Ultrasonic irrigation of periodontal pocket with surface pre-reacted glass-ionomer (S-PRG) nanofiller dispersion improves periodontal parameters in beagle dogs.

OBJECTIVES: Surface pre-reacted glass-ionomer (S-PRG) nanofiller, an antibacterial ion-releasing bioactive glass, has been shown to adhere to tooth surfaces and reported to improve inflammatory parameters in experimental periodontitis. In this study, cementum substrate was irrigated ultrasonically with dispersion to examine in-vitro nanofiller adhesion and antibacterial activity. Moreover, periodontal pockets in a beagle dog were ultrasonically irrigated with dispersion to assess periodontal healing. METHODS: The morphology of human cementum irrigated with S-PRG nanofiller dispersion was examined by scanning electron microscopy and energy dispersive X-ray spectrometry. The antibacterial activity of the treated cementum was tested using Actinomyces naeslundii. In addition, experimentally formed periodontal pockets in beagle dog were ultrasonically irrigated with S-PRG nanofiller dispersion. Periodontal parameters (gingival index, bleeding on probing, probing pocket depth, and clinical attachment level) were measured from baseline (0 weeks) through 12 weeks. Moreover, the effects of irrigation with S-PRG nanofiller on changes in periodontal microflora and bone healing were analyzed. RESULTS: After ultrasonic irrigation, S-PRG nanofiller adhered to the cementum and exhibited antibacterial activity. The periodontal parameters were shown to improve following ultrasonic irrigation with S-PRG nanofiller dispersion. Analysis by next-generation sequencing revealed that the ratio of red-complex species decreased in the pockets irrigated with S-PRG nanofiller dispersion. In addition, the S-PRG nanofiller showed the potential to promote bone healing. CONCLUSIONS: Ultrasonic irrigation with S-PRG nanofiller dispersion using an ultrasonic scaler system permitted delivery of the S-PRG nanofiller to the root surface, providing improved parameters in experimental periodontitis and modifying the composition of subgingival periodontal microflora.

Periodontal tissue engineering using an apatite/collagen scaffold obtained by a plasma- and precursor-assisted biomimetic process.

BACKGROUND AND OBJECTIVES: In the treatment of severe periodontal destruction, there is a strong demand for advanced scaffolds that can regenerate periodontal tissues with adequate quality and quantity. Recently, we developed a plasma- and precursor-assisted biomimetic process by which a porous collagen scaffold (CS) could be coated with low-crystalline apatite. The apatite-coated collagen scaffold (Ap-CS) promotes cellular ingrowth within the scaffold compared to CS in rat subcutaneous tissue. In the present study, the osteogenic activity of Ap-CS was characterized by cell culture and rat skull augmentation tests. In addition, the periodontal tissue reconstruction with Ap-CS in a beagle dog was compared to that with CS. METHODS: The plasma- and precursor-assisted biomimetic process was applied to CS to obtain Ap-CS with a low-crystalline apatite coating. The effects of apatite coating on the scaffold characteristics (i.e., surface morphology, water absorption, Ca release, protein adsorption, and enzymatic degradation resistance) were assessed. Cyto-compatibility and the osteogenic properties of Ap-CS and CS were assessed in vitro using preosteoblastic MC3T3-E1 cells. In addition, we performed in vivo studies to evaluate bone augmentation and periodontal tissue reconstruction with Ap-CS and CS in a rat skull and canine furcation lesion, respectively. RESULTS: As previously reported, the plasma- and precursor-assisted biomimetic process generated a low-crystalline apatite layer with a nanoporous structure that uniformly covered the Ap-CS surface. Ap-CS showed significantly higher water absorption, Ca release, lysozyme adsorption, and collagenase resistance than CS. Cell culture experiments revealed that Ap-CS was superior to CS in promoting the osteoblastic differentiation of MC3T3-E1 cells while suppressing their proliferation. Additionally, Ap-CS significantly promoted (compared to CS) the augmentation of the rat skull bone and showed the potential to regenerate alveolar bone in a dog furcation defect. CONCLUSION: Ap-CS fabricated by the plasma- and precursor-assisted biomimetic process provided superior promotion of osteogenic differentiation and bone neoformation compared to CS.

Antibacterial coating of tooth surface with ion-releasing pre-reacted glass-ionomer (S-PRG) nanofillers.

OBJECTIVES: Surface pre-reacted glass-ionomer (S-PRG) fillers release antibacterial borate and fluoride ions. We fabricated nanoscale S-PRG fillers (S-PRG nanofillers) for antibacterial coating of tooth surfaces and assessed the antibacterial effects of this coating in vitro. In addition, we creating a canine model of periodontitis to evaluate the effectiveness of S-PRG nanofiller application on tooth roots and improvement of periodontal parameters. METHODS: Human dentin blocks were coated with S-PRG nanofiller (average particle size: 0.48 µm) and then characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), and ion-releasing test. Antibacterial effects of dentin blocks coated with S-PRG nanofiller were examined using bacterial strains, Streptococcus mutans and Actinomyces naeslundii. Next, we created an experimental model of periodontitis in furcation of premolars of beagle dogs. Then, S-PRG nanofiller coating was applied onto exposed tooth root surfaces. Periodontal parameters, gingival index (GI), bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment level (CAL), were measured from baseline until 4 weeks. In addition, bone healing was radiographically and histologically examined. RESULTS: SEM and EDX revealed that S-PRG nanofillers uniformly covered the dentin surface after coating. Dentin blocks coated with S-PRG nanofiller showed ion-releasing property, bacterial growth inhibition, and sterilization effects. In the experimental periodontitis model, S-PRG nanofiller coating significantly reduced clinical inflammatory parameters, such as GI (P < 0.01) and BOP (P < 0.05), compared to uncoated samples. In addition, PPD and CAL significantly decreased by S-PRG nanofiller coating (2 weeks: P < 0.05; 3 and 4 weeks: P < 0.01), suggesting the improvement of periodontitis. Micro-CT and histology revealed that bone healing of furcation defects was enhanced by S-PRG nanofiller coating. CONCLUSION: S-PRG nanofiller coating provides antibacterial effects to tooth surfaces and improves clinical parameters of periodontitis.

Bone forming ability of recombinant human collagen peptide granules applied with ß-tricalcium phosphate fine particles.

Recombinant human collagen peptide, developed based on human collagen type I, contains an arginyl-glycyl-aspartic acid (RGD)-rich motif to enhance cell behavior and is anticipated as a xeno-free polymer material for use in tissue engineering. We fabricated granules containing recombinant human collagen peptide (RCP) applied with beta-tricalcium phosphate fine particles (RCP/ß-TCP) as bone filling scaffold material and assessed the bone forming ability of RCP/ß-TCP. Recombinant peptide was thermal crosslinked and freeze-dried to prepare RCP. An aqueous dispersion of ß-TCP fine particles was added to RCP to obtain RCP/ß-TCP. Subsequently, RCP/ß-TCP were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and cell culture assessments. Furthermore, RCP/ß-TCP were implanted into rat cranial bone defects for radiographic and histological evaluations. In SEM and EDX analyses of RCP/ß-TCP, ß-TCP particles dose-dependently covered the surface of RCP. Cell culture tests showed that RCP/ß-TCP remarkably promoted proliferation and mRNA expression of various genes, such as integrin ß1 and osteogenic markers, of osteoblastic MC3T3-E1 cells. Histomorphometric assessment at 4 weeks showed that RCP/ß-TCP significantly promoted new skull bone formation compared to RCP (p < 0.05) and control (no application) (p < 0.01). Accordingly, these findings suggest RCP/ß-TCP possess bone forming capability and would be beneficial for bone tissue engineering therapy.

Comparative biological assessments of endodontic root canal sealer containing surface pre-reacted glass-ionomer (S-PRG) filler or silica filler.

Surface pre-reacted glass-ionomer (S-PRG) filler releases several ions, such as fluoride, borate and strontium ions, to exert bioactive effects. We fabricated an endodontic root canal sealer containing S-PRG fillers (S-PRG sealer) and then evaluated the antibacterial and anti-inflammatory properties of S-PRG sealer compared with sealer containing conventional silica fillers (silica sealer). Antibacterial tests showed that S-PRG sealer significantly reduced the turbidity of Enterococcus faecalis compared with silica sealer. Implantation of S-PRG or silica sealer blocks in rat subcutaneous tissue showed that S-PRG sealer decreased the proinflammatory response compared with silica sealer at 10 days post-implantation. In addition, immunostaining revealed that infiltration of CD68- and peroxidase-positive cells around the S-PRG sealer was significantly lower than that in silica sealer. Therefore, it was suggested that S-PRG sealer exhibits antibacterial and anti-inflammatory effects.

Laser-assisted biomineralization on human dentin for tooth surface functionalization.

A technique for tooth surface modification with biocompatible calcium phosphate (CaP) has huge potential in dental applications. Recently, we achieved a facile and area-specific CaP coating on artificial materials by a laser-assisted biomimetic process (LAB process), which consists of pulsed laser irradiation in a supersaturated CaP solution. In this study, we induced the rapid biomineralization on the surface of human dentin by using the LAB process. A human dentin substrate was immersed in a supersaturated CaP solution, then its surface was irradiated with weak pulsed laser light for 30 min (LAB process). Ultrastructural analyses revealed that the pristine substrate had a demineralized collagenous layer on its surface due to the previous EDTA surface cleaning. After the LAB process, this collagenous layer disappeared and was replaced with a submicron-thick hydroxyapatite layer. We believe that the laser irradiation induced pseudo-biomineralization through the laser ablation of the collagenous layer, followed by CaP nucleation and growth at the dentin-liquid interface. The mineralized layer on the dentin substrate consisted of needle-like hydroxyapatite nanocrystals, whose c-axes were weakly oriented along the direction perpendicular to the substrate surface. This LAB process would offer a new tool enabling tooth surface modification and functionalization through the in situ pseudo-biomineralization.