Mixed impact of Xpert(®) MTB/RIF on tuberculosis diagnosis in Cambodia.

SETTING: National Tuberculosis (TB) Program sites in northwest Cambodia. OBJECTIVE: To evaluate the impact of Xpert(®) MTB/RIF at point of care (POC) as compared to non-POC sites on the diagnostic evaluation of people living with the human immunodeficiency virus (PLHIV) with TB symptoms and patients with possible multidrug-resistant (MDR) TB. DESIGN: Observational cohort of patients undergoing routine diagnostic evaluation for TB following the rollout of Xpert. RESULTS: Between October 2011 and June 2013, 431 of 822 (52%) PLHIV with TB symptoms and 240/493 (49%) patients with possible MDR-TB underwent Xpert. Xpert was more likely to be performed when available as POC. A smaller proportion of PLHIV at POC sites were diagnosed with TB than at non-POC sites; however, at POC sites, a higher proportion of those diagnosed with TB were bacteriologically positive. There was poor agreement between Xpert and other tests such as smear microscopy and culture. Overall, the evaluation of patients with possible MDR-TB increased following Xpert rollout, yet for patients confirmed as having drug resistance on drug susceptibility testing, only 46% had rifampin resistance that would be identified with Xpert. CONCLUSION: Although utilization of Xpert was low, it may have contributed to an increase in evaluations for possible MDR-TB and a decline in empiric treatment for PLHIV when available as POC.

Contexte : Sites du Programme National contre la Tuberculose (TB) dans le nord-ouest du Cambodge.Objectif : Evaluer l'impact du Xpert® MTB/RIF dans des sites où il est réalisé sur place (POC) comparés aux autres sites sur le diagnostic des personnes vivant avec le VIH (PVVIH) et ayant des symptômes de TB ainsi que des patients présumées de TB multirésistante (MDR).Schéma : Cohorte d'observation de patients bénéficiant d'une évaluation diagnostique de routine pour la TB après le lancement de l'Xpert.Résultats : Entre octobre 2011 et juin 2013, 431/822 (52%) PVVIH ayant des symptômes de TB et 240/493 (49%) patients avec suspicion de TB-MDR ont eu un test Xpert. L'Xpert a été réalisé plus souvent lorsqu'il était disponible en POC. Une plus faible proportion de PVVIH a eu un diagnostic de TB dans les sites POC que dans les sites non-POC ; cependant, dans les sites POC, une proportion plus élevée des patients ayant eu un diagnostic de TB a eu une bactériologie positive. L'accord entre l'Xpert et les autres tests (par exemple la microscopie de frottis ou la culture) a été médiocre. Dans l'ensemble, l'évaluation des patients présumées de TB-MDR a augmenté après le lancement de l'Xpert, mais parmi les patients ayant eu une pharmacorésistance confirmée par test de pharmacosensibilité, seulement 46% ont eu une résistance à la rifampicine qui aurait été identifiée par Xpert.Conclusion : Même si l'utilisation de l'Xpert a été faible, l'Xpert pourrait avoir contribué à une augmentation de l'évaluation des suspicions de TB-MDR et à un déclin du traitement empirique des PVVIH quand il est disponible sur place.

Marco de referencia: Los centros del Programa Nacional contra la Tuberculosis en el noroeste de Camboya.Objetivo: Evaluar la repercusión de la práctica de la prueba Xpert® MTB/RIF en el lugar de la consulta, en comparación con la realización de la prueba en otro centro, sobre la evaluación diagnóstica de las personas aquejadas de infección por el virus de la inmunodeficiencia humana (PVVIH) que presentan síntomas de tuberculosis (TB) y de los pacientes con presunción de TB multidrogorresistente (TB-MDR).Método: Fue este un estudio observacional de cohortes de pacientes en curso de evaluación diagnóstica corriente de la TB, después de la introducción de la prueba Xpert.Resultados: De octubre del 2011 a junio del 2013 se practicó la prueba Xpert a 431 de los 822 PVVIH que presentaban síntomas de TB (52%) y a 240 de los 493 pacientes con presunción de TB-MDR (49%). La probabilidad de realizar la prueba Xpert fue mayor cuando esta se podía practicar en el lugar de la consulta. La proporción de PVVIH en quienes se diagnosticó TB en los centros que practicaban localmente la prueba Xpert fue menor que en los demás centros; sin embargo, en los centros que contaban con la prueba fue más alta la proporción de casos de TB confirmados bacteriológicamente. Se observó una baja concordancia entre los resultados de la prueba Xpert y las otras pruebas (la baciloscopia y el cultivo). En general, tras el despliegue de la prueba molecular se investigó un mayor número de pacientes con presunción de TB-MDR; sin embargo, de los pacientes en quienes se confirmó la farmacorresistencia mediante pruebas de sensibilidad solo un 46% presentaba resistencia a rifampicina, que podía detectar la prueba Xpert.Conclusión: Si bien la utilización de la prueba Xpert fue muy limitada, su disponibilidad contribuyó a la investigación de más casos con presunción de TB-MDR y a una disminución del tratamiento empírico de las PPVIH, cuando la prueba Xpert se practicaba en el lugar de la consulta.

Keratocystic Odontogenic Tumour of the Mandible: a case report of decompression with a customised removable tube and review of literature.

Keratocystic odontogenic tumour (KOT or KCOT) is defined by the WHO to be 'a benign uni- or multicystic, intraosseous tumour of odontogenic origin'. In 2005, the World Health Organization renamed the lesion; previously known as an odontogenic keratocyst (OKC) as the KCOT. WHO recommends the term KCOT as it reflects its neoplastic nature. In this case report, a 21-year-old female with a histologically proven large parakeratinised KCOT of the right mandible underwent treatment that involved a 14-month period of decompression, followed by enucleation (with Carnoys application) of the residual cyst. During the period of decompression, a custom made removable mandibular chrome-cobalt appliance was used to hold the decompression tube in the oral cavity.

Epidemiology of drug-resistant tuberculosis among children and adolescents in South Africa, 2005-2010.

OBJECTIVE: To describe the demographic and clinical characteristics of children and adolescents diagnosed with resistance to any anti-tuberculosis drug (drug-resistant tuberculosis; DR-TB) in South Africa. DESIGN: We retrospectively reviewed medical records of all children (<13 years) and adolescents (13 to <18 years) with DR-TB at specialty hospitals in four South African provinces from 2005 to 2010. RESULTS: During the review period, 774 children and adolescents (median age 11.3 years) were diagnosed with DR-TB at selected facilities. A high proportion of patients had a history of previous TB treatment (285/631; 45.2%), human immunodeficiency virus (HIV) infection (375/685; 54.7%), contact with a TB case (347/454; 76.4%), and smear-positive (443/729; 60.8%), cavitary (253/680, 38.7%) disease. Eighty-two per cent of patients with HIV infection received antiretroviral therapy. Of 626 patients diagnosed with multidrug-resistant TB (MDR-TB), 561 (89.6%) received a regimen consistent with national guidelines; the median length of treatment was 22 months (IQR 16-25). Among 400 patients with any DR-TB and a known outcome, 20.3% died during treatment. CONCLUSION: Pediatric DR-TB in these provinces is characterized by complex clinical features at diagnosis, with one in five children dying during treatment. History of previous treatment and contact with a TB patient indicate opportunities for earlier diagnosis and treatment to improve outcomes.

The disconnect between a national tuberculosis drug resistance survey and treatment outcomes: a lost opportunity.

We linked results from the Fourth Botswana National Drug Resistance Survey (DRS), 2007-2008, to patient records from the national Electronic Tuberculosis Registry to determine treatment outcomes. Of 915 new patients, 651 (71%) had treatment data available. Completion or cure was achieved for 10/15 (67%, 95%CI 42-85) with isoniazid monoresistance, (6/16, 38%, 95%CI 18-61) with multidrug resistance, while 73% (391/537, 95%CI 69-76) were susceptible to first-line drugs. The analysis was limited because of unavailable treatment records and undocumented outcomes. Prospective analyses following DRSs should be considered to ensure adequate outcome data.

Rollout of Xpert(®) MTB/RIF in Northwest Cambodia for the diagnosis of tuberculosis among PLHA.

OBJECTIVE: To describe the implementation and utilization of the Xpert (®) MTB/RIF (Xpert) assay to diagnose tuberculosis (TB) among people living with the human immunodeficiency virus/acquired immune-deficiency syndrome (HIV/AIDS, PLHA) in Cambodia. DESIGN: Following the rollout of Xpert, an evaluation was conducted in four provinces of Cambodia from March to December 2012 to determine the utilization, performance, and turnaround time (TAT) of Xpert among PLHA. Data were collected from paper-based patient registers. RESULTS: Of 497 PLHA with a positive TB symptom screen, 357 (72%) were tested with smear microscopy, and 250 (50%) with Xpert; 25 (10%) PLHA tested with Xpert were positive for TB and none were rifampicin-resistant. The utilization of Xpert increased from 23% to 75%, with a median TAT of 1 day. Across districts, utilization ranged from zero to 85%, while the TAT ranged from zero to 22 days. CONCLUSION: While early data show increasing utilization of Xpert for PLHA with a positive symptom screen, most patients underwent smear microscopy as an initial diagnostic test. Training delays and challenges associated with specimen referral may have contributed to variability in Xpert uptake and TAT, particularly for sites without onsite Xpert testing. Enhanced programmatic support, particularly for specimen referral and results reporting, may facilitate appropriate utilization.

Objectif : Décrire la mise en œuvre et l'utilisation du test Xpert(R) MTB/RIF afin de diagnostiquer la tuberculose (TB) parmi des personnes vivant avec le VIH/SIDA (virus de l'mmunodéficience humaine/syndrome de l'immunodéficience acquise ; PLHA) au Cambodge.Schéma : Après le déploiement du test Xpert, une évaluation a été réalisée dans quatre provinces du Cambodge entre mars et décembre 2012 afin de déterminer l'utilisation, la performance et le délai d'exécution du Xpert parmi les PLHA. Des données ont été recueillies à partir des dossiers papiers des patients.Résultats : Sur 497 PLHA ayant une grille de symptômes de TB positive, 357 (72%) ont bénéficié d'une microscopie de frottis et 250 (50%) ont eu un test Xpert ; 25 (10%) PLHA testés par Xpert étaient positifs pour la TB et aucun n'était résistant à la rifampicine. L'utilisation du Xpert est passée de 23% à 75% avec un délai d'exécution médian d'un jour. Dans les districts, l'utilisation allait de zéro à 85% et le délai de mise en œuvre allait de zéro à 22 jours.Conclusion : Si les données précoces montrent une utilisation croissante du Xpert chez les PLHA avec une grille de symptômes positive, la majorité des patients bénéficiait initialement d'un diagnostic par examen microscopique de frottis. Les délais de formation et les problèmes posés par l'envoi des spécimens peuvent avoir contribué à la variabilité du recours au Xpert et au délai de sa mise en œuvre, particulièrement dans les endroits dépourvus de possibilité de test Xpert sur place. Davantage de soutien aux programmes, notamment en termes d'envoi des spécimens et de retour des résultats, pourrait faciliter son utilisation appropriée.

Objetivo: Describir la introducción y la utilización de la prueba Xpert(R) MTB/RIF en el diagnóstico de la tuberculosis (TB) de las personas aquejadas de infección por el virus de la inmunodeficiencia humana (VIH) y sida (PLHA) en Camboya.Método: Tras el despliegue de Xpert, se llevó a cabo una evaluación en cuatro provincias de Camboya de marzo a diciembre del 2012 con el fin de determinar el tipo de utilización, el rendimiento diagnóstico y el tiempo de obtención de los resultados de la prueba Xpert en las PLHA. Se recogieron los datos de los pacientes a partir de los registros en soporte de papel.Resultados: De los 497 PLHA y una detección positiva de síntomas de la TB, en 357 casos se practicó una baciloscopia (72%) y en 250 la Xpert (50%); 25 de las personas examinadas con Xpert obtuvieron un resultado positivo (10%) y en ninguna se observó resistencia a rifampicina. La utilización de la prueba aumentó de 23% a 75% y la mediana del lapso hasta obtener el resultado fue un día. En los diferentes distritos, el uso de la prueba osciló entre 0% y 85% y el lapso hasta la notificación del resultado fue de cero a 22 días.Conclusión: Los datos iniciales indicaron un aumento de la utilización de la prueba Xpert en las PLHA que presentan una detección positiva de síntomas de la TB, pero en la mayoría de los pacientes se practicó la baciloscopia del esputo como prueba diagnóstica inicial. Es posible que los retrasos en la capacitación y las dificultades relacionadas con la remisión de las muestras hayan contribuido a la variabilidad en la aceptación de la Xpert y en el tiempo de obtención de los resultados, sobre todo en los centros donde no se practica la prueba en el lugar de atención. Se podría fomentar el uso apropiado de esta prueba mediante un apoyo programático, dirigido especialmente a la remisión de las muestras y la notificación de los resultados.

In vitro wear of new indirect resin composites.

This in vitro study evaluated the toothbrush abrasion wear, three-body Alabama wear and two-body pin-on-disc wear of four commercial indirect resin composites. Enamel shades of Radica (R), Sculpture Plus (S), Belleglass-NG (B) and Gradia Indirect (G) were used. For measuring wear due to toothbrush abrasion, six specimens of each group were fabricated, then brushed in a toothbrush abrasion machine for 20,000 cycles. Material loss was determined by weighing and conversion to volume loss. Three-body wear was measured on six samples for each group using an Alabama-type wear testing machine for 400,000 cycles. Wear depth was measured with a contact profilometer. For two-body wear, five disc specimens were prepared and tested in a two-body wear-testing machine against hydroxypatite sliders for 25,000 cycles. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey test (alpha=0.05). Wear was the highest in Sculpture Plus by all three methods tested and the lowest wear was observed in Belleglass-NG. No statistical difference in wear was noted from Radica.

Curing of pit & fissure sealants using Light Emitting Diode curing units.

Light Emitting Diode (LED) curing units are attractive to clinicians, because most are cordless and should create less heat within tooth structure. However, questions about polymerization efficacy have surrounded this technology. This research evaluated the adequacy of the depth of cure of pit & fissure sealants provided by LED curing units. Optilux (OP) and Elipar Highlight (HL) high intensity halogen and Astralis 5 (A5) conventional halogen lights were used for comparison. The Light Emitting Diode (LED) curing units were Allegro (AL), LE Demetron I (DM), FreeLight (FL), UltraLume 2(UL), UltraLume 5 (UL5) and VersaLux (VX). Sealants used in the study were UltraSeal XT plus Clear (Uclr), Opaque (Uopq) and Teethmate F-1 Natural (Kclr) and Opaque (Kopq). Specimens were fabricated in a brass mold (2 mm thick x 6 mm diameter) and placed between two glass slides (n=5). Each specimen was cured from the top surface only. One hour after curing, four Knoop Hardness readings were made for each top and bottom surface at least 1 mm from the edge. The bottom to top (B/T) KHN ratio was calculated. Groups were fabricated with 20 and 40-second exposure times. In addition, a group using a 1 mm-thick mold was fabricated using an exposure time of 20 seconds. Differences between lights for each material at each testing condition were determined using one-way ANOVA and Student-Newman-Keuls Post-hoc test (alpha=0.05). There was no statistical difference between light curing units for Uclr cured in a 1-mm thickness for 20 seconds or cured in a 2 mm-thickness for 40 seconds. All other materials and conditions showed differences between light curing units. Both opaque materials showed significant variations in B/T KHN ratios dependent upon the light-curing unit.

Analysis of the dentin-resin interface by use of laser Raman spectroscopy.

OBJECTIVES: Adhesion of resin-bonding agents to dentin is currently believed to result from impregnation of adhesive resin into superficially demineralized dentin. The purpose of this study was to investigate the chemical composition of the resin-impregnated dentin (hybrid) layer using a micro-Raman spectroscopy. METHODS: Resin composites were bonded to bovine dentin with the two-step bonding systems, and specimens were sectioned parallel to dentinal tubules. These surfaces were then polished down to 1 microm diamond pastes. Raman spectra were successively recorded along a line perpendicular to the dentin-adhesive interface by steps of 0.2 microm on a computer controlled X-Y stage. The relative amounts of hydroxyapatite (960 cm(-1), P-O), adhesive resin (640 cm(-1), aromatic ring), and organic substrate (1450 cm(-1), C-H) in the dentin-adhesive bonding area were calculated. RESULTS: From the Raman spectroscopy results, the hybrid layer represents a gradual transition in the relative amount of adhesive from the resin side to dentin side. Evidence of poor saturation of the adhesive resin in the demineralized dentin with the one-bottle adhesive system was detected. SIGNIFICANCE: From the results of this study, inhomogeneity of the hybrid layer composition was detected, and the degree of resin impregnation was found to be different between the bonding systems tested.

Microleakage of posterior packable resin composites with and without flowable liners.

The use of flowable composites as liners in Class II packable composites has been suggested by some manufacturers. However, the contributions of this technique are unproven. This study evaluated marginal microleakage in Class II packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Microleakage at occlusal and gingival margins of Class II cavities was evaluated using 45Ca and autoradiographs. Fifty non-carious, restoration-free human molar teeth were used. Separate mesio-occlusal and disto-occlusal Class II cavity preparations were made in each tooth. Gingival margins of all cavities were placed 1 mm apical to the cementoenamel junction (CEJ). Four Packable composites (Alert, Surefil, Pyramid and Solitaire) and one conventional microhybrid composite (Renew) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The restored teeth were thermally stressed and 45Ca was used to evaluate microleakage. Two independent evaluators scored leakage based on the autoradiographs. The results showed flowable composites helped reduce microleakage at gingival margins of Class II restorations (p < 0.05). Gingival margins had higher microleakage than occlusal margins (p < 0.05). Without flowable liners, three packable composites (Alert, Pyramid and Surefil) showed higher leakage (p < 0.05) than the microhybrid control. Only Solitaire packable composite without liner showed no significant difference in microleakage to the control (p > 0.05). Although the flowable liners help reduce microleakage, Alert and Pyramid packable composites with liners still showed higher leakage than the control (p < 0.05). Surefil and Solitaire packable composites with flowable liners showed no significant difference in microleakage (p > 0.05) to the control.

The effect of double adhesive application on the shear bond strength to dentin of compomers using three one-bottle adhesive systems.

The development of one-bottle dentin adhesive systems resulted in much optimism about providing simplified predictable esthetic dentistry. However, laboratory testing of these systems continues to provide significant variations between facilities. A potential effect of the number of applications was noted in this author's laboratory. This study evaluated the effect of doubling the manufacturer's recommended number of applications on shear bond strength to dentin. Ninety human molars were divided into groups of 15. The occlusal surfaces were finished to 600 grit SiC to provide a flat dentin bonding surface. Prime & Bond NT-Dyract, Optibond Solo-Elan and One Step-Dyract were evaluated. Each material was tested using: (1) the recommended number of adhesive applications and (2) twice the number of applications recommended. All adhesive applications were accomplished before light curing the adhesive. The specimens were thermocycled after one week of storage and tested in shear after two weeks. Specimens were also fabricated after adding Rhodamine D to the adhesive to allow for visualization using confocal microscopy. These teeth were sectioned and viewed 24 hours after fabrication. A t-test was used to compare differences within product groups. The results showed a significant effect (p < 0.001) when a double application of Prime & Bond NT was used. No difference was seen with Optibond Solo or One Step. All specimens appeared to have a uniform, glossy appearance of adhesive during fabrication. Therefore, the appearance of the adhesive after application may not be a reliable predictor of acceptable bonding. Confocal microscopy showed that single application Prime & Bond NT specimens did not exhibit a uniform thickness of adhesive across the entire interface. Tubule penetration and hybridization was apparent for all specimens.

Enamel and dentin bond strengths of single application bonding systems.

PURPOSE: To investigate the bonding ability to enamel and dentin of new single application bonding systems (Reactmer and One-Up Bond) and compare these with a commercial compomer (Clicker/F2000), and 2-step resin-based composite bonding systems (Fluoro Bond/Lite-Fil II A and Single Bond/Z100). MATERIALS AND METHODS: Labial surfaces of extracted bovine teeth were ground on wet 600-grit SiC paper to expose a flattened area of enamel or dentin and then washed and dried with oil-free compressed air. These surfaces were treated according to each adhesive system's instructions and the restorative materials were condensed into a Teflon mold (2 mm height, 4 mm internal diameter) and then irradiated. The finished specimens were stored in 37 degrees C distilled water for 24 hours from the start of light exposure to the material. Then these specimens were tested in a shear mode at a crosshead speed of 1.0 mm/minute. The mean and standard deviation were subjected to an ANOVA followed by the Duncan test (P< 0.05). RESULTS: The bond strengths of the single application bonding systems were 12.3 to approximately 14.5 MPa for enamel, and 13.7 to approximately 13.8 MPa for dentin. These values were comparable to those of the compomer (12.6 MPa for enamel, and 13.1 MPa for dentin), but lower than those of the two-step resin composite bonding systems (16.8 to approximately 21.7 MPa for enamel and 18.1 to approximately 18.4 MPa for dentin).

A pilot clinical evaluation of a new injection denture base system.

The purpose of this pilot study was to determine if clinically acceptable complete denture prostheses can be consistently fabricated with a new injection system. In the first part of this investigation, 14 patients requiring complete denture fabrication had one prosthesis made with the new injection system and one made with the compression-pack technique. Polish, porosity, and esthetics were evaluated by one of three investigators at the placement visit. The percentage of the intaglio surface in contact with the mucosa before adjustment was also measured. One week after placement, the patients were questioned regarding the prostheses' stability, the presence of any undesirable taste, and overall satisfaction. The second portion of the study involved materials property testing of flexural strength and Izod toughness of conventionally packed and injection-packed specimens processed by the fast cycle or the long cycle. In every case, acceptable results were obtained for the resin's polishability, its lack of porosity, esthetics, stability, lack of unpleasant taste, and overall patient satisfaction with the prostheses. No difference in clinical adaptation was observed. These results indicated that no clinical difference was detectable between the conventionally packed and injection-packed denture bases by the investigators or patients in this study. Physical property testing indicates that the differences between groups may be more affected by the polymerization cycle used than the way that the resin was placed in the mold space.

Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials.

STATEMENT OF PROBLEM: Little published information is available comparing the properties of recently developed resin-modified gypsum and epoxy resin die materials, which are claimed to be superior to conventional type IV gypsum die materials. PURPOSE: This study compared the properties of 3 new die materials and 2 conventional type IV gypsum products. METHODS AND MATERIAL: The linear dimensional change, detail reproduction, surface hardness, abrasion resistance, and transverse strength of 2 recently introduced, resin-modified gypsum die materials (Resinrock and Milestone), a new epoxy resin die material (Epoxy-Die), and 2 conventional type IV gypsum die materials (Silky-Rock and Die-Stone) were studied. RESULTS: All gypsum products expanded, whereas the epoxy resin material contracted during setting. The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had the lowest value. CONCLUSION: The resin-modified gypsum products were not significantly superior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well-adapted castings.

Retentive strength of an amalgam bonding agent: chemical vs light vs dual curing.

Dentin bonding agents have been shown to enhance retention of amalgam restorations by mechanical means. Little research is available on which mode of curing may optimize amalgam bonding. This in vitro study compared the bond strengths exhibited by three variations of a bonding agent, each using a different curing mode, with two earlier versions of amalgam resin liners and cavity varnish. The six test groups of lining agents for amalgam restorations included [C] chemical-cured, [L] light-cured and [D] dual-cured versions of one filled adhesive resin (Clearfil Liner Bond 2V), [LF] Light-cured, Filled resin (Clearfil Liner Bond 2, Kuraray Co.); [LCF] Light- and Chemical-cured, Filled resin Clearfil Liner Bond + Protect Liner, Kuraray Co) and [V] Varnish (Copalite, Cooley & Cooley, Ltd). For each group, 20 Class V cavity preparations were cut in human molars. The preparations were 2.5 mm deep and 3 mm wide at the pulpal floor, with a slightly divergent taper. After treating the preparation with the bonding agent, a 3/4 inch, 18 gauge flat-headed wire nail was seated in the cavity with its head at the pulpal floor of the preparation, and Tytin amalgam (Kerr Corp, Romulus, MI) was condensed into the preparation around the nail. All restorations were stored for 24 hours in distilled water at 37 degrees C, then subjected to 2500 thermal cycles (8 degrees C to 58 degrees C). After one week the samples were tested to failure in tension using an Instron Universal Testing Machine (crosshead speed = 2 mm/min) and peak load (kg) was recorded. Significant differences in retention were found using ANOVA and the Games & Howell post hoc test (p = 0.05). The mean loads at failure (+/- SD) were C 13.1 (+/- 2.4), L 21.8 (+/- 6.1), D 26.8 (+/- 7.4), LCF 23.8 (+/- 7.4), LF 21.4 (+/- 3.3) and V 2.0 (+/- 1.8). All dentin-bonding agents exhibited significantly greater retention than the varnish. While the bond strengths of the dual cured (D) and the light-cured (L) liners were not significantly different from one another, both were significantly higher than the chemically-cured (C) resin liner in terms of retention.

Effect of operator variability on dentin bond strength of two-step bonding systems.

PURPOSE: To examine the influence of operator variability on adhesion to dentin of recently developed two-step bonding systems. MATERIALS AND METHODS: A self-etching primer system, Fluoro Bond/Lite-Fil II A (FB) and a one-bottle adhesive system, Single Bond/Z100 (SB) were employed. Three groups, each consisting of 15 operators, were selected from the dentists at the university (Group 1), undergraduate students (Group 2), and general practitioners (Group 3). Labial surfaces of extracted bovine teeth were ground on wet 600-grit SiC paper and then washed and dried with oil-free compressed air. These surfaces were treated according to each adhesive system's instructions and the restorative resins were condensed into a Teflon mold (2 mm height, 4 mm internal diameter) and then light-cured. The finished specimens were stored in 37 degrees C distilled water for 1 hr. These specimens were tested in a shear mode at a cross-head speed of 1.0 mm/min. The mean and standard deviation were subjected to two-way ANOVA (P < 0.05). RESULTS: Significant differences in bond strength of the two adhesives were found within each operator group. A wider variation in bond strength was seen for SB compared to FB for the three different groups. Mean bond strengths for the faculty group were statistically greater than those of the other two groups, which did not differ significantly. Even though the specimen preparation was done under in vitro conditions, the large coefficients of variation indicate it may be difficult to create suitable surface conditions for optimal bonding.

Microleakage and retention of bonded amalgam restorations.

PURPOSE: To compare the microleakage and bond strength exhibited by two light-cured, filled dentin bonding agents, a resin cement, and cavity varnish. MATERIALS AND METHODS: The four test groups of lining agents for amalgam restorations included (LF) Light-cured, Filled resin (Clearfil Liner Bond 2); (LCF) light- and chemical-cured, Filled resin (Clearfil Liner Bond + Protect Liner); (RC) Resin Cement (Panavia 21); and (V) Varnish (Copalite). For each group, 20 Class V cavity preparations were cut in human extracted molars. Tytin amalgam was condensed into the preparation. After storage for at least 24 hrs in distilled water at 37 degrees C, all restorations were subjected to 2500 thermal cycles (8 degrees C to 48 degrees C). After 1 wk, specimens were tested. For the leakage tests, teeth were immersed in 45Ca, sectioned, and radiographs of sections were evaluated and then evaluated by Ridit analysis. Retention samples were tested to failure in tension using an Instron machine and peak load (kg) was recorded. RESULTS: Compared to varnish, the two dentin bonding agents (LF and LCF) significantly decreased microleakage at the cementum margin but not at the enamel margin. The two dentin bonding agents also exhibited significantly greater retentive strength than either the resin cement or the varnish.

Resin-modified glass-ionomers: effect of dentin primer application on the development of bond strength.

The purpose of this study was to investigate the rate of development of dentin bond strengths of resin-modified glass-ionomer cements (RMGIC) with use of dentin primers. The prepared dentin surface was treated according to each manufacturer's instruction or the dentin primer. Cements were condensed into a vinyl mold and light activated. The shear bond strengths were measured at a crosshead speed of 1.0 mm/min after 1, 5, 10, 30, 60 min, 2, 5, and 24 h storage in water at 37 degrees C. Presence of a significant difference between the mean bond strength at 1 min and each of the other test times was analyzed. The first time at which there was a significant increase in bond strength was defined as the "initial increasing time". As compared with the manufacturer's suggested dentin treatments, the bond strengths increased significantly when the dentin primers were used. The initial increasing times when the specimens were made following each manufacturer's instructions were 10 approximately 60 min. When dentin primer was used, the initial increasing time shortened to 5 approximately 10 min. It was concluded that the use of dentin primers for RMGIC restorations resulted in reduction of the initial increasing time.

Friction in perspective.

In the past, most frictional resistance studies have been conducted in a steady state condition that does not simulate the dynamics of the oral environment. Various oral functions as chewing, swallowing, speaking, etc, as well as the oral tissues contacting any orthodontic appliances, result in periodic, repetitive, minute relative motion at the bracket/arch wire interfaces several thousand times each day. This in turn affects the normal forces at the interfaces, and because frictional resistance is directly proportional to the normal force, a pilot study was undertaken to emulate the dynamic environment of the oral cavity and its effect on frictional resistance. Tests of a limited sample of stainless steel arch wires and brackets typically used in sliding mechanics revealed that frictional resistance was effectively reduced to zero each time minute relative movements occurred at the bracket/arch wire interfaces. Factors such as the degree of dental tipping, relative arch wire/slot clearances, and method of tying, did not have a measurable effect on frictional resistance in the simulated dynamics of the oral environment.

Color stability and colorant effect on maxillofacial elastomers. Part I: colorant effect on physical properties.

STATEMENT OF PROBLEM: The average clinical life span of a maxillofacial prosthesis is approximately 6 months, at which point it needs to be refabricated, mainly because of degradation of the color and physical properties of the prosthesis. PURPOSE: This first part of a 3-part study evaluated the effect of coloring agents on the physical properties of maxillofacial elastomers. METHODS AND MATERIAL: Five dumbbell-shaped and 5 trouser-shaped specimens were fabricated for each of the combinations of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants), for a total of 180 specimens. Evaluations of hardness and tear strength were made with the trouser-shaped specimens. Evaluations of the ultimate tensile strength and the percentage elongation were made with the dumbbell-shaped specimens. A within elastomer analysis compared the 6 colorants using a 1-way analysis of variance for each of the 4 physical properties. When significant differences were observed, the Student-Newman-Keuls multiple range test was used to identify differences between groups at a significance level of.05. RESULTS: Physical properties of maxillofacial elastomers were changed by the incorporation of coloring agents. Dry earth pigments, kaolin, and rayon flocking acted as a solid filler without bonding to the Silicone, and artists' oils and liquid cosmetics acted as a liquid phase without bonding to the silicone matrix. CONCLUSION: No clearly superior colorant-elastomer combination was demonstrated in all the tests in this study.

Color stability and colorant effect on maxillofacial elastomers. Part II: weathering effect on physical properties.

STATEMENT OF PROBLEM: The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement. PURPOSE: This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure. MATERIAL AND METHODS: Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. RESULTS: Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time. CONCLUSION: The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.