Biomedical subjects

R D Marangoni

Publications and source records attributed to R D Marangoni.

9 recordsLinked to original sources

PubMed1997

In vitro comparison of debonding force and intrapulpal temperature changes during ceramic orthodontic bracket removal using a carbon dioxide laser.

The aim of this study was to develop a method to reduce the fracture of ceramic orthodontics brackets during debonding procedures. Lasers have been used to thermally soften the bonding resin, which reduces the tensile debonding force. Thermal effects of lasers may create adverse effects to the dental pulp. Previous studies have shown that no pulpal injury occurs when the maximum intrapulpal temperature rise stayed below 2 degrees C. This study investigated the effect of lasing time on intrapulpal temperature increase and tensile debonding force with a 18 watt carbon dioxide laser. Ceramic brackets were bonded to mandibular deciduous bovine teeth and human mandibular first premolars with a photoactivated bonding resin. Modified debonding pliers was used to accurately position the laser beam onto the ceramic bracket. Lasing time required to keep the maximum intrapulpal temperature rise below 2 degrees C was determined by the use of thermocouples inserted into the pulp chambers of the specimens. A tensile debonding force was applied on the control group without lasing and the experimental group was debonded after applying a predetermined lasing time with a carbon dioxide laser. It was found that there was a significance difference (P < 0.05) in tensile debonding force between the control group and the experimental group. It is feasible to use a laser for the debonding of ceramic brackets while keeping the intrapulpal temperature rise below the threshold of pulpal damage.

Adolescent↗

PubMed1996

Ceramic bracket debonding with the carbon dioxide laser.

The conventional removal of ceramic brackets can be complicated by bracket fracture or enamel loss. To ease this ceramic bracket removal, lasers have been previously investigated for thermally softening thermally the bonding resin. This conversion of laser light to heat can also threaten the vitality of the debonded teeth. Pilot studies and computer modeling suggest that for commonly used polycrystalline brackets debonded with the carbon dioxide laser, some form of mechanical assistance is needed during the lasing process to keep the intrapulpal temperature below the 5.5 degrees C safety threshold. One type of polycrystalline bracket was bonded to lower anterior bovine incisor teeth with one type of resin adhesive. A ceramic bracket debonding plier was modified to accommodate a laser waveguide so that a tensile debonding force could be applied simultaneously during lasing. A control group and three experimental groups were tested (n = 10). The three experimental groups were debonded with the carbon dioxide laser at 20 W and a static tensile force of 3 pounds, 1.5 pounds, or 0.75 pounds. The length of lasing time for the static force to remove the bracket was measured along with the increase in intrapulpal temperature. The mean debonding times and mean increases in intrapulpal temperature for each group were: 3 pound group, 1.64 seconds and 1.80 degrees C; 1.5 pound group, 1.83 seconds and 3.01 degrees C; and 0.75 pound group, 3.42 seconds and 4.47 degrees C.

Analysis of Variance↗

PubMed1988

The tensiometric properties of expanded guinea pig skin.

Our purpose in this study was to evaluate the tensile properties of expanded skin. In five guinea pigs, 29-cc ovoid tissue expanders were placed and sequentially expanded every 4 days until maximum volume was achieved. Five control and five expanded skins were harvested. Using an Instron tensile testing apparatus, skins were evaluated for stress-strain, maximum stiffness, and tensile strength, and the results were statistically compared. Centrally located expanded specimens demonstrated significantly weaker stress-strain values: 9.51 in.lb/in3 for expanded versus 30.11 in.lb/in3 for control (p less than 0.001). Maximum stiffness was similarly reduced: 4.56 lb/mm2 for expanded vs. 12.98 lb/mm2 for control (p less than 0.001). This is a 67.4 and 64.9 percent reduction, respectively, for the stress-strain and maximum stiffness. No statistically significant difference was seen in peripherally located expanded specimens relative to the controls: stress-strain expanded, 28.7 in.lb/in3 (p greater than 0.5); maximum stiffness expanded, 12.84 lb/mm2 (p greater than 0.5). Expanded skin demonstrated an average 35 percent reduction in tensile strength. We conclude that the tensile properties of expanded skin are significantly less than unexpanded skin and are a function of the degree of expansion.

Animals↗

PubMed1978