The results of this study indicated that the luting process could not be undertaken without the Hydrofluoric acid etching step, even though etching is hazardous and can have extreme caustic effects on the tissues. The inherent danger of HF acid gel is well known due to their rapid vaporization and the danger of inhalation. Thus, caution should be exercised during handling of this agent. In addition, etching causes the formation of acid precipitates that are deposited on the bond surface,which can result in weakening of the bond between resin cement and ceramic.

Furthermore, etching creates surface damage to the ceramic and alters the stress required to propagate a crack in biaxial exure. Under high numbers of low cyclic loads in the presence of water, it appears that surface damage caused by etching yields cumulative damage and failure at a lower load than for the as-nished specimens. Hence, it is important to establish other conditioning methods to eliminate etching of ceramics. To eliminate the use of hazardous Hydrofluoric acid gel during cementation, however, a stable silane reaction is necessary. Coupling agents containing 3-methacry-loxypropyltrimethoxy silane (MPS) are used to promote adhesion between metal-composite, ceramic-composite, and composite-composite. 

Hydrofluoric acid as a strong mineral acid is widely used in industrial areas, according to statistics of hydrofluoric acid is used in at least 57 kinds of occupations. Therefore, in the industrial city emergency room or occupational therapy center can be seen due to damage caused by use of hydrofluoric acid, but it burns compared with other causes is not very common. Hydrofluoric acid burns can lead to serious consequences.