Paulo M. Camargo, DDS, MS
Associate Professor of Periodontics
Department of Periodontics
University of California Los Angeles School of Dentistry
Los Angeles, California

Philip R. Melnick, DMD
Lecturer in Periodontics
University of California Los Angeles School of Dentistry
Los Angeles, California
Private Practice in Periodontics and Dental Implants
Cerritos, California

Omer Suleimanagich, DDS
Private Practice in Restorative and Esthetic Dentistry
Los Angeles, California

Joao G. P. Carnio, DDS, MS
Adjunct Professor of Periodontics
Periodontics Department
School of Dentistry
State University of Londrina
Londrina, Brazil

Luciano M. Camargo, DDS, MSEd
Adjunct Professor of Prosthodontics
University of Parana School of Dentistry
Parana, Brazil
Private Practice in Prosthodontics
Curitiba, Brazil

Tooth replacement through implant-supported restorations is now a widely accepted modality of dental therapy.¹ Implant-supported restorations have several advantages over conventional prostheses, including the preservation of natural tooth structure and ease of maintenance for both patients and dental professionals.

A crucial determining factor in the success of dental implants is their ability to remain in direct contact with bone, as first described by Bränemark and coworkers.² This phenomenon was later called os­seointegration.³ It should be re­membered that while osseointegration refers to the implant/bone interface at the histological level, this term is commonly used to de­scribe a clinical, nonmobile implant combined with the absence of any continuous periapical radiolucency.¹ The biological and functional success of dental implants is determined by their ability to remain osseointegrated.⁴

Using the criteria listed above,⁴ success rates reported for endosseous implants placed in native bone (bone naturally present after extraction socket healing) are generally high, with most of the data reporting rates higher than 90%.¹ While placement of implants in native bone provides clinicians with a high degree of long-term functional success, esthetic results achieved in those situations are often less gratifying because of the nature of the alveolar bone resorption that typically occurs after extraction. This can pose a significant problem for the clinician when treating the anterior maxilla.

It has been well documented that the upper alveolar ridge undergoes resorption in the palatal and apical directions after tooth extraction.^5,6 After natural healing of an extraction socket, the remaining edentulous ridge may be encountered at a position that dictates a more apical and palatal placement of an implant fixture, ultimately resulting in a compromised esthetic restorative result because crowns may be longer than those of natural teeth and also may present with a less than optimal emergence profile.

To address esthetic concerns pertinent to the placement of dental implants in the esthetic zone, several approaches aiming at preservation of extraction socket dimensions have been suggested. The immediate placement of dental implants (ie, concomitant with tooth extraction)⁷ is an approach that has become more popular in recent years because an implant fixture might be the most effective "extraction socket filler." The implant fixture provides the bony socket walls with support that prevents their collapse by mimicking the presence of a natural tooth root. This approach is reasonably successful,⁷ but concerns do exist when the tooth being extracted presents with an active infection because of periodontal, endodontic, or root fracture associated lesions. The possibility of a residual infection in the extraction area to compromise immediately placed implant osseointegration does exist. Moreover, there are situations in which primary stability to the implant cannot be achieved because the remaining extraction socket bony walls do not provide enough anchorage.

For these reasons, clinicians often opt for a staged approach when treatment-planning the placement of a dental implant in an area where a severely infected tooth is present. To preserve the extraction socket dimensions after tooth extraction and before placement of dental implants, therapeutic procedures such as guided bone regeneration (GBR),^8,9 osseous grafting,¹⁰ or a combination of both have been suggested.^11,12 The use of nonresorbable and resorbable membranes for GBR in the preservation of extraction socket dimensions has been shown to be very effective when compared with sockets where no membranes were used.^8,9 Bone grafts and substitutes, particularly when used in combination with GBR, also have shown evidence of effectiveness in the preservation of alveolar socket dimensions.^11,12

The purpose of this article is to report on the steps involved in replacing a fractured upper central incisor with an implant-supported crown. Using surgical techniques involving extraction socket preservation/augmentation and connective tissue grafting, ideal positioning of the implant was possible and gingival contours were enhanced. With this multiple step treatment, the final restoration met biological and functional results and its esthetic effects were maximized.

Case Report
A 45-year-old African American man presented to one of the author's periodontal offices for evaluation of tooth No. 8. The patient's main complaint was of looseness of tooth No. 8 with periodic gingival swelling that subsided on its own. According to the patient, the first episode of swelling occurred about 1 year before his initial periodontal consultation. The history of tooth No. 8 included a baseball bat accident when the patient was a teenager. The tooth suffered a crown fracture with pulp exposure. Im­mediately after the accident, tooth No. 8 received endodontic treatment and was re­stored with a porcelain-fused-to-metal (PFM) crown. The crown was replaced once, about 5 years before the patient's consultation at the periodontal office.

Clinical examination of tooth No. 8 re­vealed the presence of pockets in excess of 12 mm on its straight buccal and mesial aspects (Figure 1). Bleeding on probing and suppuration originating from the pocket areas as a result of digital pressure application to the gingival tissues were detected. Tooth No. 8 presented with Class 2 mobility, and approximately 1 mm of gingival recession was noticed on its buccal and mesial aspects. Probing pocket depths and mobility on the adjacent teeth were within normal limits. Radiographic examination of the tooth demonstrated adequate endo­dontic therapy and absence of any periapical radiolucency. However, a severe vertical bony defect was observed on the mesial aspect of the tooth.

Based on history and clinical and radiographic findings, the differential diagnosis for tooth No. 8 included a recurrent infection of endodontic origin as a result of a lateral canal, localized severe chronic periodontitis, a vertical fracture, or a cemental tear. As a definitive diagnosis could not be reached with the information available, an exploratory surgery was suggested, with the patient being in­formed about the possibility of needing to have tooth No. 8 extracted. In the event that extraction would be the treatment of choice, options for replacement of the tooth included an implant-supported crown, a three-unit fixed partial denture, or a re­movable partial denture. After being informed about the pros and cons of every option, the patient opted for an implant-supported crown. With that decision having been made by the patient, he also was informed that an extraction socket preservation/augmentation procedure would be advisable if the tooth needed to be extracted.

The exploratory surgery was performed under local anesthesia (2% lidocaine with epinephrine at a concentration of 1:100,000). The buccal flap design8,9 included an intrasulcular incision around tooth No. 8. The interdental papillae between teeth Nos. 7 and 8 and be­tween teeth Nos. 8 and 9 were included in the flap, and an effort was made to preserve as much of their buccal lingual dimension as possible. Vertical incisions extending beyond the gingival junction were made on the buccal proximal line angles of the adjacent teeth. A full thickness flap was then elevated to expose buccal, mesial, and distal aspects of tooth No. 8. After degranulation of the mesial angular bony defect, a vertical root fracture was diagnosed. A hopeless prognosis was assigned to tooth No. 8 and it was gently extracted with forceps. The remaining granulation tissue present in the extraction socket was removed with curettes and all bony walls of the defect were exposed. Approximately two thirds of the buccal plate and half of the mesial bone crest were lost as a result of the inflammatory process associated with the root fracture (Figure 2).

The preservative/reconstructive osseous treatment modality for the extraction socket of tooth No. 8 consisted of defect fill with bovine-de­rived porous bone mineral (BPBM) (BioOss, Osteohealth) com­bined with a porcine-derived collagen mem­brane (BioGide, Osteohealth) for GBR. The socket space was filled with BPBM to the levels of the palatal and distal bony walls. On the buccal aspect, the defect was vertically filled to the level of the bone present on the buccal of tooth No. 9 and horizontally filled to follow an imaginary, slightly convex line connecting the alveolar bone on teeth Nos. 7 and 9. On the mesial aspect, the defect was filled to a level approximately 3 mm apical to the mesial cemento­enamel junction (CEJ) of tooth No. 9 (Figure 3). BPBM was loosely packed in the extraction socket area as suggested by the manufacturer. The approach used for filling of the defect determined the procedure to be a combination of extraction socket preservation and augmentation.

A collagen membrane was shaped to cover the grafted area in the mesial distal direction. On the buccal aspect, the membrane was extended 2 mm apical to the level of the existing bony plate and fixed to the alveolar bone using two pressure-fit bone tacks (Nobel Biocare USA, Inc) (Figure 4). Limited full thickness elevation of the palatal tissue was performed to allow for tacking of the membrane between the soft tissue and the bone. Im­mobilization of the membrane was achieved in this manner.

Buccal flap mobilization was achieved through a periosteal releasing incision, and flap advancement was performed to achieve primary flap closure, including a tension-free suture line along the palatal tissues. Flaps were sutured with 4-0 extended polytetrafluorethylene su­tures (Ethicon, Inc) (Figure 5). Postoperative medications in­cluded amoxicillin 500 mg every 8 hours for 2 weeks, ibuprofen 800 mg as necessary for pain, and 0.12% chlorhexidine rinses every 8 hours for 2 weeks. Sutures were removed at 1 week after surgery and mechanical oral hygiene of the area was initiated at the beginning of the third postoperative week. Healing was un­eventful. Immediately after the surgical procedure, the PFM crown previously present on the tooth was bonded to the adjacent teeth with a bondable reinforcement Ribbond (Ribbond) and light-cured composite resin. The area was allowed to heal for 18 months before reevaluation for implant placement.

Eighteen months after the ex­traction and socket preservation/ augmentation procedures were performed, an evaluation of the area for the placement of a dental implant was conducted. The soft tissue in the area of tooth No. 8 was clinically healthy. Radiographically, the area correspondent to tooth No. 8 revealed a radiopaque mass, presumably a combination of BPBM and new bone (Figure 6). The bonded temporary restoration was removed and alginate impressions were made for fabrication of a radiographic and surgical stent. A computerized tomographic scan of the treated area re­vealed adequate mineralized tissue for implant placement (Figure 7). The radiopaque marker present in the stent revealed that the implant could be placed in an ideal buccal lingual position with a straight vertical projection of the long axis of the implant being centered at the cingulum of the future crown to be fabricated.

Because of limited mesial distal dimension and incisive canal proximity, the implant selected to replace tooth No. 8 was a root form tapered fixture measuring 3.5 mm in diameter and 13 mm in length. The radiographic stent was converted into a surgical guide by creating an orifice in the area previously occupied by the radiopaque marker.

Implant placement surgery was conducted under local anesthesia. A horizontal incision was made on the tooth No. 8 edentulous area connecting the palatal proximal line angles of teeth Nos. 7 and 9. Vertical incisions extending from the proximal ends of the horizontal incision, through the interproximal gingival sulcus of teeth Nos. 7 and 9, to the buccal nonkeratinized mucosa were made. A mucoperiosteal flap was ele­vated to expose the previously grafted area (Figure 8). Visual inspection and exploration of the grafted area with a periodontal probe revealed tissue resembling bone in color and consistency. Granules of BPBM could still be identified on the surface of the grafted area. The per­imeter of the grafted area could be visually distinguished from the adjacent preextraction bone; however, no movement of the grafted tissue was observed. No remnants of the collagen membrane were identified. The titanium pins used to immobilize the membrane were re­moved.

Implant osteotomy was performed with the surgical guide in place and particular attention was given to the buccal lingual position of the fixture (Figures 9 and 10) to avoid a final buccal implant angulation. No buccal fenestration or dehiscence was apparent on the buccal bony plate during the osteotomy process. An effort was also made to position the implant platform 3 mm to 4 mm apical to the buccal gingival line of teeth Nos. 7 and 9 (Figure 11). After placement of a cover screw on the implant fixture, the flap was secured to its original position with 4-0 e-PTFE sutures. The postsurgical protocol with respect to medications and oral hygiene of the area was exactly the same as the one adopted for the first surgical procedure on the patient. The PFM crown previously used as a temporary restoration was bonded to the adjacent teeth as performed after the extraction and socket pre­s­ervation/augmentation procedures. Healing after the implant surgery was uneventful.

Ten months after implant placement, clinical examination showed the gingival tissue in the surgical area to be healthy, but a slight buccal lingual concavity on the buccal aspect of the implant area was observed (Figure 12). A periapical radiograph taken at this same time revealed the implant fixture to have features compatible with successful osseointegration. After local anesthesia, implant exposure was conducted by elevating a flap, which used an identical design to that used in the implant placement surgery. At surgical exposure, the implant was surrounded by hard tissue to the level of the polished collar (Figure 13). Fewer granules of BPBM could be identified around the previously grafted area as compared with the time of implant placement. A healing abutment (Replace, Nobel Biocare USA, Inc) measuring 5 mm in height was connected to the im­plant with a manual screwdriver.

To correct the buccal lingual concavity pres­ent on the buccal aspect of the implant area, a palatal connective-tissue graft was placed over the buccal aspect of the implant before flap suturing. The technique used for execution of the connective-tissue graft was similar to those previously described for alveolar ridge augmentation13 or for root coverage.¹⁴ Briefly, a "trap door" flap design was used in the posterior palate. After elevation of a split thickness flap, the connective-tissue graft (about 7 mm wide, 5 mm long, and 1.5 mm thick) was removed with sharp dissection and the flap was sutured with 4-0 silk (Ethicon, Inc). The graft was trimmed to the size and shape of the recipient site and sutured in place with 5-0 plain gut (Figure 14). An effort was made to suture the graft in as coronal a position as possible, using the healing abutment as anchorage (Figure 15). The flap was then advanced and sutured over the graft with 5-0 plain gut. To achieve primary closure of the flap in the interproximal areas, minor soft-tissue scalloping of the flap was required in its buccal aspect where the soft tissue came in contact with the healing abutment. The postsurgical medication protocol was similar to the ones used for the previous two surgeries with the exception that no antibiotics were used. The PFM crown was once again bonded to the adjacent teeth and 12 weeks were allowed to elapse before executing final restoration of the implant.

Healing of the peri-implant tissues 4 months after surgery was within normal limits (Figure 16) and revealed successful buccal lingual augmentation of the gingival tissues. After removal of the healing abutment and connection of an impression coping (Figure 17), a fixture level impression of the implant was made using a polyvinyl siloxane base material. Be­cause a narrow platform implant had been used, a straight esthetic abutment measuring 10 mm in height and with a 1.5 mm margin was selected to enhance the emergence profile of the restoration. After fabrication of the PFM crown by the laboratory, the abutment was connected to the implant fixture using a torque wrench delivering 35 N/cm of force. Severe blanching of the gingival tissues around the abutment was observed after its insertion because of the different dimensions between the healing and permanent abutments. To avoid compromising blood supply to the periimplant tissues, two short horizontal incisions were made under local anesthesia in the interproximal areas adjacent to the abutment to allow for relaxation of the gingiva. A temporary acrylic crown was fabricated using a vacuum-formed stent fabricated on the master cast with the PFM crown in place and cemented with a zinc oxide base temporary cement (Figure 18). Four weeks were allowed for tissue remodeling and healing before final adjustments and cementation of the permanent PFM crown with a resin modified glass ionomer base cement (Figure 19).

The implant-supported crown has been in function for more than 2 years and is free of symptoms. The soft tissue contours around the crown are stable and a periapical radiograph of the implant shows signs suggestive of sustained os­seointegration (Figure 20).

Discussion
The case reported in this manuscript shows that an esthetically acceptable implant-supported res­toration can be fabricated if planning and execution of treatment take into consideration steps to preserve and augment the hard tissue present in the edentulous ridge. More­over, the use of soft tissue grafting on the implant site can further enhance the gingival architecture of the area to aid the implant fixture/abutment/crown complex in having the appearance similar to a natural tooth.

One of the most crucial elements in achieving an acceptable esthetic implant-supported restoration is the position of the implant fixture. To place the implant fixture in the ideal position, adequate bone volume needs to exist in the edentulous area. If hard tissue preservation/augmentation procedures are not performed at the time of tooth extraction in the anterior maxilla, remodeling of the alveolar bone will often result in the absence of adequate bone volume for ideal implant positioning. This is particularly true for patients with a narrow alveolar housing and a thin, scalloped periodontium. The patient in this case presented with severe loss of the buccal and mesial bone and, if left to heal without intervention after tooth extraction, would likely result in a deficient alveolar ridge for ideal positioning of the implant fixture.

The technique of choice for the hard tissue preservation/augmentation procedure included GBR and an osseous graft. Controlled clinical trials by Lekovic and colleagues^8,9 show that the placement of membranes over extraction sockets will result in approximately 27% less horizontal and 41% less vertical collapse of the ridge as compared with extraction sockets where membranes were not used. Re­sorbable membranes made of glycolide and lactide polymers generated similar results as e-PTFE membranes, which did not become exposed in the course of healing. Accidental exposure of e-PTFE membranes during healing compromised the final result. As 30% of e-PTFE membranes became exposed in the course of healing, evidence suggests that the use of resorbable membranes for GBR may be preferable over nonresorbable ones be­cause exposure was not observed with the latter.

There are no controlled clinical trials published to this date that examine whether there is any advantage in combining an osseous graft to GBR in the preservation/ augmentation of extraction socket dimensions. Iasella and colleagues¹¹ have shown that a combination of a resorbable membrane made of collagen and a decalcified freeze-dried bone allograft was significantly more effective in preserving extraction socket dimensions than controls, which were treated neither with a membrane nor with an osseous graft. Therefore, it is impossible to precisely identify which individual component of the combined technique was responsible for the positive result observed. When results of the experimental sites treated in the study by Iasella and colleagues¹¹ are compared with the experimental sites treated in the trials conducted by Lekovic and colleagues where only the membrane was used,^8,9 similar rates of improvement are reported. However, comparisons of results between separate clinical trials should be interpreted with caution and the advantages of combining osseous grafts with membranes as a therapeutic modality for the preservation of extraction socket dimensions need to be further investigated by well-controlled clinical trials.

A problem that is observed in large extraction sockets where severe bone loss has occurred is the fact that resorbable membranes, by virtue of their flexibility, tend to collapse into the socket space after suturing of the flap. If a membrane lacks its space maintaining capability, bone formation will not occur in the affected area. Therefore, placement of a slowly resorbing os­seous graft in the area intended for bone preservation and particularly in the area where augmentation is desirable, such as the most coronal buccal aspect of the case reported in this manuscript, might be beneficial to the clinical outcome of these preservation/augmentation procedures.

Biologically, it is ideal for any osseous graft material to be resorbed in the process of healing and be replaced by natural bone. In that way, the hard tissue in which the implant is being inserted and that will support the implant fixture is vital bone. In the case reported in this article, most of the hard tissue present on the buccal and occlusal aspects of the ridge had the clinical appearance and consistency of bone at 18 months after the preservation/augmentation procedure. However, granules of BPBM were present on the buccal hard tissue surface of the alveolar ridge and were visible in the internal walls of the osteotomy site, indicating partial resorption of the graft material. These observations are somewhat consistent with the data reported by Artzi and colleagues15,16 where BPBM granules were evident in all 15 biopsies taken from grafted extraction sockets 9 months earlier. As a point of interest, a few granules of BPBM were observed on the buccal plate of the implant during its second stage surgery, which was performed 28 months after the extraction socket was grafted. The clinical significance of residual graft material in an implant-treated edentulous ridge in the success and predictability of endosseous implants has not been evaluated.

There is no established protocol for the ideal healing period between the extraction socket preservation/ augmentation procedure and the placement of the implant. His­tological studies report between 34.7% and 59.5% viable bone present in grafted extraction sockets with decalcified freeze-dried bone and bioactive glass, respectively, be­tween 6 and 8 months after the procedure.¹⁰ In sockets grafted with BPBM, an average of 46.3% new bone was found at 9 months after grafting.¹⁵ In this case report, a period of 18 months was empirically chosen to allow for further resorption of the BPBM but, as mentioned before, was not sufficient for complete resorption of the graft material.

The implant dimensions used in this case were dictated by the mesial distal dimension of the edentulous ridge in its most coronal aspect, proximity of the roots of teeth Nos. 7 and 9, which converged in the apical direction, and proximity of the incisive canal. The narrow platform, 3.5 mm diameter implant was chosen to minimize the risk of damaging the adjacent root surfaces and violating the integrity of the incisive canal.

Precise implant placement in the esthetic zone is crucial to the outcome of restoration esthetics. There­fore, a restrictive surgical guide plays an important role in the buccal lingual and mesial lingual angulation of the osteotomy site. A common error in the osteotomy process is to angle the coronal portion of the burs in the buccal direction. An implant that has its occlusal platform with a buccal version requires an angled abutment for the restoration, increasing the likelihood of gingival recession in the area.

Correct positioning of the fixture is also important in the apico-coronal direction. It has been suggested that the ideal position of the implant platform is 3 mm to 4 mm apical to the gingival margin position on the buccal aspect of adjacent teeth, given that no gingival recession is present.¹⁷ Implant fixtures placed too coronally may result in supragingival exposure of the abutment or of the fixture itself. On the other hand, if the implant fixture is placed too apically by excessive countersinking, bone saucerization is likely to occur, which can result in deep periimplant pockets, difficult plaque control, and inflammation. In turn, peri-implantitis or gingival recession can take place, both of which can compromise implant health and esthetics.

The area in which the implant was placed healed with a buccal lingual concavity on its buccal aspect, and that anatomical situation could compromise the esthetic result of the crown. This anatomical deformity existed be­cause less than optimal buccal lingual augmentation was achieved by the hard tissue preservation/augmentation procedure. Because the implant fixture was completely surrounded by bone at placement and remained that way until the implant was exposed, a decision was made to further augment the area with palatal connective tissue. If, in combination with the buccal lingual concavity over the implant during its exposure, a bony dehiscence or fenestration had been observed, a hard tissue regenerative approach would have been the treatment of choice to correct the functional and esthetic problem. There is no solid data on the stability of soft tissue dimensions after connective-tissue grafting over implant fixtures. Similar procedures used for denuded root coverage over natural teeth have been shown in augmented grafted tissue to have a stable long-term prognosis. ^18,19

The reason for selection of a healing abutment with a straight rather than a flared profile was based on the need to graft the area with soft tissue. The straight profile of the healing abutment allows for the gingival tissues in the graft area to be sutured at and to heal in their most possible coronal position. When that objective was achieved, the permanent abutment with a flared design was used to remodel the existing tissue to accommodate for the emergence profile of the crown. Because the permanent abutment was significantly larger in diameter than the healing abutment, excessive blanching was observed in the gingival tissues. On a precautionary basis, gingival tissue incisions were made in the interproximal areas adjacent to the abutment to allow for tissue relaxation and slight remodeling before cementation of the crown. Excessive tension on the gingival tissues carries the risk of compromising blood supply and result in necrosis.

The choice of using a cemented crown or a screw-retained crown existed in this case. Both approaches have been shown to be successful. Cementation presents with the advantages of not having the possibility of screw loosening or need for restoration of the screw access orifice. However, cemented restorations are not as easily retrievable as screw-retained restorations. An important detail in the cementation pro­cess is that no excess cement be left in the subgingival environment to avoid gingival and periimplant inflammation.

Conclusion
One of the keys for success in having a functional and esthetic im­plant-supported restoration is the presence of alveolar bone volume that allows for placement of the implant fixture in an idealized position. This objective can be achieved with extraction socket preservation/augmentation procedures. Also, mi­nor gingival tissue architecture de­formities can be corrected with soft-tissue grafting. This staged, multiprocedure facilitates restorative dentistry and can result in a long-lasting restoration with good esthetics.

Disclosure
The authors declare no financial interest in any product or company cited in this article.

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