Introduction. At present, the question of the influence of carious cavity edge design on the density of the adherence of restorative material to the enamel remains discursive; there is some confusion in the open access publications on this topic.
Objectives. To study the density of the adherence of restorative material to the enamel of teeth depending on the design of the formation of carious cavity edge.
Materials and methods. The research was carried out using 30 intact third molars extracted upon clinical indications. The samples were divided into three groups, 10 in each, depending on the formation of carious cavities of the 1st class according to Black classification. In group I a classical carious cavity with even, straight-edged walls without the formation of the bevel (folds) of the enamel was formed. In group II, the outer beveling of enamel was made at an angle of 45º to the enamel-dentine border. In group III, the cavity was formed with an internal beveling of enamel. Carious cavities were restored with micro-hybrid composite light cured material LATELUX (PE "LATUS", Kharkiv). One-time vertical mechanical load with a force of 98.07 N was performed on restoration, and treated with thermocycled in a mode of 200 cycles at a temperature from 5 °C to 55 °C with an exposure of 60 seconds at each temperature. The teeth were separated in a medio-distal direction through a center of restoration with diamond disks, placed in a column of a raster electron microscope with a low vacuum chamber REM 102, and the contact area of the restoration with solid tissues of the teeth was studied, the density of their adherence, and the present gaps were measured and expressed in micrometers (μm)
Results. Electron diffraction pattern of the samples of group I showed that the density of the adherence of the restorative material to the enamel of the carious cavity was different throughout: sometimes thick, sometimes the space in the contact area was determined. Moreover, the space was formed between the adhesive layer of the material and enamel. The space size averaged 7.90 ± 0.73 μm (95% CI: 6.3: 9.5). Enamel prisms adjoined in the area of contact with the material partly linear, longitudinal along its axis or transversely, obliquely with a slanted body.
In the samples of group II restorative material was evenly in contact with the layer of adhesive, adherence of which to the enamel edge of the carious cavity was dense almost throughout. But in some areas there was a violation of the contact of the enamel with the adhesive layer, there were cracks 2.76 ± 0.52 μm (95% CI: 1.6: 3.9). Enamel prisms in the area of contact with the material were located more transversely to their axis, obliquely with a slanted body.
In the samples of group III, the adherence of the restorative material to the enamel of the carious cavity was not dense almost throughout. The restorative material had a uniform contact with the adhesive. At the same time, there was a breach of contact in the form of cracks of 16.50 ± 0.89 (95% CI: 14.6: 18.4) μm observed between adhesive and enamel. Enamel prisms in the zone of contact with the material were linear, longitudinal along its axis.
Conclusions. The greatest density of the adherence of restorative material to the enamel of teeth occurs when forming the outer beveling of the enamel edge in the carious cavities of the 1st class according to Black classification.
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