Redox and biometal status in Wistar rats after subacute exposure to fluoride and selenium counter-effects.

This study aimed to investigate the effect of 150 mg/L sodium fluoride (NaF) on redox status parameters and essential metals [copper (Cu), iron (Fe), and zinc (Zn)] in the blood, liver, kidney, brain, and spleen of Wistar rats and to determine the protective potential of selenium (Se) against fluoride (F-) toxicity. Male Wistar rats were randomly distributed in groups of five (n=5) receiving tap water (control) or water with NaF 150 mg/L, NaF 150 mg/L + Se 1.5 mg/L, and Se 1.5 mg/L solutions ad libitum for 28 days. Fluorides caused an imbalance in the redox and biometal (Cu, Fe, and Zn) status, leading to high superoxide anion (O2 .-) and malondialdehyde (MDA) levels in the blood and brain and a drop in superoxide dismutase (SOD1) activity in the liver and its increase in the brain and kidneys. Se given with NaF improved MDA, SOD1, and O2 .- in the blood, brain, and kidneys, while alone it decreased SH group levels in the liver and kidney. Biometals both reduced and increased F- toxicity. Further research is needed before Se should be considered as a promising strategy for mitigating F- toxicity.

Can Fiber-post Placement Reinforce Structurally Compromised Roots?

PURPOSE: Immature teeth are characterized by short roots, thin root canal walls, and open apices, which makes them prone to fracture. The aim was to investigate whether fiber-post placement had an influence on the fracture resistance of endodontically treated immature teeth. MATERIALS AND METHODS: To simulate immature teeth, the apical third of 20 intact mandibular premolars was resected. After the access cavity was prepared, root canals and apices were enlarged. A 4-mm apical barrier was placed using calcium-silicate based material (Biodentine, Septodont). The teeth were then randomly assigned to two groups (n = 10). Root canals in group 1 were sealed using Acroseal (Septodont, France) and gutta-percha, followed by composite resin for the coronal restoration (Evetric, Ivoclar Vivadent). In group 2, fiber posts (FRC Postec Plus, Ivoclar Vivadent) were luted using self-adhesive composite cement (SpeedCEM Plus, Ivoclar Vivadent), followed by the same coronal restoration. The teeth were then subjected to fatigue and static load testing. RESULTS: The average loads (± SD) that led to tooth fracture were: 401.40 ± 296.83 N in group 1 and 636.20 ± 204.95 N in group 2. Unfavorable fractures were noted in 9 specimens from group 1 and in 7 specimens in group 2. No statistically significant difference in fracture resistance or fracture mode was found between the groups. CONCLUSION: Fiber-post placement had no significant influence on the fracture resistance of endodontically treated immature teeth.

After-Hours Versus Office-Hours Dental Injuries in Children: Does Timing Influence Outcome?

AIM: The aim of this study was to analyze the outcomes and factors associated with after-hours dental trauma. METHODS: Study sample consisted of 1762 permanent teeth injuries in children, gender and age matched with office-hours injuries. Epidemiological and clinical data were collected from 4 university dental trauma centers. RESULTS: During median follow-up time of 4.3 years, complications have occurred in 14.5% of injured teeth. Age, type, and degree of tissue injury and after-hours time of injury were significantly associated with complications. Unfavorable outcomes were 34% more likely in the after-hours group compared with office-hours. Urgent treatment was significantly delayed in after-hours group with a delay of more than 3 hours in 90.5% versus 38.9% in the office-hours group. Multivariate regression model showed that after-hours time of injury was significant predictor of complications. CONCLUSION: Delayed urgent treatment was one of the main factors associated with unfavorable outcome of after-hours injuries.

[Hard dental tissue minimal-invasive preparation using contemporary polymer rotating instruments and laser].

Goal of contemporary dentistry is to decrease the patient's discomfort during treatment. Dentists aim to achieve maximum with the newly developed dental materials as well as with new cavity preparation techniques in the shortest time span. Since the development of the first constructed borer (drilling machine) for caries removal, the preparation techniques have considerably changed. The progress of dental materials as well as the cavity preparation techniques has led us to contemporary carbide tungsten and diamond borers that are used with obligatory water cooling. The innovation within this field represents newly developed polymer borers that can detect the difference between carious lesions and healthy tooth structure. In this way the cavity preparation may be performed without damaging dental healthy tissue. This is possible owing to their hardness which is lower than the hardness of intact dentin. Polymer borer preparation is painless with less vibration, while the increase in temperature is negligible. Lasers have been used in clinical dentistry since 1980s so it can be said that they represent a new technology. The function of lasers is based on ablation which requires water. Erbium lasers have shown the highest potential with their ability to produce effective ablation of hard dental tissues. Laser application in dentistry requires special training as well as some protective measures. Laser advantages, compared to traditional preparation techniques, involve the absence of vibration, painless preparation, possibility of preparation without anesthetic and easier patient's adjustment to dental intervention which is of importance, especially in pediatric dentistry.

[The application of air abrasion in dentistry].

One of the main objectives of contemporary dentistry is to preserve healthy tooth structure by applying techniques of noninvasive treatment. Air abrasion is a minimally invasive nonmechanical technique of tooth preparation that uses kinetic energy to remove carious tooth structure. A powerful narrow stream of moving aluminum-oxide particles hit the tooth surface and they abrade it without heat, vibration or noise. Variables that affect speed of cutting include air pressure, particle size, powder flow, tip's size, angle and distance from the tooth. It has been proposed that air abrasion can be used to diagnose early occlusal-surface lesions and treat them with minimal tooth preparation using magnifier. Reported advantages of air abrasion include reduced noise, vibration and sensitivity. Air abrasion cavity preparations have more rounded internal contours than those prepared with straight burs. This may increase the longevity of placed restorations because it reduces the incidence of fractures and a consequence of decreased internal stresses. However, air abrasion cannot be used for all patients, i.e. in cases involving severe dust allergy, asthma, chronic obstructive lung disease, recent extraction or other oral surgery, open wounds, advanced periodontal disease, recent placement of orthodontic appliances and oral abrasions, or subgingival caries removal. Many of these conditions increase the risk of air embolism in the oral soft tissues. Dust control is a challenge, and it necessitates the use of rubber dam, high-volume evacuation, protective masks and safety eyewear for both the patient and the therapist.

Shear bond strength to enamel and flexural strength of different fiber-reinforced composites.

PURPOSE: To assess the shear bond strength to unground human enamel (ESBS) and flexural strength (FS) of different reinforcing fibers used in combination with a flowable composite resin. MATERIALS AND METHODS: For ESBS testing, 90 human molars were selected and randomly divided into 9 groups (n = 10) according to the reinforcing fiber to be tested: 1. RTD Quartz Splint additionally impregnated at chairside with Quartz Splint Resin (RTD); 2. RTD Quartz Splint without additional impregnation; 3. Ribbond-THM (Ribbond) impregnated with OptiBond FL Adhesive; 4: Ribbond Triaxial (Ribbond) impregnated with OptiBond FL Adhesive; 5. Connect (Kerr) impregnated with OptiBond FL Adhesive; 6. Construct (Kerr) impregnated with Opti- Bond FL Adhesive; 7. everStick PERIO (Stick Tech); 8. everStick C&B (Stick Tech); 9. nonreinforced composite Premise flowable (Kerr). Cylinders of flowable composite reinforced with the fibers were bonded to the intact buccal surface of the teeth. After 24 h of storage, shear loading was performed until failure occurred. FS was assessed performing three-point bending test according to ISO Standard 4049/2000. ESBS and FS data were analyzed using one-way ANOVA, followed by Tukey's HSD test for post-hoc comparisons (p < 0.05). RESULTS: For each group, the ESBS and FS, respectively, in MPa were: 1. 17.07 ± 4.52 and 472.69 ± 30.49; 2. 14.98 ± 3.92 and 441.77 ± 61.43; 3. 18.59 ± 5.67 and 186.89 ± 43.89; 4. 16.74 ± 6.27 and 314.41 ± 148.52; 5. 14.38 ± 4.14 and 223.80 ± 77.35; 6. 16.00 ± 5.55 and 287.62 ± 85.91; 7. 16.42 ± 3.67 and 285.35 ± 39.68; 8. 23.24 ± 5.81 and 370.46 ± 29.26; 9. 12.58 ± 4.76 and 87.75 ± 22.87. For most fibers, no significant difference in ESBS was found compared to the control group, except for everStick C&B, which yielded higher ESBS. Nonreinforced composite exhibited the lowest FS, while all fibers positively affected the FS. CONCLUSIONS: Fiber reinforcement of flowable composite does not affect its ESBS. The flexural strength of FRCs is significantly influenced by fiber composition and pattern.

Scanning electron microscopic examination of Enamel surface after fixed orthodontic treatment: in-vivo study.

INTRODUCTION: Therapy with fixed orthodontic appliances starts with bracket bonding and ends with debonding of brackets, leaving enamel surface varied. Objective The aim of this pilot study was to examine enamel surface before and after debonding of orthodontic brackets by the use of scanning electron microscopy (SEM). METHODS: Epoxy replicas of four patients' premolars indicated for therapy with fixed orthodontic appliances were made and brackets were bonded to their teeth with a different adhesives (Enlight, No-mix, Fuji Ortho LC and Heliosit Orthodontic) (n=4).Two months later, brackets on premolars were debonded and amounts of adhesive left on the tooth surfaces and the bracket bases were evaluated with the adhesive remnant index (ARI). After resin removal, epoxy replicas were made and the surface of premolars was evaluated with the enamel surface index (ESI). All replicas of premolars (n=32) were prepared for SEM examination and compared under different magnifications. Tooth damage was estimated based on correlation between ARItooth and ESI. RESULTS: Pearson's chi2 test showed no significant differences between ARItooth and ARIbracket of four materials used. Nonparametric correlations showed significant differences between ARItooth and ARIbracket, ESI and ARItooth, and between ESI and ARIbracket. Increasing of ARItooth is followed with the descent of ARIbracket and the ascent of ESI. Multivariate regression analysis showed a significant correlation between ESI and ARItooth. CONCLUSION: Most bond failures took place at enamel-adhesive interface. ARItooth was a predictor to enamel surface damage. The type of material did not affect enamel surface damage.

Microtensile vs microshear bond strength of all-in-one adhesives to unground enamel.

PURPOSE: to determine the bond strength to unground enamel of all-in-one adhesives in comparison with an etch-andrinse system and to compare the reliability of microtensile and microshear methods in providing such measurements. MATERIALS AND METHODS: the bonding procedure was performed on enamel of 64 extracted molars. The tested all-inone adhesives were: Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply). Prime&Bond NT (Dentsply) served as control. Microtensile specimens were obtained from 4 teeth per group. Twelve teeth per group were used for microshear testing. Microtensile specimens that failed prior to testing were included in statistical calculations; they were assigned the lowest value measured in the respective group. Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive, mixed). Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive. Failure mode distributions were compared using the chi-square test. RESULTS: all-in-one adhesives had similar microshear and microtensile bond strengths. In both testing methods, the etch-and-rinse system achieved the strongest bond. For all adhesives, significantly higher bond strengths were measured with the microshear test. In microtensile testing, specimens bonded with the etch-and-rinse adhesive exhibited a significantly different distribution of failure modes. The coefficients of variation were extremely high for microtensile bond strength data, particularly of all-in-one adhesives. CONCLUSION: the adhesive potential to intact enamel of recently introduced all-in-one adhesives was inferior to that of an etch-and-rinse system. When testing bond strength to enamel of all-in-one adhesives, microshear testing may be a more accurate method than microtensile.

In vitro evaluation of bonding effectiveness to dentin of all-in-one adhesives.

OBJECTIVES: The study was aimed at assessing the bonding potential of all-in-one adhesives to dentin. METHODS: The microtensile bond strength of the all-in-one adhesives Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply) was measured in comparison with the etch-and-rinse system XP Bond (Dentsply). The ultrastructural characteristics of dentin-adhesive interface were observed under scanning electron microscope (SEM). Twenty human extracted third molars had their mid-coronal dentin exposed and ground with wet 600-grit SiC paper in order to create a standardized smear layer. Bonding procedures were performed according to the manufacturers' instructions and microtensile beams were obtained with the "non-trimming" technique. The bond strengths in MPa were statistically analyzed including pre-test failures as "zero" values (Kolmogorov-Smirnov test, Levene's test, One-Way ANOVA, Tukey's test p<0.05). RESULTS: The following bond strengths were recorded in MPa (mean+/-standard deviation): AdheSE One 31.7+/-21.3; Xeno V 42.8+/-26.4; Bond Force 43.3+/-22.1; XP Bond 51.9+/-18.6. The statistical analysis demonstrated that the bond strengths achieved by Bond Force and Xeno V were similar to that of the etch-and-rinse adhesive, whereas the bond strength of AdheSE One was significantly lower. A distinct hybrid layer with resin tags was seen only in XP Bond specimens. All-in-one adhesives demonstrated a rather superficial interaction with the dentin substrate. CONCLUSIONS: Although the strongest bond to dentin was established by the etch-and-rinse system, however the all-in-one adhesives containing organic solvents reached bond strength levels that were comparable from a statistical point of view.