International Journal of Chemical and Biochemical Sciences (ISSN 2226-9614)[/vc_column_text][/vc_column][/vc_row]
VOLUME 29(23) (2026)
Thermomechanical Aging of CAD/CAM Lithium-Silicate Occlusal Veneers: Laboratory Protocols, Fracture-Resistance Outcomes, and Reporting Priorities
Marwa Mohamed Ali Nour El Din1*, Amr Saleh El-Etreby1, Tarek Salah Morsi1,2, Bassem Sameh Mohamed Kandil1
1Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt.
2Faculty of Oral and Dental Medicine, Misr International University, Cairo, Egypt.
Abstract
Thermomechanical aging challenges bonded ceramic restorations before fracture testing, yet the term encompasses markedly different combinations of water exposure, thermal cycling, cyclic contact, sliding movement, loading magnitude, and outcome definition. This narrative review examines how protocol choices influence interpretation of computer-aided design and computer-aided manufacturing lithium-silicate occlusal-veneer studies. A focused search of PubMed/MEDLINE and reference lists was conducted through August 2026, prioritizing methodological reviews, dental-ceramic guidance, and laboratory studies of lithium-disilicate or newer lithium-silicate restorations. The evidence shows that aging is not a single dose that can be converted reliably into a fixed period of clinical service. Thermal range, dwell and transfer times, cycle count, aqueous environment, force, frequency, antagonist, contact geometry, substrate, periodontal simulation, and axial or sliding loading all alter the imposed damage. Survival during cycling and residual load to fracture answer different questions: a specimen that survives aging may contain microdamage, while a lower post-aging fracture load does not quantify fatigue life. Responses are material- and system-dependent. Some occlusal-veneer protocols produced complete survival with high residual fracture loads, whereas more demanding combined protocols generated substantial pretest failures. Newer lithium-silicate ceramics also show processing- and environment-dependent behavior. Future studies should report the entire aging configuration, distinguish failures during aging from residual static strength, calibrate simulator chambers, and add mechanistic endpoints such as damage mapping and fractography. Standardized reporting, rather than an assumed universal aging equivalence, is the most immediate route to comparable and clinically interpretable evidence.
Keywords: CAD/CAM; fracture resistance; lithium disilicate; occlusal veneers; thermomechanical aging
Full length article *Corresponding Author, e-mail: noureldinmarwa@gmail.com; Doi # https://doi.org/10.62877/31-IJCBS-26-29-23-31
Submitted: 28-05-2026; Accepted: 03-09-2026; Published: 04-09-2026