Missing lateral incisors
Missing lateral incisors
 |
| congenitally missing lateral incisor |
INTRODUCTION
Encountering a patient who has been treated orthodontically
to rectify the absence of the maxillary lateral incisors presents a unique
aesthetic and functional challenge. Maxillary lateral incisor agenesis (MLIA)
is the most common congenitally missing-permanent-tooth condition in the
maxillary anterior region and contributes to significant aesthetic compromise
and potential functional instability. Statistically, 20% of all congenitally
missing teeth are maxillary laterals, and females are affected more than males.
In addition, agenesis of both maxillary lateral incisors is
more common than agenesis of only one.
Options for treating this condition, when diagnosed early,
are:
1. Space closure with the mesial repositioning of the
canine and subsequent reshaping (enamelplasty) with possible direct restorative
procedures involving resin bonding
2. Repositioning of the canine with aesthetic preparation
and restoration involving crowning or veneering with ceramic
3. Maintenance of the cuspid in its ideal functional
position and orthodontically creating the proper mesial/distal width space for
subsequent implant placement or prosthetic replacement of the missing lateral
with bridge design
All of the above are viable choices, depending upon the
anatomical environment and aesthetic/functional expectations, along with the
immediate and long-term management challenges of a growing patient.
A consequence of tooth mass loss (missing tooth/teeth) in
the arch and movement of teeth to eliminate the space caused by that loss of
mass can result in narrowing of the arch. This can have a dramatic impact on
facial/dental aesthetics and functional stability.
However, the position of the cuspid plays an important and
significant functional role in maintaining the homeostasis of the
stomatognathic system. Canine unilateral contact on the working side is
critical to accomplish that. Therefore, the whole rehabilitation treatment,
which will often require a multidisciplinary approach
(ie,periodontic/orthodontic/restorative/prosthodontic), should aim to establish
such lateral disocclusion whenever possible. If not, such as in the case
example presented here, where the cuspid has been orthodontically moved into
the lateral position, functional design should aim for group function.
The Challenges Found With Previously Treated Cases
On occasion, as aesthetic/restorative dentists, patients
with MLIA will present who have previously had treatments done for the
condition. In the author’s experience, these individuals are often displeased
with these previous aesthetic restorative attempts. In these situations,
clinicians will often face some pretty tough treatment challenges. Available
treatment options may be limited due to the treatment choices that may have
already been offered and done by the previous doctors. Any new treatment plan,
if not carefully thought out, may then offer these patients the potential for
less than desirable aesthetic and functional results as well.
Evaluation of the pre-op condition revealed multiple
concerns that affected both intraoral and extraoral aesthetics. Both the
gingival architecture and anatomical tooth form contributed to the deficiencies
exhibited in each of these realms. Keeping in mind the principle that the most
harmonious relationship between 2 lines is when they are parallel, we can
clearly see the visual discord this condition presents
Considered individually, the gingival architecture
surrounding the anterior teeth was in reverse balance In other words, the gingival margin on the
central incisors was lower than the lateral incisor, an offense of ideal smile
design principles. This circumstance was created as a result of the cuspid
being moved into the lateral position without consideration of the proper
gingival margin relationship to the central incisor. The MLIA condition
precipitated this treatment choice but, as stated previously, was inadequate in
answering the optimal aesthetic desires of the patient and the vision of this
dentist.
Extraorally, the imbalance of the gingival architecture
detracted from the facial appearance in the lower one-third of the face. Visual
tension was created by the reverse gingival position and appearance of a “gummy
smile” and a lateral incisor/central incisor proportion discrepancy .
Another basic of proper smile design is inherent proportion
of the central incisors to one another and to what surrounds them. Anatomical
disharmony between all teeth in the upper arch (the smile zone in particular)
and even the lower arch was evident. Given this, the condition of MLIA poses a
multi-dimensional challenge requiring a multi-faceted approach to attain the
aesthetic goal.
Germane to this discussion is the obvious anatomical
difference between the lateral incisor and the cuspid and the challenge of
making one appear ideally as the other. The differences in size, shape, and
appearance between lateral incisors and canines is significant. Lateral
incisors are incisiform, with smaller and flatter labial surfaces and broad,
flat incisal edges, while the cuspids are more conical and pointed. The
surrounding bone also presents a significant difference. Cuspids, being the
cornerstones of the arch, display a prominent eminence, which is a graphic
distinction from the adjacent teeth and their bone envelopment. This is perhaps
the most significant challenge in creating “the look” of a true lateral incisor
Given this distinct anatomical difference and, as in this
case, that the cuspid is in the lateral position, one cannot make a cuspid “look”
like a lateral incisor without consideration of soft- and hard-tissue
alteration. A pre-op evaluation—periodontally, radiographically, and in
conjunction with a periodontic specialist—was imperative for correct treatment
planning. Procedurally, this was addressed through flap elevation, revealing
the true picture of osseous presence or lack thereof. Where there is bone, we
can alter it. Where there is not, we cannot (at least in this circumstance).
Decreasing clinical crown length on the existing cuspid/lateral and increasing
clinical crown length on the central incisors, at the same time, presented a
technical challenge. Being able to create clinical crown length regarding the
central incisors was attainable through osseous resection/contouring followed by
gingivectomy to the proper level, maintaining biologic width .
Gingival position regarding the cuspid (in lateral
position) required coronally repositioning the flap and flattening the cuspid
eminence . The plasty of the eminence allowed for an emergence contour that
better mimics that of a lateral incisor. Furthermore, preparation of the
coronal aspect of the cuspid by narrowing it mesial-distally allowed for the
design of an aesthetic restoration that adhered more ideally to that of a true
lateral incisor dimension.
The Importance of Material Selection and Proper Placement
The importance of proper ceramic selection in aesthetic
restorative cases such as this is critical. Feldspathic porcelain, lithium
disilicate, and zirconia each have their own specific characteristics. Proper
choice of material is contingent upon the need for strength, preparation
design, and visual/aesthetic characteristics. In cases in which there is
minimal preparation, feldspathic porcelain may be of consideration. In cases
such as this one featured, in which previous restorations have been placed and
significant preparation is present, pressed ceramics or even zirconia may be
considered. In this case, the decision was to use a pressed lithium disilicate
all-ceramic (IPS e.max [Ivoclar Vivadent]) due to its strength (500 MPa) and
natural high-end aesthetics in the smile zone.
Decisions made to ensure the proper placement of the
ceramic units also demand close scrutiny. Whenever possible, it is best to use
a composite luting resin cement with lithium disilicate. In this case, there
was a combination of veneers and full-coverage ceramic crowns in the upper
arch. Of course, this is dependent upon the light source being able to
adequately reach the ceramic/tooth interface to initiate and completely cure
the resin cement. So, the different types of restorations demanded a different
technique in placement: light-cured cement for the veneers and a dual-cured
cement for the full crowns.
CLOSING COMMENTS
We can see how dramatically the smile zone is impacted when
disproportion is exhibited as in the condition of MLIA. Even without any formal
dental training, the lay public (ie, patients), when viewing someone’s smile or
their own, can surmise when a problem exists and when something is not visually
pleasing. Visual tension is the harbinger of aesthetic need, usually combined
with an underlying functional concern. Moving a tooth into a position that is
foreign to its normal place alters the functional and aesthetic dynamic. If
consideration of repositioning or not repositioning a cuspid can be addressed
in advance of treatment, then the clinician will most often make the best
choice. However, when this is done without considering those choices,
compromise and limitations will abound. It is this compromise that challenges
us and stimulates our creativity to answer the functional and aesthetic
demands. This is what delineates cosmetics from functional aesthetics and
allows the opportunity to more fully impact the end result .
Treating MLIA requires the joint work of a
multidisciplinary team that, after evaluating all aspects of oral health
(facial aesthetics, dental aesthetics, occlusion, function, and periodontal
parameters), decides to adopt a treatment plan that provides the most
biological, cost-effective, and long-term treatment outcome.
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