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The relationship between cavity adaptation and filler content of light curing composite resins
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J. Dent, 1990;
18: No. 1
Ca++ VLC Dycal5622 pg/ml and Cavalite almost no Ca++. Two df the three light-cured cavity liners released Ca++ ions over a 6-day period but al a much lower rate than Life. (2 1 references) Author’s abstract selected by W. Kullmann
Wyptyw technologii i obr6bki na zmiane wymiar6w ramiena retencyjnego prostego. (The role of casting and processing technique on the dimensional change of straight retentive clasp arms.) Dobies K. (1989) Protet. Stomat. 38, 66-70. The changes in dimension of clasp arms following casting and associated procedures were measured using an apparatus with an accuracy of 0.05 mm. The study was carried out on two groups of eight straight tapering cobalt-chromium specimens, 20 mm in length, which had been designed to withstand a load of 5 N in undercuts of 0.2 mm and 0.5 mm respectively. After casting, an average contraction of 8 per cenr was found at the base of the specimens, 75 per cent at the mid-point and 2 1 per cent at the rip. This should be allowed for when preparing wax patterns for cast cobaltchromium clasps. (7 references) M. J. Shapiro
The relationship between cavity adaptation and filler content of light curing composite resins. Tominaga Y., Ohsawa M., Nakamura N. et a/. (1988) Jap. J. Conserv. Dent. 31, 1628-l 635. The relationship between cavity adaptation and the filler content of light-curing composite resin (Study I), and the effect of a delayed polymerization reaction by irradiation away from the composite resin surface on adaptation of the light-curing composite resin to the cavity wall (Study 2), were investigated. Six light-curing composite resins, containing different amounts of filler (1 O-55 vol. per cent) composed of the same base resin matrix, were prepared. Cylindrical dentine cavities (3 mm in diameter, approximately 1.3 mm in depth) were prepared mainly on bovine teeth. The first series of restorations was performed without a bonding agent in order to understand the fundamental behaviour of light-curing composite resin in the cavity. The second series was done with a bonding agent (Gluma Bond System, Bayer, FRG). Composite resins were filled and pressed with a glass plate. Irradiation was continued for 60 s in contact with a glass plate or resin surface. Concavity of the resin surface together with the wall-towall contraction gap was measured microscopically. Specimens were cut for inspection of adaptation between the cavity wall and composite resin. In the second study, initial work revealed that irradiation 5 cm away from the resin surface could reduce the rate of curing reaction of the composite resin. After preliminary irradiation for 30 s in this manner, the same procedure as in the first study was performed using the resin containing 55 vol. per cent filler with bonding agent. The result was compared to that from the first study. It was found that the greater the filler content, the less was the concavity of the resin surface in both groups with or without bonding agent, Accordingly, the concavity
of the resin surface was dependent on the filler content of light-curing composite resin. The wall-to-wall contraction gap was independent of The amount of filler with a bonding agent. A high correlation was found however between the wall-to-wall contraction gap and the amount of filler without a bonding agent. From the examination of sectioned specimens, a similar gap was found at the cavity floor and side wall, respectively, despite the difference in the filler content with bonding agent. The size of the gap at the side wall was dependent on the filler content in the group without a bonding agent. Adaptation of the composite resin to the cavity was improved by de/a yed polymerization caused by irradiation away from the resin surface. As the concavity of rhe resin surface was much deeper than that induced by contact irradiation, compensating flow from the excess resin would occur and it would contribute to the improved adaptation of the restoration. (8 references) H. Hisamitsu
Untersuchung zur Anwendbarkeit des Excimer-Lasers in der Zahnheilkunde. (Investigation on the application of excimer-lasers in dentistry.) Liesenhoff T., Bende Th., Lenz H. et al. (1989) Zahn. Welt/Reform. 98, 328-33 1. The influence of 308 nm excimer laser radiation was investigated on extracted human teeth. Depending on the distance of the area of radiation to the pulp, the temperature rise ranged from 3*5”C (6 mm) to 18.2”C (< 0.5 mm). SEM investigations of radiated surfaces indicated good retention of filling materials. TEM investigations of radiated dental hard tissues demonstrated that there is no structural change of the ultrastructure below the radiated surface. (9 references) Author’s abstract selected by W. Kullmann
Thermische Ausdehnung und Plastifizierungstemperatur von Dentalklebern. (Thermal expansion and plasticizing temperatures of dental adhesives.) Marx R., Eggert G. and Beldner W. (1988) Drsch. Zahn&ztl. Z. 43, 465-468. Two criteria are important for the strength of a bonded union, the adhesive bonding strength of the bonded materials and the cohesive (internal) strength of the adhesive agent. Both types of strength are affected by dimensional changes of the adhesive agent. These dimensional changes are caused by thermal expansion, as well as swelling and softening of the adhesive due to water incorporation. The coefficient of thermal expansion of an adhesive is much greater than that of a metal, and temperature changes thus produce stresses which weaken the adhesive strength in the interface. In the glass transition temperature range the adhesive loses its strength due to plasticization and is pulled out of its tongue-and-groove retentions. Furthermore, humidity leads to a reduction in the glass transition temperature, which is critical for the strength. (6 references) Author’s abstract selected by W. Kullmann
J. Dent, 1990;
18: No. 1
Ca++ VLC Dycal5622 pg/ml and Cavalite almost no Ca++. Two df the three light-cured cavity liners released Ca++ ions over a 6-day period but al a much lower rate than Life. (2 1 references) Author’s abstract selected by W. Kullmann
Wyptyw technologii i obr6bki na zmiane wymiar6w ramiena retencyjnego prostego. (The role of casting and processing technique on the dimensional change of straight retentive clasp arms.) Dobies K. (1989) Protet. Stomat. 38, 66-70. The changes in dimension of clasp arms following casting and associated procedures were measured using an apparatus with an accuracy of 0.05 mm. The study was carried out on two groups of eight straight tapering cobalt-chromium specimens, 20 mm in length, which had been designed to withstand a load of 5 N in undercuts of 0.2 mm and 0.5 mm respectively. After casting, an average contraction of 8 per cenr was found at the base of the specimens, 75 per cent at the mid-point and 2 1 per cent at the rip. This should be allowed for when preparing wax patterns for cast cobaltchromium clasps. (7 references) M. J. Shapiro
The relationship between cavity adaptation and filler content of light curing composite resins. Tominaga Y., Ohsawa M., Nakamura N. et a/. (1988) Jap. J. Conserv. Dent. 31, 1628-l 635. The relationship between cavity adaptation and the filler content of light-curing composite resin (Study I), and the effect of a delayed polymerization reaction by irradiation away from the composite resin surface on adaptation of the light-curing composite resin to the cavity wall (Study 2), were investigated. Six light-curing composite resins, containing different amounts of filler (1 O-55 vol. per cent) composed of the same base resin matrix, were prepared. Cylindrical dentine cavities (3 mm in diameter, approximately 1.3 mm in depth) were prepared mainly on bovine teeth. The first series of restorations was performed without a bonding agent in order to understand the fundamental behaviour of light-curing composite resin in the cavity. The second series was done with a bonding agent (Gluma Bond System, Bayer, FRG). Composite resins were filled and pressed with a glass plate. Irradiation was continued for 60 s in contact with a glass plate or resin surface. Concavity of the resin surface together with the wall-towall contraction gap was measured microscopically. Specimens were cut for inspection of adaptation between the cavity wall and composite resin. In the second study, initial work revealed that irradiation 5 cm away from the resin surface could reduce the rate of curing reaction of the composite resin. After preliminary irradiation for 30 s in this manner, the same procedure as in the first study was performed using the resin containing 55 vol. per cent filler with bonding agent. The result was compared to that from the first study. It was found that the greater the filler content, the less was the concavity of the resin surface in both groups with or without bonding agent, Accordingly, the concavity
of the resin surface was dependent on the filler content of light-curing composite resin. The wall-to-wall contraction gap was independent of The amount of filler with a bonding agent. A high correlation was found however between the wall-to-wall contraction gap and the amount of filler without a bonding agent. From the examination of sectioned specimens, a similar gap was found at the cavity floor and side wall, respectively, despite the difference in the filler content with bonding agent. The size of the gap at the side wall was dependent on the filler content in the group without a bonding agent. Adaptation of the composite resin to the cavity was improved by de/a yed polymerization caused by irradiation away from the resin surface. As the concavity of rhe resin surface was much deeper than that induced by contact irradiation, compensating flow from the excess resin would occur and it would contribute to the improved adaptation of the restoration. (8 references) H. Hisamitsu
Untersuchung zur Anwendbarkeit des Excimer-Lasers in der Zahnheilkunde. (Investigation on the application of excimer-lasers in dentistry.) Liesenhoff T., Bende Th., Lenz H. et al. (1989) Zahn. Welt/Reform. 98, 328-33 1. The influence of 308 nm excimer laser radiation was investigated on extracted human teeth. Depending on the distance of the area of radiation to the pulp, the temperature rise ranged from 3*5”C (6 mm) to 18.2”C (< 0.5 mm). SEM investigations of radiated surfaces indicated good retention of filling materials. TEM investigations of radiated dental hard tissues demonstrated that there is no structural change of the ultrastructure below the radiated surface. (9 references) Author’s abstract selected by W. Kullmann
Thermische Ausdehnung und Plastifizierungstemperatur von Dentalklebern. (Thermal expansion and plasticizing temperatures of dental adhesives.) Marx R., Eggert G. and Beldner W. (1988) Drsch. Zahn&ztl. Z. 43, 465-468. Two criteria are important for the strength of a bonded union, the adhesive bonding strength of the bonded materials and the cohesive (internal) strength of the adhesive agent. Both types of strength are affected by dimensional changes of the adhesive agent. These dimensional changes are caused by thermal expansion, as well as swelling and softening of the adhesive due to water incorporation. The coefficient of thermal expansion of an adhesive is much greater than that of a metal, and temperature changes thus produce stresses which weaken the adhesive strength in the interface. In the glass transition temperature range the adhesive loses its strength due to plasticization and is pulled out of its tongue-and-groove retentions. Furthermore, humidity leads to a reduction in the glass transition temperature, which is critical for the strength. (6 references) Author’s abstract selected by W. Kullmann