Dr. Brad Carson

	The old saying that “no chain is stronger than its weakest link” is certainly true in dentistry. When working with crown and bridge, one of the primary complaints from dentists to dental technicians is that “the occlusion was high and it took a long time to adjust it clinically.”

 The restorative process for an indirect restoration includes many steps that, when not carefully executed, can contribute to this problem. 

One of the most important steps is the provisional restoration, and it plays a crucial role in avoiding sensitivity, infection, and maintaining a stable position of the tooth by maintaining opposing and adjacent contacts, and thereby avoiding tooth movement. At this temporization stage, an adverse outcome could mean an emergency visit to your office, or a problematic appointment during the placement of the final prosthesis

 as mentioned by Loos, Boyarsky and Quiring (2001).

Currently amongst the provisional materials categories, bis-acrylic provisional material is the product of choice due to its low shrinkage, easy handling and esthetic properties. This year, 

, which demonstrates a dramatic improvement in its mechanical and esthetic properties.

This material has an excellent flexural strength (105 MPa) and impact strength (76 MPa). These properties combined with its diametral tensile strength (62 MPa) which is similar to restorative composites, imparts to this material the ability to withstand the challenges that the oral environment imposes on our temporary restorations. Such strong provisionals will reduce the risk of breakage, especially at the margins, where most provisionals fail if the amount of reduction it is not adequate.

Clinicians should keep in mind that wear of the proximal contacts of the provisional restoration is the main reason why the final restoration does not seat properly on the prepared tooth. Every dentist knows how frustrating it is when you have to adjust the proximal contacts of your crown and the final result is a mesial or distal open contact. Also, occlusal wear of the provisional, with resultant tooth movement, is main reason for “high” contacts. Preventing this from occurring is why 

You should also keep in mind that, at the provisional stage, not only does the temporary restoration play an important role, but the selection of the temporary cement is also crucial. An ideal temporary cement should present the following characteristics: easy removal of excess cement from around the margins; good marginal seal to help minimize sensitivity; good retention but easy removal of the temporary prosthesis; low solubility in oral fluids; and compatibility with provisional resin restorations, resin core materials, bonding agents and permanent cements. Polycarboxylate cements are the easiest to clean, and Santos & Santos (2012)

 also reported that polycarboxylate temporary luting cements present low post-operative sensitivity, adequate retention, and easy clean-up and they mentioned 

In the following clinical case, we will explore a predictable technique for preparing a strong and reliable temporary restoration where we combined these two products (

 Patient presented to the office with a lower first molar which was endodontically treated and restored with a 

Zircules Zirconium Nano-Filled Core Material (

]. Before preparation for an all-ceramic crown, a disposable and customizable metallic tray (

Clinician’s Choice) was loaded with a PVS matrix material (T

). Template is a PVS matrix material designed specifically for this step; it sets in only 30 seconds, saving time for the clinician when compared to traditional “putty” matrixes, which can take up to 6 minutes to set. Template also flows into the embrasure areas well, and will release maintaining its form as shown in 

. Due to its mechanical properties, the tray and matrix can be easily reinserted without distortions, thereby producing a provisional with virtually no flash. 

 shows the molar prepared for a full coverage ceramic restoration and, since the preparation margins were quite sub-gingival, a double cord technique was used with a #000 and #00 

Re-Cord (Clinician’s Choice) retraction cord. 

After the final impression was taken, a provisional restoration was fabricated using 

The Template matrix was reseated onto the preparation (

) and a provisional with no voids and minimal flash was produced (

). INSPIRE is easy to remove from the impression and requires little or no polishing due to its minimal surface oxygen inhibition layer. It produces a smooth, high luster, nonporous surface that will resist biofilm and plaque build-up. For this case, the clinician decided to polish the provisional and apply a final layer of a light-cured glazing material (

The temporary restoration was cemented with 

 polycarboxylate temporary luting cement and the excess was easily removed (

), due to the cement’s mechanical properties and due to the smoothness of the final surface obtained by the use of 

At the final appointment, the provisional was easily removed followed by manual clean up of the preparation. The combination of the smooth surface of temporary material and the bacteriostatic properties of the temporary cement results in a healthy gingival tissue as can be seen in 

The significant amount of frustration and wasted time that is experienced by the clinician when a final restoration needs significant adjustment can be avoided by the use of a provisional restorative material that not only resists premature fracture, but also resists wear which results in tooth movement. The above combination of 

1. Loos LG, Boyarsky HP,Quiring DJ. Procedure for occlusal refinement of mounted definitive cast to reduce clinical time required for adjustment of occlusion. J Prosthet Dent 2001;81:246-51.

2. Ramp MH, Dixon DL, Ramp LC, Breeding LC, Barber LL. Tensile bond strengths of provisional luting agents used with an implant system. J Prosthet Dent 1999;81:510-4.

3. Lind SD. INSPIRE. Strong, fracture-resistant material for temporaries. Dental Product Shopper. Nov 2013;128.

4. Santos MJMC, Santos Jr GC . Selecting a Temporary Cement: A Case report. Dentistry Today: 31(3): 96-99, Mar 2012.

Articles

 The old saying that “no chain is stronger than its weakest link” is certainly true in dentistry. When working with crown and bridge, one of the primary complaints from dentists to dental technicians is that “the occlusion was high and it took a long time to adjust it clinically.”1 The restorative process for an indirect restoration includes many steps that, when not carefully executed, can contribute to this problem. 

How to prepare a strong, reliable temporary

Current laboratory surveys and past data collected indicate that between 70-80 percent of the cases received are for single-unit crown and bridge prostheses.

Some laboratories have indicated that the number of remakes has increased from 6 percent to as high as 10 percent. With the advent and incorporation of better materials and techniques into our practices, this should not be the case.

The dual-arch impression is indicated for one or two crown and bridge units in an occlusion that is cuspid rise and relatively intact, and is generally contra-indicated for a terminal tooth preparation in the arch or group function occlusions.

It is simpler, more economical and cost effective in materials and time, is easier for the patient with less gagging potential, and has the potential for more accurate intercuspal relationships than mounted casts from single-arch impressions (12 times more accurate than full arch impressions with a bite registration)1 resulting in less chairside time seating and adjusting the prosthesis.

However, the dual-arch impression has a very high remake percentage for some dental laboratories, which easily can be eliminated or minimized if one understands the dynamics of some impression trays and PVS materials currently used, which compromise the predictable fit and occlusion of the delivered unit(s).

Plastic dual-arch trays have been extensively used in the past mainly because of their perceived low cost, while they are in fact more likely to increase our overall office overhead because of the wasted time needed to adequately seat and occlusally adjust the crown.

The plastic tray can distort because of the impression material’s hydraulics, the tray can twist around its long axis (axial roll) when impinging on hard tissues, can flex if the patient occludes on the distal bar, and the lingual bar will flex continually during polymerization of the impression material when the patient repeatedly swallows during the procedure.

The elastic memory of the plastic will drive the tray back to its original shape, distorting the impression and, unfortunately, this distortion can’t be seen when we visually evaluate the impression.

The solution is simple: as Dr. Gordon Christensen discussed in his review2, never use a plastic tray, but use a metal tray that eliminates the flex. 

The aluminum Quad-Tray Xtreme from Clinician’s Choice

 is well suited for this purpose, as it is constructed from aluminum, which has no elastic memory, and because of the sidewall design and rigidity, the flex distortion that is so common with plastic trays is eliminated.

The PVS material many clinicians generally use with dual-arch trays is the same material specifically designed for full-arch impressions. This PVS is designed to flex, because if it does not, we would not be able to remove the impression from the mouth. These materials are designed to be supported by an inflexible full-arch tray.

If we combine this flexible PVS with a flexible plastic dual-arch tray, the inevitable result is distortion in the impression and a compromised restoration. Therefore, in its review of impression materials, the American Dental Association has recommended that a very stiff PVS (a strain in compression of less than two) be used with the dual-arch technique.3

Affinity InFlex PVS impression material from Clinician’s Choice, with a strain in compression of 1.3 percent, has been specifically developed for the dual-arch impression technique, so that its stiffness will not allow distortion during the impressioning technique, but also-and equally as important-it will not distort or flex when the impression is poured up by the laboratory.4

Our patient presented with pain in a lower first molar, which was restored with a failing ceramic restoration complicated with a periapical radiolucency caused by a necrotic pulp.

The tooth was endodontically treated and restored with a MacroLock Illusion X-RO Post, 

Fibercones from RTD Dental and Zircules Zirconium Nano-Filled Core Material from Clinician’s Choice.

shows the molar re-prepared for a full coverage ceramic restoration and the initial placement of a slightly wetted #000 Re-Cord Knitted Retraction Cord from Clinician’s Choice so it would easily slip into the sulcus without attaching to the gingival tissues.

shows the final placement of the #000 retraction cord, and because the preparation margins were quite subgingival, a double cord technique was used.

shows placement of the Re-Cord #00, which was soaked in an aluminum sulphate hemostatic agent, Tissue Goo Hemostatic Gel from Clinician’s Choice, to help control any potential bleeding from manipulating the tissues.

As a general rule, any hemostatic agent should be removed prior to impressioning as hemostatic agents may compromise the setting reaction of polyvinyl siloxanes, and some may cause a discoloration of the dentin or result in a black residue (ferric sulphide).

shows the 5-7 second application of Detail Pre-Impression Cleansing Gel from Clinician’s Choice.

This is followed by a thorough water rinsing, which not only cleans the surface, but lowers the surface tension, making the impressioning easier.

The Affinity High Flow Light Body impression material is placed after the #00 Re-Cord is gently removed, making sure to keep the impression tip buried in the material while syringing 

It is critical that the dental assistant loads the Quad-Tray Xtreme with InFlex impression material in such a manner as to have the tray ready when the light body has been completely applied to the preparation.

The dual-arch tray should not be ready before nor should it be ready after, as both materials need to set simultaneously. The Quad-Tray Xtreme is inserted with the patient closing passively into the acquired centric relation and the impression material is allowed to set (

registration can be taken before the procedure starts and used later on the opposite side as a guide for the patient to bite into; this is especially useful when a mandibular block is placed.

The patient is then asked to open while holding the dual-arch tray against the prepared arch (

When using an aluminum tray, never remove the impression by torquing the handle of the tray, but gently remove it by gently rocking it laterally while holding it by its side. 

shows the final impression with all the margins captured well and the whole preparation captured in light body, which gives a more accurate die than when most of the light body is washed away because of the heavy hydraulics of some impression materials.

The final bonded ceramic restoration is shown in 

An inflexible dual-arch metal tray and an inflexible specifically designed dual-arch PVS material will systematically reduce the time required for seating and occlusally adjusting your final restoration.