Dental implant


A dental implant is a surgical component that interfaces with the bone of the jaw or skull to support a dental prosthesis.

Such prostheses include: crown, bridge, denture, facial prosthesis or an orthodontic anchor. 

The implant fixture is first placed so that it is likely to osseointegrate, then a dental prosthetic is added. 

A variable amount of healing time is required for osseointegration before either the dental prosthetic is attached to the implant.

The success of an implant relates to the health of the person receiving the treatment, drugs which affect the chances of osseointegration, and the health of the tissues in the mouth. 

The amount of stress that will be put on the implant and fixture during normal function is evaluated, and the position and number of implants is key to the long-term health of the prosthetic since biomechanical forces created during chewing can be significant. 

Implant positioning is determined by the position and angle of adjacent teeth using lab simulations with computed tomography and surgical guides called stents. 

To achieve long-term success of osseointegrated dental implants, healthy bone and gingiva are required: pre-prosthetic procedures are sometimes required to recreate ideal bone and gingiva.

Prostheses can be either fixed, where a person cannot remove the denture or teeth from their mouth, or removable, where they can remove the prosthetic. 

In each case an abutment is attached to the implant fixture. 

If the prosthetic is fixed, the crown, bridge or denture is fixed to the abutment either with lag screws or with dental cement. 

When the prosthetic is removable, a corresponding adapter is placed in the prosthetic so that the two pieces can be secured together.

The risks and complications related to implant therapy:  

Those that occur during surgery, such as excessive bleeding or nerve injury.

Those that  occur in the first six months, such as infection and failure to osseointegrate.

Those  that occur long-term, such as peri-implantitis and mechanical failures.

A healthy, well-integrated implant with appropriate biomechanical loads can have 5-year plus survival rates from 93 to 98 percent, and 10 to 15 year lifespans for the prosthetic teeth.

Studies show a 16- to 20-year implant success rate between 52% and 76%, with complications occurring up to 48% of the time.

Dental implant primary use is to support dental prosthetics, meaning false teeth.

Modern dental implants make use of 

Osseointegration the biologic process where bone fuses tightly to the surface of specific materials such as titanium and some ceramics, allows for successful dental implants.

The integration of implant and bone can support physical loads for decades without failure.

Implants are used to replace missing individual teeth, multiple teeth, or to restore edentulous dental arches, and in 

orthodontics to provide anchorage.

Implants can be used to retain obturators, removable prosthesis used to fill a communication between the oral and maxillary or nasal cavities.

Facial prosthetics, for facial deformities can use connections to implants placed in the facial bones.

Single tooth restorations are individual freestanding units used to replace missing individual teeth.

For individual tooth replacement, an implant abutment is first secured to the implant with an abutment screw. 

A crown dental prosthesis is connected to the abutment with dental cement, a small screw, or fused with the abutment as one piece during fabrication.

Dental implants can also be used to retain a multiple tooth dental prosthesis either in the form of a fixed bridge or removable dentures.

Implant-supported single crowns perform better than tooth-supported fixed partial dentures on a long-term basis. 

Dental implant therapy is the first-line strategy for single-tooth replacement. 

Implants also preserve the integrity of the adjacent teeth.

An implant supported bridge is a group of teeth secured to dental implants so the prosthetic cannot be removed by the user. 

An implant supported bridge is similar to conventional bridges, except that the prosthesis is supported and retained by one or more implants instead of natural teeth. 

Bridges typically connect to more than one implant and may also connect to teeth as anchor points. 

A removable implant supported denture prosthesis which replaces teeth, uses implants to improve support, retention and stability. 

They are most commonly complete dentures used to restore edentulous dental arches.

The dental prosthesis can be disconnected from the implant abutments with finger pressure by the wearer. 

Dental implants are used in orthodontics to replace missing teeth or as a temporary anchorage device to facilitate orthodontic movement by providing an additional anchorage point.

Implants are ideal anchor points in orthodontics, are small and do not fully osseointegrate, allowing easy removal following treatment.

Small-diameter implants provide edentulous and partially edentulous patients with immediate functioning transitional prostheses while definitive restorations are being fabricated. 

An orthodontic implant is placed beside teeth to act as an anchor point to which braces can be secured.

Typical implants consists of a titanium screw.

Ceramic zirconia-based implants exist in one-piece or two-piece systems.

Implants require a guide is made to show the desired position and angulation of the implants.

Guides are usually acrylic.

The final position and restoration of the teeth will be simulated on plaster models to help determine the number and position of implants needed.

CT scans can be loaded to CAD/CAM software to create a simulation of the desired treatment, and  virtual implants are then placed and a stent created on a 3D printer from the data.

Dental implants requires assessment of health condition of the patient, the local health condition of the mucous membranes and the jaws and the shape, size, and position of the bones of the jaws, adjacent and opposing teeth. 

Peri-implantitis a variant of gum disease that affects implants occurs at a higher risk in patients with poor oral hygiene, heavy smokers and diabetics, increasing the chance of long-term failures. 

Similarly, long-term steroid use, osteoporosis and other diseases that affect the bones can increase the risk of early failure of implants.

Radiotherapy can negatively affect the survival of implants.

Implants success is determined, in part, by the forces support. 

Implants have no periodontal ligament, there is no sensation of pressure when biting so the forces created are higher. 

The  location of implants must distribute forces evenly across the prosthetics they support.

The concentration of forces can result in fracture of the bridgework, implant components, or loss of bone adjacent the implant.

Implant location is based on both bone type, vital structures, health and mechanical factors. 

Thicker, stronger boned implants like that found in the front part of the bottom jaw have lower failure rates than implants placed in lower density bone, such as the back part of the upper jaw. 

Grinding of teeth increases the force on implants and increase the likelihood of failures.

Tests can determine the long-term mechanical reliability of implants where the implant is struck repeatedly with increasing force.

Acrylic guides and CT scans provide optimal positioning of the implant. 

CT scanning helps identify and avoid vital structures such as the inferior alveolar nerve and the sinus.

Approaches to placement dental implants after tooth extraction:

Immediate post-extraction implant placement.

Delayed immediate post-extraction implant placement at two weeks to three months after extraction.

Late implantation at three months or more after tooth extraction.

After an implant is placed, the internal components are covered with either a healing abutment, or a cover screw. 

After an integration period, a second surgery is required to reflect the mucosa and place a healing abutment.

No difference in implant survival exists between one-stage and two-stage surgeries.

The choice of one or two-stages is related to how best reconstruct the soft tissues around lost teeth.

If bone width is inadequate it can be regrown using either artificial or cadaveric bone as a scaffold for natural bone to grow around.

An implant needs to be surrounded by a healthy quantity of bone to properly osseointegrate.

For an implant to survive long-term, it needs also to have a thick healthy soft tissue gingival envelope around it. 

Bone grafting is necessary when there is a lack of bone,and it stabilizes the implant by increasing survival of the implant and decreasing marginal bone level loss.

A treatment goal is to have a minimum of 10 mm in bone height, and 6 mm in width. 

When mucosa is missing a free gingival graft of soft tissue can be transplanted.

Options for when to attach teeth to dental implants: 

Early loading-one week to twelve weeks.

Delayed loading, over three months.

The initial stability of the implant in bone is am important determinant of success of implant integration, rather than a certain period of healing time. 

The time allowed to heal is typically based on the density of bone the implant is placed in and the number of implants splinted together.

Abutments are used to retain dentures using a male-adapter attached to the implant and a female adapter in the denture. 

Two common types of adapters are the ball-and-socket style retainer and the button-style adapter, which allow movement of the denture, but enough retention to improve the quality of life for denture wearers, compared to conventional dentures.

Implants need to be cleaned with a periodontal scaler to remove any plaque. 

Implants lose bone at a rate similar to natural teeth in in the mouth.

The same kinds of techniques used for cleaning teeth are recommended for maintaining hygiene around implants.   

Peri-implantitis is a condition that may occur with implants due to bacteria, plaque, or design.

Peri-implantitis if left untreated, can lead to implant failure.

Dental implantation is a surgical procedure and carries the normal risks of surgery including infection, excessive bleeding and necrosis of the flap of tissue around the implant. 

Surrounding structures, such as the inferior alveolar nerve, the maxillary sinus and blood vessels, can also be injured when the osteotomy is created or the implant placed.

Difficulty in placement of the implant in bone to provide stability of the implant increases the risk of failure to osseointegration.

Complications of implants:

Peri-implantitis-bone loss

Recession of the gingiva

Black triangles caused by bone loss between implants and natural teeth

Fracture of an implant and abutment screw.

Abutment fracture

Screw fracture

Cement peri-implantitis

Primary implant stability refers to the stability of a dental implant immediately after implantation. 

The stability of the titanium screw implant may be non-invasively assessed using resonance frequency analysis. 

Sufficient initial stability allows immediate loading with prosthetic reconstruction, but poses a higher risk of implant failure than conventional loading.

Secondary stability results from the process of bone regrowth into the implant. 

When healing process is complete, the initial mechanical stability becomes biological stability. 

Primary stability is critical to implantation success,  when bone regrowth maximizes mechanical and biological support of the implant. 

Bone regrowth usually occurs during the 3–4 weeks after implantation. 

Insufficient primary stability, or high initial implant mobility, can lead to failure.

Pre-op antibiotics reduce the risk of implant failure by 33 percent but do not affect the risk of infection.

Risk factors:

Excessive bleeding

Flap breakdown

Failure to integrate

Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and the patient’s oral hygiene, but the most important factor is primary implant stability.    

The rate that implants fail to integrate is 1 to 6 percent.  

Immediate loading implants may have a higher rate of failure.

Osseointegration failure occurs when a patient is too unhealthy to receive the implant or engages in behavior that contraindicates proper dental hygiene:including smoking or drug use.

The long-term complications: risks associated with appearance including a high smile line, poor gingival quality and missing papillae, poor matching the form of natural teeth, unequal points of contact, bone abnormalities and unrealistic expectations of the patient.

Risks can be related to biomechanical factors, where the geometry of the implants does not support the teeth in the same way the natural teeth did, a poor crown-to-root ratio, grinding of the teeth, lack of bone or low diameter implants.

Technological risks include implant failure  due to fracture or a loss of retention to the teeth they are intended to support.

Long-term failures are due to either loss of bone around the tooth and/or gingiva due to peri-implantitis or a mechanical failure of the implant. 

Because there is no dental enamel on an implant, it does not fail due to cavities like natural teeth. 

Estimates of the long-term (five to ten years) survival of dental implants is at 93–98 percent depending on their clinical use.

Criteria for the success of the implant: at least five years in the absence of pain, mobility, radiographic lucency and peri-implant bone loss of greater than 1.5 mm on the implant, the lack of suppuration or bleeding in the soft tissues and occurrence of technical complications/prosthetic maintenance, adequate function, and esthetics in the prosthetic, absence of paraesthesia, and able to chew and taste and be pleased with the esthetics.

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