Aeskulap
Aeskulap is a free, open-source (GPL) DICOM viewer and PACS query/retrieve client for Linux. It is no longer developed: the last stable release is 0.2.1 (2006), and Debian 12 and Ubuntu 22.04 still package it. No official portable edition exists.
DicomWorks
DicomWorks is a free Windows DICOM viewer (freeware) for opening CDs and folders, anonymising studies and exporting images to JPEG, AVI or PowerPoint. Legacy software: the last build is 1.3.5b and there have been no updates since 2011.
3Shape Unite
3Shape Unite is the Windows platform that TRIOS intraoral scanners run on. It covers order forms, scanning, lab collaboration, the Unite Store and Unite Cloud. It comes free with a TRIOS scanner, while many apps are paid; Model Maker prepares scans for 3D printing.
JDicom
JDicom is a free, closed-source suite of Java DICOM tools from TIANI Medgraph for sending, receiving, querying, printing, editing and validating DICOM data. It is a connectivity-testing toolkit, not a dental viewer. The last known version is 1.7.35 and it is no longer maintained.
ONIS 2.5 Free Edition
ONIS 2.5 Free Edition is a Windows DICOM viewer from DigitalCore with PACS query/retrieve, MPR, MIP 3D and measurement tools. Shareware (conditionally free): limited to 15 patients, one monitor and no extra plugins; paid editions remove the limits.
HorliX
HorliX is a free macOS DICOM viewer derived from Horos and OsiriX, made by Hiroaki Inomata, MD (PHAZOR). It stores studies in a local database and offers 2D viewing, MPR and ROI measurement for CT and CBCT. Version 1.1.2 needs macOS 12.4 or later. It is Mac only.