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November 2008 | Dental Products Report
Techniques: Pin Diamonds™

Successful outcomes for crown-and-bridge restorations are critically dependant on the clinician’s careful management of the hard and soft dental tissues. Tooth reduction must balance preservation of tooth structure with the contours and strength of the final restoration while avoiding gingival trauma and violation of biologic width.

Background

Tooth preparation designs for full-crown restorations have long been defined with specific, widely accepted parameters. Nonetheless, actual tooth preparations vary widely in terms of these parameters (e.g., degree of taper, depth of reduction and continuity of finish lines). Additionally, soft-tissue trauma during tooth preparation complicates impression making and can cause gingival recession. Dental laboratories cite departures from optimal preparation design (e.g., under/over-reduction and indistinct margins) and poor impression quality as the most common dentist-created barriers to excellent crown and bridge results.

As the dental profession continually moves toward crown fabrication systems that are more automated and involve less human interpretation, it behooves dentists to pay even closer attention to the details of preparation design. Systems that scan prepared teeth and/or dies and CAD/CAM crown fabrications require unambiguous, easily detectable margins of consistent and appropriate depth. While highly capable, such systems are unable to interpret or compensate for departures from these and other tooth preparation criteria such as adequate taper and reduction. Failure to meet these criteria may make it impossible for the system to fabricate the final restoration.

Advantages

Pin-Diamonds™ (Komet USA) employ a key design feature that aids dentists in consistently producing optimal crown preparations. They are manufactured with a smooth, non-cutting guide pin at the tip that provides several advantages to the user:

The guide pin acts as a stop guide to limit the axial cutting depth at the margin (Fig. 1). Continuous margins with consistent depth and geometry can be achieved with ease.

Stability of the diamond/handpiece unit during cutting is significantly improved compared to standard diamonds–the guide pin adds horizontal support to the vertical support traditionally provided by the prepared chamfer or shoulder.

Fig. 1 The smooth, non-cutting pin at the tip of the Pin-Diamond controls axial cutting depth and ensures a continuous finish line with consistent depth and geometry.   Fig. 2 Non-cutting pin displaces and protects soft tissue during finish line placement. Fig. 3 Pin-Diamonds provide a range of choices for margin design and depth, as well as short and long pin lengths and coarse, medium or fine grit. From left to right: 856P, 878KP, 880P and 8372PL.

Improved stability and depth-limited cutting at the margin allow for increased pressure to be safely applied against the tooth during axial wall preparation, enhancing tactile sensation and enabling greater control over margin placement.

The stability and tactile control enable the user to efficiently place continuous margins of consistent depth, even in tooth areas that are difficult to visualize and even when visibility during cutting is restricted.

The guide pin reduces soft-tissue trauma by displacing gingival tissue (Fig. 2).

Size and control

Pin-Diamonds are available in different grits (coarse, medium and fine) and an assortment of designs and diameters for various chamfer and shoulder margin options. Margin depths, as controlled by the guide pins, range from 0.38 mm (856P.314.018 and 878KP.314.018) to 0.65 mm (880P.314.018 and 881P.314.018) (Fig. 3).

Additionally two guide pin lengths are available–short for most applications and long for added control with subgingival margins and areas with poor visibility. Once precise, homogeneous reduction is completed with a Pin-Diamond, margin depth and axial reduction can be increased using conventional diamonds if needed to satisfy requirements of specific crown-and-bridge materials.

Case Report

A 68-year-old female presented with a failing porcelain jacket crown on tooth No. 10 (Fig. 4). Crown removal revealed recurrent decay and irregular margins of inconsistent depth (Fig. 5). Following decay removal and block-out of defects with a glass ionomer restorative (Fuji IX Extra, GC America), rough preparation was completed with a conventional diamond (856.314.021, Komet USA). Definitive margin placement was performed with 856P.314.021 Pin-Diamond (Fig. 6), finishing with the matching finisher 8856P.314.021 (red ring instrument). Completed preparation displays continuous margins and consistent reduction for optimal crown fabrication (Fig. 7).

Fig. 4 Failing porcelain jacket crown on tooth No. 10.		Fig. 5  Crown removal reveals recurrent decay and inconsistent margin depth.
Fig. 6 An 856P.314.021 Pin-Diamond was used to place the definitive margin, and the matching finisher 8856P.314.021 (Pin-Diamond with red ring) was used for refinement. Note the displacement and protection of delicate gingival tissue by the non-cutting guide pin.		Fig. 7 Final preparation displaying continuous margins and consistent reduction depth completed with minimal soft-tissue trauma.