Strategies for Managing Soft Tissue Phenotype with Implant-Supported Restorations
Management strategies to maintain or improve existing soft and hard tissue architecture revolve around a goal of thick bone and thick soft tissue. A thick periodontium can optimize esthetics around implant-supported restorations. It can reduce the amount of gingival recession and create a better, more stable restorative environment93,120,121 (Fig 1-14). Periodontal plastic surgery and osseous regenerative procedures are available to convert a thin phenotype into a thick phenotype, which is easier and more predictable to manage for the restorative dentist.93,120,121 This has been examined with immediate and delayed implant placement protocols.
Fig 1-14 Occlusal view of an implant prior to impression making, demonstrating thick tissue on the facial aspect.
Immediate implant placement
Esthetic advantages of using subepithelial connective tissue grafts around dental implants have been reported. The change in the buccolingual width of the ridge around immediate implants has been evaluated with and without connective tissue grafts. After 6 months of healing, a loss of 1.063 mm of labial tissue was noted in a horizontal dimension in the nongrafted sites, while the grafted sites had a gain of
0.34 mm of labial tissue. Nine out of 12 nongrafted sites were considered to have compromised esthetics, with a “disturbing shadow” appearance, while no compromised esthetics were seen in the grafted sites.120
A successful conversion of a thin to a thick phenotype around immediate implants was demonstrated by subepithelial connective tissue graft placement in 20 patients. A thick phenotype was presented by 8 patients and thin phenotype by 12 patients prior to surgery. After a mean followup of 2 years, the mean facial free gingival margin change for the thick phenotype patients was +0.23 mm, whereas for the thin phenotype patients it was +0.06 mm. All the treated implant sites exhibited a thick phenotype.122 Thus, the enhanced facial free gingival margins can be maintained at appropriate levels regardless of the initial gingival phenotype presented by the patient.
Subepithelial connective tissue grafts should have large dimensions with a vertical height of 9 mm and a horizontal width equal to the mesiodistal extent of the recipient site. A minimal thickness of 1.5 mm is used to prevent shrinkage following surgery.123 Evaluation of long-term efficacy reveals a very predictable approach for achieving favorable functional and esthetic results around implant-supported crowns.124 Therefore, additional soft tissue volume needed in esthetically demanding areas must be established surgically.121
Delayed implant placement
Bone regeneration and soft tissue grafting procedures in conjunction with delayed implant placement has also been described.121,125,126 One clinical study reported on dimensional changes of peri-implant tissues by comparing pre- and posttreatment soft tissue dimensions. Placement of implants with simultaneous bone regenerative efforts and connective tissue grafting was successful in increasing the tissue volume. A 1.3-mm gain of buccal thickness and only 0.2 mm of recession (from crown delivery to 1 year postfunction) indicated stability of peri-implant tissues at 1 year.125
Successful esthetic outcomes can be achieved utilizing guided bone regeneration and soft tissue grafting in sites with missing facial bone. In one clinical study, implants were positioned in deficient sites followed by simultaneous horizontal and vertical augmentation. Six months later, at the time of membrane removal, connective tissue grafts were placed. The average bone gain was 3.75 ± 0.47 mm horizontally and 6.5 ± 0.81 mm vertically. The surgical procedure was able to provide predictable esthetic outcomes in deficient sites with favorable long-term soft tissue contour.126
Enhancing Existing Peri-implant Soft Tissues
Malpositioned implants may cause esthetic and maintenance complications (Fig 1-15). Improper soft tissue management may create a defect complicated by the malposition, and inadequate initial hard and soft tissue volume prior to implant placement can be extremely difficult to correct once the implant is positioned. There may be a need to repair an unesthetic situation and/or regain pre-extraction ridge contours.93 Treatment options such as implant removal, recontouring of the abutment, and soft tissue grafting should be considered. Several studies have shown improvement in cases of adverse esthetics around dental implants by means of connective tissue grafting and/or use of allogeneic bone grafts.127–130
Fig 1-15 Facial view of a failing implant-supported restoration, which may be the result of multiple factors including less than ideal implant positioning in every dimension.
Gingival phenotype again contributes to the amount and prevalence of gingival recession. One clinical study analyzing the esthetic outcomes of 42 single implant-supported restorations (mean time in function, 18.9 months) reported a mean recession of 0.9 mm. Patients with the thin phenotype had slightly greater recession compared with patients with the thick phenotype. That finding was further supported by another similar study reporting that recession was more prevalent in thin phenotype sites. Recession was present at 6 of 25 thin phenotype sites compared with 2 of 19 thick phenotype sites.105,131
Recession around implant-supported restorations
A dental prosthesis with soft tissue that truly mimics the soft tissue of the adjacent dentition and blends with the natural adjacent teeth is a challenging goal.132,133 Various studies report the apparently inevitable occurrence of marginal gingival recession around dental implants leading to adverse esthetic outcomes. Long clinical crowns, grayish appearance through the thin peri-implant tissue, and exposure of crown margins, abutments, or even implant threads are not uncommon.105,121,131,134–136
Several factors have been implicated in the etiology of marginal gingival recession. These include implant position,105,131,137–141 tissue phenotype,104,105,131,136,139 integrity and thickness of the facial bone,60,136,140,142,143 surgical approach (conventional vs flapless),136,144 and presence or lack of immediate provisionalization.144–146
Implant position within the alveolar bony housing is considered to be one of the most important contributing factors for gingival recession. Recession is more pronounced for implants placed facially compared with those implants placed lingually within the extraction socket. In addition, facially positioned implants showed three times more recession than implants positioned lingually (1.8 vs 0.6 mm).105,131 Undoubtedly, excessive lingual positioning may create unnatural buccal emergence angles or unmaintainable contours. Optimal placement is a balance of these issues.
Peri-implant soft tissue recession can be improved by employing a combination of coronally advanced flaps and connective tissue grafts. In one study,129 significant improvement was achieved in 10 patients from baseline, but complete coverage could not be achieved. Significant shrinkage (66%) at 6 months followed coronal advancement of the flap. Alternatively, a prosthetic-surgical method has been proposed to correct the peri-implant soft tissue dehiscence around single implants. After the existing crown is removed, the abutment is modified, and a coronally advanced flap in conjunction with a connective tissue graft is performed.