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Pediatric Dental Journal

journal homepage: www.elsevier .com/locate /pdj

Original Article

3-D image analysis on palate growth changes from birth to 1month in healthy infants

Fusae Ishida a,c, Masanori Mashiko a,c, Ikuko Shimabukuro b, Seiko Yamamoto c,Kunihiko Shimizu c, Takahide Maeda c,*a Ishida Dental Clinic, 28-16 Inarimae, Tsukuba, Ibaraki 305-0061, JapanbOsamu Family Dental Clinic, 1-31-2 Kyuuna, Ginowan, Okinawa 901-2222, JapancDepartment of Pediatric Dentistry, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-nishi, Matsudo, Chiba 271-8587,

Japan

a r t i c l e i n f o

Article history:

Received 3 October 2012

Received in revised form

26 December 2012

Accepted 21 January 2013

Available online 25 April 2013

Keywords:

Newborn

1-month-old infants

Palate

Growth changes

3-D measurement

* Corresponding author. Fax: þ46 47 360 9429E-mail address: maeda.takahide@nihon-u

0917-2394/$ e see front matter ª 2013 The Jahttp://dx.doi.org/10.1016/j.pdj.2013.03.006

a b s t r a c t

In order to study the relations of malocclusion formation and feeding behavior as a sci-

entific research project, we measured the 3-D morphology of 31 healthy newborns within 7

days of birth and 1 month later using dental casts. Nine characteristics were selected and

the developmental changes were analyzed using specialized software for investigating

palatal development in detail. The results revealed that the palatal width, 3 palatal

characteristics relating to depth, maximum slope location, and mean slope increased

significantly during the 1 month, but there were no significant changes observed in palate

length, cuspid ratio, and maximum slope. There was a significant correlation between

palate depth and maximum depth point location, suggesting that the deeper points tended

to be located further back. No significant correlations were observed between newborns

within 7 days of birth and 1 month after birth for cuspid ratio, maximum depth point

location, and maximum slope. Our observation of inter-characteristics correlations

revealed 7 significant (P < 0.01) combinations out of a total of 33 combinations were

observed in newborns within 7 days of birth, while only 4 were observed in 1-month-old

infants. This appears to have been because of morphological changes occurring between

individuals due to growth. Thus, it was clarified that not only size but shape (cuspid ratio,

maximum slope point location, and the mean slope) also changes over the first month

after birth.

ª 2013 The Japanese Society of Pediatric Dentistry. Published by Elsevier Ltd. All rights reserved.

1. Introduction were not caused by feeding behavior [1]. Hellman noted that

Malocclusion in children has become an increasing problem

in recent years. Malocclusion is caused by a combined influ-

ence of genetic and environmental factors. As genetic factors,

Weinberger recognized that most cases of malocclusion and

hypoplasia of palate occurred at 2e3 weeks in embryo, and

.

.ac.jp (T. Maeda).panese Society of Pediatric

the disturbance existed in the bone originally, while the teeth

only help us for its recognition [2]. The environmental factors

include oral muscle activity and oral habits. Their major

functions in infants are breathing and suckling. In particular,

suckling influences the morphology of the palate soon after

birth.

Dentistry. Published by Elsevier Ltd. All rights reserved.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 338

Leighton measured the shape variations of palate in 6-

month-old 109 infants, involving 30 pairs of twins, and stated

that shape variations were affected by physical sucking force

more than heredity [3]. While Nagaishi et al. measured palatal

morphology in predental period infants of 3 months or older

and reported that different types of feeding during infancy did

not affect changes in palatal morphology [4], Takekoshi and

Hayama reported that feedingmethod did affect palate length

in 6-month-old infants [5]. Hohoff et al. measured palatal

width, depth, and capacity in infants aged fromwithin 1 week

to older than 1 year by stereo photographymethod at 3-month

intervals [6]. The authors believe that while the interval was

too long to observe the changes in detail, also their measure-

ments cannot show 3-D morphological changes.

The influence of postnatal environment in palatal mor-

phology is thought to be insignificant in newborns within 7 days

of birth, who therefore formed the starting point for palatal

morphology inthisstudy. Ingeneral,embryologicalsciencestates

that younger subjects exhibit greatermorphological changes and

Leighton [3] andvanderLindenhad reported thatmarkedgrowth

occurs in the jaw during infancy [7]. So we analyzed infants 1

month after birth to observe the growth change.

This study involved taking dental casts within 7 days of

birth (the starting point) and 1 month later, measuring them

with 3-D measuring equipment, selecting 9 characteristics of

palatal changesandanalyzing thesewith specialized software.

The focus of the study was placed on the changes in palatal

morphology in newborns from within 7 days of birth to 1

month after birth without considering environmental factors.

Fig. 1 e Definition of the characteristics width (char. 1) and

length (char. 2). M: The most prominent part of the alveolar

crest in the central incisor segments. R: Cross point of right

lateral sulcus and alveolar crest. L: Cross point of left lateral

sulcus and alveolar crest. (1) Width (RL): Distance from R to

L (mm). (2) Length (H): Distance from M to a point where

perpendicular lines drawn to the line segment R-L (mm). (3)

Cuspid ratio (CR): Width/Length.

2. Subjects and methods

The subjects for this study were 31 dental casts taken from 20

male and 11 female Japanese full-term infants, weighing 2500 g

ormore but less than 4000 g at birth (meanmale weight: 3089 g,

mean female weight: 2982 g) within 7 days of birth (mean age

3.6 days) (hereafter referred to as newborn) and dental casts

taken from the same infants 1 month after birth (hereafter

referred to as 1-month-old infants). In this study, previously

made impressions were used, and no new impression taking

was done. Nevertheless, it is worth noting the process of how

impression taking for newborns was conducted. Although it is

difficult to take oral impressions directly after birth, we

confirmed the safety by taking impressions from newborns

within 7 days of birth with breathing and circulation manage-

ment. Before the impression taking of the infants, we first

confirmed that at least one hour had passed since the last

suckling. Ostron trays were prepared before impression taking.

Silicon heavy body type impression materials were used and

insertion time within the oral cavity was kept within 30 s. The

amount of impressionmaterial to be usedwas decided by close

attention to infants’ posture and we made sure that materials

did not flow back into their throats. Then dental plaster models

were created from the thus acquired impressions.

The following methods were applied in this study. When

investigating 3-D palatal morphology, 3-D measurement was

conducted with a laser oscillator (LK-080, Keyence Corpora-

tion, Osaka, Japan) and a stage controller (CP-500, COMS Co.

Ltd., Amagasaki, Japan) and E-Measure software (COMS Co.,

Ltd.). When conducting measurements, 3 points were used as

standards: M: the most prominent part of the alveolar crest in

the central incisor segments. R: cross point of right lateral

sulcus and alveolar crest. L: cross point of left lateral sulcus

and alveolar crest. These are the points where impressions

could be taken clearly. The measurement of these points was

conducted manually with a measuring machine using X, Y,

and Z as coordinates. The plane passing through these 3

points was set as the reference plane for 3-D measurements

and then we scanned the entire dental casts. The range of the

scanning was 40,000 mm in the X-axis (frontal plane), and

50,100 mm in the Y-axis (sagittal plane). Measurement pitch

was set at 200 mm for the X-axis and 300 mm for the Y-axis. The

X, Y, and Z coordinates at each measurement point were

saved in text file on a personal computer. The 3-D measure-

ment was conducted by the same person (the first author). In

addition, when a line was drawn (hereafter, center line) from

M, joining the midpoint O between R and L, measurement

range in the anterior direction was set as M. Left and right

measurement range was set as top of alveolar crest, with

posterior direction set as 1.2 times the distance from M to the

maximumdepth point. Image analysis and statistical analysis

of 3-D data was conducted with dental cast analysis Dentist2

software (Yasuo Ukai, unreleased) developed independently

by a collaborator in this study.

The following 9 characteristics were investigated during

the analysis of dental casts. See Figs. 1 and 2 for reference.

1. Width (RL): Distance from R to L (mm)

2. Length (H): Distance fromM to a point where perpendicular

lines drawn to the line segment R-L (mm)

3. Cuspid ratio (CR): a ratio width/length

4. Maximum depth (max dep): Distance from reference plane

to maximum depth point above the center line (mm)

5. Maximum depth point location (loc dep): Distance from M

on the center line to the maximum depth point (mm)

6. Mean depth (mean dep): Mean depth (mm) along the center

line from M to the maximum depth point

7. Maximum slope (max slp): Maximum increase (mm) of the

depth per pitch (200 mm) along the center line fromM to the

maximum depth point

Fig. 2 e A figure showing characteristics (4), (5), (7) and (8).

(4) Maximum depth (max dep): Distance from reference

plane to maximum depth point above the center line (mm).

(5) Maximum depth point location (loc dep): Distance from

M on the center line to the maximum depth point (mm). (6)

Mean depth (mean dep): Mean depth (mm) along the center

line from M to the maximum depth point. (7) Maximum

slope (max slp): Maximum increase (mm) of the depth per

pitch (200 mm) along the center line from M to the

maximum depth point. (8) Maximum slope location (loc

slp): Location of point exhibiting maximum slope on the

center line from M (mm). (9) Mean slope (mean slp): Mean

increase of depth (mm) per pitch on the center line.

Table 1 e Correlations between newborn and 1-month-old infants for 9 characteristics.

Characteristics r dfa

1 RL 0.720** 29

2 H 0.378* 29

3 CR 0.316 29

4 Max dep 0.646** 28

5 Loc dep 0.097 28

6 Mean dep 0.494** 28

7 Max slp 0.09 29

8 Loc slp 0.382* 29

9 Mean slp 0.679** 29

R: Cross point of right lateral sulcus and alveolar crest. L: Cross point

of left lateral sulcus and alveolar crest. Width (RL): Distance from R

to L (mm). Length (H): Distance from M to a point where perpendic-

ular lines drawn to the line segment R-L (mm). Cuspid ratio (CR):

Width/Length.

Maximum depth (max dep): Distance from reference plane to

maximum depth point above the center line (mm). Maximum depth

point location (loc dep): Distance from M on the center line to the

maximum depth point (mm). Mean depth (mean dep): Mean depth

(mm) along the center line from M to the maximum depth point.

Maximumslope (max slp): Maximum increase (mm) of the depth per

pitch (200 mm) along the center line from M to the maximum depth

point. Maximum slope location (loc slp): Location of point exhibit-

ing maximum slope on the center line from M (mm). Mean slope

(mean slp): Mean increase of depth (mm) per pitch on the center line.

a Degrees of freedom.

*Significant at 5% level.

**Significant at 1% level.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 3 39

8. Maximum slope location (loc slp): Location of point exhib-

iting maximum slope on the center line from M (mm)

9. Mean slope (mean slp): Mean increase of depth (mm) per

pitch on the center line

3. Statistical analysis

We calculated correlations between newborn and 1-month-

old infants (correlation over the growth period) for the 9

characteristics in addition to inter-characteristic correlations

in newborn and 1-month-old infants. We also performed the

paired t-test for differences in the mean values in newborn

and 1-month-old infants.

We used the t-test to examine gender differences in the

newborns and 1 month after birth. This study was conducted

with the approval of the Ethics Committee of the Nihon Uni-

versitySchoolofDentistryatMatsudo(Approval code: EC12-007).

4. Results

4.1. Correlations between newborn and 1-month-oldinfants for the 9 characteristics

1) There was significant correlation (P < 0.01) for the 4 char-

acteristics i.e. width (char. 1), maximum depth (char. 4),

mean depth (char. 6), and mean slope (char. 9) (Table 1).

2) The correlations for length (char. 2) and maximum slope

location (char. 8) were significant (P < 0.05).

3) The correlations for cuspid ratio (char. 3), maximum depth

point location (char. 5), and maximum slope (char. 7) were

not significant.

4.2. Inter-characteristic correlations in newborn and1-month-old infants

1) The correlation between width (char. 1) and length (char. 2)

was highly significant in newborn (P < 0.01) (Table 2) and

also significant (P < 0.05) in 1-month-old infants (Table 3).

2) AhighlysignificantnegativecorrelationP<0.01wasobserved

between length (char. 2) and cuspid ratio (char. 3) in both

newborn and 1-month-old infants.

3) The correlation between maximum depth (char. 4) and

maximum depth point location (char. 5) was significant in

newborn (P < 0.01) and in 1-month-old infants (P < 0.05).

Maximum depth was correlated with its location from the

pointM.Namely, thedeeper themaximumdepth, the further

back the location of the maximum depth was located.

4) In newborns, highly significant correlations were observed

for 7 out of the 33 combinations of the characteristics, while

only 4 combinations were highly significant in 1-month-old

infants.

4.3. Mean, standard deviations, and coefficients ofdeviation of the 9 characteristics for newborn and 1-month-old infants and paired t-test for the differences between the2 types of infants

Compared to the early infant period, the 1-month-old

period exhibited a highly significant (P < 0.01) increase in

Table 2 e Correlations between characteristics in newborn.

Characteristics Size Depth Slope

2 3 4 5 6 7 8 9

1 RL 0.463** 0.068 0.187 �0.156 �0.195 0.138 0.197 �0.108

2 H �0.847** �0.002 0.216 �0.089 0.066 0.418* �0.172

3 CR �0.106 �0.329 0.013 0.043 �0.337 0.123

4 Max dep 0.518** 0.928** 0.228 �0.105 0.768**

5 Loc dep 0.573** 0.311 0.226 �0.142

6 Mean dep 0.337 �0.166 0.654**

7 Max slp 0.017 0.063

8 Loc slp �0.299

R: Cross point of right lateral sulcus and alveolar crest. L: Cross point of left lateral sulcus and alveolar crest.Width (RL): Distance fromR to L (mm).

Length (H): Distance from M to a point where perpendicular lines drawn to the line segment R-L (mm). Cuspid ratio (CR): Width/Length.

Maximum depth (max dep): Distance from reference plane to maximum depth point above the center line (mm). Maximum depth point location

(loc dep): Distance fromM on the center line to the maximum depth point (mm). Mean depth (mean dep): Mean depth (mm) along the center line

fromMto themaximumdepthpoint.Maximumslope (maxslp):Maximumincrease (mm)of thedepthperpitch (200 mm)along the center line from

M to the maximum depth point. Maximum slope location (loc slp): Location of point exhibiting maximum slope on the center line fromM (mm).

*Significant at 5% level.

**Significant at 1% level.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 340

the mean for width and 3 depth characteristics (maximum

depth, maximum depth point location, and mean depth)

and 2 slope characteristics (maximum slope location and

mean slope). No significant differences in mean for length,

cuspid ratio, and maximum slope were observed (Table 4).

4.4. Gender differences for the 9 characteristics innewborn and 1-month old infants

Innewborns, therewere highly significant differences (P< 0.01)

inwidth, themaximumdepth, andmeandepthbetweenmales

and females (Table 5). In addition, the width of males was

significantly larger than females while the maximum depth

andmeandepthof femaleswere larger thanmales. In1-month-

old infants, significantly larger mean for males was observed

only forwidthandnogenderdifferenceswere recognized in the

other 8 characteristics.

Table 3 e Correlations between characteristics in 1-month-old

Characteristics Size

1 2 3

1 RL 0.412* �0.072 �0.072

2 H �0.925** 0.188

3 CR �0.144

4 Max dep

5 Loc dep

6 Mean dep

7 Max slp

8 Loc slp

R: Cross point of right lateral sulcus and alveolar crest. L: Cross point of left

Length (H): Distance from M to a point where perpendicular lines drawn t

Maximum depth (max dep): Distance from reference plane to maximum d

(loc dep): Distance fromM on the center line to the maximum depth point

fromMto themaximumdepthpoint.Maximumslope (maxslp):Maximum

M to the maximum depth point. Maximum slope location (loc slp): Locatio

*Significant at 5% level.

**Significant at 1% level.

4.5. Cuspid ratio

Mean cuspid ratio in newborns was 3.75 (Table 6). The mini-

mum value was 3.21 and the maximum value was 4.59. Four

newborns (13%) had a cuspid ratio of less than 3.3. and 2 of

them had an even lower cuspid ratio when they were

1-month-old infants.

5. Discussion

5.1. Measurement points and the reference plane

Whenmeasuring alveolar parts and palatal morphology in the

predental period, difficulties are encountered setting the

reference plane. Kojo [8] and Nagaishi et al. [4] set the 2 points

apart from the incisive papilla, in the maxillary tuberosity

infants.

Depth Slope

4 5 6 7 8

0.135 �0.16 �0.128 0.448* �0.183

0.383* �0.172 0.148 0.314 �0.258

�0.328 0.127 �0.206 �0.122 0.184

0.387* 0.814** 0.09 0.079 0.549**

0.305 �0.03 0.360* �0.550**

0.089 �0.1 0.440*

�0.363* 0.092

�0.236

lateral sulcus and alveolar crest.Width (RL): Distance fromR to L (mm).

o the line segment R-L (mm). Cuspid ratio (CR): Width/Length.

epth point above the center line (mm). Maximum depth point location

(mm). Mean depth (mean dep): Mean depth (mm) along the center line

increase (mm)of thedepthperpitch (200 mm)along the center line from

n of point exhibiting maximum slope on the center line fromM (mm).

Table 4 e Change in the values of the 9 characteristics between newborn and 1-month-old infants and paired t-test for thedifferences.

Characteristics Newborn 1-month-old infants Magnitude ofchange

Rate ofchange (%)c

t

Mean SDa C.V. (%)b Mean SD C.V. (%)

1 RL 25,333 1489.6 5.88 26675 1513.1 5.67 1342 5.3 6.15**

2 H 6824 781.9 11.45 7070 1130.9 15.99 245 3.6 1.34

3 CR 3.75 0.4 10.66 3.86 0.619 16.03 0.11 3 0.76

4 Max dep 7475 1260 16.85 8873 850.2 9.58 1397 18.7 9.07**

5 Loc dep 14,209 1553.3 10.93 15621 1515.4 9.7 1412 9.9 4.33**

6 Mean dep 3854 762.8 19.79 4382 564.4 12.87 527 13.7 4.78**

7 Max slp 258 86.6 33.56 321 130.7 40.71 36 12.6 1.23

8 Loc slp 6744 1614.6 23.94 7591 1410.9 18.58 847 12.6 2.78**

9 Mean slp 105 15.1 14.38 114 12.1 10.61 9 8.6 4.09**

R: Cross point of right lateral sulcus and alveolar crest. L: Cross point of left lateral sulcus and alveolar crest. Width (RL): Distance from R to L

(mm). Length (H): Distance from M to a point where perpendicular lines drawn to the line segment R-L (mm). Cuspid ratio (CR): Width/Length.

Maximum depth (max dep): Distance from reference plane to maximum depth point above the center line (mm). Maximum depth point location

(loc dep): Distance fromM on the center line to the maximum depth point (mm). Mean depth (mean dep): Mean depth (mm) along the center line

from M to the maximum depth point. Maximum slope (max slp): Maximum increase (mm) of the depth per pitch (200 mm) along the center line

from M to the maximum depth point. Maximum slope location (loc slp): Location of point exhibiting maximum slope on the center line from M

(mm). Mean slope (mean slp): Mean increase of depth (mm) per pitch on the center line.

a Standard deviation.

b C.V. (%) ¼ coefficient of variation (%) ¼ SD/mean � 100.

c Rate of change (%) ¼ magnitude of change/value of newborn � 100.

**Significant at 1% level.

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 3 41

region when setting the reference plane for 3-D dental cast

measurement of infants. In the dental casts taken from

newborns, the maxillary tuberosity region is located in a low

position and is unclear due to lack of development, as was

Table 5 e t-test for gender differences in the newborn and1-month-old infants.

Characteristics Newborn 1-month-old infants

t df T df

1 RL 2.933** 29 2.665* 29

2 H 1.4 29 0.478 29

3 CR 0.085 29 0.447 29

4 Max dep 2.604* 29 0.852 29

5 Loc dep 1.852 29 0.648 29

6 Mean dep 2.273* 29 0.638 29

7 Max slp 0.227 29 0.297 29

8 Loc slp 0.153 29 0.274 29

9 Mean slp 1.434 29 0.106 29

R:Crosspointof right lateral sulcusandalveolar crest. L:Crosspointof

left lateral sulcus and alveolar crest. Width (RL): Distance from R to L

(mm). Length (H):Distance fromMtoapointwhereperpendicular lines

drawn to the line segment R-L (mm). Cuspid ratio (CR): Width/Length.

Maximum depth (max dep): Distance from reference plane to

maximum depth point above the center line (mm). Maximum depth

point location (loc dep): Distance from M on the center line to the

maximum depth point (mm). Mean depth (mean dep): Mean depth

(mm) along the center line from M to the maximum depth point.

Maximum slope (max slp): Maximum increase (mm) of the depth per

pitch (200 mm) along the center line from M to the maximum depth

point. Maximum slope location (loc slp): Location of point exhibiting

maximum slope on the center line from M (mm). Mean slope (mean

slp): Mean increase of depth (mm) per pitch on the center line.

*Significant at 5% level.

**Significant at 1% level.

reported by Freiband [9] and Ashley-Montagu [10]. Therefore,

it is difficult to establish a reference point.When themaxillary

tuberosity region is used as a reference plane, it is not suitable

for observing anterior region changes because the anterior

region is warped by the maxillary tuberosity region being in a

much lower position than the incisive papilla region. More-

over, impression taking too far toward the back of the palate is

dangerous and places a heavy burden on infant subjects.

There are no other clear points on the alveolar crest apart

from the 3 points used by the authors that can be used to

analyze the dental casts of newborn. Takekoshi and Hayama

[5], who investigated 6-month-old infants, used the summit of

the deciduous cuspid eruption site, but this point is often not

clear in the dental casts of newborns. Although Tamura [11]

examined the palates of subjects aged 8 years and older, he

recommended reference point T6 (point extending from inner

edge of the first rugae of the hard palate to the midline pala-

tine raphe) on the palate as being a point that does not change

due to development, in newborns the rugae of the hard palate

is also not clear enough to be selected as a reference point.

Therefore, creation of the palate reference plane in the

present study was based on Sillman’s [12], Freiband’s [9],

Ashley-Montagu’s [10], and Leighton’s findings [3], and we set

a point that could be clearly distinguished in both newborn

and 1-month-old infant dental casts. We selected the incisive

papilla point at the top of the alveolar crest (M), and cross

point of lateral sulcus and alveolar crest. (R, L). The plane

passing through these 3 points was set as the reference plane.

5.2. Length changes

Although Kojo reported the palatal length increment using 3-D

measurement was seen from 1 month to 12 months [8], the

increment was not found from the first to second month after

Table 6 e Cuspid ratio of the subjects in newborn and 1-month-old infants.

Case No. Newborn 1-month-old infants

1 3.9 4.2

2 3.2 3.1

3 4.2 5.1

4 3.2 3.1

5 3.7 3.7

6 3.4 3.4

7 3.6 3.6

8 3.8 3.4

9 3.4 3.4

10 3.5 4.3

11 4.6 4.3

12 3.5 5.2

14 3.6 4.1

15 4.5 4.3

16 4.5 3.0

17 3.5 3.5

18 3.3 4.3

19 4.2 3.6

20 4.4 4.5

21 3.3 3.3

22 3.5 3.5

23 4.0 3.2

24 3.7 4.0

25 3.4 3.7

26 3.5 3.7

27 3.5 3.9

28 3.6 4.0

29 4.3 5.5

30 3.5 3.2

31 4.1 3.8

Mean 3.75 3.86

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 342

birth by his figures. There were no significant differences in the

palatal lengthbetweennewbornand1-month-old infants in this

study. It revealed that the length incrementwas not observed in

the very early stage of palatal growth and development.

5.3. Changes in morphology of the palate

Nagaishi et al. reported that few changes during the predental

period development in palate depth and area were observed

[4]. Kojo reported that although palate depth tended to in-

crease somewhat with age, it remained fairly unchanged

throughout the observation period from 1month after birth to

12 months after birth [8]. Although Kojo’s measurement re-

gionwas not strictly themaximumdepth used by the authors,

it was close to the same area. Furthermore, the present study

indicated that maximum depth increased significantly

(P < 0.01) in the period from newborn to 1 month after birth.

While both Kojo and Nagaishi et al.’s investigations included

predental period infants, their conclusions leave out the most

important reference period, that is the first month of the

newborn period.

Nagaishi et al. also did not examine the first 3 months of

the newborn period and concluded that it became clear that

only in the predental period, breastfeeding, bottle feeding, and

mixed breast and bottle feeding methods do not affect

development of the alveolar arch and palate [4]. In the present

study, large individual variation in palatal morphology

occurred commonly in newborn to 1-month-old infants.

Therefore, when investigating the palate of predental infants,

it is important to consider the early infancy period as a

starting point.

Although the present study mainly investigated the

anterior region of the palate, growth changes were not uni-

form. Leighton reported that, genetics influence the shape of

the palate of 6-month-old infants and physical forces such as

suckling and tooth eruptive force alter its state prior to tooth

eruption [3], and this was confirmed as occurring from within

the first month after birth. Thus, analysis of the changes in

the morphology of the palate could require observational

research from the early infancy period in the case of term

infants.

In addition, Melsen and Melsen conducted a historic

microradiographic study involving histological study of bone

autopsy material and asserted that bone absorption addition

occurs until late age in not only the palatine bone seam area

but also the surface [13,14]. The newborn period is one of

dynamic change and we believe that models should be

considered with this possibility in mind.

5.4. Gender differences

There are several reports on gender differences in palatal

formation. Hohoff [6], Kojo [8], and Nagaishi et al. [4] reported

there were no gender differences in morphology of palate.

Takekoshi and Hayama’s results of 6-month-old infants

showed gender differences in width and length of palate.

Leighton noted that in 6-month-old infants, although there

were no gender differences with length, there were differ-

ences observed with width [3].

In this study, width, the maximum depth, and mean depth

showed significant gender differences in newborns. Width of

palate in males was larger than females, while the maximum

depth and mean depth in females were larger than males. In

1-month-old infants, only width of palate showed significant

gender differences, and there were no significant gender dif-

ferences of palatal length in both newborns and 1-month-old

infants. Although our results of width and length changes

were similar to Leighton’s in gender differences, palatal depth

of female newborns was larger than in male newborns, and

the differences disappeared 1 month later.

5.5. Cuspid ratio

The importance of cuspid ratio for predental period was pro-

posed by Ishida [15]. Cuspid ratio is the value of cuspid area

width divided by length and can be used to display charac-

teristics of anterior portion morphology of the palate. Cuspid

ratio can be easily measured with vernier calipers, and is

easily evaluated clinically.

In newborns, there was no correlation between length and

maximum depth point location, but in 1-month-old infants a

significant positive correlation (P < 0.05) was observed. This

suggests that length enlargement led to enlargement of

maximum depth point location. There was a significant nega-

tive correlation between cuspid ratio and length (P < 0.01)

(Fig. 3).

Fig. 3 e Cast models. A: Cuspid ratio of No. 4 boy was 3.3 at

newborn (1D), and decreased to 3.1 at 1-month-old infant

stage (1M). B: Cuspid ratio of No. 16 girl was 4.5 at newborn

(4D), but decreased to 3.0 at 1-month-old infant stage (1M).

This is a case where the biggest change of cuspid ratio was

observed.C:CuspidratioofNo.14boywas3.6atnewborn (4D,

a little smaller than the average), but increased to 4.1 at 1-

month-old infant stage (1M, a little bigger than the average).

p e d i a t r i c d e n t a l j o u r n a l 2 3 ( 2 0 1 3 ) 3 7e4 3 43

6. Conclusion

Whenwe investigated palatalmorphology innewborns and the

mean values and correlative relationships in 9 characteristics,

we observed significant palate morphology changes in infants

during the short period of the firstmonth after birth. Therewas

great individual variation among infants. Although the mean

values for all 9 characteristics increased during the 1 month, a

significant increase (P < 0.01) was recognized for 5 character-

istics including width and no significant change was observed

in length, cuspid ratio, andmaximum slope. Length and width,

which are size factors, also maintained inter-individual differ-

ences observed for newborns during the 1month. However, the

lack of increasing changes in palate shape factors (cuspid ratio,

maximum slope point location, and mean slope) indicated the

importance of studying newborns as the starting point for un-

derstanding the phases of palate growth in infants.

Disclosure

None of the authors have any conflicts of interest that should

be disclosed.

Acknowledgments

Image analysis of 3-D measurement data, software develop-

ment, and statistical analysis were conducted by Dr. Yasuo

Ukai, former Professor of the Graduate School of the Univer-

sity of Tokyo. Dr Nobuko Takagi assisted in the creation of the

dental casts analyzed in this study and Dr. Keiko Shoji (Peri-

natal Clinic) aided in particular with impression taking. We

would like to express our deepest gratitude to all those

mentioned here who cooperated in this study.

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