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Authors : Dr Geoffrey M. Knight.

Abstract :

The removal of softened dentine to create a firm base for a restoration has been one of the corner stones of restorative dentistry. Students were taught that even if the tooth was asymptomatic, it was better to chase caries into the pulp rather than risk the chance of progression of a lesion.

In the late nineties an emerging bank of evidence showed that the creation of a biological seal at the cavo margin (isolating the lesion from the overlaying biofilm) reduced the viability of the bacteria remaining in the lesion and arrested further progression of caries.1 It was further shown that the infusion of dentinal tubular fluids from the pulp through the remaining hard tissues were able to assist remineralization of caries affected dentine. 2

If a glass ionomer cement restoration is placed over the remaining caries, fluoride and either strontium or calcium ions (depending upon the glass used in the cement) transfers from the cement into the underlying tooth structure and assists with remineralization. 3

Dentine forms in a biological soup resulting in hydroxy apatite crystals that are contaminated with carbonate ions and various mineral salts. The pH that this carbonated apatite demineralizes is around 5.5. If the demineralized dentine is able to remineralize without the presence of carbonate ions and with fluoride ions present, the resulting complex of hydroxy and fluor apatite is able to resist demineralization to a pH of around 4.5.

Demonstrating caries remineralization under a well sealed occlusal restoration within the strict parameters of a clinical trial is one thing, predictability achieving a biological seal in a proximal box within the cut and thrust of general dental practice is another.

One of the constraints of ART (atraumatic restorative technique) dentistry is achieving a biological seal at the restorative interface. 4 While glass ionomer cement certainly inhibits caries, a carious cavo margin restored with GIC may not seal the cavity from the adjacent biofilm.

The challenge is to find a way of predictably sealing caries from the overlying biofilm without relying on the mechanical sealing properties of a restorative material.

The infusion of ozone5 or the application of silver fluoride and potassium iodide6 to a carious lesion prior to placing a restoration reduces the viability of caries and assists remineralization by inhibiting the formation of a biofilm over the treated dentine.

Clinical case 1

A patient presented with a large carious lesion on tooth 37. Although the lesion was asymptomatic a periapical radiograph showed extensive caries that may well have involved a pulpal exposure during cavity preparation. Figure 1

Overlying caries were removed and the residual softened dentine was infused with ozone for 20 seconds using a HealOzone* instrument. Following this, a high fluoride releasing glass ionomer cement restoration was placed into the preparation. A radiograph taken immediately after this procedure shows extensive radiolucency below the restoration. Figure 2.

Twelve months later the patient was recalled and a composite resin sandwich was placed over the glass ionomer cement. Figure 3. At this appointment a further radiograph was taken showing a dramatic increase in radiopacity below the glass ionomer cement. Figure 4

 

Fig. 1: Large carious on tooth Fig. 2: Glass ionomer cement restoration places over HealOzone treated lesion
Fig. 3: Composite resin overlay sandwich restoration placed 12 months after initial GIC dressing. Fig. 4: Dramatic reminerlization 12 months after HealOzone and GIC dressing.

Clinical case 2

Large proximal carious lesions were diagnosed radiographically on teeth 45 and 46. Figure 5 After gaining access to the lesions using tunnel preparations, caries were removed around the perimeter of the lesions and left in the deepest parts of the cavities overlaying the pulps. The teeth were first etched with 37% phosphoric acid for 5 seconds, washed and dried with oil free air. Next, a solution of ammoniated silver fluoride was applied followed by a solution of potassium iodide to prevent the black staining associated with AgF. After washing and drying the preparations, the cavities were restored with glass ionomer cement restorations. Eighteen months later the teeth were again radiographed. Although this patient has a high caries rate as demonstrated by the new lesion that had formed on the distal aspect of tooth 46, there was increased radiopacity present below the restorations, especially in tooth 46. Figure 6

Theoretically, achieving a biological seal at the cavo margin will predispose to remineralization in a vital tooth. The use of ozone or silver fluoride increases the predictability of remineralization occurring by biologically sealing the cavo margins. Glass ionomer cement restorations transfer fluoride and calcium or strontium ions into the lesion and assist with remineralization and the formation of fluor apatite. 3 The use of silver fluoride and potassium iodide prior to placing a glass ionomer cement restoration increases the bond strength of GIC to dentine. 7 This is certainly a powerful argument to use a glass ionomer instead of a composite resin base when restoring a carious lesion.

Intentionally leaving caries under a restoration can predispose to dental legal problems if the patient is unaware of what has been done particularly if another practitioner should radiograph a tooth treated in this manner. Dentists who carry out remineralization procedures are well advised to provide their patients with explanatory notes on what has been done and the outcomes to be expected. A sample explanatory sheet is available on the author’s web site, www.dentalk.com.au go to seminar notes.

*Kavo, Germany

 

Fig. 1: Large proximal carious lesions teeth 45 and 46 Fig. 2: Eighteen months after AgF/KL treatment there has increased reminerazation, especially in tooth 46


Disclosure

The author’s name appears on a process patent for the application of silver fluoride and potassium iodide.

References

  1. Mertz-Fairhurst EJ, Curtis JW, Ergle JW, Rueggeberg FA, Adair SM. Ultra Conservative and Cariostatic Sealed Restorations: Results at Year 10. JADA, 1998; 129: 55-66
  2. OzoK et al. Effect of Dentinal Fluid on Dentin in vitro. J D Res 2004: 849-853
  3. Knight GM, McIntyre JM, Craig GG, Mulyani. Ion uptake into demineralized dentine from glass ionomer cement following pre-treatment with silver fluoride and potassium iodide Aust Dent J 2006; 51:237-241
  4. Kidd EA. How clean must a cavity be before restoration? Caries Res 2004:38:305-313
  5. Baysan A, Lynch E. Effect of ozone on the oral microbiota and clinical severity of primary root caries. Am J Dent 2004; 17:56-60

More references are availabe on request.