A cohort of 28 patients aged 18 to 80 years of both females (58%) and males (42%) with 50 composite restorations were recruited at the Operative Dentistry Clinic at the Dental School of the University of Chile. All participants presented with one or more clinical features that deviated from the ideal and were rated Bravo or Charlie according to the modified United States Public Health Service (USPHS) criteria 6. The protocol was approved by the Institutional Research Ethics Committee of the Dental School at the University of Chile (Project PRI-ODO-0207). All of the patients signed informed-consent forms and completed a registration form. The selection criteria are summarized below.

2.2 Treatment Group Criteria Initially, 356 restorations (28 patients) were evaluated and assigned in accordance with the modified USPHS criteria, from which 50 were selected in accordance with the inclusion criteria. Restorations with clinically diagnosed secondary caries (Charlie) or undercontoured anatomical form defects (Bravo) were randomly assigned to the Repair (n = 25) or Replacement (n = 25) group (Figure 1). The randomization was performed by the Power Analysis and Sample Size System (PASS software v. 2008, Keysville, UT, USA), and diagnosis of active secondary caries was made based on Ekstrand criteria.

2.3 Restoration Assessment The quality of the restorations was scored according to the modified USPHS criteria. Two examiners underwent calibration exercises each year (JM and EF). The Cohen's Kappa inter-examiner coefficient was 0.74 at the baseline and 0.87 at ten years. Immediately after the treatment (baseline) and 10 years later, the examiners assessed the restorations independently by direct visual and tactile examination with mouth mirror number 5 and explorer number 23 (Hu Friedy Mfg. Co. Inc., Chicago, IL, USA) and indirectly by radiographic examination (bite wing). The five parameters examined were marginal adaptation, anatomic form, surface roughness, secondary caries, and lustre. If a difference was recorded between the two examiners, and if they could not reach an agreement, a third clinician, who also underwent the calibration exercises (GM), made the final decision.

2.4 Treatment Groups 2.4.1 Repair The clinicians (PV - GM) used carbide burs (330-010 Komet, Brasseler GmbH Co., Lemgo, Germany) to explore the defective margins of the restorations, beginning with the removal of part of the restorative material adjacent to the defect to act as an exploratory cavity; this allowed a proper diagnosis and evaluation of the extent of the defect. Provided that the defect was limited and localized, the clinician then removed any defective tooth tissue. Once this material was removed, an exploratory cavity preparation was done that included removal of any demineralized and soft tooth tissue. A self-priming resin bonding system was used (Adper Prompt L-Pop; 3M ESPE, St. Paul, MN, USA), followed by restoration with a resin-based composite (RBC) restorative material (Filtek Supreme; 3M ESPE). A rubber dam isolation was used for this procedure.

2.4.2 Replacement The clinicians totally removed and replaced the defective restorations. After completing the cavity preparations, it was restored with a new resin composite (RC; Filtek Supreme; 3M ESPE). The elimination of the soft tooth tissue caries infection was done using carbide burs at high speed under full water irrigation. During the cavity preparation, no preventive extension or undercutting areas were created, and all of the cavity angles were rounded. In the deep dentin, a glass-ionomer liner was used (Vitrebond; 3M ESPE; USA). Adper Prompt L-Pop, (3M ESPE) was used per the manufacturer instructions, and RBC (Filtek Supreme; 3M ESPE) was applied by the incremental technique. The occlusion was checked, and the restorations were finished and polished following the manufacturer instructions.