BHUVANESH KUMAR .D.V

IMPLANT LOADING

IMMEDIATE

LOADING OF

IMPLANTS

Table of Contents

Terminologies

Immediate loading

Advantages, and Disadvantages,

Indications and Contraindications

Rationale of immediate loading

Factors influencing them

Immediate Occlusal Loading : An implant isplaced with adequate primary stability itscorresponding restoration has full centricocclusion in maximum intercuspation andmust be placed within 48 hours postsurgery.

• Early loading : Early Loading Protocol is wherein a

provisional prosthesis was inserted at a subsequent

visit prior to osseointegration (between 2 days to 3

months after surgery). Though the implants, were not

loaded the same day, this protocol directly challenged

the healing process by introducing loading during

wound healing. A fundamental goal of early loading is

improving bone formation in order to support occlusal

loading at two months.

• Conventional Loading Protocol : is the originalhealing periods as envisaged by different implantsystems, typically after 12 to 24 weeks.

• Delayed Loading Protocol : is one in which thehealing period was extended due to thecompromised host site conditions and, typically,prosthesis connection is later than the conventionalhealing period.

• Occlusal loading : means that the immediately orearly loaded prosthesis is in contact with theopposing dentition.

• Non-occlusal loading : means that theimmediately or early loaded prosthesis is not incontact with the opposing dentition. It should berecognized that in non-occlusal loading, forces onimplants could be generated through the oralmusculature and food bolus.

• Immediate Non Occlusal Loading : An implant is

placed with adequate primary stability but is not in

functional occlusion. These implant restorations are

essentially used for esthetic purposes, frequently in

single tooth or short span applications. Immediate

non occlusal loading is often performed to provide

the patient with aesthetic or psychological benefit

during implant therapy, particularly when a

provisional removable prosthesis is undesirable

during the healing period.

Evolution of the Concept of Implant loading

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

• BRANEMARK’S ORIGINAL PROTOCOL :

• 3 - 6 months

• Osseointegration

4-6 Months

Period

Tooth ExtractionStage I Surgery

or Implant Placement

Stage II Surgery or

Prosthesis Placement

A non submerged, one stage surgery where loading of implant with provisional restoration is done at the same appointment or shortly thereafter.

Immediate loading

Successful reports of early and immediate loading

Presently, early and immediate loading protocols are reported by an enhancing number of clinical (Schnitman et al 1990 , Henry et al 1994, Tarnow et al 1997) and experimental publications.

INDICATIONS• Adequate bone quality ( type I, II and III)

• Sufficient bone height ( i.e. approximately 12mm )for a minimum length of 10 mm implant

• Sufficient bone width ( i.e. approximately 6 mm)

• Ability to achieve an adequate antero posteriorspread between the implants. A poor AP spreaddecreases the mechanical advantage gained bysplinting and the ability to cantilever the restoration

CONTRAINDICATIONS

• Poor systemic health

• Severe parafunctional habits

• Bone of poor quality ( e.g. type IV)

• Bone height less than 10 mm

• Bone width less than 6 mm

• Inability to achieve an adequate AP spread

Rationale for Implant Immediate Loading

• Thermal injury & Surgical trauma- MINIMIZE

• Implant osteotomy & implant insertion- lamellar bone

becomes woven bone

• The interface weakest, at risk of overload at 3 to 6 weeks

after surgical insertion- failure

• Temp : 38 ˚C – 41 ˚ C (Shawaray et al 2002)

• Slow intermittent pressure with irrigation and sharp drills

I

Bone remodelling

A rationale for immediate loading- to reduce the risk of fibrous tissue

formation & to minimize woven bone formation and promote lamellar

bone maturation to sustain occlusal load.

• Bone is loaded by the implant prosthesis, the interface begins

to remodel again, the trigger for this process is strain, not the trauma

• Remodeling - bone turnover

• Reactive bone- the woven bone

formed from the mechanical response

Guidelines for immediate loading (Misch &Scortecci)

to reduce stress and resulting micro strain at thedeveloping interface.

Bone Microstrain:

Loaded bone changes its shape. This change may bemeasured as strain.

Frost has developed a microstrain language for bonebased on its biological response at different microstrainlevels.

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.

Bone fractures at 10,000 to 20,000 microstrain units. (1-

2% strain)

The ideal microstrain for bone is called the physiologic or adapted zone.

The mild overload zone corresponds to an intermediate level of microstrainbetween 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.

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

Surface area factors :

1. Implant number:

8 or more (splinted) maxillary arch

6 or more (splinted) the mandible

2. Implant size: Larger-diameter

Each 3 mm increase in length- 20% moresurface area.

Initial stability

wider root form implants provide greaterbone contact

implant diameter also varies according toregion

3. Implant design :

more threads ( Biohorizon -0.4mm, ITI -1.5 mmpitch)

deeper threads (Sterioss, NB -0.22mm, Biohorizon-0.44mm)

square or plateau-shaped threads

Threaded implant – more depth of bone from day 1.

4. Implant surface condition :

Hydroxyapatite-coated ( D4).

Rough versus smooth or machine

surface condition implants

Force factors :

1. Patient condition: Parafunction, crown height

, muscular dynamics

Parafunctional forces like clenching and

bruxism-

significant magnitude and duration of forces

with more shear component (horizontal

forces)

2. Implant position:

• maxilla- bilateral canine position & bilateral molar position

• mandible- at least three implants, one in the anterior and one in each posterior region

• Increased anticipation of forces –Increase the implant number

3. Occlusal load direction

• Narrow occlusal tables and no posterior offset loads

• Long-axis loads to the implant bodies • No posterior cantilevers should exist

on transitional restorations

FACTORS INFLUENCING IMMEDIATE LOADING

The majority of immediate implant loading studies reported similar success rates when compared to the traditional 2-stage approach.

Data from the current available literature already suggest that several factors may influence the results of immediate implant loading.

These could be divided into the following four categories:

1) Surgery-related factorsPrimary implant stabilitySurgical Technique

2) Host- related factorsBone quality and quantityWound healing

3) Implant-related factorsImplant design confiqurationImplant surface coatingImplant length

4) Occlusion-related factors.Quality and quantity of forceProsthetic design

SURGERY-RELATED FACTORS

• Primary Implant Stability

Of all factors involved, Primary Stability seems to

be the most important determining factor on

immediate implant loading.

Functional loading placed on an immobile implant

is an essential ingredient to achieve

osseointegration (Roberts et al. 1984)..

If an implant is placed in the soft spongy bone with poor initial stability, it often results in the formation of connective tissue encapsulation, similar to the pseudoarthrosis observed in an unstabilized fracture site

Micromovements of more than 100 µm are sufficient

to jeopardize healing with direct BIC.

Micromotions at the bone–implant interface beyond

150 µm resulted in fibrous encapsulation instead of

osseointegration.

It can be further speculated that these movements

would be detrimental in cases with immediate

implant loading.

• In summary, when primary stability is

achieved and a proper prosthetic

treatment plan is followed, immediate

functional implant loading is a feasible

concept.

• However, if the primary fixture stability

cannot be achieved or is questionable, it

is strongly recommended to follow a

conventional treatment protocol including

an adequate healing time before loading.

Surgical Technique

Gentle surgical placement is also a key element for

implant success regardless of the applied treatment

protocol.

Excessive surgical trauma and thermal injury may lead

to osteonecrosis and result in fibrous encapsulation

of the implant. 1988).

Heat generated during drilling without adequate

cooling is associated with bone damage.

It has been shown that a temperature over

47˚C for 1min causes ‘heat necrosis’ in the

bone (Eriksson & Albrektsson 1983).

Without irrigation, drill temperatures above

100 ˚ C are reached within seconds during

the osteotomy preparation, and consistent

temperatures above 47 ˚ C are measured

several millimeters away from the implant

osteotomy (Yacker & Klein 1996).

In addition, it is critical for the success of implants

that adequate load be placed on the drill during

the preparation of osteotomies.

It has been demonstrated that independently

increasing either the speed or the load caused an

increase in temperature in bone.

Interestingly, increasing both the speed and the

load together allowed for more efficient cutting

with no significant increase in temperature

(Brisman 1996).

Other factors related to heat generated

into bone include amount of bone

prepared (Eriksson et al. 1984a), drill

sharpness and design (Matthews & Hirsch

1972; Wiggins & Malkin 1976; Eriksson et

al. 1984b), depth of the osteotomy

(Babbush & Shimura 1993; Haider et al.

1993), and variation in cortical thickness

(Hobkirk & Rusiniak 1977; Eriksson &

Albrektsson 1984

It is shown that implant surgery generates

micro-fractures in the surrounding bone,

especially when press-fitting is intended. These

fractures heal according to the following

cascade (Schenk & Hunziker1994) :

angiogenesis,

osteoprogenitor cell migration,

woven bone scaffold formation,

When a proper surgical/prosthodontic technique

is followed, the crestal bone loss around

immediately loaded implants seems to be in the

normal range when compared to a submerged

protocol.

Crestal bone loss was found to be 0.14mm in

immediately loaded implants vs. 0.07mm in the

delayed approach in a period between 6 and 18

months (Ericsson et al. 2000a).

• Cooper et al. (2001) reported a mean change in marginal bone level of 0.4mm at 12 months in single early loaded implants

HOST-RELATED FACTORS

Bone quality & quantity

Histological data on immediately loaded implants have demonstrated not only a direct bone interface contact, but also a favorable bone quality around the fixtures.

Clinically, host bone density plays an important role in determining the predictability of the immediate implant loading success.

An implant placed in compact dense

bone is more likely to ensure initial

stability and, hence, better able to

sustain such immediate forces.

Resonance frequency analysis indicated that

implants are as stable at the time of placement

as when measured at 3–4 months postsurgery,

when placed into dense bone.

These results support the concept of direct

loading of implants when inserted in the

mandibular interforaminal regions. Therefore,

this homologous, dense bone type may

present several advantages for immediate

loading implant dentistry.

The cortical lamellar bone may heal with

little interim woven bone formation,

ensuring good bone strength while healing

next to an endosteal implant (Roberts et al.

1987; Roberts 1993).

In addition, its fine porosity (10%) favors

better mechanical interlocking compared

to soft cancellous bone.

As mentioned earlier, fine trabecular

bone presents the most difficult

endeavor to obtain rigid fixation, no

matter which implant is used.

For the reasons just mentioned, this

type of bone may be unsuitable for

immediate loading implant

techniques

Within the limited available information, it appears that primary stability, more than the arch (anatomic) location, may be the fundamental requirement for immediate implant loading techniques.

On the other hand, there has been no unanimous protocol to be followed regarding bone density and number of implants, or type of prosthesis to be used in immediate loading cases.

MECHANICAL PROPERTIES OF BONE

The modulus of elasticity is related to bone

quality. The less dense the bone, lower the

modulus. The amount of bone- implant contact is

also less – dense bone.

The strength of the bone is directly related to

density of the bone. Softer the bone, weaker the

bone trabeculae.

Wound Healing

Metabolic diseases that directly affect bone metabolism such as osteoporosis/osteopenia or hyperparathyroidism may significantly influence implant wound healing.

Human trials have demonstrated that dental implant placement in patients diagnosed with osteoporosis may be successful over a period of many years if an extended healing period is advocated.

So far, no attempt has been made in loading

implants immediately in patients who are

diagnosed with systemic diseases such as

diabetes and hyperparathyroidismas well as

smokers.

A similar situation is also true for patients who

have undergone radiation therapy. Therefore, it

is strongly suggested to follow the standard 2-

stage protocol or even utilize longer periods of

healing in patients diagnosed with these

disorders.

The same standard guidelines are

suggested to be used in smokers or

patients under radiation therapy on the

oral cavity, until future research proves

otherwise.

Prior to surgery, a medical consultation

and thorough explanation of possible risks

to patients should be mandatory.

Under optimal conditions (atraumatic surgery), it has

been demonstrated that only after 6 weeks of

implant placement, lamellar bone was present at or

near the implant surface (Roberts et al. 1984).

The surrounding bone heals according to the cascade

mentioned earlier: angiogenesis, osteoprogenitor cell

migration, woven bone scaffold formation,

deposition of parallel- fibered or lamellar bone, and

secondary bone remodeling.

In conclusion, it can be speculated that

immediate loading of dental implants

may accelerate bone formation, but it

is also imperative to state that primary

stability is essential for this process to

occur.

IMPLANT-RELATED FACTORS

Implant Design/Configuration

Implant configuration has long been considered

as an essential requirement for implant success.

As a general concept, the screw type implant

design develops higher mechanical retention as

well as greater ability to transfer compressive

forces (Skalak 1985; Wolfe & Hobkirk 1989;

Lefkove & Beals 1990; Randowet al. 1999

The screw design not only minimizes micro-

motion of the implant but also improves the

initial stability, the principal requirement for

immediate loading success.

Additionally, the thread increases surface area

(Misch 1999). Studies have shown the absence

of fibrous tissues at the interface of

screwshaped implants, even if they are loaded

immediately after insertion (Skalak 1985; Wolfe

& Hobkirk 1989).

Hence, due to its mechanical retention

properties, it is generally recommended to use

threaded-type implants for immediate loading

cases.

However, the cylinder type implant would

appear contraindicated for immediate or

early loading regimens due to lowering of

primary stability and less resistance to

vertical movement and shear stress.

Implant Surface Coating

Rough implant surfaces render a significant increase

of BIC (Buser et al. 1991; Wennerberg et al. 1995;

Trisi et al. 1999).

The shear strength of implants with a rough surface was

shown to be about 5 times as high as that of

implants with a smooth surface (Li et al. 1999).

In addition, greater forces are required to remove

implants with a rougher surface compared to

implants with a smoother surface.

Human histological data reported by Piatelli

et al. (1993, 1997b) showed that a mature,

compact, cortical bone was formed around

the immediately loaded implant, with 60–

90% BIC.

The reason for clinical success regardless of implant

surface coating may be due to the type of bone utilized

in a majority of human trials.

As mentioned before, most of the studies have

focused on using the anterior mandible, where the

densest bone is located.

It seems to suggest that the initial mechanical

interlocking between threads and dense bone may

overcome the beneficial properties that each coating

type provides.

The same parameters showed that thread design was

more of a determinant than surface characteristics for

primary stability into softer type IV bone.

• Implant Length

The implant length may also influence the outcome of

immediate implant loading.

For every 3mm increase in length, the surface area of a

cylinder-shaped implant increases by an average of 20–

30% (Misch 1999b).

One study has reported 50% failure rate with immediate

loading for implant lengths less than 10mm (Schnitman

et al. 1997).

The majority of studies have suggested that implants

should be 10mm long to ensure high success rates.

OCCLUSION-RELATED FACTORS

Quality and Quantity of Force

o Controlling functional forces is one of the ingredients for

obtaining success of immediate implant loading.

o Sagara et al. (1993) found more crestal bone loss in the

loaded 1-stage implant group when compared to the 2-stage

unloaded control group (Sagara et al. 1993).

o It was suggested that the early occlusal loading during

healing may account for this observation, since early loading

may interfere with the ability of new one being formed to

replace the necrotic bone at the implant/bone interface

resulting from surgical trauma (Albrektsson et al. 1981).

Vertical forces applied during function

are less detrimental to implant stability

rather than oblique or horizontal forces.

Therefore, bruxism/occlusal overload

has been considered as a possible

contraindication for immediate implant

loading due to higher implant failure

rates.

Prosthetic Design

Primary stability can be enhanced when cross-arch

implant splinting is performed.

Therefore, this prosthetic approach is recommended

in immediate implant loading (Ledermann 1979,

1983; Salama et al. 1995; Spiekermann et al. 1995;

Tarnow et al. 1997; Randow et al 1999). Glantz et al.

(1984a, 1984b) have demonstrated that the most

favorable loading conditions were achieved via rigid

fixed devices.

• Tarnow et al. (1997) used cast metal frame-

enforced provisional restoration to ensure

optimal stability and a high success rate for

immediately loading implants. The authors

further suggested that the temporary

prosthesis, once inserted, should not be

peaked or removed during the healing period

to avoid any unnecessary movement

• Avoid using cantilevers in the fixed implant

provisional restorations since they increase

load to the terminal fixture by 2-fold

When reviewing the literature, it seems to suggest that cross-arch splinting as well as potential load and movement caused by prostheses removal should be avoided in immediately loaded implant cases.

Careful occlusal analysis, such as assessment of parafunctional habits and distribution of occlusal support by remaining teeth, is also essential when a loading regimen for implants is considered

Implant supported immediate fixed prosthesis for completely edentulous patient

Primarily 2 different options are available for immediate

occlusal loading for the completely edentulous patient

desiring a fixed prosthesis

• The first option loads the implants the same day as the

surgery.

• The second option is to place the implants and make an

impression at the surgery. Then at the suture removal

appointment 7 to 12 days later, the dentist delivers the

transitional fixed prosthesis.

Immediate loading concept in partially edentulous arch

• Non functional immediate teeth concept (N- FIT Concept) – Carl E Misch.

• Rather than immediate loading of the implant, most

reports suggest immediate restorations rather than

full occlusal loading.

• Because the patient most often has enough remaining

teeth in contact to function, the transitional

restoration is primarily for esthetics, and the implant

prosthesis is completely out of occlusion.

• Therefore a nonfunctional immediate teeth (N-FIT) concept is suggested

REVIEW

• 1990 Schnitman et al initially described

immediate loading off mandibular

implants with a detachable hybrid

prosthesis, however a statistically

significant number of the immediately

loaded implants failed.

• 1994 Henry et al placed 6 mandibular implants in a

series of 5 patients 4/6 implants immediately

loaded with provisional removable overdenture

then , at 7 weeks a permanent prosthesis was

placed. 100% implant success.

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.

Primary guidelines for immediate loading ( Tarnow -1997)

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.

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)

SUMMARY

The requisites for predictable osseointegration of

immediately loaded implants have yet to be

determined. One parallel consideration is whether

provisional loading of a tissue borne prosthesis over

an implant during the osseointegration (healing)

period will affect the integration of that implant. To

date there is no scientific evidence (and no clearly

documented subjective clinical evidence ) that early

failure of dental implant can be attributed to early -

-loading or overload resulting from a tissue-

supported interim prosthesis being worn over a

recently placed dental implant. Loading of implant

through the use of an interim restoration has not

been documented as a cause of early implant

failure. It is also safe to state that, at this time ,

there is no scientific evidence that the factor

associated with implant restoration (provisional or

restorative) have a predictable impact on the

survival of the supporting implant.

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