to 5mm in diameter
7 to 20mm in length

As a rule root forms must achieve
osteointegration to succeed. So
they are placed in an afunctional
state during healing until they are
osteointegrated

Root Form

The Root form Implants are two
stage implants

Stage I : is submersion / semi-
submersion to permit a functional
healing.

Stage II : is attachment of an
abutment / retention mechanism


Blade Form

The Endosteal Blade implant was
introduced in 1967 by Leonard
Linkow and also by Ralph &
Harold Roberts

Shape:
as the name suggests a metal /
blade in cross-section

Available in 1 stage / 2 stage forms
2.5mm in width
Can be placed anywhere in 8 to 15mm in depth
mandible / maxilla 15 to 30mm in length


Blade Form


Ramus Form

The Ramus Frame implant was
developed in 1970
First fabricated from stainless
steel.
In 1982, the fabrication process
was changed to titantium

INDICATION: Total mandibular
edentulism with severe alveolar
ridge resoption


Ramus Form

They are technique- sensitive

They have an external attachment
bar that runs from ascending
ramus on one side to ascending
ramus on the other side.

Posteriorly on each side they have
endosteal extensions, inserts
into available bone within
ascending ramus

Anteriorly it has plate / blade
extension which is inserted into
symphysis


Endodontic Stabilizer

Differ from other endosteal implants
in terms of functional application

Rather than providing additional
abutment support for restorative
dentistry , they are used to
extend the functional length of an
existing tooth root to improve its
prognosis


Endodontic Stabilizer

Shape:
have parallel / tapered sides
smooth / threaded
Indication:
atleast 5mm of bone should be available beyond apex of
tooth being treated

2nd premolars & molars are not good candidates
in mandible as they are over inferior alveolar canal
in maxilla as they are over maxillary sinus


Intermucosal Inserts

Differ in form ,concept, function from
other modalities
They provide support for a prosthesis but
do not provide abutments
Mushroom shaped projections that are
attached to the tissue surface of RPDs
or CDs in maxilla & plug into prepared
soft tissue receptor sites in the gingiva
to provide additional retention &
stability
Indication:
where endosteal & Subperiosteal
implants are not practical


Intermucosal Inserts

Do not come into contact with bone

Mode of intergegration is not
osteointegration

Receptor sites in the tissue into which
the inserts seat become lined with
tough keritinised epithelium

Only one appointment is required


IMPLANT COMPONENTS

1. Implant body

2. Sealing screw

3. Healing cap

4. Abutment

5. Impression post

6. Laboratory analogues

7. Waxing sleeves

8. Prosthesis www.indiandentalacademy.com
retaining screw

IMPLANT COMPONENTS

1.Implant body:
Implant body is the endosteal dental
implant that is placed within the bone
during first stage surgery.
It may be either a threaded or non
threaded cylinder
It is either titanium alloy with or without
hydroxyapatite coating.

2.Sealing screw :
• A screw is placed in the implant
during the healing phase following
stage –one surgery.

Prevents the growth of the tissue over
the edge of the implant.

IMPLANT COMPONENTS

3.Healing cap:
Healing cap is dome –shaped screw .
They may range in length from 2 to 10mm
and projects through the soft tissue into
the oral cavity.
Made up of resin such as polyoxymethyline or
the titanium metals

4.Abutment:
Screws directly into implant support
prosthesis.
Primary component which provides retention
to the prosthesis.


IMPLANT COMPONENTS

5.Impression post:
Facilitates transfer of intra oral
location of abutment to similar
position in laboratory cast.
It screws directly into fixture / into
abutment; once impression post
is in place ,an impression is
made.


IMPLANT COMPONENTS

6.Laboratory analog:
Component to represent either implant
or abutment in laboratory cast.
It screws onto the impression post after
it has been removed from mouth &
placed back into impression before
pouring
7. Waxing sleeve :
Is attached to the abutment by the
prosthesis retaining screw on a
laboratory model.
8. Prosthesis retaining screw :
Penetrates the fixed restoration and
secures to the abutment


IMPLANT MATERIALS, SURFACES,
AND FORMS



The composition and nature of the surface of an implant are
important characteristics because of their effect on the
biologic development of an interfacial relationship between
the bone and the implant.

To be successful, an implant must meet 4 conditions:

1. Be biocompatible so there is no undesirable reaction
between the tissues and the implant (ie., corrosion,
dissolution and/or resorption)


To be successful, an implant must meet four conditions …

2. Have an interface that stabilizes postoperatively in as short
a time as possible

3. Be capable of carrying and transferring the occlusal stresses
placed upon it

4. Remain stable for a long period of time.



Two basic types of materials are used in implant dentistry:

Metals
Ceramics (either in a pure form or a hybrid type )

Titanium Implants

• Titanium’s biocompatibility, corrosion resistance, relatively light weight,
low density, low modulus and high tensile strength make titanium based
materials attractive for use in dentistry.

• There are six different types of titanium based materials used to
fabricate dental implants. These materials include

Four types of commercially pure titanium (cpTi)
Two titanium alloys


CP titanium is available in 4 grades. Titanium Alloys

Cp grade I Ti Ti-6Al-4V
Cp grade II Ti Ti-6Al-4V
Cp grade III Ti
Cp grade IV Ti.

The main difference between the 4 grades of titanium and the two alloys is
the increasing ultimate tensile strength either in a pure form or a hybrid
type


Measuring Surface Topography

The surface topography describes
(1) the degree of roughness that the surface exhibits and
(2) the orientation of the irregularities on the surface.
Surface roughness occurs in two principal planes: one perpendicular
to the surface and one in the plane of the
surface (Thomas 1999)

Currently 3 groups of instruments are available that may
provide such information:
1. Mechanical contact stylus instruments
2. Optical instruments
3. Scanning probe microscopes (SPM).


Titanium implant surface
characteristics may be modified
by Plasma spraying & ion sputter coating

• Additive methods
(eg.Titanium Plasma
Spray [TPS], Hydroxyapatite
[HA]-coated)

• Subtractive methods
(eg.acid etched, particle
blasted and combinations)



Plasma spraying
Involves heating the HA by a plasma flame at a temperature of
approximately 15,000° C to 20,000°C.
The HA is then propelled onto the implant body in an inert environment like
argon, to a thickness of 50 to 100 μm.
Ion-sputter coating
• Process by which a thin, dense layer of HA can be coated onto an
implant substrate.

• Machined implants had a roughness of 5 micrometers while
hydroxyapatite coated implants had a roughness of 30 to 50
micrometers

Implant Surface Modifications

Blasted Surface Blasted & Etched

Etched Hydroxyapatite Coated


Advantages of increased surface roughness of Cp Ti implant

• Increased surface area of the implant adjacent to bone.

• Improved cell attachment to the implant surface.

• Increased bone present at the implant surface.

• Increased biomechanical interactions of the implant with bone.
• Bone formation and maturation occurs at a faster rate in the initial
phases on HA coated implants than on non-coated implants


Disadvantages of Surface Coatings

• Flaking, cracking, or scaling upon insertion

• Increased plaque retention when placed above the bone.

• Increased bacterial adhesion and acts as a nidus for infection

• Complications of treating the failing implants

• Increased cost


RESPONSE OF BONE TO
IMPLANTS


Branemark (1952) Described the relationship between titanium
and bone for which they coined the term osseointegration and
defined it “as a direct structural and functional connection
between ordered, living bone and the surface of a load-
carrying implant.”

The word osseointegration consists of
“OS” the Latin word for bone and “integration” derived from
Latin word meaning the state of being combined into a complete
whole.

The Glossary of Prosthodontic Terms(GPT) refers to the term
“osseous integration”

which is defined as “the apparent direct attachment or
connection of osseous tissue to an inert, alloplastic material
without intervening connective tissue.”


Bone to Implant Interface

Two basic theories
1.Fibro-osseous integration by Linkow, James & Weis
2 Osseointegration by Branemark
Meffert divided osseointegration
Adaptive osseointegration
Biointegration
American Academy of implant dentistry defined fibrous
integration as tissue to implant contact with healthy
dense collagenous tissue between the implant and bone.

Mechanism of Osseointegration

Blood clot (between fixture & bone)

Clot transformed by phagocytic cell
(1st to 3rd day)

Procallus formation
(containing fibroblasts & phagocytes)

Procallus becomes dense connective tissue
(Differentiation of osteoblasts & fibroblasts)

Callus (Osteoblasts on the fixture)

Fibro cartilagenous callus (between
fixture & bone)

Bone callus (Penetrates & matures)

Prosthesis attached to the fixtures stimulating
bone remodeling

EVENTS AFTER IMPLANT PLACEMENT

Bone Necrosis
• About 1 mm of cortical bone adjacent to the osseous
wound (osteotomy site) undergoes post surgical necrosis in
spite of careful surgical technique.

Three phases have been described in the development of
the bone-implant interface
1.stabilization phase
• Subendosteal and subperiosteal calluses form and adhere
to the implant surface.
• The bone is relatively low in density at this time (woven
bone)

2.The Strength Phase
• The implant is stabilized
• The process of resorption begins
• Stronger, weight bearing bone is formed (lamellar bone)
• Osteoclasts resorb nonvital bone and restore it with new
lamellar bone
3. The Durability Phase
• Extensive remodeling occur and additional strength is
developed.
• With remodeling and proper prosthodontic function, the
interface bone will tend to show very mature lamellated
bone

• The fibers are arranged irregularly, parallel to the implant

body, when forces are applied they are not transmitted

through the fibers. So no bone remodeling is expected in

fibro-integration.
• A direct bone implant interface occurs when an implant is
allowed to heal in bone undisturbed.
• Main factors affecting osseointegration include
– Implant oxide layer contamination.
– Poor temperature control during drilling.

Factors influencing Osseointegration

– Biomaterial for dental implant
– Surface composition and structure
– Implant design
– Heat during osteotomy
– Contamination
– Primary stability or initial stability
– Bone quality
– Epithelial down growth
– Loading
• A minimum of 3 month healing in mandible and 6 months in
maxilla is necessary before load is applied

Bone resorption can be caused by 12 months following fixture
insertion
vertical bone loss is observed due to traumatic surgical
procedure.
– Vertical bone loss approximately 1 to 1.5 mm in first year
– Marginal bone loss of 0.05 to 0.1 mm in first year
– These measurements can be used a reference and in a
bone loss condition should be evaluated to minimize
failure.


The main contributing factor to bone resorption are
1. Local inflammation from plaque
Direct action of plaque products induces formation of
osteoclasts, destroys bone through a non cellular
mechanism
2.Trauma from occlusion
Stimulate gingival cells, which release mediators for
osteoclast formation.

3. Heat
• Heating of bone to a temperature in excess of 47°C during
implant surgery can result in cell death and denaturation of
collagen.

• As a result, osseointegration may not occur

• The implant becomes surrounded by a fibrous capsule

• The shear strength of the implant-host interface is
significantly reduced.

4. Primary stability or Initial stability

– where an implant fits tightly into its osteotomy site then
osseointegration is more likely to occur.
– This is often referred to as primary stability, and when
this happens failure is less probable.
– This property is related to the quality of fit of the implant,
its shape, and bone morphology and density.


7.BONE QUALITY & QUANTITY

• Areas of jaws – More cortical bone (anterior mandible)
Anchor implant successfully

cancellous bone- Maxilla
Difficulty to achieve initial stability for
implant osteointegration requires a longer healing period.
•


• Vertical dimension of bone - Minimal for endosteal implant
is 8mm.

It is important to leave at least 2mm of bone between the
apical end of the implant and inf..alveolar canal .

• Bone width – implants should be a minimum of 1mm of bone
on the buccal and lingual aspects of dental
implant.
Ex -for a 4mm diameter implant 6mm of available bone
width is necessary
• ; www.indiandentalacademy.com

• Vertical dimension of bone - Minimal for endosteal implant
is 8mm.

It is important to leave at least 2mm of bone between the
apical end of the implant and inferior alveolar canal .

• Bone width – implants should have a minimum of 1mm of
bone on the buccal and lingual aspects of dental implant.
Ex -for a 4mm diameter implant 6mm of available bone
width is necessary.


Bone Density Classification (Misch)


6. Contamination
– Contamination of the implant site
by organic and inorganic debris
can prejudice the achievement of
osseointegration.

– Material such as necrotic tissue,
bacteria, chemical reagents and
debris from drills can all be
harmful in this respect.

7. Loading schemes
Delayed loading:
The prosthesis is attached at the second procedure after
a conventional healing period of 3 to 6 months
Early loading:
The prosthesis is attached during a second procedure, earlier
than the conventional healing period of 3 to 6 months.
Time of loading should be stated in days to weeks
Immediate / Direct loading:
The prosthesis is attached to the implants the same day the
implants are placed.

Biomechanical Overload
BIOMECHANICAL OVER LOAD

Biomechanical Over Load

Bone Loss At Coronal Aspect

Micro Fracture At Coronal
Aspect Of Implant- Bone Interface

Loss Of Ossteointegration

Apicalgrowth Of Epitelium & C.T

The speed and degree of loss of implant-bone contact depends upon the
frequency and magnitude of the occlusal loading as well as superimposed
bactrerial invasion www.indiandentalacademy.com

Revised criteria for implant success

– Individual unattached implant is immobile when tested
clinically.
– No evidence of peri implant radiolucency is present as
assessed on an undistorted radiograph.
– Mean vertical bone loss is less than 0.2 mm after 1st year
of service.
– No persistent pain, discomfort or infection.
– A success rate of 85% at the end of a 5-year observation
period and 80% at the end of a 10-year period are
minimum levels of success.

References

1. Caranza’s Clinical Periodontology 10th Edition
2. Jan Lindhe Clinical Periodontology and Implant Dentistry 4th
edition
3. Weiss Principles and Practice of Implants
4. Carl Misch Contemporary Implant Dentistry


Thank you


Biological aspects of implants /certified fixed orthodontic courses by Indian dental academy

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