<\/span><\/h3>\n\n\n\nType I – Luting cement<\/p>\n\n\n\n
Type II – Restorative cement<\/p>\n\n\n\n
Type III – Liner<\/p>\n\n\n\n
Type IV – Fissure sealant<\/p>\n\n\n\n
Type V – Orthodontic cement<\/p>\n\n\n\n
Type VI – Core build up cement<\/p>\n\n\n\n
Type VIII Posterior packable GIC for atraumatic restorations<\/p>\n\n\n\n
Type IX<\/p>\n\n\n\n
<\/span>Glass Ionomer Cement Application<\/span><\/h3>\n\n\n\n- Anterior esthetic<\/strong> restoration for class III<\/strong> cavities.<\/li>
- Restorative material for eroded areas<\/strong> and class V<\/strong> restorations.<\/li>
- As a luting agent<\/strong> for restorations<\/strong> and orthodontic brackets<\/strong>.<\/li>
- As liners<\/strong> and bases<\/strong>.<\/li>
- For core build up<\/strong>.<\/li>
- Pit and fissure<\/strong> sealants.<\/li>
- Intermediate<\/strong> restorative material.<\/li><\/ul>\n\n\n\n
**Glass ionomer cements are not recommended for class II and class VI restorations<\/strong>, since they lack fracture toughness<\/strong> and are susceptible to wear<\/strong>.<\/p>\n\n\n\n<\/span>Glass Ionomer Cement Setting reaction:<\/span><\/h3>\n\n\n\n- Acid-Base<\/strong> reaction.<\/li>
- Not exothermic<\/strong> reaction.<\/li>
- Reaction between Polyacrylic acid (acid) & Aluminosilicate glass (base).<\/li>
- Setting time:<\/li><\/ul>\n\n\n\n
- Type \u2013 I: About 7 mins.<\/strong><\/li>
- Type \u2013 II: About 4 to 5 mins.<\/strong><\/li><\/ul>\n\n\n\n
- Powder liquid ratio<\/strong> is 3:1 by weight<\/strong>. Mixing should be done by agate or plastic spatula.<\/li>
- Setting reaction occurs in four overlapping stages.<\/strong><\/li><\/ul>\n\n\n\n
Stage \u2013 1: Decomposition of powder<\/strong><\/p>\n\n\n\n- Upon mixing powder & liquid, the glass in powder<\/strong> will be attacked by the polyalkenoic (polyacrylic) acid<\/strong> in liquid.<\/li>
- The surface of the glass particles decomposes<\/strong> and releases metal ions (Al<\/strong>3+<\/sup><\/strong>, Na<\/strong>+<\/sup><\/strong>, Ca<\/strong>2+<\/sup><\/strong> etc.)<\/strong>, fluoride<\/strong> and silicic acid<\/strong> (It will later condense into a silica gel that will surround the glass particles).<\/li><\/ul>\n\n\n\n
Stage \u2013 2: Gelation<\/strong><\/p>\n\n\n\n- As concentration of cations is increased \u2013 pH of aqueous phase increases<\/strong>.<\/li>
- Increased pH of the aqueous phase leads to greater ionization<\/strong> of polyalkenoic acid<\/strong> and create an electrostatic field.<\/strong> <\/li>
- This electrostatic field aids the migration<\/strong> of the liberated cations<\/strong> into the aqueous phase.<\/li>
- Now a gel structure<\/strong> is formed<\/strong> through weak ionic cross-links<\/strong> and hydrogen bonds.<\/strong><\/li><\/ul>\n\n\n\n
Stage \u2013 3: Hardening<\/strong><\/p>\n\n\n\n- Polymer chains unwind<\/strong> as the negative charge increases<\/strong>, and this leads to an increased viscosity.<\/strong><\/li>
- The concentration of cations<\/strong> will continue to increase<\/strong>, and they will condense on to the polyacid chain. <\/strong><\/li>
- Formation of cross-links in the polymer chains<\/strong> due to release of metallic ions leads to hardening of the cement.<\/strong><\/li>
- Powder dissolution<\/strong> will continue, and insoluble salts<\/strong> will precipitate.<\/strong> <\/li>
- This initial set<\/strong> will occur within 4 minutes<\/strong> with either a luting cement or a restorative material.<\/li>
- The final material<\/strong> consists of unreacted glass particles<\/strong> surrounded by<\/strong> the polysalt matrix<\/strong> containing crosslinks<\/strong>.<\/li><\/ul>\n\n\n\n
Stage \u2013 4: Maturation<\/strong><\/p>\n\n\n\n- Following gelation<\/strong>, the cement will continue to