Effect of doxycycline on surgically induced osteoclast recruitment in the rat

Comprehensive reparative effects of bacteriostatic poly(L-lactide-co-glycolide)/poly(L-lactide-co-ε-caprolactone) electrospinning membrane on alveolar bone defects in progressive periodontitis

Periodontitis is a chronic inflammatory disease that leads to the loss of alveolar bone, among several studies focusing on reconstructing periodontal bone caused by periodontitis, guided bone regeneration (GBR) is a promising approach. In this study a serial clinically applied antibiotics loaded poly(L-lactide-co-glycolide)/poly(L-lactide-co-ε-caprolactone) (PLGA/PLCA) fibrous mesh to prevent and reconstruct defective bone in periodontitis were prepared by electrospinning. Incorporation of antibiotics promoted the hydrophilicity but decreased the crystallinity of PLGA/PLCA membranes. Antibiotics could be sustained released from membranes. Metronidazole, minocycline, and doxycycline incorporated membranes could suppress Porphyromonas gingivalis (P. gingivalis) within 21 days in vitro. Metronidazole and minocycline incorporated membranes decreased 41% and 55.5% colony counts in rat gingival crevicular fluid in vivo. Minocycline-loaded membrane could support the proliferation of MC3T3-E1 cells and maintained 79% viability of human ligament fibroblasts cultured on it. And MC3T3-E1 cells could undergo osteoblastic differentiation when cultured with pure PLGA/PLCA membrane and minocycline incorporated membrane. Then in vivo repairable effects of those antibiotics loaded membranes were evaluated in alveolar bone defected P. gingivalis infected model. The application of minocycline loaded membranes, effectively prevented the bone resorption of periodontitis caused by P. gingivalis. After been treated with minocycline incorporated membrane, volume of defected bone of maintained at about 50% level of control rats. 8 weeks post-operation, newly regenerated bone was observed in the operative alveolar bone of the pure PLGA/PLCA membrane, metronidazole and minocycline incorporated PLGA/PLCA membrane treated groups. Minocycline/PLGA/PLCA electrospinning membrane is a promising GBR material that can be applied to guide regeneration of periodontitis-induced alveolar bone damage.

Doxycycline induces bone repair and changes in Wnt signalling

Doxycycline (DOX) exhibits anti-inflammatory and MMP inhibitory properties. The objectives of this study were to evaluate the effects of DOX on alveolar bone repair. Controls (CTL) and DOX-treated (10 and 25 mg·kg^-1) molars were extracted, and rats were killed 7 or 14 days later. The maxillae were processed and subjected to histological and immunohistochemical assays. Hematoxylin-eosin staining (7th day) revealed inflammation in the CTL group that was partly reversed after DOX treatment. On the 14th day, the CTL group exhibited bone neoformation, conjunctive tissue, re-epithelization and the absence of inflammatory infiltrate. DOX-treated groups exhibited complete re-epithelization, tissue remodelling and almost no inflammation. Picrosirius red staining in the DOX10 group (7th and 14th days) revealed an increased percentage of type I and III collagen fibres compared with the CTL and DOX25 groups. The DOX10 and DOX25 groups exhibited increases in osteoblasts on the 7th and 14th days. However, there were fewer osteoclasts in the DOX10 and DOX25 groups on the 7th and 14th days. Wnt-10b-immunopositive cells increased by 130% and 150% on the 7th and 14th days, respectively, in DOX-treated groups compared with the CTL group. On the 7th day, Dickkopf (Dkk)-1 immunostaining was decreased by 63% and 46% in the DOX10 and DOX25 groups, respectively. On the 14th day, 69% and 42% decreases in immunopositive cells were observed in the DOX10 and DOX25 groups, respectively, compared with the CTL group. By increasing osteoblasts, decreasing osteoclasts, activating Wnt 10b and neutralising Dkk, DOX is a potential candidate for bone repair in periodontal diseases.

Dramatic osteonecrosis of the jaw associated with oral bisphosphonates, periodontitis, and dental implant removal

INTRODUCTION

Osteoporosis affects millions of elderly patients, and anti-resorptive drugs (ARD) such as bisphosphonates (BP) represent the first-line therapy. Despite the benefits related to the use of these medications, osteonecrosis of the jaw is a significant complication in a subset of patients receiving these drugs.

CASE PRESENTATION

This report documents a case of dramatic bisphosphonate-related osteonecrosis associated with periodontitis and dental implant removal in an osteoporotic patient treated with per os bisphosphonates for an uninterrupted period of 15 years.

CONCLUSION

The aim of this report was to discuss the administration period of BP in the treatment of osteoporosis, the decision-making and clinical management of severe MRONJ and the indications for dental implant placement in these specific patients.

Bone regeneration using porous titanium particles versus bovine hydroxyapatite: a sinus lift study in rabbits

AIM

The first objective of this study was to qualitatively and quantitatively assess the bone formation process, particularly the long-term behavior and three-dimensional volume stability of subsinusal bone regeneration, using titanium (Ti) or bovine hydroxyapatite (BHA) granules, in a rabbit model. The second objective was to evaluate the effect of the hydration of the BHA particles with a therapeutic concentration of doxycycline solution on the osteogenesis and biomaterial resorption.

MATERIALS AND METHODS

Rabbits underwent a double sinus lift procedure using one of three materials: grade 1 porous Ti particles, BHA, or BHA hydrated with doxycycline solution (0.1mg/ml) (BHATTC). Animals were sacrificed after 1 week, 5 weeks, or 6 months. Samples were analyzed using µCT and nondecalcified histology.

RESULTS

The materials used in each of the three groups allowed an optimal bone formation; bone quantities and densities were not statistically different between the three groups. At 6 months, more stable three-dimensional volume stability was found with Ti and BHATTC (p=.0033). At 5 weeks and 6 months, bone to material contact corroborating osteoconduction was significantly higher with BHA and BHATTC than with Ti (p<.0001).

CONCLUSIONS AND CLINICAL IMPLICATIONS

Even though the studied biomaterials displayed different architectures, they are relevant candidates for sinus lift bone augmentation prior to dental implants because they allow adequate three-dimensional stability and osteogenesis. However, to recommend the clinical use of Ti, both an observation on the drilling effects of Ti particles and clinical trials are needed.

Comparisons of the effects of systemic administration of L-thyroxine and doxycycline on orthodontically induced root resorption in rats

The aim of this study was to histologically evaluate and compare the effects of the systemic administration of L-thyroxine (TX) and doxycycline (DX) on orthodontically induced root resorption, Twenty-eight male 50- to 60-day-old Wistar rats were used. Seven rats served as the baseline control. Seven animals received TX (20 μg/kg bodyweight/day) and seven DX (1.2 mg/kg bodyweight/day), by means of a mini-osmotic pump implanted subcutaneously. Seven rats were separated as a sham, in order to evaluate the pure effect of the surgical procedure on the animals' health. Tooth movement (TM) was achieved with a continuous force of 50 g by placing Elgiloy coil springs between the right maxillary first molar and incisors for 14 days. The animals were sacrificed and specimens containing the appliance and maxillary tooth-bearing segments were processed for light microscopy. The surface area of root resorption lacunae was measured histomorphometrically using digital photomicrographs. To evaluate the resorptive changes on the molar root surface of each group, scanning electron microscopy (SEM) examinations were also carried out. Statistical evaluation of root resorption percentages was performed using Kruskal-Wallis analysis of variance test. Multiple comparisons were determined by the Student-Newman-Keuls method. The level of significance was set at P < 0.05. Histomorphometric analysis of root resorption, expressed as a percentage, showed that the average relative root resorption affecting the maxillary molars on the TM side was 0.32 ± 0.25 in the TX and 0.26 ± 0.06 in the DX groups and 2.19 ± 0.86 in the control. Statistically significant inhibition of root resorption was determined both in the TX and DX groups (P < 0.001) on the TM side. There was no statistically significant difference in relative root resorption between the TX and DX groups. Systemic administration of TX and DX demonstrated similar effects on root resorption in rats and may have inhibitory effects on orthodontically induced resorptive activity.

Low-dose doxycycline inhibits bone resorption associated with apical periodontitis

AIM

To test the effect of low-dose doxycycline on bone resorption associated with apical periodontitis.

METHODOLOGY

Apical periodontitis was induced by occlusal pulp exposure in the mandibular first molars of 36 rats. Animals were divided into three groups of 12: group A received doxycycline in drinking water at a dose of 5.85 mg day(-1); group B received a dose of 1.48 mg day(-1) (one-quarter of the original dose); and group C received no medicament and served as the control. A bioassay determined the doxycycline serum levels. After 21 days, the mandibles were removed, radiographed and the radiographs scanned to generate digital images. These images were analysed morphometrically and the total area of the periapical bone resorption of the mesial and distal roots of each tooth was determined and used to compare the groups. Statistical analysis was completed using anova with repeated measures.

RESULTS

The mean doxycycline serum level in group A was 0.22(+/-0.03) microg mL(-1) and in group B below the detection level of the assay (<0.062 microg mL(-1)). The mean area of the periapical bone resorption in the control group C was 2.91(+/-0.61) mm(2). In animals treated with a low-dose doxycycline, the mean size of the bone resorption was significantly smaller at 1.59(+/-0.59) mm(2) (group A) and 1.72(+/-0.85) mm(2) (group B) (P = 0.001). No significant difference was found in the area of the bone resorption between these two groups A and B.

CONCLUSIONS

Low-dose doxycycline reduced the area of bone resorption associated with apical periodontitis in the mandibular first molar teeth of rats.

Alveolar bone loss and aging: a model for the study in mice

BACKGROUND

Several animal studies have shown a positive correlation between aging and alveolar bone loss (ABL). The purpose of this study was to develop a model for the study of ABL in mice and aging.

METHODS

Mucoperiosteal flap surgery (MFS) was performed on the buccal aspect of the left side of the mandible (BL) in 72 CF(1) Mus domesticus mice and divided into three groups as follows: males, breeding (non-virgin) females, and virgin females. The MFS was performed in 3-, 6-, 9-, and 12-month-old animals under anesthesia. The buccal aspects of right hemimandibles were used as controls (BR). Animals were sacrificed under anesthesia 21 days after surgery. Mandibles were removed, defleshed, stained with toluidine blue, and photographed in a microscope. The photographs were digitized, and ABL was measured as the exposed root surface area (mm(2)). Blinded measurements were performed using a computer-assisted image analysis system.

RESULTS

In terms of alveolar bone loss, the BL (operated) area showed a significant difference (paired Student t test; P <0.001) when compared to the BR area in all three groups. Sex and breeding differences were not observed in this experiment. ABL in the left hemimandibles was significantly larger in 3- (mean: 0.70; 95% confidence interval [CI]: 0.59 to 0.80) and 12-month-old animals (mean: 0.58; 95% CI: 0.46 to 0.71) than in 6- (mean: 0.39; 95% CI: 0.33 to 0.46) and 9-month-old animals (mean: 0.42; 95% CI: 0.35 to 0.48); P <0.001.

CONCLUSION

The results suggest that 3-month-old CF(1) mice, in a sex and breeding independent process, could be a useful model for provoked alveolar bone loss studies in aging.

Histomorphometric evaluation of the effect of doxycycline on the healing of bone defects in experimental diabetes mellitus: a pilot study

PURPOSE

Bone healing is impaired in diabetes mellitus, particularly due to increased collagen breakdown. Recently, tetracyclines have been used to treat experimental bone defects because they have anticollagenolytic properties, and positive effects on the healing process have been obtained. The objective of this study was to develop a computer-assisted histomorphometric technique to quantitatively determine the amount of regenerating bone within experimental bone defects in a diabetic rodent model.

MATERIALS AND METHODS

This study examined the effects of systemic doxycycline administration on the healing of tibial bone defects in healthy albino rats and in experimentally induced diabetic rats. Twenty-four female albino rats were assigned to 4 groups: diabetic, diabetic plus doxycycline, control, or control plus doxycycline. The standardized bone defects were histomorphometrically examined 10 and 30 days postoperatively. Histomorphometric analysis of the amount of new bone formation was performed using the Zeiss Vision image analysis program KS 400 (Kontron Elektron GmbH, Eching, Germany).

RESULTS

At 10 days of healing, the diabetic groups exhibited inferior healing compared with the control groups in terms of the amount of new bone formation within the defects. However, the effect of doxycycline administration to the diabetic and control groups was not statistically different. At 30 days of healing, there were no statistically significant differences between the amount of newly formed bone in any of the groups.

CONCLUSIONS

This study found that doxycycline administration did not significantly alter the amount of new bone formation during the healing of bone defects in control and diabetic rats.

Low-dose doxycycline prevents inflammatory bone resorption in rats

Matrix metalloproteinases (MMP) are considered to be key initiators of collagen degradation, thus contributing to bone resorption in inflammatory diseases. We determined whether subantimicrobial doses of doxycycline (DX) (< or =10 mg kg-1 day-1), a known MMP inhibitor, could inhibit bone resorption in an experimental periodontitis model. Thirty male Wistar rats (180-200 g) were subjected to placement of a nylon thread ligature around the maxillary molars and sacrificed after 7 days. Alveolar bone loss (ABL) was measured macroscopically in one hemiarcade and the contralateral hemiarcade was processed for histopathologic analysis. Groups of six animals each were treated with DX (2.5, 5 or 10 mg kg-1 day-1, sc, 7 days) and compared to nontreated (NT) rats. NT rats displayed significant ABL, severe mononuclear cell influx and increase in osteoclast numbers, which were significantly reduced by 5 or 10 mg kg-1 day-1 DX. These data show that DX inhibits inflammatory bone resorption in a manner that is independent of its antimicrobial properties.

Human periodontal ligament fibroblast behavior on chemically conditioned dentine: an in vitro study

BACKGROUND

Chemical root conditioning is widely used in an attempt to improve the outcome of regenerative periodontal surgery, but its effect on connective tissue cell proliferation and biosynthetic activity has been poorly studied. The goal of the present study was to test in vitro the consequences of conditioning human dentine by citric acid or minocycline on the behavior of attached human periodontal ligament (HPDL) cells in terms of proliferation, protein synthesis and morphological appearance.

METHODS

HPDL cells were seeded on powdered human dentine, either untreated or conditioned for 3 minutes with 3% citric acid or 2.5% minocycline HCI. Scanning (SEM) and transmission (TEM) electron microscopic observations were performed, and 3H-thymidine and 3H-proline incorporation tests were used to evaluate the proliferative and the biosynthetic activities.

RESULTS

Cell spreading was already evident and the penetration of cytoplasmic processes into dentinal tubules were frequently observed on all dentine types after 2 hours of attachment. After 24 hours of incubation, citric acid conditioning promoted an intense spreading of the cells, while minocycline HCI conditioning induced the formation of a dense feltwork of cellular processes. HPDL fibrolasts adherent to both types of surface-conditioned dentine exhibited a significantly higher rate of proliferation (P<0.01) as well as a significantly higher level of total protein and of collagen synthesis (P<0.01) than on untreated dentine.

CONCLUSIONS

These data suggest that during periodontal surgery a conditioning of the root surface by citric acid or by minocycline HCI could promote the attachment, the proliferation, and the biosynthetic activity of HDPL, prerequisites to periodontal regeneration.

In vitro stimulation of human gingival epithelial cell attachment to dentin by surface conditioning

BACKGROUND

Chemical root conditioning is widely used to improve the outcome of regenerative periodontal therapies by favoring the attachment of the regenerated periodontal structures. Although the effect of root conditioning on periodontal mesenchymal cells is well documented, very little is known about its potential effect on the re-formation of the junctional epithelium, a crucial event for the protection of the wound. The goal of the present study was to test in vitro the consequences of dentin conditioning with citric acid or minocycline on the attachment kinetics and morphology of human gingival keratinocytes (HGK).

METHODS

The attachment kinetics of HGK to samples of powdered human dentin (particle size 44 to 76 microm) were examined by use of 3H-labeled cells. The morphology of attached epithelial cells was then determined by scanning electron microscopy (SEM).

RESULTS

When the initial adhesion kinetics of cells on untreated dentin were tested, the percentage of attached HGK proved to be dependent on the number of plated cells and the time of incubation (from 0 to 12 hours). Conditioning the dentin by 3% citric acid or by minocycline-HCl (at 0.01, 0.1, or 2.5%) significantly increased (P <0.005) keratinocyte attachment beyond 6 hours, without notable differences between the 2 substances at any concentration. The attachment kinetics of HGK preincubated for 24 hours by 10 microg/ml minocyline-HCl on untreated dentin was found to be similar to that observed for non-preincubated cells. These results are in agreement with the SEM observations: indeed, the surface conditioning of dentin significantly modified the morphology of attached HGK, whereas the preincubation of these cells with minocyline-HCl did not.

CONCLUSIONS

These results suggest that minocycline-HCl does not exert a direct effect on human gingival epithelial cells. In contrast, conditioning the dentin by citric acid or by minocycline stimulates the attachment of HGK, which could lead to a rapid periodontal healing by favoring the re-formation of a junctional epithelium.