# Universal Dental Adhesives: Cost-Effectiveness and Duration of Use
## 4 Discussion  
The application of direct composite restorations is among the most commonly performed dental procedures. More than 5000 composite restorations are placed annually in a governmental dental school [17, 18, 19]. Waste during the application of the bonding technique can add up over time and contribute to the total expense of the operative procedure. Choosing a dental adhesive with less waste and more efficiency can maximize the benefit of the direct operative treatment. Thus, the aim of this study was to conduct a CEA analysis for commonly used universal dental adhesives for direct composite restorations. This would allow decision makers in governmental dental clinics and clinicians in private practices to decide on what type of adhesive to use to fit their budget and yet provide optimal effectiveness with minimal cost. However, we do not intend to provide recommendations on the actual clinical performance of the dental adhesives tested in this study since this was not the main focus of the current investigation. Readers should refer to other reports in the literature delineating actual performance of dental adhesives. The cost of adhesive should not be the sole factor for making a clinical decision. Other factors including ease of use, intended application, and the established clinical survival data should be considered. The study also outlines a method used for CEA that can be adopted and modified by researchers for future studies. The CEA was done by testing six parameters: amount of material utilized and waste per day, efficacy, efficiency, ACER, and ICER. In order to compare the performance of each dental adhesive during daily practice and use, three relative parameters (price per mL, application per mL, and price per application) were utilized. We did not depend on the absolute milliliter figure of the bottle since the capacity of each dental adhesive bottle was different. Instead, the price per milliliter was used for all CEA comparisons. The null hypothesis was rejected in part as there was significant difference in all of the CEA parameters except the ICER. Dental restorative procedures can produce a significant amount of material waste. One drop of adhesive for example can generate a lot of waste since there is always material left in the dosing plate and the applicator. Hence, with more applications, the cumulative waste associated with the adhesive bottle increases. The cumulative total waste generated from each adhesive tested in this study is illustrated in Figure 2. The cumulative waste of the OB adhesive was less than 50% of the bottle capacity (5 mL) and half of that associated with the SB adhesive. However, the SB adhesive provided nearly twice the number of applications as the OB adhesive did. Despite the fact that the SB adhesive provided the most applications (192), the cumulative waste associated with the additional number of applications almost reached 67.4% of the bottle capacity (5 mL). In comparison to other adhesives, the GP adhesive reported relatively low cumulative waste, with 34.6% of the bottle capacity (5 mL). The TN adhesive demonstrated nearly 57% cumulative waste of the VivaPen capacity (2 mL), translating into better overall efficiency. Some manufacturers have hinted towards specific engineering choices in their products, such as the VivaPen delivery system used in TN. In this delivery system, the adhesive is packed in a pen-like device with a disposable brush cannula that allows for a direct application onto the tooth. According to the manufacturer, this delivery system can provide three times more applications per milliliter compared to conventional bottles with minimal waste optimizing efficiency. Another example of waste-reducing strategy is reported with GP adhesive, the manufacturer fitted the bottle with a silicone cover and a thin nozzle to enable more precise drop dispensing as commercially promoted.