Download Orthodontic treatment with canines substitution for lateral incisors

Orthodontic treatment with canines substitution for lateral
incisors ── cases report
CHIN-YIN LIN 1 YA-HUI YANG 1,2 I CHEN 2
SANG-HENG KOK 1,3 YI-JANE CHEN 1,4 EDDIE LAI 1
CHI-YING HUANG 1
CHUNG-CHEN JANE YAO 1,4
1
Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan, ROC.
Graduate Institute of Dental Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
3
Department of Oral-maxillofacial Surgery, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
4
Department of Orthodontics, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
2
Treatment options for patients with missing maxillary lateral incisors include space closure (using
canine substitution) and space reopening (for a single tooth implant or a traditional bridge). Although
canine substitution seems to be an ideal approach for replacing missing lateral incisors without a future
prosthesis, case selection and the procedures to improve the esthetic appearance should be seriously
considered. The purpose of this article is to describe the treatment plan and treatment results of 2 cases
in which canines were protracted to mimic missing maxillary lateral incisors, and also to address the
guidelines for this camouflage approach. （J Dent Sci, 1(2):79-87, 2006）
Key words: peg lateral, canine substitution, orthodontic treatment.
Patients with a missing maxillary lateral incisor are
often encountered in orthodontic clinics. Regardless of
whether the incisor is congenitally missing or lost
because of a pathologic condition or accident, this
complicates treatment. Treatment options for patients
with a missing lateral incisor include space closure (a
canine protracted to the position of the lateral incisor
and shaped as the missing incisor) and space reopening
(a pontic space provided for a single tooth implant or
traditional bridge).
In a historical review, Angle1, Wheeler2, Dewel3,
and Strange1 all contended that the proper treatment
method for a missing lateral incisor was space
reopening because space closure would lead to improper
occlusion and a poor facial expression. But in recent
studies, emphasis has been placed on canine substitution
for missing maxillary laterals and premolar protraction to
Received: February 4, 2006
Accepted: April 4, 2006
Reprint requests to:Dr. Chin-Yin Lin, Department of Dentistry, National
Taiwan University Hospital, No. 1, Chang-Te Street,
Taipei, Taiwan 10048, ROC.
J Dent Sci 2006‧Vol 1‧No 2
the area of canine eminence to obtain a better contour
of the face without a prosthesis. Few losses of occlusion
were mentioned. Carloson4 and Turverson5 both
described the canine contouring method to improve the
appearance of the substitution.
The ideal treatment should be the least invasive
possible and one which meets the individual’s esthetic
and functional expectations. Although space closure
(canine substitution) seems to be an ideal approach,
other factors such as malocclusion, a patient’s profile,
and the shape and color of the canine should also be
considered for individual cases6.
There are also several options for orthodontic
treatment for patients with maxillary peg lateral incisors
ranging from extraction and space closure to
maintaining space and restoring the microdontic teeth
to a normal mesiodistal width. For patients with
indications for premolar extraction, 1 alternative is to
extract a peg lateral incisor instead of a premolar
followed by canine substitution.
The cases particularly suited for canine substitution
would be Angle class II malocclusions with no
crowding in the mandibular arch or class I spacedeficiency cases. Generally, patients with a straight
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C.Y. Lin, Y.H. Yang, I. Chen, et al.
profile are good candidates, but those with a mildly
convex profile may also be acceptable. The ideal canine
to use to substitute for a lateral incisor is one with a
similar color and shading as the central incisor, with
smaller dimensions both at the cementoenamel junction
(CEJ) buccolingually and mesiodistally, and with a
relatively flat labial surface and narrow midcrown width
buccolingually6,7.
CASE PRESENTATION
Case 1
This patient was a 14-year-old girl whose upper
right central incisor was impacted and had been treated
orthodontically (surgical exposure and traction to pull it
toward the line of the arch) in a local clinic. She asked
for further orthodontic treatment to correct the upper
midline deviation and interdental spacing due to a
missing upper right lateral incisor. The upper right
canine had erupted into the missing lateral incisor’s
position, resulting in a class II malocclusion on the right
side. The patient had a straight to convex profile, and no
crowding in the mandibular arch was noted (Figures 1,
2).
To correct the deviated upper dental midline and
bilateral class II canine relationship, the treatment plan
was to extract #22 and close the space of lateral incisors
(#12 and #22). Enamel-plasty was performed to shape
#13 and #14 for replacement of #12 and #13, and #23
and #24 for replacement of #22 and #23.
Results achieved. An intentional class II molar
relationship with space closure of the upper anterior
teeth, and improvement of esthetics were achieved
(Figures 3-5). Although the root axis of #23 did not
reach the ideal axis of the lateral incisor, the amount of
enamel-plasty was reduced by this compromise because
its slant on the distal side was greater than usual. Resin
additions to the canines to create “corners” would
possibly have enhanced the illusion of incisor teeth.
However, this patient refused to receive restorations
because she was completely satisfied with their
appearance.
The total treatment time was 3 years and 6 months.
Figure 1. Case 1 pretreatment photographs. The upper right lateral incisor was congenitally missing.
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Canine substitution for lateral incisors
SNA
88°
SNB
77°
ANB
5°
A-Nv
-2.5mm
Pg-Nv
-15mm
NAP
5°
SN-FH
6°
SN-OP
14°
SN-MP
33°
U1-SN
111°
U1-L1
108°
L1-OP
55°
L1-MP
105°
U1-NP
13mm
Figure 2. Case 1 pretreatment lateral cephalometric, panoramic radiograph, and cephalometric analyses.
Case 2
This patient was a 23-year-old male with
subtle manifestation of hemifacial microsomia and
mandibular deviation to the right side. A dental class
I malocclusion was noted with an anterior crossbite
and generalized spacing of the upper and lower
anteriors. The upper left lateral incisor was
congenitally missing, while the right lateral incisor
was a peg-lateral (Figures 6, 7).
The treatment plan was to restore #12 to a normal
size, contour #23 to resemble a lateral incisor, and close
Figure 3. Case 1 photographs taken during treatment.
J Dent Sci 2006‧Vol 1‧No 2
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C.Y. Lin, Y.H. Yang, I. Chen, et al.
Figure 4. Case 1 post-treatment photographs.
SNA
81°
SNB
76°
ANB
5°
A-Nv
-3.5mm
Pg-Nv
-17.5mm
NAP
13°
SN-FH
6°
SN-OP
17°
SN-MP
35°
U1-SN
109°
U1-L1
115°
L1-OP
59°
L1-MP
104°
U1-NP
12.55mm
Figure 5. Case 1 post-treatment lateral cephalometric, panoramic radiograph, and cephalometric analyses.
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Canine substitution for lateral incisors
Figure 6. Case 2 pretreatment photographs. The upper left lateral incisor was congenitally missing, and the right lateral
incisor was a peg-lateral.
the excessive space on the upper and lower arches.
Since the patient already had spacing, extraction of #12
would have created additional space which would have
had to be closed at the pre-surgical phase and which
would have led to a longer treatment time. Two-jaw
orthognathic surgery (with a LeFort 1 osteotomy in the
maxilla and intraoral vertical ramus osteotomy and
genioplasty in the mandible) was then arranged to
correct the facial asymmetry and the canted occlusal plane.
Results achieved. An efficient and functioning
occlusion with an asymmetrical molar relationship was
established since the molar relationship on the right side
was class I and on the left side was class II. Closure of
the space of the anterior teeth, although surprisingly
difficult and time-consuming, was completed, and the
facial appearance was improved (Figures 8-10).
The total treatment time was 4 years and 2 months.
DISCUSSION
Canine substitution can be a good treatment
J Dent Sci 2006‧Vol 1‧No 2
alternative for patients whose canines have a reasonable
shape to allow for recontouring and a favorable color to
match the maxillary central incisors. Space closure and
subsequent canine substitution eliminate the need for
buildup restorations on the lateral incisors.
In most canine substitution cases, the canine is
much larger than the lateral incisor. Because of the
wider crown and the more-convex labial surface, a
significant amount of reduction is often required to
achieve acceptable esthetics and a stable occlusion.
Naturally, the canine can be either one or two shades
darker than the central incisor. Therefore, in order to
correct the color difference, canine bleaching or veneer
fabrication may be indicated.
The gingival margin of the natural canine is
slightly incisal to the gingival margin of the central
incisor which helps to camouflage the canine. However,
to properly position the gingival margin, sometimes
minor surgery (e.g., a gingivectomy) may need to be
performed.
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C.Y. Lin, Y.H. Yang, I. Chen, et al.
SNA
89°
SNB
89°
ANB
0°
A-Nv
3mm
Pg-Nv
3mm
NAP
2°
SN-FN
2°
SN-OP
11°
SN-MP
35°
U1-SN
129°
U1-L1
99°
L1-OP
57°
L1-MP
100°
U1-NP
15°
FCA
12°
UL-N’Pg’
8mm
LL-N’Pg’
11mm
Figure 7. Case 2 pretreatment lateral and posterior-anterior cephalometric, panoramic radiograph, and cephalometric
analyses.
Figure 8. Case 2 photographs taken during treatment. #12 had already been restored to a normal size.
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Canine substitution for lateral incisors
Figure 9. Case 2 post-treatment photographs.
Canine contouring
procedures adopted from
5
Tuverson
1. The tip of the canine is flattened to produce an incisal
edge (Figure 11A, a).
2. Mesial and distal reduction, as indicated by the
diagnostic setup, is accomplished mostly at the
expense of the more-bell-shaped distal surface
(Figure 11A, b).
3. The distal incisal angle is slightly rounded to simulate
that of a lateral incisor (Figure 11A, c).
4. The canine eminence of the labial surface is then
reduced (Figure 11B, a) to create a flatter, moreincisor-like appearance. Extreme care should be
exercised in this reduction. The canines have a
slightly darker shade than the central incisors, and too
much labial reduction may result in a darkerappearing tooth.
5. The lingual surface is reduced at the incisal area to
permit an adequate overbite and overjet to be
established (Figure 11B, b).
The canine-contouring procedure is accomplished
without local anesthesia, as sensitivity is a useful
J Dent Sci 2006‧Vol 1‧No 2
indicator of the amount of enamel reduction. For enamel
protection, topical fluoride is applied to the tooth
immediately following the contouring procedure5.
5-7
Bracket placement and arch wire manipulation
1. The brackets on the canines should be placed at a
distance from the gingival margin that will cause these
teeth to erupt into the appropriate lateral incisor
vertical position.
2. A mesial arch wire outset is necessary to obtain a
proper contact point between the canine and the
central incisor.
3. Most canines need marked lingual root torque to look
like lateral incisors and to reduce the root eminence.
Typical canine offset bends are placed in the first
premolar area to enable these premolars to simulate
canines. Buccal root torque is also incorporated to
produce root eminence.
Orthodontic space closure in unilateral incisor
agenesis can produce problems of matching size, shape,
or color, or with midline control. The canine replacing
the missing lateral incisor might not be in esthetic
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C.Y. Lin, Y.H. Yang, I. Chen, et al.
SNA
91°
SNB
88°
ANB
3°
A-Nv
7mm
Pg-Nv
6mm
NAP
7°
SN-FH
2°
SN-OP
16°
SN-MP
30°
U1-SN
111°
U1-L1
118°
L1-OP
66°
L1-MP
91°
U1-NP
12°
FCA
14°
UL-N’Pg’
2mm
LL-N’Pg’
2mm
Figure 10. Case 2 post-treatment lateral cephalometric, panoramic radiograph, and cephalometric analyses.
Figure 11. Canine contouring procedures adopted from Tuverson, 19705. (A) a, Tip of the canine flattened to produce an incisal edge. b,
Mesial and distal reduction. Note the greater reduction at the more-bell-shaped distal surface. c, The distal incisal angle is slightly rounded.
(B) a, Canine eminence on the labial surface is reduced. b, The lingual surface is reduced in the incisal area.
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Canine substitution for lateral incisors
harmony with the existing lateral incisor. Extraction of
the existing lateral incisor has been advised for
symmetry8.
Both cases reported in this article were unilateral
incisor agenesis, but different treatment plans were
adapted. The existing lateral incisor in case 1 was
extracted and that in case 2 was preserved. In case 1, no
excessive spacing existed in the upper arch, and the
gingival line of #23 was slightly incisal to the gingival
margin of the central incisor (Figure 1). It might have
been easier to have corrected the upper midline with the
extraction space and to have camouflaged the canine
without further gingival surgery, which led to extraction
of #22. However, in case 2, since the patient already had
spacing, extraction of #12 would have created more
space which then would have had to be closed in the
pre-surgical phase leading to a longer treatment time,
which later was verified due to the difficulty of closing
the existing space during treatment. Furthermore, the
gingival line of #13 was slightly gingival to the gingival
margin of the central incisor (Figure 6). Therefore, #12
was preserved in case 2, and more enamel contouring
was required to level the gingival line for better
esthetics.
In the final results of these 2 cases, the gingival
line of the upper anterior teeth was harmonious.
Although #13 and #23 were darker than #11 and #21,
case 1 showed a better symmetrical and esthetic
appearance. In case 2, the size and shape of #23 were
harmonious with #12, but the color difference was more
obvious.
J Dent Sci 2006‧Vol 1‧No 2
CONCLUSION
Case selection is important when considering
canine substitution in cases with a missing lateral incisor.
Also, proper treatment planning is necessary to obtain
better esthetic and functional results. These guidelines
are provided to help orthodontists with this camouflage
approach.
REFERENCES
1. Senty EL. The maxillary cuspid and missing lateral incisors:
esthetics and occlusion. Angle Orthod, 46: 365-371, 1976.
2. Wheeler RC. The permanent canines, maxillary and
mandibular. In “Wheeler’s Dental Anatomy, Physiology, and
Occlusion” 6th ed, WB Saunders Co, Philadelphia, pp. 154174, 1984.
3. Dewel BF. The upper canine: its development and impaction.
Read before the Chicago Association of Orthodontics,
November, 1947.
4. Carlson H. Suggested treatment for missing lateral incisors.
Angle Orthod, 22: 205-216, 1952.
5. Tuverson DL. Orthodontic treatment using canines in place of
missing maxillary lateral incisors. Am J Orthod, 58(2):
109-127, 1970.
6. Kokich VO, Jr., Kinzer GA. Managing congenitally missing
lateral incisors. Part I: Canine substitution. J Esthet Restor
Dent, 17(1): 5-10, 2005.
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space closure in patients with missing maxillary lateral
incisors. J Clin Orthod, 35(4): 221-234, 2001.
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Am Dent Assoc, 130(1): 80-84, 1999.
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