Various desensitizing agents have been used to reduce tooth hypersensitivity prior to crown cementation. However, it was unclear if they might compromise crown retention. Objective: To investigate the effect of three desensitizing agents on tensile bond strength of crowns using three luting cements. Methods: Ninety-six freshly extracted noncarious human premolars were prepared for a crown abutment (occlusal diameter=4.2mm, cervical diameter=4.8mm, height=3mm) using a custom-made milling machine. A base metal crown was fabricated for each tooth. One of three desensitizing agents: Gluma® (G), Seal&Protect® (SP), Prime&Bond NT® (PB), was applied on the prepared teeth, prior to cementation with a luting cement: zinc phosphate (Poscal®), glass ionomer (Ketac-Cem®), or resin (Calibra®). There were nine experimental groups and three controls (n=8/each). The specimens were stored at 25°C in distilled water for 48 hours and then subjected to tensile loading to remove the crown, using a Universal testing machine, with a rate of 0.5mm/min. Tensile strengths of experimental groups were compared using ANOVA, α=0.05. Results:
Tensile bond strength (MPa)
| Cement/Desensitizing agent | Control | G | SP | PB |
| Zinc phosphate | 3.18±0.18 | 3.05±0.16 | 1.48±0.29 | 1.80±0.18 |
| Glass ionomer | 4.60±0.25 | 3.85±0.32 | 4.18±0.24 | 4.19±0.20 |
| Resin | 9.40±1.16 | 7.54±1.29 | 8.99±0.96 | 9.74±1.07 |
Descending order of crown retention fixed with various cement was: resin>glass ionomer>zinc phosphate. Tensile bond strengths of the specimens treated with SP and PB decreased significantly when cemented with zinc phosphate, and those with G reduced significantly when cemented with resin cement (p<0.05). Conclusions: Dentin desensitizers reduced tensile bond strength of crowns to a certain degree, depending on type of cement used. (Financially supported by Graduate School of Prince of Songkla University, Thailand)