Pooja Arora1, Vipin Arora2*, Ammar Al Shammrani3 and Mohammed Khalil Fahmi4
1Associate Professor (Prosthodontics), Department of Restorative Dental Sciences, Faculty of Dentistry, Taif University, Taif, Kingdom of
2Course director (Endodontics), Department of Restorative Dental Sciences, Faculty of Dentistry, Taif University, Taif, Kingdom of Saudi Arabia
3Dean, Faculty of Dentistry, Taif University, Taif, Kingdom of Saudi Arabia
4Chairman and Head, Department of Restorative Dental Sciences, Faculty of Dentistry, Taif University, Taif, Kingdom of Saudi Arabia
*Corresponding Author: Vipin Arora, Course director (Endodontics), Department of Restorative Dental Sciences Faculty of Dentistry, Taif University, Taif, Kingdom of Saudi Arabia.
Received: May 18, 2017; Published: July 19, 2017
Citation: Vipin Arora.,et al. “Innovatively Modified Glass Bead Sterilizer for Preheating/Prewarming of Dental Composite Resins”. Acta Scientific Dental Sciences 1.2 (2017).
Prewarming/Preheating of dental composites for enhancing the degree of conversion and reducing viscosity thus improving marginal adaptation of the restoration is a well-documented technique to be followed in clinical settings. Heating the composite also dramatically decreases the curing time required for light polymerization.With the added benefit of greater depth of cure of the restorative composite, increased chemical conversion, and ease of flow for easier dispensing into the cavity preparation,pre-heating or sometimes called as pre-warming has become an indispensable technique for better dentistry.
Inspite of all these advantages, the cost and availability of device is a limiting factor in its use which can be overcome by using this simpler device commonly available in all clinics to make this technique popular and economically viable. A New, simple and innovative technique for Preheating/Prewarming of Dental Composite resins is presented.
Keywords: Preheating; Prewarming; Composite; Resin; Dental
Despite developments in dental composite resins, some limitations compromise the longevity of dental composite restorations. The most commonly reported limitations are polymerization shrinkage,mismatch in thermal expansion, abrasion and wear resistance, toxicity, microleakage and recurrent caries [1-5].
To overcome these limitations, research has been directed to improve the mechanical properties of resins, including variations in the amount, size and type of fillers or use of non-methacrylate based monomer resins. Modified clinical procedures have been proposed by some researchers to compensate for the stress generatedfrom polymerization shrinkage and to allow better marginal adaptation between the dental composite and the walls of the cavity. Several placement techniques [6-9] have been suggested to improve the marginal seal of dental composite restorations, such as incremental placement to reduce the C factor,  soft-start and pulsed curing techniques to modify the reaction speed  and use of flowable resins to promote a better marginal adaptation [7,8]. Flowable composites, with the inherent marked fluidity have been advocated as stress absorbers and promote adaptation [7-9,12,13]. However, because of the low filler content greater polymerization - stress is generated in comparison to filled dental composites [14-16].
Researchers have advocated that preheating or prewarmingof traditional dental resin composites can significantly improve marginal adaptation by increasing fluidity [16, 17]. In addition to this, preheating of dental composites may improve their physical and mechanical properties through a higher degree of monomer conversion, [14,18-22] which leads to a greater mechanical strength, rigidity and resistance to degradation in the oral cavity  Conversely, incomplete polymerization can also lead to significantly increased wear due to decreased mechanical strength and unreacted monomer units may be cytotoxic in long run, leading to potential allergic and sensitivity reactions [24-26].
Heating the composite also dramatically decreases the curing time required for light polymerization.With the added benefit of greater depth of cure of the restorative composite, increased chemical conversion, and ease of flow for easier dispensing into the cavity preparation,pre-heating or sometimes called as pre-warming has become an indispensable technique for better dentistry [27- 36].
From the above-mentioned research, it is clear that the Preheating / prewarming has a significant positive effect on the Dental composite resin restorations. But Still the technique for preheating is not very much popular in developing countries and some developed countries. The main reason behind this is the lack of availability of the equipment and the cost of acquiring the equipment.
The commercially available systems available in the market are Calset (AdDent Inc, Danbury, CT, USA) and Thermaflo (vista dental, USA). The cost of such equipment’s varies between 500 - 800 dollars which is at a significantly higher side in developing countries like India where dentistry is developing at a very fast pace. The cost of device can be a limitation in adopting this useful and promising technique.
To make this technique popular and economically viable, this innovation is presented wherein a glass bead sterilizer is utilised to work as a composite warmer.Protocol for Modifications in the Equipment
In this simplified modification, we have used a glass bead sterilizer (Figure 1,2). The glass beads are replaced with common salt. The glass beads retain the heat but when it comes in contact with plastic of syringe, it sticks leading to aggregation of glass beads to the syringe. So, we replaced it with the salt. In (Figure 1) a digital thermometer is placed to show the required temperature settings.
Figure 1: Glass Bead Sterilizer with common salt and digital thermometer placed to verify temperature.
Figure 2: Glass Bead Sterilizer with common salt in which composite instruments are placed along with composite syringe.
The glass bead sterilizer has thermocouple inside in the circuit which can be altered with the help of an electrician as per required temperature settings which can be varied as per the clinician requirement. In the present scenario, we have modified the settings to 65°C.
It takes 10 minutes to pre-heat, and once the unit is warm, it takes 2 - 3 minutes to warm the composite. A standard composite compute, a syringe tray option, or pre-loaded compute guns from different manufacturers can be directly used.
It has been reported that, on an average, dental composites can achieve 50 - 70% conversion of resin monomers . During resin polymerisation, monomeric conversion occurs when exposure to light is initiated. As the polymerization reaction progresses further, the viscosity of the dental resin composite increases with the formation and growth of polymeric chains, which inturnresult in decreased movement of molecules. The enhanced viscosity further prevents completion of polymerisations movement of the molecules in this vitrified stage becomes very limited [14,19]. On the other hand, preheated dental composites display increased monomer mobility, because of higher thermal energy, which leads to less viscosity and increased molecular motion [14,26,29,37]. Also, any delay in progression of diffusion controlled reactions will lead to increased degree of conversion. Such delay results in greater number of collisions, since free radicals are able to diffuse and react before self-deceleration occurs, which in turn enhances the degree of monomeric conversion before final verification [14,19,22,31,33]. Daronch and colleagues  suggested that curing time may be reduced up to 75% with prewarming of dental composites. These authors reported that light-curing of a heateddental composite for 5 seconds led to a greater degree of conversion than light curing at room temperature for 40 seconds. In another study  these authors found that when composites were polymerized at 3°C, the final polymeric conversion was even less than 35%. This decreased monomer conversion at lower temperatures (when composites are kept in the refrigerator) was related to the higher viscosity of the material, which resulted in slower propagation of the reaction.
Inspite of all these advantages, the cost and availability of device is a limiting factor in its use which can be overcome by using this simpler device commonly available in all clinics. The glass bead compartment is filled with salt. The replacement of salt in our device is useful for retaining heat and it’s a normally available thing. Regarding the price, it hardly costs 10 dollars which means 50 times less.
In the literature search, we found only one article by MyoungUkJin  in which the author has advised using heat of the chair light for preheating. He also has described the use of hand for preheating. According to him, holding the syringe in palm of hand for 3 - 5 minutes can raise the temperature. But in our opinion, the temperature raise is not that significant to make a big change and it is unpredictable, time consuming and little bit unpractical. All other published studies describe the use of either calset or thermo flow for preheating.
The above presented device is a modification of commonly available sterilizer in the dental clinic even in the poorer nations.The affordability for this device is quite high and hardly costs 10 dollars depending on country. Nevertheless, the same unit can also be used to heat irrigate syringes and anaesthetic syringes. So, this device is a multifunctional unit which can serve multiple purposes in a dental clinic.
The above presented device is an innovation which is simple to use and has the potential to make pre-heating/Pre-warming technique popular among dentists in all parts of the world especially in the developing countries where cost is a significant factor in acceptance of any new technique in Dentistry.
Copyright: © 2017 Vipin Arora., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.