939 D3000 new imprint Word template Vol 13, No 1 (2025) ISSN 2167-8677 (online) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu Effect of Curing Technique and Emax Type on the Polymerization of Dual Cure Resin Cement Amani Abduljabar Altaie, Emad Farhan Alkhalidi University of Mosul, Mosul, Iraq Abstract Objec6ve: The objecCve of this study was to evaluate the effect of different types of curing techniques and composiCon of two different types of emax materials on degree of conver- sion and polymerizaCon of dual cure resin cement aTer 24 hours. Material and Methods: Resin cement discs (90 total) were made by polymerizaCon through two types of Emax discs: Ivoclar IPS e.max (n=30) and GC LiSi Press (n=30). 30 samples without an Emax disc were used as controls. For each group, three subgroups according to the type of curing technique were determined: 10 samples were made by a conCnuous curing technique, 10 samples were made with a soT start curing technique, 10 samples were made by an intermi^ent curing technique. Each of 90 resin discs were evaluated with the degree of conversion test by Fou- rier transform infrared spectroscopy (FTIR) aTer 24 hours. Results: GC LiSi Press had a higher polymerizaCon rate than Ivoclar IPS e.max. The intermi^ent curing technique sub-group had the highest polymerizaCon rate compared to the other techniques independent of the emax type. Significant differences between each type of emax and curing procedure type were found using a one-way ANOVA test (p<0.05). Conclusion: GC LiSi Press allowed for more light curing in comparison to Ivoclar IPS e.max, and the intermi^ent curing technique increased polymerizaCon rate of dual cure resin ce- ment. The degree of conversion for dual cure resin cement was directly influ- enced by the type of emax veneer and the curing method. Open Access Cita%on: Altaie AA, et al. (2025) Effect of Curing Tech- nique and Emax Type on the Polymeriza%on of Dual Cure Resin Cement. Den%stry 3000. 1:a001 doi:10.5195/d3000.2025.939 Received: May 7, 2025 Accepted: June 26, 2025 Published: August 6, 2025 Copyright: ©2025 Altaie AA, et al. This is an open access ar%cle licensed under a Crea%ve Commons ATribu%on Work 4.0 United States License. Email: amani.abduljabar@uomosul.edu.iq Introduc)on In recent years, the -ield of dentistry has used an increasing number of cosmetic ma- terials; this could be because of the need to satisfy patient needs and new fabrication de- velopments methods [1]. All-ceramic restorations (those lacking a metal substrate) can be used in the aesthetic area because of their increased translucency [2,3]. Lithium disilicate glass ceramics are the most widely used ceramic system be- cause of its good strength (350–450 MPa), ideal adhesion to tooth structures, easy pro- duction and superior aesthetic qualities [4]. To improve the appearance of an anterior tooth, the laminate is a conservative substi- tute for full covering. One of the most com- mon restorations in aesthetic dentistry dur- ing the past few decades is laminate veneers [5]. The current method of restoration fabricating technologies ensures tooth-col- ored restorations is computer-aided design and computer-aided manufacturing (CAD/CAM) system [6] which is simple, time ef-icient and quick using resin and ceramic materials in a timely way [7,8]. For many years, resin luting cements have been utilized in dental restorations such as crowns, bridges, inlays, and onlays. Glass -ill- ers and polymerizable methacrylates are the main component of resin cement, and they can be cured by light-curing, self-curing, or both methods [9]. For indirect restorations, the methacrylate-based resin material must chemically bond to the surfaces, which is of- ten accomplished in two or three steps. Mi- cromechanical retention for ceramic resto- rations incorporating silica is achieved by etching the surface with hydro-luoric acid (HF) and then priming it to become hydrophobic and resin friendly. Additional hydroxyl groups on the ceramic substrates are chemically activated by etching [10]. Dual-cure materials, which combine the ad- vantages of light-curing with chemical polymerization, have gained a lot of popular- ity [11]. However, it was stated that expo- sure to light is required for the resin cements to achieve the highest possible degree of con- version rate [12]. This is signi-icant as the lack of polymerization for the self-curing form of also produces reduced mechanical characteristics and increased solubility of resin cements with two curing times [13]. Hardness testing is frequently employed as a straightforward and trustworthy technique to assess appropriate resin cement polymer- ization [14,15]. Effect of Curing Technique and Emax Type on the PolymerizaCon of Dual Cure Resin Cement Vol 13, No 1 (2025) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu 2 Degree of conversion (DOC) is the percent- age of C=C double bonds that are changed into C-C single bonds or the amount that monomers react to produce polymers [16]. Several studies in the literature seem to sup- port the idea that different curing techniques improve the polymerization of direct resin materials [17]. These techniques are based on the knowledge that a slower conversion rate improves material -low, which lowers the resin's shrinkage stress and so helps avoid gap development [18]. The longevity of resin-bonded ceramic resto- rations is largely dependent on adequate polymerization. Color change may result from incomplete resin cement polymeriza- tion, postoperative sensitivity, toxicity from leftover monomer, and reduced bond strength, which raises the risk of cavities and microleakage [19]. To the best of our knowledge, no research has assessed how the Emax type and curing technique affect the degree of conversion of dual-cured resin cement. This study aimed to assess how the degree of conversion of dual- cure resin cement is affected by Emax type and curing technique. Material and Methods We used a dual cure resin cement (FGM, Join- ville, Brazil and A2 shade) and two types of lithium disilicate (Ivoclar IPS e.max Press in- gots and GC Initial Lisi Press shade A2) (Ta- ble 1). The thickness of discs that were fabri- cated was 1.2mm. Since color shade and thickness have direct effect on the light transmission, for this study we kept the color shade and thickness of Emax constant. Fig- ure 1 summarizes the design of the study. Each group was subdivided into three sub- groups according to the type of curing tech- nique: continuous mode with 700mW/cm² intensity, soft start mode with 150Mw/cm2 followed by 700Mw/cm2 intensity and inter- mittent curing technique with 700Mw/cm2 [22]. A total of 90 dual resin cement samples were put within an elastomeric mold that was 1 mm thick. Each sample's upper surface was covered with individual mylar strips to sep- arate them from the Emax disk [18]. After that an Emax disc sample was put on top of the resin cement and loaded with 200 g for 60 seconds, an LED-curing light was then used to cure the resin cement in three curing techniques at zero distance from Emax discs [19]. All samples of resin cement disc were stored in a dry and black container for 24 hours at room temperature before polymerization. Following a 24-hour storage period, an ATR- FTIR spectroscopy equipment was used to evaluate the degree of conversion (DOC). Each specimen of resin cement was placed on the surface of the zinc selenide pellet (Specac) of ATR-FTIR to obtain the absorp- tion spectra of the non-polymerized (C=C) and polymerized (C-C) forms of the speci- mens. 64 pictures at a resolution of 4 cm were obtained from the 1500–1800 cm re- gion. This region contains the reference peak of the aromatic component (discovered at 1608 cm) and the strength of the aliphatic carbon double-bond (C=C) absorption peak [23,24]. Both peaks are present in materials having aromatic vinyl bonds of bisphenol and aliphatic bonds of the methacrylate functional group. The following formulas were then used to calculate the DOC of each distinct resin cement specimen [25,26]: DOC (%) = 100 [1 – (R polymerized/R non- polymerized)] R = the ratio of the absorbance peaks at 1608 cm and 1638 cm Results The highest mean value of (DOC) was ob- served among controls. Mean value of GC emax was higher than Ivoclar’s. The inter- mittent technique of curing had the highest mean value of DOC compared to the rest. To determine whether there were signi-icant differences between the subgroups within each group, the analysis of variance (one way ANOVA) was performed. Figure 2 shows the three scenarios had the same patterns of re- sponse with differences in the absolute value (p<0.005). Figures 3, 4, and 5 show the chart of entire FTIR/ATR spectra for zero cure (unset) dual cure resin cement material for controls, Ivo- clair and GC. Discussion This study assessed how various porcelain veneer types (Ivoclar and GC emax veneer) and different curing techniques (continuous, soft start and intermittent) affected the polymerization DOC of dual cure resin ce- ment. The null hypothesis of this research was rejected because different types of emax veneer showed direct effect on DOC. The highest mean value of DOC was obtained in the controls. Ivoclar emax disk had lower DOC than GC emax disk likely because of the difference in composition of the two materi- als. IPS e.max Press (Ivoclar, Vivadent) cre- ates pressable ingots of lithium disilicate glass ceramic, a synthetic glass-based porce- lain. IPS, the microstructure of e.max Press is composed of approximately 70% glass-ma- triculated lithium disilicate (Li2 Si2 O5) crystals, which range in length from 3 to 6 µm [27]. While initial LiSi Press (GC emax) consist of lithium disilicate micro-crystals equally dispersed in a glass matrix [18], so microcrystalline containing material showed lower scattering of light and more light transmission through it [28]. In each group we found that intermittent curing technique had the highest mean value of polymerization. This method uses a dark gap between each exposure. The polymeri- zation reaction proceeds slowly at this phase. Three to -ive minutes of delay results in the largest reduction in shrinkage [29]. Additionally, the polymerization process may allow for stress release because to the lengthy curing process that allows resin ce- ment to -low [30,31]. Many authors attribute these results to elon- gation of pre-gel stage that would permit the material to -low to get the volumetric reduc- tion [32,33]. Other writers contended that chain relaxation, rather than viscous -low, would be a more acceptable explanation for the observed stress alleviation [34,35]. From the results of this research we ob- served that soft start curing technique had the lowest mean value of DOC. Soft-start polymerization uses a low irradiance at -irst, then a high irradiance cure toward the end. Better material -low is made possible by a slower rate of conversion. Before curing, the material retains its -lexibility for a long time, which also reduces contraction stresses and improves marginal adaption [19,36]. Starting the light-activation process with a low light intensity allowed for a low degree of convergence and prolonged maintenance of a higher level of molecular mobility inside the polymer matrix. Goracci et al. [37] intro- duced the "slow and gradual polymeriza- tion" in 1992 for that reason. This technique entails polymerizing the initial composite layer with progressively increasing light in- tensity over the course of four minutes to ex- tend the phase of the early setting of the composite. This allows polymerization shrinkage to occur while the molecules still can change their direction to compensate for the internal stress, reducing the contraction stress that develops during the -inal setting and making it resistant to the bonding's ad- hesive forces [37]. A light source with a consistent intensity is applied to the resin cement for an estab- lished period in continuous curing [38], mean value of DOC of this type of curing tech- nique was more than soft start and less than intermittent curing technique in the result of this study. Effect of Curing Technique and Emax Type on the PolymerizaCon of Dual Cure Resin Cement Vol 13, No 1 (2025) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu 3 Conclusions - Composition of emax veneer had direct ef- fect on the polymerization of resin cement, Initial LiSi Press GC with microcrystalline structure transported more light from light cure unit to resin cement in comparison to the IPS e.max Press Ivoclar Vivadent. - Curing technique had direct effect on polymerization of resin cement, intermit- tent curing technique displayed more de- gree of conversion for resin cement than continuous and soft start curing technique. - Effect of Continuous curing technique was increase in (DOC) of resin cement more than soft start curing technique. References [1] In7luence of different surface pretreatments on shear bond strength of an adhesive resin cement to various zirconia ceramics. Colombo M, Gallo S, Padovan S, Chiesa M, Poggio C, Scribante A. Mate- rials. 2020;13(3):652. 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[32] Shrinkage Stress and Microhardness of Com- posites Photoactivated by Intermittent-delay Cur- ing. Pfeifer C., Braga R. & Ferracane J: Operative Dentistry, 2006, 31-5, 610-615. [33] Reduction of polymerization contraction stress for dental composites by two-step light-ac- tivation. Lim BS, Ferracane JL, Sakaguchi RL & Condon JR (2002) Dental Materials, 18(6):436- 444. [34] Towards the elucidation of shrinkage stress development and relaxation in dental composites. Lu H, Stansbury JW & Bowman CN (2004) Dental Materials 20(10) 979-986. [35] Effect of stepped light intensity on polymeri- zation force and conversion in a photoactivated composite. Bouschlicher MR, Rueggeberg FA & Boyer DB (2000) Journal of Esthetic Dentistry 12(1) 23-32. [36] In7luence of light intensity on polymerization shrinkage and integrity of restoration cavity inter- face. Feilzer AJ, Dooren LH, de Gee AJ, Davidson CL. Eur J Oral Sci 1995;103:322326. [37] Curing light intensity and marginal leakage of resin composite restorations. Oracci G, Mori G, Martinis LC. Quint Int 1996;27: 355-362. [38] Effect of different modes of light curing and resin composites on microleakage of Class II resto- rations - Part II. S.T. - Hardan L.S., Amm E.W., Gha- yad A., Ghosn C. and Khraisat A. T.D.J. 2009, 32: 12- 29. Effect of Curing Technique and Emax Type on the PolymerizaCon of Dual Cure Resin Cement Vol 13, No 1 (2025) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu 4 Figure 1. Study design schematics. Table 1. Materials used in this study. Materials Composition Manufacture Color Allcem dual resin cement Bis-EMA/BisGMA/TEGDMA, -Silicate glass -Barium aluminum -Silicon dioxide 62% weight [20] FGM, Brazil A2 Initial LiSi Press Equivalently distributed lithium disilicate microcrystals in a glass matrix dispersed in a glass matrix [21]. GC A2 IPS e.max Press About 70% of Li2Si2O5 and lithium disili- cate crystals are immersed in a glassy ma- trix [21]. Ivoclar Vivadent A2 no Emax disc cover resin cement (n=30) • Continous curing mode technique (n=10) • Soft start curing technique (n=10) • Intermittent curing technique (n=10) Ivoclar Emax disc cover resin cement (n=30) • Continous curing mode technique (n=10) • Soft start curing technique (n=10) • Intermittent curing technique (n=10) GC Emax cover resin cement (n=30) • Continous curing mode technique (n=10) • Soft start curing technique (n=10) • Intermittent curing technique (n=10) 90 resin cement samples For a whole day, all resin cement discs were kept at room temperature in a dry, black container For every resin cement disc, the degree of conversion was assessed using FTIR Effect of Curing Technique and Emax Type on the PolymerizaCon of Dual Cure Resin Cement Vol 13, No 1 (2025) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu 5 Figure 2. Mean values of DOC for all groups and subgroups. Ivoclar (to the left), GC (in the middle), and controls (to the right). Blue is continuous polymerization, red is soft start, and green and intermittent. : Figure 3. Diagram of full spectra of unset (zero cure) resin cement. 0 10 20 30 40 50 11.5 24 32.5 6.25 14.25 21.75 25.5 33.75 44.25 A1 A2 A3 Effect of Curing Technique and Emax Type on the PolymerizaCon of Dual Cure Resin Cement Vol 13, No 1 (2025) DOI 10.5195/d3000/2025.939 http://dentistry3000.pitt.edu 6 Figure 4. Diagram of full spectra of polymerized controls. Figure 5. Diagram of full spectra of polymerized GC emax.