Canine substitution versus implants

Canine substitution versus implants versus dental bridge

When you have patients that are missing lateral incisors, there are multiple factors that need to be taken into consideration. The management of adult patients that happen to have their lateral incisors and need them extracted is an entirely different process than patients with congenitally missing laterals.  Single tooth implants are not suggested for young patients until they have completed their growth cycle. For these young patients that are congenitally missing their lateral incisors, canine substitution can be an excellent, esthetic treatment option.  However, there are certain criteria that must be met to help guarantee this procedure will be a success and yield predictable results:
Occlusal considerations:
From an occlusal standpoint, there are two situations that are appropriate, the first one being a Class II individual free of mandibular crowding. In this case, the molars would remain in Class II
but the pre-molar is brought forward to act as the canine, while remaining in a Class I relationship with the lower canine. The other situation is a Class I individual with sufficient mandibular anterior crowding that would necessitate pre-molar extractions on the lower arch.
Nice profile:
Ideally, the patient would have a profile that is relatively flat or slightly convex. Patients without either of these characteristics would most likely benefit from a treatment modality that manages the esthetic profile.
Canine shape and color:
If the canines are going to be sitting in the lateral site, evaluation of canine shape and color is necessary. Canines are generally larger than lateral incisors and hence the width of canines should be
evaluated. However, it’s not the overall width that is important but rather the width at the CEJ (as that cannot be narrowed). The wider the tooth at the CEJ, the more difficult it will be to make them look like lateral incisors. Color-wise, out of all the teeth in the mouth, canines are the teeth that are the most saturated with chroma. A canine that is smaller in shape and doesn’t have an over-saturation of chroma would make an excellent candidate for canine substitution.
Smiling lip level:
Depending on how high the smile line is, their lip level may show the canine eminence. Large canines often have an obvious root prominence, and high lip levels may reveal that there is an unnatural eminence in the lateral sight.

Canine substitution can be an excellent treatment alternative for congenitally missing maxillary lateral incisors. Patient selection is critical and depends on the type of malocclusion, profile, canine shape and color, and smiling lip level.  Pre-treatment evaluation of these selection criteria is necessary to insure treatment success and predictable esthetics.


What treatment modality is best?

Likely depends and you should ask your orthodontist and dentist what they prefer.  They likely prefer what they are capable of best doing.  Whether that is truly best or not is debatable, but it is likely the best treatment result you will get in their particular hands.

I will be including studies and more info in this blog as time goes on.

BDJ 2015

canine substitution implant bridge
Resin-Bonded Fixed Partial Dentures to Replace Missing Lateral Incisors [Ed.]
Posted: 28 Aug 2013 11:16 AM PDT
Three treatment options exist
for the replacement of congenitally missing lateral incisors. They
include canine substitution, a tooth supported restoration, or a
single-tooth implant.
Selecting the appropriate treatment option depends on the malocclusion, anterior relationship and specific space requirements.
In a previous article, I wrote about canine substitution as
one treatment modality for young patients with congenitally missing
lateral incisors. If the qualifications for using canine substitution
aren’t met and the patient is opposed to the placement of an implant, a
fixed restoration such as a resin fixed bridge, may be an option.
Although there are differences
in preparation design, the classic resin-bonded fixed partial denture
relies solely on adhesion, without the use of pins or grooves. The
success rate of this type of restoration varies widely from a 54 percent
failure rate over 11 months to 10 percent failure over 11 years, with
debonding being the most common cause of failure. Although these
restorations can be used successfully, specific criteria must be
addressed in order to ensure optimal esthetics and long-term
predictability. The main criteria involve tooth position and mobility of
the abutment teeth.
Tooth position as it relates to
the vertical overbite of the incisors can significantly impact the
stresses placed at the bond interface. Resin-bonded FPDs placed in a
deep overbite relationship are associated with a higher incidence of
failure.  As the overbite increases, either the surface area
available for bonding the retainer must decrease or the tooth must be
prepared and the occlusion placed on the retainer.
Therefore, the ideal anterior
relationship for a resin-bonded fixed partial denture is a shallow
overbite. The second concern regarding tooth position is inclination of
the abutment teeth. The direction of normal occlusal forces on proclined
incisors creates more of a tensile force at the bond interface, while
occlusal forces on upright incisors create more of a shear force at the
bond interface. Knowing that something can be loaded with a shear force
significantly more before it fails compared to that same thing being
loaded with a tensile force, resin-bonded FPDs don’t do well on patients
with proclined teeth.
Mobility of the abutment teeth
negatively impacts the durability of the bond in two ways. Directional
mobility: When placing a resin-bonded FPD from a mobile central incisor
to a mobile canine, each abutment wants to move under occlusal load. The
problem is their movement is on different vectors due to the position
that each tooth occupies in the arch. Differential mobility: When one
abutment is mobile and the other abutment is not, there is an increased
stress placed on the bond when only one of the abutments moves under
occlusal load. Generally, it is the least mobile of the two abutments
that will debond as the restoration moves in the direction of the more
mobile abutment.
As restorative dentists, our
goal is to always treat our patients with the most conservative
treatment possible. If the patient has a deep overbite,
proclined, or mobile abutment teeth, then a resin bonded FPD may not be
the best treatment option. It is with this in mind that today, resin
bonded FPDs are often used as more of a long-term provisional, until the
patient is old enough to have an implant placed.

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