Today's Dental Question & Answer : Dental Questions : Dental answers

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Question: halothane does not work. Is chloroform permissible in endodontic therapy or retreatment?

Answer: Chloroform is permissible. The FDA ban on the material was lifted. The literature has shown that the amount of chloroform used in retreatment is unlikely to cause any systemic effects, and the amount entering the system from extrusion is negligible. The bottom line is that all currently used solvents (xylene, halothane, rectified turpentine, chloroform, eucalyptol, etc.) are cytotoxic when in contact with cells, but when confined to a canal space, they probably pose only a minimal risk.

(Lt Col Harkacz) - May 2003

Reference
Chutich MJ, Kaminski EJ, Miller DA, Lautenschlager EP. Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment. J Endod 1998;24:213-216.

Cross compatibility of Resin Composites and Dentin Bonding Agents

Question: Our clinic has the 3M's Scotchbond Multi-Purpose Adhesive Plus as our primary bonding product. Do we need to use 3M's composite resin with it or can we use another company's composite if we want to?

Answer: This is a question that I frequently receive and it is an important one. Quite commonly, representatives from dental product companies will encourage you to purchase their company's bonding agent and resin composite by claiming that the result will not be as good if you don't. In other words, they say that using their bonding agent with a competitor's resin composite (or vice versa) will produce an inferior result. The research, however, does not support this claim. No clear evidence exists that using a bonding agent from one manufacturer with a resin composite from a different manufacturer has an adverse effect on parameters such as microleakage¹ or bond strength.^2,3 Evidence does exist that appears to show a difference in bond strength between resin composites, which has led some researchers to recommend using the same manufacturer's resin composite and bonding agent.⁴ The differences, however, may well be due to differences in strength between the types of resin composites^5,6(eg, hybrids versus microfills) rather than a result of compatibility differences between bonding agents and resins. Likewise, a difference in microleakage found in one study was attributed to the resin composite type rather than brand.¹

References
1. Crim GA. Influence of bonding agents and composites on microleakage. J Prosthet Dent 1989;61:571-574.
2. Chan DCN, Reinhardt JW, Boyer DB. Composite resin compatibility and bond longevity of a dentin bonding agent. J Dent Res 1985;64:1402-1404.
3. Baker JF, Murchison DF, Charlton DG, Vandewalle K. Cross compatibility of fifth-generation dentin bonding and composite systems [Abstract]. J Dent Res 1998;77:132.
4. Leirskar J, Øilo G, Nordbø H. In vitro shear bond strength of two resin composites to dentin with five different dentin adhesives. Quintessence Int 1998;29:787-792.
5. Perdigao J, Swift EJ, Cloe BC. Effects of etchants, surface moisture, and resin composite on dentin bond strengths. Am J Dent 1993;6:61-64.
6. Hasegawa T, Itoh K, Koike T, Yukitani W, Hisamitsu H, Wakumoto S, Fujishima A. Effect of mechanical properties of resin composites on the efficacy of the dentin bonding system. Oper Dent 1999;24:323-330.

(Col Charlton) - Jan 2000

Minimizing Bubbles in Investments and Stone

Question:How can I eliminate bubbles in my casts and investment? I have perfected my technique and am using the best fine-grain investments and stones. Is there anything else I can do to minimize or eliminate bubbles?

Answer: Assuming you have done everything possible to reduce bubbles and your vacuum investor is working properly, there is a rather simple thing you can do. Place the investment ring or poured impression in a dry pressure pot. Bubbles in artificial stones and fine-grain investments show significant reduction in the number and size of bubbles when allowed to set under pressure of 30 psi. Coarse-grain investments require 80 psi or higher to reduce bubbles. Pour some test samples, let them set under pressure, cut them in half, and then compare them to bench set samples. - (MSgt Ryerson) - Jan 2000

Captek Alloy System

Question: I hear there is a material that you can use to form metal-ceramic substructures without investing or casting. Do you have any information on this material?

Answer: Captek is an alloy system that eliminates the need for investing, burning out, and casting normally used to fabricate crown and bridge substructures with traditional metal-ceramic alloys. Captek uses a refractory die and a noble metal-impregnated wax to produce substructures for metal-ceramic restorations. The Captek substructure is made by pressing a gold-platinum-palladium impregnated wax (CAPTEK P) to the refractory die and trimming it at the margins. It is then fired in the porcelain furnace at 1967°F (1075°C) which causes molecular particles to join, creating a three-dimensional network of capillaries. A layer of gold-impregnated wax (CAPTEK G) is then pressed onto the substructure, trimmed at the margins, and fired at the same temperature. The heat treatment draws the "G" layer of gold into the capillaries. (A typical framework is shown in Figure 1.) The manufacturer recommends applying a thin layer of bonding agent called Capbond prior to applying porcelain.

This technology was developed 12 years ago and has been commercially available for the last 10 years. The manufacturer claims several advantages for it. First, the substructure is purported to be biocompatible and corrosion resistant. Second, it is reported to be extremely strong, so margins can be reduced to a thickness of only 0.1 mm. The manufacturer recommends metal margins be used (see Figure 2 which is a mirror view of a finished Captek restoration showing the circumferential margins). Because the substructure has a gold color and lacks a gray oxide coating, subgingival facial margins appear esthetic. Interestingly, some research indicates that a "bacterial inhibition zone" is present at the Captek substructure margins.¹ Plaque accumulations have been observed to be reduced by 90% in these areas compared to adjacent natural teeth. The manufacturer also claims that the stress-free construction of Captek substructures make the finished restoration more resistant to impact, load, and fatigue. Finally, the Captek company claims that the budget projections of laboratories using this material are simplified because the material itself is price stable (assuming gold remains less than $400/Troy ounce).

Naturally, as with any technology, substantial research must be performed to confirm or refute the many advantages claimed for the Captek system by its manufacturer. It should be noted that long-term clinical studies have not yet appeared in refereed journals that evaluate the performance of the Captek system. When they do, clinicians and technicians will be able to assess the value and clinical success of the product.

Reference
1. Goodson M, Shohert I, Imbert S, Som S. Captek alloy reduces dental plaque accumulation [Abstract]. J Dent Res 1999;78:262.

(MSgt Ryerson) - jan 2000

The Frustrations of Making Provisionals: Have Manufacturers Made it Any Easier?

Question: Are there any new materials on the market for making temporary crown and bridges?

Answer: Over the last few years, dental product manufacturers have spent a great deal of time and money developing provisional (i.e., temporary) crown and bridge products that are easier to use and have better physical properties. Standard acrylic-type provisional products have been the mainstay of dentistry since the 1930s and have, for the most part, worked satisfactorily. Products such as Jet Tooth Shade (Lang), Snap (Parkell), and Trim II (HJ Bosworth) are popular because of their low cost, acceptable esthetics, and versatility. These products come as two-part systems (a powder and a liquid) that are mixed immediately before use. Generally, they are best used for making short-term provisionals that will be needed for only a few months at most. They have several disadvantages, however. Among their drawbacks are an objectionable odor, significant shrinkage, heat production during setting, and a tendency to discolor. To address these shortcomings, manufacturers have begun producing provisional products that are bis-acryl resin composites. These materials shrink less (and therefore fit better), give off less heat, and can be polished at chairside. They don't polish to as high a luster as the acrylics and often have an air-inhibited layer following setting, which needs to be removed prior to finishing and polishing. They also tend to be brittle, so close attention must be paid to the occlusion if they are used to make long-span bridges. Many of these products are packaged in cartridges and mixed/dispensed using an automix gun. The bis-acryl composites polymerize (i.e., harden) in one of several ways: by chemicals (e.g., Integrity, Dentsply/Caulk; Temphase, SDS/Kerr; Protemp 3 Garant, 3M ESPE); by visible light (Revotek LC, GC America); or by both chemicals and light (Unifast LC GC America). These products generally perform very well, and differences among them primarily center around setting and working times, cost, and packaging form.

(Col Charlton) - May 2003

The Numbers: Is That All There is to It?

Question: All the ads for dentin bonding products contain claims about their bond strengths. Is this an important thing and should I base my decision to buy the product on it?

Shear test Answer: You're right in that manufacturers commonly tout the bonding ability of their products by featuring the product's shear bond strength to dentin. Often, they provide a chart and compare their product to other popular bonding agents. Obviously, they are depending on you to think higher is always better. Bond strengths are just one of many factors you should look at when deciding to buy a bonding product. In fact, it may be one of the less important ones. Let's look at how bond strength is measured. The test to measure shear bond strength is done by using the bonding agent to bond a cylinder of resin composite to the ground dentin surface of an extracted tooth. After storage in water (and possible cycling between hot water and cold water baths), the amount of force required to shear the composite cylinder from the dentin is measured. The average number for the group of specimens is then calculated and represents the "shear bond strength." As you can see, this laboratory test is only a rough approximation of what we need the bonding product to do intraorally. What it will be required to do in bonding a composite restoration to a tooth depends on many factors, including the size of the restoration, amount and type of dentin and enamel to which it will be bonded, the forces applied to the restoration, and the appropriateness of the technique used to apply the adhesive. So, the way to interpret the numbers given in an ad for a bonding agent is first to keep in mind that lab tests are only a screening test. They provide a rough idea as to how the bonding product compares to other similar products, and are most valuable in identifying products that significantly underperform. You should also be aware that just having the bond strength number alone doesn't tell the whole story. It is also important, for example, to know where the failure happened (e.g., between the adhesive and tooth, within the tooth, within the composite. etc.) because this tells something about the significance of the numbers. Finally, you should also remember that the numbers are only going to be featured by manufacturers when their products outperform their competitor's products. In other words, regardless of the number, the company that is advertising will always compare its product to competing brands which have not performed as well.

The bottom line is that bond strength is only one factor (and perhaps a minor one) to consider. More important factors are how the adhesive has performed in clinical studies, and the product's ease of use, cost, and range of clinical uses. DIS has evaluated more than 20 bonding products over the past few years and serves as a source of current information about these products. Please call us with any questions you have on selecting or using a dentin bonding agent.

(Col Charlton) - May 2003

You've Got to Heat It to Believe It!

Question: Newly arriving dental officers have requested the purchase of Obtura II and System B gutta-percha systems. Do you have any information on this equipment?

Obtura2 Answer: Obtura II is an injectable gutta-percha system whereas System B uses a heated-tip to soften gutta-percha points placed in the canal. Two totally-different injectable thermoplasticized gutta-percha systems are currently available - Obtura II (Spartan Co., Fenton, MS) and Ultrafil (Hygienic Corp., Akron, OH). Obtura II is a heated-gun system, whereby gutta-percha sticks are placed within a chamber in the gun, and a plunger is used to express the heated, flowing gutta percha through replaceable injection tips. The flow of the gutta percha is controlled through the temperature of the unit - the higher the temperature, the easier the flow. By design, the system is considered a "high heat" system, because the gutta percha provided by Spartan flows best at about 200 degrees C. You can buy "low-heat" gutta percha from other companies, which allows the gutta percha to flow at a lower temperature. The system consists of a gun connected to a temperature-control unit. The unit requires high maintenance because you must clean it after every use by submerging the nose of the gun in solvent and using a brush to clean out the chamber/plunger assembly. The gun itself is hot to touch, and to minimize risk when contacting the patient lips, special plastic-protective sleeves are slipped over the end of the gun. Obtura II is primarily used for backfilling canals with apical plugs. Canals without some form of apical plug/constriction could result in overextrusion of the gutta percha. Most of the literature seems to show that the high temperature is not detrimental to the periodontal ligament as long as the heated tip is not left in the canal for extended periods. The gutta percha cools fairly quickly, and to counteract shrinkage, must be condensed during cooling. The system allows continuous heat, so the gutta percha stays soft as long as the unit remains active.

In contrast, Ultrafil uses a pre-dosed cannula system. Cannulas containing various types of gutta percha are placed in a heating unit. When needed they are loaded into a gun (similar to a periodontal ligament injection unit), which expresses gutta percha from the cannula. The system is characterized as a "low-heat" unit, since the temperature needed to plasticize the gutta percha is much lower than the Obtura II system. Ultrafil has several advantages. The cannulas are disposable, the injection gun may be sterilized, and the heating unit is easily cleaned. Three types of gutta percha are available, which vary by firmness and length of working time, allowing the practitioner to tailor the type of gutta percha for a specific procedure. A disadvantage of the Ultrafil system is that it takes about fifteen minutes to get the cannulas to temperature, compared to the Obtura system, which only takes about one minute. Overall, the versatile Ultrafil system requires less counter space and the various types of unit-dose gutta-percha cannulas allows for better infection control. However, the cannula system is more expensive and if you are performing extensive backfilling, the Obtura II may be more cost effective.

Systemb System B (SybronEndo, Orange, CA) is not a injection technique, but rather a heated tip used to soften gutta-percha points placed in the canal. It follows the "continuous-wave" concept advocated by Steve Buchanan. In principle, you take a plugger tip and insert it in your prepared canal. The plugger tip needs to bind about 5-mm from your working length. A gutta-percha cone is then fit to length in the canal. The plugger tip with the System B is heated to a high temperature. Temperature and power is controlled digitally on the unit. The heated plugger is then inserted into the canal, melting the gutta-percha cone on insertion and creating a leading front (or wave) of heated gutta percha. When you get close to your binding point, the heat is discontinued, but apical pressure is continued to condense the now softened gutta percha and conteract any contraction during cooling. After a few seconds, the tip is activated for one second (high heat, short burst) and pulled back to remove excess gutta percha. The coronal space is then usually backfilled with a softened gutta-percha system.

Unless you have excellent apical control, these systems will lead to overfill of material past the apex and potential problems of apical periodontitis. In skilled hands, it is another tool for obturation. Practice on extracted teeth first before attempting the technique on patients. Be careful in canals which have apical lesions, resorptions, or open apices, as these clinical situations are not good candidates.

(Lt Col Harkacz) - May 2003

Just Seal It!

Question: A wide variety of sealants are available, from filled to colored to fluoride-containing. Are there really any differences?

Sealant Answer: Surprisingly, research has found that unfilled sealants perform as well as or better than filled sealants. Studies have found that unfilled sealants are significantly better retained^1,2 and have less microleakage³ than filled sealants. Although potentially more difficult to control during placement, the lower viscosity of the unfilled sealants allows them to penetrate deeper into the fissure system.⁴ Filled sealants may provide better mechanical properties and therefore less wear, but they suffer from a potential need for occlusal adjustment as part of the application procedure. If an unfilled sealant is left in occlusion, it will usually abrade rapidly.⁴ However, one study found that with filled sealants, most patients were unable to abrade the interferences to a comfortable level.⁵ Also, reduction in wear may not be as clinically significant as penetration when evaluating the sealing and retentive abilities of a sealant in the deeper depths of a pit or fissure.⁴

Colored sealants are easier to see during application and at recall examinations. A study by Rock and others found the error rate in identifying a sealant was 22.8% for a clear resin and only 1.4% for an opaque resin.⁶The latest marketing trend is to incorporate color-change chemistry into the sealant to make it easier to see during placement. One example is a product recently evaluated by DIS called Clinpro, a new fluoride-containing, light-activated pit and fissure sealant by 3M ESPE. Clinpro is pink when expressed from its delivery syringe and turns white following light activation.

While no one will argue against the substantial advantages of fluoride in caries prevention, it has been difficult to unequivocally prove any significant reduction in caries with the use of fluoride-releasing restorative materials. The actual fluoride release of fluoride-releasing resin-composite restorative materials and sealants is among the lowest of all the fluoride-releasing materials manufactured.⁷ No studies have documented a caries reduction due to fluoride in fluoride-releasing sealants, raising serious doubts about any clinical significance. The addition of fluoride is probably more of a marketing benefit than a clinical advantage.⁴

Finally, the introduction of light-activated sealants many years ago provided the advantages of command set, the ease of non-mixing, and fewer voids compared to autopolymerizing materials. However, De Craene and others found no significant difference in terms of retention or caries prevention between self-cured and visible light-cured sealants.⁸

(Col Vandewalle) - May 2003

References
1. Barrie AM, Stephan KW, Kay EJ. Fissure sealant retention: a comparison of three sealant types under field conditions. Community Dent Health 1990;7:273-277.
2. Rock WP, Weatherill S, Anderson RJ. Retention of three fissure sealant resins. The effects of etching agent and curing method. Results over 3 years. Br Dent J 1990;168:323-325.
3. Hatibovic-Kofman S, Wright GZ, Braverman I. Microleakage of sealants after conventional, bur, and air-abrasion preparation of pits and fissures. Pediatr Dent 1998;20:173-178.
4. Simonsen RJ. Pit and fissure sealant: review of the literature. Pediatr Dent 2002;24:393-414.
5. Tilliss TS, Stach DJ, Hatch RA, Cross-Poline GN. Occlusal discrepancies after sealant therapy. J Prosthet Dent 1992;68:223-228.
6. Rock WP, Potts AJ, Marchment MD, Clayton-Smith AJ, Galuszka MA. The visibility of clear and opaque fissure sealants. Br Dent J 1989;167:395-396.
7. Garcia-Godoy F, Abarzua I, De Goes MF, Chan DC. Fluoride release from fissure sealants. J Clin Pediatr Dent 1997;22:45-49.
8. De Craene GP, Martens LC, Dermaut LR, Surmont PA. A clinical evaluation of a light-cured fissure sealant (Helioseal). ASDC J Dent Child 1989;56:97-102.

I Can't Wait 'till You Obturate!

Question: Do you have any information on the Thermafil Plus system? Our clinic is considering its purchase.

Answer: Thermafil Plus (Dentsply Tulsa Dental, Milford, DE) is a system where plastic carriers are coated with alpha-phase gutta percha. The carrier/gutta percha is heated in an oven to plasticize the outer gutta perch, then inserted in the canal to length. During the insertion, the warm outer gutta percha flows into all the anatomic variances of the canal. An entire system is devoted to this method of obturation, to include size verifiers, obturators, an oven, and an epoxy endodontic sealer. The plastic carrier core has a groove to promote backflow of excess gutta percha during insertion, and to facilitate retreatment by providing an area for instrument insertion to loosen and remove the carrier.

Advantages of the system are ease of use, good three-dimensional fill, and quick obturation. Disadvantages are questionable apical seal, difficulty in retreatment and problematic post-space preparation. Sometimes the gutta percha will strip off the carrier to bare plastic by the time the carrier is at working length. However, the clinical significance of this remains unknown. Also, if you have a patent apical foramen, there is a good chance you will extrude softened gutta percha, sealer, or both. The carrier may be difficult to remove during retreatment. Also, creating post space is technique sensitive. You have to remove gutta percha and carrier for post space without disturbing the apical seal, which may be very difficult with this system.

The Thermafil Plus system is an acceptable method of obturation, but may not offer any big advantage over conventional lateral condensation. The system is more expensive when including the cost of the oven, carriers and nickel-titanium sizers. Whether a three-dimensional gutta percha fill is clinically superior to lateral condensation with sealer fill has yet to be proven. If stationed overseas, getting supplies in a timely manner is an additional concern. Once you have purchased the system, you are obligated to use the system's gutta-percha carriers and products, whereas standard gutta-percha cones with eugenol sealer can be purchased anywhere fairly quickly.

(Lt Col Harkacz) - May 2003

Best solution to save the extracted tooth

Question: Today I have started to save all the extrated teeth to practise with the rotatory instrumentation but....Which is the best solution to save them? They told me that bleach is not a good one as it makes the tooth weak. Alcohol? Clorhexidine? - Marcela (ROOTS) 30th June 2006

Answer:in NaOCl for 15 min then stored in saline with a bit of clorhexidine mouthrinse-JL
I would put it in Chlorexidine+Cetrimide solution which is availble as hospital concentrate disinfectant. It's been quite good with me foe keeping those abnormally shaped tooth that we extract - Ananya

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