Eun-Kyoung Pang

Impact of different synthetic bone fillers on healing of extraction sockets: an experimental study in dogs

OBJECTIVES The objective of this study was to elucidate the socket healing process and biodegradation of incorporating synthetic bone fillers followed by grafting of the fresh extraction socket. MATERIALS AND METHODS Third premolars in four quadrants of eight beagle dogs were extracted and randomly treated with either one of hydroxyapatite (HA), biphasic calcium phosphate (BCP), β-tricalcium phosphate (β-TCP), or no graft (C). Histologic observations and histomorphometric analysis at three zones (apical, middle, and coronal) of the socket were performed. Socket area (S) and the proportions of newly formed bone (%NB), residual biomaterials (%RB), and fibrovascular connective tissue (%FCT) at 2, 4, and 8 weeks were measured. The numbers of osteoclast-like multinucleated cells (No.OC) were also determined at the three zones. RESULTS %NB was significantly higher in control group compared with the grafted groups at all healing periods. %NB of HA and BCP increased with time, whereas %RB showed different patterns that decreased in BCP, unlike the minimal change observed in HA. %NB of β-TCP showed smallest portion compared with other grafted groups at 2 and 4 weeks, however, significantly increased at 8 weeks. %RB of β-TCP was less than HA and BCP at all healing periods. Numbers of multinucleated cells were greater in BCP and β-TCP, followed by HA and smallest in control group. CONCLUSIONS Within the limit of this study, bone formation of the extraction socket was delayed in the sockets grafted with synthetic bone fillers and showed different healing process according to the biodegradation patterns.

Effects of adjunctive daily phototherapy on chronic periodontitis: a randomized single-blind controlled trial

Purpose The purpose of this randomized single-blind controlled trial was to elucidate the clinical and antimicrobial effects of daily phototherapy (PT) as an adjunct to scaling and root planing (SRP) in patients with chronic periodontitis. Methods The study was conducted from December 2013 to May 2014 at Ewha Womans University Mokdong Hospital, Seoul, Korea. Forty-one patients with mild to moderate chronic periodontitis were randomly divided into two therapeutic groups in a 1:1 ratio: SRP+PT and SRP (control) groups. All participants underwent full-mouth SRP. PT was performed thrice a day for a month by using electric toothbrushes with embedded light-emitting diodes. Plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and bleeding on probing were assessed before (baseline) and four weeks after (follow-up) the treatment. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia, Fusobacterium nucleatum, Parvimonas micra, Campylobacter rectus, Eikenella corrodens, Streptococcus mutans, and Streptococcus sobrinus levels were detected by a real-time polymerase chain reaction at the same points in time. Results The clinical parameters improved in both the groups. At the follow-up assessment, PPD was significantly decreased in the SRP+PT group (P=0.00). Further, PPD and CAL showed significantly greater changes in the SRP+PT group than in the SRP group (PPD, P=0.03; CAL, P=0.04). P. gingivalis and T. forsythia levels decreased in this group, but no significant intergroup differences were noted. Conclusions Adjunctive PT seems to have clinical benefits, but evidence of its antimicrobial effects is not sufficient. Long-term studies are necessary to develop the most effective PT protocol and compare the effectiveness of PT with and without exogenous photosensitizers. Graphical Abstract

Histomorphometric evaluation of onlay freeze-dried block bone and deproteinized bovine bone with collagen in rat

The aim of this study was to evaluate the effect of human freeze-dried bone block (FDBB) and deproteinized bovine bone with collagen (DBBC) on bone formation when applied as an onlay graft in rat calvariums. Thirty male Sprague-Dawley rats received collagen sponge (control), FDBB, or DBBC onlay grafts trimmed into 8-mm disks measuring 4-mm height. Each graft was secured onto the calvarium surface using horizontal mattress sutures. Rats in each group were killed at 2 (n=5) or 8 (n=5) weeks postoperatively for histologic and histomorphometric analysis. The total augmented area (mm2), new bone area (mm2), and bone density (%) were measured. The FDBB and DBBC groups showed significantly more new bone formation and bone density than the control group at 2 and 8 weeks. The increased new bone area was significantly greater in the FDBB group than in the DBBC group (p<0.05). The total augmented area was significantly higher in the FDBB and DBBC groups at 2 and 8 weeks than in the control group (p<0.05), and at 8 weeks, the area was significantly decreased in the DBBC group compared to that in the FDBB group and the area at 2 weeks (p<0.05). Within the limitations of the present study, we concluded that onlay FDBB and DBBC grafts caused new bone formation through an osteoconductive mechanism. In addition, compared to FDBB, DBBC had less capacity to form new bone and maintain the space.

The effect of human freeze dried corticocancellous block onlay graft on bone formation in rat calvarium

The aim of this study was to investigate the effect of an onlay graft of human freeze dried corticocancellous bone block (FDBB) on bone formation and the added effects of collagen membrane (CM) in rat calvarium. Thirty male Sprague-Dawley rats were treated with either collagen sponge (CS), FDBB or FDBB with CM. FDBBs were placed on the calvarium surface with the CM covered or not. Rats were sacrificed at 2 and 8 weeks after surgery for histologic and histomorphometric analysis. At each period, total augmented area (TA; mm2), new bone area (NB; mm2), and bone density (BD; %) were measured. In the FDBB and the FDBB/CM group, new bone formation began at the lateral and inferior margins of the grafted block and projected into the central region of the recipient-graft interface. The cancellous portion of the graft underwent increased resorption with time. FDBB showed a significant decrease in the TA between 2 and 8 weeks (p<0.05), regardless of combined use of the CM. NB significantly increased in FDBB between 2 and 8 weeks (p<0.05), and the CM showed significant additional effect on new bone formation at 8 weeks (p<0.05). BD significantly increased in FDBB between 2 and 8 weeks (p<0.05). Within the limits of the present study, it was concluded that the maintenance of volume was achieved with onlay grafting of FDBB in early healing period to show new bone apposition onto the rat calvarial surface. In addition, using of CM improved new bone formation within in the grafted area.

Effects of block bone substitutes loaded with Escherichia Coli-produced recombinant human bone morphogenetic protein-2 on space maintenance and bone formation in rat calvarial onlay model

We aimed to evaluate the effects of onlay-type grafted human freeze-dried corticocancellous bone block (FDBB) and deproteinized bovine bone with collagen (DBBC) loaded with Escherichia coli-produced recombinant human bone morphogenetic protein-2 (ErhBMP-2) on space maintenance and new bone formation in rat calvaria. Collagen sponge (CS), FDBB, or DBBC disks (8×4 mm) with ErhBMP-2 (2.5 μg) were implanted onto the calvaria of male Sprague-Dawley rats, whereas CS with buffer was implanted onto the calvaria as controls (n=20/carrier). Rats were killed at 2 or 8 weeks post-surgery for histologic and histomorphometric analyses; total augmented area, new bone area, and bone density were evaluated. At both time-points, all ErhBMP-2 groups showed significantly higher new bone area and bone density than the control group (p<0.05). ErhBMP-2/FDBB and ErhBMP-2/DBBC groups showed significantly higher total augmented area than ErhBMP-2/CS group (8 weeks), and ErhBMP-2/FDBB group showed significantly higher new bone area and bone density than ErhBMP-2/DBBC group (p<0.05). ErhBMP-2/CS group showed the highest bone density (p<0.05). Combining ErhBMP-2 with FDBB or DBBC could significantly improve onlay graft outcomes, by new bone formation and bone density increase. Moreover, onlay-grafted FDBB and DBBC with ErhBMP-2 could be an alternative to autogenous block onlay bone graft.

The effects of platelet-rich plasma on the proliferation and release of growth factors from periodontal ligament cells

Periodontal ligament cells (PDLCs) play an important role in the regeneration of periodontium. The healing potential of PDLCs may be due to the high concentration of growth factors in platelet-rich plasma (PRP). In this study, the effects of PRP on the proliferation and activation of PDLCs and growth factor release from PDLCs were investigated. PDLCs were isolated from third molars or premolars of healthy patients. Whole blood was obtained from healthy volunteers for the preparation of activated PRP. The platelet concentration in PRP was measured and the amount of platelet-derived growth factor (PDGF)-AB, PDGF-BB, transforming growth factor-β1 (TGF-β1), and vascular endothelial growth factor (VEGF) were determined by enzyme-linked immunosorbent assay. The effects of activated PRP on PDLC proliferation, attachment, alkaline phosphatase (ALP) activity, and growth factor release were investigated. Platelet concentration was increased 5.41-fold in PRP compared to whole blood. PDGF-AB, PDGF-BB, TGF-β1, and VEGF were detected in PRP at concentrations of 273.38 ng/mL, 47.0 ng/mL, 168.42 ng/mL, and 510.56 pg/mL, respectively. PDLCs cultured with ≥10% PRP showed significantly increased cell proliferation and ALP activity compared to the control (p<0.05). PDLCs cultured with 10% PRP also presented higher cell attachment and increased release of TGF-β1 and VEGF compared to the control (p<0.05). PRP can deliver high concentrations of growth factors to a defect site to increase the proliferation, attachment, and ALP activity of PDLCs. These results suggest that PRP might effectively contribute to periodontal regeneration.

Anterior maxillary defect reconstruction with a staged bilateral rotated palatal graft.

Purpose In the anterior maxilla, hard and soft tissue augmentations are sometimes required to meet esthetic and functional demands. In such cases, primary soft tissue closure after bone grafting procedures is indispensable for a successful outcome. This report describes a simple method for soft tissue coverage of a guided bone regeneration (GBR) site using the double-rotated palatal subepithelial connective tissue graft (RPSCTG) technique for a maxillary anterior defect. Methods We present a 60-year-old man with a defect in the anterior maxilla requiring hard and soft tissue augmentations. The bone graft materials were filled above the alveolar defect and a titanium-reinforced nonresorbable membrane was placed to cover the graft materials. We used the RPSCTG technique to achieve primary soft tissue closure over the graft materials and the barrier membrane. Additional soft tissue augmentation using a contralateral RPSCTG and membrane removal were simultaneously performed 7 weeks after the stage 1 surgery to establish more abundant soft tissue architecture. Results Flap necrosis occurred after the stage 1 surgery. Signs of infection or suppuration were not observed in the donor or recipient sites after the stage 2 surgery. These procedures enhanced the alveolar ridge volume, increased the amount of keratinized tissue, and improved the esthetic profile for restorative treatment. Conclusions The use of RPSCTG could assist the soft tissue closure of the GBR sites because it provides sufficient soft tissue thickness, an ample vascular supply, protection of anatomical structures, and patient comfort. The treatment outcome was acceptable, despite membrane exposure, and the RPSCTG allowed for vitalization and harmonization with the recipient tissue. Graphical Abstract

Effects of Slow Programmable Cryopreservation on Preserving Viability of the Cultured Periodontal Ligament Cells from Human Impacted Third Molar

Purpose: This study was conducted to determine cell viability and differentiation capability of human periodontal ligament (PDL) cells and to elucidate the effects of cryopreservation on the activity of human third molar PDL cells by comparing PDL cells with and without cryopreservation. Materials and Methods: Human PDL fibroblasts obtained from immature third molars were cultured and divided into two groups. The experimental group was cryopreserved with a slow freezing rate of 0.5℃/min from 4℃ to –35℃ followed by plunging in liquid nitrogen at –196℃ and cultured after fast thawing. The control group was cultured without cryopreservation. Cell viability, growth capacity and morphology were evaluated in both groups. Bivariate statistics were used to compare 2 groups and linear mixed model analysis was used to investigate the growth trends difference over time. Result: Cell viability and growth capacity were not significantly different between the 2 groups (P>0.05). Cultured cell of both groups showed fibroblast-like in appearance, and there were no significant differences in morphology between 2 groups. The mixed model analysis revealed no significant difference of growth capacity between 2 groups over time (β=–0.0009; P=0.138). Conclusion: This study demonstrates that cryopreservation under control does not affect the biological properties of PDL cells, supporting the feasibility of autotransplantation of cryopreserved impacted third molars.