California Continuing Education Credits: 4 units
COURSE OUTLINEThere are 2 basic modalities of reconstructive osseous surgery:
There are basically three (3) different types of materials that can be used in periodontal regeneration. A fourth one is listed for informative purposes only since it is not currently being utilized.
Autogenous bone grafts can be divided into extraoral and intraoral sources.
These grafts are taken from iliac bone. Studies have shown that bone fill in periodontal defects can be achieved with iliac bone. The amount of bone fill varies between 3.3 and 3.6 mm. There have been several reports of histologic regeneration being achieved. This was determined by extracting the tooth and sectioning it for histological observations where true periodontal regeneration was confirmed.
This modality of bone graft can be used "fresh" or "frozen". A fresh graft is when the periodontal surgery is performed at the same time that the graft is retrieved from the iliac bone. A frozen graft is when the graft removal procedure from the patient is done at one appointment, and it is frozen until it is used for a second appointment at a later time when the periodontal surgical procedure is executed.
The potential problems with extraoral autogenous bone grafts are: (a) high prevalence of root resorption for unknown reasons (if used fresh) and (b) it is difficult to obtain patient acceptance of treatment since it involves a surgery which has to performed by a medical doctor in a hospital setting.
This is the ideal bone graft material for periodontal regeneration. Areas that can work as donor sites are usually the maxillary tuberosity, mandibular retromolar regions, mandibular tori, or a healed extraction socket. Bone removed during resective osseous surgery can also be used as graft if available in sufficient quantity.
Both cancellous and/or cortical bone can be used. The advantages of using cancellous bone is that it is highly cellular and its osteogenic capability is higher. The advantages of using cortical bone is that it provides a firmer to the graft material and therefore facilitates manipulation. Ideally, a combination of cortical and cancellous bone is desirable.
Studies have shown that the bone fill achieved with autogenous bone grafts varies between 1.2 and 3.4 mm.
The main limitation of this technique is the amount of bone available. Often times the retrievable amount of bone is not sufficient which will dictate the need for alternatives.
Fresh/Frozen
These are bone grafts obtained from one person and used on another patient. There are two major problems with fresh/frozen which led to discontinuation of use:
Freeze-Dried Bone
There are two types of freeze-dried bone grafts: (a) freeze-dried or (b) decalcified freeze-dried.
Freeze-dried bone is obtained by a freeze drying process of cadaveric cortical bone.
Decalcified freeze-dried bone (DFDBA) is obtained by a similar process as freeze-dried bone, except that the processing includes demineralization in hydrochloric acid. The donor bone is obtained from a cadaver, that was previously screened for syphilis, hepatitis B and C, and HIV virus and antibody. Freeze-dried bone and its decalcified for are made into a powder form which can be stored at room temperature for long periods of time. This bone graft material is purchased from tissue banks.
The freeze drying process eliminates antigenicity, preventing a foreign body type of reaction. Research of freeze-dried bone grafts has shown that 50% bone fill is obtained in 63% of defects treated. For example, in a 6 mm periodontal defect 3 mm of bone fill is gained in 63% of defects treated. The average bone fill achieved, 1.3 to 2.6 mm, is similar to other graft materials. Particle size seems to play an important role in the success of the procedure. The ideal particle size is between 250 and 750 microns. Too small of a particle tends to get resorbed quickly and too large of a particle hinders adaptation of the graft material to that defect.
The preference to use decalcified freeze-dried over freeze-dried bone has been attributed to the decalcifying process which exposes the Bone Morphogenic Protein (BMP). Thereby, the osteogenic potential of the decalcified freeze-dried is higher than the freeze-dried alone. However, the results achieved in terms of bone fill in periodontal defects are very similar between both processes. Histologically, new attachment can be gained with both types of freeze-dried bone graft materials. In theory, the exposure to BMP (Bone Morphogenic Protein) may play a significant role, however, improved clinical results have not been proven. Decalcified freeze-dried bone remains the most commonly used form of Allograft material.
In order to prevent risks of infection to patients with the placement of decalcified freeze-dried bone from a cadaver, several safety measures are undertaken. First, an extensive medical history is usually reported by the family. The cadaver is screened for the HIV antibody and virus. Polimerase chain reaction (PCR) has reduced the window of HIV exposure to two days versus 6 to 8 weeks. Moreover, studies have shown that the freeze drying process, ethyl alcohol wash and the hydrochloric acid treatment, inactivates HIV transmission. According to recent statistics, the chance of HIV transmission is 1:8,000,000 to 1:60,000,000 and to date not a single case has been documented. The contaminated cases that have been documented by the Center for Disease Control have been with the fresh bone grafts and not decalcified freeze-dried bone.
There are several different forms available. The most extensively researched alloplastic material for periodontal defects is Porous Hydroxyapatite. There are, however, several other synthetic materials available.
It is calcium carbonate material obtained from a marine coral material that has been converted into hydroxyapatite. The material is mixed with water or saline solution and then placed into the defect.
The defect bone fill observed is between 1.6 and 3.5 mm, similar to decalcified freeze-dried bone. Clinical resolution of pocket depth associated with the defect can be achieved. Hydroxyapatite granules tend to be encapsulated by connective tissue and the evidence of new attachment is limited. New attachment, or true regeneration is more unlikely to take place with alloplasts than it is with autogenous bone or allografts. Allografts and hydroxyapatite when compared, in terms of bone fill only, have a similar result.
Other forms alloplastic materials are:
The process of selecting the appropriate bone graft material is based on the clinician.
Conservative incisions are done to provide a soft tissue cover over the graft material at the end of the procedure. The soft tissue cover prevents the material from being washed away. Incision are made very close to the sulcus or many times in the sulcus.
Flap reflection to expose the recipient area (full thickness flap) is done. A relatively thick flap is preferred over a thin flap to prevent tissue necrosis and possible washing away of the graft material. The case illustrated, was part of a study done at UCLA to compare the results of decalcified freeze-dried bone with porous hydroxyapatite. The defect between tooth #29 and tooth #30 received a porous hydroxyapatite graft; the defect between tooth #28 and tooth #29 received freeze-dried bone and the defect between tooth #27 and tooth #28 received freeze-dried bone. This patient had undergone Phase I treatment (scaling and root planing).
Soft tissue debridement is an integral part of this procedure which can be accomplished by using a combination of hand curettes and an ultrasonic instrument. The graft material needs to be in contact with the patientıs own bone to receive adequate blood supply. Any remaining tissue tags may compromise the maximum contact between the graft material and the underlying bone.
Scaling and root planing is a crucial step to the success of reconstructive procedures.
It is usually done mechanically with the use of curettes and files and the ultrasonic device.
Rotary instruments such as finishing burs and white and green stones can also be used. The clinician needs to place careful attention not to create large gouges on the root when using rotary instruments. Another step taken by many clinicians is the chemical treatment of the root surface with citric acid or tetracycline hydrochloride. This process is done to decontaminate the root surface and therefore increase the compatibility of the root surface with cell attachment. Not only is the complete removal of calculus embedded in the root surface required, but removal of altered cementum will also be necessary.
Following extensive rinsing of the root surface/defect with water, this is a diagramatic view of the root preparation.
Intramarrow penetration to encourage blood supply The first step is to even out the surface of the defect. A large bur can be used. The defect is lined by a cortical wall of bone that can limit blood flow to the graft area. Small perforations with a round bur, as the slide illustrates, will encourage blood supply from the underlying cancellous bone, and provide the graft with sufficient nutrients for survival.