Bioactive rhenanite glass ceramic

#The invention relates to a bioactive rhenanite-containing glass ceramic which is characterized by a high content of P2O5, CaO and Na2O and is particularly suitable as bone restorative material in dentistry or as restorative material for dentine or tooth enamel.

#Bioactive glasses and glass ceramics are known from the state of the art. On the one hand these are materials which are based on a siliceous base system and have P2O5 as additional component and on the other hand the group of the SiO2-free phosphate glasses and glass ceramics. Characteristic for these materials is the presence of a glassy-amorphous base matrix and, in the case of the glass ceramics, additionally one or more crystalline phases.

#Moreover there is the group of crystalline, glass-free phosphates which, as single or multi-component systems, are used as bone restorative material and have an excellent resorbability.

#15 different glasses of the SiO2—Na2O—CaO—P2O5 system were produced and, depending on the composition, either by cooling of the composition in a controlled manner crystallized or directly crystallized during the cooling process. The compositions of the glasses are given in Table 1. All samples were melted at temperatures of 1200° C. to 1650° C. as 120 g batches in the Pt/Rh crucible. Depending on the composition the melting time was 1 to 3 hours. Rods with an 11 mm diameter and 55 mm length were poured from the melt into preheated steel moulds. 5 TABLE 1 Components in wt. - % No. SiO2 CaO Na2O P2O5 F K2O 1 62.4 12.9 14.6 10.1 0 0 2 70.0 8.0 16.0 5.5 0.5 0 3 69.3 16.2 6.2 7.5 0.8 0 4 60.4 5.5 26.9 6.5 0.7 0 5 29.8 21.1 25.4 23.1 0.6 0 6 55.0 12.5 25.0 6.3 1.2 0 7 39.8 22.7 27.3 9.6 0.6 0 8 55.8 12.4 25.0 6.3 0.5 0 9 59.3 13.7 20.1 6.3 0.6 0 10 45.2 22.1 22.1 10.0 0.6 0 11 65.3 15.0 12.0 7.0 0.7 0 12 54.7 16.3 19.4 9.0 0.6 0 13 35.1 22.0 22.0 20.0 0.9 0 14 35.1 22.0 9.4 20.0 0.9 12.6 15 58.9 12.5 25.0 3.0 0.6 0

#In the case of the glasses according to Examples 1, 2, 4 and 6 to 10 as well as 15 the rhenanite crystallizes by subsequent heat treatment at 750° C. for 2 to 8 hours and rhenanite glass ceramics according to the invention form. In the case of the glasses according to Examples 3, 5 and 11 to 14 the rhenanite, after being poured into a mould, crystallizes spontaneously from the melt upon cooling accompanied by the formation of rhenanite glass ceramics according to the invention.

#In Table 2 the conditions are given for Examples 8, 10, 13, 14 and 15 (melting temperature and period) under which the respective starting glasses were melted. The table also gives the appearance of the materials after cooling. For the non-spontaneously crystallizing glasses of Examples 8 and 10 details of the heat treatment are also given. Finally, the respective glass ceramics are described with regard to their material properties and in particular their crystal phases and rhenanite proportions as well as their ability to effect the formation of apatite in SBF.