Part Two....SURGICAL PROCEDURE
SURGICAL PLANNING....
Prior to commencement of surgery, careful and detailed planning is required to identify vital structures such as the inferior alveolar nerve or the sinus, as well as the shape and dimensions of the bone to properly orient the implants for the most predictable outcome. Two-dimensional radiographs, such as orthopantomographs or periapicals are often taken prior to the surgery. Sometimes, a CT scan will also be obtained. Specialized 3D CAD/CAM computer programs may be used to plan the case.
Whether CT-guided or manual, a "stent" may sometimes be used to facilitate the placement of implants. A surgical stent is an acrylic wafer that fits over either the teeth, the bone surface or the mucosa (when all the teeth are missing) with pre-drilled holes to show the position and angle of the implants to be placed. The surgical stent may be produced using stereolithography following computerized planning of a case from the CT scan. CT guided surgery may double the cost compared to more commonly accepted approaches.
BASIC PROCEDURE:
In its most basic form, the placement of an osseointergrated implant requires a preparation into the bone using either hand osteotomes or precision drills with highly regulated speed to prevent burning or pressure necrosis of the bone. After a variable amount of time to allow the bone to grow on to the surface of the implant (osseointegration) a tooth or teeth can be placed on the implant. The amount of time required to place an implant will vary depending on the experience of the practitioner, the quality and quantity of the bone and the difficulty of the individual situation.
DETAIL PROCEDURE:
At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid the vital structures (in particular the inferior alveolar nerve or IAN and the mental foramen within the mandible). Drilling into jawbone usually occurs in several separate steps. The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length). Care is taken not to damage the osteoblast or bone cells by overheating. A cooling saline or water spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwd into place at a precise torque so as not to overload the surrounding bone (overloaded bone can die, a condition called osteonecrosis, which may lead to failure of the implant to fully integrate or bond with the jawbone). Typically in most implant systems, the osteotomy or drilled hole is about 1mm deeper than the implant being placed, due to the shape of the drill tip. Surgeons must take the added length into consideration when drilling in the vicinity of vital structures.
SURGICAL INCISIONS:
Traditionally, an incision is made over the crest of the site where the implant is to be placed. This is referred to as a "flap". Some systems allow for "flapless" surgery where a piece of mucosa is punched-out from over the implant site. Proponents of "flapless" surgery believe that it decreases recovery time while its detractors believe it increases complication rates because the edge of bone cannot be visualized. Because of these visualization problems, flapless surgery is often carried out using a surgical guide constructed following computerized 3D planning of a pre-operative CT scan.
HEALING TIME:
The amount of time required for an implant to become osseointegrated is a hotly debated topic. Consequently the amount of time that practitioners allow the implant to heal before placing a restoration on it varied widely. In general, practitioners allow 2-6 months for healing but preliminary studies show that early loading of implant may not increase early or long term complications. If the implant is loaded too soon, it is possible that the implant may move which results in failure. The subsequent time to heal, possibly graft and eventually place a new implant may take up to eighteen months. For this reason many are reluctant to push the envelope for healing.
ONE -STAGE, TWO-STAGE SURGERY:
When an implant is placed either a "healing abutment", which comes through the mucosa, is placed or a "cover screw" which is flush with the surface of the dental implant is placed. When a cover screw is placed the mucosa covers the implant while it integrates then a second surgery is completed to place the healing abutment.
Two-stage surgery is sometimes chosen when a concurrent bone graft is placed or surgery on the mucosa may be required for esthetic reasons. Some implants are one piece so that no healing abutment is required.
In carefully selected cases, patients can be implanted and restored in a single surgery, in a procedure labeled "Immediate Loading". In such cases a provisional prosthetic tooth or crown is shaped to avoid the force of the bite transferring to the implant while it integrates with the bone.
CONT.....
Prior to commencement of surgery, careful and detailed planning is required to identify vital structures such as the inferior alveolar nerve or the sinus, as well as the shape and dimensions of the bone to properly orient the implants for the most predictable outcome. Two-dimensional radiographs, such as orthopantomographs or periapicals are often taken prior to the surgery. Sometimes, a CT scan will also be obtained. Specialized 3D CAD/CAM computer programs may be used to plan the case.
Whether CT-guided or manual, a "stent" may sometimes be used to facilitate the placement of implants. A surgical stent is an acrylic wafer that fits over either the teeth, the bone surface or the mucosa (when all the teeth are missing) with pre-drilled holes to show the position and angle of the implants to be placed. The surgical stent may be produced using stereolithography following computerized planning of a case from the CT scan. CT guided surgery may double the cost compared to more commonly accepted approaches.
BASIC PROCEDURE:
In its most basic form, the placement of an osseointergrated implant requires a preparation into the bone using either hand osteotomes or precision drills with highly regulated speed to prevent burning or pressure necrosis of the bone. After a variable amount of time to allow the bone to grow on to the surface of the implant (osseointegration) a tooth or teeth can be placed on the implant. The amount of time required to place an implant will vary depending on the experience of the practitioner, the quality and quantity of the bone and the difficulty of the individual situation.
DETAIL PROCEDURE:
At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid the vital structures (in particular the inferior alveolar nerve or IAN and the mental foramen within the mandible). Drilling into jawbone usually occurs in several separate steps. The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length). Care is taken not to damage the osteoblast or bone cells by overheating. A cooling saline or water spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwd into place at a precise torque so as not to overload the surrounding bone (overloaded bone can die, a condition called osteonecrosis, which may lead to failure of the implant to fully integrate or bond with the jawbone). Typically in most implant systems, the osteotomy or drilled hole is about 1mm deeper than the implant being placed, due to the shape of the drill tip. Surgeons must take the added length into consideration when drilling in the vicinity of vital structures.
SURGICAL INCISIONS:
Traditionally, an incision is made over the crest of the site where the implant is to be placed. This is referred to as a "flap". Some systems allow for "flapless" surgery where a piece of mucosa is punched-out from over the implant site. Proponents of "flapless" surgery believe that it decreases recovery time while its detractors believe it increases complication rates because the edge of bone cannot be visualized. Because of these visualization problems, flapless surgery is often carried out using a surgical guide constructed following computerized 3D planning of a pre-operative CT scan.
HEALING TIME:
The amount of time required for an implant to become osseointegrated is a hotly debated topic. Consequently the amount of time that practitioners allow the implant to heal before placing a restoration on it varied widely. In general, practitioners allow 2-6 months for healing but preliminary studies show that early loading of implant may not increase early or long term complications. If the implant is loaded too soon, it is possible that the implant may move which results in failure. The subsequent time to heal, possibly graft and eventually place a new implant may take up to eighteen months. For this reason many are reluctant to push the envelope for healing.
ONE -STAGE, TWO-STAGE SURGERY:
When an implant is placed either a "healing abutment", which comes through the mucosa, is placed or a "cover screw" which is flush with the surface of the dental implant is placed. When a cover screw is placed the mucosa covers the implant while it integrates then a second surgery is completed to place the healing abutment.
Two-stage surgery is sometimes chosen when a concurrent bone graft is placed or surgery on the mucosa may be required for esthetic reasons. Some implants are one piece so that no healing abutment is required.
In carefully selected cases, patients can be implanted and restored in a single surgery, in a procedure labeled "Immediate Loading". In such cases a provisional prosthetic tooth or crown is shaped to avoid the force of the bite transferring to the implant while it integrates with the bone.
CONT.....
