Commentary

Abstract

The significance of beveling enamel is based on two important aspects: bonding to enamel and esthetics. BONDING TO ENAMELBonding to enamel involves both clinical retention and enamel margin sealing ability. In laboratory tests, the composite bond strength to unprepared enamel is 10 to 15% lower than that obtained to instrumented or prepared enamel. In one study, Single Bond (3M ESPE) resulted in 31.5 MPa to unprepared enamel versus 34.9 MPa to prepared enamel. 1 Another study with the same etch-and-rinse adhesive obtained 31.3 MPa to unprepared enamel whereas the prepared enamel resulted in 37.7 MPa. 2 Under the scanning electron microscope (SEM), the cervical unprepared enamel acid-etching pattern ( Figure 1) is not as well defined as the classical pattern 3 created on prepared enamel (Figure 2A and 2B). In Figure 1, we can also see the presence of hypermineralized cervical enamel that was not removed by acid-etching. 4 The statistical difference in composite bond strength to enamel in laboratory tests and this distinct morphological aspect under the SEM may not translate into clinical relevance for direct composite restorations in non-carious cervical lesions (NCCL). Beveling the enamel margin does not result in better marginal sealing on incisal margin, nor better retention. 5 If we analyze Figure 1 that illustrate Costa and colleagues' article, 6 enamel area may represent between 15 and 20% of the NCCL total area. So, in this clinical situation, dentin bonding may be crucial in restoration retention. And, the composite bond strength to unprepared enamel (10-15% lower in bond strength 1,2 ) will influence just a small enamel area and probably will not reflect in clinical significance over the first 3 years. 5 This same NCCL (Figure 1 in Costa and colleagues' study 6 ) had cervical-incisal height of 2 mm. If we prepared a 2-mm enamel bevel, the enamel area would be around 50% of the NCCL area available for bonding. In this way, bonding to enamel becomes an important factor that may influence the clinical performance/retention over time. However, another clinical important aspect is the acid-etching step. For example, if the operator extends the enamel over 1 to 2 mm from the NCCL cavo-surface margin, including the enamel that was not beveled, the final bonding area may be similar compared with beveling NCCL.Beveling enamel is the most important aspect in Costa and colleagues' study. 6 Therefore, a detailed description of the bevel (cervical-incisal height, angle) and acid-etching step (how many millimeters over the enamel margin?) would help further studies to reproduce this methodology and compare results to make discussion more relevant.Three previous clinical studies reported that beveling and acid-etching together did not influence the clinical performance of resin composite restoration in NCCL. 7-9 Only one article (published 10 years ago) compared the variable enamel bevel, having resulted in restorations without clinical difference over 3 years. 5 It is important for

Fracture resistance of veneers in premolars

“…Bond strength to intact enamel is known to be between 10% and 15% lower compared to instrumented enamel. [ 27 28 ]…”