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Biomedical subjects

Daniel C N Chan

Publications and source records attributed to Daniel C N Chan.

18 recordsLinked to original sources
PubMed2006

Tensile bond strength of dual curing resin-based cements to commercially pure titanium.

OBJECTIVES: The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer. METHODS: One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine. RESULTS: The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h. SIGNIFICANCE: Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.

Adhesiveness↗
PubMed2006

Provisional anterior tooth replacement using nonimpregnated fiber and fiber-reinforced composite resin materials: a clinical report.

The loss of anterior teeth is often a serious esthetic concern. While conventional fixed partial dentures and implant-supported restorations may be the treatments of choice, nonimpregnated fibers (NFs) and fiber-reinforced composite (FRC) resins offer a conservative alternative for improving esthetics. This article describes 2 clinical situations in which NF glass ribbon and FRC were successfully used to provisionally restore anterior edentulous areas in an esthetic, functional, and timely manner.

Acrylic Resins↗
PubMed2006

Microtensile bond strength testing and failure analysis of hybrid and flowable composites.

PURPOSE: Few studies have been performed on the cohesive tensile strength of flowable resin composites and hybrids, or on the coupling strength of flowables to hybrid composites. Thus, the purpose of this study was to measure interfacial microtensile bond strengths between hybrid resin composite and flowable resin composite/compomer. MATERIALS AND METHODS: A polyvinyl siloxane mold was used to fabricate specimens for 9 groups, each consisting of 15 rectangular beams (2 x 2 x 20 mm). Flowable and hybrid resin composites and their paired couplings with each manufacturer's product line were tested. Materials include Heliomolarflow, Revolution, and Dyractflow as representative flowable resin composites and compomer. Heliomolar HB, Prodigy, and Esthet X were selected as representive hybrid resin composites. Resin specimens were cured for a total of 80 s and immersed in water for 7 days. A microspecimen former was used to trim rectangular specimens into specimens with a circular cross section (diameter = 1.0 mm) with a 2 mm gauge length. Specimens were subjected to tensile forces in a passive-gripping space mounted on a Vitrodyne machine. RESULTS: The results are expressed in MPa. Kruskal-Wallis one-way ANOVA on ranks demonstrated significant differences in microtensile bond strength among groups (p < 0.001). CONCLUSION: The cohesive tensile strength of resin composites were material dependent. Flowable and hybrid composites from the same manufacturer have comparable cohesive tensile strengths. The coupling strength of flowable/hybrid combinations were comparable to cohesive strength of the hybrid composites with the exception of Esthet X/Dyractflow, where the coupling was stronger than the cohesive strength of either resin composite alone.

Acrylic Resins↗
PubMed2006

Standardized method to produce tetracycline-stained human molar teeth in vitro.

OBJECTIVE: This study tested the hypothesis that exposure of human molar teeth to tetracycline (TCN) derivatives in vitro results in tooth discoloration resembling the clinical presentation of TCN staining. METHOD AND MATERIALS: The effects of exposure of 20 extracted human molar teeth to distilled water, chlortetracycline, doxycycline, or minocycline were compared. The baseline color of each tooth was analyzed with a dental spectrophotometer. The pulp chambers were each filled with a TCN derivative solution and then sealed. The teeth were placed in a centrifuge tube and then centrifuged at 2800 rpm for 20 minutes. Color change was monitored weekly for 7 weeks. Digital images of the surfaces were recorded. For each specimen at every evaluation period, color change from baseline was calculated using Commission Internationale d'Eclairage (CIE) Delta E 2000 (deltae00). RESULTS: There was a significant association between the type of derivative used and deltae00, as well as between the evaluation period and deltae00. There was also a significant association between the interaction term, derivative x evaluation period, and deltae00. Results of the Holm-Sidak post hoc test demonstrated that all 3 TCN derivatives were associated with significantly larger deltae00 than the control group (P < or = .05). CONCLUSIONS: All 3 TCN derivative solutions produced significant color changes as time progressed. Different TCN derivatives produced a different L* (lightness), C* (chroma), and H* (hue), with minocycline behaving distinctly differently from chlortetracycline and doxycycline. The model could be used to study the underlying mechanisms of TCN staining as well as many aspects of vital tooth

Analysis of Variance↗
PubMed2005

SEM evaluation of contemporary self-etching primers applied to ground and unground enamel.

PURPOSE: This study evaluated the etching effect of self-etching priming agents applied to intact and ground enamel. MATERIALS AND METHODS: Thirty-two human molars were used. Each tooth was divided into two halves. The buccal or lingual mid-coronal surface of 32 half-teeth was ground with 600-grit silicon carbide paper. The other half-teeth were left intact (control). Teeth were treated with Clearfil SE Bond (SE), Prompt L-Pop (PLP) or Adper (AD). Those in the control group were etched with 35% phosphoric acid. The etching effect of such systems on enamel surfaces was assessed by three different approaches using scanning electron microscopy: 1) in situ or direct morphological examination of the etched enamel; 2) indirect morphological examination, that is, evaluation of the etching pattern left on resin reproductions; 3) adhesive interface examination. RESULTS: SE exhibited the least aggressive dissolution of the intact and ground enamel, with many sites of the intact enamel remaining completely unetched. SE monomer infiltration into etched enamel was restricted to the superficial layer. PLP and AD produced equivalent etching patterns on intact and ground enamel, which resemble that produced by the phosphoric acid control group. PLP and AD monomer penetration extended along the porous subsurface enamel layer. CONCLUSION: SE produced mild morphological changes on intact and ground enamel surface, resulting in a very superficial resin infiltration particularly into intact enamel. No differences were evident among the etching and resin infiltration pattern produced by both all-in-one self-etching adhesives, PLP and AD, and the phosphoric acid system.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2004

Application of rapid prototyping to operative dentistry curriculum.

Computers are becoming an integral part of dental education and dental practice. Rapid prototyping is a technique for the production of solid objects from computer models. The variety of rapid prototyping devices and materials that can be processed is increasing all the time. In this article, the authors present a discriminative learning device and associated exercises for developing visual recognition skills and examine the potential for the application of rapid prototyping to the operative dentistry curriculum. Other rapid prototyping technologies as applied in dentistry are also discussed.

Computer Simulation↗
PubMed2004

Safety and efficacy of a nightguard bleaching agent containing sodium fluoride and potassium nitrate.

OBJECTIVES: Transient sensitivity during bleaching is generally reported to affect 67% of patients. While most people tolerate this sensitivity, some find it impossible to continue treatment. The purpose of this study was to determine the safety and efficacy of an experimental, low-sensitivity bleaching agent. METHOD AND MATERIALS: Twenty-two participants bleached for a minimum of 6 hours per night over a 2-week period. The bleaching agent used, Experimental Product E, is a 10% carbamide peroxide gel containing potassium nitrate and sodium fluoride. Evaluations were performed at baseline and 1,2,13, and 26 weeks. Color change was measured using a value-ordered Vita classic shade guide and a colorimeter. Sensitivity of the teeth, gingiva, tongue, and/or throat was measured daily using a patient log. RESULTS: The median color change after 2 weeks was eight tabs. Approximately 36% reported sensitivity during the active whitening phase of the study. As a group, participants reported sensitivity during 13.7% of the total days spent whitening. CONCLUSION: Experimental Product E was shown to be safe. Participants experienced minor sensitivity during the active bleaching phase only. Experimental Product E was shown to be an effective bleaching agent for the subjects tested in this study.

Adult↗
PubMed2004

Practical fluoride and remineralization protocols for adult patients.

There is a wealth of information on preventive measures and procedures that can be used to care for paediatric and adolescent patients. However, few studies have been conducted in adult or geriatric populations, and an understanding of preventive and non-surgical treatment regimens for these patients is lacking. Traditionally, caries incidence is high among risk groups of low income, low dental IQ and certain ethnic subgroups, but we are now witnessing a high incidence of caries among middle-income and healthy adult patients with an imbalance of protective factors and cariogenic factors. We will direct our attention to the adult population and attempt to address some of the most common questions.

Adult↗
PubMed2003

Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics.

STATEMENT OF PROBLEM: The ceramic composition and microstructure surface of all-ceramic restorations are important components of an effective bonding substrate. Both hydrofluoric acid etching and airborne aluminum oxide particle abrasion produce irregular surfaces necessary for micromechanical bonding. Although surface treatments of feldspathic and leucite porcelains have been studied previously, the high alumina-containing and lithium disilicate ceramics have not been fully investigated. PURPOSE: The purpose of this study was to assess the surface topography of 6 different ceramics after treatment with either hydrofluoric acid etching or airborne aluminum oxide particle abrasion. MATERIAL AND METHODS: Five copings each of IPS Empress, IPS Empress 2 (0.8 mm thick), Cergogold (0.7 mm thick), In-Ceram Alumina, In-Ceram Zirconia, and Procera (0.8 mm thick) were fabricated following the manufacturer's instructions. Each coping was longitudinally sectioned into 4 equal parts by a diamond disk. The resulting sections were then randomly divided into 3 groups depending on subsequent surface treatments: Group 1, specimens without additional surface treatments, as received from the laboratory (control); Group 2, specimens treated by use of airborne particle abrasion with 50-microm aluminum oxide; and Group 3, specimens treated with 10% hydrofluoric acid etching (20 seconds for IPS Empress 2; 60 seconds for IPS Empress and Cergogold; and 2 minutes for In-Ceram Alumina, In-Ceram Zirconia, and Procera). RESULTS: Airborne particle abrasion changed the morphologic surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. The surface topography of these ceramics exhibited shallow irregularities not evident in the control group. For Procera, the 50-microm aluminum oxide airborne particle abrasion produced a flattened surface. Airborne particle abrasion of In-Ceram Alumina and In-Ceram Zirconia did not change the morphologic characteristics and the same shallows pits found in the control group remained. For IPS Empress 2, 10% hydrofluoric acid etching produced elongated crystals scattered with shallow irregularities. For IPS Empress and Cergogold, the morphologic characteristic was honeycomb-like on the ceramic surface. The surface treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their superficial structure. CONCLUSION: Hydrofluoric acid etching and airborne particle abrasion with 50-microm aluminum oxide increased the irregularities on the surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. Similar treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their morphologic microstructure.

Acid Etching, Dental↗
PubMed2003

The effects of filling techniques and a low-viscosity composite liner on bond strength to class II cavities.

OBJECTIVE: The aim of this study was to test the hypothesis that the effects of filling technique, cavity configuration and use of a low-viscosity composite liner influence resin bond strength to the dentin of class II cavities gingival floor; and analyze the failure modes of fractured specimens. METHODS: Standardized class II cavities were prepared in the proximal surfaces of freshly extracted third molars, which were randomly assigned to 10 experimental groups. All prepared surfaces were acid-etched, bonded with Single Bond adhesive system and restored with TPH composite, according to each technique: G1 and G2-horizontal layering, G3 and G4-faciolingual layering, G5 and G6-oblique layering, G7 and G8-bulk filling, G9 and G10-control (flat dentin surfaces). Groups were tested, with or without a low-viscosity composite liner (Tetric Flow Chroma). After storage in water for 24h, teeth were vertically serially sectioned to yield a series of 0.8mm thick slabs. Each slab was trimmed into an hourglass shape of approximately 0.8mm(2) area at the gingival resin-dentin interface. Specimens were tested in tension at 0.5mm/min until failure. Fractured specimens were analyzed in an SEM to determine the failure modes. RESULTS: No significant difference was found between groups restored with and without a low-viscosity composite liner (p>0.05). Among filling techniques, the bulk filling groups presented the lowest bond strength values (p<0.05), while incremental filling groups did not differ from control (flat dentin surfaces). Failure modes varied significantly among groups restored with and without the low-viscosity composite liner. SIGNIFICANCE: Bond strengths were not improved when a low-viscosity composite liner was applied, but it remarkably influenced the failure modes. Incremental techniques improved bond strength.

Acid Etching, Dental↗
PubMed2003

Occluding effect of dentifrices on dentinal tubules.

OBJECTIVES: The objective of this study was to evaluate the tubule occluding ability of three commercial available dentifrices (Sensodyne, Emoform and Sorriso) by Scanning Electron Microscopy. METHODS: Fifty cervical areas from buccal and lingual surfaces of sound third human molars were used. Cervical enamel was wet abraded to expose flat dentin surfaces and further polished with diamond pastes. Specimens were randomly divided into five groups (n=10): G1-no brushing; G2-brushing without dentifrice; G3-brushing with Sensodyne; G4-brushing with Emoform; G5-brushing with Sorriso. Brushed specimens were treated for 4 min per day, for 7 days in a toothbrushing machine. Specimens were prepared and observed under SEM for calculation of the percentage of occluded tubules. In addition, slurries of toothpastes were analyzed by X-ray microanalysis. Data were statistically analyzed by ANOVA and Tukey test (p<0.05). RESULTS: Means of occluded tubules in descending order were: G5-98.83+/-3.31% (a), G4-96.02+/-5.24% (a), G3-80.12+/-24.65% (a), G1-37.31+/-24.22% (b); G2-22.92+/-15.19% (b). The three tested dentifrices produced increased dentinal occlusion as compared to controls (p<0.05) but equivalent occlusion among each other. Calcium from calcium-carbonate abrasive was identified in all dentifrices. CONCLUSIONS: Results indicated that the use of all dentifrices occluded tubules more than no brushing and brushing without dentifrices groups. Thus, the tested dentifrices seem effective for desensitization by tubule occlusion.

Analysis of Variance↗
PubMed2003

Technique for repair of multiple abutment teeth under preexisting crowns.

This technique describes a simple procedure for repairing multiple fractured or broken-down abutment teeth under existing crowns. The technique uses a Teflon tape polytetrafluoroethylene (PTFE) as a matrix and separating medium for fabrication of an autopolymerizing composite core material with digital pressure. This technique enables the dentist to solve an emergency clinical situation in a relatively short amount of time, pending further restoration with endodontic treatment and a cast post and core procedure.

Composite Resins↗
PubMed2003

Antibacterial and conventional self-etching primer system: morphological evaluation of intact primary enamel.

The aim of this study was to analyze the etching effect of a new dental adhesive system that uses an antibacterial and self-etching primer agent. Non-carious primary human molars were divided into three groups: 35% phosphoric acid etching (3M-ESPE), self-etching primer (Clearfil SE Bond--Kuraray) and antibacterial self-etching primer (ABF experimental system--Kuraray) for SEM evaluation of surface, resin replicas and interface. Both self-etching primers produced shallow grooves and no defined etching morphologies. Phosphoric acid produced definite etching patterns at the enamel surface.

Acid Etching, Dental↗
PubMedDate not supplied

Predictors of non-carious loss of cervical tooth tissues.

This Predictor Variables study is designed to determine which one of 11 factors evaluated may be correlated to Non-carious Loss of Cervical Tooth Tissues (NLCTT) using subjects with and without NLCTT. The ultimate objective is to successfully predict the path toward risky behaviors and reduce the incidence of NLCTT.

Acids↗
PubMedDate not supplied

Case report of a 40-year, five surface complex amalgam restoration.

Reports of longevity for multi-surface amalgam restoration have been limited. This paper reports a case where a five-surface complex amalgam restoration has been followed and documented for 40 years. The pictorial series will help to identify some of the factors a dentist should consider before replacing the restoration.

Adolescent↗
PubMedDate not supplied

Modified matrix adaptation for sub-gingival Class II amalgam restorations.

Proper placement of the matrix and wedge is critical for the success of Class II amalgam restorations. Improper placement of matrix and wedges can result in poor contours or contacts, overhangs or weakness resulting from poorly condensed restorative material. This paper presents a technique for adaptation of a combination of matrix bands in cases where the gingival cavosurface margin extends deep sub-gingivally.

Dental Amalgam↗
PubMedDate not supplied

Technique on restoring sub-gingival cervical lesion.

This article outlines an atraumatic isolation approach and a conservative instrumentation sequence, followed by use of a highly viscous, rapid-setting, capsulated glass ionomer cement to manage a difficult deep proximal-cervical Class V lesion.

Aged↗