IMMEDIATE IMPLANT PLACEMENT
A major potential problem after immediate implant placement is recession of the buccal gingiva. Therefore, several clinical factors need to be considered prior to placing an immediate implant in the premaxilla. It is advisable to only do immediate implants when there is a low smile-line, there is no recession on the tooth, the buccal plate is present, and the gingiva is healthy. It is also prudent to only attempt them when there is a thick biotype (85% of patients present with a thick flat gingiva) and an adequate amount of gingiva. The biotype is considered thick if you place a probe within the sulcus and you cannot see the probe; it is labeled as thin if the probe can be seen. On average, thin biotypes have 0.7 mm more recession than thick biotypes. Upon extraction, the buccal plate needs to be assessed with a probe, and immediate placement should only be done when there is an intact buccal plate of bone (the thicker the better). To help avoid recession, the implant’s trajectory should be directed to the cingulum of the future crown to preserve additional buccal bone. If there is a thin biotype, place the implant a little more palatally to decrease the chance of recession and to prevent a titanium shadow from appearing through the thin gingiva. In addition, place it a little more apically to attain a good emergence profile and avoid development of a ridge lap. Pertinently, it needs to be remembered that subsequent to insertion of standard or wide body implants in solid bone, recession was noted at the time of prosthesis placement (0.4 versus 1.15 mm) and increased at one year postinsertion (0.8 versus 1.45 mm). With regard to sites undergoing immediate placement, recession has also been noted. In case of recession, it is sometimes necessary to restore the adjacent teeth so that gingival disharmony can be corrected.
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| Figure 10. Lindemann bur used in anterior socket to create on ledge on the palatal wall. |
After an extraction in the premaxilla, the osteotomy for an immediate implant is usually initiated in the palatal bone of the socket one half to two thirds of the distance to the apex. The site can be marked several different ways: with a round bur directly into the bone (horizontally) and then after a purchase is attained, the twist drill is directed more vertically; the round bur can be used laterally to sink into the bone to create a ledge; a Lindemann bur can be employed to make a ridge on the palatal wall (Figure 10) or a pilot drill with a sharp point can be used to demarcate a purchase point for the twist drill.
When preparing an osteotomy for an immediate implant that is not going to be submerged, it is advisable to widen the orifice on the palatal wall of the osteotomy to accommodate the flare of the implant and healing abutment, or use a straight healing abutment. Otherwise, the flare of the coronal portion of the implant or component will force the implant labially and possibly into an undesirable position. If the implant achieves stability with 30 to 40 Ncm torquing force, then placement of an immediate provisional resin crown is an appropriate protocol. The provisional temporary should be kept out of occlusion.
WOUND HEALING RATES
Repair time for specific tissues significant to the implant surgeon are listed: epithelium—after a 12-hour lag time, 0.5 mm to 1 mm daily; connective tissue—0.5 mm daily; bone—50 µm daily (1.5 mm per month); sinus lift—1 to 2 mm bone per month; Schneiderian membrane—heals at the rate of epithelium. Furthermore, epithelium cannot cover a wound until connective tissue is present, because epithelium is avascular and needs a connective tissue base. With respect to healing after flap surgery, there is a specific sequence of biologic events. Initially, after suturing, the mucoperiosteal flap is attached to bone (or soft-tissue flap) by a blood clot (zero to 24 hours). At one week, the clot has been replaced by granulation tissue. If the flap is adjacent to a tooth, it is connected via an epithelial attachment and young fibroblasts. In any of the healing scenarios, after 2 weeks, fibroblasts produce collagen and the flap is attached to bone via immature collagen fibers. Hiatt, et al used a tensiometer on sacrificed dogs and reported that the force needed to separate a flap from bone was as follows: at 2 to 3 days (225 gm), one week (340 gm), and at 2 weeks, 1700 gm of force could not displace the flap. In general, flaps are attached in 10 days (dog model) and will not be easily displaced. Bear in mind that smaller mammals heal at a slightly faster rate than humans. With regard to post-surgical timing for restorative therapy, Dowling, et al suggested that after flap surgery, clinicians should wait about 8 weeks to allow for collagen maturation before proceeding with final restorations. However, if there was a thin periodontium, recession may manifest itself up until 6 months; therefore, in areas of aesthetic concern, delay of the prosthesis for 5 to 6 months may be needed to ensure gingival margin stability. Subsequent to placement of temporary restorations, 2 to 3 months should be allowed for sculpting of tissues; sometimes it can take longer. After a particulate graft is placed, 4 to 6 months is needed for graft calcification before an implant should be inserted and after a cortical block graft, 4 to 5 months is required for healing. Four to 6 months after placing a particulate graft, before scheduling implant surgery, it is advantageous to anesthetize the area and sound the bone with a 30-gauge needle to determine if the graft is calcified.