Within the last decade, implant dentistry has placed increasing importance on dental esthetics. The question is no longer how to design dental implants that allow for high survival and success rates but rather how to treatment plan placement of implants in the esthetic zone with predictable esthetic results? With the advances in regenerative techniques for both hard and soft tissues, indications for implant supported prostheses along with both dentists and patient’s expectations of such prosthesis have expanded; esthetic compromises have become unacceptable.1 In the anterior maxilla, an error in placement can lead to an esthetic nightmare, so how do we prevent these clinical failures? As Buser (2004) pointed out, it is important to establish sound clinical concepts with clearly defined parameters that lead to successful esthetics and long-term stability of the peri-implant tissues.2 Below I will outline these concepts and parameters from both a surgical and anatomical perspective.

PREOPERATIVE ANALYSIS

PATIENT EVALUATION/RISK ASSESSMENT 1, 2,3

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In every patient, a detailed preoperative analysis should be performed to assess the individual risk profile and level of difficulty of the surgical and restorative plan. This assessment includes several aspects with the goal to identify patients whose implant therapy carries a high risk of negative outcome, which is particularly important in the anterior maxilla. It is paramount that initiation of therapy starts with understanding the patient’s desires and chief concern: What is the concern in the patient’s words? What is patients’ goal of treatment? How realistic is this? It is critical to evaluate the patient’s motivations, level of understanding, compliance, and overall behavior to properly assess the likely outcome of the case.

Additionally, a thorough medical and dental examination should be completed. The medical history should include analysis of systemic disease to prevent complications during treatment. For example, non-controlled diabetics, smokers, and patients on corticosteroid therapy may have reduced healing ability, which could negatively impact the surgical outcome. Likewise, the dental examination should screen for active infections (such as endodontic lesions, caries, and periodontitis); all active infections should be treated prior to implant placement. Patients with increased periodontal susceptibility and/or a history of progressive or refractory periodontitis should be identified, as literature has shown these patients have an increased risk of biologic complications around osseointegrated implants. Additionally, the following questions should be asked: How compliant has patient been with past recommendations? What are the patients’ current oral hygiene practices? Does the patient have any parafunctional habits? If possible, occlusal conditions should be evaluated on diagnostic, mounted casts and a prosthetic wax-up completed prior to surgery.

IMPLANT SITE ANALYSIS 1, 2,3

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Implant placement in an optimal position begins with the prosthetic plan and anatomical assessment of the single-tooth space. Buser (2004) noted that an optimal esthetic implant restorations depends on 4 anatomic and surgical parameters: (1) submucosal positioning of the implant shoulder, (2) adequate 3-dimensional implant positioning, (3) long-term stability of the esthetics and peri-implant soft tissue contours, and (4) symmetry of clinical crown volumes between implant site and contra lateral teeth.2 To adequately evaluate a potential single-unit implant site, the following determinants should be considered: smile line, soft tissue morphology, tooth morphology, and osseous architecture.

I. Smile line

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The esthetic zone is defined by the lip parameter. A discerning eye is needed to determine if a smile is natural, as commonly when patients are unsatisfied with their smile they may not give a full smile when asked.1 Schincaglia & Nowzari, 2001 described the average smile as the position of the lip showing 75% to 100% of the maxillary incisior and interproximal gingival. A high smile line differs from the average smile line by showing more of the gingival tissues, while a low smile line exists when less than 75% of the maxillary teeth are displayed.4

Patients with a high smile line require maximal efforts to maintain peri-implant tissue as the restoration and the gingival tissue will be completely displayed and the soft tissue contour, color and shape of the restoration have to be perfectly reconstructed for an ideal esthetic outcome. A low smile line presents a less critical situation, as the implant-restorative interface will be hidden underneath the patient’s upper lip.4

II. Soft tissue morphology

Gingival biotype

TEETHTwo different periodontal biotypes have been described in relation to the morphology of the interdental papilla and the osseous architecture: the thin, scalloped periodontium and the thick, flat periodontium.1

The thin scalloped biotype tends to develop soft tissue recession in response to trauma or periodontal infection while the thick biotype is more resistant to trauma and infection and the presence of periodontal infection typically leads to pocket formation.4

A thin, scalloped biotype will require the implant body and shoulder to be placed at a more palatal position to mask any titanium show-through.1

Bone crest to interdental papilla height

The recession of the interproximal soft tissue creates and empty space in the interdental area termed a “black triangle.” Several studies have shown that the loss of interproximal soft tissue seems to correlate with the distance between the base of the contact area and the bone crest.1, 2, 3, 4, 5, 6

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In 2010, Cho et al. stated that Dennis Tarnow’s recommendation of 5 mm of vertical height from alveolar bone crest to interproximal contact is too optimistic to get 100% fill, instead proposing that usually with 4mm you can expect bone fill (results reported 90% fill with a vertical height of 4 mm). In 2001, Choquet concluded that when the distance from contact point to bone crest was 4mm or less the papilla was present 100%; papillae present 88% at distance of 5mm; 50% at distance of 6mm; 75% at distance of 7mm; 50% at distances of 8mm and 9mm; 75% at distances 10mm or greater. Thus when the proximal contact point to bone crest distance is 5 mm or less, papilla are predictable present 6 months after implant placement.

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In 2007, Martegani et al. examined the interradicular distance and the distance between the contact points and concluded the alveolar crest has independent and combined effects on the presence or absence of the interdental papilla. In the group of interdental sites with an interradicular distance of less than 2.4mm, an increase in the distance between contact point and the alveolar crest corresponded to an increase in the dimensions of the interdental black triangle, resulting in a less esthetic smile. When the interradicular distance was greater than 2.4mm, the distance between contact point and alveolar crest lost its influence on whether the interdental papilla would be present or absent.

III. Tooth morphology

It appears that tooth morphology is correlated with soft tissue quality. Triangular tooth shape is typically present with the thin, scalloped periodontium with the contact area located at the coronal third of the crown, underlining a long and thin papilla. Conversely, more square shaped anatomical crowns are often associated with a thick, flat periodontium with contact areas located at the middle third supporting a short and wide papilla.4 4SmilePersonalitiesThus, loss of interdental soft tissue in the presence of triangular shaped teeth is more detrimental compared to square teeth, as a larger black triangle will develop.  Although tooth morphology can be modified restoratively to help eliminate or at least reduce the black triangle (for example, making a longer, more apically placed contact area) this typically compromises restorative esthetics.

IV. Osseous Architecture

Orofacial dimension: One of the most important things to assess is orofacial ridge anatomy, including whether there is sufficient crest width and the presence or absence of facial bone atrophy; deficiencies may require bone augmentations prior to or at the time of implant placement to ensure the implant can be positioned in a correct, restoratively driven position.1

Mesiodistal dimension: Space for the implant restoration should be equal to that of the adjacent (central incisors) or contra lateral (lateral incisors and canines) tooth.1 Excesses or deficiencies must be corrected prior to implant placement (such as through use of orthodontics, enamoloplasty, etc.).

A reduced horizontal distance between the implant fixture and natural tooth may adversely affect the bone level at the tooth surface. The early Branemark studies showed circumferential, cup-shaped bone loss extending 1.5 mm around implants. From this pattern and extent of bone loss, it was first suggested that implants be placed a minimum of 1.5 mm from a natural tooth to avoid bone loss extending across to the natural tooth. In his textbook published in 1999, Misch concurred with the earlier Branemark recommendations, suggesting mesiodistal distance must allow for at least 1.5 mm between implants and teeth and 3 mm between implants (to avoid bone loss)8. That is, neither the implant body or shoulder should be closer than 1.5 mm to the adjacent root surfaces. In 2004, Gastaldo suggested that the ideal distance between two implants or an implant and a tooth is 3-4mm for an adequate fill of papilla.9

Apicocoronal dimension: Buser (2004) describes the assessment leading up to depth of implant placement to be the most critical.1 Deficient tissues in this dimension can be due to several things, such as: periodontal disease of the adjacent teeth, trauma, atrophy, infection, or congenital abnormality. Due to the complexity and unpredictability of vertical ridge augmentation, patients with deficiencies in this dimension are placed in a high anatomic risk group and must be cautioned that it is likely esthetic results will be less than ideal.

CONCLUSIONS 

images-3The literature has shown that there are several factors that individually and collectively contribute to an esthetic single tooth implant restoration in the esthetic zone, paramount of which is interproximal bone levels. As the interproximal crest height plays a role in the presence or absence of peri-implant papilla, it is of the utmost importance during treatment planning to accurately assess bone levels to ensure that if any esthetic compromise is likely due to non-ideal conditions, the patient is aware of this prior to any definitive surgical therapy.

References:

  1. Hess, D., Buser, D., Dietschi, D., Grossen, G., Schonenberger, A., & Belzer, U. Esthetics single-tooth replacement with implants: a team approach, Quintessence Int. 1998;29(2):77-86
  2. Buser, D. Optimizing esthetics for implant restorations in the anterior maxilla: anatomic and surgical considerations, The International Journal of Oral & Maxillofacial Implants, 2004; 43-61
  3. Carranza, F. A., Newman, F. G., Takei, H. H., & Klokkevold, P. R. Clinical Periodontology, 2006. Chapter 74: Clinical Aspects and Evaluation of the Implant Patient, pg. 1087-1102. Sauders Elvsevier, St. Louis, Missouri.
  4. Schincaglia, G. P. & Nowzari, H. Surgical treatment planning for the single-unit implant in aesthetic areas, Periodontology 2000;27,162-182.
  5. Chow, Yiu Cheung, Wang, HL. Factors and Techniques Influencing Peri-Implant Papillae. Implant Dentistry 2010;19:208-219.
  6. Choquet V, Hermans M, Adriaenssens P, Daelemans P, Tarnow DP, Malevez C. Clinical and radiographic evaluation of the papilla level adjacent tosingle-tooth dental implants. A retrospective study in the maxillary anterior region. J Periodontol. 2001 Oct;72(10):1364-71.
  7. Martegani P. Silvestri M, mascarello F, et al. Morphometric study of the interproximal unit in the estheti regioin to correlate anatomic variablesaffecting the aspect of soft tissue embrasure space. J Periodontol 2007;78:2260-5
  8. Misch CE. Divisions of Available Bone. Contemporary Implant Dentistry, Second Edition. 1999. pp 89-108
  9. Gastaldo JF, Cury PR, Sendyk WR. Effect of the vertical and horizontal distances between adjacent implants and between a tooth and animplant on the incidence of interproximal papilla. J Periodontol. 2004 Sep;75(9):1242-6.
  10. Penarrocha, M., Uribe, R., Balaguer, J. Immediate implants after extraction. A review of the current situation, Med Oral, 2004;9:234-42