Improve Restorability With Orthodontic Extrusion

Dental practitioners are often faced with decisions regarding teeth with coronal fractures or teeth with deep carious, subgingival lesions. While implants are quite successful, teeth with coronal fractures are often deemed unrestorable. However, steps may be taken to improve their restorability, thus saving a tooth.

Orthodontic extrusion helps to enhance the restorability of a tooth. Higher intensity orthodontic forces will move teeth rapidly away from the bone, leaving the original soft tissue margins in place. This rapid extrusion can increase the amount of healthy coronal tooth structure capable of supporting fixed restoration without causing changes in the soft tissue profile.¹ This will assist teeth with caries or fracture to develop adequate structure to improve their ability to support a long-term fixed restoration.

Another important factor is the development of adequate tooth structure around the gingival portion of the tooth. Most fractured teeth require root canal treatment, which makes them more susceptible to fracture. Adequate tooth structure is developed in an extruded tooth such that there is more retention and resistance form, which, in turn, helps to retain the crown and prevent potential fracture.^2,3

Another option is periodontal crown lengthening. Surgical removal of crestal alveolar bone and reposition of attached gingival tissue can expose more healthy tooth structure, increasing support for fixed restoration.⁴ Conversely, selective crown surgical lengthening in the anterior esthetic zone can result in uneven gingival margins, unequal crown lengths, and unacceptable esthetic outcome.⁵ In many cases, rapid orthodontic extrusion will provide the most predictable and positive results for retention of various fixed or removable prostheses.⁶

The first step of orthodontic extrusion is to restore the fractured or decayed tooth with a post-and-core restoration because adequate tooth structure is needed to bond composite and the nickel–titanium (NiTi) wire to allow for adequate movement. Additionally, proper interproximal contacts should be maintained to stabilize the extrusion movement of the tooth (Figure 1).

Following completion of the buildup, trim a NiTi .018 x .018 square orthodontic arch wire to cover the tooth to be extruded, and two teeth posterior that will serve as anchorage teeth. Next, etch and bond the anchorage teeth that will be attached to the NiTi wire. Composite buttons are then placed on the facial surfaces of the anchorage teeth, and the wire is placed in the composite. Choose a composite color that resembles the patient’s natural tooth coloring. Add more composite to secure and stabilize NiTi wire. Check the cure of the composite by tugging on the NiTi wire. Then, etch, place adhesive, and add a composite button to the tooth to be extruded. Bend the wire into an apical position relative to the composite button (Figure 2). The composite is cured, avoiding getting any composite on the NiTi wire (Figure 3). The wire should be able to be moved from its resting gingival position, allowing rapid orthodontic movement to occur (Figures 4 and 5).

After the NiTi wire is in the desired location, anesthetize and perform a circumferential supracrestal fiberotomy. We performed it with a sterilized and sharp half-Hollenback. This step ensures all supracrestal periodontal ligament fibers have been severed (Figures 6 and 7). The fiberotomy will separate the gingival fibers of the tooth, preventing relapse and the gingival and alveolar bone from moving with the tooth. A crucial finishing and polishing step is to take the extruded tooth out of occlusion. Ensure 1 to 1.5 mm of clearance in all movements. If the tooth is not taken out of occlusion, movement may be hindered. The edges of the NiTi wire should be polished so they do not irritate the patient’s mucosa. The composite buttons placed on the three teeth should also be polished to avoid irritation.

When the patient returns after 2 weeks, an additional circumferential supracrestal fiberotomy and a potential reactivation of the wire is completed. Repeat the same finishing steps with the wire, composite, and occlusion. The patient returns in 2 weeks and the extrusion extent is measured. If the desired amount of extrusion has been achieved, take a post-operative radiograph, release the flex in the NiTi wire, and stabilize the wire with more composite on the extruded tooth (Figures 8 to 10). Perform one final supracrestal fiberotomy to allow for tissue maturation and adaptation of new tooth position. Allow 6 to 8 weeks for stabilization. Once stabilized, the tooth is ready for full-coverage crown preparation (Figure 11). Table 1 provides a summary of this technique.

Discussion

Rapid orthodontic extrusion of 3 mm can be achieved within 3 weeks.⁴ Relapse of 0.5 mm and minimal resorption suggest that extrusion is a solid technique to improve restorability of teeth.⁴ Rapid extrusions are accomplished with forces higher than 50 g. Some clinicians recommend that extrusion force for adults must be between 25 and 30 g to prevent pulpal damage.⁷ Others consider a range of 50 to 75 g force as optimal.⁸

When stronger traction forces are exerted, coronal migration of the tissue supporting the tooth is less pronounced because the rapid movement exceeds their capacity for physiologic adaptation.¹ The force is so great that periodontal fibers are torn; in areas where fibers are still intact, a limited amount of osteoid forms.⁵ For the most part, this process moves the crown away from bone.⁶ In some cases, a fiberotomy also may be performed along with each increment of rapid extrusion to sever any remaining fibers attached to the crestal bone, eliminating any osteoid deposition in that area.^9,10 A fiberotomy would minimize the need for gingival recontouring.

The decision to restore or extract a tooth and replace it with a fixed prosthesis or implant can be daunting.^11,12 The extrusion technique presented here does not require the use of orthodontic bands or brackets^13,14 because the composite resin buttons achieve similar clinical outcome yet simplify armamentarium for the clinician.¹⁵ Rapid orthodontic extrusion is a helpful adjunctive therapy to improve restorability of teeth.¹

Acknowledgments

The authors thank Jeffrey P. Miles, DDS, for the illustrations and Sara Greene, DDS; Renee Greene, MS, DDS; and Marina Kosturos, DDS, MSD, for their contributions to this paper.

References

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From Decisions in Dentistry.November/December 2023; 9(10):8-10