Fracture Strength of Monolithic Endocrowns and Advanced Lithium Disilicate - A Pilot Study

Introduction Root-filled teeth with large losses of tooth substance is a challenge for dental clinicians. The restoration of choice has traditionally been post and core buildup with a crown. Monolithic endocrowns in lithium disilicate, have been suggested as an alternative to this traditional restoration. Monolithic restorations offer possibilities which could provide treatment alternatives with a more reliable prognosis. Aim The aim is to examine the fracture strength of endocrowns made of advanced lithium disilicate. Material and method Twelve root-filled molars were restored with advanced lithium disilicate (Tessera) or lithium disilicate (e.max CAD) but with two different designs: endocrown and post and core + crown. The control groups consisted of post and core and e.max CAD. The samples were thermocycled and loaded in a chewing simulator (100.000 cycles, 5-55 Celsius (oC)) simultaneously, and finally loaded until fracture. The data was analysed with One-Way ANOVA and post hoc Tukey’s test. Fracture patterns were visually divided in two groups and analysed using Chi2-test (significance level α = 0.05). Results E. max CAD in both groups of restorations showed higher fracture strength compared to Tessera. A statistical difference was noted when comparing the ECE group to the ECT (p value = 0.016) as well as the PCT group (p value = 0.009). The number of endocrown samples, regardless of material, that totalfractured was equal to the number of endocrown samples that crownfractured. Among the post and core crown samples regardless of material, there were three that crownfractured and two that totalfractured. However, there was one dropout in the post and core crown groups (PCE). No statistical difference was shown between the groups regarding the fracture modes.Conclusion The results from this study are highly unreliable due to the small sample size and no definitive conclusion can be drawn. However, the results may represent a trend indicating a higher fracture strength for the endocrowns made of lithium disilicate.