N.F.Faraschuk, vice-rector science, Smolensk state medical academy, professor, PhD chemistry
L.M.Tsepov, corresponding member of Russian Academy of Natural Science, professor, PhD medicine
S.K. Kirillov, professor, PhD biology
A.I.Nikolaev, senior lecturer, PhD medicine
P.G. Adamov, senior lecturer, PhD technical
Smolensk state medical academy
«Dental Market» journal, ¹ 2, 2005
A big number of various filling materials is used at present in therapeutic stomatology.
Micro-hybrid composites, compomers and glass ionomer cements are widely used in chargeable dental services. Recently new groups of composite materials appeared: condensable for chewing teeth, micro-filled for esthetic restoration of frontal teeth and flowable composites.
However in budget-financed medical establishments due to economic reasons silicon-phosphate cement «Silidont» is still in wide use, self-cure composites and inexpensive light-cure composites like «Prizmafil» (StomaDent), «Alpha-Dent» (Alpha-Dent) and other are used.
Usually the choice of filling material is made empirically, on the basis of financial capability of the patient and personal preference of the doctor. This explains relatively big percentage of failures even when the filling is made with new expensive composites. Breach of edge sealing and edge defects are presented on Picture 1.
We explain this phenomenon by the fact that physical and mechanical characteristics of filling material do not correspond to conditions surrounding seal in the mouth. For example, the material used for sealing carious cavity Class I, according to Black, in particular should have high compression strength and create minimal tension at seal-tooth edge during polymerization process (since cavities of Class I had high C-factor). The material used for filling carious cavities of Class II, according to Black, should have high fractural strength and reliably provide impermeability at seal-tooth edge in the area of gingival wall. The material used for sealing carious cavities of Class IV, where the filling experiences considerable pressures in various directions, apart from acceptable esthetic characteristics, should possess high diametric, fractural and twist strength.
The most frequent complication in clinical therapeutic stomatology is the destruction of composite seals in carious cavities of Classes I and II in molars experiencing chewing pressures (Picture 2). One of the reasons – insufficient mechanical strength of some modern universal composites in which strength characteristics are sometimes sacrificed for the sake of esthetic properties. It is well known that the less filler particles size the better are aesthetics of material but the lower is its strength. And vice versa: if filler particles size is increased, the material strength becomes higher but its aesthetic qualities become worse (Picture 3).
In line with above said, it is important for practical dentistry to compare strength characteristics of modern composite filling materials used for the sealing of chewing teeth.
The purpose of the current research: in vitro analysis of fractural strength of modern light-cure composite materials used in clinical therapeutic stomatology for the sealing of chewing teeth.
Research material and method
The research has been carried out in the laboratory of Smolensk State Medical Academy (head of laboratory – professor N.F.Faraschuk).
We have studied properties of the following composite materials:
- Valux Plus (3M ESPE);
- Filtek Z250 (3M ESPE);
- Charisma (Heraeus/Kulzer);
- Herculite XRV (Kerr);
- Spectrum TPH (Dentsply);
- Prizmafil (StomaDent);
- Filtek Ð 60 (3M ESPE).
The research has been made in accordance with GOST R 51202-98.
Material samples were prepared with the use of a special form, depicted on Picture 4. It allows to get filling material samples in the form of bars 25 mm length and 2 x 2 mm sectional area. The material was placed in the form slot and light-cured with polymerization lamp «Degulux» during time period recommended by producing company. After solidification the samples were held in distilled water at t 37°Ñ during 24 hours.
After that the evaluation of strength characteristics of materials took place.
For this we used a device which represented 2 linear supports holding the sample. The distance between them was 20 mm. Constantly growing pressure was applied to the middle of the sample (Picture 5). In the beginning of test process a reversible elastic deformation of material takes place. After the elasticity limit has been reached, non-reversible plastic deformation begins, and soon after that the sample breaks down. The force needed to break the sample is called fractural strength limit of material (Picture 6).
Results and their discussion
Our research has shown that strength characteristics of tested materials differ quite substantially. On average, samples made of composites (having the thickness of a match!) withstand pressure of 3-5 kilograms (Picture 7).
It should be noted that the strength of nationally-produced material «Prizmafil» (Picture 8) is not inferior, but is often superior to the strength of some modern imported composites. The results obtained during our research and our own clinical experience allow to recommend «Prizmafil» for wider clinical use, in particular for sealing carious cavities in chewing teeth.
At the same time one should remember that «Prizmafil» adhesive system provides reliable bonding of material only with etched enamel and glass ionomer cement; it does not have adhesion to dentine. Therefore when sealing with «Prizmafil» one should use either bonding-technique (Picture 9), open sandwich (Picture 10) or closed sandwich technique (Picture 11) in combination with glass ionomer cement, for example, «Dentis», «Chemfil Superior» or «BaseLine» (Pictures 12, 13, 14).
Source: www.rusdent.com/modules.php
