A laboratory evaluation of the construction of resin-bonded cast restorations.
OBJECTIVE
To compare the effect of two construction techniques and two pattern materials on the fit of resin-bonded cast restorations.


METHODS
In-vitro study carried out by one operator.


METHODS
Postgraduate university hospital.


METHODS
65 nickel-chrome castings were constructed using refractory die and lift-off techniques with wax and acrylic resin pattern material. They were cemented onto master silver dies, embedded in self-curing acrylic resin and sectioned along their long axes. Interfacial distance between the master silver die and casting was measured.


RESULTS
A significant different between the range of figures in each group (Mann-Whitney Test, P < 0.01) was found. Construction techniques can be ranked in order of fit of castings: 1. Refractory die, wax patterns: 42.6 microns (SD 12.03). 2. Refractory die, acrylic resin patterns: 53.7 microns (SD.16.06).3. Conventional technique, acrylic resin patterns: 85.5 microns (SD 31.62). 4. Lift-off technique, wax patterns: 139 microns (SD 53.15).5. Lift-off technique, acrylic patterns: 172.8 microns (SD 74.04).


CONCLUSIONS
Castings constructed using refractory die technique and subsequently cemented resulted in a more accurate and less variable fit than those produced with the lift-off technique. Wax patterns lead to more accurate castings than acrylic resin and locating indentations may interfere with the cementation of castings when lift-off techniques are used.
Chana
H S
HS
Conservation Department, Eastman Dental Institute, London.
Pearson
G J
GJ
Ibbetson
R J
RJ
D000180:Acrylic Resins / Q000737:chemistry; D002484:Cementation; D002858:Chromium Alloys / Q000737:chemistry; D001840:Dental Bonding; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique; D003793:Dental Restoration, Permanent / Q000379:methods; D005069:Evaluation Studies as Topic; D006801:Humans; D007283:Inlay Casting Wax / Q000737:chemistry; D007754:Laboratories, Dental; D003765:Models, Dental; D010710:Phosphates / Q000737:chemistry; D019279:Resin Cements; D012834:Silver; D013499:Surface Properties
D000180:Acrylic Resins; D002858:Chromium Alloys; D003734:Dental Casting Investment; D010710:Phosphates; D019279:Resin Cements; D012834:Silver; D007283:Inlay Casting Wax; C052304:Panavia EX