Written by Michael Z. Marder, DDS Saturday, 30 April 2005 19:00
With the introduction of endosseous implants by Brnemark in 1969,1 dental patients have the opportunity to replace missing teeth, or even an entire dentition, with a fully functional, fixed, and aesthetic alternative to a removable prosthesis. For the edentulous patient or for patients missing many teeth, these restorations can dramatically improve the quality of life. Osseointegrated implants are predictable2 with a high long-term success rate of 78% to 100%.3 Implants are not subjected to the ravages of dental caries,4 and the list of medical contraindications and limitations to their use is steadily declining.5
The fact that supporting alveolar jawbone will continue to resorb in the absence of teeth6 is obvious to any dentist who constructs removable prostheses. The placement of implants and restoration of dental function will stimulate load-related bone formation and minimize this loss.6,7 The development of bone augmentation techniques such as bone grafts from the same person (autogenous), a different member of the same species (allogeneic), a different species (xenogeneic), or synthetic materials (alloplastic); orthodontic techniques such as forced eruption; and orthopedic techniques such as alveolar distraction osteogenesis have also served to facilitate a "natural" and therefore aesthetic placement of implants. Indeed, the transplantation of autogenous (non-jaw) bone segments (free-flap fibula grafts with implants previously placed)8 to replace surgically resected jawbone in cancer patients is an example of how innovative and versatile osseointegrated implant therapy has become.
The infectious nature of the periodontal diseases was recognized about 50 years ago.9 Subsequently, the individuals host response to the infection was realized to be influenced by genetic, environmental, and acquired disease modifiers10 that could respond to and in certain cases be minimized by surgical, nonsurgical, and preventive techniques. This realization put an end to the resignation that many adults would inevitably become partially or totally edentulous. Further, long-term studies of patients receiving conventional periodontal treatment have demonstrated impressive success in the ability to retain the natural dentition.11-15 Patients are now keeping their teeth for longer periods of time.16 With improvements in our identification of systemic diseases and new and improved medical treatment, the average life span is also increasing.
Nevertheless, periodontal disease increases with age, and tooth loss, while reduced, will not be eliminated. Replacement of lost teeth now becomes the focus in the development of a treatment plan for patients. Despite the success of periodontal therapy, dental implants have become an alternative to the lengthy and often complex treatment regimens that may be necessary to save compromised teeth. The determination that advanced periodontal disease was not a contraindication to dental implants17-19 was an important finding. Additionally, while extensive bone loss might require bone-grafting procedures prior to implant placement, removable prostheses do not have to be the only treatment option. Indeed, newer approaches to establishing an improved osseous environment include guided bone regeneration20 for local bone defects, alveolar distraction osteogenesis21 for movement of larger bone segments, and microsurgical bone flaps22 for jaw reconstruction.
Given the success of both periodontal therapy and dental implants, a most important consideration is when to say when, or knowing at what point we extract a tooth or teeth and place implants to support a fixed prosthesis. This is opposed to continuous and possibly extensive periodontal therapy that may not limit the progression of disease but allows the retention of the natural teeth. The answer is neither simple nor consistent. It depends on many factors, not the least of which are the patients desires and expectations; in reality, a dilemma may be anticipated. Furthermore, there are important differences among a totally edentulous jaw, a partially edentulous jaw, and a single-tooth replacement that affect treatment outcomes. These include the nature of the oral microflora; quantity, quality, and location of bone; and implant stress distribution.23
The discussion of treatment planning for dental implants in this 2-part article will be divided into total edentulism (Part 1) and partial edentulism (Part 2). Additional, related topics that include implant biomechanics, implant biomaterials, surface coatings, fixture length, and prosthetic design are beyond the scope of these reviews.
For the subject of total edentulism, 5 parameters will be considered: (1) medically related factors, (2) periodontal/dental prognosis, (3) financial considerations, (4) patient motivation, and (5) aesthetic desires. Finally, a decision tree will be presented to summarize options for the dental practitioner based on the above parameters. However, ideal treatment planning should be proactive rather than responsive to assure the health of our patients.
MEDICALLY RELATED FACTORS
Table 1. Specific Medical Contraindications to Dental (Implant) Surgery.*Recent myocardial infarction (7 to 30 days)
Unstable angina pectoris
Decompensated congestive heart failure
Severe valvular disease or recent cardiovascular surgery
Uncontrolled pulmonary disease
Uncontrolled kidney disease
Uncontrolled liver disease
Uncontrolled endocrine disease
Osteogenesis imperfecta (severe form)
Generalized hypovascularized bone osteoradionecrosis
Pagets disease of bone
biphosphonates (Aredia, Zometa)
homozygosity for hereditary diseases
coagulopathies (deficiencies of clotting factors)
anemias (sickle cell, α and β thalassemia)
*It must be understood that this list is not all-inclusive and represents the more commonly occurring diseases and conditions. In addition, physician approval is required for all medically compromised patients.
Systemic diseases and destructive habits may play an important role in the decision to retain teeth or construct a removable prosthesis versus implant placement. In general, it is prudent to perform only emergency dental treatment for patients with active, uncontrolled systemic diseases that include certain cardiovascular, respiratory, endocrine, kidney, hepatic, and malignant disorders, or those who are currently receiving active radiation therapy or chemotherapy5 (Table 1). It is also wise for the practitioner to consider that dental treatment in a medically compromised patient should never be undertaken without physician approval. Further, undertaking dental surgery without consent singularly exposes the dentist to legal repercussions in the event of an untoward reaction.
Patients rarely remain in an acute, compromised medical condition indefinitely. There-fore, the dentist should employ patience and common sense until a window of op-portunity opens for treatment. Examples would include uncontrolled diabetes, stage 3 hypertension (systolic BP > 180 mm Hg diastolic BP > 110 mm Hg),24 and cancer chemotherapy. Treatment options continue to improve so that delays due to medical conditions that were previously considered absolute contraindications to dental surgery (ie, active ischemic heart disease)25 might change significantly over time.5 A pertinent example is the guideline requiring a 6-month delay in dental treatment for cardiac stabilization following myocardial infarction. Recent studies suggest that such a patient might be allowed to undergo dental surgery 6 weeks following the event if established protocols are followed.26
In the past, certain mucous membrane diseases that cause erosive or ulcerative lesions or tissue atrophy, such as lichen planus, have been considered a contraindication for implant therapy.27 However, reports exist to the contrary.28 In reality, implant-supported fixed prostheses provide far superior comfort and function than tissue-bearing prostheses. Pemphigus vulgaris and benign mu-cous membrane pemphigoid also do not pose contraindications to implant therapy. Likewise, patients with HIV infection and multiple myeloma have been treated successfully with implants.5
Osteoporosis is considered a risk factor for periodontal disease29,30 but not necessarily for dental implants.5 Diabetes is well-established as a major modifier of periodontal health31 but is not necessarily a risk factor for dental implants.5 Smoking is also a modifier of periodontal health32 but is not a contraindication for the placement of implants,5 especially if a specific protocol is followed.33 Loss of salivary function (Sjogrens disease, radiation therapy, many medications) will increase plaque formation, caries, and fungal overgrowth and cause atrophy of gingival and mucosal tissues.5 If salivary function cannot be restored with salivary stimulating agents such as pilocarpine hydrochloride (Salagen) or cevemeline hydrochloride (Evoxac), then rampant decay of natural teeth may occur, resulting in the need for multiple extractions. In this situation, implant-supported prostheses are a superior alternative to tissue-borne denture prostheses that may not be tolerated by the patient due to the thin, friable, and easily ulcerated mucosa.
Head and neck cancer treatments such as radiation will often require pretreatment extraction of periodontally and endodontically involved teeth to prevent osteoradionecrosis. However, the subsequent placement of dental implants in irradiated persons is not contraindicated.34,35 Indeed, the restoration of function with dental implants after jaw resection and subsequent replacement with vascularized bone flaps36 may provide an important contribution to the patients quality of life. Additionally, the placement and survival of dental implants in cancer patients treated with chemotherapy is possible if proper timing is considered.37,38 Of note, however, is the recent finding that cancer patients treated with the nitrogen-containing biphosphonates pamidronate (Aredia) and zoledronate (Zometa) are at risk for trauma-induced avascular nec-rosis39 and should not be treated with any form of dental surgery.
Recent evidence linking periodontal disease to cardiovascular and cerebrovascular diseases40-43 may also have a future impact on the choice of tooth retention versus implants. This relationship has resulted in a dialogue to determine if there is an indication to remove compromised teeth in order to prevent certain types of macrovascular disease. It is also documented that normal lifestyle functions such as chewing,44 tooth brushing, and flossing45 produce bacteremias that may promote metastatic infections in certain parts of the body. Chewing has been shown to cause the rupture of capillary ends, thereby providing the route of entrance into the bloodstream. While no studies exist to date, it is reasonable to speculate that an osseointegrated implant, which is in essence ankylosed to bone, theoretically does not allow such vascular trauma and therefore would not be likely to promote a bacteremia under functional loading. This might affect the decision to utilize dental implants in persons at risk for infective endocarditis. It has already been demonstrated that extraction of advanced periodontally involved teeth decreases serum C-reactive protein (CRP), a marker of systemic inflammation. When the teeth are replaced with implants, CRP did not increase over the 12-month postoperative period.46 In addition, the peri-implant microbiota in edentulous persons with a prior history of periodontitis becomes comparable to that seen in a patient with a healthy periodontium or gingivitis, which may justify the elimination of such involved teeth.47
Age, per se, is not a contraindication to dental implants.48,49 Disabilities that prevent proper, self-administered oral hygiene include paralysis and neuromuscular wasting diseases such as stroke, arthritis, multiple sclerosis, and Parkinsons disease. All may require caregiver assistance for oral hygienic maintenance. Fortunately, as noted, implants will fare better than teeth under these circumstances
In summary, while there are still some medical contraindications for dental implant treatment, their numbers are decreasing with advanced knowledge and treatment of diseases. However, physician cooperation and/or permission for dental treatment of the medically compromised patient is essential for the well-being of the patient.
|Figures 1a and 1b. Patient presents in 1968 with radiographic evidence of advanced periodontal disease with tooth mobility and caries.|
|Figures 2a and 2b. Complete maxillary and mandibular prosthetic rehabilitation 2 years later.|
|Figures 3a and 3b. Radiographs taken in 1981 demonstrating further periodontal bone and tooth loss despite regular maintenance. It is decided to remove the remaining maxillary teeth, place 6 implants, and construct a hybrid fixed partial denture.|
|Figure 4. Plastic abutments in maxillary implants. The splayed angulation of the abutments are the result of periodontal bone loss.||Figure 5. Gold cast abutments after waxing, realigned for parallelism (with preformed internal screw receptacles) and cemented into fixtures.|
|Figures 6 and 7. Two views of hybrid prosthesis on working lab model.|
|Figure 8. Clinical presentation of completed maxillary restoration. The patient expired 20 years later with intact maxillary restoration.|
|Figures 9a and 9b. Patient presents with radiographic evidence of advanced periodontal disease and tooth mobility. Implants are suggested, and the patient is cooperative. However, bone support is considered unfavorable, and complete maxillary splinting is performed.|
|Figures 10a and 10b. Patient presents 6 years later with continued loss of periodontal bone. Patient refused complete dentures, accepted implants, and also wanted to retain as many teeth as possible in the event of implant restoration failure.|
|Figures 11 and 12. Maxillary and mandibular implant-supported fixed restorations.|
|Figure 13. Pantographic radiograph taken 9 years later. Clinically there was no evidence of gingival inflammation, mobility, or intrusion of retained teeth. The natural teeth were fitted with gold copings and cemented. The superstructure is not luted. All restorations are screw-retained.|
A most important factor in the decision of whether to conserve teeth or place implants is the status of the patients periodontium. Gingivitis can be successfully treated in a cooperative patient, and while some suggest that poor oral hygiene is detrimental to implant success, a direct correlation between poor oral hygiene and marginal bone loss as a result of peri-implantitis has not been established except when smoking and/or traumatic occlusion are present.5 The dentate patient with vertical bone loss may respond to regenerative periodontal therapy. Nevertheless, there are no regenerative techniques to date for horizontal bone loss, which is considered irreversible.50 Factors to consider in the presence of horizontal bone loss include total amount of loss, tooth mobility, evidence of recent, rapid loss (despite therapy), and patient cooperation with home care. In the presence of 50% or more bone and attachment loss, tooth mobility, and inadequate plaque control (all other factors being considered acceptable), extraction is preferred to prevent further bone loss and compromise of implant support. In fact, extraction of teeth will also remove the putative pathogenic bacteria and mitigate the risk of peri-implantitis.3 Where conventional periodontal therapy has resulted in remission of periodontal disease only to have poor patient compliance result in further disease progression, serious consideration must also be given to extraction. Two clinical cases of prolonged periodontal therapy, prosthetic reconstruction, and finally, long-term, successful implant-supported prostheses are presented in Figures 1 to 13.
Prognostic indicators of peri-odontal disease outcomes may hold promise for future identification of persons at risk for loss of supporting alveolar bone. The presence of possible genetic markers in patients susceptible to aggressive periodontitis, such as the composite interleuken-1 genotype (a marker for periodontal deterioration in an affected population), may eventually become a valuable tool for treatment planning.50-54 Identification of the presence of infecting microorganisms may also be part of a risk profile for patients with periodontitis.3 In addition, a computer-based risk assessment tool, the Periodontal Risk Calculator (PRC),55 has recently been developed to identify the risk for future periodontal disease activity. Over time, the use of the PRC may improve clinical decision making, thereby reducing the need for complex periodontal procedures and ultimately improving outcomes.56
In summary, the development of prognostic indicators for periodontal disease will allow the dentist to provide alternative treatment strategies for patients. Since the primary purpose of periodontal therapy is to preserve alveolar bone for tooth, prosthesis, or implant support, the effectiveness of a particular treatment plan can be determined sooner rather than later. This will minimize tissue loss and adverse medical health effects and preserve maximal oral function far longer for the periodontally compromised individual.
|Table 2a. Retention Versus Extraction, Cost Comparison.
Clinical case example: A 50-year-old person with an essentially negative medical history presents to a dentist with 12 maxillary teeth (Nos. 3 to 14) opposing the same number of mandibular teeth (Nos. 19 to 30). We will consider the maxillary situation only. There has been 40% to 50% periodontal bone loss around 6 to 9 teeth with some angular bone loss and mobility of these teeth from 1+ to 1.5+. Below are the 2 treatment options offered. Fees quoted here were obtained from ADA 2003 Survey of Dental Fees (except where indicated) for general practitioners only, middle Atlantic region, and are rounded off to the nearest dollar.
Option A. Retention of all (maxillary) teeth, periodontal surgical procedures, splinting of teeth.
Option B. Removal of all teeth, construction of an immediate complete removable, denture placement of 6 implants, construction of an implant-supported hybrid prosthesis.
|* These fees were obtained from sources other than the ADA 2003 Survey of Dental Fees and extrapolated.|
The initial cost differential for surgical periodontal treatment plus concomitant extensive prosthodontic treatment versus extractions, implants, and prosthetic rehabilitation is about 20% less for the former treatment plan (Table 2a). When factoring in intensive periodontal maintenance for attempting to save the teeth, which is necessary 4 times per year, the cost equalizes in slightly more than 3 years. The prime considerations then become aesthetics and the prognosis of the teeth. Of course, if neither option is affordable, then the issue is moot, and the only consideration is patient comfort before extractions are performed and complete dentures are constructed. Table 2a is a comparison of the costs for the above treatment options based on the ADA 2003 Survey of Dental Fees.57
It must also be realized that additional dental therapies may have to be considered if the dentition is to be retained. Endodontic treatment, post and core restoration, and root resection may also be required. For maxillary implants, sinus lift procedures, bone and tissue grafting, or alveolar distraction osteogenesis21 may be necessary.
|Table 2b. Cost Comparison Between Complete Denture and Implant-Retained Overdenture.
Option C. Extraction of all teeth (in a jaw) and replacement with a