# Universal Dental Adhesives: Cost-Effectiveness and Duration of Use
## 1 Introduction  
Dentistry is an expensive profession, and the expense of dental care is relatively high. Some of the expense related to dental care is the amount of waste that is produced as secondary outcome for providing treatment. This is the norm for multiple procedures including impression taking, direct restoration, and liner/base application. Decreasing waste and increasing the efficiency and/or efficacy of the procedure and utilized materials are paramount in maintaining a profitable career. Calculating the cost of this waste relative to the application benefit of the procedure is the basic principle of cost-effectiveness determination [1, 2]. In the dental literature, there are multiple reports investigating the cost-effectiveness of restorative procedures. [PERSON] et al. [3] have investigated the cost-effectiveness of fissure sealants application compared to fluoride varnish. Another study reported the cost-effectiveness of the repair of composite restorations in relation to total replacement [4].  
The use of direct resin composite restorations is increasing due to the higher demand by patients for conservative esthetic solutions [5, 6]. In addition, the shift to metal-free dental practices with phasing out of dental amalgam is leading to more focus on adhesive dentistry [7, 8]. The technique sensitivity of older generation of dental adhesive led the manufacturers to develop new materials with simple use. Universal dental adhesives available in the market in 2011 are multipurpose bonding agents that can be applied either in etch-and-reins or in self-etch mode [9, 10]. The composition of this type of adhesive plays an important role since it contains a functional monomer that ionically bonds tocalcium in hydroxyapatite. One of the most used monomers is 10-methacryloyloxydecyl dihydrogen phosphate (MDP). It has mild etching properties, which enables the adhesive to be used with any etching technique. When the MDP monomer bonds to calcium, it forms a nonsoluble MDP-calcium salt, creating a strong and stable adhesion. The versatility of this type of adhesive allows the clinician to choose the most appropriate adhesion protocol for each type of procedure [10, 11]. Furthermore, the presence of marginal gaps at the tooth structure-restoration interface resulting from polymerization shrinkage can have a deleterious effect on the longevity of the restoration [12]. The utilization of an efficient and predictable bonding technique can reduce the chance of marginal gap formation around resin composite restorations.  
Although the conventional procedure for direct resin composite restoration placement is straight forward, it involves multiple steps and potential risk for waste. Among these, waste generated by unutilized adhesives can add up and progressively becomes a source of forfeiture that would be challenging to manage. Choosing a dental adhesive that can be used in an efficient manner is required in order to decrease this risk of accumulated loss. Some manufacturers have employed strategies that are aimed to decrease the resulting waste of the direct adhesive technique. The VivaPen device introduced with Tetric-N Bond Universal utilizes a replaceable micro applicator that can be used to directly apply the adhesive into the cavity, eliminating the need for a dosing plate and the accompanying waste. In addition, modifications of the geometry of the novel adhesive bottle introduced with G-Premio Bond, can restrict unnecessary and accidental dispensing of the dental adhesive.  
To the authors' knowledge, there are no studies in the literature that investigated the waste and efficacy/efficiency of dental adhesives used for direct restorative applications. Thus, the aim of this study was to conduct a cost-effectiveness analysis (CEA) for four different universal dental adhesives. The null hypothesis was that there will be no difference between the different brands of adhesives in relation to each CEA parameter.