*Article* **In Vitro Study Comparing Retention of Custom Post and Cores Fabricated Using Conventional, CAD/CAM Milling and 3D-Printing Techniques**

**Hatem Alqarni 1,2,\* , Abdulaziz A. AlHelal 3, Rami Jekki 4, Mathew T. Kattadiyil 4, Mohammed E. Sayed 5,6,\* , Saurabh Jain <sup>5</sup> , Seyed Aliakbar Vahdati 7,8 and Salem Dehom <sup>9</sup>**


**Abstract:** This study aimed to evaluate the differences in the retention of custom-cast non-precious post and cores (CCNPPCs) (control group), custom-milled titanium post and cores (CMTPCs), customprinted titanium post and cores (CPTPCs), and custom-milled zirconia post and cores (CMZPCs), and to evaluate their mode of failure. The tested null hypothesis was that there were no differences in the retention of the various custom post and cores tested. A total of 80 post-and-core patterns were made using pattern resin and were divided into four groups: Group 1—fabricated via conventional casting using a non-precious casting alloy; Group 2—fabricated using a computer-aided design/computeraided manufacturing (CAD/CAM) subtractive technique using titanium; Group 3—fabricated using a CAD/CAM additive (3D printing) technique using titanium; and Group 4—fabricated using a CAD/CAM subtractive technique using zirconia. The post and cores were cemented with resin cement and a universal pull-out test was used to check the retention. The data were statistically analyzed using one-way ANOVA tests, post hoc tests, and Tukey's adjustment for multiple comparisons. The pull-out test revealed higher retention values for CPTPCs and CMTPCs. When compared with CMZPCs, the conventional CCNPPCs revealed significantly better retention values (*p <* 0.05). Cohesive failure was observed in Groups 1, 2, and 4. However, Group 3 revealed a mixed type of failure. The CCNPPCs revealed clinically acceptable values, while the CPTPC and CMTPC groups revealed better overall values of retention and time to failure. The titanium alloy was assessed to be a promising choice for fabricating dental post-and-core restorations.

**Keywords:** titanium alloy; zirconia; retention; CAD/CAM; additive manufacturing; subtractive manufacturing; custom post and core; 3D printing; non-precious alloy
