Restoring Congenitally Missing Teeth in the Esthetic Zone

For the dental practice, cases involving con-genitally missing lateral incisors present a complex and challenging set of problems. The treatment options and considerations require a multidisciplinary approach in order to achieve a successful long-term outcome. Among the considerations to be taken into account are the patient's age, the current clinical condition of the dentition, and occlusion.⁵

A 20-year-old male patient presented with congenitally missing maxillary lateral incisors. Prior treatment by a local dentist involved orthodontia to open up the spaces on either side of the maxillary central incisors for implant placement in the lateral incisor sites after completion of the patient's developmental growth.⁵ The patient had worn a prescribed orthodontic retainer that replaced the lateral incisors for many years, after which the dentist had attempted to bond two denture teeth into the edentulous spaces. The patient reported that the pontics had debonded numerous times.

A clinical exam revealed that the dentist had reduced the proximal surfaces of teeth Nos. 6, 8, 9, and 11 in an effort to create better retention (Figure 1). Although a radiograph demonstrated that there was now sufficient space for placement of an implant in each of the edentulous sites (Figure 2), the young age of the patient precluded this approach.⁵ The patient was made aware that implant placement was not advised at this juncture because of possible changes in the ongoing growth and development of his dentition as well as the possibility of the implant restorations requiring replacement at some point in the future.

At the consultation visit, the patient selected the option to receive two all-ceramic fixed partial dentures (FPDs), spanning teeth Nos. 6 through 8 and teeth Nos. 9 through 11, with the understanding that he was not developmentally ready for the implants.

A pretreatment impression scan was taken with a wireless intraoral scanner (TRIOS^®, 3Shape) and uploaded to the in-house laboratory. Then, the dental technician used the pretreatment scan to create a virtual digital smile design of the final expected outcome. The patient approved the on-screen esthetic plan and scheduled his clinical appointments.

At the first clinical appointment, the four abutment teeth were prepared for full-contour all-ceramic crowns (Figure 3). With strength and esthetics being the primary considerations in the choice of restorative material for the two FPDs, the dental team chose to restore using a high-strength oxide ceramic material (IPS e.max^® ZirCAD^® Prime, Ivoclar Vivadent). This material is a next-generation all-ceramic material with a flexural strength of 1,200 MPa that combines 3Y-TZP (ie, high-strength tetragonal zirconia polycrystal) and 5Y-TZP (ie, highly esthetic tetragonal zirconia polycrystal) oxide ceramic powders to achieve both excellent restorative strength and exceptional esthetics.

Following tooth preparation, the soft tissues were retracted, and the preparations were scanned. The scans were uploaded to the laboratory, where the dental technician used the pretreatment digital smile design as a template for both the provisional restorations and the final ceramic restorations. In the smile design software (3Shape Dental System, 3Shape), the technician used the "morph to pre-preparation" tool to superimpose the final virtual smile design onto the scan of the preparations (Figure 4). The provisional restorations were then fabricated and seated.

For fabrication of the final restorations, the B1 shade of the high-strength oxide ceramic material was chosen, and the virtual design patterns of the two FPDs were nested optimally into a single 16 mm disc. After the full-contour highly translucent zirconia frameworks were milled (PrograMill PM7, Ivoclar Vivadent), the completed pre-sintered FPDs were removed (Figure 5) and sintered overnight (Programat^® S1 1600, Ivoclar Vivadent). After sintering (Figure 6), the two FPDs were stained and glazed (IPS Ivocolor, Ivoclar Vivadent).

A 3-dimensionally printed model with removable dies (Straumann^® Centralized Production, Straumann) was ordered and obtained (Figure 7), and the completed FPDs were readied for try-in and cementation (Figure 8).

At the second clinical appointment, the provisional restorations were removed, the preparations were cleaned, and the final restorations were tried in. After the patient approved the esthetics of the final restorations, the preparations were once again cleaned and dried, and the two FPDs were cemented using a self-adhesive self-curing resin cement (SpeedCEM^® Plus, Ivoclar Vivadent) (Figure 9).

Jonathan L. Ferencz, DDS
Diplomate
American Board of Prosthodontics
Fellow
American College of Prosthodontics
Clinical Professor
Department of AdvancedEducation in Prosthodontics
New York University
College of Dentistry
New York City, New York