A Step-by-Step Approach for Caries Removal by Protecting Healthy Tooth Structure from Excessive Dentin Removal
Lou Graham, DDS
For more than a century, since the creation of belt-driven handpieces, dentists have been removing caries based on the concept of drill, remove, and restore. Murray and colleagues1 have shown that the remaining dentin is an essential feature for long-term pulpal health. Translated, this realization clearly means that removing excess dentinal tooth structure and encroaching on the pulpal tissue directly correlate to potential negative pulpal outcomes.
In 1962, Massler2 demonstrated a more conservative cavity preparation technique. This technique required the removal of caries-infected dentin only, leaving behind soft but uninfected dentin, which he termed affected dentin. If the acid production was halted, affected dentin could be remineralized. Massler also promoted the idea that pulp dentin has great reparative power and that this power should not be ignored in managing caries.2
The key is not to simply cut into hard dentin but, in fact, remove the caries-infected dentin and maintain the caries-affected dentin. Frencken and colleagues3 demonstrated that dental cavities prepared with hand instrumentation to remove undermined enamel and soft dentin and filled with glass ionomers showed a success rate of 93% 1 year posttreatment in permanent teeth. Their premise was to remove the caries-infected dentin and allow the tooth to heal. The question still remained, was there a technique available to leave caries-affected dentin and remove caries-infected dentin?
Studies have shown that with partial caries removal and sealed restorations, bacterial numbers are reduced dramatically within the restoration.4 Yet, a recent study showed that only one in five dentists would prefer to follow these studies in lieu of direct pulpal exposure.5 Startlingly, the dental profession continues to expose pulpal tissues vs a far more conservative approach of caries removal.
Removal technique is only part of the issue. Another study showed reduced bond strengths in pulpal floors and axial walls,6 while a separate study found even further diminished bond strengths in caries-affected dentin.7
In essence, caries removal is a process that has to be done in a methodical way. The basis of such a process has to allow the clinician a level of success that minimizes the question, “Have I removed all of the decay?” Today the standard evaluation involves instruments, such as explorers and excavators, which predate the turn of the 20th century. These issues become even more questionable when such hand instruments are worn well past their clinical uses and create false negative and positive results. Advancements, such as caries-detection stains, have aided dentists in caries evaluation; however, there can be tremendous variability in outcomes.
As a profession, dentists identify with the need to better evaluate the removal of caries-infected dentin. Future advancements, such as ozone therapy or tooth-decay detection by measurement of increased light-induced fluorescence (Spectra™, Air Techniques Inc, Melville, NY), can have tremendous impacts for patients for years to come. But what about today, tomorrow, or next week? This article describes a technique available today—a technique that preserves dentin in the restorative process and ultimately improves long-term clinical outcomes. This technique is followed by a proven approach on restoring the damaged dentinal surfaces and the enamel with a variety of restorative options.
After high-speed access, the process begins with initial caries removal with a new, unused low-speed carbide bur. A round carbide bur generally works well in its removal of caries-infected dentin. These products are used in a far more conservative low-speed handpiece system, such as CeraTorque (Medidenta, Woodside, NY).
The handpiece has two speeds (1,250 rpm and 5,000 rpm). In the author’s experience, these two speeds accomplished the majority of procedures required of traditional low-speed handpieces (20,000 rpm), yet performed in a far more conservative way. For many systems, manufacturers recommend composite and porcelain polishers at speeds of 5,000 rpm. Higher speeds simply displace too much heat, creating excessive wear of burs, restorative materials, and neighboring tooth structure. By using the CeraTorque, carbides and other instruments can be run at both speeds—1,250 rpm for careful caries removal and 5,000 rpm for gross removal.
After completing initial caries removal, transillumination (Orascoptic DK™, Orascoptic, a Kerr Company, Middleton, WI; EndoTec II, Medidenta; or Radii Plus, SDI North America, Inc, Bensenville, IL) and a caries-indicator solution are used to highlight areas that require further caries removal. At this point, the CeraBur K1SM (KOMET USA LLC, Rock Hill, SC) (Figure 1) is used to remove the remaining caries-infected dentin. The K1SM is made of zircon-dioxide ceramic partly stabilized with yttrium and aluminum ceramics. In the author’s experience, using this bur at 1,250 rpm will remove caries-infected dentin easily. The user can feel when healthy dentin is reached. This is a dramatic difference from carbides at traditional low speeds, which can remove too much dentin and, in the process, place additional risk on pulpal tissue.
Then re-examine the area with transillumination and, if there is any suspicion of further decay, reapply caries-indicator solution. If the solution is reapplied, a K1SM bur is used to remove any residual product that may interfere with chemical bonding during the restorative process. In this sequence, use the ceramic bur at more conservative speeds.
Previously, the author’s standard of care was to use a spoon and an explorer for caries evaluation. While these instruments still serve a definite purpose and can be used in the described sequence, their effectiveness is unknown. Defining hard dentin by the touch of an explorer or a spoon can vary from individual to individual. After 25 years in practice, the author has found the described sequence for removing caries-infected dentin to be far more conservative and verifiable.
A 25-year-old woman came to the office for a routine exam. The patient had been seen routinely for check-ups and had a noncontributory health history. As part of her exam, the DIAGNOdent® (KaVo Dental Corp, Lake Zurich, IL) was used to document all the occlusal grooves on her posterior teeth. In the author’s practice, the use of this device as an adjunct to visual examination is an absolute because of its accuracy. The patient had occlusal DIAGNOdent readings of 30+ in multiple locations and shadowing with transillumination, but negative findings with traditional explorer evaluation. Additional tests included using the Logicon Caries Detector™ Software (Kodak Dental Systems, Atlanta, GA), which is a software tool for digital radiographs that, via logarithms, allowed analysis of the class II lesions. When the full diagnosis was completed and a class I lesion was detected, the patient was scheduled for her restorative appointment.
It was decided with a reading of 58 and a peak of 68 via the DIAGNOdent (greater than 30 is highly suspicious) on tooth No. 19 that local anesthetic was required. It has been this author’s clinical experience that the STA™ system (Milestone Scientific, Livingston, NJ) with 4% Septocaine® 1;200,000 (Septodont USA, New Castle, DE) achieves consistent and almost immediate anesthesia for lower molars and routinely eliminates the need for traditional blocks (Figure 2). On achieving anesthesia, the area was opened with a conservative preparation using burs, such as Micro Prep Kit 4519 (KOMET USA LLC) or Fissure/Anatomy Kit 4520 (KOMET USA LLC) (Figure 3). Using traditional high-speed 557 type carbides, the lesion was opened and the described protocol sequence was followed. At the 5,000 rpm mode, an unused No. 6 round carbide bur was used to remove the large amounts of softened caries-infected dentin, followed by the same bur at 1,250 rpm. Transilluimination and caries-indicator solution were used for evaluation of the preparation area. After completion and rinsing of the caries solution, final removal of caries-infected dentin was achieved using a No. 6 K1SM bur (Figure 4 and Figure 5) at 1,250 rpm.
As stated earlier in this article, leaving sound caries-affected dentin is a well-accepted approach. This conserves dentinal tooth structure and brings about the next question: Restore or rebuild the tooth? Though it is not the focus of this article, in the author’s opinion, the glass ionomer family of materials should be used as either a base or a liner. Given the eventual depth of this preparation, it was decided to use a glass ionomer base (ie, Fuji IX GP Extra, GC America, Inc, Alsip, IL; or Riva Self-Cure, SDI North America Inc) vs a liner (ie, Vitrebond™, 3M ESPE, St. Paul, MN; Fuji Lining LC, GC America, Inc; or Ionoseal, VOCO America, Inc, Sunnyside, NY)(Figure 6). The technique involves using a conditioner for 10 seconds, rinsing, blot-drying, and directly placing the glass ionomer. After 30 seconds of placement, using a microbrush or composite instrument, the material was condensed and allowed to fully set (between 2.5 and 4 minutes based on the material).
After allowing the material to fully set, a composite finishing football diamond was used to rebevel the margins and remove excess glass ionomer material. Either the FS Diamond Kit 4523 (KOMET USA LLC) or Q-Finishing Kit 4477 (KOMET USA LLC) can be used for this step. The tooth then was etched and bonded, and composite was placed buccally and lingually on the occlusal surfaces to minimize C-factor problems (Figure 7). This type of restoration allows the dentin to be replaced with a material that recharges and releases fluoride for remineralization, and creates fluorapatite crystals within the caries-affected dentin while being overlaid by a composite material, which is far more stable in occlusal load situations.
The sequential approach to decay removal is all too often rushed or neglected in the restorative phase. As studies have shown, careful removal and maintaining sound dentinal tooth structure are vital for long-term pulpal health; therefore, careful caries removal becomes paramount in the process. This article has presented a step-by-step approach for caries removal, thus protecting the tooth from excessive dentinal removal.
1. Murray PE, Smith AJ, Windsor LJ, et al. Remaining dentine thickness and human pulp responses. Int Endod J. 2003;36(1):33-43.
2. Massler M. Control of caries; a new concept. N Z Dent J. 1962;58:69-73.
3. Frencken JE, Songpaisan Y, Phantumvanit P, et al. An atraumatic restorative treatment (ART) technique: evaluation after one year. Int Dent J. 1994;44(5):460-464.
4. Mertz-Fairhurst EJ, Curtis JW Jr, Ergle JW, et al. Ultraconservative and cariostatic sealed restorations: results at year 10. J Am Dent Assoc. 1998;129(1):55-66.
5. Oen KT, Thompson VP, Vena D, et al. Attitudes and expectations of treating deep caries: a PEARL Network survey. Gen Dent. 2007;55(3):197-203.
6. Lopes GC, Vieira LC, Araujo E. Direct composite resin restorations: a review of some clinical procedures to achieve predictable results in posterior teeth. J Esthet Restor Dent. 2004;16(1):19-32.
7. Lee KW, Son HH, Yoshiyama M, et al. Sealing properties of a self-etching primer system to normal caries-affected and caries-infected dentin. Am J Dent. 2003;16(Spec No): 68A-72A.
About the Author
Lou Graham, DDS