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

BACKGROUND: 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. AIM OF THE STUDY: This study was conducted to evaluate the effect of modifying endocrown preparation design on retention and microleakage using Vita Enamic blocks in mandibular premolars. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.