Limited bone availability makes implant placement challenging and sometimes unpredictable. Candidates for implant therapy must have enough bone to enable implant placement in a position that allows for proper form, function and emergence profile of the dental prosthesis. Also, as teeth are lost, the subsequent bone resorption can result in a lack of attached gingiva on the facial aspect as the mucosal tissue relocates to the crest of the edentulous ridge, potentially compromising the esthetics of the case.
Fortunately, socket and defect grafting procedures allow us to regenerate bone at sites where deficiencies are present, facilitating implant placement for patients who might otherwise be contraindicated for treatment. This has made proper bone grafting techniques an essential part of the implant practitioner’s skill set. Indeed, the days of being restricted by limited bone availability are long gone, even in esthetically demanding situations. With the use of the appropriate materials and techniques, clinicians can prepare a site for eventual implant placement or repair a bone defect during immediate implantation with a high degree of restorative predictability.
The days of being restricted by limited bone availability are long gone, even in esthetically demanding situations.
Although autogenous grafts, which are harvested from another site on the patient’s body, were long considered the “gold standard,” they have fallen out of favor among many clinicians due to the invasiveness of this procedure. Allograft materials, harvested from the bone of human donors, have become very popular because a second surgical site is not required. With cortico/cancellous allograft materials, bone is ground into cortical and cancellous particles and processed to prevent disease transmission and antigenic response. The cortical particulate provides space maintenance during the regeneration process, while the cancellous bone remodels at a faster rate.
Mineral-collagen composite is a grafting material that becomes a moldable putty upon wetting. The calcium phosphate-based mineral is combined with a type 1 collagen derived from bovine Achilles tendon and features a carbonate apatite structure similar to natural bone. Although standard alloplastic (synthetic) and xenograft (from another species) materials are additional options, the use of cortico/cancellous allograft blend and mineral-collagen composite will be described here, as their suitability for a wide range of bone regeneration procedures is ideal for the implant armamentarium.
Simple socket regeneration techniques are an important adjunct following the atraumatic extraction of teeth. Tooth extraction is accompanied by changes in bone morphology, as the socket site will resorb, leaving a shorter, thinner residual ridge. Delayed implant placement requires adequate bone quality and quantity to achieve sufficient primary stability and eventual osseointegration, necessitating ridge preservation to help maintain available bone.
After tooth removal and thorough debridement, an allograft material or mineral-collagen composite is prepared for insertion into the extraction socket. The grafting material is hydrated and then packed firmly — but not aggressively — into the socket. Care should be taken to avoid crushing any of the grafting material, which can accelerate the rate of resorption. The grafting material is eventually replaced by the patient’s own bone and is a safe, predictable means of preserving the ridge.1
Because epithelial tissue grows significantly faster than bone regenerates, it is imperative that the extraction socket be covered with a protective membrane, which provides a barrier against epithelial downgrowth into the grafted site. Resorbable membranes are intended to last anywhere from eight weeks to several months before dissolving and are ideal for most grafting procedures because a second surgical procedure is not required to remove the membrane. Following socket grafting and in the absence of facial defects, the membrane is positioned directly over the crestal aspect prior to suturing.
Bone grafting is typically indicated when immediately placing an implant following an atraumatic extraction. Because tooth sockets are elliptical in cross section and implants are cylindrical, grafting material must be added to fill in any gaps greater than 2 mm.2 This allows osteoclastic activity to resorb the bone particulate and replace it with natural bone.
When a facial defect is present at the site of an immediate implant, allograft material is usually indicated and is placed within the void and packed firmly but not condensed. A resorbable membrane is then positioned at least 2 mm beyond the facial defect and draped over the ridge to engage a minimum of 2 mm of palatal or lingual bone. Passively placing the membrane in this way will make for a predictable bone repair process and avoid the membrane becoming dislodged during suture placement or removal.3
The following case examples illustrate the two most common bone grafting indications in implant dentistry. With the use of grafting material and straightforward surgical techniques, practitioners can maximize bone volume at the sites of tooth extractions and facial defects, establishing the foundation needed to achieve acceptable implant stability and excellent long-term functional and esthetic results.
The loss of bone following an extraction can be unpredictable and may result in conditions that impede our ability to provide routine implant therapy. Socket regeneration and other osseous grafting procedures are a proven treatment for patients, as they allow us to confidently place implants in situations where the volume or contours of bone at the edentulous site are unfavorable. Indeed, these techniques and materials have helped elevate the quality of care by expanding the patient population able to receive implant treatment.