Treating the Congenitally Deficient Smile

Congenitally missing teeth are quite common in the adult population, being found on average in about 6.5% of individuals and with little to no change in those statistics over the past century.¹ Furthermore, there is a strong association between having congenitally missing maxillary lateral incisor teeth and palatally impacted maxillary canine teeth.² This article presents a case where a patient had just such conditions and how the author was able to achieve the patient’s desired aesthetic outcome.

CASE REPORT
A 24-year-old female presented with dissatisfaction with her smile due to contour, proportion, and shade discrepancies. She was periodontally and occlusally stable, except for posterior group function in lateral excursions due to the shorter primary canine teeth. There were several composite restorations in her posterior teeth, and her anterior teeth were unrestored. She presented with no active decay, and her medical history was unremarkable.

She was diagnosed with congenitally missing upper laterals and palatally impacted upper canine teeth at age 11. She then underwent orthodontic treatment, wherein her canines were exposed and brought down into the position of the laterals, and the primary canines were left in place (Figure 1). This may have been due, in part, to the fact that retained maxillary primary canine teeth, in the presence of palatally impacted maxillary permanent canine teeth, are among the least resorbed and longest lasting of the retained primary dentition when their adult counterparts are present and impacted.3 Since that time, one of her retained primary canine teeth had become somewhat discolored. Of course, the retained primary canines had always been disproportionately smaller than the rest of her remaining upper anterior dentition. Coupled with the fact that the contours of the patient’s permanent canines (that had been moved into the lateral incisor positions) looked out of place to her, these circumstances made her increasingly dissatisfied with her smile as she matured into adulthood (Figure 2).

Figure 1. A preoperative radiograph of the patient showing the retained primary canines in place and the adult canines in the lateral incisor positions.	Figure 2. The patient’s initial clinical presentation with the same conditions.
Figure 3. The patient one week after placement of implants at the upper canine positions and insertion of their provisional crowns. Note the convexities present at the incisal aspects of the central incisors.	Figure 4. The patient’s pre-impression presentation with the maxillary canine teeth at the lateral incisor positions after preparation for the lateral-incisor-shaped restorations and after enameloplasty on the incisal aspects of the central incisor teeth.
Figure 5. The final impression of the canine implant abutments and the prepared canines occupying the lateral incisor positions.	Figure 6. The patient with her definitive restorations in place 2 days after insertion.
Figure 7. A close-up radiographic view of the patient’s No. 6 implant at 13 months after placement and provisionalization. Note the bone growth over the shoulder of the implant approaching the abutment.	Figure 8. Another close-up radiographic view, this time of the patient’s No. 11 implant, at 13 months after placement and provisionalization. Note the similar bone growth over the shoulder of the implant approaching the abutment.
Figure 9. The patient’s retracted clinical presentation 8 months after insertion of the definitive Captek (Argen) crowns.	Figure 10. The patient’s full smile at 8 months after insertion of the definitive Captek crowns.

With these issues in mind, and after a comprehensive examination had been performed, it was determined that there was no viable treatment for the retained upper primary canines that would address her aesthetic reservations other than their removal and replacement. For this reason, the patient was referred to a dental implant surgeon for a consultation and to develop a comprehensive treatment plan in collaboration with the restorative dentist. The resulting plan included the extraction of the retained primary canines with the placement of implants in those positions. Upon being informed about this phase of treatment, the patient stated that she would not accept removable temporization. Furthermore, she would not accept fixed temporization that was invasive to her virgin distally proximal teeth.⁴ Given these constraints, immediate placement was planned by using the immediate smile protocol,⁵ in which CAT scans (Green CT 2 [Vatech America]) of the patient and clinical records would be integrated using proprietary software (Simplant [Dentsply Sirona Implants]) to generate a stereolithography (STL) file by the dental laboratory team. This file would be used for the CAD/CAM fabrication of the surgical stent needed for accurate implant placement and for the abutments (Atlantis [DentsplySirona Implants]) that would support both the provisional crowns (Radica [Dentsply Sirona Implants]) and the definitive crowns. It is better to go directly to the definitive abutments in cases like these and not employ provisional ones as multiple insertions and removals of implant abutments and crowns (both provisional and definitive) have a deleterious effect on peri-implant soft tissues.⁶

The patient exhibited a discrepancy in bone levels and gingival margin heights between the 2 retained primary canines; however, it was not excessive and did not concern the patient since she did not have a high smile line. There can be uncertainty (even with some Morse taper systems) in regard to facial bone levels over time when immediate implant placement protocols are utilized, especially when concurrently restored with provisional restorations.⁷ Such uncertainty is largely the result of 2 factors; variable healing patterns between different patients and implant sites as well as micro-movement at the implant/abutment interface. This is especially an area of concern seen with internal hex connection systems⁸ and can result in bacterial infestation and colonization of that interface. Due to this, bacterial toxins can be pumped out from such an interface onto the peri-implant bone and trigger the occurrence of osseous defects around the implant. Because of these considerations, the Ankylos implant system (Dentsply Sirona Implants) was chosen. Its well documented hard- and soft-tissue preservation (and even growth) qualities⁹ as the abutment/implant interface of the Ankylos system is considered to be hermetically sealed.10 Thus, no hard or soft tissue augmentation was deemed necessary for this case.

The remainder of the treatment plan included vital tooth lightening before any invasive treatment, crowning the adult canine teeth that were occupying the lateral incisor positions to make them appear as if they were lateral incisors and minimal enameloplasties on the incisal aspects of the central incisors to correct the convexities that existed there. No other treatment beyond continuing routine preventive and diagnostic care was required at that time.

After the CAD/CAM surgical and restorative components were received from the dental lab team as described above, the patient was appointed for the implant placement visit. Atraumatic tooth removal is critical to preservation of the peri-implant hard and soft tissues with immediate implant placement and provisionalization,¹¹ which was achieved in this case by the surgical dentist. The implants were then placed using the CAD/CAM-fabricated surgical stent from the dental laboratory before their abutments were torqued into position. Next, the provisional crowns were luted to place using cementation dies fabricated by the dental lab team by which all excess provisional cement was extruded from these units prior to their insertion¹² (Figure 3).

Just under 4 months later, osseointegration was confirmed by the surgical dentist so that the definitive restorative treatment could then proceed. At her ensuing visit with the restorative dentist, the aforementioned enameloplasties were completed on the central incisors. Then the adult canine teeth in the lateral incisor positions were prepared for full-coverage restorations, and an impression (EXAMIX [GC America]) was taken that also included the implant abutments at the canine positions according to the alternative method for restoring single tooth implants¹³ (Figures 4 and 5).

At the following visit, after the 4 crowns (Captek [Argen]) were returned from the dental laboratory, the restorations were luted into place (RelyX Unicem [3M]), again using the cementation die technique for all 4 definitive restorations (Figure 6). Captek was chosen as the indirect restorative material in this case for 2 reasons: it displays better aesthetics over many other porcelain-fused-to-metal restorations on the market,¹⁴ and it can rival even all-ceramic options in terms of gingival aesthetics.¹⁵ Also, it possesses excellent occlusal qualities when used to restore implants.^16,17 Canine guidance on the distal aspects of the crowns and the mesial aspect of the first premolars was also established as this is the preferred scheme when implants are in the upper canine positions.¹⁸

Although the patient had relocated 4 hours away shortly after treatment was completed because of a job change, she did return for a family visit during the holidays. At that time, it had been 13 months since the implants had been placed and provisionally restored, and it had been 8 months since the definitive restoration of the implants and canine teeth in the lateral incisor positions were inserted. Close-up radiographs of the implant/abutment interface taken then show bone growth over the shoulders of both implants approaching their respective abutments (Figures 7 and 8). This is in contrast with other implant systems that do not have a subcrestal placement protocol or conical (true Morse taper) connection.¹⁹ Bone loss down to the first thread with these other systems (often euphemistically termed “remodeling”) has been the norm in this author’s experience due to their less stable implant/abutment interfaces and has led him to term them as members of “The First Thread Club.” These properties were also evidenced in the clinical result (Figures 9 and 10).

CLOSING COMMENTS
This case report article demonstrates the complexities associated with treating a mixed dentition in the adult aesthetic zone. Challenges of shade, relative dimension, and tooth anatomy must be resolved to create a harmonious totality that not only satisfies the aesthetic and procedural expectations of the patient, but also serves functionality. Factors required to achieve the desired results include a competent diagnosis, an appropriate and thorough treatment plan, and then the conscientious implementation of that treatment plan with the proper selection of an armamentarium necessary to accomplish the intended outcome. When all these factors are addressed systematically, an end result can be realized that not only pleases the patient, but also gratifies the doctor.

Acknowledgment:
The author wishes to thank Dr. James Spivey of Portsmouth, NH, for his expertise in surgical dental implantology and dental photography; Dr. Gregory Penney of Jericho, Vt, for his expertise in dental photography with some of the follow-up images in this case; and the team at Arrowhead Dental Laboratory in Sandy, Utah, for the excellent work in the completion of this case.

References

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16. Escalante Vasquez R. Management of occlusion over implants, part I. Three 10-year case follow-ups and evaluations. Dent Today. 2013;32:106-111.
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19. Huang B, Meng H, Zhu W, et al. Influence of placement depth on bone remodeling around tapered internal connection implants: a histologic study in dogs. Clin Oral Implants Res. 2015;26:942-949.

Dr. McArdle graduated from Tufts University School of Dental Medicine in 1985 and has been practicing general dentistry on the New Hampshire seacoast ever since. He is an alumnus of The Pankey Institute for Advanced Dental Education and on the board of directors of Priority Dental Health, the New Hampshire Dental Society’s direct reimbursement entity. He is a cofounder of the Seacoast Esthetic Dentistry Association (dentalesthetics.com), and founder of Seacoast Dental Seminars (seacoastdentalseminars.com), both headquartered in Portsmouth, NH. He has authored numerous other articles internationally in major peer-reviewed publications. He can be reached at (603) 430-1010, via e-mail at dr.mcardle@seacoastdentalseminars.com, or at the website mcardledmd.com.

Disclosure: Dr. McArdle has received compensation from Dentsply Sirona Implants for past continuing education courses and several lectures.

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