About Dental Implants Part 1 & 2 | Intelligent Dental

About Dental Implants Part 1 | Intelligent Dental

Dental implants are now increasingly used to attach crowns, bridges or dentures by anchorage to bone. Despite its benefits, placement of implants requires careful patient selection and treatment planning to ensure long-term success of implants.

History of dental implants

In 1952, professor Branemark, a Swedish surgeon, while conducting research into the healing patterns of bone tissue, accidentally discovered that pure titanium comes into direct contact with the living bone tissue, the two literally grow together to form a permanent biological adhesion. He named this phenomenon ‘osseointegration’.

Indications for dental implant treatment

© seapointclinic.ie

• Difficult toothless cases


• Long span dental bridges


• Free end saddles of partial dentures


• Single tooth replacement

Contraindications to tooth implant placement

• Acute illness


• Severe lesions of mucous membranes


• Poor bone quality


• Uncontrolled metabolic disease


• Tumor radiation to implant site


• Unrealistic expectations


• Improper motivation


• Lack of operator experience


• Unable to restore with prostheses


• Cardiac disease – patients with risk of endocarditis may be suitable but regular monitoring is advisable. Contraindicated in severe heart disease


• Hematological disease – contraindicated in hemophilia, relative contraindication for those under Warfarin therapy


• Immunological problems – implant survival may be reduced in patients on corticosteroids and this should be balanced against potential benefits. Smoking has adverse effects on implants


• Bone disorders – most bone disorders are contraindicated. Relative contraindications for osteoporosis

Osseointegation

© feppd.org

Osseointegration was defined as ‘a direct structural and functional connection between living bone and the surface of a load carrying implant’. It is in fact an ankylosis of implant to bone surface and some prefer the term functional ankylosis. Osseointegration is prerequisite for success of implant placement.

Factors required for successful osseointegration

• A suitable biocompatible material


• Host bed


• Adaptation of implant to prepared bone site


• Adequate bone quality and quantity


• Atraumatic surgery to minimize tissue damage


• An immobile, undisturbed healing phase


• Soft tissue to implant interface

Suitable biocompatible material

This is necessary to promote healing without a foreign body rejection by host tissue. If biocompatible materials are not used, bone attempts to isolate the foreign body by surrounding it with granulation tissue and then connective tissue. Researchers have demonstrated that titanium and certain calcium-phosphate ceramics are biologically inert.

Host bed

In cortical (outer layer) bone resorption of mineralized, avascular necrotic tissue must occur before new bone can form on the implant surface. In the spongious (inner layer) region of the site, on the other hand, woven bone formation and osseointegration occurs early in the process of healing.

Adaptation of implant to prepared bone site

Site of gap between the implant and the bone immediately after implant placement is critical to achieving osseointegration. Gap size can be controlled primarily by the preparation of a precise surgical bed. Precision instrumentation and technically sound surgical procedure minimize the distance between the implant and host bone.

Atraumatic surgery to minimize tissue trauma

Atraumatic surgery is required to allow minimal and thermal injury to occur.

Adequate bone quality and quantity

© berksoralsurgery.com

Implant immobility during the healing phase is affected by bone quality and quantity. Areas with high cortical (outer layer) bone such as the front of the lower jaw are more likely to anchor the implant successfully. Initial stability takes long time to achieve in cancellous (porous) bone. Implant stability increases if both superior and inferior cortical plates are used.

Upper jaw

• cortical plate of upper jaw is often thin or absent and normally crumbles,


• pattern of bone resorption  and anatomical structures in upper jaw cause problems,


• resorption causes bone loss from front and crestal surfaces

Lower jaw

• more cortical bone so better success rate,


• resorption in lower jaw does not pose problem with implant placement but there is severe loss of bone height

 Methods of improving implant success in the upper jaw

© drlampee.com

• Use additional implants to share the load


• Use connecting bars


• Use maximum length of implant


• Consider augmentation of ridge bone


• Consider sinus lift to extend available ridge


• Allow more time for osseointegration

Undisturbed healing phase

It is fundamental that undue loading is avoided until osseointegration is achieved.

Minimum integration time

Region of implant placement	Minimum integration time
Front of the lower jaw	3 months
Back of the lower jaw	4 months
Front of the upper jaw	6 months
Back of the upper jaw	6 months
Into bone graft	6 to 9 months

Soft tissue to implant interface

Successful dental implant should have an unbroken, perimucosal seal between soft tissues and implant abutment surface. To maintain the integrity of this seal, the individual must maintain a high level of oral hygiene. If the seal between soft tissue and implant is lost, the gum pocket can extend directly to bony structures. Therefore if the seal breaks down or is not present, the area is subject to peri-implant gum disease – peri-implantitis

Components of implants

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Implant

Implant is the endosteal (within bone) material that is placed within the bone during stage 1 dental implant surgery. It is either titanium or titanium alloy, with or without hydroxyapatite coating.

Cover screw

A screw is placed in the implant during the healing phase after stage 1 surgery. This crew is usually to facilitate easy suturing of the soft tissue over the implant. At stage 2 dental implant procedure screw is removed and replaced with subsequent components.

Healing cap

Healing cap is a dome-shaped screw that is placed after stage 2 surgery and before prosthesis placement. The cap may be made out of resin, such as polyoxyethylene, or one of the titanium metals.

Abutment

Abutment is that component of the implant system that screws directly into the implant. The abutment will eventually directly support the prosthesis. It is smooth, polished straight-sided titanium. The length may range from 1 to 10 millimeters.

Impression post

The impression post facilitates the transfer of intra oral location of fixture or abutment to a similar position in the laboratory cast. Impression post is then removed from the mouth and joined to the lab analogue before being transferred into the impression.

Laboratory analog

Laboratory analog is a component machined to exactly represent either the implant or the abutment in lab cast.

Waxing sleeve

Waxing sleeve is attached to the abutment by the prosthesis=retaining screw on a lab model. Waxing sleeve will eventually become a part of the prosthesis. It may be a plastic pattern that is burned out inside the investment and replaced by a cast precious alloy.

Prosthesis-retained screw

Prosthesis-retaining screw penetrates the fixed restoration and secures it to the abutment. In non-segmented restorations the screw tightens the abutment directly to implant. The screw can be made of titanium, titanium alloy, or gold alloy.

Implant material

Titanium

Titanium is the best material available at present. It oxidizes in the atmosphere to form an inert surface layer of titanium oxide. It has good mechanical properties. Other materials – niobium, hydroxyapatite are well-tolerated.  Hydroxyapatite can be used as coating which is osteoinductive. Aluminum oxides, cobalt-chrome, molybdenum ad stainless steels are less tolerated.

Examination of implant site

Clinical examination

Visual inspection and palpation is done to check for flabby excess tissue, narrow bony ridges, sharp underlying ridges and undercuts.

Radiographic examination

CT scan © http://www.orofacialsurgery.com.sg

• Orthopantomograph (OPG) – to assess vertical bone height,


• Lateral cephalometric film – width of front upper jaw and lower jaw,


• CT scan – to locate inferior alveolar canal and upper jaw sinus and to evaluate ridge form

Study casts

Duplicates can be used for diagnostic wax-up so that the tooth position can be planned. A template can be made with indicator holes drilled as an aid to the surgeon so that the implants are placed in optimal position.

Principles of dental implant surgery

First surgical phase (implant placement)

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Under local anesthesia the dentist places dental implants into the jaw bone with a very precise surgical procedure. The implant remains covered by gum tissue while fusing to the jaw bone.

Second surgical phase (implant uncover)

The length of time necessary to achieve integration varies from site to site. After satisfactory integration of implant uncovering of implant is done to attach the abutment to it with preservation of attached tissues.

Prosthetic phase

Once the gums have healed, an implant crown is fabricated and screwed down to the implant.

Post operative care

Implant survival depends on proper and timely home care and maintenance. The goal of implant maintenance is to eradicate microbial population. Recall visits should be scheduled at least every 3 months for the first year. The area surrounding the implant should be removed of calculus by using plastic or wooden scalers. A rubber cup with low abrasive polishing paste or tin oxide may be used to polish implant abutments.
Points to be evaluated during recall:

• Mobility of implant,


• bleeding,


• framework fit,


• occlusion

Problems involved in dental implants placement

Poor positioning of implants © nature.com

• Improper angulation of implant


• Improper position of implant


• Perforation of maxillary sinus


• Perforation of inferior alveolar canal


• Dehiscence (splitting up) of bucco-cortical or linguo-cortical bone plate


• Lower jaw fracture (in case of thin lower jaw)


• Soft tissue wound dehiscence

Criteria for success of implants

• The individual unattached implant is immobile when tested clinically


• No evidence of peri-implant radiolucency is present as assessed on an undistorted radiograph


• The mean vertical bone loss should be less than 0.02mm annually after the first year of service


• No persistent pain, discomfort or infection is attributable to implants


• The implant design does not preclude placement of a crown or prosthesis with an appearance that is satisfactory to the individual and the dentist.