Tight Spaces: Hand fabrication of teeth for RPD when insufficient space exits for standard denture teeth

Fabrication of removable prosthetic dentures (RPD) can create challenges fitting teeth into edentulous areas when teeth have drifted or vertical dimension has decreased. Prefabricated denture teeth may require excessive grinding to accommodate them into the space. Mesial and distal alteration of the denture tooth may alter the esthetics making the result unacceptable.

Denture base materials have been made of methylmethacrylate which is chemically different from resins used for restoration of teeth. This dissimilarity in chemistry does not permit composite resins from bonding to the underlaying acrylic. A new resin based denture base material, Eclipse (Dentsply Trubyte) was introduced for full arch removable prosthesis, non-metal base RPD and cast metal base RPD applications. Because the chemistry is similar between the Eclipse material and composite resins used for restoration of teeth, teeth can be hand fabricated for partial denture applications when a denture tooth will not fit the space available.

A cast metal RPD framework is fabricated on a master model. Additional spacing needs to be provided between the ridge and cast meshwork to accommodate the Eclipse baseplate resin and ensure encapsulation of the metal. It is recommended that a large loop design be used for the endentulous areas to provide strength to the overlaying resin covering the ridges. It is recommended that the mastercast be duplicated as fabrication of the teeth will damage the cast.

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The mastercast is brushed with Al-Cote (Dentsply Trubyte) and placed with the cast frame into the conditioning oven. The cast and frame are heated to 55 degrees Centigrade. The cast is removed from the conditioning oven and the frame removed from the cast. A segment of Eclipse baseplate resin is placed onto the warm cast in the edentulous area and the frame seated so that it engages the cast fully. Baseplate resin is molded over the cast mesh till it is completely encased in resin. The framework is removed from the cast and any flash extending under the RPD frame away from the mesh is removed with a scalpel. The frame and uncured baseplate are reinserted on the master cast and readapted.

When interarch space will accommodate a piece of Esthet-X opaque composite (Dentsply Caulk) is placed onto the uncured baseplate material in the shape of the cross section of the tooth to be fabricated. The opaque composite will aid in blockage of the metal frame showing through the tooth being fabricated and prevent a grayish tone to the tooth. The master cast is brushed with Air Barrier Coating (ABC) (Dentsply Trubyte) to prevent an air inhibited layer from being formed during curing. The cast is placed into the Eclipse processing unit and cured for 10 minutes.

Upon curing the cast is removed from the unit and an acrylic bur is used to roughen the baseplate and composite. This is done to remove the ABC and create a fresh surface to bond additional resin to. A shade of Esthet-X body composite is selected and applied over the previously placed opaque composite. General shaping is given to the body composite to create a basic tooth.

Occlusal anatomy is rough sculpted and the material cured with a hand held light. A diamond bur in a highspeed handpeice can be used to remove the tooth being fabricated from any occlusal contact with the opposing arch. A dark tinted composite staining resin can be applied to accent the occlusal pits and fissures. Finally, a translucent shade of Esthet-X composite is overlayed on the body composite with final anatomical sculpting being completed. A hand held light is used to cure the composite teeth. The occlusion is checked and adjusted as needed on the articulator.

Eclipse contour resin is applied to cover all exposed portions of the baseplate and cervical of the composite teeth. Festooning is performed and the RPD is ready for final curing. ABC is applied to all resin surfaces. The cast is placed into the processing unit and cured for 10 minutes.

Upon completion of curing the cast is soaked in water for 20-30 minutes to aid in removal of the RPD from the cast. Finishing and polishing is completed on the RPD and it is ready for patient delivery.

Fabrication of RPD when decreased mesial-distal dimensions are present or limited interarch space exists can create challenges to the laboratory technician. Denture teeth may be altered with an acrylic bur but often esthetics become difficult.

Higher quality denture teeth provide better esthetics due to layering techniques but this increases the density of the tooth making chemical adhesion with the denture base difficult or impossible.

Retention of the denture tooth is often compromised especially if minimal interarch space is present. Restorative composites have been used in the past with limited success due to incompatible chemistry between the BIS-GMA resin and the methylmethacrylate denture base.

With the introduction of the Eclipse resin denture base system, hand fabricated composite resin teeth can be chemically bonded to the underlaying base. Hand sculpturing material to form teeth allows the technician to adapt to the space available and fit portions of the cast structure in the space the tooth must occupy. The technique described provides for rapid fabrication of RPD using familiar methods.