|Year : 2015 | Volume
| Issue : 2 | Page : 58-62
Haptics: The science of touch in periodontics
Rashmi Khanna, Sapna Sharma, Monika Rana
Department of Periodontics, NIMS Dental College and Hospital, Jaipur 303121, Rajasthan, India
|Date of Web Publication||25-Jan-2016|
C/o Shri Ramphal Kaushik, House Number 256, HUDA Sector 2, Rohtak 124001, Haryana
Source of Support: None, Conflict of Interest: None
The simulation of clinical situations with the acquisition of fine motor skills is an essential component of the dental students' learning experience. The traditional approach to dental skills training has drawbacks in terms of cost, availability, lack of real-world cases, with the restraints of time, clinical supervision, and the funding of raw materials such as real and plastic teeth. The introduction of dental haptics opens the door to a more realistic clinical experience which can be free from the previous constraints. The performance of the students should be reviewed invaluably by pinpointing exactly where mistakes may have been made and directed learning should be allowed. Also, haptics offers the possibility of unlimited training hours by which students can gain skills without demands on manpower and resources. This paper provides a comprehensive review of literature on haptics for training of periodontal procedures.
Keywords: Haptics, periodontics, simulation, virtual reality
|How to cite this article:|
Khanna R, Sharma S, Rana M. Haptics: The science of touch in periodontics. Digit Med 2015;1:58-62
| Introduction|| |
Haptics (pronounced HAP-tiks) is defined as the science of applying touch (tactile) sensation and control to interaction with computer applications. The word "haptics" is derived from the Greek "haptikos," meaning able to grasp or perceive. Technology is constantly evolving with time and so is its application in medical and dental fields. Simulation has long been used in the medical field, which has increased patient safety and has reduced the risk associated with human errors. The field of dental simulation is at the verge of emergence. Webster's dictionary defines simulator as a training device that duplicates artificially the condition likely to be encountered in some operations.  Simulation can aid, improve, and advance the way dentistry is taught for future generations. This technology has significant potential to complement traditional training approaches, especially in the fields in which hands-on training is not applicable or ethical as in dentistry.  Due to the astonishing growth of computer hardware and software, virtual worlds that support the field of advanced simulation have been developed. Virtual reality creates virtual worlds using mathematical models and computer programs which allow the users to move into a created virtual world in a way very much similar to the real life. This technology is often referred to as "third dimension" or the "next generation" learning environment in medicine.  Virtual reality systems represent a powerful tool for training humans to perform tasks which are otherwise expensive or dangerous to duplicate in the real world.
Dental students obtain their surgical skills training traditionally for decades by practicing on plastic teeth or sometimes live patients under supervision of dental experts. However, it is being challenged by the new complications in surgery such as the increasing cost of training materials, the ethical concerns for safety of patients, and the unavailability of many real-world challenging cases.
Hence a system which uses virtual reality and haptics technology will be a breakthrough in learning the diagnosis and treatment of periodontal diseases by visualizing a three-dimensional virtual human mouth and feeling real tactile sensations and allowing surgeons to touch and feel the objects such as surgical tools and human organs in the virtual environment, and to perform operations like pushing, pulling, and cutting of soft or hard tissue with realistic force feedback. It also allows objective assessment of surgical competency by providing parameters such as time taken to finish a procedure, efficiency of movements, or percentage of error.
| History|| |
Wang et al.  worked on a simulator that allows probing and cutting a virtual tooth, but the virtual tool implementation was limited to a spherical shape for simplicity.
Kim et al.  developed a dental training system with a multi-modal workbench providing visual, audio, and haptic feedback. This system is a volume-based haptic modeling which represents a tooth as a volumetric implicit surface. It allows burring and drilling on the tooth with a spherical tool.
Yau et al.  proposed a dental training system utilizing material stiffness and spring force function. This simulation uses adaptive octree data structure for a tooth model and oriented bounding box for the boundary of the cutting tool. Different shapes of a cutting tool are introduced but details on how the forces are rendered for irregular-shaped cutting tools is missing as well as how to handle the torque that might occur in the case of nonspherical tool.
Luciano  developed PerioSim, which allows trainee to practice diagnosing periodontal diseases that does not require deformation of tooth surface.
| Background|| |
Dental simulators not only provide an efficient way to quickly teach dental procedures to preclinical dental students but also increase their hand skills considerably. On dental simulators, proper hand and instrument usage and placement can be learned repetitively. The simulator allows students to develop the skills needed to differentiate pathological and normal conditions, as well as to diagnose and treat periodontal diseases.
Two types of dental simulators currently available are as follows:
- Manikin-based simulators: Consist of a physical model of the patient's head and mouth on which dental procedures can be performed using real dental instruments; and
- Haptics-based simulators: Consist of a haptic device and virtual models of a human tooth or mouth which acts as a platform to facilitate dental practicing. Instead of using real dental instruments, the trainee holds the haptic device stylus to manipulate a set of virtual instruments that are shown on a monitor screen. The tactile feedback reproduces clinical sensations in the hand of the operator using dental instruments.
Unlike manikin-based, haptics-based simulators are much more fast and cost effective as no physical models need to be replaced. In addition, as the haptic device measures the forces applied by the trainee when touching the virtual patient's mouth, it is possible to detect when the student's action is potentially aggressive.
Some of the most well-known haptics-based dental simulators previously developed are virtual reality dental training system, Iowa dental surgical simulator, three-dimensional (3D)-dental, haptically enabled dental simulator, and volume-based dental simulator. All these are used for restorative purposes such as caries preparation or filling of cavities, none of them focuses on the simulation of periodontal procedures.
The field of periodontics is that field of dentistry which requires dentists to depend primarily on their tactile sensations, for both diagnostic and surgical procedures. This makes haptics ideally suited for periodontal simulators.
Currently, periodontal procedures are taught by time-consuming teaching process of instructor demonstration, use of practice manikins and, finally, by actual work in the patient's mouth which requires excessive one-on-one instructor/student interaction. Haptics-based dental simulators could be beneficial for the training of dental and hygiene students as they aid in diminishing the instruction time period, enhance the learning curve, and provide for unlimited practice of these treatments. 
Haptics allows the user to feel, manipulate, and interact with the object displayed on the personal computer monitor. The user can touch, move, and feel an existing distant object indirectly through a robotic arm. Furthermore, haptics provide force feedback to humans interacting with virtual or remote environments since the robotic arm is able to provide preprogrammed guidance. Traditionally trained students neither feel what the instructor feels nor can they be physically guided by the instructor performing a procedure. At the same time, high visual acuity is required from the student. Students can learn by feeling tactile sensations as they "touch" a computer-generated 3D model of a human upper and lower dental arches along with various oral components: Teeth (crown and roots) and gingiva with a haptic device.
Haptic hardware includes the following
- High-end computer workstation with appropriate software
- Haptic interface device (stylus)
- A stereoscopic computer monitor with stereo glasses
- Semitransparent mirrors
- Head-mounted display
- Monitor and speakers
- Gloves to feel the sensations.
The rendered image of a virtual object is reflected onto a semitransparent mirror so as to be aligned with the user's hand and haptic device. 
In the diagnosis phase, a virtual periodontal probe could be used to measure pocket depth and to determine the tissue health and, in case of pathological situations, the severity of the periodontitis.
In the treatment phase, a virtual periodontal scaler could be used to detect the presence of calculus. With the tooth surface covered by gingiva, the trainee would be forced to rely on the tactile sensation provided by the haptic device to evaluate the presence of virtual calculus on the root surface. Showing a transparent gingiva, the trainee could concomitantly see the calculus under the gum line.
In the evaluation phase, a virtual periodontal explorer may be used to determine whether the calculus has been completely removed. This evaluation could be performed with both a transparent and an opaque gingiva to contrast the results obtained by the trainee. 
How to operate a periodontal simulator
Using the control panel, one of three periodontal instruments can be selected for onscreen use: A periodontal probe, explorer, or scaler [Figure 1].
In the main window of the simulator, the user can see the full-screen 3D model of area of interest in a dental arch along with the main control panel. The main control panel [Figure 2] contains a variety of controls for navigation which include options to select and manipulate gingiva. The operator can induce varying degrees of transparency of the selected objects using a slider bar.
In the main window of the simulator, the user can control the haptic properties of the simulation process. This includes the basic ability to turn haptics on or off for each selected object. The haptic parameters such as stiffness, viscosity, static friction, dynamic friction can be controlled and altered separately for each object [Figure 2].
By moving the haptic stylus, a trainee can move the virtual instrument on the tooth surface and feel the crevice or pocket area within the margin of the gingiva (gums) along the root surface of the tooth [Figure 3].
|Figure 3: Simulator setup and comparison between handling the real instrument and the haptic stylus|
Click here to view
The 3D virtual periodontal probe can be used to determine and measure crevice or pocket depths around the gingival margins of the teeth. The textural feel of pocket areas can be differentiated and regions of sub-gingival calculus can be located. Since the root surface is covered by gingiva, the trainee cannot see the area being probed or the underlying calculus and must depend totally on haptic feedback to identify these areas. This situation corresponds to conditions encountered clinically. To assist visualization of what he/she is feeling, control panel adjustments can introduce varying degrees of gingival transparency.
Graphical and haptic parameters can be altered by an instructor using control panel adjustments to provide the "feeling" or feedback he/she wishes to impart to the trainee. The system permits any instructor to generate a diagnostic and/or treatment procedure for student use.
Record and replay functionality
Recording of the haptic experiences involves the production of instructor-driven trajectories to define correct movements of the dental instrument when performing the periodontal procedure. These recordings can be stored in the system for future use by students and will guide their performance of a procedure. The methods used by an individual instructor to both diagnose and treat a particular procedure can be demonstrated while guiding students to perform the procedure in the same fashion. Note that the instructor need not be present to provide this guidance. 
Haptics and bone surgery
In the Stanford BioRobotics Laboratory, a visuohaptic simulation of bone surgery for training and evaluation has been devised. A hybrid data structure is used to represent the bone: A volumetric array stores the density values and attributes of the data, whereas a surface triangulation is used to render the bone graphically. The volume data and surface triangles are obtained from computer tomography or magnetic resonance data after a preprocessing procedure. The simulation also provides the ability to assess the trainee's performance using predefined metrics together with visual and written feedback. Moreover, the system simulates bone dust, provides drilling sounds, and can incorporate a second haptic device as a suction and irrigation tool. 
Another computer-aided support system for implant surgery, BoneNavi, has been developed in Japan to simulate implant placement and surgical guide fabrication for dental implant surgery. To accomplish these objectives, this system involves manipulating a 3D computed tomography image of a jawbone with a virtual reality force feedback device. To achieve enhanced haptic realism, this system also provides the haptic experience of bone drilling with virtual vibration and the sound of contra-angle handpiece. These simulation features are useful for inexperienced dentists and for training dental students in bone drilling in dental implant operations. 
- Improved usability: Haptics improve usability by engaging touch, sight, and sound
- Enhanced realism: Haptics injects a sense of realism into user experiences by exciting the senses and allowing the user to feel the action of the application. The inclusion of tactile feedback provides additional context that translates into a sense of realism for the user
- Restoration of mechanical feel: By providing users with intuitive and unmistakable tactile confirmation, haptics can create a more confident user experience and can also improve safety by overcoming distractions especially during sub-gingival calculus detection, determining bone defects without flap reflection and performing periodontal surgery
- Cost effective: Haptics provide a new and low-cost approach whereby dentists can practice procedures as many times as they want at no incremental cost and training can take place anywhere
- Self-evaluation: It has the ability to give instant, consistent, and unbiased feedback based on evaluation of the procedure in the form of felt sensations in the hand
- Correct ergonomic positioning: Incorrect operator or patient positioning can result in blocking the camera from reading the light-emitting diode sensors and prevents the user from continuing by warning signals which encourages the students to support and reinforce good ergonomic habits
- Standardized evaluation: Consistency and uniformity for preclinical evaluation
- Faster acquisition of skills: Students develop skills more efficiently in a shorter period of time as compared with the traditional simulator units (phantom heads), which can result in smoother transition for students into the clinic
- Haptics provide effective learning without any fear of making mistakes on a patient
- Haptics technology along with a visual display can be used to train people for tasks requiring hand-eye coordination, such as surgery. Haptics offers an additional dimension to a virtual reality or 3D environment
- Reinforcement of learned dental concepts
- It allows proper selection and manipulation of dental instruments to perform periodontal procedures.
- The tactile perception for gingiva is not very real
- The feel of working on dental chair is lacking as it uses desktop system
- Single-hand held haptic arm does not provide the feel of using mouth mirror and working instrument together
- The initial cost of this advanced technology simulation can be substantial
- Difficult equipment to maintain and repair: Technology-based systems require faculty/engineering staff to be available for training and supervision of the laboratory.
In a study done by Koo et al., it was concluded that the haptic exercises with the manual dexterity module software were not superior in improving the dexterity of students for tooth cavity preparations in short term. Benefits of ease of use and fun learning experience can be further investigated in future studies. 
| Conclusion|| |
Advanced simulation technology simulators offer an exciting opportunity to dramatically improve student learning. Haptic technology is a powerful educational methodology which improves the level of perception, sense of touch and feel and reduces the distance between the virtual and the real world. Haptics offer an excellent complementary means of training and could be a replacement for the existing ones.
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[Figure 1], [Figure 2], [Figure 3]