Human Third Molars Research Articles

Do dual-cure bulk-fill resin composites reduce gaps and improve depth of cure.

This in vitro study aimed to evaluate the gaps length and depth of cure of dual-cure bulk-fill resin composites inserted in box-shaped preparations. Box-shaped preparations (4 mm deep) were made in fifteen human third-molars and divided into three groups according to the resin composites (n=5): Dual-cure bulk-fill BulkEZ (BEZ); Dual-cure bulk-fill HyperFIL (HF); and Tetric Evoceram Bulk-fill (TETRIC), as control. Gaps length (%) was evaluated in tooth-restoration interface with micro-computed tomography (µCT). The restorations were sectioned, and the degree of conversion (DC) and Knoop microhardness were evaluated at five depths (0.3, 1, 2, 3, and 4 mm). Microhardness data were statistically evaluated using absolute values (KHN) and relative values (microhardness percentages in relation to top). Gaps length (%) increased in the following order: BEZ=TETRIC<HF. The microhardness percentages in relation to top significantly decreased from 2 mm for TETRIC and 3 mm for HF. BEZ had constant microhardness and DC at all depths, while HF and TETRIC presented a significant decrease on DC at 4 mm. Dual-cure bulk-fill composites did not reduce gaps compared to light-cure bulk-fill, but they can improve depth of cure of bulk-filled restorations.

Effect of Nd:YAG Laser with/without Graphite Coating on Bonding of Lithium Disilicate Glass-Ceramic to Human Dentin.

This study evaluated the effect of different surface treatments on the tensile bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. Fifty truncated cone-shape glass-ceramics were divided into five groups (n = 10): G1, control: 10% hydrofluoric acid (HF); G2, Nd:YAG laser + silane; G3, Sil + Nd:YAG laser; G4, graphite + Nd:YAG laser + Sil; and G5, graphite + Sil + Nd:YAG laser. Fifty human third-molars were cut to cylindrical shape and polished to standardize the bonding surfaces. The glass-ceramic specimens were bonded to dentin with a dual-cured resin cement and stored in distilled water for 24 h at 37ºC. Tensile testing was performed on a universal testing machine (10 Kgf load cell at 1 mm/min) until failure. The bond strength values (mean ± SD) in MPa were G1 (9.4 ± 2.3), G2 (9.7 ± 2.0), G3 (6.7 ± 1.9), G4 (4.6 ± 1.1), and G5 (1.2 ± 0.3). Nd:YAG laser and HF improve the bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. The application of a graphite layer prior to Nd:YAG laser irradiation negatively affects this bonding and presented inferior results.

Effect of Hydrophilic Amide Monomers on Dentin Bonding Strength

Objective: The aim of this study was to compare the shear bond strength (SBS) to dentin of one-step bonding agent containing hydrophilic amide monomers (HMA) and 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) with one-step bonding agent containing only MDP. Materials and Methods: 20 human third molar teeth randomly were divided into two groups. Teeth was abraded with a SiC disc (Carbimet, Bisco Inc., Schaumburg, USA) to be under 1 mm of enamel-dentin junction. The dentin surface of each teeth were etched with %37 phosphoric acid for 15 s and then rinsed with water spray for 10 s and after that air dried. Cylinders of composite (Clearfil Majesty Posterior, Kuraray Noritake Inc, Okuyama, Japan) were bonded using 2 dental bonding agents. Group A used bonding agent containing HMA+MDP (Clearfil Universal Quick bond, Kuraray America, Inc. New York/NY, USA) and Group B used bonding agent containing only MDP (Clearfil S3 Bond plus, Kuraray America, Inc. New York/NY, USA) applied in accordance with the manufacturer's instructions. The speciemens were stored for 24 h in 37°C water and thermocycled between 5 and 55 C water with a 20 s dwell time for 5000 cycles. They were then submitted to a shear bond test with a universal testing machine (AGS-X, Shimadzu, Kyoto, Japan) with a 100 N load cell at 1 mm/min. The values of SBS were analyzed with ANOVA/Tukey’s test. Results: Group A was 35,96±5,47 MPa and B was 24,25±7,5 MPa There was a statistical difference between the two bonding agents (p<0.05). Group A was significantly higher than Group B. Conclusions: According to this study, bonding agents containing which type of monomers may be one of the important factors influencing dentin bond strength. When bonding agents with hydrophilic amide monomers are used, it has showed higher shear bond strength.

Longevity of Bond Strength of an Indirect Composite Resin to Dentin Using Conventional or Self-Adhesive Resin Cementation: Influence of Dentin Pretreatment with TiF₄.

The purpose was to evaluate the influence of dentin pretreatment with titanium tetrafluoride (TiF₄) on the longevity of bond strength (BS) of an indirect composite to dentin, using conventional resin cementation strategy or a self-adhesive resin cement. Forty third human molars with exposed dentin surfaces were used. The teeth were divided into groups (n = 10), according to the cementation strategy and the presence or absence of pretreatment with TiF₄. Microtensile strength testing and failure mode analysis were performed after 24 hours, 180 and 360 days of storage in water. Split-plot ANOVA and Tukey's test showed that BS was significantly higher when the conventional strategy was used, regardless of the time period, and of the application or no application of pretreatment with TiF₄ (p ⟨0.0001). When TiF₄ was used for both cementing strategies, BS was lower after 360 days (p = 0.0019). Both cementing strategies led to the formation of a shallow hybrid layer, regardless of the presence of TiF₄. BS was higher when the conventional cementation strategy was used, regardless of TiF₄ pretreatment. TiF₄ used as a pretreatment agent associated with different types of resin cementation was unable to maintain adhesive bond strength in the long term.

Microtensile Bond Strength of Adhesive Systems in Different Dentin Regions on a Class II Cavity Configuration.

The aim of this study was to evaluate microtensile bond strength (µTBS) of self-etch and etch-and-rinse adhesives systems compared in different dentin regions (central-CD or proximal-PD) in a class II cavity configuration. A class II (mesial-oclusal-distal) cavity configuration was simulated on 20 extracted human third-molars (4 mm wide/3 mm deep). Etch-and-rinse adhesive (Scotchbond Multi Purpose, n=5, SBMP and Optibond FL, n=5, OPFL) and self-etch adhesives (Clearfil SE Bond, n=5, CSE and Optibond XTR, n=5, OPXTR) were applied. Class II restorations were performed by incremental technique and photo-activated (Bluephase/G2). Samples were sectioned to beam shape (1 mm² cross-section), placed on Geraldeli's device for µTBS test (0.5 mm/min cross-head speed). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-resin, adhesive, mixed/resin or mixed/dentin. Samples (n=4) were prepared for scanning electron microscope observation. Data were submitted to one-way ANOVA with Split-Plot arrangement and Tukey's test (α=0.05). There were no statistically significant differences among SBMP, OPFL, CSE and OPXTR on CD (p>0.05). However, on PD for SBMP and OPFL, µTBS values were significantly lower compared to CSE and OPXTR (p<0.05). In all groups, mixed failure pattern was more frequently observed, except for SBMP/CD (adhesive). In class II type cavity configuration, PD location negatively influenced bond strength of etch-and-rinse adhesive systems. Opposite to self-etching adhesives, which presented higher bond strength values compared to etch-and-rinse adhesives in PD.

In-Vitro Comparative Study of In-office and Home Bleaching Agents on Surface Micro-morphology of Enamel.

To evaluate the effect of home-use bleaching agent containing 16% Carbamide Peroxide (CP) and in-office bleaching agent with 38% Hydrogen Peroxide (HP) on surface micro-morphology of enamel. An experimental study. The discs were prepared at Material Engineering Department of NED University of Engineering and Technology, Karachi, and surface morphology was analyzed at Centralized Science Laboratory of Karachi University, Pakistan. Duration of study was one year from January to December 2012. Forty five sound human third molar crowns, extracted for periodontal reason, were included in the study. Longitudinal sections were made using diamond disks (0.2 mm) under water lubrication to obtain enamel slabs measuring (3 mm x 3 mm). The slabs were embedded in polystyrene resin by using 2.0 cm diameter PVC molds, leaving the outer enamel surface uncovered by the resin. Ninety dental enamel slabs were prepared. The slabs were then randomly divided into 3 groups. Each group contained thirty specimens (n=30). Group 1 was kept in artificial saliva at 37&deg;C in incubator (Memart, Germany) during whole experiment. Group 2 was treated with power whitening gel (White Smile 2011, Germany). Group 3 was treated with tooth whitening pen (White Smile 2011, Germany). The most central region or the region that was most representative of the entire surface area was used. The SEM (Jeol-Japan-JSM6380A, JAPAN) micrographs were examined to determine the type of surface presented. The enamel changes were classified as no or mild alteration, moderate alteration and severe altered surface. Regarding micro-morphology, the enamel surface of control groups showed smooth surface in general with some scattered clear scratches due to the polishing procedure. The specimens bleached in group 2 and group 3, represented areas of mild erosion. Bleaching with 38% Hydrogen Peroxide (HP) and 16% Carbamide Peroxide (CP) resulted in mild changes in surface micro-morphology of enamel.

Effect of lipopolysaccharide on the stromal cell-derived factor-1 expression in human stem cells from apical papilla

To investigate the expression of stromal cell-derived factor-1 (SDF-1) in human stem cells from apical papilla (SCAP), and to evaluate the effect of lipopolysaccharide (LPS) on SDF-1 expression by SCAP. SCAP were isolated from dental papilla of human immature third molars. The expression of SDF-1 was evaluated by reverse transcription-PCR (RT-PCR). After SCAP being exposed to different concentrations (0.1, 1.0, 10 mg/L) of LPS for 24 and 48 h, the effect of LPS on cell proliferation and gene expression of SDF-1 was investigated by cell counting kit-8 and real-time PCR respectively, while cells without LPS stimulation were considered as negative control. LPS had no significant effect on SCAP proliferation until day 7. RT-PCR assays demonstrated that SCAP expressed SDF-1 mRNA. Different concentrations of LPS significantly promoted the SDF-1 expression in SCAP after 24 h (F = 12.102, P = 0.002) and 48 h (F = 39.054, P < 0.001) exposure, with relative gene expression ratio (experimental/control) increased to 1.4 ± 0.1, 2.2 ± 0.4, 2.3 ± 0.5 in 24 h group and 2.1 ± 0.4, 3.4 ± 0.3, 3.8 ± 0.5 in 48 h group. Isolated SCAP in cultures have the expression of SDF-1 mRNA. LPS can significantly promote the expression of SDF-1 in SCAP.

Çürük Tespit Boyalarının Çürükten Etkilenmiş Dentine Kompozitlerin Bağlanma Dayanımı Üzerine Etkisi

Objectives: The aim of this in vitro study wasto evaluate effect of three different caries detectingdyes on shear bond strength of a self etch adhesiveto caries affected dentin.Materials and Methods: 60 extracted humanthird molars which are affected by caries used inthis study. Occlusal surfaces removed to obtain flatdentinal surfaces and teeth mounted acrylic.Specimens were divided into four groups of 15 tobe tested three different caries detecting dyes. Firstgroup is control and others Caries Detector,Quadrant Cari Test, Sable Seek groups. In controlgroup decayed dentine tissues remowed with siliconcarbite papers (300 gride) and in others groupscaries detectors applied and carious dentine tissuesremowed with silicon carbite papers. Than dentinbonding systems Clearfil SE Bond applied andspecimens restorated with composite resin. Allproducts were used according to manufacturer’sinstructions. Bond strengths were tested and datawere statistically analyzed one-way Analysis ofVariance (ANOVA) and Tukey tests.Results: As results of this study, Quadrant CariTest group showed lower bond strength than otherdetecting dyes groups. While bond strengths ofCaries Detector and Sable Seek groups weresimilar, their bond strengths were significantlyhigher than Quadrant Cari Test group (p<0,05).Conclusions: According to the results of this invitro study caries detecting dyes may lead toincreased shear bond strength values obtained.derecede daha yuksek baglanma dayanimi gosterdi.

HPLC analysis of bisphenol-A elution from resin composites after aging

Purpose:To evaluate the bond strength of a universal adhesive system applied to deep dentin under different bonding strategies. Methods andmaterials: Fifteen sound human thirdmolars had the coronal portion removed exposing deep dentin and were wet polished with 600-grit SiC abrasive paper for 60 s to create a standardized smear layer. Teeth were randomly assigned into three groups according to the different adhesive systems and bonding strategies: G1 – two-step etch & rinse as control (Adper Single Bond 2); G2 – universal adhesive applied as one-step self-etch (Scotchbond Universal); G3 – universal adhesive applied as two-step etch & rinse (Scotchbond Universal). Composite build-ups (Filtek Z350) composed by 3 increments of 2mm each were performed over the dentin surfaces. After 37 ◦C distilled water storage for 24h, teeth were sectioned with a slow-speed diamond saw under water cooling in the mesio-distal and buccal-lingual directions (perpendicular to adhesive interface) in order to obtain composite-dentin sticks with sectional area of 0.9mm. The specimens were submitted to the microtensile bond strength ( TBS) test at a crosshead speed of 0.5mm/min until failure. The failures were analyzed under an optical microscope at ×200magnification. Statistical analyses were computed using one-way ANOVA and Tukey test (p=0.05). Results: Themean TBS (inMPa) were G1=22.27, G2=22.85 and G3=20.3. After statistical analysis, no significant difference were observed between the groups. The majority of failures occurred were within the adhesive interface. Conclusion: The bond strength of the universal adhesive system was not influenced by the bonding strategy (one-step self-etch or 2-step etch & rinse) and its performance was not significantly different from the control (two-step etch & rinse).

Effect of quaternary ammonium methacrylates incorporation into a dental adhesive on the resistance of enzymatic degradation of resin-dentine interfaces

To evaluate the effect of quaternary ammonium methacrylates incorporation into a dental adhesive on the resistance of enzymatic degradation of resin-dentine interfaces. Thirty caries-free extracted human third molars were randomly divided into three groups (n = 10): 2-methacryloxylethyl dodecylmethyl ammonium bromide (MAE-DB) incorporated adhesive served as the experimental group, pre-treatment with chlorhexidine (CHX) served as a positive control, Adper(TM) Single Bond 2 served as a negative control. The resin-dentin interfaces were prepared using total etch bond system. After storage in distilled water at 37 °C for 24 h, the bonded teeth were vertically sectioned into beams. Beams were respectively immersed in artificial saliva containing 2 g/L MMP-8 at 37 °C for 0 h, 24 h and 120 h (n = 30). Micro-tensile bond strength, failure modes and nanoleakage were examined. There were no significantly differences of micro-tensile bond strength between groups before hydrolysis (P > 0.05). After the enzymatic hydrolysis of 24 h and 120 h, the micro-tensile bond strength of MAE-DB groups [(31.13 ± 8.77) MPa, (24.14 ± 6.64) MPa] were significantly higher than that of the negative control groups [(25.63 ± 6.90) MPa, (15.22 ± 6.57) MPa] (P < 0.05). Most of the failures were found in the base part of the hybrid layer in the negative control group, while failures occurred through the top of the hybrid layer in CHX and MAE-DB groups after the enzymatic hydrolysis.Specimens from each immediate group showed minor silver deposits in hybrid layer. After beams being enzymatic hydrolyzed for 120 h, it was shown that the silver nitrate uptake in the negative control group were significantly different from those in the CHX and MAE-DB groups (P < 0.05). Dental adhesive incorporation of MAE-DB could improve the anti-degrade ability of resin-dentin interfaces.

Effect of different molarity cathepsins specific inhibitor E-64 on dentin-resin bonding durability

To investigate, in vitro, the effect of cathepsins specific inhibitor N-(trans-epoxysuccinyl)-L-leucine 4-guanidinobutylamide(E-64) on dental endogenous cathepsins and to find its most effective molarity to elevate dentin-resin bonding durability. Fifty recently extracted human third molars were divided into five groups according to random number table, and treated with different molarity of E-64 as follow: 0, 2.5, 5.0, 10.0 and 20.0 µmol/L. The group 0 µmol/L was control group. Then 20 specimens of dentin-resin composite were fabricated in each group. Half of the specimens were tested after 24 h water storage(37 °C) and the other half were tested after 90 days water storage(37 °C) followed by 3000 cycles'thermocyling(5-55 °C) as aging treatment. Fractured specimens were analyzed using scanning electron microscopy(SEM). After 24 h water storage, no significant differences were found in micro-tensile bond strength(µTBS) of samples between different groups (P > 0.05). However, after ageing treatment, µTBS of the samples in group 2.5, 5.0, 10.0 and 20.0 µmol/L [(18.7 ± 2.7), (20.8 ± 3.4), (18.3 ± 2.8) and (19.1 ± 2.7) MPa] were significantly higher than that in group 0 µmol/L [(15.1 ± 3.0) MPa] (P < 0.05). Only in the group 5.0 µmol/L no significant difference was found between the original and the decreased value of µTBS(P > 0.05), while the µTBS in other groups decreased significantly after aging treatment(P < 0.05). Failure types were almost adhesive and mixed types. Collagens in hybrid layer were less degraded in the groups using E-64 after aging treatment than control group. E-64 was effective on inhibiting cathepsins activity in dentin, and induced less collagens degradation in smear layer for better dentin-resin bond durability.

Evaluation of bond strength and thickness of adhesive layer according to the techniques of applying adhesives in composite resin restorations.

Adhesive restorations have increasingly been used in dentistry, and the adhesive system application technique may determine the success of the restorative procedure. The aim of this study was to evaluate the influence of the application technique of two adhesive systems (Clearfil SE Bond and Adper Scotchbond MultiPurpose) on the bond strength and adhesive layer of composite resin restorations. Eight human third molars were selected and prepared with Class I occlusal cavities. The teeth were restored with composite using various application techniques for both adhesives, according to the following groups (n = 10): group 1 (control), systems were applied and adhesive was immediately light activated for 20 seconds without removing excesses; group 2, excess adhesive was removed with a gentle jet of air for 5 seconds; group 3, excess was removed with a dry microbrushtype device; and group 4, a gentle jet of air was applied after the microbrush and then light activation was performed. After this, the teeth were submitted to microtensile testing. For the two systems tested, no statistical differences were observed between groups 1 and 2. Groups 3 and 4 presented higher bond strength values compared with the other studied groups, allowing the conclusion that excess adhesive removal with a dry microbrush could improve bond strength in composite restorations. Predominance of adhesive fracture and thicker adhesive layer were observed via scanning electron microscopy (SEM) in groups 1 and 2. For groups 3 and 4, a mixed failure pattern and thinner adhesive layer were verified. Clinicians should be aware that excess adhesive may negatively affect bond strength, whereas a thin, uniform adhesive layer appears to be favorable.

Study on the micropermeability of resin-dentin bonding interfaces with ethanol-wet bonding technique

To evaluate the micropermeability on bonding hydrophobic adhesive to dentin with ethanol-wet bonding under simulated pulp pressure. Twenty-four intact human third molars were used in the study. After the enamel of occlusal surfaces was removed, the molars were randomly divided into six groups. Adper Scotchbond Multi-Purpose was used in the control group; in the experimental groups, the dentin surfaces were saturated with ethanol for 20 s (group 1), 1 min (group 2), 2 min (group 3), 3 min (group 4) or with a series of increasing ethanol concentrations before application of hydrophobic adhesive (group 5). All the bonding procedures were done under simulated pulp pressure. After 24 hours, micro-tensile bond strength test were performed on the specimens. Bonding interfaces were observed under laser scanning confocal microscope (LSCM) after the pulp chamber were filled with a water-soluble fluoroprobe rhodamine B for 3 hours. Compared with the control group [(38.14 ± 4.97) MPa], bond strengths in group 1 [(21.02 ± 7.23) MPa] and group 2 [(29.64 ± 3.81) MPa] were statistically lower (P > 0.05), while bond strength in group 3 [(38.40 ± 5.03) MPa], group 4 [(37.26 ± 4.68) MPa] and group 5 [(40.12 ± 5.95) MPa] were similar to the control group (P < 0.05). The images taken by LSCM showed that with extension of ethanol-wet time, the deposition of fluorescent dye in hybrid layer and along the dentinal tubules decreased gradually. Especially in group 5, only spare fluorescent dye deposition could be detected in the hybrid layer. Dentin saturated with ethanol for more than 2 min before bonding hydrophobic adhesive to dentin could provide favorable bond strength and decreased the micropermeability of bonding interfaces under simulated pulp pressure.

A new method for relative Sr determination in human teeth enamel.

We present a new method to determine Sr/Ca changes in hard dental tissues based on laser ablation and spectroscopic detection. By using femtosecond Laser Induced Breakdown Spectroscopy (fs-LIBS), we micro mapped the relative amount of strontium in the enamel of three human lower third molar. We also analyzed the Sr/Ca ratio along the striae of Retzius. Results show that microlibs allows detection of variation in relative Sr/Ca ratio through enamel. The same values of Sr/Ca ratio were found along a single stria. The method has a precision better than 95% and is sensitive enough to detect Sr/Ca ratio variations among striae and within stria. Fs-LIBS generates information in a fast and simple way that can be used by non-specialists to make inferences about diet or mobility in human populations and fossil hominids.

Chlorhexidine diminishes the loss of bond strength over time under simulated pulpal pressure and thermo-mechanical stressing

The purpose of this study was to investigate the effects of chlorhexidine (CHX) digluconate at 0.2% and 2% on dentin bonding durability of etch-and-rinse and self-etch adhesive systems. In this study were used 24 extracted non-carious human third-molars. The occlusal surfaces of the molar crowns were removed with a low-speed diamond saw to expose flat dentin surfaces. The tested materials were Single-Bond (SB) (two-step etch-and-rinse adhesive) and Clearfil Tri S Bond (CTSB) (all-in-one self-etch adhesive) used in association or not with CHX at 0.2% and 2%. The bonding systems were applied according to manufacturer's instructions and followed by composite application (Z250). For each condition, half of the specimens was immediately submitted to microtensile test and half of them was submitted to long-term storage of 6 months under simulated pulpal pressure and thermo-mechanical stressing before testing. The data were analyzed using Two-Way ANOVA and Tukey post hoc test (alpha=0.05). Failure patterns of the specimens were observed using scanning electron microscopy. The falling % in bond strength over the 6-month period was: SB control-43.64%; SB/0.2%CHX-23.79%; SB/2%CHX-26.42%; CTSB control-40.94%; CTSB/0.2%CHX-37.07%; CTSB/2%CHX-22.14%. The fracture modes were predominantly adhesive, mainly in the specimens of terminal groups. CXH digluconate at 2% was able to diminish loss of microtensile bond strength over time associated to both etch-and-rinse and self-etch adhesives. Lower concentration of CHX (0.2%) was not able to diminish the loss of bond strength over time when associated to the self-etch adhesive CTSB.