Frederick C.S. Chu

Effects of surface treatments on shear bond strengths between a resin cement and an alumina core.

STATEMENT OF PROBLEM Although bonding to all-ceramic restorations is desirable, there is little information on the use of resin cements containing a phosphate monomer, and the importance of different surface treatments on their adhesion to high-strength core materials. PURPOSE This study attempted to determine the shear bond strength values between Panavia 21 resin cement (Kuraray) and an alumina core material (In-Ceram) after 3 surface treatments and the application of a silane coupling agent. MATERIAL AND METHODS Forty-five In-Ceram cylindrical rods were fabricated and assigned to 3 groups. Group I specimens were treated with a 9.5% hydrofluoric (HF) acid, group II with a 5% HF acid, and group III were sandblasted. All specimens were coated with a silane coupling agent (Cavex Clearfil Photobond and Activator) before cementation with Panavia 21 to sandblasted nickel-chromium rods. As a control, group IV consisted of 8 porcelain (Vitadur Alpha) rods treated with a 5% HF acid and silane. All specimens were subjected to a load of 1.2 kg during cementation, then stored under water for 36 hours. A jig mounted on a Hounsfield Universal Testing machine was used at a crosshead speed of 0.5 mm/min to test the shear bond strengths. RESULTS The results were 14.65 +/- 4.64 MPa for group I, 18.03 +/- 6.13 MPa for group II, and 22.35 +/- 5.98 MPa for group III In-Ceram specimens; and 18.05 +/- 8.46 MPa for control (group IV). CONCLUSION The use of Panavia 21 resin cement and a silane coupling agent can achieve a successful bond between either sandblasted or 5% HF acid-etched In-Ceram core material.

Contrast ratios and masking ability of three types of ceramic veneers

STATEMENT OF PROBLEM Although ceramic veneers have been proven to be clinically successful in longevity studies, there is little information on the contrast ratios and masking ability of the available ceramic systems because dental laboratory technology and expensive experimental equipment are required for the investigation. Moreover, the complexity in understanding how to evaluate translucent ceramic materials may also explain why information in this area is limited. PURPOSE The purpose of this study was to determine the contrast ratios and masking abilities of 3 types of all-ceramic veneers by measuring their luminance and color difference over white and black backgrounds. MATERIAL AND METHODS Disk-shaped specimens (8-mm diameter x 0.7-mm thickness) of Shade A2 (Vita Lumin) of 3 types of all-ceramic systems: Procera (n=8), Empress 2 (n=8), and Vitadur Alpha (n=10) were fabricated. The luminance (as Y) and color (as CIE L*a*b*) of the specimens were measured with a colorimeter. The contrast ratio (CR=Yb/Yw), defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The masking ability of a specimen was evaluated by calculating the color difference (DeltaE) of the veneers over white and black backgrounds. Both CR and DeltaE* data were analyzed with 1-way ANOVA and the Tukey HSD test (alpha=.05). RESULTS The mean contrast ratios (SD) of Procera, Empress 2, and Vitadur Alpha specimens were 0.50 (0.02), 0.46 (0.05), and 0.39 (0.02), respectively. CR values were significantly different among the 3 materials (P<.001). Procera veneers had a significantly higher CR compared to Empress 2 (P=.01) or Vitadur Alpha (P=.01), whereas the CR of Empress 2 was significantly higher than that of Vitadur Alpha (P=.046). Color difference (DeltaE*) (SD) of Procera, Empress 2, and Vitadur Alpha specimens over black and white backgrounds were 24.46 (1.03), 25.80 (1.03), and 31.08 (1.19), respectively. DeltaE* values were statistically different among the 3 materials (P<.001). Vitadur Alpha specimens had significantly higher DeltaE* when compared with Procera (P<.001) or Empress 2 (P<.001), whereas DeltaE* values between Procera and Empress 2 were not significantly different (P=.331). CONCLUSIONS Vitadur Alpha had significantly lower contrast ratio and poorer masking ability compared to Procera or Empress 2. The clinical application of Vitadur Alpha as a veneer material over discolored teeth is cautioned. Although the contrast ratio of Procera was significantly higher than that of Empress 2, the masking abilities of these materials were not significantly different. The clinical application of these 2 ceramics as a veneer material may still be limited when applied over intense tooth discoloration because neither can fully mask the color of a black background.

Magnet-retained auricular prosthesis with an implant-supported composite bar: a clinical report

The use of craniofacial implants to assist in retaining auricular prostheses often requires complex laboratory procedures, involving production of an accurate casting, fitting of a precious alloy bar, and the use of clips. A simplified method for the retention of an auricular prosthesis with a composite bar and magnets is described in this article.

Effect of surface treatment on shear bond strength of zirconia to human dentin.

PURPOSE The effect of surface treatment using tribochemical silica coating/silane coupling on the shear bond strengths of (1) a glass-infiltrated, zirconia-reinforced alumina (In-Ceram Zirconia) and (2) a yttria-stabilized zirconia ceramic (YZ Zirconia) to human dentin was studied. MATERIALS AND METHODS Twelve specimens of each ceramic were randomly assigned to one of three surface treatments: (1) no surface treatment (control group); (2) a chairside tribochemical silica coating/silane coupling system (CoJet group); and (3) a laboratory tribochemical silica coating/silane coupling system (Rocatac group). The mode of failure of each specimen was determined under magnification. RESULTS The shear bond strengths (mean ± SD) of In-Ceram Zirconia of the control, CoJet and Rocatec groups were 5.7 ± 4.3 MPa, 11.4 ± 5.4 MPa, and 6.5 ± 4.8 MPa, respectively. The corresponding figures for YZ Zirconia were 8.2 ± 5.4 MPa, 9.8 ± 5.4 MPa, and 7.8 ± 4.7 MPa. Two-way ANOVA revealed significant differences in bond strength due to the difference in surface treatment (p= 0.02), but the bond strengths between the two ceramics were not significantly different (p= 0.56). Post hoc tests showed that In-Ceram Zirconia treated with CoJet had significantly higher shear bond strengths than those untreated (p < 0.05) or treated with Rocatec (p < 0.05). Surface treatment did not affect the shear bond strength of YZ Zirconia significantly (p > 0.05). CONCLUSION The bonding of In-Ceram Zirconia can be improved by the chairside surface treatment system.

Direct detection of Actinomyces spp. from infected root canals in a Chinese population: a study using PCR-based, oligonucleotide-DNA hybridization technique

OBJECTIVES The poor sensitivity of phenotypic identification techniques has hampered the taxonomic differentiation of Actinomyces. Hence we developed a sensitive and specific, PCR-based oligonucleotide-DNA hybridization technique to detect Actinomyces spp. and, used this method to detect these organisms in samples directly obtained from infected root canals. METHODS A total of 32 samples from 28 Chinese patients, with primary root canal infections, aseptically exposed at the first patient visit, were studied. Whole bacterial genomic DNA was isolated directly from paper point samples. The variable regions of 16S ribosomal DNA of bacteria were amplified and labeled with digoxigenin for further hybridization and detection. A total of seven oligonucleotide probes specific for A. bovis, A. gerencseriae, A. israelii, A. meyeri, catalase-negative A. naeslundii (genospecies 1 and 2), catalase-positive A. naeslundii genospecies 2 and A. odontolyticus were used. RESULTS 16 of the 32 teeth were infected with one or more Actinomyces species. The prevalence rates of the examined species were: A. odontolyticus 31.3%, A. meyeri 9.4%, A. naeslundii 9.4%, A. israelii 6.3% and A. gerencseriae 3.1%; no A. bovis was detected in any of the canals. Furthermore, A. odontolyticus was isolated more frequently from root canals with caries or a history of caries (Fishers exact test: P=0.0496; Odds ratio=9.00, 95% confidence interval: 0.97-83.63), and A. naeslundii was significantly associated with traumatized teeth (Fishers exact test: P=0.0121; Odds ratio=57.00, 95% confidence interval: 2.10-1546.90). However, no significant correlation was found between Actinomyces spp. and clinical symptoms and signs, such as pain, swelling, percussion to tenderness, sinus and periapical radiolucency. CONCLUSION Actinomyces spp. may be important pathogens of root canal infections. A. naeslundii in particular may be related with traumatized teeth. A. odontolyticus appears to be involved in infections related to caries, exposure of dentinal tubules during cavity preparation and/or leaking restoration, but further clarification with large samples is necessary.

Restorative Management of the Worn Dentition: 3. Localized Posterior Toothwear

This is the second paper in a four-part series detailing the relative merits of the treatment strategies, clinical techniques and dental materials for the restoration of health, function and aesthetics for the dentition. In this paper the management of wear in the anterior dentition is discussed, using three case studies as illustration.

The use of lipiodol in spiral tomography for dental implant imaging.

Preoperative radiographic assessment is mandatory for the meticulous treatment planning and successful placement of implants. The precise topographical evaluation of selected implant sites, apart from the most straightforward cases, requires tomographic examination with the use of diagnostic radiographic templates. The incorporation of various radiopaque materials such as barium sulphate and lead foil as radiographic markers had not been entirely satisfactory. A new contrast medium, Lipiodol ethiodized oil (Laboratoire Guerbet, Paris, France), can easily be mixed with the monomer of autopolymerizing acrylic resin. The resultant acrylic template has several advantages. The tomographic images (Scanora; Soredex Orion Corporation, Helsinki, Finland) are radiographically homogenous and show the contour of the future prosthesis, the angulation of the planned implant, and the thickness of the soft tissue. In addition, the radiopaque template is optically transparent (with a slight yellow tint), which facilitates good visibility of surgical sites when the template is modified to become the surgical guide for implant placement. This transparent template can be further modified for implant position registration at the time of surgery. Because this multipurpose template is simple to construct and inexpensive, it can be recommended for routine use in implant dentistry.

Cough syrup addiction and rampant caries: a report of two cases.

Sugar-containing syrups such as cough medications have been recognised as potentially cariogenic, especially for chronically sick children suffering from otitis media, seizure disorder, congenital cardiac diseases and asthma. Unfortunately, an increasing number of juveniles are addicted to cough syrups containing centrally-acting drugs and these individuals not only end up with medical and social problems, but also with dental manifestations. This paper addresses the latter problem with the help of two illustrative cases.

Clonality of bacterial consortia in root canals and subjacent gingival crevices

AIM No oral niche can be considered to be segregated from the subjacent milieu because of the complex community behavior and nature of the oral biofilms. The aim of this study was to address the paucity of information on how these species are clonally related to the subjacent gingival crevice bacteria. METHODS We utilized a metagenomic approach of amplifying 16S rDNA from genomic DNA, cloning, sequencing and analysis using LIBSHUFF software to assess the genetic homogeneity of the bacterial species from two infected root canals and subjacent gingival crevices. RESULTS The four niches studied yielded 186 clones representing 54 phylotypes. Clone library comparisons using LIBSHUFF software indicated that each niche was inhabited by a unique flora. Further, 42% of the clones were of hitherto unknown phylotypes indicating the extent of bacterial diversity, especially in infected root canals and subjacent gingival crevices. CONCLUSIONS We believe data generated through this novel analytical tool shed new light on understanding oral microbial ecosystems.