Davis crown Notes
Davis crown
- This is a dental restoration supported by a dowel in the root canal over which a porcelain tube tooth is placed directly on the root face of the tooth
- It is one type of dowel crown, which is detachable or called the detached dowel type
- It is cemented in position uniting the tooth, dowel, and crown into one unit.
Methods to adapt the crown
- When excessive tooth decay has occurred, there will be a discrepancy between the fit of the crown and root planes in such cases a cast metal base can be placed between the crown and root planes. The cast base is attached to the dowel.
- Porcelain is fused and interposed between the crown and root planes.
Preparation method in Davis crown
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Davis crown Steps in preparation:
- Preparation of labial and lingual planes is done.
- A complete porcelain crown of proper mold, size, and shape is selected.
- The dowel is fitted in the root canal.
- A platinum ferrule (0.0005 inches thick) is adapted to the dowel extension.
A porcelain crown is placed over the dowel and ferrule. The crown position, with adjacent teeth and alignment, is verified and the crown is fitted to the dowel with sticky wax and removed.
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Davis Crown Laboratory steps
A platinum foil 0.001 inch is burnished onto the root face of the die and the crown, ferrule, and dowel are seated on platinum foil.
The gap between the porcelain crown and the swaged platinum matrix is sealed with melted inlay wax and removed.
This is invested and burnout done to remove the inlay wax. The temperature of the furnace is raised to 1093 degrees and medium-fusing porcelain is placed in the area where the wax has burned out.
Depending on the morphology, porcelain can be added and fired to form the correct contours. Excess porcelain is ground and glazed to complete the restoration.
Davis crown Axio-proximal grooves.
Axio-proximal grooves are grooves that are placed to provide retention to the preparation.
Preparations requiring axio-proximal grooves
- Anterior and posterior partial veneer crowns
- Three quarter crowns
- Mesial half-crowns.
Davis crown Design
Should be 1 mm wide and should not extend below the cervical line.
Davis crown Location
In the axial walls proximally.
Davis crown Instrument used
No. 170 bur or No. 169L.
Davis crown Steps in preparation
- Axial reduction is done starting from the lingual surface with a chamfer diamond.
- Before extending to the interproximal areas proximal access is gained with a short, thin tapered diamond.
- The final interproximal chamfer margin is completed with a chamfer diamond.
- The axial wall and finish line are placed with a chamfer carbide finishing bur.
Axio-proximal groove placement
- The outline of the groove is drawn on the occlusal surface of the tooth
- Proximal grooves are ideally the size of a No. 170 bur; the groove can be also placed with a No. 169L bur (minor adjustments can be made later).
Placement of Second Groove
For easy alignment of the second groove, a bur is held with utility wax in the first groove.
Making a template
- The outline form of the finished groove is made on the occlusal surface with a pencil and a template is cut which is 1 mm deep
- The template is used as a guide to extend the groove to half its length placing the bur aligned with the path of insertion or the preparation.
Proximal flare placement
- A proximal flare is placed on the walls of the proximal groove for good marginal adaptation of the restoration
- A flame-shaped diamond or enamel hatchet is used to smoothen the proximal flares.
Occlusal offset
- By connecting both the grooves on the occlusal aspect an occlusal offset is formed with No. 170 bur on the lingual incline of the buccal cusp.
- Offset provides space for more metal that reinforces the margins and the grooves.
Bevel placement
A white polishing stone is used to place a 0.5 mm finishing bevel along the bucco-occlusal finish line, which merges with the proximal flares.
Davis Crown Rules to follow
- Place grooves first in inaccessible interproximal surfaces (distal aspect) and then place the second corresponding groove on the mesial aspect.
- Alteration of grooves is easily inaccessible areas if minor corrections are required.
- Use a No. 169L bur first so that adjustments can be made if needed.
- Place the proximal grooves parallel to the incisal two-thirds of the facial surface in anterior tooth preparation.
- In case of adequate thickness of the tooth, the groove can be expanded.
- The lingual wall of the proximal grooves should have 2°–5° incisal convergence with the lingual gingival wall.
- The grooves should resist lingual displacement.
- The facial wall of the groove should be continuous with the proximal flare to add bulk to the facial margin.
- The grooves should be at least 3 mm long and terminate within 0.5 mm of the gingival finish line.
- The facial and lingual walls of the grooves should have a 2°–5° incisal divergence.
- Place the proximal groove approximately 0.5 mm from the facial and gingival finish lines.
- The axial walls of each groove should converge occlusally.
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