Mandibular Incisor Position for English Consonant Sounds C

Mandibular Incisor Position for English Consonant Sounds C. Andrew Burnett, BOS, FDS. RCPS, PhD'

Purpose: The purpose of this study was to describe the mandibtjiar incisor poiitions for the 24 consonant sounds ot" tbe English language. Further aims were to determine if the incisor format for each sound is affected by its position in a word, or by combination wfib an open or closed vowei. Materials and Methods: A total of 30 young adult subjects had their incisai positions determined using an electrognathographic technique during performance 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 a sibilant sound to 11.7 mm for the /H/ sound, and an an tero posterior range of 1.4 mm anterior for a sibilant sound to 1.8 mm posterior for the IM/ sound. The range in the mean lateral dimension was always less than 1 mm on either side of the midiine. The placement of a sound in the initial or final position in a word had no erfect on the incisai position. The degree of vertical opening was significantly greater for 8 of the consonant sounds when in combination with an open vowel sound. The anteroposterior and lateral positions were unaffected by vowel association. Conclusion: The incisor position for consonant sounds is unaffected by initial or t7nal word placement. Some consonant sound positions are affected by combination with an open or closed vowel sound. Sibilant sounds produced a clinically acceptable measure of the most superior and anterior speaking positions in all subjects, ¡nt¡ Prosthodont 1999:12:263-271.

ncisai relationships in speech function have been vocal tract articulation. The English language can be Idescribed at the/S/position'- and the/M/position,^ broadly divided into 24 consonant sounds and 17 while counting,•'•^ and during tbe recitation of pas- vowel sounds. Consonant speech sounds are pro- sages of speecb designed to simulate conversational duced by tbe vocal traa interrupting or obstructing the speecb.^^ Envelopes of maximal jaw motion during flow of air at some point, requiring specific articula- speech in 3 planes have also been described'-^ and tory formats of the tongue, lips, mandible, teetb. and shown to be reproducible.^ palate. Phonologic analysis has been traditionally Speech sounds are classified into different groups performed by investigating consonants in 3 word po- based principally on tbe acoustic properties of the sitions: initial, medial, and final. More recently it has sound, but they may also be described in terms of been suggested that consonants in the word-medial position can be divided into word-initial or word-final consonants in a principled manner.^ That study pro- 'Clinicai Lecturer, Division of Restorative Dentistry, Schooi of posed to investigate whether there was a difference Ciinicai Dentistry, The Queen's University af Belfast, The tioyai Group of Hospitals, Belfast, Northern Ireland. in tbe mandibular position required to produce consonant sounds in initial or final word positions. Reprint requests: Dr C. Andrew Burnett, Division of Restorative Vowel sounds are produced with little or no ob- Dentistry, School of Ciinicai Dentistry, The Queen's University of Beifast Grosvenor Road, Beifast BTI2 6BP, Northern Ireland, fat: struction to air flow and are created by adjustments + 01232 4Í886Í. e-mail: c.burnett&qub.ac.uk of 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 articulatory (Chi-squared) in relation to incisai classification be- patterns. It is not possible to predict whether a vowel tween the subject group and the accepted standard. sound will be produced by adaptation of the tongue, lips, or larynx. Therefore, the recording of specific in- Jaw Position Recording cisal formats for the range of vowel sounds will not capture consistent jaw positions for specific sounds. jaw positions were recorded using a sirognathograph Traditionally, however, some vowel sounds have been (SCG; Siemens), The SCO was connected to a com- known as "open" vowels, eg, /Ah/, and associated with puterized system (Bio-Pak, Bio-Research Associates) a large jaw separation; others have been known as that recorded and displayed, to the nearest 0,1 mm, "closed" vowels, eg,/E/, and associated with lesser jaw spatial coordinates in 3 planes; frontal (vertical), sagit- separation. It has been postulated that the articulation tal (anteroposterior), and coronal (lateral). The system of fhese sounds may affect the jaw position for suc- has been shown" to have linear output for up to ceeding or preceding consonant sounds.•• about 40 mm of vertical displacement when lateral Phonetic tests have long been advocated as a clin- movement is less than 10 mm; these conditions were ical aid in designing and constructing oral prosthe- fulfilled in this study. ses, especially with regard to anterior tooth position and the vertical dimension of occlusion. The /S/ Speech Protocol sound has been used to determine the adequacy of the interocclusal distance,^•^''•^' the/F/and/V/sounds The speech tests used in the experiments were de- to decide the maxillary anterior looth position,'^ and signed in conjunction with a speech therapist, A total the/M/sound to establish a desirable mandibular pos- of 24 individual consonant sounds and 2 vowel tural position,•''"' The basis for many of these clini- sounds were investigated. The consonants can be cal techniques has come from studies that did not pro- classified into 6 subgroups: sibilants, plosives, frica- duce quantitative data. tives, liquids, glides, and nasals (Table 1 ). A number The aim of this study was to describe the mandibu- of the sounds are paired as voiceless and voiced; lar incisor position in relation to intercuspal position these have the same articulatory pattern but differ in (IP) in 3 dimensions for the 24 consonant sounds of that the voiced sounds are produced with laryngeal the English language. Further aims were to deter- phonation. mine if the incisor format for each sound is affected The speech sounds were recorded in initial and by being in initial or final word position or by being final word placement and each in combination with combined with succeeding or preceding open or the open vowel /Ah/ and the closed vowel /E/, Some closed vowels. sounds are not employed in initial word placement in English and others not in final word placement. The Materials and Methods 2 vowel sounds were recorded individually to con- firm the open/closed relationship. Subjects Mandibular positions for 88 words were recorded in 17 separate tests (Table 1 ¡. Each test was limited Atotalof30 healthy subjects participated in the study; to a maximum of 6 words that were pronounced all had intact dentitions. There were 15 men and 15 with a pause between them to allow recording on a women with a mean age of 22 years (range 20 to 25 single graphic screen of the analysis system. This yearsi. The incisur relationship of each subject was permitted a straightforward visual identification and recorded and classified^ ^ on the basis of contact of the measurement of the desired consonant sound. mandibular incisors or a continuation of their axial The recording sequence was explained to the sub- planes with the palatal surface ofthe maxillary incisors jects and the speech tests were demonstrated for pro- when occluding in IP, The composition ofthis subject nunciation and rate and volume of speech. The latter group, with regard to relative numbers ofthe differ- 2 parameters were described as that of normal con- ent incisor relationship classes, was determined to versational speech and subjects were given a few closely approximate the mean of that reported for minutes to rehearse the tests. The SGG headset was young English adults,'"'-'*' which was taken as the ac- mounted and aligned with the subject seated upright cepted standard for this study. Random allocation on a plastic chair with the head firmly supported from a total sampling frame of 50 subjects to each of against the rear chair support. Subjects were instructed the 4 incisor subgroups supplied the makeup of the to keep their heads as steady as possible during record- final subject group of 13 Class I subjects, 8 Class II di- ing. Recordingartifact5 caused by head movement or vision 1, 7 Class II division 2, and 2 Class III, There displacement ofthe antenna device may occur when was no statistically significant proportional difference using the SGG.'^''^ For this reason movements ofthe

The Internationa I oí Pioslliodortii 264 Burnett Incisor Position for Con so ant Sounds

Table 1 Consonant Sounds and Word Tests

Consonant Initial + Final + Initial T- Rnal* sound open vowe open vowel closed vowel closed vowe) Sibilants Testi Test 2 Test 3 Test 4 S voiceless Sam Pass See Piece S h voiced Sham Cash She Ouictie Z voiceless 2am As Zee Ease Zh voiced Zuram Azu Zuree Em Ch voiceless Cham Patch Ches Peach J voiced Jam Madge Jee Siege ^losives Test 5 Teste Test 7 Tests P voiceless Pa Tap Pee Creep B voiced Ba Saab Bee Beeb T voiceless Ta Pat 7ee Sheet D voiced Da Mad •ee Read K voiceless Ka Rack Kee Reek G voiced Ga Rag Gee League -ricatfves Testa Test 10 Test 11 Test 12 F voiceless Fan Laugti Feel Leaf V voiced Van Calf Veto Leave Thi Thank Katti Theatre Keith TÎ12 That The H Hat He Liquids Test 13 Test U Test 15 Test 16 L Lan Val Lee Heel R Ran Car Ree Ear GHdes •SBS:.^ Y Yeah Ye W Wan We Nasals M Man Cram Me Dream N Nan Man Knee Mean Ng Sang Ing Voweis Test 17 Ah atiti E eee

headset were checked for by inspection and by hav- Table 2 Mean Dimensions (mm) of the Interocclusal ing subjects start and finish each test at tbe reference Speecti Position of 2 Vowel Sounds for ttie Subject Group (n = 30] point, IP, as identified on tbe screen; discrepancies were seldom found, but if they were the recording was Vowel Standard repeated. The intluence of recording and subject vari- sound Direction Mean deviation Range abiiity has been previousiy investigated^ with regard Afi Vertical 12.2* 3.7 5.6-20.0 to mandibular speech positions; these were shown to AfitenapDsteriof -2.1 2.9 -9.1-7.2 Lateral 1.0 0.9 0-3.4 be reproducibie after a 6-month intervai. The same E Vertical IT 2.7 2.5-14.1 method was empioyed in this investigation. Antenjposterior -1.4 2.4 -6.6-7.2 Each ofthe consonant and vowei sounds was de- Lateral 0.6 0.6 0-2.2 scribed in reiation to its verticai, anteroposterior, and 'Significant difference P i Q.01 (Student's 1 test). iaterai separation from IP. The mandibuiar position that came ciosest to iP in tbe verticai direaion during the exercise was taken to represent the superior speaking position (SSP). The most anterior mandibuiar position assumed in relation to iP was taken to represent the anterior speaking position (ASP). The positions in Results the horizontai plane that were posterior to IP were given a negative value. Statisticai anaiysis was per- Vowel Sound Positions formed by means of 2-group unpaired Student's itests and anaiysis of variance (ANOVA) muitipie compar- The group mean verticai incisai separation for/Ah/ ison tests using the Scheffé criterion, with Pvalues less was 12.2 mm. which was significantly more "open" than 0.01 interpreted as statisticaiiy significant. (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 Consonant Sounds for the Subject Group (n = 30)

Word sound Direction Mean SD Range S Vertical 2.5 1.5 0.2-7.1 Ants ro posterior 1.4 2.1 -2.9-10.0 Lateral o.a 0.7 0-2.7 Z Vertical 2.5 1.4 0.1-6.6 Anteropostefior 1.4 2.1 -2.B-9.9 Lateral 0.7 07 0-2.6 Sh Vertical 2.5 1.5 0.2-6.4 Ante ropo steri or 1.4 2.1 -2.6-9.5 Lateral 0.7 0.8 0-3.0 Zh Vertical 2.5 1.5 0.2-7.2 Anteropostenor 1.4 2.1 -3.0-9.4 Lateral 0,7 0.7 0-2.6 Ch Vertical 2.5 1.4 0.3-6.5 Anteropcsterior 1.4 2.1 -2.4-9.8 Lateral 0.7 0.8 0-3.3 J Vertical 2.5 1.4 0.3-6.1 Anteropos le ri or 1.4 2.0 -2.2-9.5 Lateral 0.7 0.8 0-3.3 P Vertical 6.3 1.6 3.5-9.5 Anteroposlerior -0.8 1.8 -2.7-6.7 \r. ^1 ._ Lateral 0.5 0.5 0-1.7 B" "" Vertical 6.3 1.5 3.4-6.9 Ante roposte rio r -0,7 1.9 -3.0-7 8 Lateral 05 0.5 0-1.9 T Vertical 3.1 1.6 0.7-6.8 Anteroposferior 0.6 2.1 -3.0-9.4 Lateral 0.4 0.5 0-2.5 D Vertical 3.2 1.6 0.4-7.1 Ante roposte rio r 0.5 2.1 -3.1-9.2 Lateral 0.4 0,5 0-2.4 K Vertical 5.9 1,6 2.4-9,6 Ante roposte rio r -0.9 1,8 -3.3-7.0 Lateral 0.5 0.6 0-2.3 G Vertical 5.9 1.6 1.8-9,5 Ante roposte rio r -0.8 1.9 -3.5-8.1 Lateral 0.5 0.6 0-2.4 F . Vertical 5,1 1.4 2.4-6.2 Ante roposte rio r -1.5 2.3 -6.4-7,4 Lateral 0,7 0.6 0-2.4

Placement of Consonant Sound in Initiai or sound (P< 0.0001). The anteroposterior and lateral Final Word Position positions of all ofthe consonants were unaffected by vowel association. The placement of the consonant sound in the initial or final word position had no effect on the incisai po- Consonant Incisai Position sition assumed for that particular sound. The data from the investigation on initial and final Sound Combination with an Open or placement and open and closed vowels were com- Closed Vowel bined to produce mean values for the 24 consonant sounds in all 3 dimensions (Table 3). The vertical di- The combination with an open or closed vowel did mension is reported for both vowels for the sounds not alter the incisai position assumed for the pro- for which vertical jaw separation was affected by duction of the sounds /S/, /Sh/, /Z/, /Zh/, /Ch/, /J/, /P/, combination with an open or closed vowel. There /B/, AT/, /D/,/K/, /G/, /F/, /V/, AhV, or/Th2/. The de- was no positional difference between any of the gree of vertical incisai separation was significantly voiceless/voiced consonant pairings. There was no greater for the sounds /H/, /L/, /R/, /Y/, /W/, /M/, /N/, gender difference in the dimension of any speech and/Ng/when in combination with the open vowel position.

Tlie Intemational Iourral of Prosthodontics 266 Í12, Number 3, 1999 Bumett Incisor Position tor Consonant Sounds

Table 3 continued

Word sound Direction Mean SD Range V Vertical 5.2 1.4 2.1-8-5 Anleroposterioi -1.4 2.4 -6.6-8.0 Lateral 0.7 0.6 Tht 0-2.1 Vertical 6.8 1.5 3.4-10.5 Anteroposterior -1.4 2-3 -6.7-7.4 Lateral 0.7 0.6 0.1-2.6 Vertical 8.3 2.1 4-2-12.8 Anteroposterior -1.2 2.1 -5.8-7.2 Lateral 0.7 0.6 0.1-2.6 H Vertical (ov) 11.7 2.8 5.2-17.2 Vertical (cv) g.o 2.6 4.3-15.0 Anteroposterior -1.7 2.4 -7.8-7.4 Lateral 0.8 0.6 0-2.5 L Vertical (ov) 11.0 2.6 5.1-16.1 Vertical (cv) 8.9 2.6 4.1-16.6 Ante roposte riot -1-6 2.3 -6.1-7-1 Lateral 0.78 0.6 0-2.3 R Vertical (ov) 10-8 2-3 6-1-15.0 Vertical (cv) 8.5 2.3 4-1-14.4 Anteroposterior -1.6 2.4 -6.8-7.2 Lateral 0.9 0.6 Q. 1-2.4 Y VerBcal (ov) 10.5 • -' • 2.8 5.0-16-9 Vertical (cv) 8.6 2.7 3.1-13.4 Ante roposte nor -1.6 2.2 -5.0-6.6 Lateral 0.7 —iniw ^St 0-1.9 W Vertical (ov¡ 11-1 2.6 7-1-17.5 Vertical (cv) 8-8 2.7 4.2-13.8 Ante re posten or -1.7 2.1 -6.7-6.1 Lateral 0.8 0.8 0-2.8 M Vertical (ov) 11-5"SiS^i Sm. 6.0-16-6 Vertical (cv) 8.3 2.3 3.&-13-3 Anteroposterior -1.B 2.8 -7.0-7.2 Latera! 0.9 0.7 0-2.5 N Vertical (ov) 11.3 2.8 5-9-17.1 Vertical (cv) 8.4 2.3 3-5-14.1 Anteroposterior -1.3 2.4 -5.8-8.0 Lateral 0.9 0.6 0-2.7 Ng Verucal (ov) g^ 5.9-15-9 Vertical (cv) 8.7 "^^^^^ 3.1-13-4 Anleroposterior -1.6 2,4 -6.9-8.2 Lateral 0.8 0,7 0-2.5

SO = standard deviaton: ov = ¡n combination wftti open vowet; cv = in comtiinatron with dosed vowel.

The mean values deduced for the 30 subjects for mm, although it was often much smaller. Nonethe- the 24 consonant sounds ¡n the vertical direction less, to precisely determine an individual's SSP it is showed a range from IP of 2.5 mm for a sibilant necessary for a subject to recite a speech exercise sound to 11.7 mm for the /H/ sound iti combitiatton containing all ofthe Sibilantsounds. The sibilant ASP with an open vowel; and an anteroposterior range of of 26 subjects was anterior to IP. with only 4 subjects 1.4 mm anterior to IP for a sibilant sound to 1.8 mm coincident or posterior to IP. In the lateral dimension posterior for the/Wsound. The relatively large stan- the sibilant position was very close or coincident dard deviations and ranges associated with the di- with the midline, with about equal numbers of sub- mensions for all incisai speech sound positions jects placed to the left or right. demonstrate the individual variability of these posi- The plosive sounds /P/, /B/, /K/, and /C/ all had a tions; this should be borre in mind when interpret- similar incisai position that was significantly greater ing mean values. |P

.Number 3.1999 267 The International loumal of Prosthodonlics r Poîition for Consonant Sounds

Fig 1 Consonant sound vertical 16- positions (mean t standard deviation) trom IP tor the subject group (n = 30). cv = in combination with open vowei; cv - ^n combination 14' with closed vowei. 1 Sibilant 2P/B 12- 3T/D 4K/G 5F/V ? ..„ 6Th1 g 10- 7Th2 BHou

ti o 9HCV o 3- IOUR0V a. ° 11 UR cu "in I2Ï/W0V •s layWcv 0) _ :AWNIMgov > 6- 15 MiN*lg cv

IP oH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Word sound

cannot be said to always cause an individual's SSP, Vertical Dimension of Speech Sounds although the size of tbe difference appears to be clinically irrelevant. The mean ASP for the sounds A"/and The word sound vertical positions in relation to IP are /D/ was just anterior to IP, with 12 individuals coin- shown in Fig 1 ; as no positional difference was ap- cident or posterior to IP. There was no difference parent among the sibilant sounds these are presented among any plosive sounds in the lateral plane. by a single position, as are the voiceless/voiced pair- The mean vertical dimensions of all of the fricative ings and the liquid, glide, and nasal groups. The sounds were significantly different from one another sounds can be statistically separated (ANOVA) into (P<0.01), with the exception of the voiceless/voiced 4 positional groups: f/J the sibilant and /TD/ positions pair/FV/. There was a difference between the mean form the smallest group: followed by (¿VP B F G F V vertical dimensions of the /H/ sound in combination Thi/; f^J/Th2/and/H LRYWMNNg/-F closed with an open and closed vowel, with the latter posi- vowel; and (4)/H L R Y WM N Ng/+ open vowel. tion significantly smaller (P< 0.0001]. Tbe mean ASP of all of these sounds was to be found posterior Anteroposterior Dimension of Speech Sounds to IP, with the only significant difference in dimension between the/Th2/and/H/positions (P< 0.01). The speecb sound anteroposterior positions in rela- There was no difference among the dimensions of the tion to IP and to one another are shown in Fig 2. Tbe speaking position in the lateral plane for any of the sounds can be statistically separated lANOVA) into fricative sounds. 3 positional groups; (ÏJthe mean sibilant position as The mean vertical dimension of the liquid, glide, tbe most anterior; (21 the mean /TD/ position as just and nasai sounds in open vowel combination demon- anterior to IP; and (3) the remaining sounds as pos- strated no significant differences among one other, terior to IP. and this was also the case when in closed vowel combination. In the anteroposterior and lateral planes Discussion there was no difference among the dimensions of the speaking position for any of these sounds, and all The mandibular incisor positions for the 24 consonant mean ASPs were posterior to I P. sounds of the English language were reported for a

The iniernationsi lourrd of Pr 268 VolJínel2, Numl-r- Incisor Position for Consonant Sounds

Fig 2 Consonant sound anteropostenor positions (mean ± stan- 4 danj deviation) from IP for the sub- jeot group (n = 30), 3

2 1 Sibilant S P/B . 3 T/D f 1 4 K/G t 5F/V o 6TT1I 7Th2 o SH CL 9 L/R .S -1 10Y/W 11 M/N/Ng o o . —¿-o • ite i •^ -3.

-4-

-5-

IP -6 • 0 1 2 3 4 5 6 7 8 9 10 11

Word sound

group of 30 subjects, A broad range in values of verti- position to be 1,8 mm vertical, 0.5 mm anterior to IP, cal incisai separation was found between the "closed" and 0,5 mm lateral, and a far/S/position of 2.9 mm ver- sounds (the sibilants,/T/, and /D/) and the more "open" tical, 2-0 mm anterior to IP, and 1.2 mm lateral. sounds t/H/and the nasal sounds). The incisor position George^ suggested that the mandible has a range of of each individual sound was unaffected by initial or movement during the production of the/S/sound that final word placement of that sound. This finding will is dependent on the sounds preceding or following the simplify and shorten the design of speech tests in future /S/, but this was not supported in the current study, studies. The incisor format for 16 of the consonant ßenediktsson-^ reported the/S/position in 2 dimensions sounds was unaffected by being enunciated in com- at2.6mm vertical, with a range of Oto 14 mm, and 1.3 bination with either an open or closed vowel. The re- mm anterior to IP, with a range of-2 to 10 mm where maining 8 consonant sounds had a larger vertical in- the negative value indicates a position posterior to IP. cisor separation when in combination with an open Benediktsson's result is very close to the sibilant posi- vowel sound. These 8 sounds were among those with tion reported here, as are the results of Gillings,'' who a larger mean incisai separation. It appears that in pro- found the sibilant position in the vertical dimension to ducing sounds that require a closed jaw relationship a be 2.5 mm (SD ± 1,7, range 0 !o 6 mm). greater constraint is placed on jaw position, in relation The /M/ sound has been advocated in determining to combination with preceding or succeeding vowels, the postural interocclusal position, or mandibular rest than is the case with more open sounds. A variation position, in complete denture prosthodontics"''-^'^' be- within individuáis was identified w ith regard to which cause it is thought to produce a vertical opening equiv- particular sound produced the smallest incisai separa- alent to the interocclusal distance required, ie, 2 to 4 tion, but the magnitude ofthe differences is probably mm. This has been supported by Gibbs et al,^ who clinically insignificant. Therefore, the use of traditional found the opening at//vVto be 3.0 mm for 4 subjects. /S/ sound speech tests, such as "Mississippi" or "sixty- Investigating lip and mandibular dynamics for 5 sub- six," should give acceptable results in the determina- jects, Sussman and Smith^- found the jaw lowering for tion of occiusai vertical dimension. The only previous /iVV to be 11.7 mm for ail vowel combinations. The cur- report in the literature of a 3-dimensional /S/ sound rent study is the first investigating the /iW sound for a position is by George,^ who found a near /S/ large 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 study A/, AV/, ¡Ml, /N/, and /Ng/, produced a larger verti- was 11.5 mm (range 6.0 to 16.6 mm| and 8.3 mm with cai incisor separation when in combination with the a ciosed vowei (range 3.6 to 13.3 mm). These resuits open vowei sound. The anteroposterior and iateral do not support the use of the/M/sound to estabiishpos- positions were unaffected by vowei association, turai interocclusai position in dentate or edentate pa- 3, The sibilant sounds caused the SSP in most sub- tients. jects, although for others the /TD/ sounds were A study protocoi in which subjects read out pre- siightiy smaiier. There was variation within indi- pared speech exercises is an artificiai situation that viduals as to which sibiiant sound caused the SSP, may lead to adoption of jaw positions that do not truiy but this difference is ciinicaliy insignificant and refiect those of uninhibited conversationai speech. words containing the/S/sound alone are recom- Variables such as rate and voiume of speech aredif- mended for ciinicai determination of this position. ficuit to standardize, but the more externai artificiai 4, A sibiiant sound aiways produced the most ante- controis that are exerted on functions increases the rior speaking position of the mandibie. potential to detract from a naturai performance. 5, The position of the mandibie during pronuncia- Abbs-' has shown that an increased speaking rate re- tion of the/M/sound wouid not aiiow a satisfac- suits in an unchanged mean displacementof the jaw tory ciinicai determination oftheposturai interoc- from the conversationai speaking rate. The voiume of clusai position. speech is mostiy dependent on the subgiottai com- ponent of speech production, consisting of the iungs Acknowledgment and the associated respiratory muscuiature, and is concerned with generating the air flow that powers The author wishes to acknowledge the assistance of Ms Christine speech production, although shouting is obviously as- Hayden, Department of Speech and Language Therapy, The Royal sociated with exaggerated mandibuiar movement.^" Belfast Hospital for Sick Children. Speech sounds are articuiated and modified by a va- riety of orai organs, of which the mandible is botone, References and the adaptability of speech must be borne in mind when interpreting mandibuiar positionai formats. It has 1. Silverman MM, Accurate measurement of vertical dimension by been shown that test subjects are abie to compensate phonetics and the speaking centric space. Part i. Dent Digest 1951;57:261-265. during speech, by appropriate adjustments of their iip 2. Benediktsson E. Variation in tongue and jaw position in "s" sound and tongue movements, to produce the same acoustic production in relation lo front teeth occlusion. Acta Odontoi Scard signai with no difference in the timing oi magnitude of 1958;] 5:275-303. muscieactivitywhiie biting on a "bite biock" between 3. Gibbs CH, Messerman T, Reswick JB, Derda HJ. Functional the posterior teeth.^^ it is suggested that speakers have movements of the mandible. J Prosthet Dent 1971 ;26:604-620. 4. Cillings BRD. law movements in young adult men during a montai representation of the supraiaryngeai vocal speech. | Prosthet Dent Í973;29:567~576. tract that they use to produce a particuiar speech sound. 5. Rivera-Mora les WC, Mohi ND. Variability of ciosest speaking Deviations from normai intraorai conditions produce space compared with interocclusal distance in dentulous subjects. appropriate movements to rearrange the vocai tract ] Ptosthet Dent 1991:65:228-232. shape in compensation. Converseiy, this argument puts 6. George JP, Using the kinesiogtaph to measure mandibuiarmove- ments during speech: A pilot study. J Pmsthet Dent I983;49; a value on descriptions of mandibuiar speech positions, 263-270. as it supports the view that unhindered speech articu- 7. Howell PGT. incisai relationships during speech. J Prosthet Dent lation positions should be stabie and reproducibie. 1936;56:93-99. 8. Burnett CA. Reproducibilityof the speech enveiopeand inteioc- Conclusions clusal dimensions in dentate subjects, int J Prosthodont 1994;7: 543-548. 9. Crunwell P. Clinical Phonology. London: Cioom Helm, 1982:157. Within the limitations of the study it was conciuded that: 10. Landa IS. The free-way space and its significance in the rehabilitation of the masticatory apparatus. J Pnasthet Dert 1952;2: 1. The incisor position for each individuai consonant 756-779. sound was unaffected by initiai or finai word 11. Pound E. The mandibular movetnentsof speech and their sever piacement of that sound. related values. J Prosthet Dent 1966;16:835-843, 12. Murrell GA. Phonetics, function and anterior occlusion. J 2. The verticai incisor position for the consonant Prosthet Dent 1974;32:23-3I. sounds /S/, /Sh/, fZj, flhl, ICr\j, ¡\l, /P/, /B/, /T/, /D/, 13. Foster TD, Day A|W. A survey of malocciusion and the need for /K/,/C/,/FA/V/./ThV, and Ah2/was unaffected by orthodontic treatrnent in a Shropshire school population. Br J being enunciated in combination with either the Orthodl974;l:73-78, open vowei sound/Ah/or the ciosed vowei sound 14. Todd IE. Children's Dental Health in England and Wales in 1973. London: Office of Population, Censuses, and Surveys, /E/. The remaining consonant sounds, /H/, ¡U, /R/, HMSO, 1975.

The Intemational Journal of Prosthodontii 270 VolLme12, Numbers. 1999 Incisor Position for Consonant Sounds

15. Houston WJB, Tulley W|. A Textbook of Orthodontics. Bristol- Wright, 1986:6. 21. MacGregor AR. Fenn, Liddelow and Gimscn's Clinical Dentai Prosthetics. London: Wright, 1989:89. 16. British Standard Giossaiy of Dental Terms. London: British 22. Siissman HM, Smith KU. Transducer tor measuring mandibular Standards Institute Publication No. BS 4492, 1983. movements, i Acoust Soc Am 1970,48:857-858. 17. Balkhi KM, Tallents RT, Goldin B. Catania |A. Error analysis cf 23. Abbs |H. The inrluence of the gamma motor system on jaw a ¡aw-tracking device. | Craniomandib Disord facial Oral Pain movements during speecti: A theoretical framework and some 1991^5:51-56. preliminary observations. | Speech Hear Res 1973;I6:i 75-200. 18. Lewin A. Electnjgnathographics. Chicago: Quintessence 1985- 24. Lieberman P, Blumstein SE. Speech physiology, speech per- 18-21. ception, and acoustic phonetics. Cambridge: Cambridge Univ 19. Michler L, Bakke M, Mailer E. Graphic assessment of natural Press, 1988:5-10. mandibular movements. | Craniomandih Disord Facial Oral 25. Folkins JW, Zimmerman GN. Jaw-muscle activity dunng speech Pain1987;1:97-114. with ihe mandible fixed.) Acoust Soc Am 1981 ;69:1,44I-1,444. 20. Mehringer EJ. The use of speech patterns as an aid in prostho- dontic reconstnicuon. J Prosthet Dent I963;13:825-836,

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 and in patients with fibromyalgia. The etiology and pathophysiology ot TMD is still unclear, but there is evidence 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 College of 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 tolerance level were assessed with an algometer. A blood sample was taken from each patent for serotonin analyses. The results showed no significant differences in serotonin blood levels among the groups, and a wide individual variation in all 3 groups. The TWD patients with localized myalgia showed a negative correlaSon between serotonin level and tendemess ot the tempommandibular muscies. in the group wrth flbn^myalgia there was also a negative con-elation between serotonin level 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 Pain 1999;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 tracing probes driven by a 2-atm pressure system. Five different implant systems were compared, also altering the closing torques of the abutment connections. A gradual increase in micrcleaking over time was observed for ail samples. Microleakage decreased significantly as the closing torque increased from 10 Nom to the manufacturers' recommended closing torques. Significant differences among the tested implant systems were found. Comparing dye microleakage values in the 5 systems at the manufacturers' recommended closing torques, the microleakage of the ITI 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 were discussed, and it was stated that abutment ciosure at the recommended torques would help fo minimize 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 Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel—SP

r^;-\:~--. '.2. Number 3,1999271 The Internationa al of Prosthodontii