Natural teeth or implants? Informing the decision-making process

Drs. George Pelekos and Nikos Mardas offer some considerations for all implant dentists to address when making their treatment choices

Teeth constitute an important part of the human body that are responsible for many different functions like mastication and phonetics, while also important for maintaining acceptable facial cosmetics. Tooth loss is thus a devastating life event with significant psychological side effects for the patient, meaning that tooth extractions should be considered as a last resort treatment (John, et al., 2007).

The dental community has traditionally focused its efforts in the management of periodontal, pulpal, traumatic, or carious pathologies (Avila, et al., 2009) in order to preserve — and when necessary, rehabilitate — natural teeth. When conservative restorative approaches for the treatment of all these pathologies fail, and tooth extraction is unavoidable, prosthodontic replacement of teeth should be considered to restore lost function and esthetics. In the case of single tooth loss or partial edentulism, fixed partial dentures (FPD) appeared to be a promising prosthodontic treatment modality.

A low incidence of complications and high survival rate of conventional bridgework have been reported in the literature for the first 5 years of function over up to a 20-year period (Svanborg, et al., 2013). Other alternatives, especially in cases of multiple missing teeth, are removable partial dentures (RPD) that can also improve appearance, mastication, prevent undesirable tooth movement, and improve occlusal load (Davenport, et al., 2000; Shugars, et al., 1998). However, the survival of periodontally compromised teeth is negatively associated with the use of RPDs when compared with no treatment or the use of an FPD (Aquillino, et al., 2001; Yamazaki, et al., 2013).

Complete dentures that rely on the volume of the residual alveolar ridge and mucosa for retention have been used for years as the standard prosthetic solution in case of full edentulism, with high level of patient satisfaction especially in the upper jaw (Larking, et al., 2004).

However, a lot of patients are not satisfied with lower complete dentures because of their poor retention, increased denture mobility, and compromised chewing function (Feine, et al., 2002). Historically, the development of osseointegrated implants (Brånemark, et al., 1977; Schroeder, et al., 1981) came as a response to this problem; therefore, the first dental implants were used to increase the retention of dentures in lower jaw.

Today, implant-supported restorations are often considered the treatment of choice in most of the cases of partial or full edentulism (Salvi, et al., 2001). The wide acceptance of implant dentistry changed the paradigm in everyday clinical practice where treatment for retention of natural teeth is often challenged by “new trends in implant industry.”

There is a strong impression among clinicians that teeth extraction and their substitution with dental implants is superior to their preservation with other conservative treatments in terms of survival and complications rates (Donos, et al., 2012), although such an impression is not necessarily always based on scientific evidence.

When clinicians face the dilemma of whether to retain/restore a compromised tooth or replace it with an implant, their personal experience, access to technology, postgraduate education in combination with local factors (periodontal, endodontic, restorative) together with patient-related parameters should guide the final decision (Tepper, et al., 2003; Kao, et al., 2006; Donos, et al., 2012). Clinical decisions should also be based on the best available evidence regarding the predictability and effectiveness of each the suggested treatment protocols. Systematic reviews (Egger and Smith, 1997), where the majority of the studies assessed are randomized controlled clinical trials (RCTs) present usually the highest level of evidence (Glasziou, et al., 2004). However, for several clinical scenarios, an evidence-based decision-making process may not always be possible since in prosthetic dentistry there are hardly any RCTs addressing whether an implant-supported restoration is superior to a tooth-supported restoration (Pjetursson, et al., 2007).

In such a case, dentists involved in implant dentistry should take into consideration well-documented evidence from other disciplines like periodontics (Lundgren, et al., 2008) or endodontics (Iqbal, et al., 2008) regarding the longevity and complication rate of periodontally and endodontically affected teeth following treatment.

The following questions quite often need to be addressed during treatment planning:

Endodontic treatment versus implants
Root canal treatment is most often a treatment of necessity to alleviate symptomatic pathology and reduce the risk for tooth loss.

Successfully treated endodontically involved teeth present high survival rates (up to 97%) (Salehrabi, et al., 2004; Imura, et al., 2007) that are comparable to those for a single crown implant restoration (Noack, et al., 1999; Jung, et al., 2012). When comparing these two treatment modalities, the clinician should be able to estimate both the endodontic and the restorative prognosis of a tooth (John, et al., 2009).

Clinical factors, such as the presence/size of a periapical lesion or the necessity of repetition of an older failing root canal treatment have been negatively related with prognosis of those teeth (Stoll, et al., 2005). Furthermore, the experience of the operator seems crucial since specialists in endodontics were reported to have higher success (up to 98% in a 5-year period) than general practitioners (Alley, et al., 2004).

Although there is lack of RCTs directly comparing the two treatment principles (Friedman, et al., 2002; Eckert, et al., 2005), endodontically treated teeth as well as dental implants are valuable treatment options that should be equally considered, in a cost benefit analysis, before any clinical decision making for tooth extraction.

Natural teeth versus implants as abutments for fixed partial dentures
A direct comparison between teeth and implants as abutments for fixed partial dentures (FPDs) is currently very difficult because most of the available clinical studies are retrospective cohort studies without stringent inclusion criteria, characterized by high levels of heterogeneity and bias. Nevertheless, a series of systematic reviews (Pjetursson, et al., 2004; Tan, et al., 2004) reported 10-year survival rates of 85% to 95% for conventional tooth-supported FPDs. In another systematic review (Pjetursson, et al., 2007) comparing tooth and implant-supported FPDs by the use of meta-analysis, the survival rate was 89.2% and 86.7%, respectively, for tooth and implant-supported prostheses, indicating equal long-term outcomes for teeth and implants as abutments for FPDs. Similar survival rates (up to 90% over 10 years) were reported from studies where teeth with reduced but healthy periodontal tissues were used as abutments in cross arch bridges (Laurell, et al., 1991; Lulic, et al., 2007).

Despite the limitations of these studies, it can be concluded that periodontally healthy teeth present high survival rates that are comparable to those of dental implants (Tomassi, et al., 2008) and can serve as reliable abutments for FPDs. It should be mentioned, however, that most of the implant data in these systematic reviews was related to implant systems and surfaces that are not extensively used anymore.

Treatment of periodontal disease versus dental implants
Current clinical evidence has positioned implants as one of the first choices of treatment for partially or fully edentulous patients and has influenced the decision to extract periodontally affected teeth, which in a number of cases may be treatable (Greenstein, et al., 2007).

It has been suggested that “pro-active” or “strategic extractions” will prevent further bone destruction in a potential future implant site (Kao, et al., 2008). However, this approach is not supported by the current evidence considering that, otherwise, tooth extraction will result in resorption of alveolar bone that cannot be completely controlled even with alveolar ridge preservation techniques (Mardas, et al., 2010) or immediate implant placement (Sanz, et al., 2010).

The concept of early extraction of periodontally involved teeth and their replacement with dental implants is therefore of questionable value since is not supported by evidence (Donos, et al., 2012) but rather on “clinicians’ belief” that implants are better than teeth in terms of the following:

Survival rates of teeth following treatment of periodontal disease
Severe periodontal disease has an overall prevalence of approximately 10% in the industrial countries (Hugoson, et al., 2008).

Poor plaque control and smoking are well-established risk factors for developing periodontitis (Lee, et al., 2010). Similarly, residual pocketing is a significant risk factor for periodontal disease progression and tooth loss even after periodontal treatment (Matuliene, et al., 2008).

On the other hand, long-term, follow-up studies have demonstrated that treatment of periodontal disease could successfully arrest disease progression and minimize further tooth loss, according to Tonetti and colleagues (2000).

Long-term prognosis of implant-supported restorations in comparison to teeth-supported restorations
Management of patients with advanced periodontal disease, which includes extraction and replacement of teeth with a hopeless prognosis, will be followed with a restorative phase usually involving tooth-supported or implant-supported FPDs or alternatively removable partial dentures RPDs. As mentioned previously, long-term follow-up studies have confirmed comparable survival rates of teeth and implants as abutments for FPDs in patients with advanced periodontal breakdown.

Better cost-benefit ratio
Implant-supported prostheses are more expensive than other prosthodontic alternatives (Lewis, et al., 1998), the maintenance of periodontally involved teeth (Pretzl, et al., 2009), or efforts to save endodontically compromised teeth (Iqbal, et al., 2008). Therefore, their overall economic effectiveness has yet to be proven, considering that implants are inaccessible economically to a significant number of patients who would need them (Zimmer, et al., 1992).

Esthetic result
Quite often, periodontally compromised teeth present esthetic considerations for both the patient and the clinician due to gingival recession resulting in a clinical crown elongation, the loss of interdental papillae, and drifting or extrusion of teeth with reduced periodontium.

The decision whether to conserve or extract esthetically compromised teeth depends on the patient’s smile line, gingival biotype, local bone availability, but most of all, the patient’s expectations regarding the final esthetic outcome. Tooth extraction for esthetic reasons may be recommended if the prosthetic restoration (either implant- or tooth-supported) will significantly improve the esthetic outcome and satisfy the patient’s expectations (Donos, et al., 2012). Predictable and pleasing esthetic outcomes could be achieved in several cases of single-tooth replacement with a dental implant when tissue support provided by the adjacent natural teeth is preserved (Belser, et al., 2004).

However, the esthetics following replacement of multiple missing teeth with dental implants in the anterior maxilla may be unpredictable, and esthetic failures (poor emergence profiles, loss or distortion of the papillae, and exposure of the metallic implant components) are common (Goodacre, et al., 2003). Therefore, extraction of periodontally compromised teeth for esthetic reasons should be considered only under the condition that the future implant-supported restoration could predictably provide an improved esthetic outcome.

Reduced complication rate for implants in comparison to teeth
The comparison of clinical outcomes between teeth treated for periodontal disease and dental implants, which very often have been placed in healthy dentitions not previously affected by periodontal disease, should be based on implant success rather than survival rates. Implant survival rate refers to the proportion of implants still in place at a certain time without considering biological and/or technical complication, function, or clinical value. From a clinical point of view, survival rates are not always representative of success, since the risk of biological, technical, and mechanical complications in implant-supported restorations is not presented. Treatments of all these complications require extra time, increased cost and morbidity, and may result in lower patient satisfaction levels with implant treatment. Biological complications are mainly related to peri-implant mucositis describing “the presence of inflammation in the mucosa of an implant with no signs of loss of supporting bone” or peri-implantitis describing “the inflammation of the mucosa characterized by loss of supporting bone” (Lindhe, et al., 2008).

In a recent systematic review, Zitzmann and colleagues (2008) reported that the prevalence of peri-mucositis was approximately 80% on the subject and 50% on the implant level while the prevalence of peri-implantitis varied between 28% and 56% on a patient level and 12%-43% on an implant level. Similarly, technical complications in fixed partial dentures (loosening of occlusal screw, porcelain chipping, loss of retention, fracture of implant component) for implant-supported reconstructions was 39% as compared to 16% for tooth-supported reconstruction (Bragger, et al., 2011).

Conclusion
The notion that “implants survive longer than teeth,” as sometimes suggested in implant companies’ marketing, has no scientific support.

Periodontally compromised but successfully treated teeth in well-maintained patients present comparable long-term survival rates of more than 90%. Implant therapy in periodontally or endodontically affected dentitions should include proper diagnosis and treatment for the remaining natural teeth when possible and a patient assessment of all the related risk factors for periodontal/peri-implant diseases.

Such risk estimation should always be considered in any implant treatment planning and should include a general health and oral hygiene assessment, an evaluation of periodontal disease control, and a detailed cost-benefit analysis based on patients’ expectations.