Dental implants in the esthetic zone of the oral cavity have always posed a challenge to the oral surgeon. Multiple variables must be considered, such as available soft and hard tissues, gingival phenotype, position of the lip upon smiling, and other factors that pertain to patient compliance and expectations. It is essential to pay attention to the factors that might compromise the long-term stability of these implants. In this article, a deep exploration of the current consensus regarding the long-term survival of implants in the esthetic zone will be performed. A case-series of the authors is included.
Key points
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Patient compliance and expectations are the most critical factors regarding implants in the esthetic zone.
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Before implant surgery, a deep analysis of the available soft and hard tissues must be performed.
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A risk assessment must be made, and identification of risk factors is helpful in predicting the long-term stability of our implants; these risk factors must be addressed before, during, or after implant surgery.
Introduction
Implants in the esthetic zone pose a challenge to any oral surgeon. Initially, the first consensus that attempted to assess the complexity of an implant case was released in 2007 by the International Team for Implantology; they called it the S = Simple, A = Advanced, C = Complex (SAC) classification. Today, we know that a manifold of elements and factors must be considered before engaging in implant surgery in the esthetic sector of the oral cavity. It is essential to understand that a significant portion of successful long-term implant survival will depend on an integral and systematized pre-surgical evaluation and adequate choice of techniques during the surgery phase. Consequently, these factors will contribute to our implants’ long-term survival. ,
The initial assessment should include a thorough medical history, also including simple but important factors such as a patient’s oral hygiene, smoking status, and treatment compliance. These factors will greatly influence the long-term stability of our implants. , A local surgical site assessment must also be done previously, where adjacent teeth’ pathology and periodontal status are significant. Controlling and resolving a pathologic environment is imperative to successful and long-lasting results. It must also be noted if other surgeries have already been performed. Furthermore, discussion regarding the patient’s expectations must be engaged with the patient before undergoing a new surgical procedure.
Upon a hard tissue assessment, it is important not only to quantify the amount of native bone but also to assess its quality. Important local bone factors include the width of the buccal table and overall bone density. Ideally, buccal walls thicker than 2 mm of bone thickness are at reduced risk of implant exposure in the Long-term. , , Furthermore, the surgeon must evaluate the dentoalveolar position of the anterior maxilla, the anteroposterior projection, bone inclination, buco-palatal dimension, and alveolar height. These factors will heavily determine the occlusion parameters for the final restorations. All these hard tissue characteristics will determine if the recipient’s alveolar bone is ideal for dental implant placement or if grafting will be required. ,
Regarding soft tissue, the amount of keratinized gingiva and overall periodontium phenotype must be assessed. The presence of previous surgical scars and muscular insertions must be noted, which can be a negative factor for primary closure and wound healing. The papillae and interproximal attachment are some of the most essential features in the esthetic zone; it is known that in patients where the distance between the contact point and the bone crest is higher than 5 mm, it will traduce an additional risk of under-developing healthy and esthetic papillae.
Augmentation procedures of soft and hard tissue increase the complexity and length of the case, but can aid to add stability in the Long-term in deficient edentulous sites.
Finally, the most important questions that we, as oral surgeons, must ask ourselves areWhat is our patient’s chief complaint, and what are his/her treatment goals? It is fundamental to understand and align ourselves with the answers to these 2 questions.
Imaging and adjunct software technologies
Advanced Imaging Techniques
In-depth analysis must include 3-dimensional (3D) imaging studies. Technologies such as cone beam computed tomography (CBCT) offer images that are crucial for assessing bone structure, density, and vital anatomic landmarks. These details are essential for surgical planning particularly in the esthetic zone. Today, surgical planning software allows the fabrication of surgical guides which offer a fast and precise option. However, it is important to note that software discrepancies can cause errors (>2 mm). The CBCT must be taken with with the surgical-radiological stent; with an adequate dental form and cervical emergence profile. Therefore, it will serve to project where future implants will be placed, and allow for the whole procedure to be prosthetically guided.
Digital Smile Design
Digital smile design (DSD) is a diagnostic tool that integrates the analysis of the patient’s dental and facial proportions using high-quality digital photographs and videos (Sao Paulo, Brazil, 2007). DSD permits visualization of the relationship between the teeth, gums, lips, and smile characteristics, allowing for comprehensive planning and simulation of the result before the treatment begins. DSD also contributes to determine if the final restoration will require a custom abutment to compensate for the vertical and horizontal hard and soft tissue defects.
Comprehensive treatment planning
Interdisciplinary Treatment Coordination
Co-ordinating care across an interdisciplinary team, including oral surgeons, orthodontists, and prosthodontists, is crucial for complex esthetic zone implantations. Each specialist brings unique insights that contribute to a comprehensive treatment plan, ensuring all aspects of oral health, functionality, and esthetics are considered. For example, orthodontic treatment might be necessary to align or also to orthodontically produce dento-alveolar changes to improve projection and angulation of the implant placement. Also, orthodontic dental extrusion to obtain better vertical soft and hard tissue position for a proper dental implant placement guided adjacent teeth movements and optimized the implant’s spacing and angulation.
Prosthetic considerations
Selection of Prosthetic Materials
Material selection of the prosthetic components plays a significant role in esthetics and long-term success of implants. Porcelain offers excellent color-matching options and light-reflecting properties which are similar to natural teeth; however, zirconia seems to have better long-term success since it allows for better periodontium fiber attachment, which in turn reduces the probability of peri-implantitis. Literature is inconclusive regarding if screw-retained restorations are better than cement-retained prostheses; nonetheless, it is known that the presence of excess cement below the restorative margins can cause chronic inflammation even years after exposure. As a general rule, the closer the cement is to the crestal bone, the higher the chances for bone resorption, this is why a screw retained prostheses is preferred. On the other side, provisional restorations are critical to shaping the peri-implant soft tissues and achieving the desired esthetic contour. These temporaries help guide the healing process and allow for adjustments in the appearance of the gingiva before the final restoration is placed. Custom temporary restorations can also be designed with a 3D-printer which aims to guide the healing of soft tissues.
Abutment Design
The design of the implant abutments, whether custom or prefabricated, plays a significant role in the final appearance and function of the implant-supported crown. Salama first proposed the concept of custom abutments over 20 years ago, but these have just begun to gain popularity in the last decade. , , , , More recently, Su and colleagues first described concepts of critical and subcritical contours of the implant emergence profile. Modern abutment designs are divided into 3 zones: (1) esthetic zone (E), (2) bounded zone (B), and (3) crestal zone (C) ( Table 1 ). When an abutment is crafted, it should follow certain design rules which allow for a harmonic relationship between the dental implant and the periodontium to be maintained. Gomez-Meda et al. further describe the design considerations an abutment must follow in order to preserve soft and hard tissues around implants. , ( Fig. 1 ). An excessive concave or convex E zone can compromise the gingival margin and even cause recession of soft tissues. The B zone is apical to the E zone, and its design will be majorly influenced by soft tissue thickness. Thin soft tissue can be compensated with a convex B-zone and vice versa. It is important to take in consideration if these sites have been previously augmented with soft tissue grafts or will be grafted in the future. The C-zone is immediately coronal to the implant platform, it should be straight to avoid compression of the surrounding bone and avoid crestal bone loss. Ideally, implants should be placed 3 to 4 mm below the restorative zenith point. Of note, implants with platform switching should be cautiously placed subcrestally, in these cases a longer and thinner C-zone would be needed to avoid generating pressure in the crestal bone, this in turn modifies the rest of the zones and in narrow diameter implants these modifications might not be always possible because of available space. On the other side, tissue level implants already have a C-zone built in their design; in these cases, a straight or concave B-zone is advantageous for a natural look. Also, in recent years, longer abutments also known as transepithelial or transition abutments have been successfully employed to reduce stress forces and avoid bacteria colonization. This longer designs have proven to be advantageous to reduced crestal bone loss and soft tissue migration especially in shorter implants ( Fig. 2 A–C ).
| Zone | Function | Design | Tissue | Histology | Length |
|---|---|---|---|---|---|
| E | Esthetic conditioning | Convex to provide support to gingival margin | Sulcular epithelium | Stratified squamous epithelium | 1 mm |
| B | Biologic boundary area | Dependent on implant position and soft tissue thickness | Junctional epithelium | Non-keratinized epithelium | 1–2 mm |
| C | Crestal bone stability | Straight | Connective tissue | Connective tissue | 1–1.5 mm |
Anatomic considerations
Buccal Plate
It is known that a buccal wall ≤ 1 mm has an increased chance of resorption, which reduces the long-term stability and compromises esthetics. Chappuis and colleagues demonstrated that thinner buccal plates can present a mean vertical bone loss of 7.5 mm. In sites where a tooth has been extracted previously, the implants are advised to be placed in the early phases of healing before further bone loss occurs (type II and III) Immediate implants can be performed after a successful atraumatic extraction ( Table 2 ) to prevent further bone loss, along with adjunct bone grafting ( Fig. 3 A-E ). Immediate implants must be performed after a successful atraumatic and flapless approach; this can be achieved through acquired operator experience, and adequate instrumentation such as periotomes and diamond-tipped extraction forceps.
| Type | Description |
|---|---|
| 1 | Immediate implant placement |
| 2 | Early implant placement with soft-tissue healing (4–6 wk) |
| 3 | Early implant placement with partial bone healing (12–16 wk) |
| 4 | Late implant placement in healed sites (6 mo or more) |
It is estimated that less than 5% of central incisors have a buccal plate thicker than 1 mm, which raises concerns about long-term survival and obliges the operator to seek techniques to prevent buccal plate perforation, as well as to consider soft and hard tissue grafting. Regarding the mucoperiosteal flap, a design sparing the papilla should be utilized to avoid soft tissue defects after cicatrization. If extended access is required, then a single vertical incision can be performed posterior to the canine. A flapless design is not advised in the anterior zone. , ,
Implant Design and Angulation
It is known that implants with platform switching present less crestal bone loss; according to Atieh and coworkers, Bone level (BL) implants and soft tissue level (STL) implants can provide adequate esthetics in the anterior zone. , STLimplants can compensate when a vertical bone loss is present, and on the other side, BL implants seem to have better long-term outcomes when placed in single tooth sites, according to Chappuis and colleagues In general, BL implants should be placed 3 mm below the bone crest, while STL implants should be placed about 2 mm below the crest, since they can compensate with their machined necks. Implants with a length of 10 mm are adequate, however, implants between 6 and 8 mm are not recommended since their reduced area of osseointegration makes them less stable in the Long-term. Other implant material options, such as zirconia implants emerged over 15 years ago, at this point, it is known that osseointegration is comparable to Ti implants; nevertheless, this alternative remains to be tested in more extended longitudinal studies.
A proper relationship between implant, abutment, and crown can only be attained with adequate depth and angulation of the implant, in relation to adjacent teeth. Implants should be placed from 1 to 2 mm palataly from the future incisal edge to allow for a screw- retained crown to be used, it also allows for a proper emergence profile to be formed. Studies have shown that the angulation of the emergence profile of restorations also has the potential to cause bone resorption. , Prostheses with an angulation beyond 45 0 tend to cause bone loss, while restorations with an angulation between 15 and 25 tend to be more stable in the Long-term. ( Fig. 4 A, B ).
Fully guided implants have been gaining popularity, especially in general practitioners since they offer faster surgeries and less intra operative complications. Nonetheless, ideal positions for implants can only be attained if the surrounding tissues are adequate in shape and size, these anatomic characteristics must be evaluated prior to implant surgery. ( Fig. 5 A-U )
