Research Papers

Design and Fabrication of a Disposable Dental Handpiece for Clinical Use of a New Laser-Based Therapy-Monitoring System

[+] Author and Article Information
Amanda L. Rugg

Department of Bioengineering,
University of Washington,
Seattle, WA 98195
e-mail: samsama@uw.edu

Leonard Y. Nelson

Department of Mechanical Engineering,
University of Washington,
Seattle, WA 98195

Mari-Alina I. Timoshchuk

Human Photonics Lab,
University of Washington,
Seattle, WA 98195

Eric J. Seibel

Department of Bioengineering,
University of Washington,
Seattle, WA 98195;
Department of Mechanical Engineering,
University of Washington,
Seattle, WA 98195;
Human Photonics Lab,
University of Washington,
Seattle, WA 98195

Manuscript received May 5, 2015; final manuscript received October 2, 2015; published online December 4, 2015. Assoc. Editor: Rosaire Mongrain.

J. Med. Devices 10(1), 011005 (Dec 04, 2015) (10 pages) Paper No: MED-15-1178; doi: 10.1115/1.4031800 History: Received May 05, 2015; Revised October 02, 2015

Dental caries, the breakdown of tooth enamel by bacteria infection that causes cavities in the enamel, is the most common chronic disease in individuals 6–19 years of age in the U.S. Optical detection of caries has been shown to be sensitive to the presence of bacteria and the resulting demineralization of enamel. The scanning fiber endoscope (SFE) is a miniature camera system that can detect early stages of caries by performing high-quality imaging and laser fluorescence spectroscopy with 405 nm excitation. Because optical imaging of caries does not involve radiation risk, repeated imaging of the teeth is acceptable during treatment of the bacterial infection to monitor healing. A disposable handpiece was designed and fabricated to position the flexible fiber optic SFE probe for quantitative measurements. Plastic 3D-printed handpiece prototypes were tested with the SFE and a fluorescence calibration standard to verify mechanical fit and absence of signal contamination. Design feedback was provided by pediatric dentists and staff engineers to guide iterations. The final design configuration was based on the need to image interproximal regions (contact surfaces between adjacent teeth), ergonomics, and probe safety. The final handpiece design: (1) is safe for both the patient and the probe, (2) allows easy SFE insertion and removal, (3) does not interfere with spectral measurements, (4) standardizes the SFE's positioning during imaging by maintaining a consistent distance from the target surface, and (5) is significantly less expensive to produce and use than purchasing sanitary endoscope sheaths. The device will be used to help determine if new medicinal therapies can arrest caries and repair early interproximal demineralization under the clinical monitoring program. Ultimately, we anticipate that this handpiece will help us move closer toward widespread implementation of a dental diagnostic laser system that is safer and more sensitive than conventional methods for early caries detection.

Copyright © 2016 by ASME
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Fig. 1

X-ray radiograph and pictorial representation of interproximal caries at the contact surface of adjacent teeth. Lighter gray areas represent demineralization in the pictorial representation, which is reverse contrast from radiograph. The carious decay is suspected to be present in both contacting teeth but can be seen only in one tooth from the radiograph. If left untreated, the caries can progress into the dentin of both teeth and be too late for medicinal therapies.

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Fig. 2

SFE functional diagram showing light coming into the endoscope distal end from a single illumination optical fiber, scanning the imaging surface in an outward spiral pattern with 405 nm laser light, and reflectance and fluorescence light being collected in a ring of optical return fibers

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Fig. 3

SFE system. Laptop with labview program (left) and black spectrometer module housing the laser (bottom right). Researcher imaging collagen calibration standard with the probe (far left) with image shown on the screen (top right).

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Fig. 4

Normalized emission profiles at 405 nm excitation for sound enamel (in vivo) [7], carious region (in vivo) [7], and the calibration standard. The three channels collect light at 405 nm, between 425 and 575 nm, and between 575 and 750 nm, respectively. Data collected in these last two channels undergo an algorithm to extract the spectral contribution due to caries.

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Fig. 5

SFE imaging and spectroscopy operation. The default is reflectance and fluorescence imaging mode. Pressing a button halts imaging mode; fluorescence spectroscopy takes place. Imaging mode resumes after about 1 s.

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Fig. 6

SFE probe (middle) and sheath previously used with the SFE for taking clinical data (bottom), shown with their distal ends to the left and a 30 cm ruler for scaling (top). The probe has an outer diameter of 1.6 mm and the sheath has an outer diameter of about 5 mm.

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Fig. 7

List of design criteria for the handpiece in conjunction with the SFE probe. There are six main categories of criteria (orange). Blue boxes represent criteria for the handpiece itself and green boxes represent criteria related to the handpiece and probe together.

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Fig. 8

Design specifications for the handpiece. The specifications fall into six main categories. Some specifications fall into more than one category.

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Fig. 9

Three-dimensional printing of a handpiece prototype. Each prototype takes about 30 min to print.

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Fig. 10

Emission profiles of sound enamel and type I collagen from bovine Achilles tendon at 405 nm excitation measured with our SFE. The collagen is a close spectral match in both profile shape and intensity.

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Fig. 11

Setup for taking spectral data of the collagen calibration standard with a handpiece prototype attached to determine if there is any signal distortion

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Fig. 12

Different views of the final handpiece design (all units in millimeter). Handpiece incorporates a handle with a depression for thumb placement, a 90 deg bend, tabs to hold the probe inside the handpiece, feature to prevent the probe's rigid tip from entering the bend, and a series of steps to lift the probe out of the handle for applying electrical tape as strain relief.

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Fig. 13

Visual instructions for inserting the SFE probe into the handpiece, going from top left to bottom right. Key insertion and removal instructions are written on the handle (bottom right). Two pieces of tape are used to ensure adequate strain relief.

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Fig. 14

Visual instructions for removing the SFE probe from the handpiece

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Fig. 15

Normalized emission profiles of the collagen standard with and without handpieces attached. The intermediate prototype causes an obvious distortion of the profile and is modified so that the final prototype causes no visible distortion.

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Fig. 16

Multimode image of an in vivo tooth taken with the SFE probe alone (left) [7] and a USAF 1951 resolution chart taken with the final handpiece attached to the probe at a close (≤2 mm) working distance (middle, multimodal of reflectance and fluorescence). The SFE's typical resolution, calculated from the chart, is about 0.020 mm (4:5) from (group:element) line width in the resolution chart. Scanner phase distortion is introduced when SFE is held in therigid handpiece. Most of this distortion can be eliminated with recalibration as shown in the monochrome reflectance image of the checkerboard pattern (right). The dimensions of the squares are 2 × 2 mm.



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