Intra-pulpal and subsurface temperature rise during tooth irradiation with 808 nm diode laser: an in vitro study.

AIM: This in vitro study evaluated the pulpal and subsurface temperatures during proximal tooth surface irradiation with different settings of an 808 nm diode laser. MATERIALS AND METHODS: The elevation of pulpal and subsurface temperature during irradiation was measured using thermocouples positioned in the centre of the pulp chamber (n=30) and in the centre of a prepared 1.5 mm deep coronal cavity (n=30). Each sample was irradiated 3 times within one-week interval using different exposure settings. A temperature increase of 3.5°C was regarded as critical value for pulpal heath. Results were analysed with one-way ANOVA and Duncan post hoc tests. Micromorphological investigation by digital microscopy was carried out for the irradiated and non-irradiated tooth surface. RESULTS Measurable temperature increase within the pulp chamber (delta PT) and the subsurface (delta ST) were observed with all laser settings tested. The highest recorded delta PT and delta ST were 3.1°C and 8.5°C, respectively. Delivery mode, beam diameter, and exposure time influenced the temperature rise. No alterations on the enamel surface were observed when inspected by the digital microscope after undergoing irradiation with the tested parameters. Cconclusion: From the thermal point of view, under the conditions of the present study the application of an 808 nm diode laser on the outer surface of the tooth at 1W in the continuous mode and at 5W in the pulsed mode for two cycles of 30 s each proved to be safe.

Immediate endodontic access cavity sealing: fundamentals of a new restorative technique.

Endodontic access cavity sealing is conventionally performed after endodontic irrigation, referred to as delayed endodontic sealing (DES). Evidence shows that endodontic irrigation with NaOCl decreases dentinal bond quality and could cause coronal leakage. Access cavity sealing before endodontic irrigation is a new restorative approach, referred to as immediate endodontic sealing (IES). The primary aim of this in vitro study was to investigate whether IES improved internal adaptation. The secondary aim was to investigate the influence of the viscosity of the composite used to seal the dentine, on the internal adaptation in both IES and DES groups. Third molars (n= 40) with fully developed apices were used. The teeth were prepared into standard Class II MO cavities, and divided in 4 groups according to the approach, and composite viscosity was used for sealing. Group 1: IES + low viscosity composite; group 2: IES + high viscosity composite; group 3: DES + low viscosity composite; and group 4: DES + high viscosity composite. Samples were then sectioned axially for observation using scanning electron microscopy. Outcome was evaluated by determining the internal adaptation of the samples, which was judged based on the percentage of a continuous margin at the tooth-composite interface. The results were analyzed using a two-way analysis of variance and Mann-Whitney test. IES groups exhibited significantly greater internal adaptation (p = 0.000) as compared with DES groups. Composite viscosity did not significantly affect internal adaptation in either IES or DES groups (p > 0.005).

Tunable DNA cleavage activity promoted by copper(ii) ternary complexes with N-donor heterocyclic ligands.

Several small molecules have the capacity to cleave DNA promptly at high yields, even under mild conditions. Usually, this activity has no constraints, occurring without external or user control. Here, we demonstrate that UV-light exposure can greatly enhance the DNA cleavage activity promoted by four ternary copper(ii) complexes. A remarkable photocontrolled activity was achieved, which may be interesting for chemical and biochemical applications.

Composite vs ceramic computer-aided design/computer-assisted manufacturing crowns in endodontically treated teeth: analysis of marginal adaptation.

OBJECTIVES: To compare the marginal adaptation between ceramic and composite CEREC crowns in endodontically treated teeth restored with endocrowns or with a short or a long post. METHODOLOGY: Forty-eight intact maxillary incisors were used. After endodontic treatment, the crowns were sectioned 2 mm coronally to the cemento-enamel junction, which provided a ferrule of 2 mm. The prepared teeth were divided randomly into six groups (n=8). Group 1 was restored with a large fiberglass post, composite core, and ceramic full-coverage computer-aided design/computer-assisted manufacturing (CAD-CAM) crown. Group 2 was restored with a short fiberglass post, composite core, and ceramic full-coverage CAD-CAM crown. Group 3 was restored with a large fiberglass post, composite core, and composite full-coverage CAD-CAM crown (LPCpr). Group 4 was restored with a short fiberglass post, composite core, and composite full-coverage CAD-CAM crown (SPCpr). Groups 5 and 6 were restored with ceramic and composite CEREC machined endocrowns, respectively (EndoCer and EndoCpr). The restored teeth were loaded thermomechanically in a computer-controlled chewing machine. Impressions of each restoration were made in a polyvinylsiloxane material before and after loading. Gold-coated epoxy replicas were prepared for scanning electron microscopy examination at 200× magnification. RESULTS: Loading had a statistically significant effect (p<0.05) on the percentage of "continuous margin" in all groups. The LPCpr, SPCpr, and EndoCpr groups showed the highest percentage of continuous margin initially and after loading. The effect of the different post lengths on marginal adaptation was not significant (p>0.05). CONCLUSION: CAD-CAM crowns fabricated from millable composite resin blocks (Paradigm MZ100) offer a superior option to all-ceramic crowns (IPS Empress CAD).

Marginal adaptation of direct class II composite restorations with different cavity liners.

UNLABELLED: The aim of this study was to evaluate how cavity linings with different elastic modulus can influence the marginal adaptation (MA) of Class II composite restorations before and after thermo-mechanical loading. MATERIALS AND METHODS: Forty Class II cavities with margins extending 1 mm below the cement-enamel junction were prepared in extracted human third molars. In each group except the control group, a lining material of 1-mm thickness was applied to the bottom of the cavity and polymerized before placing the resin composite Herculite XRV Ultra (group A: control; group B: Premise Flowable lining; group C: Herculite XRV Ultra lining; and group D: Optibond FL lining). MA was evaluated (with a scanning electron microscope) before and after loading (200,000 loading cycles). Statistical analysis was done using the Shapiro-Wilks test, the analysis of variance test, and Duncan post hoc test at p<0.05. RESULTS: Before loading, the percentages of continuous margins in dentin were superior (p<0.05) for groups C and D (71.1% and 87.2%, respectively) compared to groups A and B (55.7% and 48.3%, respectively). After loading, group D (79.8%) was statistically superior in dentin compared to all of the other groups (43.6%, 35.9%, and 54.4%, respectively). In occlusal enamel, no significant difference was found between groups. The percentage of enamel fractures and the percentage of noncontinuous margins in proximal enamel were high, with no significant difference between liners. It can be concluded that for the materials used in this study, a 1-mm-thick lining with an extremely low elastic modulus (2-3 GPa) could redistribute shrinkage stress. The use of a flowable composite did not significantly improve MA.

Proximal direct composite restorations and chairside CAD/CAM inlays: marginal adaptation of a two-step self-etch adhesive with and without selective enamel conditioning.

The aim of this study was to evaluate the marginal adaptation of CEREC ceramic inlays, CEREC composite inlays and direct composite restorations in unbeveled proximal slot cavities under artificial aging conditions. Two groups of each restoration type were prepared (n = 6), one group with a self-etch adhesive, the other group with H(3)PO(4) enamel etching before the self-etch adhesive application. Replicas were generated before and after long-term thermo-mechanical loading under dentinal fluid simulation and margins were evaluated at x200 magnification in the scanning electron miscroscope (SEM). Statistically, significant differences were found before and after loading with respect to the percentages of "continuous margins", the direct composite filling with H(3)PO(4) enamel etching giving the lowest percentages of "continuous margins" after loading (p < 0.05). The highest percentage of "continuous margin" was attained by composite inlays without H(3)PO(4) enamel etching. However, these results were not significantly different from ceramic inlays after stressing. Polymerization shrinkage is still one critical property of composite restorative materials. The marginal adaptation of indirect adhesive proximal slot restorations without enamel bevels both fabricated out of composite and ceramic is better than that of directly placed composite restorations.