Ridge preservation: what is it and when should it be considered

Transcription

1 REVIEW Australian Dental Journal 2008; 53: doi: /j x Ridge preservation: what is it and when should it be considered I Darby,* S Chen,* R De Poi* *School of Dental Science, The University of Melbourne, Victoria. ABSTRACT The resorption of bone following extraction may present a significant problem in implant and restorative dentistry. Ridge preservation is a technique whereby the amount of bone loss is limited. This paper discusses the scientific literature examining the healing post-extraction and ridge preserving techniques, primarily from the perspective of implant dentistry. Some indications for ridge preservation and methods considered appropriate are discussed. Key words: Extraction, bone resorption, grafting, membranes, implants. Abbreviation: eptfe = expanded polytetrafluoroethylene. (Accepted for publication 26 March 2007.) INTRODUCTION Prerequisites for successful implant therapy are integration of the implant, ideal implant position and appropriate hard and soft tissue contours. These require sufficient alveolar bone volume and favourable ridge architecture coupled with an appropriate surgical technique. However, following extraction of teeth the alveolar ridge resorbs, the rate of which may vary between sites and subjects. This may result in inadequate bone volume and unfavourable ridge architecture for dental implant placement (Figs 1 and 2). The aim of this article is to discuss events following extraction and how these can be optimized to facilitate successful implant therapy. The same principles may be applied to edentulous areas in order to enhance aesthetic outcomes for fixed bridges and removable dentures. However, the primary focus of this article is to improve the outcome of implant therapy. Events following an extraction Healing of an extraction socket is characterized by internal changes that lead to formation of bone within the socket, and external changes that lead to loss of alveolar ridge width and height. 1 Internal changes When a tooth is removed, there is haemorrhage followed by formation of a blood clot that fills the entire socket. 2 With this is an inflammatory reaction that stimulates recruitment of cells to form granulation tissue. Within 48 to 72 hours after extraction the clot starts to breakdown as granulation tissue begins to infiltrate the clot especially at the base of the socket. By four days the epithelium proliferates along the socket periphery and immature connective tissue is apparent. After seven days the granulation tissue has completely infiltrated and replaced the clot. At this stage, osteoid is evident at the base of the socket as uncalcified bone spicules. Over the next 2 3 weeks (3 4 weeks after extraction) this begins to mineralize from the base of the socket coronally. This is accompanied by continued re-epithelialization which completely covers the socket by six weeks post-extraction. Further infill of bone takes place with maximum radiographic density at around 100 days. A number of factors may affect the healing of undisturbed sockets. The size of the socket is important with wider sockets requiring more time to bridge the defect compared with narrower sockets; it takes longer to completely form bone at molar sites compared to single-rooted sites. The sockets of teeth with horizontal bone loss heal more quickly as the lower level of the ª 2008 Australian Dental Association 11

2 I Darby et al. Fig 1. Favourable ridge dimensions for implant placement. Fig 2. Unfavourable ridge dimensions for implant placement. alveolar bone means less infill is required. It should be noted that bone does not regenerate to a level coronal to the horizontal level of the bone crest or to the level of the neighbouring teeth (i.e., 100 per cent socket fill does not occur). 1 External changes A recent study by Araujo and Lindhe 3 showed that in the first eight weeks following extraction in a dog model there is marked osteoclastic activity resulting in the resorption of the buccal and lingual crestal walls. They noted that the reduction of height was more pronounced at the buccal wall and was accompanied by a horizontal loss on both buccal and lingual walls. This is an important finding because an adequate width and height of buccal bone is important for optimal implant aesthetics, and this study suggests that loss of buccal bone may result in poorer, suboptimal aesthetics. Dimensional changes following an extraction Resorption of the external buccal and lingual socket walls results in a change in the dimensions of the ridge. Pietrokovski 4 in an examination of healed sockets in dried skulls showed that, from the occlusal aspect, the crest of the residual ridge shifts lingually, and from the lateral aspect, the ridge formed a concavity or flattened to form a wall running straight between the alveolar crests of the adjacent remaining teeth. Earlier studies have shown a wide variation between subjects in the dimensional changes both clinically and radiographically following removal of teeth, characterized by very rapid reduction in both height and width. 5,6 More recent studies by Lekovic et al. 7,8 have shown that there is greater loss of alveolar ridge width than height and that some degree of loss was observed at all extraction sites. It has been suggested that this variability is due to anatomic, prosthetic, metabolic, functional, genetic and iatrogenic factors. 9 The most rapid changes were found in the early post-extraction period, from six months to two years. 10,11 In addition, Atwood and Coy 11 showed that there were differences in the rate of resorption between maxillary and mandibular sites. They found that the average change was four times greater in the mandible than the maxilla. It should be noted that the above studies were performed on edentulous subjects. Schropp et al. 1 studied the effect of a single tooth extraction of premolar or molar teeth on bone healing and soft tissue changes using clinical and radiographic measurements as well as digital subtraction radiography. They showed that major changes take place in the 12 months following an extraction with an average of 50 per cent reduction in the width of the alveolar ridge. Two-thirds of this reduction occurred within the first three months. This loss averaged between 5 and 7 mm and was similar at all sites in the mouth. Importantly, most of the subjects did not wear a denture after extraction. Immediately after tooth extraction the width of the ridge was an average of 12 mm ( mm) and 12 months later 5.9 mm ( mm). Given that a standard body implant requires a minimum of 6 7 mm of bone dimension, many of these sites would not be suitable for implant placement. The authors conclude it would be advantageous if this loss of bone dimension could be prevented. Ridge preservation Ridge preservation is any procedure undertaken at the time of or following an extraction that is designed to minimize external resorption of the ridge and maximize bone formation within the socket. However, there are clinical situations where it is not advisable to undertake ridge preservation at the time of extraction (e.g., in the presence of acute infection). In these situations, preservation of the ridge may be delayed by six to eight weeks. A recent consensus report suggested that minimal dimensional change occurs within six to eight weeks of an extraction. 12 Some ridge preservation 12 ª 2008 Australian Dental Association

3 Ridge preservation techniques are based on the principles of guided tissue bone regeneration. Many procedures have been suggested including minimally traumatic tooth extraction, soft and hard tissue grafting, concomitant use of barrier membranes and immediate implant placement. (a) Minimally traumatic tooth extraction Although tooth extraction is by necessity a traumatic procedure, the application of appropriate instruments with minimal force is recommended to limit damage to the hard and soft tissues. Fine luxators or periotomes can be inserted into the periodontal ligament to sever the coronal fibre attachment, thereby loosening the tooth until forceps can gently deliver the tooth from its socket (Figs 3a and 3b). Multi-rooted teeth can be decoronated and the roots sectioned and extracted individually to facilitate this procedure (Figs 4a (b) (a) Fig 4. (a) Decoronation and sectioning of a molar for extraction. (b) Appearance of socket after roots sectioned and removed individually. and 4b). Given the increasing acceptance of implant therapy, it may be argued that all extractions should be undertaken with as minimally traumatic a technique as possible. Even if an implant is not planned at the time of tooth removal, the site may subsequently be considered for implant placement. (b) Timing of extractions The summary of the literature above shows that most resorption takes place within the first three months after extraction. Therefore, if possible, the tooth should be retained for as long as possible and the extraction scheduled in accordance with the chosen time for implant placement. A detailed discussion and classification for timing of implant placement after tooth extraction may be found in the proceedings of the 3rd ITI Consensus Conference. 12,13 However, it is not always possible to retain all teeth in this manner with pain and infection often necessitating immediate removal of the offending tooth. Fig 3. (a) Use of a periotome to aid in the minimally traumatic removal of an upper right central incisor. (b) Appearance of the socket immediately following extraction using periotome and the forceps only to lift the tooth out of its socket. Debridement and decortication of the socket Some studies recommend that the sockets be debrided to remove anything that may interfere with healing, ª 2008 Australian Dental Association 13

4 I Darby et al. whilst others suggest that a round bur should be used to perforate the socket walls a number of times to allow greater access for blood vessels into the socket and any grafting material in an attempt to improve bony infill. 14 Conversely, it has been shown in an experimental study that retention of the periodontal ligament along the socket walls facilitated retention of the clot during the early stages of wound healing. 15 Thus, apart from removal of chronically inflamed tissue and foreign materials, extensive debridement or perforation of the socket walls may not be required. Coverage of the socket by soft tissue The literature is divided over whether soft tissue coverage of the socket at the time of extraction is necessary for optimum healing of the socket and aesthetics. Soft tissue coverage procedures may be considered to retain, stabilize and protect grafting materials. It is a critical step when using non-resorbable membranes. Many techniques have been suggested and include displacing neighbouring tissue to cover the socket, such as coronal advancement of a buccal flap, rotating grafts from tissue adjacent to cover the defect, or using free gingival or subepithelial connective tissue grafts Alternatively, the site may be left for six to eight weeks to allow healing and regeneration of mucosa over the socket. The added volume of soft tissue at this stage may facilitate optimum closure over the socket when ridge preservation procedures are undertaken. In a similar manner, procedures allowing spontaneous soft tissue proliferation could be considered prior to extraction to increase soft tissue coverage, such as removing the crown and burying the remaining root. 19 The Bio-Col technique 20 involves the placement of an anorganic bovine bone graft (Bio-Oss) protected by a resorbable collagen sponge (Collaplug see below) and then allowing spontaneous epithelialization of the socket under a denture tooth or bridge pontic. However, there is a paucity of research evidence to support this technique. Mobilization of tissue can be a difficult procedure, but splitting the periosteum at the base of a flap is fairly straightforward and as a result may be the technique of choice. However, coronally advanced flaps need to be undermined and advanced a relatively great distance to completely cover an extraction socket. This may cause complications such as altering the mucogingival line and creating a shallow vestibule, either of which may require subsequent surgery to correct. 21 These problems may be avoided using a subepithelial connective tissue graft taken by a window or envelope procedure from the palate. This requires an appropriate donor site and sufficient coverage by soft tissue around the extraction socket to prevent necrosis of the graft in the initial phase of healing. The question remains that these techniques may increase soft tissue coverage, but do they result in increased bone fill when used on their own. Recent work by Araujo and Lindhe 3 in a dog model showed that this is not the case, a finding which may argue for a space filler to be placed in the socket or use of a membrane to maximize bone infill. Bone or bone-substitute grafts only Many grafting materials have been used and these include autogenous bone, demineralized freeze-dried bone allografts (DFDBA), xenografts, bioactive glass, hydroxyapatite and calcium sulphate (Table 1). Autogenous bone is thought of as the gold standard. 22 Becker et al. 22 compared demineralized freezedried bone against autogenous bone in seven paired sites finding that after three months new bone was formed at sites where autogenous bone was placed, but not in six of seven sites using DFDBA. Common sites intra-orally to harvest autogenous bone are around the surgical site, ascending ramus, chin and tuberosity. Table 1. Summary of the studies quoted investigating ridge preservation using bone grafts only, membranes only or a combination Method used Authors Material(s) used Outcome Bone Graft only Becker et al Autogenous bone compared to DFDBA Little new bone formation around DFDBA Artzi et al Bio-Oss On average 82.3% bone infill Nemcovsky & Serfaty 1996 Hydroxyapatite Predictable ridge preservation Froum et al DFDBA and Bioactive glass Biogran 60% infill, DFDBA 33% infill Guarnieri et al Calcium sulfate 100% bone infill Camargo et al Bioactive glass mixed calcium sulfate Of some benefit Membranes only Lekovic et al epfte Signif greater infill and bone height width preservation than untreated control Lekovic et al Resolut Signif greater infill and bone height width preservation than untreated control Bone graft and membrane Iasella et al DFDBA and Bio-Mend Less ridge width loss and more bone infill than untreated control Fowler et al DFDBA and acelluar dermal graft No loss of ridge width or height 14 ª 2008 Australian Dental Association

5 Ridge preservation Post-surgery the patient may experience considerable discomfort in the donor. A study using DFDBA 23 showed that DFDBA cannot speed up bone formation. Both Becker et al. 22 and Froum et al. 24 showed little new bone formed around DFDBA. It is not available in Australia, but it is often mentioned in studies from North America and included here for the sake of completeness. Recently, Artzi et al. 25 used a common porous bovine bone graft (Bio-Oss) in 15 fresh extraction sockets, covering the graft with soft tissue and re-entering nine months later. They reported that there was 82.3 per cent bone infill and all sites allowed safe insertion of fixtures. Histologic appearance showed a mixture of Bio-Oss and new bone formation, increasing in bone fraction apically. The use of a xenograft does not require a donor site, thus reducing morbidity following harvesting and simplifying the procedure. Figure 5 shows Bio-Oss placed in an extraction socket. Hydroxyapatite use in fresh extraction sockets in a series of 23 cases was reported by Nemcovsky and Serfaty. 26 They achieved primary closure by rotating split thickness flaps and were followed for 24 months. They showed that there was predictable ridge preservation with minimal postoperative ridge deformation (1.4 mm vertically and 0.6 mm horizontally). This would retain sufficient bone volume to allow implants to be inserted. However, over half the patients experienced some exfoliation of hydroxyapatite suggesting that the flap design was not predictable in maintaining soft tissue closure. A bioactive glass (Biogran) was investigated in fresh extraction sockets by Froum et al. 24 and compared to control sockets and those with DFDBA. All sites were covered by flap advancement and re-entered six to eight months later. The placement of Biogran resulted in 60 per cent bone Fig 5. Bio-Oss placed in an extraction socket for ridge preservation. It will require something to hold it in place. vitality, a measure of new bone formation, with the control and DFDBA sites showing approximately 33 per cent. However, it should be noted that all sites were to receive implants, which suggests that there may be little benefit of using a graft material. The placement of calcium sulphate has been studied in a recent paper. Guarnieri et al. 27 placed calcium sulphate in 10 extraction sockets without a barrier membrane and re-entered the sites at three months. The graft material had readily resorbed with 100 per cent bone infill and implants were able to be placed at all sites. It should be noted that there is again a general lack of studies reporting on the use of calcium sulphate, with which the authors of the above paper concur. One study has looked at the use of bioactive glass and calcium sulphate together. 28 No statistical difference was found between experimental and control groups, casting doubt on the use of these materials in combination. Another product that was used to graft extraction sockets is BioPlant HTR TM. It is a biocompatible microporous composite of methacrylate and calcium hydroxide. Haris et al. 29 reported that after a period of 8 to 12 months there was sufficient hard tissue to place implants. More recently, biphasic calcium phosphate has become available in Australia. This is a combination of hydroxyapatite and tricalcium phosphate. However, the authors are not aware of any peer-reviewed papers investigating its use in ridge preservation. Except for the study by Guarnieri et al. 27 in each of the above papers residual particles of the graft were found at time of re-entry and raises the question of what effect this may have on implant placement. The evidence above may argue for use of calcium sulphate which resorbs completely, but as mentioned earlier there are few studies. Materials like Bio-Oss have been much more widely researched. However, the authors feel that the question remains Does it matter if particles are left?. If most bone infill is along the socket walls and base, 25 then any remaining particles may be removed during the osteotomy. However, in a dog study of implants placed in sites three months after grafting with Bio-Oss there was still a substantial portion of the graft present, and no osseointegration occurred to the implants within the augmented portion of the crest. 30 This paper reinforces the need to wait six to eight months post-grafting before implant placement. These papers show many different techniques for improving the bony healing in extraction sockets, but fail to answer what is the clinical relevance. Can a particular technique reproducibly achieve a level of bone fill that allows implant placement and reduces tissue loss to a minimum? The above reports only answer this question obliquely by indicating whether or not implants were placed. ª 2008 Australian Dental Association 15

6 I Darby et al. Membranes only It is also possible to cover the socket to prevent ingress of soft tissue, thereby promoting maximal bony healing. Generally, there are two types of membrane used, resorbable and non-resorbable. Table 1 summarizes the papers quoted in this article. In 1997, Lekovic et al. 7 investigated the use of a non-resorbable expanded polytetrafluoroethylene (eptfe) membrane to maintain the alveolar ridge after extraction. Two sites each in 10 patients were used, one site receiving a membrane and the other site as a control. All sockets were debrided and flaps displaced to cover the membrane and socket. Reassessment took place at six months, with significantly greater loss of bone height and width in the control group and more infill in the eptfe group. However, 30 per cent of membranes became exposed and this resulted in similar results to the control group. Giving the high rate of exposure, this paper suggests the use of eptfe membranes should perhaps be avoided. Figure 6 shows the use of an eptfe membrane. A later paper by the same group 8 looked at the use of a resorbable membrane compared to a control site in 16 patients. A polyglycolide lactide membrane (Resolute, WL Gore & Associates) was placed and reassessed at six months. The experimental sites showed significantly less loss of alveolar bone height, more internal socket fill and less horizontal resorption of the ridge. Importantly, there were no exposures. Therefore, it seems that Fig 7. Bio-Gide membrane used in ridge preservation. These membranes usually require a bone graft in the socket to sufficient support to prevent them collapsing into the socket. resorbable membranes should be preferred over nonresorbable. Unfortunately, the authors did not report on whether the ridges were suitable for implants irrespective of technique, which limits the usefulness of these papers. Although an animal-derived membrane, Bio-Gide is available in Australia and used widely in clinical periodontal practice. We are unaware of any ridge preservation studies reporting its use, but there seems to be no reason why it could not be used in this manner. Figure 7 shows the placement of a Bio-Gide membrane. Fig 6. eptfe (Goretex) membrane in place. This later became exposed, with consequent infection and soft and hard tissue loss. PTFE membrane intentionally left exposed and removed at 4 6 weeks. Bone grafts and membranes together Some studies have investigated the use of bone grafts and membranes together (Table 1). Iasella et al. 31 reported on the use of tetracycline hydrated freeze-dried bone allograft and a resorbable membrane (Bio-Mend) compared to extraction alone in 24 patients. They replaced the flap without complete socket coverage and reassessed four to six months later. Both groups lost ridge width, although the experimental group lost less width and had more bone infill. The test group sites were more suitable for implant placement, but all sites were still able to receive implants. In a case report, Fowler et al. 32 used DFDBA and an acellular dermal graft for ridge preservation. An acellular dermal graft is an allograft harvested surgically and with all cellular material and epidermal layer removed. The authors found the height of tissue to be acceptable for implant placement and suggested this technique be used where primary closure couldnõt be achieved. Recently, 16 ª 2008 Australian Dental Association

7 Ridge preservation however, the American Academy of Periodontology (AAP) issued a notice describing the recall of one particular brand due to incomplete medical information regarding the origin of the graft. Interestingly, Fugazzotto 33 in a report on a comparison of resorbable and titanium-reinforced membranes used with Bio-Oss found that significant bucco-lingual ridge collapse was noted upon re-entry. The findings of this paper are supported by the work of Zubillaga et al. 34 who showed that tacked membranes in place results in less loss of augmented bone than non-tacked membranes. (a) Other space fillers It appears that insertion of a filler material into the socket is important to preserve as much bone as possible, but does it always have to be a bone graft? In addition, the presence of graft particles at time of placement may not be desirable. Serino and co-workers 35 placed in 36 patients a commercially available bioabsorbable sponge of polylactide-polyglycolide. The teeth were surgically extracted, sockets debrided, the sponge inserted and flaps replaced with no primary closure. Six months later all sites were reassessed and implants placed. There were 26 test sockets and 13 control. All test sockets healed with less bone resorption than the controls especially in the mid-buccal region. The authors suggested that the sponge served as a support to prevent the collapse of the surrounding soft tissue into the socket during the healing process. A similar product is available commercially in Australia and is a collagen plug (Collaplug, Zimmer Dental). This and the sponge above can be placed into the socket without raising a flap, but there is little research in this area and the materials may only act to stabilize the clot and not to preserve the ridge. Figure 8a shows Collaplug before it is placed, Fig 8b after placement in the socket and Fig 8c demonstrates healing after three weeks. (b) (c) Implants as ridge preservers The third ITI consensus report showed that immediate implants are a very successful form of therapy. 12 However, it has been reported that implants do not preserve the ridge they are placed into Araujo et al. 36 demonstrated that immediate implant placement in a dog model failed to prevent resorption of the socket walls, especially buccally. They suggested that this may be due in part to the early disappearance of the bundle bone and also disruption of the blood supply buccally due to elevation of a flap. Bundle bone, in the presence of a tooth, occupies a larger fraction of the marginal portion of the bone wall in the buccal than lingual and has a large number of fibres from the periodontal Fig 8. (a) Collaplug before placement. (b) Collaplug placed in an extraction socket. It quickly soaks up blood and reduces in size. (c) Healing after three weeks after Collaplug placement. ligament inserting. It seems that when a tooth is removed bundle bone is resorbed rather than replaced. If one thinks in terms of solely being able to place an implant ª 2008 Australian Dental Association 17

8 I Darby et al. then this may not matter at all as long as there is enough bone initially, but this may cause problems later especially in aesthetic areas if there is buccal tissue loss. 39 The future Given the current advances in stem cell technology we may in the future be able to place tooth buds in sockets to regrow teeth or place a cellular scaffold in the socket to maintain the bone. Cultivated scaffolds from bone marrow mesenchymal stem cells have been placed into fresh extraction sockets with results that show promise. 40 Complications It needs to be mentioned that any surgical procedure may have complications. These commonly are postoperative pain and swelling, and occasionally infection. Any surgery on the gingival tissues will cause some recession. It is well known that in GTR procedures up to 70 per cent of non-resorbable membranes may become exposed to the oral environment, severely reducing the amount of new tissue formed. 41 In addition, Girard et al. 42 reported a case of a foreign body granuloma following placement of a graft into an extraction socket with pain and sensation disturbance. It should be noted that the site was already compromised by previous infection and may serve as a reminder to debride sockets fully or not to undertake preservation in the presence of infection. DISCUSSION Although the literature presents a confusing picture with difficulty in comparing studies, ridge preservation does appear to limit the loss of hard and soft tissue at extraction sites, and can provide less bone loss compared to non-preserved sites. While there were extraction-only sites that were suitable for implant therapy, the most predictable maintenance of ridge width, height and position was achieved using ridge preservation. Ideally, a technique for socket preservation ought to be easy to use, not involve surgery, leave no residual foreign bone particles, involve no floppy membranes likely to collapse into the socket and result in no bone loss. However, it appears that no material or technique fully meets these criteria. The authors experience with Collaplug (Zimmer) is that, after six to eight weeks, resorption is similar to that seen in a normal extraction socket; the material therefore does not seem to do much to preserve the ridge. The PGA PLA plug reported by Serino et al. 35 may have been designed to have a much slower resorption rate. Although no one procedure or technique meets all of the above criteria, a reasonable choice would seem to be a surgical procedure involving placing an osteoconductive bone graft with a slow resorption rate (Bio- Oss or a synthetic material) covered with a resorbable membrane which may be tacked into place. This appears to be a method that may preserve sufficient volume and contour to permit subsequent implant placement and achievement of acceptable aesthetic results. Compared to the plugs this technique has been proven to provide adequate ridge height and width for implant placement. The authorsõ recommendation is that if a ridge is to be preserved with predictable bone-fill, then a material with osteoconductive properties and slow rate of resorption (Bio-Oss or other synthetic material) should be used. The socket should be sealed with a CT graft or the Bio-Col technique used to effect soft tissue closure. The implant would then be placed four to six months later to provide sufficient time for maturation of the graft. If it is planned that the implant be placed within six to eight weeks of extraction, then techniques and materials designed to promote bone fill are not necessary. Instead, the authors would recommend using a resorbable collagen sponge (Collaplug or other similar material) to aid with initial clot stabilization, but the authors would not be relying on it to preserve the ridge. Indications for ridge preservation The review of the literature above shows that ridge preservation should be considered if an implant is to be placed more than six to eight weeks after tooth extraction. If an implant is to be placed at the time of extraction or within six to eight weeks following extraction, there appears to be little benefit in carrying out ridge preservation procedures at the time of extraction. Even when an implant might not be planned in the near future, ridge preservation should be considered in strategically important sites to retain the possibility of an implant option for the patient in the future. Ridge preservation should also be considered for aesthetic reasons at pontic sites in conventional fixed prosthodontics. Figure 9 presents an outline of the questions that the authors suggest should be asked at the time when extraction is considered and the suggested approaches that should followed. Specific indications for ridge preservation include the following: (1) sites where the buccal plate is less than mm thick (virtually always in the anterior and aesthetic zone) and sites where there has been damage or loss of one or more of the socket walls. These sites may lose a clinically significant amount of the buccal plate upon healing 3,42 18 ª 2008 Australian Dental Association

9 Ridge preservation Should the alveolar ridge be preserved? Is implant placement being considered within the next 6 to 8 weeks? YES...Does the tooth need to be extracted immediately? Yes...Is there anything stopping placement of a ridge preserving material, such as acute infection or medical issues? NO...Why no? Is the site extremely compromised, the buccal plate more than 2 mm thick, bone volume does not have to be maintained or have previous extraction sites healed up well? No...Try to keep the tooth until time of implant therapy NO... there is significant damage to the socket walls, primary implant stability cannot be assured or implant placement has to be delayed due to scheduling problems Select a material that has a slow rate of resorption and which will eventually form new bone anorganic bovine bone bioactive glass biphasic calcium phosphate Delay implant placement for 4 to 6 months YES...is a graft required? NO... the socket walls are intact and significant resorption is not anticipated in the following 6 to 8 weeks no graft required YES... One or more of the socket walls have been lost, and collapse of the ridge needs to be minimized. Select a material that will rapidly resorb collagen plug calcium sulfate Yes...Debride socket as much as possible and leave to heal. Consider some form of ridge preservation 6 8 weeks later Yes... consider the use of bone grafts and membranes to promote as much bone preservation as possible and to build out the buccal plate. Also consider soft tissue coverage of the socket No...Is it a surgical extraction? No... use a material that can be easily contained in the socket to preserve the ridge Fig 9. An evidence-based outline of the questions that should be asked at the time when extraction is considered and suggested approaches that should followed. and are more likely to present a challenge for successful implant therapy; (2) sites where maintaining bone volume is crucial to minimize the risk of involving anatomical structures, such as the posterior maxilla or mandible, where the maxillary sinus or inferior alveolar nerve may present as a complication if further bone is lost; (3) a patient with high aesthetic demands, such as a high lip line or a thin biotype, which is prone to more recession; and (4) in patients where many teeth are to be extracted and preservation of the bone is important of further restoration. It should be noted that it is difficult to predict how sites will heal. Some sockets will heal without much resorption, whereas others will lose a lot of hard and soft tissue. If the patient has had a number of previous extractions then the loss of supporting ridge at these sites might provide an indication of what will happen. It appears that if there is any doubt about hard and soft tissue loss then one should try to preserve the ridge. Figure 10 presents an outline of the questions we suggest that should be asked to assist with the selection of materials, etc. The first consideration is timing of implant placement. Will it be within six to eight weeks or will implant placement be delayed beyond this time? Fig 10. Questions to be asked to assist with selection of an appropriate material to be used for ridge preservation. If not then the next question is Is there significant damage to the socket that prevents primary stability and requires grafting?, which will not only require new bone formation, but the maintenance of as much existing bone as possible. A slowly resorbing material which will support the tissues and eventually form bone is the material of choice. If the implant will be placed within six to eight weeks then we suggest that the following question should be Is a graft required?. The answer will be in the negative if the socket walls are intact and significant resorption is not anticipated. However, if there has been damage, i.e., where one wall has been lost and collapse of the ridge must be minimized that a rapidly resorbing material could be chosen. Contraindications to ridge preservation are acute infection, where unassisted socket healing is likely to result in good ridge morphology, when maintaining bone volume is not critical and where surgery is contraindicated by medical issues. The patient must consent to the procedure also, which will involve explaining the source of all materials. There might be religious and ethical issues with some of the materials (i.e., vegetarians and vegans with animal products). Limitations Ridge preservation has been developed recently. There are a great number of techniques that have been presented, but with only few research reports to support. Further long-term studies are required especially to assess the ridge dimension following preservation and implant placement. From the studies reviewed above there is no ideal technique to achieve 100 per cent bone preservation every time. No one technique is appropriate for all situations and a flap might ª 2008 Australian Dental Association 19

10 I Darby et al. have to be raised in some cases. Much may depend on the general health and habits of the patient, such as smoking. CONCLUSIONS Implant treatment can be facilitated at the time of extraction by considering ridge preservation and maintaining sufficient bone for optimal implant placement and consequently appearance. Consideration has been given to healing of extraction sockets and previously published studies that have attempted to preserve the alveolar ridge. Based on these studies the authors have designed an outline of the questions the authors feel should be asked when considering ridge preservation. This article also covers some of the materials available. The majority of teeth are extracted by general dental practitioners and it is hoped that this article will stimulate some thought on the topic of ridge preservation. Not all extraction sockets need to be preserved, but the authors feel that ridge preservation ought to be considered at the time of tooth removal. 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11 Ridge preservation 33. Fugazzotto PA. GBR using bovine bone matrix and resorbable and nonresorbable membranes. Part 1: Histologic results. Int J Periodontics Restorative Dent 2003;23: Zubillaga G, Von Hagen S, Simon BI, Deasy MJ. Changes in alveolar bone height and width following post-extraction ridge augmentation using a fixed bioabsorbable membrane and demineralised freeze-dried bone osteoinductive graft. J Periodontol 2003;74: Serino G, Biancu S, Iezzi G, Piattelli A. Ridge preservation following tooth extraction using a polylactide and polyglycolide sponge as space filler: a clinical and histological study in humans. Clin Oral Implants Res 2003;14: Araujo MG, Sukekava F, Wennstrom JL, Lindhe J. Ridge alterations following implant placement in fresh extraction sockets: an experimental study in the dog. J Clin Periodontol 2005;32: Botticelli D, Berglundh T, Lindhe J. Hard-tissue alterations following immediate implant placement at extraction sites. J Clin Periodontol 2004;31: Chen ST, Darby IB, Adams GG, Reynolds EC. A prospective clinical study of bone augmentation techniques at immediate implants. Clin Oral Implants Res 2005;16: Araujo MG, Wennstrom JL, Lindhe J. Modeling of the buccal and lingual bone walls of fresh extraction sites following implant installation. Clin Oral Implants Res 2006;17: Marei MK, Nouh SR, Saad MM, Ismail NS. Preservation and regeneration of alveolar bone by tissue-engineered implants. Tissue Eng 2005;11: Cortellini P, Tonetti MS. Focus on intrabony defects: guided tissue regeneration. Periodontol ;22: Girard B, Baker G, Mock D. Foreign body granuloma following placement of hard tissue replacement material: a case report. J Periodontol 2000;71: Address for correspondence: Dr Ivan Darby Senior Lecturer and Head of Periodontics School of Dental Science The University of Melbourne 720 Swanston Street Parkville, Victoria idarby@unimelb.edu.au ª 2008 Australian Dental Association 21