  Patient's understanding on forthcoming dental surgeries is required by
patient-centered care and helps reduce fear and anxiety. Due to the gap of
expertise between patients and dentists, conventional techniques of patient
education are usually not effective for explaining surgical steps. In this
paper, we present \textit{OralViewer} -- the first interactive application that
enables dentist's demonstration of dental surgeries in 3D to promote patients'
understanding. \textit{OralViewer} takes a single 2D panoramic dental X-ray to
reconstruct patient-specific 3D teeth structures, which are then assembled with
registered gum and jaw bone models for complete oral cavity modeling. During
the demonstration, \textit{OralViewer} enables dentists to show surgery steps
with virtual dental instruments that can animate effects on a 3D model in
real-time. A technical evaluation shows our deep learning based model achieves
a mean Intersection over Union (IoU) of 0.771 for 3D teeth reconstruction. A
patient study with 12 participants shows \textit{OralViewer} can improve
patients' understanding of surgeries. An expert study with 3 board-certified
dentists further verifies the clinical validity of our system.
