METHOD OF PRODUCING WORKPIECE, AS WELL AS WORKPIECE Russian patent published in 2019 - IPC A61K6/27 A61C13/00 C03B32/02 C03C10/00 C03C4/00 

FIELD: chemistry.

SUBSTANCE: disclosed workpiece contains lithium silicate crystals in amount of more than 10 vol. %, wherein blank consists of glass ceramics with density between 30 % and 60 % of theoretical density of sintered workpiece and with fraction of lithium silicate crystals, which is from more than 10 vol. % to 90 vol. %, with pores value of 0.1 mcm to 5 mcm, and is made by pressing particles of crystallized glass-ceramic powder with composition, wt. %: SiO₂ 46.0–72.0, Li₂O 10.0–25.0, ZrO₂ 6.5–14.0, P₂O₅ 1.0–10.0, Al₂O₃ 0.1–8.0, K₂O 0.1–5.0, CeO₂ 0.1–4.0, B₂O₃ 0.0–4.0, Na₂O 0.0–4.0, Tb₄O7 0.0–2.5, as well as 0.0 to 4.0 at least one additive and with grain size distribution d₉₀ ≤ 80 mcm and d₅₀ ≤ 25 mcm. Method of making said dental molded part includes steps of: making a melt with said composition; making glass frit by melt spraying and rapid cooling in medium; crystallisation of lithium silicate crystals with volume fraction between 10 % and 90 % using first heat treatment or glass frit, or particles of glass powder made from glass frit with grain size distribution d₉₀ ≤ 80 mcm and d₅₀ ≤ 25 mcm in first temperature range at temperature T₁ under condition of 500 °C ≤ T₁ ≤ 750 °C, for a time t₁ provided 5 min ≤ t₁ ≤ 120 min; wherein, if glass frit is subjected to thermal treatment, particles of glass-ceramic powder with grain size distribution d are made from glass frit subjected to thermal treatment d₉₀ ≤ 80 mcm and d₅₀ ≤ 25 mcm; pressing the glass-ceramic powder particles to form a billet with density between 30 % and 60 % of the theoretical density of the sintered workpiece and a pore value of 0.1 mcm to 5 mcm; processing the workpiece by milling to produce a semi-finished product corresponding to the dental molded part, taking into account the shrinkage characteristics of the workpiece, and semifinished product sintering at temperature T₂ under condition 800 °C ≤ T₂ ≤ 1050 °C, for a time t₂ provided 5 min ≤ t₂ ≤ 60 min. Disclosed also is a monolithic dental molded part (insert, pad, crown or bridge) made by said method and/or using said billet. Dental molded part with thin walls can be made with good mechanical properties. Tool wear during machining is negligible.

EFFECT: group of inventions relates to a workpiece for making a dental molded part, such as an insert, an overlay, a crown or a bridge, as well as a corresponding dental molded part and a method for production thereof.

25 cl, 3 ex, 1 dwg