Several human and animal studies have documented the effectiveness of ridge preservation procedures. These procedures limit, but may not totally prevent, the ridge alterations in both horizontal and vertical dimensions. Lekovic et al161 evaluated alterations in ridge dimensions in 10 subjects by covering the experimental sites with expanded polytetrafluoroethylene barrier membranes with primary closure. Control sites remained ungrafted. The clinical measurements demonstrated increased remodeling in the control group of 0.7 mm vertically and 2.6 mm horizontally compared with the test group. Another clinical study compared a ridge preservation approach using mineralized freeze-dried bone allograft and resorbable collagen membranes without primary closure.167 The horizontal width changed from 9.2 ± 1.2 mm to 8.0 ± 1.4 mm for the test group and 9.1 ± 1.0 mm to 6.4 ± 2.2 mm for the extraction-only control group. The difference horizontally was 1.6 mm between the groups. In vertical change, the test group had a gain of 1.3 ± 2.0 mm while the control group lost 0.9 ± 1.6 mm, for a vertical difference of 2.2 mm between the groups.
Fu et al168 proposed increasing the soft tissue thickness around dental implants by means of a method they called PDP, which stands for implant position, implant diameter, and prosthetic design. The authors advocated three steps: (1) a more palatal and apical positioning of the implant platform so more soft tissue volume is present on the facial aspect; (2) use of smaller-diameter or platform-switched implants to maintain an adequate amount of bone thickness, thus limiting the amount of gingival recession; and (3) use of concave subgingival contours for the abutments or crowns to allow ingrowth of peri-implant soft tissue. This article highlights the importance of not only the surgical methods but also the prosthetic methods or combinations thereof when it comes to soft tissue management.
Soft tissue–bone relationship
For proper decision-making, it is critical for the clinician to predict how different gingival phenotypes respond differently to implant-related therapy. If the soft tissue morphology and the underlying bony architecture differ from one another, the clinician should employ different management strategies (ie, for thin vs thick phenotypes). Bundle bone is the alveolar bone that receives the Sharpey’s fibers of the periodontal ligament. After extraction, the function of the bundle bone is no longer needed, usually resulting in substantial horizontal and vertical bone reduction. Following the removal of teeth, the bundle bone has minimal potential for remodeling and is therefore lost. Where bone is thinner, there is no capacity for this bone to be regenerated.169
There is evidence of a positive relationship between the gingival phenotype and the thickness of facial bone. Patients with thin phenotype are associated with thinner facial bone thickness, a narrow band of keratinized tissue, substantial distance from the CEJ to the alveolar bone crest, and a high prevalence of dehiscence and fenestration.159,170
The thickness of the facial bone is one of the most important clinical parameters in achieving predictable esthetic outcomes with dental implants. Facial bone thickness of 1 to 2 mm has been suggested to provide adequate soft tissue support and to prevent or minimize the amount of bone resorption. This minimizes the risk of soft tissue recession around implant-supported restorations.121,171–173 Around immediate dental implants, substantial bone fill was observed when the thickness of buccal bone was greater than 1 mm.141
Several animal and clinical studies demonstrate the correlation between soft tissue thickness and crestal bone remodeling following implant placement. In histologic studies conducted in dogs, thin tissue around dental implants consistently resulted in more bone resorption following abutment connection. There was also a tendency to form angular bony defects, whereas thick tissues tended to maintain more stable crestal bone.59,174 Similar results were reported in human studies. Implants placed in naturally thick soft tissue resulted in minor remodeling of bone, while implants placed in naturally thin soft tissues resulted in more bone remodeling with crestal bone loss of up to 1.45 mm.60,142,143 It is interesting to note that implants restored with a platform switching design were not able to preserve the crestal bone when compared with conventional matched-abutment implants in the presence of thin soft tissue.175
Presence of keratinized gingiva
The presence of keratinized gingiva is considered to be beneficial for the stability of peri-implant soft tissue because of its ability to form a microbial barrier. It plays an important role in the long-term maintenance and survival of dental implants.176
The relationship between keratinized gingiva and health status of the peri-implant mucosa was evaluated around implant-supported overdentures. The absence of adequate width of keratinized tissue (less than 2 mm) resulted in higher gingival and plaque index scores, a higher tendency for bleeding, and more radiographic bone loss.177 In a 5-year clinical study, even when patients were performing good oral hygiene and received regular maintenance therapy, buccal soft tissue recession, more bleeding, and plaque accumulation was noted at sites with less than 2 mm of keratinized gingiva.178,179
Interdental Papillae
The papillae between natural teeth fill the space under the proximal contacts. They have vertical, facial, and lingual surfaces, with a gingival col under the contact. With bone loss, the distance from the bone to the apical portion of the contact increases. Having a limited height range, the papilla may no longer reach the contact, resulting in a dark space between the teeth. The distance from the contact point to the crest of bone is a major factor in the esthetic adequacy of the papilla. Papillae are present around natural teeth 100% of the time when the distance from the contact point to the crest of bone is ≤ 5 mm. If the distance is 6 mm, the papilla is present only 56% of the time, and the papilla is present less than 27% of the time if that distance is ≥ 7 mm.101 After complete denudation of the interproximal bone, a mean distance of 4.33 mm between the location of the interproximal papilla tip and the contact had developed 3 years post-treatment, demonstrating the body’s tendency to return to a normal level.180
Single implants
The presence of normal interdental papillae is a key part of achieving optimal esthetics around implant-supported restorations. Papillae can be influenced by several factors. Tissue phenotype, implant-implant or implant-tooth distance, and level of interproximal bone crest of the adjacent teeth can all affect bone healing at the interproximal area and subsequently the presence or absence of a papilla. The space between the interproximal contact point of the definitive restoration and underlying interdental bone crest forms the interproximal gingival embrasure. As with natural dentition, the distance between the apical aspect of the interproximal contact and the interdental bone crest predicts the fill of the gingival embrasure space. Consequently, the presence or absence of an unfilled gingival embrasure space is dependent on both the surgical and prosthetic phases of the implant therapy.100,131,139,181–184
Single implants and phenotype
The complete fill of the interdental space by the papilla around natural teeth and implants can be influenced by the gingival phenotype of the patient. In a study evaluating the presence of papillae around natural teeth, the thin phenotype presented a significantly higher presence of papillae (71.1%) than did the thick phenotype group (59.6%).100 The papilla was considered present when there was no visible space apical to the contact point. The high prevalence of interproximal papilla fill around natural teeth for the thin phenotype may be explained by gingival architecture characteristics, because subjects with thin tissue also have accentuated tissue scalloping with a tendency for taller papillae. However, these subjects are also more susceptible to loss of gingival tissue following surgical procedures or tooth removal.
In evaluating the presence