This study investigated the impact of a separate silanization step on the repair bond strength of composite substrates using a universal adhesive after various mechanical surface treatments. Composite specimens were aged and exposed to the following mechanical roughening treatments: diamond bur abrasion, aluminum oxide sandblasting, or silica coating. The specimens were then either left untreated or conditioned with universal adhesive (Scotchbond Universal), or a silane coupling agent was applied before the use of the universal adhesive or a conventional adhesive (Optibond FL). The conditioned surfaces and fresh substrate (positive control group) were covered with repair composite, and microtensile bond strength testing was performed. The significantly highest bond strength was obtained in the positive control group. Repair bond strength of the universal adhesive applied after a separate silanization step was similar to that without prior silanization, independent of the mechanical surface treatment. Moreover, after silica coating, no significant differences in the repair bond strength were detected among the different adhesive treatments. In conclusion, a separate silanization step before surface conditioning with the universal adhesive does not enhance the repair bond strength. On silica-coated composite substrates, repair bond strength values of the universal adhesive were similar to those of the conventional adhesive.

Enzymes in toothpastes can support host immune responses, and thus maintain oral health. This study aimed to investigate gingival health and the plaque-reducing effects of enzyme-containing toothpastes. A laboratory study tested the antimicrobial potential of different enzyme-containing toothpaste formulations. Two promising formulations (enzyme-containing toothpastes with glucose oxidase and D-glucose with (C+) and without Citrox (C−) Citrox) were investigated in a clinical crossover trial (two slurries: sodium lauryl sulfate-containing (SLS), a toothpaste without SLS (reference), and water). Subjects (n = 20) abstained from toothbrushing for four days and rinsed with a toothpaste slurry. Bleeding on probing (BOP) and plaque indices (PI) were measured. A mixed linear model was used to statistically compare the slurries with respect to BOP and PI change. The in vitro bacterial growth-inhibiting evaluation showed the best results for SLS, followed by C+ and C−. The change in BOP and PI exhibited statistically significant differences to water rinsing (BOP; PI changes in % points (difference of the baseline and post-rinse values: water = 8.8%; 90.0%; C+ = −1.4%; 80.4%; SLS = 1.5%; 72.1%; reference = 0.8%; 77.5%; C− = −1.8%; 75.1%). All slurries exhibited anti-gingivitis and anti-plaque effects, resulting in a prophylactic benefit for limited-access regions during brushing.

Laser-activated irrigation (LAI) of root canal systems depends on the generation of cavitation bubbles in the endodontic irrigant. Physical studies thus far focused on pulse energy, pulse length, frequency, and fiber tip shape, mostly in plain water. This study investigated the effect of endodontically relevant molecules (sodium hypochlorite (NaOCl), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), and their combination) in water on physical properties of the resulting solution, and their impact on primary cavitation bubble features. A commercially available 3% NaOCl irrigant was used, as well as an etidronate powder (Dual Rinse HEDP) to be admixed. Physical parameters (density, surface tension, and viscosity) of these solutions were assessed, including HEDP effects in an ascending concentration series of up to 20%. Primary cavitation bubble features (dimensional and temporal) in conjunction with a pulsed erbium-doped yttrium aluminium garnet (Er: YAG) laser equipped with a flat or conical fiber tip were studied in these liquids using a high-speed camera. Solutes increased the solution’s density, surface tension, and viscosity, with an almost linear response to HEDP dosage (Pearson correlation coefficient > 0.95). This reduced the speed of the primary cavitation bubble, and increased its size and lifetime. Increased HEDP concentrations had a pronounced effect on the shape of bubbles generated at the flat tip. NaOCl and HEDP alter the physical properties of water, which, in turn, affect its cavitation behavior.

The aim of this study was to weigh dissolving versus physical effects of laser-activated irrigation (LAI) when cleaning simulated human root canals. Dentin debris was selected as the composite organic/inorganic substrate. The cleaning effects of plain 3% sodium hypochlorite (NaOCl, proteolytic), plain 9% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP, decalcifying), or combined 3% NaOCl + 9% HEDP (NaOCl+HEDP, combined effect) were compared to those of deionized water (no dissolving effect on substrate). Properties of test and control solutions were assessed, including their absorption of infrared light and their viscosity. The isthmus of transparent root canal models (n = 22) was filled with dentin debris obtained from bovine tooth roots. Activated irrigation was done on the models in random order in 3 cycles of 30 s each, at 612 mW/18 Hz. The area of removed debris was measured using digital microscopy. The influence of the irrigating solution on debris removal was assessed by one-way ANOVA and Tukey’s HSD, alpha = 0.05. Infrared absorbance spectra were similar between solutions. Density and viscosity increased cumulatively with the solutes under investigation. The combined NaOCl+HEDP solution displayed a significantly (p = 0.002) better cleaning effect than the plain counterparts, which did not remove more debris from the isthmus than water (p>0.05). Under current conditions, the known dissolving effects by NaOCl and HEDP per se did not affect dentin debris removal by LAI, which was mainly due to physical dislodgment of the debris. The enhanced LAI-endorsed cleaning by the combined NaOCl+HEDP irrigant could be related to altered fluid properties and should be explored in further experiments.

Introduction: The impact of contemporary endodontic motors on shaping outcomes has not been weighed against that of the motor operators.Materials and methods: One motor (X-Smart Pro+) specifically developed for the reciprocating files that were used (Reciproc Blue R25) was compared to three cordless counterparts, two of which lacked a designated reciprocation mode. Standardized J-shaped canals in bovine incisor roots were instrumented by four different operators, who were residents with similar levels of education and clinical experience. One reciprocating file per simulated root canal was used. The root canal models were pre-warmed and kept in a vice at 37°C in a water bath. The operators were instructed to instrument two simulated canals per motor in a random sequence, applying three pecking motions and alternating with 3% NaOCl irrigation. Instrumentation time was measured. Pre- and postoperative images obtained using a digital microscope were superimposed to assess canal transportation. Parametric tests (two-way ANOVA) were applied to weigh the overall effects of the motor and operator on instrumentation time and canal transportation. The impact of the motor and operator on the number of unwound flutes was explored using likelihood ratio tests. The level of significance was set at 5% (P < 0.05).Results: Operators had a highly significant (P < 0.001) impact on instrumentation time and file unwinding, while motors did not (P > 0.05). File unwinding was negatively correlated with instrumentation time (P < 0.001). There was no effect of either the motor or the operator on canal transportation (P > 0.05).Conclusion: Technological advancements in endodontic motors do not necessarily compensate for operator variability.