observations on healing of human tooth extraction sockets ... · were placed into trephine-drilled...
TRANSCRIPT
Observations on healing of human tooth extraction sockets implanted
with bioabsorbable polylactic-polyglycolic acids (PLGA) copolymer
root replicas: A clinical, radiographic, and histologic follow-up
report of 8 cases
P. N. Ramachandran Nair, BVSc, DVM, Dr.Odont.h.c.,a and Jens Schug, DMD,b Zurich, Switzerland
UNIVERSITY OF ZURICH CENTER OF DENTAL AND ORAL MEDICINE
Objective. The objective was to conduct a clinical, radiographic, and histologic follow-up of alveolar socket healing in 8human cases in which the extraction sockets of the involved teeth were treated with biodegradable root replicas beforemetallic implants were placed.Study design. Chair side prepared solid and porous forms of root replicas made out of polylactic-polyglycolic acids(PLGA) copolymer were utilized. Five patients were treated with the solid form and 3 with the porous form of thereplicas. The cases were followed up at regular intervals postoperatively, and standardized photographs and radiographswere taken. The cylindrical core of biopsies that were removed with trephine for placement of titanium implants wereprocessed and examined by light and transmission-electron microscopy.Results. Both forms of the root replicas were well tolerated and biodegraded by the body. There were no histologicallyobservable pathological tissue reactions at the time of implant application. However, the solid form seemed to cause aninitial decalcification of the bone surrounding the extraction sockets that was subsequently repaired along with the bonehealing of the extraction sockets. Such initial decalcification of the alveolar process was not observed in the cases thatwere treated with the porous form of root replicas. There was wide variation in the osseous component of the trephine-harvested biopsies in both treatment groups that suggests inconsistency in bone healing of the alveolar sockets.Conclusion. The 2 forms of root replicas under investigation were found to be biocompatible and biodegradable. But thecompact solid form may cause an initial temporary lactic acid induced decalcification of the alveolar process, whichmakes it unsuitable for regular clinical application as compared to the granular porous form. The observed inconsistentand unpredictable bone regeneration calls for further research to develop more optimal replica materials.(Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;97:559-69)
The use of osseointegrated prostheses has become an
important treatment mode in edentulous patients. The
prerequisite for an expected long-term prognosis of such
implant surgery is the presence of sufficient volume of
healthy bone at the implant recipient site,1 a requirement
that depends on the nature of postextraction healing and
rehabilitation of the alveolar process. The histologic and
histochemical events of human alveolar socket healing in
undisturbed extraction wounds have been reviewed and
described.2 A striking feature of the extraction socket
healing is the life-long catabolic remodeling of the
residual alveolar process that results in removal of a large
volume of bone structure.3 This unique atrophy of the
alveolar process has been described as reduction of
residual ridges4 (RRR) and is considered to be a ‘‘chronic
progressive, irreversible and disabling disease’’5 of
aInstitute of Oral Biology, Section for Oral Structures and Develop-
ment.bClinic for Preventive Dentistry, Periodontics and Cariology.
Received for publication Jul 21, 2003; returned for revision Oct 8,
2003; accepted for publication Oct 27, 2003.
1079-2104/$ - see front matter
� 2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.tripleo.2003.10.013
multifactoral origin. Although the causes and tissue
dynamics of the process are poorly understood, both
systemic and local factors have been suggested to be
involved.4,6 The rate of RRR is rapid in the first 6 months
of tooth extraction and takes place mostly in the areas of
the jawbones where the roots of the extracted teeth are
situated. Consequently, the size of the alveolar process is
substantially reduced in buccolingual and coronoapical
directions,5 particularly in the anterior maxilla. The
remodeled alveolar process cannot properly accommo-
date cylindrical implants, thereby causing functional and
esthetic problems of implant restoration. Therefore, it is
essential to maintain or achieve the original dimensions
of the alveolar process for successful long-term outcome
of the treatment.
In order to preserve the height, width, and contour of
the alveolar process, various prophylactic and post-
extraction therapeutic measures have been attempted
with widely varying outcomes. In general, all measures
that minimize injury to the alveolar process and
surrounding soft tissues during tooth extraction also
minimize bone resorption during the wound healing
process. The postextraction therapeutic measures in-
clude (a) physiologic preservation of the alveolar process
559
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560 Nair and Schug
Table I. Summary of clinical patient data
Case* Toothy Birth Replica insertion Trepanning Age/Sex Observation (months) Remarks
HG 7 (12) 08/31/66 12/01/98 11/10/99 34/F 11 Solid
SNV 9 (21) 07/23/42 10/01/96 04/16/97 55/F 6 Solid
UR 4 (15) 02/17/28 03/31/99 01/12/00 72/F 9 Solid
KU 3 (16) 07/16/51 07/13/98 01/13/99 48/F 6 Solid
SCV 19 (36) 11/05/62 04/21/99 01/12/00 38/F 8 Porous
MO 20 (35) 11/22/45 05/07/98 01/15/99 54/F 8 Solid
NJ 4 (15) 07/13/59 06/14/99 06/14/00 41/M 12 Porous
CD 5 (14) 09/29/48 04/13/99 08/06/99 51/F 4 Porous
*Highlighted cases are illustrated and described in the results.yFDA tooth indices in parenthesis.
by retention of the natural roots, (b) application of
prefabricated semianalogous root form implants, and (c)
modified versions of guided tissue regeneration (GTR)
techniques. In the latter, alloplastic bone substitutes7-17
and bone or bone derivatives of isogenic,1,18-20 allo-
genic,7,11,21,22 and xenogenic23-26 origin have been used
as osseoinductive and/or osteoconductive materials.
Based on the successful use27,28 of biodegradable
osteosynthesis devices in the internal fracture fixation in
maxillofacial and orthopaedic sugeries, Suhonen et al29
hypothesized that custom-made biodegradable root
replicas placed as immediate implants in extraction
sockets could preserve the dimensions of the alveolar
processes. Experiments in rabbits29 revealed that in-
sertion of custom made biodegradable root replicas into
the extraction sockets of second maxillary incisors
prevented palatal collapse of the implanted area. In
a human case it was later reported30 that ridge height
could be successfully preserved during 21 months of
radiographic observation by immediate postextraction
application of a polylactic acid (PLA) root replica into
the extraction socket of 1 maxillary incisor in a 42-year-
old women.
The purpose of this communication is to report on the
clinical, radiographic, histologic, and fine structural
follow-up observations of postextraction socket healing
in 8 human cases in which the extraction sockets of the
involved teeth were treated with 2 forms of biodegrad-
able root replicas before titanium implants were placed.
MATERIALS AND METHODSEight human patients whose clinical data are sum-
marized in Table I were studied. They were treated in
accordance with the Helsinki declaration. Informed
consent of each patient was obtained after explaining
the clinical procedures, risks involved, and benefits and
clarifying all questions raised by the patients. A total of
8 biopsies derived from clinically healed extraction
sockets of teeth that were implanted with root replicas
after varying periods of tooth extraction were histolog-
ically investigated.
Preparation of the root replicasIn general, the roots of extracted teeth were copied
chair-side to provide solid or porous root replicas. After
extraction, the teeth were rinsed briefly in running cold
water and the soft tissue attached to the root surface
was removed mechanically. The solid root replicas were
prepared from polylactic-polyglycolic acids copolymer
(PLGA85:25; Resomer RG858; Boehringer Ingelheim,
Germany) granules. The granules were placed in glass
vials, sterilized with y-radiation (25 kGy) and heated in
the vials at 1308C. The resulting melt was then poured
into the root-impression mold. By cooling, the polymer
solidified into solid root replicas for application into
patients. The porous replicas were prepared with
PLGA75:25 (Resomer RG756, Boehringer Ingelheim)
as described elsewhere.31 Briefly, porous PLGA75:25
granules (500-800 mm) where poured into the root-
impression mold. The mold containing the granules was
then placed into a high-pressure vessel and exposed to
a CO2 atmosphere (50 bar) for about 30 seconds. The
CO2 acts as a solvent32 for the polymer so that the
granules glue together to form a root-shaped body.
The replicas reveal a porosity of 50% (v/v) with an aver-
age pore-diameter of 200 mm.
Clinical proceduresAfter extracting the teeth, each patient was first treated
for a period varying from 4 to 12 months (Table I) with
one of the biodegradable root replicas that were prepared
by the chair side as described above. The root replicas
were inserted into the alveoli immediately after careful
extraction of the teeth so as to avoid damaging the
alveolar processes. Five of them received the solid and 3
the porous form of the root replicas (Table I). Thereafter,
the edges of the gingival wounds were held together by
sutures so that the replicas remained in the alveoli. The
sutures were removed after 10 days of application. The
patients were clinically examined at 1, 3, and 6 months
postoperatively. Standardized photographs and radio-
graphs were taken during recalls until single implants
(Institute of Straumann AG, Waldenburg, Switzerland)
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were placed into trephine-drilled bone-beds. The tre-
phine-bur-harvested cylindrical biopsies were processed
for light and transmission-electron microscopy.
Tissue processingImmediately after removal, the biopsies were fixed by
immersion in a solution consisting of glutaraldehyde and
paraformaldehyde33 for a period of 1 week. Thereafter,
the specimens were decalcified in 0.25 mol/L ethyl-
enediamine tetraacetic acid (Titriplex-III; Merck,
Damstadt, Germany) and 4% glutaraldehyde, sub-
divided in the axial plane into 2 halves, postfixed in
1.33% OsO4, dehydrated in ascending grades of ethanol,
and embedded in epon. From each epon block, 1- to 2-
mm thick survey sections and from selected blocks serial
sections were prepared using glass or histodiamond
knives (DiatomeAG, Biel, Switzerland) and the Reichert
Ultracut E microtome (Leica, Glattbrugg, Switzerland).
The sections were stained in periodic acid-Schiff (PAS)
and methylene blue-Azur II and photomicrographed in
a Dialux 20 photomicroscope (Leica) equipped with the
digital camera Progress C14 (Jenoptik, Eching,
Germany) and a digital imaging system (ImageAccess;
Imagic, Glattbrugg, Switzerland). The sections were
studied in a light microscope for any physcial and/or
pathobiological changes in the biopsies. Thereafter,
areas in the epon blocks were determined for ultra-
sectioning. Such selected tissue sites were target-
trimmed and thin-sectioned with the Reichert Ultracut
E microtome (Leica). The thin sections were double-
contrasted with lead and uranium salts34,35 and examined
in a Philips EM400T transmission electron microscope
(Philips, Endoven, The Netherlands).
Because of the small sample sizes and nonstand-
ardized variables involved in the cases, no attempt was
made to quantify the tissue components of the biopsies
by stereologic means because it was unlikely to have
resulted in statistically reliable data.
RESULTSThe healing of the postextraction wounds of all the
patients was uneventful and satisfactory by qualitative
clinical and radiographic assessments at regular in-
tervals. Clinically, the gingival heights and widths
appeared to maintain the respective preoperative di-
mensions as can be judged by standardized photographic
and radiographic means. However, some of the patients
who received the solid form root replicas revealed an
initial decline of radiodensity of the alveolar processes
surrounding the extraction sockets that was subsequently
replenished. Histologic examination of the trephine-
harvested biopsies revealed considerable variation in the
density of the trabucular bone at the implant sites. These
clinical observations and histologic variations are de-
scribed and illustrated in detail for 2 sample cases each
for the recipients of the solid and of the porous replicas.
Solid replica recipientsCase HG. The right maxillary second incisor (tooth
7) of a 34-year-old female patient was involved in this
case. The tooth had extensive cervical resorption (Fig
1, A). It was scheduled to be replaced with a titanium
implant and was removed by careful extraction. Within
minutes of tooth removal, the alveolus was closed by
inserting a solid PLGA root replica that was prepared
chair-side as described above (Fig 1, B-D). A control
radiograph taken immediately thereafter showed a ra-
diolucent alveolus delimited by a distinct radiodense
line representing the alveolar bone (Fig 1, E). Clinically,the gingival healing was uneventful, and at the time of
suture removal, 10 days postoperatively, no signs of mi-
crobial infection, exudation, or dehiscence of the wound
were observed.
Threemonths after the extraction, a clear decline in the
radiodensity of the alveolar process was observed.
Concurrently the radiolucent area that was limited to
the alveolus seemed to expand into the spongiosa of the
alveolar process (Fig 1, F). However, by 11 months
postextraction the radiolucency disappeared and a radi-
odensity reminiscent of a healthy alveolar process
appeared uniformly in the vertical and horizontal planes
of the interdental bone between teeth 6 and 8 (Fig 1, G).There was no observable ridge reduction, and a bone bed
that was sufficient for insertion of the titanium implant
was present (Fig 1, H). Histologically, the trephine-
harvested core of tissue (Fig 1, I and J) showed loose
trabecular bone separated by soft connective tissue that
was devoid of any inflammatory cellular infiltration. No
osteoclastic activity or other pathological features could
be observed around the bony trabeculae.
Case UR. The right maxillary second premolar
(tooth 4) of a 72-year-old female was scheduled to be
replaced by an implant. The crown of the tooth was
completely damaged (Fig 2, A), the root was carefully
extracted and the alveolus was closed minutes thereafter
by inserting a chair-side-prepared solid PLGA root
replica as described above. Clinically, the gingival
wound healed without complications (Fig 2, B). A
control radiograph taken immediately after insertion of
the root replica revealed a radiolucent alveolus with ill-
defined radiodense contour (Fig 2, C). By 6 months post
operatively the alveolar socket appeared to be filled with
a radiopaque tissue except for the cervical most portion
of the alveolus. The trephine-harvested cylindrical shaft
of tissue showed similar histologic features (Fig 3, A) asthose described for Case HG (Table I). No signs of bone
resorption or inflammation of the intertrabecular soft
tissue could be observed. The trabecular bone was lined
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Fig 1. Radiographic (A) and photographic (B) records of the right maxillary second incisor (tooth 7) of a 34-year-old female patient
before (A) and the socket after tooth extraction (B). Note the cervical resorption of the incisor (A). A PLA replica (RP in C) of theextracted root of the tooth (RO in C) in position immediately after insertion into the extraction socket (D). Radiograph does not
reveal the PLA replica (E). Control radiograph taken 3 months postinsertion of the replica (F) reveals partial dissolution of the
radiodense contour of the alveolar socket and extension of the radiolucency. By 11 months postextraction, there is complete (G)
bone healing of the extraction socket and the surrounding alveolar bone. Note the definite titanium implant in position (H) well
within the bone-healed extraction socket 11 months postextraction. Histologically (I), trabecular bone (BO in I) separated by soft
connective tissue (SC) can be seen in the trephine-harvested biopsy (J). (Original magnification: I 330.)
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Fig 2. Selected occlusal photographic and lateral radiographic records of the right maxillary second premolar (tooth 4) of a 72-year-
old female patient before (A) and 6 months after (B) extraction of the tooth. Note the damaged crown of the tooth (A) and closure ofthe extraction wound by gingival healing (B). The postextraction radiograph (C) does not reveal the PLA root replica of the extracted
tooth that was inserted into the alveolar socket immediately after the tooth extraction. The control radiograph taken 6 months post
extraction (D) reveals increased radiographic density due to bone healing of the extraction socket.
on the outer aspect by cuboidal osteoblast-like cells
and contained intact osteocytes within the bone (Fig 3, Band C).
Porous replica recipientsCase SCV. The biopsy originated from a 38-year-
old female patient. The first left mandibular molar (tooth
19), scheduled for replacement by an implant, was
extracted with regular oral hygiene, aseptic, and
postextraction measures. A chair-side-prepared porous
PLGA replica of the distal root was inserted into the
extraction socket and the gingival wound closed as
described above. There was uneventful healing of the
gingiva. However, a macroscopically distinguishable
reduction in the bucco-oral width of the gingival segment
of the extracted tooth could be observed in occlusal view
between 1 week (Fig 4, A) and 6 months (Fig 4, B) ofpostextraction respectively. The lateral photographs (Fig
4, C and D) taken concurrently did not reveal any
observable reduction of gingival margin in the axial
(apical-coronal) plane of the tooth. Radiographic records
(Fig 4, E) taken immediately before extraction showed
apical radiolucencies of the tooth which was more
pronounced for the mesial root. The control radiograph
taken 6 months postextraction revealed a distinctly
radiodense healing of the extraction socket which was
more evident and complete for the distal root as
compared to that of the mesial root without any replica
treatment (Fig 4, F). Histologic examination (Fig 5, A-C)of the trephine-harvested tissue of the distal root showed
dense trabecular bone separated by soft connective tissue
having no infiltration of inflammatory cells. Any bone-
resorptive activity or other pathological features could be
detected in association with the osseous tissue. The latter
was lined by osteoblast-like cells. Numerous uniformly
distributed lacunae within the bone contained osteocyte-
like cells that in many instances filled the lacunae
completely, as can be seen in the electron micrograph in
Fig 5, D.Case NJ. The right maxillary second premolar
(tooth 4) with extensive coronal decay (Fig 6, A) wasto be replaced by an implant in a 41-year-old male
patient (Table I). The diseased tooth was extracted and
the alveolus was treated as described above. The
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564 Nair and Schug
Fig 3. Low-magnification overview photomicrograph (A) of a midaxial section of the trephine bur-harvested cylindrical tissue shaft
from the replica-implanted extraction socket of the tooth shown in Fig 2. The rectangular demarcated areas in A and B are magnified
in B and C, respectively. Note the newly formed trabecular bone (BO) separated by soft connective tissue. The circular demarcated
area in C is magnified in the insert in B. Note the osteocyte (OC) within the bone. (Original magnifications: A 330,
B 375, C 3225.)
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Fig 4. Selected photographic and radiographic records of the left mandibular first molar (tooth 19) of a 38-year-old female patient.
PhotographsA and B are occlusal views of the gingival ridge 1 week and 6 months postextraction, respectively. Note the healing (A)andwell healed (B) gingival wound and the reduction in bucco-oral width of the dental arch at the tooth segment. In lateral views of the
extraction site at 1 week and 6months post extraction respectively (C andD) there is no caving-in of the alveolar ridge. Note the apicalradiolucency (arrowhead) on the distal root of the tooth (E). The rectangular demarcated area in the control radiograph taken 6months
postextraction (F) represents the replica inserted distal root extraction socket. Note the bone healing and minimal ridge reduction.
postextraction healing of the gingival wound was
satisfactory (Fig 6, B). A control radiograph taken
immediately after insertion of the chair-side-prepared
porous PLGA root replica (Fig 6, C) revealed
a radiolucent alveolus delimited by a radiodense line
representing the alveolar bone (Fig 6, D). At 6 months
postinsertion of the root replica, a control radiograph
showed filling of the alveolus-bottom with a radiodense
material and persisting radiolucency of the cervical
portion of the alveolus (Fig 6, E). The premolar site
was trephine-drilled and a definite implant was placed
12 months postextraction. Histologically, the trephine-
harvested biopsy (Fig 6, F and G) revealed both
osseous and soft connective tissue. However, unlike
the biopsies described for the previous 3 cases, the
bone was not distributed uniformly within the central
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Fig 5. Low-magnification photomicrograph (A) of an axial histologic section of the cylindrical tissue core from the replica
implanted extraction socket of the tooth shown in Fig 4. The demarcated areas in A and B are magnified in B and C, respectively.Note the newly formed dense trabecular bone (BO) separated by soft connective tissue (SC). The transmission electron micrograph
(D) reveals an intact osteocyte (OC) within the newly formed bone. (Original magnifications: A320, B365, C3125, D35,750.)
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Fig 6. Clinical, radiographic, and histologic follow-up records of Case NJ (Table I). The right maxillary second premolar (tooth 4)
revealed extensive coronal decay (A). The postextraction gingival wound healed (B) uneventfully after treating the alveolus with
a porous chair-side-prepared PLA root replica (C). The radiograph taken immediately after inserting the root replica (D) does notreveal the replica but shows a distinct radiolucent alveolus delimited by radiodense alveolar bone-line. Control radiograph (E) showshealing of the socket-bottom with a radiodense material and radiolucent cervical areas. Note the absence of trabecular bone, presence
of a soft connective tissue-filled alveolus-like area surrounded by bone in the central axial plane of the biopsy (F and G).
axial plane of the biopsy but was surrounding an area
resembling an alveolar cavity filled with delicate soft
connective tissue.
DISCUSSIONThis report presents clinical, radiographic, histologic,
and fine structural qualitative observations on po-
stextraction healing of 8 alveolar sockets that were
treated with the 2 forms of biodegradable root replicas
before definite implants were placed.
There has been several attempts to prevent post-
extraction atrophy of the alveolar ridge so as to
maintain7,9-15,18,23,25,26,36-38 or regenerate (aug-
ment)1,8,16,17,19-22,39,40 the alveolar process when they
were seriously diminished due to periodontal or other
diseases before extraction of the affected tooth.
Most of the publications were human case
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568 Nair and Schug
reports7,10,14,16,18,20,22,23,26,37,38 or animal stud-
ies9,12,17,19,21,36,39 in which bone grafts or bone sub-
stitutes were used to preserve or augment the alveolar
process with varying and often conflicting outcomes. In
several cases histologic examination of the tissues
removed during implant surgery was also
done.1,7,10,11,16-19,21,23,25,26,39However, the treatment out-
come of the cases presented here cannot be objectively
compared with those of the above cited reports.
To our knowledge, there are only 2 publications in
the literature29,30 in which the extraction sockets were
treated with biodegradable root replicas. The final
radiographic outcomes in all of the 8 cases reported
here broadly agreed with that of the 2 previous
reports.29,30 In the pioneer study in rabbits,29 it was
revealed that insertion of custom-made root replicas
made out of polyglycolic acid (PGA) into the
extraction sockets of second maxillary incisors pre-
vented palatal collapse of the implanted area. Collateral
control sockets that did not receive any root replicas
showed clear collapse of the area. The idea of using
biodegradable root replicas was extended to a human
patient30 in whom 1 extraction socket was treated with
a chair-side-made solid PLGA root replica. Based on
radiographic follow-up it was reported that ridge height
could be preserved during 21 months of observation
and with time the radiographic density of the can-
cellous bone increased in the replica-implanted area.
However, in some of the 5 cases in which the solid
PLGA root replicas were used and reported here, the
radiographic healing of the extraction sockets and
remodeling of the bone surrounding them were more
eventful as those stated in the previous report.30 In
certain cases there were initial decline in the radiodensity
of the alveolar processes surrounding the extraction
socket that resulted in total disappearance of the radio-
dense contours of the respective alveolar bone (Fig 1,
F and G). This is suggestive of an initial expanding
demineralization of the bones that surrounded the root
replica. However, such initial decline in the radiodensity
of the alveolar process were not observed in the 3 cases
in which the porous form of root replicas were used.
It is known that hydraulic degradation of the PLGA
copolymers results in the release of lactic acid mono-
mers that are oxidized to pyruvic acid.15 The latter
eventually enters the citric acid cycle and is metabolized
to yield energy, CO2, and water. The release of organic
acids from the solid PLGA root replicas might have
been in quantities that could not be immediately
metabolized by the body that possibly resulted in the
initial demineralization of the bone surrounding the
solid replicas. This was visualized as the initial decline
in the radiodensity of the bone. Unlike the solid form
PLGA mass, the porous form of the root replicas were
composed of copolymer particles that were glued
together so as to leave plenty of interconnected spaces
that reduced the overall quantity the polymer compo-
nents in the latter. As a result, the amount of lactic acid
released from the porous form may be substantially
lower than that from the solid form replicas. Further,
body cells that were involved in the socket healing
process might have entered the network of spaces in the
porous replicas,9 resulting in a more efficient recycling
and repair process.
Histologic findings of the biopsies harvested several
but varying months after tooth extraction, at the time of
insertion of the definite implants, suggest healing of the
extraction sockets without complications. Absence of
inflammatory and foreign-body giant cells in the
biopsies indicate a complete biodegradation of the root
replicas during the period of observation. The normal
fine structure of the osteocytes suggests healthy rege-
neration of bone in the alveolar socket. However, the
relative volume of bone within the biopsies, as can be
qualitatively and subjectively assessed from 2-dimen-
sional tissue sections, varied substantially in both groups
of patients that were treated with the solid and porous
forms of root replicas. For instance, the biopsy from
Case SCV (Fig 5) revealed an optimal bony trabecular
distribution, but the socket healing in Case NJ (Fig 6)
was mostly accomplished by soft connective tissue. This
suggests inconsistency in bone regeneration of the
extraction sockets. The reasons for the inconsistent bone
healing of the extraction sockets are unknown.
A quantitative determination of the volume densities
of the various tissue components of the biopsies was not
attempted, because it was unlikely to have resulted in
statistically reliable or biologically more meaningful
data owing to the limitations of the material, such as the
smallness of the sample sizes and noncomparable
variables involved. The number of cases could not be
increased owing to technical reasons. It may be further
pointed out that the reported observations were on 8
patients who were under regular dental health care. They
were not subjects of an experimental study. Therefore, it
was ethically not possible to provide controls.
Nevertheless, a conclusion may be drawn that the 2
forms of root replicas under observation were bio-
compatible and biodegradable. The initial lactic acid-
induced decalcification of the alveolar process by the
solid form of root replica and the inconsistent bone
regeneration call for further research to develop optimal
materials that can be applied in human patients after
adequate animal experimentation.
We thank Valerie Pulver and Margrit Amstad-Jossi for their
excellent clinical and technical assistance respectively. The
root replica materials and instruments to prepare them were
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provided by the kind courtesy of Dr. F. A. Maspero
(Degradable Solutions AG, Schlieren, Switzerland).
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