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OBJECTIVES To examine factors influencing the primary stability of dental implants when stabilized in over-sized osteotomies using a calcium phosphate-based adhesive cement was the objective. METHODS Using implant removal torque measurements as a surrogate for primary stability, we examined the influence of implant design features (diameter, surface area, and thread design), along with cement gap size and curing time, on the resulting primary implant stability. RESULTS Removal torque values scaled with implant surface area and increasing implant diameters. Cement gap size did not alter the median removal torque values; however, larger gaps were associated with an increased spread of the measured values. Among the removal torque values measured, all were found to be above 32 Ncm which is an insertion torque threshold value commonly recommended for immediate loading protocols. CONCLUSION The adhesive cement show potential for offering primary implant stability for different dental implant designs. In this study, the primary parameters influencing the measured removal torque values were the implant surface area and diameter. As the liquid cement prevents the use of insertion torque, considering the relationship between insertion and removal torque, removal torque can be considered a reliable surrogate for primary implant stability for bench and pre-clinical settings. CLINICAL RELEVANCE At present, the primary stability of dental implants is linked to the quality of the host bone, the drill protocol, and the specific implant design. The adhesive cement might find applications in future clinical settings for enhancing primary stability of implants under circumstances where this cannot be achieved conventionally.

The aim of the present study was to evaluate the soft tissue bond strength of a newly developed, monomeric, biomimetic, tissue adhesive called phosphoserine modified cement (PMC). Two types of PMCs were evaluated using lap shear strength (LSS) testing, on porcine skin: a calcium metasilicate (CS1), and alpha tricalcium phosphate (&alpha, TCP) PMC. CS1 PCM bonded strongly to skin, reaching a peak LSS of 84, 132, and 154 KPa after curing for 0.5, 1.5, and 4 h, respectively. Cyanoacrylate and fibrin glues reached an LSS of 207 kPa and 33 kPa, respectively. &alpha, TCP PMCs reached a final LSS of &asymp, 110 kPa. In soft tissues, stronger bond strengths were obtained with &alpha, TCP PMCs containing large amounts of amino acid (70&ndash, 90 mol%), in contrast to prior studies in calcified tissues (30&ndash, 50 mol%). When &alpha, TCP particle size was reduced by wet milling, and for CS1 PMCs, the strongest bonding was obtained with mole ratios of 30&ndash, 50% phosphoserine. While PM-CPCs behave like stiff ceramics after setting, they bond to soft tissues, and warrant further investigation as tissue adhesives, particularly at the interface between hard and soft tissues.

Calcium phosphate cements (CPCs) are clinically effective void fillers that are capable of bridging calcified tissue defects and facilitating regeneration. However, CPCs are completely synthetic/inorganic, unlike the calcium phosphate that is found in calcified tissues, and they lack an architectural organization, controlled assembly mechanisms, and have moderate biomechanical strength, which limits their clinical effectiveness. Herein, we describe a new class of bioinspired CPCs that can glue tissues together and bond tissues to metallic and polymeric biomaterials. Surprisingly, alpha tricalcium phosphate cements that are modified with simple phosphorylated amino acid monomers of phosphoserine (PM-CPCs) bond tissues up to 40-fold stronger (2.5–4 MPa) than commercial cyanoacrylates (0.1 MPa), and 100-fold stronger than surgical fibrin glue (0.04 MPa), when cured in wet-field conditions. In addition to adhesion, phosphoserine creates other novel properties in bioceramics, including a nanoscale organic/inorganic composite microstructure, and templating of nanoscale amorphous calcium phosphate nucleation. PM-CPCs are made of the biocompatible precursors calcium, phosphate, and amino acid, and these represent the first amorphous nano-ceramic composites that are stable in liquids.

Locally applied bisphosphonates, such as Zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and Zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-Zoledronate-combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of Zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either Zoledronate-loaded nHA or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that were predrilled in rat femoral condyles before insertion of miniature screws. MicroCT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of Zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound Zoledronate. Hyaluronic acid with Zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation.