New theoretical model to measure pressure produced during impression procedure for complete dentures—Visual inspection of impression material flow
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New theoretical model to measure pressure producedduring impression procedure for complete denturesVisualinspe
G. Nishia Occlusion b DepartmenShikata-choc DepartmenPharmaceut
a r t i c
E-mail a0109-5641/$http://dx.doction of impression material ow
gawaa,, Y. Maruoa, M. Irieb, M. Okac, Y. Tamadaa, S. Minagi c
and Removable Prosthodontics, Okayama University Hospital, 2-5-1, Shikata-cho, Okayama 700-8525, Japant of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1,
, Kitaku, Okayama City 700-8525, Japant of Occlusal and Oral Functional Rehabilitation, Okayama University Graduate School of Medicine, Dentistry andical Sciences, 2-5-1, Shikata-cho, Kitaku, Okayama City 700-8525, Japan
l e i n f o
a b s t r a c t
Objective. A theoretical model, based on uid dynamics, was developed to measure impres-
sion pressure. The purpose of this study was to evaluate the validity of this theoretical model
by comparing its theoretical analysis against actual pressure measurements conducted
using an impression tray and edentulous oral mucosa analog embedded with pressure
Methods. In the theoretical model, a hollow tube was mounted onto an impression tray
by penetrating through the tray. When force was applied to the tray, pressure was pro-
duced which then caused the impression material to ow into the hollow tube. Length of
impression material which owed into tube was denoted as l. In the calculation formula
for theoretical model, pressure impulse I was expressed as a function of impression ow
length l. For actual pressure measurements, four electric pressure sensors were embedded
in an experimental edentulous arch. To visually observe and measure length of impression
material ow, four transparent silicon tubes were mounted vertically at different positions
on tray. During tray seating, impression material owed into tubes and pressure which
caused material ow movement was measured by the embedded sensor at each tubes
Results. Based on actual pressure measurements under one experimental condition,
regression analysis of pressure data acquired from electric sensors yielded the formula,
Y = 0.056X2 + 0.124X. Based on theoretical analysis using a particular viscosity value, the
numerical formula yielded was Y = 0.057X2, which resembled that of the regression formula.
Signicance. Theoretical model presented in this paper augured well for clinical application
as an easy and economical means to examine magnitude and distribution of impression
pressure by measuring lengths of impression material ow in tubes xed to impression
2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
ding author at: Occlusion and Removable Prosthodontics, Okayama University Hospital, 2-5-1, Shikata-cho,yama City 700-8525, Japan. Tel.: +81 86 235 6687; fax: +81 86 235 6689.ddress: firstname.lastname@example.org (G. Nishigawa).
see front matter 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.i.org/10.1016/j.dental.2013.02.005
d e n t a l m a t e r i a l s 2 9 ( 2 0 1 3 ) 530534 531
1.1. Precomplete desensors
To design ation area isimpressionexerted by tseating thetissue, andrial causesdistributionan importaresult in anarea .
In dentaimpressionimpressionsion pressuinvestigatio[2,11,12].
Apart fremerged onpressure. Nvisually exon the dynatray seatinments in aupper dent
Today, tmainstreamimpressionin impressipressure [1devices mucostly. Theon the edension makinpressure dumeasuremeprohibitivetask due tolies the imto measure
During theor grooves,when trappthe impresor grooves.esized thais a functimaterial onrmed, it c
alternative and a more affordable means than electric pres-sure sensors to measure pressure.
luatdel ntulre sehe ase to
m ofnstrudel, sional walculnsored.tatisticalion ed frsionf extr
retic showty F appe prmoventu
tubeas asuid iis in
modbe exal, l,
perim mossure involved in making impressions forntures and pressure measurement using
complete denture, the contour of denture founda- obtained by using an impression material and an
tray. During the impression procedure, pressure ishe impression material on basal seat mucosa while
impression tray. Basal seat mucosa is compressive pressure applied upon it by the impression mate-
slight distortion. Therefore, the magnitude and of impression material-produced pressure hasnt impact on impression making, because it may
inaccurate record of a distorted denture-bearing
l clinics, escape holes and/or relief space in the tray provide relief for the pressure built up in the material . To evaluate the changes in impres-re caused by relief space and escape holes, severalns were carried out using electric pressure sensors
om electric pressure sensors, few reports have using alternative means to measure impressionishigawa et al.  used video camera recording toamine the effects of escape holes and relief spacemics of the impression material during impressiong. In another study, Rihani  used uid move-
manometer to measure the pressure exerted onure-bearing area during impression making.he use of electric pressure sensors remains the
method of measuring pressure produced during making. In many studies, they are either mountedon trays or on experimental jaw models to measure1,1517]. However, as these sensors and measuringst be custom-made, they are usually complex and
magnitude and distribution of pressure producedtulous mucosa play a decisive role in nal impres-g, as the mucosa was distorted easily by excessivering impression taking. For this reason, pressurent should not be viewed by patients as a cost-
task or by dental practitioners as an intimidating the need for many measuring points. Thus, hereinpetus to develop an easy and economical method
vel theoretical model to measure pressure using material ow
seating of an impression tray with escape holes pressure buildup within the impression materialed between the tray and edentulous mucosa forcession material to extrude through the escape holes
On this premise, the authors of this paper hypoth-t the volume of impression material extrudedon of the pressure exerted by the impression
basal seat mucosa. If this hypothesis were con-ould be used to develop an apparatus to be an
To evatal moan edepressutime, trespon
The aithe cocal moimpresmateriwas casure seextrud
If stheoreregressacquirimpresume o
A theomodelviscosiForce producrial to The evsilicon
It wcous analysreticalcould materi
The exacrylicrm this hypothesis, theoretical analysis was per-ed on a uid dynamics model of exerted pressureression material ow.
pothesis evaluation using electric pressurebedded in edentulous oral mucosa analog andession material ow
e the hypothesis of this study, an experimen-was constructed in the laboratory. It comprisedous oral mucosa analog embedded with electricnsors to measure exerted pressure. At the samectual volume of impression material extruded in
each pressure magnitude was also recorded.
of this study
this study was to prove the hypothesis by usingcted experimental model. Based on the theoreti-a theoretical formula between pressure exerted by
material and the volume of extruded impressions derived. On the other hand, regression equation
ated for the pressure measured by electric pres-s and the volume of impression material actually
tical similarity could be observed between the formula derived from theoretical model and theequation calculated from actual measurementsom the experimental model, it would prove that
pressure could be measured by measuring the vol-uded impression material.
terials and methods
eoretical model of impression pressure versus material ow
al analysis was performed using the uid dynamicsn in Fig. 1. In this model, impression material of
was assumed to be a Newtonian viscoelastic uid.lied to impression material caused the latter to
essure P, which then caused the impression mate-e through silicone tube of diameter d at speed .al length of impression material which owed into
was l.sumed that the numerical formula for ow of a vis-n a channel  could be applied to the theoretical
this study. The calculation formula for the theo-el given in Table 1 shows that pressure impulse Ipressed as a function of the length of impressionowing into the silicon tube.
erimental edentulous arch model and material ow
ental edentulous arch was a at, circular-shaped,del of 60 mm diameter. Four electric pressure
532 d e n t a l m a t e r i a l s 2 9 ( 2 0 1 3 ) 530534
(viscosit y: )
: speed of impress ion materia l
moved through si licone tube
Fig. 1 Theoretical model of impression pressure versusimpression material ow. Force F applied to impressionmaterial (vimpressiontube (diamtube is l.
Table 1 analysis b
P = (/2)(l/=32(l/
= dl dl =
l2/2 =I = (1
sensors (PSthe edentuactually ex
Flat imclosely wit
made from transparent acrylic. To enable visual observationand recording of the volume of impression material extrudedfrom holes in tray, four transparent silicone tubes (diame-ter: 1.0 mm, length: 60 mm) were vertically mounted on theimpression tray and positioned at the center of each of the fourpressure sensors embedded in the experimental arch model(Fig. 2). With this setup, the volume of impression materialextruded from the inside of tray could be visually observed; atthe same time, the pressure which caused the extrusion couldbe recorded from the corresponding pressure sensor embed-ded in the experimental arch model.
2.3. Measurement of impression pressure and volumeof impression material extruded from tray intotransparent tubes
A polysulde rubber impression material (Surex F Regular,GC Corp., Japan) was mixed and placed into the impres-
ray. . Traode
ting mg con
Fig. 2 Meelectrical piscosity ) caused pressure P to build up within material. P forced material to ow into siliconeeter d) with speed . Length of material ow into
sion t1.0 mmarch msal tesSeatinCalculation formula for theoretical model andased on uid dynamics.
d)2 = (/2)(64/d)(l/d)2
d2)ient of friction of tube, : density of uid).
l/dt = (P/32)d2/l(d2/32)P dt
once, we obtain,
results, impression pressure I(
d as a function of length of impression material into tube l.
10KB, Kyowa Dengyo, Japan) were embedded inlous oral mucosa analog to measure the pressureerted by the impression material (Fig. 2).pression tray (2 mm thickness), designed to th the experimental edentulous arch model, was
or 1.0 mm oDuring t
sensors emwere transJapan) (Fig.were calculrial which as caused b
During the cosity valuea rheometeical formulobtained frtheoreticalsure impulimpressionrial: 350, 40
asurement of actual impression ow and pressure using an ederessure sensors.Two tray spacer thicknesses were used: 0.5 andy was then seated on the experimental edentulousl at a speed of 10 or 20 mm/min using a univer-achine (Autograph DCSC-2000, Shimadzu, Japan).tinued until each tray generated, respectively, 0.5f impression material movement.ray seating, signals registered by the four pressurebedded in the experimental edentulous arch modelmitted to a Signal Processor (Nihon Denki San-ei,
2). Pressure impulses detected from each sensorated by this processor. Lengths of impression mate-were extruded into the transparent silicone tubes,y built-up pressure, were measured.
tray seating procedure of the experiment, three vis-s of the impression material were measured usingr: 350, 400, and 450 Pa s. Accordingly, three numer-ae each corresponding to a viscosity value wereom the calculation formula of [I = (16 /d2)l2] for the
model: Y = 0.057X2, 0.065X2, and 0.073X2 (Y: pres-se produced by impression material; X: length of
material in tube; viscosity of impression mate-0, or 450 Pa s; d: 1.0 mm).
ntulous oral mucosa analog with embedded
d e n t a l m a t e r i a l s 2 9 ( 2 0 1 3 ) 530534 533
Fig. 3 Relation between length of impression material extruded into tube and pressure measured by sensors afxed onexperimental edentulous arch model surface (tray spacer thickness: 0.5 mm).
Relations between the length of impression materialextruded into the transparent silicon tubes (X-axis) and themagnitudeshown in Fsion formutray spacer
As seenregression fless, curvesthe experimthe area of most part. results seem
4.1. Tharch model
function of the pressure built up during tray seating. In theconceptualizing of the theoretical model, volume of extruded
siontrudus thperimn fon pral whe eensoe, noressuarennter uilt u
withn bebe abe ex.
Fig. 4 Relexperimen of pressure measured by the sensors (Y-axis) areigs. 3 and 4. Using regression analysis, four regres-lae were obtained from two seating speeds and two/impression material thicknesses.
in Figs. 3 and 4, coefcients of the theoretical andormulae did not show proximate values. Nonethe-
of the four regression formulae calculated fromental edentulous arch model were drawn within
the curves of the three theoretical formulae for theTherefore, both the experimental and theoreticaled to show some similarity.
eoretical model versus experimental edentulous to measure pressure
s of this paper hypothesized that the volume of material extruded from escape holes in tray is a
impresrial exand ththe exculatiobetweemateri
At tsure ssurfacting, pTranspthe cesure bagreedrelatiointo tucould modelation between length of impression material extruded into tube tal edentulous arch model surface (tray spacer thickness: 1.0 mm was represented by the length of impression mate-ed into transparent tube to simplify the model e vertical mounting of silicon tubes into tray onental model. From the theoretical model, a cal-
rmula of [I = (16 /d2)l2] showing the relationshipessure impulse and volume of extruded impressionas obtained.xperimental edentulous arch model, electric pres-rs were afxed on the experimental jaw modelt on the tray surface. During impression tray sea-re signals registered by the sensors were recorded.t silicon tubes were xed in the tray right aboveof each pressure sensor, ensuring that the pres-p in the impression and at each tubes position
the pressure at sensor surface. On this premise,tween length of impression material extrudednd pr...