Restoring function and esthetics in a patient with amelogenesis imperfecta: a case report.

J Contemp Dent Pract. 2007;8(4):95-101

Authors: Gokce K, Canpolat C, Ozel E

AIM: The purpose of this case report is to present the esthetic and functional rehabilitation of the teeth in a 22-year-old patient with Amelogenesis imperfecta (AI). BACKGROUND: AI is a group of hereditary defects of enamel, unassociated with any other generalized defects. It is a rare developmental abnormality of the enamel, with a variable occurrence of approximately 1:4000 to 1:14000 in Western populations. Al results in poor development or complete absence of the enamel of the teeth caused by improper differentiation of the ameloblasts. REPORT: This report describes the diagnosis and treatment of a young male patient with AI and missing molar teeth using contemporary restorative strategies. Initially, the tooth surfaces were treated with a professional cleaning along with conservative restorative treatment. Later, metal-ceramic crowns for posterior teeth and full-ceramic crowns for anterior teeth were utilized for final restorations. SUMMARY: The complexity of the management of patients with AI supports the suggestion the dental profession should have appropriate methods for the rehabilitation of rare dental disorders. The treatment of patients with AI should start with early diagnosis and intervention to prevent later restorative problems.

PMID: 17486193 [PubMed - indexed for MEDLINE]

The influence of commercially pure titanium and titanium-aluminum-vanadium alloy on the final shade of low-fusing porcelain.

J Contemp Dent Pract. 2007;8(2):97-104

Authors: Al Wazzan KA, Al Hussaini IS

AIMS: The aims of this study were to investigate the influence of commercially pure titanium (PTi) and titanium-aluminum-vanadium (Ti-6Al-4V) alloys (TiA) on the final shade of low-fusing porcelain bonded to them and to compare the shade changes with those of three conventional metal-ceramic systems. METHODS AND MATERIALS: A titanium casting unit was used to cast PTi and Ti-6Al-4V alloy specimens followed by A3 shade low-fusing porcelain (Noritake) being bonded to them. Gold-based (AuA), palladium-based (PdA), and nickel-chromium (Ni-Cr) alloys were cast with an automatic centrifugal casting machine, then A3 shade conventional porcelain material (Vita, VMK 95) was applied to them. Ten specimens of each metal were then fabricated. The CIE L* a* b* color coordinates of the specimens were measured with a spectrophotometer. RESULTS: All alloys had significant color changes when compared with A3 shade tabs. The color differences from the shade tabs were 5.79 for the Ti-6Al-4V group, 6.46 for PdA alloy, 8.12 for AuA alloy, 8.15 for Ni-Cr alloy, and 12.58 for PTi. The specimens differed from the shade tabs primarily because of the differences in a* and b* coordinate values. CONCLUSIONS: Predictable shade reproduction of metal-ceramic restorations (MCRs) may be impaired by the underlying metal. The PTi had the greatest color differences among all the tested metal when compared with the shade tabs, whereas the Ti-6Al-4V alloy had the lowest. PTi is more likely to affect the final shade of low-fusing porcelain than Ti-6Al-4V alloy.

PMID: 17277832 [PubMed - indexed for MEDLINE]

Cobalt-chromium head wear following revision hip arthroplasty performed after ceramic fracture--a case report.

Acta Orthop. 2006 Oct;77(5):833-5

Authors: Hasegawa M, Sudo A, Uchida A

PMID: 17068720 [PubMed - indexed for MEDLINE]

Severe cobalt poisoning with loss of sight after ceramic-metal pairing in a hip--a case report.

Acta Orthop. 2006 Oct;77(5):830-2

Authors: Steens W, von Foerster G, Katzer A

PMID: 17068719 [PubMed - indexed for MEDLINE]

Metal release mechanisms in hip replacement.

Acta Orthop. 2006 Oct;77(5):695-6

Authors: Virtanen S

PMID: 17068697 [PubMed - indexed for MEDLINE]

Longevity of posterior tooth dental restorations.

J Am Dent Assoc. 2005 Feb;136(2):201-3

Authors: Christensen GJ

Several forms of restorative techniques are used for posterior teeth. They vary significantly in cost and longevity. The following restorative concepts are the most commonly used: amalgam, resin-based composite, PFM, cast gold alloy restorations and all-ceramic restorations. I suggest that patients be informed about the potential longevity of restorative treatment for posterior teeth as they make decisions about treatment for their oral restorative needs.

PMID: 15782524 [PubMed - indexed for MEDLINE]

Restoring a single anterior tooth: solutions to a dental dilemma.

J Am Dent Assoc. 2004 Dec;135(12):1725-7

Authors: Christensen GJ

PMID: 15646607 [PubMed - indexed for MEDLINE]

[Allergic reactions of Ni-Cr alloy-porcelain crown: report of four cases]

Shanghai Kou Qiang Yi Xue. 2004 Aug;13(4):350-2

Authors: Wang S, Hu XY, Chu AD

Four cases, who had allergic reactions of Ni-Cr alloy-porcelain crown, were reported. Their main clinical features, causes of symptoms, methods of diagnosis and treatment were analyzed.

PMID: 15349688 [PubMed - indexed for MEDLINE]

[Treatment of gingival recessions of teeth with ceramic full crown by autogenous connective tissue graft]

Shanghai Kou Qiang Yi Xue. 2004 Aug;13(4):343-5

Authors: Liu P

PURPOSE: The aim of this clinical study was to evaluate gingival recession of teeth with ceramic full crown treated with subepithelial connective tissue grafts. METHODS: In 20 systemically healthy, whose ages ranging from 31 to 58 years, 32 teeth with ceramic full crown developed gingival recession. Selection of gingival recession defects was based upon the following criteria: A minimum of 2 mm of root surface exposure in coronal-apical height. Miller class I and II recession. Interproximal and labial probing depth </=4 mm. No active caries or restorations on the tooth surfaces. Gingival recession were treated with subepithelial connective tissue grafts technique. RESULTS: The results indicated that subepithelial connective tissue grafts increased the height of gingival recession (GR) and gingival thickness (GT), the mean percentage of root coverage (RC) was 85.1%. CONCLUSION: These results suggest that subepithelial connective tissue grafts were able to successfully treat gingival recession defects. Moreover, the results has significant clinical benefit for aesthetics and treatment outcomes.

PMID: 15349685 [PubMed - indexed for MEDLINE]

[The test of metal-ceramic bonding strength among three ceramic alloies]

Shanghai Kou Qiang Yi Xue. 2004 Jun;13(3):186-8

Authors: Ding WS, Wang D, Lan J, Du ZX, Liu WX

PURPOSE: To compare the metal-ceramic bonding strength of different ceramic alloies. METHODS: 30 wax sheets were divided into 6 groups at random.Each group included 5 sheets.After being invested conventionally with Bellaves SH,the samples were casted and fused with porcelain.The metal-ceramic bonding strength was evaluated. RESULTS: The highest bonding strength was found in Bio Herador N alloy, and then in TILITE alloy and Heraenium S alloy respectively. Bio Herador N alloy and TILITE alloy all had significant differences of the bonding strength before and after treatment (P<0.05). There was no significant differences in the bonding strength of the Heraenium S alloy after treatment (P>0.05). CONCLUSION: The bonding strength of precious metal-ceramic was higher than that of non-precious metal-ceramic.Pre-oxygen treatment can improve the metal-ceramic bonding strength of Bio Herador N alloy and TILITE alloy,but it had no effect on the metal-ceramic bonding strength of the Heraenium S alloy.

PMID: 15269855 [PubMed - indexed for MEDLINE]

[The use of computer-aided colorimeter in porcelain-fused-to-metal (PFM) crowns among patients with special colored teeth]

Shanghai Kou Qiang Yi Xue. 2004 Feb;13(1):76-7

Authors: Fu YF, Weng WM

PURPOSE: To evaluate the roll of ShadeEye-NCC, a computer-aided colorimeter, in Porcelain-Fused-to-Metal crowns among patients with special colored Teeth. METHODS: The first step was to choose the proper patients. The next was to use the colorimeter to measure the base shade of tooth and fabricate the PFM crowns according to the recipe given by the colorimeter. At last, the effects of the PFM crowns were evaluated subjectively by patients and doctor. RESULTS: The satisfaction rates of patients and doctor were 83.7% and 81.4% respectively, there was no significant difference between the two rates. CONCLUSIONS: The computer-aided colorimeter can offer good base shade recipe for fabricating PFM crowns of patients with special colored teeth.

PMID: 15007490 [PubMed - indexed for MEDLINE]

[Causes and prevention of "black line" in porcelain-fused-to-metal crown margins]

Shanghai Kou Qiang Yi Xue. 2003 Dec;12(6):460-2

Authors: Dong ZJ, Xu K

PMID: 14966592 [PubMed - indexed for MEDLINE]

The confusing array of tooth-colored crowns.

J Am Dent Assoc. 2003 Sep;134(9):1253-5

Authors: Christensen GJ

The venerable PFM crown or fixed prosthesis still dominates the tooth-colored restoration market. However, use of PFMs is declining slightly, as the many new all-ceramic and resin-based composite crowns and fixed-prosthesis products flood the market. Several situations may indicate the use of materials other than PFM. They include patients requiring a high level of esthetic acceptability, patients with proven or perceived allergies to the metals used in dentistry and bruxing or clenching patients with metal allergies or desire to eliminate metal from their mouths. PFM restorations have been proven during 40 years of successful use. They provide acceptable esthetics for most situations, minimal fracture during service, proven ability to serve in multiple-unit situations and excellent fit, and the profession has detailed knowledge of these restorations' advantages, disadvantages and physical characteristics. PFM restorations have only a few well-known negative characteristics. Be cautious as you elect to move from the reliability and positive history of PFM to relatively unknown types of restorations.

PMID: 14528998 [PubMed - indexed for MEDLINE]

Repairing fractured porcelain-fused-to-metal bridge pontics.

J Am Dent Assoc. 2003 Aug;134(8):1097-100

Authors: Quarnstrom FC, Aw TC

PMID: 12956351 [PubMed - indexed for MEDLINE]

Direct and indirect restorative materials.

J Am Dent Assoc. 2003 Apr;134(4):463-72

Authors:

BACKGROUND: In recent years, dentistry has benefited from a marked increase in the development of esthetic materials, including ceramic and plastic compounds. But the advent of these new materials has not eliminated the usefulness of more traditional restorative materials such as gold, base metal alloys and dental amalgam. OVERVIEW: This report outlines important features of direct and indirect restoratives, with an emphasis on the safety and efficacy of each material. CONCLUSIONS AND PRACTICE IMPLICATIONS: This article was developed to help dentists explain to their patients the relative pros and cons of various materials used in dental restorations, which include fillings, crowns, bridges and inlays. The weight of the scientific evidence indicates that all of these materials are safe and effective for their intended use. Patients, in consultation with their dentists, are free to choose the most appropriate among them for their particular needs.

PMID: 12733780 [PubMed - indexed for MEDLINE]

Shade match.

J Am Dent Assoc. 2003 Jan;134(1):16; author reply 16

Authors: Scollard M

PMID: 12555951 [PubMed - indexed for MEDLINE]

Shade-match perception of porcelain-fused-to-metal restorations: a comparison between dentist and patient.

J Am Dent Assoc. 2002 Sep;133(9):1220-5; quiz 1260-1

Authors: Al-Wahadni A, Ajlouni R, Al-Omari Q, Cobb D, Dawson D

BACKGROUND: Patient satisfaction with the shade match of restorations has not been appraised carefully in the dental literature. This study compared patients' and a prosthodontist's satisfaction with the shade o f existing porcelain-fused-to-metal, or PFM, restorations. METHODS: The authors selected a convenience sample of 212 patients for this study. Patients and a prosthodontist were asked independently, under standardized conditions, to express their satisfaction with the shade match of the patient's restoration. Kendall's tau-b statistic was used to measure the strength of the association between the shade satisfaction rating of the patient and that of the prosthodontist. The authors also examined patient satisfaction with respect to sex, treatment location and clinician. RESULTS: The prosthodontist was less satisfied than the patient with the shade match in a significant number of cases. The authors found no difference in patient satisfaction with respect to sex. They did find that patients were more satisfied with the shade match of restorations placed by a prosthodontist or placed under the supervision of a prosthodontist than they were with restorations placed by general practitioners. CONCLUSIONS: Patients were more satisfied with the shade match of their PFM restorations than was the prosthodontist. Patients also were more satisfied with restorations placed by a prosthodontist or placed under the supervision of a prosthodontist in a hospital or academic setting. Clinical Implications. Patient satisfaction with shade match is important when constructing or replacing a restoration, and the level of satisfaction might be different from that of the clinician. When selecting restoration shades, clinicians should take into consideration the opinions of their patients.

PMID: 12356253 [PubMed - indexed for MEDLINE]

Infrared spectrometric study of acid-degradable glasses.

J Dent Res. 2002 Aug;81(8):552-5

Authors: De Maeyer EA, Verbeeck RM, Vercruysse CW

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.

PMID: 12147746 [PubMed - indexed for MEDLINE]

Comparative microstructural study of the diffusion zone between NiCr alloy and different dental ceramics.

J Dent Res. 2002 May;81(5):334-7

Authors: Hegedus C, Dar&#xF3;czi L, Kökényesi V, Beke DL

Our knowledge on the bonding mechanisms between the metal and ceramic parts of dental systems is very limited. This work tested the hypothesis that the details of the interface processes can be described in the framework of a chemical diffusion model. The development of interfacial phases was investigated by cross-sectional analytical transmission electron microscopy between a NiCr (Wiron 99) alloy and three different dental ceramics (Carat, Vita VMK 95, and Vision). All systems were investigated at normal firing conditions (suggested by the manufacturer) and at increased firing times as well. The conclusions are based on the results that the formation of a nanocrystalline Cr(2)O(3) layer and amorphous silicon oxide inclusions were detected in the early stage of the firing process in all investigated systems, and that, in the case of Carat and Vision ceramics, formation of complex NiCr and NiCrTi oxides was also observed at longer annealing times.

PMID: 12097447 [PubMed - indexed for MEDLINE]

Cast gold restorations. Has the esthetic dentistry pendulum swung too far?

J Am Dent Assoc. 2001 Jun;132(6):809-11

Authors: Christensen GJ

PMID: 11433863 [PubMed - indexed for MEDLINE]

Clinical performance of a condensable metal-reinforced glass ionomer cement in primary molars.

Br Dent J. 2001 Mar 24;190(6):317-21

Authors: Kr&#xE4;mer N, Frankenberger R

OBJECTIVE: Aim of the present study was to evaluate the clinical suitability of the condensable metal-reinforced glass ionomer cement Hi-Dense in classes I and II cavities of primary molars. METHODS: Seventeen children received a total of fifty four Hi-Dense fillings (nineteen class I and thirty five class II). The restorations were clinically assessed at baseline, after one and after two years of clinical service according to modified USPHS codes and criteria. The restorations were replicated in each recall and representative samples were qualitatively analysed under a SEM. RESULTS: Over the observation period of two years, five restorations failed due to total retention loss, two fillings needed replacement because of persisting hypersensitivity, one filling was lost because of an unsuccessful endodontic treatment, and four restorations remained intact until natural exfoliation (Two year survival rate: 92% for Class I and 66% for Class II). The SEM analysis of surfaces and marginal areas exhibited an inferior adhesive performance primarily in proximal areas, whereas a negative step formation due to wear was frequently observed in occlusal parts. CONCLUSIONS: The results clearly indicate that the condensable, metal-reinforced GIC Hi-Dense reveals no enhanced performance and lifetime expectancy for class II restorations in primary molars when compared to other non-resin-modified GICs.

PMID: 11325157 [PubMed - indexed for MEDLINE]

Porcelain esthetics for the 21st century.

J Am Dent Assoc. 2000 Jun;131 Suppl:47S-51S

Authors: Leinfelder KF

BACKGROUND: Dental procedures play a vital role in the modern dental practice. Considerable research has addressed improvements in the properties of dental porcelains. CLINICAL IMPLICATIONS: This article examines the trends in the scientific advances in dental porcelains. It highlights properties of the new low-fusing porcelains and describes indications for their use. New luting cements also are addressed.

PMID: 10860345 [PubMed - indexed for MEDLINE]

Stoichiometry of the leaching process of fluoride-containing aluminosilicate glass-ionomer glasses.

J Dent Res. 1999 Jul;78(7):1312-8

Authors: De Maeyer EA, Verbeeck RM, Vercruysse CW

Dental glass-ionomer cements (GIC) set by an acid-base reaction between a polyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not yet fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulations to correlate the glass composition with its leaching properties. The leaching experiments were performed in acetic acid solutions at pH = 3.4 by means of a pH-stat method. After predetermined time intervals, the suspension was filtered and the filtrate was analyzed for the glass constituents. The usefulness of the pH-stat method for the determination of glass reactivity was corroborated. The deviation of the leaching stoichiometry with respect to the pure glass stoichiometry decreased with increasing relative content of mono- and bivalent glass network dwellers and modifiers. Indications were found that the latter can be leached out independently and preferentially, while the leaching of network dwellers is coupled with the aluminum release. The F content as well as the reactivity of the glass affect the amount of fluoride available for release from a set GIC. It could be concluded that the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition.

PMID: 10403458 [PubMed - indexed for MEDLINE]

Porcelain-fused-to-metal vs. nonmetal crowns.

J Am Dent Assoc. 1999 Mar;130(3):409-11

Authors: Christensen GJ

PMID: 10085664 [PubMed - indexed for MEDLINE]

The state of the art in esthetic restorative dentistry.

J Am Dent Assoc. 1997 Sep;128(9):1315-7

Authors: Christensen GJ

Esthetic restorative procedures are routine in most dental practices. The procedures considered to be standard and acceptable by practitioners are bleaching teeth outside the dental office; bonding; intracoronal direct resin restorations; tooth-colored inlays and onlays; porcelain veneers; all-ceramic crowns; and PFM crowns. Unfortunately, some third-party payment organizations do not pay adequately for numerous esthetic restorative procedures, and continued education of these groups about the reliability of esthetic restorative procedures is necessary.

PMID: 9297955 [PubMed - indexed for MEDLINE]

Cementing porcelain-fused-to-metal crowns.

J Am Dent Assoc. 1997 Aug;128(8):1165-7

Authors: Christensen GJ

PMID: 9260430 [PubMed - indexed for MEDLINE]

Early and long-term wear of conventional and resin-modified glass ionomers.

J Dent Res. 1996 Aug;75(8):1613-9

Authors: de Gee AJ, van Duinen RN, Werner A, Davidson CL

Various studies have shown that glass ionomers are susceptible to brittle fracture and acid conditions and that they undergo long-term changes in their mechanical properties. Little information is available on how brittleness, acid susceptibility, and long-term changes are reflected in the wear characteristics of glass ionomers. The purpose of this study was to evaluate long-term changes in conventional glass ionomers, metal-reinforced glass ionomers (including a cermet), and (light-curing) resinmodified glass ionomers by wear experiments simulating the wear process in occlusal contact-free areas. The wear tests were conducted periodically over a period of one year. In addition, wear was determined after one year at a pH of 5 or 6, for assessment of acid susceptibility, and at a condition as found in the occlusal contact areas. All materials showed high early-wear rates which decreased significantly during the one-year test period. This long-term process may be related to a slow progression of the acid-base reaction extending over several months. At each stage, the resinmodified glass ionomers wore significantly faster than the acid-base setting glass ionomers. Most of these materials were not affected at a pH of 6.0, while at a pH of 5.0 only the conventional and the metal-reinforced glass ionomers showed increased wear. Direct contacts with the antagonist led to a significant increase in wear in comparison with contact-free wear, probably as a result of sub-surface fatigue phenomena. In view of the unfavorable wear characteristics of the resin-modified glass ionomers and the high early wear of the conventional glass ionomers, including the metal-reinforced glass ionomers, it was concluded that none of these materials can yet be recommended for use in high-stress-bearing situations.

PMID: 8906131 [PubMed - indexed for MEDLINE]

Microcracks in dental porcelain and their behavior during multiple firing.

J Dent Res. 1996 Jul;75(7):1484-90

Authors: Mackert JR, Williams AL

Dental porcelains rely on the high-thermal-expansion mineral leucite to elevate their bulk thermal expansion to levels compatible with dental PFM alloys. The microcracks that form around these leucite particles when cooled during porcelain manufacture are a potential source of change in bulk porcelain thermal expansion during fabrication of porcelain-fused-to-metal crowns and bridges. The purpose of the present study was to determine whether multiple firings of commercial dental porcelains could produce changes in microcrack density. Specimens of six commercial porcelains and the "Component No. 1" of the Weinstein patent were fabricated and subjected to 1, 2, 4, 8, and 16 firings. The microcrack densities were determined by quantitative stereology, whereby intersections of microcracks were counted with a test grid. The microcrack data were subjected to linear regression analysis and analysis of variance. The microcrack densities of four of the six porcelains and the Component No. 1 frit were not significantly affected by the number of firings (p > 0.05). One porcelain exhibited a weak but highly significant positive correlation between microcrack density and multiple firings (r2 = 0.24, p = 0.0003), while the remaining porcelain exhibited a weak but statistically significant negative correlation between microcrack density and multiple firings (r2 = 0.15, p = 0.006). The results of this study indicate that even for porcelains that exhibit a measurable change in microcrack density as a function of multiple firings, the magnitude of the increase or decrease in microcrack density after several firings is sufficiently small to cause only negligible shifts in porcelain bulk thermal expansion.

PMID: 8876600 [PubMed - indexed for MEDLINE]

Repairing fractured porcelain: how surface preparation affects shear force resistance.

J Am Dent Assoc. 1996 Feb;127(2):203-9

Authors: Pameijer CH, Louw NP, Fischer D

This article reports on a study of the shear bond strength of porcelain repaired with any of several currently available dentin bonding systems and composite resin. The authors describe the benefits of the use of silane and the decrease in shear bond strength values after thermocycling. The results should be helpful to any practitioner confronted with a restoration that is a candidate for intraoral repair of fractured porcelain.

PMID: 8682989 [PubMed - indexed for MEDLINE]

Analysis of tempering stresses in metal-ceramic disks.

J Dent Res. 1996 Feb;75(2):743-51

Authors: DeHoff PH, Anusavice KJ, Vontivillu SB

Previous studies showed that residual compressive stresses induced by thermal tempering retarded the growth of surface cracks in bilayered porcelain disks. The objectives of the present study were: (1) to determine whether thermal tempering by air blasting reduces the length of cracks induced by microhardness indentation in metal-ceramic disks, and (2) to use visco-elastic finite element analyses to calculate transient and residual stresses in metal-ceramic disks. Ni-Cr-Be disks, 16 mm in diameter and 0.3 mm in thickness, were prepared with a 0.5-mm-thick layer of opaque porcelain and a 1.5-mm-thick layer of body porcelain. Metal-porcelain combinations were selected to provide a range of thermal contraction mismatch values. The disks were fired to the maturing temperature of body porcelain and then were subjected to three cooling procedures: (1) slow cooling in a furnace (SC), (2) cooling in air (FC), and (3) air tempering (T) by blasting the surface of the body porcelain with compressed air. The lengths of cracks induced in the surface of the body porcelain by a microhardness indenter were measured immediately after indentation at 20 points along diametral lines. The results of Tukey's multiple-contrast analyses indicated that the mean crack lengths of air-tempered specimens were significantly smaller (p < or = 0.05) than the crack lengths of the fast-cooled and slow-cooled groups. Except for one case, there were no statistically significant differences in the mean crack lengths between FC and SC specimens independent of thermal contraction mismatch. Residual tensile stresses were calculated for SC and FC specimens for all thermal contraction mismatch cases, with the largest values being associated with combinations containing the body porcelain with the smaller contraction coefficient. Calculations by use of the model confirmed that tempering induces large residual compressive stresses in the surface of body porcelain for all of the thermal contraction mismatch cases included in this study.

PMID: 8655770 [PubMed - indexed for MEDLINE]

Clinical evaluation of restored maxillary incisors: veneers vs. PFM crowns.

J Am Dent Assoc. 1995 Nov;126(11):1523-9

Authors: Pippin DJ, Mixson JM, Soldan-Els AP

This cross-sectional study compared the periodontal health and clinical acceptability of maxillary incisors restored with porcelain veneers vs. porcelain-fused-to-metal crowns. The authors evaluated 60 patients, a total of 120 restorations, in groups according to the age of the restorations (zero to 60 months). Margins of veneers were generally more supragingival with less gingival inflammation. All veneers were clinically acceptable, while 5 percent of PFMs failed because of secondary caries.

PMID: 7499649 [PubMed - indexed for MEDLINE]

Isothermal anneal effect on leucite content in dental porcelains.

J Dent Res. 1995 Jun;74(6):1259-65

Authors: Mackert JR, Twiggs SW, Evans-Williams AL

Porcelain thermal expansion behavior is a function of leucite content, and leucite changes can produce porcelain-metal incompatibilities. The purpose of the present study was to determine whether isothermal anneal treatments (such as are encountered during "post-soldering" operations) could result in alterations of leucite content of dental porcelain. Six commercial dental porcelains and the "Component No. 1" frit of the Weinstein et al. patent (1962) were studied. Twenty-eight coupon specimens of each porcelain were fired and divided randomly into seven groups of four specimens each. One group served as a control, while the other six groups were subjected to isothermal anneal treatments--three groups at 500 degrees C and three groups at 750 degrees C, for 4, 8, and 16 min, respectively. Leucite volume fraction was measured via quantitative x-ray diffraction. From an equation for the growth of particles in competition for diffusing material, an expression was derived for the potential simultaneous processes of leucite crystallization and reaction of leucite+glass to form sanidine or other compounds. This exponential growth/decay curve was fit through the experimental data for each porcelain by minimization of the sum of the squares of the residuals through iteration. For each porcelain, a statistically significant correlation was obtained between leucite volume fraction and isothermal anneal duration at 750 degrees C (p < 0.01), whereas at 500 degrees C, only CII exhibited a statistically significant correlation (p < 0.01). The control (non-annealed) leucite volume fractions for the commercial porcelains ranged from (mean +/- SD) 0.155 +/- 0.002 for WIL to 0.442 +/- 0.003 for Component No. 1. The 750 degrees C isothermal anneal increased the leucite volume fraction by between 6.1% and 21.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 7629334 [PubMed - indexed for MEDLINE]

Isothermal anneal effect on microcrack density around leucite particles in dental porcelain.

J Dent Res. 1994 Jun;73(6):1221-7

Authors: Mackert JR, Rueggeberg FA, Lockwood PE, Evans AL, Thompson WO

Because of the large differential in thermal expansion coefficient between leucite and the surrounding glass matrix, microcracks form around the leucite crystallites during the manufacture of dental porcelain frits. These microcracks decouple leucite from the surrounding glass matrix and affect the bulk thermal expansion of the porcelain frit (Binns, 1983). The purpose of this study was to determine if the microcrack density in a dental porcelain decreased as a result of isothermal heat treatment. Ten specimens of a commercial dental porcelain that had previously exhibited an increase in thermal expansion as a function of isothermal heat treatment were prepared and divided into two groups. The experimental group was heated to 750 degrees C and held for 16 minutes at that temperature. The control group received no anneal. The mean microcrack densities were determined by quantitative stereology to be 575 cm2/cm3 +/- 75 cm2/cm3 (mean +/- SEM) for the control group (no anneal) and 231 cm2/cm3 +/- 25 cm2/cm3 for the experimental group (16-minute anneal at 750 degrees C). The specimens annealed at 750 degrees C had a significantly lower microcrack density (p < 0.001) than those that received no anneal. A model was developed to estimate the effect of microcracking on thermal expansion of the porcelain, and a 6% increase in the coefficient of thermal expansion of the porcelain was predicted from this model as a result of this decrease in microcrack density.

PMID: 8046112 [PubMed - indexed for MEDLINE]

The effect of fluoride application on fluoride release and the antibacterial action of glass ionomers.

J Dent Res. 1993 Sep;72(9):1310-4

Authors: Sepp&#xE4; L, Forss H, Ogaard B

The aim of this study was to investigate whether the release of fluoride and the antimicrobial effect of freshly mixed glass ionomers could be prolonged by application of fluoride on aged material. Test slabs of freshly mixed and aged (14 d in water) conventional and silver glass ionomer (Ketac-Fil and Ketac-Silver, Espe, Seefeld, Germany) and composite (Silux Plus, 3M, St. Paul, MN) were fitted into the bottom of a test tube. A layer of S. mutans Ingbritt cells was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% sucrose solution. After the incubation, pH, F, and Ca contents of the fluid phase, and F, Mg, P, and K contents of the cells were determined. The aged glass-ionomer samples were then covered with toothpaste (0.1% F) or with fluoride gel (1.25% F), and the composite samples with fluoride gel. After being thoroughly rinsed, S. mutans cells were incubated on the samples as above. The pH fall was significantly inhibited by freshly mixed glass ionomers, and there were changes in cellular cation and phosphorus contents. Large amounts of fluoride were found in the fluid and cells. For old glass ionomers, no inhibitory effect on pH fall could be seen. Fluoride release had decreased to a low level.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 8360380 [PubMed - indexed for MEDLINE]

Release of fluoride and other elements from light-cured glass ionomers in neutral and acidic conditions.

J Dent Res. 1993 Aug;72(8):1257-62

Authors: Forss H

The purpose of this study was to measure the release of fluoride, sodium, silicon, calcium, strontium, and aluminum from light-cured glass ionomers. The materials tested were: (1) Baseline VLC thick mix; (2) Baseline VLC thin mix; (3) Fuji Lining LC; (4) Vitrebond; and (5) XR-Ionomer. A conventional glass ionomer, Ketac-FilAplicap, and a silver-reinforced glass ionomer, Ketac-Silver, were used as controls. Each test specimen was first stored for 16 days in de-ionized water, followed by a further 16 days in 0.01 mol/L lactic acid (pH 4.0); both solutions were replaced at predetermined intervals. After that, the specimens were immersed for up to 122 days in de-ionized water. During the immersion, light-cured glass ionomers showed considerable variation in the release of fluoride and other elements. In lactic acid, all cements eluted the matrix-forming cations, aluminum and calcium or strontium. This suggests that light-cured materials are as equally susceptible to erosion as are chemically cured glass ionomers. During the immersion, some of the light-cured materials showed a considerable weight gain.

PMID: 8360372 [PubMed - indexed for MEDLINE]

Early bond strength of luting cements to a precious alloy.

J Dent Res. 1992 Sep;71(9):1633-9

Authors: Mojon P, Hawbolt EB, MacEntee MI, Ma PH

Previous studies have reported that glass-ionomer and adhesive resin cements can bond to various alloys, while zinc phosphate cements lack this adhesive property. This study evaluated the bonding properties of three luting cements during the first seven days after cementation. Thirty cylinders were cast with a high-noble porcelain-fused-to-metal (PFM) alloy and luted in pairs with one of the cements. The joints were stored in water at 37 degrees C for one, two, or seven days before being fractured in shear. The cylinders were re-used to provide 40 joints within each test group. The data were subjected to a Weibull analysis, a curve-fitting method shown to be appropriate for comparing the bond strengths of dental materials. The results showed that the zinc phosphate cement was the weakest material, whereas the adhesive resin produced the strongest joints. Microscopic observations of the fractured samples did not reveal any specific differences between the samples in terms of their mechanism of fracture. The glass-ionomer cement reached its maximum bond strength after two days, whereas storage time had no influence on the zinc phosphate cement. The adhesive resin cement was slightly, but not significantly, weaker after one week in water. We suggest that excessive loading of restorations cemented with glass ionomer should be avoided for the first two days after the placement. The use of an adhesive resin cement can be recommended on endodontically treated teeth, but further studies are needed to evaluate its biocompatibility and adhesion to dentin.

PMID: 1522298 [PubMed - indexed for MEDLINE]

Dental ceramics: the state of the science.

Adv Dent Res. 1992 Sep;6:78-81

Authors: Fairhurst CW

This review covers the properties of dental ceramics. Castable systems, bioactive glass, PMF systems, CAD/CAM, and ceramic brackets in orthodontics are briefly discussed. Many of the advances made between 1960 and 1975 were directed toward the understanding, controlling, and developing of new ceramic processes. New and deeper understanding of the structure of non-crystalline solids, structural imperfections, sintering physics, and other physical phenomena related to the melting and solidification processes has brought ceramics from the near-total art form process of the mid-century to the status of a highly sophisticated science it enjoyed in the 1980's.

PMID: 1292467 [PubMed - indexed for MEDLINE]

Dental composites/glass ionomers: the materials.

Adv Dent Res. 1992 Sep;6:44-9

Authors: Bowen RL, Marjenhoff WA

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 1292462 [PubMed - indexed for MEDLINE]

Mutans streptococci in plaque from margins of amalgam, composite, and glass-ionomer restorations.

J Dent Res. 1990 Mar;69(3):861-4

Authors: Svanberg M, Mj&#xF6;r IA, Orstavik D

Levels of mutans streptococci in plaque samples from margins of Class II amalgam (Dispersalloy), composite (P-10), and glass-ionomer (Ketac Silver) restorations were compared. Fifty-one children, each having one of the restorations in a permanent first molar, were part of an inter-individual comparison, giving 17 restorations of each material. The age of the children, the age of the restorations, and the salivary levels of mutans streptococci were comparable in the three groups. Another seven children--each having both a composite and a glass-ionomer restoration of the same age placed on contralateral premolar or molar teeth--were part of an intra-individual comparison. The percentage mutans streptococci of total CFU count in plaque was higher on composite (mean 13.7) and amalgam (mean 4.3) than on glass-ionomer (mean 1.1) restorations in the inter-individual comparison, and higher on composite (mean 4.2) than on glass-ionomer (mean 0.4) restorations in the intra-individual comparison. In both comparisons, the differences in values between samples from glass-ionomer restorations and samples from composite or amalgam restorations were statistically significant (p less than 0.05).

PMID: 2109000 [PubMed - indexed for MEDLINE]

In vitro caries-inhibitory properties of a silver cermet.

J Dent Res. 1989 Jun;68(6):1088-93

Authors: Swift EJ

Recurrent caries is one of the primary causes of failure of dental restorations. One method for reducing the frequency and severity of this problem is the use of fluoride-releasing restorative materials. The glass-ionomer cements are a type of fluoride-releasing material. They have been used extensively in recent years for a variety of clinical applications. However, in comparison with other restorative materials such as amalgam and composite resins, glass ionomers have relatively poor physical properties. Sintering of silver particles to glass-ionomer powder is a means of improving these physical properties. The sintered material is called a silver-glass ionomer or silver cermet. This study examined the in vitro caries-inhibitory potential of a silver cement by means of two methods. First, long-term fluoride release was measured. Second, an artificial caries system was used for evaluation of caries inhibition by cerment restorations in extracted teeth. In comparison with a standard glass-ionomer restorative material, fluoride release from the cermet material was significantly less throughout a 12-month period. The results from the artificial caries system indicated that this decreased fluoride release corresponded with a lesser degree of caries inhibition. Lesions around cermet restorations in both enamel and root surfaces were significantly more severe than those around conventional glass-ionomer restorations. However, in comparison with amalgam and composite resin restorations, the cermet did have some cariostatic activity.

PMID: 2509525 [PubMed - indexed for MEDLINE]

Wear and microhardness of a silver-sintered glass-ionomer cement.

J Dent Res. 1988 May;67(5):831-5

Authors: McKinney JE, Antonucci JM, Rupp NW

Knoop Hardness and pin-and-disc-wear measurements were made on a commercial silver-sintered glass-ionomer cement. The objective was to determine whether the incorporation of a bonded-metal-to-glass filler would enhance durability as determined by the above measurements. As with the previous work on conventional (non-metalized) glass-ionomer cements, the specimens were preconditioned at 37 degrees C in air, water, 0.02 mol/L lactic acid (pH 2.67), and heptane. The influence of these media on the microhardness of the silver-sintered material was about the same as that on the conventional materials. Storing in air produced dehydration, which increased the hardness considerably. Heptane storage increased the hardness less, but this increase is attributed to continued curing during storage. After storage in water, the hardness was essentially unchanged; the influence of increased cure is believed to be offset by softening or plasticization from water uptake. Lactic acid produced a decrease in hardness from chemical dissolution as seen from the SEM observations. In most cases, in particular for the air-stored specimens, the wear resistance was enhanced markedly over that of the conventional materials evaluated previously. The exception was the lactic acid-stored specimens for which little, or no, improvement was observed during early periods of wear. The incorporation of silver appeared to provide lubrication, thus reducing wear. However, catastrophic failure from brittle fracture was still a problem, but its occurrence was less frequent.

PMID: 2966819 [PubMed - indexed for MEDLINE]

The relationship between oxide adherence and porcelain-metal bonding.

J Dent Res. 1988 Feb;67(2):474-8

Authors: Mackert JR, Ringle RD, Parry EE, Evans AL, Fairhurst CW

The lack of a reliable bond test has hindered the elucidation of the mechanism for porcelain-metal bonding in dental systems, because a test capable of detecting differences among porcelain-metal bonds of various qualities is required before the reasons for these differences may be ascertained. A method was developed in the present study whereby specimens of alloys with differing physical properties may be deformed to a constant strain to yield a fracture surface suitable for measurement of the area fraction of retained porcelain by an x-ray spectrometric technique described previously. The method proved sufficiently discriminating that significant differences could be found in 48 of the possible 66 comparisons among alloys and treatments. Linear regression analysis revealed a strong correlation (r2 = 0.947) between the area fractions of retained porcelain measured in the present study and the oxide adherence strength values measured previously. This strong correlation, when considered in light of the literature evidence for the presence of an oxide layer at the porcelain-metal interface, provides compelling support for the oxide layer theory of porcelain-metal bonding in dental alloy systems.

PMID: 11039060 [PubMed - indexed for MEDLINE]

Influence of contraction mismatch and cooling rate on flexural failure of PFM systems.

J Dent Res. 1988 Jan;67(1):61-5

Authors: Coffey JP, Anusavice KJ, DeHoff PH, Lee RB, Hojjatie B

The interactive influence of cooling rate and the sign and magnitude of thermal contraction difference between metals and ceramic veneers on bond strength have not been extensively analyzed, although numerous bond-test studies have been reported during the past two decades. A previous analytical study of residual incompatibility stress in bond-test specimens indicated that bond strength values may be of relatively little value if the residual stress state of the metal-ceramic specimens is not considered. The objective of this study was to determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips. Specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface. The residual stress states in the ceramic region were estimated from finite element stress analyses of the bond-test specimens by use of dilatometry data obtained at the cooling rate of 3 degrees C/min. The total stress induced from the residual stress and the applied flexural load was also determined for these specimens. Statistical analyses of the experimental data revealed that the slowly cooled specimens exhibited a significantly lower (p < 0.05) flexural strength compared with rapidly cooled specimens. Regardless of the cooling technique, metal-ceramic specimens with a negative thermal contraction difference (alpha m - alpha p < 0) failed at significantly lower (p < 0.05) flexural loads than did specimens with a positive thermal contraction difference.

PMID: 11039047 [PubMed - indexed for MEDLINE]