Vital Primary Canine Teeth Used for Socket-Shielded Dental Implants With 5- and 6-Year Follow-up

Socket-shielded dental implants for permanent teeth have been shown to be a successful treatment option for replacing a missing tooth and preserving adjacent buccal soft- and hard-tissue contours.^1,2 This case report proposes that this same treatment and result is possible for deciduous primary canine teeth, and because of angulation of the primary teeth the pulp can remain intact and vital.

In 2006, Siormpas et al were reportedly the first to intentionally leave a tooth root fragment adjacent to a dental implant.¹ Their theory was that this residual root fragment could resist the usual tissue resorption. Their belief was that the dental implant could integrate in the healing bone. A space was left between the implant and the root fragment. This space was observed to fill with healthy bone. The authors named this procedure the "root membrane" technique.

Hürzeler et al in 2010 described a similar technique, which they named "socket shield."² They published a proof-of-principle paper at the time, which showed histology of the technique from a beagle dog. Gluckman et al reported on 128 socket-shield cases with up to 4 years follow-up.³ Their group and others have refined the socket-shield technique for permanent teeth. Siormpas et al have shown 10-year results for the root membrane technique.¹

The present case (Figure 1 through Figure 23) demonstrates that a similar result is possible for retained primary teeth and also that pulpal tissue can remain vital.

In this case report two primary maxillary canines were prepared to act as socket shields for two immediate dental implants. Because of the vertical orientation of the primary canines, space for the implants could be created palatal to the primary teeth without removing the pulpal tissue or palatal portion of the canine root.

The patient was a 60-year-old Caucasian woman who presented for dental treatment for two retained maxillary canines. These canines demonstrated +1 to +2 of 4 mobility and had been composite bonded for esthetic reasons in the past. It was decided to prepare these teeth as socket shields for immediate dental implants and provisional crowns. Each canine was treated at separate appointments a year apart.

The patient was prepared for surgery with intravenous sedation and local anesthesia. The primary tooth was decoronated with dental burs. The remaining tooth crown at bone level was then sectioned mesio-distally with carbide #557 25 mm high-speed surgical burs to create room for the immediate dental implant. The residual root was contoured to approximately 1.5 mm in thickness near the facial gingivae. The shape was "C-shaped" when viewed occlusally, extending to the mesial and distal line angles. It was observed that the residual pulpal root canal tissue was vital. This vital tissue was left intact and not removed.

The implant socket was then prepared using sequentially sized implant burs. Care was taken not to contact the residual tooth fragment to avoid displacing the root fragment. A 3.4 mm x 12 mm implant was placed below the socket-shield preparation shoulder margin. The implant was torqued to 50 Ncm. The resultant space between the socket shield and implant was grafted with a mixture of MinerOss^® (BioHorizons, biohorizons.com) and saline. A stock abutment was placed on the dental implant and later prepared for full coverage. Healing was uneventful for both canines. A crown was fabricated and cemented with glass-ionomer cement (GC Fuji Plus^®, GC America, gcamerica.com). These procedures were repeated with similar results one year later for the contralateral tooth.

The now restored socket-shielded dental implants are, at the time of this writing, 5 and 6 years postoperative. Both implant-crowns show no mobility, no inflammation, acceptable esthetics, minimal changes in tissue contours, and unremarkable radiographic changes.

Deciduous teeth may be retained to adulthood due to congenital absence or impaction of secondary permanent teeth. Often the retained primary tooth becomes resorbed and is exfoliated. However, in some cases the primary tooth has minimal or no mobility but is still otherwise in good health. Also, these teeth may have insufficient root and crown size to provide long-term function and esthetics.⁴ It is proposed that a socket-shielded implant and crown can satisfy these needs.

An important consideration is treatment of the pulp and canal of the retained primary tooth. In the present case, the primary canines were quite vertical as seen in CBCT cross-section, whereby the volume of alveolar bone has a long axis at a more palatal angle. Thus, as compared to a permanent tooth, less tooth root needs to be removed to allow space for the implant. In this case the residual pulp tissue was vital and not removed. If it had been found necrotic, it would have been extirpated and the canal filled, or the palatal portion of the root and canal tissue would have been removed. It could certainly be argued that the pulp, although vital, should have been removed and the canal endodontically filled while access was available, thus avoiding possible necrosis, infection, and difficult treatment at a later date.

A stock abutment was used for each implant, and a cement-retained crown was used for each abutment. When possible the author prefers a screw-retained crown and abutment. The soft-tissue emergence profile can thus be formed with a custom abutment (eg, Cervico System, VP Innovato Holdings, Innovatoholdings.com) eliminating the need for cement.

An implant in the canine position is probably better suited to withstand canine disclusion than a mobile primary tooth. This procedure needs to be validated by other clinicians.

Two deciduous canine teeth were prepared as socket shields for immediate dental implants. Their pulp tissue remained vital. After healing, the implants were restored with stock abutments and cement-retained crowns. The two canine procedures were done approximately 1 year apart. The most recent photographs and radiographs show results at 4-1/2 and 5-1/2 years postoperative.

The presented case demonstrates that primary tooth roots can provide socket shielding for dental implants similar to permanent teeth roots. Also, it was demonstrated that residual pulp tissue can remain vital.

To view a brief video synopsis, click here: https://we.tl/t-E5RPhrXs3Y.

This case report was self-funded. The author declares no conflict of interest. The author performed both surgical and restorative phases of this case.

Paul S. Kozy, DDS
Private Practice in Implant, Surgical, and Restorative Dentistry, Toledo, Ohio; Former Chief-of- Staff, St. Vincent Hospital, Toledo, Ohio

1. Siormpas KD, Mitsias ME, Kotsakis GA, et al. The root membrane technique: a retrospective clinical study with up to 10 years of follow-up. Implant Dent. 2018;27(5):564-574.

2. Hürzeler MB, Zuhr O, Schupbach P, et al. The socket-shield technique: a proof-of-principle report. J Clin Periodontol. 2010;37(9):855-862.

3. Gluckman H, Salama M, Du Toit J. A retrospective evaluation of 128 socket-shield cases in the esthetic zone and posterior sites: partial extraction therapy with up to 4 years follow-up. Clin Implant Dent Relat Res. 2018;20(2):122-129.

4. Aktan AM, Kara I, Sener I, et al. An evaluation of factors associated with persistent primary teeth. Eur J Orthod. 2012;34(2):208-212.