The alternative to accepting commercial trends in dental implant therapy is to redefine basic-needs treatment of the partially and fully edentulous patient. Unfounded yet persistent assumptions about what patients want and what implant therapies can provide cloud treatment decisions. Studies on the outcomes of different implant treatment modalities are incomplete yet cite that conventional and less complex implant treatments have good outcomes, often showing better patient acceptance than the more involved alternatives.
Different from the routine dental patient, these patients requiring full mouth implant prosthodontics have unique needs requiring advocacy due to the significant quality of life issues. Patients find their situation troubling, decision making difficult, and welcome guidance. Through practicing patient advocacy, the patient experience is optimized and a mutually satisfying solution is found. The ability to successfully treat more patients with simplified yet evidence based implant treatments should not be overlooked for being cost-effective with predictable oral health outcomes.
When Northwest Dentistry created its Clinical Observations sub-department more than 20 years ago, its initial contributions were written primarily as support for lead clinical articles such as the new laser surgery that was appearing on the scene. We followed each of these articles with the invitation to readers to share their particular expertise with their colleagues, and over the years these contributions evolved along with the science and the practice of dentistry. Our most recent offering, “Insights into Occlusal Problems Through the Use of Centric Relation Procedures, Parts One and Two” by Gary L. Carlson, D.D.S., M.S.D.**, was received with great interest and discussion, and our mission was again achieved.
In this issue, it is our pleasure to present another such feature. Dr. Walter Warpeha Jr. is a prosthodontist in private practice in Minneapolis, Minnesota. He is a panel member of the Cleft Palate Clinics at the University of Minnesota School of Dentistry and Children’s Hospital/Minneapolis, and is a prosthodontic consultant to the Minnesota State Board of Dentistry. His article is done in two parts in order to separate the seldom discussed science of full-mouth dentistry from some personal insights on meeting patient needs gained from a 40-year career as a practicing and teaching prosthodontist. Part Two, “Effectively Communicating Costs and Outcomes as a Patient Advocate in Prosthodontic Treatment Planning”, will appear in the March-April 2011 issue.
My intent with this article is to review the full range of implant assisted tooth replacement modalities with a focus on patient-centered treatment planning. Part One will reflect on the validity of how practitioners currently make treatment recommendations and which treatments are supported by strong evidence in the literature.
Part Two will follow with a less formal discussion of the unique patient requiring full mouth treatment and how a disciplined patient advocacy best serves the doctor/patient relationship in obtaining a successful outcome. A case presentation approach will be offered that matches patient’s needs and desires with the most appropriate treatment recommendations.
We have arrived at a time in the profession when both patients and practitioners are struggling with how to handle the commercial influences in dentistry. In particular, as treatment planning becomes more involved in full-mouth implant dentistry, there are conflicting views about desired outcomes. At a time when minimally invasive dentistry is taught in our schools, implant dentistry curiously abandons anything near a keep-it-simple philosophy. Current implant continuing education emphasizes 3D-CT aided treatment planning and guided surgery, surgical ridge enhancements, custom CAD/CAM abutments and frameworks all aimed at a so called prosthodontic ideal; fixed ceramic maxillary and mandibular bridgework on multiple implants. These treatments may be viable yet are expensive, complex, and demanding on patient and provider while offering limited practice enhancement for most practitioners.
We all can fall prey to hype whether it is from implant suppliers, dental laboratories, or paid speakers. Through their zeal for promotion they confuse our understanding of Standard of Care, which is patient based, with the far different, procedure-centered State of the Art. Rather than solely focus on technical aspects of an oral prosthesis, a contemporary strategy should include concerns for prevention of tooth loss, evaluation of residual alveolar ridge resorption, continual evaluation of oral mucosal health, and related issues of denture function. Include in that list the compassionate management of maladaptive patients, a rationale for timely replacement of dentures, along with the continued development of dental implant therapies.1
Recognizing Professional Bias
In making treatment recommendations, most would agree it is our obligation to consider the best available science to come up with effective and efficient treatments. Yet the 2009 report Initial National Priorities for Comparative Effectiveness Research finds more than half of the medical treatments delivered today are without clear evidence of effectiveness.2 I contend that dental treatments in general may not be as well studied. I am fearful that the current knowledge base appears to be ignored or misinterpreted in implant treatment planning.
From 1995 through 2005 there have been more than 5,000 articles in refereed publications on implant dentistry. Most studies used implant survival as the success criteria, not patient satisfaction or cost effectiveness. No systematic reviews or consensus statements compared the outcomes of the different implant modalities. Among studies that address the subject, only a few provide the validity of a Randomized Clinical Trials (RCT.)
Without accepted parameters to give clear direction, health providers fall back on commonly held assumptions to guide treatment regimens. These assumptions, left unchallenged, become a substitute for reviewed scientific evidence. The danger in basing treatment planning on these taken-for-granted perceptions is that an unconscious bias may be unavoidable. That is, in the absence of a credible evidence base, one’s frame of reference is narrowed, and the influence of a personal self-interest is likely.3
Consider the example of Extension for Prevention as was taught in every U.S. dental school. Well-meaning dentists embraced the assumption that restorative margins must be placed on “self-cleaning” areas of the tooth. Teeth were routinely over-prepared for most of the twentieth century, making them susceptible to further breakdown or fracture. In challenging the assumption in the mid-century, Dr. Miles Markley found that it was an uphill battle to change dogma.4 It took 50 more years for dentistry to officially abandon the concept!5
A pioneer in North American implantology, Dr. George Zarb, observes in a Journal of Prosthodontics editorial, “The integrity of purpose and scientific rigor that characterized the original osseo-integration clinical research has been largely discarded as passé.”6 I believe I can demonstrate how non-scientific assumptions about dental implant treatment are held and repeated by dentists to their patients. Also, a careful reading of the literature can separate out the facts from hypotheses.
A review of the recent prosthodontic literature may not supply definitive answers on best practices yet may offer guidance on common perceptions and their validity. Older implant literature, where external hex implants, telescoped abutments, O-ring, or metal clip or ball attachments were commonly used, has questionable relevance when compared to modern hardware. Recognizing that prosthodontic implant maintenance or failure is primarily biomechanical,7 under-engineered parts could very likely skew those early conclusions.
For illustration, consider several references in a well respected implant text’s latest edition.8a,8b When discussing potential screw loosening, the author cites a 1996 study reporting 48% of single tooth molar implant crowns had loose screws within three years.9 This older study used undersized external hex implants and interlocking or UCLA abutments that would no longer be used for this purpose. The inference that splinting implants is beneficial in preventing mechanical complications conflicts with a newer systematic review that finds that screw loosening of a non-splinted abutment is a rare occurrence provided that proper anti-rotational features and torque are employed.10
The same text comes to the weakly supported conclusion that implant bridgework requires significantly less maintenance based on a literature review of overdenture complications 1981-2001 representing a great number of studies using obsolete, 20-year-old attachment systems.7
To avoid those troublesome comparisons, I limited my search in PubMed for articles published in years 2004 though 2010. I added the American Dental Association’s systematic review list, Consensus articles, and pertinent books. Additionally, those articles with more reliable evidence designs as well as the contemporary implant texts were hand searched for reference articles of any age directly supporting their conclusions.
Perceptions versus Evidence
My search did not provide an evidence base for these common assumptions or misconceptions:
1. Implants are a good replacement for natural teeth. Studies do not show implants having greater survival rates than natural teeth.11,12 A more true statement is that dental implants are a viable alternative to edentulism.
2. My dentist told me I don’t have a good mouth for wearing dentures. A number of studies conclude that clinical assessment of the denture-supporting tissue areas is a poor indicator of potential denture satisfaction.13,14 There may be other good reasons for recommending the use of dental implants, but unfavorable anatomy or dissatisfaction with a worn or defective denture need not be the primary indication.
3. Implants are expensive! One or two implants can add great value by making an unwearable removable partial denture (RPD) or complete denture (CD) become functional.15 The cost effectiveness increases with each year of health maintenance.16
4. Implants versus dentures? This is the wrong question. Implants can be used extremely effectively with natural teeth either as bridgework or overlay RPDs.17,18
5. Patients only want “permanent” teeth. Most reviews find that the vast majority of patients are well satisfied with their existing maxillary CD.19,20 Conversely, a survey of new denture wearers reported 66% were dissatisfied with their mandibular CD.21 Even so, the less costly removable option of an implant overdenture (IOD) in the lower mouth addresses most problems of the CD while providing a highly satisfying appliance.22
6. Splinted implants are a treatment upgrade over implant snaps. Bar and clip systems have four negatives: They are higher in cost, space intensive, difficult to clean, and require greater maintenance compared to modern snaps. A ten-year RCT investigation found a two-implant mandibular overdenture population had an excellent prognosis irrespective of whether splinted or not.23
When 95 patients were surveyed after rehabilitation with 107 IODs, they expressed a high level of overall satisfaction independent of number of implants per overdenture, whether splinted or non-splinted, and type of attachment.24 In addition, a literature review shows an increased risk of instability of an upper CD when opposed by a mandibular bar-supported IOD.25
7. Use of implants makes prosthodontic principles unimportant. Violating basic prosthodontic precepts such as proper occlusion, vertical dimension, neutral zone, and base extension will negatively impact the appearance, function, and longevity of an implant prosthesis, the supporting structures, or the implants themselves.26
A New York Times article on health care relates that Americans mistakenly believe that more medical treatment is better medical treatment.27 A similar misconception by dentists about prosthodontic dentistry is that there are a number of ways (differentiated only by fee) to get the same result. While it is true that there are several ways or procedures to replace missing teeth, in my experience there is only one way to attain a specific result that perfectly matches the individual patient’s needs and ability. I found no evidence other than opinion that the most costly, the most technically challenging, or using unproven treatment protocols is the best way to obtain a successful outcome. So the very complexities celebrated as State of the Art, likely to be seen as negatives by patients, raise the stakes that things can go wrong or that patient tolerance will be exceeded.
Rationale for Implants in Prosthodontic Treatment Planning
When teeth are lost, denture wearers experience both soft tissue and bone loss usually ongoing and detrimental to appearance and function. Hence, in many cases inadequate full dentures are only a matter of time. While the changes often stabilize in the maxilla, the effect is greater in the mandible, where continuing bone loss is seen cephalometrically for 20 years.28 By using osseointegrated dental implants, tissue changes in the edentulous maxilla or mandible can be reduced29 or bone can be actually stimulated.30 Moreover, even with only minimal implant support, all aspects of mandibular denture performance were enhanced in a multi-center ten-year study.31
In his third edition text, noted authority Dr. Carl Misch is a clear advocate of multiple implants for bone preservation. By using his concept of biomechanical sections of the jaws, implant placement in key arch positions are required to absorb the forces that would otherwise contribute to bone loss. Although Misch shows repeatedly examples of many implants per arch, he states the minimum for this purpose is three implants in the mandible and five in the maxilla.8c
How is the practitioner to help the patient decide among conventional prosthodontics, implant assisted removable, implant supported removable, or fixed implant prosthodontics? I think my review of the literature offers some indication of unique benefits of each modality that can be useful in attaining a particular outcome.
For example, in the more critical lower mouth, a systematic review demonstrates no single standard of care for the edentulous mandible as defined by a specific treatment modality.32 Two implants with snap retention, an implant retained denture, has been shown both in a consensus report and a systematic review to provide a high level of patient satisfaction when ridges are sufficient to add support.22,33 Other studies show that more posterior bone resorption occurs using that regiment shortly after extractions,30 and with healed ridges still more annual bone loss than with an implant supported prosthesis.34 Full implant support may be accomplished in some cases with conservative placement of three or four implants under an IOD or use four or five with the original Branemark protocol to support implant bridgework.35 Data concerning upper denture instability when opposed by a mandibular IOD is contradictory, though evidence suggests some increase in fracture and frequency of reline.30 Removable partial dentures with tooth and implant support are under-utilized; they are cost effective, retain the benefits of a periodontal ligament, minimize treatment time, and the functional loading of an implant fixture reduces tissue forces in distal extension areas.18,36,37 An implant supported partial (ISRPD) can be delivered shortly after implant placement with the snap overdenture housing left empty until the implant is ready to be loaded. Another major benefit of supplementing some treatable, even mobile, mandibular teeth with one or more dental implants is that they can actually improve the prognosis of the adjacent teeth.38
Dr.Misch states that while not a contraindication, bruxism “dramatically influence(s) treatment planning”. He notes the ability to remove an opposing full denture eliminates the possibility of night parafunction.8d,8e The stress relief inherent in an ISRPD or IOD is perhaps the safest method to control excess forces where bruxism/clenching were likely a factor in the preceding tooth loss.39
Misch recognizes using dental implants to aid the more difficult mandibular prosthesis in combination with a conventional maxillary denture is a common treatment. In spite of much slower bone loss associated with a maxillary CD, he recommends implant support because many patients are unaware that they abuse their oral tissue by not relining or replacing dentures at five-year intervals or by removing them at night. Still a study by McGill University showed patients generally did not prefer a maxillary IOD over their CD.40 Reasons that some patients may readily choose the fixed alternative of a maxillary implant bridge (IB) or an implant hybrid bridge (IHB) often could be tied to self image rather than superior performance or appearance.8f,8g,8h
Despite the prominent exposure in non-subscription dental magazines and at implant continuing education of low evidence “case studies”, more reliable studies do not show maxillary fixed IB or IHB appliances to be superior to the less costly CD or IOD.41,42 In a systematic review comparing tooth-borne fixed partial denture to IB, the incidence of technical complications was significantly higher for the implant-supported reconstructions.43 Problems with lip support, speech, esthetics, and breakage make a maxillary fixed prosthesis a demanding restoration.44,45
In nicely designed “within-patient” comparisons, the McGill group showed a fairly even split when allowing patients to choose between a maxillary IHB and an IOD.41 The findings were similar in mandibular “within-patient” comparisons where younger, less experienced CD patients preferred the fixed option, while older, more experienced denture wearers appreciated the ease of cleaning a denture they can take out.46 Even so, posterior bone loss occurs at a rate higher with the maxillary IB or IHB than the maxillary IOD.47
Outcomes using newer low profile retention systems such as Locator* have not as yet been well studied, but the wide acceptance of these improved snaps may make connector bars a less desirable alternative for all IODs.48 The palateless maxillary IOD can be held by four or more unsplinted snaps unless divergent implants require a bar.49 A systematic review of IODs demonstrated that scientific evidence shows a lower rate of implant survival and a higher frequency of prosthetic complications for maxillary implant-retained or implant-supported overdentures.50
Unchallenged conventional wisdom may have a greater influence on treatment decision making in implant prosthodontics than is generally thought. Though the evidence for best practices in implant prosthodontics is far from complete, studies are consistent in that many of the simpler, less involved treatments using implants with or without natural teeth have predictable outcomes. These treatments are more easily integrated into a general dental practice allowing more dentists to treat and more patients to be treated. Simplified yet evidence based prosthodontic implant treatments should not be overlooked as viable treatment options.
* Zest Anchors LLC, Escondido, CA
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47. Jacobs R, Schotte A, van Steenberghe D, Quirrynen M, Naert I. Posterior jaw bone resorption in osseointegrated implant supported overdentures. Clin Oral Impl Res 3,2;Jun 1992:63-70.
48. Chikunov, I., Doan, P. and Vahidi, F. Implant-retained partial overdenture with resilient attachments. J Prosth 17;2008:141–148.
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*Dr. Warpeha is a board certified prosthodontist in private practice in Minneapolis, Minnesota. He is a panel member of the Cleft Palate Clinics at the University of Minnesota School of Dentistry and Children’s Hospital/Minneapolis, and is a prosthodontic consultant to the Minnesota State Board of Dentistry. Email address is firstname.lastname@example.org.
**“Insight into Occlusal Problems Through the Use of Centric Relation Procedures”, by Gary L. Carlson, D.D.S., M.S.D. Part One: January-February 2007, pages 12-24. Part Two: March-April 2007, pages 31-43.