ABSTRACT
OBJECTIVE: The aim of the present study was to investigate the effect of sub-ablative Er:YAG and Er:YSGG laser radiation on the demineralization of human dental enamel in situ. METHODS: Eighteen enamel specimens were prepared to this end, nine of which were irradiated at 8 J/cm(2) with the Er:YSGG laser and nine at 6 J/cm(2) with the Er:YAG laser (125 pulses per surface). Each test surface was assigned a control surface on the same specimen. Three healthy volunteers from each group subsequently wore three enamel specimens in situ for a period of 1 week. The demineralization was assessed by determining the surface microhardness according to Knoop (KH) before and after wearing. RESULTS: Before wearing, the mean surface hardness measured on the control surfaces was 233 (SD 99) KH (CYSGG) and 162 (SD 59) KH (CYAG). After sub-ablative laser irradiation, the surface hardness values measured were already found to be lower compared to the untreated control surfaces (YSGG: 195 [SD 110] KH/YAG: 112 [SD 72] KH). Marked demineralization was observed on the control surfaces after 1 week of wearing in situ (CYSGG*: 60 [SD 57] KH; CYAG*: 53 [SD 9] KH). After wearing, the hardness on the irradiated test surfaces was ErYSGG*: 133 [SD 58] KH and ErYAG*: 89 [SD 28] KH, and was thus higher than on the control surfaces. CONCLUSIONS: The results indicate a tendency towards increased caries resistance following sub-ablative erbium laser irradiation. However, in an analysis of variance model with repeated measures, the tendency in this study failed to reach statistical significance (alpha = 0.05).
Subject(s)
Dental Enamel/radiation effects , Low-Level Light Therapy/methods , Tooth Demineralization/prevention & control , Dental Caries/prevention & control , Dental Enamel Solubility/radiation effects , Humans , Models, Theoretical , Neodymium , Pilot Projects , Sampling Studies , Sensitivity and SpecificityABSTRACT
The irritative response of uninvolved skin is a serious limitation of dithranol therapy in psoriasis. A characterisation in cell biological terms may be helpful in finding an effective counteraction to this well-known irritation. Therefore, we studied the effect of single and repeated applications of dithranol on normal human skin. Besides a clinical evaluation, we studied aspects of epidermal proliferation, differentiation and inflammation. On day 2, after single dithranol challenge, we observed an induction of both the cornified envelope precursor protein involucrin and the cross-linking enzyme transglutaminase I. Subsequently, epidermal hyperproliferation was observed with a maximum on day 8. The epidermal response to dithranol appears to be a reinforcement of the barrier function. Remarkably, however, filaggrin was found to be decreased. Profilaggrin breakdown might be an attempt to compensate for xerosis of uninvolved skin that accompanies dithranol therapy. T lymphocytes and to a lesser extent polymorphonucleocytes were found to be significantly increased. The reduction of Langerhans cells suggests a dose-dependent toxic effect of dithranol or one of its metabolites on Langerhans cells. The dynamics in the induction of changes after repeated challenge are comparable with those after single challenge. However, the induction of hyperproliferation following repeated application appeared to continue between day 8 and 12. Based on the dynamics of dithranol-induced irritation, it may be of interest to study the efficacy of intermittent dithranol treatment. Our results indicate that an optimal timing for biopsies in future dithranol irritation studies lies between 4 and 8 days after the first dithranol challenge.
