Indications
Sealing of
susceptible pits and fissures is carried out as soon after eruption as
possible. First, second, and third permanent molars are obvious candidates, but
all molars are not automatically fissure sealed. Where plaque control is good (and
this should be checked with disclosing solution) and where no lesion is
visible, a sealant is not needed. However, caries or missing teeth which have
been extracted because of caries in a child’s mouth indicate caries risk and
will favour the use of sealants. Similarly, if a young adult requires restoration
of one second molar, fissure sealing the remaining second molars seems to be a
logical preventive measure. Fissure morphology is also relevant. A fissure
pattern of shallow rounded grooves is unlikely to decay, but a deep fissure
pattern is more susceptible since it is difficult to clean. Where the dentist
believes that the patient’s diet contains frequent sugar intakes or when poor
oral hygiene cannot be improved – for example where patients are mentally or
physically disabled – fissures should be sealed. Children with significant
medical conditions which put them at risk from the consequences of dental
disease should also be offered sealant treatment. These medical conditions
include cardiac problems, immunosuppression, bleeding disorders, blood dyscrasias,
and metabolic and endocrine problems. Finally, the tooth to be fissure sealed
must be capable of being isolated from salivary contamination since
contamination while placing the sealant is the most common cause of failure. At
best, salivary contamination will result in the sealant falling off, with no
permanent harm. At worst, however, the sealant will be partly retained but
leak, so that caries can progress beneath it, safe from salivary protection, fluoride
ions, and detection by the dentist. Therefore good isolation from saliva is an
essential part of the clinical technique, with a rubber dam being the preferred
method.
Clinical technique for
resin sealers
Anaesthesia and
isolation
If
necessary, a little local anaesthetic is infiltrated or topical anaesthetic is
applied to avoid discomfort from the rubber dam clamp.
Cleaning
The tooth
surface to be etched and sealed may be cleaned with a bristle brush in a
handpiece and a pumice and water slurry. Oil-based polishing pastes or those
containing fluoride should not be used, as these may interfere with etching.
The pumice is washed away using the three-in-one syringe. Some dentists clean the
fissure with a high-pressure spray of sodium hydrogen carbonate; this is known
as ‘air polishing’. This is similar to ‘air abrasion’ as already
described in earlier posts. In this format a high-velocity air stream contains soft
sodium bicarbonate powder (baking soda), shrouded by water, and has little
cutting effect on intact enamel. The powder is water-soluble and is easily
removed after cleaning.
Etching
The tooth
is now etched with phosphoric acid (30–50 per cent). The acid
etchant is supplied by the manufacturer in the form of a coloured gel. The
etchant is applied over the whole occlusal surface extending onto the lingual
or buccal surface where grooves require sealing. Etching the entire
occlusal surface avoids the danger of covering an unetched surface with sealant
and thus inviting leakage. The acid can be applied with a brush, or
alternatively the gel can be placed accurately with a disposable syringe and
blunt needle. As soon as the complete area to be etched is covered with acid, the time is noted and the enamel
is etched for 15–20 seconds.
(a) A brush is used to apply the etchant gel
over the occlusal surface of the tooth to be fissure sealed. (b) Dried etched
enamel appears matt, white, and frosty. (c) The sealant is applied to the
etched surface using a small disposable brush or a syringe with a disposable
tip. (d) Light-curing a fissure sealant. (e) A fluoride-containing varnish is
applied to the etched enamel at the periphery of the restoration where it has
not been covered with sealant.
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Washing
After 20
seconds the acid is washed away. Initially a water jet from the three-in-one
syringe is used to remove most of the acid. If a rubber dam is not in place,
careful aspiration is important to avoid damage to soft tissue by the acid.
After approximately 5 seconds of water, the air button is also pressed, forming
a strong water–air spray which should be played over the etched surface for
20–30 seconds. With coloured gels, it is tempting to stop washing when the
colour has gone. However, the purpose is not just to remove the surplus acid,
but to flush the precipitates out of the newly formed etch pits, and this takes
a full 20–30 seconds.
Drying
Many
fissure sealants are still based on hydrophobic resins and so a careful drying
regime is required. It is good practice to check that the airline is not
contaminated by water or oil by blowing it at a clean glass or paper surface.
The tooth surface is now thoroughly dried with air from the three-in-one syringe.
This drying is most important since any moisture on the etched surface will
stop penetration of the hydrophobic resin into the enamel. A minimum of 15
seconds drying is recommended. At this stage the etched area should appear matt,
white, and frosty. With a rubber dam, there should be no danger of
salivary contamination of the etched surface. If this does occur, however, it
is essential to re-etch the enamel because adherent organic material in saliva
will block the pores and it cannot be removed completely, even by vigorous
washing.
Applying the sealant
Fissure
sealants are supplied both as light-curing and chemically-curing materials. A
light-cured resin does not require mixing but a chemically-cured resin has two
components which are gently mixed together with a brush.
A sealant
is applied to the etched surface using a small disposable brush or applicator
supplied by the manufacturer.
The
sealant is applied to the etched pits and fissures and up the etched cuspal
slopes. If a light-cured material has been chosen, the light should
be placed directly over the sealant but should not touch it. With a
molar tooth, if the light source is of a smaller diameter than the tooth it
should be directed at the distal part of the occlusal surface for the full
curing time recommended by the manufacturer of the resin and then moved
mesially for a similar period. Any buccal or palatal groove or pit should be
similarly cured with the light source directly over it. Since the polymerizing
lights are potentially damaging to the operator’s eyes, special eye-protective
glasses should be used or the dental nurse should hold a special filter screen in
the operator’s line of vision. Some lights Fissure sealing 123
have protective cups which can be placed over the end of the light guide. Most
chemically-cured sealants polymerize in 1–3 minutes and the manufacturer’s
instructions should be followed. The outer surface layer of any sealant will
not polymerize due to the inhibiting effect of oxygen in the atmosphere. The
sealant will therefore always appear to have a greasy film after
polymerization. Finally, a fluoride-containing varnish may be applied to the
etched enamel at the periphery of the restoration where it has not been covered
with sealant.
Checking the occlusion
The rubber
dam is now removed and the occlusion checked with articulating paper. Whilst it
is considered acceptable to allow any high spots to be abraded away when
unfilled resin fissure sealants are used, with the lightly-filled materials it
is wiser to reduce high spots by grinding with a small round diamond stone in a
low-speed handpiece.
Clinical technique for
glass ionomer cement sealers
The authors would
rarely choose a glass ionomer cement for fissure sealing because the scientific
evidence on retention and caries prevention has shown these not to be as
effective as resin sealants. It is possible that the fluoride in the material may
exert a cariostatic effect. However, they are the material of choice on an
erupting tooth, where oral hygiene is poor, caries risk is high, and good
moisture control is difficult. They should be considered a temporary measure in
these circumstances. The tooth to be sealed is isolated and the fissure is
cleaned with 10 per cent polyacrylic acid-conditioning agent, supplied by the
manufacturer, for 20 seconds. It is then washed and dried, and the glass
ionomer material, mixed to a flowable consistency, is applied along the fissure
and firmly burnished into position. Excess material is easily removed with the
burnisher. Although glass ionomer will almost certainly be less well
retained than a resin-based system, the material may have a protective effect
for high-risk fissures whilst the tooth is at its most vulnerable: in this
situation a resin sealant would not work because the tooth may be impossible to
isolate satisfactorily.
A glass ionomer
fissure sealant which has been in place for 14 years.
The sealant
restoration (or preventive resin restoration)
Indications
The sealant
restoration was born out of the use of pit and fissure sealants. It is a
natural extension of the technique where pit and fissure decay is confined to
one area in the fissure system. The technique restores the carious area and seals
the rest of the fissures. The restoration is indicated where a cavity is
present (either a microcavity in the enamel, or a cavity with dentine at its
base). The lesion will usually be visible on a bitewing radiograph as an area
of radiolucency in the dentine.
Clinical technique
(a) a lower second molar isolated with a
rubber dam prior to placing a sealant restoration.
(b) Enamel is removed
to gain access to obvious caries.
(c) Soft caries over
the pulp is removed.
(d) Exposed dentine is
covered with a calcium hydroxide-containing cement: smaller amounts of this type
of cement would be used nowadays – simply covering the deepest dentine, close
to the pulp.
(e) A second layer of
glass ionomer lining may be placed in a deep cavity.
(f) The enamel walls
of the cavity and the occlusal surface of the tooth are etched with acid.
(g) Etched enamel
after washing and drying.
(h) Bonding resin is
applied to the cavity walls and occlusal surface.
(i) The cavity is
filled with composite resin. Use of the glass ionomer lining in this tooth
allowed the composite to be placed and cured in a single 2 mm
increment.
(j) A fissure sealant
is applied to the whole occlusal surface.
(k) The occlusion is
checked with articulating paper which will locate areas of occlusal contact
with a coloured mark.
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Cavity preparation
Occlusal contacts
should be marked with articulating paper prior to preparation so that the
dentist can remember where these contacts are. A local anaesthetic is given. A
rubber dam is applied and the tooth is thoroughly cleaned as before (Fig.
7.3a). A small, pear-shaped tungsten carbide bur (Jet 330) is used in the air
turbine to widen slightly and deepen the fissure and to gain access to caries
in dentine. The air turbine is also used to remove the minimum amount of enamel
necessary to gain access to caries. A small round bur is now used
in the low-speed handpiece to remove soft, demineralized dentine, which is often
stained, from the enamel–dentine junction. During this process the access
cavity may require further enlargement to allow access to caries on the
enamel-dentine junction. Thus high- and low-speed handpieces are used alternately
so that the cavity is kept as small as possible commensurate with removing the
soft dentine from the enamel–dentine junction so that it feels hard when a
sharp probe is run along it. Finally, any soft caries overlying the pulp is
removed with either a slowly rotating round bur in the slow-speed handpiece or
a sharp excavator.
Lining and etching
If the cavity is much
larger than expected, the deep dentine directly overlying the pulp may be
covered with a calcium hydroxide-containing cement. A second layer of resin-modified
glass ionomer may be placed in a deep cavity to act as a dentine replacement. The polyacrylic acid conditioning liquid supplied by the
manufacturer should be applied to any exposed dentine with a brush. After 10
seconds the cavity is washed and dried and the glass ionomer cement placed.
Once this material has set, any glass ionomer material on the enamel walls
should be removed with a bur. The enamel walls of the cavity and the occlusal
surface of the tooth are now etched with acid. After 20 seconds
this is washed and dried as before.
Filling the cavity
A composite, designed
for use in posterior teeth, is selected. It is supplied with a bonding resin
which should be painted on the etched enamel walls and occlusal surface and
blown with dry air to form a thin layer, avoiding puddles of material in the
cavity. The resin is polymerized with light as before. The cavity
is now filled with the posterior composite. These light-cured
materials will not cure reliably in depths exceeding 2 mm. Thus, if the cavity
is deeper than this (a graduated pocket-measuring probe can be used to check
depth), the material must be placed in increments. Each increment is then cured
before the next is placed, taking care not to dispense more than is needed because
normal light in the surgery will polymerize the unused material. An increment of
composite is placed or syringed directly into the cavity and gently nudged into
position using a small ‘non-stick’ instrument. Care should be taken not to trap
air under the material. When the final increment is placed an instrument is
used to shape the occlusal surface, restoring cuspal inclines in the larger
cavity before light-curing the material. Alternatively, the glass ionomer
material is brought up to the enamel–dentine junction to replace all the missing
dentine so that only one increment of composite, the thickness of the enamel,
is required. An alternative to the glass ionomer/composite layered technique
is to bond the composite filling materials directly to the etched dentine and
enamel. This is called the all-etch technique. The enamel and dentine of the
cavity and the enamel of the occlusal surface are etched for 15 seconds and then
washed and gently dried. The dentine in particular should not be over-dried. Now a dentine bonding agent is applied following
the exact descriptions of the manufacturer. The bonding agent is polymerized and
then the composite is built up in increments as described previously.
Whether the layered
technique or the all-etch technique have been used, the remaining fissure
system has already been covered by the bonding resin. A layer of fissure
sealant is now painted over the entire occlusal surface and polymerized. Alternatively, composite can be gently agitated with a plastic instrument
into the adjacent pits and fissures, and light-cured to act as a heavily-filled
pit and fissure sealant.
Finishing the
restoration
Excess resin is
carefully removed with 12-bladed tungsten carbide finishing burs or with fine
diamond composite finishing burs. Once the rubber dam has been removed,
the occlusal contacts should be checked with thin articulating paper.
This is placed between the dried teeth and the patient is asked to move the
teeth over each other as if eating. Any ‘high’ spot on the restoration will be
located by a mark and can be reduced; the aim is to have the restoration in
harmonious occlusion. The restoration can finally be smoothed with
aluminium-impregnated rubber points.
Larger posterior
composites
It is not uncommon for
occlusal caries to undermine the occlusal enamel widely. In
the past such restorations have often been restored with amalgam after all the
overhanging enamel has been cut away. With posterior composite materials and glass
ionomer cements, it is now possible to use these adhesive materials to restore
the missing tooth tissue and support the remaining enamel without needing to
remove so much of it. Therefore once soft demineralized dentine has been removed,
decisions have to be made about the strength of the remaining tooth tissue.
Figure c shows a large occlusal cavity with a considerable amount of
overhanging enamel. This cavity was restored with a calcium hydroxide lining
over the deepest pulpal part of the cavity used as an indirect pulp cap
followed by a layer of glass ionomer cement to replace much of the missing
dentine. Finally, the enamel walls were acid-etched and the remainder
of the tooth restored with a posterior composite which was built up in
increments as described previously. The same restoration is shown
after 5, 9, and 14 years in Figs. In these large restorations as much
sound tissue should be preserved as possible. Undermined and overhanging enamel
can be supported with adhesive posterior composite materials and glass ionomer
cements. Where mastication pressure is obvious, a minimum thickness of 2 mm of
composite material is required. Where the outline of the preparation is placed
beyond the occlusal surface, perhaps because a cusp has fractured or been
completely undermined by extensive caries, a bevel should be prepared to
optimize the adaptation of the composite to the enamel.
(a) A large occlusal cavity is present in the
lower first molar.
(b) Access to caries
begins to reveal the extent of the lesion.
(c) The enamel–dentine
junction is made caries-free, soft caries is excavated over the pulp, and a
calcium hydroxide-containing cement is placed in the depth of the cavity.
d) Much of the missing
dentine is replaced by a second lining of glass ionomer cement. Today this
would be brought up to the enamel–dentine junction and only one increment of
composite would be required.
(e) An increment of
composite being lightcured.
(f) The final
increment of composite can now be placed.
(g) The completed
restoration.
(h) The restoration
after five years.
(i) The restoration
after nine years. There is some wear, but the margins are intact and the restoration
can still be considered a success. If this wear was thought to be excessive,
the surface layer of composite could be removed and the restoration resurfaced
with more composite. Such repairs, or maintenance procedures, are not possible
with amalgam.
Modern composites are
likely to be more durable than the materials available when the restoration was
placed.
(j) The restoration
after 14 years. Additional composite was not added as suggested
in (i) and there has been no significant change in the last five years. The
restoration can now be
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