PGE2 Activates Cementoclastogenesis by Cementoblasts via EP4

Destruction of cementum and alveolar bone is the main causative event for the exfoliation of teeth as a consequence of periodontitis. Prostaglandin E2 (PGE2) and PGE receptor subtypes (EPs) play an important role in modulating osteoblast-mediated osteoclastogenesis; however, no information is available on the role of PGE2 and EPs in regulating cementoblast-mediated cementoclastogenesis. We hypothesized that the PGE2-EPs pathway also regulates cementoblasts’ ability to activate cementoclasts. For these studies, OCCM-30 cells (a mouse cementoblast cell line) were exposed to PGE2 and specific EP agonists. PGE2 (100 ng/mL) and EP4 agonist (1 μM) up-regulated RANKL and IL-6 mRNA levels, while they down-regulated OPG mRNA expression. The EP4 antagonist (1 μM) eliminated these effects of PGE2. PGE2 treatment of co-cultures of OCCM-30 cells with bone marrow cells induced TRAP-positive cells via the EP4 pathway. These findings suggest that PGE2 promotes cementoblast-mediated cementoclastogenesis by regulating the expression of RANKL and OPG via the EP4 pathway.

Understanding root resorption with diagnostic imaging

This article presents the clinical, radiographic and histopathologic features of various types of tooth root resorption. Tooth resorption may occur in a tooth internally or externally with distinctively different treatment approaches for each type of resorption. Given that proper diagnosis of the type of resorption is important, the use of cone beam computed tomography (CBCT) and conventional 2-D intraoral images in evaluation of resorptive lesions is discussed.

Stem cell regulatory gene expression in human adult dental pulp and periodontal ligament cells undergoing odontogenic/osteogenic differentiation

INTRODUCTION

During development and regeneration, odontogenesis and osteogenesis are initiated by a cascade of signals driven by several master regulatory genes.

METHODS

In this study, we investigated the differential expression of 84 stem cell-related genes in dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) undergoing odontogenic/osteogenic differentiation.

RESULTS

Our results showed that, although there was considerable overlap, certain genes had more differential expression in PDLCs than in DPCs. CCND2, DLL1, and MME were the major upregulated genes in both PDLCs and DPCs, whereas KRT15 was the only gene significantly downregulated in PDLCs and DPCs in both odontogenic and osteogenic differentiation. Interestingly, a large number of regulatory genes in odontogenic and osteogenic differentiation interact or crosstalk via Notch, Wnt, transforming growth factor beta (TGF-beta)/bone morphogenic protein (BMP), and cadherin signaling pathways, such as the regulation of APC, DLL1, CCND2, BMP2, and CDH1. Using a rat dental pulp and periodontal defect model, the expression and distribution of both BMP2 and CDH1 have been verified for their spatial localization in dental pulp and periodontal tissue regeneration.

CONCLUSIONS

This study has generated an overview of stem cell-related gene expression in DPCs and PDLCs during odontogenic/osteogenic differentiation and revealed that these genes may interact through the Notch, Wnt, TGF-beta/BMP, and cadherin signaling pathways to play a crucial role in determining the fate of dental derived cell and dental tissue regeneration. These findings provided a new insight into the molecular mechanisms of the dental tissue mineralization and regeneration.

FEM analysis of different dental root canal-post systems in young permanent teeth

AIM

Aim of this work was to carry out a comparative evaluation of the structural behaviour of different root canal posts (cylindrical, conical and triple conical) fitted in a second lower bicuspid and subjected to compression and bending test.

MATERIALS AND METHODS

This study has been carried out by numerical method of structural analysis of finite elements (FEM, Finite Element Method). Different tridimensional models were obtained by CAT images of an extracted tooth, endodontically treated, filled with guttapercha and triple conical glass post. Images have been elaborated by a software for images (Mimics and Ansys) and CAD (Rhinoceros 3 D). In the models a II Class restoration has been virtually created. In the numerical simulation dental tissues (enamel, dentine and root cement), guttapercha, root canal cement, different posts, different techniques of cementation and crown restoration (composites and adhesive systems) have been considered.

RESULTS

Strain distributions in dental tissues, in root canal cement and in posts have been compared. The equivalent tensions and the single components (traction, compression and cut) have been analysed. In all examined posts, the most strained part is resulted the coronal one, even if the total tension, in the different tooth-post analyzed systems, resulted uniformly distributed. A similar behaviour was shown by the root canal cement.

CONCLUSIONS

According to the analyzed conditions of bond and load, varying according to the geometry of the considered posts, our results confirm that there is no substantial difference of deformation in posts, root canal cement and treated tooth.

The side effects of orthodontic mechanics in orthodontic treatments

The side effects of orthodontic mechanics at each tissue level (alveolar bone, periodontal ligament, gingiva, pulp, cementum, and enamel) are addressed, along with the issue of pain following orthodontic appointments, and psychobehavioral alterations observed in orthodontic patients. It is necessary to know how orthodontic treatment affects enamel health, including methods to manage these side effects, which are still a dilemma for orthodontic clinicians. It is interesting to note that the dental pulp, which lies deep in the tooth core, also reacts to orthodontic force. The way the periodontal ligament responds to light and heavy forces, in young and adult patients, with or without periodontal disease, should be considered. Root resorption is a well-recognized phenomenon following orthodontic treatment. Advances made in this area of research to identify the parameters and genes associated with this process are developing.

Root resorption repair in mandibular first premolars after rotation. A transmission electron microscopy analysis combined with immunolabeling of osteopontin

INTRODUCTION

A previous study with scanning electron microscopy showed that orthodontic root resorption occurs at the lateral surfaces of premolar roots for 2 to 6 weeks after orthodontic rotation. The purpose of this investigation was to observe how resorbed cementum repairs during rotation movement.

METHODS

Twenty-one mandibular first premolars from 12 patients, orthodontically indicated for extraction, were used. They were intra-individually divided into 2 groups: 8 teeth were not moved (control group), and 13 were rotated (experimental group). In the experimental group, a rotational force (25 g both buccally and lingually) with a precise biomechanical model, individually calibrated, was applied for 2, 3, 4, or 6 weeks. After extraction, the teeth were fixed and decalcified, and 8 were conventionally processed for transmission electron microscopy, and 13 teeth were processed for high-resolution immunocytochemistry by using an antibody against osteopontin. The samples were analyzed in a transmission electron microscope.

RESULTS

This examination showed areas of repair in previously resorbed lacunae in the experimental group. Both the clastic cells and the root surface showed immunolabeling for osteopontin. In addition to areas of cementum resorption and various degrees of cell and extracellular matrix degeneration, active cementoblasts and fibroblasts in several stages of differentiation and activity appeared adjacent to newly synthesized collagen fibers, thus reestablishing the function of the periodontal ligament.

CONCLUSIONS

We concluded that cementum repair occurs after resorption during rotation movement and that noncollagenous matrix protein osteopontin plays a role in both resorbing and repairing.

Histologic and clinical evaluation of an allogeneic bone matrix for the treatment of periodontal osseous defects

The objective of this study was to evaluate the potential of an allogeneic bone matrix (Grafton, Osteotech) to regenerate new bone, new cementum, and a new periodontal ligament around teeth previously contaminated by bacterial plaque. Four patients with chronic advanced periodontitis and who were scheduled for full-mouth extraction were enrolled in the study. One patient dropped out from the study before any therapy began. One tooth with an intraosseous defect in each patient was selected for treatment. Measurements of probing depth, gingival recession, and clinical attachment level were made. After flap reflection, a root notch was placed at the apical level of calculus, the root was debrided, and allogenic bone matrix was inserted into the defect. After 6 months of healing, the teeth were removed en bloc and evaluated histologically for a new attachment apparatus. Two of the three teeth demonstrated regeneration of new bone, cementum, and periodontal ligament.

Insulin-like growth factor system components in the periodontium during tooth root resorption and early repair processes in the rat

There is evidence that growth factors, such as the insulin-like growth factors (IGFs), are involved in biological and pathological processes in oro-dento-facial tissues. To investigate their roles in tooth movement, root resorption, and repair, the occurrence of components of the IGF system, including the ligands IGF-I and -II, the IGF receptor 1 (IGF1R) and six IGF-binding proteins (IGFBP-1 to -6), was investigated by immunohistochemistry on sections from rat maxillae where the first molar had been moved mesially by means of an orthodontic appliance for 9 d to induce root resorption. After force deactivation on day 0, early repair was studied after a further 5, 7, 10, 12, 14, and 17 d. The immunostaining pattern in the periodontal ligament, cementum, and bone of control animals showed similarities known from studies in human teeth. Increased immunostaining for nearly all components in pressure sides and resorption lacunae indicated an involvement in resorption processes and clastic activities. During early stages of repair, the occurrence of several components (e.g. IGF-II, IGFBP-5 or -6) within lacunae and in cementoblasts showed an involvement in the resorption-repair sequence, which is considered to be a coupling process as known from bone.

Susceptibility of GTR-regenerated periodontal attachment to ligature-induced periodontitis. An experiment in the monkey

AIM

This study aimed to compare the susceptibility of guided tissue regeneration (GTR)-regenerated periodontal attachment to ligature-induced periodontitis with that of the pristine periodontium.

METHODS

Periodontal breakdown was produced in four monkeys by the placement of orthodontic elastics around experimental teeth (test teeth). During a flap operation, the root surfaces were scaled and planed, and a notch indicating the apical termination of scaling and root planing was made in the root surface. Following resection of the crowns and endodontic treatment, an e-PTFE membrane was adapted over the roots. Subsequently, the flaps were sutured to complete closure of the wound (submerged). At membrane removal after 5 weeks, the crowns of the contralateral teeth serving as controls were resected, and the roots treated endodontically during a flap operation. Artificial composite crowns were then placed on both test and control roots. After 3 months of tooth cleaning, cotton floss ligatures were placed passively around both test and control teeth for a period of 6 months. Two weeks later the animals were sacrificed.

RESULTS

Histological analysis demonstrated that the instrumented root surfaces of the test teeth were covered by newly formed cementum of the reparative, cellular, extrinsic and intrinsic fiber type, while the cementum on the controls was mainly acellular extrinsic fiber cementum. Histometric assessments demonstrated that similar attachment loss had occurred on test (1.0+/-0.5 mm) and control roots (1.0+/-0.4 mm) during the 6 months of ligature-induced plaque accumulation.

CONCLUSION

The results indicate that teeth with a periodontal attachment apparatus formed by GTR is not more susceptible to periodontitis than those with a pristine periodontium.

Temperature change at the root surface when enlarging a root canal with a holmium: YAG (Ho:YAG) laser, using six different fiber-optic sizes

This in vitro study was designed to determine if enlarging a canal with a holmium: YAG (Ho:YAG) laser (using six different-sized fiber-optic tips) would increase the change in temperature at the root surface and if fiber-optic tips spaced more closely would enlarge the canal more efficiently and consistently.

Ultrastructural and histochemical examination of alveolar bone at the pressure areas of rat molars submitted to continuous orthodontic force

It is usually believed that repair in alveolar bone during orthodontic movement occurs after decreasing of force. However, we have recently observed signs of repair in previously resorbed cementum from human teeth exposed to continuous forces. In order to test the hypothesis that bone resorption and deposition occur concomitantly at the pressure areas, a continuous 15 cN force was applied in a buccal direction to upper first molars from eight 2.5-month-old male Wistar rats for 3 d (n = 4) and 7 d (n = 4). As a control, two additional rats did not have their molars moved. Maxillae were fixed in 2% glutaraldehyde + 2.5% formaldehyde, under microwave irradiation, decalcified in ethylenediaminetetraacetic acid, and processed for transmission electron microscopy. Specimens from one rat from each group were processed for tartrate-resistant acid phosphatase (TRAP) histochemistry. At both the times studied, the alveolar bone surface at the pressure areas showed numerous TRAP-positive osteoclasts, which were apposed to resorption lacunae. In addition, osteoblasts with numerous synthesis organelles were present in the neighboring areas overlying an organic matrix. Thus, this study provides evidence that the application of continuous forces produces concomitant bone resorption and formation at the pressure areas in rat molars.

Periodontal Regeneration with a Combination of Enamel Matrix Proteins and Autogenous Bone Grafting

BACKGROUND

Attempts to stimulate periodontal regeneration in the past have focused on either filling the defect with some type of material or providing a space for host cells to repopulate the site and elicit new tissue. In some cases, these approaches have been combined with the assumption that the filler material will help maintain the space necessary for the host cells to invade the area. Growth stimulating substances such as growth factors and other proteins have also been used to encourage periodontal tissue regeneration and histological evaluation supports the use of these substances. Thus, the role for and the necessity of a certain amount of space maintenance for periodontal regeneration is not exactly understood. In addition, it is not known if there is some critical size required for space maintenance or for exactly how long the space must be maintained in order for the host cells to stimulate new cementum, periodontal ligament, and bone. The goal of this study was to evaluate periodontal regeneration in intrabony defects of various sizes treated with a combination of enamel matrix proteins and autogenous bone graft.

METHODS

Periodontal defects ranging in size from 1 to 6 mm were randomized and created bilaterally beside three teeth in the mandibles of baboons. Plaque was allowed to accumulate around wire ligatures placed into the defects. After 2 months, the wire ligatures were removed, the teeth and roots scaled and root planed, and a notch was placed with a chisel at the base of the defect. On one side of the mandible, neutral ethylene diamine tetracetic acid and enamel matrix derivative (EMD) were first used to treat the defect. Autogenous bone taken from the same surgical site was treated with enamel matrix derivative in a dampen dish and then added to the EMD-treated defects. The other side of the mandible served as control with neutral ethylene diamine tetracetic acid and scaling and root planing. Flaps were sutured and the animals were allowed to heal without oral hygiene procedures. After 5 months, the animals were sacrificed and the teeth were processed for histological evaluation.

RESULTS

The results revealed new cementum, periodontal ligament with Sharpey's fibers, and new bone tissue similar to native periodontal tissues. Remnants of the autogenous bone chips were still present at this 5-month post-healing period. Thus periodontal regeneration occurred in all sizes of the periodontal defects. In general, EMD plus autogenous graft treatment resulted in greater tissue formation than controls. In fact, in many cases, very dramatic tissue formation occurred far coronal to the base of the defects in the EMD plus autogenous graft-treated lesions. In addition, horizontal bone fill occurred in the defects and was prominent in the 4 or 6 mm wide lesions. When evaluating the combined 1 and 2 mm defects, the height of new cementum with EMD plus graft was 3.88 mm versus 2.03 mm in the controls, a statistically significant (P < 0.005) difference. In the wider (4 and 6 mm) lesions, this difference was not significant and was much less between treated and control lesions with 2.78 and 2.57 mm of new cementum respectively. In the case of new bone height, in the smaller lesions EMD plus graft resulted in 4.00 mm new bone versus 2.22 mm in the controls, again a statistically significant (P < 0.005) difference. In the larger lesions, EMD plus autogenous bone graft had 3.24 mm new bone height compared to 2.71 mm in the controls, a difference that was not statistically significant. Additionally, in the smaller lesions, new cementum width at the level of the notch was twice as great (statistically significant, P < 0.015) in the EMD plus graft sites compared to control. The width of the periodontal ligament at the coronal aspect of the new bone tissue was similar in the smaller lesions between treated and control sites. The results from the wider defects must be interpreted cautiously as the interproximal bone heights were remodeled adjacent to the wider defects and likely limited the potential for regeneration.

CONCLUSIONS

The combination of enamel matrix derivative plus autogenous bone graft stimulated statistically significant periodontal regeneration in the more narrow 1 and 2 mm lesions. No statistically significant difference was observed in the wider 4 and 6 mm lesions. In many cases, dramatic amounts of new cementum, Sharpey's fibers, periodontal ligament, and bone tissue were formed far above the notch placed at the base of the contaminated defects. This was especially significant considering the width of some of the defects and the fact that no oral hygiene was performed over the 5-month healing period. This periodontal regeneration occurred in the absence of exogenous growth factors or barrier membranes. In summary, the combination of enamel matrix derivative and autogenous bone represents a therapeutic combination that can be highly effective in stimulating significant amounts of periodontal regeneration.

Periodontal repair in dogs: a bioabsorbable calcium carbonate coral implant enhances space provision for alveolar bone regeneration in conjunction with guided tissue regeneration

BACKGROUND

Collapse or compression of a barrier device into a periodontal defect or onto the root surface compromises outcomes following guided tissue regeneration (GTR). Bone biomaterials have been suggested to support regeneration of alveolar bone and to improve space provision with GTR devices. The objective of this study was to evaluate space provision, alveolar bone, and cementum regeneration following use of a bioabsorbable, calcium carbonate biomaterial in conjunction with GTR.

METHODS

Routine, critical size, 5 to 6 mm, supraalveolar, periodontal defects were created in 5 young adult beagle dogs. Alternate jaw quadrants in consecutive animals received GTR and the coral biomaterial (cGTR) or GTR alone. The animals were euthanized 4 weeks postsurgery and tissue blocks processed for histometric analysis.

RESULTS

The coral implant particles were surrounded by newly-formed bone or immersed in connective tissue and appeared to resorb and be replaced by bone. There was limited, if any, appreciable cementum regeneration. Space provision was enhanced in cGTR compared to GTR sites (6.1 +/- 1.6 versus 2.4 +/- 0.8 mm2; P<0.05). Bone regeneration (height) was significantly increased in cGTR compared to GTR sites averaging 1.9 +/- 0.6 and 1.2 +/- 0.6 mm, respectively (P<0.05). Bone regeneration (area) was 2-fold greater in cGTR sites compared to the GTR control (3.3 +/- 1.8 versus 1.4 +/- 0.5 mm2), however the difference was not statistically significant (P>0.05).

CONCLUSIONS

The coral implant significantly enhanced space provision for GTR while alveolar bone formation appeared to be enhanced by its use. Increased healing intervals are needed to fully understand the biologic value of the coral implant as an adjunct to GTR.

Abfraction: 3D analysis by means of the finite element method

OBJECTIVE

Tooth deflections under functional loads are considered to be the etiologic factor of noncarious cervical lesions. There are several studies on the materials used to restore these lesions; however, there are few discussing this phenomenon's etiology from a biomechanic point of view. This study was undertaken to evaluate tooth behavior when forces were applied from different directions.

METHOD AND MATERIALS

A 3D finite element model of a maxillary central incisor was designed. A distributed force of 1.5 N was applied on the palatal side of the crown in five stages, with varying directions progressing from tipping to intrusion. Two separate approaches (displacement and stress) were considered to evaluate the cervical area from a stress perspective.

RESULTS

The displacement approach resulted in a curved path when compared to a straight line connecting the apical and incisal areas. The maximum deflections were in the cementoenamel junction area. The same area was shown to undergo the maximum of von Mises stress and stress intensity. Patterns of the von Mises stress when evaluated in a mesiodistal direction were in complete agreement with the shape of the cervical lesions (except for the application of the intrusive force, which rules out its effect in producing such lesions).

CONCLUSION

Force applications, except for intrusive force, can produce increases in the von Mises stress and tooth deflections that can answer the question of the etiology of noncarious cervical lesions. The highest amounts of deflection and von Mises stress were produced by the 45-degree force application.

Orthodontic movement of teeth with intraosseous defects: Histologic and histometric study in dogs

The purpose of this study was to evaluate histologically, in dogs, the periodontal healing of 1-walled intraosseous defects in teeth that were subjected to orthodontic movement toward the defects. The defects were surgically created bilaterally at the mesial aspects of the maxillary second premolars and distal aspects of the mandibular second premolars of 4 mongrel dogs. One week after creating the defects, an orthodontic appliance was installed, and the teeth were randomly assigned to 1 of 2 treatment groups: those in the test group received a titanium-molybdenum alloy rectangular wire spring that performed a controlled tipping root movement, and those in the control group received a passive stainless steel wire. Active orthodontic movement of the test teeth lasted 2 months and was followed by a stabilization period of another 2 months, after which the animals were killed. Throughout the study, routine daily plaque control was performed on the dogs with a topical application of a 2% chlorhexidine gel. The results showed no difference between the groups, with some regularization of the defects and periodontal regeneration limited to the apical portion of the defects. Histometric analysis showed a significant difference in bone height; on average, it was 0.53 mm smaller in the test group. It was concluded that orthodontic movement does not interfere with the healing of 1-walled intraosseous defects, with the exception of the linear extent of new bone apposition.

Periodontal repair in dogs: evaluation of a bioabsorbable space-providing macroporous membrane with recombinant human bone morphogenetic protein-2

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) technologies have been shown to significantly support alveolar bone formation. Biomaterial limitations, however, have restricted the biologic potential for onlay indications. The objective of this study was to evaluate regeneration of alveolar bone and periodontal attachment, and biomaterials reaction following surgical implantation of a space-providing, bioabsorbable, macroporous, polyglycolic acid-trimethylene carbonate (PGA-TMC) membrane combined with a rhBMP-2 construct in a discriminating onlay defect model.

METHODS

Routine supraalveolar periodontal defects were created at the mandibular premolar teeth in 9 beagle dogs. Contralateral jaw quadrants in subsequent animals were randomly assigned to receive the dome-shaped PGA-TMC (100 to 120 microm pores) membrane with rhBMP-2 (0.2 mg/mL) in a bioresorbable hyaluronan (Hy) carrier or the PGA-TMC membrane with Hy alone (control). The gingival flaps were advanced to submerge the membranes and teeth and sutured. Animals were euthanized at 8 and 24 weeks postsurgery for histologic observations.

RESULTS

Jaw quadrants receiving the PGA-TMC membrane alone experienced exposures at various time points throughout the study. Jaw quadrants receiving the PGA-TMC/rhBMP-2 combination remained intact, although one site experienced a late minor exposure. Newly formed alveolar bone approached and became incorporated into the macroporous PGA-TMC membrane in sites receiving rhBMP-2. The PGA-TMC biomaterial was occasionally associated with a limited inflammatory reaction. Residual PGA-TMC could not be observed at 24 weeks postsurgery. Residual Hy could not be observed at any time interval. Regeneration of alveolar bone height (means +/- SD) was significantly increased in sites receiving the PGA-TMC/rhBMP 2 combination compared to control (3.8 +/- 1.3 versus 0.7 +/- 0.5 mm at 8 weeks and 4.6 +/- 0.8 versus 2.1 +/- 0.4 mm at 24 weeks; P < 0.05). Limited cementum regeneration was observed for PGA-TMC/rhBMP-2 and PGA-TMC control sites. Ankylosis compromised regeneration in sites receiving PGA-TMC/rhBMP-2.

CONCLUSIONS

The bioabsorbable, space-providing, macroporous PGA-TMC membrane appears to be a compatible biomaterial for bone augmentation procedures. rhBMP-2 significantly enhances alveolar bone augmentation and soft tissue healing when combined with the PGA-TMC membrane.

Immunohistochemical characteristics of epithelial cell rests of Malassez during cementum repair

To clarify the roles of epithelial cell rests of Malassez (ECRM) during periodontal repair, experimental root resorption was induced in rats and then the ECRM that existed in periodontal ligament during cementum repair was investigated using morphological and immunohistochemical approaches. At day 7, after mechanical injury, root resorption was observed and ECRM were present adjacent to the site of resorption lacunae. They were observed in periodontal ligament adjacent to site of the resorption lacunae. These ECRM were immunoreactive for bone morphogenetic protein-2. During the stage of early cementum repair, the ECRM were immunoreactive for osteopontin and ameloblastin. They strongly reacted to proliferating cell nuclear antigen. In uninjured control sections, ECRM located in the periodontal ligament adjacent to cementum were not immunoreactive for any antibodies. These findings suggested that ECRM may be related to cementum repair by activating their potential to secrete matrix proteins which have been expressed in tooth development.

Cementum formation around a titanium implant: a case report

Animal studies have shown that a periodontal ligament may be produced around a titanium implant when it is in contact with fractured and retained roots. Formation of cementum and attachment connective tissue around titanium implants confirms that cementum progenitor cells are located in the periodontal ligament, since cementum and periodontal ligament are present at the implant-root interface, whereas the remainder of the implant, which is not in contact with the root, shows osseointegration. The aim was to evaluate histologically the characteristics of the tissue present between a titanium implant and a retained root, which were subsequently extracted as a result of peri-implantitis. The histologic examination revealed a continuous layer of cementum and numerous cementocytes on the implant surface. No blood vessel or collagen fibers were detected in the periodontal space. In contrast to experimental studies carried out on animals, the lack of connective tissue fibers and the presence of hypercementosis in this specimen could have been caused by the inflammatory process. Furthermore, the extrusive movement of the root might explain the presence of cementum hypertrophy. Further studies are required to establish whether the neoformation of cementum and collagen fibers on an implant in the presence of root residues occurs only in animal models or whether it may also occur in humans.

Bone morphogenetic protein-2 stimulates cell recruitment and cementogenesis during early wound healing

BACKGROUND

The unique action of bone morphogenetic proteins (BMPs) on mineralised tissue formation indicates that BMPs are good candidates for use in stimulating periodontal regeneration. Relatively little is known about the mechanisms of actions of BMPs during periodontal regeneration, although recent evidence from our laboratory suggests that the effects of BMPs may be profoundly influenced by various factors including root surface conditioning, delivery systems and masticatory forces.

AIM

The aim of this study was to investigate the effect of rhBMP-2 on cell recruitment during periodontal regeneration using a pulse-chase technique where cells are labelled with a thymidine analogue (BrdU) (pulse) and the migration of their progeny is followed (chase) during early wound healing. The relationship between the rhBMP-2 influence on cell recruitment from the periodontal ligament (PDL) and its ability to stimulate cementogenesis was also evaluated.

METHOD

The buccal aspect of the distal root of the first molar was denuded of its PDL, cementum and superficial dentine through a bony window created in the mandible of 64 Wistar rats under general anaesthesia. Test animals were treated with 10 microL of 500 microg/ml rhBMP-2 in a collagen membrane sponge (n=32) and control defects received 10 microl of saline in a collagen sponge (n=32). All animals received an intraperitoneal single pulse injection of 40 mg/kg BrdU label 2 days postoperatively. Groups of test and control animals (n=8) were killed 2 hours later on day 2 and at 4, 7 and 10 days postoperatively. Mandibles were processed for histological examination.

RESULTS

The results show that rhBMP-2 had a profound effect on proliferation and migration of cells in the adjacent and deeper aspects of the PDL at 7 and 10 days post periodontal wounding (p<0.05). Significantly greater new cementum formation occurred in the test group at 10 days (p=0.03).

CONCLUSION

This study shows that following periodontal wounding rhBMP-2 stimulates cell recruitment by increasing proliferation and migration of cells from the adjacent unwounded PDL into the wounded area, thus promoting periodontal regeneration by increasing new cementum formation.

Histologic evaluation of root coverage obtained with GTR in humans: a case report

The purpose of this study was to histologically evaluate four teeth with recession defects that were treated with guided tissue regeneration (GTR). The amount of root coverage obtained ranged from 16.7% to 50.0%. In one of the defects treated, new bone was formed but none of the new bone was coronal to the original gingival margin. Additionally, in this one case new cementum and connective tissue attachment was formed. However, because the new bone, new cementum, and new connective tissue were not coronal to the original gingival margin, this result could not be classified as regeneration. The vast majority of the attachment in this defect was long junctional epithelial attachment in the portion of the recession defect covered by the root-coverage procedure. In the other three defects treated, there was a loss of bone. All of the root coverage obtained was a long junctional epithelial attachment in three of the four defects. The results of this study do not show regeneration in any of the four defects treated.

Histological evaluation of healing and revascularization of the subepithelial connective tissue graft

BACKGROUND

The goal of this investigation was to histologically evaluate the healing and revascularization of the subepithelial connective tissue graft in dogs.

METHODS

Six beagle dogs were used in this study. Recession defects were surgically created on maxillary left P2 and right P2, and maxillary and mandibular left central and lateral incisors. The defects were left untreated for 35 days. After elevating a split thickness flap, the graft was harvested from the palate and placed over the denuded root surfaces. The flap was then coronally repositioned and sutured. Three dogs provided the specimens for 7- and 14-day time points and 3 dogs for 28- and 60-day time points. The animals were sacrificed and the blocks obtained were divided in half. One half was processed following the Spalteholtz method and the other was processed for routine histologic examination.

RESULTS

At 7 days, a clot was present at the demarcation zones and it was more organized at 14 days. At 28 days, the junctional epithelium was formed and the demarcation zones could not be delineated. At 60 days, the oral epithelium had regained its normal appearance. The attachment of the graft to the root surface was mediated by a combination of epithelial downgrowth and connective tissue attachment. Minimal new bone and cementum formation was observed. The vascularization of the graft at 7 days originated from the periodontal plexus and the overlying flap. At 14 days, the graft was completely vascularized. At 28 and 60 days, normal vascularization was present.

CONCLUSIONS

The vascularization of the connective tissue graft originates from the periodontal plexus, the supraperiosteal plexus, and the overlying flap. The attachment of the graft to the root surface appears to be mediated by a combination of epithelial downgrowth and connective tissue attachment. There is little potential for new cementum and new bone formation.

Root resorption in elderly patients

Root resorption in permanent teeth is a frequently observed pathology that may originate in various causes. Life expectancy is progressively rising, odontological preventive care is becoming more widespread and professionals are educating their patients in the importance of preventive practices. Because senior citizens are thus losing fewer teeth prematurely they will be conversely more at risk for dental problems later in life. The knowledge of the alterations that may appear in the roots of geriatric patients is particularly relevant to devising therapy and establishing prognosis. The aim of the present study was to evaluate the nature and magnitude of the histologic and histomorphometric features of root resorption and the eventual possibility of repair in elderly people. Seventy-seven uniradicular teeth of patients aged between 65 and 90 years and 18 premolars of patients aged between 14 and 20 years, were removed, fixed in 90% formalin, decalcified in EDTA and embedded in paraffin. Vestibulo-lingual sections were stained with hematoxylin-eosin and employed to perform histological and histomorphometric studies. The results showed that 30% of the teeth of younger patients and 94% of the teeth of elderly patients exhibited areas of root resorption. From the 416 resorptive areas found in elderly patients, 173 exhibited signs of repair being the volume/surface ratio of these areas 0.69 +/- 0.06. These data show that root resorption is a frequent finding in the older population under study. Resorptions are characterized by scarce depth, large areas and a high incidence of repair despite the old age of the patients.

The use of distraction osteogenesis to induce new suprabony periodontal attachment in the beagle dog

Using a technique called distraction osteogenesis (DO), orthopedic surgeons are capable of reconstructing 4 to 5 cm of bone and soft tissue without bone grafts or pedicle flap procedures. DO has been used recently to generate maxillofacial bone as an alternative to maxillary and mandibular osteotomies. Using DO methodology, this study attempted to regenerate supraalveolar buccal periodontium on the mandibular second, third, and fourth premolars of beagle dogs. A small but statistically significantly greater amount of new cementum was generated in experimental teeth, with no difference found between experimental and control groups with respect to regenerating alveolar bone. Further studies using modifications of this technique are warranted to explore the potential of DO as an alternative to conventional regenerative approaches.

Intraradicular space: what happens within roots of infected teeth?

The pulpo-dentine complex is normally protected from exogenous substances in the oral cavity by the overlying enamel or cementum. Dental caries, dental trauma, enamel/dentine cracks, and restorative procedures commonly breach the integrity of enamel or cementum and may allow infection of the pulpo-dentine complex to occur, possibly leading to pulp and periapical inflammatory disease. Infection of the intraradicular space is a complex and dynamic process involving interactions between host and microbial factors. An understanding of these factors has led to the development of endodontic techniques that offer predictable success.

Periodontal repair in dogs: effect of transforming growth factor-beta 1 on alveolar bone and cementum regeneration

BACKGROUND

Transforming growth factor-beta (TGF-beta) represents a family of growth-modulating proteins with fundamental roles in connective tissue and bone development. The objective of this study was to evaluate the potential for regeneration of alveolar bone and cementum following surgical implantation of recombinant human TGF-beta 1 (rhTGF-beta 1).

METHOD

Bilateral, critical size, supra-alveolar periodontal defects in 5 beagle dogs were surgically implanted with rhTGF-beta 1 in a calcium carbonate carrier (CaCO3) or with carrier alone. The animals were euthanized at 4 weeks postsurgery and block-biopsies of the defects were processed for histologic and histometric analysis.

RESULTS

Surgical implantation of rhTGF-beta 1 resulted in minimal, if any, stimulation of alveolar bone or cementum regeneration. Linear bone and cementum regeneration in rhTGF-beta 1-treated defects was 1.2+/-0.6 and 0.01+0.01 mm, respectively. Corresponding values for the controls were 1.0+/-0.6 and 0.01+/-0.03 mm.

CONCLUSIONS

The results suggest that, under the conditions (dose, carrier, defect type) evaluated here, treatment of periodontal defects in beagle dogs with rhTGF-beta 1 may be of limited clinical benefit.

Clinical and histologic evaluation of human intrabony defects treated with an enamel matrix protein derivative (Emdogain)

An enamel matrix protein derivative (Emdogain) has been recently shown to promote periodontal regeneration in experimentally created recession-type defects. However, only limited histologic data from human material are available concerning the healing of intrabony periodontal defects following treatment with Emdogain. The aim of the present study was therefore to present the clinical and histologic results following the application of Emdogain in intrabony defects. Two patients with marginal periodontitis and deep intrabony defects adjacent to teeth scheduled for extraction were treated with Emdogain. The postoperative healing phase was uneventful in both cases. At 6 months following treatment, newly formed cementum with inserting collagen fibers was found in both specimens. In one case, the new attachment formation was also accompanied by bone neoformation. The results of this human histologic study indicate that Emdogain possesses the potential to stimulate new connective tissue attachment formation in human intrabony defects.

Enamel matrix derivative in periodontal reconstructive surgery. A new approach in periodontal regeneration

True periodontal regeneration is the goal of any periodontal regenerative techniques. Cementum formation is a key event in the development of root and supporting periodontium. Due to its distribution, acellular cementum is the type most affected by early to moderate periodontitis. Studies over the past twenty years demonstrated that, enamel matrix proteins from the root sheath are involved in the formation of acellular, during tooth development. Thus the adjunctive use of enamel matrix derivatives in conjunction with regenerative periodontal surgery could possibly lead to true periodontal regeneration. The purpose of this article is to review the use of enamel matrix derivative in true periodontal regeneration.

Studies of dental root surface caries. 2: The role of cementum in root surface caries

Artificial caries lesions were produced in roots of teeth using an acetate buffer system, when the layer of cementum was either normal in thickness, excessively thickened by hypercementosis, or had been removed completely. The rates of lesion progression were measured in each case using polarized light microscopy to measure lesion depth. Analysis of calcium (Ca) and phosphorus (P) loss during the demineralizing process was carried out. The removal of cementum was found to significantly increase the initial rate of penetration of the lesion into the root, although this rate progressively reduced to a level consistent with that found in normal roots after seven days of demineralization. The overall depth remained consistently greater than that observed in normal roots, or when lesions were produced entirely within hyperplastic cementum. Chemical analysis also showed removal of cementum resulted in an initial doubling of the Ca and P lost from the root surface. Prior direct exposure of segments of normal roots to the oral environment was found not to significantly alter the rate of artificial lesion progression, in comparison with that in the originally protected segment of the root surface. It was concluded that an intact cementum layer has the intrinsic ability to protect the underlying dentine of exposed tooth roots against acidic demineralization and that prior exposure to the oral environment does not significantly alter this ability.

The effects of attachment factors on initial attachment of human periodontal ligament fibroblasts on different root surfaces: a light and scanning electron microscopic study

This study was aimed to test the effect of fibronectin (FN), vitronectin (VN) and a fibronectin analog (fibronectin-like engineered protein) on the attachment of periodontal ligament cells to mechanically-treated and mechanically non-treated periodontally involved and non-diseased root surfaces in vitro. Periodontal ligament fibroblasts were incubated with a total of 44 periodontally diseased and non-diseased root slices which had been treated in the following manner: 1) FN applied to mechanically-treated and non-treated root slices, 2) VN applied to mechanically-treated and non-treated root slices, 3) FN-like engineered protein applied to mechanically-treated and non-treated root slices, and 4) mechanically-treated and non-treated root slices. After the 1 hour incubation period in a humidified atmosphere of 95% air and 5% CO2 at 37 degrees C, the adherence of the fibroblasts was determined using light microscopy with an ocular grid system and orientation was evaluated by scanning electron microscopy. The results indicated that the number of attached cells to non-diseased cementum sites was significantly greater than the number of attached cells to diseased cementum sites for all of the groups (p < 0.05). Likewise, the number of attached cells to mechanically-treated diseased cementum sites was significantly greater than the number of attached cells to mechanically-non-treated diseased cementum sites (p < 0.05). Our findings suggest that these attachment factors cannot promote cell attachment to different cementum sites.

Analysis of the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery

AIM

To analyse the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery.

METHODOLOGY

Periradicular surgery was completed using the mandibular second, third and fourth premolar teeth from nine male mongrel dogs. The six roots on one side of the mouth were randomly allocated to one of the following groups: group A: a resected root end and a burnished gutta-percha root filling; group B: cavities were prepared to a depth of 4.0 mm, using ultrasonic root-end preparation and filled with Diaket. The response was evaluated histologically at 55 (nine specimens) and 150 (three specimens) days post operatively.

RESULTS

The data for the 55-day period was analysed statistically using Wilcoxon's Signed Ranks test. No statistical analysis was carried out on the 150-day group due to the small number of specimens. The level of significance was set at P < 0.05. No statistical significance was observed in the healing response between Diaket and gutta-percha in the following categories at 55 days: inflammatory response, angiogenesis, root-end resorption, and cementum deposition. Statistically significant differences were observed in the healing categories: bone apposition (P < 0.05) and periodontal ligament formation (P < 0.05).

CONCLUSIONS

At both time intervals, Diaket had a better healing response that was characterized by hard tissue formation adjacent to the root-end filling material bordered by occasional multinucleated giant cells. The nature of both the hard tissue formation and the adjacent cells, however, remains undetermined. Diaket displayed the best healing of either material used in this study.

[Is periodontal guided tissue regeneration a reproducible technic? A review of the literature]

Guided tissue regeneration (GTR) has been developed as a surgical technique enabling the complete regeneration of the periodontal attachment apparatus. Among various periodontal tissues, the root, cementum and the alveolar bone, as well the Sharpey collagenic fibers linking the cementum to the bone, are of particular interest. As demonstrated in this literature review, we could globally conclude to date, that most of the publications confirm the biological and clinical potential of GTR, although in some publications, this opinion is not being shared. A number of factors influence the outcome of the regenerative therapy, some relating to the patient such as the smoking habits and the level of oral hygiene, others relating to the type of implanted biomaterial or the surgical technique. A better understanding of the periodontal healing mechanisms as well as the continuous research and progress in the field of biomaterials, chemical mediators and growth factors, are likely to further increase the predictibility of the periodontal regenerative treatments.

The early reparative process of orthodontically induced root resorption in adolescents--location and type of tissue

The aim of this investigation was to determine the pattern of repair of root resorption regarding the location and type of tissue in adolescents after application of a well-controlled force magnitude. In 16 adolescents (mean age 13.8 years), the maxillary first premolars were buccally moved with a weekly reactivated force of 50 cN (approximately 50 g) for 6 weeks following which the appliance was made passive for 2, 3, 6, and 7 weeks. The subjects were divided into two groups of eight individuals for which the retention periods were 2 and 6 weeks (Group I), or 3 and 7 weeks (Group II), implying intra-individual differences of 4 weeks. Reparative cementum in the resorption cavities was seen in all test teeth, significantly more often after 6 and 7 weeks of retention (82 per cent) compared with 2 and 3 weeks (35 and 44 per cent, respectively). The reparative process appeared to commence in the bottom of the resorption cavity, frequently covered by a thin layer of acellular cementum. However, most of the reparative cementum was of the cellular type and always covered the initially formed acellular cementum. There were great individual variations regarding the occurrence of healing of orthodontically-induced root resorption.

Acceptance Program Guidelines. Products designed to regenerate periodontal tissues. Council on Scientific Affairs. American Dental Association

SCOPE

These Guidelines apply to products used to promote the regeneration of periodontal tissues lost due to periodontal diseases or other causes. Periodontal regeneration is defined histologically as regeneration of the tooth's supporting tissues, including alveolar bone, periodontal ligament, and cementum over a previously diseased root surface. Regenerative procedures must enhance the formation of a new attachment apparatus demonstrated by randomized controlled histological studies in animals, verified by human histologic evidence, and supported by beneficial results in human randomized controlled clinical trials.

Effect of a calcium sulfate implant with calcium sulfate barrier on periodontal healing in 3-wall intrabony defects in dogs

This controlled, split-mouth, preclinical study was designed to evaluate outcome following surgical implantation of an allogeneic, freeze-dried demineralized bone matrix-calcium sulfate (DBM+CS) composite with a CS barrier in 3-wall intrabony periodontal defects in 4 dogs. Control conditions included surgical implantation of DBM or CS and gingival flap surgery (GFS) alone. Three-wall intrabony defects (4x4x4 mm) were surgically created at the mesial and distal aspect of the maxillary and mandibular first and third premolars, respectively. Maxillary and mandibular defects each received 1 of the 4 experimental conditions. Experimental conditions were rotated between defect sites in subsequent animals. Block sections of the defects were collected at sacrifice 8 weeks postsurgery and processed for histometric analysis. Histometric defect height (means +/- SD) for the DBM+CS, DBM, CS, and GFS groups amounted to 4.2 +/- 0.5, 4.3 +/- 0.7, 4.0 +/- 0.2, and 4.1 +/- 0.2 mm, respectively. Connective tissue adhesion (connective tissue contact to the root without apparent cementum formation) amounted to 0.4 +/- 0.3, 0.4 +/- 0.3, 0.5 +/- 0.2, and 1.6 +/- 0.5 mm for the DBM+CS, DBM, CS, and GFS groups, respectively; the DBM+CS, DBM, and CS groups being significantly different from the GFS group (P < 0.05). Cementum regeneration amounted to 3.0 +/- 0.3, 3.1 +/- 0.4, 2.5 +/- 0.4, and 1.6 +/- 0.3 mm for the DBM+CS, DBM, CS, and GFS groups, respectively; the DBM+CS, DBM, and CS groups being significantly different from the GFS group (P < 0.05). Alveolar bone regeneration amounted to 2.7 +/- 0.4, 2.7 +/- 0.3, 1.8 +/- 0.5, and 0.7 +/- 0.1 mm for the DBM+CS, DBM, CS, and GFS groups, respectively; the DBM+CS, DBM, and CS groups being different from the GFS group (P < 0.05), and the DBM+CS and DBM groups being different from the CS group (P < 0.05). None of the DBM-containing implants provided evidence of bone metabolic activity. In summary, surgical implantation of DBM and CS, alone or in combination, may result in significantly improved regeneration of alveolar bone and cementum in this preclinical model. Observed regeneration is likely unrelated to a biologic activity inherent in DBM. Rather it appears that space-providing properties of the implants supported observed regeneration.

Pulpal injury: pathology, diagnosis and periodontal reactions

Diagnosis of pulpal disease can be difficult due to the lack of diagnostic signs and symptoms available to the practitioner. An understanding of the possible underlying pathological processes, combined with an exact assessment of the pain history, and appropriate clinical tests, should aid the practitioner in determining the nature of pulpal inflammation, and differentiating it from dentine sensitivity and cracked teeth. The responses of the pulp to traumatic injury to the periodontal membrane (PDM) require special consideration, particularly with respect to the assessment of pulp vitality, and the determination of cases requiring pulp extirpation in order to avoid inflammatory root resorption. Although the pulp is relatively isolated from the rest of the dentoalveolar complex by a dentine/cementum barrier, it is important to remember that it can communicate with the PDM through apical and lateral foramina, and areas of damaged cementum. Hence, it is a priority to both preserve the integrity of the cemental layer in cases of traumatic injury and periodontal disease, and to prevent the inflammation and resorption associated with periapical lesions by accurate diagnosis of irreversible pulpitis and pulp necrosis, followed by appropriate endodontic debridement procedures.

Biologic and clinical considerations for autografts and allografts in periodontal regeneration therapy

Although complete periodontal regeneration is unpredictable with any regenerative therapy currently used, periodontal bone grafts show strong potential. A large body of clinical evidence clearly indicates that grafts consistently lead to better bone fill than nongrafted controls. Regardless of which material is used, the average bone fill is 3 mm, or about 60% defect fill according to reported studies. In addition, histologic analyses now show conclusively that regenerative treatment with bone grafting leads to some degree of regenerated bone, cementum, and periodontal ligament. Although bone grafts and other periodontal treatments have improved clinicians' ability to promote osteogeneration, the outcomes are still somewhat unpredictable. Part of the problem is that it is still unclear how periodontal disease affects the supporting bone's regenerative potential and what specific biologic factors are involved. In recent years, however, clinicians have begun to learn much more about how periodontal regeneration works on a cellular and molecular level. This is a key step to developing strategies and materials that allow clinicians to promote periodontal regeneration predictably. Since its introduction during the last decade, GTR has been an invaluable addition to the armamentarium, as has the recognized importance of early wound stability. As more is learned about the biologic process of periodontal regeneration, new materials and techniques, such as growth factors, absorbable membranes, and new graft materials, are expected to make the task of periodontal regeneration even more predictable. It is likely that some combination of techniques may eventually prove to yield the best results.

Regressive changes of the dental pulp complex in retained primary molars with congenitally missing successor teeth

This study was undertaken to investigate the regressive changes occurring in the dental pulp complex (pulp, dentin, and cementum) of retained mandibular primary second molars with congenitally missing bicuspid teeth. Seventeen retained, caries free, primary molars were used. The specimens were fixed in 10% neutral buffered formalin. Fixed samples were decalcified, routinely prepared, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. The results demonstrated a reduction in the pulp size, abnormal odontoblastic pattern, declined vascularity, pulp degeneration, pulp stones, accelerated formation of secondary dentin, and hypercementosis. This study suggests that these findings may be from aging and physiological defensive changes. These normal, age-induced changes are of considerable importance in the fields of endodontics, orthodontics, and pediatric dentistry.

Effect of two delivery systems for recombinant human bone morphogenetic protein-2 on periodontal regeneration in vivo

Resorbable collagen membranes for guided tissue regeneration in periodontal therapy have shown promise but are not osteoinductive. As recombinant human bone morphogenetic protein-2 (rhBMP-2) is known to have an affinity for collagen, the use of this osteoinductive agent incorporated into a collagen vehicle may act as a suitable carrier to promote periodontal regeneration. The aim of this study was to investigate the effects of two different collagen delivery systems for rhBMP-2 in rat periodontal fenestration defects. Using the collagen membrane delivery system, 3 groups of adult Wistar rats which had surgical defects created on the right side of the mandible involving the removal of bone and exposure of the molar roots were treated with either rhBMP-2 in colagen membrane (BMPm) (n = 12 animals), or collagen membrane only (COLm) (n = 12), or were left untreated (UN) (n = 14). Using the collagen gel delivery system, surgical defects were treated with either rhBMP-2 incorporated in a collagen gel carrier (BMPg) (n = 5) or had collagen gel only (COLg) (n = 6). Animals were killed 10 d postoperatively and tissues processed for histology. New bone formation was significantly greater in BMPg compared with both BMPm and controls (p < 0.05). However, new cementum formation was significantly greater in BMPm (721 +/- 166 micron2, mean +/- SE) compared with COLm, COLg and UN (p < 0.02) (190 +/- 44 micron2, 327 +/- 114 micron2 and 172 +/- 33 micron2, respectively) and more than 1.5 times BMPg (451 +/- 158 micron2). In conclusion, both carrier systems for rhBMP-2 significantly increased new bone formation compared with controls during the early stages of periodontal wound healing. However, the more slowly dissolving collagen membrane carrier system for rhBMP-2 produced significantly greater new cementum compared with the collagen gel carrier, suggesting that a more prolonged exposure of rhBMP-2 is required to increased cementogenesis.

Recombinant human osteogenic protein-1 (OP-1) stimulates periodontal wound healing in class III furcation defects

Osteogenic protein-1 (OP-1) is a member of the transforming growth factor beta superfamily and is a potent modulator of osteogenesis and bone cell differentiation. This preclinical study in dogs sought to assess the effects of OP-1 on periodontal wound healing in surgically created critical size Class III furcation defects. Eighteen male beagle dogs were subjected to the creation of bilateral mandibular 5 mm osseous defects. A split-mouth design was utilized which randomly assigned opposing quadrants to control therapy (surgery alone or collagen vehicle) or 1 of 3 ascending concentrations of OP-1 in a collagen vehicle (0.75 mg OP-1/g collagen, 2.5 mg/g, or 7.5 mg/g). Thus, 9 quadrants per test group received OP-1, 9 quadrants per control group received surgery alone, and 9 quadrants received collagen vehicle alone. Test articles were delivered by a surgeon masked to the treatment, and fluorogenic bone labels were injected at specified intervals post-treatment. Eight weeks after defect creation and OP-1 delivery, tissue blocks of the mandibulae were taken for masked histomorphometric analysis to assess parameters of periodontal regeneration (e.g., bone height, bone area, new attachment formation, and percent of defect filled with new bone). Histomorphometry revealed limited evidence of osteogenesis, cementogenesis, and new attachment formation in either vehicle or surgery-alone sites. In contrast, sites treated with all 3 concentrations of OP-1 showed pronounced stimulation of osteogenesis, regenerative cementum, and new attachment formation. Lesions treated with 7.5 mg/g of OP-1 in collagen regenerated 3.9+/-1.7 mm and 6.1+/-3.4 mm2 (mean +/-S.D.) of linear bone height and bone area, respectively. Furthermore, these differences were statistically different from both control therapies for all wound healing parameters (P < 0.0001). No significant increase in tooth root ankylosis was found among the treatment groups when compared to the surgery-alone group. We conclude that OP-1 offers promise as an attractive candidate for treating severe periodontal lesions.

Periodontal repair in dogs: effect of allogenic freeze-dried demineralized bone matrix implants on alveolar bone and cementum regeneration

The objective of this study was to evaluate alveolar bone and cementum regeneration following surgical placement of an allogenic, freeze-dried, demineralized bone matrix (DBM) cortical strip implant. Critical size, supraalveolar periodontal defects were surgically created around the second, third, and fourth mandibular premolar teeth in eight mongrel dogs. Contralateral jaw quadrants in six animals were randomly assigned to receive the DBM implant, or serve as surgical control. Two additional animals received bilateral DBM implants. Flaps were coronally advanced to submerge teeth and implants, and sutured. Three animals were exited from the study due to extensive early wound failure. Remaining animals were sacrificed at 8 weeks postsurgery. Histometric recordings included defect height, bone regeneration/DBM implant height, cementum regeneration height, root resorption, and ankylosis. Large areas of unresorbed DBM exhibiting fragmentation and empty osteocyte lacunae were observed adjacent to new bone formation, or bone formation was observed adjacent to or within the implant, often exhibiting ankylosis. Cementum regeneration appeared enhanced in shelter of the DBM implant. Histometric recordings (mean+/-SD) for DBM and control defects, respectively, were: defect height, 4.8+/-0.2 mm and 4.4+/-0.2 mm; bone regeneration/DBM implant height, 4.0+/-1.3 mm and 1.2+/-0.6 mm; cementum regeneration height, 1.4+/-0.4 mm and 0.7+/-0.2 mm; root resorption, 0.5+/-0.3 mm and 1.2+/-0.3 mm; and ankylosis, 0.5+/-0.2 mm and 0.1+/-0.1 mm without statistically significant differences between experimental conditions (N=3). Within the limitations of this study, the histologic observations suggest that surgical implantation of allogenic, freeze-dried DBM cortical strip implants may have a potential to support cementum regeneration, possibly by providing conditions for guided tissue regeneration, however, alveolar regeneration appears unpredictable.

On the dynamics of periodontal tissue formation in degree III furcation defects. An experimental study in dogs

The aim of the experiment was to describe the formation of periodontal tissues in degree III furcation defects following GTR therapy. The study was performed in 8 foxhound dogs. The 2nd and 4th premolars in both sides of the mandible were extracted. Furcation defects were produced in the 3rd mandibular premolars. 3 weeks later, reconstructive surgery was performed. The dogs were scheduled for sacrifice 2, 4, 8, and 20 weeks after GTR therapy. Tissue blocks containing the experimental teeth were excised, demineralized in EDTA and embedded in paraffin. Serial sections were cut in the mesio-distal plane and parallel with the long axis of the roots. The microtome was set at 7 microns. The sections were stained in hematoxyline and eosin. From each biopsy, 3 sections representing the central part of the furcation, were selected for light microscopic examination. In the healed furcation sites, descriptive histological analysis of the newly-formed tissues was performed and the relative proportions of the hard and soft tissues were determined. It was demonstrated that at 2 weeks, the furcation defect contained granulation tissue and cell-rich connective tissue, while at 4 weeks the furcation was mainly occupied by connective tissue. At 8 weeks, woven bone occupied the central portion of the furcation, whereas connective tissue and cementum were observed in the lateral portions. The furcation area at 20 weeks was comprised of newly-formed cementum, periodontal ligament and bone. The onset of cementum formation had started as early as 2 weeks after GTR therapy. The cementum formation apparently occurred in 3 phases: organisation of collagen fibers adjacent and perpendicular to the root surface (phase 1), assembly of the collagen fibers and deposition of matrix (phase 2), and addition of cells and collagen fibers organised parallel to the root surface (phase 3). Bone formation took place through a process that included (1) organisation of a fibrous connective tissue, (2) differentiation of this tissue into woven bone and, (3) maturation of the woven bone into lamellar bone and bone marrow.

Periodontal regeneration with enamel matrix derivative in one human experimental defect. A case report

The purpose of the present study was to histologically assess the effect of enamel matrix derivative on periodontal regeneration in one human experimental defect. Experimental surgery was performed in a healthy male volunteer to create a buccal dehiscence defect in a mandibular incisor. Following bone removal and conditioning of the exposed root surface, enamel matrix derivative was applied onto the root surface. The flaps were then replaced and sutured. Clinical healing was uneventful. After 4 months, the experimental tooth together with the surrounding soft and hard tissues were removed surgically for histological evaluation. The microscopic examination revealed formation of a new acellular extrinsic fibre cementum, which was firmly attached to the underlying dentin. A new periodontal ligament with inserting and functionally-oriented collagen fibres and an associated alveolar bone was also present. The new cementum covered 73% of the original defect. Regain of bone was 65% of the presurgical bone height. It was concluded that adjunctive use of enamel matrix derivative could provide a regenerative technology with a potential for true periodontal regeneration.

Healing of intrabony defects and its relationship to root canal therapy. A histologic and histometric study in dogs

The purpose of this study was to evaluate the importance of root canal therapy in the healing process of severe intrabony defects. Four beagle dogs were used and 32 interproximal intrabony defects, up to the apical third, were created. Wire ligatures were placed into these defects for plaque accumulation. Three weeks later, the ligatures were removed and 4 different treatment modalities were employed: group 1) scaling and root planing (SRP); group 2) modified Widman flap (MWF); group 3) modified Widman flap and root canal therapy performed at the same time (RCT/MWF); and group 4) modified Widman flap and root canal therapy performed 3 weeks after the surgical procedure (MWF + RCT). Postoperative oral hygiene was obtained by spraying a 0.12% chlorhexidine solution 3 times a week. The animals were sacrificed 7 weeks after treatment. Blocks were obtained and processed for routine histology. Results were expressed as a percentage of the total defect length (TDL). No differences were observed when SRP was compared to MWF. New bone formation (BF) presented better results for SRP (43.4%) and MWF (53.4%) when compared to RCT/MWF (15.5%). New cementum formation (CF) presented better results for SRP (59.8%) and MWF (64.6%) when compared to RCT/MWF (19.3%) and MWF + RCT (31.5%). Connective tissue repair (CTR) presented better results for SRP (72.4%) and MWF (74.2%) when compared to RCT/MWF (47.5%) and MWF + RCT (44.4%). Results were statistically significant at the level of 0.05. Within the limits of this study, it was concluded that root canal therapy performed simultaneously or 3 weeks after surgery modified the healing of intrabony defects, impairing new bone formation, new cementum formation and new attachment.

Collagen gel and membrane in guided tissue regeneration in periodontal fenestration defects in dogs

The effect of a collagen gel matrix as a submembranous space-maintaining material was evaluated in guided tissue regeneration procedures. In 4 dogs, contralateral surgical circular fenestration defects, 5 mm in diameter, were produced at the midbuccal aspect of the alveolar bone in 8 maxillary canines. Removal of bone, PDL and cementum was complete. Experimental sites were filled with collagen gel and covered with collagen membranes; control sites were covered with collagen membranes and the underlying space was spontaneously filled with blood. Mucogingival flaps were repositioned. Histological and histomorphometric observations, 6 weeks post-surgery, indicated that defects covered by collagen membranes presented the most impressive regeneration with almost complete coverage of the denuded root by new cementum (98.4%) and new bone (63.2%). In the experimental defects, 83.5% coverage of new cementum with only 21.9% new bone regeneration was observed. These results suggest that collagen gel, interfered with healing by PDL and bone-derived cells in the submembranous space.

The origin of fibroblasts and their role in the early stages of horizontal furcation defect healing in the beagle dog

The origin of fibroblasts, their proliferative activity and roles in the early stages of periodontal repair were investigated in order to better understand the periodontal healing process in furcation defects of the beagle dog after guided tissue regenerative therapy. Newly divided cells were identified by immunolocalization of bromodeoxyuridine (BrdU) injected 1 hour prior to sacrificing the animals. At 1 and 2 weeks after creation of the defects, the lesions were occupied primarily by granulation tissue. Under this condition, periodontal ligaments (PDL) fibroblasts in a coronal portion of the remaining PDL close to wounds proliferated actively, migrated along the root surface and formed fibrous connective tissue on the surface. Similarly, the fibroblasts adjacent to the bone surface also showed proliferative activity and engaged in active formation of fibrous connective tissue on the bone surface. The majority of labeled cells in both areas were located in the extravascular area. At 3 and 4 weeks, the defects were filled with an increased amount of new connective tissue and bone. The labeled fibroblasts were preferentially found in the most coronal portion of connective tissue formed on the root surface that was in direct contact with inflamed tissue, and the collagen fibers projected into granulation tissue. In areas of active bone formation, numerous labeled fibroblasts were located in connective tissue adjacent to the newly-formed bone. However, fibroblasts in the endosteum of new bone were rarely labeled These results indicate that fibroblasts involved in periodontal repair originate primarily from both the remaining PDL and alveolar bone, and actively engage in fibrous connective tissue formation in the early stages of periodontal repair The ability of PDL fibroblasts to proliferate, migrate, and form connective tissue on the root surfaces in the early repair stages appears to play a crucial role in the formation of the PDL and cementum, and consequently, in periodontal regeneration in the absence of root resorption and ankylosis. As the formation of new connective tissue and bone continues, the precursor cells for fibroblasts and osteoblasts are supplied locally through the continued divisions of the fibroblastic cells in association with the newly-formed connective tissue. Paravascular and endosteal cells appear to be minor contributors to new cell population during furcation defect repair in the beagle dog.

Localization of uncalcified cementum in adult rat molar roots and its relation to physiological tooth movement

The study was designed to elucidate the effect of physiological tooth movement on cellular cementum, using the upper molar roots of 10-week-old rats. Paraffin sections stained with haematoxylin and eosin displayed two types of cellular cementum, lightly and darkly staining. The lightly stained was present on the distal half of all molar roots except the mesial root of the first molar. The alveolar bone facing the lightly stained cementum showed resorption lacunae and multinucleated osteoclasts, while the opposite bone surface was lined with osteoblasts. In contact microradiographs of undemineralized ground sections, the X-ray density of the lightly stained cementum was similar to that of the periodontal ligament and pulp, while the X-ray density of the darkly stained cementum was similar to that of alveolar bone. Tetracycline labelling lines were seen at the interface between the two types of cellular cementum as well as on surfaces of bone and cementum located mesially to the root dentine. The results suggest that the mechanical stress of tooth movement differently affects the alveolar bone and cellular cementum; the bone is resorbed whereas the cementum resists resorption and its calcification is inhibited under the compressive force of tooth movement.

Multi-nucleated cells remove the main hyalinized tissue and start resorption of adjacent root surfaces

Recent studies revealed that the initial root resorption occurred in the peripheries of the necrotic periodontal ligament (PDL) and was performed by mono-nucleated non-clast macrophage- and fibroblast-like cells (Brudvik and Rygh, 1993a, b). The aim of the present transmission electron microscopic (TEM) investigation was to study in more detail the cells involved in removal of the main hyalinized tissue and those involved in root resorption, occurring on the root surface situated beneath the main hyalinized tissue. Twelve male Wistar rats were used. The maxillary first molar was moved mesially by a fixed orthodontic appliance for 7 and 10 days. The results indicate that multi-nucleated giant cells (MNGC) without a ruffled border surface, as well as mono-nucleated macrophage-like cells were responsible for removal of the necrotic tissue and also for resorption of the surface parts of the root cementum. Although the present MNGC showed many morphological traits similar to the observed odontoclasts and osteoclasts, except for their lack of ruffled borders, it is assumed that they are derived from the mono-nucleated phagocytic system. Multi-nucleated clast-like cells with ruffled border were never observed near the remnants of the necrotic tissue. Such cells were found only in the resorption lacunae on root and bone surfaces.

Effect of root canal status on periodontal healing after surgical injury in dogs

This study was carried out to observe if the status of the root canal might influence the healing process of surgically prepared experimental periodontal lesions. Forty tooth roots from four dogs were divided into four different groups: a) root canals with vital pulps, b) root canals open to the oral environment, c) root canals infected and filled with zinc oxide eugenol cement, and d) root canals infected and filled with calcium hydroxide. By means of a surgical intervention, a cavity was prepared in the medium portion of the roots. Six months later, the specimens were removed and prepared for histological analysis. The results, which were submitted to statistical analysis, showed that the status of the root canals influenced the healing process of the experimental periodontal lesions. In the groups where the root canals were filled, calcium hydroxide gave the best results. In the group with root canals left open to the oral environment, resorption of the dentin of the experimental cavities, was the most obvious observation. However, it did not prevent the repair process, only slowed it down.