Oral Health Group
Feature

The Complete Technology-Driven Restoration

April 1, 2013
by Les Rykiss DMD, Sherri Mitani DMD


We are all restoring teeth today with a conscious effort to be minimally invasive. Our preparations are no longer extension for prevention. Everything is conservative. However, even with the decline in dental caries, and the decreased need for restorative treatment, we sometimes are still faced with complex treatment that becomes a bit of a restorative challenge. Fortunately, technology today makes the restorative challenges somewhat routine.

This article will summarize the entire buildup of a severely broken down tooth from endodontic treatment to final crown cementation. We will go through the techniques and materials used and the rationale for each.

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CASE STUDY
The patient presents with pain in tooth #35. Upon close examination, it is determined that the crown, with which the tooth has been restored previously, is completely compromised and in need of removal (Fig. 1).

Once the crown was removed, caries was visible completely obliterating the distal wall and very deep subgingivally. The caries had also gone into the pulp necessitating endodontic treatment. The patient was given the option to either fully restore this tooth, or extract it and replace it with either an implant or multiple implant bridge, or a partial denture. The patient chose to restore this tooth fully now and was not contemplating any further treatment in that area for now. The treatment plan for this tooth is shown below.

TREATMENT PLAN #35

1. Endodontics.

2. Laser closed flap crown lengthening.

3. Fibre post and composite core buildup.

4. Lava (3M) porcelain bonded to zirconium crown.

ENDODONTICS
Tooth #35 was well isolated from oral fluids with rubber dam and accessed into the pulp chamber. The coronal aspect of the pulp chamber was enlarged with numbers 2, 3, and 4 gates glidden drills as well. At this point a #10 k file (Kerr) was inserted and using a root ZX apex locator the working length was achieved. Once the working length radiograph was taken and confirmed, files #10, 15 and 20 were worked to the working length. The intracanal lubricant Glyde (Dentsply) is always introduced on the files prior to entering the canal space. At the point, Protaper (Tulsa) files S1, S2, F1, F2, and F3 are introduced cleaning and shaping the canals to the working length, irrigating and recapitulating with each file.

Irrigation of the canal was done with 5 % sodium hypochlorite (NaOCl), and patency was maintained between each file with a #10 file. Once the canal is smooth and clear with an F3 file, The guttapercha point is fit and a confirmation radiograph is taken. Final irrigation is done with EDTA. The canal is then dried with an endovac (Discus Dental) and then completely dried with paper points. The sealant of choice here is Thermoseal (Dentsply), and it is spiraled into the canal with a lentulo-spiral and the point is inserted. The point is then seared using the Touch ‘n Heat, and warm vertical condensation ensued, until a 5mm fill was achieved.

The canal was then sealed with a cotton pellet blocking the entrance at the pulp chamber, and the temporary restoration was bonded in place using Bisco’s One Step Plus, and Build It FR Gold core material (Pentron Clinical). Figure 2 shows the completed endodontic procedure on tooth #35.

CROWN LENGTHENING
After the endodontic treatment, the tooth was visualized with the temporary core in place to keep the canal space from being contaminated by oral fluids. Figure 3 shows the distal aspect with the restoration extending subgingivally close to the bony crest

The tooth was severely broken down and carious on the distal necessitating the use of the Waterlase iPlus to help us restore this tooth.

The iPlus is an Erbium Chromium YSGG laser at the wavelength of 2780 nm. The properties of this laser are enhanced by the wavelength. Everything we do with this laser is indeed minimally invasive, with the added benefit that the laser actually imparts healing to the tissues and speeds up the healing process.

This bicuspids visualized margin was so deep on the distal wall that we needed to use the iPlus to recreate the biological width by reducing the bone height along that wall. We did a procedure called closed flap crown lengthening and this was done with a Z6 9mm zirconium tip using the “crown lengthening setting” on the interactive display screen of the iPlus. This newest Biolase hard tissue laser has a much reduced learning curve. Thanks to its intelligent display screen, which allows you to select the procedure that you are going to do,and the iPlus tells you what tip to use with the correct settings, the iPlus is flawless. The first step is to reduce the gingiva on the distal to where the anticipated final crown margin will be (Fig. 4).

This will allow for adequate ferrule for integrity of the final restoration. I then probed the area, sounded the bone, and determined that I needed to remove 2mm of bone in order to maintain the 3mm zone for biologic width. Using the crown lengthening setting and a Z6 zirconium tip for the iPlus (marked with a sharpie as seen in Fig. 5).

I created potholes in the bone to the desired depth. Then I removed the rest of the bone between the potholes to the same depth (Fig. 6). Once I had probed and confirmed biological width, I then changed my tip to the C3 chisel tip to ramp the bone away from the edge of the tooth and blend the bone smoothly. At that point, I created a laser bandage over the open wound site using the laser bandage setting and a Z6 tip.

Because there is virtually no bleeding when you do this procedure with laser, the visibility is excellent, and it allows you to continue on with the procedure and prep the tooth completely after core placement.

Most often, I would continue on with the final impression temporize and seat the final restoration at their next appointment 1-2 weeks later. Crown Lengthening done with a scalpel will delay the healing and the restorative treatment 6 weeks minimum. At the crown insertion appointment the tissues will be almost completely healed.

POST AND COMPOSITE CORE 
Now that we have ferrule after the crown lengthening, and have verified that we have a sound biologic width, we can now begin the repair process, as you can see from the photo (Fig. 7).

There was barely enough ferrule on the distal wall. However, after the laser work, we definitely have a healthy restorative situation whereby a proper ferrule could be achieved for stability of the future crown. I decided to use a fibrepost for a number of reasons. My practice has an esthetic focus and the use of metal in my restorations is very minimal, especially when there are equally as good, if not better esthetic solutions available. Secondly, I feel that the use of a fibre post (when it is necessary to use a post), as opposed to stainless steel or other metals, is a better post from a compatibility standpoint. I have found so many metal points to cause fractures in the root because of the inflexibility of metal posts. Martinez-Insua, Da Silva, And Rilo found that the main characteristic of fiber posts is the similarity of the modulus of elasticity to dentin.1 Guzy and Nicholls commented that traditionally posts that have been machined from metal are known to weaken roots and lead to root fractures.2 The other causes of failure with posts is post fracture, or post decementation, but the greatest concern clinically is irreversible failure with root fracture necessitating extraction of the tooth.3 I believe that a well bonded fibrepost will still minimally flex with the natural tooth structure and cause fewer root fractures. This is what I have experienced in my clinical practice. It has been suggested that the failure with fibre-based posts is less likely to include irreparable root fracture than with metal posts.4-7

Here we will use a conventional fibre post technique, using a Superpost, (Dental Saving
s Club, Montreal, Canada) (Fig. 8).

We will etch prime and bond the post to the root surface using Bisco’s One Step Plus, and Duolink. The Duolink will not only act as the composite cement but also can be used as a core material as well. Figures9 and 10 shows the bonding of the post and the addition of Build-It FR Gold (Pentron Clinical) to complete the buildup.

Aside from being a very resilient core material, the colour contrast of Build-It FR Gold (Pentron Clinical) core to tooth structure is easy to see. Figure 11 shows the radiograph of the completed fibre post and composite core buildup in place.

CROWN PREPARATION 
Now that the core has been completed, we will continue the preparation for a Lava crown (3M). The guidelines that I use for my Lava preparations are 1.5- 2.00mm occlusal reduction with a 1.00mm chamfer margin. These reductions are done with the Kut 2135 coarse and medium diamond burs (Dental Savings Club). It is so important to adhere to the recommended tooth preparations for the Lava crowns because inadequate tooth reduction can lead to failure of the crown. The most likely cause of failure in this case would be porcelain fracture. Clinically, an even reduction of the occlusal surface can be done by creating depth cuts on the occlusal surface by using a 1.5mm long cutting area on a bur such as a #330 bur. Failure to reduce the occlusal surface evenly can cause fractures, most often seen at the marginal ridge areas. Once the preparation is complete, traditionally one would expose the marginal area by packing cord, and potentially using a stringent to control bleeding. Since I have the Waterlase iPlus by my side at all times, my preference is to trough the tissues rather than packing cord. The use of cord and astringents can cause damage to the tissues which can result in gingival recession, irritation to the tissues, stripping of the junctional epithelium (if too aggressive packing the cord). By using the laser, there is very minimal damage to the tissues as we gently create a gap between the tooth and the gingival crest. Again, minimally invasive dentistry is of the utmost importance, and this is where technology helps us. Figure 12 shows the use of the iPlus and an MZ6 9mm bur on the troughing setting creating space between the gingival margin and the restorative tooth margin.

Again, when using the iPlus, by simply selecting the procedure that you want to accomplish,the machines preset settings will allow one to carry out the tasks with ease. It will suggest the correct tip to use and set the machine accordingly for optimum cutting efficiency. As we can see in Figure 13, there is no need for astringents because there is no bleeding.

All margins are visible so impression taking is accomplished with ease. Most often in an endodontically treated situation, there is no need for anesthesia because of the gentle nature of the troughing procedure. This is truly a bonus for the patient. To be able to go through a major restorative procedure without anesthesia allows the patient to leave the office and continue on with their day with minimal disruption to their daily routine. Even with laser closed flap crown lengthening, often we can accomplish this without anesthesia as well (which was the case here).

We then took our final impression using Affinity Heavy body and light body (Clinicians Choice). Once happy with our impression, a Blu Mousse (Parkell) bite record was taken of the prepped area. Finally a provisional crown was made using a VPS stent and Integrity (Dentsply), and temporarily cemented with Temp Grip (Dentsply).

INSERT APPOINTMENT
Typically, the LAVA crowns take a full week to return to our office. Once returned, they are checked for fit on the die, and then the uncut model to verify that the fit is perfect. Then carried to the mouth, the crown is tried in and marginal fit, proximal contacts and occlusion is verified. Most often, the fit of a LAVA crown is exceptional. Here is no exception. The tooth is then cleansed with a chlorhexidine scrub, readying it for final cementation. The cement of choice here is Ceramir (Doxa Dental). Ceramir is a biocompatible self-adhesive luting cement. The beauty of Ceramir is that it stimulates hydroxyl apatite formation and decreases post op sensitivity. It gives unsurpassed bond strengths immediately and the bond strength actually increases over time because it fosters the build-up of nano-crystals that integrate with both tooth structure and the material. This cement also works extremely well with zirconium. Figure 14 shows the final restoration in place.

CONCLUSION
Technology, as demonstrated here allows the practioner to perform a complete restoration using minimally invasive procedures. The use of fibre posts, properly bonded to the tooth will not only make for a wonderful restorative choice, but will also leave the tooth restored with a better solution than a metal post due to its ability to be less rigid. This results in fewer root fractures and a perfectly bonded post to the root. Minimally invasive laser crown lengthening allows the practioner to continue with the restorative process that much quicker as was seen here. After endodontics, this tooth was fully restored in less than two weeks, as opposed to traditional scalpel crown lengthening, which would have necessitated a 6-8 week healing period prior to embarking on the restorative phase. The choice of crown was LAVA which uses CAD/CAM technology to mill a zirconium core as opposed to a metal substructure. It should be noted that there are other options for technology that could have been used here, such as digital impressions for milling with either the Cerec or E4D units. Both are also fine choices that should not be overlooked.OH


Dr. Rykiss maintains his private practice in Winnipeg, MB. He is a graduate of the University of Manitoba as well as a graduate and Mentor at the Nash Institute for Dental Learning in Charlotte, N.C. He has his associate Fellowship from the World Clinical Laser Institute, and is a member of the American Society of Dental Aesthetics (ASDA). He teaches, lectures, and writes articles on restorative, cosmetic dentistry, and hard and soft tissue laser use.

Oral Health welcomes this original article.

REFERENCES
1. Martinez-Insua A, Da Silva L, Rilo B, et al. Comparison of tise fracture resistances of pulpless teeth restored with a cast post and core or carbonfiber post and composite core. J Prosthet Dent 1998;80:527-532.

2. Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J Prosthet Dent 1979; 42:.39-44.

3. Bateman G, Ricketts D N J, Saunders W P. Fibre-based post systems: A review. British Dent J 2003; 195: 43-48.

4. King PA, Setchell DJ. An in-vitro evaluation of a prptotype CFRC prefabricated post developed for the restoration of pulpless teeth. J Oral Rehabil 1990; 17: 599-609.

5. Akkayan B, Gulmez T. Resistance to fracture of endodontically treated teeth restored with different post systems. J Prostht Dent 2002; 87: 431-437.

6. Cormier CJ, Burns DR, Moon P. In vitro comparison of the fracture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration. J Prosthodont 2001; 10: 26-36.

7. Dean JP, Jeansonne BG, Sarkar N.In vitro evaluation of a carbon fiber post. J Endod 1998; 24: 807-810.


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