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