ORIGINAL ARTICLE

Orthodontic intervention in the early mixed
dentition: A prospective, controlled study on
the effects of the eruption guidance applianceKatri Keski-Nisula,a Riitta Hernesniemi,b Maritta Heiskanen,c Leo Keski-Nisula,d and Juha Varrelae
Vaasa, Kurikka, Jalasjärvi, Tampere, and Turku, Finland
Introduction: A prospective, controlled cohort study was started in 1998 to investigate the effects oforthodontic treatment in the early mixed dentition with the eruption guidance appliance. Methods: Occlusal
changes were recorded in 167 treated children and 104 controls after they had reached the middle
mixed-dentition stage. Treatment began when the first deciduous incisor was exfoliated (T1) and ended when
all permanent incisors and first molars were fully erupted (T2). The children’s mean ages were 5.1 years (SD0.5) at T1 and 8.4 years (SD 0.5) at T2. Results: From T1 to T2, overjet in the treatment group decreased from
3.1 to 1.9 mm and overbite from 3.2 to 2.1 mm. In the control group, overjet increased from 2.9 to 4.1 mm
and overbite from 3.3 to 4.1 mm. At T2, the differences between the groups were highly significant (P ⬍.001).
At T1, 18% of the children in the treatment group and 22% of the controls had tooth-to-tooth contact
between the maxillary and mandibular incisors. All others had an open bite, or the mandibular incisors werein contact with the palatal gingiva. At T2, tooth-to-tooth contact was observed in 99% of the treated children
and 24% of the controls (P ⬍.001). Almost half of children in both groups showed incisor crowding at T1.
Good alignment of the incisors was observed in 98% of the treated children at T2, whereas maxillary
crowding was found in 32% and mandibular crowding in 47% of the controls (P ⬍.001). At T1, 41% of thechildren in the treatment group and 53% of the controls had a Class I relationship; the rest had either aunilateral or a bilateral Class II relationship. At T2, a Class I relationship was found in 90% of the treatedchildren and 48% of the controls (P ⬍.001). At least 1 occlusal deviation, including overjet ⱖ5 mm, overbite
ⱖ5 mm, open bite, gingival contact of the mandibular incisors, crowding, or Class II relationship, wasobserved in 13% of the treated children, but the deviations were mild, and no child was considered to needtreatment. In the control group, 88% of the children showed at least 1 occlusal deviation (P ⬍.001).
Conclusions: Treatment in the early mixed dentition with the eruption guidance appliance is an effective
method to restore normal occlusion and eliminate the need for further orthodontic treatment. Only a few
spontaneous corrective changes can be expected without active intervention. (Am J Orthod Dentofacial
Orthop 2008;133:254-60)

Timing of treatment is a controversial area inorthodontics. Opinions among clinicians show
great diversity; some recommend intervention
in the early stages of occlusal development, and othersaChief orthodontist, Vaasa Central Hospital, Vaasa, Finland.
General practitioner, Kurikka Health Center, Kurikka, Finland.
cGeneral practitioner, Jalasjärvi Health Center, Jalasjärvi, Finland.
dAssistant professor, Department of Radiology, Tampere University Hospital,
Tampere, Finland.
eProfessor and chair, Department of Oral Development and Orthodontics;
director, Postgraduate School of Oral Health Sciences; vice dean, Institute of
Dentistry, University of Turku, Turku, Finland.
Supported by the Finnish Dental Society Apollonia, the Medical Research Fundof Turku University Central Hospital, the Medical Research Fund of Vaasa
Hospital District, and Plandent Oyj.
Reprint requests to: Juha Varrela, Department of Oral Development andOrthodontics, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2,
FIN-20520 Turku, Finland; e-mail, juha.varrela@utu.fi.
Submitted, February 2006; revised and accepted, May 2006.
0889-5406/$34.00
Copyright © 2008 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2006.05.039
b254

argue in favor of treatment in the late mixed or early
permanent dentition. It has been suggested that, although almost all types of malocclusion could benefit
from early treatment, the effectiveness of intervention
depends on malocclusion.1 For example, treatment of
posterior crossbite in the deciduous or early mixed
dentition is generally considered more beneficial thanearly correction of a Class II relationship. The main
reason for the controversy seems to be that our present
knowledge about the timing of treatment is largely
based on clinical experience and reflects various approaches and clinical traditions of orthodontic practice.
Scientific evidence is limited, and few studies havespecifically targeted questions about the effects of early
treatment.
Clinical trials in the United States2-4 and the United
Kingdom5 focused on the effectiveness of 2 alternative
treatment modalities in Class II treatment. In theseKeski-Nisula et al 255

American Journal of Orthodontics and Dentofacial Orthopedics
Volume 133, Number 2

trials, 2-phase treatment that included an early growthmodification phase and a second phase was comparedwith single-phase treatment in the early permanentdentition. The results showed that, apart from improved
self-esteem, only minor benefits were obtained by theearly treatment phase.6 These studies provided valuable
scientific evidence for clinical decision making, particularly when considering 2-phase treatment protocols.
However, only a few treatment modalities and appliances were studied, and any generalizations drawn
from the results should be limited to these. For example, rather low forces were used in the activation of theheadgear. A similar growth-modification phase withhigher orthopedic forces could have resulted in betterand more consistent effects, as indicated by the findingsof Kirjavainen et al7-9 and Mäntysaari et al.10 Furthermore, only a few of the children in the trials started thegrowth modification phase in the early mixed dentition.2-5 Many questions therefore remain about theeffectiveness of orthodontic intervention in the mixed
dentition.
In Finland, where orthodontics is included in the
public dental care, treatment modalities that emphasize
early intervention are becoming increasingly popular.11-13 After screening of malocclusions in the deciduous dentition, treatment is frequently started in theearly mixed or, in some cases, even in the late deciduous dentition; appliances typically include expansive
arches, orthopedic headgear, activators, and activatortype appliances.12 Clinical experience suggests thatsystematic early intervention offers advantages in a
publicly funded health care system. For example, treatment can be offered to more children without extra
manpower or cost increases.12,13 Recently, the eruption
guidance appliance has been used more often in theorthodontic clinics focusing on early treatment.12 Thisappliance has many indications and has been found tobe effective in the treatment of many malocclusions
including crowding, deepbite, excessive overjet, anddistal bite. In addition, the eruption guidance appliancenormally requires only minimal adjustments, allowing
less chair-side time and longer intervals between checkups. Furthermore, retention can be carried out with thesame appliance as the treatment. Clinical experience
indicates good and stable results.
A clinical investigation was started in 1998 in 2
municipalities in western Finland, Jalasjärvi and
Kurikka. Orthodontic care in the dental clinics of thesecities is based on comprehensive early treatment; mostpatients are treated in the early mixed dentition with theeruption guidance appliance as the main therapeutic
device. Children with a skeletal Class III relationshipand those with a posterior crossbite are usually treatedin the deciduous dentition, the former with a combination of expansive appliance and facemask, and the latterwith a quad-helix appliance. Other appliances— eg,
Van Beek activator—are used occasionally.
Our goal in this prospective, controlled cohort study
was to investigate the treatment effects of the eruption
guidance appliance. Early treatment was studied in areal-world situation where the established treatment
protocols were followed with only minor adjustments,
mainly to ensure timely and controlled data collection.
Ethical, practical, and financial restrictions prevented
random assignment of the participants into treatment
and follow-up groups in each municipality. The neighboring town of Seinäjoki, where orthodontic treatment
is not given until the late mixed dentition, agreed toprovide untreated control subjects for the study. Matching of the treatment and control groups was achieved byusing large unselected and representative samples.
We describe the occlusal findings in 167 children
treated in the early mixed dentition using the eruption
guidance appliance as the only therapeutic device. The
treatment effects were compared with the spontaneouschanges in the occlusion of 104 control children during
the same period—ie, the period that started when thefirst deciduous incisor was exfoliated (T1) and ended
when all permanent incisors and first molars were fully
erupted (T2).
MATERIAL AND METHODSThe treatment group was derived from the entire
1992 and 1993 age cohorts in Jalasjärvi (population,9000) and the 1992 age cohort in Kurikka (population,
11,000). All children were screened in the late deciduous dentition, and a full clinical examination was madeat the onset of the mixed dentition period of those who
were considered to potentially need treatment. Children
with at least 1 of the following occlusal characteristics
were included: (1) distal step of ⱖ1 mm, (2) Class II
canine relationship of ⱖ1 mm, (3) crowding, (4) overjetof ⱖ3 mm and lack of tooth-to-tooth contact between
the incisors, (5) overbite of ⱖ3 mm and lack of
tooth-to-tooth contact between the incisors, (6) anteriorcrossbite, and (7) buccal crossbite (scissorsbite).
The number of children fulfilling these criteria was
315. Of them, 33 were treated with other appliances,
mainly the quad-helix, and they were excluded from thestudy sample. In 27 cases, the child or the family
refused orthodontic treatment. Treatment with an eruption guidance appliance was started in 255 children.
During the treatment, 12 children moved to anothermunicipality and could not complete the treatment;
their records were excluded from the analysis. Of the256 Keski-Nisula et alremaining 243 children, 167 completed the treatment
successfully.
Seventy-six children (31%) were excluded from thestudy because they did not wear the appliance. The
reasons for difficulties in cooperation were mostly
psychosocial. In these patients, treatment was terminated when it became clear that the children did notcooperate, usually within a few months after starting
treatment. In 3 patients, a serious illness prevented thecompletion of the orthodontic treatment. No further
records of these children were collected or included in
the analyses.
A random sample of 104 children from the same
1992 and 1993 age cohorts in Seinäjoki (population,
30,000) who fulfilled the inclusion criteria formed thecontrol group. The ethnic background of all children in
the treatment and control samples was Finnish. All
were healthy, and none had had earlier orthodontic
treatment. All treatment and control children and theirparents were free to decline their participation in the
study at any time.
The timing of all examinations and interventions
throughout the study was based on each child’s stage ofdental development rather than on chronologic age. The
treatment began immediately after the clinical examination at T1, the beginning of the mixed dentition
period, defined as the time immediately after the
exfoliation of the first deciduous tooth. The evaluationsof the occlusal changes in the treatment and control
groups were made at T2, after full eruption of allpermanent incisors and first molars. At this point, theearly treatment group entered the retention period, andtreatment was started in the control group.
We analyzed the occlusal changes from T1 to T2 of
167 children in the treatment group (85 boys, 82 girls)
and 104 children in the control group (52 boys, 52
girls). The mean ages in both groups were 5.1 years(SD 0.5) at T1 and 8.4 years (SD 0.5) at T2.
Two or 3 prefabricated eruption guidance appliances (Nite-Guide or Occlus-o-Guide; Ortho-Tain,
Winnetka, Ill) were used in each patient (Fig). A
Nite-Guide was the first appliance in only a few
patients whose first permanent molars had not yet
started to erupt. The appropriate size of the appliance
was determined as recommended by the manufacturer.
The appliances were worn during the night only. If
difficulties were encountered, daytime wear of 1 hour
was recommended until the problems with night wear
disappeared. Active treatment was defined as the time
between T1 and T2. The average duration of active
treatment was 3.3 years. At T2, all treated children
entered the retention period, when the last of the 2 or 3
appliances was used as a retainer, 2 nights a week. The

American Journal of Orthodontics and Dentofacial Orthopedics
February 2008

Fig. Eruption guidance appliance (Occlus-o-Guide).

retention was to be continued until all permanent
canines, premolars, and second molars were fully
erupted. Appointments were every 12 weeks during theactive period and once every 6 months during theretention period.
Full clinical examinations, including collecting ofdental casts, of all children were carried out at T1 andT2. Overbite and overjet were measured directly in themouth with the mandible manipulated in centric relation as described earlier.14 The measurement was taken
between the mandibular and maxillary right central
incisors, as suggested by Moorrees,15 by using a metal
ruler with accuracy of 0.1 mm. The values for overbite
in the deciduous dentition were not corrected for incisal
wear. The type of contact of the mandibular incisors to
the maxilla was also registered directly in the mouthwith the mandible in centric relation; it was classified as
tooth-to-tooth contact when contact with the maxillary
incisors was established, gingival contact when themandibular incisors contacted the palatal gingiva or
mucosa, and open contact when an open bite waspresent. Crowding in the anterior segment was assessedfrom the dental casts by registering overlapping teeth.
The terminal plane relationship was measured from thedental casts, trimmed to centric relation, between perpendicular projections, on the occlusal plane, from the
distal surfaces of the maxillary and mandibular second
deciduous molars as suggested by Bishara et al.16 A
child was considered to have a Class II relationshipwith a distal step of ⱖ1 mm. The terminal plane
relationship of the second deciduous molars was used

Keski-Nisula et al 257

American Journal of Orthodontics and Dentofacial Orthopedics
Volume 133, Number 2

Table I. Overjet and overbite at T1 and T2
Treatment group(n ⫽ 167)

Overjet
T1
T2
Overbite
T1
T2

Control group(n ⫽ 104)

Mean

SD

Mean

SD

P

95% CI

3.1
1.9

1.4
0.7

2.9
4.1

1.8
1.9

⬎.05
⬍.001

–0.19 to 0.63
–2.51 to –1.76

3.2
2.1

1.7
0.9

3.3
4.1

1.9
1.3

⬎.05
⬍.001

–0.55 to 0.35
–2.41 to –1.62

to classify the occlusion as Class I or Class II at T1 andT2. Analogously, the distance from the tip of themaxillary canine to the contact point between themandibular canine and first molar on the occlusal plane
was measured.
All dental assessments and measurements were
performed by the first author (K.K.N.). The measurements were made with a digital caliper to the nearest
0.01 mm. Method error for the measurements, assessedby means of the standard error of a single determination
on repeated measurements of 30 randomly selectedsubjects, was 0.14 mm.17 In the statistical assessment,
the chi-square test and the t test were used. P values
less than .05 were considered statistically significant.
RESULTSAt T1, overjet varied from ⫺2 to 10 mm andoverbite from ⫺3 to 7 mm; no statistically significant
difference was found between the groups (Table I).
Changes in overjet from T1 to T2 were ⫺1.2 mm (SD1.6) in the treatment group and 1.2 mm (SD 1.5) in thecontrol group. The difference in overjet between thegroups from T1 to T2 was highly significant (P ⬍.001).
Changes in overbite from T1 to T2 were ⫺1.1 mm (SD1.9) in the treatment group and 0.9 mm (SD 1.3) in thecontrol group; this difference was highly significant(P ⬍.001).
The contact point of the mandibular incisors was
registered at centric relation at T1 and T2. At T1,
tooth-to-tooth contact was found in 30 children (18%)
in the treatment group and 23 children (22%) in thecontrol group; all others had an open bite, or themandibular incisors were in contact with the maxillary
gingival or palatal mucosa. At T2, 165 of the treatedchildren (99%) and 25 control children (24%) showed
tooth-to-tooth contact between incisors (P ⬍.001). In
the treatment group, 50 children (30%) had gingival
contact, and 86 (51%) had an open bite at T1. At T2, amild open bite persisted in 2 treated children. In thecontrol group, the situation did not change significantly
from T1 to T2. Gingival contact was observed in 50

Table II. Incisor crowding at T1 and T2

MaxillaT1
T2
Mandible
T1
T2

Treatment group(n ⫽ 167)

Control group(n ⫽ 104)P

19 (11%)3 (2%)

9 (9%)
33 (32%)

⬎.05
⬍.001

80 (48%)2 (1%)

46 (44%)49 (47%)

⬎.05
⬍.001

control children (48%) at T1 and in 42 (40%) at T2.
The respective figures for open bite were 31 (30%) and37 (36%).
The treatment and control groups showed similar
figures for crowding at T1 (Table II). At T2, all but 4
children in the treatment group showed well-aligned
incisors; mild crowding was still present in the mandible of 1 child, in the maxilla of 2 children, and in bothjaws of 1 child. The control children had significantly
more crowding at T2 (P ⬍.001).
The mean sagittal relationship of the canines at T1
indicated a Class II tendency in both groups: 1.6 mm(SD 1.5) in the treatment group and 1.4 mm (SD 1.7) inthe control group. The difference was statisticallynonsignificant (P ⫽ .25; 95% CI ⫺0.12 to 0.44). At T2,
the canine relationship had decreased to 0.2 mm (SD0.7) in the treatment group but remained at 1.4 mm (SD1.6) in the control group. The difference at T2 washighly significant (P ⬍.001; 95% CI ⫺1.49 to ⫺1.04).
The mean terminal plane relationship at T1 showeda slight distal tendency in both groups: 0.7 mm (SD 1.7)
in the treatment group and 0.5 mm (SD 1.7) in thecontrol group. The difference was not statisticallysignificant (P ⫽ .20; 95% CI 0.2 to 0.48). At T2, theterminal plane relationships had changed to ⫺1.3 mm(SD 1.2) in the treatment group and 0.4 mm (SD 1.9) inthe control group. The difference at T2 was highly
significant (P ⬍.001; 95% CI ⫺1.91 to ⫺1.34). The
numbers of children with Class I, Class I/Class II, andClass II relationships are shown in Table III. The

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American Journal of Orthodontics and Dentofacial Orthopedics
February 2008

Table III. Sagittal relationship of the posterior segments

at T1 and T2
Treatment group(n ⫽ 167)

Control group(n ⫽ 104)P

68 (41%)151 (90%)55 (53%)50 (48%)

⬎.05
⬍.001

33 (20%)11 (7%)

18 (17%)18 (17%)

⬎.05
⬍.001

66 (40%)5 (3%)

31 (30%)36 (35%)

⬎.05
⬍.001

Class I
T1
T2
Class I/II
T1
T2
Class II
T1
T2

Table IV. Frequencies of deviating occlusal characteristics at T2

Overjet ⱖ5 mm
Overbite ⱖ5 mm
Open bite
Gingival contact ofmandibular incisors
Maxillary crowding
Mandibular crowding
Unilateral Class II
Bilateral Class II

Treatment group(n ⫽ 167)

Control group(n ⫽ 104)

0 (0%)
1 (1%)
2 (1%)
0 (0%)

31 (30%)40 (38%)37 (36%)42 (40%)3 (2%)
2 (1%)
11 (7%)
5 (3%)

33 (32%)49 (47%)18 (17%)36 (35%)The difference in the distribution of the characteristics between thegroups is highly significant (P ⬍ .001).

distribution in the treatment and control groups was not
significantly different at T1 (P ⫽ .14). A highly
significant difference was found at T2 (P ⬍.001).
Table IV shows the frequencies of deviating occlusal characteristics, including overjet ⱖ5 mm, overbite
ⱖ5 mm, open bite, gingival contact of the mandibular
incisors, crowding, and Class II relationship at T2. The
numbers of children in the treatment and control groups
with at least 1 deviation in the middle mixed dentition
were 22 (13%) and 91 (88%), respectively.
DISCUSSION

The guidelines for orthodontic treatment at thedental clinics of Jalasjärvi and Kurikka are designed tooutline a comprehensive early treatment protocol. Potential malocclusion cases are screened and diagnosedin the deciduous dentition. Depending on the type ofthe malocclusion, treatment is started either in thedeciduous dentition or at the beginning of the mixed
dentition. A similar approach to early treatment was
described by Dugoni,18 although the suggested time tostart the treatment was later in the mixed dentition,
between 7 and 9 years of age. Early diagnosis of

malocclusions is largely based on the deciduous occlusion, and, in most cases, it is straightforward.14 Early
treatment at Jalasjärvi and Kurikka is intended to be 1phase—ie, the treatment plan does not normally include
a second phase of treatment. Conditions that cannot be
detected early, such as congenitally missing premolars,
ectopically erupting molars, and impacted canines are
diagnosed and treated later.
Our findings indicate that significant improvementin the occlusion was achieved with early intervention.
After reaching the middle mixed-dentition stage, mosttreated children showed favorable intermaxillary relationships in the incisor, canine, and molar segments.
Overbite and overjet were both close to 2 mm, theincisors had tooth-to-tooth contact and good alignment,a mesial step was established in the molar region, andthe canines showed almost full Class I relationships. As
shown by Table IV, the need for further treatment had
markedly decreased through the intervention. Only 22(13%) of the 167 children in the treatment group had
persisting mild deviations. None of these children wasconsidered to need further treatment at this point. In thecontrol group, on the other hand, 92 (88%) of the 104
children had at least 1 deviating occlusal characteristic.
Early orthodontic intervention is frequently opposed on
the basis of findings that occlusal development canshow spontaneous correction in a growing child.15
However, the results in the control group indicate that
this is the exception rather than the rule. During theobservation period from early to middle mixed dentition, the frequencies of the occlusal deviations remained relatively unchanged in the control group.
In our sample, the time from T1 to T2 was 3.3
years. Because the eruption guidance appliance wasused to guide the erupting permanent teeth to theircorrect positions in the dental arches, the length of theactive treatment period was the same. On the other
hand, the total chair-side time that was required for thecompletion of the treatment was relatively short because routine checkups, every 12 weeks, normally took
no more than 5 to 10 minutes each. An advantage of theeruption guidance appliance is that it not only guides
the eruption of the teeth but also simultaneously acts on
the transversal, sagittal, and vertical relationships ofboth dental arches.
Several attempts were previously made to reduce or
eliminate malocclusion by early interceptive measureswith and without appliance therapy.13,19-23 Although all
investigations reported beneficial effects, the results
were variable, probably reflecting the diversity of theinterceptive protocols and the wide age ranges of thechildren. Two studies were carried out in countries
where orthodontic treatment is publicly subsidized.13,23

Keski-Nisula et al 259

American Journal of Orthodontics and Dentofacial Orthopedics
Volume 133, Number 2Those findings indicated that early interceptive measures, when applied in the community, can result insignificant reductions in treatment needs.13,23 A similar
but even more extensive improvement of the occlusion
was observed in our study.
The prefabricated eruption guidance appliance westudied has wide treatment indications, but it is usually
recommended for mild to moderate malocclusions
only.24 However, clinical experience has shown that, if
treatment is started in the early mixed dentition, theseverity of the malocclusion seldom appears to be acontraindication. At this stage of occlusal development,
almost all cases can be considered as mild or moderate
and are therefore suitable for treatment with the appliance. The eruption guidance appliance is designed to
guide the erupting teeth into the correct positions before
the fibers of the periodontal ligament mature.25 By
starting active treatment at the onset of the mixed
dentition period, as in this investigation, the action of
the appliance can be exerted on all permanent incisors
and first molars.
Although the effectiveness of the eruption guidance
appliance is not limited to the period of active eruption,clinical experience indicates that treatment tends tobecome more complicated if it is started later.26 Aftermaturation of the periodontal ligament, daytime wear isregularly needed to achieve the desired effect because tooth movement requires higher forces andlonger treatment times. Often, combined treatment
with other appliances such as headgear, rapid palatal
expansion, or fixed appliances might be necessary.27
On the other hand, if treatment is carried out during
the active eruption of the teeth, the appliance seems
to be effective in most patients.
Parental guidance and support are always essential
when treating young children with removable appliances, particularly at the beginning of the treatment. Of
the children in this study who completed the treatment
successfully, 4 had problems with the appliance at the
beginning, but they overcame the difficulties quickly.
On the other hand, treatment of 76 children (31%) had
to be discontinued because of persistent problems withcompliance, because either the child was not willing towear the appliance or the parents were not motivatedenough to support the child. Various psychosocial
disturbances in the families of these children were themain reasons for poor cooperation. Our rate of noncompliance was somewhat higher than reported for theTwin-block appliance5 and about the same as the
Fränkel appliance.2 It has been suggested that young
age of the patients would be a major limiting factor forearly treatment in the community.28 Our findings indicate that family background seems to be the single mostimportant factor affecting compliance, not the age ofthe patients per se. In spite of problems with cooperation, 43% of the children of the entire 1992 and 1993
age cohorts in Jalasjärvi and Kurikka were successfully
treated with the eruption guidance appliance.
Intervention in the early mixed dentition with theeruption guidance appliance appears to be an effective
method to reduce the need for orthodontic treatment.
Clinical experience indicates that, with proper retention, treatment results remain good with little or no
relapse. However, the long-term effectiveness of thistreatment modality can be assessed only after theretention period and the out-of-retention follow-up.
CONCLUSIONS

The results indicate that orthodontic intervention
with the eruption guidance appliance in the early mixed
dentition is an effective treatment modality for malocclusions with Class II or Class II tendency, excess
overjet, deepbite, open bite, crowding, anterior crossbite, or buccal crossbite. During the treatment, theerupting permanent incisors and first molars wereguided into their correct positions in the dental arches.
At the same time, intermaxillary relationships in theincisor, canine, and molar segments were largely corrected. During the observation period, only a few
spontaneous corrective changes occurred in the control
children. By the time the children reached the middle
mixed dentition, little treatment need was left in thetreatment group compared with the control group,
where deviating occlusal characteristics were commonly observed.
We thank the staff, the patients, and their parents at
the health centers of Jalasjärvi, Kurikka, and Seinäjoki
for their cooperation and assistance.

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