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Stuart J. Froum, D.D.S.
Dental implants have become a predicable treatment modality for prosthetic restoration of fully and partially edentulous patients.1-4Albrektsson et al. reported 5- to 8-year implant success rates of 99.1% in the mandible and 84.9% in the maxilla.5 These rates were predicated on a traditional implant approach by Branemark et al. and Adell et al. recommending a 6- to 12-month healing period after tooth extraction and prior to implant placement.6,7 This time frame and the
additional 3 to 6 months required for osseointegration of the implants, along with the time necessary for loading and fabrication of the restoration, often resulted in a treatment time of 1 to 2 years before the patient received the final implant supported restoration. In an attempt to reduce this treatment time, implant companies produced textured implants, which allowed earlier loading.8,9 One-stage implants requiring no second surgery for abutment placement were also introduced.10-12 In selected cases, implants were loaded with provisional restorations on the day of implant placement13-18 Finally, reports by Schulte et
al. in Germany, Lazzara in the United States and others established immediate implant placement (IIP) as a routine clinical procedure.19-26
The purpose of this article is to review the rationale, indications, techniques, and contraindications for
IIP in extraction sockets.
Rationale for IIP
Literature reviews by Schwartz-Arad and Chaushu, Chen et al. and Mayfield delineated the advantages of immediate versus delayed implant placement as follows27-29:
1. Treatment time is reduced.
2. Amount of surgery is reduced.
3. Width and height of the alveolar bone are preserved.
4. Ideal implant location can be achieved provided that the extracted tooth has a desirable alignment and there is maximum soft tissue support.
As an adjunct to these advantages, several others accrue, which include less surgical morbidity, a reduction in treatment expense, if additional regenerative techniques (bone grafts and membrane use) are not applied and better patient acceptance of the treatment plan.
The biologic advantage often mentioned in the immediate implant literature is the contention that the implant will prevent postsurgical bone resorption seen following tooth extraction as a normal part of the socket healing.
This resorption has been documented in several studies and has been reported to result in a 45% reduction in the alveolar crest. The majority of this bone loss occurs over the first 6 months following extraction and the wearing of a denture.30, 31 In the posterior maxilla, horizontal bone resorption amounting to 3 to 7 mm after 6 months has been shown to nearly correspond to the vertical bone
Resorption.32 Two studies by Lekovic et al and another by Iasella et al demonstrated significant occlusoapical and buccolingual resorption following tooth extraction in sockets allowed to heal for 4 to 6 months in the absence of any treatment.33-35 Changes in the horizontal dimension of these sockets showed an average loss of 4.5 mm in buccolingual width and an average 1.5 mm vertical resorption of the buccal plate of bone.34 Other articles proposed that the placement of an implant immediately after tooth extraction may help preserve the alveolar bone dimension, allowing placement of longer and wider implants.36-38 However, Covani et al. measured the buccal to lingual bone at the time of HP {15 implants in 15 patients) and again at second-stage surgery 6 months later.39 In spite of the implant being immediately placed, the mean distance in the buccolingual direction decreased from an average of 10.5 mm (± 1.54) to 6.8 mm (± 1.33). A more recent article by Covani compared buccolingual bone resorption in cases of immediate versus delayed (6-8 weeks) implant placement; the results demonstrated that less resorption occurred in sockets receiving the immediate
implants (1.9 mm) than in sockets allowed to heal naturally (3.06 mm).40Although reduced by IIP, this degree of horizontal resorption may present problems, especially in the esthetic zone, and will be discussed later in this article.
Evaluating Outcomes of IIP
Ideally, randomized controlled human trials reporting on implant success would present the highest level of scientific rigor to evaluate the efficacy of IIP. However, a recent literature review reported that no studies of this type have been published to date.28 Therefore, controlled clinical trials, documenting implant survival, prospective and retrospective case series and case reports, as well as the few available histologic reports, are used to assess the results of IIP. This article will also rely heavily on the literature reviews and associated consensus statements.27-29
A number of studies reported demonstrate high levels of survival for implants placed immediately after tooth extraction (Table 1). However, differences in technique, use of graft or bone replacement graft and the nonuse or use of nonabsorbable or absorbable membrane barriers, soft tissue closure over the implant, use of implants with different surface textures and sizes and different locations of placement make it difficult to compare and evaluate which variables are crucial for implant success. In reviewing these studies, it will therefore be helpful to describe the materials used and whether soft tissue coverage of the implant was achieved. Wagenberg and Ginsberg retrospectively analyzed 1,081 implants placed into extraction sockets.41 Of these, 35% were followed for
1 year, 46% followed for 2 to 5 years and 19% for 5 to 11 years postloading. No mention was made of the type of implant surface used. Mineralized freeze-dried
bone was packed around the implants, and a polyglactin 910 (Vicryl) membrane was placed extending over the implant 2 to 3 mm beyond the borders of the alveolar defect. No attempt was made to obtain complete flap closure over the membrane. The overall implant survival rate was 95%. Implant failure was twice as high for maxillary molars as for mandibular molars. Becker et al., in a prospective clinical trial, evaluated 134 implants in 81 patients placed in fresh extraction sockets that were not augmented with barrier membranes or graft materials.42 All implants had machined (turned) surfaces. Pedicle flaps were rotated, covering the implant sites. The authors noted that all implants were placed into good jaw bone anatomy and quality. The 7-year cumulative success rate (CSR) was 93.3%.
Schwartz-Arad et al. evaluated 56 immediately placed implants in 43 patients, all molars, from 1989 to 1996.43 They recorded the influence of the following parameters on implant failure: gender, arch, smoking, pre extraction vertical bone loss and implant length. The 5-year CSR was 89%; for men, it was 84%, and for women, it was 93.5%. The 5-year CSR was 82% in the maxilla and 92% in the mandible. Nonsmokers had a CSR of 90%, whereas smokers had a CSR of 83%. The authors stated that small autogenous bone chips (from bone adjacent to the implant site or bur debris) were used "when needed" as a graft between the socket walls and implant. Six collagen bioabsorbable and two expanded polytetrafluoroethylene (e-PTFE) nonabsorbable membranes were used
"according to the clinical judgment of the operator." Primary flap closure was obtained according to the authors "in all cases with bone grafting and membranes." Neither mean implant length and diameter nor pre-extraction vertical bone loss had any effect on implant survival. The authors concluded that although immediate implantation was a predictable procedure, implant prognosis was better in the posterior mandible than in the posterior maxilla.
Rosenquist and Grenthe evaluated 109 machine-surface immediately placed implants following extraction in 51 patients.44 The mean follow-up period was 30.5 months (range 1-67 months) and "no effort was made to fill the gap between the implant and the surrounding socket gap with a graft." Closure over the implant varied from using pedicles or free mucosal grafts to using e-PTFE membranes in five patients. The implant survival rate was 93.66%. The survival rates differed depending on whether the teeth were extracted for periodontal reasons (survival rate = 92.0%) versus nonperiodontal reasons (survival rate = 95.8%).44 Kan et al., in a prospective study, placed 35 threaded hydroxyapatite (HA)- coated implants in 35 patients with immediate provisionalization. 45 All implants at 12 months remained osseointegrated. However, implants were placed only in sockets with intact labial plates. Midfacial gingival, mesial and distal papilla shrinkage was recorded to be -0.55 ± 0.53 mm, -0.53 ± 0.39 mm and -0.39 ± 0.40 mm, respectively. Gomez-Roman et al. placed 124 stepped-screw implants (grit-blasted and acid-etched surface) in 104 patients immediately following extraction or implant explanation in a retrospective study.46 Grafts included autogenous bone (n = 9) or bone substitutes {n = 24). Membranes were used "if the periosteum was not intact.” Implant survival rates remained at 97% from 1 to 5.65 years after implant placement. The average observation period following prosthesis placement was 2.6 years, with the longest observation period, post-implant placement, being 6.3 years. The technique of implant placement was performed without incisions, and "an attempt was
made to cover the implant with flap closure."46
Gelb retrospectively reported on 50 consecutively placed immediate implants in 35 partially edentulous patients over a 3-year period.26 All implants had turned surfaces. Treatment protocol varied depending on the defect type surrounding the implant. In three wall defects and circumferential defects, decalcified freeze-dried bone allograft (DFDBA) was packed into the defect and covered with an e-PTFK membrane contoured to cover the defect margins by 2 mm. In no-wall defects in which ridge expansion was necessary, DFDBA was used, together with e-PTFE membranes. Treatment and use of DFDBA alone or with a membrane were not part of a controlled protocol but were selected according to bone morphology and then arbitrarily "for comparison.” Primary closure was obtained in 36 cases, secondary closure, including connective tissue grafts, in 3 cases, free gingival graft in 1 case, exposed e-PTFE membrane in 6 cases and
exposed DFDBA in 4 cases. The patients were followed from August 1989 to April 1993, with a reported implant survival rate of 98%. No mention was made as to whether primary closure had any effect on implant survival. The author concluded that in three-wall and circumferential defects, "e-PTFE membranes provide predictable regeneration of bone and thread coverage."
The variability in technique in the above mentioned reviews of immediate implant studies with no control groups emphasizes the need for compare son studies to attempt to assess the most efficacious method of IIP. Covani et al. evaluated IIP in fresh extraction sockets with and without guided bone regeneration (GBR).47 All implants had acid-etched, sandblasted surfaces. One hundred sixty-three implants were placed, 95 in the maxilla and 68 in the mandible. The longest and widest possible implants were used, and all were placed at the level of the bone
crest. No grafting materials were used for 58 implants, which presented with no fenestrations or dehiscences and in which the gap distance did not exceed 2 mm.
The remaining 105 implants with bone fenestrations or dehiscences or in which the gap between implant surface and surrounding bone exceeded 2 mm were grafted with small autogenous bone chips and covered with bioabsorbable membranes. Flaps were repositioned to obtain primary wound closure. The 4-year CSR (calculated from time of implant placement) was 97%. All implants supported single ceramometal restorations with no splinting. There were no statistically significant differences in clinical attachment level or survival of implants treated with GBR and those treated without GBR.
Schwartz Arad et al. placed a total of 380 implants: 316 machine screw-type, 51 HA-coated screw-type and 13 cylinder HA-coated submerged implants.48 Of the
implants placed, 117 were immediate (31%) and 263 were nonimmediate. The authors used small autogenous bone chips (from bone adjacent to the implant
or bur debris) between the implant and socket walls "when needed.” No mention was made regarding flap closure. The 5-year CSR of all implants was 92%, which included 96% in the mandible and 90% in the maxilla. Immediate implants had a higher 5-year CSR compared to nonimmediate implants (96% vs. 89%, respectively). The main difference was in the maxilla, where the CSR for IIP was 95% versus 88% for nonimmediate placement. Prosper et al., in a randomized
study, placed 111 implants, 56 in combination with resorbable HA (HA group) and 55 with a resorbable polyglycolic and polylactic membranes (MR group),49 All implants were sandblasted, selfthreading, pure titanium cylinders with a diameter of 5.9 mm and a length of 11 or 13 mm. All of the fresh extraction sockets had four walls, and < 2 mm discrepancy existed between the implant head and
cementoename] junction of the adjacent teeth. The surgeon "tried to appose the two flaps by first intention." The overall incidence of implant success 4 years after placement was 97.3% and did not differ significantly between the HA group (98.2%) and the MR group (96.4%).
Mensdorff-Poully et al. retrospectively studied 190 implants, 93 placed immediately postextraction (64 rough surface, 29 machined-surface) and 97
placed delayed (6 to 8 weeks postextraction), which included 57 with a rough surface and 40 with a machined surface.50 In 76 implant placements, a non
absorbable e-PTFE membrane was used. For 13 implants, HA or autologous bone grafts were used to fill the gap alone or in combination with GBR. For
114 implants, no membrane was used. After an average of 12.4 months, 85 of 93 IIP implants were available for follow-up. For the delayed group, 88 of 97 were available for evaluation. Survival rates were 92.5% for IIP and 94.9% for delayed implants, showing no statistically significant difference in these values. Grunder et al., in a prospective multicentered study, evaluated 264 machined-surface implants in 143 patients.51 One year postloading, a follow-up was done on 125 patients. One hundred seven patients were followed for 3 years postloading. Over this period of 3 years, the implant survival rate was 92.4% in the maxilla and 94.7% in the mandible. Five methods of placement were used as follows:
- Group 1: 146 implants had IIP.
- Group 2: 34 implants were placed after 3 to 5 weeks of healing (no membranes were used).
- Group 3: 64 implants were placed with membranes over the extraction socket.
- Group 4: 8 implants were placed, and freeze dried bone bone grafts or collagen was used.
- Group 5: 12 implants were placed with a combination of the above.
There was no clinical difference in the survival rate between the immediately placed implants (group 1) and implants placed with a 3- to 5-week delayed protocol (group 2).
Krump and Barnett compared 41 implants placed immediately after extraction to a control group of 154 implants placed into the anterior mandible without extraction.52 All implants had turned surfaces, and no data were given on the use of any regenerative material in the IIP group. The implant survival rate for the IIP group was 92.7%. Implant survival in the control group was 98.1%. The differences in survival rates were not statistically significant.
Bianchi and San Filippo evaluated 116 single solid-screw immediately placed implants from 1 to 9 years post-implant placement.53 A subepithelial connective tissue graft was performed at the same time as implant placement to achieve wound closure over 96 implants. No bone graft or membrane was used. Implant survival rates were 100% for implants with and without wound closure. The authors noted that better peri-implant results in terms of stability of probing depths and esthetics were seen around the implants receiving the connective tissue grafts.
Although the survival rates of immediately placed implants appear to be similar to those of implants placed with a delayed protocol in healed bone, the question of the bone-to-implant contact (BIC) that occurs in the gap between the implant surface and socket wall should be addressed. Carlsson et al. evaluated titanium implants with initial gap widths of 0.00, 0.35 and 0.85 mm.54 At 6 weeks, the control (no-gap group) had bone contact approaching 90%, whereas the 0.35 and 0.85 mm sites had residual gaps of 0.22 and 0.54 mm, respectively. Knox et al., in a histologic study, placed eight 3.25 x 10 mm implants in each of six dogs.55 Two sites, one on each side, remained as a control, whereas 0.5, 1.0 and 2.0 mm defects were created circumferentially around the test implants. One side received HA-coated implants, and the other side received grit-blasted titanium (GBT) implants of similar dimension. All dogs were sacrificed at 8 weeks. The HA and GBT implants had levels of osseointegration similar to those of the
control group and around implants with the 0.5 mm gap defects. For all other defects, the HA group showed more coronal levels of osseointegration and
smaller residual defects than did the GBT group. However, in the larger defects (2.0 mm gap), HA and GBT implants showed larger residual defects and more apical levels of osseointegration than the controls. The authors concluded that "combination therapy using guided tissue regeneration, bone grafts, or both may be indicated in sites with larger bone gaps."
Barzilay et al. histologically compared levels of bone integration of immediate implants with implants placed in healed (control) sites in four monkeys 7 months postloading (13 months postimplantation). 56 Histologic findings from 30 immediate and 9 control turned-surface implants were compared. The percentage of bone integration was similar in both groups. However, the authors noted that "bone patterns peripheral to the interface region differed, suggesting that special consideration be given to implants placed in the posterior regions of the maxilla and mandible." They suggested using wider implants or implants in narrow posterior ridges to allow the immediate implants to engage cortical bone. This has implications in the discussion of immediate implant indications and techniques later in this article.
Akimoto et al. evaluated the effect of gap width on bone healing around commercially pure titanium machined-surface implants placed into simulated
extraction sockets of varying widths in 10 mongrel dogs.57 All implants were 10 mm long by 3.3 mm in diameter. Gap sizes of 0.5, 1.0 and 1.4 mm, all 6 mm
deep, were created for implant placement. Controls had no gaps. All dogs were sacrificed at 12 weeks, and the percentage of BIC was measured histologically. As the gaps widened, the amount of BIC decreased and the point of the highest BIC shifted apically. These changes were statistically significant for the gap areas and not statistically significant in the 4 mm of apical native bone that surrounded test and control implants. Clinically, the simulated extraction socket
defects healed with complete bone fill regardless of flap size. However, the width of the gap at the time of implant placement had a significant impact on the histologic percentage and height of BIC. Similar results in one human were reported by Wilson et al., who placed five titanium plasma-sprayed implants. 58
One served as the control in native bone, and four were placed in immediate extraction sockets. The results showed that all implants integrated with varying
percentages of direct BIC. All implants were removed in block sections 6 months postplacement. The BIC of the control implant was 72.14%. The mean BIC of the two immediate implants with small peri-implant bone defects at the time of placement (horizontal defect dimension [HDD] = 1.5 mm) was approximately 50%. Two immediate implants on which the HDD measured more than 4 mm and in which e-PTFE membrane barriers were used and stabilized by the cover screws showed a mean BIC of 17%. The authors concluded that "the horizontal
component of the defects was most critical in dictating the final amount of bone-implant contact during a 6 months healing period." They further concluded
that in spite of this small sample size, membranes were not necessary in sites in which the HDD does not exceed 1.5 mm.58 Another histologic study in a dog model by Novaes Jr et al. looked at the effect that periapical pathology of the extracted tooth had on the success of the immediately placed implant.59Nine months after the induction of periapical lesions, experimental and control (no lesions) teeth were extracted, and sockets were debrided and rinsed with 50 mg/mL solution of tetracycline hydroxide. Twenty-eight IntraMobile Cylinder (IMZ) implants were placed, 15 experimental and 13 controls. These implants were slightly larger than the extracted roots. Flaps were sutured over all implants to obtain complete coverage. AH dogs were sacrificed after 12 weeks. The mean percentage of BIC around the experimental implants was 28.6 ± 24.8%, with a
range of 25 to 100%. The mean percentage of BIC around the 12 control implants was 38.7 ± 25.5%, with a range of 3.9 to 91.2%. The difference was not
statistically significant. The conclusion of this study supported the results of clinical Findings in humans: that chronically infected sites, those showing periapical pathology, may not be contraindicated for IIP if meticulous cleansing and debridement are performed and appropriate antibiotics are administered
pre- and postoperatively.60
Indications and Techniques of IIP
A review of various implant site classifications and indications for IIP was presented by Saadoun and Landsberg.61 The classification system suggested by Garber and Belser proposed IIP in class I sites (dehiscence of less than 5 mm with no loss of hard or soft tissue) and class II sites (dehiscence equal to 5 mm demonstrating hard and soft tissue collapse in a buccolingual direction only with no alteration in vertical height).62 In both cases, the authors recommended avoiding flap elevation, the use of a barrier membrane and a bone graft where necessary (to support the membrane), and sealing the socket orifice with an
epithelial connective tissue graft.63 The essential requirement mentioned was the attainment of primary implant stability by drilling the osteotomy site 4 to 5 mm apical to the alveolar socket. For class III sites (dehiscences of greater than 5 mm, characterized by a notable collapse of hard and soft tissue with no significant loss of vertical dimension) a delayed approach was recommended with rebuilding the ridge and placing implants 6 to 9 months postsurgery, or IIP using a bone graft, membrane and connective tissue graft. The decision to use delayed placement or IIP would be dependant on the ability to achieve primary
implant stability and how critical the esthetic result. In class IV sites, representing severely compromised sockets with insufficient buccolingual bone and no vertical bone loss, the authors suggested a staged approach using autogenous bone grafts and GBR. The delayed implant placement would be performed 6 to 9
months postsurgery using a connective tissue graft. Although these approaches are clearly delineated, the more a clinician combines and compresses the various regeneration procedures in efforts to expedite treatment, the greater the risk and severity of surgical healing and complications.64
A recent consensus report based on available literature obtained from a thorough MEDI.INE review of studies published between 1990 and June 2003, combined with the clinical experience of the consensus group, classified and defined four different types of implant placement, stating the advantages and disadvantages
of each.28 Type 1 was defined as “implant placement immediately following tooth extraction as part of the same surgical procedure." Type 2 was defined as placement of the implant following complete soft tissue coverage of the socket (typically 4 to 8 weeks postsurgery). Type 3 was defined as implant placement "following substantial clinical and/or radiographic fill of the socket (typically 12-16 weeks).” Type 4 was defined as implant placement in the healed site (typically more than 16 weeks).
The indications for a type 1 placement (IIP) were based on the ability to attain primary implant stability with an "appropriately sized implant in an ideal restorative position." Although the majority of comparative data, albeit limited, show that the survival rate for implants placed immediately following extraction of teeth with local pathology is similar to that of implants placed in healed ridges, factors such as soft tissue and bone quantity and quality, as well as the presence of pathology and the condition of the adjacent teeth, enter into the decision of timing of implant placement. For example, in a patient with a thin Biotype (thin scalloped gingiva) in whom the buccal plate is lost or anticipated to resorb, esthetics becomes a primary consideration as to implant timing. If IIP is performed, a barrier membrane and supporting graft are recommended. This presents more risk for complications, leading to an unacceptable esthetic result. In these cases, delayed placement (types 2-4) may be indicated to allow placement in greater bone quantity with improved soft tissue coverage. A thick Biotype (thicker, less scalloped gingival architecture) causes less of a risk of buccal plate resorption, especially where the plate is intact following extraction. These cases present a better indication for IIP. The above guidelines may serve as a foundation for more closely analyzing factors that may contribute to the success of the IIP procedure from both functional (implant survival) and esthetic (implant success in the esthetic zone) aspects.
Reviews of the literature on IIP have concluded that there is no consensus on whether the use of bone grafts, bone replacement grafts and/or membranes in combination with implants placed in extraction sockets yields better results than those obtained with unaugmented immediately placed implants.27-29
Schropp et al. noted that following placement of 46 acid-etched Osseotite implants, 23 with an immediate (10 days postextraction) and 23 with a delayed
(3 months after extraction) protocol in both groups, a higher degree of bone healing was achieved in the infrabony defects surrounding the implant (> 60% of
depth) than in dehiscence-type defects (approximately 25%). 65 These results were reported using only autogenous bone chips grafted to the exposed implant threads in cases of dehiscences that were present in the delayed implant group. The potential for spontaneous bone healing in three-wall infrabony defects with 1 to 3 mm gaps was approximately 70%. This inability of dehiscence-type defects to heal with bone grafts alone would indicate the need for barrier membranes in these cases. When using barrier membranes, reports of membrane exposure leading to complications such as bone loss, infection and even implant loss ranging between 8 and 100% have been published.66-67 However, Lekholm et al., in a canine study, reported greater amounts of bone with membrane-treated implants, with late removal of the membranes resulting in maximal bone formation.68
Considering the above results, the clinician should base the decision to perform IIP on the anatomy of the extraction socket, the availability of bone apical to the socket and the quality of soft tissue surrounding the socket. The possible esthetic compromise of the final restoration should be weighed against the advantage of a decrease in the number of surgeries, cost and delivery time of the final restoration. A successful result with IIP is most predictable when an atraumatic extraction of the hopeless tooth can be accomplished in a flapless surgery, preserving the hard and soft tissue morphology of the extraction socket. In the esthetic zone, it is essential to maintain the interproximal papillae and interproximal bone on the adjacent teeth. Predictability for favorable esthetic
outcomes is also increased in patients with a flatter and thicker gingival architecture (thick Biotype) (Table 2 and Figures 1 to 7). Thorough socket debridement is also essential, and although success has been reported with IIP in infected sockets, 59, 60 in terms of biologic principles and predictability, a delayed implant approach in these cases may be preferable.27, 28 Osteotomies should extend 4 to 5 mm apical to the apex of the socket. In the maxillary anterior area, these osteotomies should be guided with a surgical stent, be made on the lingual incline of the extraction socket and be aimed toward the ideal cingulum
area of the replaced tooth. The implant should be placed in such a way that it does not place pressure on the buccal plate and cause resorption. In cases in which the gingiva is highly scalloped and the buccal plate is thin, maintaining a small gap < 1.5 mm between the buccal surface of the implant and buccal
plate is advisable. In the mandibular anterior and premolar areas, the implant should be slightly larger than the socket to eliminate any gap between the
implant and the socket walls (Figures 8 to 14). In the posterior areas, the implant should be placed in the interseptal bone or, if this bone is missing, in the
socket with the greatest number of surrounding walls in a position to engage cortical bone. A wider implant or two implants may be indicated depending
on posterior socket morphology. All implants must exhibit primary stability after placement. Limiting the gap between the immediately placed implant and the socket wall to < 2.0 mm allows implant placement without the use of filling materials and barrier membranes. This decreases the potential complications of the immediate implant procedure.47,58,69 This was demonstrated in a study by Paolantonio et al. in 2001 with 96 experimental titanium plasma-sprayed mini-implants placed, 48 in extraction sockets with horizontal defects < 2 mm and 48 into mature bone to serve as controls without the use of grafts or membranes and with primary closure.69 Reentry at 6 months showed complete fill of all defects. Histologic examination showed no statistically significant differences between test and control sites in the percentage of BIC and the initial level of BIC. Thus, with a gap of < 2 mm, especially in circumference defects, complete bone fill can be obtained without the adjunctive use of bone and membranes.69 This may also be accomplished using larger-diameter implants.47 However, recent research has shown that a 2 to 3 mm distance between natural teeth and implants and a minimum 3 mm distance between adjacent implants is necessary to preserve the interdental (interimplant) papillae.70, 71
In light of these findings, smaller-diameter implants may be indicated in the esthetic zone to maintain the necessary 2 to 3 mm implant-to-tooth relationship. In cases in which the gap between implant surface and socket wails exceeds 1.5 to 2.0 mm, bone graft or bone replacement graft materials, together with barrier membranes, may be indicated. However, in a 7-year follow-up study on immediately placed implants, Schwartz-Arad and Chaushu used autogenous bone chips to fill peri-implant defects without using barrier membranes and showed a high survival rate, with very few complications.72 When immediate implants can be placed within the alveolar confines, high survival rates were reported without using grafting materials or barrier membranes. 42 The small circumferential defects between implants and surrounding bone walls were filled with blood and then covered by a pedicle flap. The defects filled with bone, and a 93.3% implant survival rate after 4 years was reported. The use of barrier membranes appears to be advantageous when attempting to regenerate a dehiscence or buccal fenestration with exposed implant threads. Absorbable membranes are less prone to bacterial contamination, especially when exposures occur, and are therefore better suited for these purposes. They also exhibit a lower incidence of premature membrane exposure (Figures 15 to 20).73, 74
A recent study by Cornelini et al. compared 6-month hard and soft tissue healing around immediately placed implants using two different groups. 75 The test group received Bio-Oss and Bio-Gide membranes to treat the gap (defect around the implant), whereas the control group received a Bio-Gide membrane alone. Treatment outcomes showed no differences between test and control implants in radiographic bone levels. Both showed no change from baseline levels and no difference in probing attachment level. However, at the proximal site, the soft tissue margin was located 2.6 mm more coronally than the implant shoulder in the test group compared with 1.3 mm in the control group. The corresponding
buccal figures were 2.1 and 0.9 mm in the test and control groups, respectively. Thus, the use of anorganic bovine bone matrix to support the barrier membranes resulted in better soft tissue support for the final restoration. This, again, is critical in the esthetic zone. A recent prospective study of 62 single IIP in 62 patients used five randomly selected groups, one with a nonabsorbable membrane only, two with an absorbable membrane only, group 3 with an absorbable membrane and autogenous bone, group 4 with autogenous bone alone and group 5 with no
membrane or bone. The best outcomes in terms of complete bone fill of the defects around the IIP was obtained in the group treated with an absorbable membrane and autogenous bone.76
The immediately placed implant should be positioned 0 to 3 mm apical to the crestal bone. If a dehiscence exists, the implant may be placed 3 mm apical to the cementoenamel junction of the adjacent teeth margins. Primary flap closure may be obtained by periosteal releasing and vertical incisions to allow flap advancement. Other methods, including rotational flaps, splint flaps or connective tissue grafts, have also been recommended.77-81 However, high levels of implant survival have been reported without primary flap closure, providing that an absorbable membrane was used to cover the implant.41 In the esthetic zone, a soft tissue graft placed over the implant and membrane barrier (where used) may
avoid any additional mucogingival surgical procedures necessary to reestablish a lost vestibule and repair the soft tissue-implant morphology.
In cases in which implant placement is required in a highly esthetic zone, in a patient with a high smile line, IIP may be contraindicated. This is especially true when a thin, highly scalloped gingiva (thin Biotype) is present. Based on studies demonstrating horizontal39 and midfacial45buccal plate and gingival resorption 6 to 12 months post-IIP, the risks of a compromised esthetic result would, in my opinion, contraindicate this approach. A delayed approach, type 2 or 3, would allow better tissue control. Moreover, if soft or hard tissue augmentation were necessary, it may be performed more predictably prior to implant placement. Other contraindications for IIP would include the inability to place the implant in an ideal restorative position because of a compromised socket architecture following tooth extraction.
Antibiotic coverage pre- and postsurgery appears to be an important part of most IIP protocols. The use of amoxicillin (1 to 2 g) 1 hour preoperatively and 500 mg three times daily for 7 to 10 days postsurgery is recommended by most authors. Postsurgical use of chlorhexidine rinses twice daily for at least 3 weeks is also recommended. Many authors recommend taking one ibuprofen tablet 800 mg four times a day for 7 to 10 days postsurgery to decrease pain, inflammation, and swelling.27
In conclusion, high implant survival rates have been reported for implants placed in fresh extraction sockets (comparable to implants placed in healed ridges).27-29 Moreover, the advantages afforded by IIP make it a valuable modality in implant therapy for both the clinician and the patient. However, as emphasized in a recent literature review, the many variations in treatment protocol for immediately placed implants, together with the paucity of long-term studies of implant success, indicate the necessity for controlled clinical trials to establish predictable
and reproducible techniques and results.28
Figures
Figure 1 Clinical view of a maxillary deciduous molar prior to extraction (site 13) (case by Dominick Galasso)
Figure 2 Periapical radiograph of a hopeless tooth prior to extraction
Figure 3 Occlusal view of the fractured tooth in Figure 1
Figure 4 Clinical view following extraction, immediate implant placement, and temporization
Figure 5 Occlusal view of a healing implant
Figure 6 Radiograph of a final implant-supported restoration
Figure 7 Clinical view of an implant-supported restoration with intact inrterproximal papillae
Figure 8 Clinical view of four hopeless mandibular incisors prior to extraction (case by Dennis Tarnow)
Figure 9 Radiograph of teeth in Figure 8
Figure 10 Atraumatic flapless extraction is performed to preserve the socket walls
Figure 11 Three immediate implants are placed in the mandibular left lateral incisor and right central and lateral incisor
Figure 12 Final restoration prior to insertion
Figure 13 Radiograph of the final supported restoration
Figure 14 Clinical view of the restoration 1 year postloading
Figure 15 Radiographic view of the hopeless maxillary left central incisor (case by Barry Wagenberg)
Figure 16 Socket with deficient buccal plate following extraction
Figure 17 Use of mineralized bone and an absorbable membrane to treat the dehiscence defect associated with IIP
Figure 18 Six months post IIP, prior to abutment placement
Figure 19 Final implant prosthesis 5 years postloading
Figure 20 Clinical view of the restoration 5 year postloading
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