## 1 Introduction  
The objective of restorative dentistry is to replicate the dental structures both functionally and aesthetically. Adhesive techniques have developed over the years to allow for minimal intervention on the tooth [1, 2]. Most restorative materials can be adhesively cemented, among which resin composite materials have greatly improved over time [3, 4, 5]. Direct anterior and posterior restorations can be placed directly with adhesive systems and resin composites due to their mechanical and optical properties [6, 7], which are increasingly growing similar to the natural tissues [8, 9, 10]. Alternatively, these materials can be used indirectly, with the restoration created out of the mouth on a model, then cured, obtaining a higher degree of conversion, and finally adhesively cemented. In addition to these \"manual\" direct and indirect techniques, digital dentistry has developed in the last few years. The general purpose of the CAD/CAM procedure is to design the restoration with a CAD process over a virtual model and produce the restorations with a CAM process [11]. CAD/CAM resin composite blocks for milling were introduced in early 2000 and are increasingly used [12, 13]. Along with milling, which still represents the state of the art for producing digital restorations, more recently, a growing technology is the possibility of 3D print CAD-designed restorations [14; 15; 16]. Processes like Stereolithography (SLA) and Digital Light Projection (DLP) are becoming progressively familiar to dentists and dental technicians. Both processes use light--laser for SLA and LED for DLP--to polymerize targeted areas with clinically suitable 'precision'. While 3D printing of ceramic in dentistry is still in its infancy, the use of resin is widespread, and recently, resin products for permanent restorations have been developed and marketed. In the 3D printing process, the resin has to flow into the tank, and for this reason, the current possibility of loading the resin with the inorganic filler at a direct/indirect composite level is precluded. It has been reported that the physical characteristics of 3D-printed resins are comparable to flowable composite [17]. To complete the process, after 3D-printing, the restoration, a cleaning procedure to remove the uncured portions of the printed object/restoration and a post-curing process to increase the degree of conversion need to be carried out. When restoration is ready after post-curing, it still lacks some surface characteristics, such as optimal gloss and roughness, and requires a final finishing and polishing (F&P) step to meet the clinical standards. In most cases, the manufacturer indicates nonspecific F&P systems for these materials, and manufacturer guidance often refers to a \"standard procedure for polishing and finishing traditional composite\". Polishability is an important property for dental materials, and surface properties such as roughness and gloss significantly influence the clinical outcome of the restorations [18]. Surfaces not adequately finished and polished are more susceptible to plaque accumulation, wear, increased risk of staining and secondary caries, and may concur in increased gingival inflammation [19; 20], associated with possibly reduced clinical success [21; 22; 23]. Moreover, restorations with smoother surfaces are more comfortable for the patient and more aesthetically pleasing [24; 25]. The aim of this study was to evaluate the surface roughness and gloss of a 3D-printed resin for permanent restorations. Several different procedures were used. Each was representative of the most commonly used systems for in-office and laboratory F&P systems, ranging from clinical systems with silicone points with decreasing granulometry that can be used at the chairside to a similar silicon laboratory used when the restoration is produced by the dental technician, as well as resin-glazing systems including a recently developed procedure that uses a nitrogen curing device.