Marita Luomanen

Myofibroblasts in healing laser excision wounds

The lack of myofibroblasts, cells responsible for wound contraction, has been suggested to be the underlying factor to the clinically observed minimal contraction in CO2 laser wounds. However, the histologic background to this phenomenon in laser excisions has not been thoroughly clarified. Therefore, we analyzed the expression of myofibroblasts in healing laser excisions and control excisions made by scalpel.

Transformation of Hydroxyapatite to Fluorapatite by Irradiation with High-Energy CO2 Laser

High-energy laser irradiation has been shown to cause crystalline transformations in apatites, which may lead to the formation of tricalcium phosphates with a resulting decrease in acid resistance. Depending on the nature and energy density of laser irradiation used, however, an increase of acid resistance of dental enamel has also been reported after laser irradiation. The aim of the present study was to investigate the phase transformation of hydroxyapatite (HA) to fluorapatite (FA) in a model system that incorporates sodium fluoride (NaF) into apatite structure by using laser irradiation. A CO2 laser was used at energy densities ranging from 21 to 500 J/cm2. Synthetic HA mixed with NaF (10:1) was the target of laser irradiation. The crystalline structures were then investigated using X-ray diffraction analysis. The results showed that a phase transformation of HA to FA could be realized, and that the threshold energy density needed was 38 J/cm2. Not only is the finding crystallographically important, but it also opens new perspectives for future research regarding the development of laser technology for clinical purposes.

Myofibroblasts in healing laser wounds of rat tongue mucosa

The distribution of myofibroblasts was studied in healing laser incisions compared with scalpel-incision and excision wounds in dorsal tongue mucosa and excision wounds in back skin. Myofibroblasts (m-f-b) were visualized by staining with NBD-phallacidin, a fluorescent probe specific for F-actin, and by electron microscopy. Few, randomly-orientated m-f-b were found in laser wounds over 28 days. Neither m-f-b nor contraction were seen in the scalpel-incisions. No contraction was observed in the laser wounds whereas an organized network of m-f-b with substantial contraction occurred in excision wounds. It is suggested that lack of contraction in laser wounds is partially due to the fewness of m-f-b. The residual connective tissue matrix resisting the laser treatment also seems to play a role in preventing the wound contraction.

Treatment of bisphosphonate-induced osteonecrosis of the jaws with Nd:YAG laser biostimulation.

Bisphosphonates are pharmaceuticals that are increasingly used in the treatment and management of bone disorders like osteoporosis, metabolic bone disease, and bone metastases associated with cancer and multiple myeloma. However, in recent years innumerous cases of necrosis of the jawbone have been documented in patients treated with bisphosphonates and consequently bisphosphonate-induced osteonecrosis of the jaws (ONJ-BP) has been described as a complication secondary to bisphosphonate therapy [1–4]. The risk for bone necrosis has proven to be considerably higher in those cases where bisphosphonates have been given intravenously than per os [3]. Osteonecrosis in patients medicated with bisphosphonates may establish in the maxilla, mandible, or both. Mandibular involvement is, however, more common. The exposed avascular necrotic bone becomes generally infected and the condition can be very painful for the patient, making eating and speaking difficult. If the necrosis is extensive and near the mandibular nerve, paresthesia of the lower lip may occur. Swelling of the jaw, loose teeth, sinusitis, oral or cutaneous fistulae, and fracture of the mandible are symptoms frequently connected with ONJ-BP. The symptoms adversely affect the quality of life and produce significant morbidity in the patients suffering from this condition [3]. Treatment strategies of ONJ-BP have so far been controversial since medical and surgical methods of curing have not clearly been effective [5]. Patients with exposed bone are mainly treated with systemic antibiotics, antimycotics and/or oral antimicrobial rinses. Patients in whom the symptoms in spite of medication persist are subjected to surgical procedures. However, little efficacy has been shown for the surgical removal of bone since it frequently results in additional areas of exposed necrotic bone [2, 6, 7]. Interestingly, recent results on a surgical approach with Er:YAG laser and on biostimulation of the ONJ-BP–affected jaws with Nd:YAG laser have been promising [4, 8, 9]. Several studies both in vitro and in vivo have shown that both low-energy and high-intensity lasers are capable of stimulating the regeneration of cells in healing wounds. Low-energy laser light has been suggested to be absorbed by the cellular molecules and its photostimulatory effect seems to result in an increase in the production of mitochondrial enzymes, porphyrins, flavins, and cytochromes [10, 11]. On the other hand, high-intensity infrared laser wavelengths have proven to be capable of stimulating the proliferation of blood and lymphatic vessels in healing wounds [12, 13]. Moreover, high-intensive laser irradiation has been shown to elevate the activity of osteoblast-like cells stimulate bone formation and to increase the mineralization of the healing bone verified by Raman spectroscopy [14–16]. Additionally, Nd:YAG laser irradiation has proven to have an antimicrobial effect [17]. M. Luomanen (*) Institute of Biomedicine/Anatomy, University of Helsinki, PO Box 63, Haartmaninkatu 8, 00014 Helsinki, Finland e-mail: marita.luomanen@helsinki.fi

Tenascin expression in mucocutaneous diseases and related lesions of human oral mucosa

The expression of tenascin was assessed immunohistochemically. In normal oral mucosa, immunoreactivity for tenascin was seen either as a delicate line underlining the epithelium or in the stromal papillae. In oral lichen planus, a marked enhancement of tenascin immunoreactivity in the lamina propria was associated with focal infiltrates of inflammatory cells and seemed to reflect the intensity of inflammation. In lichenoid reactions in which only a sparse inflammatory infiltrate was present a band-like tenascin reactivity was seen. Oral psoriform reactions and chronic hyperplastic candidosis showed a prominent tenascin reaction in the connective tissue papillae among infiltrates of inflammatory cells. The results show that tenascin content is increased in oral mucocutaneous diseases and related lesions and that the abundance of tenascin reflects the intensity of the inflammatory reaction.