⚡ electrical engineering

Development and Evaluation of an Extended Reality-Based Remote Toothbrushing Training System: A Randomized Controlled Trial

This randomized controlled trial demonstrates that an extended reality-based remote training system, which visualizes brushing force and motion in real time, is more effective than conventional instruction in helping learners acquire the critical skill of controlling brushing force for oral hygiene.

Original authors: Takaaki Ito, Ryo Tagaino, Taichi Narihara, Kimiko Sato, Hiroshi Egusa, Nobuhiro Yoda, Makoto Sasaki

Published 2026-07-07

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CC BY 4.0

Original authors: Takaaki Ito, Ryo Tagaino, Taichi Narihara, Kimiko Sato, Hiroshi Egusa, Nobuhiro Yoda, Makoto Sasaki

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are trying to learn how to paint a tiny, perfect circle on a friend's fingernail. If you stand behind them, you can't see exactly where their brush is going. If you stand in front, your own hand blocks the view. And the biggest problem? You can't feel how hard they are pressing. If they press too hard, they might hurt the nail; too soft, and the paint won't stick.

This is exactly the problem with teaching someone how to brush their teeth, especially when the "student" is a caregiver trying to help an elderly person, or a student learning from a dentist. The view is blocked, and the feeling of pressure is impossible to share.

The "Magic Glasses" Solution
To solve this, the researchers at Iwate and Tohoku Universities built a special training system using Extended Reality (XR). Think of this as a pair of "magic glasses" (Head-Mounted Displays) that let a teacher and a student see the exact same 3D world, even if they are in different rooms.

Here is how the system works, using some simple metaphors:

The Ghost Brush: When the teacher brushes a model tooth, the student sees a glowing green ghost brush moving in their own view, showing exactly where the teacher is going. When the student brushes, the teacher sees a pink ghost brush doing the same. It's like having a transparent, floating copy of the other person's hand right in front of your eyes.
The Pressure Lightbulb: The toothbrush has a special sensor that measures how hard you are pushing. In the magic glasses, this force turns into a color-coded gauge:
- Blue: You are pressing too lightly (like a feather touch).
- Green: You are in the "Goldilocks zone"—just right (1.5 to 2.0 Newtons of force).
- Red: You are pressing too hard (like a sledgehammer).
  This lets the student "see" their own pressure instantly, something you can't do with just your eyes or hands.

The Experiment: Remote vs. In-Person
The researchers tested this system against the old-fashioned way of teaching (standing next to someone and talking). They had 24 healthy adults learn to brush a model tooth.

Group A learned face-to-face with a teacher standing right next to them.
Group B learned remotely using the XR "magic glasses" and the color-coded pressure gauge.

What They Found
Both groups got better at two things:

Position: They learned to put the brush in the right spot.
Angle: They learned to tilt the brush correctly.

However, there was one major difference that makes this study special: Force Control.

The Face-to-Face group did not get significantly better at controlling how hard they pressed. They still struggled to find that "Goldilocks" pressure.
The XR Group became experts at controlling their pressure. Because they could see the color change from blue to green in real-time, they learned to push just right. Even after they took the glasses off and the color gauge disappeared, they remembered how to press correctly.

Why This Matters
The paper concludes that this XR system is a powerful tool because it bridges a gap that normal teaching cannot cross: sharing the feeling of pressure.

While the old method is good for showing where to move, the XR system is superior for teaching how hard to push. This is crucial because brushing too hard can damage gums, while brushing too softly doesn't clean the teeth. By turning invisible pressure into visible colors, the system allows learners to master a skill that is usually very hard to teach, especially when the teacher and student are far apart.

The researchers suggest this could be very helpful for training caregivers in nursing homes or teaching people in rural areas where dentists are scarce, allowing them to learn precise brushing techniques without needing a physical expert in the room.

Technical Summary: Development and Evaluation of an XR-Based Remote Toothbrushing Training System

Problem Statement
Oral hygiene is critical for preventing functional decline and systemic diseases, particularly in older adults. However, teaching proper brushing techniques to caregivers, parents, or students is inherently difficult due to the narrow operative field and the inability to share a visual perspective. In conventional face-to-face instruction, learners often cannot observe the instructor's hand movements, trajectories, or stroke length due to line-of-sight obstructions. Furthermore, brushing force—a critical parameter for preventing tissue injury—cannot be conveyed through visual observation alone. Existing Extended Reality (XR) studies in dental training have demonstrated potential but often lack the integration of shared visual perspectives, motion tracking, and force feedback in a remote educational setting.

Methodology
The authors developed an XR-based remote toothbrushing training system and conducted a randomized controlled trial to evaluate its efficacy against conventional instruction.

System Architecture: The system integrates an optical motion-capture system (OMCS; OptiTrack), a six-axis strain-gauge force sensor, and a head-mounted display (HMD; HTC VIVE Pro2).
- Motion Capture: Infrared cameras track reflective markers on the toothbrush handle and HMD to determine position and orientation.
- Force Sensing: A force sensor attached to the toothbrush neck measures applied force.
- Visual Interface: Using Unity3D and a stereo camera (ZED Mini), the system overlays computer-generated data onto the real environment. It displays the instructor's movements as a green 3D model and the participant's movements as a pink 3D model.
- Force Feedback: A gauge-based interface provides real-time visual feedback on brushing force: blue (<1.5 N), green (1.5–2.0 N, the target range), and red (>2.0 N).
Experimental Design: Twenty-four healthy adults were randomly assigned to either the XR remote group ( $n=12$ ) or the conventional face-to-face group ( $n=12$ ). Four dental hygienists served as instructors.
Protocol: Both groups underwent a standardized protocol involving grip demonstration, positioning, force demonstration, practice, and feedback. Training focused on the upper left central incisor.
Evaluation Metrics: Skill acquisition was assessed via three trials of 10 brushing strokes before and after training. Metrics included:
- Spatial Accuracy: Mean error in position ( $P_x, P_y, P_z$ ) relative to the instructor's reference.
- Angular Accuracy: Mean error in roll, pitch, and yaw angles.
- Brushing Force: Mean force applied, with a target of 1.5–2.0 N.
- Generalization: Performance was also tested on the untrained upper right canine to assess skill transfer.

Key Contributions

System Development: The creation of a remote training system that uniquely combines real-time visualization of brushing motion and force feedback, allowing instructors and learners to share perspectives and force data simultaneously.
Bidirectional Monitoring: The system enables instructors to monitor learners' movements and force in real-time while allowing learners to observe the instructor's technique from arbitrary viewpoints, overcoming physical obstructions common in intraoral care.
Empirical Validation: A randomized controlled trial demonstrating that XR remote training can achieve skill acquisition comparable to, and in specific aspects superior to, conventional face-to-face instruction.

Results

Spatial and Angular Accuracy: Both the XR and conventional groups showed significant improvements in toothbrush position and roll angle after training. The XR group achieved median spatial mean errors of <2 mm in specific areas and median roll angle errors of <1° in key regions.
Brushing Force: A distinct difference was observed in force control. While both groups approached the target force range, only the XR group demonstrated a statistically significant improvement in brushing force across all evaluated regions.
Retention and Generalization: The improvement in force control in the XR group remained reproducible even after the removal of visual feedback (the gauge). Additionally, the XR group showed reduced roll angle errors in untrained regions (the canine), suggesting skill generalization.
Conventional Limitations: The conventional face-to-face group did not show significant improvement in brushing force, highlighting the difficulty of teaching this parameter without direct biofeedback.

Significance and Claims
The paper claims that the XR remote system effectively bridges the gap between instructors and learners by providing intuitive, real-time guidance that mitigates the effects of physical separation. The authors assert that the system functions effectively as a biofeedback tool, translating physical pressure into immediate visual cues that learners can internalize.

The study concludes that the XR system enhances skill acquisition beyond conventional instruction, particularly regarding force control, a parameter difficult to improve through visual observation alone. The authors suggest this technology holds potential for supporting oral hygiene education in remote, home-care, and long-term care settings, as well as in areas with shortages of dental professionals. They note that the system may also support scalable training models, including one-to-many instruction and self-directed learning using prerecorded expert movements.

The authors maintain a modest tone regarding limitations, acknowledging that long-term skill retention was not evaluated, the system's cost and complexity may hinder widespread adoption, and the use of standardized dental models may not fully reflect clinical variability. Future work is suggested to assess long-term outcomes and performance in diverse clinical settings.

Technical Summary: Development and Evaluation of an XR-Based Remote Toothbrushing Training System

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