Nontraumatic final impressions for fixed partial dentures

A Digital Technique to Fabricate Segmental Individual Tooth Trays for Making an Impression of Multiple Crown Preparations

A digital technique is described for designing and fabricating segmental individual tooth trays that can be used to make an impression of multiple preparations with high accuracy and efficiency. A digital model of prepared dentition was acquired. The segmental individual tooth trays with retention attachments and tissue stops were designed and 3D printed with light-polymerizing resin. The segmental impression of each section of the prepared dentition was made with the corresponding individual tooth tray loaded with the impression material. A final overall impression was made to pick up the segmental individual tooth trays with a full arch tray.

A digitally designed and 3D printed individual tooth tray for taking subgingival impression of complete crown preparation

A digital technique for designing and fabricating an individual tooth tray used for taking subgingival impression of complete crown preparation was described. The digital model of required dentition region was obtained before performing crown preparation. An individual tooth tray with retention attachments was designed and printed with plastic material. After conducting crown preparation, the individual tooth tray loaded with the final impression material was placed onto the abutment to deliver the impression material subgingivally. A final overall impression was made with full arch stock tray to pick up the individual tooth tray with the accurate impression of abutment.

[In vitro evaluation of the application of digital individual tooth tray in the impression making of mandibular full-arch crown abutments]

OBJECTIVE

To establish a method for the production of digital individual tooth tray based on three-dimensional (3D) scan, computer-aided design (CAD) and 3D printing, and to evaluate the effect of impression taking of full-arch crown abutments by digital individual tooth tray technique and conventional method through in vitro study.

METHODS

The full crown preparation was performed on all the fourteen resin teeth in a standard model of mandibular dentition. The surface data of prepared abutments was collected by 3D scanning. A new project was created in a dental CAD software including all the fourteen teeth in the mandibular dentition. The design modules of anatomy crown and coping were selected for each tooth. The dentition was divided for three sections: right posterior teeth, anterior teeth, and left posterior teeth areas. The connector design was added between the abutments within the same section. The scanned data of the abutments were imported. The occlusal plane and insertion path were determined. The position of margin line, as well as the shape of anatomy crown and connector as the main body of the individual tooth tray were designed for each abutment. The shape of coping was generated as the space for holding the impression material. The finalized data of the main body was imported into Geomagic software. The retentive attachment was added at the external surface and the tissue stop was formed at the internal surface. The completed individual tooth tray was manufactured by 3D printing with resin material. The data of full-arch crown abutments were modified and printed. The conventional dentition trays A and B, as well as digital individual tooth tray were designed and printed for four copies each. The polyether impressions of the full-arch abutments were made by conventional one-step method using dentition tray A, and by sectional-impression technique using digital individual tooth tray and dentition tray B for four times each. The time spent for each impression taking and the numbers of defects at the shoulder and axial/occlusal surface in each impression were recorded. The impression quality of each abutment was evaluated. The overall quality distribution and the pass rate of abutments between the two methods were analyzed.

RESULTS

The impressions made by conventional method had more defects at shoulder than those made by digital individual tooth tray technique. No difference of the number of defects at axial/occlusal surface between the two methods was observed. The digital individual tooth tray technique for the full-arch abutment impression exhibited higher pass rate of abutments and better quality of impression, compared with conventional methods.

CONCLUSION

A new method for the production of digital individual tooth tray based on digital scanning, CAD and 3D printing was established. Compared with conventional method, using digital individual tooth tray technique for impression taking of full-arch abutments can achieve better effect.

Modified custom tray

The use of a custom tray is highly desirable for accurate impression making in situations with multiple abutments. This article describes a modified custom tray fabrication method using autopolymerizing acrylic resin. The custom tray is fabricated by intraoral relining with autopolymerizing resin that is polymerized extraorally. The final impression is obtained during the same session after tray polymerization at 100 degrees C for 5 minutes. Relined areas are refined by trimming excess resin with burs of a known diameter to create a 2-mm clearance for the elastomer. For areas with subgingival finish lines, only 0.5 mm of resin is removed to direct the elastomer into the gingival sulcus. The procedure is time-saving because it reduces the need for a retraction cord and minimizes inaccuracies that would necessitate another impression.

The matrix impression system for fixed prosthodontics

This article describes the instrumentation, materials, and clinical procedures for the matrix impression system. The matrix impression system uses a custom matrix to control the sulcular environment and to deliver impression material to the subgingival parts to be impressed. It describes the four types of forces involved in gingival displacement during impressions, effective delivery of impression material with simultaneous sulcular cleansing, and simplification of complex impressions with or without segmentation. The application of the matrix impression system is described for making routine impressions and for some atypical problems. The article also provides a detailed description of the formation and design of the matrix.

Trouble-shooting dual arch impressions

Dual arch impression techniques enable the dentist to capture an impression of the prepared tooth, the opposing teeth and the occlusal registration in one procedure. This saves chair time and impression material.

A procedure for making fixed prosthodontic impressions with the use of preformed crown shells

Void-free impressions of tooth preparations for fixed prosthodontics are essential for accurately fitting restorations; however, commonly used impression methods are arduous and time-consuming. A procedure has been developed in which an impression is made in a preformed temporary crown shell for each tooth preparation and then a final over impression is made. The result is an atraumatic and uncomplicated complete-arch impression that incorporates an accurate impression of each prepared tooth.