changes in cheek pres surer me

8/9/2019 Changes in Cheek Pres Surer Me

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European Journal of Orthodontics 16 (1994) 295-300 O 1994 European Orthodontic Society

Changes in cheek pressure following rapid maxillaryexpansionDe me trios J. Halazonetis, Elias Katsavrias, and Me rop i N. Sp yrop oulo sDepartment of Orthodontics, Athens University, Greece

SUMMARY The purpose of the present investigation was to study the effects of rapid maxil-lary expansion on the pressures exerted by the cheeks on the maxillary arch. The sampleconsisted of 15 patients (five males, ten females) who received either a Hyrax or Haas typeexpansion appliance for treatment of a bilateral m axillary constriction of more than 5 mm .The median age of the sample was 12 years. Buccal pressures were measured at the upperfirst molar on the left and right side, before and after active expansion, and also after anaverage of 3-4 months of retention with the appliance in place.Buccal pressures on the maxillary first molar averaged approximately 3 g/cm2 beforeexpansion and increased significantly to a value of approximately 9 g/cm 2 after expansion.Pressure change was approx imately 0.6 g/cm2 for each millimetre of expansion. During the3-4-month period of stabilization of the appliance, the pressures remained at the post-expansion levels and no adaptation of the soft tissues was observed. These results lead tothe conclusion that cheek pressures on the maxillary arch may be implicated in the relapseoccurring after rapid expansion, even after the usual 3-month period of stabilization.

IntroductionRapid maxillary expansion is probably uniquein orthodontics for achieving such a large andevident orthopaedic effect. The separation ofthe maxillae is, however, followed by a largetendency for relapse. Skeletal relapse is due tothe high stresses accumulated between thearticulations of the craniofacial complex and isusually no longer present once the mid-palatalsuture remineralizes, during the third monthafter expansion (Zimring and Isaacson, 1965,Wertz, 1970; Ekstrom et al, 1977; Wertz andDreskin, 1977; Bishara and Staley, 1987).Dental relapse may be attributed to such factorsas the tension produced in the palatal mucosaland supracrestal fibres (Muguerza and Shapiro,1980), the buccal axial inclination assumed bythe upper teeth, and the resulting imbalancebetween the buccal and lingual pressures.The teeth are thought to reside in a state ofequilibrium, balanced between the cheek andtongue pressures. Experimental evidence, how-ever, seems to suggest that such an equilibriumof forces does not exist, tongue pressures beingsignificantly greater during almost all functional

movements and resting positions (Gouldand Picton, 1962, 1968; Weinstein et al, 1963;Lear et al, 1965; Lear and Moorrees, 1969;Luffingham, 1969; Prom t, 1975, 1987a,b; Tinieret al, 1985; Thtter and Ingervall, 1986; Katoet al, 1989; Lindeman and Moore, 1990). Thisimbalance remains a puzzle and various factorshave been implicated to explain it, includingforces resulting from the occlusion, from theperiodontal ligament and from the transversegingival fibres. Recently, studies of lingual pres-sures using new instrumentation have reportedsignificantly lower values, indicating that per-haps the observed imbalance of forces may beattributed to limitations of the experimentalapparatus (Frohlich et al, 1991, 1992).The purpose of the present investigation wasto study the effects of rapid maxillary expansionon the pressures exerted by the cheeks on themaxillary arch. These pressures may be implic-ated in the dental relapse seen after expansion,and it would, therefore, be interesting to observeif there is an increase in pressure during theexpansion phase of treatment and if the pres-sures return to pre-expansion levels during thestabilization of the appliance.


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296 D. J . H A L A Z O N E T I S E T A L .Table 1 Distribution of sample by sex and age.Patient

11a456789101112131415

Median age:

Sexmalemalefemalefemalefemalemalefemalefemalefemalemalefemalefemalefemalefemalemale

Age11.311.812.311.810.1011.012.011.912.312.711.615.311.613.216.111.9

Subjects and methodsFifteen subjects (five male and ten female) par ti-cipated in the study. The age of the subjectsranged from 10.10 to 16.1 years (Table 1). Allsubjects were diagnosed as having a bilateralmaxillary constriction with posterior cross-bite(bilateral or unilateral), requiring expansion ofat least 5 mm . A Haas or Hyrax type appliancewas used for correction of the maxillary con-striction, as the first stage of the orthodontictreatment. The appliance was then stabilizedand left in place for retention.InstrumentationThe pressure measuring device was constructedbased on the same principle used by Thuer et al.(1985) with modifications. The device was self-contained and portable, and air was used

000.00 digital displayg r / c m 4e le c t ro n ic p re s s u re

t ra n s d u c e r

a i r p u mp

instead of water. The diagram and photographof the device are shown in Figs 1 and 2. Airwas pumped into the tube assembly and escapedthrough the hole in the mouthpiece. The mou th-piece was held on the buccal aspect of the firstmaxillary molar, so that the opening facedtowards the cheek. When the opening wascovered by the cheek, the air pressure in the

Figure 2 (a,b) The pressure measu ring device with detailof the mouthpiece.

m o u t h p i e c e

6m m

Figure 1 Diagram of the pressure measuring device with detail of the mouthpiece (measurements are in mm).


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CHEEK PRESSURE AND RAPID EXPANSION 29 7tube assembly increased, depending on the pres-sure of the cheek on the mouthpiece. Theincrease in air pressure was measured by anelectronic transducer (SCX05DNC, SenSymInc, 1255 Ream wood Ave, Sunnyvale,CA 94089), converted to a digital signal by anA/D converter (ICL7135 Intersil) and displayedon the digital display of the device. The mouth-piece had a size of 6 x 3.5 x 1 mm. The max-imum pressure that could be recorded by thedevice was approximately 150 g/cm2, as limitedby the air-pump capacity.

Calibration of the pressure measuring devicewas carried out by immersing it at variousdepths in distilled water. Calibration waschecked at various times during the experi-mental period and no recalibration was foundnecessary.MeasurementsThe distance between the buccal surfaces of theupper first molars was measured before, during,and after active expansion, and also during theretention period. Pre-expansion width wasmeasured without the appliance in place, andassigned a value of zero. Increase of widthduring expansion is reported based on this pre-expansion width. The thickness of the molarband and the palatal attachments was includedin the measurements, because the cheek and themouthpiece of the pressure measuring devicewould be displaced additionally by this amount.Some of the expansion values that are reportedare, for this reason, greater than the 10 or11 mm that are usually produced by expansionscrews.

Pressure from the cheek was recorded oppos-ite the first maxillary molar on the left and rightside. Measurements were taken with the patientrelaxed. The patient was positioned so that theFrankfort plane was horizontal and the teethlightly in occlusion. At each measurement ses-

sion, three readings were taken and the averageof the three was used. To allow the patient tobecome accustomed to the mouthpiece, a coupleof sham measurements were performed. Thenreadings were taken alternatively from the twosides of the arch, with a couple of minutesbetween measurements. All measurements wereperformed by the same investigator using thesame mouthpiece. The size of the mouthpiecewas similar to the attachment on the buccalsurface of the molar and this facilitated theplacement of the mouthpiece at approximatelythe same position for each measurement.ResultsDescriptive statistics of the variables measuredat the three time points are shown in Table 2.A two-factor analysis of variance of the pressuremeasurements showed a statistically significantdifference between the pressure measurementsat the three time points, but no statistical differ-ence between the right and left side mea-surements.

The changes in pressure between the timepoints were further investigated using the pairedMest (Table 3). During the expansion phase,the cheek pressure on the right side increasedfrom 3.43 to 8.94 g/cm2 (P


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298 D . J. HALAZONETIS ET AL.Table 3 Chan ges in

Mean of differencet-Value (paired Mest)Probability (P )

cheek pressure during theExpansion phase,right side5.516.280.000

expansion and retention phase.Expansion phase,left side6.488.430.OM

Retention phase,right side0.220.730.48*

Retention phase,left side-0 .29-1 .010.33*

*NS, change not statistically significant.R i g h t L e f t

R i g h t L e f t R i g h t L e t t R i g h t L e f tInitial Post-expans ion Post-rete ntion

Figure 3 Mean pressures at the three time points for theright and left sites. Vertical lines represent one standarddeviation above and below the mean.The sample was not divided according to sex

or type of malocclusion, mainly because of itslimited size, but also because the purpose wasto study changes in pressure for the individualand not differences in pressure between indi-viduals. It was, therefore, assumed that allsubjects would respond in a similar manner tothe treatment performed. Moreover, Thtier andIngervall (1986) did not find any correlationbetween cheek pressure and sex. Differences inthe design of the expansion appliance (Haasversus Hyrax) are not thought to have influ-enced the results, as these differences are mainlylocated in the palatal aspect of the appliance.The expansion protocol was similar in all cases.

The measuring device was a simplified versionof the device used by Thiier et al. (1985) andothers (Thiier and Ingervall, 1986; Frohlichet al, 1991, 1992). The use of air instead ofwater reduced the time response of the device,but this was not a consideration in this study,as mean rest pressures were recorded and notpressures during swallowing or other functionalactivities. The device was capable of measuring

20 15 10 5 0 0 5^ P r e s s u r e ( g r / c m 2 )

| o Mite l Post-expansion Post-re tention |

Figure 4 Bar graph of the pressure values of the 15 patientsfor the three time points measured. Missing bars signify avalue of zero.

negative pressures, but no negative readingswere obtained, in contrast to other studies(Thiier and Ingervall, 1986; Frohlich et al,1991, 1992). The negative pressures reported inthese studies are possibly due to a negativeatmospheric pressure that arises in the oralcavity during breathing or swallowing. Thisnegative pressure, which probably affects theteeth from both the buccal and lingual side,would not be present without a complete lipseal. Therefore, the fact that no negative pres-sures were observed may be attributed to twofactors. First, the lips were slightly apart in thearea of insertion of the mouthpiece. This pre-vented any negative atmospheric pressure fromaccumulating in the oral cavity, and recordings


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CHEEK PRESSURE AND RAPID EXPANSION 299of zero pressure were observed when the cheekwas not in contact with the upper molar.Secondly, the use of air instead of water elimin-ated the need to swallow, which could beresponsible for the build up of negative pres-sures in the above mentioned studies.Pre-expansion pressures were lower than thepressures reported by Luffingham (1969) andProffit (1975), who found a mean value of 7.2and 8.7 g/cm 2, respectively. This is to beexpected according to the results of Gould andPicton (1968) and Proffit (1975, 1978a,b), whoconclude that the cheek pressures are adaptivein nature and, therefore, lower pressures wouldbe expected in subjects with constricted arches.Seven subjects in the present study had a pre-expansion pressure of zero in at least one sideof the dental arch, due to the lingual positionof the upper molar, which precluded the cheekfrom coming into contact with it.During expansion, pressure increased signi-ficantly in all subjects, except for patients 11and 15 on the right side. Pressure increase wasof the order of 0.6 g/cm2 for each mm of expan-sion. Post-expansion pressures were slightlyhigher than those reported by Luffingham(1969) and Proffit (1975), probably due to theover-expansion of the maxillary arch and thebuccal position of the mouthpiece, because ofthe presence of the molar attachments of theexpansion appliance.The appliance was stabilized for the usualperiod of 3 months, although in some patientsit was retained longer. During the stabilizationperiod there was no significant decrease in thecheek pressures measured. McNulty et al.(1968) reported on a sample of five patientswho had their upper incisor denture teeth posi-tioned labially. Two of the subjects showed agradual adaptation of the soft tissues and returnof the labial pressures to initial levels. The restof the sample showed inconsistent responses.Soo and Moore (1991) placed a lip bumperappliance, and studied the labial pressures atthe incisor and canine areas. After an expectedinitial rise in pressure, they reported a gradualdecrease in pressure at the incisor area, as thelips adapted to the lip bumper appliance duringa period of 1-2 months. No such change wasobserved for the canine region, where the place-ment of the appliance resulted in an initial dropin pressure, which continued during the periodof the experiment. This result could not beexplained by the investigators.

The results of the present study seem tosuggest that the constriction of the maxillaryarch in these patients was not caused by ahyperactive buccal musculature, pushing theteeth towards the tongue. Rather, the con-stricted position of the teeth (caused by otherfactors) resulted in low buccal pressures, as thecheeks were left hanging passively without sup-port, other than the mandibular arch. Afterexpansion, the maxillary teeth, now closer totheir normal position, could provide this sup-port and w ould bear increased buccal pressures.This probably relieves the lower arch of someof the buccal pressures that were exerted on itpreviously and this can be an explanation ofthe automatic expansion that is observed in thelower arch during rapid maxillary expansion.During expansion, the cheek pressures at theupper molar increase, and remain high for atleast the usual period of stabilization and reten-tion of the expansion. This does not, however,necessarily mean that these high pressures areresponsible for the dental relapse that almostalways follows the removal of the palatal expan-sion appliance, even though they are of a magni-tude capable of producing tooth movements(Weinstein, 1967). The skeletal and dentalchanges that accompany rapid maxillary expan-sion alter the tongue position as well and,therefore, the whole dental equilibrium.Furthermore, the cheek pressures after expan-sion, although higher than the pre-expansionpressures, were close to the normal range ofpressures reported for patients with dentalarches of normal width. Thus, the changesobserved in this study may signify a normaliza-tion in dental equilibrium. Further study isneeded to better resolve these issues.Simultaneous measurement of cheek and lingualpressures during rapid expansion would beinteresting, but is hampered by the inevitablebulkiness of the expansion appliances, whichdoes not allow a normal tongue position.Address for correspondenceD. Halazonetis,19 Likavittou Street,Athens 106 72GreeceAcknowledgementsWe would like to express our thanks to Drs E.Anastasopoulou, D. Kardara, M. Nasika,


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300 D . J. HALAZONETIS ET AL.N. Souleles and A. Sotiriadou for kindly provid-ing us with material for this study.ReferencesBishara S E, Staley R N 1987 Maxillary expansion: Clinicalimplications. American Journal of Orthodontics andDentofacial Orthopedics 91: 3-14Ekstrdm C, Henrikson C O, Jensen R 1977 Mineralizationin the midpalatal suture after orthodontic expansion.American Journal of Orthodontics 71: 449-455Frohlich K, Ingervall B, Thiier U 1992 Further studies ofthe pressure from the tongue on the teeth in young adults.European Journal of Orthodontics 14: 229-239Frohlich K, ThUer U, Ingervall B 1991 Pressure from thetongue on the teeth in young adults. Angle Orthodontist61: 17-24Gould M S E, Picton D C A 1962 A method of measuringforces acting on the teeth from the lips, cheeks and

tongue. British Dental Journal 112: 235-242Gould M S E, Picton D C A 1968 A study of pressuresexerted by the lips and cheeks on the teeth of subjectswith Angle's Class II division 1, Class II division 2 andClass III malocclusions compared with those of subjectswith normal occlusions. Archives of Oral Biology 13:527-541Kato Y, Kuroda T, Togawa T 1989 Perioral force m easure-ment by a radiotelemetry device. American Journal ofOrthodontics and Dentofacial Orthopedics 95: 410-414Lear C S C , Moorrees C F A 1969 Buccolingual muscleforce and dental arch form. American Journal ofOrthodontics 56: 379-393Lear C S C , Catz J, Grossman R C, Flanagan J B, MoorreesC F A 1965 Measurement of lateral muscle forces on thedental arches. Archives of Oral Biology 10: 669-689Lindeman D E, Moore R N 1990 Measurement of intraoralmuscle forces during functional exercises. AmericanJournal of Orthodontics and Dentofacial Orthopedics97: 289-300Luffingham J K 1969 Lip and cheek pressure exerted uponteeth in three adult groups with different occlusions.Archives of Oral Biology 14: 337-350

McNulty E C, Lear C S C , Moorees C F A 1968 Variabilityin lip adaptation to changes in incisor position. Journalof Dental Research 47: 537-547Muguerza O E, Shapiro P A 1980 Palatal mucoperiostomy:An attempt to reduce relapse after slow maxillary expan-sion. American Journal of Orthodontics 78: 548-558Proffit W R 1975 Muscle pressures and tooth position:North American whites and Australian aborigines. AngleOrthodontist 45: 1IIProffit W R 1978a Equilibrium theory revisited: Factorsinfluencing position of the teeth. Angle Orthodontist48: 175-186Proffit W R 1978b The facial musculature and its' relationto the dental occlusion. In: McNamara J A Jr (ed.)Muscle adaptations in the craniofacial region.Monograph 8, Craniofacial Growth Series, Center forHuman Growth and Development, University ofMichigan Ann Arbor, 73-89Soo N D, Moore R N 1991 A technique for measurementof intraoral lip pressures with lip bumper therapy.

American Journal of Orthodontics and DentofacialOrthopedics 99: 409-417Thtter U, Ingervall B 1986 Pressure from the lips on theteeth and malocclusion. American Journal ofOrthodontics and Dentofacial Orthopedics 90: 234-242Thiier U, Janson T, Ingervall B 1985 A pplication in childrenof a new method for the measurement of forces from thelips on the teeth. European Journal of Orthodontics7: 63-78Weinstein S 1967 Minimal forces in tooth movement.American Journal of Orthodontics 53: 881-903Weinstein S, Haack D C, Morris L Y, Snyder B B, AttawayH E 1963 On an equilibrium theory of tooth position.Angle Orthodontist 33: 1-26Wertz R A 1970 Skeletal and dental changes accompanyingrapid midpalatal suture opening. American Journal ofOrthodontics 58: 41-66Wertz R, Dreskin M, 1977 Midpalatal suture opening: Anormative study. American Journal of Orthodontics 71:367-381Zimring J F, Isaacson R J 1965 Forces produced by rapidmaxillary expansion. III. Forces present during retention.Angle Orthodontist 35: 178-186

changes in cheek pres surer me

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