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This retrospective study evaluated the performance of posterior composites after up to 33 years of clinical service and investigated factors associated with the risk of failures over time including patient- and tooth-related variables.Patients who received at least one Class I or Class II direct composite restoration in a private office in 1986-1992 and had follow-up appointments were included. Failures and interventions over time were investigated using the dental records. A follow-up clinical recall was carried out in 2020. Two scenarios were considered: restorations that did not require any intervention (success) or restorations that were repaired and still functional (survival). Multivariate Cox regression analyses and Kaplan-Meier curves were performed using success and survival rates (p 0.05).One hundred patient records and 683 restorations were included. A total of 353 failures were reported (success rate= 48%). Main reasons for failure were fracture and secondary caries. Most interventions after failures were repairs. Replacements were registered in 183 cases (survival rate= 73%). Annual failure rates were below 2.5% (success) and 1.1% (survival). Larger restorations and maxillary molars had higher failure risks. No significant differences in success rates among different resin composites was observed. A typical observation in this sample of restorations was the presence of moderate to advanced signs of aging, including marginal and surface staining, wear, chipping, changes in anatomical shape and translucency. Clearly aged restorations were still clinically satisfactory.This long-term, practice-based study indicates that resin composites can be used to restore posterior teeth with a long-lasting durability.

Objective To present through a systematic review a qualitative analysis of studies published on stereolithography-based 3D printing of restorative materials and their clinical applicability. Methods The literature search was conducted based on the question: “What is the state-of-the-art of available restorative materials for 3D printing based on stereolithography?" Online search was conducted in three databases (MEDLINE/PubMed, Scopus and Web of Science) with no restriction for year of publication. Data are reported based on PRISMA, including publication details such as authors and their countries, year and journal of publication, and study design. The synthesis is focused on describing the dental restorative materials and properties evaluated, applied methods, 3D printers used and clinical applicability. Results Studies that fit the inclusion criteria were performed in Asia (21), Europe (16) and USA (10), mostly using polymer-based restorative materials (38) for 3D printing constructs. Stereolithographic-printed ceramic-based restorative structures were evaluated by 9 studies. Many studies reported on dimensional accuracy (14), strength (11) and surface morphology (9) of the printed structures. Antibacterial response, cytotoxicity, internal and marginal fit, fracture and wear resistance, density, viscosity, elastic modulus, hardness, structural shrinkage and reliability, degree of conversion, layer cure depth, fatigue, and color were also evaluated by the included studies. Many of them (11) published a proof of concept as an attempt to demonstrate the clinical feasibility and applicability of the technology to print restorative materials, but only 5 studies actually applied the 3D printed restorative structures in patients, which highlights an increasing interest but limited early-stage translation. Significance The fast expansion of stereolithographic-based 3D printing has been impressive and represents a great technological progress with significant disruptive potential. Dentistry has demonstrated an incredible willingness to adapt materials, methods and workflows to this promising digital technology. However, esthetic appearance, wear resistance, wet strength and dimensional accuracy are the main current clinical limitations restricting the progression to functional part production with 3D printing, which may explain the absence of clinical trials and reports on permanent/definitive dental restorative materials and structures.

Clinical research of restorative materials is confounded by problems of study designs, length of trials, type of information collected, and costs for trials, despite increasing numbers and considerable development of trials during the past 50 years. This opinion paper aims to discuss advantages and disadvantages of different study designs and outcomes for evaluating survival of dental restorations and to make recommendations for future study designs. Advantages and disadvantages of randomized trials, prospective and retrospective longitudinal studies, practice-based, pragmatic and cohort studies are addressed and discussed. The recommendations of the paper are that clinical trials should have rational control groups, include confounders such as patient risk factors in the data and analysis and should use outcome parameters relevant for profession and patients.