Int Poster J Dent Oral Med 2 (2000), No. 3 15. Sep. 2000
Int Poster J Dent Oral Med 2000, Vol 2 No 3, Poster 48
Anaerobic microflora under class I and class II composite and amalgam fillings
Authors: Annegret Heinrich*, Olaf Bernhardt, Christian Splieth, Georg Meyer
University of Greifswald, Department of Restorative Dentistry, Periodontology
and Pediatric Dentistry
The determination of the microflora beneath restorations is of special interest,
because the impermeability of a restoration to bacteria has a decisive influence
on the survival time of this restoration. During the past years, tooth-colored
resinous filling materials have been increasingly used for premolars and
molars. It has been proven that these materials do not bear the load of chewing
pressure in the posterior-tooth region as well as amalgam fillings and inlays
or onlays do. During function, cracking and microleakage of the composites
may occur and microbes may penetrate into the filled cavity. Furthermore,
composites in contrast to amalgam do not have any antibacterial
The aerobic and microaerobic bacterial spectrum of carious dentine and under
fillings is well known.
The aim of the present study was to determine the anaerobic microbial spectrum
under composite fillings compared to that found under amalgam fillings.
Material and Methods
10 composite and 5 amalgam fillings of 15 patients were chosen for removal
using rotating diamond instruments with rubber-dam in place, then using sterile
The fillings were evaluated for occlusal loss of material, marginal gaps,
and secondary caries. The clinical examination was conducted with a dental
probe and magnifying lenses (2x).
A sample of carious dentine just below the filling was taken under sterile
conditions with a second hand instrument, stored in 1 ml prereduced transport
medium for anaerobes, and immediately transfered to a laboratory for microbial
diagnosis and then incubated in an anaerobic chamber.
The cultures were incubated in a glove box at 37° C for 2-4 days using
Wilkens Chalgren blood agar plates (Difco) and a selective Wilkens Chalgren
blood agar plate (Oxoid) for gram-negative and non-sporeforming rods.
The quantities of different colony types were estimated. Gram staining, growth
in air, sensitivity to antibiotics, fermentation of carbohydrates, and production
of indole and nitrate were investigated for a group diagnosis. For a further
classification of the anaerobic gram-negative bacteria, the computer-guided
ANI- Identification Card System (bio Merieux Vitek) was used.
|First upper premolar before and after the removal
of a composite filling
Results I (Clinical examination)
Occlusal loss of material:
Half of all composite fillings and 3 of 5 amalgam fillings showed a loss
None of the restorations exhibited a perfect margin (degree 0) or marginal
caries (degree 3).
Seven composite and 4 amalgam fillings had a marginal gap within the enamel
(degree 1); 3 composite fillings and 1 amalgam showed a marginal gap detectable
with a probe (degree 2).
In 9 cases, secondary caries was found under composite restorations, and
in 3 amalgam-filled teeth, secondary caries was diagnosed.
The condition of the pulp:
After caries removal was completed in one composite case, a direct capping
with calcium hydroxide was necessary. One other composite-filled tooth had
already been endodontically treated.
Results II (Microbial diagnostics)
All cavities included, a total of 83 different bacterial species were isolated,
of which 70 were found in composite-filled teeth and 13 in amalgam-filled
The ratios of aerobic to anaerobic flora were comparable: under composite
11.4%:88.6 %, under amalgam 15.4%:84.5%. Anaerobic species dominated. The
microbial variety under composite fillings was much greater compared to amalgam
(34 strains of strictly anaerobic non-sporeforming gram-negative rods,
17 strains of anaerobic or facultatively anaerobic non-sporeforming
gram-positive rods, 9 strains of anaerobic gram-positive cocci and 2 strains
of anaerobic gram-negative cocci). Beneath amalgam, we found 1 strain of
strictly anaerobic non-sporeforming gram-negative rods, 7 strains anaerobic
or facultatively anaerobic non-sporeforming gram-positive rods, and
3 strains of anaerobic gram-positive cocci. Quantitatively, there were up
to 8 times more microorganisms under composite fillings. Beneath amalgam,
we found microbes similar to the flora of carious dentine and carious plaque,
with anaerobic and facultatively anaerobic gram-positive rods dominating.
|Bacterial sample on selective blood agar typical for
a composite filling.
||Bacterial sample on selective blood agar typical for
an amalgam filling.
Quantity in CFU/ml
X2 X3 X5
number of isolated strains
Amalgam: Opatients number
Quantitative degree of bacterial growth beneath composite and amalgam
Discussion and Conclusions
The microflora that we found under composite restorations had a great variety
of anaerobes. This spectrum is similar to the microflora of infected root
canals. The shift from a dental-plaque-like flora to an anaerobic microbial
spectrum may be attributable not only to the age of the composite fillings
because amalgam fillings showed a quite different spectrum with
streptococci, Lactobacilli and Actinomyces but also to the composition
of the composite material itself.
Hence, under certain circumstances, inadaquate composite fillings resulting
in secondary caries can promote pulpal infection with obligate anaerobes.
Although the low number of cases does not allow generalization, our results
do suggest that the kind of filling material used has a determining influence
on the composition of the remaining or penetrating microflora under restorations.
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This Poster was submitted on 26.07.00 by
Dr. Annegret Heinrich.
Dr. Annegret Heinrich
Zentrum für Zahn-, Mund- und Kieferheilkunde Greifswald
D - 17487 Greifswald