-
Mandibular Incisor Position forEnglish Consonant Sounds C.
Andrew Burnett, BOS, FDS. RCPS, PhD'
Purpose: The purpose of this study was to describe the
mandibtjiar incisor poiitions forthe 24 consonant sounds ot" tbe
English language. Further aims were to determine if theincisor
format for each sound is affected by its position in a word, or by
combination wfiban open or closed vowei. Materials and Methods: A
total of 30 young adult subjects hadtheir incisai positions
determined using an electrognathographic technique
duringperformance of a number of speech tests. Results: The mean
values of the 24 consonants,in fhe vertical direction, showed a
range from the Intercuspal position or 2.5 mm for asibilant sound
to 11.7 mm for the /H/ sound, and an an tero posterior range of 1.4
mmanterior for a sibilant sound to 1.8 mm posterior for the IM/
sound. The range in the meanlateral dimension was always less than
1 mm on either side of the midiine. Theplacement of a sound in the
initial or final position in a word had no erfect on the
incisaiposition. The degree of vertical opening was significantly
greater for 8 of the consonantsounds when in combination with an
open vowel sound. The anteroposterior and lateralpositions were
unaffected by vowel association. Conclusion: The incisor position
forconsonant sounds is unaffected by initial or t7nal word
placement. Some consonantsound positions are affected by
combination with an open or closed vowel sound.Sibilant sounds
produced a clinically acceptable measure of the most superior
andanterior speaking positions in all subjects, ¡nt¡ Prosthodont
1999:12:263-271.
Incisai relationships in speech function have beendescribed at
the/S/position'- and the/M/position,^while counting,•'•^ and during
tbe recitation of pas-sages of speecb designed to simulate
conversationalspeecb.^^ Envelopes of maximal jaw motion
duringspeech in 3 planes have also been described'-^ andshown to be
reproducible.^
Speech sounds are classified into different groupsbased
principally on tbe acoustic properties of thesound, but they may
also be described in terms of
'Clinicai Lecturer, Division of Restorative Dentistry, Schooi
ofCiinicai Dentistry, The Queen's University af Belfast, The
tioyaiGroup of Hospitals, Belfast, Northern Ireland.
Reprint requests: Dr C. Andrew Burnett, Division of
RestorativeDentistry, School of Ciinicai Dentistry, The Queen's
University ofBeifast Grosvenor Road, Beifast BTI2 6BP, Northern
Ireland, fat:+ 01232 4Í886Í. e-mail: c.burnett&qub.ac.uk
vocal tract articulation. The English language can bebroadly
divided into 24 consonant sounds and 17vowel sounds. Consonant
speech sounds are pro-duced by tbe vocal traa interrupting or
obstructing theflow of air at some point, requiring specific
articula-tory formats of the tongue, lips, mandible, teetb.
andpalate. Phonologic analysis has been traditionallyperformed by
investigating consonants in 3 word po-sitions: initial, medial, and
final. More recently it hasbeen suggested that consonants in the
word-medialposition can be divided into word-initial or
word-finalconsonants in a principled manner.^ That study pro-posed
to investigate whether there was a differencein tbe mandibular
position required to produce con-sonant sounds in initial or final
word positions.
Vowel sounds are produced with little or no ob-struction to air
flow and are created by adjustmentsof lip opening and total vocal
tract length. Most can
„,;¡.¡-'.Number3.1999 263 The International loumal of
Prosthodontics
-
Incisor Po5Ítion for Consonant Sounds
be generated by means of many different articulatorypatterns. It
is not possible to predict whether a vowelsound will be produced by
adaptation of the tongue,lips, or larynx. Therefore, the recording
of specific in-cisal formats for the range of vowel sounds will
notcapture consistent jaw positions for specific
sounds.Traditionally, however, some vowel sounds have beenknown as
"open" vowels, eg, /Ah/, and associated witha large jaw separation;
others have been known as"closed" vowels, eg,/E/, and associated
with lesser jawseparation. It has been postulated that the
articulationof fhese sounds may affect the jaw position for
suc-ceeding or preceding consonant sounds.••
Phonetic tests have long been advocated as a clin-ical aid in
designing and constructing oral prosthe-ses, especially with regard
to anterior tooth positionand the vertical dimension of occlusion.
The /S/sound has been used to determine the adequacy ofthe
interocclusal distance,^• '̂'• '̂ the/F/and/V/soundsto decide the
maxillary anterior looth position,'^ andthe/M/sound to establish a
desirable mandibular pos-tural position,•''"' The basis for many of
these clini-cal techniques has come from studies that did not
pro-duce quantitative data.
The aim of this study was to describe the mandibu-lar incisor
position in relation to intercuspal position(IP) in 3 dimensions
for the 24 consonant sounds ofthe English language. Further aims
were to deter-mine if the incisor format for each sound is
affectedby being in initial or final word position or by
beingcombined with succeeding or preceding open orclosed
vowels.
Materials and Methods
Subjects
Atotalof30 healthy subjects participated in the study;all had
intact dentitions. There were 15 men and 15women with a mean age of
22 years (range 20 to 25yearsi. The incisur relationship of each
subject wasrecorded and classified^ ̂ on the basis of contact of
themandibular incisors or a continuation of their axialplanes with
the palatal surface ofthe maxillary incisorswhen occluding in IP,
The composition ofthis subjectgroup, with regard to relative
numbers ofthe differ-ent incisor relationship classes, was
determined toclosely approximate the mean of that reported foryoung
English adults,'"'-'*' which was taken as the ac-cepted standard
for this study. Random allocationfrom a total sampling frame of 50
subjects to each ofthe 4 incisor subgroups supplied the makeup of
thefinal subject group of 13 Class I subjects, 8 Class II di-vision
1, 7 Class II division 2, and 2 Class III, Therewas no
statistically significant proportional difference
(Chi-squared) in relation to incisai classification be-tween the
subject group and the accepted standard.
Jaw Position Recording
jaw positions were recorded using a sirognathograph(SCG;
Siemens), The SCO was connected to a com-puterized system (Bio-Pak,
Bio-Research Associates)that recorded and displayed, to the nearest
0,1 mm,spatial coordinates in 3 planes; frontal (vertical),
sagit-tal (anteroposterior), and coronal (lateral). The systemhas
been shown" to have linear output for up toabout 40 mm of vertical
displacement when lateralmovement is less than 10 mm; these
conditions werefulfilled in this study.
Speech Protocol
The speech tests used in the experiments were de-signed in
conjunction with a speech therapist, A totalof 24 individual
consonant sounds and 2 vowelsounds were investigated. The
consonants can beclassified into 6 subgroups: sibilants, plosives,
frica-tives, liquids, glides, and nasals (Table 1 ). A numberof the
sounds are paired as voiceless and voiced;these have the same
articulatory pattern but differ inthat the voiced sounds are
produced with laryngealphonation.
The speech sounds were recorded in initial andfinal word
placement and each in combination withthe open vowel /Ah/ and the
closed vowel /E/, Somesounds are not employed in initial word
placementin English and others not in final word placement. The2
vowel sounds were recorded individually to con-firm the open/closed
relationship.
Mandibular positions for 88 words were recordedin 17 separate
tests (Table 1 ¡. Each test was limitedto a maximum of 6 words that
were pronouncedwith a pause between them to allow recording on
asingle graphic screen of the analysis system. Thispermitted a
straightforward visual identification andmeasurement of the desired
consonant sound.
The recording sequence was explained to the sub-jects and the
speech tests were demonstrated for pro-nunciation and rate and
volume of speech. The latter2 parameters were described as that of
normal con-versational speech and subjects were given a fewminutes
to rehearse the tests. The SGG headset wasmounted and aligned with
the subject seated uprighton a plastic chair with the head firmly
supportedagainst the rear chair support. Subjects were instructedto
keep their heads as steady as possible during record-ing.
Recordingartifact5 caused by head movement ordisplacement ofthe
antenna device may occur whenusing the SGG.'^''^ For this reason
movements ofthe
The Internationa I oí Pioslliodortii 264
-
Burnett Incisor Position for Con so
Table 1 Consonant Sounds and Word Tests
Consonantsound
SibilantsS voicelessS h voicedZ voicelessZh voicedCh voicelessJ
voiced
^losivesP voicelessB voicedT voicelessD voicedK voicelessG
voiced
-ricatfvesF voicelessV voicedT h iTÎ12H
LiquidsLR
GHdesYW
NasalsMNNg
VoweisAhE
Initial +open vowe
Test iSamSham2amZuramChamJamTest
5PaBaTaDaKaGaTestaFanVanThankThatHatTest 13LanRan
YeahWan
ManNan
Test 17atitieee
Final +open vowel
Test 2PassCashAsAzuPatchMadgeTesteTapSaabPatMadRackRagTest
10LaugtiCalfKatti
Test UValCar
CramManSang
Initial T-closed vowel
Test 3SeeSheZeeZureeChesJeeTest 7PeeBee7ee•eeKeeGeeTest
11FeelVetoTheatreTheHeTest 15LeeRee
YeWe
MeKnee
ant Sounds
Rnal*closed vowe)
Test
4PieceOuictieEaseEmPeachSiegeTestsCreepBeebSheetReadReekLeagueTest
12LeafLeaveKeith
Test 16HeelEar
•SBS:.^
DreamMeanIng
headset were checked for by inspection and by hav-ing subjects
start and finish each test at tbe referencepoint, IP, as identified
on tbe screen; discrepancieswere seldom found, but if they were the
recording wasrepeated. The intluence of recording and subject
vari-abiiity has been previousiy investigated^ with regardto
mandibular speech positions; these were shown tobe reproducibie
after a 6-month intervai. The samemethod was empioyed in this
investigation.
Each ofthe consonant and vowei sounds was de-scribed in reiation
to its verticai, anteroposterior, andiaterai separation from IP.
The mandibuiar positionthat came ciosest to iP in tbe verticai
direaion duringthe exercise was taken to represent the superior
speak-ing position (SSP). The most anterior mandibuiar po-sition
assumed in relation to iP was taken to representthe anterior
speaking position (ASP). The positions inthe horizontai plane that
were posterior to IP weregiven a negative value. Statisticai
anaiysis was per-formed by means of 2-group unpaired Student's
itestsand anaiysis of variance (ANOVA) muitipie compar-ison tests
using the Scheffé criterion, with Pvalues lessthan 0.01 interpreted
as statisticaiiy significant.
Table 2 Mean Dimensions (mm) of the InterocclusalSpeecti
Position of 2 Vowel Sounds for ttie SubjectGroup (n = 30]
Vowelsound
Afi
E
Direction
VerticalAfitenapDsteriofLateralVerticalAntenjposteriorLateral
Mean
12.2*-2.1
1.0IT
-1.40.6
Standarddeviation
3.72.90.92.72.4
0.6
Range
5.6-20.0-9.1-7.2
0-3.42.5-14.1
-6.6-7.20-2.2
'Significant difference P i Q.01 (Student's 1 test).
Results
Vowel Sound Positions
The group mean verticai incisai separation for/Ah/was 12.2 mm.
which was significantly more "open"(P < 0.0001 ) than /E/ at 7.7
mm (Tabie 2).
265 The International Journal of PriBIhodontics
-
Inciser Position for Consonant Soundi
Table 3 Dimensions (mm) of the Interocclusal Speech Position of
the ConsonantSounds for the Subject Group (n = 30)
Word sound
S
Z
Sh
Zh
Ch
J
P
\r. 1̂ ._B" ""
T
D
K
G
F .
Direction
VerticalAnts ro
posteriorLateralVerticalAnteropostefiorLateralVerticalAnte ropo
steri
orLateralVerticalAnteropostenorLateralVerticalAnteropcsteriorLateralVerticalAnteropos
le ri orLateralVerticalAnteroposleriorLateralVerticalAnte roposte
rio rLateralVerticalAnteroposferiorLateralVerticalAnte roposte rio
rLateralVerticalAnte roposte rio rLateralVerticalAnte roposte rio
rLateralVerticalAnte roposte rio rLateral
Mean
2.51.4o.a2.51.40.72.51.40.72.51.40,72.51.40.72.51.40.76.3
-0.80.56.3
-0,7053.10.60.43.20.50.45.9
-0.90.55.9
-0.80.55,1
-1.50,7
SD
1.52.10.71.42.1071.52.10.81.52.10.71.42.10.81.42.00.81.61.80.51.51.90.51.62.10.51.62.10,51,61,80.61.61.90.61.42.30.6
Range
0.2-7.1-2.9-10.0
0-2.70.1-6.6
-2.B-9.90-2.6
0.2-6.4-2.6-9.5
0-3.00.2-7.2
-3.0-9.40-2.6
0.3-6.5-2.4-9.8
0-3.30.3-6.1
-2.2-9.50-3.3
3.5-9.5-2.7-6.7
0-1.73.4-6.9
-3.0-7 80-1.9
0.7-6.8-3.0-9.4
0-2.50.4-7.1
-3.1-9.20-2.4
2.4-9,6-3.3-7.0
0-2.31.8-9,5
-3.5-8.10-2.4
2.4-6.2-6.4-7,4
0-2.4
Placement of Consonant Sound in Initiai orFinal Word
Position
The placement of the consonant sound in the initialor final word
position had no effect on the incisai po-sition assumed for that
particular sound.
Sound Combination with an Open orClosed Vowel
The combination with an open or closed vowel didnot alter the
incisai position assumed for the pro-duction of the sounds /S/,
/Sh/, /Z/, /Zh/, /Ch/, /J/, /P/,/B/, AT/, /D/,/K/, /G/, /F/, /V/,
AhV, or/Th2/. The de-gree of vertical incisai separation was
significantlygreater for the sounds /H/, /L/, /R/, /Y/, /W/, /M/,
/N/,and/Ng/when in combination with the open vowel
sound (P< 0.0001). The anteroposterior and lateralpositions
of all ofthe consonants were unaffected byvowel association.
Consonant Incisai Position
The data from the investigation on initial and finalplacement
and open and closed vowels were com-bined to produce mean values
for the 24 consonantsounds in all 3 dimensions (Table 3). The
vertical di-mension is reported for both vowels for the soundsfor
which vertical jaw separation was affected bycombination with an
open or closed vowel. Therewas no positional difference between any
of thevoiceless/voiced consonant pairings. There was nogender
difference in the dimension of any speechposition.
Tlie Intemational Iourral of Prosthodontics 266 Í12, Number 3,
1999
-
Table 3
Bumett
continued
Word sound Direction
V
Tht
H
L
R
Y
W
M
N
Ng
VerticalAnleroposterioiLateralVerticalAnteroposteriorLateralVerticalAnteroposteriorLateralVertical
(ov)Vertical (cv)AnteroposteriorLateralVertical (ov)Vertical
(cv)Ante roposte riotLateralVertical (ov)Vertical
(cv)AnteroposteriorLateralVerBcal (ov)Vertical (cv)Ante roposte
norLateralVertical (ov¡Vertical (cv)Ante re posten
orLateralVertical (ov)Vertical (cv)AnteroposteriorLatera!Vertical
(ov)Vertical (cv)AnteroposteriorLateralVerucal (ov)Vertical
(cv)AnleroposteriorLateral
Incisor Position tor Consonant Sounds
Mean
5.2-1.40.76.8
-1.40.78.3
-1.20.7
11.7g.o
-1.70.8
11.08.9
-1-60.78
10-88.5
-1.60.9
10.5 • - '8.6
-1.60.7 —iniw
11-18-8
-1.70.8
11-5"SiS^i8.3
-1.B0.9
11.38.4
-1.30.9
8.7 "^^^^^-1.6
0.8
SD
1.42.40.61.52-30.62.12.10.62.82.62.40.62.62.62.30.62-32.32.40.6
• 2.82.72.2
2.62.72.10.8
2.32.80.72.82.32.40.6
2,40,7
Range
2.1-8-5-6.6-8.0
0-2.13.4-10.5
-6.7-7.40.1-2.64-2-12.8
-5.8-7.20.1-2.65.2-17.24.3-15.0
-7.8-7.40-2.5
5.1-16.14.1-16.6
-6.1-7-10-2.3
6-1-15.04-1-14.4
-6.8-7.2Q. 1-2.45.0-16-93.1-13.4
-5.0-6.6^ S t 0-1.9
7-1-17.54.2-13.8
-6.7-6.10-2.8
Sm. 6.0-16-63.&-13-3
-7.0-7.20-2.5
5-9-17.13-5-14.1
-5.8-8.00-2.7
g ^ 5.9-15-93.1-13-4
-6.9-8.20-2.5
SO = standard deviaton: ov = ¡n combination wftti open vowet; cv
= in comtiinatron with dosed vowel.
The mean values deduced for the 30 subjects forthe 24 consonant
sounds ¡n the vertical directionshowed a range from IP of 2.5 mm
for a sibilantsound to 11.7 mm for the /H / sound iti
combitiattonwith an open vowel; and an anteroposterior range of1.4
mm anterior to IP for a sibilant sound to 1.8 mmposterior for
the/Wsound. The relatively large stan-dard deviations and ranges
associated with the di-mensions for all incisai speech sound
positionsdemonstrate the individual variability of these
posi-tions; this should be borre in mind when interpret-ing mean
values.
There was no difference among any of the sibilantsotjnds with
regard to their mean mandibular incisorposition; however, there was
variation within each in-dividual with regard to which ofthe 6
sounds pro-duced the SSP. This variation could be as large as
2.0
mm, although it was often much smaller. Nonethe-less, to
precisely determine an individual's SSP it isnecessary for a
subject to recite a speech exercisecontaining all ofthe
Sibilantsounds. The sibilant ASPof 26 subjects was anterior to IP.
with only 4 subjectscoincident or posterior to IP. In the lateral
dimensionthe sibilant position was very close or coincidentwith the
midline, with about equal numbers of sub-jects placed to the left
or right.
The plosive sounds /P/, /B/, /K/, and /C/ all had asimilar
incisai position that was significantly greater|P
-
r Poîition for Consonant Sounds
16-
1 4 '
12-
? ..„g 10-
tio
o 3-a. °"in•s0) _
> 6-
4 -
2 -
IP oH
1 Sibilant2P/B3T/D4K/G5F/V6Th17Th2BHou9HCV
IOUR0V11 UR cuI2Ï/W0V
layWcv:AWNIMgov
15 MiN*lg cv
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Word sound
Fig 1 Consonant sound verticalpositions (mean t standard
devia-tion) trom IP tor the subject group(n = 30). cv = in
combination withopen vowei; cv - n̂ combinationwith closed
vowei.
cannot be said to always cause an individual's SSP,although the
size of tbe difference appears to be clin-ically irrelevant. The
mean ASP for the sounds A"/and/D/ was just anterior to IP, with 12
individuals coin-cident or posterior to IP. There was no
differenceamong any plosive sounds in the lateral plane.
The mean vertical dimensions of all of the fricativesounds were
significantly different from one another(P
-
Incisor Position for Consonant Sounds
Fig 2 Consonant sound antero-postenor positions (mean ±
stan-danj deviation) from IP for the sub-jeot group (n = 30),
4
3
2
.f 1t
o
oCL
.S -1
oo. oo —¿- •
itei
•^ - 3 .
- 4 -
- 5 -
IP - 6 •0 1 2 3 4 5 6 7
Word sound
8
1 SibilantS P/B3 T/D4 K/G5F/V6TT1I7Th2SH9 L/R
10Y/W11 M/N/Ng
9 10 11
group of 30 subjects, A broad range in values of verti-cal
incisai separation was found between the "closed"sounds (the
sibilants,/T/, and /D/) and the more "open"sounds t/H/and the nasal
sounds). The incisor positionof each individual sound was
unaffected by initial orfinal word placement of that sound. This
finding willsimplify and shorten the design of speech tests in
futurestudies. The incisor format for 16 of the consonantsounds was
unaffected by being enunciated in com-bination with either an open
or closed vowel. The re-maining 8 consonant sounds had a larger
vertical in-cisor separation when in combination with an openvowel
sound. These 8 sounds were among those witha larger mean incisai
separation. It appears that in pro-ducing sounds that require a
closed jaw relationship agreater constraint is placed on jaw
position, in relationto combination with preceding or succeeding
vowels,than is the case with more open sounds. A variationwithin
individuáis was identified w ith regard to whichparticular sound
produced the smallest incisai separa-tion, but the magnitude ofthe
differences is probablyclinically insignificant. Therefore, the use
of traditional/S/ sound speech tests, such as "Mississippi" or
"sixty-six," should give acceptable results in the determina-tion
of occiusai vertical dimension. The only previousreport in the
literature of a 3-dimensional /S/ soundposition is by George,^ who
found a near /S/
position to be 1,8 mm vertical, 0.5 mm anterior to IP,and 0,5 mm
lateral, and a far/S/position of 2.9 mm ver-tical, 2-0 mm anterior
to IP, and 1.2 mm lateral.George^ suggested that the mandible has a
range ofmovement during the production of the/S/sound thatis
dependent on the sounds preceding or following the/S/, but this was
not supported in the current study,ßenediktsson-̂ reported
the/S/position in 2 dimensionsat2.6mm vertical, with a range of Oto
14 mm, and 1.3mm anterior to IP, with a range of-2 to 10 mm
wherethe negative value indicates a position posterior to
IP.Benediktsson's result is very close to the sibilant posi-tion
reported here, as are the results of Gillings,'' whofound the
sibilant position in the vertical dimension tobe 2.5 mm (SD ± 1,7,
range 0 !o 6 mm).
The /M/ sound has been advocated in determiningthe postural
interocclusal position, or mandibular restposition, in complete
denture prosthodontics"''-^'^' be-cause it is thought to produce a
vertical opening equiv-alent to the interocclusal distance
required, ie, 2 to 4mm. This has been supported by Gibbs et al,^
whofound the opening at//vVto be 3.0 mm for 4
subjects.Investigating lip and mandibular dynamics for 5 sub-jects,
Sussman and Smith^- found the jaw lowering for/iVV to be 11.7 mm
for ail vowel combinations. The cur-rent study is the first
investigating the /iW sound for alarge sample of English speakers;
the vertical opening
"Z, Number 3, 1999 269 The Interraiional Journal of
Prosttiodontics
-
lncÍ50f Position for Consonant Sounds
of the//vV sound with an open vowei found in this studywas 11.5
mm (range 6.0 to 16.6 mm| and 8.3 mm witha ciosed vowei (range 3.6
to 13.3 mm). These resuitsdo not support the use of the/M/sound to
estabiishpos-turai interocclusai position in dentate or edentate
pa-tients.
A study protocoi in which subjects read out pre-pared speech
exercises is an artificiai situation thatmay lead to adoption of
jaw positions that do not truiyrefiect those of uninhibited
conversationai speech.Variables such as rate and voiume of speech
aredif-ficuit to standardize, but the more externai
artificiaicontrois that are exerted on functions increases
thepotential to detract from a naturai performance.Abbs-' has shown
that an increased speaking rate re-suits in an unchanged mean
displacementof the jawfrom the conversationai speaking rate. The
voiume ofspeech is mostiy dependent on the subgiottai com-ponent of
speech production, consisting of the iungsand the associated
respiratory muscuiature, and isconcerned with generating the air
flow that powersspeech production, although shouting is obviously
as-sociated with exaggerated mandibuiar movement.^"
Speech sounds are articuiated and modified by a va-riety of orai
organs, of which the mandible is botone,and the adaptability of
speech must be borne in mindwhen interpreting mandibuiar positionai
formats. It hasbeen shown that test subjects are abie to
compensateduring speech, by appropriate adjustments of their iipand
tongue movements, to produce the same acousticsignai with no
difference in the timing oi magnitude ofmuscieactivitywhiie biting
on a "bite biock" betweenthe posterior teeth.^^ it is suggested
that speakers havea montai representation of the supraiaryngeai
vocaltract that they use to produce a particuiar speech
sound.Deviations from normai intraorai conditions
produceappropriate movements to rearrange the vocai tractshape in
compensation. Converseiy, this argument putsa value on descriptions
of mandibuiar speech positions,as it supports the view that
unhindered speech articu-lation positions should be stabie and
reproducibie.
Conclusions
Within the limitations of the study it was conciuded that:
1. The incisor position for each individuai consonantsound was
unaffected by initiai or finai wordpiacement of that sound.
2. The verticai incisor position for the consonantsounds /S/,
/Sh/, fZj, flhl, ICr\j, ¡\l, /P/, /B/, /T/,
/D/,/K/,/C/,/FA/V/./ThV, and Ah2/was unaffected bybeing enunciated
in combination with either theopen vowei sound/Ah/or the ciosed
vowei sound/E/. The remaining consonant sounds, /H/, ¡U, /R/,
A/ , AV/, ¡Ml, /N/, and /Ng/, produced a larger verti-cai
incisor separation when in combination with theopen vowei sound.
The anteroposterior and iateralpositions were unaffected by vowei
association,
3, The sibilant sounds caused the SSP in most sub-jects,
although for others the /TD/ sounds weresiightiy smaiier. There was
variation within indi-viduals as to which sibiiant sound caused the
SSP,but this difference is ciinicaliy insignificant andwords
containing the/S/sound alone are recom-mended for ciinicai
determination of this position.
4, A sibiiant sound aiways produced the most ante-rior speaking
position of the mandibie.
5, The position of the mandibie during pronuncia-tion of
the/M/sound wouid not aiiow a satisfac-tory ciinicai determination
oftheposturai interoc-clusai position.
Acknowledgment
The author wishes to acknowledge the assistance of Ms
ChristineHayden, Department of Speech and Language Therapy, The
RoyalBelfast Hospital for Sick Children.
References
1. Silverman MM, Accurate measurement of vertical dimension
byphonetics and the speaking centric space. Part i. Dent
Digest1951;57:261-265.
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Literature Abstracts-
Pain, allodynfa, and serum serotonin level in orofacial pain of
muscular origin.
TTiis interesting study investigated the blood semm level of
serotonin in patients with femporo.mandibular disorders fTMD] of
muscular origin and compared rt with levels in healthy subjecis
andin patients with fibromyalgia. The etiology and pathophysiology
ot TMD is still unclear, but there isevidence ttiat serotonin is
involved in the pathophysiolcgy cf chronic pain. The study groups
com-prised 20 patients wrth localized myalgia (TMD). 20 healthy
subjects (age- and gender-matched),and 20 female fibromyalgia
patients (cfiagnosed according to the criteria ot the American
Collegeof Rheumatology). All participants were examined clinically
for signs of dysfunction in the temporo-mandibular region by
nDufine methods, and pressure pain threshold and pressure pain
tolerancelevel were assessed with an algometer. A blood sample was
taken from each patent for serotoninanalyses. The results showed no
significant differences in serotonin blood levels among thegroups,
and a wide individual variation in all 3 groups. The TWD patients
with localized myalgiashowed a negative correlaSon between
serotonin level and tendemess ot the tempommandibularmuscies. in
the group wrth flbn^myalgia there was also a negative con-elation
between serotoninlevel and number ot painful musculoskeletal body
regions. It was concluded tfiat allodynia of crofa-dal muscies in
patients with TMD is significantly related to the serotonin
concentration.
Emberg M. Hedenberg-Magnusson B, Alstergren P, Lundeberg T, Kopp
S, J Omfac Pain1999;13:55-62. References: 22. Reprints: Or Malm
Emberg. Department of Cliricaj Oral Physiology,ScliocI of
Dentistry, Box 4064, SE-141 04 Huddlngs. Sweden, e-mail:
maJinembergaota.ki.se—,41V
Microleakage of the abutment-implant Interface of os sea inte g
rated implants:A comparative study.
The microleakage at the abutment-implant interface was studied
in vitro using colored tracingprobes driven by a 2-atm pressure
system. Five different implant systems were compared, alsoaltering
the closing torques of the abutment connections. A gradual increase
in micrcleakingover time was observed for ail samples. Microleakage
decreased significantly as the closingtorque increased from 10 Nom
to the manufacturers' recommended closing torques.
Significantdifferences among the tested implant systems were found.
Comparing dye microleakage valuesin the 5 systems at the
manufacturers' recommended closing torques, the microleakage of
theITI assemblies (Straumann) appeared to be higher than that of
the other 4 systems. However,the difference was significant only
after 20 minutes. The clinical implications of the results
werediscussed, and it was stated that abutment ciosure at the
recommended torques would help fominimize the potential adverse
effecfs of microieakage.
GrossM, Abramovich I. Weiss E./nl JOfa/Waxiïtofac/mpianis
1999:14:94-100. References: 26.Reprints: Dr Martin Gross,
Department of Oral Rehabilitation. The Maurice and Gabriela
GoldschlegerSchool of Dental Medicine, Tel Aviv University, Tel
Aviv, Israel—SP
r^;-\:~--. '.2. Number 3,1999271 The Internationa al of
Prosthodontii
