Tooth Guard for the Laryngoscope

University of PittsburghSenior Design – BioE 1160/1161

Nate AngeloffMike Matthews

Virginia Penascino Sean Ritchie

April 18, 2006

Mentors: Jim Menegazzi, PhD

Manuel Vallejo, DMD, MD

Overview

• A Laryngoscope is an instrument used to examine the interior of the larynx during intubation. The traditional laryngoscope can be difficult to use. It can cause oral cavity and soft tissue damage

• Oral cavity damage can include tooth fracturing

• We designed a tooth guard that would slide over the Miller blade to provide a cushion against the forces applied to the upper and lower teeth

• This product is used in pre-hospital emergency care and in the hospital setting

Background

• Dental injury is the most common medical legal complaint against anesthesia providers (33%-38%)

• Average cost = $1,672 ± $2,378 (0 – $8,038)• 62% of teeth damaged by the laryngoscope have

been previously restored or are associated with periodontal disease

• Incidence of dental injury• 0.02% - 0.7% (retrospective) • 12.1% (prospective)

• UPMC paid for $25,000 worth of dental repair from October to June 2000

Teeth Most at Risk

• Upper maxillary central incisors are most at risk

• Single tooth usually involved - only 13% > 1 tooth

• Upper left maxillary central incisor is most at risk (51%*)

5% 8% 16% 51% 19% 0%5% 8% 16% 51% 19% 0%

*

Facts

• Damage is 5x more likely with a pre-existing dental condition

• Most injuries crown fractures + partial dislocations• Non restored teeth incisal chipping• Isolated teeth dislodgement• Orthodontic treatment tooth mobility and root

resorption

Problem Statement

• Current Solutions• Gauze roll

• Oropharyngeal Airway

• Bite Block• Bitegard• Endoscopic

• Not for emergency situations

• Won’t work during a difficult intubation

Features & Benefits

• The laryngoscope is not being redesigned. Instead we are manufacturing a sheath to cover the points on the blade that apply pressure to the teeth

• The sheath will be made out of a soft, elastic material to provide ample cushioning for the patient’s teeth

• The guard was manufactured and fitted to the blade so that visibility and lighting are minimally affected

Design Requirements

• The guard must fit in the oral cavity• It needs to cover the area of the blade that

contacts the upper maxillary incisors• The width of the guard must be larger than

the blade so that it contacts more teeth• Using a soft material will cut down on

incidental impact damages• The least amount of material should be used

to ensure greatest amount of visibility. This also minimizes cost

Proposed Solution

• The insertion site is machined to the exact specification of the Miller blade• This could easily be made universal for other sizes and

different manufactured blades

• The increased width and flattened sides of the guard helps distribute the force over more than one tooth

Prototype Fabrication

• SolidWorks model was sent to quickparts.com

• The prototype was fabricated using PolyJet Tango Elastomer in stereolithography

Materials

• New PolyJet Tango material that simulates the feel of flexible materials such as rubber or silicone

• Tango Black is the softest material they provide with a SHORE A hardness of 61 durometers

• Shore (Durometer) test measures the resistance of plastics toward indentation and provides an empirical hardness value • Silicone rubber tubing

ranges from 40 to more than 65

Set Up

• Two models of the upper jaw were obtained from the Wiser center

• The teeth in the model were all joined

• The sides of the upper maxillary incisors were shaved down using a razor blade

• Each jaw model was super glued and screwed to a piece of wood

• The wood was on a hinge which allowed the model jaw to pivot while the force transducer was placed directly underneath

• Using a prying motion with the laryngoscope, the teeth were broken

Testing

• First we broke model teeth with the guard and without the guard

• After the model teeth were broken, we inserted human teeth into the jaw mold• The teeth were supplied by Dr. Vallejo and

drilled at the dental school• We were hoping for a larger force on the jaw

when the guard was used• Indicating the force was being dispersed over

more teeth, preventing any of them from breaking

Results

• First the teeth were broken without the guard, the average force required for fracture was 203.6 N

• These forces are for the model teeth, not real human teeth

Results (con’t)

• This is us breaking a tooth without the guard on the laryngoscope

Results (con’t)

• Next we attempted to break the teeth with the guard but were unsuccessful

• The guard spread the force out so much that none of the teeth broke, even when using as much force as possible

Results (con’t)

• This is us attempting to break a tooth with the guard on the laryngoscope

Results (con’t)

Force Required to Fracture Without Guard

1

2

3

4

Avg

170

180

190

200

210

220

230

Run

Fo

rce

(N)

Force Required to Fracture WithoutGuard

Force Required to Fracture Without Guard

170

180

190

200

210

220

230

Trial 1 Trial 2 Trial 3 Trial 4 Average

Fo

rce

(N)

Force Required to Fracture WithoutGuard

 Force Required to Fracture

Without Guard (N)Force Required to Fracture With Guard

(N)

Trial 1 221 No Fracture

Trial 2 211.5 No Fracture

Trial 3 188.2 No Fracture

Trial 4 193.8 No Fracture

Average 203.625 No Fracture

Results (con’t)

• Once the model teeth had been broken we drilled a hole in the model and inserted the human teeth

• We were unable to obtain data from the human teeth because the models broke before the teeth fractured

Jaw model after failure

Competitive Analysis

• Disposable and/or Sterilizable Cushioning Device for the Laryngoscope

• Teeth Protector for Laryngoscope Blade

Free Patents Online: freepatentsonline.com

• Laryngoscope Blade with Protective Insert

Competitive Analysis

• Current Solutions

(on the market)• Gauze roll

• 10/box – 10 boxes for $7.38

• Oropharyngeal Airway• ($0.70 each – in bulk $0.50

each)

• Bite Block – • BiteGard™ (50/box) ($65)• Endoscopic ($4.90 each)

• Used in approximately 2% of cases

• Our price - $1.20 per guard

BiteGard™

Competitive Analysis

• Strengths • Distributes load over more teeth to decrease force on

primary tooth• Disposable• Can be universal – Mac and Miller• For emergency use

• Weaknesses• Bulky• Slipping from desired location

Quality System Considerations

• Manufacturability• Simple Design

• Made out of PolyJet Tango Elastomer • Stereo lithography to simulate rubber

• Proposed Siloxane manufacturing

• Human Factors• Decrease the damage to the oral cavity caused by

intubation • Universal - Slides over Miller Blade but can be made

to slide over Mac Blade also • Easy to use• Disposable

FDA Regulation

• TITLE 21--FOOD AND DRUGS • CHAPTER I—FOOD AND DRUG ADMINISTRATION DEPARTMENT OF

HEALTH AND HUMAN SERVICES • SUBCHAPTER H--MEDICAL DEVICES  • PART 868 – ANESTHESIOLOGY DEVICES

• Subpart F – Therapeutic Devices • Sec 868.5820 Dental protector

• Identification: A dental protector is a device intended to protect a patient's teeth

during manipulative procedures within a patient's oral cavity • Classification: Class 1 • Class I (general controls): The device is exempt from the pre-market

notification procedures in subpart E of part 807 of this chapter subject to the limitations in 868.9

US Food and Drug Administration: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?FR=868.5820

Economic Considerations

Market size• One study indicates 500,000

intubations are performed worldwide per day

• http://web.mit.edu/cortiz/www/KristinThesis.PDF

• A second study stated that 12,000 intubations were performed by paramedics per year in Pennsylvania

• This number does not include in-hospital intubations

• http://www.medicalnewstoday.com/medicalnews.php?newsid=27634

Economic Considerations

• Siloxane with a shore hardness of 60 A will be manufactured by Instrumentation Industries or Injection-moldings.com• Cost = $15,000 + $0.20per• Selling price = $1.20 per guard• Potential market size =

• Earning potential

PopulationWolrdwide

US%3.4

105.6

102809

6

perYear000,845,7$)20.0)(1086.7(000,15$)20.1)($1086.7( 66

..1086.7105.182%)3.4( 66 SsUIntubationyear

sIntubation

Design Alternatives

• The width is the most important component in the design

• The height was decreased to remove unnecessary material

Work Breakdown

Nate

AngeloffMike

MatthewsVirginia

PenascinoSean

Ritchie

Design X X    

Clinical Interviews X   X  X

Material Research X X    

Stress Analysis   X  X

Prototype X X    

Testing X X  X X

DHF X X X X

Acknowledgements

• Manuel Vallejo, DMD, MD • John O’Donnell, CRNA, MSN• Jim Menegazzi, PhD• Mark Gartner• Generous gift from Dr. Linda

Baker and Dr. Hal Wrigley