# A conservative approach to localize loose implant screw through cemented crown: an in vitro experimental study

## TL;DR

This study explores methods to accurately locate and retrieve loose implant screws through cemented crowns to minimize damage.

## Contribution

The study introduces a conservative method using CBCT and MAR to localize loose implant screws with reduced crown damage.

## Key findings

- CBCT with MAR significantly improved the accuracy of creating screw access holes.
- Zirconia crowns showed significant differences in cracking compared to CFM restorations.
- Using CBCT reduced injury to restorations and abutments during screw retrieval.

## Abstract

Retrieval of cement-retained implant-supported restorations is intriguing in cases of screw loosening. Detecting the estimated size of the screw access hole (SAH) could decrease destruction to the prosthesis and preserve the crown.

To precisely localize loose implant screws through cemented crowns to reduce crown damage after screw loosening.

In this in vitro study, 60 cement-retained implants supported 30 zirconia-based, and 30 ceramics fused to metal (CFM) lower molar crowns were invented, and each was subdivided into three subgroups (10 each). In group I (AI/BI) (control), SAH was created with the aid of orthopantomography (OPG). In contrast, in group II (zirconia-crown), SAH was created with the aid of CBCT + 3D printed surgical guide with a 2 mm metal sleeve in subgroups IIA/IIIA and CBCT + MAR was used to develop SAH in subgroups IIB/IIIB. SEM and Micro-CT scanned the SAH openings to determine the diameter of the hole, cracking, chipping, and chipping volume.

Regarding the effect of plane CBCT and CBCT + MAR on prepared crowns, a highly significant association between group I with group II (p = 0.001) and group III (p = 0.002) was detected. Regarding the cracking of SAH, significant differences between the zirconium crown and CFM restoration (p = 0.009) were found, while for the chipping, no significant association was seen between groups (p = 0.19).

CBCT, either as a plane CBCT or with MAR, significantly improved the accuracy of drilling the screw channel and decreased injury to the existing restoration and abutment, aiding in better localization of SAH in loosened implant abutment screws.