Effect of irrigation protocols on smear layer removal, bond strength and nanoleakage of fiber posts using a self-adhesive resin cement

Objectives

This study aimed to investigate the effect of the application method of 2% chlorhexidine (CHX) and its influence on the adhesion of fiberglass posts cemented with a self-adhesive resin cement.

Materials and Methods

Sixty human mandibular premolars were endodontically treated and divided into 5 groups (n = 12), according to the canal irrigant and its application method: 2 groups with conventional syringe irrigation (CSI)-2.5% sodium hypochlorite (NaOCl) (control) and 2% CHX- and 3 groups with 2% CHX irrigation/activation-by passive ultrasonic irrigation (PUI), Easy Clean file, and XP-Endo Finisher file. Two roots per group were evaluated for smear layer (SL) removal by scanning electron microscopy. For other roots, fiber posts were luted using a self-adhesive resin cement. The roots were sectioned into 6 slices for push-out bond strength (BS) (7/group) and nanoleakage (NL) (3/group). Data from SL removal were submitted to Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05). Data from BS and NL were evaluated by 2-way analysis of variance and Tukey's test (α = 0.05).

Results

For SL removal and BS, the CHX irrigation/activation promoted better values than CSI with CHX (p < 0.05), but it was not significantly different from CSI with NaOCl (p > 0.05). For NL, the lowest values were obtained by the chlorhexidine irrigation/activation groups (p < 0.05).

Conclusions

Active 2% CHX irrigation can be used to improve the post space cleaning and adhesion before fiber post cementation with self-adhesive resin cements.

Influence of Alternative Restoration Technique with Different Composite Resins for Flared Root Reinforcement

PURPOSE

To evaluate the influence of type and viscosity of composite resins used for root reinforcement in the adhesion of glass-fiber posts to flared root canals.

MATERIALS AND METHODS

The crowns of 78 uniradicular permanent teeth were removed and the teeth were endodontically treated. After one week, the roots were prepared for root reinforcement and randomly divided into 6 groups (n = 13): positive control group ([PCG] the root canals were not enlarged), negative control group ([NCG] root canals were enlarged, no reinforcement), and in the remaining 4 groups, root canals were enlarged to receive root reinforcement according to a combination of the factors composite resin type (bulk-fill or conventional) and viscosity (flowable or regular). After fiber post cementation, six slices were obtained from each root (2 each from the cervical, middle, and apical thirds). For each group, 7 teeth underwent push-out bond strength testing, and 6 teeth were evaluated for nanoleakage and Vickers microhardness. Bond strength and nanoleakage data were submitted to two-way ANOVA and Tukey's test (α = 0.05), and microhardness data to one-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The root reinforcement groups with regular and flowable bulk-fill composite resins showed statistically superior adhesion results (higher bond strength and less nanoleakage) compared to the negative control in all root regions. Microhardness values were higher in the cervical third followed by the middle third.

CONCLUSION

Regular or flowable bulk-fill composite resins should be chosen for root reinforcement of flared root canals prior to fiber post cementation.

Effect of surface treatments on repair strength, roughness and morphology in aged metal-free crowns

Aim: The roughness and micromorphology of various surface treatments in aged metal-free crowns and the bond strength of these crowns repaired with composite resin (CR) was evaluated in vitro. Methods: A CR core build-up was confectioned in 60 premolars and prepared for metal-free crowns. Prepared teeth were molded with the addition of silicone, and the laboratory ceromer/fiber-reinforced crowns (SR Adoro/Fibrex Lab) were fabricated. Subsequently, the crowns were cemented and artificially aged in a mechanical fatigue device (1.2 X 106 cycles), then divided into 4 groups (n = 15) according to the surface treatment: 1) phosphoric acid etching (PA); 2) PA + silane application; 3) roughening with a diamond bur + PA; and 4) sandblasting with Al2O3 + PA. After the treatments, the crowns (n = 2) were qualitatively analyzed by scanning electron microscope (SEM) and surface roughness (n = 5) was analyzed before and after the surface treatment (Ra parameter). The remaining crowns (n = 8) received standard repair with an adhesive system (Tetric N-Bond) and a nanohybrid CR (Tetric N-Ceram), and the microshear bond strength (SBS) test was performed (0.5 mm/min). Roughness and SBS data were analyzed by one- and two-way ANOVA, respectively, as well as Tukey’s post-test (α = 0.05). Results: Sandblasting with Al2O3 + PA resulted in the highest final roughness and SBS values. The lowest results were observed in the PA group, whereas the silane and diamond bur groups showed intermediate values. Conclusion: It may be concluded that indirect ceromer crowns sandblasted with aluminum oxide prior to PA etching promote increased roughness surface and bond strength values.

Effect of Root Canal Irrigants on Fiber Post Bonding Using Self-adhesive Composite Cements

PURPOSE

To evaluate the effect of different irrigation solutions on the bonding of self-adhesive composite cements to the root canal during fiber-post cementation.

MATERIALS AND METHODS

One hundred twenty single-rooted human teeth were endodontically treated. The post spaces were prepared and specimens were randomly divided into ten groups, according to the combination of the factors: post space irrigation (distilled water, 2.5% NaOCl, 17% EDTA, 26% polyacrylic acid, and 17% EDTA + 2.5% NaOCl) and self-adhesive composite cement (RelyX U200 [3M Oral Care] and Multilink Speed [Ivoclar Vivadent]). The proportion of open dentinal tubules was evaluated by SEM. After fiber post cementation, six slices were obtained from each root (coronal, middle, and apical thirds) for evaluation of push-out bond strength (BS), nanoleakage (NL), and Vickers microhardness (VHN) of the composite cement. Data from open dentinal tubules were submitted to Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05). Data from BS, NL, and VHN were evaluated by two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

Irrigation with EDTA, polyacrylic acid, and EDTA + NaOCl increased the proportion of open dentinal tubules. For RelyX U200, NaOCl, distilled water and EDTA resulted in the highest BS and VHN values, while for Multi- link Speed, these values were higher only for distilled water. Both composite cements presented lower BS and VHN with polyacrylic acid. NL did not differ between experimental groups (p > 0.05).

CONCLUSION

For both composite cements tested, distilled water showed better results in push-out and microhardness tests.

Effect of Conditioning Protocols and Ultrasonic Application of an Infiltrant Resin in White Spot Lesions

The aim of this study was to evaluate different conditioning protocols and sonic/ultrasonic application of an infiltrant resin (IR) in artificial white spot lesions (AWSL). the V/L surfaces of 48 molars were induced to an AWSL and divided in 6 groups, according to the conditioning protocols and application technique: 15% hydrochloric acid (HA) + manual application of the IR; HA + 37% phosphoric acid (PA) + manual application of the IR; HA + ultrasonic application (U) of the IR; HA + sonic application (S) of the IR; PA+HA+S; and PA+HA+U. For the Penetration Depth (PD), the crowns were etched with HA for 120s. The IR Icon® (DMG) was applied according to the manufacturer`s instructions. The crowns were dye penetrated (0.1% red fluorophore rhodamine B isothiocyanate for 12h) and bleached with 30% hydrogen peroxide for 12 h. The discs were immersed in a 50% ethanol solution, containing 100 µM of sodium fluorescein. The PD (in µm) was measured using confocal laser scanning microscopy (20x). The bond strength (BS) was performed by michoshear test (0.5 mm/min). Data were submitted to 2-way ANOVA and Tukey (α=0.05). For BS, the interaction was not significant (p>0.05). For PD, the main factors were significant (application - p<0.001; conditioning technique - p=0.003). The ultrasonic application showed the highest PD values. PA+HA presented higher results than HA. The sonic/ultrasonic applications and the use of phosphoric acid prior to hydrochloric acid improved PD of the infiltrant resin. Conditioning protocols or application techniques did not influence BS values.

Influence of different burs and acid ultrasonic agitation on the bonding of fiber posts to root dentin

Aim: The objective is to evaluate the influence of different burs used to prepare the root canal space and acid ultrasonic agitation on bond strength (BS) between glass fiber posts (GFP) and root dentin. Methods: After endodontic treatment, the root canal spaces of 36 extracted human canines were prepared, according to the rotary instrument used (n=18): carbide bur (CB), provided by the post manufacturer and a diamond bur (DB). In both groups, the fiber posts were cemented with the adhesive system Ambar and resin cement Allcem, following the manufacturer`s instructions. Previously to the cementation procedures, the groups were subdivided into 2 groups (n=9), according to the phosphoric acid application mode: conventional etching (CE) and active etching (AE), performed by ultrasonic tip, both for 15s. Before the cementation procedures and after the acid application, 1 root of each group was randomly selected for ultrastructural morphological evaluation by SEM. After 1 week of the cementation, 8 specimens per group were transversely sectioned into six 1-mm thick slices, the root canal regions (cervical, medium and apical) were identified and the push-out test was performed to evaluate BS. Data were analyzed by 3-way ANOVA and Tukey test (α=0.05). Results: The results showed that the cross-product interaction of all factors was significant (P=0.035). Higher bond strength values were obtained when a DB with conventional etching, instead of CB, was used to prepare the root post space. Conclusion: It may be concluded that the use of diamond burs with conventional etching yields high BS values in all root canal thirds.

Effect of the Bis-Dimethylamino Benzydrol Coinitiator on the Mechanical and Biological Properties of a Composite

To examine the effect of the alternative coinitiator 4,4'bis dimethylamino benzydrol (BZN) in degree of conversion (DC), mechanical and biological properties of experimental composites. The coinitiator BZN was used in three concentrations (0.2, 0.5 and 1.2%), and the coinitiator DMAEMA was used as control at the same concentrations as above. The molar concentration of camphorquinone (CQ) and coinitiators was kept constant (1:1). The composites were manipulated and submitted to microhardness test (VHN), flexural and compressive strength (in MPa), elastic modulus (GPa), DC (FT-IR) and in vitro cytotoxicity (against 3T3 fibroblastic cells) of the experimental resins. Data were subjected to two-way ANOVA and Tukey post-test (α=0.05). The experimental composite resin with BZN showed higher DC values compared to control DMAEMA groups. For the mechanical properties, microhardness values were higher in BZN groups; flexural strength and elastic modulus were similar between all the groups. Compressive strength for groups BZN0.5 and DMAEMA0.5 were not statistically different, being the lowest values attributed to group BZN0.2. The experimental resins with BZN and DMAEMA were considered nontoxic against 3T3 fibroblasts. The inclusion of the coinitiator BZN in experimental composites was considered nontoxic against 3T3 fibroblast cells, without compromising DC and mechanical properties.

Clinical evaluation of the whitening effect of over-the-counter dentifrices on vital teeth

This randomized clinical trial evaluated the whitening potential of commercially available toothpastes. Sixty patients were selected and randomly divided into 4 groups (n=15), according to the dentifrice used: GI (control) - Colgate Total 12, GII - Close-up White Now, GIII: Oral-B 3D White, GIV: Colgate Luminous White. Three daily brushings were performed for 2 to 3 min each, during a period of 15 days. Patients had the color of their teeth evaluated before and after the treatment by means of a spectrophotometer (Vita EasyShade - CIE L*a*b*). Data obtained from L values were analyzed by one-way ANOVA and t test. ∆E was also evaluated to calculate color alteration, by NBS criteria. Mean (standard deviation) of initial values were GI: 82.9 (4.9); GII: 83.9 (5.8); GIII: 83.9 (7.2); GIV: 86.4 (3.4) and final values were GI: 84.1 (6.3); GII: 84.6 (6.1); GIII: 84.2 (7.1); GIV: 88.2 (2.8). In conclusion, the dentifrices showed no lightening action on vital teeth, except for Colgate Luminous White; but according to NBS criteria, there was no noticeable visible change to the patients in any group.

Active and Passive Application of the Phosphoric Acid on the Bond Strength of Lithium Disilicate

The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey's post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p<0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was concluded that the active application of 37% PA after 9.6% HA increases the microshear bond strength values between the resin cement and lithium disilicate ceramic.

Shrinkage stress of resin composites: Effect of material composition – Sistematic Review

The longevity of resin, depends on its binding between the margin of restorations and the polymer, and one factor that influences this aspect is the shrinkage stress, so the working group makes the following systematic review which looks at the influence of the composite resin composition of the shrinkage stress.

Alternative coinitiators applicable to photocurable resin composites

This review aimed to examine the evolution of the composite resins`s photoinitiator system, with emphasis on those developed in recent years. This review covered literature from 1990 to 2013 and only papers with the key words of interest were included: "coinitiators", "amines", "composite resins", "photopolymerization". The search used full-text papers from PubMed and Science Direct databasis. It was included only English papers, and meeting abstracts and short communications were excluded. Hand search of the references completed the review. A total of 29 articles were studied. Many coinitiators are being researched as an alternative to traditional tertiary amines, particularly in order to improve the physical and mechanical properties of the final polymer and its biocompatibility with oral tissues. Polymerizable amines, natural compounds, and coinitiators with low toxicity and antiseptic properties were studied, and the results found they would be promising substitutes. These materials must present appropriate concentration and reactivity to obtain adequate physical and mechanical properties and high biocompatibility. However, further in vivo studies are required to verify the performance of these alternative coinitiators in the composite materials, mainly when in contact with oral tissues and the stomatognathic system.

Influence of two different methods of delivering fluoride on bond strength and degree of conversion of an adhesive after bleaching

PURPOSE

To evaluate the influence of fluoride delivery and restoration time point on the microshear bond strength (mSBS) and degree of conversion (DC) values of an adhesive applied on bleached enamel.

MATERIALS AND METHODS

Fifty-four enamel specimens were submitted to bleaching and divided into 3 groups of n = 18: group HP: 35% hydrogen peroxide (HP); group HPF: HP + 1.23% sodium fluoride application (F); group PF: 38% HP with F. A control group of n = 6 was neither bleached nor fluoridated. Subsequently, each group except the control was subdivided into 3 subgroups (n = 6) to be restored immediately, or at 7 or 14 days. Tygon tubes were filled with composite resin and placed on enamel surfaces, then the mSBS test was performed. The DC of the interface was observed with Raman spectroscopy. The data were submitted to two-way ANOVA and Tukey's and Dunnet's post-hoc test (α = 0.05).

RESULTS

The mSBS results showed higher values for groups HP and HPF at 14 days compared with immediate and 7 days (p < 0.05). Lower DC values were obtained in the immediately restored groups HP and HPF, which were significantly different from 7 and 14 days (p < 0.05). mSBS and DC for group PF was similar at all restoration time points and to the control group (p > 0.05).

CONCLUSION

Only the use of a fluoridated in-office bleaching agent (Opalescence Boost PF) proved to be effective for immediately reversing the side effects of low mSBS and DC values when in-office bleaching is used.