Traumatic fractures of the anterior dentition occur for a variety of reasons. Effective management of traumatic fractures raises several important treatment planning concerns. Although studies indicate that the majority of traumatic injuries involve only one tooth, multiple fractures are not uncommon.1
The nature and depth of the fracture will often dictate the type of treatment that is required. In order to provide predictable esthetics, function, structure and biologic health, it is imperative that an interdisciplinary treatment approach is followed. This is especially true if the fracture extends into the attachment apparatus or below the osseous crest. The first question the clinician must consider when treatment planning the traumatic fracture is, can the tooth/teeth be saved? If the fracture extends so far apically that no matter what treatment is provided the resulting crown-to-root ratio will be inadequate or the amount of coronal tooth structure will not allow restoration, extraction of the tooth may be the best treatment option. When the extraction of the fractured tooth is warranted, placement of an endosseous implant is the treatment of choice. This article addresses the treatment concerns that arise when treating traumatic fractures. In addition, this article presents a step-by-step guide to decision making in order to provide the most predictable results.
A 25-year-old female presented with a traumatic injury to teeth 7, 8 and 9. (Figures 1a and 1b.) Tooth #9 was diagnosed with the most complicated crown-root fracture as defined by Andreason et al. 2 At the time of the accident the patient was seen for emergency treatment by her general dentist and once the injured area was stabilized, she was referred to an endodontist for root canal therapy on 8 and 9. It was only after the definitive root canal therapy was completed that the patient presented for initial examination.
Although the patient was anxious to have the teeth restored, the question still remained as to whether or not there is enough tooth structure left to warrant restoration of #9. To complicate this decision making process further is the fact that root canal therapy had already been completed. This means that the patient already has vested interest in keeping the teeth. With this in mind it is not uncommon for the restorative dentist to feel pressured to grant the patient's wish to save the teeth even though this may not be the best treatment plan. Regardless of any treatment that has already been performed or the patient's emotional investment in saving the teeth, it is the responsibility of the restorative dentist to educate the patient with regard to the risks and benefits of the different treatment options. True interdisciplinary treatment only occurs when all of the treating clinicians develop the treatment plan together. It is only after the final treatment plan has been decided that definitive treatment should begin.
The first step in the process of determining if the teeth should be saved or extracted, is to locate the most apical extent of the fracture. This can be accomplished both clinically and radiographically. Click this link for more on excellence in oral radiography.
Traumatically fractured maxillary anterior teeth generally have an oblique fracture angle with the most apical portion located on the palatal. (Figure 2) Depending on the extent and acuteness of the fracture angle it may be challenging to identify where the fracture ends radiographically. Thus, it is vital to locate the extent of the fracture clinically. In this case it is determined that the fracture extends 4 to 5 mm subgingival. (Figure 3)
Taking measurements on the facial of the teeth reveals that this patient has a 2 mm biologic width and a sounding depth of 3 mm. Given these measurements it is noted that the palatal fracture extends significantly below the osseous crest. In order to be able to properly restore the teeth the fractures must be exposed. The critical question becomes how much tooth structure needs to be exposed.
It must be remembered that just exposing the fracture is not enough. The amount of tooth structure that needs to be exposed must be adequate enough to provide room for the biologic width as well as the ferrule. In order to accomplish this it is generally necessary to expose 4 mm of tooth structure below the level of the fracture. This will provide 2 mm of tooth structure for recreation of the biologic width and 1.5mm of tooth structure for a ferrule with 0.5 mm of sulcular space separating them. (Figure 4)
It has been shown in the literature that one of the most important factors in the predictable restoration of endodontically treated teeth is having an adequate ferrule.3 The purpose of the ferrule is to help transfer occlusal load to the tooth-root complex while minimizing the amount of load that is transferred to the post core. The location of the ferrule on the tooth is critical. Given the direction of load on a maxillary anterior tooth, it is the palatal surface that is under tension when the tooth is loaded by the lower incisor. Therefore, it is in this location that the ferrule is most important. Unpublished research from the Graduate Prosthodontics program at the University of Washington School of Dentistry shows that there is no difference in the fatigue rate of maxillary anterior teeth restored with a ferrule that is present 360 degrees around the tooth compared to teeth restored with the ferrule limited to the palatal and buccal surfaces only (no ferrule interproximally).
The last thing that needs to be addressed with regard to the structure of the potential restoration is the preparation length. It is well documented that the use of resin cements can aid in the retention of restorations on teeth with excessive taper or short clinical crowns. 4,5,6 However, even if resin cements are used, it is not enough to just have an adequate ferrule. Although the ferrule is extremely important, it does not provide the restoration with the needed resistance/retention form. The resistance of a restoration to rotational dislodgement is influenced by the height and taper of the preparation. In order to provide adequate resistance form to the preparation it is recommended that there be approximately 2 to 3 mm of preparation height. (Figure 4)
This measurement of the preparation height should be taken interproximally as this area generally has the least preparation height due to the amount of interproximal scallop. In order to provide the needed preparation height with severely fractured teeth, restoration with a post core is often necessary.
Exposure of Fracture
Given that we need to expose 4 mm of tooth structure below the level of the fracture, one must choose the optimum method for exposure. Two options exist to properly expose traumatic fractures: osseous surgery (crown lengthening) or orthodontic eruption. In order to decide which treatment option to use, the position of the tissue must be evaluated. If having the tissue move apically would detract from the esthetics, osseous surgery is contraindicated. If osseous surgery were to be performed, the removal of any bone interproximally to expose the fracture would result in the papilla moving apically as well, thus detracting from the gingival symmetry. In addition, given the amount of palatal ostectomy that would be required in this patient, a significant amount of osseous surgery would also have to be done on the palatal surfaces of the adjacent teeth in order to blend the bony contours so that a bony defect is not created. This would unnecessarily remove bony support and expose the root surfaces of the adjacent teeth.
If the soft tissue levels are correct, the treatment option of choice to expose the fracture is orthodontic eruption. The efficacy of eruptive tooth movement to improve the soft and hard tissue architecture is well documented in the literature. 7,8,9 With conventional orthodontics, the placement of an eruptive force on a tooth will cause the tooth to move coronally. In turn, this movement will create tension in the gingival fiber apparatus causing the bone and periodontium to also move coronally. As a result of this movement, the tissue levels will now be more coronal than the adjacent teeth. In order to correct the aberrant tissue levels, osseous surgery is needed to place the bone and tissue in the ideal position.
Once the tooth is orthodontically erupted it must be retained for approximately four to six months in order to prevent relapse. An alternative method for performing orthodontic eruption is to supplement the eruption with fiber resection.10 Given that it is the tension on the fiber apparatus that directs the movement of the bone and periodontium, severing the fiber apparatus can inhibit the movement of the bone and tissue while still allowing eruption of the tooth. Typically, the fibers must be severed circumferentially around the tooth all the way to the osseous crest. It is recommended to sever the attachment one- time weekly until the tooth has erupted. Once the eruption has been completed, the tooth must still be retained for approximately four to six months to prevent relapse. After stabilization, the position of the bone and tissue must be evaluated. It is not uncommon for either the tissue or the bone / tissue complex to still move coronally despite the weekly fiber releases. If this occurs either a gingivectomy or osseous surgery will be needed depending on whether only the tissue moved coronally or the bone and tissue moved coronally.
External/Internal Root Form
Regardless of the method to expose the fracture, the external and internal dimensions of the tooth must be evaluated. Specifically, the expected crown-to-root ratio, the width of the tooth at the level of the future crown margin, and the internal anatomy of the root at the level of the future crown margin. Traditionally, the desired crown-to-root ratio is 1:1.11 Although the 1:1 ratio is a good reference, it does not imply that if a 1:1 ratio cannot be achieved the tooth should be extracted. We have all seen the lateral incisor that has had significant root resorption post orthodontic treatment. Despite having as little as 3 to 4 mm of root remaining, these teeth can remain stable for years. If the expected crown-to-root ratio will not be 1:1, the occlusion and function of the patient as well as the relative mobilities of the other teeth need to be evaluated to determine if extraction is warranted.
Typically the external root form of an anterior tooth narrows from the CEJ to the apex. The amount of root taper is an important factor due to the emergence profile of the crown any time root structure has to be exposed and the restorative margin placed apically. The contours of a crown that emerge from a root that is significantly narrower than the tooth at the CEJ level, must be abrupt. This is especially true when restoring a central incisor, due to the larger diameter of the crown. This is similar to the contour changes that have to take place on an implant crown that emerges from a 3.75 mm diameter fixture. The difference is that the contours of the implant restoration can begin at a more apical position due to the depth of the implant. In the case of a natural tooth, given the level of the gingival attachment, the preparation cannot begin as deep. Consequently, the crown requires more abrupt contours, which may ultimately affect the shape and form of the gingival architecture.
The internal anatomy of the root at the level of the anticipated crown margin is also important. Ideally, the anatomy in this area should be divided into equal thirds. Radiographically the middle one-third of the root dimension should be the canal space with the one-third on either side being root structure. This ratio allows enough thickness of tooth structure on either side of the canal to allow preparation of the tooth for a full coverage restoration while still maintaining an adequate thickness of the axial walls for structural support. Therefore, it is crucial that the endodontic shaping of the canal be as conservative as possible. Canals that are over prepared will leave little axial wall thickness once the tooth is prepared.
Upon examination, the fracture of tooth #8 ended 4 to 5 mm below the tissue on the palatal surface. In order to expose the fracture and provide 4 mm of sound tooth structure above the osseous crest, these teeth would need to be orthodontically erupted approximately 6-7 mm. Given the existing root length of 14 mm, if these teeth were erupted 6 to 7 mm the resulting length of root remaining in bone would be minimal. In addition, the remaining root from would be fairly tapered. Rather than create a compromised tooth or extracting the tooth, it was decided to use a combination of orthodontic eruption and osseous surgery. The goal of the orthodontic treatment is to erupt the tooth so that the location of the fracture interproximally is at a restorable level. In doing so the height of the interproximal bone would remain in the same location as it is currently, thus ensuring a predictable papillary position. The remaining fracture residing on the palatal surface could be exposed with osseous surgery without detracting from the esthetics.
The first step in the procedure was to access the level of the fracture so that the teeth could be built up and provisionalized. This provides the patient with immediate dentition and allows the orthodontist easy access to position and bond orthodontic brackets. After anesthetizing the palatal tissues, electrosurgery was performed to expose the complete fracture (Figure 5) The canal was prepared and shaped leaving approximately 5 mm of gutta percha at the apex. A smooth plastic impression post (ParaPost XP, Coltene/Whaledent Inc. Cuyahoga Falls, Ohio) were placed into the canal and picked up in a final impression to allow the fabrication of definitive post core in the laboratory. On the model, a zirconia post (CeraPost, Brasseler USA, Savannah, Ga.) was fit into the canal and the core were waxed up to their desired shape. The ceramic core (IPS Empress Cosmo Ingots, Ivoclar Williams, Amherst, N.Y.) was fabricated using the “lost wax” technique.
Once the core were pressed and re-fit on the working model, the zirconia was sandblasted with Al203 (110 μm) and the porcelain was etched with 4.8 percent HF acid. Clinically, the canal were cleaned and prepared. The post core was bonded with a dual-curing resin cement (Panavia F, J. Morita, Tustin, Calif.). (Figures 6 and 7) Once the preparations were refined, the provisional was relined (Protemp Plus Garant, 3 ESPE, St. Paul, Minn.) and cemented with a self-curing resin cement to prevent loosening during the orthodontic eruption. (Figure 8) The use of a resin cement will also maintain stability of the provisional even if occlusal adjustment during the eruption process perforates the provisional.
The patient was then referred to the orthodontist to erupt tooth #9 approximately 3 mm. This amount of eruption was chosen to bring the interproximal fracture up to a restorable level. Given that both teeth needed to be erupted and osseous surgery was already planned in order to expose the remaining fracture on the palatal, conventional orthodontic tooth movement was chosen without the use of fiber release. Once the tooth was erupted 3 mm, it was retained in this position for six months. (See Fig. 9.) Osseous surgery was completed during this time to place the bone and tissue in the ideal position as well as expose the remaining fracture on the palatal. The tissue was allowed to mature for three months before the teeth were re-prepared and new provisionals were placed. (Figures 10a and 10b)
The final restorations consisted of three all-ceramic crowns (Procera AllCeram, Nobel Biocare USA Inc., Yorb Linda, Calif.). The restorations were tried in and bonded to the prepared teeth with resin cement. The treatment performed has held up well as is shown in the 10-year follow up. (Figure 11a,b)
The management of traumatically fractured teeth raises several important treatment planning considerations. Proper diagnosis of the fracture is critical. In order to provide the most comprehensive treatment, an interdisciplinary treatment approach is necessary. Specific treatment procedures and methods must be carefully selected and sequentially followed to ensure the long-term predictability. This article describes many concerns inherent in the treatment of traumatic fractures and presents a step-by-step guide to decision making and treatment protocol.
(Click this link for more articles by Dr. Gregg Kinzer.)
- Dietschi D. Jacoby T. Dietchi JM. Schatz JP. Treatment of traumatic injuries in the front teeth: Restorative aspect in crown fractures. Pract Periodont Aesthet Dent 2000 Jul;12(8):751-758.
- Andreasen JO. Andreason FM. Clasification, etiology and epidemiology. In Andreason JO, Andreason FM, eds. Textbook and Color Atlas of Traumatic Injuries to Teeth. 3rd ed. Copenhagen, Denmark: Munksgaard; 1994:151-180.
- Libman WJ. Nichols JI. Load fatigue of teeth restored with cast post cores and complete crowns. Int J Prostho 1995; 11: 311-324.
- Zidan O. Ferguson GG. The retention of complete crowns prepared with three different tapers and luted with four different cements. J Prosthet Dent 2003 June; 89(6): 565-571.
- Browning WD. Nelson SK. Cibirka R. Meyers ML. Comparison of luting cements for minimally retentive crown preparations. Quintessence Int 2002 Feb; 33(2):95-100.
- Ergin S. Gemalmaz D. Retentive properties of five different luting cements on base a noble metal copings. J Prosthet Dent 2002 Nov; 88(5):491-497
- Ingber JS. Forced eruption. Part II: Method of treating non-restorable teeth- periodontal and restorative considerations. J Periodontal 1976; 47:203-216.
- Lemon RR. Simplified esthetic root extrusion techniques. Oral Surg Orla Med Oral Pathol 1982; 54:93-99.
- Berglundh T. Marinello CP. Linde J. Thilander B. Liljenberg B. Periodontal tissue reactions to orthodontic extrusion. J Clin Periodontal 1991; 18:330-336.
- Pontoriero A. Celenza F Jr. Ricci G. Carnevale G. Rapid extrusion with fiber resection: A combined orthodontic-periodontic treatment modality. Int J Perio Rest Dent 1987; 5:31-43.
- Penny RE. Kraal JH. Crown-to-root ratio: its significance in restorative dentistry. J Prosthet Dent 1979 Jul; 42(1):34-38.