Michael Rosin

Polymerization shrinkage-strain and microleakage in dentin-bordered cavities of chemically and light-cured restorative materials.

OBJECTIVES The aim of this study was to evaluate in vitro the relationship between polymerization shrinkage and microleakage in dentin-bordered restorations. METHODS Four light-cured restorative materials in combination with their respective dental bonding agents (DBA) were investigated: Tetric Ceram/Syntac classic (Vivadent), Solitaire/Gluma Solid bond (Heraeus Kulzer), Definite/Etch & Prime 3.0 (Degussa), Solitaire 2/Gluma Solid bond (Heraeus Kulzer). The chemically cured resin Degufill sc microhybrid (Degussa) in combination with ART Bond (Coltène) was also included. Polymerization shrinkage of the restorative materials was measured using three different methods (dilatometer, linometer, buoyancy method) and analyzed with ANOVA. For the determination of microleakage, caries-free human molars were embedded in acrylic resin and subsequently abraded with a wet abrasion machine to produce four level dentin surfaces. One hundred sixty cavities (3 mm diameter/1.5 mm deep) were randomly assigned to four groups of equal size. The groups were restored without (group 1 and 2) and with DBA (group 3 and 4), and either not subjected (group 1 and 3) or subjected (group 2 and 4) to 2000 cycles from 5-55 degrees C. Each group was further divided into five material subgroups of eight cavities each. Microleakage was determined using a dye penetration test assessed at depths of 200, 400 and 600 microm into the fillings. Data were analyzed with the Kruskal-Wallis and the Mann-Whitney test. RESULTS All three methods of measuring polymerization shrinkage (PS) generated the same, statistically secured ranking for the four light-cured restorative materials: PS Definite < PS Tetric Ceram < PS Solitaire 2 < PS Solitaire. In the microleakage study, only a few statistically significant differences were observed. Etch & Prime 3.0/Definite in group 3 and Solid Bond/Solitaire 2 in group 4 tended to exhibit the least microleakage. Correlation coefficients between aggregated shrinkage and microleakage data were 0.3 for group 3 and -0.2 for group 4. SIGNIFICANCE The results do not suggest any correlation between polymerization shrinkage and microleakage in dentin of direct adhesive restorations.

Effect of cement type on retention of a tapered post with a self-cutting double thread.

OBJECTIVES The aim of this in vitro study was to examine the effect of varying the cement type on the retention of a prefabricated tapered titanium post with a self-cutting double thread (Perma-tex activ). METHODS A total of 130 suitable roots from extracted human permanent teeth were selected. Post holes were prepared using the instruments supplied with the post system. One-hundred-twenty posts (medium size) were luted with one of four luting agents: a zinc-phosphate cement (Harvard), a glass-ionomer cement (Ketac Cem), a compomer luting agent (Dyract Cem), and a new capsulated composite luting system (Compolute). The cement groups were subdivided into three treatment groups with 10 posts each: group 1 (4-week water storage at 37 degrees C), group 2 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C), group 3 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C, 3 x 4 min mechanical stress: 40N vibrations). Another 10 posts inserted without cement and stored like group 1 served as a control. Retention was measured on a universal testing machine (Zwick Z050/TH3A) with a crosshead speed of 0.1cm/min. Data were analyzed using ANOVA with a Bonferroni or Tamhane adjustment for multiple comparisons (significance level alpha=0.05). RESULTS In group 1, Dyract Cem was significantly more retentive than the other three cements and the control group (no cement). In group 2, Compolute demonstrated significantly higher retention than Harvard and Ketac Cem. In group 3, Compolute, Dyract Cem, and Ketac Cem obtained higher retentive values than Harvard without differing from one another. Within the cement groups, thermocycling (group 2) caused a significant decrease in retention compared to group 1 only for Dyract Cem. All cements except Compolute were different from group 1 after a combination of thermocycling and mechanical stress (group 3). CONCLUSIONS The retention of the tapered post with a self-cutting double thread was significantly influenced by the cement type used.

The Peritoneal Explant Test for Evaluating Tissue Tolerance to Mouthrinses

The tissue cultures of explants of neonatal rat peritoneum have been demonstrated to be a sensitive test for tissue compatibility with wound antiseptics. The present study investigated the suitability of this method to assess the relative toxicity of mouthrinses to tissue. Mouthrinses containing 0.1% chlorhexidine (Chlorhexamed® Fluid 0.1%) (A), 0.3% triclosan (Colgate®) (B), essential oil in ethanolic solution (Listerine®) (C), and amine/stannous fluoride (Meridol®) (D) were tested at use concentration and in dilutions of 10, 1, and 0.1% with exposure times of 1, 10, and 30 min, respectively. The mouthrinses (test) and Ringer’s solutions (control) were applied to opened rat peritoneum. After thorough irrigation with Ringer’s solution, a piece of peritoneum was removed and 1 × 1 mm explants were cut. The explants were cultivated with a bovine serum culture medium in 24-well plates at 37°C in a CO2 incubator (95% air, 5% CO2). After 10 days, the tissue proliferation for the explants was assessed by a stereo microscope at 10× magnification after ethanol fixing and hemalaun staining. With 24 grafts per test, the proliferation rate was calculated relative to a control, which was run for each mouthrinse and concentration/time combination. Data were analyzed using ANOVA (SPSS 11.0) and post-hoc paired t test. Statistical significance of all correlations was tested by setting the significance level at p < 0.05. At most concentrations, D caused significantly less tissue damage than A or B. There was no difference between C and A or C and B at 100%. However, the toxicity of C was significantly less than A or B at 10, 1, and 0.1%. C and D behaved similarly except for the 10% (30 min) and the 1% (10 min) solutions in which C was significantly less toxic. We concluded that the rat peritoneum explant test was demonstrated to be a sensitive test to assess the relative toxicity of mouthrinses to tissue.

Activities of lysozyme and salivary peroxidase in unstimulated whole saliva in relation to plaque and gingivitis scores in healthy young males.

Abstract The purpose of the present investigation was to study the suitability of the salivary activity of lysozyme and salivary peroxidase for monitoring the inflammatory state of the gingiva. Salivary peroxidase and lysozyme activities in resting whole saliva were measured in a group of 140 male subjects (aged 18–30 years). A full mouth, clinical assessment of the plaque index (PI) and the sulcus bleeding index (SBI) was made and gingival crevicular fluid (GCF) flow was measured at teeth 16, 12, 24, 36, 32 and 44 with the Periotron 6000. There were no significant differences in the mean values of lysozyme and salivary peroxidase activities between groups with different PI, SBI and GCF flow values. Statistically significant correlations were found among the clinical parameters, with SBI and PI showing the strongest relation (r=0.47). The correlation between GCF flow and PI was higher (r=0.43) than the correlation between GCF flow and SBI (r=0.20). However, there were no statistically significant correlations between the activities of salivary peroxide and lysozyme and the clinical measures of gingival health.