Palatal suture closure in man from 15

to 35 years of age
Maurits Persson, D.D.S., Odont.Dr.,* and
Birgit Thilander, ‘D.D.S., Odont.Dr.**
Giiteborg, Xwedelb

T he sutures of the skull have been convincingly demonstrated to be sites

of skeletal growth. Remodeling apposition and resorption, which are necessary for
the preservation of the over-all shape and dimensions of the bones during growth,
are also integral parts of sutural growth. Several well-documented studies have
shown that the application of controlled mechanical forces during the skeletal
growth period will affect craniofacial growth through remodeling changes in
sutural articulations. With advancing age, however, sutures are normally obliter-
ated by calcified tissue (synostosis) .
From an orthodontic point of view, two events in this physiologic closure of
facial sutures are of clinical importance : (1) the age at which the first sign of
closure indicates that the upper limit of sutural growth has been reached and
(2) the age at which the advance of the sutural obliteration makes orthopedic
regulation of the maxillary bones impossible.
According to earlier studies,7, I71I92~7 ~8 27, 3o,31 sutures of the cranial vault
mostly start to obliterate during the third decade of life (Table I). Hansman,‘*
however, reported that, judging from roentgenograms, sutures in a few cases start
to close as early as 6 years of age.
The conflicting views about the time of closure of facial sutures in the few
studies available have recently been reviewed by K0kich.l” According to Scott25
and Xicher,26 the circummaxillary sutures, as far as is known, remain open at
least up to the middle of adult life. This contradicts the results of Davida and

From the Department of Orthodontics, Faculty of Odontology, University of Gb;te-

horg.
This study wu supported by Swedish Medical Research Council Grant No. B74-24X-
3797-03.
“Associate Professor. Present address: Department of Anatomy, School of Medicine,
University of Virginia, Charlottesville, Vn.
“*Professor and Head of the Department of Orthodontics.

42
 Llmzde
l fern&e

l 0nfl000n n r-mu-ma0 w--inn 0 +

15 20 25 30 35 YEARS

Fig. 1. Distribution of the material, fourteen males and ten females, according to sex and
age.

Table I. Start of closure of cranial sutures

Age at which sutures

Investigator start to close (ye&s)
Schmidt (1888) 25 to 30
Dwight (I 890) 30
Parsons and Box (1905) 30
Loeschcke and Weinnoldt (1922) 25 to 30 (single casesbefore 20!)
Todd and Lyon (1924-1925) 24 to 26
Singer (1953) 25 to 30
Schmitt and Tamaska (1970) 22 to 35 (single case at 14!)

of Cobb,5 based on skull material, which indicate that the closure of facial sutures
begins at the same time as that of cranial sutures but does not advance to the
same degree.
Kokich,15 employing histologic methods on autopsy material, found that
the frontozygomatic suture does not undergo synostosis until the eighth
decade of life. In his review, he also mentioned the observations made by one of US
on midpalatal suture closure in juvenileszo but believed that the disparities in the
results show the inadequate methods and documentation in earlier studies.
In the present study, attempts were made to answer the following questions:
When do the intermaxillary and transverse palatal sutures actually start to be
obliterated? How does the degree of obliteration in palatal sutures change wit,h
age in young adults?
In a separate study, we have described the nature of the initial process of
obliteration and related this event to specific morphologic or topographic fea-
ture.s.*l

Material and methods

Material. The material was made up of necropsy specimens from twenty-four

male and female subjects, between 15 and 35 years of age (Fig. l), who had died
suddenly, usually in accidents. The specimens were dissected out at the post-
mortem examination and consisted of the intermaxillary and transverse palatine
suture areas inside the alveolar arch.
Histologic methods. For the preparation of conventional histologic sections,
three areas were selected in all specimens. From the intermaxillary suture, sec-
tions were taken just posterior to the incisive foramen and also from a posterior
 Am. J. Orthod.
44 Perssofl mad Thiltrnder duly 1977

part just anterior to the transverse palatine suture. E’rom the transverse palatine
suture, sections were taken from the right-hand side, just lateral to the midpalatal
suture. The specimens were fixed in alcoholic formalin (3 :I) and were embedded
by a double technique in celloidin-paraffin. Sixty-six microtome sections, 7
microns thick, were taken in the vertical plane from each area. Every fourth sec-
tion was stained with Mayer’s hemalum-eosin, 22 followed by a section stained for
fibers according to the method of Weigert and Hansenzz
Quantification of closure. In order to demonstrate the te&ency of a suture to
obliterate, nine sections from each of the three areas (twenty-seven sections from
each specimen) were classified with regard to synostosis. When every second sec-
tion is used for the histologic procedure, the distance between classified sections
will be 105 p, and the total suture length studied in each area will be about
0.9 mm.
An obliteration index was used as a quantitative description of the advance
of sutural closure with age. Four sections of the hemalum-eosin-stained sections
in each area were randomly selected (288 sections in all). Microphotographs of
the sutures were taken and further enlarged to a total enlargement of x25. The
oronasal course of the suture was transferred to paper (Fig. 2). According to
specific criteria, a central suture line was drawn, representing the shortest course
of the suture from the oral to the nasal side of the palate. With a map-measuring
instrument (Opisometer, Ingut, Gteborg, Sweden), numerical values of the oro-
nasal length of a suture and the length of the obliterated parts of the suture were
obtained. The obliteration index for these randomly selected sections was calcu-
lated as the relationship between the obliterated suture length and the total su-
ture length, times 100.
The usefulness of the index for future application and by different examiners
was tested. The precision in calculating the index was determined as the measur-
ing error and the accidental error, s(i) , of double determinations by two different
observers (error of the method). These determinations were made on ten areas
demonstrating closure. The calculations were ma.de according to the formula
s(i) = d X (x1-x2)z/2n and demonstrated that an index can be calculated with
a precision<f s(i) = 0.075. With a 95 per cent confidence limit (t =2.26), the
precision in determining the degree of closure will be within + 0.17 per cent of
the suture length.

Results

The bone histology of a partly obliterated suture and the corresponding trac-
ing of the suture area are presented in Figs. 3 and 2, respectively. The ossified
part of a suture was, in most cases, easily discernible in the bone, because of the
presence of basophilic cement lines at the sites of the earlier, resting-suture mar-
gins. This made it possible to calculate the length of the obliterated part of the
suture.
The earliest obliteratiolb in the studied areas was found in the posterior part
of the intermaxillary suture in a 15-year-old girl. In four of seven specimens from
persons younger than 20 years of age, synostosis could not be found ; nor could it
be found in two of the remaining seventeen specimens from persons up to 35
Fig. 2. Tracing of a section in the frontal plane from the posterior area of the intermaxillary
suture in a 31-year-old man with a partially obliterated suture. Bony bridges at the
arrows. A central suture line from the nasal (N) to the oral (0) side has been drawn
for the calculation of the obliteration index as the ratio between the obliterated suture
length and the total length of the suture. (Magnification, x100.)
Fig. 3. An ossified part of the suture in the section shown in Fig. 2. Note the heavy baso-
philic staining at the site of the earlier, resting-suture margin (arrows] by which the course
of the suture can be traced, even in its ossified parts. (Mayer’s hemalum-eosin stain.
Magnification, x250.)

years of age. The oldest person without any observed union of the suture margins
was a 27-year-old woman.
The number of histologic sections demonstrating obliteration in each specimen
according to age is given in Fig. 4. Three of the specimens in the age group 15 to
19 years demonstrated bony bridges across the sutures in isolated sections. From
the middle of the third decade, bridges were more numerous but still were often
made up of slender bony spiculae. In the cildest age group, 31 to 35 years, the
46 Persso?b and Thilander Am. J. Orthod.
Jull/ 1977

ssctkms exkmned

0 randomizMsection
showing c#teration
0 llosectii
with oMbr~tion

15 16 17 18 19 20 30 35 YEAR3

Fig. 4. Distribution of sections demonstrating obliteration according to age. The graph is

based on nine sections from three sutural areas in each specimen. The expected number
of sections demonstrating obliteration as a function of age [dotted line) has been calcu-
lated under the restriction that the function is not decreasing. Distribution of randomized
sections showing obliteration, used for the calculation of obliteration indexes, is also given
in the bars.

longest single continuous obliteration in a single section was measured as 2.5 mm.,
amounting to 33.5 per cent of the oronasal length of the suture. Calculation of a
mean curve1 (Fig. 4) demonstrated a moderate increase of obliterated sections
throughout the age range studied.
The distribution of sections demonstrating obliteration according to age was
also recorded with each suture area separately. This showed that obliterations in
the younger age groups were most frequent in the posterior area of the inter-
maxillary suture. In the 15- to 19-year age group all three obliterations were
found in this part of the suture.
The advance of closure with age, as represented by the obliteration indexes
for all areas, is presented in Fig. 5. Large interindividual variations characterized
the sample. One of seven persons in the 15- to 19-year age group demonstrated
closure in sampled sections, amounting to 0.9 per cent of the calculated suture
length. After this age, there was a markedly greater degree of closure ill most
specimens, indicating a rapid increase in obliteration during the third decade.
Concomitant with a general advance of obliteration with age in a single su-
ture, more of the palatal suture areas were involved (Fig. 6). The highest obli-
teration index in any of the three areas studied was found in the posterior part
of the intermaxillary suture. This indicated that at least 17 per cent of the oro-
nasal length of the suture in this area was ossified.
No marked difference in closure with regard to sex was apparent, but the
large interindividual distribution of the indexes gave no reason for further statis-
 Palatal suture closure in rna?l 47

4 male
$liJ~tion l

. female
20.

15-

10. l

.
l * l

5.
4.
l

3-

l
l
2. l

.
l- .

.
0.5.
0.4. .
0.3. l l

l
l

0.2.

Fig. 5. Distribution of the obliteration index according to age. A logarithmic scale to the
base of 10 is used along the y axis. The indexes are calculated on four sampled sections
and given for three areas in each specimen. Note the great variations in degree of
closure between persons of older ages.

tical analysis in this sample. On the other hand, a comparison between the
obliteration indexes for the oral halves and the nasal halves of the sutures with
regard to a possible difference revealed a significantly greater degree of oblit.era-
tion orally than nasally (I’ < 0.01; Wilcoxon signed rank test).

Discussion

Most data on suture closure originate from forensic and anthropologic studies
carried out with the purpose of finding a method of age estimation. However,
the anatomic appraisal of sutural closure in skull materials, most frequently used
in these studies, may reflect only surface changes. In evaluating the roentgeno-
graphic method of determining suture closure, Christensen and colleagues”
frequently and surprisingly noted a roentgenographic “opening-up” of anatomi-
cally closed sutures. Besides this unreliability in the method, roentgenography
48 Persso~l nno? Thilmder Am. J. Orthod.
July 1977

B = 1% of the oro-nasal length

--
----7---
1: 24 2: 36YEARS
Fig. 6. Graphic description of the advances of closure with age in palatal sutures, based
on the indexes given in Fig. 5. Concomitant with an increase in degree of obliteration with
age, there is a spreading of the obliteration to more suture areas. Areas A and B, Inter-
maxillary suture, posterior and anterior parts, respectively; C, Transverse palatal suture.

seems to have limited value in the study of facial sutures because of the com-
plexity of the facial skeleton.
In Kokich’s’” recent study, microradiography was used in combination with
stained sections from the contralateral suture. Histologic methods have been
used earlier in only a few limited studies on sutures of the vault.ll, lF, 17,28 These
studies give no reliable documentation of the start of physiologic obliteration and
only a few data on the advance of closure with age. Though superior in revealing
details, even the histologic method has disadvantages, because observations on
restricted areas cannot exclude an incipient closure or a greater degree of closure
outside these areas. The data on sutural closure reported here must therefore
be accepted as a maximu?,l age for the beginning of closure and a minimum
degree of obliteration in the sutures in question.
The initial bridges across the suture are made up of slender bony spicules
which are frequently found to be fractured, perhaps traumatically, and are pos-
sibly also removed by osteoclast resorption. 21 However, once a firm union of the
sutural margins has been established, ossification of the suture can be expected to
spread progressively, with large interindividual variations as a result (see experi-
ments by Giblin and Alley”). An obliteration index will therefore be the best
may to describe the advance of the degree of obliteration. On the other hand,
the tendency to obliterate will be better reflected by the number of histologic
sections demonstrating any bony bridges across the sutures.
Start of closure. Our results give clear evidence that some facial sut’ures
start to close in the juvenile period, that is, at markedly younger ages than has
been supposed in the orthodontic literature, A close, time-linked connection thus
appears to exist between the earlier-demonstrated cessation of sutural growth of
the face23 I8720 and the beginning of palatal suture closure reported here. With
the end of growth, these sutures are apparently likely to close.
Growth of facial sutures was found by Bji3rk2 to be intimately related to
growth in height. Bjiirk’s data consequently demonstrate a range in boys be-
tween 14 and 20 years of age as regards the end of the growth of sutures. It is
logical to presume that skeletal age also influences the start of closure, thus partly
explaining the interindividual variation observed here. Roentgenograms of the
digits of the hands were available for seven persons in the younger age groups.
As all subjects demonstrated union of the epiphyses of the phalanges, indicating
that skeletal growth had almost ceased,” further analysis of a skeletal-age rela-
tionship was impossible.
The results also indicate that the intermaxillary suture starts to be obliterated
earlier in its posterior part than in its anterior part. This is in agreement with
Davida@ opinion, published in 1926, that the median palatine suture in skulls,
almost without exception, starts to close posteriorly. Davida also observed that
the transverse palatine suture ossifies less frequently than the median palatine
suture. These differences in order of closure between different parts of the palate,
and also between different suture systems in the skull,6, 3o,31 indicate that other
factors than skeletal maturing greatly influence the closure of sutures.
In a recent study of the initial events of sutural closure, we found that bony
spicules crossing the suture were frequently fractured physiologically or that the
suture was reopened by osteoclastic resorption.z’ We concluded that these reac-
tions during the early stages of sutural closure were the results of functional
forces acting on sutural articulations. In the light of these observations, we agree
with the assumptions by Herring’” and Kokich’” that the age at which synostosis
occurs in a suture is directly determined by extrinsic functional demands af-
fecting that specific suture area.
The adoance of closure with age. It is well known from several earlier studies
that closure of sutures is generally, though weakly, correlated with age.x, “4 The
mean curve of sections demonstrating obliteration and the obliteration indexes
indicate that there is great activity in the sutural closure of the palate between
20 and 25 years of age. Similarly, Schmitt and TamLska’” found a rapid ossifica-
tion of cranial sutures around the same ages, but with minor differences between
ectocranial and endocranial surfaces. However, though no figures are previously
reported on the degree of closure, using an ordinate scale as here, our figures for
the oldest age group appear low when compared with the interpreted figures of
the cranial vault.s~ 24 If so, this would be in agreement, with Cobb’s5 opinion that
facial suture closure, in general terms, begins at the same time but does not ad-
vance to the same degree as closure of cranial sutures.
Great variations in the advance of closure with age have also been found in
50 Perssou wd Thilnnder Am. b. Ovthcd.
rrILI~ 19:;

studies of the vault in skull material, and the closure of sutures as a basis for age
estimation for medicolegal and ant,hropologic purposes has been proved to be
quite unreliable.“9 24 Nor could a relationship between closure and sex be verified
statistically in these studies of the vault. By variance analysis, Schmitt and
Tamaskaz4 found that, as rega.rds sutures of the vaults, age determines a maxi-
mum of half of the total variance of suture closure. Our observations indicate
that the same variability between closure and age apparently also holds trw
with regard to facial sutures. Considering the possible role of functional forces
in suture closure, not the least those originating in the masticatory apparatus,‘:’
quantified data on suture closure in different suture systems related to functional
stress may shed light on the biology of sutural closure.
C%hicnl implicntious is dentofncial orthopedics. In studies of the effect of
heavy forces on the sutural articulations, experiments have been performed on
dry skulls and on experimental animals. IXfferences in sequence and in degree ol
closure in different animal species” and a continuing lack of basic knowledge ot
human suture closure throw doubt upon the reliability of these animal experi-
ments for clinical guidance. (This is also stressed by Melsen’” because of dif-
ferences in suture morphology.) The closer the age of physiologic suture closure,
the more unreliability is to be expected. Though our material is limited, some
speculations on the mechanical regulation of orofacial structures in juveniles and
young adults seem justified.
Minor remodeling of the sutural surfaces is found in most nonunified facial
sutures. An obliteration index below 0.5 indicates that minor spicules have been
formed across a suture, but they are often broken up by forces within physiologic
limits. Minor changes in the position of the maxillary bones seem to be brought
about, for example, by the use of a reversed headgear. According to the progress
of suture closure in our study, such forces would theoretically be effective in or-
thopedic treatment of the jaws of most persons up to the age of 20 (Fig. 6).
In palate splitting with rapid maxillary expansion devices, it has been shown
that most of the resistance to separation is due to circummaxillary structures.‘4. ”
This may explain why, during treatment, forces of up to 22 pounds may accumu-
1ate.l’ Tt seems logical to suppose that these heavy forces will easily fracture
minor synostosed areas in the palate, all the more so, as a continuous load may
lcad to fracture of a bone, but not the same load tleliverctl rapidly by impact to
the bone.2” If a 5 per cent closure is set as a limit for splitting the intermaxillary
suture, this n-ill not be reached in most patients younger than 25 years of age.
In isolated cases, this suture may be found open even at later ages.

Summary and conclusions

The age at incipient obliteration and the advancement of this closure with
age in the intermaxillary and transverse palatal sutures were studied in autopsy
spccimcns from twenty-four persons ranging in age from 15 to 35 years. The
degree of closure was quantified on stained sections by the use of an obliteration
index. The tendency to obliterate was described by the number of sections demon-
strating closure. The study led to the following conclusions :
 1. Quantified calculations of the degree of closure can be made from paraffin
sections, owing to the presence of basophilic cement lines at the sites of the
earlier, resting-suture margins.
2. Palatal sutures may show obliteration during the juvenile period, but, ;I
marked degree of closure is rarely found until the third decade of lift.
3. Great variations exist among individuals with regard to the start 01’
closure as well as the advance of closure with age. Besides variations in the dr-
gree of closure between sutures, variations also exist between different parts ot
the same suture.
4. Suture closure progresses more rapidly in the oral than in the nasal part
of the palatal vault. The results also seem to verify earlier observations that the
intermaxillary suture starts to close more often in its posterior part than in its
anterior part.
5. Though the literature is lacking in comparable quantified data, it is sup-
posed that the closure of palatal sutures begins, in general terms, at about the
same age but does not advance to the same degree as does the closure of the
cranial vault sutures. Large interindividual differences are to be expected.
6. The observations indicate that more fact,ors than age strongly influence th(i
start and the advancement of suture closure.

REFERENCES
1. Barlow, R. E., Bartholomew, D. J., Bremner, J. M., and Brunk, H. D.: Statistical inter-
ference under order restrictions, London, 1972, John Wiley & Sons.
2. Bjork, A.: Sutural growth of the upper face studied by the implant method, Acta Odontol.
Stand. 24: 109-127, 1966.
3. Bolk, L.: tiber die Obliteration der Nlhte am Affensehadel zugleich ein Beitrag zur
Kenntnis der Nahtanomalien, 2. Morphol. Anthropol. 15: l-206, 1912.
4. Christensen, J. B., Lachman, E., and Brues, A. M.: A study of the roentgen appearance
of cranial vault sutures: Correlation with their anatomy, Am. J. Roentgenol. 83: 615.62T,
1960.
5. Cobb, W. M. : The age incidence of suture closure (Ahstr.), Am. J. Anthropol. 13: 394,
1955.
6. Davida, E. : Untersuchungen iiber die Ohliteration der Sehadelnahte und Synchondrosen, Z.
Anat. Entw. 81: 465529, 1926.
7. Dwight, T.: The closure of the sutures as a sign of age, Boston Med. Surg. J. 122: 389-
422, 1890.
8. Erlnko, O., and Kihlherg, J.: Closure of cranial sutures and age, Ann. Acad. Sci. Fenn.
43: l-31, 1955.
9. Giblin, N., and Alley, A.: Studies in skull growth: Coronal fixation, Anat. Rec. 8: 143-153,
1944.
10. Hansman, Ch. F.: Growth of interorbital distance and skull thickness as observed in roent-
genographic measurements, Radiology 86: 87-96, 1966.
11. Hauschild, M. W.: Histologische Untersuchungen iiber normale und ahnormale Verknoche-
rung der Hirnschldelnahte, Anat. Arm. 54: 85-93, 1921.
12. Helm, S., Siersbaek-Nielsen, S., Skieller, V., and Bjork, A.: Skeletal maturation of the
hand in relation to maximum puberal growth in body height, Tandlaegebladet 75: 12%
1234, 1971.
13. Herring, S. W.: Sutures-A tool in functional cranial analysis, Acta Anxt. 83: 222247,
1972.
52 Person awl l’hilamier Am. J. Orthod.
J&l 1977

14. Isaacson, R. J., and Ingram, A. H.: Forces produced by rapid maxillary expansion. II.
Forces present during treatment, Angle Orthod. 34: 261-270, 1964.
15. Kokich, V. G.: Age changes in the human frontozygomatic suture from 20 to 95 years,
AN J. ORTHOD. 69: 411-430, 1976.
16. Laitinen, L.: Craniosynostosis, Ann. Paediatr. 2: Supp. 6, 1956.
17. Loeschcke, H., and Weinnoldt, H.: t?ber den Einfluss von Druck und Entspannung auf
das Knochenwachstum des HirnschLdels, Beitr. Pathol. Anat. 70: 406439, 1922.
18. Melsen, B.: Palatal growth studied on human autopsy material, AM. J. ORTHOD. 68: 42-54,
1975.
19. Parsons, F. G., and Box, C. R.: The relation of sutures to age, J. R. Anthropol. Inst.
(Lond.) 35: 30-38, 1905.
20. Persson, M.: Structure and growth of facial sutures, Thesis, Odontol. Revy 24: Supp.
26, 1973.
21. Persson, M.: Studies on sutural closure: Preliminary report, Trans. Eur. Orthod. Sot. 52nd
Congress 1976. (In press.)
22. Romeis, B.: Mikroskopische Technik, Munich, 1948, R. Oldenbourg.
23. Schmidt, E.: Anthropologische Metoden zum Beobachten und Sammeln fiir Laboratorium
und Reise, Leipzig, 1888, Veit & Company.
24. Schmitt, H. P., and Tamaska, L. : Beitriige zur forensischen Osteologie. IV. Untersuchungen
iiber die VerknGcherung der Schideltihte unter besonderer Beriicksichtigung der Frage
der Altersbestimmung, 2. Rechtsmed. 67: 230-248, 1970.
25. Scott, J. H.: Dentofacial development and growth, Oxford, 1967, Pergamon Press.
26. Sicher, H.: Oral anatomy, ed. 4, St. Louis, 1965, The C. V. Mosby Company.
27. Singer, R.: Estimation of age from cranial suture closure: A report on its unreliability,
J. Forensic Med. 1: 52-59, 1953.
28. Sitsen, A. E.: 1935: fiber die Ursachen der Verkniicherung der SchLdelnLhte, Frankfurt.
Z. Pathol. 48: 499-524, 1935.
29. Storey, E.: Growth and remodelling of bone and bones, AM. J. ORTHOD. 67: 142-165, 1972.
30. Todd, T. W., and Lyon, D. W., Jr.: Endocranial suture closure. Its progress and age rela-
tionship, Am. J. Phys. Anthropol. 7: 325-384, 1924.
31. Todd, T. W., and Lyon, D. W., Jr.: Cranial suture closure, Am. J. Phys. Anthropol. 8:
23-168, 1925.
32. Wertz, R. A: Skeletal and dental changes accompanying rapid midpalatal suture open-
ing, AM. J. ORTHOD. 58: 41-66, 1970.

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