Inhibition of the activity of matrix metalloproteinase 2 by triethylene glycol dimethacrylate

The aim of this study was to evaluate the effect of different concentrations of triethylene glycol dimethacrylate (TEGDMA) on the inhibition of matrix metalloproteinase 2 (MMP-2). Mouse gingival explants were cultured overnight in DMEM and the expression of secreted enzymes was analyzed by gelatin zymography in buffers containing 5 mM CaCl₂ (Tris-CaCl₂) in 50 mM Tris-HCl buffer with the addition of TEGDMA at different concentrations (0.62%, 1.25%, 2.5%, or 5.0% (v/v)). The gelatinolytic proteinase present in the conditioned media was characterized as matrix metalloproteinase by means of specific chemical inhibition. The matrix metalloproteinases present in the conditioned media were characterized as MMP-2 by immunoprecipitation. The eletrophoretic bands were scanned and the transmittance values were analyzed. Data was plotted and submitted to linear regression to investigate MMP-2 inhibition as a function of TEGDMA concentration. Three major bands were detected in the zymographic assays. These bands were characterized as MMP-2. Zymogene (72 kDa), intermediate (66 kDa) and active forms of MMP-2 (62 kDa) were inhibited by TEGDMA in a dose-dependent way. These findings suggest that TEGDMA could inhibit MMP-2 expression even at small concentrations.     

Influence of fluoride- or triclosan-based desensitizing agents on adhesion of resin cements to dentin

Effect of desensitizers on the bond strength of resin cements to dentin was evaluated. Intact premolars (N = 90) were embedded in polymethyl methacrylate; dentin surfaces were exposed, and they were randomly divided into two main groups of cements (Duolink (D), Variolink II (V); n = 45 per group) and then into three desensitizer subgroups (n = 15 per subgroup). Teeth in controls (C) were treated according to cements’ adhesion protocols; the other two groups received either fluoride- [Aqua-Prep F (F)] or triclosan-based [Seal&Protect (T)] desensitizers. Ceramic disks (Empress 2) were adhered; specimens were thermocycled (×5,000 cycles, 5–55 ± 1°C, dwell time 30 s) and subjected to shear bond strength test (MPa ± SD) in a universal testing machine (crosshead speed 1 mm/min). Failure types were classified using scanning electron microscope. For V, application of both desensitizers (29.6 ± 7.8 and 22.8 ± 2.8 for F and T, respectively) did not present significantly different results than that of the VC (21.2 ± 2.3; p > 0.05, one-way ANOVA). In D, F (20.6 ± 2.4) showed significantly higher results (p < 0.05) than those in T (16.1 ± 3.9) and DC group (15.2 ± 2.3). V showed significantly higher results than D (p < 0.05, Bonferroni). F and T did not negatively affect the bond strength results with D and V. Adhesive failures were more frequent with both T (84%) and F (66%) in D; cohesive failures in the cement (88%) were more commonly observed with F in V. Both F and T desensitizers can be safely used prior to final cementation but F in combination with V seems to be more reliable, considering both the bond strength and the failure types.     

Impact of Gluma Desensitizer on the tensile strength of zirconia crowns bonded to dentin: an in vitro study

This study tested the impact of Gluma Desensitizer on the tensile strength of zirconia crowns bonded to dentin. Human teeth were prepared and randomly divided into six groups (N = 144, n = 24 per group). For each tooth, a zirconia crown was manufactured. The zirconia crowns were cemented with: (1) Panavia21 (PAN), (2) Panavia21 combined with Gluma Desensitizer (PAN-G), (3) RelyX Unicem (RXU), (4) RelyX Unicem combined with Gluma Desensitizer (RXU-G), (5) G-Cem (GCM) and (6) G-Cem combined with Gluma Desensitizer (GCM-G). The initial tensile strength was measured in half (n = 12) of each group and the other half (n = 12) subjected to a chewing machine (1.2 Mio, 49 N, 5°C/50°C). The cemented crowns were pulled in a Universal Testing Machine (1 mm/min, Zwick Z010) until failure occurred and tensile strength was calculated. Data were analyzed with one-way and two-way ANOVA followed by a post hoc Scheffé test, t test and Kaplan–Meier analysis with a Breslow–Gehan analysis test (α = 0.05). After the chewing simulation, the self-adhesive resin cements combined with Gluma Desensitizer showed significantly higher tensile strength (RXU-G, 12.8 ± 4.3 MPa; GCM-G, 13.4 ± 6.2 MPa) than PAN (7.3 ± 1.7 MPa) and PAN-G (0.9 ± 0.6). Within the groups, PAN, PAN-G and RXU resulted in significantly lower values when compared to the initial tensile strength; the values of all other test groups were stable. In this study, self-adhesive resin cements combined with Gluma Desensitizer reached better long-term stability compared to PAN and PAN-G after chewing simulation.     

Shear bond strength of self-adhesive resins compared to resin cements with etch and rinse adhesives to enamel and dentin in vitro

Self-adhesive resin cements should ease the placement of dental restorations. The purpose of this study was to evaluate their shear bond strength to enamel and dentin. Sixty molars were randomly assigned to 12 test groups (each n = 10), and the approximal surfaces were ground flat to get an enamel and dentin surface with a diameter of at least 4 mm. Ceramic specimens were bonded to the surfaces with either Variolink/Syntac Classic (VSC), Panavia F2.0 (PAF), RelyX Unicem (RLX), Maxcem Elite (MCE), iCem (IC), or an experimental self-adhesive resin cement (EXP). The shear bond strength (crosshead speed: 1 mm/min) was measured after 24-h storage in NaCl (37°C). The fracture modes were determined with a stereomicroscope (magnification, 8–50-fold). VSC had the highest shear bond strength within the enamel groups (42.9 ± 9 MPa) and IC the lowest (10.5 ± 4.2 MPa, p < 0.001). The highest dentin shear bond strength was determined for VSC (39.2 ± 8.9 MPa, p < 0.001) and the lowest for EXP (7.8 ± 3.9 MPa, p < 0.001). Self-adhesive resin cements fractured mainly between resin and enamel or dentin. The shear bond strength of self-adhesive resin cements was inferior compared to conventional composite resin cements.     

Effects of citric acid administration on femoral trabecular structures in ovariectomized mice

Objectives To examine the effects of citric acid administration on trabecular structures. Methods Ovariectomized female ICR mice (n = 39), 8 weeks of age, were divided into four groups: ovariectomized control (OVX-control, n = 9, standard diet); citric acid (CIT, n = 10, citric acid 5 g/100 g diet); vitamin K₂ (menaquinone 7; VK2, n = 10, vitamin K₂ 50 μg/100 g diet); and citric acid + vitamin K₂ (CIT + VK2, n = 10, citric acid 5 g/100 g diet and vitamin K₂ 50 μg/100 g diet). After 12 weeks, the bone mass of the right femur was measured using peripheral quantitative computed tomography and the three-dimensional (3-D) trabecular structure of the right femur was assessed using microfocus computed tomography. Results The bone mineral density was significantly increased in the VK2 group versus the OVX-control group (P < 0.05). In the 3-D trabecular structure analysis, skeletal perimeter and number were significantly greater in the CIT, VK2, and CIT + VK2 groups than in the OVX-control group. Skeletal separation, spacing, and trabecular bone pattern factor were significantly lower in the CIT, VK2, and CIT + VK2 groups than in the OVX-control group. Almost all parameters in node–strut analysis were significantly greater in the CIT, VK2, and CIT + VK2 groups than in the OVX-control group. Conclusions These results suggest that citric acid improved trabecular structures. However, simultaneous administration of citric acid and vitamin K₂ did not have any additional effect.     

Effects of a composition containing lactoferrin and lactoperoxidase on oral malodor and salivary bacteria: a randomized,double-blind,crossover, placebo-controlled clinical trial

We report a clinical trial of the effects of test tablets containing bovine lactoferrin and lactoperoxidase on oral malodor and salivary bacteria. Fifteen subjects with volatile sulfur compounds (VSCs) in mouth air above the olfactory threshold (H₂S >1.5 or CH₃SH >0.5 ng/10 ml) as detected by gas chromatography were enrolled in the trial. Either a test or a placebo tablet was ingested twice at 1-h intervals in two crossover phases. Mouth air was monitored for VSC levels at the baseline before ingestion of a tablet, 10 min after the first ingestion, 1 h (just before the second ingestion), and 2 h after the first ingestion. Whole saliva was analyzed at the baseline and at 2 h for bacterial numbers. At 10 min, the level of CH₃SH was significantly lower in the test group (median [interquartile range] = 0.28 [0.00–0.68] ng/10 ml) compared to that in the placebo group (0.73 [0.47–1.00] ng/10 ml; P = 0.011). The median concentration of CH₃SH in the test group was below the olfactory threshold after 10 min until 2 h, whereas the level in the placebo group was above the threshold during the experimental period. No difference in the numbers of salivary bacteria was detected by culturing or quantitative PCR, but terminal restriction fragment length polymorphism detected one fragment with a significantly lower copy number at 2 h in the test group (mean ± standard error, 4.89 ± 0.11 log₁₀ copies/10 μl) compared to that in the placebo group (5.38 ± 0.15 log₁₀ copies/10 μl; P = 0.033). These results indicate a suppressive effect of the test composition on oral malodor and suggest an influence on oral bacteria.     

Influence of ozone on the composite-to-composite bond

The study evaluated the effect of ozone application on the composite-to-composite bond. Three hundred and twenty cylindrical composite specimens were divided into two groups: group 1 was subjected to a 60 s ozone application, whereas group 2 remained untreated. Four subgroups were obtained from each group according to the intermediate repair agent: an adhesive, a silane, silane/adhesive combination, or flowable composite. Repair composite cylinders were built-up. The composite repair strength was tested after 24 h and after thermocycling with a shear test. Additionally, 4 mm × 4 mm × 2 mm composite specimens were prepared and stored 24 h in deionized water. Half of the specimens were subjected to ozone application and the other served as control. The elastic modulus (E) and the Vicker’s hardness (VH) of the composite surfaces were tested immediately and after thermocycling. Significant differences among the experimental groups were detected (p < 0.001). The composite repair strength was affected by the pretreatment and by the intermediate agent, whereas, the thermocycling was not significant. The partial eta-squared statistics showed that the intermediate agent was the main factor affecting the composite repair strength, whereas the pretreatment played a minor role. No differences were observed between ozone and control groups when the same intermediate agent and the same aging conditions were applied. Repairing with flowable composite tended to achieve higher bond strengths (20.7 and 26.5 MPa in ozone and control groups, respectively, after 24 h). The use of silane coupling agent showed the lowest composite repair strengths. Ozone did not affect E and VH (p > 0.05) and the thermocycling affected only E (p < 0.05). In conclusion, the application of ozone does not impair the composite-to-composite bond.     

Physical properties of self-, dual-, and light-cured direct core materials

The objective of this study is to evaluate flexural strength, flexural modulus, compressive strength, curing temperature, curing depth, volumetric shrinkage, water sorption, and hygroscopic expansion of two self-, three dual-, and three light-curing resin-based core materials. Flexural strength and water sorption were measured according to ISO 4049, flexural modulus, compressive strength, curing temperature, and curing depth according to well-proven, literature-known methods, and the volumetric behavior was determined by the Archimedes’ principle. ANOVA was calculated to find differences between the materials’ properties, and correlation of water sorption and hygroscopic expansion was analysed according to Pearson (p < 0.05). Clearfil Photo Core demonstrated the highest flexural strength (125 ± 12 MPa) and curing depth (15.2 ± 0.1 mm) and had the highest flexural modulus (≈12.6 ± 1.2 GPa) concertedly with Multicore HB. The best compressive strength was measured for Voco Rebilda SC and Clearfil DC Core Auto (≈260 ± 10 MPa). Encore SuperCure Contrast had the lowest water sorption (11.8 ± 3.3 μg mm⁻³) and hygroscopic expansion (0.0 ± 0.2 vol.%). Clearfil Photo Core and Encore SuperCure Contrast demonstrated the lowest shrinkage (≈2.1 ± 0.1 vol.%). Water sorption and hygroscopic expansion had a very strong positive correlation. The investigated core materials significantly differed in the tested properties. The performance of the materials depended on their formulation, as well as on the respective curing process.     

Long-term evaluation of direct pulp capping—treatment outcomes over an average period of 6.1 years

To assess the treatment outcomes of direct pulp capping with calcium hydroxide, 248 teeth were examined 0.4–16.6 years (mean, 6.1 ± 4.4) after pulp capping. Only teeth diagnosed to be clinical healthy or with spontaneous pain were capped. The treatment outcome was assessed by interviewing for signs or symptoms responsiveness and sensibility testing with CO₂. The overall survival rate was 76.3% after 13.3 years. Of the teeth, 80.2% were found to have a favourable treatment outcome. The pulps of 60-year-old patients showed a significant lower favourable treatment outcome when compared to patients younger than 40 years (p < 0.05). The treatment outcome was significantly less favourable in teeth restored with glass ionomer cement compared to all other teeth (p < 0.01). The likelihood to show an unfavourable treatment outcome after direct pulp capping was significantly higher for teeth with spontaneous pain than for teeth with clinically healthy pulps (p < 0.001). In addition, the likelihood for a tooth to become non-vital after direct pulp capping was significantly higher within the first 5 years after treatment than after more than 5 years (p < 0.001) after treatment.     

Ex vivo radiographic tooth length measurements with the reference sphere method (RSM)

A reference-based radiographic “reference sphere method” (RSM) for accurate length measurements in (dental) projection radiographs for the assessment of tooth length in dry human mandible sections is evaluated. RSM determines the depth coordinates of reference spheres placed in the object plane from the elliptical distortion of their shadows. Two segments (one canine and one molar) of dry human mandibles were exposed 95 times at different angulations (0–40°) on a dental charge-coupled device receptor. Three steel spheres (diameters d ₁ = 2.00 mm, d ₂ = 3.00 mm) were attached roughly coplanar with the tooth’s main axis. Radiographs were assessed once by visual inspection plus manual landmark identification with a mouse-driven cursor. The results were compared to the true tooth length assessed after extraction and to a conventional method (C), i.e., the rule of proportion based on magnification of the sphere shadows. Mean relative length error was 2.28% (d ₁) and 0.46% (d ₂) for RSM and −13.58% (d ₁) and −9.90% (d ₂) for C. For both methods, length errors were significantly (p < 0.0001) correlated with the inclination relative to the receptor. RSM allows for complete a posteriori determination of the imaging geometry under the assumption of a known source-to-receptor distance. One specific application is foreshortening correction of objects coplanar with the reference spheres. Remaining errors are mainly due to incorrect landmark definition. In our setup, these were exaggerated by the visual/manual image-evaluation process. Automated image analysis has been shown for similar tasks to minimize these errors considerably.     

Analysis of inflammatory periimplant lesions during a 12-week period of undisturbed plaque accumulation—a comparison between flapless and flap surgery in the mini-pig

This study’s aim was to clarify the influence of soft tissue management on the development of periimplant infection. Four weeks after removal of all maxillary premolars in 12 mini-pigs, four BEGO Semados RI implants were inserted in each maxillary quadrant. Employing a split-mouth design, one quadrant was randomized to flapless insertion while the contralateral side was chosen for flap surgery. Following 1, 2, 4 and 12 weeks of transmucosal implant, healing biopsies were retrieved from the periimplant soft tissue and subjected to further analysis. Histomorphometrically, a significant reduction of transmigration of polymorphonuclear neutrophils (week 1, p = 0.007; week 2, p = 0.021; week 4, p = 0.023; week 12, p = 0.013) as well as the density of the subepithelial inflammatory infiltrates (week 1, p = 0.007; week 2, p = 0.046; week 4, p = 0.003; week 12, p = 0.032) was verified following flapless surgery. Quantification of inducible nitric oxide synthase showed significantly reduced expression in the flapless group 2 (p = 0.027), 4 (p = 0.005) and 12 (p = 0.004) weeks post-insertion. Analysis of CD31 and collagen I immunostained sections revealed more regular capillary distribution as well as higher vessel and collagen density in the flapless group. The data of the present study indicate that flapless placement reduces the incidence of inflammatory periimplant soft tissue lesions during a 12-week period. Considering the beneficial effects of flapless placement on early soft tissue healing and stability, the technique might be preferred in case of an uncomplicated locoregional anatomy with sufficient hard and soft tissue. However, this positive effect might disappear after manipulation of the implant and soft tissue during impression taking or try in of the prosthodontic supraconstruction.     

Influence of type of luting cement used with all-ceramic crowns on load capability of post-restored endodontically treated maxillary central incisors

Adhesive luting of the final restorations is supposed to support the overall strength of post-endodontically restored teeth. For evaluating adhesive vs conventional cementation, the load capability of adhesively restored endodontically treated teeth (ETT) with glass fibre-reinforced composite posts (GFRCP), resin composite cores and all-ceramic crowns was determined. Thirty-two caries-free human upper, central incisors were randomly assigned to four groups, endodontically treated and cut 2 mm above the cemento-enamel junction. All teeth were restored with GFRCP, composite core build-ups and all-ceramic crowns. All-ceramic crowns were cemented with zinc phosphate cement (I), glass ionomer cement (II), and a self-adhesive resin cement (III and IV). After thermo-mechanical loading, the specimens were loaded to fracture. Maximum load capability F _max and fracture patterns were compared using non-parametric statistics. Median values for the maximum load capability F _max (minimum/maximum) in [N] were: I = 503 (416/1,038), II = 442 (369/711), III = 502 (326/561) and IV = 518 (416/652). No statistically significant differences were found for F _max (p = 0.761) and fracture patterns (p = 0.094) between the experimental groups. The type of cementation of all-ceramic crowns, whether self-adhesive or conventional, appears to have no impact on the load capability of ETT restored with GFRCP and composite core build-ups.     

Effect of tree types of light-curing units on 5-year colour changes of light-cured composite

The purpose of this study was to determine colour changes in a composite cured with tungsten-halogen, light-emitting diode (LED) or a plasma arc after 5 years. Five specimens 10 mm in diameter and 2 mm in height were prepared using Hybrid (Clearfil AP-X) composite for each test group. The corresponding specimens were cured with a tungsten-halogen curing light, a LED unit or with a plasma arc. Specimens were stored in light-proof boxes for 5 years after the curing procedure to avoid further exposure to light and stored in 37°C in 100% humidity. Colorimetric values of the specimens immediately after curing and after 5 years were measured using colorimeter. The ΔE* _ab values varied significantly depending on the curing unit used (p < 0.001). Curing time did not affect the colour changes of the specimens (p = 0.4). The results of this study suggest that composite materials undergo measurable changes due to the curing unit exposure.     

Effect of three radicular dentine treatments and two luting cements on the regional bond strength of quartz fibre posts

The purpose was to investigate by push-out tests and scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) the effect, after first acid etching the post space walls, of three radicular dentine treatments on the regional bond strength of quartz fibre posts placed using two heavily filled resin luting cements. The crowns of 39 extracted maxillary central incisors were sectioned transversely 2 mm coronal to the labial cement-enamel junction and the roots endodontically treated. After standardized post space preparations and etching 15 s with 32% phosphoric acid, 36 roots were randomly divided into six equal groups. Quartz fibre posts (D.T. LIGHT-POST) were placed using three radicular dentine treatments (0.9% sodium chloride (NaCl) for 60 s, 10% sodium hypochlorite (NaOCl) for 60 s, 17% ethylenediaminetetraacetic acid (EDTA) for 60 s followed by 5.25% NaOCl for 60 s) and two resin composite luting cements (ONE-STEP PLUS/DUO-LINK; ONE-STEP PLUS/LuxaCore Dual). Transverse segments (S1–S7), 1.00 mm (SD = 0.05 mm) thick, were sectioned from the coronal 8 mm of each root. Push-out bond strength tests were performed on coronal, middle and apical post space segments (S2, S4, S6) at a crosshead speed of 0.5 mm/min. Data were recorded and analyzed using a two-way mixed ANOVA design (a = 0.05). Three segments (S1, S5, S7) from roots in each group were examined using SEM/EDS. After post space preparation, acid etching and using each of the three radicular dentine treatments, the three remaining roots were sectioned longitudinally for SEM observation of the post space walls. At all root segment sites, the mean bond strengths from using 0.9% NaCl were significantly lower than for the other two radicular dentine treatments (P ≤ 0.02), and DUO-LINK cement had significantly higher mean bond strengths than LuxaCore Dual cement (P ≤ 0.01). There was a significant linear trend for reduced bond strengths from coronal to apical post space segments (P < 0.001), which was supported by the SEM/EDS observations of dentine tubule appearance and resin tag formation. Acid etching followed by either 10% NaOCl or 17% EDTA and 5.25% NaOCl dentine treatments of the post spaces provided good adhesion and resin luting cement tag infiltration of dentinal tubules in the coronal and middle segments in particular.     

Oral malodorous compound activates mitochondrial pathway inducing apoptosis in human gingival fibroblasts

Hydrogen sulfide (H₂S) is a main cause of physiologic halitosis. H₂S induces apoptosis in human gingival cells, which may play an important role in periodontal pathology. Recently, it has been reported that H₂S induced apoptosis and DNA damage in human gingival fibroblasts (HGFs) by increasing the levels of reactive oxygen species. However, the mechanisms of H₂S-induced apoptosis have not been clarified in HGFs. The objective of this study was to determine the apoptotic pathway activated by H₂S in HGFs. The HGFs were exposed to 50 ng/mL H₂S, resulting in 18 ng/mL in the culture medium, which is lower than the concentration in periodontal pockets. The number of apoptotic cells after 24 and 48 h incubation was significantly higher than that in the control cultures (p < 0.05). Mitochondrial membrane depolarization and the release of cytochrome c, and caspase-3, and caspase-9 were also significantly increased after both 24- and 48-h incubation (p < 0.05), whereas caspase-8, a key enzyme in the receptor ligand-mediated pathway causing apoptosis, was not activated. The present study shows that H₂S triggered the mitochondrial pathway causing apoptosis in HGFs but did not activate the receptor ligand-mediated pathway.     

Characterisation of lysozyme activity in the in situ pellicle using a fluorimetric assay

Lysozyme is among the most protective enzymes in the pellicle layer. The aim of the present study was to establish a precise fluorimetric assay for determination and characterisation of lysozyme activity immobilised in the initial in situ formed pellicle. For in situ pellicle formation, bovine enamel slabs were fixed on maxillary splints and carried by six subjects for different times (3, 30 min) on buccal and palatal sites. The enzymatic assay was based on hydrolysis of cell walls from Micrococcus lysodeicticus linked to a fluorogenic substance. When the substrate is hydrolysed, a fluorescing product is released. Furthermore, the effects of chlorhexidine and black tea on lysozyme in the in situ pellicle were investigated. The fluorimetric method allowed direct determination of the enzyme activity with the slab inside the well of a microtiter plate. The mean immobilised activity over all samples amounted to 68.67 ± 27.35 U/cm² (desorbed activity = 46.76 ± 21.18 U/cm²). The enzyme activity exposed at the pellicles’ surfaces increased in a time-dependant manner and showed a Michaelis–Menten kinetic. Chlorhexidine and black tea reduced lysozyme activity of the in situ pellicle significantly. After rinsing with tea or chlorhexidine, V _max was reduced, whereas K _m remained unaffected indicating a negative allosteric effect of the V type. The fluorimetric method is appropriate for determination of pellicle lysozyme activity. The influence of effectors on immobilised lysozyme activity can be monitored.     

Direct pulp capping effect with experimentally developed adhesive resin systems containing reparative dentin-promoting agents on rat pulp: mixed amounts of additives and their effect on wound healing

This study examined the wound-healing process of exposed rat pulp when treated with experimental adhesive resin systems. The experimental direct pulp capping adhesive resin systems were composed of primer-I, primer-II and an experimental bonding agent. Primer-I was Clearfil SE Bond (CSE) primer containing 1.0 or 5.0 wt% CaCl₂, and primer-II was CSE primer containing 0.1, 1.0 or 5.0 wt% compound of equal mole of pA and pB with synthetic peptides derived from dentin matrix protein 1 (DMP1). Primer-I containing 1.0 and 5.0 wt% CaCl₂ was assigned to the experimental groups 1–3 and 4–6, respectively. Primer-II containing 0.1, 1.0 or 5.0 wt% compound of pA and pB was assigned to the experimental groups 1 and 4, 2 and 5, and 3 and 6, respectively. In all experimental groups, CSE bond containing 10 wt% hydroxyapatite powder was used as the experimental bonding agent. The positive control teeth were capped with calcium hydroxide preparation (Dycal), and the negative control teeth were capped with CSE. The specimens were alternately stained with Mayer’s H&E and the enhanced polymer one-step staining methods. Experimental groups 1, 4, 5 and 6 showed a higher level of reparative dentin formation compared to the negative control 14 days postoperatively. At 28 days postoperatively, all experimental groups showed the formation of extensive reparative dentin, and experimental groups 4, 5 and 6 demonstrated similar dentin bridge formation as that of the positive control. How quickly reparative dentin formation occurs may depend on the concentration of CaCl₂ and the compound of pA and pB in the experimental primer.     

Effect of different surface treatments on the composite–composite repair bond strength

The aim of this study was to investigate the effect of different mechanical and adhesive treatments on the bond strength between pre-existing composite and repair composite using two aging times of the composite to be repaired. Standardized cylinders were made of a microhybrid composite (Spectrum TPH) and stored in saline at 37°C for 24 h (n = 140) or 6 months (n = 140). Three types of mechanical roughening were selected: diamond-coated bur followed by phosphoric acid etching, mini sandblaster with 50-μm aluminum oxide powder, and 30-μm silica-coated aluminum oxide powder (CoJet Sand), respectively. Adhesive treatment was performed with the components of a multi-step bonding system (OptiBond FL) or with a one-bottle primer–adhesive (Excite). In the CoJet Sand group, the effect of a silane coupling agent (Monobond-S) was also investigated. The repair composite (Spectrum TPH) was applied into a mould in three layers of 1 mm, each separately light-cured for 40 s. Repair tensile bond strengths were determined after 24-h storage. Mechanical and adhesive treatment had significant effects on repair bond strength (P < 0.001). The age of the pre-existing composite had no significant effect (P = 0.955). With one exception (CoJet Sand/OptiBond FL Adhesive), adhesive treatments significantly increased repair bond strengths to 6-month-old composite when compared to the controls without adhesive. Adhesive treatment of the mechanically roughened composite is essential for achieving acceptable repair bond strengths. The more complicated use of silica-coated particles for sandblasting followed by a silane coupling agent had no advantage over common bonding systems.     

Effect of carbamide peroxide and hydrogen peroxide on enamel surface: an in vitro study

The aim of the study was to investigate changes in the micromorphologyl and microhardness of the enamel surface after bleaching with two different concentrations of hydrogen peroxide (HP) and carbamide peroxide (CP). Bovine enamel samples were embedded in resin blocks, and polished. Specimens in the experimental groups (n = 10) were treated with bleaching gels containing 10% CP, 35% CP, 3.6% HP, and 10% HP, respectively, for 2 h every second day over a period of 2 weeks. The gels had the identical composition and pH and differed only in their HP or CP content. The roughness and morphology of the enamel surface were analyzed using laser profilometry and SEM. Microhardness was measured using a Knoop hardness tester. The data were evaluated statistically. Specimens in the 10% HP group showed significantly higher roughness after bleaching compared to the control group (ΔRa, p = 0.01). Bleaching with 35% CP showed only a tendency to increase roughness (ΔRa, p = 0.06). Application of 10% CP or 3.6% HP had no significant influence on Ra. Enamel microhardness was significantly higher after application of 10% HP compared to the control (ΔMic = 8 KHN, p = 0.0002) and 35% CP (ΔMic = 20KHN, p = 0.01) groups. In summary, application of CP and HP showed only small quantitative and qualitative differences. In addition, the influence of bleaching procedure on the morphology and hardness of the enamel surface depended on the concentration of the active ingredients.     

Efficacy of tin-containing solutions on erosive mineral loss in enamel and dentine in situ

The addition of tin to mouth rinses is, at least in vitro, a promising strategy for symptomatic therapy of dental erosion. The aim of this study was to evaluate the in situ efficacy of an experimental tin-containing fluoride solution on erosive tissue loss in human enamel and dentine. The study was a three-cell (7 days each) crossover design involving eight healthy participants. Samples were mounted on buccal shields of mandibular mouth appliances, which were worn for 24 h except during meals and drinks. Specimens were demineralised extraorally with 0.05 M citric acid (pH 2.3) for 6 × 5 min daily and were treated with test solutions intraorally once per day for 30 s after the first demineralisation. Three solutions were used: placebo (negative control), a commercially available tin- and fluoride-containing (SnF₂) mouth rinse (positive control, 409 ppm Sn²⁺, 250 ppm F⁻, pH 4.2) and an experimental solution (pH 4.5) containing 1,900 ppm Sn²⁺ (SnCl₂) and 1,000 ppm F⁻ (AmF/NaF). Tissue loss (micrometre) was determined profilometrically. In enamel, tissue loss was 54.8 ± 8.6 in the placebo, 24.5 ± 14.4 in the positive control and 9.7 ± 4.1 in the experimental solution group. The respective values for dentine were 48.5 ± 13.0 in the placebo, 32.8 ± 9.6 in the positive control and 26.2 ± 6.7 in the experimental solution group. The experimental solution was notably effective for enamel but was less effective for dentine. The positive control solution was less effective than the experimental solution; its effects for enamel and dentine were similar.