Objective: To assess and compare the accuracy of the marginal and internal fit of lithium disilicate crowns and onlays fabricated by conventional and digital methods. Sources: An electronic search was carried out on MEDLINE, Embase, Web of Science and Cochrane Library between 2010 and 2021. Study selection: Seventeen studies published between 2014 & 2021 were included, of which thirteen were in vitro laboratory-based studies; three were in vivo clinical studies and one randomised controlled trial. Data: Twelve studies focused on the marginal fit, five focused on the marginal and internal fit. Five studies found that the marginal and internal fit of crowns were more accurate using digital techniques. Five studies noted that there was no difference using either technique and two noted that conventional methods had a more accurate marginal fit. Conclusion: Digital techniques were comparable to conventional methods in terms of accuracy although there was insufficient evidence to indicate that one technique was more accurate than the other with respect to Lithium Disilicate restorations. Clinical significance: Digital impressions are reliable and viable alternatives for clinicians compared to conventional impression techniques when restoring teeth with lithium disilicate restorations.

The development of dental materials needs to be supported with sound evidence. This in vitro study aimed to measure the fracture toughness of a short fibre-reinforced composite (sFRC), at differing thicknesses. In this study, 2 mm, 3 mm and 4 mm depths of sFRC were prepared. Using ISO4049, each preparation was tested to failure. A total of 60 samples were tested: 10 samples for each combination of sFRC and depth. Fractured samples were viewed, and outcomes were analysed. EXF showed greater toughness than EXP, with a mean of 2.49 (95%CI: 2.25, 2.73) MPa.m^1/2 compared to a mean of 2.13 (95%CI: 1.95, 2.31) MPa.m^1/2, (F(1,54) = 21.28; p < 0.001). This difference was particularly pronounced at 2 mm depths where the mean (95%CI) values were 2.72 (2.49, 2.95) for EXF and 1.90 (1.78, 2.02) for EXP (Interaction F(2,54) = 7.93; p < 0.001). Both materials performed similarly at the depths of 3 mm and 4 mm. The results for both materials were within the accepted fracture toughness values of dentine of 1.79–3.08 MPa.m^1/2. Analysis showed crack deflection and bridging fibre behaviour. The optimal thickness at the cavity base for EXF was 2 mm and for EXP 4 mm. Crack deflection and bridging behaviour indicated that restorations incorporating sFRCs are not prone to catastrophic failure and confirmed that sFRCs have similar fracture toughness to dentine. sFRCs could be a suitable biomimetic material to replace dentine.

This paper aims to determine the influence of varying the maxillary incisor shape of an individual on perceived smile aesthetics. A photograph of a female smile displaying maxillary teeth only was digitally altered to produce five different incisor shapes. They consisted of three basic shapes: square (S), ovoid (O), triangular (T) and two variations, tapered-ovoid (TO) and square-tapering (ST). The images were ranked from the most to the least attractive by 30 dentists, 30 technicians and 30 patients. The TO maxillary incisor shape was perceived to be the most attractive smile overall (50%), and amongst dentists (70%), technicians (50%) and patients (30%). The O shape maxillary incisors were ranked the second most attractive overall (36.7%) and the most attractive amongst patients (56%). The S shape maxillary incisors were perceived as the least attractive overall (43.3%), and amongst dentists (47%), technicians (50%) and patients (33%). The tapered-ovoid incisor tooth form for females is preferred to the square form, which corresponds with the findings in the dental literature. However, the results also suggest that there is not one 'ideal' incisor shape and that dental professionals are more critical than patients with respect to the shapes of maxillary incisors. Dental professionals should take the individual variability in patient response into consideration during treatment planning, to produce an aesthetic outcome that is acceptable for the patient. As a general rule, the tapered-ovoid tooth form is perceived to be more desirable than the square tooth form. The dental team should therefore keep this finding in mind and liaise with the patients accordingly, in order to help to produce desirable aesthetic clinical outcomes.