effect of mouthguards on head responses and mandible...

Effect of Mouthguards on Head Responses and Mandible Forces

in Football Helmet Impacts

DAVID C. VIANO,1 CHRIS WITHNALL,2 and MICHAEL WONNACOTT2

1ProBiomechanics LLC, 265 Warrington Rd., Bloomfield Hills, MI 48304-2952, USA; and 2Biokinetics and Associates Ltd.,2470 Don Reid Drive, Ottawa, ON K1H 1E1, Canada

(Received 21 June 2011; accepted 8 September 2011)

Associate Editor Stefan M. Duma oversaw the review of this article.

Abstract—The potential formouthguards to change the risk ofconcussionwas studied in football helmet impacts. TheHybridIII headwasmodifiedwith an articulatingmandible, dentition,and compliant temporomandibular joints (TMJ). It wasinstrumented for triaxial head acceleration and triaxial forceat the TMJs and upper dentition. Mandible force anddisplacement were validated against cadaver impacts to thechin. In phase 1, one of fivemouthguards significantly loweredHIC in 6.7 m/s impacts (p = 0.025) from the no mouthguardcondition but not in 9.5 m/s tests. In phase 2, eight mouth-guards increasedHIC from+1 to+17% in facemask impactsthat loaded the chinstraps and mandible; one was statisticallyhigher (p = 0.018). Peak head acceleration was +1 to +15%higher with six mouthguards and 2–3% lower with two others.The differences were not statistically significant. Five of eightmouthguards significantly reduced forces on the upper den-tition by 40.8–63.9%. Mouthguards tested in this study withthe Hybrid III articulating mandible lowered forces on thedentition and TMJ, but generally did not influence HIC orconcussion risks.

Keywords—Protective headgear, Recreation and sport,

Concussion, Helmets, Sport equipment.

INTRODUCTION

Mouthguards are effective in protecting the mouthfrom orofacial injuries in contact sports and their use isrequired in many sports.3,15,17,20,39 While there is aconsensus that mouthguards prevent oral injuries, theireffectiveness in preventing concussion is either un-proven or they have no effect on risks. A number ofstudies have found no effect of mouthguards on con-cussion risks.12,13,17,19,21,22,25 Two have found no dif-ference with custom made mouthguards compared to

the boil and bite design.2,40 Other studies haveattempted to find an effect but found the data incon-clusive.4,31 A key reason for this state of knowledge is alack of suitable test methodologies to evaluatemouthguards in conditions where concussions occur,the relatively low rate of concussion during sportactivities and the difficulty in determining concussionon the field.

There is currently no validated test device to assessmouthguards, head responses, and concussion risksdue to impacts to the head, jaw or helmet, and therehas been limited testing.15,39 This study describes thedevelopment of an articulating mandible, compliantTMJ joints, dentition, and instrumentation for theHybrid III headform.1 The design and development wereconducted by Biokinetics (www.biokinetics.com).41

The temporomandibular joint (TMJ) is the locationwhere the condyles of the mandible (jaw) attach to thetubercle of the temporal bone of the skull. It is a hingetype of synovial joint, which allows the jaw to openand close.27 Loading of the jaw in a front to reardirection (anterior to posterior direction) or upward(inferior to superior direction) compresses the TMJand dentition causing head acceleration. The mandiblebiomechanics used to validate the biofidelity of thearticulating mandible and compliant TMJ joints weredeveloped in a doctoral thesis involving chin impactsof cadavers.6,8,9 What follows is an overview of themandible, design of the dentition and TMJ, biome-chanics of chin impacts and validation of an articu-lating mandible for Hybrid III testing of mouthguards.

The research reported here evaluated differentmouthguards in facemask impacts to the helmet fit onthe Hybrid III head with the articulating mandible.The chinstrap provided the loading of the mandible infacemask impacts to the helmet. Additional tests wereperformed with different helmets and impact conditions

Address correspondence to David C. Viano, ProBiomechanics

LLC, 265 Warrington Rd., Bloomfield Hills, MI 48304-2952, USA.

Electronic mail: [email protected]

Annals of Biomedical Engineering (� 2011)

DOI: 10.1007/s10439-011-0399-x

� 2011 Biomedical Engineering Society

https://webgateway.dartmouth.edu/,DanaInfo=www.biokinetics.com+

to assess the transfer of force to the mandible. The goalof the research was to establish test requirements forthe evaluation of mouthguards to address theirpotential to reduce concussion risks.

Pellman et al.28 presented an analysis of 182 severehelmet impacts of struck players in NFL games. In 174cases, the location of the helmet impact could bedetermined. Impacts were categorized as being at thefacemask (51 cases, 29.3%), facemask attachment tothe shell and brow pad of the shell (53 cases, 30.5%) orside and rear of the helmet shell (40.2%). The data wasrefined to the quadrant of the helmet and height ofcontact.29

Craig6 analyzed the facemask impacts of Pellmanet al.28,29 and subdivided them into those loading themandible as the helmet moved on the head and loadedthe chinstraps. That analysis showed that there werethree primary orientations of facemask impact, calledcondition A (31 cases, 17.8%), A¢ (11 cases, 6.3%), andA¢¢ (9 cases, 5.2%). The other impacts to the front ofthe helmet involved the frontal shell (F) and attach-ment of the facemask to the shell (B and UT). Theseimpact conditions were F (15 cases, 8.6%) on the frontbrow pad and B–UT (38 cases, 21.8%) on the face-mask attachment to the side of the shell. Based on thatanalysis, 29.3% of severe helmet impacts associatedwith concussion involved the facemask (A, A¢, and A¢¢)and 21.8% involved the facemask attachment to theshell (B and UT) where the helmet may move rearwardon the head. This indicates that 29.3–51.1% of helmetimpacts to struck players in the NFL sample involvedthe front of the helmet and the potential for the helmetto move rearward on the head loading the chinstrapand mandible.

MATERIALS AND METHODS

The mouthguard tests reported here were the cul-mination of a multi-year effort to define the biome-chanics of the mandible with chin loading, design anarticulating mandible for the Hybrid III dummy, vali-date the dummy to the biomechanical data from thecadaver testing and then conduct three series of testswith the mandible and mouthguards. Since much of theearlier work was part of a doctoral thesis by Craig6 andthe Hybrid III mandible design was reported at SAE,41

a condensed overview is provided to establish the basisfor the testing reported here. The interested reader canfind more details in the earlier studies.6–9,28,29,38,41

The Temporomandibular Joint (TMJ)

The TMJ involves the mandibular condyles, whicharticulate with the mandibular fossa and articular

tubercle of the temporal bone.26,37 The articular discconsists of fibrocartilage that is positioned between thearticular surfaces dividing the joint into two com-partments.26,37 The TMJ condyles rotate and translatein the inferior, anterior, and lateral directions. Rota-tion of the condyles occurs in the joint cavity inferiorto the articular disc; and, it translates in the cavitysuperior to the disc.

The mechanical TMJ design replicates the essentialranges of motion of the human temporomandibularjoint in rotation and inferio-anterior direction. It isconstrained to only small lateral motion in this design.The TMJ design mimics the maximum range of motionof the condyles. When in a neutral position with teethin contact, the condyles are against the mandibularfossa and supported on the posterior and superiorsurfaces. From this position, there is only about 2 mmposterior movement.32 From the neutral position,the condyles move about 10–12 mm anteriorly and5–6 mm inferiorly.32 There is also 0.75 mm of travel inthe medial and lateral directions.32

The 5–6 mm inferior movement of the condyles iscritical to normal function of the TMJ joint. TheTMJ joint rotates like a plain hinge to open themouth. Maximum mouth opening is approximately40–60 mm.42 The rotation produces approximately25 mm of the mouth opening. The mandible can alsomove laterally about 10 mm with one condyle remain-ing stationary and the other moving anteriorly.32 Forany anterior movement, the condyle must drop and notimpinge on the articular tubercle. This lateral move-ment is not addressed in the current design, but may beimportant is some loadings of the jaw. When the jaw isat rest, the teeth are typically not in contact and themandible descends a distance of 3.5–4.8 mm.14 Thisvertical drop is necessary when evaluating mouth-guards, because the mandible needs to drop withouthinging to keep the upper and lower teeth parallel toeach other and in contact with the mouthguard.

Design Criteria

The articulating mandible for the Hybrid III dum-my was designed and developed by Biokinetics.41 Thedesign provides the following biofidelity: (1) theheadform has an articulating mandible fit with upperand lower dentition to allow the installation ofmouthguards, (2) the design is based on the 50th Hy-brid III headform to allow use of the Hybrid III 50thneck and standard triaxial accelerometers inside theheadform, (3) the mass and center of gravity of thedesign is similar to the Hybrid III headform, (4)the headform, mandible, and dentition represent a 50thpercentile male, and (5) the packaging of the mandibleand associated instrumentation permits the headform

VIANO et al.

to be fit inside current football helmets and securelyattach the chinstraps.

Figure 1 is an expanded view of the articulatingmandible added to a Hybrid III headform. The HybridIII headform was selected for a number of reasons. Itfacilitated prototyping and manufacturing because thealuminum skull of the Hybrid III. The aluminum skullalso provided a solid base for the attachment of theforce transducers.

Mandible and Dentition

The mandible design simplified the complex humangeometry to facilitate manufacturing. The mandiblewas developed using the HUMOS project geometry33

and simplified geometry.11 The mandible was initiallylocated in the Hybrid III skull using the internalgnathion landmark and the Hybrid III Frankfort-mandibular plane angle of 20�.16 The normal Frank-fort-mandibular plane angle (FMA) is 25� ± 5�.10 Themandible angle matches the NOCSAE chin locationwhile maintaining the TMJ location. This resulted inthe headform having a FMA of 26�.41

The dentition geometry was from a physical modelof an ideal dentition (Class 1 Ideal Arch, Models Plus,Kingsford Heights, IN). Points on this model weredigitized and used to create the dentition for thearticulated mandible. A common reference plane wasestablished between the upper and lower dentitionmodels so that the relationship between the two sets of

FIGURE 1. Schematic of the articulating mandible, dentition, and instrumentation used in the modified Hybrid III headform.

Effect of Mouthguards

teeth could be maintained in the CAD model. Bothparts were manufactured from stainless steel. The up-per and lower dentitions are simplified representationsof the human anatomical geometry to facilitate man-ufacturing. The occlusal contact surfaces of bothdentitions involve planar surfaces.

Mandible and Head Instrumentation

Three triaxial force sensors (Model 260A11, PCBPiezotronics, Depew, NY) were designed into thearticulating mandible headform. One force sensor issituated between the upper dentition and the skull. Theother twowere placed at left and right TMJ. The sensorshad a sensing range of x–y = 2,220 N and z = 4,450 N.Fxz is the resultant shear force in the xz-plane, while FYm

is the y-direction force in the medial direction. For thedentition, Fz is the force in the z-direction (compression)and Fxy is the resultant shear force in the xy-plane. Theheadform used the typical triaxial accelerometers at thehead center of gravity.35,36

Hybrid III Mandible Design

A modification was made at the base of the HybridIII skull. The TMJ assemblies, upper dentition, neckbracket, and instrumentation attach to the modifiedskull base. The modified Hybrid III skull was loweredonto and fixed to the base completing the assembly. Afeature was added to simulate the muscle and tissuesthat maintain the mandible in a neutral position. Theability to simulate a clenched jaw was not considered inthis stage of the design. Extension springs were at-tached to the lower dentition and connect to the baseof the skull. They are angled so that the mandiblemaintains a neutral position that is centered on theocclusion and shifted to the posterior limits of themandible range of motion. When the jaw is closed withno mouthguard, there is about 22.3 N clenching forcefrom the springs.

Figure 2 shows that the TMJ joint allows 5 mm ofinferior travel and 10 mm of anterior travel. The TMJjoint incorporates a triangular slot in the mandiblewhich replicates human motion under impact loading.The triangle allows 5 mm of anterior travel in theinitial vertical descent and the mandible drops the full5 mm inferior displacement to obtain the maximumanterior motion. The articulating mandible is strongerand stiffer than a human mandible so that it is not afrangible component. The mandible was considered arigid object and all of the compliance in the TMJ-mandible system was designed into the TMJ joint.Based upon the cadaver work,6,8,9 the design goal wasto have the TMJ–mandible system deflect 2.5 mmunder a load of 1,000 N.

An annular ring and polyurethane bumper providethe compliance in the articulating mandible.41 Thebumper supports a pin which extends laterally into themandible slot. When the pin bottoms out in the slot,the bumper provides up to 3 mm of compliance inanterior–posterior and superior–inferior directions. Inthe medial–lateral direction, 1 mm of travel is allowedboth ways. The bumper attaches to the force sensor.The design of the condyle bumper assembly allowedfor the use of different stiffness materials to match thebiofidelity characteristics of the human impact bio-mechanics.6,8,9

The mandible design maintained the mass andcenter of gravity as the Hybrid III headform. Theunballasted mass of the design was 0.569 kg lighterthan a Hybrid III skull. This includes the articulatingmandible, dentitions, TMJ joints, and force transduc-ers but not the acceleration instrumentation. Ballastwas used (R.A Denton, Inc., Rochester Hills, MI). Thecenter of gravity (cg) of the unballasted headform wasestablished using a balance beam, and the ballast was

FIGURE 2. Articulating mandible fit to the Hybrid III headwith head skin (upper right) and without skin (upper left) andexpanded view of the TMJ joint and range of motion (lower).

VIANO et al.

added to bring the cg within the Hybrid III specifica-tion. The mass of the mandible and lower dentitionassembly is 301 g. Zhang et al.43 defined a mandibularlength, which would suggest a 108 g mass with mar-row. This mass does not include the surrounding softtissue. Koolstra and van Eijden18 weighed a sectionfrom a cadaver and obtained a 440 g mass, which in-cluded all of the surrounding soft tissue. Maintainingthe Hybird III moments of inertia was not a designcriterion and any changes with the articulating man-dible have not been determined.

Preliminary tests were conducted at Biokinetics toevaluate the articulating mandible, ensure the mandi-ble–TMJ mechanism behaved as intended and the loadsensing instrumentation functioned. This involved theheadform being placed on an adjustable yoke so a twinwire guided mass dropped on the mid-point of theskin-covered chin. This directed the force through theTMJ condyle pins. The mass of the impactor was2.4 kg and it was dropped from a height of 0.3 m. Anaccelerometer (7702A-50, Endevco Corp., San JuanCapistrano, CA) was mounted to the impactor tomeasure the force on the mandible. A thin piece ofrubber was placed between the upper and lower den-tition to prevent ringing due to teeth-to-teeth impact.Displacements were not measured. The results fromthis series showed reasonable forces compared to thecadaver response.41

Articulating Mandible Validation

The impact biomechanics of the human mandiblewas studied by Craig et al.6–9. The work producedcorridors for impact force vs. chin resultant displace-ment as a result of impacting the mandible of 8 post-mortem human specimens. For the dummy validation,two bumper combinations were evaluated. One had aShore 70A durometer and the other a 95A durometer.Both bumpers had annular slots to achieve a bi-linearstiffness response.7

Figure 3 shows data from a 2.4 kg guided mass thatwas dropped from 0.3, 0.4, and 0.5 m and a 5.2 kg massdropped from 0.5 m. The headform was impacted incondition #1, which was a midsaggital impact throughthe chin and condyles.7,8 Impact force was measuredusing an accelerometer on the impactor and displace-ment was measured from high-speed video. The biofi-delity comparison showed that the Hybrid IIIarticulating mandible had the best biofidelity with 70Adurometer TMJ bumpers. The 70A durometer bumperresponse followed the stiffer side of the force–dis-placement curve for human biomechanical responseduring initial loading, but then was in the middle of thecorridors as the force and displacement increased.41

These tests caused no damage to the mandible or

instrumentation; and, there were no abnormalities inthe mechanical responses of the articulating mandible.

A standard drop test was conducted with the Hy-brid III head verifying that the structural modificationsof the Hybrid III headform did not affect the foreheadimpact characteristics. The headform was dropped376 mm with forehead impact on a steel plate.16 Thepeak resultant acceleration must be within 225–275 g,lateral acceleration must be <15 g, and oscillations inthe acceleration cannot >5% of the pulse. The artic-ulating mandible headform met these requirements.1,35

Phase 1: Mouthguard Testing

The first series of tests of mouthguards evaluated thesensitivity, utility, and function of the articulatingmandible headform. Five commercially available boil

2.8 kg, 300 mm 2.8 kg, 400 mm

2.8 kg, 500 mm 5.2 kg, 500 mm

0

1000

2000

3000

4000

0 1 2 3

Displacement (mm)

Fo

rce

(N)

FIGURE 3. Biokinetics’ drop stand set up with Hybrid IIIhead with chin-skin removed for the photo (bottom) and val-idation results with a 70A durometer condyles joint washer(top).41 The straight black lines are boundaries for the cadavertesting.6–9


and bite mouthguards were sourced for this testing,including (1) generic, (2) mouth and lip, (3) ShockDoctor Ultra, (4) RBK Elite, and (5) Brain PadPRO + PLUS. The mouthguards were formed in aspecially designed jig, which used the upper and lowerdentition from the dummy head and maintained thecorrect alignment. A servo-motor controlled forcefeedback press was used to apply the ‘bite’ force to theheated mouthguards. The manufacturers’ forminginstructions were followed for each mouthguard. Inaddition, the no mouthguard condition was tested toprovide a reference for themandible andhead responses.

Figure 4 shows an example of the neutral position ofthe pin in the TMJ joint without a mouthguard and thedisplacement of the mandible slot with the insertion ofthe mouthguard. The mandible headform was mountedon a Hybrid III neck, which was attached to a table on alinear bearing slider system. The neck mount and tableprovide adjustment of the rotation and pitch angles ofthe head–neck assembly. The headform was subjectedto football helmet impacts using the linear impactordescribed by Pellman et al.30 The impactor uses a linearram that is energized by a pneumatic piston. Theimpacting face of the ram has a foam and plastic capassembly, which simulates the impact and frictioncharacteristics of an impacting football helmet.

The phase 1 impacts were directed at a locationlabeled site 5, which is low on the facemask andslightly offset to load the chinstrap and mandible.Figure 5 shows the impact orientation. Various siteswere evaluated in earlier tests using a Hybrid IIIheadform, which had the chin machined off and re-attached though a load cell. Site 5 was determined tobe the impact location which produced the greatestloading through the chinstrap (see Appendix). Thesetests guided research on helmet impacts in footballcausing high mandible loads.6

The search for sites causing high chinstrap loadspreceded Craig’s work6 defining the A¢ and A¢¢ condi-tions. Site 5 is similar to the A¢ condition used in a largeseries of helmets,38 but it is oblique to the midsaggitalplane. The mandible development and mouthguard

testing preceded those tests, and site 5 was eventuallyreplaced by the A¢ and A¢¢ conditions.38 Additionaltests were conducted with the articulating mandibleand again showed higher mandible loads for site 5(see Appendix). The alignment of the head and table38

for site 5 had y = 51 mm and z = 76 mm tableadjustment and a = 228� and b = 0� neck angles. Forsite A¢, y = 15 mm, z = 35 mm, a = 0�, and b =

210�. For site A, y = 27 mm, z = 20 mm, a = 225�,and b = 7�.

Impacts were at a target velocity of 6.7 and 9.5 m/susing a Schutt Air Varsity Commander helmet. Pell-man et al.28,29 determined that 9.3 m/s was the averageimpact speed for a series 25 NFL game impacts caus-ing concussion. The lower speed impact represents animpact having half the impact energy. Three trials wereconducted at each speed and with each mouthguardgiving two sets of 18 tests. Triaxial head accelerationwas recorded and used to calculate severity index (SI)and head injury criterion (HIC). In this study, two SIvalues are reported using a 2 and 5 g trigger for thecalculation. HIC was calculated using a 36 ms dura-tion (HIC36). Triaxial forces at the upper dentition andat both TMJ joints were measured.

Phase 2: Evaluation of Mouthguards

A second series of helmet impacts was conducted toexplore the influence of different mouthguards on headacceleration, HIC, upper dentition force, and TMJjoint forces. The eight mouthguards tested includedthe: (1) mouth and lip, (2) Gel Max, (3) gravity, (4)power double, (5) PRO + PLUS, (6) EVA 4 + 3, (7)EVA 3 + 3, and (8) EVA 4 + PRO 3. Custom EVAmouthguards were supplied by Dr. Paul Piccinini,team dentist for the Toronto Argonauts of the Cana-dian Football League (CFL) who used the upper

FIGURE 4. Articulating mandible fit to the Hybrid III headwith (right) and without (left) a mouthguard in place showingthe change in the condyle position in the TMJ.8,41

FIGURE 5. Impact site 5 oblique on the faceguard. This isclose to the A¢ condition eventually used in football helmettests.8,38

VIANO et al.

dentition from the mandible headform to customlaminate the mouthguards. Baseline tests were againconducted without a mouthguard.

The 27 tests used the Schutt DNA Pro helmet,because the helmet used in the preliminary testing hadbecome discontinued. The Schutt DNA Pro was foundto be one the best performing helmets in terms of headresponses in a recent evaluation of football helmets.38

The impacts were at a target speed of 7.4 m/s at site A¢.This velocity was intermediate of the phase 1 testingcondition. Again, triaxial head acceleration wasrecorded and used to calculate SI and HIC. For thesetests, HIC was calculated using 15 ms duration (HIC15)because the safety community had moved to that pro-tocol with the revision of FMVSS 208 injury criteria.

Phase 3: Effects of Different Helmets

The third series of helmet impacts was conductedusing the linear impactor to explore the influence ofdifferent helmet designs on mandible forces. The hel-mets evaluated were the: (1) Speed, (2) Revolution, (3)Air XP, (4) DNA, (5) Air Varsity Commander, and (5)VSR-4. The first four helmets are considered ‘‘mod-ern’’ designs that have been produced over the pastyears recognizing the impact conditions causing con-cussion in NFL players as well as performing to thestandard NOCSAE certification requirements. The lasttwo are typical of the ‘‘older’’ helmets designed solelyfor the NOCSAE requirements. Impacts were per-formed at site A¢, which was one of the facemask im-pacts in recent helmet testing.6,28,29 The target impactvelocity was 7.4 m/s. Three repeats were conducted foreach test condition. The mandible was fit with a cus-tom formed 2 mm thick EVA mouthguard for all ofthe tests.

Statistical Analyses

The average and standard deviation in responses aregiven for repeat tests. The significance of differences inresponses for the different mouthguards from thebaseline (no mouthguard) condition and between2010s and 1990s helmets was determined using Studentt test assuming unequal variance and a two-sided dis-tribution. The t test was performed using the analysispackage in Excel.

RESULTS


The first series of tests is summarized in Table 1.The lower speed tests averaged 6.85 ± 0.05 m/s and

higher speed tests 9.41 ± 0.02 m/s. Peak head accel-eration and HIC36 are shown in Fig. 6. The testingshowed that the mouthguard remained in place andcould affect the mandible and head responses in thesame test condition compared to a no mouthguardcondition, proving a means of studying the perfor-mance of the mouthguards in helmet impacts. Thistesting provided a first opportunity to view the kine-matics of the articulating mandible in helmeted im-pacts typical of on-field play and measure impactresponses. The design proved robust and no functionalissues were found.

Table 2 lists the normalized responses and stan-dard deviations along with the t value and p valuefrom the Student t testing for significance of differ-ence with the mouthguards. Those conditions withsignificantly different responses (p< 0.05) comparedto the no mouthguard response are highlighted withgrey background for the target 6.7 and 9.5 m/s im-pacts. In terms of head responses, the Brain Pad ProPlus had significantly lower head responses in the6.7 m/s tests; but, there was not a significant differ-ence in head acceleration and HIC in the higher speedimpacts with the Brain Pad Pro Plus. Several of themouthguards significantly lowered the total mandibleforce in the low and high-speed tests; there was onethat significantly increased the load in the higherspeed impacts.


Table 3 gives the peak responses for each test of themouthguards and baseline no mouthguard condition.The data includes head acceleration and HIC15, theupper dentition loads, and the left and right TMJ jointforces along with the total load on the mandible. Theaverage impact velocity was 7.35 ± 0.06 m/s for the 27tests. Figure 7 shows the peak head acceleration andHIC15 for the eight different mouthguards normalizedby the impact response of the no mouthguard condi-tion. This shows the relative responses using the nomouthguard condition as the baseline. The normalizedstandard deviation is also shown. Table 4 lists thenormalized responses and standard deviations alongwith the t value and p value from the Student t testingfor significance of difference with the mouthguards.Those conditions with significantly lower responseshave the p value shown with grey background.

Figure 7 and Tables 3 and 4 show that for six of theeight mouthguards tested, the average peak headacceleration increased above that of the no mouth-guard condition. In two cases, the average peakacceleration was lower, but none of the mouthguardsproduced a statistically significant change in peak headacceleration. For all mouthguards, HIC15 increased.


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Mandib

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Tota

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(g)

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Upper

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Left

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(2g)

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FR

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Fxz

Peak

FY

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FR

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Fxz

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FY

m

6.7

m/s

impacts

No

guard

6.8

53.8

101

99

84

276

252

150

607

433

518

846

845

88

1,2

82

6.9

57.7

111

106

85

211

178

160

599

444

489

869

863

103

1,2

85

6.8

52.7

105

101

85

286

247

152

601

441

474

866

865

90

1,3

08

Generic

6.8

55.6

111

101

79

227

190

133

538

430

451

790

787

74

1,1

69

6.8

55.5

112

107

86

222

184

128

567

436

497

820

814

93

1,1

95

6.8

51.0

109

101

89

229

191

142

570

380

505

819

813

106

1,1

62

Mouth

and

lip6.9

51.1

111

103

87

188

135

144

542

378

503

767

766

79

1,1

39

6.9

58.6

118

115

82

204

148

142

601

441

465

797

797

86

1,2

47

6.9

64.3

129

124

90

164

72

148

603

461

517

772

772

97

1,2

56

Shock

Docto

rU

ltra

6.8

50.3

105

93

74

348

290

193

474

302

458

736

736

72

1,0

43

6.9

49.1

111

111

87

216

176

131

552

357

513

750

749

77

1,1

22

6.9

51.7

115

102

86

291

252

150

522

312

432

740

738

83

1,1

10

RB

Kelit

e6.9

50.4

113

105

89

243

172

174

518

401

450

762

762

67

1,1

62

6.9

56.4

125

116

90

210

150

153

608

432

498

790

790

80

1,2

46

6.9

49.0

113

113

96

248

186

179

583

388

526

774

769

80

1,2

03

Bra

inP

ad

PR

O+

PLU

S

6.7

43.4

76

76

57

187

170

104

340

152

334

540

540

82

844

6.8

47.8

90

89

61

210

188

117

493

190

480

539

539

80

854

6.9

41.9

89

89

69

218

192

110

476

173

463

586

586

75

922

9.5

m/s

impacts

No

guard

9.4

62.5

357

341

286

507

495

299

1,0

14

397

1,0

07

1,1

25

1,0

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VIANO et al.

One HIC15 was 17.4% higher, which was highlightedin grey and was significantly different than the nomouthguard condition. This was a statistically signifi-cant increase in HIC15 (p< 0.02). There were a fewstatistically higher right TMJ FYm with three mouth-guards, but the force levels were very low, typicallybelow 65 N.

Figure 8 shows the peak resultant dentition forceand the peak vertical (z-axis) and shear dentition force(xy-axes). All mouthguards reduced forces on thedentition. In five of the eight mouthguards, thereduction was statistically significant varying from40.8–63.9% lower in dentition forces (see Table 4).

Figure 9 shows the peak resultant force, peakbilateral force (xz-axes), and the peak lateral force(FYm) on the left and right TMJ. Many of the left TMJloads were lower with mouthguards, although four hadhigher average values. The left TMJ was on the impactside of the helmet. For the right TMJ, the peak lateralforce (FYm) was substantially higher for four of themouthguards, however, the peak value was only 18 Nfor the no mouthguard condition. The other forces onthe TMJ were generally lower.

Phase 3: Effects of Different Helmets

Table 5 shows the peak resultant head accelerationand HIC for the tests with different helmets: (1) Speed,

(2) Revolution, (3) air XP, (4) DNA, (5) Air VarsityCommander, and (5) VSR-4 tested at the target speedof 7.4 m/s in the A¢ impact condition. These 18 testsaveraged 7.33 ± 0.17 m/s. Figure 10 plots the peakresultant head acceleration and HIC15 for the differenthelmets tested. Figure 11 shows the upper dentition z-direction force time histories for the different helmets.The Schutt Air XP had the highest early dentitionloads and the Riddell Revolution had essentially no z-direction dentition forces in the tests. These differencesare a result of different helmet kinematics in the test-ing. The head and mandible responses with the four2010s helmet were compared to the two 1990s styles.None of the head responses was significantly differentand only two of the mandible loads were statisticallydifferent. The peak upper dentition shear was 33.9%lower (t = 22.96, p = 0.03) and the left TMJ peakFYm lateral force was 43.7% lower (t = 3.31, p = 0.01)with the 2010s compared to the 1990s helmets. Boththese responses involve the lateral or shearing effects ofthe mandible movement by the chinstrap loading.

DISCUSSION

Effect of Mouthguards on Head Responses

The phase 2 tests reported here found that mouth-guards generally increase HIC for impacts to thefacemask of a modern helmet and would not be ex-pected to reduce concussion risks in conditions wherethere are high loads on the chinstraps and mandible.The majority of tests show no statistically differenthead acceleration or HIC. In the phase 1 testing, theBrain Pad Pro Plus mouthguard had significantlylower head accelerations in the 6.7 m/s tests comparedto the no mouthguard condition. The peak accelera-tion was reduced from 54.7 to 44.4 g (t = 4.45,p = 0.011) and HIC36 from 85 to 62 (t = 6.23,p = 0.024). However, there was no statistical differ-ence in head acceleration (68.1 vs. 57.3, t = 2.21,p = 0.11) and HIC36 (282 vs. 264, t = 1.41, p = 0.29)in the 9.5 m/s tests. Since the low speed tests involvedlow head responses, the higher speed tests are morerelevant to the conditions associated with concussion.In the higher speed tests, there was no significant effectof the Pro Plus mouthguard on head responses. Inaddition, the model of football helmet used in thephase 1 tests caused a noticeable upward deflection ofthe facemask on impact, which caused a distinctiveupward pull of the helmet strap on the chin. In thephase 2 testing with a 2010 helmet, the upwarddeflection was not observed. Considering the vastcombination of old vs. new helmets, chinstrap geom-etries and attachments, facemask shapes, there remains

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FIGURE 6. Peak resultant head acceleration, SI5g and HIC36

in phase 1 tests with different mouthguards normalized by theno mouthguard response in helmet impacts at 6.7 and 9.5 m/starget velocities.


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a need for further study of helmets, chinstraps andmouthguards.

To our knowledge, this study is the first to evaluatethe effects of mouthguards in laboratory testing withan articulating mandible designed into the Hybrid IIIdummy. It establishes methods for evaluating theinfluence of mouthguards, chinstraps and facemaskson TMJ, dentition and head responses. The methodsprovide controlled laboratory testing with a dummyhead and mandible that has biofidelity in mimickingthe essential responses of the mandible and head dur-ing helmet impacts and loading by the chinstrap.7,8,41

The test methods and modified Hybrid III dummyhead provide a basis for the development of a standardtest procedure for the evaluation of mouthguards;however, no specific target performance levels havebeen established. Our analysis focused on comparingthe mouthguard performance to the no mouthguardcondition for helmet impact sites that load the chin-straps.

Mouthguards tested in this study generally did notinfluence head responses. As noted by Craig,6 theremay be more potential to lower head responses bydesigning load-limiting chinstraps that reduce the forcetransferred to the mandible and head from the chin-strap. In addition, these tests show that only thethickest mouthguards may influence head responses inthe facemask impacts. For impacts with force directlyon the helmet shell and helmet padding, the fraction offorce on the head from the mouthguard is low com-pared to the direct loading by the helmet padding (seeAppendix). This reduces the possibility that a mouth-guard may influence head responses. With impacts onthe facemask and loads on the head primarily from thechinstrap, a greater fraction of the load on the head isfrom the mandible. In these cases, the compliance ofthe facemask, chinstraps, and mouthguard arepotential factors related to head responses.

Mandible Loads

There has been only one study of the forces on themandible from chinstraps in football helmet impacts.Rowson et al.34 instrumented chinstraps in a VSR4helmet and determined mandible loads of 568 ± 80 Nat 6.5 m/s and 805 ± 64 N at 9.0 m/s for a frontalimpact to the brow region. These loads are about halfof what was found in the phase 1 testing reported here.The peak mandible load was 1142 ± 142 N at 6.8 and1542 ± 145 N at 9.4 m/s. Obviously, the test condi-tions are different. The current series did not includefrontal impacts to the brow region of the shell, whichmay explain the higher loads in these tests. The highestmandible loads occurred in the phase 3 testing. Theywere 2105 ± 356 N for impacts at 7.3 m/s.

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Effects of Different Helmets

Table 5 shows that different helmets, faceguardgeometry, and chinstrap attachments can affect howthe mandible is loaded during faceguard impacts, suchas in the A¢ condition. If the faceguard deflects thehelmet upwards, the chinstraps pull upwards on the

chin, loading the mouthguard, followed by rearwardmovement causing varying loads on the mandible. Ifthe faceguard deflects the helmet downward, thechinstrap pulls the chin open immediately, eliminatingany involvement of the mouthguard.

Figure 12 is an example of helmet motion down-ward for a site A impact. The impact causes the face-guard to rotate downward pulling on the chinstrap andopening the mouth as the helmet rotates about thebrow region of the shell. Newer helmets, such as theSchutt DNA and Riddell Revolution, cause the man-dible to open quickly in A and A¢ faceguard impacts.Older helmets, such as the Schutt Air Varsity Com-mander and Riddell VSR-4, cause loading into themouthguards tending to compress the teeth against themouthguard. These effects deserve further evaluation.

Energy Absorbed by Mouthguards vs. Head KineticEnergy

There is a theoretical question about the potentialfor energy to be absorbed in a head impact by com-pression of a mouthguard. For the limited conditionswhere the mandible is compressed in a football helmet

TABLE 3. Impact responses in phase 2 testing of different mouthguards at 7.4 m/s at site A¢.

Mouthguard Trial Speed

Head responses Mandible forces (N)

Total

Peak

accel. (g) SI (2 g) HIC

Upper dentition Left TMJ Right TMJ

Peak

FR

Peak

Fz

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Fxy

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FR

Peak

Fxz

Peak

Fxz

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FR

Peak

Fxz

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FYm

None 1 7.2 46.0 122 98 380 379 172 1,121 1,120 129 796 769 12 1,791

2 7.3 55.4 124 99 494 489 201 1,103 1,100 185 966 930 30 1,959

3 7.4 52.1 139 109 383 381 209 679 648 268 1,177 1,153 12 1,742

Shield mouth and lip 1 7.4 55.9 135 116 192 191 151 572 564 151 930 917 7 1,429

2 7.4 55.5 150 124 171 170 150 692 682 174 1,004 987 2 1,635

3 7.4 51.3 125 102 174 155 161 691 677 213 921 911 38 1,540

Shock Doctor Gel Max 1 7.4 50.3 127 106 208 205 107 860 855 109 561 554 44 1,330

2 7.4 49.2 130 110 126 122 116 817 810 125 580 571 41 1,259

3 7.4 48.8 115 93 120 94 117 821 819 138 588 575 61 1,201

Shock Doctor Gravity 1 7.4 45.9 118 98 237 235 111 890 888 130 664 654 33 1,480

2 7.3 48.9 119 104 317 315 139 980 978 136 741 729 18 1,603

3 7.3 54.1 139 121 297 296 138 933 927 141 873 861 14 1,732

Shock Doctor Power Double 1 7.3 55.3 136 111 362 359 111 715 709 169 517 505 41 1,237

2 7.4 55.9 146 124 111 106 109 619 614 140 473 470 53 1,097

3 7.4 51.4 133 111 288 285 127 686 684 114 671 659 39 1,390

Brain Pad Pro + Plus 1 7.4 54.3 133 109 363 359 131 666 660 157 568 559 59 1,265

2 7.4 48.7 118 99 348 347 120 601 598 147 623 612 69 1,336

3 7.3 52.6 136 113 318 316 117 583 577 118 649 638 42 1,354

Laminated EVA 3 + 4 1 7.4 54.6 143 119 242 238 144 1,027 1,025 169 586 577 22 1,511

2 7.3 56.9 155 125 182 181 166 1,109 1,105 169 827 810 36 1,863

3 7.3 52.3 146 115 317 308 168 947 946 185 1,057 1,036 65 1,917

Laminated EVA 3 + 3 1 7.3 51.1 132 109 160 73 138 790 783 198 756 739 5 1,456

2 7.3 53.3 133 107 199 193 140 874 869 145 853 831 3 1,637

3 7.5 51.8 132 108 239 239 128 849 843 178 848 826 10 1,555

Laminated EVA4 + PRO3 1 7.3 54.1 135 105 244 243 139 1,224 1,221 139 770 754 23 1,937

2 7.3 56.4 158 129 218 215 142 932 930 163 839 826 25 1,689

3 7.3 52.2 136 112 281 281 133 903 897 157 828 812 7 1,674

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FIGURE 7. Peak resultant head acceleration and HIC15 inphase 2 tests with different mouthguards normalized by theno mouthguard response in helmet impacts at a target 7.4 m/sat site A¢.

VIANO et al.

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impact, it is possible to estimate the kinetic energy thatcan be absorbed by deformation of a thickness ofmouthguard. This is a simple calculation aimed atframing the amount of energy a mouthguard mayabsorb by compression. It does not include lateraldeformation or rate-dependent effects that are part ofthe overall deformation of a mouthguard in a helmetimpact. For example, the resultant dentition loadswere 24% higher than the z load (232 N vs. 187 N) forthe 6.8 m/s impacts and 15% higher (600 N vs. 542 N)for 9.4 m/s impacts because of shear loading in thephase 1 testing. Nonetheless, a simple model offersinsights about the level of energy that can be absorbedby a thickness of padding.

The kinetic energy of the head was determined byusing the re-creation of NFL game impacts.28,29 Thatstudy found the average helmet impact velocity of9.31 ± 1.90 m/s and change in velocity of the struckplayer’s head (delta V or DV) was 7.22 ± 1.80 m/s.Four different head sizes were considered, two youthsat 6 and 10 years old and two adults at the 50th and95th percentile size male adult. The head mass (m) wastaken from Mertz et al.23,24 The kinetic energy ofthe struck player’s head was calculated by KE =

0.5 mDV2. Three different thickness mouthguards wereconsidered, 4, 12, and 20 mm. The amount of ab-sorbed energy (EA) by compression of the mouthguardwas determined by assuming a peak force (F) of 500 Nat full compression. Since mouthguards are made ofpolymer materials, full compression occurs at about60% of the initial thickness (D). A linear increase inforce was assumed with compression of the mouth-guard, so the absorbed energy was calculated byEA = 0.3FD.

Table 6 shows the calculations of head kineticenergy, absorbed energy and the fraction of EA fromthe mouthguard for various helmet impacts. Forexample, the average condition for concussion in the

NFL involves a head delta V of 7.22 m/s. A 12 mmthick mouthguard has the potential to absorb 2.0% fora 6-year-old child but on 1.4% of the energy trans-ferred to the head of a 95th male. The thickestmouthguards have the potential to absorb only 2–3%of the energy transfer in typical NFL helmet impactscausing concussion.

Mouthguard Influence on HIC

In most of the tests reported here, HIC was statis-tically similar with the mouthguards tested comparedto the no mouthguard condition. Some tests involvedhigher and one lower HIC indicating the generalfinding that mouthguards do not have a significantinfluence on head responses or concussion risks. Forthe situations with higher HIC, the mouthguard maychange the orientation of the TMJ by the insertion ofthe mouthguard allowing the forces on the mandible tobetter transfer to the head increasing head accelera-tions, the duration of loading or the pulse shape. HICis related to the peak head acceleration raised to the 2.5power times the duration of impact.5 The role ofmouthguards to change head acceleration, duration,and pulse shape needs further investigation. Themouthguards tested here generally did not influencehead responses or concussion risks based on HIC withthe Hybrid III articulating mandible; however,mouthguards are only one aspect of the compliance

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FIGURE 8. Peak forces on the upper dentition, including theresults, vertical (z), and shear (xy) loads normalized by the nomouthguard response for phase 2 tests at a target 7.4 m/s atsite A¢.

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FIGURE 9. Left and right TMJ joint forces responses withdifferent mouthguards normalized by the no mouthguardresponse in helmet impacts at the target 7.4 m/s at site A¢.

VIANO et al.

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provided by the faceguard, chinstraps, and mouth-guard in facemask impacts.

LIMITATIONS

As with any dummy development and testing, thereare limitations from the constraints of designing adurable test device with sufficient anthropometry,range of motion, and biofidelity to approximate ahuman. There are always trade-offs between designinga simple, robust device compared to the complexitiesof the human anatomy and impact response. While wehave strived to achieve a reasonable balance with the

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100

120

140

160

Sp

eed

Rev

olu

tio

n

Air

XP

DN

A

Air

Var

sity

VS

R-4

0

10

20

30

40

50

60

70

Peak Resultant Accel. (g)

FIGURE 10. Peak head acceleration and HIC15 with differentfootball helmets in phase 3 in a 7.4 m/s impact at site A¢ withthe Eva 2 mouthguard.

-200

-100

0

100

200

300

400

0 5 10 15 20 25 30 35

0 5 10 15 20 25 30 35

0 5 10 15 20 25 30 35

0 5 10 15 20 25 30 35

0 5 10 15 20 25 30 350 5 10 15 20 25 30 35

Up

per

Den

titi

on

Fz

(N)

Riddell Speed

Test 1

Test 2

Test 3

-200

-100

0

100

200

300

400

Up

per

Den

titi

on

Fz

(N)

Riddell Revolution

Test 1

Test 2

Test 3

-200

-100

0

100

200

300

400

Up

per

Den

titi

on

Fz

(N)

Time (ms)

Schutt Air XP

Test 1

Test 2

Test 3

-200

-100

0

100

200

300

400

Up

per

Den

titi

on

Fz

(N)

Time (ms)

Schutt DNA

Test 1

Test 2

Test 3

-200

-100

0

100

200

300

400

Up

per

Den

titi

on

Fz

(N)

Time (ms)

Schutt Air Varsity Commander

Test 1

Test 2

Test 3

-200

-100

0

100

200

300

400

Up

per

Den

titi

on

Fz

(N)

Time (ms)

Riddell VSR-4

Test 1

Test 2

Test 3

FIGURE 11. Upper dentition z-direction force with different football helmets in phase 3 tests at target 7.4 m/s impact at site A¢.

VIANO et al.

Hybrid III mandible, there are understandable limita-tions. For example, the shape of the Hybrid III chin isa simplification of a more complex anatomical feature1

and may be an area of further refinement to ensure agood interaction with the chincup.

Another limitation is the design of the TMJ. Weemphasized the xz range of motion and biomechanicalresponse, but understand the jaw can undergo rela-tively large lateral rotations. Adding more y-axismovement into the TMJ would increase the complexityof the mechanical joints. At the outset, we decided to

limit the joint compliance to the xz direction andprovide only a limited y-direction movement. Fornearly symmetric hits on the facemask, the mandibleloading is primarily in the xz-plane with minimal lat-eral (y-axis) loading. However, there are forces in thelateral direction for oblique impacts. The Hybrid IIImandible has limited compliance in the lateral direc-tion and there are no biofidelity requirements for thisdirection of loading.

FIGURE 12. Impact at site A causing the faceguard to rotatedownward pulling the chinstraps down to open the mouth.

TABLE 6. Calculation of the fraction of head kinetic energyabsorbed by different mouthguard thicknesses.

Youthb Adultb

6 yo 10 yo 50th 95th

Head mass (kg)

3.47 3.66 4.54 4.95

Impact

velocity

(m/s)a

Head

delta

V (m/s)a Head kinetic energy (J)

Avg 22sd 5.51 3.62 22.7 23.9 29.7 32.4

Avg 21sd 7.41 5.42 50.9 53.7 66.6 72.7

Avg 9.31 7.22 90.4 95.4 118.3 129.0

Avg +1sd 11.21 9.02 141.2 149.0 184.8 201.5

Thickness

(mm)

Absorbed

energy (J)c

Head

delta

V (m/s)a % Absorbed energy

4 0.6 3.62 2.6 2.5 2.0 1.9

5.42 1.2 1.1 0.9 0.8

7.22 0.7 0.6 0.5 0.5

9.02 0.4 0.4 0.3 0.3

12 1.8 3.62 7.9 7.5 6.1 5.6

5.42 3.5 3.4 2.7 2.5

7.22 2.0 1.9 1.5 1.4

9.02 1.3 1.2 1.0 0.9

20 3.0 3.62 13.2 12.5 10.1 9.3

5.42 5.9 5.6 4.5 4.1

7.22 3.3 3.1 2.5 2.3

9.02 2.1 2.0 1.6 1.5

aFrom Pellman et al.28,29 re-creation of NFL game impacts.bFrom Mertz et al.23,24

cAssumes 500 N peak force at maximum compression, which is

60% of mouthguard thickness.

TABLE A1. Position of the sliding table and neckangle6,29,30,38,41 for the six impact sites.

Impact

site

Table adjustment

(mm)

Neck

angle (�)

y z a b

1 33 223 290 0

2 32 210 265 18

3 70 27 282 211

4 37 26 255 15

5 51 76 228 0

A 27 20 225 7

A¢ 15 35 0 210


In these test, we used only a slight compressionforce closing the teeth on the mouthguard. Undoubt-edly, there is a range of clenching force in game con-ditions that we did not try to include in these tests. Thespring force closing the mouth can be varied in futuretests, but was beyond the scope of these tests.

The Student t test was used in this study to deter-mine the significance of response differences. The sta-tistic assumes the data are normally distributed. Inother helmet testing,38 12 tests were performed on thebaseline (1990s) helmets. That data were normallydistributed; however, the limited sample of repeat testswith the different mouthguards does not allow proofthat the data is normally distributed.

The head biomechanical responses reported herewere limited to ones related to translational accelera-tions, which were used to compute the peak resultantacceleration, SI and HIC. A more complete assessmentwould include rotational accelerations.38 In addition,while HIC has a long history of being used to assess therisks for serious head injury, it has limited validationfor concussions.28

Probably the biggest variable in generalizing theresults of these tests is with the helmets, facemasks, andchinstraps available on the market. Our tests showedthere is an influence on how the helmet moves in animpact and loads the chinstraps (see Appendix). This isthe input to the chin and something that can vary withdifferent tests and game conditions. We have selectedspecific helmet models, faceguards, and chinstraps andvaried either the type of mouthguard (phase 1 and 2)or used one mouthguard and varied the helmet

(phase 3). Obviously, the range of test conditions andequipment is extensive.

APPENDIX: IMPACT SITES CAUSING HIGH

MANDIBLE LOADS

Initial Testing

In 2004, helmet testing was conducted with a load-measuring jaw on the Hybrid III dummy. Five impactsites were tested at 5 and 7 m/s with an pendulumimpactor.30 Figure A1 shows the impact sites 1–5 andTable A1 gives the setup position of the sliding tableand neck angles.6,29,30,38,41 The alpha angle is therotation of the eyes right or left around the z-axis. Thebeta angle is the flexion angle of the lower neck bracketaround the y-axis. The y-position is the lateral offset ofthe head with respect to the centerline and the z-posi-tion is the adjustment of the table up or down. Ta-ble A2 gives the head responses and jaw loads withvarious football helmets. These tests were intended toguide the development of impact conditions for cada-ver testing and the eventual development of an artic-ulating jaw for the Hybrid III.6,8,41 The tests showedthat site 5 generally produced the highest loads on thejaw.

Site 5 also gave the greatest opportunity for amouthguard to influence the head responses because ofthe relatively low head accelerations in the test. Theimpact was on the faceguard, so the helmet shell andpadding did not directly load the head except through

FIGURE A1. Pendulum impact testing with a load-measuring jaw on the Hybrid III.

VIANO et al.

the browpad. For the other impacts, the relative con-tribution from the mandible to the head accelerationwas proportionately lower than for site 5. Obviously,there is a complex relationship between the helmetimpact, load in the chinstraps, and forces transferred to

the head from the mandible. The tests in Table A2and analysis of NFL game films6,28,38 show that theinfluence of a mouthguard on head accelerations maybe limited to a fraction of the helmet impacts on thefield.

TABLE A2. Results of helmet testing with a load-measuring jaw.

Site

Head responses Peak resultant jaw force

Pendulum

speed (m/s) SI HIC

Linear

Accel. (g) X (N) Y (N) Z (N) Resultant (N)

Old VSR4

1 5.6 449 325 104 2133 2515 83 538

2 4.9 227 161 72 2238 2449 113 520

3 5.4 266 208 73 2265 21400 423 1486

4 5.5 258 188 70 2575 2568 285 857

5 5.5 76 64 33 21149 21379 1089 2099

A 5.4 92 76 43 21325 2943 315 1657

B 5.4 282 209 70 2469 2666 412 913

C 5.4 281 208 79 31 2259 266 373

1 6.9 928 662 144 2112 2627 464 788

2 7.0 777 525 128 2263 2711 231 759

3 6.9 782 609 128 2386 22282 662 2407

4 7.0 556 389 99 2823 2695 491 1184

5 6.9 246 195 58 22484 22044 2293 3951

A 7.3 420 325 81 21837 21213 1046 2437

B 7.0 656 447 105 2628 2810 676 1228

C 6.3 499 365 106 262 2392 350 529

New VSR4

1 5.6 217 167 81 249 2452 198 496

2 4.9 214 154 72 2121 2343 125 384

3 5.4 200 161 62 2482 2783 1154 1475

4 5.5 223 165 58 2506 2525 213 760

5 5.5 67 52 37 21053 2695 834 1513

1 7.0 516 362 116 273 2570 309 653

2 7.0 639 432 114 2242 2521 327 661

3 6.9 774 589 138 2351 22122 576 2226

4 7.0 514 378 90 2638 2735 450 1072

5 7.0 193 150 53 22095 21492 2010 3264

Revolution

1 5.6 217 167 65 286 2288 342 455

2 4.9 169 121 50 2312 2387 232 548

3 5.4 194 142 63 2244 21346 531 1467

4 5.5 217 156 60 2408 2534 188 698

5 5.5 53 42 41 2758 21066 614 1445

1 N/A 516 362 96 273 2448 620 768

2 7.0 674 459 106 2569 2753 527 1081

3 6.9 458 329 101 2445 22152 676 2300

4 7.0 612 436 107 2663 2510 379 919

5 6.9 162 138 48 21549 21870 1258 2735

Air Varsity Commander

1 5.6 315 222 78 17 239 460 462

2 4.9 211 157 66 2142 2273 275 317

3 5.4 271 214 77 261 21390 408 1450

4 5.5 220 166 68 2396 2520 86 659

5 5.5 39 69 30 2855 2768 1133 1614

1 6.9 655 449 109 219 267 717 721

2 6.9 696 471 115 2327 2335 392 611

3 6.9 736 587 135 2161 22329 671 2429

4 7.0 462 301 87 2629 2654 563 1068

5 7.0 139 165 50 21836 21701 1877 3129


Later Testing

The Schutt DNA Pro helmet caused high mandibleloads due to flexing of the lower shell and loading ofthe chinstraps in lateral impacts on the shell. A laterseries of modern helmet impacts was conducted withthe Hybrid III mandible to explore conditions withhigh mandible loads. Figure A2 shows the six config-urations of helmet shell and facemask impacts at atarget velocity of 7.4 m/s. The numbering of theimpact sites is not consistent with the earlier testing in2004, so the setup photos need to be considered andthe six impact sites are labeled with an asterisks. Ta-ble A3 shows the position of the table and neck anglefor the linear impacts.38

Table A3 also shows the head and mandibleresponses for three repeat tests with the Hybrid IIImandible at the six impact sites. The highest man-dible loads were for site 5 at 1843 ± 27 followed bysite 6 at 1486 ± 63. The tests also show that theimpact site causing high mandible loads may nothave correspondingly high HIC. For example, thehighest HIC occurred in impacts at sites 1 (254 ± 6)and site 6 (252 ± 6), while the lowest HIC was in thetesting at site 5 (77 ± 1). Site 5 again gave thegreatest opportunity for the mouthguard to influencehead responses because of the relatively lowhead acceleration with the facemask impact. Forimpacts at site 1 and 6, the impact loads the shell

TABLE A2. Continued.

Site

Head responses Peak resultant jaw force

Pendulum

speed (m/s) SI HIC

Linear

Accel. (g) X (N) Y (N) Z (N) Resultant (N)

Adams A4

1 5.6 341 237 74 273 2429 557 707

2 4.9 227 169 70 2257 2446 214 515

3 5.4 264 196 71 2296 2613 1058 1258

4 5.5 254 169 62 2571 2371 480 833

5 5.5 113 97 45 21724 2878 1558 2484

1 6.9 727 471 100 262 2403 671 785

2 6.9 721 457 110 2396 2619 402 837

3 6.9 817 610 136 2328 21529 880 1794

4 7.0 602 380 98 2643 2444 625 1000

5 6.9 347 239 76 22781 21422 2241 3845

FIGURE A2. Impacts conducted to identify conditions with high mandible forces with a modern football helmet.

VIANO et al.

TA

BL

EA

3.

Imp

acts

at

six

sit

es

on

the

helm

ets

at

ata

rget

7.4

m/s

.

Site

Positio

nin

g

Trial

Velo

city

(m/s

)

Head

responses

Mandib

lefo

rce

(N)

Tota

la

by

z

Accel.

(g)

SI

(2g)

HIC

Upper

dentition

Left

TM

JR

ight

TM

J

Peak

FR

Peak

Fz

Peak

Fxy

Peak

FR

Peak

Fxz

Peak

FY

mP

eak

FR

Peak

Fxz

Peak

FY

m

No

mouth

guard

1*

259

210

73

122

17.6

79.7

281

219

463

443

360

417

171

402

639

636

111

1,1

67

27.5

88.9

342

265

457

421

448

531

217

518

789

787

130

1,4

52

37.5

91.7

343

260

441

400

421

567

198

553

774

773

143

1,3

92

With

mouth

guard

47.6

89.2

325

248

337

332

205

470

275

430

723

722

103

1,2

02

57.5

91.9

340

258

322

267

321

555

211

546

772

771

116

1,3

03

67.6

90.8

336

257

294

241

293

483

241

469

748

747

120

1,2

81

2*

297

220

73

113

17.6

76.2

287

220

658

281

630

337

111

333

229

227

124

968

27.5

73.0

289

222

705

288

677

286

103

282

304

271

120

1,0

52

37.4

73.6

280

213

758

556

730

241

93

240

211

162

117

985

3*

02

10

73

186

1a

7.6

53.4

124

96

247

199

61

844

844

165

648

637

16

1,5

42

2b

7.5

65.1

162

129

216

201

81

877

876

156

535

529

46

1,4

86

3c

7.6

52.2

119

92

212

200

72

962

961

202

497

496

50

1,5

28

4*

234

220

73

125

17.5

47.9

119

88

530

423

327

417

202

409

808

800

117

1,3

28

27.5

51.1

127

89

507

451

313

425

249

420

815

811

109

1,3

72

37.5

57.2

156

117

492

203

486

531

149

524

751

743

130

1,3

78

5*

220

210

85

199

17.6

49.7

97

77

550

308

487

766

223

740

1,1

15

1,1

02

124

1,8

12

27.6

53.3

98

76

565

247

510

785

255

752

1,1

02

1,0

90

145

1,8

55

37.6

49.4

98

78

577

266

526

803

232

780

1,1

24

1,1

03

83

1,8

62

6*

275

220

85

150

17.5

85.2

315

258

663

238

651

913

453

797

318

317

128

1,4

21

27.6

82.0

316

252

539

177

518

994

477

880

498

494

135

1,4

89

37.6

80.8

310

246

530

228

528

1,0

33

503

902

521

516

130

1,5

47

aC

hin

str

ap

bro

ke.

bC

hin

str

ap

bro

ke

(less

severe

than

test

1).

cS

evere

dchin

str

ap

at

buckle

.


and causes higher head accelerations from the helmetpadding.

Impacts to the side of the helmet, such as at sites 1,2, and 6, cause the shell to flex inward as the helmetdisplaces. This creates tension in the chinstraps. Theshell bending is more pronounced in modern helmetswith lower and more forward sides of the shell com-pared to the older style VSR4. Figure A3 shows anexample of a side hit to the Schutt DNA Pro helmetthat flexes the lower edges of the shell as the upperattachment of the faceguard to the shell braces thebrow area and the helmet displaces laterally on thehead. The impact was at 7.5 m/s and caused peak headresponses of 56.4 g and HIC 168. Flexing of the loweredges of the shell can be rapid enough to unlatch thechinstrap,38 as occurred in this impact (see the bottomimage in Figure A3).

ACKNOWLEDGMENTS

The testing at Biokinetics and Associates Ltd. wasfunded by the National Football League. Their sup-port of the research on the effects of mouthguards onhead responses is appreciated. The opinions presentedhere are those of the authors and not necessarily thoseof the NFL. The development of the articulatingmandible for the Hybrid III,8,41 cadaver testing anddevelopment of biofidelity corridors for impacts to thechin6,7,9 and the series of helmet testing reported herewere completed while the lead author was a member ofthe NFL’s MTBI Committee and oversaw theresearch.

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