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Intraoral photographs at initial examination. I-bar clasp on the canine is broken.
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Although the clasp of the RPD on the tooth 33 abutment was broken, there was no loss of clinical stability, and the patient was satisfied with the prosthesis (Figure 1).
(A) Intraoral photographs and (B) X ray image obtained at initial examination. Caries of the mandibular left second canine.
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On dental examination, dental caries of tooth 33 that extended into the pulp was found and diagnosed as acute pulpitis (Figure 2).
(A) Intraoral scan images after root canal treatment (frontal view). (B) Intraoral scan images after root canal treatment (lingual view). Intraoral scan of the mandibular left canine before preparation.
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The anterior teeth containing the unprepared abutment tooth were captured by an intraoral scanner (Trios3; 3Shape, Copenhagen, Denmark) (Figure 3).
Design of the provisional restoration. The thickness was designed 0.65-mm.
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Automatically filled data after the trim that was hollowed out to a 0.65-mm thickness were used as the provisional restoration data (Figure 4).
Preparation data and crown design. (A) The crown was designed by superimposing the pre-preparation scan and (B) the post-preparation scan of the prepared abutment tooth.
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A zirconia crown was designed by superimposing the pre-preparation scan and the post-preparation scan of the prepared abutment tooth (Figure 5).
Adjustment of the crown contour. Blue line: Tooth outline of the pre-preparation scan. Black line: Design outline of the zirconia crown.
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The crown contour was adjusted to 0.5-mm undercut on the mesiolabial surface using a 2D cross-section and a distance measuring tool (Figure 6).
Intraoral scan images for fabricating clasp. (A) Intraoral scan of the mandible with the RPD. (B) Rescan proximal guide plane of the abutment tooth without the RPD.
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An intraoral scan of the crown with RPD was taken, and the RPD was removed to rescan the proximal guide plane of the abutment tooth (Figure 7).
Design of I-bar clasp. CAD software view of the scan with the removed RPD (gray) and merged with the RPD worn (blue). Between the yellow and the orange on the clasp tip is undercut of 0.5 mm.
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Asiga, Sydney, Australia), and the casting pattern was built. After printing, the pattern was rapidly invested, and cobalt-chromium alloy (Zeta-cast co; ODIC, Osaka, Japan) was used to cast the clasp (Figure 8).
CAD software view of the resin matrix. Resin matrix was designed using individual tray mode of CAD software.
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The design data were sent to the 5-axis milling machine, and the matrix was milled from a resin disc (M-PM Disk Clear; Shofu, Kyoto, Japan) (Figure 9).
(A) Denture photographs and (B and C) intraoral after treatment. Retrofitted zirconia crown and I-bar clasp under the existing RPD.
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The patient reported satisfactory retention and aesthetics of the RPD after treatment completion (Figure 10).