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Journal of Dental Research

DOI: 10.1177/00220345990780031201 1999; 78; 790 J DENT RES

D. Locker, A. Liddell, L. Dempster and D. Shapiro

Age of Onset of Dental Anxiety

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(2)

Age

of Onset of Dental Anxiety

D.

Lockerl*,

A.

Liddell2,

L.

Dempster',

and D.

Shapirol

'Facultyof Dentistry, Universityof Toronto, 124Edward Street,Toronto,Ontario, Canada M5G 1G6; and 2DepartmentofPsychology, Memorial University, StJohn's,Newfoundland,Canada;*correspondingauthor

Abstract. Little attentionhas been given tothe issue of the

age ofonsetof dental anxiety, even thoughit may have a bearingonthe origins of thistypeoffear. This

study

aimed

to

identify

theageofonsetofdental anxiety andto

identify

differencesbyageofonsetwithrespect to

potential

etiologi-cal factors, such asnegative dental experiences, family

his-tory of dentalanxiety, and general

psychological

states. Data werecollected bymeansoftwomailsurveys ofa

ran-dom sample of the adult

population.

Of 1420 subjects returningquestionnaires,16.4% weredentallyanxious.Half, 50.9%,

reported

onset in childhood, 22.0% in adolescence, and 27.1% inadulthood. Logistic regression

analyses

indi-cated that negative dental experiences were

predictive

of dental fearregardless ofage of onset.A family history of dental anxiety was predictive of child onset only. Adolescent-onset subjects were

characterized

by trait anxi-ety and adult-onset subjects by multiple severe fears and symptoms indicative of psychiatric problems. The three

groups were similarin terms of their

physiological,

cogni-tive, and behavioral responses to dental treatment. However, adolescent- and adult-onset subjects weremore

hostile toward and lesstrusting of dentists. These results indicate that child-onset subjects were morelikely tofall intothe exogenousetiological category suggested byWeiner

and Sheehan (1990), whileadult-onset subjects were more

likelytofallintotheendogenous category.

Key words: dental anxiety, etiology, age, psychological factors.

Received October7, 1997;Last Revision May 27, 1998; Accepted June 5, 1998

Introduction

Dentally anxiousindividuals are not a

homogenous

group

but differ in terms of the origins

and/or

manifestations of

their fears of dental treatment

(Milgrom

et

al., 1985).

For

example, Weiner and Sheehan

(1990)

suggested

that

they

could be classifiedinto twogroups, exogenousand

endoge-nous,withrespect to thesourceof theiranxiety. Inthe

for-mer, dental anxiety is the result of conditioning via traumaticdental experiences orvicariouslearning, whilein

thelatter,ithasitsorigins in a

constitutional

vulnerabilityto anxiety disorders, as evidenced by

general

anxiety states,

multipleseverefears, and disordersof mood. This

classifica-tion suggests thatnot all dentallyanxious

subjects

become

fearful

asaresult of

conditioning.

Evidence for the role of conditioning in dental anxiety,

through either aversive experiences or family influences, has beenprovided by Shoben and Borland (1954), Lautch (1971), Kleinknecht et al. (1973), Berggren and Meynert

(1984),

Ost

andHugdahl (1985),Davey

(1989),

Milgromet

al.

(1995), Locker etal.

(1996a),

and Poulton et al. (1997). Evidence for therole of additional severe fears and

psychi-atric problems has been provided by Fiset et al. (1989),

Mooreetal.

(1991),

and Roy-Byrneetal. (1994).However, to

date,no study has addressed the relative contributions of

negativeexperiences,familial attitudes, and general

psycho-logicalstates todentalanxiety.

One issue which may have abearing on the originsof dental anxiety is that of ageof onset (Marks and Gelder,

1966). Ina studyofsixdifferenttypesof phobia,

Ost

(1987) found significantdifferences in age of onset. Animal and bloodphobias were largely acquired inchildhood, social

phobias in adolescence, and agoraphobia and

claustropho-biain adulthood. Of some importance was thefact that

these different ages ofonset were associated with distinct modesof acquisition anddifferencesin psychological char-acteristics.

(3)

Onsetof DentalAnxiety

The age of onset with respect to dental anxiety has received relatively littleattention(Ost,1987),largely because dental anxietyis usually viewed as a fear originating in childhood which persists into later life. However, two stud-ies that haveaddressed thisissue donotsupport this point of view. Ost (1987) studied a groupof dental phobicsand found that almost 20% reported onset after the ageof 14 years.Similarly, apopulation-based study by Milgrometal.

(1988) foundthat 33.3% becameanxiousduring adolescence oradulthood.

Apartfrom these data, littleisknown aboutvariations in the age ofonset of dental anxiety and itsimplications in terms of etiology. This paper reportsthe results ofa study which aimedto: (1) describe the distribution of the dentally anxious populationaccording to ageofonset, and (2) iden-tify differencesby ageof onset with respect toetiological

factors such asnegative dental experiences, family history,

and general psychologicalstates. The main hypothesis we testedwasthatchild-onsetsubjectswould bemorelikelyto fallinto the exogenous categorydescribed byWeiner and

Sheehan (1990), having acquired theiranxietythrough con-ditioning experiences, while adult-onset subjectswould be morelikelytofall into the endogenouscategoryand demon-strate a heightened constitutional vulnerability to anxiety

disorders.

Methods

Thedesign of the study,itsdatacollection methods, and proce-duresforobtaininginformedconsentandensuring confidential-ity were approved by the UniversityofToronto's Human SubjectsCertificationprocess.

Surveyprocedures

The datawere collected during the baselinephase ofa

longitu-dinal, population-basedstudy of the epidemiology of dental anxiety. The target population for the studywas all persons aged 18 years and overlivinginthe City ofEtobicoke,oneof five municipalities whichcomprise MetropolitanToronto. The sampling framewasthe listofvoterscovering thiscommunity. Since this iscompiledbyahouseholdenumerationprocedure,it containsthenamesofapproximately97% ofpersonseligibleto vote. Atwo-stage random-startsystematic samplingprocedure wasused,withsampling fractionsdesignedtogiveasampleof 6360subjects.

Data werecollectedbymeansoftwomailsurveysbasedon the Total Design Methodrecommended by Dillman

(1978).

Initially, all 6360 subjects were sent abasicquestionnaire on

dentalanxiety. To maximizethe response rate,wesentthree fol-low-upmailings.Subsequently,a60% subsampleof those com-pleting the firstquestionnairewere sent asecondquestionnaire containinganumber ofpsychologicalmeasures.

Measures

Dental anxiety. Dental anxietywas measured with Corah's Dental Anxiety Scale (DAS) (Corah, 1969), theGatchel Fear Scale(Gatchel, 1989),and thesingleitemusedby

Milgrom

etal.

(1988). Any subjects who scored 12 and above on the DAS, 8 or above on the Gatchel FS, or reported being very afraid or terri-fied of dentaltreatment were considered to be dentally anxious. This approachwasadopted since each of these measures alone fails to identify somedentally anxious subjects (Locker et al., 1996b). The Dental Fear Survey (DFS) (Kleinknecht and Bernstein, 1978) was used to assess the severity of dental anxi-ety. Subjects rated the amount of anxiety evoked by nine inva-siveand sixnon-invasive stimuli in the dental setting, using a six-pointscalerangingfrom 1 (not at all) to 6 (very much).

Age of onset. Subjects were asked toindicate whether they became dentally anxious during childhood (12 years of age or less), adolescence (age 13 to 17 years), or adulthood (18 years and over).

Conditioning experiences. Questions were asked about negative experiences in the dentalsetting, such as events whichwere painful, frightening,orembarrassing, andthe age at whichthey firstoccurred. The familyhistory withregardto dental anxiety wasassessed byitemspertaining tofear ofdentaltreatment on the part ofeach subject's mother,father,and siblings.

Psychological characteristics. General fearfulness was measured by a short form of theFearSurveySchedule II (FSSII) (Geer, 1966). Thedegreeof fearoranxietycreatedbyeach of20objects orevents was rated on a scaleranging from 0 (none)to 6 (ter-ror). Fearsrated5 or 6 wereconsideredtobe severe. Trait anxi-ety wasassessedby the20-itemSpeilbergerTraitAnxiety Index (STAI) (Speilberger etal., 1983). Inresponse to each item, sub-jects rate howthey generally feel using a four-point scale in which 1 indicates 'almost never' and 4 indicates 'almost always'. The 12-item version of the General Health Questionnaire (GHQ) (Goldberg and Williams, 1988) wasused tomeasurethefrequency ofsymptomspotentiallyindicativeof psychiatric disturbance. This also uses afour-point response scale whichvariesaccordingtoeachitem. Foreachscale,scores were generated from the sum of the responses toeach item. Subsequently, acut-off ofthe mean score plus one standard deviation wasused to differentiatebetween subjectswho had 'high' and thosewhohad 'low'scores.

Other characteristics.Physiologicalresponsesduringdental treat-ment wereassessedbysix itemsfromthe DFS. These included events suchasincreases inbreathingrate,increased heart rate, and feelingnauseous. Cognitiveresponses were measured

by

meansof a 13-item scaleconcerning thenegativethoughts sub-jects had prior to and during dental treatment (Kent and Gibbons, 1987). Behavioralresponses todental anxiety were

measuredby meansofquestions concerningthe use of dental services,avoidanceofdentalcare,cancelingappointments,and failingto showupbecause ofanxiety about dentaltreatment. The Dental Beliefs Survey (Milgromet al.,1985) was used to

assess subjects' perceptions offour components of the dentist-patientrelationship that have a bearing on dental anxiety;

namely, communication,belittlement,lack ofcontrol,andtrust.

Dataanalysis

Subjectswereclassifiedintooneof fourgroups:(1)not

dentally

(4)

anxious, (2) dentally anxious-childhood onset,(3) dentally anxious-adolescent onset, and(4) dentally anxious-adult

onset. Two sets of analyses wereundertaken, the first compar-ing the threedentally anxious groups with eachother, andthe second comparing each of thesegroups with thenon-anxious. Inthisrespect, those who were not dentally anxious were used as a normative orreference group.Chi-squaretests wereused to assess thesignificance ofdifferences inproportions, and odds

ratiosand their 95% confidence intervals wereused to indicate andcompare the strengths of associations. The significance of

differences in means was assessedwith one-way analysis of

variance. Logistic regression analysiswas used to assess the

independenteffects ofpotential etiologicalfactors on the

proba-bility of dental anxiety.

Results

Response

The initial questionnairewas completed by 3055 subjects.

This represents 60.4% of the5061 individualspresumed to

be alive and livingatthe listed address. Of these,1420

com-pleted thesecondpsychological questionnaire. Census data indicated that, when compared with thetarget population,

subjects completing

both questionnaires were somewhat older and better educated.

Ageofonset

Usingthe definition cited above, we classified 16.4% (n = 233)ofsubjects as beingdentallyanxious. One half, 50.9% (n

= 111), reported becoming fearful of dental treatment in

childhood,22.0% (n=48) sufferedonset inadolescence, and

27.1%(n=59) becameanxious asadults.There were no dif-ferences amongthe three groups in terms of gender. The

mean(SD)agesof the threegroups atthetimeof data

collec-tionwere 45.1 (13.7)years, 43.8 (13.7) years, and 49.6 (14.9)

years, respectively

(ns:

one-wayanalysis ofvariance). The

mean(SD)age of the non-anxious referencegroup was 48.7

(16.6) years.

Themean (SD) DASscores of thethree groups were 14.1

Table1.Ageatfirsttraumaticdentalexperiencebydental anxiety status(%)

AgeatFirstTraumatic DentalExperience DentalAnxiety Status Child Adolescent Adult

Notdentallyanxious 39.4 22.3 38.3 (n= 1187)

Child-onset 67.9 18.3 13.8

(n= 111)

Adolescent-onset 31.1 46.7 22.2 (n=48)

Adult-onset 27.3 10.9 61.8

(n=59)

Differencesinproportions between dentally anxious groups: p < 0.0001:Chi-squaretest.

(2.7),13.7

(2.8),

and 13.5

(2.7), respectively;

thesewere not

significantly

different. However, those with child-onset den-talanxiety

reported

significantly

moredistress than

adoles-cent-andadult-onset

subjects

withrespecttosixof thenine DFSitems concerned withinvasive

procedures

and two of the six DFS items referring to non-invasive

procedures.

Consequently,

those with childonsethad

significantly

higher

scoresthan theothersonascale

constructed

by summing

the

responsecodesto all15DFSitems

(means

of54.5,

49.7,

and

48.0,respectively;p<0.01,one-way

analysis

of

variance).

Conditioning

experiences

and

family history

Overall, 74.8%

reported

painful

dental

experiences,

30.7%

experiences whichwere

frightening,

and 13.3%

experiences

whichwereembarrassing. Therewas anassociationbetween

dental anxiety status and theage atwhich negative

experi-ences werefirst encountered

(Table 1).

Those with

child-onset anxiety werethemost

likely

to have had their first experiencein

childhood,

those with adolescent onset were the mostlikelyto have had their first experiencein

adoles-cence, and those with adultonset werethe most

likely

to have had their first experience asadults. Forthe non-anx-ious,thefirstnegativedentalexperiences were moreevenly distributed withrespect to age.

There were no differences among the three groups of dentallyanxioussubjectsinthe proportionsreporting nega-tivedental experiences

(Table

2). However, all threegroups were significantly different from the non-anxious. Odds

ratios, obtained by comparing each dentally anxious group

with the non-anxious reference group, indicated that the

associationbetweenaversive eventsand dentalanxiety was strongestfor the child-onset group(OR = 9.2) and weakest for the adult-onsetgroup

(OR

=

3.7).

Ageofonsetofdentalanxietyand family history of den-talanxiety were associated (Table 2). Half (55.9%) of those with childhood onset had a mother, father, or sibling who

was anxiousabout dental treatment compared with

one-third

(35.6%)

of those with adultonset(p<0.05). The

associ-ated odds ratios and their

95%

confidence intervals indicated that afamily history of dentalanxiety was a

pre-dictorof child-onsetanxietyonly.

Psychological characteristics

Table 3 shows the proportions in each group with high scores on the three scales measuring general psychological

states.The oddsratiosand95% confidence intervals indicate

no differences between child-onset subjects and the non-anxiousreference group. Adolescent-onset subjects were

significantly

different on two ofthe three measures, and

adult-onsetsubjectsweresignificantly differentonall three. The odds ratios indicated that the associations were strongest foradult-onsetsubjects.

Independent predictorsofdental anxiety by age of onset

Threelogisticregressionanalyses wereundertaken.Thefirst

(5)

sub-OnsetofDentalAnxiety

jects withthe reference group,and the third Table 2.Perc( compared the adult-onset subjects with the tory of dental reference group. The three types of negative ious

reference

dental experiences (painful, frightening,

embarrassing) were entered asseparatevari- Dental

ables. Gender was included inthemodels as Anxiety

a control variable. All dependent and inde- Status pendent variables were in a binaryformat

coded0and 1. The resultsaresummarized in

Table 4. Not dentallya

Inthemodelpredictingchild-onset dental Child- t

anxiety, only a family history of dental

anxi-ety and the three variables describing aver- Adolescent-oi

sive experiences entered the regression Adult-onset

equation. Foradolescent-onset anxiety, nega- aDifferences tive experiences and the score on the Trait anxious refe Anxiety Index were significant predictors, bDifferences:

while for adult-onset anxiety, frightening anxious refe experiences and thescores ontheFSS II and

the GHQ emerged as significantpredictors.

Theseresults tend to confirmthe hypothesis beingtested. Direct andvicarious conditioning experiences are important with respect to child-onset dental anxiety, while general

psychological states play a more prominent role in adult-onsetanxiety.

Other characteristics

Therewere nodifferences among the three groups in terms

ofphysiological,cognitive, orbehavioralresponses todental

treatment. However, the Dental Belief Scale scores ofthe

three groups (4.5, 5.9, and 5.9,respectively; p < 0.05, one-way analysis of variance) indicated that adolescent- and adult-onset subjects were significantly morenegative

con-cerning dentists and their behavior toward patients than

werechild-onsetsubjects.

Discussion

Although theresponse tothe study

was acceptable, there were differ-

Table

3. Proportions wi ences between study subjects and Comparisonofeach

der

the population from which they

weredrawn. Theformerwereolder and somewhat bettereducated than

the latter. Since the

magnitude

and Dental

Anxiety

Status direction ofbias induced

by

these

differences are difficult to

judge,

some caution needsto be exercised Not dentallyanxious when the results of the study are Child-onset

generalized.

Among thedentallyanxioussub- Adolescent-onset jects identified in this population- Adult-onset

based study, only half

reported

a Difference between th

becoming

dentally anxious in child-

cant;

p <

0.05,

Chi-squ hood.One-fifth reportedadolescent b Differencebetween th onset, and almost one-third cant; p <0.01: Chi-squ

reported onset in adulthood. These c Differencebetween th results confirm the earlier observa- cant; p<0.001,Chi-sq

entreporting one or more negative dental experiences and a family his-anxiety:Comparisonof eachdentally anxious group with the

non-anx-egroup

PercentReporting Percent Reporting Negative Dental Family History of Experiences Dental Anxiety

Odds Odds

% Ratio 95%CI % Ratio 95% CI

anxious 74.4 1.0 35.4 1.0

96.4a 9.2 3.2-21.6 55.9a 2.3 1.5-3.5 nset 93.8b 5.2 1.5-15.8 47.9 1.7 0.9-3.1

91.5b 3.7 1.4-10.7 35.6 1.0 0.8-1.8

inproportionsbetween the dentallyanxious group andthe non-dentally zrencegroupsignificant: Chi-squaretest p < 0.0001.

inproportionsbetweenthedentallyanxious group andthe non-dentally Zrencegroupsignificant: Chi-squaretest p < 0.01.

tions ofMilgrom et al. (1988) and challenge the view that

dental anxiety isinvariably a fear which has its origins in

childhood. Although the DAS scores of the three groups were similar, scoresderived from the Dental Fear Survey

suggested that the anxiety ofchild-onset subjects wasmore severe than that of adolescent-onset and adult-onset

sub-jects. This was largely dueto the fact that the former reported significantly more anxiety withrespect to stimuli associated withinvasivedentalprocedures, suchas restora-tions and the extraction of teeth. Kleinknecht and Lenz

(1989) have suggested that since such treatments involve

blood and body injury types of stimuli, these anxiety responses may be linked to blood and body injury fears, whichtypicallyarise inchildhood(Ost, 1987). Such fearsare

characteristicofapproximately one-third of

dentally

anxious

adults(Lockeretal., 1997).

Rachman (1977) hassuggested that threetypesof condi-tioning may play a role inthe acquisition of fears. While many fears have their origins in direct experience, others

ithhighscoresonthe threemeasuresofgeneral anxiety and fearfulness: ntallyanxious groupwith thenon-anxiousreferencegroup

GeneralAnxiety and Fearfulness

FearSurvey Trait General Health ScheduleII AnxietyIndex Questionnaire

Odds Ratio OddsRatio OddsRatio % 95%CI % 95%CI % 95%CI

15.3 1.0 12.5 1.0 7.7 1.0 21.6 1.5/0.9-2.5 16.2 1.4/0.7-2.4 12.6 1.7/0.9-3.3 27.1a 2.1/1.1-4.1 27.1b 2.6/1.3-5.2 14.6 2.0/0.8-3.9 42.4c 4.0/2.3-7.2 28.8c 2.8/1.5-5.3 23.3c 3.7/1.9-7.4

edentallyanxiousgroup and the non-anxious reference group

signifi-iare test.

iedentallyanxiousgroup and the non-anxious reference group

signifi-iare test.

iedentallyanxiousgroup and the non-anxious reference group

signifi-juare

test.

(6)

Table4.Resultsof thelogistic regressionanalyses

Model1 Model2 Independent Child-onsetvs. Adolescent-onsi

Variable: ReferenceGroup vs.ReferenceGro p Odds Ratio p Odds Rati

Familyhistory of dental anxiety

(Yes=1; No=0) <0.05 1.8 ns

Painful dental experiences

(Yes=1,No=0) <0.01 4.5 <0.05 3.1 Frightening dental

experiences

(Yes=1;No=0) <0.001 4.2 <0.05 2.4 Embarrassing dental

experiences

(Yes=1;No=0) <0.05 2.2 <0.05 2.8 FearSchedule

SurveyII score

(High=1;Low=0) ns ns TraitAnxiety

Indexscore

(High=1; Low=0) ns <0.05 2.6 General Health

Questionnairescore

(High=1;Low=0) ns ns

Sex(Male=1;Female=0) ns ns

Modelchi-square 87.4 38.1

df 8 8

p <0.0001 <0.0001

may arise viamodeling orexposure tothreatening

informa-tion. This

theory helps

explain

why

notallfearful individu-alshave beenexposedto atraumaticconditioning episode.

With respect to direct

conditioning

experiences, there

were nodifferences among the three groups of dentally anx-ioussubjects interms of theirreports of dentalexperiences

involving pain,

fear,

or

embarrassment.

However, inboth bivariate and multivariate

analyses,

the associated odds

ratiosindicate that such experiencesmadea greater

contri-bution to child-onset anxiety than adult-onset anxiety. The multivariate analyses also suggested that while all three

typesofexperiences were importantwith respecttothe

for-mer, only

frightening

experiences were influential with

respect to the latter. That child-onset subjects were more fearful of invasive procedures and adolescent- and adult-onset subjects morenegative concerning dentists' behavior

may also reflect differences in the types of conditioning

experiences giving rise to dental anxiety (Locker etal.,

1996a).

Although therewas anassociationbetween age of onset and age of first negativedental experience, there was a

degree

ofdiscordance ineach group of dentallyanxious subjectswithrespect tothetiming of traumaticexperiences.

Almost one-third ofchild-onsetsubjects reported that their first traumaticexperiencedidnot occur untiladolescenceor

adulthood,

andalmost two-fifths of adult-onset

subjects

reported

Model 3 such experiences prior to

becom-et Adult-onset vs.

up ReferenceGroup

ing

dentally

anxious.

Davey o p Odds Ratio

(1989),

in exploring the latent inhibition

hypothesis,

has

pro-vided evidence to demonstrate

that the relationship between

ns traumatic experiences and dental

anxiety

isnot a

simple

one.Inhis

studies,

traumatic

experiences

ns were more

likely

to

give

riseto

dental anxietyif theyoccurred <0.05 2.5

early

in anindividual's dental

care

history

than if

they

were

pre-ceded

by

a series of

relatively

ns -painless dental visits. Whilethis

explains

why

many

non-dentally

anxioussubjects reporttraumatic

<0.05 2.6 dental experiences, it does not

accountfor thepatternsobserved

in this study. Milgrom and

ns - Weinstein (1993) have suggested

that the consequences of trau-matic experiences aredependent <0.05 2.8 upon the context in which they

occur.Thatis, pain inflicted bya ns dentist who isperceived as caring

is likely to have less

psychologi-38.0 cal impact than pain inflicted bya

dentist who is cold and

control-8 ling.

<0.0001 These observations indicate that while direct conditioning experiences areimportant in the genesisof dental anxietyregardless ofage ofonset,factors other thantraumaappear tobe involved. Rachman's (1977) model of fearacquisition suggeststhat the

family history

of fears andphobias is important, while Weiner and Sheehan (1990) suggestthatgeneral

psychological

traits and states

playarole.

In this study, a

family history

of dental anxiety was important with respect to child-onset anxiety only. This

finding

isconsistent withthe study by Ost

(1987),

who reported thatphobias acquiredinadulthoodwerelesslikely thanthose acquiredinchildhoodtobe ascribedtomodeling and/orvicariouslearning. Itisalsoconsistentwith the find-ings ofMilgromet al.

(1995),

who found that direct

condi-tioning and modeling were bothimportant predictors of

dentalanxietyoriginatinginchildhood.

Bivariate andmultivariateanalyses ofourdata suggested

thatgeneralpsychologicalstatesand traitsmadea contribu-tionto adolescent- andadult-onset anxietybut not

child-onsetanxiety.Adolescent-onset subjectsweremorelikelyto

have high trait anxiety, while adult-onset subjects were morelikely to have multiple severe fearsand symptoms

potentially

indicativeofpsychiatric disorder. Thereis grow-ing evidence that, for some dentallyanxious adults, fears

concerningdental treatment arelinkedto orsymptomatic of

(7)

Onsetof DentalAnxiety

with respect to children is less clear, perhaps because appro-priatemeasures have not been widely used in studies of

children. Milgrometal. (1995) found no association between

dentalanxiety and a measure of behavioral problems and

socialcompetency inchildren. However, studies have found a link between child temperament and anxiety regarding dental treatment (Liddell, 1990).

The role played by general psychological factors in the acquisition of dental anxiety appears to be a complex one. Davey (1997), in describing howcontemporaryconditioning

models help explain the acquisition and maintenance of phobias, has suggested that they are associated with a

ten-dency to focus onand rehearse the negative outcomes of encounters with feared objects and events. Since subjects with high traitanxiety selectively process threatening infor-mation, theyinflate the unpleasantness ofunconditioned

stimuli and experience conditioned responses of a higher

magnitude. Davey (1997) cites experimental evidence in supportof thischaracterization of theway inwhich fears are induced.

The datapresented here support the classification of den-tally anxious subjects suggested by Weiner and Sheehan (1990) and indicate that child-onset subjects were more likely tobeexogenous, whileadult-onsetsubjects were more

likely to beendogenous. There was, however,a degree of overlapinthat allsubjectswerecharacterized byexogenous

factors. Consequently, this classification scheme should be

considered to bedimensional rather than categorical.

A majorlimitation of the study was its cross-sectional design. Eventhough theanalysis approximated a

case-con-trolstudy, temporal relationships cannotbe established. At

best,we have documented associations between potential etiological factors and dentalanxietyoriginatingatdifferent

points inthe life span. Even so, the associationsbetween direct conditioning experiences and dental anxiety were

basedonsubjects' retrospective reports,which maybe

sub-ject toproblems of recallandretrospectivere-interpretation.

For example, Kent (1985) found that

dentally

anxious patients reported morepain threemonths after treatment than was reported immediately

following

treatment. This

reconstruction made their actual experiences more consis-tentwith theiranxieties andexpectationsabout dental treat-ment.

These caveats also apply to thefindings concerning the family history of dental anxiety.

Although

the data

clearly

suggest that negative attitudes on thepart of the mother and/or siblings, and vicarious

learning

processes, make a greater contributionto child- onset dentalanxiety than to adolescent-oradult-onset dental

anxiety,

problems

of recall

and retrospective re-interpretation may also have had an influence on these

findings

(Kent,

1989).

Because of these

problems,

conclusions

regarding

the role of

conditioning

events andvicarious

learning

in theonset of dental

anxiety

arebestframedas

hypotheses

rather thanasdefinitive find-ings. Consequently,

although

the data are consistent with theviewthat the

psychological

characteristics ofasubset of thepopulationrender them vulnerabletodental

anxiety,

the precise role of exogenous and

endogenous

factors,

and the sequence in which

they

occur in groups defined

by

age of

onset,canbeelucidated

only by

meansof

longitudinal

stud-iesandqualitative research. It is entirely plausible, for exam-ple, that the psychological states which characterize

adult-onsetsubjects are related more to the maintenance ofdental anxiety than to its origins. In this regard, Liddell andLocker (1994) reportedthat adults who carried their dental anxiety into old age were more generally fearful than subjectswho hadbeen dentally anxious but recovered withaging.

Another implication of the study for research into dental

anxietyis that greaterrecognition needs to be given to the factthat thedentally anxious population is nothomogenous butis comprised of groups which differ along several

psy-chological and other dimensions. If data are not analyzed specifictothesesubgroups, thenimportant associationsmay be masked or attenuated. For example, when the logistic regression analysis was repeated comparing all dentally anxious subjectswith the non-anxious reference group,a family history of dentalanxiety and scores on the FSS II and theMHQ didnotenterthemodel.

Themainimplication ofthis study for dental practice is

that the dental team needs to take as much care with adult patients as withchild patients and use appropriate commu-nicationtechniqueswhichenhance trust and feelings of

con-trol. This preventiveapproach mayreducetheincidenceof dentalanxiety inpsychologically vulnerable individuals. In

addition, although child-onset subjects have more severe anxiety concerning dentaltreatment, adult-onset patients,

because of theirpsychological characteristics and greater

hostilitytowarddentists,maybemoredifficult for the prac-titionerto manage.Informationondentalanxietyandageof

onset,

then,

shouldbe collected from dentalpatients sothat dentistsmayplananappropriate managementand/or treat-mentstrategy.

Acknowledgments

Theresearchonwhich thispaper isbasedwassupportedby GrantNo. 5RO1 DE10622-02from the

NIDR/NIH.

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