Influenza surveillance during the post-pandemic influenza 2010/11 season in Greece, 04 October 2010 to 22 May 2011.

In this manuscript, we summarise the experience of Greece during the post-pandemic influenza season 2010/11 from 04 October 2010 to 22 May 2011. The spread of the disease and its impact were monitored using multiple surveillance systems, such as sentinel surveillance, virological surveillance and all-cause mortality surveillance. We also focus on the characteristics of laboratory-confirmed severe influenza cases who required admission to an intensive care unit (ICU) (n=368), and/or with a fatal outcome (n=180). The influenza-like illness rate reported from sentinel surveillance started rising in early January 2011 and peaked between 31 January and 6 February 2011. The total number of ICU admissions was higher in the post-pandemic influenza season than during the pandemic period causing a lot of pressure on ICUs. The overall population mortality rate due to influenza A(H1N1)2009 was higher than during the pandemic period (15.9 vs 13.2 fatal cases per million, p=0.087). Our data suggest that the severity of clinical illness in the first post-pandemic influenza season was comparable or even higher than during the pandemic.

Deproteinized bovine bone and gentamicin as an adjunct to GTR in the treatment of intrabony defects: a randomized controlled clinical study.

OBJECTIVES: To evaluate whether Bio-Oss used as an adjunct to guided tissue regeneration (GTR) improves the healing of 1- or 2-wall intrabony defects as compared with GTR alone, and to examine whether impregnation of Bio-Oss with gentamicin may have an added effect. MATERIAL AND METHODS: Sixty patients, with at least one interproximal intrabony defect with probing pocket depth (PPD) > or =7 mm and radiographic evidence of an intrabony component (IC) > or =4 mm, were treated at random with either a resorbable membrane (GTR), a resorbable membrane in combination with Bio-Oss impregnated with saline (DBB-), a resorbable membrane in combination with Bio-Oss impregnated with gentamicin (DBB+), or with flap surgery (RBF). RESULTS: All treatment modalities resulted in statistically significant clinical improvements after 1 year. Defects treated with GTR alone presented a probing attachment level (PAL) gain of 2.9 mm, a residual PPD (PPD12) of 4.9 mm, a radiographic bone level (RBL) gain of 3.1 mm, and a residual IC (IC12) of 2.7 mm. GTR combined with Bio-Oss did not improve the healing outcome (PAL gain: 2.5 mm; PPD12: 4.9 mm; RBL gain: 2.8 mm; IC12: 3.3 mm). Impregnation of the Bio-Oss with gentamicin 2% mg/ml resulted in clinical improvements (PAL gain: 3.8 mm; PPD12: 4.2 mm; RBL gain: 4.7 mm; IC12: 2.1 mm), superior to those of the other treatment modalities, but the difference was not statistically significant. Defects treated with only flap surgery showed the most inferior clinical response (PAL gain: 1.5 mm; PPD12: 5.1 mm; RBL gain: 1.2 mm; IC12: 4.2 mm) of all groups. CONCLUSION: The results failed to demonstrate an added effect of Bio-Oss implantation in combination with GTR on the healing of deep interproximal 1- or 2-wall, or combined 1- and 2-wall intrabony defects compared with GTR alone. Local application of gentamicin, on the other hand, improved the treatment outcome but not to an extent that it was statistically significant.

Gentamicin used as an adjunct to GTR.

OBJECTIVES: To evaluate in a discriminating "capsule" model whether local application of gentamicin may have an added effect on bone formation produced by Bio-Oss and guide tissue regeneration (GTR). MATERIAL AND METHODS: Thirty male 3-month-old Wistar rats were used. After elevation of muscle-periosteal flaps, a rigid hemispherical Teflon capsule, loosely packed with 0.025 g of Bio-Oss impregnated with 2 mg/ml gentamicin sulfate (Garamycin), was placed with its open part facing the lateral bone surface of the mandibular ramus (test) in one side of the jaw. A capsule filled only with Bio-Oss (control) was placed on the contralateral side of the jaw. After healing periods of 1, 2 and 4 months, groups of 10 animals were sacrificed and the specimens were processed for histological examination. The volumes of (1) the space created by the capsule, (2) newly formed bone, (3) Bio-Oss particles, (4) loose connective tissue, and (5) acellular space in the capsule were estimated by a point-counting technique in three to four histological sections of each specimen, taken by uniformly random sampling. RESULTS: The histological evaluation showed limited but increasing bone fill in the capsules from 1 to 4 months in both the test and control sides. After 4 months, the newly formed bone occupied 11.9% (CV: 0.39) of the space created by the capsules at the test sides versus 13.2% (CV: 0.41) at the control sides. There was no statistical significant difference between test and control specimens at any observation time (p>0.05). CONCLUSION: It is concluded that local application of gentamicin has no added effect on bone formation when combined with Bio-Oss and GTR.

Osteogenesis by guided tissue regeneration and demineralized bone matrix.

AIM: To evaluate in a discriminating capsule model whether bone formation by guided tissue regeneration (GTR) may be influenced by concomitant implantation of demineralized bone matrix (DBM). MATERIALS AND METHODS: Thirty 4-month-old male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical, Teflon capsule (5.0 mm in diameter), loosely packed with a standardized amount of DBM, was placed with its open part facing the lateral bone surface of the ramus. At the contralateral side, an empty capsule was placed, serving as control. After healing periods of 15, 30, and 120 days, groups of 10 animals were sacrificed and 40-70 microm thick undecalcified sections of the capsules were produced. In the sections, the cross-sectional areas of (1) the space created by the capsule, (2) newly formed bone, (3) DBM particles, (4) loose connective tissue as well as the (5) height of the capsules, and (6) that of the newly formed bone were measured. RESULTS: Increasing bone fill was observed in both test and control sites from 30 to 120 days. After 30 days of healing, the mean amount of bone was approx. 3% of the cross-sectional area of the capsules at the test sites while it was 8% in the control sites (p<0.05). However, no statistically significant differences were observed between the test (46%) and control (64%) sites after 120 days regarding any of the measured parameters (p>0.05). The newly formed bone in the DBM group at 120 days, on the other hand, appeared more dense than that in the control capsules. CONCLUSION: DBM used as an adjunct to GTR did not provide any added effect on bone formation but increased the density of the newly formed bone.

Denaturation of demineralized bone matrix significantly reduces bone formation by guided tissue regeneration.

AIM: To examine in a discriminating capsule model whether denaturation of demineralized bone matrix (DBM) by heating may influence bone formation. MATERIALS AND METHODS: DBM was produced from the long bones of rats. Half the portion of DBM was denatured by heating in distilled water for 20 min at temperatures between 70 degrees C and 90 degrees C. Prior to the study, the destruction of the osteoinductive properties of the DBM was confirmed in three rats following intramuscular implantation. Thirty, 4-month-old, male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical Teflon capsule (internal diameter = 5.0 mm) was placed, with its open part facing the lateral aspect of the ramus. On one side (test side), the capsule was loosely packed with denatured DBM, while on the contralateral side, serving as control, the capsule was loosely packed with the same amount of non-denatured DBM. After healing periods of 30, 60, and 120 days, groups of 10 animals were killed and 40-70 microm thick undecalcified sections of the capsules were produced. Three sections from each specimen, representing the mid-portion of the capsule, were subjected to histological analysis and computer-assisted planimetric measurements. RESULTS: Increasing amounts of newly formed bone were observed in both test and control capsules during the experimental period. At 4 months, the new bone formed in the control capsules occupied 46.7% of the cross-sectional area of the capsules, while it was only 19.1% in the test capsules (P<0.05). CONCLUSION: Denaturation of DBM by heating significantly reduces bone formation by guided tissue regeneration.

Evaluation of a cell-permeable barrier for guided tissue regeneration combined with demineralized bone matrix.

AIM: To evaluate whether bone formation by guided tissue regeneration (GTR) and demineralized bone matrix (DBM) can be enhanced by the use of a cell-permeable Teflon barrier allowing the penetration of undifferentiated mesenchymal cells from the surrounding soft tissues. MATERIAL AND METHODS: DBM was produced from the long bones of rats, and its bone-inductive properties were tested in three rats prior to the study by intramuscular implantation. Thirty, 4-month-old, male albino rats of the Wistar strain were used. Following surgical exposure of the mandibular ramus, a cell-permeable Teflon capsule, loosely packed with DBM, was placed with its opening facing the lateral surface of the ramus (test side). At the contralateral side, serving as control, a non-perforated (cell-occlusive) Teflon capsule, loosely packed with the same amount of DBM, was placed. After healing periods of 30, 60, and 120 days, groups of 10 animals were killed, and 40-70 microm thick undecalcified sections of the capsules were produced. RESULTS: Computer-assisted planimetric measurements on the histological sections disclosed similar amounts of newly formed bone in both test and control capsules. After 4 months, the new bone in the control capsules occupied 45.0% of the cross-sectional area of the capsule, while it was 50.5% in the test capsules. This difference was not statistically significant (P<0.05). CONCLUSION: Similar amounts of bone formed in cell-permeable and cell-occlusive capsules grafted with DBM, suggesting that invasion of undifferentiated mesenchymal cells from the surrounding soft tissues into the barrier-protected area is unnecessary for bone formation with GTR.

Family-based transmission disequilibrium test (TDT) and case-control association studies reveal surfactant protein A (SP-A) susceptibility alleles for respiratory distress syndrome (RDS) and possible race differences.

A key cause of respiratory distress syndrome (RDS) in the prematurely born infant is deficiency of pulmonary surfactant, a lipoprotein complex. Both low levels of surfactant protein A (SP-A) and SP-A alleles have been associated with RDS. Using the candidate gene approach, we performed family-based linkage studies to discern linkage of SP-A to RDS and identify SP-A susceptibility or protective alleles. Moreover, we performed case-control studies of whites and blacks to detect association between RDS and SP-A alleles. Transmission disequilibrium test (TDT) analysis revealed that the frequency of transmission (from parent to the offspring with RDS) of alleles 6A(2) and 1A(0) and of 1A(0)/6A(2) haplotype in RDS was increased, whereas transmission of alleles 1A(5) and 6A(4) and of haplotype 1A(5)/6A(4) was decreased. Extended TDT analysis further strengthened the observations made. The case-control studies showed that in whites or blacks with RDS the frequencies of specific genotypes, 1A(0) and 6A(2) or 1A(0), were increased, respectively, but the frequency of specific 6A(3) genotypes was increased in certain white subgroups and decreased in blacks. Regression analysis revealed gestational age (GA) and 6A(3) genotypes are significant factors in blacks with RDS. In whites with RDS, GA and antenatal steroids are important factors. The data together indicate linkage between SP-A and RDS; certain SP-A alleles/haplotypes are susceptibility (1A(0), 6A(2), 1A(0)/6A(2)) or protective (1A(5), 6A(4), 1A(5)/6A(4)) factors for RDS. Some differences between blacks and whites with regard to SP-A alleles may exist.

Impact of conventional tomography on prediction of the appropriate implant size.

AIM: The purpose of this study was to evaluate the efficacy of conventional cross-sectional tomography in predicting the appropriate implant size. METHODS: The implant length and width of 46 patients referred for single tooth implant treatment were determined presurgically by periapical + panoramic images (record 1) and after surgery by periapical + panoramic images + tomograms (record 2). These dimensions were compared with the dimensions of the implants actually installed (record 3), as well as the dimensions assessed to be the "appropriate" ones according to defined criteria for success (record 4). RESULTS: In 70% of the cases, the implant length or width, or both, was changed after the tomogram was available. The implant dimensions determined with tomography were maintained at surgery in 87% of the cases. In only 33% of the cases did the implant size predicted without tomography correspond with the size of the installed implants. The agreement between records 2 and 3 was significantly higher than between records 1 and 3 (P < .001). Similarly, the agreement between records 2 and 4 was significantly higher than between records 1 and 4 (P < .001). CONCLUSIONS: This study demonstrated that the use of tomograms increases the efficacy of periapical + panoramic images, with respect to the prediction of appropriate implant size, by a factor of 2.5. Therefore, conventional cross-sectional tomography is recommended for treatment planning before installation of single tooth implants.

Role of chitin beads in the formation of jaw bone by guided tissue regeneration. An experiment in the rat.

It has been reported that local application of bone grafts or synthetic bone substitutes (filler materials) may favour bone formation when used in combination with guided tissue regeneration (GTR). Therefore, the aim of the present investigation was to evaluate the effect of application of chitin beads (a bioabsorbable natural polymer) as a bone substitute in bone formation by GTR. The experiment was carried out in 25 rats. The mandibular ramus was exposed on one side after elevation of a muscle-periosteal flap, and a teflon capsule filled with chitin beads (2.0 mm in diameter) was placed with its opening facing the lateral aspect of the ramus. On the contralateral side of the jaw, serving as control, an empty teflon capsule was placed in the same manner. Groups of 5 animals were sacrificed at 7, 15, 30, 60 and 120 days following capsule placement. Histological analysis demonstrated that the amount of newly formed bone was similar in both experimental and control specimens, amounting to approximately 3% of the central/largest, cross-sectional area created by the capsule at 15 days, and to approximately 9% of this area at 30 days following capsule placement. At 60 and 120 days, however, the amount of newly formed bone observed in the control specimens was twice as large as that observed in the test specimens, amounting to approximately 31% of the cross-sectional area created by the capsule at 60 days, and to approximately 45% at 120 days. It is concluded that, although chitin beads (2.0 mm in diameter) are biocompatible, their presence retards bone formation in the model system used.

Deproteinized bovine bone used as an adjunct to guided bone augmentation: an experimental study in the rat.

BACKGROUND: Promising results have been reported following treatment of periodontal and peri-implant bone defects with deproteinized bovine bone grafts, but their influence on bone formation has not been clarified. PURPOSE: The goal of this study was to examine whether implantation of deproteinized bovine bone (Bio-Oss, Geistlich AG, Wolhusen, Switzerland) influences bone formation when used as an adjunct to guided bone augmentation (GBA). MATERIALS AND METHODS: A rigid, hemispherical, Teflon capsule was loosely packed with a standardized quantity of Bio-Oss and placed with its open part facing the lateral surface of the mandibular ramus (test) in 30 rats. At the contralateral side of the jaw, an empty capsule was placed (control). Groups of 10 animals were sacrificed after 1, 2, and 4 months. The volumes of the space created by the capsule and of the (1) newly formed bone, (2) remaining Bio-Oss particles, (3) soft connective tissue, and (4) acellular space in the capsule were estimated by a point-counting technique in three or four histologic sections, taken by uniformly random sampling. RESULTS: Bone formation at 1 month was limited in both tests and controls. After 2 months, the mean volume of the newly formed bone occupied 9.0% of the space created by the capsule in the test specimens compared with 23.8% in the control specimens (p < .01). After 4 months, the respective figures were 11.6% (tests) versus 38.7% (controls) (p < .01). CONCLUSION: It can be concluded that Bio-Oss, used as an adjunct to GBA, interferes with bone formation.

Regeneration of the sagittal suture by GTR and its impact on growth of the cranial vault.

The aim of this study was to investigate the effect of bone grafting, suture transplantation, and guided tissue regeneration (GTR) treatment on healing of craniectomy defects involving the sagittal cranial suture and on the growth of the cranial vault. Fifty 4-week-old rats were included in the study. A 5.0 mm wide trephine defect was created with its midline corresponding to the sagittal cranial suture between the coronal and occipital cranial vault sutures. The animals were randomly allocated to five groups of 10 animals. Group A: The cranial defect was left untreated. Group B: An occipital bone graft was placed into the cranial defect. Group C: A cranial bone graft including a portion of the frontal suture was placed in the cranial defect. Group D: The cerebral and galeal aspect of the defect were covered with an e-PTFE membrane. Group E: The animals were sham-operated, no defect was created. In all animals, two gutta-percha points were placed demarcating the lateral borders of the parietal bones. Histological analysis at 4 months following surgery showed that the untreated cranial defects healed with fibrous connective tissue. The bone-grafted defects healed partially with bone and connective tissue in the periphery of the bone graft. The healing of suture-grafted defects resembled that of the bone-grafted defects, since the transplanted suture became completely obliterated with bone. The membrane-treated defects healed with bone and a suture-like tissue resembling the sagittal suture of the sham-operated controls. Cephalometric measurements demonstrated that membrane-treated and sham-operated control animals exhibited significantly more (P < 0.05) coronal growth (approximately 1.2 mm) than that of the remaining three groups of animals (approximately 0.7 mm). These findings were supported by the craniometry measurements demonstrating that sham-operated control and membrane-treated specimens presented significantly more cranial width than that of the remaining groups of animals (P < 0.05). It can be concluded that complete osseous healing, creation of a new sagittal suture, and increased cranial growth can be achieved by the treatment of craniectomy defects with the GTR technique.

Long-term stability of jaw bone tuberosities formed by "guided tissue regeneration".

The aim of the present study was to evaluate whether bone tuberosities produced by GTR on the lateral surface of the mandibular ramus in rats are stable on a long-term basis. Thirty male 6-month-old albino rats of the Wistar strain were used in the study. Tissue flaps were elevated on the lateral aspect of the mandibular ramus. The periosteum was preserved (P+) on one side of the jaw while the bone was denuded (P-) on the other. A rigid, non-porous oval-shaped teflon capsule was placed on both sides with its opening facing the ramus. Six months following surgery, 10 rats were sacrificed and prepared for histology while the remaining 20 rats were subjected to a second operation during which the capsules were removed. Standardized radiographs, taken immediately before and after removal of the capsule and after 3, 6, 9 and 12 months, were subjected to planimetric measurements and subtraction radiography. Ten animals were sacrificed and prepared for histological analysis after 6 months following removal of the capsules and the remaining 10 animals after 12 months. Histology revealed that at 6 months after the placement of the capsules, 17 were completely filled with new bone. The remaining 3 capsules which were displaced exhibited only partial bone fill. The radiographic analysis revealed that after 6 months 98.6 +/- 7.6% (mean +/- SD) in average of the cross-sectional area created by the capsules was filled with new bone. Within 3 months after removal of the capsules a slight resorption of the new bone had occurred, thereby reducing the area of the bone tuberosities by 4 to 8%. No further resorption of the bone tuberosities took place from 3 to 12 months. These observations indicating that new bone produced by GTR is stable on a long-term basis, may question the general belief that non-functional bone will resorb over time.

Tirilazad inhibits surgically induced edema and interleukin-1 production. An experimental study in rats.

The aim of this study was to evaluate the anti-inflammatory effect of tirilazad mesylate on edema and interleukin-1 (IL-1) levels in serum following standardized surgical procedures. Four groups, each containing eight rats, were randomized for treatment as follows: A) no medication, B) low-dose tirilazad, C) high-dose tirilazad, and D) corticosteroids. The animals were examined by nuclear magnetic resonance imaging (NMRI) 24 and 72 hours after surgery and the NMRI data were used in the determination of soft tissue edema. In addition, serum was obtained for analysis of IL-1 levels. Four other groups of animals were subjected to the same treatment regimen as groups A-D), respectively, and 24 hours after surgery the animals were killed, whereafter serum was obtained for analysis of IL-1 levels. The present study demonstrated that low-dose tirilazad significantly reduces soft tissue edema compared with all other treatment regimens 24 hours postoperatively. At 72 hours postoperatively significant reduction of soft tissue edema was achieved at low-dose tirilazad when compared to high-dose tirilazad and steroids. In addition, a significant suppression of the expression of IL-1 was observed at 24 and 72 hours when comparing low-dose tirilazad and the control group.

Healing of osseous submucous cleft palates with guided bone regeneration.

The aim of this study was to develop an experimental model in rats of an osseous submucous cleft palate and to examine if bone regeneration can be achieved in such defects by the placement of membranes according to the principle of guided tissue regeneration (GTR). An osseous submucous cleft palate defect (5 mm x 2 mm) was created surgically in Wistar rats. Membranes of expanded polytetrafluoroethylene were placed so that they covered both the nasal and the palatal aspect of the defect before the palatal mucoperiosteal flap was repositioned and sutured. Histological analysis after seven weeks of healing showed that significantly more test animals (5/9) healed with newly formed bone and a suture-like tissue in the middle of the defects than controls treated without membranes (0/17). In specimens evaluated macroscopically after 12 weeks, the corresponding rates for the test group were 12/12 compared with 0/13. These observations indicate that an experimental model of an osseous submucous cleft palate can be established in rats, and that complete osseous healing and creation of a midpalatal suture-like tissue in the bony defect is favoured by the placement of membranes according to the principle of GTR.

Role of periosteum in the formation of jaw bone. An experiment in the rat.

The aim of the present investigation was to evaluate the bone-forming capacity of the outer (fibrous) and inner (cambium) layer of the mandibular periosteum in skeletally mature rats. The experiment was carried out in 25 rats. The mandibular ramus was exposed on one side (experimental side) after elevation of a muscle-periosteal flap. A teflon capsule was placed with its opening facing the periosteum at the subsurface of the raised muscle-periosteal flap after suturing. In the contralateral side serving as control, the periosteum of the lateral aspect of the mandibular ramus was left intact. This time the teflon capsule was placed with its opening facing the periosteum left behind at the ramus. The histological analysis demonstrated that in all experimental and control specimens, some bone was produced at 7 days after operation. In the experimental specimens, however, both the incidence and the amount of newly-formed bone in the teflon capsules gradually decreased from 7 to 120 days, while increasing in the control capsules placed over the periosteum. At 120 days, the mean amount of new bone produced in the experimental capsules was 3% (range 0-15%) of the total space created by the capsule, while it was 68% (range 41-85%) for the control capsules. The results demonstrated that substantial amounts of bone can be produced predictably by the placement of an occlusive teflon capsule facing mandibular covered with periosteum. Bone produced from the periosteum and without continuity with existing bone becomes resorbed with time.

Formation of jawbone tuberosities by guided tissue regeneration. An experimental study in the rat.

The aim of this study was to explore the possibility of creating bone tuberosities on the mandibular ramus in rats, using a rigid, occlusive, Teflon capsule. The experiment was carried out in 30 rats. The mandibular ramus was exposed bilaterally. On the test side, the periosteum was left covering the lateral surface of the ramus. On the contralateral side (control), the periosteum was elevated from the lateral surface together with the flap. A hemispherical, Teflon capsule was then placed to face the periosteum or the bone surface with its open part before closure of the wound. The healing periods comprised 7-120 days. Histological analysis demonstrated increasing bone fill in the test specimens from 7 to 60 days, and a limited further increase was observed from 60 to 120 days. In the control specimens, limited bone fill was seen within the first month after surgery, but substantial amounts of new bone were produced from 30-120 days. At 120 days, the mean amount of bone obtained in the test specimens was 56% (range 39%-71%) of the total space created by the capsules, and it was 52% (range 32%-85%) in the controls. The amount of newly formed bone was equivalent to a 5-6 times increase of the original width of the mandibular ramus. These findings indicate that a secluded space created by an occlusive barrier adjacent to existing bone or periosteum may be filled out with bone tissue. This may have a great clinical impact in cranial and maxillofacial surgery.

Guided bone regeneration in mandibular defects in rats using a bioresorbable polymer.

The aim of this study was to explore the possibility of obtaining bone regeneration in jaw bone defects in rats after coverage of the defects with an occlusive bioresorbable membrane. The experiment was carried out in 31 rats. The mandibular ramus was exposed in both sides and a 2 x 3 mm defect was produced at its lower border. A gutta-percha point was placed to indicate the original level of the border. The defect on one side was covered with a polyhydroxybutyrate resorbable membrane, whereas the contralateral side received no membrane before closure of the wound. Macerated jaw specimens representing 3 and 6 months of healing demonstrated minimal bone fill in the control defects, whereas all test defects healed to or close to the gutta-percha point, indicating the original inferior border of the jaw. The histological analysis demonstrated increasing bone fill in the test specimens from 15-180 days, whereas only 35-40% of the defect area in the control sides was filled with bone after 3-6 months. Ingrowth of muscular, glandular and connective tissue was consistently occurring in the control defects during healing. It can be concluded that selective repopulation of bone defects with bone-forming cells can be ensured by excluding surrounding soft tissues from the wound area with an occlusive bioresorbable membrane.

Augmentation of the rat mandible using guided tissue regeneration.

The aim of the present study was to investigate whether it is possible to increase the height of the rat mandible at its inferior border using a bioresorbable membrane adapted to create a secluded space for ingrowth of bone tissue. The experiment was carried out in 18 rats. The mandibular ramus was exposed at both sides. A standardized titanium microimplant was then inserted in the naturally existing curvature at the inferior border of the mandible, serving as a fixed reference and space maker. The mandibular border on one side was covered with a polyhydroxybutyrate bioresorbable membrane, and the contralateral side, serving as control, received no membrane before closure of the wound. The membranes were placed in such a way that a space was created in the curvature between the membrane and the inferior border of the mandible. Macerated jaw specimens representing 6 months of healing demonstrated substantial amounts of bone formation in the curvature of the inferior border of the mandible, resulting in a flattening of the inferior border. Negligible amounts of bone formation had occurred in the control sides. Histological analysis demonstrated that, in 4 of 6 experimental specimens, the space created by the membrane was completely filled with new bone after 6 months of healing, but in some specimens soft tissue seemed to have migrated into the space through ruptures of the membrane or because of poor membrane adaptation at its lateral borders, thereby inhibiting bone formation. Only negligible bone formation had occurred at the control sides.(ABSTRACT TRUNCATED AT 250 WORDS)