Regeneration of periodontal ligament fibers around mini dental implants and their attachment to the bone in an animal model: A radiographic and histological study.

Background: Tissue-engineered periodontal ligament (PDL) around a dental implant by using PDL stem cells (PDLSCs) may be useful in periodontal regeneration and can reduce or eliminate certain shortcomings of dental implants. Materials and Methods: PDLSCs were isolated from extracted human PDL cells and cultured in a bioreactor. They were identified using markers CD45, CD73, CD90, CD105, and CD146. After the formation of multiple cellular layers, they were then attached on titanium mini dental implants and placed in rabbit tibia. The rabbits were sacrificed after 9 months, and the implants were analyzed histologically and radiographically by Cone beam computed tomography (CBCT). Results: Isolated PDLSCs obtained from human premolars showed a colony-forming ability on the 7th day and 14th day. Immunocytochemistry revealed that cells had taken up the adequate positive stains for primary antibodies CD73, CD90, CD105, and CD146 and negative staining for CD45. The histological sections obtained from sacrificed rabbits, when viewed under the light microscope, clearly showed the presence of PDL around dental implants. CBCT examination showed that the implant was well within the bone and did not migrate. The site appeared to be normal without any lytic changes in the bone. Conclusion: It can safely be postulated from the present study that tissue engineering of PDL can be achieved around dental implants using PDLSCs. Important inter-tissue interactions like the formation of a functional PDL around the implantation site, and induction of bone formation in the vicinity of the implants may be possible. Future research in humans is required for further research.

Three-Dimensional Finite Element Analysis of Maxillary Protraction Using Diverse Modes of Rapid Palatal Expansion.

INTRODUCTION: Three-dimensional finite elemental analysis (FEA) is a contemporary research instrument for the numeric simulation of a real physical system's mechanical process. FEA can be used as a very effective tool to analyze and compare various aspects of rapid palatal expanders and to determine the stress distribution in maxillofacial bones and displacement and the biomechanical effects it has on the circummaxillary sutures. This study evaluates the effects of different modes of rapid palatal expansion on maxillary protraction as a treatment modality in skeletal Class III malocclusion by determining the stress and displacement along the circummaxillary sutures using the FEA. MATERIALS AND METHODS: Initially, a three-dimensional finite element simulation of the maxillofacial skeleton and sutures was obtained by Mimics software (Leuven, Belgium) from the cone-beam computed tomography (Dentsply Sirona, USA) images of a 30-year-old adult with normal occlusion. A geometrical preparation of the three expansion appliances, (A) hybrid MARPE (miniscrew-assisted rapid palatal expander) appliance (Fav anchor, India), (B) tooth-borne HYRAX (hygenic rapid expander) appliance (Welcare orthodontics, Kerela), and (C) bone-borne modified MARPE appliance (Biomaterials, Korea), was transferred to ANSYS WORKBENCH, 2020 R1 software (ANSYS, Inc., USA), and three finite element models with each appliance were prepared. A protraction force of 500g was applied to the occlusal plane that is directed 20 degrees inferiorly. The tensile stress, compressive stress, and the amount of displacement on the circummaxillary sutures were assessed and compared in all the three appliances. Young's modulus (kg/mm2) and Poisson's ratio (V) were used to calculate the stress and displacement in sutures adjacent to the maxilla in different aspects. RESULTS: On analyzing the stress distribution, the tensile stress was found to be maximum in the medial aspect of the frontomaxillary suture of the bone-borne modified MARPE appliance (C), and the minimum tensile stress was found in the lateral aspect of the sphenozygomatic suture in hybrid MARPE (A). Again, the compressive stress distribution was found to be maximum in the medial aspect of the frontomaxillary suture in all three simulations and the minimum compressive stress in the superior aspect of the internasal suture in hybrid MARPE (A) along with the frontonasal suture at its medial aspect for tooth-borne HYRAX (B) and bone-borne modified MARPE (C). Displacement of the maxilla in all the planes was observed to be the largest for the bone-borne modified MARPE (C) appliance. On the contrary, the minimum displacement was found in the tooth-borne HYRAX (B) appliance.  Conclusion: The findings reveal that all three modes of rapid palatal expanders produced stress and displacement along the circummaxillary sutures on the application of protraction force with bone-borne modified MARPE being more effective in treating posterior crossbites thereby correcting the skeletal Class III malocclusions successfully.

Isolation and immunohistochemical characterization of periodontal ligament stem cells: A preliminary study.

CONTEXT: It is a known fact that periodontal tissue regeneration can be achieved by the use of periodontal ligament stem cells (PDLSCs). Current mainstay of periodontal treatment is focusing on stem cell tissue engineering as an effective therapy, making it important to isolate PDLSCs from periodontal tissues. AIMS: The present research endeavor was undertaken to elucidate a technique for isolating PDLSCs for in vivo reconstructing the natural PDL tissue. SETTINGS AND DESIGN: The study design involves In vitro prospective study. MATERIALS AND METHODS: Premolar teeth were extracted from 12 patients who were under orthodontic treatment. PDL cells were scraped from their roots. Using 10 ml of Dulbecco's modified Eagle's medium with pH 7.2, the specimens of the periodontal tissue were transferred to laboratory where cell culture was done. Isolated stem cells were grown on 24-well microtiter plates-containing cover slips. They were incubated overnight at approximately 37°C in 95% air and 5% humidification. Anti-CD 45, CD73, CD90, CD105, and CD146 antibodies were used. After staining, cells were observed under phase-contrast microscopy and in inverted microscope. RESULTS: The cells showed a marked growth and 90% confluence at day 6. Cells presented thin and long fibroblastic spindle morphology. Isolated PDLSCs showed colony-forming ability at the 14th day after seeding. Immunohistochemical staining of PDLSCs showed positive uptake for CD146, CD90, CD73, CD105, and negative uptake for CD45. CONCLUSIONS: The human PDLSCs can be clearly isolated and characterized by using CD90, CD73, CD146, and CD105 markers of stem cells.

Evaluation of the Effect of Different Types of Fluoride on Tensile Properties and Surface Roughness of Different Titanium-Based Archwires: An In vivo Study.

OBJECTIVES: The purpose of the study was to evaluate the effect of different types of fluoride on tensile properties and surface roughness of titanium based archwires clinically. MATERIALS AND METHODS: Three groups of archwires, namely nickel-titanium (NiTi), heat activated NiTi, and TMA was evaluated clinically. Each group comprised four subgroups, namely as received group, nonfluoride control group, APF gel group (received one application of 1.23% APF gel), and sodium fluoride mouthwash group (patients rinsed twice daily with 0.2% sodium fluoride mouthwash). All the archwires were removed after 3 weeks of clinical use and evaluated for surface roughness with three dimensional optical profiler. Tensile strength and elongation rate was determined with Instron universal testing machine. RESULTS: NiTi, heat activated NiTi, and TMA archwires with APF gel application showed the highest reduction in tensile strength and elongation rate and highest value for surface roughness, followed by sodium fluoride mouthwash group and finally wires without fluoride application. NiTi wires had the highest reduction in tensile strength with APF gel followed by heat activated NiTi and TMA. CONCLUSION: APF gel with highest concentration of fluoride caused most degradation in the tensile properties and surface roughness of titanium based arch wires.

Comparative antimicrobial efficacy of Metapex, Metronidazole, BioPure MTAD, Aztreonam on Bacteroides fragilis and Propionibacterium acne.

AIM: The purpose of this study was to evaluate the comparative antibacterial efficacy of Biopure MTAD, Metapex, Metronidazole, and Aztreonam against two obligate anerobic bacteria. MATERIALS AND METHODS: Antimicrobial efficacy of selected medicaments against two obligate anaerobic bacteria Bacteroides fragilis and Propionibacterium acnes was done by Agar disc-diffusion method. Pre-sterilized Whatman paper discs, 6 mm in diameter and soaked with the test solution, were prepared and placed onto the previously seeded agar Petri plates. Each plate was incubated in anaerobic jar for anerobic environment at 37°C for 48 hours. A zone of inhibition was recorded for each plate and the results were analysed statistically. Saline and ethanol used as control group in this study. RESULTS: Biopure MTAD, Metapex and Metronidazole were effective against all the selected microorganisms. Aztreonam was effective against Bacteroides fragilis. Saline and ethanol used as control were ineffective. CONCLUSIONS: Metronidazole showed the superior antibacterial property amongst the tested medicaments.

High-resolution crystal structure of AKR11C1 from Bacillus halodurans: an NADPH-dependent 4-hydroxy-2,3-trans-nonenal reductase.

Aldo-keto reductase AKR11C1 from Bacillus halodurans, a new member of aldo-keto reductase (AKR) family 11, has been characterized structurally and biochemically. The structures of the apo and NADPH bound form of AKR11C1 have been solved to 1.25 A and 1.3 A resolution, respectively. AKR11C1 possesses a novel non-aromatic stacking interaction of an arginine residue with the cofactor, which may favor release of the oxidized cofactor. Our biochemical studies have revealed an NADPH-dependent activity of AKR11C1 with 4-hydroxy-2,3-trans-nonenal (HNE). HNE is a cytotoxic lipid peroxidation product, and detoxification in alkaliphilic bacteria, such as B.halodurans, plays a crucial role in survival. AKR11C1 could thus be part of the detoxification system, which ensures the well being of the microorganism. The very poor activity of AKR11C1 on standard, small substrates such as benzaldehyde or DL-glyeraldehyde is consistent with the observed, very open active site lacking a binding pocket for these substrates. In contrast, modeling of HNE with its aldehyde function suitably positioned in the active site suggests that its elongated hydrophobic tail occupies a groove defined by hydrophobic side-chains. Multiple sequence alignment of AKR11C1 with the highly homologous iolS and YqkF proteins shows a high level of conservation in this putative substrate-binding site. We suggest that AKR11C1 is the first structurally characterized member of a new class of AKRs with specificity for substrates with long aliphatic tails.