Greggory A. Kinzer, DDS, MSD
Traumatic injury of the anterior dentition can range from a simple fracture of coronal tooth structure to a complex crown–root fracture. The management of traumatically fractured teeth raises several important treatment planning considerations. To properly restore these teeth and ensure the most predictable result, it is often necessary to use an interdisciplinary approach. This article addresses the concerns that are inherent in the treatment of traumatic fractures.
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 tooth, multiple fractures are not uncommon.1 The nature and depth of the fracture often will dictate the type of treatment that is required. To provide predictable esthetics, function, 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. When treatment planning the traumatic fracture, the clinician must first consider whether the tooth/teeth can be saved. If the fracture extends so far apically that the resulting crown-to-root ratio will be inadequate or the amount of coronal tooth structure will not allow restoration no matter what treatment is provided, then extraction may be the best treatment option. When extraction is warranted, placement of an endosseous implant is the treatment of choice. This article addresses the treatment concerns that arise when treating traumatic fractures and presents a step-by-step guide to decision making to provide the most predictable results.
An 18-year-old man presented with oblique fractures of teeth Nos. 7 and 8 (Figures 1A and 1B). The teeth were diagnosed with complicated crown–root fractures as defined by Andreason et al.2 The fractures occurred nearly 1 month earlier from trauma sustained during a sporting activity. At that time, he was seen for emergency treatment by his general dentist. Once the injured area was stabilized, he was referred to an endodontist for root canal therapy. It was after the definitive root canal therapy was completed that he presented for initial examination. At that time, there was approximately 1 mm of tooth structure remaining above the free gingival margin on the facial surface of these teeth, with the fracture extending toward the palate.
The patient was anxious to have these teeth restored, but whether there was enough tooth structure left to warrant restoration remained to be seen. Complicating this decision-making process was the fact that root canal therapy had already been completed, which meant that the patient had a vested interest in keeping the teeth. 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 what treatment has already been performed or the patient’s emotional investment in saving the teeth, it is the restorative dentist’s responsibility to educate the patient about the risks and benefits of different treatment options. True interdisciplinary treatment occurs only when all of the treating clinicians develop the treatment plan together. Only after the final treatment plan has been decided can definitive treatment begin.
The first step in determining whether 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. Traumatically fractured maxillary anterior teeth generally have an oblique fracture angle, with the most apical portion located on the palatal surface (Figure 2). Depending on the extent and acuteness of the fracture angle, it may be a challenge to identify where the fracture ends radiographically (Figure 3). Thus, it is vital to locate the extent of the fracture clinically. In this case, it was determined that the fracture extended 4 mm to 5 mm subgingivally (Figure 4). Measurements taken on the facial surface revealed a 2-mm biologic width and a sounding depth of 3 mm. Given these measurements, the palatal fracture extended significantly below the osseous crest. To properly restore the teeth, the fractures must be exposed. The critical question became how much tooth structure needed to be exposed.
It must be understood 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. 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 re-creation of the biologic width and 1.5 mm of tooth structure for a ferrule, with 0.5 mm of sulcular space separating them (Figure 5). It has been shown in the literature that one of the most important factors in the predictable restoration of endodontically treated teeth is having a 1.5-mm ferrule.3 The ferrule helps to transfer the occlusal load to the tooth–root complex while minimizing the amount of the load that is transferred to the post core. The location of the ferrule on the tooth is critical. Given the direction of the load on a maxillary anterior tooth, the palatal surface is under tension when the tooth is loaded by the lower incisor. Therefore, it is in this location that the ferrule is most important. Soon-to-be-published research shows that there is no difference in the failure rate of maxillary anterior teeth restored with a ferrule that is present 360° around the tooth compared to teeth restored with the ferrule limited to the palatal and buccal surfaces only, with no ferrule interproximally.4
The last thing that needs to be addressed regarding structure is preparation length. It has been well documented that the use of resin cements can aid in the retention of restorations on teeth with an excessive taper or short clinical crowns.5-7 However, even if resin cements are used, just having a 1.5-mm ferrule is not enough. Although the ferrule is extremely important, it does not provide the restoration with the necessary resistance form. The resistance of a restoration to rotational dislodgement is influenced by the height and taper of the preparation. To provide adequate resistance form, approximately 3 mm of preparation height is recommended (Figure 5). This measurement of the preparation height should be taken interproximally because this area generally has the least preparation height as a result of the interproximal scallop. To provide the necessary preparation height with severely fractured teeth, restoration with a post core often is necessary.
As stated earlier, 4 mm of tooth structure below the level of the fracture needs to be exposed. Two options exist to properly expose traumatic fractures: osseous surgery (crown lengthening) and orthodontic eruption. To decide which treatment option to use, the position of the tissue must be evaluated. If the tissue moving apically would detract from 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, thus detracting from the gingival symmetry. In addition, given the amount of palatal ostectomy that would be required, a significant amount of osseous surgery also would have to be done on the palatal surfaces of the adjacent teeth 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 preferred treatment option 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.8-10 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 also to move coronally. As a result of this movement, the tissue levels will now be more coronal than the adjacent teeth. To correct the aberrant tissue levels, osseous surgery is needed to place the bone and tissue in the ideal position. An alternative method for orthodontic eruption is to supplement the eruption with fiber resection.11 Because the tension on the fiber apparatus 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. Typically, the fibers must be severed circumferentially around the tooth all the way to the osseous crest. Severing the attachment once a week until the tooth has erupted is recommended. Once the eruption has been completed, the tooth still must be retained for approximately 4 to 6 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 both the bone and tissue moved coronally.
Regardless of the method used 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 1:1.12 Although the 1:1 ratio is a good reference, it does not imply that the tooth should be extracted if the ratio is greater than 1:1. We have all seen the lateral incisor that has had significant root resorption after orthodontic treatment. Despite having as little as 3 mm 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 occlusal scheme 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 cementoenamel junction (CEJ) to the apex. The amount of root taper is an important factor because of the emergence profile of the crown any time the root structure has to be exposed and the restorative margin is placed apically. The contours of a crown that emerges from a root significantly narrower than the tooth at the CEJ level must be abrupt. This is especially true when restoring a central incisor because of the larger diameter of the crown. This is similar to the contour changes that must 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 because of the depth of the implant. In the case of a natural tooth, the preparation cannot begin as deep given the level of the gingival attachment. Consequently, the crown requires more abrupt contours, which may ultimately affect the shape and form of the papilla.
The internal anatomy of the root at the level of the anticipated crown margin also is 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 one third on either side being the root structure. This ratio allows enough tooth structure on either side of the canal to allow preparation of the tooth for a full-coverage restoration while still maintaining 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 overprepared will leave little axial wall thickness once the tooth is prepared.
On examination, the fracture of teeth Nos. 7 and 8 ended 4 mm to 5 mm below the tissue on the palatal surface. 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 mm. The existing root length was 14 mm, so if these teeth were erupted 6 mm the resulting length of root remaining in the bone would be 8 mm. In addition, the remaining root form would be fairly tapered. Rather than create compromised teeth or extracting the teeth, it was decided that a combination of orthodontic eruption and osseous surgery would be used. The goal of the orthodontics was to erupt the teeth so that the location of the fracture interproximally was at a restorable level. In doing so, the height of the interproximal bone remained in the same location, thus ensuring a predictable papillary position. The remaining fracture residing on the palatal surface could be exposed with osseous surgery, without detracting from 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 provided the patient with immediate dentition and allowed the orthodontist easy access to position and bond orthodontic brackets. After anesthetizing the palatal tissues, electrosurgery was performed to expose the complete fracture (Figure 6). The canals were prepared and shaped, leaving approximately 6 mm of gutta percha at the apex of each tooth. Smooth plastic impression posts (ParaPost® XP, Coltène/Whaledent®, Inc, Cuyahoga Falls, OH) were placed into the canals and picked up in a final impression to allow the fabrication of definitive post cores in the laboratory. On the model, zirconia posts (Cera- Post, Brasseler USA®, Savannah, GA) were fitted into the canals and the cores were waxed up to their desired shape. The ceramic cores (IPS Empress® Cosmo Ingots, Ivoclar Vivadent®, Inc, Amherst, NY) were fabricated using the lost wax technique. Once the cores were pressed and refitted on the working model, the zirconia was sandblasted with aluminum oxide (110 µm) and the feldspathic porcelain was etched with 4.8% hydrofluoric acid. Clinically, the canals were cleaned and prepared. The post cores were cemented with a self-curing resin cement (Panavia® 21 TC, D Kuraray America, Inc, New York, NY) (Figure 7). Once the preparations were refined, the provisionals were relined (Protemp™ 3 Garant™, 3M ESPE, St. Paul, MN) and cemented with a self-curing resin cement to prevent loosening during the orthodontic eruption (Figure 8). The use of a resin cement maintains the stability of the provisionals even if occlusal adjustment during the eruption process perforates the provisional.
The patient was then referred to the orthodontist to erupt the teeth 3 mm. This much eruption was chosen to bring the fracture up to a restorable level interproximally. Because both teeth needed to be erupted and osseous surgery was already planned to expose the remaining fracture on the palatal surface, conventional orthodontic tooth movement was chosen without severing the fibers. Once the teeth were erupted 3 mm, they were retained in this position for 6 months (Figures 9A and 9B). Osseous surgery was then completed around both teeth to place the bone and tissue in the ideal position. The tissue was allowed to mature for 3 months before the teeth were reprepared and new provisionals were placed (Figure 10). The final preparations were finished with a circumferential chamfer shoulder (Figure 11). The final restorations consisted of two all-ceramic crowns (Procera® All- Ceram, Nobel Biocare™ USA Inc, Yorba Linda, CA). The restorations were tried in and bonded to the prepared teeth with resin cement (Figure 12). The use of the all-ceramic post cores and definitive restorations allowed optimal light transmission.
The management of traumatically fractured teeth raises several important treatment planning considerations. Proper diagnosis of the fracture is critical. 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 long-term predictability.
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