Cement

• Cement material


  Also called cement base or lining, used underneath the filling material to act as a barrier against thermal, electrical & chemical stimuli & irritant fillings
• Luting cement


  Cement base used for cementation of crown & bridges
• Cement used for


  • Cavity lining to protect the pulp and as a base under filling materials
  • Luting applications: to bond crowns & bridges and orthodontic attachments in or on the tooth
  • Sealing root canals in endodontic treatment
  • Some cements are specifically formulated as filling materials
  • Gingival tissue pack & surgical dressing
  • Cementation of orthodontic bands & orthodontic bonding
• Classification of cement materials

  • Cements based on phosphoric acid
  • Cements based on organo metallic chelate compounds
  • Cement based on polyalkenioc acid
  • Polymeric cement
• Cements based on phosphoric acid

  • Zinc phosphate cement
  • Silico phosphate cement
  • Copper cement
• Cements based on organo metallic chelate compounds


  • Zinc oxide\ eugenol cement
  • Ortho-ethoxybenzioc acid(EBA)
  • Calcium hydroxide cement
• Cement based on polyalkenioc acid

  • Zinc polycarboxylate cement
  • Glass ionomer cement
• Requirement of an ideal dental cement

  • Adequate strength to withstand forces applied
  • Protect the pulp from chemical irritants of the filling
  • Form protective barrier against thermal stimuli
  • Protect pulp from electrical current
  • Low solubility specially if used as luting material
  • Small film thickness specially if used as luting material
  • Not irritant to dental tissue and compatible with the filling materials
  • Good working time and fast setting time
  • Easy to manipulate
  • Dimensional stability
• Phosphate cements


  Supplied as Powder and liquid or two paste system. Powder: zinc oxide (reactive component) and other oxides like magnesium oxide. Liquid: aqueous solution of phosphoric acid buffered by zinc oxide and aluminum oxide
• Uses of phosphate cements

  • Lining materials
  • Luting materials
  • Sometimes used as a temporary filling material

  
• Phosphate cements


  • P/L ratio: normally it is 3.5:1. Low P/L ratio (more liquid): low strength & high acidity which will irritate the pulp. High P/L ratio (more powder): thick mix & short working time
  • Good thermal insulator
  • Freshly mixed zinc phosphate is highly acidic with a pH of around 2-4 after mixing
  • High compressive strength so it is used under the amalgam filling material
  • Low solubility in water & oral fluid
  • Sufficient working time
  • Moisture adversely affects cement
  • Proper film thickness depends on particle size and P/L ratio
  • Opaque due to the high amount of the unreacted zinc oxide so should not be used under porcelain teeth
• Manipulation of phosphate cements

  Powder is divided into increments. It is critical that the powder be added to the liquid in very small increments. Cement must be spatulated slowly over a wide area of a cool, dry, thick glass slab to increase working time & more powder incorporation which will increase strength
• Silicophosphate cement


  Liquid: phosphoric acid. Powder: mixture of zinc oxide and aluminosilicate glass. Set material is more soluble than zinc phosphate cement, but more translucent cement so can be used under porcelain restoration. Contains sufficient amount of fluoride ion has a significant anticariogenic influence on the surrounding tooth substance

  
• Copper cement


  Powder: is a mixture of zinc oxide and copper oxide. Liquid: phosphoric acid. Has a bactericidal effect produced by the presence of copper has black appearance. Used in deciduous teeth

  
• Zinc oxide-eugenol cements


  Powder is pure zinc oxide, silica, zinc acetate or sulfate, may be present to accelerate the setting. Liquid oil of cloves (85% eugenol) & olive oil to control the viscosity

  
• Uses of zinc oxide-eugenol cements

  • Temporary filling
  • Retention of temporary crowns
  • Cement base especially resin reinforced zinc oxide eugenol
  • Root canal paste but has certain additives
• Zinc oxide-eugenol cements


  • Compressive strength 20 MPa so not used under amalgam, but the reinforced material has a higher strength 40MPa so can be used under amalgam
  • Effective thermal barrier
  • Biocompatible & antibacterial action so could be used in deep cavities without subliner
  • Solubility is high so not used as luting material
  • Eugenol interferes with polymerization of resin based filling material cause discoloration so not used as a lining under these filling
• Polycarboxylate cements


  Powder is zinc oxide with, aluminum oxide filler to improve mechanical properties. Liquid is approximately a 40% aqueous solution of polyacrylic acid or an acrylic acid copolymer with other organic acids

  
• Polycarboxylate cements


  • Adequate compressive strength (80 MPa) which is enough to withstand condensation force of amalgam
  • Mild acidity but less irritant to the pulp than the zinc phosphate cement
  • Higher solubility than zinc phosphate cement so not used as luting material in crown & bridge
  • Forms band with enamel & dentine & strong band with stainless steel; this is why it is used to bond the orthodontic bands with the teeth
  • Opaque so it is not used under porcelain
• Glass-Ionomer Cements


  Powder is calcium aluminum fluorosilicate glass. Liquid is 47% solution of 2:1 polymeric acid \Taconic acid in water

  
• Uses of Glass-Ionomer Cements

  • Cement base
  • Luting agent for crown and bridge
  • Bonding of ortho bands
  • Restoration of deciduous teeth

  
• Manipulation of Glass-Ionomer Cements


  P\L ratio 1.3:1. P\W ratio3.3:1. Mixing on paper pad with stiff spatula, mixing time is 30-60 seconds, the cement should be used immediately because the working time is 2 minutes. Working time can be increased when mixing is done on cold slab
• Glass-Ionomer Cements


  • High compressive strength (compressive strength 60 to 220 MPa) so it could be used as filling material
  • Low solubility in mouth
  • Adhere well to the tooth due to the free carboxyl group that bond to the hydroxyapatite crystals of enamel & dentine
  • Highly acidic in the fresh mix but PH increases gradually
  • Sustained fluoride release
  • Translucent due to the presence of unreacted glass, so could be used as luting under porcelain
• Calcium hydroxide cements


  Suspension of Ca (OH)2 in water or mostly as 2 pastes. One paste contains Ca (OH)2 and accelerator (zinc stearate). Other contains glycol salicylate with inert fillers, pigments and radio-opacifiers
• Indication of Calcium hydroxide cements

  • As a subliner material
  • Pulp capping

  
• Calcium hydroxide cements


  • Working time is very short & rapid setting occurs within few seconds. Working time decreases in case of presence of moisture
  • Low compressive strength (29 MPa) so not used as a base under amalgam filling
  • Sufficient biocompatibility when placed adjacent to pulp & can destroy bacteria. It can stimulate formation of secondary dentine at the base of cavity so it is used for capping
  • Used as a base material under resin filling material
  • Highly soluble so it is not used as a luting material