observations on healing of human tooth extraction sockets ... · were placed into trephine-drilled...

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

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGYMay 2004

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)

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGYVolume 97, Number 5

Nair and Schug 561

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


562 Nair and Schug

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.)


Nair and Schug 563

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


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.)


Nair and Schug 565

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


566 Nair and Schug

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.)


Nair and Schug 567

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


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


Nair and Schug 569

provided by the kind courtesy of Dr. F. A. Maspero

(Degradable Solutions AG, Schlieren, Switzerland).

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Institute of Oral Biology

Oral Structures & Development (OSD)

Plattenstrasse 11

CH-8028 Zurich

Switzerland

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observations on healing of human tooth extraction sockets ... · were placed into trephine-drilled...

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