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In this issue we bring you lot of interesting articles to improve your clinical practice.

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What are Giomers
What are the Benefits of Pre procedural mouth rinsing?
To Bond Or not to Bond Amalgam
Flowable Composites

What are Giomers

Giomers are a relatively new type of restorative material. The name "giomer" is a hybrid of the words "glass ionomer" and "composite", which pretty well describes what a giomer is claimed to be. Although glass-ionomer restorative materials such as Ketac-Fil (3M ESPE) and Fuji Type II (GC America) have some very important properties, such as fluoride release, fluoride rechargeability, and chemical bonding to tooth structure, they also have well-known shortcomings. Their esthetics, for example, are less than ideal and make them a poor second choice to resin composites for restoring esthetically-demanding areas. Also, they are sensitive to moisture contamination and desiccation, which can present the clinician with challenges during their placement. In the 1990s manufacturers improved these shortcomings by adding resins to glass ionomers to produce resin-modified glass ionomers. These products (e.g., Fuji II LC, GC America; Vitremer, 3M ESPE; Photac-Fil Quick, 3M ESPE) have much better esthetics and handling characteristics than glass ionomers. Importantly, they also retain many of the glass ionomer's beneficial properties, such as long-term fluoride release and the ability to be recharged with topically-applied fluoride. They tend, however, to discolor over time. In another attempt to "better" the glass ionomer restorative materials, compomers were also developed. They were touted as being similar to glass ionomers but having much better esthetics and being easier to place and polish. Unfortunately, some of the manufacturer's claims were not confirmed by published research. Although they handled better than GICs, they released much less fluoride and could not be recharged.

In the continuing quest for improved glass ionomer-like restoratives, manufacturers have developed and introduced a new class of materials called "giomers." As noted earlier, the term implies they are combinations of glass ionomers and composites. Their manufacturers claim they have properties of both glass ionomers (fluoride release, fluoride recharge) and resin composites (excellent esthetics, easy polishability, biocompatibility). Giomers are distinguished by the fact that, while they are resin-based, they contain pre-reacted glass-ionomer (PRG) particles. The particles are made of fluorosilicate glass that has been reacted with polyacrylic acid prior to being incorporated into the resin. The pre-reaction can involve only the surface of the glass particles (called surface pre-reacted glass ionomer or S-PRG) or almost the entire particle (termed fully pre-reacted glass ionomer or F-PRG). Giomers are similar to compomers and resin composites in being light activated and requiring the use of a bonding agent to adhere to tooth structure. Only one giomer is commercially available at the time of this writing, Shofu's Beautiful, (see at right) which uses the S-PRG technology. According to Shofu, Beautiful is indicated for restoring Class I through V lesions as well as for treating cervical erosion lesions and root caries. It is available in 13 shades and is supplied in syringes.

Little published research is available on the properties or performance of giomers. One recently published study compared the fluoride release of a glass ionomer, a resin-modified glass ionomer, a giomer, and a compomer. It found that while the giomer released fluoride, it did not have an initial "burst" type of release like glass ionomers, and its long-term (i.e., 28-day) release was lower than that of the other materials.¹ Another study found that a giomer, after polishing with Sof-Lex disks, had a smoother surface than a glass ionomer, and one that was comparable to that of a compomer and a resin composite.² A three-year clinical study comparing the performance of a giomer with that of a microfill resin composite in Class V erosion/abrasion/abfraction lesions has also been done. After measuring eight performance characteristics, no significant differences between the two materials were found.³

Almost assuredly, many other giomer products will become available in the future.

References
1. Yap AUJ, Tham SY, Zhu LY, Lee HK. Short-term fluoride release from various aesthetic restorative materials. Oper Dent 2002;27:259-265.
2. Yap AUJ, Mok BYY. Surface finish of a new hybrid aesthetic restorative material. Oper Dent 2002;27:161-166.
3. Matis BA, Cochran MA, Carlson TJ, Eckert GJ, Kulapongs KJ. Giomer composite and microfilled composite in clinical double blind study [Abstract]. J Dent Res 2002;81:A-80.

What are the Benefits of Pre procedural mouth rinsing?

Pre-procedural mouth rinsing is the use of an antimicrobial mouth rinse by the patient before a dental procedure. Its objective is to reduce the number of oral microorganisms that may be released as an aerosol or spatter from a patient's mouth during dental care that subsequently contaminate equipment, operatory surfaces, and dental healthcare personnel.

A visible spray is created during the use of rotary dental and surgical instruments (e.g., handpieces, ultrasonic scalers) and air-water syringes. This spray contains, primarily, large-particle spatter of water, saliva, blood, microorganisms, and other debris. Spatter travels only a short distance and settles out quickly, landing either on the floor, nearby equipment and operatory surfaces, the dental healthcare personnel providing care, or the patient. The spray may also contain some aerosol. Aerosols take considerable energy to generate, consist of particles less than 10 microns in diameter, and are not typically visible to the naked eye. Aerosols can remain airborne for extended periods of time and may be inhaled; they should not be confused with the large-particle spatter that makes up the bulk of the spray from handpieces and ultrasonic scalers. Appropriate use of dental dams, high-velocity air evacuation, and proper patient positioning should minimize the formation of droplets, spatter, and aerosols during patient treatment.

To date, no scientific evidence supports the claim that pre-procedural mouth rinsing actually prevents disease transmission in the dental operatory, but studies have shown that a pre-procedural rinse with a product containing an antimicrobial agent (e.g., chlorhexidine gluconate, essential oils, povidone iodine) can reduce the level of oral microorganisms generated when performing routine dental procedures with rotary instruments. Pre-procedural mouth rinses may be most beneficial before a prophylaxis using a prophylaxis cup or ultrasonic scaler since rubber dams cannot be used to minimize aerosol and spatter generation, and unless the provider has an assistant, high-volume evacuation is not commonly used.

To Bond Or not to Bond Amalgam

Multiple laboratory studies have found definite advantages for bonded amalgam restorations including increased retention,¹ fracture resistance,^2,3 and marginal seal.⁴ Staninec found that the use of adhesives provided greater retention than grooves or dovetails.¹ Oliveira and others found improved fracture resistance in large MOD preparations when bonding amalgam compared to the use of Copalite alone.² A study by Burgess and others found no difference in the strength of complex amalgam restorations using four TMS pins or bonding, but the combination of the two significantly increased the forces necessary for fracture.³ Studies have also shown increased retention of amalgam when bonding with resins containing filler particles.⁵ The more viscous bonding agent may improve penetration into the amalgam during condensation.⁶ Also, research has shown a reinforcement of remaining tooth structure with bonded amalgam restorations.⁷However, the ability to maintain this reinforcement over time remains equivocal with some studies showing no increase in fracture resistance after aging and thermocycling.^8,9 The use of an adhesive agent under amalgam has been shown in laboratory studies to decrease microleakage.⁴ Again, the long-term significance of this decrease is unknown.

Most of the clinical studies have found no decrease in post-operative sensitivity^10,11 and no difference in the performance of bonded amalgam restorations compared with traditional mechanically-retained restorations.^6,12 Contrary to popular belief, the preponderance of clinical investigations has demonstrated no difference in sensitivity reported by patients receiving amalgam restorations with or without resin adhesives.^10,11 Summitt and others published a clinical study comparing the performance of bonded versus pin-retained complex amalgam restorations and found no difference after five years between the two techniques. They concluded that bonding with a filled bonding resin (Amalgabond Plus, Parkell Inc., Farmingdale, NY) was a satisfactory method of retaining large amalgam restorations replacing entire cusps.⁶ So, should you place an adhesive agent under all of your amalgam restorations? Given the added cost, time and technique sensitivity of using adhesive liners, there appears to be no clinically-demonstrated benefit in bonding conventional preparations which contain customary retentive features.¹³ However, given the advantages of increased retention, strength and marginal seal found in laboratory studies, the bonding of amalgam may be justified adjunctively with traditional mechanical retention in large restorations replacing a cusp, when tooth structure may need some reinforcement, and for crown foundations.¹³

References
1. Staninec M. Retention of amalgam restorations: undercuts versus bonding. Quintessence Int 1989;20:347-351.
2. Oliveira JP, Cochran MA, Moore BK. Influence of bonded amalgam restorations on the fracture strength of teeth. Oper Dent 1996;21:110-115.
3. Burgess JO, Alvarez A, Summitt JB. Fracture resistance of complex amalgam restorations. Oper Dent 1997;22:128-132.
4. Meiers JC, Turner EW. Microleakage of dentin/amalgam alloy bonding agents: results after 1 year. Oper Dent 1998;23:30-35.
5. Diefenderfer KE, Reinhardt JW. Shear bond strengths of 10 adhesive resin/amalgam combinations. Oper Dent 1997;22:50-56.
6. Summitt JB, Burgess JO, Berry TG, Robbins JW, Osborne JW, Haveman CW. The performance of bonded vs. pin-retained complex amalgam restorations: a five-year clinical evaluation. J Am Dent Assoc 2001;132:923-931.
7. el-Badrawy WA. Cuspal deflection of maxillary premolars restored with bonded amalgam. Oper Dent 1999;24:337-343.
8. Santos AC, Meiers JC. Fracture resistance of premolars with MOD amalgam restorations lined with Amalgabond. Oper Dent 1994;19:2-6.
9. Bonilla E, White SN. Fatigue of resin-bonded amalgam restorations. Oper Dent 1996;21:122-126.
10. Mahler DB, Engle JH, Simms LE, Terkla LG. One-year clinical evaluation of bonded amalgam restorations. J Am Dent Assoc 1996;127:345-349.
11. Smales RJ, Wetherell JD. Review of bonded amalgam restorations and assessment in general practice over 5 years. Oper Dent 2000;25:374-381.
12. Browning WD, Johnson WW, Gregory PN. Clinical performance of bonded amalgam restorations at 42 months. J Am Dent Assoc 2000;131:607-611.
13. Setcos JC, Staninec M, Wilson NHF. Bonding of amalgam restorations: existing knowledge and future prospects. Oper Dent 2000;25:121-129.

Flowable Composites

It has become popular to routinely place a flowable composite (e.g., Filtek Flow, Flow-It ALC, Tetric Flow, Revolution Formula 2) on the pulpal floor and axial wall of a Class II preparation prior to restoring the tooth with a packable resin composite (e.g., Pyramid, SureFil, Solitaire 2, Prodigy Condensable).¹ In fact, some manufacturers of packable and flowable composites include recommendations in their instructions to do so. Clinicians usually place a flowable liner because it reduces the bulk of packable composite that has to be placed. This makes it easier and less time consuming to restore the tooth. Others believe it helps reduce leakage at the tooth/resin interface because the liner is flexible and absorbs some of the packable composite's shrinkage as it cures. This, at least theoretically, may result in a better bond between the resin and tooth with little or no gap being formed. There is some evidence supporting this theory.^2,3 Finally, some users place a flowable because it contains fluoride, and they believe that the fluoride release will have a anti-cariogenic effect.

If you routinely place a flowable composite as a liner before restoring a tooth with a resin composite, be it a microhybrid or packable, you should be aware of some precautions to take. First, the flowables are essentially "thinned down" composite resins, which accounts for their appealing characteristic of easy placement. The thinning down process is accomplished, at least in part, by incorporating fewer filler particles into the resin. As a result, physical properties such as strength and resistance to fracture are lower. So we should be mindful of the need to place a flowable in a relatively thin layer. Also, a study published a few years ago found that a number of then currently-available flowable composites lacked a sufficient degree of radiopacity.⁴ This means that on radiograph the flowable would appear as a thin, radiolucent line extending from the margin to the axial wall. Without a well-documented record, a clinician could misinterpret this as caries, possibly secondary to microleakage. Unfortunately, cases have been reported where the otherwise acceptable resin composite restoration has been removed only to find that the radiolucent "line" was a non-radiopaque flowable resin.

Perhaps the best reason for using a flowable resin as a liner beneath a packable composite is to make it easier to pack the composite into the preparation. Packables are thick, and it can be difficult to place them in a preparation (especially one that is irregular with undercuts) without producing voids. By placing a flowable resin liner into areas of the preparation that are difficult to access, the potential for producing voids is reduced.

The bottom line is not that we shouldn't use flowable resins as liners, but that we need to be aware of their limitations, so that we choose the right flowable product and use it sparingly so that its lesser physical properties do not compromise the clinical success of the packable resin restoration.

References
1. Fortin D, Vargas M. The spectrum of composites: new materials and techniques. J Am Dent Assoc 2000;131:26S-30S.
2. Payne JH IV. The marginal seal of Class II restorations: flowable composite resin compared to injectable glass ionomer. J Clin Pediatr Dent 1999;23:123-130.
3. Ferdianakis K. Microleakage reduction from newer esthetic restorative materials in permanent molars. J Clin Pediatr Dent 1998;22:221-229.
4. Murchison DF, Charlton DG, Moore WS. Comparative radiopacity of flowable resin composites. Quintessence Int 1999;30:179-184.