A Novel Approach to Strengthening the Microtensile Bond Between Lithium Disilicate Ceramics Manufactured by CAD/CAM and Dentin Using Coatings of Natural and Synthetic Bio-Modifiers

Substantial tooth bonding is the defining characteristic of effective minimally invasive all-ceramic restorations. Natural and synthetic cross-linkers that could strengthen the bonding quality are currently drawing enormous interest. Thus, this study aimed to assess the microtensile bond strength and nanoleakage of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated ceramics to pretreated dentin with chlorhexidine or Salvadora persica extract, compared to no pretreatment, after thermomechanical cyclic loading. Consequently, forty-five extracted third-molar teeth (n = 45) were utilized to obtain mid-coronal dentin and assigned into three groups (n = 15) in accordance with dentin pretreatment; (group I: no dentin pretreatment (control), group II: 2% chlorhexidine, and group III: Salvadora persica extract pretreatments). Ceramic onlays were milled from lithium disilicate IPS e.max CAD/CAM blocks and cemented to prepared teeth with etch-and-rinse resin cement (Variolink Esthetic DC system kit). Microtensile bond strength and interfacial nanoleakage were accessed after thermomechanical cyclic loading. Statistical analysis was performed using one-way ANOVA, followed by Tukey’s post hoc test. Additionally, p-values < 0.05 were considered statistically significant. The chlorhexidine pretreated group showed the most favorable outcome compared to the control group. Conversely, using Salvadora persica pretreatment did not affect the bond strength and nanoleakage compared to the control group (p > 0.05). Consequently, unlike Salvadora persica extract, chlorhexidine–dentin pretreatment maintained superior bonding strength to ceramics after thermomechanical cyclic loading, facilitating minimally invasive, yet lasting, aesthetic restoration.