Dental Implant Treatment Planning of End-Stage Tooth Failure: Endodontic Perspective
Emanuel Alvaro, DDS, MMedSc
Osseointegration in dentistry has been one of the greatest contributions to our armamentaria in the 20th century. Never before have we seen such an explosion of clinical research, establishment of institutes and organizations, treatment planning paradigm shifts, and industry–university research collaboration. This has also resulted in a profession-wide increase in interest in complete edentulism, occlusion, and the importance of continued bone resorption after tooth loss. Backlashes of ethical questions have also emerged, as have questions on possible conflicts of interest in the realm of industry-sponsored university research and within our own practices in terms of recommended treatment plans.
There is a concept of esthetics that is swinging the pendulum toward dental implants. The concept that we can replace body parts is appealing. Most of us felt a euphoric sensation after placing our first implant, a sensation that we probably did not feel after our first root canal obturation. Compounded by efficient marketing from the implant industry and comparisons of success between root canal treated teeth and dental implants using studies dissimilar in study design and content of data collection, these factors may have influenced a segment of dental practitioners to preferentially replace an endodontically failing tooth with an implant.
The last 20 years has also been marked by significant advances in surgical and nonsurgical endodontics. The introduction of microscopic techniques, endodontic materials with cementogenic and osteogenic properties, endo-restorative advances, and, most importantly, the identification of factors that improve endodontic success, have also catapulted into our domain of knowledge and armamentaria to help predicatively save teeth.
The routine selection of single-tooth implants cannot be recommended for the replacement of compromised teeth that could otherwise be saved by endodontic therapy. Endodontic treatments and implant dentistry have both been refined and their long-term outcomes have become better understood. For the benefit of our patients, it is important to identify a true end-stage tooth failure that will not benefit from endodontic therapy and a tooth failure that can be saved with modern endodontic treatment modalities. Thus, endodontic therapy and single-tooth implant replacement are two different treatment modalities for different dental diagnoses.1
The goal of this article is to illustrate the criteria for an end-stage tooth failure, dental implant replacement strategies for such teeth, and the role of pre-emptive endodontic therapy in dental implant treatment planning.
Restorability is primordial to endodontic success. A tooth with a crown with inadequate ferrule effect resulting from insufficient sound tooth structure will be prone to coronal microleakage under dynamic load,2 resulting in canal reinfection.3,4 All restorations, unsupported tooth structure, and decay must be removed before endodontic treatment planning in order to assess that there is 360° of adequate ferrule in height and thickness for the future restoration. If the height and thickness is inadequate, the possibility of crown lengthening or orthodontic extrusion should be evaluated, taking into consideration any furcation or crown-to-root ratio problem that may develop.
Vertical fractures must be ruled out. Meticulous periodontal probing in combination with translumination and radiographic evaluation of the integrity of the surrounding lamina dura are only part of the evaluation process. Again, total dismantlement of all coronal restorations and evaluation of the integrity of the remaining tooth structure under high magnification is essential to rule out a fracture.
Pre-emptive removal of all intracoronal restorations will also allow for the disclosure of any horizontal or cusp fracture. Once the incomplete horizontal fractures are identified, the weak, unsupported dental segments can be removed, and the remaining tooth structure evaluated for restorability. The author has observed that these horizontal coronal incomplete fractures, when located at or just apical to the crestal bone level, are the frequent cause of post-endodontic hyperalgesia, with clinical presentations of mild discomfort to horizontal percussion.
The presence of old perforations in previously endodontically treated teeth may also influence outcome. Old perforations close to the crestal bone level or with an associated periodontal pocket are considered to be end-stage tooth failure, whereas an old perforation without a periodontal pocket, with or without attachment loss (periradicular lesion), and apically positioned is amenable to a good outcome when properly endodontically managed.
All of the above is in the domain of endodontic diagnosis. Proper endodontic diagnosis is one of the three important components of the endodontic success equation. Canal debridement and knowledge of the canal anatomy are the remaining components of endodontic success. Today, with the advances in endodontic microscopy, availability of ultrasonic and post removal machines used to atraumatically extract posts, availability of osteogenic and cementogenic materials, and advances in canal instrumentation metallurgy, the domains of canal anatomy and canal debridement can be properly fulfilled.
A previously endodontically treated tooth undergoing reinfection or producing symptoms must be properly diagnosed and restorability must be established before characterizing it as an end-stage tooth failure. Identifying the source of the problem, understanding the canal anatomy, and envisioning it thorough debridement by nonsurgical and/or surgical endodontic therapy are some of the questions the endodontist will reflect on during her or his assessment. If a component of the equation is compromised, so is the outcome.
The assessment for dental implant replacement of a tooth in end-stage dental failure requires just as much scrutiny as identifying whether a tooth is end-stage or not. The assessment is restoratively driven, and takes into account medical status, occlusion, overall dental status, and most importantly, patient acceptance of all of the possible courses the treatment plan may take during the treatment.
The use of allograft or autogenous bone grafts in socket preservation techniques immediately following an atraumatic extraction are very predictable and widely used when a boney wall defect is present or the buccal wall is less than 1.5 mm thick. In the esthetic zone, because of the vulnerable thin buccal wall and the importance of adequate bone volume for correct hard and soft tissue contours, we cannot rely on the body’s repair mechanism that occurs after an extraction. We need to intervene with socket grafting, guided bone regeneration procedures, and soft tissue grafting. This is especially true when an anterior tooth with a lesion of endodontic origin is anticipated to be replaced with a dental implant. In such a case, immediate implant insertion after extraction is not prudent and loss of the buccal wall resulting from the endodontic pathology may require multiple site development procedures.5
A tooth in end-stage failure, whether previously endodontically treated or not, and indicated for dental implant replacement, with a lesion of endodontic origin (LEO), must be closely evaluated and treatment planned before intervening with atraumatic extraction and site development.
A tooth with a LEO and clinical signs of tenderness to palpation, a draining fistula, or associated with a large diffuse periradicular lesion are not amenable to socket grafting or extraction-guided bone regeneration procedures. For the purpose of this article, we will refer to a tooth with a LEO accompanied with one of these manifestations as an active LEO.
When the patient is asymptomatic and the tooth in question has a discrete LEO, no tenderness to periapical palpation, or any draining fistula, extraction and socket grafting or extraction-guided bone regeneration can be instituted in a single stage (Figure 1, Figure 2, Figure 3). A posterior tooth with an active LEO and end-stage dental failure treatment planned to be replaced by a dental implant should not be extracted and socket grafted in the same session. A 6-week interval is recommended between the atraumatic extraction and site development, for the bone reorganization stage occurs at least 6 weeks after extraction.6
Socket grafting or extraction-guided bone regeneration procedures at the site occupied by a tooth with an active LEO is prone to site infection, loss of the graft material, pain, and, if in close proximity to the maxillary sinus, acute sinusitis (Figure 4, Figure 5 , Figure 6 , Figure 7).
A tooth in the esthetic zone treatment planned for implant replacement but not favorable to an one-stage extraction and grafting procedure because of an active LEO may benefit from pre-emptive endodontic therapy by eliminating or reducing the number of site development procedures that often are necessary in the esthetic zone. In such cases the endodontic therapy may be as simple as a calcium-hydroxide–pulpectomy or, for a previously endodontically treated tooth, canal debridement–calcium hydroxide treatment. This will eliminate the critical mass of infected pulp tissue or reinfected obturation material to render the tooth favorable to a single-stage extraction-grafting procedure once periapical healing has commenced.
Teeth with active or asymptomatic LEO in the esthetic zone of patients with an unfavorable periodontal biotype may benefit the most from pre-emptive endodontic therapy. Eliminating the LEO may open up more conservative options, such as immediate implant insertion, after extraction. Often, these teeth are end-stage because of inadequate coronal tooth structure to ensure restorability. In such cases, pre-emptive endodontic therapy coupled with decoronation can turn the situation amenable to placing an implant in an immediate-extraction site.
Decoronation involves the removal of the clinical crown to the crestal bone level. This allows the growth of gingival tissue over the occlusal surface of the submerged root. This vascularized tissue provides a soft tissue drape that can be used to cover the allograft after the atraumatic extraction of the submerged root or, in the case of immediate implant insertion after extraction, this tissue drape can be used to cover the implant and the bone allograft can be placed between the implant and the cribiform plate of the extraction site. This secures the immediately placed submerged implant and bone allograft from the oral cavity, and reduces the number of soft tissue interventions in the esthetic zone.
Other strategies may involve pulpectomy, canal debridement, or calcium hydroxide canal obturation with the coronal third of the canal space obturated with a glass-ionomer restoration. The periradicular tissue is then left to heal during rapid orthodontic extrusion.
Orthodontic extrusion of a root treatment planned to be replaced by an implant in an immediate-extraction site allows for a more predictable primary rigid fixation of the implant, greater faciopalatal freedom to allow for an ideal implant angulation, less likelihood of buccal cortical bone loss from the extraction, and the creation of a smaller jump space between the implant and the remaining cribeform plate of the extracted site. If the extruded root is then decoronated, the implant placed in the immediate-extraction site can be submerged under the newly grown vascularized soft tissue overgrowth.
The above strategies serve to preserve the native form of the bone volume to maintain correct hard and soft tissue contours, especially in the esthetic zone, where site development techniques by guided bone regeneration may be eliminated or reduced in number and extent.
The above are just additional adjuncts to the treatment planning armamentarium that should be available to the restorative dentist faced with an end-stage tooth failure planned to be replaced with a dental implant.
The best implant remains the natural root, provided that all the criteriaof success are fulfilled. Overzealous universalextraction and implant tooth replacement is just as unjustifiable as overzealously treating every tooth. Prudent endodontic treatment with proper diagnosis, conservative removal of sound tooth structure during endodontic access opening and canalpreparation, proper selection of what to treatand what to refer, as well as dental implantreplacement of a tooth properly identified as being end-stage tooth failure remain the most beneficial approach for our patients.
References
1. Iqbal MK, Kim S. Areview of factors influencing treatmentplanning decisions of single-tooth implantsversus preserving natural teeth withnonsurgical endodontic therapy. J Endod. 2008;34(5):519-529.
2. Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont. 1995;8(2):155-161.
3. Bergenholtz B, Cox CF, Loesche WJ, Syed SA. Bacterial leakage around dental restorations, its effects on the pulp. J Oral Pathol. 1982;11:443-450.
4. Madison S, Wilcox LR. An evaluation of coronal microleakage in endodontically treated teeth. Part III. J Endodont. 1988;14:455-458.
5. Misch Carl E. Contemporary Implant Dentistry. 3rd ed. Mosby Elsevier; 2008.
6. Ohta Y. Comparative changes in microvasculature and bone healing of implant and extraction sites. J Oral Implant. 1993;184-198.
About the Author
Emanuel Alvaro, DDS, MMedSc
Private Practice in Endodontic and Implant Dentistry
Drummondville, Quebec, Canada
