The role of polymerization in adhesive dentistry Cadenaro, Milena; Maravic, Tatjana; Comba, Allegra ...
Dental materials,
January 2019, 2019-Jan, 2019-01-00, 20190101, Letnik:
35, Številka:
1
Journal Article
Recenzirano
•Factors that influence polymerization of adhesives are described.•Accurate evaporation of the solvents may improve the polymerization of adhesive system.•Prolonged curing time increase the ...performance and stability of adhesive systems.•The effect on curing reaction of molecules added to adhesive formulations to counteract the degradation of the adhesive interface over time has to be clarified.
Adhesive systems are resin-based materials that reach their final mechanical properties through a polymerization process. Previous literature correlated the failure of the adhesive interface to low polymer setting. Adhesives systems are elaborate mixtures of different molecules of both hydrophilic and hydrophobic nature, included in the formulation to adequately infiltrate the complex dental substrate or added to prolong the stability of the adhesive layer over time. Each adhesive component may influence the polymerization reaction of the material. Photopolymerization is a complex reaction that has several clinical implications, and besides the material composition, it is influenced by multiple factors, including the substrate characteristics, the operator technique, and the light cure unit properties. This review is focused on the analysis of factors that have a potential role in the setting of adhesive materials and thus the ultimate characteristics of the adhesive layer and the stability of the resin-dentin interface.
The aim of this in vitro study was to evaluate the effects of substrate and cement shades on the translucency and color of lithium-disilicate and zirconia CAD/CAM materials. Two light-cured resin ...cements (RelyX Veneer Cement; 3M; Choice 2 Veneer Cement; Bisco Dental) with a standardized thickness (0.1 mm) were tested in combination with two different monolithic CAD/CAM materials (E-Max CAD (LI2SI2O5); Ivoclar Vivadent; Katana (ZrO2); Kuraray-Noritake Dental) on two different colored composite substrates used as a dentin (Filtek Supreme XTE; 3M); for a total of 12 combinations (n = 10). The specimens’ color was measured with a spectrophotometer (Spectroshade; MHT). Measurements were taken using the CIELAB color coordinate system (L*a*b*) against black and white backgrounds. L*a*b* values were statistically analyzed for the variables Substrate, Ceramic, and Cement by applying a Three-Way ANOVA followed by the Tukey Test for post-hoc comparison (p < 0.05). Translucency Parameter (TP) and Constant Ratio (CR) were assessed to evaluate translucency; acceptability and perceptibility thresholds (ΔE00 1.8 and 0.8) were used. Statistically significant influence was found for factors ceramic material, cement shade, and substrate color (p < 0.05). Unacceptable color differences were reported for Li2Si2O5. Opacity was significantly higher when white opaque cement shade was employed. Ceramic type and cement shade significantly influenced L*a*b* color coordinates. The final translucency and color of ceramic restorations can, therefore, be influenced by ceramic material, cement shade, and substrate color.
Objectives
The survival rate of indirect partial adhesive restorations on vital versus endodontically treated teeth is still controversial. The hypothesis is that there may be a difference in the ...survival rate of partial adhesive restorations performed on non-vital teeth compared to vital teeth.
Materials and methods
This systematic review was conducted following the PRISMA guidelines. The considered clinical studies investigated the outcomes of adhesive inlays, onlays, and overlays conducted over the past 40 years, focusing on Kaplan–Meier survival curves to calculate the hazard ratio (primary objective) and the survival rate (secondary objective) between vital and non-vital teeth. The risk of bias was assessed using the Newcastle–Ottawa Scale. Studies included in the review were identified through bibliographic research on electronic databases (“PubMed,” “Scopus,” “Cochrane Central Register of Controlled Trial,” and “Embase”). The
K
agreement between the two screening reviewers was evaluated.
Results
A total of 55,793 records were identified on PubMed, Scopus, and other bibliographic sources, and after the application of the eligibility and inclusion criteria, eight articles were included for qualitative analysis and six for quantitative analysis. The meta-analysis of the primary and secondary outcomes demonstrated that hazard ratios (HR = 8.41, 95% CI: 4.50, 15.72) and survival rates (OR = 3.24, 95% CI: 1.76, 5.82) seemed more favorable for indirect partial adhesive restorations on vital teeth than for those on endodontically treated teeth.
Conclusions
Within the limits of this study, these findings suggest that the risk of failure of indirect partial adhesive restorations on endodontically treated teeth is higher than on vital teeth.
Clinical relevance
The use of partial adhesive restorations on vital and endodontically treated teeth showed different long-term clinical outcomes.
•EDC pre-treatment efficiently preserves bond strength over time.•Pre-treatment with EDC resulted in an almost complete inhibition of MMPs.•Changes within the dentin matrix promoted by EDC are not ...adhesive-system-dependent.
The objectives of the study were to evaluate the ability of a 1-ethyl-3 (3-dimethylaminopropyl) carbodiimide (EDC)-containing primer to improve immediate bond strength of either self-etch or etch-and-rinse adhesive systems and to stabilize the adhesive interfaces over time. A further objective was to investigate the effect of EDC on the dentinal MMPs activity using zymographic analysis.
Freshly extracted molars (n=80, 20 for each group) were selected to conduct microtensile bond strength tests. The following groups were tested, immediately or after 1-year aging in artificial saliva: G1: Clearfil SE (CSE) primer applied on unetched dentin, pretreated with 0.3M EDC water-solution for 1min and bonded with CSE Bond; G2: as G1 but without EDC pre-treatment; G3: acid-etched (35% phosphoric-acid for 15s) dentin pretreated with 0.3M EDC, then bonded with XP Bond (XPB); Group 4 (G4): as G3 without EDC pre-treatment. Further, gelatinase activity in dentin powder treated with CSE and XPB with and without EDC pre-treatment, was analyzed using gelatin zymography.
The use of 0.3M EDC-containing conditioner did not affect the immediate bond strength of XPB or CSE adhesive systems (p>0.05), while it improved the bond strength after 1year of aging (p<0.05). Pre-treatment with EDC followed by the application of CSE resulted in an incomplete MMPs inactivation, while EDC pretreatment followed by the application of XPB resulted in an almost complete inactivation of dentinal gelatinases.
The μTBS and zymography results support the efficacy of EDC over time and reveal that changes within the dentin matrix promoted by EDC are not adhesive-system-dependent.
Abstract Objectives The study evaluated the fracture resistance and fracture patterns of endodontically treated mandibular first molars restored with glass-fiber-reinforced direct composite ...restorations. Methods In total, 60 extracted intact first molars were treated endodontically; a mesio-occluso-distal (MOD) cavity was prepared and specimens were then divided into six groups: sound teeth (G1), no restoration (G2), direct composite restoration (G3), fiber-post-supported direct composite restoration (G4), direct composite reinforced with horizontal mesio-distal glass-fibers (G5), and buccal-palatal glass-fibers (G6). Specimens were subjected to 5000 thermocycles and 20,000 cycles of 45° oblique loading force at 1.3 Hz and 50 N; they were then loaded until fracture. The maximum fracture loads were recorded in Newtons (N) and data were analyzed with one-way ANOVA and post-hoc Tukey tests (p < 0.05). Fractured specimens were analyzed with a scanning electron microscope (SEM). Results The mean static loads (in Newtons) were: G1, 831.83; G2, 282.86; G3, 364.18; G4, 502.93; G5, 499.26; and G6, 582.22. Fracture resistance did not differ among G4, G5, and G6, but was significantly higher than G3 (p = 0.001). All specimens fractured in a catastrophic way. In G6, glass fibers inducted a partial deflection of the fracture, although they were not able to stop crack propagation. Conclusions For the direct restoration of endodontically treated molars, reinforcement of composite resins with glass-fibers or fiber posts can enhance fracture resistance. The SEM analysis showed a low ability of horizontal glass-fibers to deviate the fracture, but this effect was not sufficient to lead to more favorable fracture patterns above the cement-enamel junction (CEJ). Clinical significance The fracture resistance of endodontically treated molars restored with direct composite restorations seems to be increased by reinforcement with fibers, even if it is insufficient to restore sound molar fracture resistance and cannot avoid vertical fractures.
Abstract
Objectives of the study were to investigate biomechanical properties of severely compromised premolars restored with composite restorations using finite element analysis (FEA), and in vitro ...fracture resistance test. A 3-D model of an endodontically treated premolar was created in Solidworks. Different composite restorations were modelled (direct restoration-DR; endo-crown-EC; post, core, and crown-C) with two different supporting tissues: periodontal ligament/alveolar bone (B), and polymethyl methacrylate (PMMA). Models were two-point axially loaded occlusally (850 N). Von Mises stresses and strains were calculated. The same groups were further tested for static fracture resistance in vitro (n = 5, 6.0 mm-diameter ball indenter, vertical load). Fracture resistance data were statistically analyzed (
p
< 0.050). The highest stresses and strains in all FEA models were observed on occlusal and vestibular cervical surfaces, corresponding to fracture propagation demonstrated in vitro. C showed the lowest stress in dentin, while EC showed lower stresses and strains in crown cement. B models demonstrated larger high stress areas in the root than PMMA models. No significant differences in fracture resistance (N) were observed between groups (DR: 747.7 ± 164.0, EC: 867.3 ± 108.1, C: 866.9 ± 126.3;
p
= 0.307). More conservative restorations seem a feasible alternative for endodontically treated premolars to conventional post-core-crown.
Objective
To investigate the long-term microtensile bond strength (µTBS), interfacial nanoleakage expression (NL), and adhesive stability of dual-cure resin cements with/out light activation to ...dentin.
Materials and methods
Composite overlays (
N
= 20) were luted to deep dentin surfaces with RelyX Ultimate (RXU, 3M) or Variolink EstheticDC (VAR, Ivoclar-Vivadent). A universal adhesive was used for bonding procedures (iBond universal, Heraeus Kulzer). The resin cements were either self-cured (SC; 1 h at 37 °C) or dual-cured (DC; 20s light-cure followed by 15 min self-cure at 37 °C). Specimens were submitted to µTBS immediately (
T
0
) or after 1 year of laboratory storage (
T
12
). The fracture pattern was evaluated using scanning electron microscopy (SEM). Data were statistically analyzed with two-way ANOVA/Tukey test. Further, the NL was quantified and analyzed (chi-square test) and in situ zymography was performed to evaluate the endogenous enzymatic activity within the hybrid layer (HL) at
T
0
and
T
12
(Mann–Whitney test)
.
The significance level for all statistical tests was set at
p
= 0.05.
Results
DC resulted in higher bond strength and decreased fluorescence at the adhesive interface, irrespective of the material and the storage period (
p
< 0.05). Significantly lower bonding performances (
p
< 0.05) and higher endogenous enzymatic activity (
p
< 0.05) were observed within the HL at
T
12
compared to
T
0
in all tested groups.
Conclusions
Light-curing the dual-cure resin cements, more than the cement materials, accounted for good bonding performances and higher HL stability over time when used with a universal adhesive.
Clinical significance
The curing condition influences the bonding performances of dual-cure resin cements to dentin when used with a universal adhesive.
Objectives
Matrix metalloproteases (MMPs) are a family of enzymes that operate a proteolytic activity at the level of the extracellular matrix. MMPs are regulated by tissue inhibitors of ...metalloproteinases (TIMPs) that can ubiquitously bind different enzyme forms. The study aims to identify a morfo-functional association between TIMP-1 and MMP-2 and -9 in human dentin.
Materials and methods
Proteins were extracted from demineralized human sound dentin powder and centrifuged to separate two aliquots with different molecular weights of proteins, higher and lower than 30 kDa. In each aliquot, the evaluation of the presence of TIMP-1/MMP-2 and TIMP-1/MMP-9 was performed using co-immunoprecipitation/immunoblotting analysis. The distribution of TIMP-1, in association with MMP-2 and -9, was investigated using a double immunohistochemical technique. Furthermore, the activity of TIMP-1 was measured by reverse zymography, where acrylamide gel was copolymerized with gelatin and recombinant MMP-2.
Results
Co-immunoprecipitation/immunoblotting analysis showed the association TIMP-1/MMP-2 and TIMP-1/MMP-9 in human sound dentin. Electron microscopy evaluation revealed a diffuse presence of TIMP-1 tightly associated with MMP-2 and -9. Reverse zymography analysis confirmed that TIMP-1 present in human dentin is active and can bind different MMPs isoforms.
Conclusions
The strict association of TIMP-1 with MMP-2 and -9 in situ appeared a constant finding in the human sound dentin.
Clinical relevance
Considering the role of TIMP-1, MMP-2, and MMP-9 within the connective tissues, clinically applicable protocols could be developed in the future to increase or decrease the level of TIMPs in human dentin to regulate the activity of MMPs, contributing to reduce caries progression and collagen degradation.
Various materials and systems for bonding lithium disilicate to the tooth substrate are available to clinicians, who can adapt the materials to each clinical situation to maximize the performance of ...indirect esthetic restorations. This study aimed to evaluate the degree of conversion (DC) and the microhardness (MH) of a dual-curing and a light-curing cement under lithium disilicate discs of different thicknesses.
A total of 48 lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) samples were prepared and divided into three groups (n = 16) according to the thickness (group A was 0.6 mm; group B was 1.0 mm; group C was 1.5 mm). Each group was further divided into two subgroups (n = 8) according to the resin cement employed, NX3 (Kerr) or Choice 2 (Bisco). A standardized quantity of cement was placed on the sample, and DC was evaluated with an attenuated total reflectance Fourier transformed infrared spectrophotometer (Nicolet IS10, Thermo Scientific). Twenty-four hours after DC was established, Vickers test was performed on the cement with a microindentometer (Leica Microsystems). Results were statistically analyzed with analysis of variance test and significance set at P < .05.
Statistical analysis showed cement type had a significant influence (P = .005) on DC. MH results were influenced by thicknesses only between 0.6 and 1.5 mm when light-cured cement was employed.
The light-curing and the dual-curing cements reached comparable DCs between 0.6 and 1.5 mm. However, the light-curing resin showed a higher DC and MH.
The aim of the present study was to evaluate the fatigue to cyclic and static resistance of indirect restorations with different preparation designs made either of lithium disilicate (LS) or ...polymer-infiltrated ceramic network (PICN). Eighty-four (
= 84) molars were chosen, endodontically treated, and prepared with standardized MOD cavities. The molars were randomly divided into 6 study groups (
= 14) taking into account the "preparation design'' (occlusal veneer with 1.2 mm occlusal thickness; overlay with 1.6 mm occlusal thickness; adhesive crown with 2 mm occlusal thickness) and the "CAD/CAM material'' (E-max CAD, Ivoclar vivadent; Vita Enamic, Vita). A fatigue test was conducted with a chewing simulator set at 50 N for 1,500,000 cycles. Fracture resistance was assessed using a universal testing machine with a 6 mm diameter steel sphere applied to the specimens at a constant speed of 1 mm/min. A SEM analysis before the fracture test was performed to visually analyze the tooth-restoration margins. A statistical analysis was performed with a two-way ANOVA and a post-hoc pairwise comparison was performed using the Tukey test. The two-way ANOVA test showed that both the preparation design factor (
= 0.0429) and the CAD/CAM material factor (
= 0.0002) had a significant influence on the fracture resistance of the adhesive indirect restorations. The interaction between the two variables did not show any significance (
= 0.8218). The occlusal veneer had a lower fracture resistance than the adhesive crown (
= 0.042) but not lower than the overlay preparation (
= 0.095). LS was more resistant than PICN (
= 0.002). In conclusion, in the case of endodontically treated teeth, overlay preparation seems to be a valid alternative to the traditional full crown preparation, while occlusal veneers should be avoided in restoring non-vital molars with a high loss of residual tooth structure. LS material is more resistant compared to PICN.
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