Immediate Implant Placement:

Transcription

1 Immediate Implant Placement: Parameters Influencing Tissue Remodeling Bernard Touati, DDS and Mario Groisman, DDS In esthetic implant therapy, the patient s objective is to obtain an imperceptible, natural-looking prosthetic restoration. For the clinician, however, the challenge is to find and preserve or to regenerate hard and soft tissues that will allow for a thick, stable peri-implant environment. In the anterior zone, the loss of a tooth or teeth is often due to trauma, infection, or poor treatment. Such tooth loss may affect the bone and/or the gingival architecture, making immediate implantation after extraction impossible or more difficult to achieve. Fig. 1 Moreover, there are several specific anatomical features of anterior sockets that make this treatment more challenging. How the latter should be managed, and how and when the implant should be installed are among the many parameters that make implant surgical and prosthetic treatments successful and their bioesthetic integration harmonious and stable. Socket Management In the 90s, the hypothesis was that implant placement into an extraction socket may counteract hard tissue resorption (Denissen et al 1993 IJOMI, Watzek et al 1995 IJOMI). In 2004, Botticelli determined that while newly formed hard tissue had filled the marginal gaps surrounding implants in extractions sites, the buccolingual dimensions of the ridge were considerably altered. On 18 patients with 21 implants, he observed after four months a buccal loss greater than 50% and a lingual loss of approximately 30%. Recently, several investigators have confirmed the occurrence of this tissue alteration, despite the presence of an immediately placed implant (Covani et al 2004, Ferrus et al 2009, Sanz et al 2009, Araujo et al 2005, Cardarpoli et al Fig. 2 8 I Clinical and Practical Oral Implantology - Vol.1 No.3 - Fall 2010

2 Fig. 3 Fig. 6 Fig. 4 Fig. 7 Fig , Fickl et al 2008, Fugazzoto 2005, Chen et al 2005, Huynh-Ba et al 2010). Therefore, a bone substitute needs to be grafted in the alveolus around the implant in order for these large gaps to be completely resolved and resorption to be prevented (Ferrus et al). It must be noted that not all sockets show the same magnitude and speed of remodeling. Patients classified as having a thin tissue biotype show greater recession, vertically and horizontally, than do those with thick biotypes. Evans et al found 1 mm recession (±0.9 mm) in patients with a thin biotype versus 0.7 mm (±0.57 mm) in thick biotypes (Evans et al 2008). While tissue thickness plays a crucial role in this alteration process, it has to be considered that most buccal bone plates are thin or very thin in the anterior zone. According to Huynh-Ba et al (2010), only 2.6% of maxillary incisors and canines have their bone plate widths greater than or equal to 2 mm which, according to Spray et al (2004), would be the critical thickness of the facial bone plate in extraction sites to reduce the remodeling; this dimension has been confirmed by Belser et al (2007) for healed sites. In computed tomography images, it is common to observe very thin buccal plates (sometimes nearly undetectable) around teeth or with large dehiscences even while the gingival architecture remains stable for many years with small, if any, soft tissue recession around these teeth. In the case of extraction or immediate Clinical and Practical Oral Implantology - Vol.1 No.3 - Fall 2010 I 9

3 Fig. 8 implantation, however, and even with bone substitute in the gap (i.e., socket preservation), thin bone plates tend to slowly disappear. Consequently, some clinicians routinely graft connective tissue in this situation to counteract the possible perforation or dehiscence of the soft tissue. Fig. 11 Fig. 9 Fig. 12 This ongoing alteration of the socket wall is very likely due to the quality of this bone, predominantly composed of bundle bone, and underlines the importance of tissue biotype. The lack of stimulation and function caused by the absence of Sharpey s fibers and the periodontal ligament may explain this remodeling, yet it is less pronounced in lingual walls that have more lamellar bone. Fig I Clinical and Practical Oral Implantology - Vol.1 No.3 - Fall 2010

4 After a simple extraction, a tight blood clot containing growth factors is formed. The socket heals in approximately 8 weeks, with internal bone regeneration as well as resorption of the buccal and lingual walls (Rompen 2010). As possible, socket management performed at the time of implant insertion aims at preventing this resorption rather than aiding in regeneration, for which the blood clot is sufficient. About the Gap Fig. 13 When an implant is inserted in a socket, a horizontal gap exists between the implant body and neck and the bony walls. Since buccal gaps will not predictably and completely resolve alone, grafting materials have become increasingly popular among clinicians (Ferrus et al), and their role is to reduce the bone alteration, especially horizontally, around the implant. The latter and its cervical diameter may influence the amount of bone loss. Sanz et al (2010) have studied this impact and concluded that alterations in the buccal ridge, as well as the horizontal and vertical gaps between implants and bone walls, were greater in cases involving a smaller implant neck design. A small gap is not the solution (Araujo et al 2005), and the widest implant should not be selected, particularly with modern implant designs that offer high initial stability. A wide gap is not desirable either (Ferrus et al 2010) and will not be completely filled with bone if one relies only on the blood clot. Ideally, implants should be installed into extraction sockets in a lingual position, often partially at the expense of the lingual bone plate, and approximately 1 mm deeper than the level of the buccal alveolar crest (Caneva et al 2010, Becker et al 2008, Buser et al 2008). Therefore, a horizontal buccal gap of 1 mm to 2 mm seems clinically acceptable and should be filled with a bone substitute. Fig. 14 Fig. 15 In the anterior zone prior to any extraction and/or planning of immediate implant placement, a pretreatment risk assessment and full understanding of the patient's esthetic expectations should be conducted. The quantity and quality of hard and soft tissues must be carefully evaluated to validate this treatment option. Some deficiencies require delayed implant placement after socket management and tissue healing have occurred. Immediate implant placement and temporization is a valid, evidence-based procedure but technique sensitive and influenced by multiple parameters (anatomical, surgical, prosthetic, infection, implant and abutment design/surface/material, etc.). As this technique does not prevent some type of remodeling of hard and soft tissues, especially for thin and moderate biotypes, soft tissue grafting may also be considered at the time of surgery or later, with connective tissue or recent collagen substitutes. Clinically, in patients with a thin biotype, the extraction/implantation procedure is now a more invasive treatment if the practitioner s underlying objective is to avoid esthetic complications. Clinical and Practical Oral Implantology - Vol.1 No.3 - Fall 2010 I 11

5 Fig. 16 In immediate temporization, a definitive abutment is preferred to a temporary abutment (particularly if it is a non-biocompatible material such as a polymer), which is usually connected and disconnected several times. Its transmucosal aspect must be undercontoured and inwardly oriented (i.e., Curvy Nobel Biocare) or display a platform-switching contour. Touati et al (2005) and Rompen et al (2003 and Fig ) have shown that by augmenting and stabilizing the soft tissue through connective tissue thickening and locking tissue remodeling is reduced, improving the esthetic outcome and the natural integration of the prosthetic restoration. Canullo et al (2010) have recently shown in a randomized, controlled study that marginal bone levels were better maintained in implants restored according to the platform-switching concept. This creates a similar effect as Curvy Nobel Biocare abutments and augments the horizontal distance between the implant/abutment connection and the inflammatory infiltrate in the connective tissue. Several other parameters, while beyond the scope of this article, also impact tissue remodeling and should be always taken into account. About the Authors Bernard Touati, DDS, MS is a visiting professor at the Hadassah Faculty of Dental Medicine in Jerusalem. He is past-president of the European Academy of Esthetic Dentistry and founder/past-president of the French Society of Esthetic Dentistry. He is a member of the American Academy of Restorative Dentistry and the American Academy of Esthetic Dentistry. He is Editor-in-chief of Practical Procedures and Aesthetic Dentistry, an international lecturer and author of numerous publications. Bernard is co-academic director of the Global Institute for Dental Education. Mario Groisman, DDS, MSc is a professor of the post-graduate course in oral implantology at São Leopoldo Mandic University and has a private practice in Rio de Janeiro, Brazil. He is a specialist in Periodontology at the University of State of Rio de Janeiro, as well as a specialist in oral implantology, CFO. 12 I Clinical and Practical Oral Implantology - Vol.1 No.3 - Fall 2010