Effect of endocrown design modification on retention & microleakage: an in vitro study

Recently, conservative approaches in prosthodontics have gained attention, especially with the use of endocrowns that preserve tooth structure and utilize retention through the pulp chamber.

This study was conducted to evaluate the effect of modifying endocrown preparation design on retention and microleakage using Vita Enamic blocks in mandibular premolars.

Forty sound human mandibular premolars were treated endodontically and divided into two equal groups (n = 20) according to preparation design: group1: conventional design, and group2: with added buccal groove design. Then each group was further subdivided into 2 equal subgroups (n = 10) according to intra-radicular extension: subgroup A: 3 mm; subgroup B: 5 mm intraradicular extensions. Each subgroup was further subdivided randomly into 2 classes (n = 5) according to the testing procedure. One class (n = 5) was subjected to a retention test using a universal testing machine. The other class (n = 5) was subjected to microleakage testing by soaking in 2% methylene blue in an incubator at room temperature for 24 h. All samples were assessed using a digital microscope to evaluate the extent of dye penetration and modes of failure.

Retention testing revealed no statistically significant difference between the two preparation designs within both intraradicular extension subgroups. However, increased intra-radicular extension 5 mm significantly enhanced retention compared to 3 mm in both designs (p < 0.001). Regarding microleakage, the buccal groove design showed significantly lower values than the conventional design in both subgroups (p = 0.015 and p < 0.001, respectively). A significant difference between the two extensions was observed in the conventional group only, with higher microleakage in the 3 mm subgroup (p < 0.001), while no significant difference was found in the buccal groove group (p = 0.189).

5 mm intra-radicular extension significantly improved the retention of the endocrowns, performing better than 3 mm, while the buccal groove design enhanced retention and resulted in lower microleakage.