MRIcroGL
MRIcroGL is a free, open-source volume viewer for DICOM and NIfTI images with fast 3D rendering, scripting and a DICOM-to-NIfTI converter. It can open CBCT series for research and teaching, but it is not a dental or clinical product. Windows, macOS and Linux.
DTX Studio Clinic
DTX Studio Clinic by Nobel Biocare and DEXIS combines intraoral X-rays, CBCT, intraoral scans and photos in one workspace with AI sorting and implant planning. Shareware (conditionally free): a free Starter licence covers viewing; full use needs a paid licence. Windows and macOS.
dcm4che DICOM Toolkit
dcm4che is a free, open-source Java DICOM toolkit and library with more than 50 command-line tools for sending, receiving, querying, converting and checking DICOM data. It is not a viewer; the dcm4chee archive is a separate project built on it.
SMILI (Simple Medical Imaging Library Interface)
SMILI is a free, open-source (BSD-style, CSIRO) framework for biomedical imaging apps; its sMILX viewer opens images and STL/PLY/OBJ models by drag and drop, overlays labels and smooths or decimates meshes. General research tool, no dental features.
Sante DICOM Viewer Lite
Sante DICOM Viewer Lite by Santesoft is a free 2D/3D DICOM viewer for Windows and macOS. Open CBCT and CT exports or patient CDs, scroll MPR slices and measure. The paid Pro edition (shareware, free demo) adds anonymising, editing and CD burning.
K-PACS
K-PACS is a free Windows DICOM workstation: viewer, local archive, store and query/retrieve, CD burning. The vendor allows evaluation and non-commercial use only. It is legacy software; the last version is 1.6 and it is no longer developed.
dicompyler
dicompyler is a free, open-source (BSD) radiation therapy research platform and DICOM RT viewer. It shows dose and structure overlays and DVHs. The project is archived; the last release is 0.4.2 from 2014.
OpenREM
OpenREM is a free, open-source (GPLv3) web application for patient radiation dose monitoring. It imports dose data from X-ray, CT, fluoroscopy and mammography equipment and shows charts and exports. Stable version 0.10.0; version 1.0 is in beta.