dental luting agents

• all dental cements are luting agents, but not all luting agents are dental cements • can be >composite resins >self-adhesive composite resins > surface modifying chemicals

• size of powder or filler particles in the material as well as flow characteristics of material itself

• low to allow seating of the restoration without interference from cement • film thickness should be as thin as possible = ideally 25 µm or less

• should be easy to use • most are encapsulated with a clicker system • working time should be long to allow for seating of restoration • setting time should be short = ideally command set

• allows you to see margins easier - easier to see marginal breakdown

• ideal it should bone chemically to the tooth and the indirect restoration with a permanent and impenetrable bond

• tooth coloured • variety of shades and translucency • non-staining

• low - if it is high then it will wash away under influence of saliva and fall out

• fluoride releasing and antibacterial - important in preventing secondary caries around crown margins

• not toxic • not damaging to the pulp • low thermal conductivity as a lot of restorations are metal based

• high compressive strength • high tensile strength • high hardness value • Young’s modulus similar to tooth • but no luting agents will get close to tooth values for any more than a couple of these*

• dental cement >zinc phosphate >zinc polycarboxylate • glass ionomer cement >conventional >Resin modified • composite resin luting agents > total etch for use with DBA > self-etch

• zinc oxide = 90% > main reactive ingredient • magnesium dioxide = <10% >gives white colour >increases compressive strength -alumina and silica >Improve physical properties >alter shade of set material

• phosphoric acid - 50% • oxides which buffer solution >aluminium oxide ensures even consistency of set material > zinc oxide slows reaction giving better working time

• acid base reaction initially - followed by hydration reaction resulting in crystallised phosphate matrix

• prevents crystallisation leading to an amorphous glassy matrix fo acid salt surrounding unreacted ZnO powder

• it is almost insoluble, but it is porous and contains free water from the setting reaction • as it sets more it becomes harder • cement matures, binding this water leading to a stronger, less porous material

- low initial pH of 2 > cause pulpal irritation - exothermic reaction not good for pulp - not adhesive to tooth or restoration > retention may be slightly micro mechanical but that is all - not cariostatic - final set can take 24 hours - brittle - opaque >cloudy yellow colour

• phosphoric acid replaced by poly acrylic acid

• bonds to tooth surfaces in similar way to GI • less heat of reaction • pH low to begin with but return to neutral quicker and longer chain acids don’t penetrate dentine as easily • cheap

• difficult to mix • difficult to manipulate • soluble in oral environment at lower pH • opaque = cloudy white colour • lower modulus and compressive strength than zinc phosphate

• particle size of glass which is less than 20µm to allow for suitable film thickness

• acid base reaction between glass and acid

• SiO2, Al2O3 and CaF2