Immunolocalization of bone matrix macromolecules in human tissues regenerated from periodontal defects treated with expanded polytetrafluoroethylene membranes

Guided tissue regeneration (GTR) is a concept that evolved from the development of membrane barrier techniques which allow the repopulation of periodontal wounds by desirable cells, resulting in a so-called new attachment apparatus. To understand the biological mechanisms involved in membrane barrier-led periodontal healing, the histological localization of macromolecules phenotypical of bone and cementum formation was investigated in regenerating human periodontal tissues harvested after healing by placing barriers on teeth untreatable except by extraction. Using immunolocalization techniques, frozen sections of soft tissues and hard tissues under GTR barriers were stained with antibodies to osteonectin (LB-BON-II) and bone sialoprotein (BSP) (LF-6); alkaline phosphatase (AP) was detected histochemically. Frozen sections of regenerating periodontal tissue demonstrated the presence of spindle-shaped, fibroblast-like cells entrapped in a dense fibrillar extracellular matrix. Rounded cells aggregated to form nodules heavily stained by the Alcian blue method, indicating the presence of proteoglycans and strongly resembling those noted in hard-tissue sections. At the electron-microscopic level, the cytoplasm of the elongated cells had numerous cisternae of endoplasmic reticulum and Golgi saccules, indicating metabolic activity. Striated collagen fibres were scattered throughout the field of the sections. AP-stained soft-tissue sections demonstrated the presence cell-bound and extracellular AP. Osteonectin antibody staining confirmed the presence of this macromolecule in the extracellular matrix, particularly in the area of the cellular nodules. The dense network of connective tissue fibres was also stained.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of periodontal ligament fibroblasts by cementum and alveolar bone extracts

This study investigated the effect of acetic acid extracted proteins of bone and cementum on periodontal ligament fibroblasts. Alveolar bone and cementum obtained from clinically healthy subjects were subjected to 0.5 M acetic acid extraction, dialysis and lyophilization. Effects of both extracts on cell attachment and stimulation of DNA synthesis were studied in fibroblast-like cells cultured from human periodontal ligament tissue. A wide spectrum of proteins, such as 11-14, 17, 19, 22, 24, 27, 30, 34-44, 47 and 55 kDa, were detected in 10% SDS-polyacrylamide gel electrophoresis of both extracts. A few tissue-specific bands (19, 22, 47 kDa in cementum extract; 34-44, 55 kDa in bone extract) were noted. These extracts were found to promote cell attachment and stimulate DNA synthesis of periodontal fibroblasts. Cementum extract appeared to have a higher activity in stimulating DNA synthesis than bone extract, while promotion of cell attachment was similar with both extracts. Addition of serum evoked a synergistic effect on the promotion of DNA synthesis of both extracts. These preliminary observations suggest that acetic acid extracts from bone and cementum contain distinct components capable of modulating cellular activities of periodontal fibroblasts.

Transition and determinants of orthodontic root resorption-repair sequence

When severe root resorption is observed during orthodontic treatment the clinician needs to know how the active process can be stopped. It is generally assumed that if active force is discontinued, the root resorption will end. The determinants of the resorption/repair sequence are, however, not well understood. The aim of the present study was to register and analyse determinants that may influence the extent of resorbed root surface, as well as the transition of a process of active root resorption into a process of tissue deposition/repair in the resorption lacunae. Using an experimental model that would simulate the first force-activation cycle, the upper first molars of rats were moved mesially by a fixed orthodontic appliance for periods between 2 and 21 days. The results revealed that (1) the extent of root resorption after 21 days corresponded with the maximal extent of the hyalinized zone; (2) a process of repair started from the periphery in the resorbed lacunae where the periodontal ligament (PDL) had been re-established, while ongoing active resorption was observed beneath the existing hyalinized tissue; and (3) root resorption continued in the area where hyalinized tissue persisted even after active force had terminated. It is hypothesized that determinants of continued resorption/repair generally seem to be associated with the persistence and removal of the necrotic tissue.

The repair of orthodontic root resorption: an ultrastructural study

It has previously been shown by light (LM) and scanning electron microscopy (SEM), that after force is terminated, repair of the orthodontic root resorption lacunae occur by deposition of new cementum. The ultrastructural details of the process are not well established. Since it has been hypothesized that a new barrier to protect the root surface is formed during the reparative phase, new information on this aspect of orthodontic root resorption may be valuable. The aim of the present investigation was, by using transmission electron microscopy (TEM), to study in more detail the repair of orthodontic root resorption lacunae and the re-establishment of the adjacent periodontal membrane (PM). Three experimental tooth movement groups of rats (age 40-45 days) were used. The maxillary first molar was moved mesially by a closed coil spring for 10, 14, and 21 days. The results indicate that transition of active root resorption into a process of repair which occurs even in the presence of a light force, is associated with invasion of fibroblast-like cells from the circumference into the active root resorption site. After 10 days, formation of new tooth supporting structures was seen in the periphery of the resorption lacunae, while active resorption by multinucleated odontoclast-like cells (OD) took place in the central parts. In the later phases, after termination of force, the repair process is similar to the early cementogenesis occurring during tooth development. New mineralized cementum was observed on the resorbed root surface by 21 days. After deposition of the new cementum, the structures of a new periodontal ligament (PDL) were comparable with the control specimens.

Human histologic tissue response after long-term orthodontic tooth movement

The maxilla of a deceased 19-year-old young woman who had been treated with an edgewise appliance was removed during autopsy. The specimen was prepared histologically in the horizontal plane. The type of tooth movement was reconstructed by comparing the treatment documents at outset (photograph of dental cast, radiograph) with the photograph and radiographs of the specimen. This permitted the histological findings to be correlated to the type of tooth movement.

RESULTS

the localization and extent of tissue changes at the roots depend on the type of tooth movement and the structure of the bone. In case of an atrophied alveolar bone in front of the tooth movement direction, a partial increase of osseous tissue may be induced by bone apposition in the subperiosteal layer. After tooth movement in the maxillary sinus region, however, bone resorption was found in the subperiosteal layer in front of the roots. The histologic findings are more pronounced than the radiographs would suggest. Histologically verified bony dehiscences or fenestrations in the facial or oral cortical plate could not be diagnosed by macroscopic inspection of the specimen.

Collagen formation at the tooth-cell interface: comparative ultrastructural study on the effect of partial demineralization of cementum with dentin

In order to compare the effect of partial demineralization with root planing and partial demineralization of cementum with that of dentin on healing, the ultrastructural morphology of the interface between the layer of human periodontal ligament-derived, fibroblast-like cells (HPF) and the treated root surface was studied in an in vitro culture system. Sixty (60) pairs made from transversally-cut root slices, 500 microns thick, were obtained from extracted human periodontally diseased teeth. Thirty (30) pairs of the root slices were preliminarily root planed (RP). The remaining half were root planed and then partially demineralized in a solution of citric acid (RP+CA). The opposite surface of paired slices was made uniform by using either cementum or dentin. Consequently, all root slices were classified into four experimental groups: RP-cementum and RP-cementum pairs (group 1), RP-dentin and RP-dentin pairs (group 2), RP+CA-cementum and RP+CA-cementum pairs (group 3), and RP+CA-dentin and RP+CA-dentin pairs (group 4). Each pair of root slices was placed on the floor of a 35-mm culture dish. HPF were seeded at a concentration of 4 x 10(5) cells/dish. Co-cultures of HPF and the root slices were examined using phase contrast and electron microscope after 4, 6, and 10 weeks. Electron-dense material covered non-demineralized root surfaces and the lining cells in accumulating cell layers were oriented parallel to the root surface and attached to the material in groups 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Histopathological observations of periapical repair in teeth with radiolucent areas submitted to two different methods of root canal treatment

Dogs' teeth with induced chronic periapical periodontitis were treated endodontically by two different methods, and the results were compared. A total of 40 root canals from the upper and lower premolars of two dogs were prepared chemomechanically. In method 1, a high-concentration (5.25%) hypochlorite solution was used during the instrumentation of the root canal, and an antibacterial dressing was applied between sessions, followed by filling of the root canal. In method 2, a low-concentration (0.5%) sodium hypochlorite solution was used as an adjunct to mechanical debridement, and the root canal was filled during the same session. The histopathological results showed that method 1 led to better periapical repair than method 2.

Use of the carbon dioxide laser in retarding epithelial migration: a pilot histological human study utilizing case reports

Predictable regeneration of tooth-supporting tissues lost to periodontal disease is the aim of periodontal therapy. Often the result of conventional treatment is healing with a long junctional epithelium along the root surface and little regeneration of the complete attachment apparatus. The purpose of this pilot study was to evaluate whether de-epithelialization with a CO2 laser at the time of flap surgery and at 10-day intervals over the first 30 days of healing has the potential to enhance the formation of a connective tissue attachment. Six mandibular incisors in two patients were selected for the study. Each patient received oral hygiene instruction and initial therapy prior to surgery. The teeth were splinted together, open flap debridement was performed on all teeth, a notch was placed on the roots at the height of the crest of the alveolar bone, and the flaps were sutured in place. The test side received controlled de-epithelialization of the outer (oral) gingiva with the carbon dioxide laser, and the inner gingival flap. The de-epithelialization was repeated on the test side at 10, 20, and 30 days postsurgically. Controls received open debridement only. Block sections were taken at 90 days and processed for histologic analysis. The results showed that for both patients, junctional epithelium (JE) was formed on both test and control teeth. In all control teeth, the JE extended the entire length of the root to the base of the reference notch.(ABSTRACT TRUNCATED AT 250 WORDS)

Cementum-impregnated gelatine membrane: its effect on periodontal tissue regeneration

This study was designed to evaluate the ability of cementum-impregnated gelatine membranes (CGM) to stimulate regeneration of periodontal ligament following surgery. Three monkeys with no periodontal disease were used. Following flap elevation, recession type defects were created on the buccal side of maxillary lateral incisors and second premolars, and roots were subsequently planed. Experimental sites received CGM at approximately 2-3 mm below the cementoenamel junction while control sites received gelatine membrane (GM) free of cementum. Wounds were allowed to heal for 3 weeks, during which time daily plaque control measures were maintained. Tissues prepared from sacrificed animals revealed that experimental specimens exhibited formation of new cementum, new bone, and periodontal ligament. Control specimens exhibited connective tissue adhesion without either new cementum or significant new bone formation. Histometric analysis showed that the average vertical growth of cementum (NC) and bone (NB) at experimental sites were 3.48 +/- 0.29 and 0.64 +/- 0.43 mm, respectively. At the control sites the corresponding results were NC = 0.09 +/- 0.03 and NB = 0.06 +/- 0.28. It was concluded that placement of CGM resulted in significantly greater postsurgical cementum and bone formation than that of GM alone.

Periodontal repair in dogs: recombinant human bone morphogenetic protein-2 significantly enhances periodontal regeneration

This study evaluated bone and cementum regeneration following periodontal reconstructive surgery using recombinant human bone morphogenetic protein-2 (rhBMP-2) in six beagle dogs. Surgically created mandibular supraalveolar premolar tooth defects in contralateral jaw quadrants were randomly assigned to receive rhBMP-2 or control vehicle. Clinical defect height was prepared to 5 mm. rhBMP-2 was applied with synthetic bioerodable particles and autologous blood using 20 micrograms rhBMP-2 per 100 microliters implant volume. Flaps were advanced to submerge the teeth and sutured. The dogs were sacrificed 8 weeks postsurgery. Histometric recordings included defect height, height and area of alveolar bone regeneration, height of cementum regeneration, root resorption, and ankylosis. Group means, standard deviations, and P values are shown (Student t test; n = 6). Histometric defect height for rhBMP-2 and control defects was 3.7 +/- 0.3 and 3.9 +/- 0.4 mm, respectively (P = 0.446). Height of alveolar bone regeneration amounted to 3.5 +/- 0.6 and 0.8 +/- 0.6 mm for rhBMP-2 and control defects, respectively (P = 0.000). Corresponding values for bone area were 8.4 +/- 4.5 and 0.4 +/- 0.5 mm2, respectively (P = 0.006). Cementum regeneration was observed in all experimental defects (17/17) and in 15 out of 17 controls, averaging 1.6 +/- 0.6 and 0.4 +/- 0.3 mm for rhBMP-2 and control defects, respectively (P = 0.005). Small amounts of root resorption were seen in rhBMP-2 defects, whereas controls exhibited substantial resorption (0.2 +/- 0.1 and 1.1 +/- 0.3 mm, respectively; P = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Overview of effects of electrical stimulation on osteogenesis and alveolar bone

One endpoint of periodontal therapy is to regenerate structure lost to periodontal disease. Periodontal regeneration requires both formation of a new connective tissue attachment to the tooth and formation of alveolar bone. Several procedural advances may support regeneration of the attachment, however, regeneration of alveolar bone does not occur consistently. Therefore, factors which stimulate bone repair are areas for research in periodontal reconstructive therapy. Effects of cytokines or growth factors on bone repair are examples of such areas. Another one is electrical stimulation which naturally occurs in bone, and as such bone may be particularly susceptible to electrical therapy. This overview describes the potential of electrical stimulation for bone regeneration and applications in alveolar and periodontal research.

Models for the study of cementogenesis

Cementum is a mineralized tissue that acts to connect the periodontal ligament to the tooth root surface. Its composition is very much like bone, being comprised mainly of type I collagen, inorganic mineral and noncollagenous proteins, however the origin of the cells and factors necessary for cementum formation have yet to be elucidated. Our laboratory has focused on the role that adhesion molecules, and their cell surface receptors, play in the formation of cementum and tooth root. In order to study this, we used a mouse molar as a model system. This system enabled us to study the formation of four distinct mineralized tissues; bone, cementum, dentin and enamel at various stages of their development. For these studies, we initiated experiments to examine potential cementoblast progenitor cells, in vitro. As a first step, we show that dental papilla and dental follicle cells, n vitro, obtained from molar tissues at day 21 of development, induce mineralized nodules, in vitro. In addition, we obtained tissues from mice where defects in root development may exist and determined bone sialoprotein (BSP) protein expression, a mineralized tissue specific adhesion molecule, in such tissues. As discussed here, we found that osteopetrotic (op/op) mice have delayed and/or defective root development and BSP does not localize in the dental tissues, at day 33 of development. In addition, dentin formation was defective and odontoblasts appeared immature, based on morphological examination. In contrast, the day 33 control molars demonstrated positive staining for BSP localized to root cementum, with normal formation of dentin.

Role of two mineral-associated adhesion molecules, osteopontin and bone sialoprotein, during cementogenesis

Adhesion molecules and their cell membrane receptors are known to play important regulatory roles in cell differentiation. Consequently, the following experiments were conducted to determine the role of two adhesion molecules, bone sialoprotein (BSP) and osteopontin (OPN) in tooth root formation. Developing murine molar tooth germs at sequential stages of development (developmental days 21-42) were analyzed using immunohistochemical and in situ hybridization techniques. While BSP was localized to alveolar bone and odontoblasts early in development, BSP was distinctly localized to the cemental root surface at latter periods coincident with the initiation of root formation and cementogenesis. Conversely, OPN was distributed in a nonspecific fashion throughout the PDL and the eruption pathway of the forming tooth. In situ hybridization confirmed that cells lining the root surface express BSP. The fact that BSP is specifically localized to the cemental surface suggests that this protein is involved in cementoblast differentiation and/or early mineralization of the cementum matrix. Localization of OPN to non-mineralized tissues further suggests that OPN functions as an inhibitor of mineralization during periodontal ligament formation. These findings collectively suggest that BSP and OPN are intimately involved in the sequence of cellular and molecular events accompanying cementogenesis.

Cementum specific components which influence periodontal connective tissue cells

We have isolated two polypeptides from cementum one of which promotes the growth and the other the attachment of periodontal cells. One polypeptide, the cementum derived growth factor (CGF), was extracted from healthy human and bovine teeth by 1 M CH3COOH and purified by heparin-affinity chromatography and HPLC. The CGF is a 23 kDa polypeptide which is mitogenic to fibroblasts and smooth muscle cells. It is active alone, but its activity is highly potentiated by plasma-derived serum or EGF. It induces classical mitogenic signaling events, which include Ca++ mobilization, inositol phosphate hydrolysis, activation of phosphokinase C (PKC) and transcription of cellular protooncogenes c-fos and jun-B. The magnitude and pattern of activation of signaling events and their susceptibility to PKC inhibitors and pertussis toxin indicated that the CGF may be a distinct molecular species. The CAP is a 55 kDa polypeptide which promotes the attachment and spreading of fibroblasts, smooth muscle cells, bone cells and endothelial cells, but not epithelial cells. Antibodies to CAP immunostain cementum, but not other tissues. Root surfaces bind CAP. The CGF and CAP do not appear to be present in adjacent periodontal structures. Our data show that the CAP and CGF selectively interact with periodontal cell populations and affect their biological activities, and thus may influence the formation and regeneration of periodontal connective tissues.

Periodontal repair in dogs: supraalveolar defect models for evaluation of safety and efficacy of periodontal reconstructive therapy

It is increasingly evident that controlled preclinical models with reproducible defect characteristics and biologic reaction are critical for evaluation of safety and efficacy of periodontal reconstructive protocols. Our investigations have characterized a supraalveolar periodontal defect in the mandibular premolar region in the beagle dog. This surgically-created critical size defect heals with almost complete connective tissue attachment following immediate reconstructive surgery. When the defect is exposed to periodontitis-simulating conditions prior to surgery the new connective tissue attachment is reduced. Bone and cementum regeneration is limited for both defect variations. Critical aspects relative to animal selection and management, surgical protocol, histologic and statistical analysis are discussed. This preclinical model has proven effective for evaluation of safety and efficacy of devices and biologics used adjunctive to periodontal reconstructive therapy.

Disturbances of cementum formation induced by single injection of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) in rats: light and scanning electron microscopic studies

With the rat molar as a model, evidence is presented that dentin mineralization influences formation of acellular cementum. Formation of acellular cementum did not occur on the surface of experimentally induced unmineralized dentin. Instead, an atypical hyperplastic cementum was formed. The disturbance in acellular cementum formation was permanent.

Response of regenerative tissues to plaque: a histological study in monkeys

This study was designed to determine the histologic response of regenerated tissue to plaque, using an adult Taiwan monkey model with chronically-inflamed, surgically-created, periodontal defects. Standardized 2-walled periodontal defects were surgically created at the mesial of the mandibular lateral incisor on one side. Sutures, 3-0 braided silk, were placed for 8 weeks and tissues positioned so that denuded root surfaces were exposed to plaque, with the subsequent development of the chronically-inflamed periodontal tissues. At 8 weeks the defects were subjected to guided tissue regeneration procedures using expanded polytetrafluoroethylene membrane and allowed to heal for 6 months. Contralateral clinically healthy sites, without surgical procedures, were used as controls. In both experimental (membrane) and control sites, silk ligatures were placed to allow plaque accumulation for 2 or 10 weeks. Four monkeys were sacrificed at each time point and specimens processed for histologic and histometric study. The results indicated that plaque-induced inflammation was less at sites treated by guided tissue regenerative procedures when compared to originally clinically-healthy sites exposed to plaque for the same duration. However, histologically the newly formed osseous tissue was compromised under these conditions.

A comparison of two different rapid palatal expansion techniques from the point of root resorption

The aim of this investigation is to compare Haas and Cast Cap Splint devices from the point of root resorption. The material comprised thirty-eight upper and twelve lower premolar teeth derived from nineteen patients who required RME and subsequent removal of the first premolars as part of their full banded orthodontic treatment. Root resorption and repair areas were observed on the buccal surfaces of premolars. Repair tissue was cellular cementum in both groups. There was no significant difference between these two techniques from the point of root resorption amount.

Dependence of mechanical properties on fibre angle in narwhal tusk, a highly oriented biological composite

The successful modelling of the mechanical properties of mineralized tissues depends critically on the knowledge of the off-axis behaviour of individual unidirectional lamellae. Information on this is lacking. In this work we attempt to rectify the situation. Young's modulus, measured in bending and tension, and the tensile strength and ultimate strain to failure of the dentine of the narwhal Monodon monoceros, were determined on specimens that had almost unidirectional fibres, whose direction differed considerably from specimen to specimen. Modulus and strength decreased steadily with the degree of off-angle loading, falling to about 45% of maximum for modulus, and 35% of maximum for strength. Ultimate strain showed a less uniform behaviour, and remained remarkably high at large angles. Differences in mechanical behaviour were not related to the very small differences in mineral content measured between specimens. These findings have strong implications for modelling the anisotropic behaviour of bone, because dentine is very much like bone in most important respects. Predictions using classical composite theory are reasonably satisfactory, as long as the mineral crystals are assumed to be platelets, not rods.

Periodontal guided tissue regeneration with a new resorbable polylactic acid membrane

The aim of the present study was to evaluate the use of 3 types of biodegradable, high molecular weight DL-lactic acid (PLA) membranes containing respectively 0%, 10%, and 30% low molecular weight oligomers for obtaining guided tissue regeneration following treatment of experimental buccal periodontal defects created surgically in 6 young adult beagle dogs. On the buccal aspects of test and control teeth, a mucoperiostal flap was raised and the buccal alveolar bone removed. The exposed root surfaces were scaled and a notch was prepared in the root surface at the level of the reduced crest. PLA membranes containing respectively 0%, 10% and 30% oligomers, drawn at random, were placed over the experimental defects, while no membrane was placed over the control roots. The animals were sacrificed 2, 4, and 6 months after surgery. For comparison between control sites (without membrane) and experimental sites (with 3 types of membrane), serial bucco-lingual sections were made of the experimental and control sites and studied histologically and histometrically. It appeared that a satisfactory regeneration of the periodontal tissues could be obtained with all 3 types of experimental PLA membranes and statistically significant differences could be observed for epithelial attachment, alveolar bone regrowth, connective tissue attachment, and new cementum formation in the experimental group when compared with the controls. All 3 types of membranes were well tolerated. The resorption of the membranes started in the coronal portions and extended progressively in an apical direction and the resorption time seemed to be related to the content of oligomers. PLA membranes could be used as interesting alternatives for GTR in advanced human periodontal lesions.

Periodontal repair in dogs: space provision by reinforced ePTFE membranes enhances bone and cementum regeneration in large supraalveolar defects

Regeneration of alveolar bone and cementum following reconstructive therapy with reinforced space providing expanded polytetrafluorethylene (ePTFE) membranes was evaluated in supraalveolar mandibular premolar periodontal defects in five beagle dogs. The surgically-created defects in contralateral jaw quadrants were randomly assigned to receive the dome-shaped membrane or serve as surgical control. Flaps were positioned to completely submerge the teeth and sutured. The dogs were sacrificed 8 weeks after surgery and tissue blocks including teeth and surrounding structures processed for histology. Membrane treated defects in two animals became exposed and infected leaving intact quadrants in three dogs for histometric analysis. Parameters evaluated included defect height, height and area of regenerated alveolar bone, height of regenerated cementum, root resorption, and ankylosis. Mean defect height approximated 4.1 mm. Mean height (+/- s.d.) of regenerated alveolar bone amounted to 2.9 +/- 0.6 and 0.6 +/- 0.2 mm for membrane and control defects, respectively (P = 0.006). Corresponding values for bone area were 1.4 +/- 0.7 and 0.4 +/- 0.4 mm2 (P = 0.02). Cementum regeneration was observed in all teeth averaging (+/- s.d.) 1.6 +/- 0.3 mm for membrane treated and 0.1 +/- 0.1 mm for control defects (P = 0.01). Small amounts of root resorption were seen in all teeth with no significant difference between treatments. Ankylosis was noticed in three membrane treated and two control teeth. The present study provides a biologic rationale for space provision for enhanced bone and cementum regeneration in periodontal defects subject to reconstructive therapy.

Local delivery of prostaglandin E1 induces periodontal regeneration in adult dogs

Formation of cementum, alveolar bone and periodontal ligament was produced in 18 sites on buccal surfaces of mandibular premolars and molars of 11 adult dogs near to sites of local delivery of prostaglandin E1 (PGE) for three weeks. Mineralizing bone and cementum were labelled with fluorescent dyes and polarizing microscopy showed periodontal ligament fibers between these new mineralized tissues. These observations extend recent demonstrations that local application of PGE causes formation of new bone on the mandible and suggest the potential for predictable, site-directed periodontal regeneration.

Dynamic variations in the expression of type I collagen and its molecular chaperone Hsp47 in cells of the mouse dental follicle during tooth eruption

Tooth eruption is a precisely timed and sequenced event that brings the tooth from within bone into a functional position in the mouth. Every part of the developing tooth has been theoretically implicated as a primary factor in this process, but it now appears that eruption is multifactorial, with the dental follicle and type I collagen playing an important part. Immunological probes were used here to investigate in vivo and in vitro the temporal and spatial expression of type I collagen and its molecular chaperone Hsp47 in the dental follicle during eruption. Mandibles were dissected from 2-, 5-, 9- and 11-day-old neonatal mice and fixed in 95% ethanol overnight. Sections of 7 microns were obtained and reacted with antibodies directed against type I collagen. Dental follicles were isolated from 2-, 5-, 9- and 11-day-old neonates and cells were grown in culture for 8 days. Slides were then reacted with antibodies directed against type I collagen and Hsp47. The production of type I collagen and Hsp47 in the follicle varied with the stage of dental development and eruption. There was a progressive decrease of type I collagen in the coronal part of the follicle, leading to an arrest of its production in these areas. These findings support the notion that cells of the coronal portion of the dental follicle stop producing type I collagen as a prerequisite to the initiation of tooth eruption and that this phenotype persists in vitro.

Chemotactic response of fibroblasts to root surface components in wound healing following flap surgery

The purpose of this study was two-fold; first to investigate the chemotactic response of periodontal cells to root surface components during wound healing following flap surgery; second, to investigate the chemoattractive effect of the root components on cell migration. Cells were obtained by culturing cells from monkey periodontal tissues and rat calvarial cells. Root surface components were obtained from teeth extracted at 4, 7, 10 and 14 days after flap surgery. The chemotactic response of the isolated cells to root surface components was quantitated by an in vitro assay using a 48 well microchemotaxis chamber. The effect of root components or other growth factors on the cell migration was evaluated using a three-dimensional gel system. Cemental components produced a strong chemotactic response for gingival fibroblasts, alveolar bone cells and rat calvarial cells. Kinetics of the chemotactic potential of cementum was characterized by an initial increase (up to 7 days after surgery), a transient decline (at 10 days after surgery) and a second increase (at 14 days after surgery). Cemental components obtained 7 days after surgery most profoundly facilitated invasion of gingival fibroblasts with comparable effects induced by PDGF and TGF-beta. These results suggest that cemental components influence the chemotactic migration of gingival fibroblasts at the initial stage of wound healing, and therefore, cementum plays an important role in periodontal regeneration.

Effect of root conditioning on periodontal wound healing with and without guided tissue regeneration: a pilot study. 1. Histologic evaluation

Closed fenestration wounds in four mongrel dogs were used to study the source of fibroblast proliferation and extracellular matrix production during healing; the arrangement and attachment of newly formed collagenous fibers; and the cementogenesis and osteogenesis at healing sites. Fenestration wounds were made through the alveolar bone, periodontal ligament, cementum, and dentin, and citric acid, tetracycline, or sterile water was applied to the dentinal walls for 3 minutes. Nonresorbable membranes were randomly placed over half of the defects. Animals were killed at 1, 3, 7, or 21 days and routine histologic examinations with hematoxylin and eosin staining followed. Results of this pilot study suggest that the periodontal ligament and/or alveolar bone are the main source of fibroblast proliferation and migration as well as extracellular matrix formation at the initial stages of healing, and that at 21 days, citric acid stimulated more cementogenesis than tetracycline or sterile water. Also, while the tetracycline influenced the maximal deposition of alveolar bone, no differences in healing were found between the citric acid, tetracycline, and sterile water with and without the use of membrane barriers.