Fatigue reliability and failure modes of metal-ceramic, monolithic zirconia, and lithium disilicate implant-supported crowns cemented to titanium bases: A step-stress accelerated life testing study.
The fatigue behavior under clinically relevant loading conditions of implant-supported screw-retained crowns cemented to titanium bases fabricated from different restorative materials remains insufficiently understood. This study evaluated the failure modes, fatigue reliability, and survival probabilities of metal-ceramic (MC), monolithic zirconia (3Y-TZP), and lithium disilicate (LD) implant-supported screw-retained crowns cemented to titanium bases using step-stress accelerated life testing (SSALT). Sixty crowns were bonded to titanium bases connected to internal hexagon implants embedded in acrylic resin blocks and subjected to three stress profiles under underwater polarized light stereomicroscopy. Use-level probability Weibull curves were calculated to estimate reliability for a mission of 100,000 cycles at 200 and 300 N. Failed specimens underwent polarized light stereomicroscopy and scanning electron microscopy (SEM) for fractographic analysis. All specimens failed during SSALT loading, with Weibull β values greater than 1 for all groups, indicating fatigue-driven failure behavior. Monolithic zirconia demonstrated the highest fatigue reliability, with survival probabilities up to 98% at the tested load levels, followed by lithium disilicate, whereas metal-ceramic crowns exhibited the lowest survival probabilities. Fractographic analysis revealed material-specific fracture origins and crack propagation patterns. Overall, all crown types demonstrated high survival probabilities, with monolithic zirconia exhibiting superior fatigue reliability compared with metal-ceramic restorations and lithium disilicate demonstrating intermediate performance.
A histological and histomorphometric evaluation of an allograft, xenograft, and alloplast graft for alveolar ridge preservation: randomized clinical trial.
To evaluate through histological and histomorphometric analysis of human biopsies the guided bone regeneration (GBR) potential of allograft, xenograft, and alloplastic materials in combination with resorbable membranes in sockets following extraction. This randomized controlled clinical trial comprised three experimental groups and one negative control group (n=8). Thirty-two patients were randomized and pos-extraction sockets received either an allograft (human cancellous bone, freeze dried, DIZG, Berlin), xenograft (BioOss; Geistlich Biomaterials, Switzerland), or alloplast (biphasic calcium sulphate, Bondbone, MIS) graft material, while sockets of the negative control group were left empty for spontaneous healing. At re-entry after three months, bone core biopsies of the treated sites were obtained using a 3.2 mm trephine drill. Bone samples were histologically processed for histomorphometric, qualitatively and quantitatively, analyses with respect to percentages of new vital bone, graft particle content, soft tissue, and bone marrow. Statistical analyses were performed through Kruskal-Wallis test, and p -values were recalculated using Monte Carlo permutation tests ( p <0.05). All three groups presented bone volume suitable for the placement of a dental implant. The xenograft yielded significantly less amount of vital bone in comparison to the allograft and alloplast groups. Comparing the percentage of residual graft particles, there was a significantly greater amount in the xenograft group in contrast to the allograft and alloplast. Similarly, a significant amount of soft tissue (as a function of percentage) was observed within the xenograft group relative to the other groups. No significant differences were detected in the percentage of residual graft particles between the allograft and alloplast groups. Additionally, there was no significant differences observed in vital bone percentage between the allograft, alloplast and control groups. Regarding the evaluation of bone marrow percentage, the only significant difference detected was between the xenograft and the alloplast material. All studied bone substitute materials exhibited bone apposition and adequate properties for their efficient use in alveolar ridge preservation procedures. Of the three grafting materials, allograft evidenced the greatest GBR potential with the highest percentage of vital bone and the lowest percentage of residual graft particles, while xenografts presented the lowest GBR potential after three months in vivo.
Is Aseptic Bone Necrosis a Cause For Early Implant Failure in Patients with Metal Allergies? - A case report and review of the literature.
Given the widespread use of titanium and its alloys in dental implantology, implant failures will most likely arise, and there will still remain many gray areas with regard to the biology and physiology of the interaction of dental implant alloys and the host. Medical literature is abundant with reports of aseptic prosthetic loosening following arthroplasty that may be attributed to many reasons, yet the most important factor appears to be the periprosthetic osteolysis due to unbalanced homeostasis of bone formation and re-sorption. Although it was previously believed to be a simple mechanical complication resulting from the instability of the implant, it is now widely accepted that particulate implant debris induces local in ammation and osteolysis. e purpose of the current study is to report the atypical and unexpected early implant loss of a titanium implant in an otherwise healthy 60-year-old patient with a previously undiagnosed nickel, palladium, and cobalt allergy. A er veri cation by MELISA Test© the patient was successfully treated with a ceramic implant. A literature review was performed , which demonstrated that there is abundant scientific evidence that suggests an established correlation between the di erent metals alloys and peri-implant aseptic bone loosening leading to a failure of implant osseointegration.