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.     

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.     

Evaluation of stress patterns generated by reduction forceps within a photoelastic mandibular model.

INTRODUCTION: Little attention has been paid to the mechanical effects of fracture reduction forceps. AIM: This study aims to evaluate the stress patterns within the fractured mandible generated by reduction forceps. MATERIAL AND METHODS: Thirty-six mandibular models were fabricated using a photoelastic resin. Each of the three sets of mandibular models was osteotomized according to one of three different fracture types. After reducing the cut segments, reduction forceps were placed into different engagement holes to compress the segments. Photoelastic stress analysis was used to visualize the stress patterns within the fractured mandibular models as generated by the reduction forceps. RESULTS: In the case of symphyseal or parasymphyseal fractures, an optimum distribution of stresses over the fracture site was achieved when placing the reduction forceps more than 12mm away from either side of the fracture line, between the midway level of the mandibular height (bisecting the mandible) and 5mm below this level. In the case of body fractures, optimum stress distribution was achieved when the reduction forceps were placed more than 16mm from the fracture line at the midway level. CONCLUSION: Correct use of the reduction forceps helps to provide a precise three-dimensional reduction for mandibular fractures.     

Measuring the residual stress in dental composites using a ring slitting method.

OBJECTIVES: The objective of this experiment was to employ the ring slitting method for the measurement of the residual stress (RS) produced in dental composite materials after polymerization. This study was designed to determine the effect of slitting and measuring time on the residual stress. METHODS: Rings were made in a split brass mold from three composites (Z100/3MESPE; Herculite/Kerr; Heliomolar/Ivoclar) and cured in a Triad II (Dentsply). Two points were scribed, and the rings were slit at either 1 h (Early-group) or 24 h (Delayed-group) after curing the composite. The change in the distance between the scribed points was measured using an image analyzer system at both 1 and 24 h after slitting. From the measured change, circumferential RS was calculated and statistically analyzed with ANOVA/Tukey's (P<0.05). The degree of conversion of each composite at 1 and 24 h was measured with FTIR and analyzed using Student's t-test (P<0.05). RESULTS: In general, the residual stress (range=0.42-2.84 MPa) was highest for Z100 and lowest for Heliomolar, but this depended upon the test conditions. The early cut (1 h slitting), 24 h measurement groups showed the highest residual stress values. SIGNIFICANCE: This study, describes a ring slitting method to measure residual stress generated in dental composites during and after curing. The stress of composite can be affected by the cutting and measurement time.     

Group distal movement of teeth using microscrew implant anchorage

The purpose of this study was to quantify the treatment effects of distalization of the maxillary and mandibular molars using microscrew implants. The success rate and clinical considerations in the use of the microscrew implants were also evaluated. Thirteen patients who had undergone distalization of the posterior teeth using forces applied against microscrew implants were selected. Among them, 11 patients had mandibular microscrew implants and four patients had maxillary implants, including two patients who had both maxillary and mandibular ones at the same time. The maxillary first premolar and first molars showed significant distal movement, with no significant distal movement of the anterior teeth. The mandibular first premolar and first and second molars showed significant distal movement, but no significant movement of the mandibular incisor was observed. The microscrew implant success rate was 90% over a mean application period of 12.3 +/- 5.7 months. The results might support the use of the microscrew implants as an anchorage for group distal movement of the teeth.     

The role of hospital-based dentistry in providing treatment for persons with developmental delay

Hospital dentistry is important to the delivery of oral health care to persons with disabilities. Recent cuts in funding for hospital dentistry in Ontario have placed a great strain on the health care system"s ability to meet the demand for such care. General anesthesia is an accepted treatment option for patients who are uncooperative, but involves inherent risks. In this paper, we present the case of a person with developmental delay who received dental treatment under general anesthesia and subsequently developed complications to support the position that a dental program for persons with special needs should be provided in a hospital setting to minimize their risk of suffering serious complications and to ensure their safety.     

The association of osteoprotegerin gene polymorphisms with periodontitis

Background:  It has been demonstrated that genetic variation accounts for approximately half of the variance in periodontitis. The reported association of polymorphisms in the osteoprotegerin (OPG) gene with osteoporosis suggests that the OPG gene may also influence the genetic risk for periodontitis.
Subjects and methods:  We investigated the distribution of OPG gene polymorphisms in 49 patients with aggressive ( n  =   14) or chronic ( n  =   35) periodontitis and 49 control subjects without periodontitis, using polymerase chain reaction (PCR)–restriction fragment length polymorphism and PCR–single strand conformation polymorphism followed by direct sequencing.
Results:  A total of seven known polymorphisms and one new mutation, G373A, were identified. The T950 and G1181 alleles were more common in patients with periodontitis ( P  =   0.028 and P  =   0.047, respectively) than in control subjects. Especially, G1181 allele was associated with patients with aggressive periodontitis.
Conclusion:  The TG haplotype of T950C and G1181C polymorphisms in the OPG gene may be useful genetic markers for the prediction of periodontitis. Further studies in a larger population are required to determine whether these alleles directly contribute to periodontitis susceptibility.     

Sudden change of a large congenital melanocytic nevus to neurocutaneous melanosis

Neurocutaneous melanosis (NCM) is a congenital phakomatosis in which large congenital melanocytic nevi are associated with a benign or malignant melanocytic tumor of the leptomeninges. Because the prognosis of patients with symptomatic NCM is poor, it is essential to monitor the large congenital melanocytic patient regularly for a neurological evaluation. However, it has not been reported how quickly the lesion could appear. We observed a case of NCM suddenly developing in a large congenital melanocytic nevi patient. With this case, the NCM had developed within six months and was aggravated during the subsequent six months.