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European Journal of Orthodontics 35
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Re-examination of ‘Einige Beiträge zur Theorie der
Zahnregulierung’ (Some contributions to the theory of the
regulation of teeth) published in 1904–1905 by Carl Sandstedt
Dirk Bister* and Murray C. Meikle**
*Department of Orthodontics, Guy’s and St Thomas’ NHS Foundation Trust, London, UK, **Faculty of Dentistry,
National University of Singapore, Republic of Singapore
Correspondence to: Dirk Bister, Department of Orthodontics, 22nd Floor, Tower Wing, Guy’s Hospital, Great Maze
Pond, London SE1 9RT, UK. E-mail: [email protected]
The original histological investigation that forms the basis of our present understanding of
tooth movement was carried out on dogs by the Swedish dentist Carl Sandstedt at the Karolinska Institute,
Stockholm. His findings were published in 1901 as a monograph in Swedish, and shortly after his death
in 1904, as three articles in German entitled ‘Einige Beiträge zur Theorie der Zahnregulierung’. Sandstedt
observed that the bone was deposited on the alveolar wall of the tension side with both heavy and light
forces, new bone spicules following the orientation of the periodontal fibres. On the pressure side, with
light forces, osteoclasts resorbed the surface of the alveolar bone, but heavy forces compressed the
periodontal ligament resulting in hyalinization—the formation of localized cell-free areas. At these sites,
bone removal resulted from undermining resorption by osteoclasts from adjacent marrow spaces. He
also observed root resorption and commented on the centre of rotation of the teeth. No English version
of Sandstedt’s research has ever been published, and in view of its importance, one of us (DB) has
translated his three articles from the original German. The aim was to persuade an orthodontic journal
to publish the articles in full—however, weighing-in at 21 000 words, the impracticality of this plan soon
became clear. We concluded that excerpts from the text plus commentary would be the most practical
solution. Where possible and without materially changing the intended meaning, we have translated the
German text into something resembling contemporary English, accompanied by the original 16 figures.
SUMMARY
Introduction
The idea that orthodontic tooth movement is dependent on
the resorption and deposition of the bone of the socket dates
back at least to 1839 with publication of ‘The Dental Art’
by Chapin Harris (Harris, 1839, p. 104). It was not until
the turn of the 20th century, however, that the original
histological investigation that forms the foundation of our
present knowledge of tooth movement was carried out on
dogs by the Swedish dentist Carl Sandstedt (1864–1904).
His ndings were published in 1901 (Sandstedt, 1901) as a
monograph in Swedish from the Anatomy Department of
the Karolinska Institute in Stockholm entitled ‘Några bidrag
till tandregleringens teori’ (Some contributions to the theory
of tooth movement). Later, three articles in German based on
the same work entitled ‘Einige Beiträge zur Theorie der
Zahnregulierung’ (Sandstedt, 1904, 1905) which is the source
of the present commentary were published in the journal
‘Nordisk Tandläkare Tidskrift (renamed Svensk Tandläkare
Tidskrift in 1908)’ shortly after his death (Persson, 2005).
As the centenary of the publication of ‘Einige Beiträge
zur Theorie der Zahnregulierung’ approached and a review
to celebrate the event was being prepared (Meikle, 2006), it
transpired that neither of the present authors, we are
embarrassed to admit, had ever laid eyes on Sandstedt’s
articles, either in the German translation or in the original
thesis. In the circumstances, it seemed unlikely that we
were alone since as far as we were aware, no English
translations of Sandstedt’s research had ever been published.
In view of the importance of being familiar with the primary
source literature and the origin of ideas, one of us (DB)
‘volunteered’ to translate Sandstedt’s articles into English and
make them available to a wider audience. The full translations
of Sandstedt’s original publications are available as
supplementary material in European Journal of Orthodontics
online. In the spirit of Edmund Burke (1729–1797), Irish
statesman and philosopher: ‘Those who know nothing of
history are destined to repeat it’.
Our original aim was to persuade an orthodontic journal
to publish the three articles in full—however, weighing-in
at 21000 words and written in a rhetorical style that would
test the patience of the most dedicated postgraduate student,
the impracticality of this plan soon became apparent. We
concluded that excerpts from the text plus commentary
would be the most practical solution and where possible,
without materially changing the intended meaning, have
attempted to translate the original German into something
resembling contemporary English. It is not clear who was
responsible for preparing Sandstedt’s manuscript for
CARL
SANDSTEDT’ S TOOTH MOVEMENT RESEARCH
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D. BISTER AND M. C. MEIKLE
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40 years not only impeded the progress of tooth movement
research for almost 50 years but also the establishment of
clinical orthodontics based on sound biological principles.
One orthodontist who did recognize the signicance of his
work at the time and discussed it in Chapter 8 of his textbook
‘Atlas und Grundriss der Zahnärztlichen Orthopädie’ was
Herbst (1910), but the lack of English translations and his
premature death meant Sandstedt became the forgotten man
of tooth movement research. It was not until 1932 (Schwarz,
1932) when the Austrian orthodontist Martin Schwarz
attempted the difcult task of trying to reconcile the
differences between the experimental ndings of Sandstedt
and Albin Oppenheim (not entirely successfully one might
add) in what eventually became the American Journal of
Orthodontics that Sandstedt became partially rescued from
obscurity and introduced to the English-speaking world.
***
Part I: Sandstedt C (1904). Einige Beiträge zur Theorie
der Zahnregulierung. ‘Nordisk Tandläkare Tidskrift’ 5,
236–256
Introduction
publication, but a rather complex historical review included
in ‘Tandregleringens Teori’ (1901) was omitted because of
insufcient space. A total of ve plates with 16 gures were
included in the three articles but were not accompanied by
gure legends. These have been added by the present authors
to the best of their ability. All the histological images (Figures
9–16) were hand drawn without magnications and are from
tissue blocks sectioned horizontally. Referencing of the
gures in the original text is occasionally incorrect.
Much of the narrative is in the rst person and one could not
accuse Sandstedt of using one word when several would
sufce, exhibiting a fondness for particularly long sentences.
Nevertheless, in spite of the often turgid prose and the tendency
to repeat phrases, it does contain a good deal of what we
understand today about the histology of tooth movement.
Sandstedt was a man who was clearly ahead of his time and
has to be admired for applying the experimental method to
what he regarded as a very important problem that ‘nobody
had ever thought it worthwhile to investigate’ (pp. 242). There
seems little doubt that Sandstedt’s tragic death at the age of
The rst paragraph of the Introduction describes the
background to the emergence of dentistry from the barber
surgeons into a separate profession (p. 236):
Orthodontics or the discipline of the regulation of teeth is a
relatively new branch of dentistry. Even in the middle of the
19th century, none or indeed very little attention was paid in
the orthodontic literature regarding the anomaly of the position
of the teeth or their treatment. It is indeed natural that during a
time when the activity of a dentist was mainly conned to the
extraction of painful teeth or the manufacture of more or less
satisfactory tooth replacement, very little importance was
attributed to such an unimportant factor as the irregularity of
tooth position. But to the same degree that dentistry developed
from a surgical craft at the same level as that of a barber to a
specic branch within medicine, starting to have a different
opinion of the duty of a dentist found wider acclaim. The rich
and varied developments that affected all branches of medicine
in the latter half of 19th century also paid dividends for the
development of dentistry. Scientically minded men,
dedicated and zealous, studied purely odontological problems
and among the representatives of general dentistry, more and
more were interested in scientic research. The darkness that
covered a lot of the diseases affecting the dentition lifted
gradually and dentistry was provided with new methods as
well as new aims and assignments.
The following is a footnote on page 236: The dentist Carl
Sandstedt passed away as a teacher at the Dental Institute of the
Swedish State during the year. The presented article sheds light
on a particularly interesting, as well as an unexplored area
within dentistry. Unfortunately, the author was not allowed to
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SANDSTEDT’S TOOTH MOVEMENT RESEARCH
nish his work on the theory of the regulation of the dentition.
What he has left behind is indeed only a part of his intended
work, which nevertheless demands the greatest attention.
Pages 238–240: There is a brief description of the
deformities affecting the teeth and jaws and how they can
be corrected by suitable ‘regulating’ appliances and in the
second paragraph various theories of tooth movement:
It is clear that every such change of shape of the alveolar
process and the jawbones as well as the position of the teeth as
outlined in the examples above goes hand in hand with
signicant changes to the hard and soft tissues affected by such
treatment. A thorough knowledge of the anatomy of those
skeletal parts and their tissues as well as the manner in which
the changes produced by the operation is indispensable if
treatment is to be undertaken in a rational way. The apparatus
that is used to straighten or regulate the teeth so that the purpose
achieved is a relatively simple task but to undertake the
treatment and use it without unnecessary loss of time,
unpredictable side effects, unnecessary discomfort, and pain
and still achieve the end result, all require a mature assessment
and thorough knowledge of the dynamic and physiological
principles which underline the movement of teeth.
The need for an explanation seems natural; however, it has
only been in the last three decades that an important chapter
of orthodontics that we call the physiology of tooth regulation
has been paid attention to and even to this day, there are a
variety of contradictory opinions between various authors on
the physiological processes which underlie the movement of
teeth. While one group is of the opinion that the movement of
the teeth is accompanied simultaneously by new building of
bone on one side and resorption on the other side, the other
group appears to think that resorption and apposition are
completely impossible and that the above changes in the
position of the teeth can only be explained by the elasticity of
the bone tissue which allows compression and elastic
deformation of the spongiosa caused by the operation, which
due to changes on a molecular level will eventually
equilibrate. Yet, another group of authors takes into account
the elasticity of the bony tissues as well as the resorption and
apposition processes as they think that the latter would not by
themselves be able to explain the speed with which the
phenomena, i.e. the movement of the teeth take place.
Experimental investigations
Pages 241–242: Because I was unable to arrive at a clear
view by means of reading the related literature regarding
the processes relating to the causes of tooth movement in
the jawbones, nor of the dynamic physiological processes,
which must regulate the rules of the treatment of orthodontic
malformations of the jawbones and the position of the teeth
within, I naturally asked myself how to get a clear view
among the confusing unproven conceptions. The laws of
probability could support both views but none of the above
views relied on direct anatomical investigations or brought any
D. BISTER AND M. C. 3MEIKLE
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other proof. It appeared to me that nobody had ever thought it
worthwhile to use investigations during the movement of teeth
within the jawbones, to prove or disprove a theory. Walkhoff
also points this out, complaining about the lack of it. Mentioning
the processes which take place during the straightening of
teeth, he remarks: unfortunately, we do not possess any precise
anatomical investigations on the changes of the tissues during
the movement of teeth. Apart from our own desire to get a clear
and determined view of one of the most important questions on
the subject in orthodontics, it was also mainly the statement
of Walkhoff, which prompted me to start the experimental
investigations on which I am about to report.
Friedrich Otto Walkhoff (1860–1934) was a dentist from
Brunswick in Germany who in 1901 published an atlas on
the anatomy and histology of teeth and their supporting
structures entitled: ‘Die normale Histologie menschlicher
Zähne; einschliesslich der mikroskopischen Technik’.
Following Roentgen’s discovery of x-rays in 1896, Walkhoff
is credited with taking the rst dental radiograph—of his
own teeth with an exposure time of 25 minutes.
The remaining sections of Part I are concerned with the
reason he chose dogs for the experiments: ‘without much
hesitation I decided on the dog’, plus descriptions of the
appliance used to move the teeth, and the use of plaster
models and radiographs to measure the amount of tooth
movement. The methods of xation, decalcication, and
embedding of tissue blocks taken from the jaws as well as
the preparation of stained histological sections cut in the
horizontal and sagittal plane are discussed in considerable
detail. Measurements of the amount of tooth movement
were made from both plaster casts and radiographs.
Page 250: During the rst experiments, I used a very
simple but equally satisfactory apparatus. This consisted of a
brace, which followed the labial surface of the upper front
teeth exactly and consisted of rings (bands) and caps, which
were cemented to the canines. Rings were cemented on the
labial surface of the canine with horizontal tubes through
which the brace ran. The ends of the latter were applied with
a ne thread and tail ends were xed with a screw–nut. Plate
I (Figure 1) shows such an apparatus that is still xed to a
previously sacriced animal. Due to the design of the
apparatus, it was a relatively simple task through slow
tightening of the screw–nuts to produce a movement of the
upper front teeth to the palatal plane, with the canine teeth
moving anterior along the line of the arch. . . . To get a better
idea about the dimension of the changes, which were induced
by the apparatus on the alveolar process, I took impressions
of the jaws before and after the experiment (Plate II; Figures
3 and 4). For one experiment in which I managed to get two
identically sized dogs which came from the same litter, I
managed to take photographs as you can see in Plate I: one
dog was used as the experimental dog and the other as a
control. From these photographs, one can see the apparatus
used and the changes produced in the position of the teeth.
The front teeth of the upper jaw in the experimental animal
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D. BISTER AND M. C. MEIKLE
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Plate I [Sw: Plansch] Photographs of the control (1) and experimental (2)
dogs at sacrice. The mandibular canines were removed to allow movement of
the maxillary teeth. The appliance consisted ofan archwire inserted into tubes
attached to bands on the canines; distal to the tubes was a screw mechanism,
which when tightened, moved the incisors lingually and the canines mesially.
(Figure 2) show the above mentioned position bite against
the lingual surface of the opposing teeth in the lower jaw. In
the control animal (Figure 1), this relationship is normal.
Page 251: Apart from these photographs, I have in all
experimental and control animals, taken radiographs of the
anterior parts of the jaws apart from the rst animal used in
the experiment. These radiographs on Plate II (Figures 5–8)
show particularly well and better than all descriptions, the
signicant changes in the anterior part of the alveolar process,
and the position of the teeth produced by the experiment.
***
Part II: Sandstedt C (1905). Einige Beiträge zur
Theorie der Zahnregulierung. ‘Nordisk Tandläkare
Tidskrift’ 6, 1–25
The rst experiment
Design of the experiment
Page 1: The rst experiment was conducted with a
14-month-old male dog of undetermined pedigree. On 28
November 1899, two lower canine teeth were fractured
trying to extract them. Two days later, the above-described
brace was xed. Due to daily tightening of the screw–nut,
I achieved the movement of the incisal teeth palatally with
the canine teeth moving forwards along the line of the arch. At
Plate II Study models and radiographs used to document the amount of
tooth movement. Left: control and right: experimental dogs. The experiment
lasted 3 weeks and during that time, the crowns of the incisor teeth moved
approximately 3 mm palatally. (The X-rays of the day, referred to as skiagrams,
produced a positive image, not the negative image of contemporary radiographs.)
the time of the dog’s sacrice after 3 weeks, the upper front
teeth had moved palatally to such a degree that they contacted
the lingual faces of the opposing teeth in the lower jaw. We
took impressions of the jawbone. The lower jaw was sectioned
into two parts after all soft tissues had been removed. On
one mandibular half, we used a section just anterior to the
premolar. Equally, the upper jaw was sectioned in the midline.
Histology
Pages 2–7 are concerned with a detailed description of the
structure of alveolar bone, the periodontal ligament, and the
location of osteoblasts on the surface of the cementum and
alveolar wall between Sharpey’s bres. At the time, the name
for the periodontal ligament had not been settled upon. In
D. BISTER AND M. C. 5MEIKLE
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the original text on page 4, Sandstedt says: ‘the space between
the alveolus and the tooth is occupied by a brous sturdy tissue
that was given the most varied names by individual authors,
such as ‘Wurzelhaut (skin of the root)’, ‘Wurzelperiost
(periosteum of the root)’, ‘Pericement and AlveoloDentalmembran among others’. He then continues ‘Die
Wurzelhaut’ without giving a reason why he chose this term
in particular. Later on, he uses ‘Wurzelperiost’ and these are
the two most commonly used ones in the text. The role of
osteoclasts in the development and growth of bone is described
in order to understand how these cells relate to changes in
the tissues during tooth movement—the rst reference in the
literature to hyalinization of the periodontal ligament (PDL) is
on page 10 and undermining resorption of the adjacent bone by
osteoclasts is on page 11. The rst description of root resorption
associated with orthodontic tooth movement is on page 22.
Page 2: To get a clear impression of the manner and
quality of the changes which have been caused by
orthodontics, it is necessary to recall the normal structures
which are involved when moving teeth inclusive of their
surrounding tissues, namely, apart from the teeth themselves,
the periodontal ligament of the tooth, the alveolar process
and the periosteum of the latter.
Pages 7 and 8: After this short review on the normal
structures of the tissues, which are more or less affected by the
movement of teeth, I will now give a more detailed description
on the observations, which I gained through sections of the
rst series of experiments. To highlight the details of the
relevant changes individually, it should be appropriate to
choose the most instructive sections and describe them in
detail. For this purpose, I will show the following:
1. Horizontal section through a piece of the alveolus on the
right side of the upper jaw, which contains the roots of
the canine and the rst premolar.
2. Horizontal section through the anterior segment of the
left side of the upper jaw, which contains the roots of the
incisors and half of the root of the canine.
Pages 8 and 9: The following is a description of the
changes associated with the forward movement of the right
canine: We only nd something really remarkable on the
distal aspect of the alveolar wall. This is not as the usually
described lamellar bony structure consisting of regular
arches building a border to the alveolus but instead consists
of irregular beams (trabeculae) strips of a light-gleaming
bony substance. Between and within the lamellae, we also
observe larger and smaller completely enclosed hollows or
encapsulations, which are lled with cell-rich connective
tissue. Even under low magnication, it is unambiguous
that there is periosteal bone deposition (Plate III; Figures 9
and 10). Larger magnication allows us to look into the
process in more detail (Plate IV A: Figure 11). The newly
laid bony depositions arranged radial to the wall and at right
angles show particularly clearly characteristics of crude
bony tissue. Numerous large and irregularly built bony
lacunae lie densely packed without any clear structure
within the bony substance, which itself is perforated by
Sharpey’s bres, the direction of the latter representing
clearly the direction of the lamellae of the original wall. The
border between the latter and the newly built alveolar wall
is clearly demarcated in the von Ebner ’s cement (reversal)
line (Plates III and IV A and B).
Page 10: On the buccal alveolar wall, however, there is
very active resorption in progress. The periodontal ligament
is completely detached on a rather large area, which itself
shows the same irregular porous morphology which
characterizes Howship’s lacunae in the resorption areas.
Wherever the osteoclasts are starting to destroy the walls of the
alveolus, they tear apart the connection between Sharpey’s
bres and the connective tissue within the periodontal ligament.
It is only where osteoclasts appear in a closed bulk that we
observe the completely disconnected periodontal ligament.
Apart from the posterior half of the buccal wall, there is
also a demarcated resorption process on the anterior palatal
wall. The osteoclasts have completely broken down the part
of the wall that separated the alveolus from the surrounding
marrow and are now busy undermining (Ger: untergraben)
the residual part of the original alveolar wall.
Page 11: . . . the existing periodontal ligament also has
a very different appearance. In low magnication, it appears
to have a homogenous, white and shiny appearance
(Ger: homogenes, weisses, glänzendes Feld) in which we
distinguish individual light blue coloured speckles or small
blue bands, but no other elements that we normally nd in the
periodontium. Even in larger magnication, we cannot nd
nuclei. They seem to have disappeared altogether or they
seem to have lost their ability to stain. The above-mentioned
blue speckles or stripes can be interpreted as residues of tissue
walls or nerves. Also, the typical brillary structure is lost
and has been replaced by a regular homogenous substance
(Ger: homogene Substanz) pierced by shiny cracks (Plate IV
A: Figure 12). It is quite clear that what we see is a product of
the residual degeneration, a hyalinization of the soft tissues, a
sclerotic periodontium in which we now see regenerative
processes (ein Degenrationsprodukt, eine Hyalinumwandlung
des Bindegewebes, eine sklerosierte Wurzelhaut). Sandstedt
subsequently used ‘hyaline Substanz’ and ‘hyalines
Bindegewebe’ (hyaline connective tissue) interchangeably.
***
Part III: Sandstedt C (1905). Einige Beiträge zur
Theorie der Zahnregulierung. ‘Nordisk Tandläkare
Tidskrift’ 6, 141–168
The second experiment
Page 141: The results from my rst experiment appear to be
quite satisfactory. It gave me good insight into the processes,
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D. BISTER AND M. C. MEIKLE
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Plate III Horizontal sections through the right maxillary canine; the direction of movement is towards the top. Figure 9 is a section cut in close proximity
to the alveolar rim. (A) At the site of presumptive compression, the periodontal ligament (PDL) shows the glassy appearance characteristic of hyalinization,
with osteoclasts undermining the adjacent alveolar wall. (B) On the buccal side of the root, a thin layer of lighter staining new bone is demarcated from the
old bone by a von Ebner ’s (reversal) line. At the bottom, new bone takes the form of lighter staining bony trabeculae of woven bone orientated in the
direction of pull. (C) On the right side, osteoclasts are resorbing the alveolar wall; on the left, the detachment of the PDL from the bone is the result of a
tear during sectioning. Figure 10 is a section through the middle third of the same tooth. (In dogs, the pulp canal expands towards the middle third of the
root before narrowing towards the apex.) General remodelling activity at the bone–PDL interface is seen, but evidence of the accelerated bone formation
and resorption is absent. This area corresponds to the centre of rotation of the tooth.
which appear in the surroundings of the regulatory apparatus
of the teeth, which are inuenced by it. It appears, beyond
doubt, that the changes in the position of the teeth which are
caused during the operation (the force application during xed
appliance treatment) are inuenced at least to a large extent by
resorption and apposition, which are in direct connection with
the pressure and tension and cause the movement of the teeth.
Sandstedt then goes on to compare the tissue changes
introduced by experimental means with the corresponding
parts of the alveolar process in a control animal. The jaws
were sectioned in both horizontal and sagittal section and
the description of the changes he observed occupies several
pages. Much of it is repetitive, but does include the rst
references to the centre of rotation of the teeth being near
the middle of the root (pages 153 and 157), as well as a
description of root resorption (page 160).
Page 157: The intensity of resorption and new bone
formation appeared directly proportionate to the amount of
pressure and tension. In the areas of the alveolus where the
effects were not as prominent, such near the middle of
the root, there was relative quiescence; apposition and
resorption were less vibrant here (see Plate III; Figures 9
and 10). The largest intensity of those processes was in the
proximity of the alveolar rim and close to the tip of the
root. . . . Occasionally, it was demonstrated that the resorption
process started in the bone marrow cavity and developed
signicant intensity there, while the alveolar wall was still
intact. This appeared to be continuously repetitive in areas
where the alveolar wall was covered by periodontal tissue,
which had become sclerotic.
Page 160: In all the investigations that I have undertaken
so far, in only two cases, could I demonstrate a pathological
change of the tooth itself. The rst case was demonstrated
in series 2 (described in Part II, page 21) where the tip of the
root of the second incisor was strongly overgrown (Ger:
usuriert), so that it was embedded in signicant inltration
tissue. It is very likely that the tooth was in this case exposed
to strong pressure, apart from the pressure, it was exposed
to by the regulatory apparatus . . . It was demonstrated that
the intensive resorption process (Ger: der intensive
Resorptionsprozess) . . . attacked the tooth itself and caused
a defect in it, which extended deeply into the tooth structure
itself (Plate IV B: Figure 14). These resorption processes
are as already known, a constant returning feature to roots
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SANDSTEDT’S TOOTH MOVEMENT RESEARCH
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Plate IV A: These sections show at a higher power the cellular and tissue
changes in the periodontal ligament (PDL) and bone at sites of presumptive
tension and compression. Figure 11: Tension (B) newly laid down woven
bone with vascular spaces clearly demarcated from the older lamellar bone,
(C) highly vascular PDL, (D) cementum, (E) dentine. Figure 12:
Compression (A) bone of the original alveolar wall, (B) numerous darkstaining osteoclasts lining the bone surface, (C) the PDL in which the
brillar stucture has been lost and replaced by a glassy homogeneous or
hyalinized tissue, (D) cementum, (E) dentine.
Plate IV B Figure 13: Direct resorption. (A) periodontal ligament
(PDL) at a compression site showing its normal brillar appearance. (B)
Numerous multinucleate osteoclasts in Howship’s lacunae are resorbing
the surface of the bone. (C) Cortical bone of the alveolus; two Haversian
systems or secondary osteones are clearly visible. Figure 14: (A) PDL with
hyalinized PDL. (B) Although one cannot be absolutely sure, this section
was likely to have been included to represent resorption of the root
cementum at (C) by multinucleate giant cells.
of temporary as well as retransplanted and transplanted
teeth. That these occurrences appear on teeth that have been
under the inuence of a regulatory apparatus I assume is
extremely likely.
Page 164: Summarizing the above observations, we
now nd that the periodontal ligament in the areas of the
alveolus where new bone formation is taking place, has a
normal appearance, but that this appearance under the
inuence of larger or lesser pressure undergoes more or
less signicant changes depending on the amount of
pressure it is subjected to. Relatively moderate pressure,
as it is usually found during orthodontic treatment, results
in only little inammatory reaction of the periodontal
ligament and subsequent atrophy of the alveolar wall. If
however the pressure increases to such a degree that
persistent circulatory disturbance is caused, the pressure
will cause deeply degenerated changes of the periodontal
ligament which either lead to gradual death or to quick
necrosis of the tissue. But the disturbance of the circulation
is not only conned to the periodontal ligament but also
causes serious disturbances of the circulation in the
surrounding parts of the alveolar process. That this is the
case can be best demonstrated by the consistent thrombosis
of the vessels.
Sandstedt ends Part III by discussing the possible role
of bone bending in tooth movement. This had been
proposed by Kingsley (1880), based on observations made
while treating prognathic bites that tooth movement was
due to the exibility of the alveolar bone. Much of the
argument is not easy to follow, but Sandstedt does
appreciate the difculty of demonstrating bone bending
experimentally.
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SANDSTEDT’ S TOOTH MOVEMENT RESEARCH
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Page 165: Regarding the second particular issue in the
programme of my investigation, in how far apart from the
above above-mentioned processes, there is also compression
and stretching of the cancellous bone, and if this was the
case whether purely interstitial changes take place, I am not
able to answer unequivocally at this stage. . . . That the
alveolar structures in young individuals are extraordinarily
pliable should be as I already mentioned earlier without any
doubt, but in how far, this exibility plays a role during
tooth movement is a different matter. The observations,
which I made during my rst experiments, do not in any
way support such a theory. I was indeed fully aware, even
before my rst investigations began of the difculties which
I would encounter attempting to investigate such changes
histologically. A nearly satisfactory resolution of these
questions can only be derived at by way of experimentation
in such a way that quick and signicant remodelling of the
alveolar process can be affected that would be impossible to
be caused by resorption and apposition (Plate V; Figure 15
and 16).
D. BISTER AND M. C. MEIKLE
167
applied force, or how far the teeth were moved. The time
course of the experiments was 40 days at which point the
animals were sacriced.
Space does not permit a full evaluation of all the
experiments described in the paper by Oppenheim
(1911), but he concluded that bone reacts to pressure by
a transformation of its entire architecture. This he
believed occurred by resorption of the existing bone and
Postscript
The enduring question, bearing in mind that both the
illustrations and the descriptions of tooth movement quoted
above are ones we would recognize today, is why Sandstedt’s
research languished in obscurity for so many years? His
premature death and publishing in Swedish and German
certainly played their part but are not the whole story. At
this point, Edward Hartley Angle enters the narrative.
In 1911, the Viennese orthodontist Albin Josef Oppenheim
(1875–1945), published his famous article entitled
‘Tissue changes, particularly of the bone, incident to tooth
movement’ in the Transactions of the European Orthodontic
Society, forerunner to this journal. Oppenheim’s research
was brought to the attention of Angle who invited him to
give a series of lectures at the Angle School, at the time
located in New London, Connecticut. Oppenheim clearly
made an impression, his theories being enthusiastically
endorsed by Angle, and members of the Angle Society.
Oppenheim rejected both the pressure–tension hypothesis
supported by the histological evidence of Sandstedt and the
theory of bone bending advanced by Kingsley (1880) based
on the elastic properties of bone. To explain his ndings,
Oppenheim proposed an alternative: The Law of Bone
Transformation, in which the alveolar bone was completely
reorganized in accordance with Wolff’s Law (1892).
Oppenheim carried out his experiments on the lower
deciduous incisors of baboons, although it is not clear
exactly how many animals were involved. The tooth
movements reported were labial, lingual, depression,
elongation and rotation—one half of the jaw being operated
upon and the other half being used as an internal control; the
paper fails to include either a description or an illustration
of the orthodontic appliances used, the magnitude of the
Plate V Figure 15: Sanstedt used this image to exemplify septum
displacment between two teeth caused by orthodontic forces and shows the
appearance of the tissue in those areas with signicant resorption, close to
the tooth the periodontal ligament (PDL) still shows some hyalinization.
The clear areas are likely to be processing artifacts or tears produced while
sectioning. (A) Dentine with small zone of hyalinized tissue adjacent to it,
(B) disorganized PDL tissue, (C) remnant of bone with several osteoclasts,
(D) Haversian system surrounding a large blood vessel, (E) lipid droplet in
marrow cavity, (F) likely to be aggregates of lymphocytes and plasma
cells, (G) multinucleate giant cells resorbing hyalinized tissue. Figure 16:
Horizontal section of the bone between adjacent teeth. (A) Dentine, (B)
PDL, (C) newly deposited bone clearly demarkated from the darker
staining old bone.
D. BISTER AND M. C. 9MEIKLE
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CARL
168
SANDSTEDT’S TOOTH MOVEMENT RESEARCH
its replacement by new bone, both processes occurring
simultaneously until nally deposition preponderates
over resorption. He emphasized that bone transformation
occurred only with very light physiological forces;
should the applied load be excessive the result was
vascular occlusion and damage to the PDL and supporting
tissues. It is therefore noteworthy that Oppenheim was
unable to conrm Sandstedt’s observations regarding
hyalinization of the PDL and associated undermining
resorption. In view of the later ndings of Reitan (1957)
that hyalinization of the PDL occurred in human subjects
with forces as low as 30 gm (0.3 Newtons), this suggests
the forces Oppenheim applied to the teeth were very light
indeed. In fact, Oppenheim’s illustrations bear more than
a passing resemblance to the trabeculation of alveolar
bone observed at the bone—PDL interface in a rat model
of tooth movement—the result of stress shielding of
the tooth supporting structures by the presence of an
orthodontic appliance activated or otherwise (Milne et al.,
2009).
Interestingly, although Oppenheim rejected the pressure–
tension hypothesis, he still refers to the side of pressure
and the side of pull and regarded his experiments as
indubitable refutation (sic) of the pressure theory. There is
also a certain amount of ambiguity in his attitude to bone
bending and it is apparent that he recognized the elasticity
of bone and the role that property might play in tooth
movement, particularly in children and young adults.
Finally, since he was of the opinion that the fulcrum of
movement was at the apex of the tooth and having found
bone formation and bone resorption on both sides of the
teeth, it is unclear precisely how Oppenheim thought teeth
were moved into a new position. In retrospect, Oppenheim’s
theory of bone transformation made such little sense it’s
surprising that anyone believed it.
Be that as it may, the theory did seem to support
Angle’s non-extraction philosophy and the widespread
belief at the time that orthodontic appliances could ‘grow
bone’. More importantly, Oppenheim remained research
active and continued to publish in German and English
language journals up until the time of his death in Los
Angeles, having managed to escape from Austria in 1938
following the ‘Anschluss’ (Atkinson, 1957). He also
had the support of many inuential pupils of Angle
including Frederick Noyes, Professor of Histology and
Orthodontics, and later Dean (1924–1940) of the College
of Dentistry, University of Illinois Chicago. In a
posthumous tribute to Oppenheim’s research, Noyes
(1945) was contemptuous of the ndings of other
workers, writing in a rather pejorative tone: ‘one
investigator thought that the bone was bent and another
that the tooth plowed (sic) through the substance of the
bone by means of absorption on one side and deposit on
the other ’. The latter comment presumably a reference to
Sandstedt.
With the centre of gravity of orthodontics becoming
rmly embedded in North America during the 20th century,
the outcome was that Oppenheim’s research appeared in
mainstream English language textbooks to the exclusion of
all others (if any reference to the histology of tooth
movement appeared at all), until the aftermath of World
War II and the expansion of university-based orthodontic
training programmes—a salutary reminder of how
ideologies or dogmas can become entrenched by powerful
and dominant personalities. The problem of course with
ideologies is that they provide all the answers—lack of
evidence or evidence to the contrary is completely irrelevant.
In closing, it is therefore perhaps worth bearing in mind the
motto of the Royal Society of London, founded in 1660 to
promote scientic research and discussion: ‘Nullius in
verba’—‘Nothing upon another ’s word’.
Supplementary material
Full translations of Sandstedt’s original publications are
available as supplemental material in European Journal of
Orthodontics online.
References
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