Читать книгу Management of Complications in Oral and Maxillofacial Surgery - Группа авторов - Страница 82

A thorough clinical examination prior to implant treatment planning is imperative not only to assess the implant recipient site itself, but also to evaluate the patient's current dentition and dental and gingival health, signs of parafunctional habits, malocclusion, or other factors that may impact upon implant failure. The clinician must keep in mind that while the recipient site may be optimal for implant placement and osseointegration (e.g., adequate local hard and soft tissues), if the implant cannot be restored to proper function and esthetics (e.g., inadequate interocclusal clearance), then the overall implant‐prosthetic plan may result in failure.

The concern with implant placement in a patient with a history of periodontal disease has been a topic of controversy since the introduction of dental implants. In the published studies, there exist several factors that make it difficult to compare outcomes. For example, each study may have different parameters with respect to the definition of periodontitis, the severity and treatment of periodontitis, the outcomes measures, the periodontal status at the time of implant placement, and so forth. Due to this heterogeneity in study design, it is uncertain whether a patient who experiences tooth loss due to prior or current periodontitis has a higher risk of developing peri‐implantitis or other implant osseointegration complications.

Parafunctional habits and bruxism have been implicated as factors potentially responsible for implant component fractures (e.g., implant platforms, abutment screws, and implant bodies). Although no actual causal relationship exists, the general consensus in the literature recognizes an association between implant fracture and parafunctional habits. When developing an implant treatment plan for a patient with bruxism, the clinician should plan to minimize eccentric forces, eliminate cantilevers, and consider the placement of additional implants to share the occlusal load. When considering implant fracture, two other main causes have been implicated: manufacturing error and poor prosthetic fit [5]. Although these factors may also contribute to implant fracture, they are much less frequently cited when compared with the impact of parafunctional issues. Implant fractures are preceded commonly by multiple incidents of abutment screw breakage and resultant bone loss, and may provide the clinician with an indication that there is an underlying occlusal and/or functional problem. One study [5] analyzed 4045 implants that were in function for five years, and found only eight fractured implants (0.2%). Six were supporting posterior prostheses, and, interestingly, all patients were diagnosed with parafunctional habits. Most of these patients also had preceding problems with loosening or fractured prosthetic or abutment screws prior to implant fracture.

When examining the soft tissues surrounding the areas of interest for dental implant placement, traditionally it was thought that there must be a proper amount of keratinized gingiva present for the prevention of chronic issues such as peri‐implant mucositis or peri‐implantitis, as well as for proper maintenance of the implants. Recent studies, however, indicate that the amount of keratinized gingiva may only be a matter of cosmesis, and not implant and peri‐implant health. There are no studies that show an increased loss of implants in areas of inadequate (<2 mm) keratinized mucosa. One study [6] suggested that there may be an increased risk of gingival recession and marginal bone loss in areas of deficient keratinized mucosa, but this does not necessarily cause adverse effects unless it is in the esthetic zone and with compromised esthetics. Another study [7] reported similar findings as part of a prospective five‐year follow‐up of patients who underwent edentulous reconstruction with a fixed, mandibular implant prosthesis. Plaque accumulation and bleeding on probing (BOP) on the lingual implant surfaces were greater in patients with <2 mm of keratinized mucosa surrounding the implants. Buccal soft tissue recession was also reported to be greater over a five‐year period in patients with inadequate keratinized gingiva. These studies suggest that patients with inadequate keratinized mucosa around implants may have greater challenges with routine hygiene requirements leading to subsequent periodontal issues that may or may not impact upon the overall success of the implant and prosthetic reconstruction.

Bone quality has been implicated as one of the most important factors for initial implant stability and subsequent osseointegration. However, it is difficult to evaluate bone quality preoperatively using computed tomography (CT) with calculation of Hounsfield units, and, further, this is a factor that cannot be altered prior to surgery without bone grafting and ridge augmentation if there is also a bone volume deficiency. It is widely accepted that Misch type 2 or 3 alveolar bone is the most favorable for initial osseointegration, but many times, the surgeon may be faced with type 1 or 4 bone at the time of surgery, even if the patient has a fairly normal anatomical and radiographic examination [3]. Sometimes, it is not difficult to predict based upon the patient's initial presentation; for instance, a patient with a severely atrophic mandible who has used a complete denture for many years will likely have mostly cortical (versus cancellous) bone in the anterior mandible. The surgeon must familiarize themselves with these types of patient presentations in order to make adjustments in implant choice and placement while considering the bone quality. For example, a tapered implant may be preferred over a straight implant, or vice versa, the post‐implant bone healing time may need to be extended, or a two‐stage, or delayed, implant placement, as opposed to a one‐stage procedure, may be indicated.