Effects of HB-EGF and epiregulin on wound healing of gingival cells in vitro

Oral Diseases (2011) 17 , 785–793 Objective: Gingival wound healing is important to periodontal disease and surgery. This in vitro study was conducted to assess the manner in which heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) and epiregulin cooperatively participate in the wound‐healing process in the gingival epithelial and fibroblast cells of the oral mucosa. Material and Methods: Gingival epithelium and fibroblast were separated from gingival tissue biopsies and prepared to primary cultures. The changes in the mRNA expression were evaluated via real‐time PCR. The effects on cell proliferation, migration, and repopulation were evaluated in vitro. Results: The different regulation of expressions of HB‐EGF, epiregulin, and epidermal growth factor receptors was observed over time and with different gingival cell types. HB‐EGF exerted a cell migration‐inducing effect on both epithelial and fibroblast cells, whereas epiregulin did not. Both growth factors functioned as mitogens for epithelial cell proliferation, but not for fibroblast proliferation. HB‐EGF strongly promoted epithelial cell repopulation and mildly promoted fibroblast repopulation, whereas epiregulin promoted only fibroblast repopulation. Conclusion: These results indicated that both growth factors might function importantly in the wound‐healing process of human gingival tissue via the different regulation of the expression, cell migration, proliferation, and repopulation.     

Effect of bisphosphonates on anodized and heat-treated titanium surfaces: an animal experimental study

Background: Recent investigations reported that osseointegration of titanium implants can be significantly reinforced with a nanostructure treated with anodic oxidation and heat treatment. This experimental study investigates the effect of bisphosphonates on the nanotubular implant surface in rats. Methods: Thirty‐six titanium implants were divided into three groups: 1) machine‐turned (MT), 2) anodized and heat‐treated (AH), and 3) anodized and heat‐ and bisphosphonate‐treated (AHB) groups. The 36 implants were randomly placed in both tibias of 18 male Wistar rats. After 2 and 4 weeks, the levels of osseointegration of the implants were evaluated by a removal torque test and microcomputerized tomography (μCT). Peri‐implant bone tissue on the extracted region was examined for the expression of type I collagen and osteocalcin. Results: The AHB group showed the highest removal torque at 2 and 4 weeks (13.92 ± 1.51 Ncm and 18.10 ± 2.15 Ncm, respectively) followed, in order, by the AH group (11.63 ± 1.58 Ncm at 2 weeks and 14.80 ± 2.34 Ncm at 4 weeks) and MT group (4.30 ± 0.76 Ncm at 2 weeks and 6.20 ± 1.33 Ncm at 4 weeks) with statistically significant differences between the MT and other two groups at both time points. μCT images also revealed a denser appearance around implants in the AHB group than in the other groups. Levels of type I collagen and osteocalcin expression were similar between the MT and AH groups; however, the values were significantly higher in the AHB group compared to the other groups, which were 220.85% ± 71.09% and 363.04% ± 100.21%, respectively (P <0.05). Conclusion: Within the limits of this experiment, it was concluded that surface loading with bisphosphonates significantly improved the degree of osseointegration of titanium implants with a nanostructure.     

Plasma-arc generated light inhibits proliferation and induces apoptosis of human gingival fibroblasts in a dose-dependent manner.

OBJECTIVE: This study examined the effects of blue light exposure on the proliferation and cytotoxicity of human gingival fibroblasts (HGF). Cellular mechanism by which blue light causes cytotoxic effects was also investigated. METHODS: HGF were exposed to the plasma-arc generated blue light with various energy densities ranging from 2 to 48J/cm(2). After light exposure of the cells, they were processed for analyzing tritium incorporation, succinate dehydrogenase (SDH) activity, trypan blue exclusion, and DNA fragmentation. In addition, possible mechanism of the light-mediated cytotoxicity was investigated through flow cytometric and Western blot analyses. RESULTS: Blue light exposure significantly inhibited proliferation and SDH activity of HGF in a dose-dependent manner; exposure more than 12J/cm(2) had a toxic effect on the cells. The blue light-induced cytotoxicity of the cells resulted from apoptosis, as proven by the migration of many cells to the sub-G(1) phase of cell cycle and the appearance of DNA ladders. Additional experiments revealed that blue light induces apoptosis of HGF through mitochondrial stress and poly (ADP ribose) polymerase cleavage. SIGNIFICANCE: This study suggests that plasma-arc generated blue light exerts some harm to cells, particularly damaging effect to DNA, and thus a long curing time more than recommended can cause biological damage on the oral tissue.     

Dental magnetic resonance imaging for periodontal indication – a new approach of imaging residual periodontal bone support

Objective: The standard imaging techniques used in dentistry consist of two-dimensional radiographic techniques like intraoral periapical (PA) radiographs, bitewings or extraoral panoramic X-rays. Three-dimensional methods, such as cone beam computed tomography (CBCT), are not standard procedures. In several fields of dentistry, such as oral surgery or implantology, dental magnetic resonance imaging (DMRI), a technique without radiation exposure, has already been introduced as a new promising diagnostic tool. The aim of this study was to compare the agreement of DMRI and PA radiographs in measuring residual periodontal bone support.

Material and methods: In this study, the residual periodontal bone support of 21 teeth was investigated and compared with DMRI and PA radiographs by two independent raters. Intra-class correlation coefficients (ICCs) were calculated using the software R to identify the intra-rater and inter-rater agreement of the two modalities. Bland–Altman plots were created to directly compare the two methods.

Results: Overall, all calculated ICC values showed an excellent intra-rater and inter-rater agreement (>0.9) for DMRI, as well as PA radiographs. Bland–Altman analysis also showed a strong agreement between both diagnostic methods in this study.

Conclusions: In conclusion, there was a strong agreement between DMRI and PA. Thus, DMRI proved to be a comparable method to PA radiographs for evaluating the proportion of residual periodontal bone support.     

Silicone rubber mould cast polyethylmethacrylate-hydroxyapatite plate used for repairing a large skull defect.

INTRODUCTION: Reconstruction of the cranial vault is performed for various reasons and precise repair of the defect is important. A modified method of cranioplasty is presented using three-dimensional (3D) models and polyethylmethacrylate mixed with hydroxyapatite, cast in a silicone rubber mould. PATIENT AND METHOD: A large custom made cranial implant was produced using data acquired from 3D computer tomography, rapid prototyping and cast in a silicone rubber mould. This plate was then applied to a 53 year-old man who had undergone a decompressive fronto-parieto-temporo-occipital craniotomy. The bone flap had been lost due to infection. The cranioplasty was performed at 1 year after the initial operation. RESULTS: The cranial plate fitted precisely into the defect and needed no correction at the time of surgery. The stability of the reconstruction plate was increased by the presence of thin margins allowed by silicone rubber elasticity. No complications occurred and the final functional and aesthetic results were good. CONCLUSION: The use of 3D imaging and rapid prototyping allow precise repair of large skull defects, with good aesthetic and functional results. At the same time, silicone rubber moulds permit the production of very thin details needed not only for cosmetic reasons but for reconstruction plate stability as well.     

A longitudinal controlled study of factors associated with mutans streptococci infection and caries lesion initiation in children 21 to 72 months old

PURPOSE: The purpose of this longitudinal study was to determine factors associated with mutans streptococci (MS) infection and development of caries lesions in a group of children 21 to 72 months old. METHODS: The 63 caries-free children, recruited since birth, were divided into: (1) a study group of 24 children who were colonized with MS; and (2) a control group of 39 children without MS. The children were recalled every 3 months for approximately 24 months, and their social, medical, and dental histories were updated. At each recall, the teeth were checked for presence or absence of plaque, enamel hypoplasia, and caries lesions, and their MS status was assessed using a commercial test kit. RESULTS: MS infection was associated with: (1) visible plaque (P < .01); (2) enamel hypoplasia (P < .05); (3) commencement of tooth-brushing after 12 months of age (P < .05); (4) lack of parental assistance with tooth-brushing (P < .025); and (5) increased hours of child care/school (P < .05). Four children (20%) were colonized at an age range of 21 to 36 months, 9 (45%) at 37 to 48 months, and 7 (35%) at 49 to 72 months (P < .001). Eight children who developed caries lesions: (1) had more hypoplastic teeth (P < .001); (2) ate sugar-containing snacks (P < .05); and (3) did not brush regularly with chlorhexidine gel (P < .01) compared to those who remained free of caries lesions. CONCLUSIONS: Lack of oral hygiene, consumption of sugar-containing snacks, and enamel hypoplasia are significant factors for both MS infection and caries lesion initiation.     

Effect of bismuth subgallate (local hemostatic agent) on wound healing in rats. Histological and histometric findings

The aim of this research was to evaluate the effect of bismuth subgallate on wound healing. In 40 Wistar rats, two standard wounds (3.5 mm x 2 mm) were made using a biopsy punch on the back of each animal. Test wounds were filled with bismuth subgallate and control wounds with 0.9% saline. At 1, 4, 7, 11 and 18 days, the qualitative evolution of the granulation tissue morphology was observed and digitalized histologic images were evaluated. There were no significant histological differences between test and control. Histometrically, there were statistically significant differences between test and control (ANOVA--days 1 and 4; Student t test, p < 0.05--days 7, 11 and 18) in terms of the following parameters: area of ulceration--day 1; distance between epithelial edges--day 4; area of granulation tissue--days 7, 11 and 18. It was concluded that bismuth subgallate is biocompatible to the healing tissue, and did not interfere with the normal development of wound healing.