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Quartz-containing glass-ceramics in the SiO <sub/>2</sub> -Li <sub/>2</sub> O-K <sub/>2</sub> O-MgO-CaO-Al <sub/>2</sub> O <sub/>3</sub> -P <sub/>2</sub> O <sub/>5</sub> system
摘要： Volume crystallization of quartz, triggered by adding P2O5, was investigated in the multicomponent SiO2–Li2O–K2O–MgO–CaO–Al2O3–P2O5 glass system. Glass‐ceramics comprising quartz as the main crystal phase besides lithium disilicate (Li2Si2O5) as a minor crystal phase were produced by controlled crystallization from the parent glass. According to quantitative crystal phase analysis by means of Rietveld refinement the mass fraction of the minor Li2Si2O5 phase decreased with increasing P2O5 content, while the fraction of quartz increased. Scanning electron microscopy revealed lath‐like Li2Si2O5 embedded in a matrix of rather globular quartz crystals forming an interlocking microstructure. Well machinable glass‐ceramics with a mean biaxial flexural strength of about 300 MPa and a fracture toughness of about 2.0 MPa × m0.5 could be realized. With mean values ≥13.6 × 10?6 K?1 the glass‐ceramics coefficient of thermal expansion is close to the one reported for low‐quartz crystals. The ease of production based on conventional glass melting and fabrication technology together with the good mechanical, optical, and machining properties enables the application of these materials in prosthodontics.
关键词： nucleation,lithium disilicate,low-quartz,glass-ceramics,quartz
更新于2025-09-23 15:22:29
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Efficacy of phototherapy with different conventional surface treatments on adhesive quality of lithium disilicate ceramics
摘要： Aim: The aim of the present study was to evaluate shear bond strength (SBS) of LDC and resin composite in combination with phototherapy and different ceramic surface treatments. Materials and Method: Forty Lithium Disilicate Glass Ceramic (LDC) disks measuring (4x4x9mm) were fabricated. The specimens were randomly divided into four groups (n=10 each) according to the surface treatment. Group 1 HF+ Silane (Control); Group 2 HF+ Ultrasonic bath + Silane; Group 3 SECP (Self etch ceramic primer) and Group 4 phototherapy (Er, Cr: YSGG) + Silane. On each ceramic disk a resin build-up was done. For SBS the specimens were subjected to increasing load with a transversal velocity of 1ml/min on a universal testing machine on a ceramic resin interface. Failure mode was evaluated using digital microscope. The failure modes were divided into adhesive, cohesive and admixed interface. Data through bond strength testing was tabulated using statistical program for social science (SPSS). Means and standard deviations were compared using analysis of variance and Tukey's post hoc test (p<0.05) Results: The maximum and minimum bond strength was observed in group 2 [19.58(1.011)] and group 1 [17.14(1.122)] respectively. The bond strength among experimental group 1 [17.14 (1.122)] and group 4 [17.48(1.145)] were found to be comparable. Specimens in Group 2 displayed significantly higher bond strength among all experimental groups. Commonly adhesive failure mode was observed in the present study, with an incidence of 60%, 100% and 70% in groups 1,2 and 3 correspondingly Conclusion: Phototherapy using laser at frequency 30Hz and 4.5 W can be used as a surface conditioner for LDC alternate to HF acid. Conditioning of LDC using Self-etch ceramic primer showed better SBS outcomes as compared to phototherapy (Er, Cr: YSGG laser).
关键词： bond strength,microleakage,Phototherapy,lithium disilicate ceramics
更新于2025-09-23 15:22:29
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Atomic picture of crack propagation in Li <sub/>2</sub> Oa??2SiO <sub/>2</sub> glassa??ceramics revealed by molecular dynamics simulations
摘要： Fundamental understanding of the interaction between glass and ceramic phases with a running crack and the mechanisms by which propagation is hindered or altered as compared to the precursor parent glasses remains elusive for the lithium disilicate glass-ceramics. We herein conduct extensive molecular dynamics simulations to reveal some atomic details that are otherwise extremely challenging to be probed by experiments. The results show that the crack propagation pathway in glass-ceramics is dramatically different as compared to the precursor parent glass. In glassy sample, clean crack branching seems to be triggered by multiple cavitation events ahead of crack tip. In glass-ceramic samples, however, branching is characterized by microcracks at multiple glass-nanocrystal interface sites, clean nanocrystal cleavage along certain crystalline plane, and even secondary cracks due to the percolation of multiple microcracks. Additionally, the nanocrystal distribution, total volume fraction, and aspect ratio also have pronounced effects on the propagation of a primary crack and can lead to very diverse crack patterns.
关键词： lithium disilicate glass-ceramics,crack branching,microcracks,crack propagation
更新于2025-09-23 15:21:01
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Using Er:YAG laser to remove lithium disilicate crowns from zirconia implant abutments: An in vitro study
摘要： When implants are restored with cement-retained restorations, prosthetic retrievability can be difficult and often requires sectioning using rotary instruments. Sometimes repeated removals of a cement-retained implant crown are needed such as for treatment of peri-implantitis or immediate implant provisionalization. The purpose of this study was to evaluate the effect of erbium-doped yttrium aluminum garnet (Er:YAG) laser as a non-invasive treatment modality to remove lithium disilicate crowns from zirconia implant abutments following long-term cementation, repetitive debonding and re-cementation, and short-term retrieval.
关键词： cement-retained restorations,zirconia implant abutments,lithium disilicate crowns,Er:YAG laser,prosthetic retrievability
更新于2025-09-11 14:15:04