CASE REPORT
A 14-year-old female patient presented to the University of Pennsylvania Faculty Practice with congenitally missing maxillary lateral incisors. She was nearing completion of a 5-year orthodontic treatment phase that included palatal expansion and she was seeking consultation for subsequent prosthetic treatment of the edentulous lateral incisor areas. Her medical history was unremarkable, and her dental history included orthodontic treatment, routine recall visits, minor operative dentistry, and sealants on permanent molars. A comprehensive examination was conducted, including radiographic (Fig 1) and dental examinations, periodontal probing, and temporomandibular evaluation. Preliminary study casts were mounted in an articulator.
(Fig 1)
Diagnosis and treatment planning
Extraoral findings were normal, and intraoral and radiographic findings revealed no caries lesions. All soft tissues
were normal and healthy. The anterior
teeth had a shade of A3 (VITA Shade
guide, Vident). Mild-to-moderate enamel hypoplasia was noted throughout the
dentition. The maxillary canines had
markedly pointed cusps, and mamelons were present on the mandibular lateral incisors. The patient was unhappy
with both the shade of her teeth and the
mandibular mamelons but did not want
any changes to the characteristic hypoplastic markings, other tooth morphology, or position and angulations of her
natural teeth. The edentulous alveolar
ridges were mildly deficient in the orofacial dimension. Denture teeth were fixed
to the orthodontic archwire to occupy
the missing lateral incisor spaces. The
patient had a Class I skeletal relationship with bilateral Class I molar relationships and canine guidance.
All other findings were normal. The
dentofacial diagnosis was good. Anterior spacing was adequate for restorative
replacement. The periodontal diagnosis
was type I according to American
Academy of Periodontology criteria. The biomechanical diagnosis showed no compromised areas. The functional diagnosis was normal, consistent with the current degree of tooth eruption.
The prognosis for this dentition and
for patient compliance was good. All
treatment options were discussed with
the patient and her parents. Dental implants were not recommended at that
time due to the patient’s incomplete
growth. The treatment goals were as
follows: (1) provide minimally invasive,
prosthetic replacement of the missing
lateral incisors; (2) meet the patient’s
and parents’ esthetic expectations;
and (3) achieve stable occlusion.
The definitive treatment plan included
tooth bleaching and zirconia-based
CRBFPDs, which would allow for implant placement at a later time.
Clinical treatment
The patient returned 3 months later
following the completion of orthodontic treatment. A Hawley-type retainer32
with denture teeth for the edentulous
spaces had already been fabricated.
New diagnostic casts were made
and mounted in an articulator for occlusal analysis, preparation planning,
and framework design. Bleaching
trays were fabricated on a second set
of diagnostic casts. The patient followed an at-home bleaching protocol
(Opalescence PF 10%, Ultradent) and
was advised to bleach one arch at a
time, nightly, for 1 week per arch. Shade
B1 was selected at the postbleaching
follow-up appointment. Figures 2 and
3 show the preoperative situation with
the retainer in place. Due to the occlusal scheme and canine guidance,
the central incisors were selected as
abutment teeth for the single retainers.
Figures 4 and 5 show the preoperative
intraoral situation without the retainer in
place. During the preparation appointment, a 0.6-mm reduction of the lingual
surfaces of the maxillary central incisors was carried out using a tapered
chamfer diamond bur (no. 856-016,
Brasseler). A slight interproximal elbow
preparation was completed to counter
dislodging forces and increase frame
work connector strength. Finally, a small
indentation was placed in the center
of the lingual fossa preparation to facilitate exact three-dimensional seating
of the framework (Fig 6).
( figure 2) (figure 3)
( figure 4) (figure 5)
(figure 6)
Final impressions were made using a vinyl polysiloxane (VPS) putty in a full-arch stock
impression tray and a light-body wash
material syringed onto the prepared
teeth (Aquasil Easy Mix putty, Aquasil
Ultra LV). An opposing cast impression
was also made with VPS putty, and interocclusal records were taken using
Regisil 2X (Dentsply).
Master casts and opposing casts
were fabricated in the dental laboratory, mounted, and scanned. The frameworks were designed on the computer
(Figs 7 and 8) and milled from zirconia
ceramic. A small, extra wing was fabricated on each framework to facilitate
correct placement during try-in (Fig 9).
These wings would later be removed.
The frameworks were designed to provide optimal support for the veneering
porcelain (Fig 10).
( figure 7) (figure 8)
( figure 9 (figure 10)
A try-in visit was scheduled to verify
the path of draw, fit, and margins of the
frameworks. Three-dimensional seating of the wings was confirmed, assisted by the small indentations prepared
in the lingual fossa areas. The final
shade was selected. In the laboratory,
master casts were slightly trimmed in
the edentulous ridge areas to accommodate ovate pontics and optimize the
soft tissue architecture and esthetics.
External layers of feldspathic veneering porcelain were fired onto the frameworks, matching the characteristics of
the adjacent natural teeth (eg, enamel
hypoplasia and stains) (Fig 11). The
definitive restorations can be seen in
Fig 12.
( figure 11) (figure 12)
The definitive CRBFPDs were tried
in to verify the fit, pontic relief, and esthetics. A small lateral incision (approximately 3 mm wide and 1.5 mm deep)
was placed in the alveolar crest area
of the maxillary lateral incisors with an
electrosurgical unit to decrease tension
of the soft tissue and allow for intimate
seating of the ovate pontic. The intaglio surfaces of the frameworks were
then cleaned in an ultrasonic bath with
alcohol. The bonding surfaces of the
retainer wings were airborne-particle
abraded with 30-μm aluminum oxide
particles at a pressure of 1.5 bar for
5 seconds at a distance of 1 cm. Care
was taken to protect the feldspathic
veneering porcelain during this procedure. Next, Clearfil Ceramic Primer
(Kuraray) was applied in a thin layer
(Fig 13) and left to air dry. The adherent
surfaces of the maxillary central incisors
were cleaned with pumice and rinsed.
The area was isolated and prepared for
final cementation with Panavia 21 TC
(Kuraray). For better control, the two
FPDs were bonded independently, one
after the other. The enamel bonding surfaces were acid etched with 40% phosphoric acid (K-Etchant gel, Kuraray) for
30 seconds. After thorough rinsing and
drying, self-etching ED Primer (Kuraray)
was applied and lightly dried. Each
restoration was placed in position, and
excess cement was removed from the
margins with microbrushes. Oxyguard II
(Kuraray) was applied onto the marginal areas and sprayed off after complete
polymerization of the composite resin
luting agent.
(figure 13)
Any excess cement still remaining
was removed with an explorer and a
sharp scaler. Occlusion was confirmed
in maximum intercuspation, protrusion,
and lateral excursions. Proper management of the occlusion of the pontic is crucial for the long-term success
of cantilever prostheses. If eccentric
contact remains on the pontic, the
potential risks include loosening of
the restoration, migration of the abutment, and fracture.33,34
Therefore, all
contacts in protrusive and excursive
movements were removed from the
cantilever. Any adjusted ceramic surfaces were polished (Dialite Polishing
Kit, Brasseler). Mamelons on the mandibular lateral incisors were smoothed
flat using polishing disks (Super Snap,
Shofu). Alginate impressions were
made from each arch, and an occlusal
guard was fabricated for the patient
to wear at night. All esthetic and functional parameters were verified during
the subsequent follow-up visits, which
were initially scheduled at 1 week,
4 weeks, 8 weeks, and 6 months and
then at 6-month intervals thereafter.
CONCLUSIONS
Zirconia-based cantilever resin-bonded
fixed partial dentures provide a viable
treatment option for missing lateral incisors in select cases. These restorations
are cost effective and require few treatment steps. Specific design and clinical handling protocols must be followed
to achieve long-term clinical success.
Further clinical trials are necessary to
confirm the already promising results
of these restorations.
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