EXPERIMENTAL STUDY OF THE SAFETY OF INDIRECT CERAMIC RESTORATIONS REMOVAL BY COMPARING THE DYNAMICS OF THERMOMETRIC INDICATORS
Abstract. Today, porcelain laminate veneers are mainly used to optimize tooth form and position, close diastema, replace discoloured or unaesthetic composite resin restorations, restore teeth with incisal abrasions or tooth erosion, and mask or reduce tooth discoloration. They are a valid alternative to complete-coverage restorations since they avoid aggressive dental preparation, thus maintaining tooth structure. However, even such high-precision restorations have a failure rate and complications.
Veneer removal is generally performed with a rotary instrument. Using this method, the veneer removal is complete, but is relatively time consuming and this technique is not ideal as the underlying tooth structure may be damaged. Moreover, the irritating noise, uncomfortable vibration and pain during veneer removal with high-speed handpieces are unpleasant for the patients. These disadvantages led to the search for new techniques for hard dental tissue removal, such as lasers, which would make treatment less painful to patients, with no need of local anaesthetics. With the recent introduction of lasers in dentistry, there may be beneficial application of lasers in removing veneers with lasers. Using an Er:YAG laser allows debonding porcelain veneers from teeth without aggressive destruction or removal of underlying tooth structure and without destroying the veneers.
Purpose. The aim of our experimental study was to investigate the safety of indirect ceramic restorations removal by comparing the dynamics of thermometric indicators.
Materials and methods. Experimental studies conducted at Shupyk National Medical Academy of Postgraduate Education. According to our study following groups were created: group 1 (control) – veneer removal using rotary instruments (24 veneers): IА–ceramic veneers, fabricated from VITABLOCS MarkII, IB – ceramic veneers, fabricated from IPS e.max CAD; group II – veneer removal using a solid-state laser (Er: YAG) (32 veneers): IIА – ceramic veneers, fabricated from VITABLOCS MarkII, IIB - ceramic veneers, fabricated from IPS e.max CAD; group III – veneer removal using a solid-state laser (Er, Cr: YSGG) (34 veneers): IIIА – ceramic veneers, fabricated from VITABLOCS MarkII, IIIB – ceramic veneers, fabricated from IPS e.max CAD.
The intrapulpal temperature measurements were performed with thermocouple.
Results of the study: According to the results of our study using an Er:YAG and Er, Cr: YSGG lasers allows debonding porcelain veneers from teeth without aggressive destruction or removal of underlying tooth structure and in most cases without destroying the veneers, make veneer debonding less painful to patients. Both laser groups generated significantly less heat compared to bur group (p<0,05). None of the laser groups increased pulpul axial wall heat temperature above the critical 5,5˚С (3,4˚С for Er:YAG and 2,3 for Er,Cr:YSGG lasers). The bur group generated higher heat (more than 5,5˚С).
According to the results of our experimental study on thermal safety Er:YAG and Er, Cr:YSGG lasers allow to remove indirect ceramic restorations (veneers) below the critical threshold described of 5,5˚С (Zach and Cohen).
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