Efekti primene sredstava za retrakciju gingive na eksperimentalnim modelima
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When creating fixed prosthetic devices it is necessary to respect the integrity of the
periodontal structures and ensure maximum possible accuracy at the junction site of
artificial crown and biological tissue. When the preparation border area is situated at the
level or below the gingival margin, demarcation line should be made by reversible
temporary shift in apical direction to enable access of impression material. The most
commonly used gingival retraction agents are astringents (metal salts) and vasoconstrictors
(adrenalin). They are applied in the gingival sulcus of prepared tooth, thus dilating and
drying it out and creating optimal conditions for impression taking in indirect dental
restoration. Given that the retraction agents are in direct contact with the gingival tissue
their biocompatibility is of primary importance.
Biocompatibility of dental materials implies the capability of performing a
specific function in the oral cavity without causing side effects. However, it was...
established that the retraction agents might have iatrogenic effect on gingival tissue,
especially if the patient had already had periodontal disease or was prone to such
problems. The use of adrenalin may cause systemic reactions of the organism.
The study was based on the assumption that commercially available gingival
retraction agents exhibit some toxic effect on the surrounding tissues, and the degree of
damage varies depending on the type, concentration and the effect duration. Biologically
acceptable gingival retraction agents based on aluminum chloride and adrenalin should
be sought among sympathomimetic vasoconstrictors (tetrahydrozoline).
The aim of the study was comparison analysis of potentially toxic effects of
gingival retraction agents and tetrahydrozoline in vitro and in vivo conditions.
The tested material included three agents used for gingival retraction in dental
practice: two materials based on aluminum chloride (10% and 25% solution), 8%
adrenalin and 0.05% tetrahydrozoline solution.
Biocompatibility of gingival retraction agents was examined under in vitro
conditions on MDCK (Madin-Darby canine kidney) continuous cell line and under in
vivo conditions on experimental animals. MDCK cells may be considered analogous to
gingival epithelial cells, and the structure of gingival tissue and the depth of gingival
sulcus of the rabbit is almost identical to that in humans.
The effect of retraction agents and tetrahydrozoline on the viability and recovery
of MDCK cell line was observed using vital staining with trypan blue and non-standard
MTT assay. The solutions of the examined retraction materials obtained by dilution in
Ringer solution in 5%, 10%, 25% and 50% concentrations were used. Measurements of
the intensity of MTT reduction were performed immediately after a three, six and ten
minute effect period of materials to determine the viability, or after a period of one day
of cell recovery in a nutritious medium to determine the degree of recovery of cells.
The values obtained in in vitro conditions represented the basis for the statistical analysis
and were analyzed by SPSS 15.0. The analysis of variance (ANOVA) was used followed
by Post-Hoc analysis, and the levels of p <0.05 were considered statistically significant.
Quantitative changes in cell viability were presented descriptively as well.
In vivo research included the effect of retraction agents and tetrahydrozoline on
gingival tissue of experimental rabbits. The procedure and the seven minute application
period were identical to clinical setting. The negative control (absence of intervention)
and a false treatment (application of retraction floss without test agent) were predicted.
The biopsy of gingival tissues and control was carried out after the observational period
of one hour, one, seven and thirty days. The preparations were stained by means of
traditional method – Hematoxylin & Eosin and analyzed histologically. The distribution
of collagen fibers was determined under polarizing light. Evaluation of the results was
performed semiquantitatively, based on the presence of inflammatory reaction and
fibrosis tissue, as well as destructive-necrotic changes
In an in vitro study the hypothesis was proved that the viability and recovery of
the cell culture depended on the concentrations of the examined solution, the effect
duration, as well as the type of the applied material. As the concentration and duration
of action of the tested solutions of gingival retraction agents increased the cell viability
statistically significantly decreased, indicating the potential toxicity of tested materials.
Solutions of commercially available retraction agents proved to have no cytotoxic or
slightly cytotoxic effect at the lowest concentrations (5% and 10%) and upon the
observational period of three and six minutes. On the other hand, serious cytotoxic
effect was observed after a ten-minute period at higher solution concentrations (25%
and 50%) based on aluminum chloride. The results of the study proved the lowest
cytotoxic effect of alternative gingival retraction agents based on tetrahydrozoline. In
this type of material, decline of cell viability with an increase of effect duration and
solution concentration was noticed as well.
Comparison analysis showed statistically significant higher values of intensity
reduction of MTT immediately after effects of retraction agents compared to the results
obtained after the cell recovery. Taking into account the fact that cytotoxic effect of
tetrahydrozoline was low, the results of cell recovery in culture were expectedly
positive. In contrast, significantly higher values of cell viability immediately after the
effects of commercial agents in relation to the values after further incubation of cells
indicated the prolonged harmful effects of aluminum chloride and the possibility of
initiating a secondary inflammatory response.
The results of in vivo research pointed to the reversible damage of gingival tissue
after local application of materials based on aluminum chloride and adrenalin. An hour
after the removal no significant changes in the tissue structure were found. However, their
use resulted in an acute inflammatory response after the observation period of one and
seven days. After thirty days reparation of the damaged tissue was observed. Inflammatory
changes due to tetrahydrozoline application were of significantly lower intensity compared
to aluminum chloride and adrenalin and resulted in advanced healing after seven day
obsevation period and full tissue reparation tissue after thirty day observation period.
Tetrahydrozoline proved to be biologically more acceptable in relation to the retraction
agents tested.
The preparation based on tetrahydrozoline showed a higher degree of biocompatibility
in vitro and in vivo conditions, and is therefore recommended for everyday use in dental
practice. In order to prevent damage to the gingival tissue it is necessary to decrease the
concentration of the agent used for gingival retraction by rinsing gingival sulcus with saline
or water spray, reduce the duration of the retraction procedure to three to six minutes, as
well as controlled teeth preparing with minimal tissue damage.