Dental Implantology and Osseointegration

Introduction to Dental Implantology

• Dental implantology involves using prosthetic devices or alloplastic materials.
• These materials are implanted into the oral tissue beneath the mucosal and/or periosteal layer, or in the bone
• This provides retention and support for fixed and removable prostheses.

Osseointegration

• This is defined histologically as a direct connection between living bone and a load-bearing endosseous implant at the light microscopic level.

Factors for Successful Osseointegration

• A biocompatible material is needed for a successful bone-to-implant interface
• The implant must be precisely adapted to the prepared bony site
• Atraumatic surgery is required to minimize tissue damage
• An immobile, undisturbed healing phase

Importance of Perimucosal Seal

• A successful dental implant requires an unbroken perimucosal seal between the soft tissue and the implant abutment surface.
• Maintenance of this seal requires high levels of oral hygiene specific to dental implants.
• Implant survival depends on proper and timely home care.
• Schedule recall visits at least every 3 months for the first year.

Clinical Implant Components

• The different components are: Implant, Cover Screw, Healing cap, Abutment, Impression post, Laboratory analogue, and Prosthesis-Retaining screw

Indications for Dental Implants

• Implants indicated for the following patients: Edentulous patients, Partially edentulous patients with difficulty wearing R.P.D., Patients requiring long span F.P.D. treatment, and Patients refusing removable prostheses
• Also indicated with: Severe changes in C.D. bearing tissues, Poor oral muscular coordination, Parafunctional habits that compromise prosthesis stability, and Unrealistic patient expectation for complete dentures
• More indications include: Hyperactive gag reflex, Psychological aversion to removable prostheses, unfavorable abutment number/location, and Single tooth loss (to avoid preparing sound teeth).

Absolute Contraindications for Dental Implants

• Recent myocardial infarction
• Valvular prosthesis
• Severe renal disorder
• Uncontrolled diabetes
• Uncontrolled hypertension
• Generalized osteoporosis
• Chronic severe alcoholism
• Radiotherapy in progress
• Heavy smoking

Relative Contraindications for Dental Implants

• Cardiovascular problems
• Congestive heart failure
• Coronary artery disease
• Prosthetic heart valves
• Rheumatic heart disease
• Endocrine disorders(calcium, iron, avitaminosis, low estrogen in females)
• Hyperactive involuntary muscle movements (Parkinson's, Huntington's)
• Bone disorders (osteomyelitis, osteopetrosis, osteoporosis)
• Benign/malignant bone neoplasms or cysts and fibro-osseous disease
• Pregnancy

Advantages of Dental Implants

• Preservation of bone
• Improved function
• Esthetics
• Stability and retention
• Comfort

Disadvantages of Dental Implants

• Expense
• Unsuitability for medically compromised patients or those unable to undergo surgery
• Longer treatment duration and tedious fabrication procedures
• Higher requirement for patient cooperation
• Anatomical limitations making universal placement impossible.

Classification of Implants by Placement

• Epiosteal/Subperiosteal implants
• Endosteal implants
• Transosteal implants

Metallic Implant Materials

• Titanium
• Cobalt chromium molybdenum alloy- Titanium aluminum vanadium
• Cobalt chromium molybdenum
• Stainless steel
• Tantalum
• Gold
• Platinum

Non-Metallic Implant Materials

• Ceramics
• Carbon

Classification of Implants by Reaction with Bone

• Bio-active: Hydroxyapatite, Tri Calcium Phosphate, Calcium Phosphate
• Bio inert - metals

Titanium in Dental Implants

• Commercially used as pure titanium
• Can also be a Titanium-aluminum-vanadium alloy (Ti-6Al-4V)
• Stronger alloy is used with smaller diameter implants
• It is lightweight and biocompatible
• Titanium is corrosion resistant due to a dynamic inert oxide layer, strong & low-priced
• It is 6 times stronger than compact bone.
• The modulus of elasticity is 5 times greater than compact bone, which ensures equal mechanical stress transfer.

Prosthetic Options of Implants

• Misch reported five prosthetic options of implants in 1989.
• Fixed prosthesis can replace only the crown, appearing like natural teeth
• Fixed prosthesis can replace the crown and a portion of the root
• Fixed prosthesis can replace missing crowns, gingival color, and a portion of edentulous sites
• Removal prosthesis; overdenture supported completely by the implant
• Removal prosthesis; overdenture supported by soft tissue and implant.

Endosteal Dental Implants

• They are placed within the bone during stage I surgery.
• They may be either threaded or nonthreaded cylinders.
• They are made of either titanium or titanium alloy, with or without hydroxyapatite (HA) coating.

Healing Screw

• It is placed in the implant during the healing phase after stage I surgery.
• This screw is low profile to facilitate easy suturing of the soft tissue over the implant.

Healing Cap

• It is a dome-shaped screw placed after the stage II surgery and before prosthesis placement.
• These range in length from 2mm to 10mm and project through the soft tissue into the oral cavity.
• They may be resin-based, such as polyoxyethylene, or made of titanium metals.

Preoperative Medical Evaluation Contraindications

• Acute illness, terminal illness, uncontrolled metabolic disease, pregnancy
• Patients with abnormal bone metabolism and poor oral hygiene
• Previous (tumoricidal) radiation to the implant site
• Other metabolic bone disorders (osteopetrosis, fibrous dysplasia, chronic diffuse sclerosing osteomyelitis, florid osseous dysplasia)
• Smoking and a improper motivation
• Lack of operator experience and being unable to restore prosthodontically

Surgical Phase: Treatment Planning

• Clinical and radiographic evaluation of the planned implant site is essential to determining whether adequate bone and if anatomic structures will interfere with implant placement.
• Higher implant success is associated with more cortical bone and denser cancellous bone as opposed to thinner cortical bone with loose cancellous marrow.
• Implant success is predictably high in type I-III bone, regardless of length.
• Short implants (<10mm) in type IV bone have significantly higher failure rates.

Bone Density Classification

• Dense cortical (D1) bone: Highest bone implant contact (BIC) > 80%, Anterior region of mandible very dense compact bone.
• Dense to thick porous cortical and coarse trabecular bone (D2): BIC = 70%, Dense to porous compact bone on the outside and coarse trabecular bone on the inside, Anterior and posterior mandible
• Thin porus cortical and fine trabecular bone (d3) BIC = 50%:Thinner porous compact bone and fine trabecular bone, Anterior or posterior maxilla and posterior mandible
• Fine trabecular bone (d4): BIC = < 25%, No cortical crestal bone, posterior maxilla in long term edentulous patients

Diagnostic Evaluation for Implants

• Iopa
• Occlussal radiographs
• Lateral cephalometric radiographs
• OPG and CBCT

Steps for Dental Implant Procedure

• Steps involved: initial surgery, osseointegration period, abutment connection, and final prosthetic restoration

Osseointegration Success

• Success Rates are >90%
• Definition –“direct connection between living bone and loadbearing endosseous implants at the light microscopic level."
• Factors affecting this: Biocompatibility of implant material, Implant design, Surface conditions, Status of host bed, Surgical technikque and Implant loading

Fibro-osseous Integration

• “Tissue to implant contact with dense collagenous tissue between the implant and bone"
• Was seen in earlier implant systems for implants.
• Had initially good success rates but extremely poor long term success and is considered a “failure” by todays standards.

Anatomical Limits for Implant Placement in the Maxilla

• Low bone quality and quantity as bone height decreases, the remaining bone narrows to close proximity with nasal cavity, maxillary sinus, incisive canal.
• Placement is limited to canine eminence areas.
• Therefore,CANINE EMINENCE AREA MUCH SUITABLE FOR IMPLANT PLACEMENT IN MAXILLARY ARCH

Maxillary Posterior Region Implant Placement

• Implants are rarely placed here due to: resorption pattern, proximity of sinuses and quality of bone
• Severe bone resorption and low palatal vault also creates a difficult situation.

Mandibular Anterior Region Implant Placement

• This region between mental foramina has adequate bone for 4-6 implants.
• Minimum of 7 mm is required from inferior border of mandible to the crestal ridge.
• In resorbed ridges the mental foramina is located on top of the ridge: care is necessary to prevent damage to it and possible paresthesia.

Mandibular Posterior Region Implant Placement

• Difficult because of inferior alveolar nerve
• There should be approximately 1mm clearance between the implant apex and the canal
• Pattern of bone resorption is the same on buccal and lingual sides.
• Resorption in crestal region creates variety of shapes from sharp edge to flat and wide
• Shorter length implants are therefore necessary.

Limiting Anatomical Sites

• Maxillary sinus
• Inferior alveolar canal

Complications for Dental Implants

• Membrane perforation
• Presence of bony septae which divide sinus into separate compartments
• Postoperative infection
• Wound dehiscence
• Barrier Membrane exposure
• Transient sinusitis

Surgical Complications Leading to Implant Failure

• Inoperative Complications
  • Oversize Osteotomy.
  • Perforation of cortical plates.
  • Inadequate soft tissue flaps for Implant coverage.
  • Broken burs.
  • Improper Instrumentation
  • Hemorrhage.
  • Poor angulations & Position of Implant.

Prosthetic related Complications

• Component & framework breakage
• Fractured Frameworks & Mesostructure bars
• Partial loosening of cemented bars and prostheses
• Inaccurate fit of castings
• Inadequate Torque application
• In accurate frame work abutment interface
• Occlusal factors
• Implant Fracture

Ailing Implant

• Least seriously affected Implants.
• Radiographic evidence only showsstatic bone loss

Failing Implant

• Osseointegration develops apically and is responsible for the implants stability
• Routine radiography shows progressive bone loss around the cervical areas of the implant.

Failing implants due to specific bacteria:

• Actinobacillus
• Actinomycetemcomitans
• Porphyromonas gingivalis

Failed Implant Definition

• Mobility. may be diagnosed by:
• Tapping and receiving a dull sound.
• Manipulating by two mirror handles and detecting movement.
• By the use of the Periotest and eliciting a response of +9 or higher