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Are There Acceptable Alternatives to Amalgam?
Promising new dental materials on the horizon
The effect of ultrasonic post instrumentation on root surface temperature
Light-emitting diode curing light irradiance and polymerization of resin-based composite
Controlling the fluoride dosage in a patient with compromised salivary function
Amorphous calcium phosphates for tooth mineralization
Probing the origins and control of shrinkage stress in dental resin-composites: I 
Probing the origins and control of shrinkage stress in dental resin composites. II
Effect of thermal cycling on whisker-reinforced dental resin composites
Effects of fiber length and volume fraction on the reinforcement of calcium phosphate cement
Three-body wear of dental resin composites reinforced with silica-fused whiskers
The clinical effect of amorphous calcium phosphate (ACP) on root surface hypersensitivity
The periodontal response to cantilevered resin-bonded bridgework

Are There Acceptable Alternatives to Amalgam?
JULY.2004.VOL.32.NO.7.CDA.JOURNAL 601
J. Rodway Mackert, Jr., DMD, PhD, and Michael J. Wahl, DDS
Authors / J. Rodway Mackert, Jr., DMD, PhD, is a professor, Section of Dental Materials, School of
Dentistry, at Medical College of Georgia in Augusta.
Michael J. Wahl, DDS, practices dentistry in Wilmington, Del. Amalgam Alternat i ves F

A B S T R A C T

Amalgam has been the material of choice for restoring posterior teeth for more than 100 years. The past 25 years have
witnessed significant advances in restorative materials themselves and in the bonding systems for retaining a restoration
in the prepared tooth. As a result, there has been a shift toward resin composite materials during this same period
because of concerns about the esthetics and biocompatibility of dental amalgam. In addition, other materials such as glass
ionomer cements, ceramic inlays and onlays, and gold alloys have been used as alternatives to amalgam. This article will
review recent studies on the longevity and biocompatibility of these alternatives to dental amalgam.

For more than 100 years, amalgam has been the material of choice for the filling of posterior teeth. More than 75 percent
of dentists surveyed in 2001 placed amalgam. Dentist in the United States placed about 71 million amalgam restorations
versus only about 46 million posterior composite restorations in 1999, about a 60 percent amalgam to 40 percent composite
resin ratio.2 Data is limited, but glass ionomer, gold, and ceramic restorations combined probably comprised about one
percent of all fillings placed by United States dentists in 1999. Still, the use of resin composites and other amalgam
alternatives was up sharply over the last decade, and these are likely to surpass the use of amalgam in coming years
both because of perceived cosmetic, clinical, or health issues, or a combination of these. The amalgam alternatives
we will focus on are resin composite, glass ionomer, ceramic, and gold restorations.

Promising new dental materials on the horizon
Eichmiller FC. American Dental Association Health Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, Maryland, USA. The rapidly evolving field of materials science is providing dentistry with new treatments and alternatives. Calcium phosphate materials are under development for bone repair and replacement, root surface desensitization, and for caries prevention, by greatly increasing the remineralizing efficiency of fluorides. Composites fabricated from calcium phosphates and polymers may have application as pulp capping and cavity-basing materials. An alternative to mercury dental amalgam is being investigated; it is composed of silver powders that are cold-welded in the presence of a dilute acid. These materials are only a few of the technologies that may profoundly affect the future delivery of dental care. J Endod. 2006 Nov;32(11):1085-7. Epub 2006 Sep 25. The effect of ultrasonic post instrumentation on root surface temperature Huttula AS, Tordik PA, Imamura G, Eichmiller FC,McClanahan SB. Naval Postgraduate Dental School, Bethesda, Maryland, USA. This study measured root surface temperature changes when ultrasonic vibration, with and without irrigation, was applied to cemented endodontic posts. Twenty-six, extracted, single-rooted premolars were randomly divided into two groups. Root lengths were standardized, canals instrumented, obturated, and posts cemented into prepared spaces. Thermocouples were positioned at two locations on the proximal root surfaces. Samples were embedded in plaster and brought to 37 degrees C in a water bath. Posts were ultrasonically vibrated for 4 minutes while continuously measuring temperature. Two-way ANOVA compared effects of water coolant and thermocouple location on temperature change. Root surface temperatures were significantly higher (p < 0.001) when posts were instrumented dry. A trend for higher temperatures was observed at coronal thermocouples of nonirrigated teeth and at apical thermocouples of irrigated teeth (p = 0.057). Irrigation during post removal with ultrasonics had a significant impact on the temperature measured at the external root surface. PMID: 17055912 [PubMed - indexed for MEDLINE] Light-emitting diode curing light irradiance and polymerization of resin-based composite Aravamudhan K, Floyd CJ, Rakowski D, Flaim G, Dickens SH, Eichmiller FC, Fan PL. Product Evaluations, Research and Laboratories, Division of Science, American Dental Association, 211 East Chicago Ave., Chicago, Ill 60611, USA. aravamudhank@ada.org BACKGROUND: Light-emitting diode (LED) curing lights are becoming popular; however, questions about their efficiency remain. The authors performed a comprehensive analysis of the properties of resin-based composites cured with LED lights. METHODS: The authors evaluated seven LED lights and one quartz-tungsten-halogen light (control). They measured intensity, depth of cure (DOC), degree of conversion (DC), hardness and temperature rise. They used three shades of a hybrid resin based composite and a microfill composite, as well as one shade of another hybrid composite. RESULTS: Two LED lights required additional cure time to reach a DOC similar to that of the control light. DC at the top of the samples was independent of the light used. At 2.0 millimeters, the DC for several LED lights was significantly lower than that for the control light and was correlated strongly to the light's intensity. The bottom-to-top ratio for hardness of resin-based composites cured by all but one light was greater than 0.80. All LED lights except one had smaller temperature rise than did the control light. CONCLUSIONS: Six of the seven LED curing lights performed similarly to a quartz-tungsten-halogen curing light in curing resin-based composites. Clinical Implications. While LED curing lights and a quartz-tungsten halogen light could cure resin-based composites, some resin-based composites cured with LED lights may require additional curing time or smaller increments of thickness. PMID: 16521388 [PubMed - indexed for MEDLINE] Controlling the fluoride dosage in a patient with compromised salivary function Eichmiller FC, Eidelman N, Carey CM. American Dental Association Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD 20899-8546, USA. Frederick.Eichmiller@nist.gov BACKGROUND: High-concentration topical fluorides are used commonly to with compromised salivary function due to irradiation and chemotherapy. CASE DESCRIPTION: The authors describe a 50-year-old man with previously treated cancer who was using tray-applied topical fluoride gel. He complained of gastric symptoms, difficulty in swallowing, leg muscle soreness and knee joint soreness. A computed tomographic scan revealed thickening of the esophageal walls. An upper endoscopy revealed abnormal motility. The motility test indicated high-amplitude peristalsis and hypertensive lower esophageal sphincter, and urine testing indicated high levels of systemic fluoride. The patient's fluoride regimen was altered, and within a short period his urinary fluoride levels returned to normal and his symptoms resolved. CLINICAL IMPLICATIONS: Clinicians prescribing home-applied high-concentration fluorides need to be cognizant of the symptoms of fluoride toxicity, carefully monitor the patient's compliance with the treatment regimen, and adjust the dosage or mode of application to control the total ingested dose of fluoride. PMID: 15693498 [PubMed - indexed for MEDLINE] Compend Contin Educ Dent. 2004 Sep;25(9 Suppl 1):9-13. Amorphous calcium phosphates for tooth mineralization Tung MS, Eichmiller FC. American Dental Association Foundation, National Institute of Standards and Technology, Gaithersburg, Maryland, USA. The destruction of tooth structure through caries and erosive processes is due to two types of acidic challenges that affect the tooth in different ways. Acidic attack by cariogenic bacteria initially produces subsurface lesions that weaken the enamel and, if left unchecked, can progress through the enamel and dentin and eventually into the pulpal cavity. Erosive attack by acidic foods and beverages removes mineral from the surface of enamel and initially causes dulling and loss of tooth luster; if left unchecked, it can progress to a more severe loss of enamel thickness and contour. This article focuses on the potential means of improving the cosmetic appearance of teeth by depositing mineral into surface defects. Several approaches use the unique properties of amorphous calcium phosphate (ACP) compounds, which have the highest rates of formation and dissolution among all the calcium phosphates. ACP has been shown to rapidly hydrolyze to form apatite, similar to carbonated apatite, the tooth mineral. Products containing ACP or ingredients that form ACP can include toothpastes, mouth rinses, artificial saliva, chewing gums, topically applied coatings, and other vehicles for topical use. When applied, they readily precipitate ACPs on and into tooth-surface defects. These products hopefully will provide users with new tools to restore and enhance the smoothness and luster of their teeth. PMID: 15645902 [PubMed - indexed for MEDLINE] J Mater Sci Mater Med. 2004 Oct;15(10):1097-103. Probing the origins and control of shrinkage stress in dental resin-composites: I Shrinkage stress characterization technique Lu H, Stansbury JW, Dickens SH, Eichmiller FC, Bowman CN. Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA. The accurate and reliable characterization of the polymerization shrinkage stress is becoming increasingly important, as the shrinkage stress still is a major drawback of current dimethacrylate-based dental materials and restricts its range of applications. The purpose of this research is to develop a novel shrinkage stress measurement device to elucidate the shrinkage stress evolution of dental restorative composites while allowing for controlled sample deformation during the polymerization. Furthermore, the device is designed to mimic the clinically relevant cusp-to-cusp displacement by systematically adjusting the instrument compliance, the bonded surface area/unbonded area by sample geometry, and the total bonded area by sample diameter. The stress measurement device based on the cantilever beam deflection theory has been successfully developed and characterized using a commercial dental composite. It was shown that this device is a highly effective, practical and reliable shrinkage stress measurement tool, which enables its facile applications to the investigation of shrinkage stress kinetics of both commercial and experimental composites, as well as for probing various aspects that dictate shrinkage stress development. PMID: 15516870 [PubMed - indexed for MEDLINE] J Biomed Mater Res B Appl Biomater. 2004 Oct 15;71(1):206-13. Links Probing the origins and control of shrinkage stress in dental resin composites II Novel method of simultaneous measurement of polymerization shrinkage stress and conversion Lu H, Stansbury JW, Dickens SH, Eichmiller FC, Bowman CN. Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, USA. This study probes the interrelationships between polymerization shrinkage stress development and the polymerization progress with a novel experimental technique. This technique is capable of real time, simultaneous measurement of double bond conversion and shrinkage stress with the use of a noninvasive near-infrared fiber-optic system, along with a cantilever beam-based tensometer. The results from both filled and unfilled bis-GMA/TEGDMA (70:30 mass ratio) systems showed that the shrinkage stress buildup was concentrated in the latter stages of polymerization, with its dramatic increase linked to the asymptotic approach of conversion to its limiting value. The monotonic increase of shrinkage stress with conversion in the vitrified state is attributed to the dramatic increase of the sample's elastic modulus during the vitrification stage and a certain amount of cooling stress as the sample cools down from the temperature rise caused by the exothermic polymerization and light absorption. Excellent reproducibility of both the polymerization kinetics assessment and the shrinkage stress measurement has been achieved. PMID: 15368247 [PubMed - indexed for MEDLINE] Effect of thermal cycling on whisker-reinforced dental resin composites Xu HH, Eichmiller FC, Smith DT, Schumacher GE,Giuseppetti AA, Antonucci JM. Paffenbarger Research Center, American Dental Association Health Foundation, National Institute of Standards and Technology, Gaithersburg, MD 20899-8546, USA. hockin.xu@nist.gov The mechanical properties of dental resin composites need to be improved in order to extend their use to high stress bearing applications such as crown and bridge restorations. Recent studies used single crystal ceramic whiskers to reinforce dental composites. The aim of this study was to investigate the effects of thermal cycling on whisker-reinforced composites. It was hypothesized that the whisker composites would not show a reduction in mechanical properties or the breakdown of whisker-resin interface after thermal cycling. Silicon carbide whiskers were mixed with silica particles, thermally fused, then silanized and incorporated into resin to make flexural specimens. The filler mass fraction ranged from 0% to 70%. The specimens were thermal cycled in 5 degrees C and 60 degrees C water baths, and then fractured in three point bending to measure strength. Nano-indentation was used to measure modulus and hardness. No significant loss in composite strength, modulus and hardness was found after 10(5) thermal cycles (family confidence coefficient=0.95; Tukey's multiple comparison test). The strength of whisker composite increased with filler level up to 60%, then plateaued when filler level was further increased to 70%; the modulus and hardness increased monotonically with filler level. The strength and modulus of whisker composite at 70% filler level were significantly higher than the non-whisker controls both before and after thermal cycling. SEM revealed no separation at the whisker-matrix interfaces, and observed resin remnants on the pulled-out whiskers, indicating strong whisker-resin bonding even after 10(5) thermal cycles. In conclusion, novel dental resin composites containing silica-fused whiskers possessed superior strength and modulus compared to non-whisker composites both before and after thermal cycling. The whisker-resin bonding appeared to be resistant to thermal cycling in water, so that no loss in composite strength or stiffness occurred after prolonged thermal cycling. PMID: 15348553 [PubMed] J Mater Sci Mater Med. 2001 Jan;12(1):57-65. Effects of fiber length and volume fraction on the reinforcement of calcium phosphate cement Xu HH, Eichmiller FC, Barndt PR. Paffenbarger Research Center, American Dental Association Health Foundation at National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. hockin.xu@nist.gov A self-setting calcium phosphate cement (CPC) transforms into solid hydroxyapatite during setting at body temperature, and has been used in a number of medical and dental procedures. However, the inferior mechanical properties of CPC prohibits its use in unsupported defects, stress-bearing locations or reconstruction of thin bones. The aim of the present study was to strengthen CPC with fiber reinforcement, to examine the effect of fiber length and volume fraction, and to investigate the reinforcement mechanisms. Previous studies employed either short fibers for random distributions, or continuous fibers that were as long as the specimen size with preferred orientations such as unidirectional alignment. In the present study, a novel methodology was developed in which fibers several times longer than the specimen mold size were randomly mixed with the CPC paste to approximate the isotropy associated with short fibers, and at the same time achieve the high reinforcement efficacy associated with continuous fibers. Carbon fibers of 8 microm diameter were used with fiber lengths ranging from 3 mm to 200 mm, and fiber volume fraction from 1.9% to 9.5%. A three-point flexural test was used to fracture the specimens. Scanning electron microscopy was used to examine crack-fiber interactions and specimen fracture surfaces. The composite containing fibers of 75 mm in length at a volume fraction of 5.7% achieved a flexural strength about 4 times, and work-of-fracture 100 times, greater than the unreinforced CPC. It is concluded that randomly mixing the CPC paste with carbon fibers that were several times longer than the specimen mold size resulted in substantial improvements in strength and fracture resistance; the reinforcement mechanisms were crack bridging and fiber pullout; and fiber length and volume fraction were key microstructural parameters that determined the cement properties. Copyright 2001 Kluwer Academic Publishers PMID: 15348378 [PubMed] 1: Dent Mater. 2004 Mar;20(3):220-7. Three-body wear of dental resin composites reinforced with silica-fused whiskers Xu HH, Quinn JB, Giuseppetti AA,Eichmiller FC, Parry EE, Schumacher GE. Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. hockin.xu@nist.gov OBJECTIVE: Recent studies used silica-fused whiskers to increase the strength and toughness of resin composites. This study investigated the three-body wear of whisker composites. It was hypothesized that the whisker composites would be more wear resistant than composites reinforced with fine glass particles, and the whisker-to-silica filler ratio would significantly affect wear. METHODS: Silica particles were mixed with silicon nitride whiskers at seven different whisker/(whisker + silica) mass fractions (%): 0, 16.7, 33.3, 50, 66.7, 83.3, and 100. Each mixture was heated at 800 degrees C to fuse the silica particles onto the whiskers. Each powder was then silanized and incorporated into a dental resin to make the wear specimens. A four-station wear machine was used with specimens immersed in a slurry containing polymethyl methacrylate beads, and a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. RESULTS: Whisker-to-silica ratio had significant effects (one-way ANOVA; p < 0.001) on wear. After 4 x 10(5) wear cycles, the whisker composite at whisker/(whisker + silica) of 16.7% had a wear scar diameter (mean +/- sd; n = 6) of (643 +/- 39) microm and a wear depth of (82 +/- 19) microm, significantly less than a wear scar diameter of (1184 +/- 34) microm and a wear depth of (173 +/- 15) microm of a commercial prosthetic composite reinforced with fine glass particles (Tukey's multiple comparison). SEM examination revealed that, instead of whiskers protruding from the worn surface, the whiskers were worn with the composite surface, resulting in relatively smooth wear surfaces. SIGNIFICANCE: Silica-fused whisker reinforcement produced dental resin composites that exhibited high resistance to wear with smooth wear surfaces. These properties, together with the strength and fracture toughness being twice those of current glass particle-reinforced composites, may help extend the use of resin composite to large stress-bearing posterior restorations. PMID: 15209227 [PubMed - indexed for MEDLINE] 1: Oper Dent. 2003 Sep-Oct;28(5):496-500. The clinical effect of amorphous calcium phosphate (ACP) on root surface hypersensitivity Geiger S, Matalon S, Blasbalg J, Tung M, Eichmiller FC. The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. Dentin hypersensitivity is a transient condition that often resolves with the natural sclerotic obturation of dentin tubules. A method of rapidly forming calcium phosphate compounds within these tubules can mimic sclerosis and lead to rapid reduction in hypersensitivity. Amorphous calcium phosphates (ACP) can be formed in situ by the sequential application of calcium and phosphate solutions. In this clinical study, 30 patients with reported dentin hypersensitivity were randomly assigned to parallel treatment or placebo groups. In the experimental treatment group, ACP was formed by topical application of a 1.5 mol/L aqueous solution of CaCl2 followed by topical application of 1.0 mol/L aqueous K3PO4. The placebo group was treated with a topical application of 1.0 mol/L aqueous solution of KCl followed by topical application of distilled water. Treatments were repeated at the 7-day and 28-day recall appointments. Response to air and tactile stimuli were measured immediately before treatment using a visual analog scale initially on day 1, then on days 7, 28 and 180. The results showed that both the experimental and placebo treatments resulted in a reduction in hypersensitivity at 180 days. However, the ACP treatment group showed a much more rapid reduction in hypersensitivity over time. The change in sensitivity was much more apparent using the air stimulus than the tactile stimulus. These results show that topical placement of ACP can rapidly reduce dentin hypersensitivity. PMID: 14531593 [PubMed - indexed for MEDLINE] More abstracts The periodontal response to cantilevered resin-bonded bridgework Journal of Oral Rehabilitation Volume 26 Issue 11 Page 912 - November 1999 To cite this article: S. A. Rashid, A. M. Al-Wahadni, D. L. Hussey (1999) The periodontal response to cantilevered resin-bonded bridgework Journal of Oral Rehabilitation 26 (11), 912917. doi:10.1046/j.1365-2842.1999.00376.x The periodontal response to cantilevered resin-bonded bridgework S. A. Rashid , A. M. Al-Wahadni & D. L. Hussey Department of Restorative Dentistry, School of Clinical Dentistry, Queen's University, Belfast, Northern Ireland Correspondence: Mr D. L. Hussey, Department of Restorative Dentistry, School of Clinical Dentistry, Queen's University, Belfast BT 12 6BP, Northern Ireland. E-mail: d.hussey@qub.ac.uk Abstract This study investigated 84 cantilevered resin-bonded bridges (CRBB) in 60 patients. These CRBB (single retainer, single pontic) had been in place for an average of 436 months. Periodontal health was assessed on abutment teeth and contralateral control teeth. Periodontal indices utilized were Plaque Index (PI), Gingival Index (GI), Bleeding Index (BI), Pocket Depth (PD) and mobility. The marginal adaptation, the gingival extension of the retainers and the presence or absence of caries around each retainer margin were also assessed. Information about the history of debonding was collected and a success rate of 93% was reported. PI, GI and mean PD compared statistically significantly, less favourably, with scores of the control teeth. Marginal adaptation of the retainers was of a high standard and caries did not appear to be a problem. This article is cited by: L. M. ANWEIGI, H. M. ZIADA & P. F. ALLEN. (2007) The clinical performance of hybrid bridges delivered by undergraduate dental students: a retrospective study. Journal of Oral Rehabilitation 34:4, 291296 AM Al-Wahadni, Y Mansour and Y Khader. (2006) Periodontal response to all-ceramic crowns (IPS Empress) in general practice. International Journal of Dental Hygiene 4:1, 4146