COVID-19: The immediate response of european academic dental institutions and future implications for dental education.

The COVID-19 pandemic has had an immediate and dramatic impact on dental education. The Association of Dental Education in Europe decided to carry out an investigation to assess the immediate response of European Academic Dental Institutions. An online survey was sent to both member and non-member dental schools to investigate the impact on non-clinical and clinical education, assessment and the well-being/pastoral care measures implemented. The preliminary findings and discussion are presented in this paper, for the responses collected between the 25 March and 5 April 2020. The survey at this time of publication is ongoing, and detailed results can be accessed https://adee.org/covid-19-european-dental-education%E2%80%99s-immediate-response.

Bond strength of composite resin to glass ceramic after saliva contamination.

OBJECTIVES: Purpose of this study was to investigate the effect of cleaning methods of glass ceramic specimens contaminated with saliva on tensile bond strength (TBS) to composite resin. Additionally, effect of water storage on bond strength was evaluated. MATERIALS AND METHODS: Glass ceramic discs (IPS Empress, Ivoclar-Vivadent, FL) distributed among five groups (n = 28) were etched with hydrofluoric acid, silanized, contaminated with human saliva, and in group W rinsed with water, group WS additionally silanized, group E rinsed with water and cleaned with ethanol, and group ES additionally silanized. Group C served as a control without contamination. Plastic screws were bonded to the glass ceramic discs using Variolink II (Ivoclar-Vivadent). TBS was measured after 24 h and after 150 days of storage. Failure modes were examined. ANOVA was applied to explore group effect on TBS. Pair-wise comparisons were calculated. RESULTS: The mean TBS [in megapascals] were for W 46 ± 14, WS 55 ± 8, E 48 ± 11, ES 52 ± 10, and C 50 ± 8 after 24 h, and W 39 ± 11, WS 53 ± 9, E 48 ± 8, ES 48 ± 11, and C 50 ± 8 after 150 days. After 150 days specimens of group W showed significantly lower TBS compared to group C (p = 0.05). Additional silanization in group WS led to a significant increase of TBS compared to specimens of group W (p = 0.003). Adhesive fractures were observed only in specimens without second application of silane. CONCLUSIONS: The cleaning of the contaminated glass ceramic surface by rinsing only did not result in a durable bond. CLINICAL RELEVANCE: Pre-silanized glass ceramic restorations need to be rinsed and treated with a fresh layer of silane after saliva contamination.

Efficacy of tooth bleaching with and without light activation and its effect on the pulp temperature: an in vitro study.

The aim of this in vitro study was to evaluate the colour stability of bleaching after light activation with halogen unit, laser, LED unit or chemical activation up to 3 months after treatment. Four groups of teeth (n = 20) were bleached with Opalescence Xtra Boost (38% hydrogen peroxide) using four different methods: activation with halogen, LED, laser or chemical activation only. All teeth were bleached in one session for four times (4 × 15 min) and the colour was evaluated using a spectrophotometer at the following time points: before bleaching, immediately after bleaching, 1 day, and 1 and 3 months after the end of bleaching. Between the tested time points, the teeth were stored in 0.9% NaCl solution. Additionally, the temperature increase in the pulp chamber was measured using a measuring sensor connected to a computer. Bleaching with the halogen unit showed the highest colour change. Halogen unit, laser and chemical activation resulted in whiter teeth after 1 and 3 months compared to the colour after the end of the bleaching procedure (p ≤ 0.05). Three months after the end of bleaching, the shade changes observed were-halogen: 7.1 > chemical activation: 6.2 > LED: 5.4 > laser: 5.2. Halogen showed the highest temperature increase (17.39°C ± 1.96) followed by laser (14.06°C ± 2.55) and LED (0.41°C ± 0.66) (p < 0.0001). Chemical activation did not affect the temperature in the pulp chamber. The use of light activation did not show any advantages compared to chemical bleaching. Although halogen unit showed the higher shade's change, its use resulted also in the higher pulp temperature. According to the present findings, light activation of the bleaching agent seems not to be beneficial compared to bleaching without light activation, concerning the colour stability up to 3 months after bleaching and the pulp temperature caused during the bleaching procedure.

The antibacterial effect of gas ozone after 2 months of in vitro evaluation.

The aim of this study was to evaluate the effect of HealOzone on two microorganisms, 4 and 8 weeks after treatment, using a tooth cavity model. Four groups of caries-free third molars (n = 12) were used (A, B, C and D). Three cavities were prepared into each tooth. After sterilization, groups A and B were inoculated with Streptococcus mutans, and groups C and D, with Lactobacillus casei for 48 h. One cavity of each tooth was used to evaluate the infection. After inoculation, groups B and D were treated with ozone (60 s), and groups A and C were used as controls. Then, the two cavities of each tooth were filled with composite, and the teeth were stored in sucrose medium. The restorations were removed after 4 and 8 weeks, respectively; dentin chips were collected, and the amount of microorganisms was determined. Ozone treatment reduced significantly the amount of S. mutans compared to the control group (p ≤ 0.05). This antibacterial effect was able to be seen after 4 (p = 0.0005) and 8 (p = 0.0002) weeks. No significant difference was found between the control and treated group as far as L. casei is concerned (p > 0.05). HealOzone (60 s) can provide some antibacterial treatment against S. mutans even after 8 weeks. However, an elimination of the microorganisms through HealOzone seems not to be possible. L. casei was more resistant to ozone. Although ozone exerts a significant antibacterial effect against S. mutans, it is probably not enough as the only antibacterial method, during the fillings therapy.

Effect of carbamide peroxide and hydrogen peroxide on enamel surface: an in vitro study.

The aim of the study was to investigate changes in the micromorphologyl and microhardness of the enamel surface after bleaching with two different concentrations of hydrogen peroxide (HP) and carbamide peroxide (CP). Bovine enamel samples were embedded in resin blocks, and polished. Specimens in the experimental groups (n = 10) were treated with bleaching gels containing 10% CP, 35% CP, 3.6% HP, and 10% HP, respectively, for 2 h every second day over a period of 2 weeks. The gels had the identical composition and pH and differed only in their HP or CP content. The roughness and morphology of the enamel surface were analyzed using laser profilometry and SEM. Microhardness was measured using a Knoop hardness tester. The data were evaluated statistically. Specimens in the 10% HP group showed significantly higher roughness after bleaching compared to the control group (ΔRa, p = 0.01). Bleaching with 35% CP showed only a tendency to increase roughness (ΔRa, p = 0.06). Application of 10% CP or 3.6% HP had no significant influence on Ra. Enamel microhardness was significantly higher after application of 10% HP compared to the control (ΔMic = 8 KHN, p = 0.0002) and 35% CP (ΔMic = 20KHN, p = 0.01) groups. In summary, application of CP and HP showed only small quantitative and qualitative differences. In addition, the influence of bleaching procedure on the morphology and hardness of the enamel surface depended on the concentration of the active ingredients.

Four-year evaluation of a resin composite including nanofillers in posterior cavities.

PURPOSE: The aim of this prospective study was to evaluate the clinical performance of the restorative material Ceram.X in combination with an experimental one-bottle etch-and-rinse adhesive (K-0127). MATERIALS AND METHODS: A single operator placed two Class I or II restorations in molars of 43 patients. One molar was restored with Ceram.X/K-0127 (Dentsply DeTrey), the other one with Tetric Ceram/Syntac Classic (Ivoclar Vivadent). At baseline, after one, two, and four years the restorations were evaluated by a second dentist using modified Ryge's criteria. After four years, 27 patients were examined. RESULTS: In one patient, both restorations (Class II) had to be removed for root canal treatment due to pulpitis. Another Class II Ceram.X restoration (3.8%; 4.3% [1 of 23] of Class II restorations) showed score C with regard to wear/anatomical form. Thus, the cumulative failure rate was 7.4% in the Ceram.X group (8.3% of Class II restorations [2 of 24]) and 3.7% in the Tetric Ceram group (4.2% of Class II restorations [1 of 24]). Furthermore, three restorations (11.5%) in each group showed score B for anatomical form and marginal integrity. Slight marginal discoloration (score B) was found at five Ceram.X restorations (19.2%) and four Tetric Ceram restorations (15.4%). Two restorations (7.7%) in each group showed slight changes in color stability (score B). No sensitivity, recurrent caries, or changes in surface texture were recorded after four years. No statistically significant differences were found between the two restorative materials (p > 0.05). CONCLUSION: After four years of clinical service, 92.6% of Ceram.X/K-0127 and 96.3% of Tetric Ceram/Syntac Classic restorations performed clinically well.

Dental caries experience of schoolchildren of two different oral health care delivery systems.

OBJECTIVES: To report on the dental caries experience in schoolchildren from a region with a needs-based dental service compared with a region with a demand-led dental service. DESIGN: Cross-sectional study with clustered sampling. SETTING: Urban primary schools in Dublin (Ireland) and Freiburg (Germany). PARTICIPANTS: 12-year-old schoolchildren. METHOD: A trained and calibrated dentist examined a representative, random sample of schoolchildren under the same standardised conditions. Social class was recorded using the 'Goldthorpe-Social-Class-Schema'. Dental caries was recorded using WHO criteria. RESULTS: Atotal of 567 schoolchildren were examined, 332 in Ireland and 249 in Germany. For Ireland the mean DMFT in SC-1 (highest social class) was 0.28, in SC-2 (middle social class) it was 1.1 and in SC-3 (lowest social class) it was 0.94. For Germany the mean DMFT in SC-1 was 0.31, in SC-2 it was 0.61 and in SC-3 it was 1.33. CONCLUSIONS: This study demonstrated the existence of social gradients in dental caries levels in both samples but the magnitude of the difference varied across the two populations and appeared to be smaller in the needs-based dental service.

Influence of delayed light curing on the cuspal deflection and microleakage of a dual-cured composite resin in Class 2 restorations.

OBJECTIVE: The objective of this study was to evaluate the influence of delayed light curing on a dual-cured composite resin on cuspal deflection, microleakage, and enamel cracks. METHOD AND MATERIALS: Forty-eight standardized Class 2 cavities were prepared in maxillary third molars and restored with a dual-cure composite resin (Core-X Flow) in bulk-fill technique. The samples were divided into four groups (n = 12) and either self-cured (1) or light cured immediately (2), with 1 minute (3) or 2 minutes of delay (4) after placement. Cuspal deflection was measured before preparation, 6 minutes after placement, after 24 hours, and after 120 days of storage and thermocycling. The margins of the restorations were examined under a stereomicroscope after 24 hours and 120 days. Samples were immersed in a 0.2% basic fuchsin solution for 24 hours at room temperature and then sectioned vertically and mesiodistally, and dye penetration and enamel cracks were recorded under a stereomicroscope using a scoring system. RESULTS: Six minutes after placement the cuspal deflections were between 20 ± 2.1 µm and 39.3 ± 1.9 µm. After 120 days the cuspal deflection in all groups was reduced to almost complete recovery, while the percentage of perfect margin decreased. Differences in microleakage, dye penetration, and enamel cracks were observed between different locations but not between the groups. Statistical analysis did not show a correlation between cuspal deflection, margin quality, or enamel cracks. CONCLUSION: A short delay in light curing of a dual-cure composite resin could significantly reduce the initial cuspal deflection measured 6 minutes after light curing, thereby probably reducing the polymerization shrinkage stress. However, the curing mode did not significantly influence microleakage and enamel cracks.

Kinetic model for the coupled volumetric and thermal behavior of dental composites.

OBJECTIVE: The volume and thermal behavior of dental composites during the curing reaction was analyzed for different modes of initiation using a combination of experiments and models for polymerization kinetics. METHODS: The volume behavior of four dental composites (Venus, Tetric Ceram, Ceram X mono and Filtek Supreme) was studied with buoyancy measurements during the initiation and dark phase of the curing process. The volume and temperature development of the composites were described for different intensities of the photo-initiation with a mathematical model based on the "mixed termination model" for the polymerization reaction. RESULTS: A good agreement between volumetric data and the model function was achieved. A non-linear regression of the experimental data with the model yields results for the adjustable parameters describing the kinetics of the polymerization reaction which are typical for comparable polymerization reactions. Using kinetic models of the polymerization reaction for analyzing the volume behavior of radically crosslinking curing dental composites, thermal and polymerization-specific components of the overall shrinkage of the composites can be distinguished and compared for different materials. SIGNIFICANCE: With the developed methodology, a more detailed insight into the curing process can be achieved which can contribute to the understanding of the build-up of internal stresses in dental fillings. These stresses can negatively affect the marginal integrity of the filling, which is a relevant precondition of long-term chemical, biological and mechanical stability.

The efficacy of three different in-office bleaching systems and their effect on enamel microhardness.

This in vitro study evaluated and compared the efficacy of three in-office bleaching systems and investigated their effect on enamel microhardness. Three groups of 12 teeth (third molars) each were bleached as follows: Group A: Opalescence Xtra Boost (38% HP), Group B: Easywhite Ready (30% HP) with plasma unit and Group C: Zoom2 system (25% HP with the Zoom2 unit). The teeth were stained with tea for 24 hours, followed by the appropriate bleaching procedure. Each bleaching cycle was conducted for 15 minutes. The bleaching procedure was repeated until a shade change of six tabs (VITA shade guide) was obtained. The shade of the teeth was evaluated before, immediately after bleaching and one month later, both visually and digitally. Additionally, the "change of shade tabs per minute" was calculated. For the digital evaluation, the photos were taken under the same circumstances and the L*a*b* values were calculated using Photoshop. Five additional enamel samples for each group were prepared, and Knoop microhardness was evaluated before and after 15 minutes of bleaching. According to the visual shade evaluation, the treatment cycles required to reach the defined level of bleaching were: 1.58 for Group A (23.7 minutes), 1.02 for Group B (16.2 minutes) and 1.25 for Group C (18.7 minutes). Immediately after bleaching, a significant difference was found between Groups A and B (p = 0.0094). However, one month after the bleaching procedure, no significant difference could be observed among the three groups. According to the digital evaluation, no significant differences were found among the three bleaching systems for each of the L*a*b* values and the three times tested (p > 0.05). No significant difference (p = 0.055) was noticed among the three groups regarding microhardness after bleaching.

Marginal and internal adaptation of composite restorations to dentin in vivo and in vitro.

PURPOSE: To compare the influence of in vivo and in vitro conditions on marginal and internal adaptation of composite restorations using three adhesive systems. METHODS: 60 human teeth were distributed among three material groups. In each root, three Class V cavities were prepared and filled with the same material, one in vivo and, after extraction, one in perfused and one in not-perfused dentin specimens. RESULTS: Evaluation of gap formation at the composite/dentin interface with SEM revealed no significant differences between marginal and internal adaptation. Adaptation data were different according to the materials used (P = 0.002), and to experimental conditions (P = 0.04). According to the gap frequency concerning experimental conditions, it was concluded that in vivo adaptation of composite restorations to dentin seemed to be better compared to in vitro results achieved with perfused dentin, and worse compared to in vitro results achieved without perfused dentin. Additionally, it was noted that the impact of the experimental conditions on the performance of different adhesive materials was dependent on the composition of the materials. Least adaptation was found for the perfused specimens in most groups, and least gap formation for the non-perfused in vitro specimens. A material dependent influence of experimental conditions on the study influenced the results. In vitro adaptation to perfused dentin seems to be undervalued compared to the clinical situation in certain circumstances.

The development of a directed population approach to tackle inequalities in dental caries prevalence among secondary school children based on a small area profile.

BACKGROUND: It has been observed that the prevalence of dental caries among children has declined in the last decade in Germany. However, despite of these improvements there is still a proportion of children suffering from dental decay. AIMS: The aims of this study were to evaluate if a social gradient in the prevalence of dental caries exists and, based on those findings, to develop a strategy to target those children with heightened risk to develop dental caries in order to assist oral health care professionals to refocus the current uniform school-based dental health programme to a caries preventive strategy based on a directed population approach. DESIGN: A representative, random sample of 12-year olds in Freiburg (Germany) was examined and dental caries was recorded using WHO criteria. Educational attainment of the child's parents was used as an indicator of socio-economic status and classified by use of the CASMIN Educational Classification. RESULTS: A total of 322 children participated. An examination of dental caries score revealed that its distribution was positively skewed. For this reason this study provides summary analyses based on medians and a non-parametric rank-sum test. The Kruskal-Wallis H-test showed a significant difference between median scores across the different educational levels (p-value = 0.015) which was due to lower dental caries levels in children with non-deprived social background. CONCLUSIONS: In order to reduce current social inequalities in child oral health the current uniform school-based dental health programme at secondary school level should be developed to a targeted school-based screening and prevention programme.

Shear bond strength of repaired adhesive filling materials using different repair procedures.

PURPOSE: Matrices of adhesive restorative materials and repair procedures may both influence bond strength of repaired adhesive materials. This study examined the bond strength of adhesive filling materials to mature adhesive materials after pretreatment with Co-Jet, Monobond S, and Silibond. MATERIALS AND METHODS: A hybrid composite (Tetric Ceram), a polyacid-modified composite resin (Dyract), and an ormocer (Definite) and their corresponding bonding agents were tested in combination with the repair systems. Restorative materials were placed in molds and polymerized. In group A (control), homologous materials were applied on the polymerized surface directly. In group B, homologous filling materials were placed onto the respective material with the corresponding bonding agent. In group C, adhesive repair filling material was applied after solely pretreating with the repair systems. In group D, the restorative material was applied after pretreatment with the repair systems and application of the corresponding bonding agent. Each subgroup consisted of 20 specimens. The shear bond strength of the samples was measured in a universal testing machine according to the test procedure ISO 10477. RESULTS: The significantly best bond strength of repair filling material on Tetric was achieved by pretreating with Co-Jet followed by application of the corresponding bonding agent (25.5 +/- 5.4 MPa, p < 0.05). A single application of the bonding agent or use of Monobond with bonding agent also yielded bond strengths of 20 MPa or more on Tetric. For Dyract or Definite, bond strengths of 15.5 +/- 5.3 MPa or less were achieved with the different repair procedures. CONCLUSION: Successful pretreatment of hybrid composites for repair can be achieved by application of Co-Jet followed by the corresponding bonding material, whereas sufficient repair of ormocers and polyacid-modified resin composites is limited.

Factors affecting patient valuations of caries prevention: Using and validating the willingness to pay method.

OBJECTIVES: Determining the value of, or strength of preference for health care interventions is useful for policy makers in planning health care services. Willingness to pay (WTP) is an established economic technique to determine the strength of preferences for interventions by eliciting monetary valuations from individuals in hypothetical situations. The objective of this study was to elicit WTP values for a dental preventive intervention and to analyze the factors affecting these as well as investigating the validity of the WTP method. METHODS: Patients aged 40 years plus attending dental practices in the UK and Germany were recruited on a consecutive basis over one month. Participants received information about a novel root caries prevention intervention. They then completed a questionnaire including a WTP task. Where the coating was indicated, patients were offered this for a payment and acceptance was recorded. Analysis included econometric modelling and comparison of expected (based on stated WTP) versus actual behaviour. RESULTS: The mean WTP for the coating was £96.41 (standard deviation 60.61). Econometric models showed that no demographic or dental history factors were significant predictors of WTP. 63% of the sample behaved as expected when using stated WTP to predict whether they would buy the coating. The remainder were split almost equally between those expected to pay but who did not and those who were expected to refuse but paid. CONCLUSIONS: Values for a caries preventive intervention had a large and unpredictable variance. In comparing hypothetical versus real preferences both under- and over-valuation occurs. CLINICAL SIGNIFICANCE: Wide and unpredictable variation in valuations for prevention may mean that there are difficult policy questions around what resource should be allocated to dental prevention and how to target this resource.

Influence of different repair procedures on bond strength of adhesive filling materials to etched enamel in vitro.

Contamination of etched enamel with repair bond agents during repair of dental restorations may interfere with the bonding of composite to enamel. This study examined the bond strength of adhesive filling materials to etched bovine enamel after pre-treatment with the repair systems Monobond S, Silibond and Co-Jet. The materials Tetric Ceram, Dyract and Definite and their corresponding bonding agents (Syntac Single Comp, Prime & Bond NT, Etch and Prime) were tested in combination with the repair systems. One hundred and thirty-five enamel specimens were etched (37% phosphoric acid, 60 seconds) and equally distributed among three groups (A-C). In Group A, the repair materials were applied on etched enamel followed by applying the composite materials without using their respective bonding material. In Group B, the composite materials were placed on etched enamel after applying the repair materials and bonding agents. In control Group C, the composite materials and bonding agents were applied on etched enamel without using the repair systems. In each sub-group, every composite material was applied on 15 specimens. Samples were stored in artificial saliva for 14 days and thermocycled 1,000 times (5 degrees C/55 degrees C). The shear bond strength of the samples were then determined in a universal testing machine (ISO 10477). Applying Monobond or Silibond followed by the use of its respective bonding agents resulted in a bond strength that was not statistically different from the controls for all filling materials (Group C). The three composites that used Monobond and Silibond without applying the corresponding bonding agent resulted in bond strengths that were significantly lower than the controls. Utilizing the Co-Jet-System drastically reduced the bond strength of composites on etched enamel. Contamination of etched enamel with the repairing bonding agents Monobond and Silibond does not interfere with bond strength if the application of Monobond and Silibond is followed by using its corresponding bonding system of the composites tested.

A material model for internal stress of dental composites caused by the curing process.

OBJECTIVE: To compare the build-up of internal stresses in four different dental composites (Venus, Tetric Ceram, Ceram X mono and Filtek Supreme) during the curing reaction, based on the results of a former paper on polymerization kinetics, and to characterize the developing mechanical behavior for different modes of activation using experimental methods and simulation tools. METHODS: A four-parameter viscoelastic model combined with a curing model and a kinetic model was developed to simulate the mechanical behavior in three dimensions using the finite element software ABAQUS. In order to study the influence of slow polymerization behavior on the mechanical properties, the length of the activation period was doubled at half intensity of the curing light. RESULTS: Using a model which describes the complex interplay of stiffness, flowability, curing speed and activation intensity during the curing process gives deeper insight into the spatial and temporal build-up of stresses. An advantageous reaction kinetic or a lower stiffness can compensate for the effect of a higher polymerization shrinkage on the resulting peak stress. The evolution of stress is not directly proportional to the level of shrinkage of the composites. SIGNIFICANCE: A material model which includes the developing mechanical characteristics of a curing dental composite can be used to develop and optimize dental materials and to assess the effect of different treatment strategies (i.e. mode of photo-polymerization, filling geometries, interfacial strength).

Evaluation of the curing depth of two translucent composite materials using a halogen and two LED curing units.

This in vitro study evaluated the influence of one halogen and two light-emitting diode (LED) curing units on the curing depth of a conventional hybrid and two translucent resin composites by measuring the Knoop microhardness. In the first part of the study, a conventional hybrid resin composite and three curing units (one halogen: 40 s polymerization time, two LEDs: 10 and 20 s) were used. Ten cylindrical resin composite samples were prepared for each curing unit and each polymerization time tested. After polymerization, the soft part of the samples was removed. The samples were embedded in a polyacrylic resin and separated in the middle towards the direction, top-bottom. On the section plane, Knoop microhardness measurements were performed every 1 mm, starting at 0.5 mm under the surface. In the second part of the study, two translucent resin composites and a conventional hybrid composite resin were cured with the three curing units, and the microhardness was measured as mentioned above. The difference between the curing units tested was found statistically significant (p = 0.0009), as well as the difference between the materials concerning curing depth (p = 0.0001). Both translucent materials achieved microhardness values equal to the 80% of the surface values, in depths 3.5-5.5 mm, depending on the curing units used.

Influence of pressure application before light-curing on the bond strength of adhesive systems to dentin.

This study evaluated the influence of defined pressure application before light-curing on the tensile bond strength (TBS) of two adhesive systems to wet and perfused dentin. Bonding sites were analyzed by scanning electron microscopy (SEM) to assess morphological changes. Dentin discs from 120 human third molars were prepared in such a way to allow simulation of intrapulpal pressure. The specimens were randomly assigned to 6 groups (n=20) according to different experimental conditions. The adhesive systems (Scotchbond Multi-Purpose and Syntac) were applied either to wet or perfused dentin. In the latter, compression was applied before adhesive light-curing . TBS was recorded using an universal testing machine. Qualitative examination of the bonding sites was performed by SEM after dissolving the dentin with 50% nitric acid. Pressure application prior to light-curing resulted in a remarkable decrease of TBS for Syntac, while no significant change was observed for Scotchbond MP. SEM analysis showed no considerable lengthening of the resin tags after pressure application. These findings suggest that application of adhesive systems to dentin under pressure before light-curing had no positive effect on TBS.

Antibacterial effect of an ozone device and its comparison with two dentin-bonding systems.

Microorganisms remaining beneath restorations can cause secondary caries and pulp damage. Because of this, antimicrobial treatment could be useful. The aim of this study was to evaluate the antibacterial effect of the HealOzone device on Streptococcus mutans and to compare it with the already proven activity of two dentin-bonding systems. Thirty-five human molars were divided into 5 groups. Cavities were then cut into the teeth (n = 28 cavities per group). After sterilization, the teeth were left in broth cultures of 10(6) colony-forming units (CFU) ml(-1) of S. mutans at 36 degrees C for 48 h. The appropriate treatment followed (group A, control; group B, Clearfil SE Bond; group C, Clearfil Protect Bond; group D, 40 s of treatment with ozone; and group E, 80 s of treatment with ozone), and the cavities were then filled with composite resin. After 72 h, the restorations were removed, dentin chips were collected with an excavator, and the total number of microorganisms was determined. All treatments significantly reduced the number of S. mutans present compared with the control group. The antimicrobial effect of both bonding systems and treatment with 80 s of ozone was significantly higher than the 40 s ozone treatment. In conclusion, HealOzone and the bonding systems show striking antimicrobial effects against S. mutans.

Influence of pressure application before light-curing on the bond strength of adhesive systems to dentin

This study evaluated the influence of defined pressure application before light-curing on the tensile bond strength (TBS) of two adhesive systems to wet and perfused dentin. Bonding sites were analyzed by scanning electron microscopy (SEM) to assess morphological changes. Dentin discs from 120 human third molars were prepared in such a way to allow simulation of intrapulpal pressure. The specimens were randomly assigned to 6 groups (n=20) according to different experimental conditions. The adhesive systems (ScotchbondTM Multi-Purpose and Syntac®) were applied either to wet or perfused dentin. In the latter, compression was applied before adhesive light-curing . TBS was recorded using an universal testing machine. Qualitative examination of the bonding sites was performed by SEM after dissolving the dentin with 50 percent nitric acid. Pressure application prior to light-curing resulted in a remarkable decrease of TBS for Syntac®, while no significant change was observed for ScotchbondTM MP. SEM analysis showed no considerable lengthening of the resin tags after pressure application. These findings suggest that application of adhesive systems to dentin under pressure before light-curing had no positive effect on TBS.

Este estudo avaliou a influência da aplicação de uma pressão definida antes da polimerização sobre a resistência à tração de dois sistemas adesivos à dentina molhada e perfundida. Os sítios de adesão foram analisados em microscopia eletrônica de varredura (MEV) a fim de determinar a ocorrência de alterações morfológicas. Discos de dentina de 120 terceiros molares humanos foram preparados de tal forma a simular a pressão intrapulpar. Os espécimes foram alocados aleatoriamente em 6 grupos (n=20), de acordo com as diferentes condições experimentais propostas. Os sistemas adesivos (Syntac® e ScotchbondTM Multi-Purpose) foram aplicados sobre a dentina molhada ou perfundida. Nesta última, compressão (7 N) foi aplicada antes da polimerização do sistema adesivo. A resistência à tração foi registrada em máquina universal de ensaios. A análise qualitativa dos sítios de adesão foi realizada em MEV após dissolução da dentina em 50 por cento de ácido nítrico. A aplicação da pressão antes da polimerização do sistema adesivo resultou em diminuição significativa da resistência à tração do Syntac®, ao passo que para o ScotchbondTM MP nenhuma alteração significativa foi observada. A análise em MEV não mostrou aumento considerável do tamanho dos tags de resina após a aplicação da pressão. Esses achados sugerem que a aplicação de sistemas adesivos à dentina sob pressão previamente à polimerização não teve efeito positivo sobre a resistência à tração.