Microleakage of composite resin restorations in cervical cavities prepared by Er,Cr: YSGG laser radiation

Background: Evaluation of microleakage is important for assessing the success of new methods for surface preparation and new adhesive restorative materials. The aim of this laboratory study was to assess microleakage at the margins of composite restorations in Er,Cr:YSGG laser prepared cavities on the cervical aspects of teeth by means of dye penetration, and compare this with conventionally prepared and conditioned cavities. Methods: Class V cavities were produced on sound extracted human teeth, which had been assigned randomly to one of three groups (N = 10 each), as follows: Group 1 – prepared using a diamond cylindrical bur and then treated with 37% phosphoric acid; Group 2 – irradiated with an Er,Cr:YSGG laser (Biolase Waterlase) and then treated with 37% phosphoric acid; Group 3 – irradiated only with the laser. After application of bonding agent (Excite, Ivoclar Vivadent), all cavities were restored with composite resin (Heliomolar). After polishing the restorations, the teeth were thermocycled from 5–50°C for 500 cycles. Dye leakage was assessed after immersion in methylene blue, by examining longitudinal sections in a stereomicroscope at ×30 magnification. Results: The extent of dye penetration was lowest in the laser only group (Group 3). Penetration of dye to dentine and axial walls occurred in 80 per cent of conventionally prepared (bur + acid) specimens, but in the laser group, dye penetration to the axial wall occurred in only 30 per cent of cases. There was a strong statistical association between treatment group and the distribution of microleakage scores (Chi-square, P = 0.0023). Conclusions: For Class V cavities, with the adhesive materials employed, higher microleakage occurs with phosphoric acid etching of bur- or laser-cut surfaces, than with the surface created by use of the laser alone without additional conditioning

Paradigms in multiple sclerosis: time for a change, time for a unifying concept

It has recently been suggested that, rather than being an autoimmune disease, multiple sclerosis (MS) is an example of a neurocristopathy, a pathological process resulting from a faulty development of the neural crest. Whilst several characteristics of the disease suggest a neurocristopathy, other aetiological factors require consideration, including hygiene-related factors that alter the immune responses to common pathogens resulting in an eclipse of immune reactivity that could protect against MS, the possible role of human endogenous retroviruses (HERVs) in pathogenesis and autoimmune phenomena, HLA polymorphism, vitamin D levels before and after birth and immune repair mechanisms. A postulated aetiological factor in MS, associated with altered vitamin D metabolism and abnormal HERV expression, is a long-lasting disturbed redox regulation in the biosynthesis of a melanoma-like melanin pigment. Although intensive further studies on melanin pigments in nerve tissue in MS are required, the known properties of a pathological form of such pigments in melanoma could explain a number of observations in MS, including the impact of light, UV-light, and vitamin D, and could explain the clinical manifestations of MS on the basis of an oscillating process of oxidative charge and discharge of the pigments and a threshold phenomenon with a change of the quasi-catalytic function of the pigment from destroying reactive oxygen radicals or species to transforming them to more harmful long-persisting highly reactive species. Taken together with the consequences of an adaptive process in partly demyelinated neurons, resulting in an increase in number of mitochondria, and the impact of stressful life events, these conditions are necessary and sufficient to explain the disease process of MS with its spatial (plaques) and temporal (attacks and remissions) characteristics. This suggested unifying concept of the pathogenesis of MS may open perspectives for prevention, diagnosis and therapy. In particular, prevention may be achieved by vaccinating against Epstein-Barr virus in early childhood

Microleakage of glass ionomer formulations after erbium:yttrium-aluminium-garnet laser preparation.

The aim of this study was to investigate the microleakage in class V cavities restored with four conventionally setting glass ionomers (CGIs) and one resin-modified glass ionomer (RMGI) following erbium:yttrium-aluminium-garnet (Er:YAG) laser or conventional preparation. Four hundred class V cavities were assigned to four groups: A and B were prepared by an Er:YAG laser; C and D were conventionally prepared. In groups B and D, the surface was additionally conditioned with Ketac conditioner. Each group was divided into five subgroups according to the glass ionomer cement (GIC) used: groups 1 (Ketac Fil), 2 (Ketac Molar), 3 (Ionofil Molar), 4 (Ionofil Molar Quick) and 5 (Photac Fil Quick). After thermocycling, a 2% methylene blue solution was used as dye. Scanning electron microscope (SEM) photographs were taken to show the conditioner's effect. Complete marginal sealing could not be reached. PhotacFil showed less microleakage than the conventionally setting glass ionomer cements (CGICs) investigated. Conditioning laser-prepared cavities did not negatively influence microleakage results except for Ionofil Molar Quick