IMPLANT LOADING

BHUVANESH KUMAR.D.V

Terminologies

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 protocolNon-submerged implants, flush within 1-2 mm of gingival level

Soft diet

Immediate functional loadingTemporary restoration fitted on the same day as surgery, in occlusion

Soft diet

Immediate non-functional loadingTemporary restoration fitted on the same day as surgery, not in occlusionSoft diet

Early loadingFinal crowns within 3 weeks from surgery, in occlusionSoft/ hard diet

Delayed loadingImplant subjected to loading after more than 6 weeks post surgerySoft/ hard diet

Anticipated loadingProvisional prosthesis is fitted after about 2 months after surgerySoft/ hard diet

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.

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

In contrast to all the 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.

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.

After an initial direct bone–implant interface has been obtained and confirmed at the post healing stage II surgery, the implant is most at risk for failure or crestal bone loss within the first year after loading

The three most common causes of early prosthetic-related implant complications are non-passive superstructures, partially unretained restorations, and loading of the implant support system beyond the strength of the bone– implant interface

The external (cortical) and internal (trabecular) structure of bone may be described in terms of quality or density which reflects the

The density of available bone in an edentulous site is a determining factor in treatment planning, surgical approach, implant design, healing time, and the need for initial progressive bone loading during prosthetic reconstruction.

Misch first proposed the concept of progressive or gradual bone loading during prosthetic reconstruction to decrease early implant failure Misch et al. reported on 364 consecutive implants in 104 patients with 98.9% survival at stage II uncovery followed by a progressive loading format and found no early loading failures during the first year of function

Misch CE, Hoar JE, Hazen R, et al: Bone quality based implant system: a prospective study of the first two years of prosthetic loading, J Oral Implantol 25:185–197, 1999.

Misch CE: Gradual load on an implant restoration, St Petersburg,FL, 1980, Tatum Implant Seminars lectureMisch CE, Poitras Y, Dietsh-Misch F: Endosteal implants in theedentulous posterior maxilla—rationale and clinical results, OralHealth 90:7–16, 2000Kline R, Hoar JE, Beck GH: A prospective multicenter clinical investigation of a bone quality based dental implant system,Implant Dent 11:224–234, 2002.

Scientific Rationale of Bone Density–BasedImplant Treatment

Bone Strength and Density Bone density is directly related to the strength of bone before microfracture

The different densities of bone have adifferent strength. Type D1 bone is strongest, and type D4 bone isthe weakest.

It should be noted that the strength of bone studies were performed on mature bone types. Bone is 60% mineralized at 4 months after implant surgery, and the strength of bone is related to the amount of mineralization

Hence , a healing period after surgery of 3 to 4 months is adequate for D1 and D2 bone. A healing period of 5 to 6 months is beneficial in D3 to D4 bone.

Elastic Modulus and Density

The elastic modulus of bone is more flexible than titanium.The difference between the two materials may create microstrain conditions of pathologic overload and cause implant failure. When the stresses applied to the implant are low, the microstrain difference between titanium and bone is minimized and remains in the adapted window zone, maintaining load-bearing lamellar bone at the interface

Misch et al. found the elastic modulus of the trabecular bone in the human jaw to be different for each bone density

when a stress is applied to an implant prosthesis in D1 bone, the Ti–D1 bone interface exhibits very small microstrain difference. In comparison, when the same amount of stress is applied to an implant in D4 bone, the microstrain difference between is greater and may be in the pathologic overload zone

Bone Density and Bone–Implant Contact Percentage

Misch noted that the bone density influences the amount of bone in contact with the implant surface.

The BIC percentage is significantly greater in cortical bone than in trabecular bone.

D1 bone provides the highest percentage of bone in contact with an endosteal implant and may approximate more than 85% BIC. D2 bone, after initial healing, usually has 65% to 75% BIC. D3 bone typically has 40% to 50% BIC after initial healingThe bone–implant contact for D4 bone is less than 30% after initial healing.

Bone stress Crestal bone loss after loading may occur from excess stress at the implant–bone interface. A range of marginal bone loss has been observed in implants in different bone densities with similar load conditions. Tada et al. evaluated the three-dimensional changes around different length implants in different bone qualities

Since these variables cannot be eliminated relative to bone density, the treatment plans - including implant number, size, and design should be modified to achieve a successful prosthesis.

Studies Supporting Progressive Loading

Many studies were done to assess the pros and cons of progressive loading one such clinical assessment was done using 250 implants over a 2-year period using a Periotest

Misch CE: Progressive bone loading. In Misch CE, editor:Contemporary implant dentistry, St Louis, 1993, Mosby

This instrument evaluates the dampening effect of implants, prostheses, and teeth, which is related directly to mobility.

The Periotest values can range from −8 to +99. A range of −8 to + 9 Periotest value is applicable to a structure with an absence of clinical mobility.

The implants in D1 bone, after progressive loading, did not improve statistically, although a −7 Periotest value was recorded more often.

The implants in D2 bone exhibited a mean decrease of 1 Periotest value.

The implants in D3 bone had a slightly greater than 2 Periotest value decrease after progressive loading.

The greatest change was seen in D4 bone where the mean decrease in Periotest value was almost 4 units.

Therefore, the poorer the bone density -- D3 and D4 -- the more dramatic the decrease in Periotest values –which relates to mobility and density of bone around the implant.

The implementation of progressive loading is more critical for lesser bone densities because they are several times weaker than those with significant cortical bone.

Parafunction, cantilevers, and other stress magnifiers can increase the forces applied to the prosthesis and their shear components and cause bone microfracture or microstrains in the pathologic zone around the implant. Progressive bone loading aims at oincreasing the density of bone,odecreasing the risk of implant–bone failure, and odecreasing crestal bone loss.

Progressive Loading Protocol

The concept of progressive loading is to allow the bone to adapt to increasing amounts of biomechanical stress.

Hence, rather than immediately loading the bone–implant interface, methods to slowly increase the stress over time are a benefit.

The progressive loading protocol uses a cement-retained prosthesis when implants are splinted together.

Because a screw retained splinted restoration is not completely passive and a torque force applied to a screw is greater than a bite force, a traditional screw-retained restoration cannot use progressive loading to gradually load the bone

A longer healing time between stage I and stage II is suggested when forces are greater or bone is softer.

This time allows greater mineralization of bone and a more mature lamellar bone interface to form next to the implants before the load of the screws is applied to the implant bodies

Time - Initial HealingThe ideal bone for implant

prosthetic support is lamellar bone.

Lamellar bone is highly organized but takes about 1 year to mineralize completely after the trauma induced by implant placement.

Woven bone is the fastest and first type of bone to form around the implant interface; however, it is mineralized only partly and demonstrates an unorganized structure

At 16 weeks, the surrounding bone is only 70% mineralized and still exhibits woven bone as a component.

The percentage of bone mineralization and the type of supporting bone influence whether a load to the bone– implant interface is within its physiologic limits.

Four prosthodontic steps are suggested for the reconstruction of a partially or completely edentulous patient, with endosteal Implants & they are separated by a period of time related to the bone density observed at the initial time of surgery.

The four prosthetic steps are

(1) abutment insertion, preparation, final impression and temporary (of the esthetic zone);(2) a metal try-in and new bite registration; (3) initial delivery of the prosthesis; and (4) final evaluation of the restoration and hygiene appointment

This schedule allows sufficient time for mature lamellar, mineralized bone to develop at the interface and increases the numbers of trabeculae in direct contact and within the network region of the implant

When the dentist uses multiple implants, the weakest bone area determines the gradual load protocol.

Hence, if the anterior maxilla and posterior maxilla are restored together, the posterior maxilla would determine the initial healing period and the time period between each prosthetic appointment

DietDuring the initial healing phase, the dentist instructs the patient to avoid chewing in the area, especially when the implants are placed in a one-stage approach.

The implant connected to an abutment for cement retention is at greater risk of loading during mastication.

The patient is limited to a soft diet such as pasta and fish, from the final impression stage until the initial delivery of the final prosthesis

The masticatory force for this type of food is about 10 psi

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 of fracture or uncementation

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 after evaluation of the final prosthesis function, occlusion, and proper cementation

Occlusal MaterialDuring the initial steps, the implant has no occlusal contact but at subsequent appointments, the dentist uses acrylic as the occlusal material, with the benefit of a lower impact force than metal or porcelain.

Either metal or porcelain can be used as the final occlusal material.

If parafunction or cantilever length causes concern relative to the amount of force on the early implant–bone interface, the dentist may extend the softer diet and acrylic restoration phase several months.

In this way, the bone has a longer time to mineralize and organize to accommodate the higher forces.

OcclusionNo occlusal contacts are permitted during initial healing (step 1).

The first transitional prosthesis is left out of occlusion in partially edentulous patients (step 2)

The occlusal contacts then are similar to those of the final restoration for areas supported by implants. However, no occlusal contacts are made on cantilevers or offset loads (step 3)

Prosthesis DesignThe first transitional acrylic restoration in partially edentulous patients has no occlusal contact and no cantilevers.

Its purpose is to splint the implants together and reduce stress by the mechanical advantage and to have implants sustain masticatory forces solely from chewing.

The second acrylic transitional restoration has occlusal contacts placed over the implants with occlusal tables similar to the final restoration but with no cantilevers in nonesthetic regions.

The final restoration has narrow occlusal tables and cantilevers designed with occlusal contacts following implant-protective occlusion guidelines

Progressive Loading Phases

The dentist instructs the patient with a posterior implant in a partially edentulous arch not to wear any removable restoration.

If anterior teeth are part of the removable prosthesis, a 7-mm-diameter hole is placed completely through the partial denture framework around each PMEso it will not load the implant.

In completely edentulous patients, the tissue surface of the denture is relieved at least 5 mm over and around the implants and replaced by a tissue conditioner.

The conditioner also is relieved a few millimeters. The patient returns in 2 weeks for suture removal and to replace the tissue conditioner with a soft liner.

An abutment for cement retention is inserted and torqued into the implant bodies

The final abutment for cement retention is torqued into position after a radiograph confirms its position.

The first transitional restoration is cemented with temporary cement. It is completely out of occlusion.

The laboratory technician fabricates a metal framework that splints the abutments together

A metal try-in evaluates the casting

A closed-mouth centric recording is made over the metal framework.

The original transitional restoration is modified by adding acrylic on the occlusal surface, and a heavy bite force occlusal adjustment is made.

The final restoration is evaluated in the mouth

A radiograph is made for baseline evaluation of the prosthesis.

Completely Edentulous Patient ProtocolBefore or during surgical phases, the dentist may fabricate treatment prosthesis that restores the patient to the proper occlusal vertical dimension (OVD) and determines the correct tooth position for the final prosthesis.

A clear template (0.008 inch) is made over the patient’s denture and trimmed to the soft tissue borders.

This acts as a customized impression tray and records a bite registration to the opposing arch

A two-piece transfer coping engages the hexagon of the implant body. A closed-tray impression is made with the customized impression tray over these implant body transfers

The customized impression tray with the occlusal bite registration in centric relation occlusion

The impression transfer copings are attached to the implant bodies, poured, and mounted to the opposing arch with the customized impression tray.

The final abutments are selected and prepared for parallelism and tooth position.

A transitional restoration is made over the prepared implant abutments.

The transitional prosthesis does not have a cantilever.

The laboratory-prepared abutments are positioned over the anti-rotation component of the implant body and are secured with an abutment screw at 30 N-cm of torque.

The first transitional restoration, without cantilever, is delivered.

The patient is instructed to limit the diet to only soft food.

At the metal try-in appointment, the framework of the prosthesis is evaluated.

White wax is used to evaluate theincisal edge position.

Acrylic posterior indexes are used to evaluate the occlusal vertical dimension and centric occlusal registration

The final restoration is delivered to the patient.

The progressive bone loading approach provides the environment favorable for the development of load-bearing bone at the implant interface in two ways:• the development of an extended time period

before the introduction of full-magnitude functional forces and

• the limitation of these forces to vertical forces as the dominant component.

This gradual increase in loads permits the adaptation of the bone , increase in bone density and improved crestal bone conditions around the implant compared with a more sudden loading protocol results in increased implant survival and less crestal bone loss.

Immediate loading …

Thursday …

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 durability 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.

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