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CLINICAL SCIENCE AND TECHNIQUES

Treatment Planning for Implants Versus Root Canal Therapy: A Contemporary Dilemma

Bader, Herbert I. DDS*

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Abstract

Although there is considerable literature available describing the placement of implant fixtures under various conditions, there is a relative paucity of data-based results for indications and contraindications of endosseous root-form implants. 1 This is particularly applicable to the decision-making process regarding the endodontically treated tooth that may require retreatment. The literature is also sparse with regard to initial root canal therapy versus extraction and implant placement. 2 The continued growth of treatment planning using endosseous root-form fixtures dictates the establishment of some sort of guidelines for decision making, with regard to extraction versus retention. 3

The science of endosseous root-form implant placement has advanced with the development of new implants, thread designs, and implant surfaces. 4 The clinical literature reports success rates up to and exceeding 97%, depending on location in the arch and bone density. 4–6 Success, meaning solid osseointegration suitable for prosthetic restoration, has been shown to be higher in the mandible than the maxilla. 7Fig. 1 shows an 8-year postoperative result for an endosseous root-form implant, illustrating successful long-term osseointegration. Note the distinctive saucerization of the crestal bone, which appears to have stopped at the first thread. These success rates compare favorably with the reported success rates for conventional root canal (Figs. 2 and 3) treatment of up to 95%, 8 to 10 years after treatment, 8 and some anecdotal reports using microscopic visualization of up to 100%. 9–12 The success rate of endodontically retreated teeth is very high as well. 13 There are, therefore, two very viable options in treatment planning, making these decisions all the more important because of the implications of extracting teeth. The development of a predictably successful long-term restorative/prosthetic treatment plan requires careful evaluation of the various factors that will influence the prognosis of the involved teeth and the possible choice of extraction and replacement with implant fixtures. This discussion will cover those considerations and attempt to create a workable algorithm for the decision-making process.

Fig. 1
Fig. 1:
Implant restoration: 8-year result.
Fig. 2
Fig. 2:
Eight-year endodontic result.
Fig. 3
Fig. 3:
Ten-year endodontic result.

It should be pointed out, at the outset, that there are no absolutes applicable to this complex decision-making process. Each situation is unique and must be evaluated on its merits. At best, we can discuss the general guidelines for establishing the algorithm, and the parameters, which should be considered. The concept of assessing prognosis by assigning risk to specific sites has proven to be a valuable tool. 14 The use of risk assessment for prognosis is an essential part of the treatment-planning process. The process of risk assessment consists of identifying all of the clinical attributes, both local and systemic, which can affect the functional retention of a tooth. 15,16 This assessment also consists of addressing the strategic value of the tooth. Will it serve as an abutment for a fixed or a removable prosthesis? Will it bear a significant occlusal load, etc.? Table 1 illustrates the major factors considered in determining the periodontal prognosis of teeth.

Table 1
Table 1:
Factors Considered in Periodontal Risk Assessment

Periodontitis is characterized by attachment loss, resulting in various types of osseous deformities, all of which lead to loss of support around the tooth. 17 The literature provides ample support for the efficacy of regenerative procedures. 18–20Figs. 4 and 5 show osseous defects on the distal surfaces of stable mandibular bicuspids and molars with 12- and 16-month postoperative results after osseous grafts, with a guided tissue regeneration and xenografting technique. The predictability depends upon the configuration of the deformity, location, stability of the tooth, and a number of other factors, some of which are listed in Table 1. The presence of a furcation involvement whose fill is not entirely predictable 15 (Figs. 6 and 7) alters the risk level for long-term success. If the tooth is to be treated endodontically, or retreated, the extent of furcation opening and accessibility for daily disease control must be considered. If the tooth is not to be used as an abutment for a fixed prosthesis and is, therefore, of less strategic necessity, retention by reconstructive surgery and root canal therapy, if indicated, may be a reasonable choice as opposed to extraction and implant therapy. Fig. 8 shows a nonvital molar with furcation involvement, which illustrates a tooth whose retention is definitely indicated. The first molar shown in Fig. 9 presents with a distal osseous lesion extending to the third apical. In an endodontically treated tooth, with posts, this appearance is highly suggestive of a fracture, and the decision to extract early, before the bone on the mesial root surface of the second molar is affected, is a reasonable one. This was followed by implant placement at a later date.

Fig. 4
Fig. 4:
Distal osseous defect, second premolar graft with 16-month postoperative result.Fig. 5. Mandibular molar osseous defect graft with 12-month postoperative result.
Fig. 6
Fig. 6:
Flap exposed furcation involvement of a nonvital molar.
Fig. 7
Fig. 7:
Radiograph with gutta percha point showing extent of lesion.
Fig. 8
Fig. 8:
Nonvital molar.Fig. 9. Possible fracture of distal root in an endodontically treated molar.

Mobility of a tooth is a critical factor in terms of biomechanical considerations. The risk of a tooth whose support has been compromised to the point of mobility is high enough to preclude retention, if it is to be used in a prosthesis. If it requires root canal therapy as well, then extraction is usually the treatment of choice. Figs. 10 and 11 illustrate anterior teeth whose roots have been blunted by previous orthodontic therapy. The right central incisor is nonvital and mobile. The adjacent teeth, although having obviously compromised roots, are firm, vital, and nonprobing. Extraction of number 8 and replacement with an implant is shown in the 5-year follow-up radiograph. It is important to remember that treatment planning must always include the prognosis of adjacent teeth in any prosthetic plan. Strategic “extraction” of one or more compromised teeth is an important treatment approach that should be considered.

Fig. 10
Fig. 10:
Nonvital central incisor showing blunted root.Fig. 11. Implant replacement: 2-year postoperative result. Fig. 12. Short-rooted incisor with large posthole preparation. Fig. 13. Extraction and placement of implant fixture.

An endodontically treated (or retreated) tooth with a large posthole and a short root with 40% or more bone loss is a very weak link in terms of risk assessment. Figs. 12 and 13 illustrate a typical situation. Surgical crown lengthening for a tooth already compromised by a large posthole, and a poor crown:root ratio, does not represent a predictable treatment approach. Extraction and implant placement are appropriate alternatives. This is especially true in a multirooted tooth with furcation involvement (Fig. 14).

Fig. 14
Fig. 14:
Periodontally compromised, nonvital first mandibular molar.Fig. 15. Possible failing implant: 9-year postoperative result.

Splinting of mobile or otherwise compromised teeth to implants by fixed cemented prostheses is generally not recommended for biomechanical predictability. This does not include the use of implants as abutments for removable partial dentures, where well-supported abutment teeth with or without endodontic therapy may be included in the treatment plan. This approach has been shown by some clinicians to produce very favorable long-term results, 21 and limited 5- to 10-year survivability by others. 22 The removable partial denture may be considered as a transitional appliance with eventual extraction and further implant therapy to follow.

Assessing Prognosis

An obvious consideration for retention of a tooth compromised by periodontal disease, or requiring endodontic retreatment, is consideration of the probability of further attachment loss, despite aggressive reconstructive osseous surgery. Risk factor assessment, in addition to site specific considerations, includes systemic contributions as well. Poorly controlled diabetes mellitus is an obvious concern. The patient’s genetic susceptibility to periodontal disease activity may also be a critical risk factor. Patients can be evaluated by a simple, noninvasive test (PST, Medical Science Systems; Straumann Implant Co., Cambridge, MA) for the presence of a genotype involving altered production of an important inflammatory mediator (interleukin 1-B). 23,24 These patients are considerably more likely to undergo further disease progression, given the same stimuli as the genotype-negative patient. It is believed to affect about 30 to 35% of patients of Northern European heritage. This severity factor impacts on prognosis and tooth survival 25 and should be considered as one of the more important factors in risk assessment.

There is, at this time, no accumulation of evidence to suggest that patients who are at risk for progressive periodontal disease are at greater risk for implant failure. 26,27 There is evidence that the factors that lead to implant failure are different in terms of etiology, than teeth, 28 and there are no reported studies relating periodontal disease-susceptible patients to an increased rate of implant failure. Failure of well-integrated endosseous implants, although uncommon after the first year of restoration, is more commonly associated with occlusal problems, related, for example, to improper loading of the fixture(s). 29,30Fig. 15 shows a large restoration with considerable antaxial force on the distal implant. Note the gradual loss of integration to the third and fourth threads. Despite the possible biomechanical problem, this is a 9-year postoperative result.

Osseointegrated implants were developed to replace natural teeth that were lost because of caries and chronic periodontitis. 31,32 There are, at this time, no clearly defined gold standards to define implant failure, 33 but it seems that implants fail as a result of mechanical and infectious complications. 34,35

Conclusions

Retention of endodontically involved teeth as opposed to extraction and implant therapy is a decision based on a number of different factors, not the least of which is the long-term predictability of the treatment outcome. Periodontally compromised teeth, requirements for crown lengthening, biologic width, and the condition and location of remaining teeth must be considered. A long-term comprehensive plan, taking into consideration the patient’s needs and wishes, should be part of the decision-making algorithm. Based in part on the patient’s expectations, this may include strategic extractions, sacrifice of teeth that may have some short to medium term longevity, and/or endodontic treatment or retreatment in lieu of extractions. 36,37 There is no generic answer to this clinical issue, and every patient, indeed every site, must be examined on an individual basis.

Use of an algorithm based on the premises outlined in this article may be helpful in decision making. The key factors to consider regarding implant therapy versus endodontic treatment are:

  1. Crown:root ratio
  2. Mobility
  3. Predictability of endodontic success
  4. Risk of recurrent periodontal infection
  5. Strategic nature of the tooth: eg, abutment for prosthesis, etc.
  6. Patient’s expectations.

As noted in Fig. 16, the triad of Implant variables, Patient variables, and Dental (clinical) variables form a decision-making algorithm to be used in treatment planning. Determining the most appropriate treatment for a patient that is the most cost-effective and offers the best long-term prognosis can be difficult, and the decision should be based on good clinical judgment and an understanding of the risks involved with either choice.

Fig. 16
Fig. 16:
Algorithm for decision making.

References

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Disclosure

The author claims to have no financial interest in any company or any of the products mentioned in this article.

Abstract Translations [German, Spanish, Portuguese, Japanese]

AUTOR: Herbert I. Bader, DDS*. *privat praktizierender Arzt, Concord, Massachusetts; Dozent, Abteilung für Orthodontie, Harvard Zahnmedizinische Fachschule. Schriftverkehr: Herbert I. Bader, DDS, 290 Baker Avenue, Concord, MA 01742. Telefon:978–369–5066, Fax: 978– 369–8928.

ZUSSAMENFASSUNG: Der Einsatz von Implantatbefestigungen als Langzeitlösung bei Zahnverlust verspricht inzwischen einen so guten Behandlungserfolg, dass inzwischen vielerorts diese Methode als Standard an die Stelle des Zahnersatzes mittels fester Prothesen getreten ist. Gleichzeitig beobachtet man aber auch eine gute Erfolgsquote bei wurzelbehandelten Zähnen oder solchen, die generell einer erhaltenden Behandlung bedürfen. Nun steht der behandelnde Zahnarzt also vor der schweren Entscheidung, wann eine zahnerhaltende Aufbaubehandlung dem Ziehen eines Zahnes und dem anschließenden Ersatz durch ein wurzelförmiges Implantat vorzuziehen ist und umgekehrt. Eine Beurteilung der durch die Behandlung möglichen Risiken ist bei der Entscheidungsfindung von wesentlicher Bedeutung. Die speziell klinischen sowie die allgemeinen Einflüsse auf die Langlebigkeit eines Zahnes müssen ebenso wie Sitz, Knochengewebsqualität und –quantität und Allgemeinzustand der übrigen Zähne des Patienten in den Entscheidungsprozess mit einbezogen werden. Die vorliegende Arbeit möchte hierzu einen sinnvollen Algorithmus als Basis für die Auswahl des passenden Behandlungsansatzes vorstellen.

SCHLÜSSELWÖRTER: Wurzelbehandlung, Risikoanalyse bei zahnerhaltenden Aufbaubehandlungen

AUTOR: Herbert I. Bader, DDS*. *Práctica Privada, Concord, Massachusetts; Disertante, Departamento de Periodontología, Escuela de Medicina Dental de Harvard. Correspondencia a: Herbert I. Bader, DDS, 290 Baker Avenue, Concord, MA 01742. Tteléfono: 978-369-5066, Fax: 978-369-8928.

ABSTRACTO: La previsibilidad de los implantes como solución a largo plazo para las áreas edentulosas ha mejorado hasta el punto en que se han convertido en la norma de atención en muchas situaciones, en lugar de prótesis fijas. Al mismo tiempo, la tasa de éxito de los dientes tratados endodó nticamente y de los que requieren el retratamiento también es muy alta. El dilema que se presenta al clínico en la planificación del tratamiento es cuándo volver a tratar a un diente o extraerlo y colocar un implante endoóseo con forma de raíz. La evaluación del riesgo de la evaluación de pronóstico juega un importante papel en el proceso de toma de decisión. Los factores clínicos y sistémicos que afectan la longevidad del diente necesitan ser considerados, así como la ubicación, calidad y cantidad de hueso, y el estado de los otros dientes del paciente. El artículo trata de proporcionar un algoritmo significativo para proporcionar una base para elegir la terapia apropiada.

PALABRAS CLAVES: retratamiento endodóntico, evaluación del riesgo endodó ntico,

AUTOR: Herbert I. Bader, DDS*. * Clínica particular, Concord, Massachusetts; Pal-estrante, Departamento de Periodontia, Faculdade de Medicina Odontológica de Harvard. Correspondências devem ser enviadas a: Herbert I. Bader, DDS, 290 Baker Avenue, Concord, MA 01742. Telefone: (978) 369-5066, Fax: (978) 369-8928.

SINOPSE: a previsibilidade das fixações de implantes como uma solução a longo prazo para as áreas edêntulas progrediu a ponto de torná-los padrão de tratamento em muitas situações, ao invés de próteses fixas. Ao mesmo tempo, o índice de sucesso do dente tratado endodonticamente e dos dentes que requerem retratamento também é elevado. O dilema que o clínico enfrente no planejamento de tratamento trata-se de quando tratar um dente ou quando extrai-lo e colocar um implante endósseo em forma de raiz. A análise de risco para a avaliação prognóstica desempenha um papel importante no processo de tomada de decisão. Os fatores clínicos e sistê micos que afetam a longevidade de um dente devem ser levados em consideração, bem como a posição, a quantidade e a qualidade do osso e as condições dos outros dentes do paciente. O artigo tenta proporcionar um algoritmo com significado para proporcionar uma base para uma opção apropriada de terapia.

PALAVRAS-CHAVES: retratamento endodôntico, análise de risco endodôntica.

FIGURE

Figure
Figure
Keywords:

endodontic retreatment; endodontic risk assessment

© 2002 Lippincott Williams & Wilkins, Inc.