Pressures generated in vitro during Stabident

intraosseous iniections

J. M. Whitworth, R. A. M. Ramlee & J G' Meechan

Sctrool olD€ntâl Sciêtrcd. Newcastle Uni!æitv Newcastle upot Tvne uK

Whitworth JM, Ramlee FAM, Me'chtn JG Pressùres

generâred in waro during srâbidên: inÙaosseous inledbns

lnteûananêl Endôdonti. Jouthal sa, 291-296 2045'

Aim To test the hvpothesis lhat the Stabident Ûrtra-

ôseous injection is a potetrtiatlv high-pressure tech-

rique, which cMies serious nsks of anaesthetic

Methodology A s1ândard Àstra detrtal sr{inge was

moiliiled to meâsure the internal pressure of locar

anaesthetic cartridges during injection' Intra-cairidge

Dre,sur , wL-e measurêd âr I s in tervals du:nB dos

i ,sp ' ,v i .or" tv l5 sr and raPid r<10 s ' in iecr tnns ot

z l xvto.o in" w' rh | :80o0o adrerahe ro/c

cartridge volùmeo inlo at {no tisslr€ resistance) or

irto freshly prepâred Stabident perforâtion sites in the

anterior maùdibie ot freshLv cuiled voung aûd old sheep

(against tissue resistaqce) Each iniection 'as repeated

l0 times oler 3 dats. Absolute maaimum pressÙres

Êenelated by each câtegorv of injection mean p'es

;ùres at t s interals iD each series of injections ând

slanilsd deviations were calcûtated Ctves oi mean

maximum ùÛa-cârtndge pressure development with

ume w.F prorLcd lor slo$ Ùd raoid rniecL:on'

and onÈway À\ovA (P < 0 05) conducted to .deter-

mine sisûitcani diiterences behdeen categorles or

injætion.Rèsults Presures created when iniecnng tn!Ô atr

sere leqs l tdn,bo5'ncÊded ro in iecr In lo r icsue

{P<0.001). East iojection produced sreate' rnÛa-

"*iar" p.rrtu.ut than slow deliverv (P <! 05)

IDjeciion pressur€s rose more quicklv and to htsner

leiels in smau vouûg sheep matdibles than it Larger'

old sheep maùdibles. The absolute maximuû intra_

cfftridge pressu.e developed durins the stùdv was

1.31 MPa which is less than thât needed !o ka'ture

glass cartri'1gesCônclusions Stabident irtraosseous'qecrton'on-

itucted iD ac.ordatrce wilh the manufactùrer: instruc-

tions does noi present a serious risk of dâùserous

pre$ure build-ùp in local araesthelic cadndges'

Keywords: Nraosseous. locâl anaesthelic pressure

R..eitud 6 ocLùbù )aoq atttpted 1 i Deûtnh{ 2001

lntroduction

SùlDlemeDtary injections Ùe olten reeded to pro

Ioundtv anaesthetize irreversiblv inllded pulps (Mee_

chan 2002). These coûtrol Pain bv ilcreæitg drug

dose, biocking vùiatt nêÙal pathwâvs or simplv

concusing sensorv neûd Sone ee high-pressure

CoÛ€sbonde!æ: Dr loht M. WhitwÛrth School o' D'nlal

sci€.c;. uewdstle Unive6iit, F.adlinelon Plâ'e New'ârdê

ùDon lvne NE2 4BW, UK (Tel : +44 791 222 7A2\ iu: +44

191 2i2 6117: €-nàil: i m.whit{orth@ncl a' ùk)

@ 200t rûrenaf onâl Endododic J 0um r

methods which tnâv cause anaeslhetic cartridscs to tâiL

(Meæhan & Mccabe 1986 MeechàD ct41 1990)

although detailed eviden e h otten lackrng'

ln(raoseoJs Inle'r:on .s d elTecr:ve adiun l in

emersency êndodorriLs \us'lein '! dl 'LnOJ) and rh

Stabràenl \L(1 'Paùfax Denra lnc \4rdnr 'FL USAIb

on" o l lhe prJ\en commer ' i " ' d6 i8ns | \us ran / r ' l

1 9 9 8 ! a l l . ' r ' 1 a l ? n 0 r r ' I l t F s v r e m d c l i v e ' s I n à l

anaeslhetic soluliorl into can'ellous bone with a siand

ârd dental slnnge and ultra_shorl (6 nml 27-gauge

needle- cortical pertorators aûd ûædles de siæ-marcnea

iRamlee & \\'hitworth 2001) to avoid backJlo\t and toss

ofdrug during iniection into a 1ow compliance tissÙe

rnc'id]onâlFndodÔilicJoÙmà|'33.291296,2005 E

PGs!rc on sràbidên injedion whitudb d'r'

I

1

The mmulactllEk inskuctroN lecolmelrd slow

delivery of on€ quârter cartridge of maestheti'

sôlutioû but make no obs€Fations on the risk ol

pressure build-up dÙing injætiot 'nto a croser

This study wâs designed to a€st the hvpothBis that

th€ Stabidert iDtraosseoN technique is a potêntiallv

high-pr6s,Ie technique, which cùies serious risks ôt

anaesthetic cdtridge tailure.

Materials and methods

Development of a syst€m to m€asure fhe internalpressure ofdental local am€sthctic cartridges during

injection

Où e{perjmental system was based on the modiÊed

Astra sylinge model of Maita & Hooichi (1984)

(Iis. r).B.ieliy, a standard Astra (Asûazeneca Maccles_

ffeld, iJK) dental syringe w6 modifled bv the additioD

of a 2o'gaùge slâintes steel needle inserted ând

secùed through the hoEing of the bdrel (Depart

ment of lngineeriog, University ol N€w@stle, UK)

This was connæted to a pressure transduær IRDPËlectronics. WoLverhampton. UKi pressure range

0 1000 psi (0-6.89 MPâ)l which was nounted

on the syringe bùrel. This in turn wâs conrected

to a mic.ôprocssoÈbased strain ânplitier (E525

Cyphec Â)P Electronics). fftted with a stlndârd

RS2J2 :nrr ldcp to .ommunnrt .on wir l lhe h l ! " -

terniûal progranme for Windows 95 (Hilgraele Inc..

Monroe. MI, USA), allowing the capture ot presure

readiûgs from the strain âmplifier and pressure

transdùcer. The presure transducêr and slrain

amplifier were calibrated by the sùpplier p.ior to

Pressurc m€asurement

stmdard l@al amesthetic câ.tridges 122ûl' oî 2%

xylocaine with 1 : 80 ooo âdrenaline (Astrazeneca)l

r{ere marked to indicate 0.25 cùtridge volumes belo.e

loading irto the modi{ied Àstra sFioge {Astrazereca)carrying a StabideDt ultra short (6 nm) 27-gauBe

need e A sene< otpr6'ure rtrordinBc was màde dLrrins

thê injection ot 0-25 cartridge volumes iDto:

l. Âir (no tissue resktance).2. Fresh Stabident perforalion sites in the dentate

anterior mandible ot:

{a) two lreshly cûlled young (approxiûatelv I vea.old)

tb) tso lreshly culled old {approximately 4 vears old)

New pùnctur€ holes. needles aûd ca.tridg6 were

employed for each injection.The presures which deleloped in the svringe ca!t-

ridse were recorded at 1 s itrtertâls drring a seri.s .l

10 slow lapproximâtely r; d ând 10 .apid (as rapidl!

s possible: <10 s) itjectioDs inlo air and irio shæp

lnjections it each series dere spreâd over I dâvs 1o

avoid operâtor fatigue and to allow dispereal ot local

ârâesthetic $'ithit the specimeù- AU injections we.c

made b! a slngle. Iemale inlestigator (RAMRI Locâl

anâ.sthetic câ.l.idges employed in this study $€re

stôred aùd adûitistered at rôom temp€râture Sheep

rândibles {.re stored ùùde. retrige.alioD l'l 'C) and

allos'ed to eqùilibrate to foorn tempe.ature for 2 I h

hçlore injection.

'lhe absolure naximum presures senerateil bv each

series of iùjecdons. meàt pressu.es and standa.d

oenlalcarl dge synnge, modiilêd by:. p@s*rc lÉnsduær mounlêd I

. addiuonai 20 oause nædlê !re€nêd Ihrcugh

Fisur. 1 Sch€naôc diagGn ollocal

aùacstheti. presu.€ tdtina syslen.

@ 2005 Inrârôarionâl Êndodoûit Jou'iallitmâtonâl E ndodonli. J oo n 3 L 3a, 291-296, 2005

$fti@nh d dr PG.su€ on srabidsnr injedion

deviations were catculated with Microsott E\cel f'r

Windows XP. Cunes of mean maximum nEa{d

hidge pressue development with flme were plott€d lor

slow ùil rapid idections in Microsoft ExæI, and oft-

way ^NovA (coDfdence intewal P < 0 05) condD't€d

to.letemine significmt di,Ierences betwæn the vmoùs

câa€gories of iDiectios.Mdimum pressùe recorditgs were @mpaEd with

publshe{t Weibûl curves of local anâesthetic cartridge

failure iMeechan st al. 1990) to Provide iûsight info the

tikelihood of systen lailure rÊsulting ftom the intra-

cârtriilse pressures senerated dÙing use of the Siab_

ident intrâosseous method

Results

The ntatr ndimum md absolute maximum intra-

cartridge Pressures gen€rated dÙing iniecaioDs ifto aa'

and sheep nâtdibles are show! in Table 1

Mdimùm anil meaû mdimum intra-carbldge prs_

sures were alwâys greater duriDg irjectioE iDto tisue

compard with air. where there was no exi"nai

resistance (P < 0.001)

Tâblè 1 P'6sùes genPraL"d duing inic.uo''MPal Ir -- l0l

Râpid iljection alwavs generated highd absolut€

md mean mâximum intrâ{artridge prsMes thân

their respe.tive slo& injection (P < 0 05) The'e were,

howwer, no statisticallv sigtiflcæt dilTerences between

the meân maximum and absotute maximum inrra-

carûidee pressùes geDerated durins slow iûjection Dto

yoùs or old sheep mandibles, or .apid iniection idto

youns or old she€P mandibles

Curves illoitra!'ls the development of intra'câ'bidge

prcssure Ùirh ÙmP tor slow iniecrions zre shown i"

Fig. 2. Slow itrj€.tion into air (ûo tissue resistanæl

creatld a small nse ilr intra'cartddge pressure' whi'h

peaked after approximatelv 4 s and remaiDed steadv

throughout the iojectiot period- Âll iniections 'ntÔ

tissue $€.e arsociated with similâr profrles of pressùre

inc.@se, Peakins between 7 and 10 s at lêvels

betwætr 1.4 and 1.68 MPa. before declining towards

the end of the injectionGrcate. vaiation wæ sæn âûongst the rapid

injectiom (Fig. l). Iûjecting as quickLv as pos$D€

without tissùe rsistance resulted in a pattern ol

pressùe beha\iolr which wd similar to the dow

irjection. Intra-cartridge pre$u.e rose to a peak àt

approximâiely 5 s. and remained relativelv co!'shnr

until the end ol the injection pedod

Sharp increases in presure wêre noted dûring the

tust 4.{ s ot injeciioD against issue resistance wiih

both the rate of developnent ând peak valùe being

greatest ill the relatieelv snaLL voùng sheep mandible-

Discussion

Pressure generation is .ele!an! to the €lIectiveness ând

safery of sme local anaesihetic melhods (Lht 't dl'

1988. Vancheluwe & Walion 1997) The intrari-

Meân m6timum Absôlure môimumprêssu@ (MPal pressÙrc (MPâ)

in 3eri6 {sDl in sêries

1 .6

o.2

Fisurê 2 Me& danmm in[a@-aidse presù€ {MPa) vesùs t'me (s).

€ 2005 lniemarion:l €ndôd onti. Jô!md @

Presurc on sbbidsnt injsdion vr'hr'en' er ar

gamentary iniection mây, ior exmple, gene.ate hish

p.essures, aspæially in combinaiion with commer'ial

pressure syring6 (walnslev .tal 1989) Few data

hdvê bepn âvailable on presrùrs senerared durins

iDtra{seous injection where sÔLution is deposited intd

a low compliânce tissæ spâce.

A tumber of researchers have desclibed svsteds l'r

measùring pressure in local anaesthetic svstems (Pâsh-

Ley st al. 19s1, Maitâ & Horuichj 1984, Rieu .t dl.

1989, Walnrsley et 41 1989) Our spæific interest was

intrarartridse pre$ure which wâs readilv neasured

by the Maita & ltôruichi (1984) method as de$ribed

Simulation môdels are wideLv enploved in biomcdi

cal reseârch. 'Ihe iimited availabilitv of whole denrâte

humân cadaver mandibles necessitated lhe use ol an

alternative. rnedium-siæd mâlnûâlian model io the

cunent research. Fresh. dentate ovine mandibles were

leadily sourced. and only the anierior mandible was

utilired. where tooth shape and efangemeD! was

comparable to the humù We are unable to specrrlâte

on the compârability of our own results with thôse

llkety from injætion into the jaws oi iiving creatures.

De. prre .on.iderdble elTo't ro ôrandâ'diæ 'nic' ri^n'

soûe degree of operator vanâbilitv w6 ioevitable.

lh.s was panjculaly ço lor rapio iniections neces i

tatiûg trequent breaks and spreâding iniections over

I days. It was r&e for even the slow iûiections tÔ be

siven absoluteLy smoothlv and consistentlv due tô the

behaviour oi the cdtridse rubber pilnger' s'hi.h

iypicalljr moved along the cartridse berel with a

judderûg motion. Even a mechanical svringe driver

could not deliver truly smooth iniections. ttowever.

the iniections were clinicallv realbtic and the stând-

ed denarion( 'ndi@te ân a..eptable l.\el ot consiJ_

Multiple cortical perlbrâtions and iojeclions did not

resùlt in aoy clear pattern of presure reduction or

incrêase as lhe series lrog.essed. Flùid was not ûoted 1()

emerge through perloration sites

This inv€stigation provides some ol the first evidencc

on prelsùres generâted in locai anaesthctic cartridges

during the lrse ofcontemporârv intraosseous iniecnôn

techniqùes in the ùandible. Presure rccordings s'ere

compùrable,1 i lb those ot Pashlev e ln i (1981) s 'h '

repo.tcd maximuù injeclion prcssurs into the iasa ol

dogs in rhe raùge bet$cen 1 91 àtd 1 24 MPa It was

noted thât iniectiot pressùres rvere highcsi iu less

dhtensible dssues. $ith the int.à{sseous i'rlecnon

developiug highe. maxirDum pressure (2.1j8 I'lPa)Lhaù

incisive papilla r2.11 lttPa). periodotlal lisam'ùr

{2.15 NlPa). hârd palate {151 MPa) ând int rapulpàl

l1-19l\'lPâr i]liections. Other fesear.heb hâre nolcd

even higher iùtra-cariridgc PressLre genc.ârinn

(4 MPa) during rr !ùro simulalion oi inraliganreÔtârl

ând inrao$eous irjecLiôns. Bv con!|ast. Shephdd

.t dj. (2001rùr€àsured the iùtrabÔnv prcssure Dcr'âçe

during iùection of $vi,re oràtdibles. and reporred

pressure iDcrcases an orderoll0lo$€r thaù the los'est

intra'.ârtridle presure dùrins slow iniectioù agâ'nsf

no resistance .ecorded it the prcsent study

Some ot this itconsistency must reflect detôls ol

protocol. inclùdilg the iniection recipietrt. the vohrmc

ot anaestheric deln'ered. lhe rale of deposition thc

measudùg sFreû. the tempefature ot the cartridge

(Me€chan .l al. 199t) .;rl the site measured Lù

additiot. the len$h and sâùge otthe leedle influences

pressure generated in denlal local ânaeslhelic cÙ-

ûidges (i\ieechât & Mccabe 1986)- It cân be inlerred

thât loca1 anâesthetic iniection svstems do not develop

consisteDt in.reases in pressùre th.oùghout ID the

Flgure 3 I'teat maximÙm int.a{âr_

tridse prcssué {MP€) ve6us time G)-

@

whiôrcnn e. aL Fcsure on Srâbident inj€dion

prserlt work, the small mandibles otvoung sheep were

associaleil with morè rapid and hisher peak pressure ol

inj€ction than la4er, mature sh€ep There is a næd to

standùdize methods lor evaluating this importÙt

elemeDt ol local anaesthetic deliverv ând safetv.

So$,ray (1983) stated thât anaesthetic cartridges

were desi$ed to resist approximatelv 4-1 MPa oi

pressur€. Previous investigations (Meæhan & M'câbe

1986) have shom that ihe rangc ol pressDres causing

fracture of 2.2 mL Xylocaine (Astrazeneca) dettâl

ânaeslhetic cartridges ot the tvpe emploved h this

srudy were bejond rh i r !à4BP r( \ l lq 7 VPa

The mdimum p!6su.es etrcoùntered, even whet

injections were aiininistered as rapidlv as phlsicallv

possible. were no higher thaû 3- I 1 MPâ- lt is impor.ant

to poitrt out that the operator iû lhis studv was iemâle-

A previous investigation has shown that mâle opera-

to6 can geDerate 8r@te! prssÛes thatr females (Maita

& Horuichi 1984). In thât studv (ùlaita & HÔnri'hi

r9S4), maLes could produce approxinateLv 28% sreâ!-

e. maximum lorce. If the forces recordcd in the prcsent

study were inùeased by 28%, this is still below that

ûeeded to lracture glæs cârtndges. lt cÙ be concluded'

therefo.e, that glass Xvlocâine (Âstrazeneca) ânaes-

thetic carkidges we.e at no significant risk ot iracture

during iûkaoseous injætion bv the Stabidenl detbod

The forc€s reported in this investigation are less thÙ

lhât reported duritg intrâligametta4' iDjcctions

i\4'almsley el al. l989l Inlrâlisameitarv injections

ire considered â type ol intraosseous ânâesthesia

rsmitb & Walton 1983). AltlDugh iùtràligamertaq'

anàesthesia may be cotsidered an intraosseoùs ûijec'

tbt from a physiological poilt of view. the trûe

intrao$eous technique dilïe6 in a nechanical sense

in that less force is generated in the ca.tridge ltith lhe

l'laslic Locâl anaestheti. cartridges are known to tail

b.lween 3.Ol and 6.89 MPa. The peak intra{artridge

F.esure developed durins slow intraosseous njccuonwas <1-67 MPa, thus plastic cartridses are at litde riskol tailure during Stabident injections when the iniectionis given slowly. Examitation ol Weibull dhtribution.un'es (Meæhan st 41. 19901 suggests thât if hhaos-srus injection was given very râpidly (peak pressurel.]l MPa). there may be a lO-15% risk oi plasti.ca(ridge tàilure. Plastic cartridees fail dùe to dislo.tionot lhe câdridse plunger wilh loss of an'estheticdution. .ather than daûgerous tàilure otlhe cartridseNalls 1Meæhan er di. 1990). It can be susgested thattlanic and gls anaesthetic cart.idges may be usedrvirh safety iD the Stabident inbaosseous tæhnique,

C2005]n&hdioiâ]EndodonlicJouftâ|

plovided thât the mmufacturer's instructions ior slow

injeclion ùe followâj.Within the timitations ot this slùdv, the working

hypothesis that the Stabident intraosseous technique r â

potentially high prssure technique which ce.ies serr-

oN risk oiânaesthehc cdtridge failure was disproved

Conclusions

Stabidett intraoss€os injection conducted in accord

anæ with the manu-facturer's instructions does not

p-esenl â sûious ' l5k o ldânseruÙr prP$ur bLr ld up n

local anâ$thetic cartridges lt is importarlt to note that

the.recomended needle letgrh atrd gâuge was used

As the lorces prodùced withitr the cartridge û'iLt

increâse with longer atrd naûower needles (Meechât

& M.Cabe 1986) the present resultr should not be

ertrapolated to cover all intrao$eous injectioos

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@ l.kalional Endodo.iÈ .lou mal, 3ô 29 r æô 2005 o 2005ldè'uuos Endododi( Jomà