Search PubMed⌕ Search

Biomedical subjects

V Jerolimov

Publications and source records attributed to V Jerolimov.

At least 37 records · Page 2Linked to original sources
PubMed1997

The response of human premolars to cyclic loading.

The aim of the study was to obtain data on the dynamic strength of both intact and prepared premolars for partial veneer crowns. Cyclic loading was performed in a modified Amslers high-frequency pulsator with varying force (between 400 and 1400 N). The greatest dynamic strength was exhibited by the intact samples. The greater the load the fewer the cycles necessary to fracture the tooth. A statically significant difference was found (P < 0.05) between the magnitude of cyclic loads and the different types of specimens tested.

Analysis of Variance↗
PubMed1997

Comparative review of gnathometric characteristics in total dentures and eugnathic subjects.

The problem of determining the position and lining of the teeth in total dentures is presented by a comparative examination of gnathometric variables in eugnathic subjects and in those wearing total dentures. The material consisted of 51 plaster casts of eugnathic subjects and 49 subjects wearing total dentures. The following were examined: upper total number of incisors (T1), anterior width (AW), posterior width (PW), anterior length (AL) and posterior length (PL) of models. Analysis of the investigated variables was carried out by means of sliding calipers MECANIC Type 6901 (IVOCLAR, Lichtenstein) with a scale of 0-130 mm, and reading accuracy 97.5%. A three-dimensional pair of compasses according to Korhaus (Dentaurum, Germany) was used to measure the anterior and posterior lengths of models, with a scale 10-60 mm and reading accuracy 95%. No significant difference was observed between the eugnathic subjects and subjects wearing total dentures (p > 0.05). The results of this comparative gnathometric analysis of examined variables (Tl, AW, PW, AL and PL) are a contribution to the rules when lining anterior and posterior teeth in total dentures.

Dentition↗
PubMed1997

Radiographic cephalometry of the facial profile.

Radiographic cephalometry is a biomorphological measuring method used in the prosthodontics as well, and for the facial profile analysis of persons with complete dentures. The purpose of this examination was to objectivize the facial esthetics in patients with complete dentures. The measurements were taken from LL X-ray radiographs obtained by the apparatus "Ortoceph 10" (Siemens, Bensheim, Germany). On the sample of 80 subjects a convexity angle of facial bone structures (N-A: A-Pg) and profile angle of soft facial tissue (ft-unt: lnt-ct) have been examined. The subjects were divided into a group with upper and lower complete dentures (20 males and 20 females) and a group with natural teeth of eugnatic characteristics (20 male and 20 female). The measurements were taken by standard protractor at 0.5% precision. The statistical analysis within and among groups has been made by F-test and t-test respectively. The results showed that the bone structure convexity angle span a range between 0 degree and 5.5 degrees (X = 2.5 degrees), and the facial profile angle between 139.5 degrees and 155 degrees (X = 149 degrees) in persons with complete dentures. In persons with natural teeth the values of bone structure convexity angles span a range between -0.5 degree and 4.8 degrees (X = 2 degrees), and the facial profile angle between 136 degrees and 155.5 degrees (X = 151 degrees). The results of tests proved that there were no statistically significant differences in examined variables between persons with natural teeth and those with complete dentures (p > 0.05). The conclusion is that clinical methods of determining the vertical and horizontal intermaxilliary relations used in the designing procedures of complete dentures were reliable enough in reconstruction of examined angles of soft and hard facial profile structures.

Case-Control Studies↗
PubMed1996

Dynamic mechanical thermal analysis of denture soft lining materials.

The purpose of this study was to characterize the deformation properties of a range of long-term denture soft lining materials using dynamic mechanical thermal analysis. Specimens were subjected to sinusoidal shear deformation at a frequency of 1 Hz and a strain of 64 microns peak to peak over a temperature range of 30-70 degrees C. The technique simulated the type and rate of deformation soft lining materials would experience clinically, thus producing more relevant results than previously used methods. Shear modulus G', dissipative modulus G' and mechanical loss tangent G'/G' were obtained for each material. With increasing temperature the moduli of the acrylic materials decreased, indicating an increased compliance and greater deformation. The silicone (Molloplast B) and alternative formulation (Novus) properties were generally insensitive to temperature over the range chosen. The mechanical loss tangent values of the acrylics fell continuously with temperature, suggesting that the plasticization process lowered the Tg values below 30 degrees C, the lowest temperature of testing.

Acrylates↗
PubMed1995

Wettability of denture soft-lining materials.

Data on the wettability of long-term resilient denture base lining materials have previously been obtained by static methods. This study determined the dynamic contact angle of a range of long-term resilient lining materials and the surface free energy properties of these materials. This method was a rapid and convenient method for determining wettability parameters. The equilibrium contact angle revealed the Flexor and Novus materials to be the least wetted with the Molloplast-B material, and CoeSuper-Soft material was wetted similarly to Trevalon material. The contact angle hysteresis indicated that all the soft-lining materials tested would improve denture stability under dislodgment forces. The surface-free energies appeared to be similar for all the soft-lining materials but were significantly lower than that of Trevalon.

Acrylic Resins↗
PubMed1991

Effect of the curing cycle on acrylic denture base glass transition temperatures.

Glass transition temperature of a polymer is an important physical property which may have a major effect on the dimensional stability of denture base materials. Thermomechanical analysis has been used to determine the glass transition temperature of specimens of denture base materials which had been produced by various selected curing cycles. It was found that different curing cycles produced variations in glass transition temperature of up to 20 degrees C.

Acrylic Resins↗
PubMed1991

The role of residual monomer in PMMA powder and methods of polymerization in the finding of residual monomer in poly(methylmethacrylate) denture base.

The amount of residual monomer in methylmethacrylate resins used for denture bases is directly dependent on the polymerization procedure chosen. Residual monomer in PMMA powder has not yet been fully clarified. The aim of this study was to determine the amount of residual monomer in some PMMA powders used for denture bases. The study included determination of the amount of residual monomer in specimens polymerized by various methods of polymerization, attempting to test the interrelationship between the finding of residual monomer in PMMA powder and the respective group of heath-cured resin specimens. Materials from the group of poly(methylmethacrylate) resins type I, class 1 (1--Biocryl R, Galenika, Belgrade-Zemun, and 2--Major Base R, Major Dental Industry, Torino) were used in the study. Experimental specimens were divided into two groups: (1) original PMMA powders; and (2) polymerized specimens obtained by two short curing cycles (a--fractional, classical, heterogeneous polymerization; b--using the Prestherm, Bego device) and three long-curing cycles of polymerization (a--14 h at 70 degrees C; b--7 h at 70 degrees C and 3 h at 100 degrees C; and c--14 h at 70 degrees C and 3 h at 100 degrees C). By 2 g of each powder/specimen were extracted with methanol for residual monomer to be demonstrated by a modified method of gas chromatography on a device manufactured by Perkin Elmer Co. (Norwalk, Conn., USA). Original PMMA powders contained a high but varying percentage of residual monomer. Polymerized specimens had significantly lower values of residual monomer as compared to PMMA powders.(ABSTRACT TRUNCATED AT 250 WORDS)

Denture Bases↗
PubMed1990

[Gas-chromatographic determination of residual monomer in polymethylmethacrylate dental materials].

A gas-chromatographic method for fast and quantitative determination of residual monomer (methylmethacrylate, MMA) in the polymethylmethacrylate mixture obtained by mixing polymerized powder and monomer from two different manufacturers (Biocryl and Mayor) was established. The material was prepared in two different ways: by the so-called classic and by current procedures. Pulverized material was extracted by methanol and the content of free methylmethacrylate in the extract measured using a flame ionization detector on a 1.5 m, 6/3 mm glass column with a DC-200 filling (10%) on a Chromosorb WHP, 100/120 mesh and at constant temperature of 170 degrees C. For Biocryl, mean values x = 2.147 g/100 g of ground specimen (SD, 0.111) obtained by the "classic" procedure, and x = 2.199 g/100 g of ground specimen (SD, 0.166) for polymerisate obtained in a Presstherm device, respectively, were obtained. For Mayor, mean values x = 1.544 g/100 g of ground specimen (SD, 0.222) of the polymer obtained by the "classic" procedure, and x = 1.205 g/100 g of ground specimen (SD, 0.317) for polymerisate obtained in a Presstherm device, respectively, were recorded. The lower limit of MMA detection under chromatographic conditions was 0.01 mg.

Chromatography, Gas↗
PubMed1989

Rapid curing of acrylic denture-base materials.

A rapid-cure polymerization of cure, including a terminal boil, with respect to transparency, residual monomer, mechanical properties, and generation of gaseous porosity. It was found that in order for porosity-free resin to be produced during rapid curing, a low concentration (approximately 0.26%) of benzoyl peroxide initiator in the powder component is vital, and a very small concentration (approximately 0.025%) of the chemical activator dimethyl-p-toluidine in the monomer component is an advantage. Mechanical properties were only influenced where substantial porosity existed, but it was recognized that a material "tailor-made" for rapid curing would be most welcome.

Acrylic Resins↗
PubMedDate not supplied

Some effects of varying denture base resin polymer/monomer ratios.

Variations in the polymer/monomer mixing ratios from 1.5:1 to 4.5:1 vol/vol have been evaluated to determine the effect on dimensional accuracy and impact resistance of a PMMA homopolymer. Two polymerisation cycles were used. It was shown that a wide variation in mixing ratios (1.5:1 to 4:1) had no effect on dimensional accuracy or impact resistance and that a polymerisation cycle that includes a final boiling period is preferred. It was further found that notched impact resistance was almost an order of magnitude below unnotched impact resistance, emphasising the weakening effect of sharp contours on the impact resistance of denture resins.

Acrylic Resins↗