Clinical Evaluation of Freeze-

Fifty-three periodontists from military and civilian practices have been evaluating the effectiveness of freeze-dried allogeneic bone as a grafting material in periodontal osseous defects for more than 3 years. The allografts were placed in one-wall, two-wall, widemouthed three-wall, combination, and furcation defects. Narrow three-wall defects were excluded from the study because experience has shown that these defects are often repaired without using a grafting material. Signed consent was obtained from each patient prior to grafting procedures. Each patient was informed that the transplant had been "obtained from another human body; that the tissue was procured, processed and preserved in accordance with established medical procedures; that the graft was believed to be free from bacterial contamination; that the success of the transplant was not guaranteed; and that therapy was planned as a two-stage procedure, with the second operation to occur 1 year postgrafting to allow for evaluation and additional therapy as needed." The protocol to be followed by each collaborator stated that patients should be performing effective plaque control prior to transplantation, that all calculus should be removed, and that an occlusal adjustment should be performed, if indicated. Likewise, all patients were to receive an oral prophylaxis. Only one bottle of bone tissue (0.05 oz.) was to be used per patient per sitting, and any remaining bone was to be discarded. The collaborators were asked to provide narrative summaries of the patient's medical status. The clinician was given the option of flap design, root planing, specific antibiotic regimen, intramarrow penetration, periodontal dressings, and either " f i l l i n g " or "overfilling" of the defect. A l l defects were to be completely debrided of granulomatous tissue. U p o n completion of surgery, each clinician was required to submit the data form indicating specifically how he had managed the treatment of the patient with regard to the foregoing parameters. The clinicians were asked to reenter the graft site in 1 year's time to estimate the amount of osseous regeneration, or lack thereof. A s described in the initial article, this was accomplished by comparing preoperative measurements, intraoral photographs, radiographs, and drawings with similar data obtained at the time of reentry. The collaborators were then asked to estimate and record whether the amount of osseous regeneration and pocket elimination was complete, greater than 5 0 % , less than 5 0 % , or none. The data were then submitted to the tissue bank, where they were compiled and tabulated by the authors. O f the 53 investigators, 41 submitted data included in this report.

dried Bone Allografts i n Periodontal Osseous D e f e c t s - P a r t II* by WALTER W . SEPE, D.M.D.,

M.s.f

GERALD M . BOWERS, D.D.S., M.S. JOSEPH J . LAWRENCE, D.D.S., M.S.§ GARY E . FRIEDLAENDER, M.D.|| ROBERT W . KOCH, D.M.D.H H A S B E E N R E P O R T E D that freeze-dried crushed cortical bone allografts have potential as a grafting material in certain periodontal osseous defects in humans. The following report supplies additional data that reinforce the conclusion drawn in the initial publication. This paper also includes other clinical data not previously presented.

IT

1

MATERIALS

A N D METHODS

The freeze-dried crushed cortical bone used in this investigation was supplied by the Navy Tissue B a n k , Naval Medical Research Institute, Bethesda, M a r y land. The bone was obtained aseptically from cadavers within 24 hours after death and processed in accordance with procedures established by the Navy Tissue Bank over the past 25 years. The bony tissue was ground to a powderlike consistency of 100 to 300/A.** The powdered bone was placed in evacuated ½ oz glass bottles. Each bottle was plugged with a rubber stopper, sealed with silicone to maintain the vacuum and ensure sterility, and topped with a metal cap. A s long as the vacuum within the bottle is maintained, the freeze-dried tissue may be stored indefinitely at room temperature. * This investigation was supported through funds provided under Bureau of Medicine and Surgery, Department of the N a v y , Research W o r k U n i t M R 0 4 1 . 2 0 . 0 2 - 6 0 5 2 B 3 I D and Clinical Investigation Proposal N o . 5-06-600. The opinions or assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Department of the N a v y . f Periodontist, Branch Dental C l i n i c , Naval Submarine Base, New L o n d o n , Connecticut 06340. t Director, Postgraduate Studies in Periodontics, University of Maryland School of Dentistry, Baltimore, Maryland 21201. § Chairman, Periodontics Department, Louisiana State University School of Dentistry, N e w Orleans, Louisiana. || Associate Professor of Surgery, Section of Orthopaedic Surgery, Yale University School of M e d i c i n e , N e w H a v e n , Connecticut 06510 1f Chairman, Periodontics Department, National Naval Dental Center, Bethesda, M a r y l a n d 20014. ** Tekmar Analytical M i l l , M o d e l A - 1 0 , Tekmar C o . , Cincinnati, Ohio 45222.

RESULTS

Over 800 defects were treated with freeze-dried crushed cortical bone allografts in 350 patients during 9

10

Sepe, Bowers,

Lawrence,

Friedlaender,

T A B L E 1.

^ , R o o t planing

Flap type

r

Surgical Data on 189 Defects

(6) (6) (1) (7) (17)

Defects (No.)

Erythromycin Tetracycline Keflex Penicillin Cleomycin Other None

(7) (12) (5) (2) (11)

N o r m a l : 161 Delayed: 6 Unrecorded: 22 Reentry postsurgery

Antibiotic (type) (123) (29)

T A B L E 2.

Defect morphology

Complete: 169 Incomplete: 20

Yes: 135 N o : 47 Unrecorded: 7

Professional Products Coe-Pak Baer-Sumner Kirkland Orahesive ZnOE None

Healing

Closure

penetration

Dressing (type) (117) (35)

Wound

Intramarrow

&

Y e s : 184 No: 5

F u l l : 180 Partial: 9

J. Periodontol. January, 1978

Koch

9 10 11 12 13 14 15 16 17 18

(6) (1) (6) (103) (44) (14) (?) (3) (0) (5)

mo. mo. mo. mo. mo. mo. mo. mo. mo. mo.

Osseous Regeneration Repair Failed

%*

50%

17% (40%)

(60%) * Percentage of defects exhibiting complete or > 5 0 % osseous regeneration.

the period of this report. Surgical reentries were performed on 189 sites in 97 patients. The disparity between the number of reentered cases and osseous allografts was due to a 12-month lapse between grafting and reentry. Other causes were inability to contact patients and relocations involving some patients and clinicians. O n 42 additional sites (12 patients), documentation was accomplished without reentry. Thus, a total of 231 grafts were evaluated in 109 patients. O n sites where reentry was not performed, the data for pocket elimination were included. Only surgically reentered sites (189) were included in the data for osseous regeneration. There were 84 male and 25 female participants, ranging in age from 22 to 68 years, with a mean age of 47.2 years. The surgical data on 189 reentries in 97 recipients are shown in Table 1. The majority of clinicians stated that they used full thickness flaps and accomplished root planing. Normal wound healing was reported at

161 sites; delayed healing was noted at six sites; and data were not reported on the remaining 22 sites. O f the six delayed healing sites, two initially had incomplete closure, two were furcation defects which ultimately failed, and two were reentries which showed osseous regeneration to be complete in one case and less than 5 0 % in the other. Wound closure was considered complete at 169 sites and incomplete at 20 sites. Intramarrow penetration using burs and/or sharp hand instruments was accomplished in 135 sites and not utilized in 47 sites. Data on the remaining 7 sites were not reported. Periodontal dressings were placed on 172 sites, but were not used on the remaining 17 sites. Antibiotic coverage was used-by the majority of investigators, with erythromycin being the most frequently prescribed drug. Surgical reentries were performed from 9 to 18 months after transplantation, with the majority of sites being reentered in 1 year's time.

Volume 49 Number 1

Freeze-dried T A B L E 3. Intramarrow

Bone

Allografts

11

Penetration Osseous regeneration

Status

Total Complete

50%

47

7

(22) 4

0

(3) 77

37

189

T A B L E 4. Wound

2

1

(4) Total

6

16

19

6 (25)

Unrecorded

24 (51)

(84) No

Failed

32

43

Closure Osseous regeneration

Complete Complete closure

34

>50%

50%

4

20

(11) 31

17

(30) 26

16 (42)

A s shown in Table 2, complete regeneration was reported in 37 defects, whereas 77 were listed as having greater than 5 0 % regeneration. Forty-three sites demonstrated less than 5 0 % regeneration and 32 failed. It was determined that osseous regeneration of greater than 5 0 % occurred in 6 0 % of all grafted defects. Partial regeneration was observed in 2 3 % of the defects, while 1 7 % failed. Complete or greater than 5 0 % osseous regeneration occurred most frequently in the combination one/threewall defects (92%). The next highest percentage was reported with the combination two/three-wall (75%) followed by the widemouthed three-wall (74%), twowall (66%), one-wall (57%), and combination one/ two-wall defects ( 5 4 % ) . Only 2 4 % of the furcations treated demonstrated greater than 5 0 % or complete regeneration. Various surgical data were evaluated for relationship to osseous regeneration. A n analysis of data (Table 3) indicated what appeared to be a greater chance for osseous regeneration when intramarrow penetration

14

16

(48) 51 and older

4

7

(24) 36 through 50

Failed

0.05).* Complete wound closure was accomplished at 169 sites compared with 20 sites of incomplete closure. A s shown in Table 4, there was a greater tendency toward osseous regeneration when complete wound closure was obtained, but the results were not statistically significant (P > 0.05).* There were 15 defects associated with endodontically treated teeth. Five of these defects demonstrated osseous regeneration of greater than 5 0 % , while 10 showed less than 5 0 % regeneration. In Table 5, the amount of osseous regeneration is correlated with various recipient age groups. There was no significant difference (P > 0.05)* between the various age groups and the amount of osseous regeneration. The grafting material utilized in this study was obtained from several donors. The age range of the * According to chi square analysis.

12

Sepe, Bowers,

Lawrence,

Friedlaender,

T A B L E 6. Freeze-dried Bone Study: Osseous Regeneration 2 0 grafts using bone from donor P S X 1 1 8 4 (age 36) Complete

>50%

1

50%

0.05).* Sixty-three percent of all grafted defects demonstrated pocket reduction of greater than 5 0 % . A l s o , 2 7 % of the defects showed a lesser degree of pocket reduction while 1 0 % remained the same. The percentage of pocket reduction as related to the number of osseous walls is documented in Table 7. Pocket reduction of greater than 5 0 % occurred most frequently in combination one/three-wall defects (100%), combination one/two-wall ( 8 3 % ) , combination two/three-wall ( 7 6 % ) , one-wall (68%) and two-wall defects (64%). Likewise, 4 9 % of widemouthed three-wall defects and 2 8 % of furcations demonstrated pocket reduction of greater than 5 0 % . A s previously reported, residual pocket depths continued to be inversely proportional to the amount of regeneration of the defect. A s yet there are no reported instances of postoperative infection, graft rejection, root resorption, or ankylosis. DISCUSSION

Preserved bone allografts have been used successfully in human reconstructive surgery for almost 100 years. Freeze-drying of osseous tissues for the purpose of long-term preservation was begun in the U . S . Navy Tissue Bank in 1950, and since then freeze-dried graft material has been used to treat a variety of orthopaedic and oral surgical problems. Military periodontists have utilized freeze-dried bone allografts, on a limited basis, for over 14 years in the treatment of osseous defects. U n t i l recently, 1 to 2 mm fragments of cancellous bone have been used to treat periodontal defects with varied results and no specific documentation. There is a consensus among many clinicians who have used the material, that the basic problems encountered are graft sequestration and slow incorporation and resorption of the graft material. Recent studies suggest that fine 2

* According to chi square analysis.

J. Periodontol. January, 1978

Koch

particles of bone may enhance regeneration of the alveolar process, and that cortical freeze-dried bone is comparable to cancellous bone when used in cystictype defects. In addition, clinical experience indicates that sequestration is much less a problem with fine particles of cortical bone. Consequently, small particles (100-300//,) of cortical freeze-dried bone have been utilized in this study. A basic concern to both patient and clinician is the safety of the material to be implanted. Repeated bacterial evaluation of graft material by the tissue bank since 1950 has shown that the freeze-dried bone can be stored indefinitely at room temperature without contamination when a vacuum is maintained within the storage container. In this study, as well as in numerous studies in the medical and dental literature, bacterial infection was not a problem. In addition, there were no reported signs of immunologic rejection in this study, which is in keeping with the 25-year history of the use of this graft material. Studies continue to demonstrate that both deep-freezing and freeze-drying of bone allografts are associated with a marked reduction in antigenicity. Although not a part of this protocol, the study of the immune response to preserved allograft in animals and humans has been evaluated by the Navy Tissue Bank in other ongoing research projects. A Cr-release assay for humoral and cellular immunity has demonstrated that crushed cortical bone allografts in rabbits are not associated with detectable immune responses. This same assay demonstrated the antigenicity of fresh cortical, cancellous, and deep-frozen (—170°C) cancellous bone allografts and the weak response evoked by freeze-dried cancellous and deep-frozen cortical tissues. Human recipients of tissue-typed crushed cortical freeze-dried bone may become "sensitized" to graft specific H L - A antigens. While 8% of the patients participating in a study of the antigenicity of bone tissue exhibited this "sensitivity," no clinical evidence of tissue rejection was reported and the postoperative course of these recipients was indistinguishable from that of "non-sensitized" recipients. The clinical significance of weak bone allograft antigenicity has yet to be clearly defined. 3-5

6

7

8-10

51

11-12

13

Freeze-dried crushed cortical bone allografts produced favorable results in the majority of the transplantation procedures documented in this study. Complete or greater than 5 0 % osseous regeneration was recorded in 6 0 % of all defects grafted. Some clinicians reported that even though bone regeneration was not complete, favorable changes in the original morphology were observed. One could rationalize that the grafting procedures often served to narrow the defect or increase the number of osseous walls, thereby enhancing the predictability of a second transplant procedure. The treatment of furcation defects demonstrated the least predictability in obtaining osseous regeneration

Volume 49 Number 1

Freeze-dried Bone Allografts 13 T A B L E 7. Pocket Defects (No.)

Defect morphology

Reduction Reduction

Complete

>50%

%*

Failed

5 0 % pocket reduction.

and pocket elimination. Failure to induce osseous regeneration in furcations cannot be attributed solely to any deficiency of the graft material. It would appear that the inability to instrument most furcations effectively may partially account for the poor results obtained with freeze-dried bone as well as other grafting materials used in the treatment of these defects. Interestingly, if the data on furcations are deleted from Tables 2 and 7, the percentage of osseous regeneration and pocket reduction of greater than 5 0 % increases to 6 7 % and 6 9 % , respectively. This study is not without limitations. Controls are lacking and the methods used for determining the amount of osseous regeneration are for the most part subjective. The histologic evaluation of the formation of a new attachment apparatus was not part of this study. A s yet there is no published human study to indicate the long-term effects, if any, of using freezedried bone in the treatment of periodontal defects. Nevertheless, the use of this grafting material has demonstrated favorable results under a variety of operating conditions and techniques. The documentation and results presented in this study substantiate the conclusion of the initial paper (Part I) that freezedried bone allografts have definite potential as grafting material in certain periodontal osseous defects. Another study is in progress to evaluate the combination of freeze-dried bone allograft and various forms of autogenous bone. Fresh and frozen, as well as intraand extra-oral, autogenous tissues are being utilized. It has been speculated that the combination of allograft and autograft may provide a grafting material superior to either material used a l o n e . Likewise, freezedried bone may prove to be an immediate, readily available augmentation for autogenous bone grafts. Data from this new study are being accumulated and will be reported at a later date. 14,15

SUMMARY

A N D

CONCLUSIONS

Freeze-dried crushed cortical bone allografts were implanted into widemouthed three-wall, two-wall, onewall, combination, and furcation defects. One hundred eighty-nine sites were reentered in 97 patients and of these 6 0 % had osseous regeneration of greater than 5 0 % . A total of 231 sites were evaluated for pocket elimination, of which 6 3 % demonstrated greater than 5 0 % pocket reduction. This study presented additional evidence indicating that freeze-dried bone allografts have definite potential as grafting material in certain periodontal osseous defects. Information from additional cases is being tabulated as it becomes available and will supplement the current data. Send reprint requests to: D r . George B . Pelleu, J r . , Chairman, Research Department, National Naval Dental Center, Bethesda, Maryland 20014. REFERENCES

1. Mellonig, J . T . , Bowers, G . M . , Bright, R . W . , and Lawrence, J . J . : Clinical evaluation of freeze-dried bone allografts in periodontal osseous defects. / Periodontol 4 7 : 125,1976. 2. Mace wen, W . : Observations concerning transplantation of bone illustrated by a case of inter-human osseous transplantation, whereby over two-thirds of the shaft of the humerus was restored. Proc R Soc Lond [Biol] 32: 232, 1881. 3. Robinson, E . : Osseous coagulum for bone induction. J Periodontol 40: 503, 1969. 4. D i e m , C . R . , Bowers, G . M . , and Moffitt, W . C : Bone blending: A technique for osseous implants. J Periodontol 4 3 : 2 9 5 , 1 9 7 2 . 5. Rivault, A . F . , Toto, P . D . , Levy, S., and Gargiulo, A . W . : Autogenous bone grafts: Osseous coagulum and osseous retrograde procedures in primates. / Periodontol 42: 787,1971. 6. Spence, K . F . , Bright, R . W . , Fitsgerald, S. P . , and

J . Periodontol. January, 1978

Sepe, Bowers, Lawrence, Friedlaender, Koch

14

S e l l , K . W . : Solitary unicameral bone cyst: Treatment with

11.

Friedlaender, G . E . , S t r o n g , D . M . , and S e l l , K . W . :

freeze-dried crushed cortical bone allograft — I I . A review of

Studies

one

hundred and forty-four

deep-frozen

58:

636,1976.

7.

A

cases. /

Bone Joint Surg

[Am]

Personal

Cummunication. 8.

ografting. J Bone Joint Surg [Br] 41: 160,

1959.

factors i n homogenous bone

transplantation. I V . T h e effect of various methods of prepa-

10. The

and

irradiation

4 5 : 1617,

[Am]

on

antigenicity. J Bone

Joint

Surg

1963.

854,

of

bone.

I.

Freeze-dried

i n rabbits. /

Bone

and

Joint

Surg

1976.

of

bone allografts. Cryoimmunology

62:

INSERM

preserved

Meet Orthop Res Soc 1: 130,

allografts.

Tran

22nd

Ann

1976.

209,

1976.

Friedlaender, G . E . , Strong, D . M . , and S e l l , K . W . :

Studies on the antigenicity of bone I I . D o n o r anti-HL-A

antibodies

i n human

recipients

graft specific

of

freeze-dried

bone (in preparation). 14.

Burwell,

R.

G.:

Studies

i n the

transplantation

bone. V I I I / Bone Joint Surg [Br] 48: 3 5 2 ,

F r i e d l a e n d e r , G . E . , Strong, D . M . , and S e l l , K . W . :

antigenicity

antigenicity

bone allografts

Strong, D . M . , F r i e d l a e n d e r , G . E . , A h m e d , A . , and

13.

B r o o k s , D . B . , H e i p l e , K . G . , H e r n d o n , C . H . , and

P o w e l l , A . E . : Immunological ration

12.

the

S e l l , K . W . : Immunogenicity of freeze-dried and deep-frozen

C h a l m e r s , J . : Transplantation immunity i n bone h o m -

9.

58:

[,4m]

study conducted by Thomas R . T e m p e l .

on

15.

of

1966.

N a d e , S.: Bone-graft surgery reappraised: T h e contri-

bution of the cell to the ultimate success. Brit J Surg

57:

752,1970.

Announcements STATE UNIVERSITY

OFNEW YORK

AT BUFFALO,

3:05-3:45 PM

SCHOOL OF DENTISTRY The State University of N e w Y o r k at B u f f a l o , School of Dentistry

3:45-4:25 PM

announces the James A . E n g l i s h Symposium on O r a l Perspectives on B o n e B i o l o g y , T h u r s d a y , A p r i l 2 0 , 1 9 7 8 at the Sheraton M o t o r Inn Buffalo E a s t , B u f f a l o , N . Y . It is the aim of the symposium to present

4:25-4:40 PM

the state of the art of bone biology as it applies to oral diseases and therapy. The Program follows: 8:30-8:40 AM

8:40-8:50 AM

Welcome

Introductory marks

D r . Carter F . Pannill, Jr., Vice President, Faculty of Health Sciences, State University of New York at Buffalo and Dr. William M . Feagans, Dean, School of Dentistry, State University of New York at Buffalo Re- D r . Solon A . Ellison, Professor, Oral Biology, School of Dentistry, State University of New York at Buffalo

Morning Session: Moderator—DR. ROBERT J . G E N C O 8:50-9:30 AM

9:30-10:10 AM

Physiologic and Pharmacologic Regulation of Bone Resorption Bone Loss in Periodontal Disease

D r . Lawrence Raisz, Professor of Medicine, University of Connecticut Health Center

10:10-10:25 AM Coffee Break 10:25-11:05 A M Bone Loss of D r . Douglas Atwood, Professor of Edentulous A l - Prosthetic Dentistry, Harvard School veolar Ridges of Dental Medicine 11:05-11:45 AM Bone Metabolism D r . Zeev Davidovitch, Associate ProAssociated with fessor of Orthodontics, School of Orthodontic Dentistry, University of PennsylTooth Movevania ment and Tooth Eruption 11:45-12:00 PM Morning Discussion 12:00-1:30 PM Lunch Afternoon Session: Moderator — D R . NORMAN H . M O H L 1:30-2:10 PM

2:10-2:50 PM

Growth and D e velopment of Bones of the Face Alveolar Bone Mass Using I Absorptiometry Coffee Break 125

2:50-3:05 PM

D r . Melvin L . Moss, Professor of Anatomy and Oral Biology, College of Physicians and Surgeons, Columbia University Professor Carl O . Henrikson, Professor of Oral Roentgenology, Dean, Karolinska Institut, Stockholm, Sweden

D r . Daniel A . Garcia, Veterans A d ministration Hospital, West Roxbury, Mass. D r . William F . Neuman, Professor of Radiation Biology and Biophysics, University of Rochester School of Medicine and Dentistry

Afternoon Discussion

For further information concerning reservations or about the scientific program contact: D r . Ernest Hausmann, Department of Oral Biology, State University of New York at Buffalo, 4510 Main Street, Buffalo, N . Y . 14226

POSTGRADUATE DENTAL PROGRAM,

ALBERT

EINSTEIN

COLLEGE OF MEDICINE The following courses are available during the academic year, 1977-1978: P E R I O D O N T I C S , D P D 6 6 ( A 2 0 Session Periodontics Participation Course), M A R V I N N . O K U N , D . D . S . ,

IRVING Y U D O F F ,

D.D.S.,

J O S E P H F . P u c c i o , D . D . S . , B E R T R A M S. B I L D N E R , D . D . S . , E D M U N D D . D ' O N O F R I O , D . M . D . , K A L M E N D . E I N B I N D E R , D . D . S . , and D A N I E L M . N A C H M A N O F F , D . D . S . , 2 0 Wednesdays January

D r . Ernest Hausmann, Professor of Oral Biology, School of Dentistry, State University of New York at Buffalo

Radionuclide Imaging of A l veolar Bone Summary and Analysis of Symposium

4,

commencing

1 9 7 8 through M a y 1 7 , 1 9 7 8 ; $ 1 9 5 0 .

(including

manuals). P E R I O D O N T I C S , D P D 6 3 (Immunologic Aspects of P e r i o d o n t a l D i s ease),

ROBERT

J . GENCO,

D.D.S.,

Ph.D.,

and D A N I E L

FINE,

D . M . D . , F r i d a y , January 2 0 , 1 9 7 8 ; $ 6 5 . PERIODONTICS,

D P D 6 4 (Reconstruction

Reparative P e r i o d o n t a l

Therapy — A Rationale and Objectives), H E N R Y M . G O L D M A N , D . M . D . , Friday A p r i l 2 8 , 1 9 7 8 ; $ 6 5 . PERIODONTICS, D P D 6 5 , EIGHTEENTH A N N I V E R S A R Y A L U M N I L E C T U R E , THE

D R . ZACHARY

DEMBO

MEMORIAL

LECTURE

(Effective and

Simplified Periodontal Procedures for G e n e r a l Practice), I R V I N G B . S T E R N , D . D . S . , Wednesday, M a y 1 0 , 1 9 7 8 ; $ 6 5 . POSTGRADUATE

E X T E N S I O N P R O G R A M (off campus courses):

Faculty

members of the Postgraduate D e n t a l P r o g r a m , who are specialists i n their fields, are available for short, intensive courses that can be given i n various cities, if a sufficient number of practitioners evince interest. If clinical facilities are available, these courses can be a combination of lectures and demonstrations. For

further information and application, write to: D r . Irving

Y u d k o f f D i r e c t o r , Postgraduate D e n t a l P r o g r a m , A l b e r t E i n s t e i n College of M e d i c i n e , 1 1 6 5 M o r r i s Park A v e n u e , B r o n x , N e w Y o r k 10461.

Clinical evaluation of freeze-dried bone allografts in periodontal osseous defects--part II.

Clinical Evaluation of Freeze- Fifty-three periodontists from military and civilian practices have been evaluating the effectiveness of freeze-dried...
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