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Dyract
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Update on Compomers
Update on Compomers
Physical
and clinical data on compomer restoratives
Reinhard
Hickel
University of Munich / Germany
1. Introduction
In
the last decade the number of amalgam fillings
decreased in many countries. Simultaneously
adhesive tooth-coloured restorations in
particularly hybrid composites and compomers
became the preferred materials also in posterior
teeth.
Compomers
(also called polyacid modified resins) are
defined as a subgroup of composites, which
contain a new type of hydrophilic monomer
and filler particles from glass ionomers
which release fluoride [Hickel et al. 1998
Int Dent J 48: 3-16].
As a new group of filling materials advantages
and disadvantages of Compomers were frequently
and controversially discussed and questioned
whether they can be used in load bearing
posterior areas of permanent teeth, too.
2.
Physical data (strength and wear)
Before
clinical use in vitro data for new materials
are necessary to estimate whether it is
reasonable or not to go into clinical studies.
Main problems in daily practice with tooth-coloured
fillings especially in posterior teeth are
gap formation, fractures and wear.
Gap formation depends not only on the restorative
but mainly on the adhesive whereas fractures
and wear are primarily problems of the material
itself.
For
best comparison of different products first
in vitro tests have to be done and all tests
under same conditions. Therefore in the
department for restorative dentistry in
Munich was built up a data base with important
parameters of filling materials (flexural
strength, diametral tensile strength, compressive
strength, fracture toughness - K1c, hardness,
water uptake, polymerisation shrinkage and
stress formation, E-modulus, wear etc.)
for nearly all of the tooth-coloured restoratives
which were available or introduced in the
last years (publication in progress).
These
data base shows that the different brands
within the group of compomers have an extraordinary
wide range. Flexural strength (FS) e.g.
is only one but an important parameter when
looking at fracture resistance in vivo.
Table 1 shows very impressively that the
range from 31 MPa to 131 MPa is extremely
wide. In the group of compomers are some
products (like Dyract AP or Hytec) which
show much higher strength than e.g. some
packable composites which are recommended
for class II cavities. From many clinical
studies we know that materials with a FS
of more than 90 to 100 MPa showed no remarkable
fractures in vivo whereas materials which
were far below this value had frequent failures.
Table
1. Flexural strength of different groups of
filling materials. (n= number of different
brands included in this group, for each brand
12 samples were tested). Some compomers show
by far better results than e.g. some packable
composites despite the mean value of packable
composites is higher than that of compomers.
Looking
at compomers there are some products which
are far below the values what should be
required for stress bearing class II fillings
but on the other side there are products
strong enough to recommend them in this
aspect. But as already mentioned this is
only one parameter and in vivo beside maximum
load especially fatigue problems are interesting.
Fatigue is highly influencing fracture rate
but also wear.
Looking
at wear rates the same picture can be seen.
Compomers again show a wide range from 120
to 260  ,
which means more than twice. Modern hybrid
composites are nearly comparable with amalgam
and some compomers (Dyract AP or Elan) have
similar low wear rates. In contrast to this
other compomers show much lower wear resistance
(Table 2 and 3).
Table
3 and 4. Wear rates of compomers in comparison
with other types of filling materials.
But
before recommending a product to the dentists
after in vitro screening clinical studies
have to be done.
3.
Clinical data
When
doing statistical analysis of longevity
data it is very important not to pool but
to differentiate the results for the different
indications (e.g. class I - V).
Looking at all clinical studies with a period
of at least 3 years and more than 20 fillings
we have calculated the annual failure rates.
According to the recommendations of the
ADA for posterior fillings a failure rate
below 5 % after 2 years and 10 % after 4
years is targeted at. That means that an
annual failure rate of 2.5 % should not
be exceeded. For compomers in class II cavities
only 3 studies with 3 and 4 years are available.
Two of these studies tested Dyract AP and
showed excellent results with a failure
rate of 0 - 1.5 %. Therefore only Dyract
AP is at present fulfilling the recommendations
of the ADA and can be used as direct filling
material in stress bearing posterior areas
of permanent teeth.
Furthermore
compomers showed best results in primary
molars and can also be recommended for class
V and class III cavities (Table 5).
Table
5 shows all longevity data of compomers
in different indications. Several compomer
products were tested. Despite clinical results
in children are in general worse compared
with adults. Compomers had good longevity
also in primary molar. For load bearing
class II fillings at present only one compomer
material (Dyract AP) was sufficiently tested
and showed good results.
4.
Conclusions
The
controversial discussion about compomers
was not seldom done with emotions and without
differentiating the various products. Some
said that compomers are the better materials
others that compomers are bad composites.
It is wrong to generalize this and to say
that compomers cannot be used in Class I/II
cavities. But is also wrong that all compomers
can be used in posterior stress bearing
areas. It depends on the product! The group
of compomers has a very wide range in physical
properties of the different brands. High
strength is especially necessary in class
II and IV cavities but not so in class III
or V. Therefore many compomers can be used
for cervical lesions but only Dyract AP
has shown clinical evidence that it works
well in posterior teeth.
Which
material should be used now? It depends
on the size and location of the cavity on
the one hand and on the experience of the
dentists on the other hand. But also the
patient has influence and the right to decide.
Therefore an informed decision is necessary
in which the most suitable and successful
but also cost effective material should
be used.
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| Prof.
Dr. Reinhard Hickel is Dean
of Dental School and Head
of Department for Conservative
Dentistry (Restorative and
Endo), Periodontology and
Paediatric Dentistry of
the Ludwig-Maximilians University
of Munich, Germany. Prof.
Hickel's research subjects
include the properties and
side effects of new restorative
materials, and he has over
200 publications. |
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