Optimizing cleaning procedures for MEP residues: insights from a novel HPLC-MS analysis

To develop a highly sensitive and reliable method for detecting Monobond Etch & Prime (MEP) residues on lithium disilicate glass ceramic (LDGC) surfaces treated with different cleaning procedures after MEP treating.

A sensitive and reliable high performance liquid chromatography-tandem triple quadrupole mass spectrometry (HPLC-TTQ/MS) method was developed for the accurate quantitative determination of tetrabutylammonium dihydrogen trifluoride (TDTF) in MEP. 100 rectangular LDGC specimens (8.0 × 5.0 × 2.0 mm) were fabricated using CAD/CAM and then treating with MEP. The residual amount of TDTF in the LDGC specimens surface was tested after different cleaning procedures with different experience dentists (Junior Dentist, Experienced Dentist), different rinsing times (3 s, 6 s, 9 s) and with or without ultrasonic cleaning (UC) (n = 10).

The developed method showed good linearity (r² > 0.999) over a wide concentration range. The limit of quantification of TDTF for MEP residue was less than 5 ng/mL. The method was then applied to a comparative study of MEP residues after various cleaning procedures of LDGC specimens. Residual TDTF was detected in all experimental groups with masses ranging from 62.42 ng to 74,611.74 ng. In the absence of UC, the Experienced Dentist group had lower TDTF residual levels (5,930.74 ng) than the Junior Dentist group (30,802.05 ng) (P < 0.001). The TDTF residue level was significantly lower in the rinsing 9 s group (3,102.89 ng) compared to the rinsing 3 s group (25,348.57 ng) (P < 0.05). After UC, for the same rinsing time there was no significant difference in TDTF residue between groups (P ≥ 0.062). Notably, TDTF residue levels were substantially lower after UC with the same cleaning dentist and rinsing time (P ≤ 0.012).

No cleaning procedure can completely remove MEP residues, the dentist's clinical experience affects the degree of MEP cleaning, extended rinsing time improves cleaning efficiency, and ultrasonic cleaning is an effective method of removing MEP residues.

No cleaning procedure can completely remove MEP, and dentists can increase the efficiency of cleaning by extending the rinsing time and using ultrasonic cleaning.