Dental Hypotheses

: 2022  |  Volume : 13  |  Issue : 1  |  Page : 16--19

Influence of Monowave and Polywave LED Unites on G-Aenial Resin Composites’ Polymerization: An In Vitro Study

Azadeh Ghaemi1, Milad Molayi2, Rayan Chaharmahali3,  
1 Department of Operative and Esthetic Dentistry, Faculty of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2 Department of Prosthodontics, Dental School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3 Department of Orthodontics, Dental School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Correspondence Address:
Rayan Chaharmahali
Department of Orthodontics, Dental School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz


Objectives: Trimethylbenzoyldiphenylphosphine oxide and phenylpropanedione photoinitiator components in resin composites have been used widely due to their white color. However, it seems that there are some limitations in the required polymerization initiator wavelength. This study aimed to evaluate the polywave and monowave light-activating devices (LEDs) on polymerization and shrinkage strain of two dental composites with different photoinitiator systems. Methods: In this experimental study, 24 samples were prepared in two groups, including G-Aenial A2 and bleach composites. Each group was divided into two subgroups: one cured by monowave LED unit and the other by polywave device. Then shrinkage strain of samples was evaluated using bonded disk technique. Results: Results showed the shrinkage strain of A2 and bleach composites using PW device was significantly greater than MW device. In addition, the A2 composite shrinkage action polymerized with MW device was significantly lower than shrinkage action of A2 and bleach composite using PW machine. Conclusion: The findings of this study revealed that polywave LEDs were more beneficial for the polymerization of resin composites.

How to cite this article:
Ghaemi A, Molayi M, Chaharmahali R. Influence of Monowave and Polywave LED Unites on G-Aenial Resin Composites’ Polymerization: An In Vitro Study.Dent Hypotheses 2022;13:16-19

How to cite this URL:
Ghaemi A, Molayi M, Chaharmahali R. Influence of Monowave and Polywave LED Unites on G-Aenial Resin Composites’ Polymerization: An In Vitro Study. Dent Hypotheses [serial online] 2022 [cited 2022 May 20 ];13:16-19
Available from:

Full Text


Composites are tooth-colored restorative materials increasingly used in modern dentistry.[1] Due to their advantages, including beauty, less and more conservative cutting of teeth, desirable physical, chemical properties, and increasing the structural strength of teeth, in some countries, they have been wholly replaced with restorations such as amalgam, which have drawbacks such as corrosion and toxic components.[1]

Most of these composites contain optical photoinitiators to initiate the polymerization reaction, which need optically activating devices in a specific wavelength.[2],[3] Camphorquinone (CQ) is the most widely used optical photoinitiator in dental resin composition.[4],[5] This substance is a yellow solid, and its high percentage in containing composites causes restorations’ yellow color, affecting their absolute beauty.[2],[6]

To address this problem and due to patients’ increasing desire for whiter and more beautiful color restorations, a new group of composites has been introduced with a lower percentage of CQ or other optical initiators instead.[1],[5],[7]

Trimethylbenzoyldiphenylphosphine oxide (TPO) and phenylpropanedione (PPD) are initiators used in bleach composites because of their white color.[8] The absorption spectrum of these materials is in the range of 380 to 410 nm.[8]

Furthermore, the most common light-activating devices in dental offices emit a narrowwave spectrum in the range of 420 to 490 nm, which is efficient for CQ composites with an absorption spectrum in the visible light range.[6] Nevertheless, it is inappropriate for composites containing TPO and PPD.[8] Because in these wavelengths, polymerization of all monomer particles of bleach composites was not completed, resulting in weaker physical properties, coronary microleakage, and the entry of toxic unreacted monomers into the oral environment.[5],[7],[9] Moreover, they become even more discolored than the usual composites after a while due to more colorability.[8]

A group of light-activating devices (LED) have recently been presented that emit a broader spectrum of light and have several wavelengths (polywave)[10],[11] because the absorption spectrum range can also produce bleach composites and seem suitable for curing and more complete polymerization.[11],[12]

Hence, this study aimed to measure the degree of polymerization of monomers of ordinary and bleach composites using two different optical devices.

 Material and Methods

Study design and sample preparation

This in vitro experimental study was conducted on two main groups of A2 and bleach composites (G-Aenial resin composites, GC India dental company, India). Then each group was divided into two subgroups of six samples and cured with the two light sources, including PW (Valo; Ultradent, South Jordan, UT, USA) and MW devices (Smart Lite, Dentsply, Germany) for 20 seconds. In this study, the groups were divided completely randomly. The study was based on the approval of the Medical Ethics Committee (Reference Number: IR.AJUMS.REC.1395.20). In this study, bonded disk technique was applied to measure the shrinkage strain of polymerization. The Bioman device (Manchester, UK) was used to obtain the polymerization rate.

The samples were placed in 1 × 8 mm discs on a glass slide which a 1-mm high brass ring was installed to control the sample thicknesses. To prevent the effect of surface oxidation, we placed glass talc on each sample.

The samples were placed in the machine, the fixed light source was lit under the glass plate, and the linear variable differential transformer (LVDT) converter tip was contacted to the talc on the composite disk. Data were recorded for 10 minutes (20 seconds exposure time and 580 seconds postcuring time) continuously through a data receiving system connected to a computer.

Statistical analysis

The descriptive statistical analysis described the variables, including frequency distribution tables, charts, and central indicators. The data normality distribution was checked by the Kolmogorov–Smirnov test. Then, using one-way analysis of variance and the Tukey samples, the values of the DC resulting from the contractile action were compared between the four groups. The significance level was considered less than 0.05. Data analysis was performed using SPSS (v.22) software.


The results of the present study revealed that the contractile action of G-Aenial composite bleach when polymerized with PW machine was significantly greater in comparison with MW device (P < 0.001) [Table 2]. On the other hand, the contractile action of bleach composite using MW device was significantly lower than all studied groups, indicating the presence of fewer double bonds in the reaction (P < 0.01) [Table 1].{Table 1}{Table 2}

In addition, the shrinkage action of the A2 composite that was polymerized with MW device was significantly lower than the shrinkage action of the A2 and bleach composite using PW machine (P < 0.001) [Table 2]. The mean and standard deviation of shrinkage strain in different groups are given in [Table 1]. The shrinkage strain of A2 and bleach composites using PW devices has not a significant difference [Table 2].

In addition, the shrinkage strain diagram was plotted for 10 minutes to obtain the postcure rate of the composites in the darkroom [Figure 1].{Figure 1}


In the present study, we assessed the DC in ordinary and bleach composites using two optical devices. Both optical devices applied in this study were LEDs with 3600 mw/cm radiation intensity. As the radiation intensity of both devices was the same in 20 seconds, the amount of irradiated energy to composites and its effect on activating the free radical polymerization reaction was equal.

The two composites used in this experiment belonged to the GC corporation with unspecified composition in terms of resin monomers, which may affect the amount and speed of polymerization. They differ in their color that indicates the difference in the type and amount of their light initiator. A2 color is one of the natural teeth colors, and bleach (BW) color is the white color used for bleached teeth or beauty applications. The optical device for polymerization of composites was another variable in this study. The percentage of double bonds and the amount of polymerization were inferred from the shrinkage strain. Shrinkage polymerization is spatial (μm) and depends on various factors such as monomer size or molecular weight, curing time, and type of light cure.[10] Hence, shrinkage strain was measured, and the final value up to 10 minutes after curing was considered a measure of polymerization.

The results of the present study showed a significant increase in the contractile action of BW composite when using PW compared to MW devices. In addition, the contractile action of A2 composite with PW device increased slightly compared to MW device. In the technology of making BW color composites, the percentage of CQ is reduced, and a white photoinitiator is added to obtain a white color.[13] These white primers, either TPO or PPD, react at a radiation wavelength of 380 to 410 nm[14] and provide free radicals to the monomers, which is not found in our MW device and can be justified with less shrinkage strain of BW color. On the other hand, the white color of the A2 composite may be due to having some optical primers in addition to CQ. The presence of this optical initiator results in more participating dual bands when using PW device and causes the increase of contractile action of A2 composite in the application of PW device compared to MW.

In line with our findings, Ramos Salles de Oliveira et al.[6] conducted an experimental study on laboratory composites and illustrated that the highest degree of polymerization for a TPO-containing composite is achieved when using a PW device. Similarly, Santini et al.[16] showed that DC in TPO-containing composites elevated significantly using PW machine compared to MW.

By contrast, some reports claimed no result variations in using different optical devices. For instance, Celerino et al.[17] studied TPO- and CQ-containing composites using LED and halogen optical devices and declared that different devices’ curing rate is the same. Such contradictions may be due to different composites, the percentage of their components, and the different devices.

In this regard, Atai et al.[15] evaluated different composites to obtain the amount of polymerization shrinkage and the degree of conversion (DC) using the bonded disk technique and the fourier transform infrared spectroscopy (FTIR) method, respectively. They concluded that there is a direct correlation between the polymerization shrinkage and DC of the composites, so both methods can be used to determine the degree of polymerization.

Meanwhile, the standard ratio of the contractile action to the complete shrinkage and the specific DC has not been stated in the available studies, so it cannot be stated certainly that the G-Aenail BW composite has acceptable clinical properties at this rate of polymerization. However, it seems that most of the monowave optical devices currently used in clinics do not react to the dual bands to the optimum of the manufacturer. Further studies on the color fastness, physical and mechanical properties of these composites should be performed to generalize conclusions for clinical applications.

Moreover, it should be noted that although the results of the present study and other similar researches approved that the PW devices are beneficial to resin composites polymerization, most are in vitro and experimental studies. Hence, to establish any procedures in the human oral environment, more researches are demanded.


The present study’s findings with the limitation of being an in vitro study showed that the degree of polymerization of A2 and G-Aenial bleach composites using the LED polywave device was significantly higher than the monowave device. Hence, polywave optical devices may be more appropriate machines for better clinical performance of resin composites. More clinical studies on the efficacy of different optically activating devices can help the better performance of available composites.

Authors’ contributions

RCh conceived the manuscript and revised it. AGh and MM performed the statistical analysis, wrote the manuscript, and prepared tables and figures.


The authors thank all the colleagues in the Faculty of Dentistry of Ahvaz Jondishapur University of Medical Sciences.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Aminoroaya A, Neisiany RE, Khorasani SN, et al. A review of dental composites: challenges, chemistry aspects, filler influences, and future insights. Compos Part B Eng 2021;216:108852.
2Segreto DR, Naufel FS, Brandt WC, Guiraldo RD, Correr-Sobrinho L, Sinhoreti MAC. Influence of photoinitiator and light-curing source on bond strength of experimental resin cements to dentin. Braz Dent J 2016;27:83-9.
3Brandt WC, Schneider LFJ, Frollini E, Correr-Sobrinho L, Sinhoreti MAC. Effect of different photoinitiators and light curing units on degree of conversion of composites. Braz Oral Res 2010;24:263-70.
4Kowalska A, Sokolowski J, Bociong K. The photoinitiators used in resin based dental composite—a review and future perspectives. Polymers 2021;13.
5Hotta M, Murase Y, Shimizu S, Kusakabe S, Takagaki T, Nikaido T. Color changes in bulk-fill resin composites as a result of visible light-curing. Dent Mater J 2021;advpub.
6Ramos Salles de Oliveira DC, Garcia Rocha M, Gatti A, Bortolazzo Correr A, Liborio Ferracane J, Sinhoreti MAC. Effect of different photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths. J Dent 2015;43:1565-72.
7Carvalho Andrade K, Pavesi Pini NI, Dias Moda M, de Souza e Silva Ramos F, Dos Santos PH, Fraga Briso AL. Influence of different light-curing units in surface roughness and gloss of resin composites for bleached teeth after challenges. J Mech Behav Biomed Mater 2020;102:103458.
8Radzi Z, Diab RA, Yahya NA, Gonzalez MAG. Resin-Based Composites in Dentistry—A Review. Compos Biomed Appl. 2020;71-98.
9Jeong TS, Kang HS, Kim SK, Kim S, Kim HI, Kwon YH. The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins. Dent Mater J 2009;28:438-45.
10Teimourian H, Farahmandpour N, Moghadam MZ, Pouyanfar H, Panahandeh N. Effect of light intensity and curing time on color stability of a methacrylate-based composite resin using an LED light-curing unit. Hamadan Univ Med Sci 2019;11:83-8.
11Derchi G, Vano M, Ceseracciu L, Diaspro A, Salerno M. Stiffness effect of using polywave or monowave LED units for photo-curing different bulk fill composites. Dent Mater J 2018;advpub.
12Contreras SCM, Jurema ALB, Claudino ES, Bresciani E, Caneppele TMF. Monowave and polywave light-curing of bulk-fill resin composites: degree of conversion and marginal adaptation following thermomechanical aging. Biomater Investig Dent 2021;8:72-8.
13Neumann MG, Schmitt CC, Ferreira GC, Corre IC. The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units. Dent Mater 2006;22:576-84.
14Aung SZ, Takagaki T, Ikeda M, et al. The effect of different light curing units on Vickers microhardness and degree of conversion of flowable resin composites. Dent Mater J. 2021;40:44-51.
15Atai M, Watts DC, Atai Z. Shrinkage strain-rates of dental resin-monomer and composite systems. Biomaterials 2005;26:5015-20.
16Santini A, Miletic V, Swift MD, Bradley M. Degree of conversion and microhardness of TPO-containing resin-based composites cured by polywave and monowave LED units. J Dent 2012;40:577-84.
17Celerino De Moraes Porto IC, Silva Soares LE, Abrahão Martin A, Cavalli V, Suzy Liporoni PC. Influence of the photoinitiator system and light photoactivation units on the degree of conversion of dental composites. Braz Oral Res 2010;24:475-81.