Endosseous dental implants and their retained prostheses have had great success over the past few decades following the landmark research and development of osseointegrated implants by Brånemark et al.15-17 Initially, most prosthetic reconstructions with osseointegrated implants were limited to use in the edentulous patient, with many reports documenting excellent long-term success of implant-retained prostheses for edentulous patients.1,2,25
Following much success with implants in edentulous patients, the original implant treatment protocols were adapted for use in partially edentulous patients. Although some transitional problems were associated with the early use of dental implants in the partially edentulous patient, successes were achieved for this population as well. Subsequently, modifications in implant design, procedural techniques, and treatment planning greatly improved implant therapy for the partially edentulous patient. Currently, the long-term success of dental implants used to replace single and multiple missing teeth in the partially edentulous patient is very good29,40,42,48,52 (see Chapter 84). Additionally, with the implementation of bone augmentation procedures, even patients with inadequate bone volume have a good opportunity to be successfully restored with implant-retained prostheses.27,34,53 Virtually any patient with an edentulous space is a candidate for endosseous implants, and studies suggest that greater than 90% to 95% success rates can be expected in healthy patients with good bone and normal healing capacity.24
The ultimate goal of dental implant therapy is to satisfy the patient’s desire to replace one or more missing teeth in an esthetic, secure, functional, and long-lasting manner. To achieve this goal, clinicians must accurately diagnose the current dentoalveolar condition, as well as the overall mental and physical well-being of the patient to determine whether implant therapy is possible or practical and perhaps most importantly, whether it is indicated for a particular patient. Local evaluation of potential jaw sites for implant placement (e.g., measuring available alveolar bone height, width, and spatial relationship) and prosthetic restorability are an essential part of determining whether an implant(s) is possible. However, determining whether the patient is a good candidate for implants is an equally important aspect of the evaluation process. This aspect of the patient evaluation includes identifying factors that might increase the risk of failure or complications, as well as determining whether the patient’s expectations are reasonable.
This chapter presents an overview of the clinical aspects of dental implant therapy, including an assessment of possible risk factors and contraindications. It also provides guidelines for the pretreatment evaluation of potential implant patients and the posttreatment evaluation of patients with implants.
The patients who seem to benefit most from dental implants are those with fully edentulous arches. These patients can be effectively restored, both esthetically and functionally, with an implant-assisted removable prosthesis or an implant-supported fixed prosthesis.
The original design for the edentulous arch was a fixed-bone–anchored bridge that used five to six implants in the anterior area of the mandible or the maxilla to support a fixed, hybrid prosthesis. The design is a denture-like complete arch of teeth attached to a substructure (metal framework), which in turn is attached to the implants with cylindrical titanium abutments (Figure 72-1). The prosthesis is fabricated without flange extensions and does not rely on any soft tissue support. It is entirely implant supported (see Figure 75-13). Usually, the prosthesis includes bilateral distal cantilevers, which extend to replace posterior teeth (back to premolars or first molars).
Another implant-supported design used to restore an edentulous arch is the ceramic-metal fixed bridge (Figure 72-2). Some patients prefer this design because the ceramic restoration emerges directly from the gingival tissues in a manner similar to the appearance of natural teeth. Depending on the volume of existing bone, the jaw relationship, the amount of lip support, and phonetics, some patients may not be able to be rehabilitated with an implant-supported fixed prosthesis.
One limitation of both hybrid and ceramometal implant-supported fixed prostheses is that they provide very little lip support and thus may not be indicated for patients who have lost significant alveolar dimension. This is often more problematic for maxillary reconstructions because lip support is more critical in the upper arch. Furthermore, for some patients, the lack of a complete seal (i.e., spaces under the framework) allows air to escape during speech, thus creating phonetic problems.
Depending on the volume of existing bone, the jaw relationship, the amount of lip support, and phonetics, some patients may not be able to be rehabilitated with an implant-supported fixed prosthesis. For these patients, a removable, complete-denture type of prosthesis is a better choice because it provides a flange extension that can be adjusted and contoured to support the lip, and there are no spaces for unwanted air escape during speech. This type of prosthesis can be retained and stabilized by two or more implants placed in the anterior region of the maxilla or mandible. Methods used to secure the denture to the implants vary from separate attachments on each individual implant to clips or other attachments that connect to a bar, which splints the implants together (Figure 72-3). Advantages and disadvantages of these attachment designs are discussed in Chapter 76.
Although the stability of the implant-retained overdenture does not compare to the rigidly attached, implant-supported fixed prosthesis, the increased retention and stability over conventional complete dentures is an important advantage for denture wearers.55 Additionally, implant-assisted and implant-supported prostheses are thought to protect alveolar bone from additional bone loss caused by long-term use of removable prostheses that are bearing directly on the alveolar ridges.
Partially edentulous patients with multiple missing teeth represent another viable treatment population for osseointegrated implants, but the remaining natural dentition (occlusal schemes, periodontal health status, spatial relationships, and esthetics) introduces additional challenges for successful rehabilitation.41 The juxtaposition of implants with natural teeth in the partially edentulous patient presents the clinician with challenges not encountered with implants in the edentulous patient. As a result of distinct differences in the biology and function of implants compared with natural teeth, clinicians must educate themselves and use a prescribed approach to the evaluation and treatment planning of implants for partially edentulous patients (see Chapter 74). In general, endosseous dental implants can support a freestanding fixed partial denture. Adjacent natural teeth are not necessary for support, but their close proximity requires special attention and planning.11 The major advantage of implant-supported restorations in partially edentulous patients is that they replace missing teeth without invasion or alteration of adjacent teeth. Preparation of natural teeth becomes unnecessary, and larger edentulous spans can be restored with implant-supported fixed bridges.49 Moreover, patients who previously did not have a fixed option, such as those with Kennedy Class I and II partially edentulous situations, can be restored with an implant-supported fixed restoration (Figure 72-4).
Early attempts to use endosseous implants to replace missing teeth in the partially edentulous patient were a challenge partly because the implants and armamentarium were designed for the edentulous patient and did not have much flexibility for adaptation and use in the partially edentulous patient. Today, clinicians have many choices in terms of implant length, diameter, and abutment connection to choose for the optimal replacement of any missing tooth, large or small (Figure 72-5).
The primary challenge with partially edentulous cases is an underestimation of the importance of treatment planning for implant-retained restorations with an adequate number of implants to withstand occlusal loads. For example, one problem that required correction was the misconception that two implants could be used to support a long-span, multiunit fixed bridge in the posterior area. Multiunit fixed restorations in the posterior jaw are more likely to experience complications or failures (mechanical or biologic) when they are inadequately supported either in terms of the number of implants, quality of bone, or strength of the implant material (see Chapter 74). The use of implants of adequate width and length and better treatment planning (more implants used to support more restorative units), particularly in areas of poor-quality bone, has solved many of these problems.
Patients with a missing single tooth (anterior or posterior) represent another type of patient who benefits greatly from the success and predictability of endosseous dental implants (see Video 72-1: Single Esthetic Implant Slide Show ). Replacement of a single missing tooth with an implant-supported crown is a much more conservative approach than preparing two adjacent teeth for the fabrication of a tooth-supported fixed partial denture. It is no longer necessary to “cut” healthy or minimally restored adjacent teeth to replace a missing tooth with a nonremovable prosthetic replacement (Figure 72-6). Reported success rates for single-tooth implants are excellent.23
Replacement of an individual missing posterior tooth with an implant-supported restoration has been successful as well. The greatest challenges to overcome with the single-tooth implant restorations were screw loosening and implant or component fracture. Because of increased potential to generate forces in the posterior area, the implants, components, and screws often failed. Both these problems have been addressed with the use of wider-diameter implants and internal fixation of components (Figure 72-7). Wide-diameter implants often have a wider platform (restorative interface) that resists tipping forces and thus reduces screw loosening. The wide-diameter implant also provides greater strength and resistance to fracture as a result of increased wall thickness (the thickness of the implant between the inner screw thread and the outer screw thread). Implants with an internal connection are inherently more resistant to screw loosening and thus have an added advantage for single-tooth applications.
Anterior single-tooth implants present some of the same challenges as the single posterior tooth supported by an implant, but they also are an esthetic concern for patients. Some cases are more esthetically challenging than others because of the nature of each individual’s smile and display of teeth. The prominence and occlusal relationship of existing teeth, the thickness and health of periodontal tissues, and the patient’s own psychologic perception of esthetics all play a role in the esthetic challenge of the case. Cases with good bone volume, bone height, and tissue thickness can be predictable in terms of achieving satisfactory esthetic results (see Figure 72-6). However, achieving esthetic results for patients with less-than-ideal tissue qualities poses difficult challenges for the restorative and surgical team.12 Replacing a single tooth with an implant-supported crown in a patient with a high smile line, compromised or thin periodontium, inadequate hard or soft tissues, and high expectations is probably one of the most difficult challenges in implant dentistry and should not be attempted by novice clinicians.
A comprehensive evaluation is indicated for any patient who is being considered for dental implant therapy. The evaluation should assess all aspects of the patient’s current health status, including a review the patient’s past medical history, medications, and medical treatments. Patients should be questioned about parafunctional habits, such as clenching or grinding teeth, as well as any substance use or abuse, including tobacco, alcohol, and drugs. The assessment should also include an evaluation of the patient’s motivations, level of understanding, compliance, and overall behavior. For most patients, this involves simply observing their demeanor and listening to their comments for an impression of their overall sensibility and coherence with other patient norms.
An intraoral and radiographic examination must be done to determine whether it is possible to place implant(s) in the desired location(s). Properly mounted diagnostic study models and intraoral clinical photographs are a useful part of the clinical examination and treatment-planning process to aid in assessment of spatial and occlusal relationships. Once the data collection is completed, the clinician will be able to determine whether implant therapy is possible, practical, and indicated for the patient.
Conducting an organized, systematic history and examination is essential to obtaining an accurate diagnosis and creating a treatment plan that is appropriate for the patient. Each treatment plan should be comprehensive and provide several treatment options for the patient, including periodontal and restorative therapies. Then, in consultation, the clinician can agree on the final treatment plan with the patient. Information gathered throughout the process will help the clinician’s decision making and determination of whether a patient is a good candidate for dental implants. A thoughtful and well-executed evaluation can also reveal deficiencies and indicate what additional surgical procedures may be necessary to accomplish the desired goals of therapy (e.g., localized ridge augmentation, sinus bone augmentation). Each part of the pretreatment evaluation is briefly discussed here.
What is the problem or concern in the patient’s own words? What is the patient’s goal of treatment, and how realistic are the patient’s expectations? The patient’s chief concern, desires for treatment, and vision of the successful outcome must be taken into consideration. The patient will measure implant success according to personal criteria. The overall comfort and function of the implant restoration are often the most important factors, but satisfaction with the appearance of the final restoration will also influence the patient’s perception of success. Furthermore, patient satisfaction may be influenced simply by the impact that the treatment has on the patient’s perceived quality of life. Patients will evaluate for themselves whether the treatment helped them to eat better, look better, or feel better about themselves.
The clinician could consider an implant(s) and the retained prosthesis a success using standard criteria of symptom-free implant function, implant stability, and lack of periimplant infection or bone loss. At the same time, however, the patient who does not like the esthetic result or does not think the condition has improved could consider the treatment a failure. Therefore it is critical to inquire, as specifically as possible, about the patient’s expectations before initiating implant therapy and to appreciate the patient’s desires and values. With this goal in mind, it is often helpful and advisable to invite patients to bring their spouses or family members to the consultation and treatment-planning visits to add an independent “trusted” observer to the discussion of treatment options. Ultimately, it is the clinician’s responsibility to determine if the patient has realistic expectations for the outcome of therapy and to educate the patient about realistic outcomes for each treatment option.
A thorough medical history is required for any patient in need of dental treatment, regardless of whether implants are part of the plan. This history should be documented in writing by the patient’s completion of a standard health history form and verbally through an interview with the treating clinician. The patient’s health history should be reviewed for any condition that might put the patient at risk for adverse reactions or complications.
Patients must be in reasonably good health to undergo surgical therapy for the placement of dental implants. Any disorder that may impair the normal wound-healing process, especially as it relates to bone metabolism, should be carefully considered as a possible risk factor or contraindication to implant therapy (see later discussion).
A thorough physical examination is warranted if any questions arise about the health status of the patient.15 Appropriate laboratory tests (e.g., coagulation tests for a patient receiving anticoagulant therapy) should be requested to evaluate further any conditions that may affect the patient’s ability to undergo the planned surgical and restorative procedures safely and effectively. If any questions remain about the patient’s health status, a medical clearance for surgery should be obtained from the patient’s treating physician.
A review of a patient’s past dental experiences can be a valuable part of the overall evaluation. Does the patient report a history of recurrent or frequent abscesses, which may indicate a susceptibility to infections or diabetes? Does the patient have many restorations? How compliant has the patient been with previous dental recommendations? What are the patient’s current oral hygiene practices?
The individual’s previous experiences with surgery and prosthetics should be discussed. If a patient reports numerous problems and difficulties with past dental care, including a history of dissatisfaction with past treatment, the patient may have similar difficulties with implant therapy. It is essential to identify past problems and to elucidate any contributing factors. The clinician must also assess the patient’s dental knowledge and understanding of the proposed treatment, as well as the patient’s attitude and motivation toward implants.
The oral examination is performed to assess the current health and condition of existing teeth, as well as to evaluate the condition of the oral hard and soft tissues. It is imperative that no pathologic conditions are present in any of the hard or soft tissues in the maxillofacial region. All oral lesions, especially infections, should be diagnosed and appropriately treated before implant therapy. Additional criteria to consider include the patient’s habits, level of oral hygiene, overall dental and periodontal health, occlusion, jaw relationship, temporomandibular joint condition, and ability to open wide.
After a thorough intraoral examination, the clinician can evaluate potential implant sites. All sites should be clinically evaluated to measure the available space in the bone for the placement of implants and in the dental space for prosthetic tooth replacement (Box 72-1). The mesial-distal and buccal-lingual dimensions of edentulous spaces can be approximated with a periodontal probe or other measuring instrument. The orientation or tilt of adjacent teeth and their roots should be noted as well. There may be enough space in the coronal area for the restoration but not enough space in the apical region for the implant if roots are directed into the area of interest (Figure 72-8). Conversely, there may be adequate space between roots, but the coronal aspects of the teeth may be too close for emergence and restoration of the implant. If either of these conditions is discovered, orthodontic tooth movement may be indicated. Ultimately, edentulous areas need to be precisely measured using diagnostic study models and imaging techniques to determine whether space is available and whether adequate bone volume exists to replace missing teeth with implants and implant restorations. Figure 72-9 diagr/>