Dental Implants Chapter 11

Implant Materials Implant metals have been used in orthopedic medicine for many years. In dentistry, titanium is the metal of choice. Implants are anchors for prosthetic devices that are fixed to the bone:  Subperiosteal  Transosteal  Endosseous

Implant Utilization Implants can be used to replace one or more single units as individual crowns or as fixed bridges, or they can support a partial or full denture. In the mandible, atrophy of the alveolar ridge is common in patients who have lost teeth at a relatively young age. Implants can help to retain and stabilize the denture.

Subperiosteal Implants These are placed under the periosteum and rest on the bone. They are constructed and placed in three stages.  First, a surgical incision is made to expose the bony ridge by reflecting the soft tissue and periosteum overlying the bone.  An impression is made of the exposed bone.  The surgical wound is closed.

Subperiosteal Implants (cont’d)  Second, a replica is made of the bony ridge from the impression.  A metal framework is cast in the laboratory to fit over the bone.  This framework has metal projections on which the prosthesis will be attached that extend through the tissues covering the ridge.

Subperiosteal Implants (cont’d)  Third, a second incision is made to reopen the initial wound and once again expose the bone.  The implant framework is inserted over the bone and under the periosteum.  Overlying tissues are sutured closed, with the metal projections for the prosthesis protruding into the oral cavity.  This approach is rarely used in present-day dentistry and has been replaced by endosseous implants.

Transosteal Implant The transosteal implant is used to support a mandibular denture when the patient has severe resorption and lacks enough bone support for endosseous or subperiosteal implants. It consists of a horizontal support beam attached to metal rods that are inserted into holes drilled all the way through the mandible from its superior border to its inferior border.

Transosteal Implant (cont’d) A metal plate through which the ends of the rods pass is bolted to the underside of the mandible. A transosteal implant requires both intraoral and extraoral incisions for its placement and stabilization. It is seldom used because of its highly invasive nature.

Endosseous Implants Endosseous implants are surgically placed into the bone. They are the most popular implants currently in use. Clinical studies have shown these implants to be very successful, with long-term survival (longer than 10 years) of approximately 85% in the maxilla and 95% in the mandible.

Endosseous Implants (cont’d) Titanium and titanium alloys are the metals most commonly used because of their biocompatibility with oral tissues. Titanium is a lightweight, corrosion-resistant material. Bone will grow around and fuse to titanium implants to retain them.

Endosseous Implant Placement and Restoration Surgical approaches to implant placement have variations. Part of the decision on surgical approach depends on whether a healed edentulous space is already present, or whether a tooth needs to be extracted first.

Two-Stage Approach When an implant is placed in two stages, the first stage involves exposing the bone at the chosen placement site with a surgical flap. Next, a hole is drilled in the bone that has the shape and length of the implant cylinder and a size that is just slightly smaller than that of the cylinder. The implant may be lightly tapped into place to have a frictional fit with the bone, or it may be screwed into place.

Two-Stage Approach (cont’d) After the implant fixture is placed in the bone, a screw is placed into the opening at the top of the fixture. The surgical flap is re-positioned and is sutured closed over the implant. Approximately 3 months later, the surgeon uncovers the top of the implant fixture, removes the screw, and places a smooth, dome-shaped component called a healing abutment.

One-Stage Surgical Procedure In the one-stage procedure, surgery for placement of the implant is performed just as in the two-stage procedure. The difference is that with the one-stage procedure, the top of the fixture projects through the soft tissue at the time of surgery and a healing abutment is placed.  The soft tissue is sutured around it rather than covering it.

Immediate-Placement Surgical Procedure When the implant procedure involves the extraction of a tooth, some clinicians place the implant fixture at the time of extraction directly into the new socket.  This is called an immediate-placement surgical procedure. A soft tissue flap is used to cover the extraction site until bone fills in and integrates with the fixture.

Immediate Loading Most clinicians wait for healing of the bone around the implant; others place a provisional crown on the implant fixture immediately after surgical placement. This causes loading of the implant under chewing forces before the bone exhibits healing around the implant. Careful consideration must be made to ensure a successful osseointegration.

Restorative Phase Restoration of the single-tooth implant is usually done with a prosthetic crown. With the one- or two-stage procedure, once the soft tissue has healed around the top of the implant, the impression for the crown can begin. The implant crown may be attached with a screw or through luting cementation.

Maintenance It is critically important to the success of the implant for the patient to employ meticulous oral hygiene techniques and work with the dentist and dental hygienist to implement an effective tissue management program. The dental hygienist plays an integral role in helping the patient maintain the health of the implants and in reinforcing home care techniques.

Home Care Home care should be customized to the patient’s needs. A gentle sulcus brush can help maintain the tissue around the implant. Interproximal brushes should be mounted on plastic instead of metal. Flossing should be done as recommended. Balsa wood toothpicks can aid in plaque removal. Antibacterial mouth rinses can help reduce bacterial load. Refer to home care aids for implant patients pg. 141

Hygiene Visits Hygiene visits should be made as recommended by the dentist. Instruments made of metal should not be used on exposed titanium implants. Plastic or graphite scalers should be used. Medium or coarse prophy pastes should not be used. Tin oxide should be used instead.

Failure Early failure of an implant is usually caused by failure of the bone to integrate with the implant. Failure of the implant that occurs after the initial integration is often caused by bacterial infection extending from the peri-implant tissues into the bone or overloading the implant during function, leading to loss of the supporting bone.

Summary The use of implants is increasing, and titanium implants are enjoying a high degree of success. Diligent home care and professional care are essential for successful procedures.