Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part III: marginal and internal fit

Statement of problem

Trials comparing the overall performance of digital with that of conventional workflows in restorative dentistry are needed.

Purpose

The purpose of the third part of a series of investigations was to test whether the marginal and internal fit of monolithic crowns fabricated with fully digital workflows differed from that of crowns fabricated with the conventional workflow.

Material and methods

In each of 10 participants, 5 monolithic lithium disilicate crowns were fabricated for the same abutment tooth according to a randomly generated sequence. Digital workflows were applied for the fabrication of 4 crowns using the Lava, iTero, Cerec inLab, and Cerec infinident systems. The conventional workflow included a polyvinyl siloxane impression, manual waxing, and heat-press technique. The discrepancy between the crown and the tooth was registered using the replica technique with polyvinyl siloxane material. The dimensions of the marginal discrepancy (Discrepancy_marginal) and the internal discrepancy in 4 different regions of interest (Discrepancy_shoulder, Discrepancy_axial, Discrepancy_cusp, and Discrepancy_occlusal) were assessed using light microscopy. Post hoc Student t test with Bonferroni correction was applied to detect differences (α=.05).

Results

Discrepancy_marginal was 83.6 ±51.1 μm for the Cerec infinident, 90.4 ±66.1 μm for the conventional, 94.3 ±58.3 μm for the Lava, 127.8 ±58.3 μm for the iTero, and 141.5 ±106.2 μm for the Cerec inLab workflow. The differences between the treatment modalities were not statistically significant (P>.05). Discrepancy_shoulder was 82.2 ±42.4 μm for the Cerec infinident, 97.2 ±63.8 μm for the conventional, 103.4 ±52.0 μm for the Lava, 133.5 ±73.0 μm for the iTero, and 140.0 ±86.6 μm for the Cerec inLab workflow. Only the differences between the Cerec infinident and the Cerec inLab were statistically significant (P=.036). The conventionally fabricated crowns revealed significantly lower values in Discrepancy_cusp and Discrepancy_occlusal than all the crowns fabricated with digital workflows (P<.05).

Conclusions

In terms of marginal crown fit, no significant differences were found between the conventional and digital workflows for the fabrication of monolithic lithium disilicate crowns. In the occlusal regions, the conventionally manufactured crowns revealed better fit than the digitally fabricated crowns. Chairside milling resulted in less favorable crown fit than centralized milling production.