In vitro evaluation of the shear bond strength and bioactivity of a bioceramic cement for bonding monolithic zirconia

Bioactive Materials for Direct and Indirect Restorations: Concepts and Applications

Currently, minimally invasive restorations could be made in dentistry applying adhesive materials and adhesion principles to the dental structures. Following this philosophy, endodontic interventions have been avoided largely, preserving hard tissues, and maintaining dental vitality. Advances in biologically favorable bioactive materials enabled clinicans to induce repair and regeneration of dental tissues. Such materials are primarily used for pulp protection and cementation of indirect restorations. This review highlights current bioactive materials available, principles of bioactivity and their mechanisms of action.

Long-term retention of lithium disilicate crowns with a current bioactive cement

OBJECTIVE

To determine if a recent bioactive cement provides acceptable lithium disilicate crown retention after long-term aging with monthly thermocycling.

MATERIALS AND METHODS

Extracted molars prepared with flat occlusal, 20° taper, ~4 mm axial. Prepared teeth assigned to two groups for equal mean surface areas per group. Lithium disilicate crowns fabricated with occlusal bar to facilitate removal. Crowns etched with 9.5%HF and cleaned. Cements were Ceramir Crown & Bridge QuikCap (CM) and Ketac Cem Maxicap (KC). Before cementation, specimens stored in 37°C water. Crowns cemented with 196 N force, placed in 37°C, 100% humidity oven for setting. Specimens thermocycled (5-55°C) 5000 cycles monthly for 6 months; otherwise stored in phosphate buffered saline solution. Crowns removed axially at 0.5 mm/min. Removal forces recorded and stresses calculated using areas. Independent t-test (α = 0.05).

RESULTS

Levene test not significant (P = 0.649). CM removal stresses and forces (P < 0.001) were higher (1.93 MPa, 261.4 N) compared to KC (1.06 MPa, 139.4 N). CM cement found principally on crown intaglio, KC found with most cement on prepared tooth. Chi-square significant (P < 0.001).

CONCLUSIONS

Following long-term aging with monthly thermocycling, lithium disilicate crowns were best retained by CM cement, however both cements are capable of retaining lithium disilicate crowns with preparations of ideal taper and length.

CLINICAL SIGNIFICANCE

Results serve as a basis for bioactive cement selection for retaining lithium disilicate crowns. Without optimal axial length, taper of preparation or retentive features, Ceramir Crown and Bridge QuikCap offers a bioactive cement with improved long-term retention when compared to Ketac Cem Maxicap for lithium disilicate crowns.

In vitro and in vivo evaluations of nano-hydroxyapatite/polyamide 66/yttria-stabilized zirconia as a novel bioactive material for bone screws: Biocompatibility and bioactivity

Zirconia and its derivatives have been receiving increased levels of attention with regard to their potential application in bone tissue engineering. These materials are of particular interest because of their excellent characteristics, such as superior biological and mechanical properties. In this study, yttria-stabilized tetragonal zirconia (YTZ)-reinforced nanohydroxyapatite/polyamide 66 (nHA/PA66) bone screws were prepared. The biocompatibility and bioactivity of nHA/PA66/YTZ were evaluated in vitro using MC3T3-E1 cells. Biocompatibility and bioactivity experiments (cell counting kit-8 tests, cell immunofluorescence analysis, and polymerase chain reaction) showed that nHA/PA66/YTZ could facilitate the biological functions of MC3T3-E1 cells. The attachment, proliferation, spreading, and expression of genes associated with osteogenesis (collagen 1, osteopontin, and osteocalcin) in cells cultured with the nHA/PA66/YTZ composite were all superior compared with the control groups (P < 0.05). In addition, nHA/PA66/YTZ bone screws were implanted into the femoral condyles of rabbits, and titanium screws were employed as a control group; postoperative histology and blood analysis revealed no obvious damage to the liver, kidneys, or any other major organs in either of the experimental groups. Moreover, nHA/PA66/YTZ screws resulted in significantly better bone-implant contact interfaces and enhanced formation of trabecular bone (P < 0.05); these characteristics were markedly better than those in the group that received titanium screws. These observations indicate that YTZ-reinforced nHA/PA66 composites have significant potential for applications in bone tissue engineering.