REPLACEMENT OF MISSING TEETH
HOW ARE
TEETH LOST?
Teeth can
be lost by severe physical trauma, which is a complicated way of saying they
can be knocked out. That is not, however, the most common reason for losing a
tooth. More often it is due to unrestorable destruction from decay, fracture,
bone loss, or untreatable infection which makes it necessary for the dentist
to extract (pull) the tooth.
WHY DO
MISSING TEETH NEED TO BE REPLACED?
Leaving
an empty space after a tooth is lost can result in:
shifting, tipping or super eruption of remaining
teeth (super erupting is a tooth erupting into a space on the opposite
jaw);
bite collapse (the jaw closes farther than
it should because shifting teeth no longer give proper support);
an increased chance of fracture, root canals or
accelerated bone loss due to excessive force on the remaining teeth; or,
pain in the joint of the jaw due to improper bite
(you may have heard the term TMJ which is short for the jaw joint, the
Tempromandibular Joint).
The longer missing teeth are not replaced, the
more complex the treatment may become. Dramatic tipping, shifting or super
eruption of teeth may require braces to be straightened.
Replacing
missing teeth can be accomplished by bridges, partial dentures, or implants.
Complete tooth loss requires full dentures or implants.
WHAT IS A
FIXED BRIDGE?
A
fixed bridge is a permanent replacement for missing teeth which can not be
removed by the patient. Bridges are sometimes referred to as "crown and
bridge" or a "fixed bridge".
A bridge
is constructed by preparing the teeth on both sides of a space so they can
receive crowns. The teeth are reduced and shaped around the outside and across
the top so a crown can fit tightly over them. Crowns are joined together to
replace the missing teeth and cover the prepared teeth on each side providing
support of the replacement.
A bridge
can be used only if there is enough strength to support the replacement teeth.
This generally means there should be as many teeth providing support as there
are being replaced. The type of replacement needed is also determined by
careful evaluation of bone loss, size and shape of the root structure, the
force which will be generated on the bridge and the strength of the remaining
tooth structure.
A missing
tooth is replaced by a fixed bridge. Teeth on either side of the space are
prepared for crowns. Three crowns are joined together so crowns on either
side can support the missing tooth in the middle.
IS IT
DIFFICULT TO MAKE A BRIDGE?
Bridges
require two or more appointments. At the first appointment, precise drilling
is done, impressions are taken to make plaster models and a temporary bridge
is placed. The permanent bridge is fabricated in a dental laboratory through a
series of complicated procedures and is then returned to the dentist.
At the
second appointment, the temporary bridge is removed, the permanent bridge is
tried in the mouth, checked to ensure proper health, function and aesthetics
and is then cemented into place. Occasionally bridges need subsequent
adjustments which require additional appointments.
ARE THERE
DIFFERENT TYPES OF BRIDGES?
Yes.
Bridges are classified by the materials used in constructing them. Porcelain
fused to metal or all metal bridges are most common. Metal bridges, such as
gold, give maximum strength with poor aesthetic quality due to color.
Porcelain fused to metal retains much of the strength from the metal core
while the outer porcelain layer improves the aesthetics. Further
classification of bridges is based on bridge design and the method of
construction.
The
Maryland Bridge is one alternative to the standard "crown and bridge"
design. There is less drilling and expense with this type of bridge as it does
not require full crowns on the teeth adjacent to the space. The replacement
teeth, usually porcelain, have metal wings which are bonded to adjacent teeth
to provide support. The Maryland Bridge can only replace a limited number of
teeth and must have strong teeth to support it. There can not be excessive
force which may dislodge it. For these reasons, it is not used as often as the
standard design.
Badly
broken down teeth are restored and missing teeth replaced with a complex
restoration referred to as a full mouth reconstruction. The full mouth
reconstruction consisted of individual crowns and two fixed bridges.
WHAT ARE
PARTIAL AND FULL DENTURES?
Dentures
are removable replacements for missing teeth. Partial dentures are used
when there are remaining healthy teeth which help provide retention and
strength in resisting chewing forces. Complete, or full, dentures are
used when all of the teeth in a jaw are missing, and retention is achieved
through suction.
Complete
dentures are combinations of plastics carefully molded to fit the gums
comfortably and securely while providing natural color and aesthetics. Partial
dentures also use a combination of plastics, but some sections are made of
metal to join parts together and provide strength. The replacement teeth may
be made of porcelain or plastic.
WHEN ARE
DENTURES USED?
Partial
dentures are used in instances similar to those where a fixed bridge might be
used. Partial dentures, however, are used exclusively when the remaining teeth
are not strong enough to support the missing teeth as they do with fixed
bridges. With a partial denture the gums and bone of surrounding areas provide
additional support. Full dentures are supported entirely by the gums and bone
structure.
A
partial denture for the upper jaw replaces missing teeth. Clasps, which look
like hooks, clip onto teeth to provide retention. A metal connector which
sits on the roof of the mouth joins the parts together.
HOW ARE
DENTURES MADE?
Dentures
are fabricated in a dental laboratory. Plaster models are constructed from
impressions of the teeth and gums. Full dentures require impressions which may
be done in several phases so precisely made models can be constructed. Tooth
color, shape and size are selected and the relationship of one jaw to another
is registered.
With full
dentures, the denture teeth are mounted in wax for evaluation in the mouth. If
the appearance, bite and fit look correct, the denture is finalized. If a
partial denture is elaborate, the metal framework or denture teeth will also
be evaluated in the mouth before being finalized. Follow up appointments for
adjustments can be expected, especially with full dentures.
WHAT
KEEPS DENTURES FROM FALLING OUT?
With
partial dentures, metal clasps are used to grip teeth and hold the denture in
place. Drilling modifies the teeth to maximize retention and resistance while
minimizing adverse forces to teeth. Full dentures are retained through
suction. That is why the precise design and fit of full dentures are so
important.
Retention
and aesthetics of partial dentures can also be improved by the use of
precision attachments. Precision attachments are snap like devices which are
placed in crowns and partial dentures so partial dentures can "lock" into
place. Partial dentures designed this way, in combination with crowns, can
eliminate clasps so no metal shows and less adverse force is placed on teeth.
WHAT DO
DENTURES LOOK LIKE?
The
classic denture look is pearl-white perfectly straight teeth. Fortunately,
people today want their teeth to look more natural. For a natural appearance,
your own teeth are the best indicator of color, shape, and position. If a
dentist can not use your own teeth as indicators, correct color is matched to
your skin tones, shape is matched to your face shape and position is
determined by profile, jaw position, etc.
HOW
SUCCESSFUL ARE DENTURES?
Partial
dentures have a very high success rate. Most people are able to adapt to their
use without great difficulty. There is a substantial difference, however,
between full dentures and your own teeth since it is only suction which holds
a full denture in place.
Dentures
may move or come loose when the tongue, lips, cheeks and muscles push against
it. Good impressions provide an accurate fit and seal around the edges.
Retention and stabilization can be aided by the shape of bone and firmness of
gums which make it more difficult to break the suction.
It is
difficult to predict how a patient will adapt to dentures. A stable, retentive
denture increases success, but people must adapt psychologically and learn
techniques of functioning with a denture. Speech patterns must be relearned
and chewing efficiency may be dramatically reduced. For these reasons, full
dentures are the last resort of dentistry.
ARE THERE
ALTERNATIVES TO DENTURES?
Yes.
There are two alternatives to full dentures: overdentures and implants.
Occasionally weak teeth can be used to stabilize dentures. Teeth reduced in
height are much stronger because forces are closer to the gums reducing the
force generated on their roots.
Overdentures are dentures which fit over weak teeth reduced in height
after root canals. In addition, precision attachments can be placed in these
teeth and dentures for added retention. Retaining roots will also help
maintain bone height which might recede if roots were not there.
WHEN CAN
OVERDENTURES BE USED?
There
must be adequate root structure and bone support around teeth to be beneficial
to overdentures. Tooth support can increase stability dramatically. Ideally,
teeth on both sides of the mouth should be used.
Two
implants have been placed to provide retention for a full overdenture.
The
denture has rubber like rings that clip onto the implant attachments.
WHAT ARE
IMPLANTS?
Implants, usually made of titanium metal similar to that used in pins to
join fractured bones, are permanent replacements for missing teeth. Part of
the implant acts as the root of a tooth and supports a section which extends
above the gums. Replacement teeth may be permanently fixed to the sections
above the gums, like fixed bridges, or can be removable similar to
overdentures.
Implants
are used for patients who can not wear full or partial dentures or when more
retention is needed for full dentures. There must be adequate bone support,
good general health and patient motivation to do implants.
HOW ARE
IMPLANTS DONE?
There are
different types of implants so procedures will vary. Bone integration implants
(osteointegrated) are done in stages. The first stage inserts implants
directly into the jawbone below the level of the gums. The gums are closed and
healing takes place over many months. The bone actually heals to the implant
on a microscopic level.
In the
second stage, access to the implants is attained through small incisions in
the gums. Sections which extend above the gums are then attached. Different
types of sections are utilized depending on the function required. Crowns,
bridges or dentures are then constructed onto the implants.
WHAT TYPE
OF REPLACEMENT TEETH SHOULD BE USED?
Implants
hold the replacement teeth very securely whether the replacement teeth are
removable or permanent.
Removable
appliances are used if there is not adequate amounts of bone to place multiple
implants. Underlying gums and bone provide additional support for removable
appliances used with implants. The appliance looks similar to full dentures.
Being less expensive, removable appliances are used if cost is a factor.
A fixed
appliance requires adequate numbers of implants to support it. The size is
smaller so they are often more comfortable than removable appliances. There
are different types of fixed appliances and selection is based on cost and
esthetics. They are, however, much more expensive than removable appliances.
ARE
IMPLANTS PAINFUL?
Implants
are surgical procedures so post operative pain may occur. The degree of pain
varies greatly from patient to patient and is hard to predict. The actual
procedure is not painful and may be done in the office.
ARE
IMPLANTS SUCCESSFUL?
Yes. At
one time implants had only limited success because infection would destroy
bone around the implants. The bone did not heal directly to the implant and
made infection more likely.
The
success rate is very high with osteointegrated implants because the bone grows
directly into the implant and there is better gum response. It is important,
however, to keep the area around the implants very clean to avoid infections.
There are now studies which have been done over twenty year periods which
confirm the long term success rate of implants. As the implant procedures and
techniques are refined, implant use will be more and more common as
alternatives to classic dentures.
