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81
demineralized surface of the dentine, which acts somewhat like a sponge and into which the low-
viscosity resins penetrate.
Indirect onlays
Either composite, porcelain or metal-based onlays can be used to restore the coronal surfaces.
Again, these materials rely on the bond strength between the dentine-bonding agent and the tooth to
retain the restoration. The advantage of an indirect technique is that the technician controls the contact
points. Maintaining contact points with direct techniques can be difficult, especially when there is little
tooth tissue remaining.
Recent developments in indirect composites have overcome the early problems of staining and
fractures. Together with all ceramics, the most important principle is to ensure that onlays are
sufficiently thick to resist fracture. Porcelain and indirect composites are weak in thin section.
Therefore, at least 2 mm of interocclusal space should be left to overcome this problem.
Amalgam
In the present case, the cavity lacks conventional retention, which would be needed for an
amalgam. Therefore undercuts would be necessary underneath the buccal cusp and probably a pin on
the palatal margin. The use of pins has reduced over recent years because of the development of
adhesives; however, it is generally not prudent to rely upon the adhesive bond between amalgam and
tooth to provide retention of a restoration. Pins, slots and grooves and undercuts, where appropriate,
are still needed to create the necessary retention for amalgam restorations.
In this case, substantial amounts of tooth would need removing to create an undercut on the
buccal wall, together with pins and grooves to aid retention of an amalgam. Therefore, it is not the
most appropriate material to use to restore this tooth. If an amalgam were used it would almost
certainly need a three-quarter crown for its final restorations.
Glass ionomers
Glass ionomers adhere to enamel and dentine, but their bond strengths do not approach those of
dentine-bonding agents. Some clinicians use sandwich restorations to restore broken-down teeth. The
area of dentine exposure combined with the relatively low bond strength between the glass ionomer
and the dentine is unlikely to be strong enough to retain the restoration. Even the benefit of the
composite bonding to the enamel may not overcome this problem. But, more importantly, the glass
ionomer will dissolve in the acid originating from the stomach. Therefore, glass ionomers should not
be used in patients with dietary or regurgitation erosion.
Elective root treatments
An elective root treatment would be particularly destructive and remove significant amounts of
tooth tissue in a patient who has an already compromised dentition. The coronal access would
demineralized surface of the dentine, which acts somewhat like a sponge and into which the low- viscosity resins penetrate. Indirect onlays Either composite, porcelain or metal-based onlays can be used to restore the coronal surfaces. Again, these materials rely on the bond strength between the dentine-bonding agent and the tooth to retain the restoration. The advantage of an indirect technique is that the technician controls the contact points. Maintaining contact points with direct techniques can be difficult, especially when there is little tooth tissue remaining. Recent developments in indirect composites have overcome the early problems of staining and fractures. Together with all ceramics, the most important principle is to ensure that onlays are sufficiently thick to resist fracture. Porcelain and indirect composites are weak in thin section. Therefore, at least 2 mm of interocclusal space should be left to overcome this problem. Amalgam In the present case, the cavity lacks conventional retention, which would be needed for an amalgam. Therefore undercuts would be necessary underneath the buccal cusp and probably a pin on the palatal margin. The use of pins has reduced over recent years because of the development of adhesives; however, it is generally not prudent to rely upon the adhesive bond between amalgam and tooth to provide retention of a restoration. Pins, slots and grooves and undercuts, where appropriate, are still needed to create the necessary retention for amalgam restorations. In this case, substantial amounts of tooth would need removing to create an undercut on the buccal wall, together with pins and grooves to aid retention of an amalgam. Therefore, it is not the most appropriate material to use to restore this tooth. If an amalgam were used it would almost certainly need a three-quarter crown for its final restorations. Glass ionomers Glass ionomers adhere to enamel and dentine, but their bond strengths do not approach those of dentine-bonding agents. Some clinicians use sandwich restorations to restore broken-down teeth. The area of dentine exposure combined with the relatively low bond strength between the glass ionomer and the dentine is unlikely to be strong enough to retain the restoration. Even the benefit of the composite bonding to the enamel may not overcome this problem. But, more importantly, the glass ionomer will dissolve in the acid originating from the stomach. Therefore, glass ionomers should not be used in patients with dietary or regurgitation erosion. Elective root treatments An elective root treatment would be particularly destructive and remove significant amounts of tooth tissue in a patient who has an already compromised dentition. The coronal access would 81
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