Sara Barsness, D.D.S., and Tom Nguy, D.D.S.
Division of Endodontics
University of Minnesota
Repair of External Root Resorption Defects Using MTA Placed With Ultrasonic Activation: A Case Series
Resorption of teeth may occur as a result of inflammatory conditions, mechanical stimulation, or neoplastic processes.1 Invasive cervical resorption is a category of external root resorption that can occur with or without a vital pulp.2,3 This process has also been referred to as extracanal invasive resorption4 and external cervical resorption.5 There is a strong association between the incidence of invasive cervical resorption and orthodontic treatment, intracoronal bleaching, and dental trauma.6 In cases of invasive cervical resorption, an entry point at the root surface is present with resorption extending into the tooth structure.4 Tissue from the periodontal ligament is involved in the formation of clastic cells responsible for root resorption.7 Anti-invasive factors are believed to be present in cementum,8 predentin, and dentin.9 The entry point seen in invasive cervical root resorption is thought to represent an area of the root that was made vulnerable to clastic cells via some form of mechanical or chemical trauma damaging the cementum, predentin, or dentin.
Heithersay described four classifications of invasive cervical root resorption depending upon the extent of the resorptive defect, with smaller defects having a better prognosis. Class 1 involves a small lesion with shallow penetration into coronal dentin. As the lesion penetrates the coronal dentin close to the pulp, it is classified as Class 2. Class 3 lesions have a similar depth of penetration to that of a Class 2 lesion, but an extension into the coronal third of root dentin is also present. Class 4 lesions extend apically past the coronal third of root dentin. In a series of cases treated by Heithersay, nearly all Class 1 and 2 lesions healed successfully after treatment, while Class 3 and 4 cases had a 77% and 12.5% healing rate, respectively.10
When invasive cervical resorption is diagnosed, there are typically three options: (1) postponement of treatment (usually extraction) until symptoms occur, (2) immediate extraction, and (3) treatment of the resorptive lesion. Debridement and obliteration of the portal of entry and the extracanal defect are the main treatment objectives in cases of cervical invasive resorption.4 Literature review of treatment options includes surgical access with topical application of a 90% solution of trichloroacetic acid, curettage, and restoration with glass ionomer cement.6 Dressing root canals with calcitonin or calcium hydroxide11,12 to prevent further progression of resorption has been advocated in an effort to turn off clastic cells by providing a more alkaline environment. A downside of calcium hydroxide use is increased risk of tooth fracture.13,14 Another dental material, mineral trioxide aggregate, has also been shown to increase the alkalinity at the root surface when applied in simulated resorption lesions.
Mineral trioxide aggregate (MTA) was originally developed by Dr. Mahmoud Torabinejad at Loma Linda University. In its commercially available form under the marketing label of ProRoot MTA® by Dentsply, MTA consists of tricalcium silicate, dicalcium silicate, tricalcium aluminate, calcium sulfate dehydrate, tetracalcium aluminoferrite, and bismuth oxide. Chemically, MTA is similar to Portland cement, but contains the addition of bismuth oxidecfor added radiopacity, and being a medical grade material means that it is of higher purity. ProRoot MTA is available in two varieties, gray and white, with an absence of tetracalcium aluminate and lower iron content in the latter.15
As a dental material, MTA has been found to be superior to many materials in terms of its sealing ability and biocompatibility.16 In addition, it has been shown to promote the deposition of cementum17 and adhesion of osteoblasts,18 and thus significantly improve hard tissue healing. With a pH of 12.5 when set, it has also been demonstrated to have some antibacterial properties.16
The ideal properties of MTA have seen it being used as the material of choice in many endodontic applications, including root-end filling,16 vital pulp therapy,20,21 apexification,22 and perforation repairs.23,24 Due to its high pH, there is the potential for MTA to have ability to turn off osteoclastic activities, a feature seen in calcium hydroxide.11 This is particularly important when it comes to inflammatory resorption, and has led to a series of case reports documenting the use of MTA to repair external resorptive defects.25,26
The purpose of our table clinic was to present a series of cases of external cervical root resorption that were managed with removal of the resorptive tissues either during non-surgical or surgical treatment and repair of the defect with MTA placed via ultrasonic activation. Use of indirect ultrasonic activation allows MTA to flow into irregular defects present in invasive cervical resorption. Endodontic therapy may be indicated if the lesion extends to the pulp. Sequence of treatment varied depending upon the location and size of the defect and diagnosis. In all cases, the patients were informed of the risks and benefits of their treatment options, and each elected to proceed with the treatments described.
Case 1:This 47-year-old male was referred to the endodontic division for an asymptomatic radiolucent lesion associated with the distal aspect of tooth #31 that was noted during routine radiographic survey. The patient’s medical and dental history revealed no significant findings. Aside from the presence of a PFM crown, pulp testing revealed a normal pulpal and apical status. The resorptive lesion was classified as a Heithersay Class 2, as the defect had penetrated close to the pulp chamber but had not affected the coronal one-third of the root dentin. Elective non-surgical root canal treatment was planned due to complication with access for surgical treatment, and the patient was informed of the questionable prognosis. The tooth was accessed non-surgically, followed by pulpal tissue debridement. Along with hand and rotary instrumentation, copious irrigation with 6% NaOCl was utilized to remove tissue. Once a dry field was obtained, the root canalwas obturated with gutta-percha and Roth’s 801 sealer. MTA was placed into the defect with a MAP system tip, and a Buchanan condenser was used to indirectly activate the material into the irregular space. An amalgam restoration was placed into the access.
Case 2:An asymptomatic radiolucent lesion associated with the distal aspect of tooth #18 was noted during a routine radiographic survey of this 28-year-old female. A review of the patient’s medical and dental history revealed no significant findings. Aside from the presence of a PFM crown, pulp testing revealed a normal pulpal and apical status. The resorptive lesion was classified as a Heithersay Class 2, as the defect had penetrated close to the pulp chamber but had not affected the coronal one-third of the root dentin. Elective non-surgical root canal treatment was planned due to complication with access for surgical treatment, and patient was informed of the questionable prognosis. The tooth was accessed non-surgically, followed by pulpal tissue debridement. Along with hand and rotary instrumentation, copious irrigation with 6% NaOCl was utilized to remove tissue. Once a dry field was obtained, the root canal was obturated with gutta-percha and Roth’s 801 sealer. MTA was placed into the defect with a MAP system tip, and a Buchanan condenser was used to indirectly activate the material into the irregular space. An amalgam restoration was placed into the access.
Case 3:This 27-year-old female patient had a history of a motor vehicle accident 12 years previously, with trauma to her anterior teeth, resulting in need for a non-surgical root canal treatment for tooth #24 at that time. Medical history was significant for smoking and attention deficit hyperactivity disorder. She was currently seeking several lower anterior crowns for esthetic reasons. A radiolucency of the mesial aspect of the root of #24 at the level of the alveolar crest was noted by her graduate prosthodontics resident. Tooth #24 was asymptomatic and was diagnosed as previously treated with normal apical tissues and a Class 2 cervical resorption defect. The lesion was located on the mesiofacial interproximal area of the root at the level of the alveolar crest. A surgical approach was utilized for curettage of the tissue of the root and in the defect, with placement of MTA with ultrasonic activation to allow flow into the depths of the defect. Due to the larger surface area of the entry point and the location, a glass ionomer restoration was placed over the MTA (after its initial set). A non-surgical retreatment was done two weeks later due to exposure of the gutta-percha to saliva through the defect. The tooth was then restored with a buildup and a full coverage crown in the graduate prosthodontics clinic. At six-month recall, the patient continued to be asymptomatic and did not exhibit attachment or further bone loss at the surgical site.
Case 4: An asymptomatic radiolucent lesion associated with tooth #27 was noted during routine radiographic survey of this 51-year-old male. Review of medical history revealed a negative review of systems and no medications. This patient had a dental history of a bilateral sagital split surgical procedure for orthodontic purposes and history of orthodontics. Due to the size and apical extension of the missing tooth structure, it was classified as a Class 3 invasive cervical resorptive lesion. The tooth was diagnosed as normal pulpal and normal apical tissue. Elective non-surgical root canal treatment was planned due to the large size and close approximation of the lesion to the canal. The tooth was accessed non-surgically, and tissue was debrided from the canal and the resorptive defect. Copious irrigation with 6% NaOCl was utilized to remove tissue and to allow a dry field. Once a dry field was obtained, the root canal was filled with guttapercha and Roth’s 801 sealer. MTA was placed into the defect with a MAP system tip, and a Buchanan condenser was used to indirectly activate the material into the irregular space. A composite restoration was placed in the access. During the same appointment, surgical access was made due to the large size of the entry point to allow curettage and sealing of the root surface with a glass ionomer material.
All cases will continue to be followed at six month to one year recall intervals at the University of Minnesota Department of Endodontics. In cases 1 and 2, where surgical access and curettage were not part of the initial treatment, any further resorption the point of entry could be addressed surgically.
In cases of invasive cervical resorption, placement of MTA via indirect ultrasonic activation allows placement of an alkaline material with good sealing capabilities into the irregular defect after removal of the resorptive tissue. This is particularly helpful in cases where the lesion is difficult to access surgically. Sequence of treatment is dictated by the pulpal and apical diagnosis, size and location of the lesion.
Acknowledgment: The authors thank Drs. Brian Meade (cases 1 and 2) and Andrew Wiswall (case 4) for the use of their cases in our table clinic and this article.
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Tim Morse, D.D.S.
University of Minnesota
Department of Oral and
Minneapolis, Minnesota 55455
The discovery of bone morphogenetic proteins (BMPs) is a significant advantage to dentistry. BMPs are a group of naturally occurring proteins found in human cortical bone which stimulate new bone growth via osteoinduction. BMPs help direct complex signaling processes that induce basic cells (mesenchymal) to differentiate into bone-forming cells called osteoblasts. Osteoblasts secrete extracellular matrix as a precursor for bone production. In addition, osteoblasts setup environmental conditions that favor the calcification of extracellular matrix into bone.
Since 2007, neurosurgeons have used BMP to aid in spinal fusion. In dentistry, BMP-2 is FDA approved for sinus and localized alveolar ridge augmentation prior to dental implant rehabilitation. Clinical studies demonstrate that the use of BMP is equivalent to autogenous iliac crest bone graft with regard to both bone fusion rates and clinical outcomes.* Traditional approaches to restoration of alveolar defects and vertical sinus augmentation have included non-vascularized autograft as the “gold standard”. BMP has the potential to change our thinking about reconstruction of alveolar bone defects because it provides the benefits of an autograft, including new bone formation but without the donor site morbidity, increased operating room time, cost, and longer hospital stay associated with iliac crest bone grafting.
Moreover, recent clinical research suggests that BMPs may provide benefit in restoring critical size defects often requiring vascularized bone grafting such as microvascular free tissue transfer including vascularized free fibula grafts@.
Bone morphogenetic protein is a noteworthy example of the importance of basic science research transitioned into clinical dentistry with significant decrease in patient morbidity and potential increase in quality of life.
*Triplett et al 2009. Pivotal, Randomized, Parallel Evaluation of Recombinant Human Bone Morphogenetic Protein-2/Absorbable Collagen Sponge and Autogenous Bone Graft for Maxillary Sinus Floor Augmentation. J Oral Maxillofacial Surg 67:1,947-1,960, 2009.
@Herford AS, Boyne PJ 2008. Reconstruction of mandibular continuity defects with bone morphogenic protein-2 (rhBMP-2). J Oral Maxillofac Surg 66:616, 2008.