Cassoni Alessandra

Prof. Dr. Alessandra Cassoni (Brazil)

Erbium Laser irradiation as a pre-treatment surface between zirconia and resin cement

In oral rehabilitation, dental ceramics are used to make dental crowns, thus providing natural aesthetic characteristics to restore teeth. The Yttria-Stabilized tetragonal zirconia Polycrystal (Y-TZP), has demonstrated excellent resistance to bending and fracture, flexural strength, chemical stability, biocompatibility and optical properties, having become a good choice for crowns, fixed partial dentures and implant abutments. Studies have suggested the application of lasers such as CO2, Er:YAG and Nd:YAG previously or after sinterization to roughen the zirconia surface in order to improve the tooth structures adhesion.

Our studies found that Er:Cr;YSGG laser irradiation at pre-sintered ZrO2 improved  shear bond strength (uSBS) values to groups that received ceramic primer. Er:Cr;YSGG laser irradiation at pre-sintered ZrO2 followed by ceramic primer achieved similar uSBS values that tribochemical silica-coating treatment and surface roughness data showed a strong positive Pearson correlation (p<0.01) with r=0.9 and 95% IC 0.84-0.94. The surface roughness is an important parameter and could increase bonding strength values. Control group (no laser) showed statistically significant differences from irradiated groups.

The application of Er,Cr:YSGG (λ=2780nm) laser irradiation of ZrO2 as a surface treatment have potencial to be a promising field of study.


On-line: Cavity preparation with erbium laser and its potential for prevent secondary caries lesions

Patients with high caries risk usually require dental restoration replacement because of secondary caries lesions. The preventive characteristics of glass-ionomer based restorative materials are related to fluoride release and its capacity to inhibit secondary caries lesions (Poppof et al., 2000).

Erbium wavelength coincides with the water absorption spectrum and results in termal energy and surface temperature rise. After irradiation with laser, chemical and structural alterations in enamel, such as decreased carbonates, fusion and re crystallization of hydroxyapatite crystals, make enamel more resistant to acid attacks (Farhadian et al., 2017; Jorge et al., 2015).

Erbium lasers may promote chemical and/or morphological alterations on dentin and enamel surface after cavity preparation. Our studies found that Er:YAG laser irradiation removed the smear layer and the dentin surface presented opened dentin tubules with no evidence of thermal damage such as cracking or carbonization (Leonetti et al., 2012; Leonetti et al., 2011).

Some in vitro and in situ studies were able to demonstrate the potential of erbium lasers to increase enamel acid resistance (Jorge et al., 2015; Perito et al., 2009). There was less development of caries lesion around laser prepared cavities than around the drill groups regardless of fluoride presence in the restorative material (Jorge et al., 2015; Perito et al., 2009).

The use of Er,Cr:YSGG laser with pulse frequency of 30 Hz and power of 0.50 W seems to be a safe parameter to improve enamel erosive challenge (Oliveira et al., 2017). There are positive indications that demonstrate the potential of erbium lasers to increase enamel acid resistance.