Microporosity and polymerization contraction as function of depth in dental resin cements by X-ray computed microtomography.

This research aimed to obtain the depth dependence of polymerization contraction and microporosity from irradiated dental resin cements by X-ray computed microtomography (µCT). Samples (n = 5) of commercial Relyx U200 (RU) and AllCem Core (AC) dual-cure resin cements were injected in a cylindrical Teflon sampler (25 mm3 ) and separated according to polymerization mechanism: self-cured (not irradiated) and dual-cured (irradiated from the top surface with a LED device). The cement's volume was scanned with the µCT scanning conditions kept constant. To assess the depth dependence of polymerization contraction, it was measured the displacement of the cement mass from the sample holder at 30 vertical cuts (0.1 mm distant). To probe the microporosity, the percentage of area with presence of porosity by slice was obtained. All data were statistically treated. It was observed a positive linear correlation between depth and polymerization contraction in the irradiated groups. In the other hand, the concentration of micropores decreased with increasing depth. Furthermore, the composition of the resin cement was determinant for the correlation's coefficients of these physical properties with depth. The µCT technique showed to be useful to probe physical properties of dental restorative materials that influence in the clinical outcomes, revealing that, for thin specimens, when light cured the RU cement presented mechanical behavior more favorable for clinical applications.

[Curing mode of universal adhesives affects the bond strength of resin cements to dentin].

OBJECTIVE: To determine the effects of curing mode of one-step and two-step universal adhesives on the micro-tensile bond strength (µTBS) of different dual-cure resin cements to dentin. METHODS: One-step universal adhesive Single Bond Universal (SBU), and two-step universal adhesive OptiBond Versa (VSA) were chosen as the subjects, one-step self-etching adhesive OptiBond All in One (AIO) and two-step self-etching adhesive Clearfil SE Bond (SEB) were control groups, and two dual-cure resin cements RelyX Ultimate (RLX) and Nexus 3 Universal (NX3) were used in this study. In this study, 80 extracted human molars were selected and the dentin surface was exposed using diamond saw. The teeth were divided into 16 groups according to the adhesives (AIO, SBU, SEB, VSA), cure modes of adhesives (light cure, non-light cure) and resin cements (RLX, NX3). The adhesives were applied on the dentin surface following the instruction and whether light cured or not, then the resin cements were applied on the adhesives with 1 mm thickness and light cured (650 mW/cm(2) for 20 s. A resin was built up (5 mm) on the cements and light cured layer by layer. After water storage for 24 h, the specimens were cut into resin-cement-dentin strips with a cross sectional area of 1 mm×1 mm and the µTBS was measured. RESULTS: Regarding one-step universal adhesive (SBU) light cured, the µTBS with RLX [(35.45±7.04) MPa] or NX3 [(26.84±10.39) MPa] were higher than SBU non-light cured with RLX [(17.93±8.93) MPa)] or NX3 [(10.07±5.89) MPa, P<0.001]. Compared with AIO, light-cured SBU combined with RLX presented higher µTBS than AIO group [(35.45±7.04) MPa vs. (24.86±8.42) MPa, P<0.05]. When SBU was not lighted, the µTBS was lower than AIO [(17.93±8.93) MPa vs. (22.28±7.57) MPa, P<0.05]. For two-step universal adhesive (VSA) and control adhesive (SEB), curing mode did not affect the µTBS when used with either RLX or NX3 (25.98-32.24 MPa, P>0.05). CONCLUSION: Curing mode of one-step universal adhesive may affect the µTBS between dual-cure resin cements and dentin, while for two-step universal adhesive, the curing mode and the type of resin cements did not influence the µTBS.

Adhesive sealing of dentin surfaces in vitro: A review.

PURPOSE: This review describes the evolution of the use of dental adhesives to form a tight seal of freshly prepared dentin to protect the pulp from bacterial products, during the time between crown preparation and final cementation of full crowns. The evolution of these "immediate dentin sealants" follows the evolution of dental adhesives, in general. That is, they began with multiple-step, etch-and-rinse adhesives, and then switched to the use of simplified adhesives. METHODS: Literature was reviewed for evidence that bacteria or bacterial products diffusing across dentin can irritate pulpal tissues before and after smear layer removal. Smear layers can be solubilized by plaque organisms within 7-10 days if they are directly exposed to oral fluids. It is likely that smear layers covered by temporary restorations may last more than 1 month. As long as smear layers remain in place, they can partially seal dentin. Thus, many in vitro studies evaluating the sealing ability of adhesive resins use smear layer-covered dentin as a reference condition. Surprisingly, many adhesives do not seal dentin as well as do smear layers. RESULTS: Both in vitro and in vivo studies show that resin- covered dentin allows dentin fluid to cross polymerized resins. The use of simplified single bottle adhesives to seal dentin was a step backwards. Currently, most authorities use either 3-step adhesives such as Scotchbond Multi-Purpose or OptiBond FL or two-step self-etching primer adhesives, such as Clearfil SE, Unifil Bond or AdheSE.

Cementation of indirect restorations: an overview of resin cements.

The process of ensuring proper retention, marginal seal, and durability of indirect restorations depends heavily on effective cementation. Careful consideration must be made when selecting an adhesive cement for a given application. This article provides information on resin cements that can guide clinicians in determining which type of cement is best suited to their clinical needs regarding cementation of indirect restorations. Emphasis is placed on successful cementation of all-ceramic restorations.

Shear bond strength of porcelain laminate veneers to enamel, dentine and enamel-dentine complex bonded with different adhesive luting systems.

OBJECTIVES: The aim of this study was to evaluate the shear bond strength of porcelain laminate veneers to 3 different surfaces by means of enamel, dentine, and enamel-dentine complex. METHODS: One hundred thirty-five extracted human maxillary central teeth were used, and the teeth were randomly divided into 9 groups (n=15). The teeth were prepared with 3 different levels for bonding surfaces of enamel (E), dentine (D), and enamel-dentine complex (E-D). Porcelain discs (IPS e.max Press, Ivoclar Vivadent) of 2mm in thickness and 4mm in diameter were luted to the tooth surfaces by using 2 light-curing (RelyX Veneer [RV], 3M ESPE; Variolink Veneer [VV], Ivoclar Vivadent) and a dual-curing (Variolink II [V2], Ivoclar Vivadent) adhesive systems according to the manufacturers' instructions. Shear bond strength test was performed in a universal testing machine at 0.5mm/min until bonding failure. Failure modes were determined under a stereomicroscope, and fracture surfaces were evaluated with a scanning electron microscope. The data were statistically analysed (SPSS 17.0) (p=0.05). RESULTS: Group RV-D exhibited the lowest bond strength value (5.42±6.6MPa). There was statistically no difference among RV-D, V2-D (13.78±8.8MPa) and VV-D (13.84±6.2MPa) groups (p>0.05). Group VV-E exhibited the highest bond strength value (24.76±8.8MPa). CONCLUSIONS: The type of tooth structure affected the shear bond strength of the porcelain laminate veneers to the 3 different types of tooth structures (enamel, dentine, and enamel-dentine complex). CLINICAL SIGNIFICANCE: When dentine exposure is necessary during preparation, enough sound enamel must be protected as much as possible to maintain a good bonding; to obtain maximum bond strength, preparation margins should be on sound enamel.

In vitro shear bond strength of resin-based luting cements to dentin.

The aim of this study was to determine how resin cement, self-adhesive resin cement, and resin-modified glass ionomer cement affected shear bond strength to dentin. Sixty composite resin disks (3 mm in diameter x 3 mm in length) were prepared and divided into four groups (n = 15): Group 1, composite disk bonded to dentin with composite resin and a bonding agent; Group 2, composite disk bonded to dentin with a self-adhesive resin cement; Group 3, composite disk bonded to dentin with a different self-adhesive resin cement; and Group 4, composite disk bonded to dentin with a resin-modified glass ionomer cement. The composite resin was loaded into a syringe (internal diameter 3 mm), photocured in an oven, and cut into 3 mm slices with a low-speed saw. The samples were bonded to dentin per the manufacturer's instructions. All specimens were stored in distilled water (at 37 degrees C) for 24 hours. The shear bond strength test was conducted using a universal testing machine at a crosshead speed of 0.5 mm/min until failure. Conventional resin cement and a bonding agent exhibited significantly higher shear bond strength values than all other materials tested.

Nuevas tendencias para la cementación de postes / New trends in post cementation

A lo largo de la historia hemos restaurado órganos dentales con gran destrucción de su estructura, empleando diferentes materiales y métodos, siendo como primera opción el uso depernos o postes intrarradiculares adheridos al tejido dentinario, utilizando algún agente cementante. Es importante destacar que para cada caso en particular se aplica diferente técnica o método, al igual que los materiales a colocar; deberá ser obligación del clínico estudiar y seleccionar la forma en que se llevará a cabo cada restauración.

Bond degradation behavior of self-adhesive cement and conventional resin cements bonded to silanized ceramic.

STATEMENT OF PROBLEM: Self-adhesive resin cement with the characteristics of glass ionomer cement is more susceptible to water than conventional resin cements. It is unknown if there is a higher risk of bond degradation at the interface with silanized ceramic in an oral environment. PURPOSE: The purpose of this study was to evaluate the bond degradation behavior of self-adhesive cement under simulated oral conditions, by comparing it with the behavior of 3 conventional resin cements. MATERIAL AND METHODS: Three conventional resin cements, Linkamx HV (LMHV), Clearfil Esthetic Cement (CEC), and SuperBond (SB), were bonded to silanized ceramic (ProCAD) with the manufacturer's recommended silane coupler (GC Ceramic Primer (GCCP), Clearfil Ceramic Primer (CCP), and Porcelain Liner M (PLM), respectively), while a self-adhesive cement (G-CEM) was bonded with each of the 3 silane couplers. Maximum water sorption and solubility of the resin cements were measured according to the ISO 4049 standard during 6 weeks of water storage. The microshear bond strength of each silane/cement group (n=10 per thermal cycling subgroup) was tested after 0, 10,000, and 30,000 thermal cycles (TC), and bond failure types were counted. One- and two-way ANOVAs and the Tukey multiple comparisons test (α=.05) were used to evaluate the bond strength data. RESULTS: G-CEM had significantly higher water sorption (P<.001) and solubility than conventional resin cements. Statistical analysis showed that the bond strength of all silane/cement groups was reduced significantly by thermal cycling (P=.01 for CCP/G-CEM, P=.003 for GCCP/LMHV, P<.001 for other groups). The bond strength of G-CEM with the 3 silane couplers was significantly degraded from TC 0 to 10,000 (P<.001 for GCCP/G-CEM and PLM/G-CEM, P=.01 for CCP/G-CEM); however, the bond strength appeared to stabilize with no significant degradation from TC 10,000 to 30,000. This behavior was different from that of conventional resin cements, which demonstrated bond degradation throughout TC 0-30,000. After TC 30,000, the bond strength of G-CEM did not differ significantly from that of the 3 conventional resin cements. CONCLUSIONS: The bond degradation behavior of G-CEM under thermal cycling conditions differs from that of conventional resin cements.

The effects of adhesive type and thickness on stress distribution in molars restored with all-ceramic crowns.

PURPOSE: This study investigated the effects of luting cement type and thickness on the stress distribution within all-ceramic crowns using finite element analysis. MATERIALS AND METHODS: An all-ceramic crown restoration of the mandibular right first molar was prepared according to standard dental processes and scanned using micro-computed tomography. Eight 3D FE models were then developed that accounted for two adhesive systems, each with cement thickness of 60 µm, 90 µm, 120 µm, and 150 µm. The models were subjected to four loading conditions, and stresses in the veneer and core layers were evaluated. RESULTS: The stress distribution and maximum stresses in the veneer, core, and cement are presented in corresponding loading conditions. The cement with higher elastic modulus resulted in lower tensile stresses in the veneer and core layers, and the shear strength of the cement was critical to the intactness of the all-ceramic crown. CONCLUSION: The cement thickness acts as a cushion between the crown and dentin substrate. Although there is an optimal thickness (approximately 90 µm) that can reduce the stress level in ceramic crowns, cement thickness is not very important to stresses in the core or veneer in most cases when compared to the influence of loading conditions or cement moduli.

Considerations for the selection of a luting cement.

UNLABELLED: Selection of a luting material for optimal cementation of indirect restorations requires the consideration of several factors relating to the properties of both the cement and of the restoration. Contemporary restorations (for example, dentine-bonded crowns or resin-retained bridges) often rely on bonding, and advances in dental materials science have resulted in simplified resin systems. Their ease of use and other favourable properties also offer advantages when used for more conventional restorations. Traditional luting cements remain commonplace and their benefits and shortcomings are discussed in terms of handling and clinical performance. Developments and trends in adhesive dentistry are explored. CLINICAL RELEVANCE: Luting cement selection and application is integral to the optimal performance of indirect restorations.

One-component self-etching primer: a seventh generation of orthodontic bonding system?

The purpose of this study was to compare the bond strengths and to evaluate the debonding site using the adhesive remnant index (ARI) provided by a conventional acid-etch conditioner and a new self-etching adhesive system, Xeno IV (Dentsply Caulk). One hundred and eighty bovine lower incisors were randomly divided into six groups (n = 30). In groups 1, 2, and 3, Transbond XT (3M Unitek) composite was used to bond the brackets to enamel samples conditioned with 37 per cent phosphoric acid + XT primer (3M Unitek), Xeno IV + XT primer, or Xeno IV only, respectively. In groups 4, 5, and 6, the bonding procedures were performed using Fuji Ortho LC (GC Corp.) resin-modified glass ionomer cement unconditioned, enamel conditioned with 37 per cent phosphoric acid, or Xeno IV, respectively. All samples underwent thermocycling and then shear bond strength (SBS) testing was performed using a universal testing machine (Emic DL 10.000). Analysis of variance was applied. For the post hoc test, the Tukey's test was used. Kruskal-Wallis and Mann-Whitney U-tests were used to assess ARI scores. The results demonstrated no statistical differences between groups 1, 2, and 3. However, statistically significant differences were found between these samples and groups 4, 5, and 6. With regard to ARI score, the highest mean value was found in group 5 (Fuji Ortho LC + 37 per cent acid conditioning), whereas group 4 (Fuji Ortho LC + no conditioning) had the lowest SBS. Xeno IV self-etching bonding agent was able to bond orthodontic brackets in association with Transbond XT composite as well as with Fuji Ortho LC, thus maximizing bracket bonding.

The effect of moisture on the shear bond strength of gold alloy rods bonded to enamel with a self-adhesive and a hydrophobic resin cement.

The aim of this in vitro study was to investigate the influence of enamel moisture on the shear bond strength (SBS) of a hydrophobic resin cement, Maximum Cure (MC), and a self-adhesive resin cement, Multilink Sprint (MLS), after etching of the enamel. Forty cylindrical gold alloy rods were used to simulate the Incognito lingual bracket system. They were bonded to the enamel of 40 human teeth embedded in self-cured acrylic resin. Twenty were bonded with MC (10 on dry and 10 on wet enamel) and 20 with MLS (10 on dry and 10 on wet enamel). The SBS of MC and MLS was determined in a universal testing machine and the site of bond failure was defined by the adhesive remnant index (ARI). A Kruskal-Wallis test was performed followed by Games-Howell post hoc pairwise comparison tests on the SBS results (P < 0.05) and a chi-square test was used for the analysis of ARI scores (P < 0.05). On dry enamel, no significant differences between MC (58 +/- 5 MPa) and MLS (64 +/- 13 MPa) were noted. On wet enamel, the adherence of MC (6 +/- 8 MPa) and MLS (37 +/- 13 MPa) significantly decreased but to a lesser extent for MLS. The ARI scores corroborated these results. In conclusion, MC did not tolerate moisture. MLS was also affected but maintained sufficient adherence.

Understanding adhesive dentistry.

This review paper firstly provides an outline of the development of resin-based adhesives. A simple classification method is described based on whether an acid etching agent requiring a washing and drying step is used. These systems are called etch and rinse systems. The other adhesives that do not have the washing and drying steps are referred to as self-etching adhesives. The advantages and disadvantages of these groups of adhesives are discussed. Methods of adhering to the tooth surface are provided, especially where the resin-based adhesive reliability is difficult to control.

Evaluation of shear and tensile bond strength between dentin and ceramics using dual-polymerizing resin cements.

STATEMENT OF PROBLEM: The applications of dual-polymerizing resin cements for all-ceramic restorations have considerably increased. For a successful clinical outcome, the luting agent should have high bond strength, not only to the ceramic surface, but also to the tooth surface. PURPOSE: The purpose of this study was to examine shear (S) and tensile (T) bond strengths between 2 all-ceramic systems and human dentin using 3 dual-polymerizing resin cements. MATERIAL AND METHODS: The buccal surfaces of 120 freshly extracted human third molars were ground flat, parallel to the long axis. Sixty specimens were prepared from each of 2 all-ceramic systems (IPS Empress 2 (E) and Cergo Pressable Ceramic (C)). Twenty specimens were luted with each of the following resin cements: Nexus 2 (N) with Self-Etch Primer, Duo-Link (D), and Variolink II (V), with their respective bonding systems. All specimens were immersed in water at 37 degrees C for 1 week, before being thermal cycled for 500 cycles in 5 degrees C and 55 degrees C water. Shear (S) and tensile (T) bond strength tests were applied to 10 specimens from each group. Fractured surfaces were inspected by scanning electron microscopy (SEM). Statistical analyses were performed using nonparametric 1-way ANOVA (Kruskal-Wallis) followed by Duncan's multiple range tests for post hoc comparison and Mann-Whitney U test for 2 ceramic systems (alpha=.05). RESULTS: Significant differences were observed in shear and tensile bond strength values of the adhesive systems used (P<.05). Duo-Link showed the highest mean bond strength values, whereas Nexus 2 revealed lower shear and tensile bond strength values. Fracture modes were hybrid at the dentin interface and/or cohesive in dentin. CONCLUSIONS: Cementing agents/adhesive systems may influence the bond to dental hard tissues. Dual-polymerizing activators may have a negative effect on polymerization of the bonding agent.