osseointegration

Definition

• Direct structural and functional connection between ordered living bone and the surface of a loading carrying implant (complete adaptation of bone to the surface configuration of the implant without soft noncalcified connective tissue intervening).

Factors Affecting Osseointegration

The preparation of the recipient bone site

• Careful, gentle and a traumatic handling is mandatory.
• Drilling should be made using a low speed high torque rotator instrument not exceeding 2000 rpm according to bone density.
• Temperature maintained well below 4’7°C to avoid impaired healing and connective tissue interfaces between bone and implant surface.

The time scheduled for healing before functional loading of the dental implant

• Leaving the implant whether submerged or non-submerged in bone before loading for a healing period of 3-4 months in the mandible and 6-9 months in maxilla with regular follow up is essential for osseointegration (classical protocol “delayed loading”)
• However, immediate loading of implants with good initial stability or multiple implants splinted together or with natural teeth may prove to be a valuable adjunct therapy.

Indication

1. Good oral hygiene
2. Good general health
3. Adequate qualitative and quantitative characteristics of bone

• Healthy bone i.e. No periodonitis or Osteomyelitis
• Sufficient amount of bone width and height for the desired size implant

4. Healthy mucosal tissues

Dental implant is indicated for partially or completely edentulous patients for

• Single tooth replacement
• Patients with unfavorable number and/or location of abutments to support FPD
• Complete edentulous patients with inability to wear RPD

Contraindication

Relative contraindications

1. Inadequate bone quantity at implant site or excessive bone concavities. “Can be corrected by bone graft and guided tissue regeneration”.

2. Inadequate vertical height.  “Can be corrected by sinus left procedure or inferior alveolar nerve transposition, or vertical ridge augmentation, or distraction osteogenesis”

3. Controlled diabetes.

Absolute Contraindications

1. Local and systemic bone diseases

• Radiolucent lesions in the intended implant site.
• Metabolic bone disease.
• Osteomyelitis.
• Chemotherapy & radiotherapy (due to the effect on bone healing).

2. Generalized medical problems

• Patients with chronic bleeding problems (hemophilia, thrombocytopenic purpura and anemia) or cardiovascular disease due to problems in healing
• Patients with allergies and rheumatic diseases
• Patients with endocrinal diseases such as pituitary and adrenal insufficiency and hypothyroidism, as they have healing problems
• Uncontrolled diabetes due to the liability of infection and delayed wound healing probably caused by thinning and fragility of blood vessels
• Smoking, as it leads to:

3. Psychological problems

• Psychiatric behavior.
• Parafunctional habits (Bruxism & clenching)    induce excessive loading.

4. Drug & alcohol abuse
5. Patients with very bad oral hygiene

Advantages

1. No preparation of natural teeth.
2. Bone stabilization and maintenance.                                                           
3. Retrievability.
4. Improvement of function.
5. Psychological improvement.

Disadvantages

1. Risk of screw loosening.
2. Risk of fixture failure.
3. Length of treatment time.
4. Challenging esthetics.
5. Need for multiple surgeries “classical two stage protocol”.

Types of Dental Implants

Submucosal insert

• Retentive implants consist of mushroom shaped titanium projections fastened to the tissue surface of complete or partial removable dentures in either the maxilla or the mandible.
• About 14 inserts (7 on each side of a complete denture) are passed into prepared receptor sites in mucosa.

Subperiosteal Implants

• The metallic framework of subperiosteal implants is placed directly on the surface of the alveolar ridge under the periosteum, and so, they are not considered osseointegrated implants.
• used in completely edentulous jaws (edentulous mandibles)

Transosteal Implants

• type of orthopedic bone plate attached to the mandible at the inferior border and communicates with oral cavity by means of transosteal pins.

Endosseous Implants

• an alloplaytic, biologically compatible material surgically inserted into edentulous bony ridge, which serves as a foundation for a prosthodontic restoration.

Types

According to the form

1. Root Form:

         Screw   or   Cylinder

2. Blade Form.

According to the Shape and Surface

• Tapered or parallel sided.
• Smooth, pebbled, or textured.
• Solid, hollow or vented.
• Coated or non-coated.
• Tapping or self tapping.

According to the Insertion

1. Single stage: (one piece implant, inserted into bone, extends through oral M)
2. Two stages: the bony implant “fixture” is separate from the transmucosal portion “abutment”. The fixture is inserted into bone and left for a healing period of 3-6 months before abutment connection.

According to the Material

1.  Pure titanium:

2.  Titanium alloy

3. Zirconium.

Diagnosis

Dental evaluation

Dental history Obtaining a record for the cause of loosing natural teeth, (periodontal diseases, caries, trauma and tumors)

Evaluation of the oral cavity

Teeth

• Number and condition of existing teeth.
• Size, shape, and diameter of existing dentition.
• Tooth and root angulations and proximity.   

Edentulous Space

• Mesiodistal width of edentulous space
• The required distance is as follows:

    7 mm from center of implant to center of implant for edentulous area

Periodontium

Mucogingival Problems

Bone Support

Bone quality

D1: Almost the entire jaw is composed of homogenous compact bone.

D2: A thick layer of compact bone surrounds a core of dense trabecular bone.

D3: A thin layer of cortical bone surrounds a core of dense trabecular bone of   

       favorable strength.

D4: A thin layer of cortical bone surrounds a core of low density trabecular bone

The best bone to place an implant into is D2,                                                                                       best Area: mandiblulur symphysis, and poorest area: posterior regions.

Bone quantity

A.  Most of the alveolar ridge is present.

B.  Moderate residual ridge resorption has occurred

C.  Advanced residual ridge resorption has occurred and only basal bone remains

D. Some resorption of basal bone taken place.

E.  Extreme resorption of the basal bone taken place.

The required bone quantity is as follows

• 6 mm bucco-lingual width with sufficient tissue volume
• 8 mm interradicular bone width.
• At least 10 mm alveolar bone above inferior alveolar canal or below M.Sinus

If inadequate bone support is present, augmentation may be needed

Esthetic Evaluation

smile line

• Smile line should be evaluated (usually high in maxilla & low in mandible).
• If an existing ridge defect is visible with high smile line, ridge augmentation should be considered.

implant emergence profile

• Restored implant should appear emerging from the gingival, providing a very natural and desirable appearance.
• Avoid “Tomato on stick” crowns as in addition to bad esthetics, periodontal problems may develop.

Medical Evaluation

• General health of the patient should be evaluated carefully.
• Medical history of systemic diseases should be taken (e.g. diabetics have delayed healing), osteoporosis, hyperparathyroidism, vit. D deficiency)
• Destructive habits such as smoking contraindicate implant placement, as delayed or inadequate tissue healing and osseointegration is noted. 

Study Casts (occlusal analysis)

Mounted articulated study casts are essential for evaluation of:

1. Centric arch relationship
2. Inter arch occlusal clearance.
3. Occlusal discrepancies
4. Ridge width.

Photographs

Pre-treatment facial and intra-oral photographs are desirable to:

Radiographic Evaluation

Radiographs provide data regarding

1. The anticipated area of implantation.
2. Surrounding and adjacent structures e.g.

• Floor maxillary sinus
• Floor of nasal cavity.
• inferior alveolar canal

3. Vertical bone height in the edentulous area (a minimum of 10 mm alveolar bone above inferior alveolar canal and below maxillary sinus)
4. Interradicular area (8mm is required).
5. Bone quality & quaintly (as before).
6. Presence of pathological condition

Radiographic examination may be done using

Panoramic periapical radiographs: determine the amount of the space & bone.

C.T. scan gives more accurate and reliable assessment of:

• Bone quality and quantity.
• Location of anatomic structure, such as maxillary sinus position and inferior dental canal
• Bone width.

Radiographic stent:

An acrylic stent (which can be used as the surgical stent later on) with ball bearing (5mm) placed in the proposed fixture locations to allow more accurate radiographic interpretation.

Surgical analysis

1. Surgical guide stent

• The surgical stent is one of the most critical factors for obtaining ideal surgical and esthetic results. It is used during implant fixture installation as guide for the optimal bucco-lingual and mesio-distal position).

2. Implant length / diameter

• Determined by the quantity of bone apical to extraction site (length) and bucco-lingual ridge width (diameter)
• Length typically ranges from 7 to 21 mm
• The surface and design should be evaluated for each anatomical location, along with size, length and diameter.
• Most endosseous implants favor a two stage approach.
• For FPD, it is advised to use screw-retained restorations with two fixtures when restoring posterior spaces not bound by natural teeth.

Treatment Options

Implant placement

1. Immediate implant: placed at the time of tooth extraction.
2. Delayed immediate: placed 8-10 week after tooth extraction.
3. Delayed: placed 9—10 months or longer after tooth extraction.

Some surgeons feels that immediate implant placement is better as it preserves bone (bone does not resorb following extraction). Others feel delayed placement allows for better bone fill for implant stabilization.

Implant loading

1. Immediate   loading:   the   implant   is   immediately   loaded   after placement.
2. Delayed Loading: the implant is leh without any loading for a period of 6 months in maxilla and 3 months in the mandible (classical protocol)

Ideal criteria for host site

Mucosa

Healthy Keratinized mucosa of 2–3 in thickness is optimal for implant placement

Bone

• Bone must be present in adequate quantity and quality.
• The edentulous ridge must be large enough to accept the fixture installation without fenestration (5-6 mm in width and 10 mm in length).

Site

Mandible

• area between the 2 mental foramina is the ideal site for implant insertion.
• In the posterior area of the mandible there is often insufficient bone over the inferior alveolar canal for the fixture placement unless the content of the canal are repositioned.                

Maxilla

• The pyramid of bone between the medial wall of the antrum and the lateral wall of the nose is frequently the ideal site for implant placement.
• There is often insufficient bone over the antrum posteriorly and over the nasal fossa anteriorly. This may necessitate sinus lifting procedure.

Surgery technique

general requirements

• The surgery for obtaining osseointegrated fixtures with adequate function and healthy tissues around abutments requires the following:

stages of implant surgery

• Most endosseous dental implants favor a two-stage approach.  The surgery is usually performed under local anesthesia.
• In stage I surgery, implant fixture is inserted into bone then covered with the “covering screw” and left undisturbed for a healing period of 3 months in the mandible and 6 months in maxilla.
• covering screw prevents soft & hard tissue ingrowth into implant fixture
• In stage II surgery, the fixture is uncovered and a transmucosal healing abutment (healing cap) is placed for 4-6 weeks, to allow for soft tissue healing, after which the abutment is connected to start prosthetic phase.
• The one-piece implant is designed for immediate loading, and so, it has an integrated transmucosal part that serves as a foundation for the prosthesis. This type of implant is inserted in a single-phase surgery.

stage I surgery (fixture installation)

Incision and flap reflection

• A single crystal incision is made through the mucoperiostuim for a single implant placement & For multiple implants placement      a pyramidal flap
• The flap is reflected both buccally and lingually.

Preparation of the implant site

• Any sharpness or irregularities of the ridge at the implant site should be trimmed carefully to maintain the bone height.

Drilling of the bone

• All cutting procedures must be performed with a low speed, high torque internally and externally irrigated hand piece to reduce heat generation, to keep the temperature below 47°C and preserve bone vitality.
• High temperature leads to bone necrosis and eventual fibrous connective tissue healing around the inserted implant.
• Using a graded series of drills the implant site is prepared as follow:

1. Initial drilling (acts as a guide).

2. Intermediate drilling.
3. Final drilling.

Implant fixture placement

• The implant site is irrigated with sterile saline.
• Bone tape is used to produce the initial serration in the implant site for the recipient of the fixture.
• Rateched     remove the implant fixture from its sterile double package.
• With the aid of the stent at the time of implant installation the surgeon will note the position of the teeth and should be able to place the fixture in the proper location.
• The implant fixture is then threaded into the prepared site in a clockwise direction using hex-tool. Initial friction must exist to obtain initial stability.
• The fixture is then covered with the surgical cover screw to prevent ingrowth of tissues into the opening of the abutment screw.
• The mucosa is then sutured over the inserted implant fixture

stage ll surgery (abutment connection)

• During the healing period, about 95 % of mineralized newly formed bone occurs (osseointegration). After that, the second stage is performed.
• The implant fixture is exposed by excising the overlying mucosa. The acrylic resin stent is used to locate the site of the implant.
• The surgical cover screw is removed.
• The titanium abutment is then attached to the fixture.

Prosthetic procedures

These procedures include impression making and laboratory fabrication of the final restoration, which is then fixed to the abutment be screw or cement.

Criteria of success

Subjective criteria

1. Adequate function.
2. Improved esthetics
3. Absence of discomfort.
4. Improved emotional & psychological attitudes.

Objective criteria

1. No peri-implantitis (sulcular plaque accumulation with associated loss of epithelial attachment).
2. No peri-implant radiographic radiolucency.
3. Marginal bone loss within 1.0-1.5 mm in the first year after placement, then 0.1-0.2 mm bone loss per year.
4. Tissue integration (bone/soft tissue).
5. Absence of mobility.
6. Stable clinical attachment level.
7. 7- Absence of bleeding on probing or excessive probing depths.

Maintenance and recall

Frequency of recall:

1. 24 h after placement.
2. One week after placement.
3. Two weeks after placement.
4. 6 Months after placement.

Oral hygiene

Plaque is the primary etiologic factor in tissue destruction, so review of oral hygiene is important at each recall session.

hygiene aids

• Scaling of the implant abutment surfaces. Plastic sealers only should be used to prevent abrasion, of the titanium metal fixture. Scaling is done in one direction starting at the gingiva.
• Any surface damage of the implant will facilitate increased plaque and calculus retention and may hinder tissue attachment thus recommendation is for use fine pumice or fine prophy paste with blue rubber tipped prophy cups.
• Chlorohexidine m.w is used during episodes of soft tissue inflammation
• Fluoride rinses or gels. Neutral sodium fluoride only should be used, as acidulated types may damage the titanium fixture.

Implant Stability

• Mobility is the key indicator of fixture health.
• Minimal mobility is associated with osseointegrated fixtures.
• Implant may sustain extensive bone loss without increasing mobility if a critical amount of bone remains.

   

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