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Introduction
Pre-load and After-load
Physiology of bone and loading
Modeling and remodeling
Early functional loading
Consequences of biomechanical overload
Evolution of the concept of implant loading

Protocols of implant loading
Elements of implant loading
Immediate occlusal loading
Factors that decrease risk
Guidelines for immediate loading
Conclusion
References

Prosthetic rehabilitation of missing structures in the
oral and maxillofacial region in accordance with
DeVan's principle of preservation has been the
ultimate challenge to the prosthodontist. Over the
years, traditional methods of tooth replacement are
slowly and steadily being replaced by newer
modalities like implants.

High success rates of implants and the advantages
that go with them have earned them the name of
the "third dentition".
Implants have come a long way from cast cobalt
chromium tubes, pins, subperiosteal vitallium
implants, endosseous blade implants, ceramic
implants to the modern day root form implants
made of titanium and its alloys.

Dental implants were commonly loaded at
placement because immediate bone stimulation
was considered to avoid crestal bone loss
(Linkow & Chercheve 1970). Fibrous tissue
interposition was considered the optimal
response to implants as it was mimicking the
natural periodontal ligament.

In contrast to all other experimental studies of that
time, Branemark et al (1969) showed that direct
bone apposition at the implant surface was possible
and lasting under loading at the condition that
implants were left to heal in a submerged way.

The basis of the increasing popularity of dental
implants is the coincidental discovery by Per-Ingvar
Branemark and his co-workers of the tenacious
affinity between living bone and titanium oxides,
termed “Osseointegration”.

Success with Brànemark's protocol still has a
deterring factor in the form of extended treatment
period, which sometimes preclude patients from
resorting to implant therapy. Increasing functional
and aesthetic challenges have prompted
implantologists to reduce the treatment period by
loading the implant immediately at the time of
placement.

The protocol has yielded encouraging results
although they still need to match the time tested
two-stage procedure, by way of success over an
extended period of time.

The Immediate loading of dental implants clearly
represents the change in dogma. To load the
implant immediately or not to load is indeed the
question today and the rationale that goes with the
protocol which warrants discussion.

The preloading or stretching the screw
places the components under enough tension
to create elongation of the material within its
elastic limit. Preloading may reduce screw
loosening.

As a result the components stretch and
maintain fixation in spite of vibration and
external forces. The elongation of metal is
related to the modulus of elasticity, which is
dependent on the type of material, its width,
design, and the amount of stress applied per
area.

Thus a gold screw exhibits greater elongation
but lower yield strength than a screw made of
titanium alloy. A prosthesis screw may exhibit a
torsional ductile fracture at 16.5 N-cm Vs 40 N-cm
for an abutment screw of different material and
size.

The material the screw is made from (eg.
Titanium alloy or gold) has a specific
modulus of elasticity. The plastic deformation
or permanent distortion of the screw is the end
point of the elasticity modulus. When the
screw is stretched with a force 75% of its
elastic length, it is able to better resist
vibration and screw loosening.

In order to stretch the screw, a torque wrench
is necessary, although not completely
accurate. Even an experienced clinician is
unable to determine the amount of correct
torque on the screw by tactile sense only.

A screw may be described to permit more
preload on the components.

The after-loading of implants is achieved by
means of prosthesis brought into occlusion.

As a result of unique physiological
mechanisms, bone serves two antagonistic
functions:
structural support and calcium metabolism.
The strength of a bone (quantity, quality and
distribution of osseous tissue) is directly
related to loading.

As an energy conservation measure, bone that
is not adequately loaded is resorbed, and the
skeletal system continuously adapts to
achieve optimal strength with minimal mass.
The delicate structural balance is further
challenged by metabolic function.

An adequate reserve of osseous tissue must be
maintained to provide a continuous stream of
ionic calcium without compromising
structural integrity. To provide for a variety of
conflicting demands, the skeleton has evolved
structural and metabolic fractions.

Osteopenia (inadequate bone mass) is a
common clinical problem. It may be due to
functional atrophy and/or negative calcium
balance.
Prospective oral implant patients are likely to
present with localized and systemic skeletal
problems for three rea-sons:

Bone in edentulous areas is usually atrophic.
Metabolic bone disease is prevalent in
middle-aged and older adults.
Integrated implants are often indicated for
patients with a history of severe bone loss.

The clinical success and longevity of
endosteal dental implants as load bearing
abutments are controlled largely by the
mechanical setting in which they function.
The treatment plan is responsible for the
design, number, and position of the implant.

Unique mechanisms of bone adaptation have
evolved to maintain structural integrity, repair
fatigue damage, and provide a continuous
source of metabolic calcium.

Modeling involves individual uncoupled sites
of bone formation or resorption that change
the shape or form of a bone. This is the
principal mechanism for adapting osseous
structure to functional loading.

Remodeling is the mechanism of bone
turnover. It involves coupled sequences of
cell activation (A), bone resorption (R) and
bone formation (F). The duration of the ARF
remodeling cycle (sigma) is about 4 months in
humans.

Modeling is the principal means of skeletal
adaptation to functional and therapeutic loads.
Relatively modest changes in the distribution
of osseous tissue along cortical bone surfaces
can dramatically change the overall load
bearing capability.

By a mechanism of focused bone resorption
and formation events, trabeculae can form,
reorient and change in size as a result of
"micromodelling" to resist functional loads
optimally.

A good example of this process is the network
of secondary tissues that forms in the marrow
cavity to support an integrated fixture.

Under most circumstances, cortical bone
remodels at a rate of about 2-10% per year.
Since only a portion of the cortex is in the
metabolic fraction. The remodeling rate for
cortical bone is usually 3-10 times less than
for adjacent trabecular bone (metabolic
fraction).

This complex interaction involves not only
biomaterial and biocompatibility issues, but
also the alteration of the mechanical
environment that occurs when placement of
an implant disturbs the normal physiologic
distribution of forces, fluids, and cell
communication.

In 1977, Branemark & coworkers published the first
long-term follow up study on dental implants, thus
providing the scientific foundation of today's implant
treatment. The successful use of jaw bone anchored
(osseointegrated) titanium dental implants to retain
prosthetic constructions in the rehabilitation of the
edentulous and partially edentulous patients has been
well documented in several publications.

The original two-stage surgical protocol using
a two-piece implant pillar was applied. The
main reasons for this approach have been to
Minimize the risk of infection
Prevent apical down growth of mucosal
epithelium, and
Minimize the risk of undue early loading
during the initial healing period.

In addition, a stress-free healing period of 3 to
6 months before the mucosa piercing
abutments are placed and the supra-
construction is connected to the implants was
emphasized to predict a successful treatment
outcome. Such a stress free period was even
considered to be an ultimate prerequisite to
achieve proper osseointegration.

In other words, early stress on the implants
was thought to jeopardize the osseointegration
process.

Over the years, however, the high level
of predictability in implant therapy has
resulted in a re-evaluation of the original
Branemark protocol for implant placement.
Schroeder & coworkers were the first to show
the possibility to achieve demonstrated
successful clinical treatment outcome using
the one- stage surgical protocol with the
Branemark system.

Similar successful clinical treatment
outcomes, in the edentulous as well as the
partially edentulous situation, have been
reported using one-piece implants (ITI,
Straumann) placed according to the original
one-stage surgical protocol.

In several clinical studies the original dentures most
often were adjusted and relined by a soft tissue
conditioner 10 to 12 days following implant
placement to minimize unfavorable functional
loading, i.e., undue early loading. However, it has to
be anticipated that implants placed according to a
one-stage surgical procedure to some extent will be
directly and unpredictably loaded during function in
the initial healing period via the adjusted and relined
denture.

Furthermore, such loading might be
unfavorable for the implants, as the
deformation pattern of complete denture base
material would cause micromovements.
In other words, "an initial and direct loading
of implants piercing the mucosa via the
adjusted and relined denture obviously does
not jeopardize a proper osseointegration of the
fixtures".

Such a statement is in agreement with clinical
observations reported by Henry & Rosenberg,
who concluded that “controlled immediate
loading” of adequately installed, non-
submerged implants, by reinsertion of a
modified denture, does not appear to
jeopardize the process of osseointegration in
the anterior mandible.

" Similar observations were reported by
Cooper et al. Furthermore, Becker et al
concluded that" one-step Branemark
implants may be considered a viable
alternative to two-step implants."

In former days, it was postulated "too-early loading
of an implant leads to interfacial formation of fibrous
tissue instead of bone".
Others claimed "controlled immediate loading does
not appear to jeopardize the process of
osseointegration".
Today's knowledge indicates that the degree of
micromotion at the bone-implant interface during the
initial healing phase and it may be not premature
loading.

Premature loading
leads to implant
movement
The end result
“Soft tissue
interface”
“Bony interface”

As favorable loading conditions of tooth
abutments are obtained via a rigid fixed
appliance, it is reasonable to believe that
successful treatment outcomes can be reached
also when rigid fixed supraconstructions are
connected to implants soon after implant
placement.

To reduce the period during which the
individual implants are exposed to direct and
unpredictable loading, splinting of the
individual implants through a rigid fixed
device will most certainly decrease the
micromotion at the bone-implant interface,
thus facilitating proper bone healing
(osseointegration).

Based on the available information, Randow et al
believed it to be of interest to compare the
rehabilitation of edentulous mandibles by fixed
supraconstructions connected to implants placed
according to either an early loaded one-stage surgical
procedure or the original two-stage concept, with the
working hypothesis that there are no differences
between the two methods concerning the treatment
outcome.

A total of 88 implants (16 patients) were
placed according to the one-stage protocol
and loaded via a fixed appliance within 20
days. The implants placed according to the
original protocol were loaded about 4 months
following placement. At the time of delivery
of the fixed appliances, all patients were
radiographically examined, an ex-amination
that was repeated at the 18-month follow-up.

The analysis of the radiographs revealed that
during the 18-month observation period the
mean loss of bone support amounted to about
0.5 mm around the implants, irrespective of
early loading. All implants were at all
observation intervals found to be clinically
stable.

The authors concluded that it is “possible to
successfully load titanium dental implants
immediately following installation via a
permanent fixed rigid cross-arch
supraconstruction”. However, such a
treatment approach has so far to be strictly
limited to the inter-foramina area of the
edentulous mandible.

Schnitman and coworkers reported on 63
Branemark implants placed in 10 patients. Of
these 63 implants, 28 were placed and
"immediately loaded to support an interim
fixed bridge." The remaining 35 implants
were placed according to the 'original two-
stage protocol, osseointegrated properly, and
are still in function. Of the 28 implants
immediately loaded, four failed.

In other words, the survival rate for the
immediately loaded implants was found to be
about 85%.

Early implant failure
Early crestal bone loss
Intermediate to late implant failure
Intermediate to late implant bone loss
Screw loosening (abutment and prosthesis coping)
Uncemented restoration
Component fracture
Porcelain fracture
Prosthesis fracture
Periimplant disease (from bone loss)

The surgical and prosthetic protocols for the
development of a predictable direct bone-to-
implant interface with root-form implants
were developed and reported by Branemark
et al.

About 25 years ago, Branemark et al (1977)
published the first long-term follow-up on oral
implant, providing the scientific foundation of
modern dental implantology. The predictability of
implant integration according to Branemark and
collaborators was obtained by adherence to a strict
surgical and prosthodontic protocol. One of the most
emphasized requirements was a stress-free healing
period of 3-6 months, making implant treatment
lengthy.

Presently however, early and immediate
loading protocols are reported by an
enhancing number of clinical (Chiapasco et
al 1997, Schnitman et al 1997, Tarnow et al
1997) and experimental publications.

Following their 10-year clinical experience,
recommendations ensuring durable
osseointegration of dental implants were set.
The most important were:

 Use of sterile conditions as "in a fully equipped
operatory"
 Use a mucobuccal incision and avoid a crestal one
 Use of an atraumatic surgery involving low-speed
drilling
 Use of a biocompatible material i.e. titanium
 Use of titanium ancillary
 Use of a 2-stage procedure
 Use of a stress-free healing period of 3-6 months before
loading
 Avoid X-radiographs before the end of the healing
period
 Use of acrylic occlusal contact surfaces

Early loading was identified as a detrimental factor
for osseointegration' by Branemark et al During 'the
course of their clinical trial (Branemark et al 1977).
BUT TODAY THE SCENARIO HAS CAHNGED
TO LOADING AND IMMEDIATE LOADING.

Brànemark's loading protocol
Flush with bone level, cover with gingiva.
Final prosthesis after 3 to 6 months of initial healing.
Soft/ hard diet.

Progressive loading
Flush with bone level, covered with gingiva.
Provisional prosthesis brought progressively into
occlusion, depending upon bone density.
Soft/ hard diet.

Non submerged single stage protocol
Non-submerged implants, flush within 1-2 mm of
gingival level
Soft diet
Immediate functional loading
Temporary restoration fitted on the same day as
surgery, in occlusion
Soft diet

Immediate non-functional loading
Temporary restoration fitted on the same day as
surgery, not in occlusion
Soft diet
Early loading
Final crowns within 3 weeks from surgery, in
occlusion
Soft/ hard diet

Delayed loading
Implant subjected to loading after more than 6 weeks
post surgery
Soft/ hard diet
Anticipated loading
Provisional prosthesis is fitted after about 2 months
after surgery
Soft/ hard diet

Time interval
Diet
Occlusal material
Occlusal contacts
Prosthesis design

The masticatory force for soft food is about
10 psi. This diet not only minimizes the
masticatory force on the implants but also
decreases the risk of temporary restoration
fracture or partially decemented restoration.
Either of these consequences can overload an
implant and cause unwanted complications.

The diet protocol should not be overlooked
during the restorative procedure because most
dentists have observed the fracture of acrylic
prostheses with harder foods and greater
occurrence of decemented restorations when
they ignore type of diet during the transitional
prosthesis stages.

After the initial delivery of the final
prosthesis, the patient may include meat in the
diet, which requires, about 21 psi in bite
force. The final restoration can bear the
greater force without risk or fracture or
decementation.

After the final evaluation appointment, the
patient may include raw vegetables, which
require an average 27 psi of force. A normal
diet is permitted only evaluation of the final
prosthesis function, occlusion, and proper
cementation.

Occlusal material:
The occlusal material may be varied to load
the bone-to-implant interface gradually. During the
initial steps, the implant has no occlusal material
over it. At subsequent appointments, the dentist
chooses acrylic as the occlusal material, with the
benefit of a lower implant force than metal or
porcelain.

Either metal or porcelain can be used as the
final occlusal material. If para function or
cantilever length cause concern relative to the
amount of force on the early implant bone
interface, the dentist may extend the softer
diet and acrylic restoration phase for several
months. In this way, the bone has a longer
time to mineralize and organize to
accommodate the higher forces.

Occlusion:
The dentist gradually intensifies the occlusal
contacts during prosthesis fabrication. No occlusal
contacts are permitted during initial healing. The
first transitional prosthesis is left out of occlusion in
partially edentulous patients.

The occlusal contacts then are similar to those
of the final restoration for areas supported by
implants. The occlusal contacts of the final
restoration follow the implant-protective
occlusion concepts.

Prosthesis design:
During initial healing, the dentist
attempts to avoid any load on the implants,
including soft tissue loads. The first
transitional acrylic restoration in partially
edentulous patients has no occlusal contacts.

Its purpose is to splint the implants together,
to reduce stress by the mechanical advantage,
and to have implants sustain masticatory
forces solely from chewing. In the second
acrylic transitional restoration, occlusal
contacts are placed on the implants with
occlusal tables similar to the final restoration
but with no cantilevers in nonesthetic regions

Indirect impression transfer coping

Transitional restoration –
no occlusal contacts

Abutments in position
Radiographic confirmation
Transitional prosthesis in place

Metal substructure with
metal occlusals

Second transitional prosthesis with
occlusal contact

Final prosthesis in place Radiographic
evaluation

On day of surgery Transfer impression copings
Custom impression tray Addition silicone impression
Master cast Transitional restoration

Immediate functional loading protocol
Clinical trials successful osseointegration
(95-100% success rate- Completely edentulous patients)
 Bone quality is good
Functional forces are controlled
More favourable in mandible compared to maxilla
Over loading – Stress concentration, undermining bone
resorption without apposition (Branemark 1984)

The other protocol for immediate occlusal loading of
dental implants initially loads all of the implants
inserted. The implants are splinted together, which
decreases the stresses on all the developing
interfaces and increases the stability, retention, and
strength of the transitional prosthesis during the
initial haling phase.

Often additional implants also are used with this
technique compared with the traditional healing
method.
The immediate load concept provides all the
advantages of the one-stage surgical approach. In
addition, implants are splinted together, which
decreases the risk of overload because of a greater
surface area and improved biomechanical
distribution.

Over the last few years, authors have
reported on immediate loading in the
completely edentulous patient, with 95% to
100% success rates.

However, the influence of immediate loading
on crestal bone loss has few animal and
clinical reports so as to compare the
differences of immediate loading to a more
traditional bone healing time with no
functional load.

High success rates from immediately loaded
implants in humans were first documented in the
middle 1980s, when the 1-stage implant protocol
gained popularity.
Babbush et al (1986) reported a cumulative success
rate of 88% on 1739 immediately loading TPS
implants. Subsequently, many authors have shown
the possibility of loading implants immediately.

Bone Microstrain:
Loaded bone changes its shape. This change may be
measured as strain. Microstrain conditions 100 times
less than the ultimate strength of bone may trigger a
cellular response. Frost has developed a microstrain
language for bone based on its biological response at
different microstrain levels. Bone fractures at 10,000
to 20,000 microstrain units.

However, at levels of 20% to 40% of this
value, bone already starts to disappear or form
fibrous tissue and is called the pathologic
overload zone. The ideal microstrain for bone
is called the physiologic or adapted zone. The
remodeling rate of the bone in the jaws of a
dentate canine or human being that is in the
physiologic zone is about 40% each year.

At these levels of strain the bone is allowed to
remodel and remain as an organized, mineralized
lamellar structure. This is called the ideal load-
bearing zone for an implant interface. The mild
overload zone corresponds to an intermediate level
of microstrain between the ideal load bearing zone
and pathologic overload. In this strain region, bone
begins a healing process to repair micro fractures,
which are often caused by fatigue. Histologically, the
bone in this range is called reactive woven bone.

Rather than the surgical trauma causing this
accelerated bone repair, the microstrain
causes the trauma from overload. In either
condition, the bone is less mineralized, less
organized, weaker, and has a lower modulus
of elasticity.

One goal for an immediately loaded
implant/prosthesis system is to decrease the
risk of occlusal overload and its resultant
increase in the remodeling rate of bone. Under
these conditions the surgical regional
acceleratory phenomenon may replace the
bone interface without the additional risk of
biomechanical overload.

When strain is placed on the horizontal
axis and stress is positioned on the vertical
axis, the relationship between these two
mechanical indexes results in the flexibilities
or modulus of elasticity of a material. Hence
the modulus conveys the amount of
deformation in a material (strain) for a given
load (stress) level.

The lower the stress applied to the bone (force
divided by the functional surface area that
receives the load), the lower the microstrain in
the bone. Therefore one method to decrease
microstrain and the remodeling rate in bone is
to provide conditions that increase functional
surface area to the implant-bone interface.

The surface area of load may be increased in a
number of ways:
implant number,
implant size,
implant design,
and implant body surface conditions.
The force to the prosthesis also is related to the strain
and may be altered in magnitude, duration, direction,
or type. Methods that affect the amount of force
include patient conditions; implant position, and
direction of occlusal load.

Increase Surface Area:
Implant number: The dentist may increase the
functional surface are of occlusal load at an implant
interface by increasing implant number. Hence rather
than three to five implants to support a fixed
restoration, use of additional implants when
immediate loading is planned is more prudent.
Immediate loading reports in the literature with the
lowest percentage survival correspond to fewer
implants loaded.

More implants typically are used in the
maxilla (8 to 12) compared with the mandible
(5 to 9). This approach helps compensate for
the less dense bone and increased directions of
force often found in the upper arch.

Implant size:
The dentist also may increase the surface area of
implant support by the size of the implant. The
length of the implant in most systems increases in
increments of 2 to 4mm. Each 3 mm increase in
length can improve surface area support by more
than 20%. However, the benefit of increased length
is not found at the crestal bone interface but rather in
initial stability of the bone-implant interface.

Implant body design:
The implant body design should be more specific for
immediate loading because the bone has not had
time to grow into recesses or undercuts in the design
or attach to a surface condition before the application
of occlusal load. For example, a press-fit implant
with a cylinder design does not have bone
integration the day of implant placement.

An implant body with a series of horizontal
plates that is tapped or pressed into place does
not have bone present between the plates the
day of surgical placement. Macrospheres on
an implant surface do not have bone present
within or around the porous surface of the
implant the day of implant placement.

For a threaded implant, bone is present
in the depth of the threads form the day of
insertion. Therefore the functional surface
area is greater during the immediate load
format. The number of the threads also affects
the amount of area available to resist the
forces during immediate loading.

The greater the number of threads, the greater
the functional surface area at the time of
immediate loading. Some threaded implants
have a 1.5 mm distance between the threads
(e.g., BioHorizons dental implants). The
smaller the distance between the threads, the
greater the thread number and corresponding
surface area.

Implant thread design may affect the
bone turnover rate (remodeling rate) during
occlusal load conditions. For a V-shaped
thread design, a 10 times greater shear force is
applied to bone compared with a square
thread shape. Bone is strongest to
compression and weakest to shear loading.
Compressive forces decrease the microstrain
to bone compared with shear forces.

Hence the thread shape and implant design
may decrease the early risks of immediate
loading while the bone is repairing the
surgical trauma.

Implant design affects functional surface area
more than implant size. A larger-diameter cylinder
implant has less surface area than a smaller-diameter
threaded implant. As a result, thread implants present
considerable advantages compared with pres-fit
implants for immediate load protocols because their
design features do not require histologic integration
to resist loads and they have greater surface are to
resist occlusal forces.

A tapered implant design presents some
disadvantages for immediate load applications.
When the tapered osteotomy is prepared using
tapered drills, the implant does not engage the bone
physically until the implant is seated almost
completely into the bone site. This reduces the initial
fixation. In addition, the tapered implant has less
overall surface areas compared with a parallel-
walled, threaded implant.

However, few clinical trials have compared
immediate loading with different implant thread
design and tapered implant bodies in the completely
edentulous patient. The short-term clinical reports
indicate a high success rate, regardless of implant
design. As a result, overall shape and thread
geometry apparently may not be the most important
aspect for immediate occlusal load survival. Implant
number, implant position, and patient factors most
likely are more relevant components of success.
Future studies in this area certainly are needed.

Implant surface conditions:
Implant surface conditions may affect the rate of bone
contact, lamellar bone formation, and the percentage of bone
contact. The surface condition that allows bone formation in
greatest percentage, higher bone-implant contact percentage
with higher mineralization rate, and fastest lamellar bone
formation would be of benefit in immediate loading. These
factors have been noted in delayed and immediate loading
environments with hydroxyapatite coatings.

Implant design and surface condition are
independent issues that use a different
mechanism to reduce the risk of overloading.
For example, a hydroxyapatite surface may be
applied to a cylinder or a threaded implant.
The thread design would be more beneficial
to an immediate load application.

Yet the hydroxyapatite or roughened surface
also may be of benefit during the following
healing period, especially at the 3 to 5 weeks
when the bone is weakest. The majority of
clinical studies have been made with threaded
implant designs.

Surface conditions are more difficult to
ascertain in the literature and have included a
smooth machined surface, a roughened
titanium plasma spray surface, and a
hydroxyapatite surface condition without a
clear deference in clinical survival. However,
evidence is increasing that the machine
surface condition is inferior in softer bone
types.

Decreased Force Conditions:
The dentist may evaluate forces by
magnitude, duration, duration, and type. The
dentist should reduce conditions that magnify
the noxious effects of these forces.

Patient factors:
The greater the occlusal force applied to the
prosthesis. The greater the stress at the implant-bone
interface and the greater the strain to the bone.
Therefore force conditions that increase occlusal
load increase the risks of immediate loading.
Parafunction such as bruxism and clenching
represents significant force factors because
magnitude of the force is increased, the duration of
the force is increased, and the direction of the force
is more horizontal than axial to the implants with a
greater shear component.

Occlusal load direction:
The occlusal load direction may affect
the remodeling rate. An axial load to an
implant body maintains more lamellar bone
and has a lower remodeling rate compared
with an implant with an offset load..

Therefore one should eliminate posterior
cantilevers in the immediate-load transitional
restoration because they magnify the
detrimental effects of force direction.

Implant position:
Dental implants have been used widely to
retain and support cross-arch fixed partial dentures.
Implant position is often as important as implants
supporting three teeth is often as important as
implant number. For example, elimination of
cantilevers on two implants supporting three teeth is
recommended, rather than positioning the implants
next to each other with a cantilever.

The cross-arch splint forming an arch is an
effective design to reduce stress to the entire
implant support system. Hence the splinted
arch position concept for the completely
edentulous is advantageous for the
immediate-load transitional prosthesis.

Implant position is one of the more
important factors in immediate loading for
completely edentulous patients. The mandible
may be divided into three sections around the
arch:
the canine-to-canine area
and the bilateral posterior sections.

The maxilla requires more implant
support than the mandible because the bone is
less dense and the direction of force is outside
of the arch and the force is outside of the arch
in all the eccentric movements. The maxilla is
divided into at least four to five sections,
depending on the intensity of the force
conditions and the shape of the arch.

The minimum four sections are the bilateral
canine area and the bilateral posterior regions.
When force factors are greater, the regions of
the maxilla are increase to five and include
the incisor area. At least one implant should
be inserted into each maxillary section and
splinted together during the immediate-
loading process.

Concerns have been raised regarding cross-
arch splinting in the mandible because of mandibular
flexure and torsion distal to the mental foramens.
Clinical reports indicate the acrylic used in the
transitional prosthesis is flexible enough to alleviate
these concerns. However, the final restoration should
be fabricated in at least two independent sections
when implants are placed in both posterior
quadrants.

Mechanical properties of bone:
The modulus of elasticity is related to bone
quality. The less dense the bone, the lower the
modulus. The amount of bone-implant contact
is also less for less-dense bone. The strength
of the bone also is related directly to the
density of the bone.

The softer the bone, the weaker the bone
trabeculae. In addition, the remodeling rate of
cortical bone is slower than that of trabecular
bone. As such, the cortical bone is more likely
to remain lamellar in structure during the
immediate loading process compared with
trabecular bone.

Bone grafting must depend on several factors
to be predictable. Adequate blood supply and a lack
of micromovement are two important conditions.
The developing bone is woven bone and more at risk
of overload. The bone graft in the region of the
implant body may lead to less fixation and lower
initial bone-implant contact percentages. Bone
augmentation is more predictable when soft tissue
completely covers the graft (and membranes when
present).

All of these conditions make bone grafting, implant
insertion, and immediate loading more at risk.
Therefore the suggestion is that implants that are
immediately loaded be placed in an existing bone
volume adequate for early loading and the overall
proper prosthetic design. Bone grafting, before
implant placement and immediate loading, is
suggested when inadequate bone volume is present
for proper reconstructive procedures.

In cases where early loading is deemed appropriate, Tarnow
has suggested a set of guidelines to help achieve clinical
success:
Immediate loading should be attempted in edentulous arches
only to create cross-arch stability.
Implants should be at least 10 mm long.
A diagnostic wax-up should be used for template and
provisional restoration fabrication.

A rigid metal casting should be used where possible.
A screw-retained provisional restoration should be used
where possible.
If cemented, the provisional restoration should not he
removed during the 4- to 6-month healing period.

All implants should be evaluated with Periotest (a
measure of the degree of resistance to
perpendicular force) at stage 1, and the implants
that show the least mobility should be utilized to
provide resistance to rotational forces.
The widest possible anterior- posterior
distribution of implants should be utilized to
provide resistance to rotational forces.
Cantilevers should be avoided in the provisional
restorations.

The emergence of a 1-stage early loading
protocol does not imply that submersion is no
longer necessary, but rather suggests that is
not always essential. The 2-stage procedure
remains the treatment of choice. However,
under the right circumstances successful early
loading can reduce the length of prosthetic
rehabilitation.

Success criteria of implants
Schuitman and Schulman criteria (1979)
1) The mobility of the implant must be less than 1mm when
tested clinically.
2) There must be no evidence of radiolucency
3) Bone loss should be less than 1/3rd
of the height of the
implant
4) There should be an absence of infection, damage to structure
or violation of body cavity, inflammation present must be
amneable to treatment.
5) The success rate must be 75% or more after 5 years of
functional service.

Albrektson and Zarb G (1980)
1) The individual unattached implant should be immobile when
tested clinically
2) The radiographic evaluation should not show any peri - implant
radiolucency
3) Vertical bone loss around the fixtures should be less than
0.2mm annually after first year of implant loading.
4) The implant should not show any sign and symptom of pain,
infection, neuropathies, parastehsia, violation of mandibular
canal and sinus drainage.
5) Success rate of 85% at the end of 5 year observation period and
80% at the end of 10 year service.
6) Implant design allow the restoration satisfactory to patient and
dentist. - Smith and Zarb (1989)

The patient demand for esthetics is increasing day by
day and the replacement of teeth immediately
following extraction is attaining popularity. In this
respect even the replacement of teeth immediately
following the implant placement has to be considered
as a serious issue. Therefore it is very much essential
to know the requirements and bone responses to the
occlusal loading in the healing period. Also the
modifications in treatment plan to achieve the success
of restoration are necessary.

Carl E Misch: Contemporary Implant Dentistry.
Sumiya Hobo: Osseointegration and Occlusal
Rehabilitation.
W E Roberts: Fundamental principles of bone
physiology, metabolism and loading.

Osseointegration in clinical dentistry – Branemark, Zarb,
Albrektsson
Endosseous implants for Maxillofacial reconstruction – Block
and Kent
Implants in Dentistry –Block and Kent
Dental and Maxillofacial Implantology – John. A. Hobkrik,
Roger Watson

DCNA, 1986 vol. 30:151-174
Int J Oral Surg, 1981 vol. 10: 387-416
Int J Oral Maxillofac Implants, 1991 vol. 6: 405-412
Clin Oral Impl Res, 2000 vol.11: 12-25
Clin Oral Impl Res, 2003 vol.14: 515-527
J Periodontol, 1997 vol. 68: 591 597

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