Comparison of human alveolar osteoblasts cultured on polymer-ceramic composite scaffolds and tissue culture plates

The effects of medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) (80:20) scaffolds on primary human alveolar osteoblasts (AOs) were compared with standard tissue-culture plates. Of the seeded AOs, 70% adhered to and proliferated on the scaffold surface and within open and interconnected pores; they formed multi-layered sheets and collagen fibers with uniform distribution within 28 days. Elevation of alkaline phosphatase activity occurred in scaffold-cell constructs independent of osteogenic induction. AO proliferation rate increased and significant decrease in calcium concentration of the medium for both scaffolds and plates under induction conditions were seen. mPCL-TCP scaffolds significantly influenced the AO expression pattern of osterix and osteocalcin (OCN). Osteogenic induction down-regulated OCN at both RNA and protein level on scaffolds (3D) by day 7, and up-regulated OCN in cell-culture plates (2D) by day 14, but OCN levels on scaffolds were higher than on cell-culture plates. Immunocytochemical signals for type I collagen, osteopontin and osteocalcin were detected at the outer parts of scaffold-cell constructs. More mineral nodules were found in induced than in non-induced constructs. Only induced 2D cultures showed nodule formation. mPCL-TCP scaffolds appear to stimulate osteogenesis in vitro by activating a cellular response in AO's to form mineralized tissue. There is a fundamental difference between culturing AOs on 2D and 3D environments that should be considered when studying osteogenesis in vitro.     

Effect of systemic tetracycline and amoxicillin on inflammatory root resorption of replanted dogs' teeth

Abstract— The use of systemic penicillin after an avulsion injury has been recommended as a way to decrease the occurrence of resorption complications. Our previous study has shown systemic tetracycline to possess anti-resorptive properties independent of potential anti-bacterial actions. The purpose of this study was to compare histologically the effectiveness of tetracycline and amoxicillin in limiting inflammatory root resorption (IR) secondary to pulpal infection, in replanted dogs' teeth. Thirty root canals in five dogs were infected with plaque. The roots were extracted, the lingual mid-roots were shaved with a fissure bur ensuring cemental damage and immediately replanted. Dogs were given either tetracycline hydro-chloride or amoxicillin, administered orally, on the day of extraction and replantation and for the following 6 days. The control group was teeth in these animals treated in the same manner but where no antibiotics were given. After approximately 6 months, the dogs were sacrificed and the teeth prepared for histologic evaluation. The shaved root surface was identified in cross-sections and eight equidistant points along the cut root surface were evaluated for healing (H) or IR in eight sections per tooth. For the tetracycline group, H averaged 67.22% and IR 32.!8%, which was not statistically different from the amoxicillin group with H averaging 56.88% and IR 43.12%. The tetracycline group was superior to the control group with H= 27.86% and IR=72.14%. Since tetracycline has been shown to have anti-resorptive properties in addition to the antibacterial properties demonstrated here, it could be considered as an alternative to amoxicillin after avulsion injuries.     

Local dexamethasone improves periodontal healing of replanted dogs' teeth

Abstract— The purpose of the present investigation was to evaluate histologically the effect of dexamethasone on root resorption in stored and replanted dogs' teeth. Twenty-nine roots from three beagle dogs were endodontically treated to prevent subsequent inflammatory root resorption of pulpal origin. The teeth were extracted and randomly assigned to three groups for 18-h storage. Group 1: control group teeth ( n = 13) were stored in vials containing ViaSpan only; Group 2: topical treatment teeth ( n =10) were stored in vials containing ViaSpan and dexamethasone (16 μg/ml); and Group 3: systemic treatment teeth ( n =6) were stored in bids containing ViaSpan without any additives. Dexamethasone was administered intramuscularly (0.5 mg/kg body weight) 2 days prior to, on the day of, and every other day after extraction and replantation for two administrations. After 12 weeks, the dogs were sacrificed, and the teeth histologically prepared and evaluated according to the analysis of Andreasen. Significant differences were found for complete healing ( P= 0.0583) and inflammatory root resorption ( P= 0.0568) but not for replacement resorption ( P= 0.1952). In addition, comparing local to systemic administration of dexamethasone (Group 2 vs. Group 3), statistically significant differences were found for healing, 85% (Group 2) vs. 67% (Group 3) ( P =0.0125) and inflammatory root resorption, 13% (Group 2) vs. 28% (Group 3) ( P =0.0126). This study indicated that topical use of dexamethasone enhances healing and results in fewer resorption complications.     

Comparison of acidic fibroblast growth factor on collagen carrier with calcium hydroxide as pulp capping agents in monkeys

Acidic fibroblast growth factor (aFGF) has been shown to facilitate wound healing by stimulating fibroblast proliferation and angiogenesis. It has also been reported to possess a powerful anti-apoptotic function This study compared the histological pulp responses to aFGF on collagen carrier and Ca(OH)(2) placed on the mechanically exposed dental pulp in monkeys at two observation periods. Thirty-six teeth with pulp exposures were distributed into three groups according to the capping agents used prior to application of the coronal seal: collagen-based matrix carrier (group 1), aFGF on the collagen-based matrix carrier (group 2) and aqueous calcium hydroxide [Ca(OH)(2)] paste (group 3). Specimens were harvested at 6 and 13 weeks postoperatively and prepared for hematoxylin and eosin, and Gram staining. Histological qualitative evaluation of pulp responses were performed under the light microscope following criteria modified from Cox et al. (17) and Hu et al. (18). Semi-quantitative analysis was also carried out using Kruskal-Wallis and Mann-Whitney U-tests. There was neither negligible inflammatory infiltrates with no bacteria present in the three groups at both timings, nor was there any significant difference in the soft tissue organization among the three groups at or between the 6- and 13-week observation periods. At 6 weeks, the hard tissue barrier produced by Ca(OH)(2) group (1.040 +/- 0.089) was significantly more superior than aFGF/collagen carrier group (1.930 +/- 0.825) (P = 0.030) as well as collagen carrier group (3.142 +/- 1.069, P = 0.018). At 13 weeks, both aFGF/collagen carrier group (1.214 +/- 0.485) and the collagen carrier group (1.457 +/- 0.814) produced significantly better hard tissue barrier (P = 0.040 and P = 0.017, respectively) than earlier timing. However, these two groups did not induce significantly improved hard tissue barrier compared to that produced by aqueous Ca(OH)(2) paste which stimulated matrix secretion in a polar tubular dentin-like pattern.     

pH changes in root dentin after intracanal placement of improved calcium hydroxide containing gutta-percha points

The in vitro pH changes in root dentin over a period of 2 weeks was investigated in 48 extracted bicuspids after intracanal placement of either Roeko Calcium Hydroxide Plus Points, aqueous calcium hydroxide paste, or gutta-percha points (control group) after root canal preparation. Microelectrodes were placed in outer and inner root dentin at cervical, middle, and apical thirds of the root to measure the pH at 1 h, 2 h, 3 h, 1 day, 3 days, 7 days, and 14 days. Roeko Calcium Hydroxide Plus Points reached a peak inner dentine pH of 11.67 and a peak outer dentine pH of 10.82 at 3 h. In addition, Roeko Calcium Hydroxide Plus Points maintained an outer dentine pH above 9.5 for approximately 2 days, whereas the aqueous calcium hydroxide paste did not reach this pH. However, the alkalinity in dentin with Roeko Calcium Hydroxide Plus Points was maintained for 7 days only, whereas aqueous calcium hydroxide paste maintained an alkaline environment throughout the 2-week period.     

The effect of topical minocycline on replacement resorption of replanted monkeys' teeth

Abstract – Tetracycline has been reported to possess antiresorptive properties in addition to antimicrobial actions. Systemic administration of tetracycline showed variable results in the control of replacement resorption after replantation with good results in half of the cases, and almost no healing in the rest. The purpose of this study was to evaluate histologically the effect of topically applied minocycline on replacement resorption of replanted monkeys' teeth. Thirty‐two roots from seven monkeys were endodontically treated aseptically to prevent inflammatory resorption of pulpal origin, a common sequela after avulsion injury. Teeth were then extracted as atraumatically as possible. Teeth in the negative control group (10 roots) were replanted almost immediately, while teeth in the positive control group (12 roots) were allowed to bench‐dry for 1 h prior to replantation, both without further treatment. Teeth in the experimental group (10 roots) were bench‐dried for 1 h, rinsed with saline, and then immersed in 1 ml of 50 mg ml^?1 minocycline hydrochloride for 5 min before replantation. No splinting was used. After 12 weeks, the animals were sacrificed and histological sections were prepared and evaluated according to a morphometric analysis modified from that described by Andreasen (1987) as complete healing, inflammatory resorption, and replacement resorption. Kruskal–Wallis test showed significant differences among the three groups in all the three healing categories. Further analysis with Mann–Whitney U‐test showed teeth in the negative control group to have significantly higher complete healing and significant lower unfavorable healing, comprising of replacement resorption and inflammatory root resorption than the positive control group and the minocycline group. Topical application of minocycline to the root surface appeared to result in slightly higher occurrence of complete healing (32.46%) compared to the delayed replantation group with no minocycline treatment (positive control) (16.58%), but the difference was not statistically significant (P = 0.09).     

Tissue engineering of a periodontal ligament-alveolar bone graft construct

PURPOSE: This paper reports on a 2-phase study of a novel membrane-scaffold graft construct, its ability to support periodontal ligament fibroblast (PDLF) and alveolar osteoblast (AO) growth in vitro, and its use for tissue engineering a PDL-AO interface in vivo. MATERIALS AND METHODS: Human PDLFs were seeded onto perforated poly(epsilon-caprolactone) membranes (n=30) at 78,000 cells/cm2; human AOs were seeded on poly(epsilon-caprolactone) scaffolds (n=30) with fibrin glue at 625,000 cells/cm3. Cell attachment, morphology, viability, and metabolic activity were monitored for 3 weeks in vitro. Subsequently, cell-seeded membrane-scaffold constructs (experimental group, n=9) and nonseeded constructs (control group, n=4) assembled with fibrin glue were implanted subcutaneously into 7 athymic mice for 4 weeks. RESULTS: PDLFs formed confluent layers on membranes, whereas AOs produced mineralized matrices within scaffolds upon osteoinduction in vitro. Well-vascularized tissue formation was observed after implantation. Integration at the membrane-scaffold interface was enhanced in the experimental group. Type I collagen, type III collagen, fibronectin, and vitronectin were found adjacent to membranes and within constructs. Bone sialoprotein expression and bone formation were undetectable. DISCUSSION: Membrane perforation and scaffold porosity facilitated tissue integration and vascularization at the construct-recipient site. However, the interaction between PDLF and AO could have interfered with osteogenesis at the interface of soft and mineralizing tissues. CONCLUSIONS: Both matrices supported PDLF and AO attachment and proliferation in vitro. The membrane-scaffold construct facilitated tissue growth and vascularization while providing strength and form in vivo.     

Effectiveness of ProFile .04 taper rotary instruments in endodontic retreatment

This study investigated the retreatment effectiveness of .04 Taper nickel-titanium rotary ProFiles. Thirty extracted single-rooted anterior teeth were instrumented and obturated with gutta-percha/Roth's Sealer using lateral condensation. They were distributed into three groups of 10 each. Retreatment for group A was done using Profile alone, group B using Profile and chloroform, and group C using hand files with chloroform. The teeth were then split longitudinally into halves. The remaining gutta-percha/sealer on the root canal wall in the cervical, middle, apical thirds, and the whole canals were visually scored with the aid of light microscopes. The results showed that the mean scores in groups A and B were generally lower (better) than group C. Mean scores of the apical thirds tended to be higher (worse) than the middle and the cervical thirds, except in group A. ProFile with or without chloroform seemed to be a viable alternative retreatment method.