Oncogenic somatic events in tissue-specific stem cells: a role in cancer recurrence?

Tissue-specific stem cells (TSSCs) are a very unique cell type, with critical and well-defined roles for the homeostasis of high turnover tissues (such as the blood and the skin). Emerging evidence suggests that TSSCs are implicated in malignancies, with several theories being proposed and tested, including many attempts to identify the cells of origin and studies deigned to understand how TSSCs participate in age-related increase in cancer risk. A currently unexplored possibility in this respect is the plausible theory that an oncogenic event that arises at a TSSC would promote tissue replenishment by cells containing these mutations, with progressive propagation of such mutated TSSCs in the niche. Therefore, the effect of a somatic oncogenic event in a single TSSC may have more important implications than previously anticipated, resulting in sustained and progressively higher cancer risk. This model could have important implications for tumor recurrence, since in some cases the underlying cause might be the development of a new tumor originated from daughter cells of the TSSC that suffered the first oncogenic hit, rather than proliferation of residual cancer cells. In this review, we present and discuss approaches for testing the proposed theory of tumorigenesis and cancer risk, as well as practical implications for biomedical research and clinical practice.

Are obesity and overweight associated with gingivitis occurrence in Brazilian schoolchildren?

AIM

This cross-sectional study aimed to assess the relationship between weight status and gingival inflammation in Brazilian schoolchildren aged 8- to 12-year old, when controlling for potential confounders.

METHODS

Overall, 1211 children aged 8- to 12-year old from public and private schools in Southern Brazil were selected by a two-stage cluster method. Questionnaires were used to assess socio-demographic data and oral hygiene habits. Oral examination evaluated presence of plaque and gingival bleeding. Anthropometric measures were collected to obtain body mass index. Multivariate Poisson regression was used for data analysis (Prevalence Ratio/95% Confidence Interval).

RESULTS

Prevalence of gingivitis was 44.0%. Mean and median values of gingival bleeding sites were 3.10 and 2.0 respectively. Obese/overweight children totalized 34.6%. In multivariate adjusted analysis, sex (PR 0.86; 95%CI 0.75;0.98), maternal schooling (PR 1.09; 95% CI 1.01;1.18), plaque (PR 1.37; 95% CI 1.26;1.50), dental caries experience (PR 1.16; 95% CI 1.01;1.36) and bleeding during tooth brushing (PR 1.27; 95% CI 1.11;1.48) were associated with the outcome. In the sex-stratified analysis, overweight/obese boys presented a greater risk for gingivitis (PR 1.22 95% CI 1.01;1.48).

CONCLUSIONS

Gingivitis was not associated with obesity/overweight in the total sample. Gender differences seem to influence the relationship between gingivitis and obesity/overweight; a stronger association was noted among boys than girls.

Influence of different photo-activation distances on cytotoxicity of a dental adhesive model resin

AIM

This study evaluated the cytotoxicity of a dental bonding model resin (DBMR) submitted to different photo-activation distances.

METHODS

A monomer mixture based on Bis-GMA and HEMA was used to assess the cytotoxicity in a mouse fibroblast-cell line. To promote different photo-activation distances glass slides were interposed between DBMR surface and halogen light curing unit (LCU) tip. Afterwards, the specimens were immersed in RPMI culture medium for 24 h to obtain extracts. The extracts were incubated in contact with the cells for 24 h. Finally, an MTT colorimetric assay was used to assess the cytotoxicity. The cell viability data (absorbance) were analyzed by one way ANOVA followed by Tukey's test (P<0.05).

RESULTS

The light output decreased according to the increase in the number of glass slides between the halogen LCU tip and DBMR surface. Yet, the distance between the tip of the curing light system and the specimens had significant influence on the cytotoxicity. All extracts produced by groups submitted to different photo-activation distances showed cytotoxic effect after 24h of incubation.

CONCLUSION

The photo-activation distance and the interposition of glass slides between LCU tip and DBMR was shown to play an important role in the cytotoxic effect.

Caries is the main cause for dental pain in childhood: findings from a birth cohort

AIM

The aim of the study was to evaluate the prevalence of dental pain in preschool children and its association with socioeconomic, demographic, clinical, and behavior variables.

SUBJECTS AND METHODS

The study was nested in a population-based birth cohort from Pelotas, Brazil, started in 2004. A sample of 1,129 children aged 5 years was dentally examined, and their mothers were interviewed. Exploratory variables included demographics, socioeconomic status, mothers' oral health status and associated behaviors, and caries in primary teeth. Data were analyzed using multivariable Poisson regression.

RESULTS

The prevalence of dental pain was 16.5% (95% CI: 14.4-18.8). Multivariate analysis showed that dark-skinned children (prevalence ratio, PR = 1.6, 95% CI: 1.1-2.4) from low socioeconomic level (PR 1.9, 1.2-3.0) whose mothers had less than 4 years of education (PR 1.9, 1.0-3.6), from mothers with less than 10 teeth in at least one arch (PR 1.7, 1.2-2.5) and less than 10 in two arches (PR 1.6, 1.0-2.6), and those with high caries prevalence at the age of 5 years (PR 4.8, 3.3-7.1) were more likely to experience dental pain.

CONCLUSIONS

Unrestored caries is the main factor associated with dental pain in childhood. Socioeconomic aspects and family context in which dental pain occurs should also be taken into account when dental pain preventive measures are implemented.

Children's use of dental services: influence of maternal dental anxiety, attendance pattern, and perception of children's quality of life

OBJECTIVES

The purpose of the study was to investigate the influence of a child's clinical condition; maternal characteristics such as dental anxiety and dental visit pattern; socioeconomic conditions; and maternal perception of the child's oral health-related quality of life (OHRQoL) on a child's use of dental care services.

METHODS

A cross-sectional study of 608 mother-child dyads was conducted during the Children's Immunization Campaign in Pelotas, Brazil. Mothers answered a questionnaire regarding their use of dental services, dental anxiety (Dental Anxiety Scale), socioeconomic status, and perception of their children's OHRQoL (the Early Childhood Oral Health Impact Scale). Clinical examination of the children was performed to assess dental caries (dmf-t). Associations between the above-mentioned factors and child use of dental services were assessed using Poisson regression models (prevalence ratio [PR]; 95% CI; P ≤ 0.05).

RESULTS

The majority of children (79.3%) had never had a dental appointment and of the children who had visited a dentist, 55 (43.65%) presented with untreated dental caries at the time of examination. More than half the mothers (60.2%) did not visit a dentist regularly. In the final model, low schooling level of mothers (PR, 0.64) and irregular visits to a dentist by the mother (PR, 0.48) were factors because of which a child did not have a dental appointment. Children who had experienced pain (PR, 1.56), those who had poor OHRQoL (PR, 1.49), and older children (PR, 2.14) visited a dentist with higher frequency.

CONCLUSIONS

Use of dental care services by preschool children was low, and treatment was neglected even among children who had visited a dentist. Children of mothers with low schooling level who do not visit a dentist regularly were at greater risk of not receiving dental care. Maternal perception of their child's oral health motivated visits to the dentist.

Validity of partial protocols to assess the prevalence of periodontal outcomes and associated sociodemographic and behavior factors in adolescents and young adults

BACKGROUND

Most studies comparing prevalence of periodontal disease and risk factors by using partial protocols were performed in adult populations, with several studies being conducted in clinical settings. The aim of this study is to assess the accuracy of partial protocols in estimating the prevalence of periodontal outcomes in adolescents and young adults from two population-based birth cohorts from Pelotas, Brazil, and to assess differences in the estimation and strength of the effect measures when partial protocols are adopted compared to full-mouth examination.

METHODS

Gingival bleeding at probing among adolescents (n = 339) and young adults (n = 720) and dental calculus and periodontal probing depth among young adults were assessed using full-mouth examinations and four partial protocols: Ramfjord teeth (RT), community periodontal index (CPI), and two random diagonal quadrants (1 and 3, 2 and 4). Socioeconomic, demographic, and periodontal health-related variables were also collected. Sensitivity, absolute and relative bias, and inflation factors were calculated. Prevalence ratio for each periodontal outcome for the risk factors was estimated.

RESULTS

Two diagonal quadrants showed better accuracy; RT had the worst, whereas CPI presented an intermediate pattern when compared to full-mouth examination. For bleeding assessment in adolescence, RT and CPI underestimated by 18.4% and 16.2%, respectively, the true outcome prevalence, whereas among young adults, all partial protocols underestimated the prevalence. All partial protocols presented similar magnitude of association measures for all investigated periodontal potential risk factors.

CONCLUSION

Two diagonal quadrants protocol may be effective in identifying the risk factors for the most relevant periodontal outcomes in adolescence and in young adulthood.

Odontoblast RNA stability in different temperature-based protocols for tooth storage

AIM

To evaluate the effect of four tooth storage temperature-based methods on quality of RNA obtained from cells retrieved from human dental pulps and human pre-dentine.

METHODOLOGY

RNA was isolated from dental pulp tissue and from cells retrieved by scraping the pre-dentine of freshly extracted human third molars (n = 15) using TRIzol(®) reagent. Teeth were randomly assigned to the following temperature conditions: immediate RNA isolation after tooth extraction, liquid nitrogen (24 h), -80 °C (24 h), 20 °C (24 h) and 4 °C (6 h). RNA integrity was checked by the density of 28S and 18S ribosomal RNA. RT-PCR was used to analyse the expression of odontoblast makers (DSPP, DMP1 and MEPE) and the housekeeping gene GAPDH.

RESULTS

All experimental conditions evaluated preserved RNA integrity. The three odontoblastic markers were amplified from the pulp tissue and from the cells associated with pre-dentine.

CONCLUSION

The four storage options allowed RNA isolation for RT-PCR analysis. These findings may facilitate the use of clinically derived human dental pulp and odontoblasts for endodontic research.

Influence of maternal dental anxiety on the child's dental caries experience

This study assessed the influence of maternal dental anxiety-related behavior on the child's caries experience. A cross-sectional study with 608 mother-child dyads during the Children's National Immunization Campaign in Pelotas, Brazil was performed. Mothers were asked to answer a questionnaire and dental examination of the children was performed (dmft). The association assessment used Poisson regression. Children from anxious mothers were more likely to present untreated caries even after covariate adjustment. Boys, older children and low-income family children presented a higher dmft mean. Preventive strategies should focus not only on child and family characteristics, but also on maternal dental anxiety-related behaviors.

22-Year clinical evaluation of the performance of two posterior composites with different filler characteristics

OBJECTIVES

This retrospective longitudinal study investigated the longevity of posterior restorations placed in a single general practice using 2 different composites in filler characteristics and material properties: P-50 APC (3M ESPE) with 70vol.% inorganic filler loading (midfilled) and Herculite XR (Kerr) with 55vol.% filler loading (minifilled).

METHODS

Patient records were used for collecting data. Patients with at least 2 posterior composite restorations placed between 1986 and 1990, and still in the practice for regular check-up visits, were selected. 61 patients (20 male, 41 female, age 31.2-65.1) presenting 362 restorations (121 Class I, 241 Class II) placed using a closed sandwich technique were evaluated by 2 operators using the FDI criteria. Data were analyzed with Fisher's exact test, Kaplan-Meier statistics, and Cox regression analysis (p<0.05).

RESULTS

110 failures were detected. Similar survival rates for both composites were observed considering the full period of observation; better performance for the midfilled was detected considering the last 12 years. There was higher probability of failure in molars and for multi-surface restorations.

SIGNIFICANCE

Both evaluated composites showed good clinical performance over 22 years with 1.5% (midfilled) and 2.2% (minifilled) annual failure rate. Superior longevity for the higher filler loaded composite (midfilled) was observed in the second part of the observation period with constant annual failure rate between 10 years and 20 years, whereas the minifilled material showed an increase in annual failure rate between 10 years and 20 years, suggesting that physical properties of the composite may have some impact on restoration longevity.

Histologic Response and Tenascin and Fibronectin Expression After Pulp Capping in Pig Primary Teeth With Mineral Trioxide Aggregate or Calcium Hydroxide

Mineral trioxide aggregate produces a lower initial inflammatory response than calcium hydroxide. However, both capping materials produce dentin barriers after seventy days.

Comparative analysis of two colorimetric assays in dental pulp cell density

AIM

To compare and contrast two colorimetric assays used for the measurement of proliferation using two dental pulp cell types: dental pulp stem cells (DPSC) and human dental pulp fibroblasts (HDPF).

METHODOLOGY

Dental pulp stem cells or HDPF were seeded at 0.25×10(4) cells per well in 96-well plates. Cell proliferation was evaluated after 24-72h. At the end of the experimental period, the sulforhodamine B (SRB) assay or a water-soluble tetrazolium salt (WST-1) assay was performed. Optical densities were determined in a microplate reader (Genius; TECAN). Data were analysed by Student's t-test (comparison between cell types) and one-way anova followed by Tukey test (time-point intervals). Pearson' correlation tests were performed to compare the two assays for each cell line.

RESULTS

Both assays showed that DPSC had higher proliferation rates than HDPF. A positive significant correlation between the two colorimetric assays tested for both cell types DPSC (Pearson's correlation coefficient=0.847; P<0.05) and HDPF (Pearson's correlation coefficient=0.775; P<0.05).

CONCLUSION

Both tests demonstrated similar trends of cell proliferation, and thus are both appropriate for the evaluation of DPSC and HDPF. The choice of assay is therefore one of the practical applications. SRB stained plates can be dried and stored so may have utility in laboratories where data may require review or when access to analytical equipment is limited. WST-1 assays have the benefit of both ease and speed and may have utility in laboratories requiring either high throughput or rapid analyses.

A double-blind randomized clinical trial of two carbamide peroxide tooth bleaching agents: 2-year follow-up

OBJECTIVES

This double-blind randomized clinical trial aimed to evaluate the whitening effect of two at-home tooth bleaching agents and the effect of dietary habits after 2 years. The patients' view about bleaching longevity was also investigated.

METHODS

Ninety-two subjects with mean shade of C1 or darker for the six maxillary anterior teeth were randomized into two groups (n=46) according to the carbamide peroxide (CP) concentration: 10% (CP10) or 16% (CP16). The treatment was performed using the whitening agent in a tray for 2h/day during 3 weeks. Shade evaluations were done with a shade guide and a spectrophotometer at baseline, 1-month, 6-month, 1-year and 2-year post-bleaching.

RESULTS

Eighty-one (88%) of the original 92 subjects enrolled in the study were recalled at 2-year follow-up and, the tooth shade remained significantly lighter than at baseline, in both treatment groups, considering the tooth shade median values (p<0.001) or the color parameters: L*a* (p<0.001) for CP10 and, L*b* for CP16 group (p<0.001). Subjects from CP10 and CP16 reported a consumption of beverage and food stains as high as at 6-month and 1-year recalls and, more than 66% of the participants from each group reported a tooth shade relapse from mild to moderate (p=0.6).

SIGNIFICANCE

At 2-year post-bleaching, tooth shade remained lighter than at baseline for both CP concentrations tested. Tooth shade relapse associated to increasing of a* and b* color parameters were observed for both groups when compared to the end of the treatment (CEP # 37/05).

Impact of immediate and delayed light activation on self-polymerization of dual-cured dental resin luting agents

This study investigated the impact of immediate and delayed light activation on self-polymerization of a model dual-cured luting agent. The material presented the following components: base paste - 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycol dimethacrylate (TEGDMA), camphorquinone, dimethyl-p-toluidine, butylated hydroxytoluene (BHT), glass fillers; catalyst paste - bisphenol-A ethoxylated dimethacrylate/TEGDMA, benzoyl peroxide, BHT, fillers. The pastes were mixed and seven polymerization scenarios tested: immediate light activation using low (5Jcm(-2)) or high (20Jcm(-2)) energy dose; delayed light activation (after 2min - short delay) using low or high dose; delayed light activation (after 10min - long delay) using low or high dose; and self-polymerization only. The degree of conversion (DC) and rate of polymerization (R(p)) were evaluated for 30min by real-time infrared spectroscopy. The lowest DC was detected for the self-polymerized and immediate-low dose groups, whereas the immediate-high dose and short delay-high dose groups showed the highest values. For the self-polymerized and immediate-high dose samples, R(p)(max) was detected after approximately 7s, whereas this took approximately 14s for the immediate-low dose group. R(p)(max) for the immediate-high dose group was higher than for the self-polymerized sample, which in turn was higher than for the immediate-low dose group. R(p)(max) for the short delay groups was higher than for the long delay groups. In conclusion, the extent of self-polymerization was influenced by the light dose reaching the material, which was dependent on high radiant exposure for optimal polymerization and the moment at which the light was applied; the short delay increased the DC for lower doses, while also generally decreasing the R(p) for all scenarios.

Characterization and surface treatment effects on topography of a glass-infiltrated alumina/zirconia-reinforced ceramic

OBJECTIVE

Characterize the microstructure, composition and some physical properties of a glass-infiltrated alumina/zirconia-reinforced ceramic (IZ) and the effect of surface treatment on topography.

METHODS

IZ ceramic specimens were fabricated according to ISO6872 instructions and polished through 1 microm alumina abrasive. Quantitative and qualitative analyses were performed using scanning electron microscopy (SEM), backscattered imaging (BSI), electron dispersive spectroscopy (EDS) and stereology. The elastic modulus (E) and Poisson's ratio (nu) were determined using ultrasonic waves, and the density (rho) using a helium pycnometer. The following ceramic surface treatments were used: AP-as-polished; HF-etching with 9.5% hydrofluoric acid for 90 s; SB-sandblasting with 25 microm aluminum oxide particles for 15s and SC-blasting with 30 microm aluminum oxide particles modified by silica (silica coating) for 15s. An optical profilometer was used to examine the surface roughness (Ra) and SEM-EDS were used to measure the amount of silica after all treatments.

RESULTS

The IZ mean property values were as follows: rho=4.45+/-0.01 g/cm(3); nu=0.26 and E=245 GPa. Mean Ra values were similar for AP- and HF-treated IZ but significantly increased after either SC or SB treatment (p<or=0.05). The surface concentration of Si(K) increased 76% after SC treatment.

SIGNIFICANCE

HF is an inadequate surface treatment for bonding resins to IZ ceramic. Treating IZ with either SB or SC produced greater Ra values and the SC showed a significant increase in the surface concentration of silica, which may enhance bonding to resin via silane coupling.

Microleakage in full-crown all-ceramic restorations: influence of internal surface treatment, silane application, alumina system, and substrate

This study investigated the influence of internal surface treatment and margin location on the microleakage of 2 alumina-reinforced ceramic crown systems: In-Ceram (VITA Zahnfabrik) and Procera (Nobel Biocare). Full crowns were produced for each of the 2 systems (n = 24) in human premolars, with margins located in enamel and dentin, and luted with Single Bond and RelyX ARC (3M ESPE). Four internal ceramic treatments were tested: (1) aluminum oxide blasting (AO), (2) AO plus silane, (3) hydrofluoric acid etching (HF), and (4) HF plus silane. After thermal cycling, leakage was measured quantitatively. Statistical analysis (P < .05) showed higher leakage in dentin margins compared to enamel. In enamel, Procera showed greater leakage compared to In-Ceram. Generally, lower microleakage was observed for the AO plus silane treatment.

Clinical Performance and Wear Resistance of Two Compomers in Posterior Occlusal Restorations of Permanent Teeth: Six-Year Follow-up

The restoration quality has decreased and the wear increased for two compomers placed in the occlusal surface of permanent posterior teeth after six years; however, the restorations were clinically acceptable at the end of the evaluation.

Immunohistochemical expression of fibronectin and tenascin after direct pulp capping with calcium hydroxide

The aim of this study was to investigate the expression of 2 extracellullar matrix glycoproteins, fibronectin (FNC) and tenascin (TNC), following direct pulp capping with calcium hydroxide (CH). Third molars scheduled for extraction were used. Standardized class I cavities with pulp exposures were prepared. After control of bleeding, CH powder was applied in the exposure sites, which were covered with CH cement (Dycal; Dentsply) and the cavities were filled with zinc oxide-eugenol cement. Three teeth were extracted at each post-treatment period (1, 7, 14, and 30 days). Demineralized and paraffin-embedded specimens were stained for histologic technique (hematoxylin-eosin) and for immunohistochemical analysis. Anti-TNC and anti-FNC monoclonal antibodies were used with the streptavidin-biotin complex method. Generally, similar patterns of immunohistochemical expression were observed for TNC and FNC in the pulp tissue as a whole. In the exposure site, TNC immunostaining increased over time, exhibiting a thicker immunostaining pattern within 30 days. The imunohistochemical technique showed expression of both glycoproteins during pulp healing process.

The influence of haemostatic agents on healing of healthy human dental pulp tissue capped with calcium hydroxide

AIM

To investigate the hypothesis that different haemostatic agents could impair the histological response of human pulps capped with calcium hydroxide.

METHODOLOGY

Forty-five third molars scheduled for extraction were selected. Class I cavities with pulp exposures were prepared. Three agents were used to control bleeding: 0.9% saline solution (control, n = 14), 5.25% sodium hypochlorite (n = 16) and 2% chlorhexidine digluconate (n = 15). The pulps were dressed with hard-setting calcium hydroxide cement. After 7, 30 or 90 days, teeth were extracted, formalin-fixed and prepared for histochemical techniques. The biological response was categorized using the following criteria: inflammatory response, soft tissue organization, reactionary dentine and reparative dentine. Data were submitted to statistical analysis, using nonparametric Kruskal-Wallis one-way analysis of variance on ranks. Differences amongst groups were detected using Dunn's method.

RESULTS

The statistical analysis disclosed that whilst inflammatory response decreased over time, reactionary dentine deposition and reparative dentine formation increased in the latter periods of evaluation (P < 0.05). The three agents had similar performances for all criteria evaluated. The conventional pulp response to calcium hydroxide was observed over time, and complete pulp healing was observed in 88% of the specimens after 90 days.

CONCLUSION

The three haemostatic agents did not impair the healing process following pulp exposure and capping with calcium hydroxide at different time intervals investigated.

Fracture Resistance of Premolars Restored with Partial Ceramic Restorations and Submitted to Two Different Loading Stresses

The fracture resistance of ceramic restorations is associated with the quantity of the dental structure removed. In relation to the fracture resistance, preference should be given to inlay restorations rather than to onlays; however, no restorative technique was able to attain the fracture resistance of intact teeth.

In situ and in vitro effects of bleaching with carbamide peroxide on human enamel

This study evaluated in vitro and in situ the potential adverse effects of 10% carbamide peroxide on human enamel using microhardness, calcium loss and surface morphology analysis. Twenty-four enamel slices (4 mm2) were obtained from recently extracted premolars. The specimens were polished under water-cooling down to 1,200-grade sandpaper. After initial microhardness readings (100 g), the specimens were randomly divided into two groups for in situ and in vitro conditions. The specimens were covered with 10% carbamide peroxide for eight hours. After removing the bleaching gel, the in vitro specimens were stored in deionized water and the in situ specimens, included in an intra-oral appliance, were placed in the oral cavity of four volunteers. These cycling sequences took place for 14 days. Upon conclusion of the bleaching treatment, new microhardness readings were performed on all specimens. Calcium dosage was assessed from the bleaching gel collected after initial exposure on day one, then from gel collected between days two and seven and gel collected between day eight and 14 using an atomic absorption spectrophotometer. Surface morphology was observed from two non-treated control specimens and two specimens of each experimental bleached group under SEM evaluation. Statistical analysis (ANOVA and Tukey tests) disclosed that specimens bleached in situ showed similar microhardness to unbleached specimens and had statistically higher (p < 0.01) hardness than in vitro bleached specimens. The loss of calcium in the in vitro situation at 14 days was 2.5 times higher than the in situ condition. SEM micrographs demonstrated that surface alterations were more pronounced in the in vitro condition. The adverse effects of carbamide peroxide on enamel were evident in specimens bleached in vitro but were not seen in situ. The presence of saliva could prevent the demineralizing effect of bleaching gel in situ.

Flexural strength of composites: influences of polyethylene fiber reinforcement and type of composite

MAIN PROBLEM

The microfill veneering of hybrid composite restorations has been indicated to improve esthetics. Also, polyethylene fiber reinforcement has been proposed for use in composite restorations in high-stress clinical situations. However, minimal information in the literature addresses the influence of such combinations on the resistance to fracture. The purpose of this study was to investigate the flexural strength of two composites, a microfill and a hybrid, the effect of their combination, and the influence of polyethylene fiber reinforcement.

MATERIALS AND METHODS

Twenty-eight specimens were prepared using a standard metallic mold (20x2x2 mm) and divided into groups of seven each: Filtek Z-250 (3M ESPE, St. Paul, Minn., USA) (group I), Filtek A-110 (3M ESPE) (group II), Filtek Z-250 combined with Filtek A-110 (group III), and Filtek Z-250 combined with polyethylene fiber (Ribbond, Seattle, Wash., USA) (group IV). The specimens were stress-loaded to fracture in a three-point bending device according to International Standardization Organization (ISO) 4049.

RESULTS

Data were analyzed using analysis of variance and Tukey's test at a 0.05 level of significance. No statistically significant differences were observed between groups I and IV. Group II, however, exhibited statistically lower resistance to fracture than the other groups. Group III presented intermediate results, showing statistically higher fracture resistance than group II but lower than group I.

CONCLUSIONS

With the methodology employed, microfill composite presented the lowest flexural strength, but its association with hybrid composite increased the resistance to fracture. The combination of polyethylene fiber and hybrid composite did not present higher flexural strength than hybrid composite alone.

Dyes for caries detection: influence on composite and compomer microleakage

The aim of this study was to evaluate the influence of caries-detecting dyes on the microleakage of adhesive materials. Sixty cubic class V cavities were prepared on buccal and lingual surfaces of 30 human third molars. Coronal margins were located in enamel and gingival margins in cementum. The teeth were randomly divided into six groups of ten restorations each. Cavities were restored with an adhesive system (Single Bond, 3M ESPE, St. Paul, Minn., USA), a compomer (F2000, 3M ESPE), or a composite resin (Z100, 3M ESPE) according to the manufacturer's directions. Acid red dye (Seek, Ultradent, South Jordan, Ut., USA) and basic fuchsin dye (Vide Cárie, Inodon, Porto Alegre, Brazil) were tested. Control groups were prepared without the use of dyes. After 7 days of storage in distilled water, the restorations were polished and the teeth were subjected to thermal cycling followed by immersion in 2% methylene blue. The teeth were sectioned, and microleakage scores were evaluated under magnification (40x). Data were submitted to statistical analysis using the nonparametric Kruskal-Wallis test. A statistically significant difference ( P<0.05) in microleakage was found between the materials in cementum (Z100>F2000) but not in enamel. Control and experimental groups using dyes showed similar results. It was concluded that dyes for caries detection did not increase microleakage of the adhesive materials tested.

Microleakage in endodontically treated teeth: influence of calcium hydroxide dressing following bleaching

AIM

The purpose of the present study was to evaluate microleakage of a fourth generation dentine-bonding agent and composite restoration during a walking bleach treatment.

METHODOLOGY

Thirty extracted non-carious incisors were selected and conventional root canal treatment was performed. Teeth were randomly divided into 3 groups (n = 10): group A (control), access cavities were restored with a fourth generation dentine-bonding agent, and incrementally restored with composite resin; group B, a paste composed of sodium perborate and hydrogen peroxide was placed into the pulp chamber and sealed with glass ionomer cement for 7 days, teeth were then restored in the same manner as group A; group C, a paste of sodium perborate and hydrogen peroxide was placed in the pulp chamber for 7 days and then after removal of the bleaching mixture, pulp chambers were filled with a calcium hydroxide paste and cavities sealed with glass ionomer for 1 week. The cavities were then restored with bonded restorations as in groups A and B. Teeth were subjected to thermal cycling and immersed in methylene blue for 8 h. Teeth were sectioned from buccal to lingual, through the centre of the restoration, using a diamond disk. Leakage was assessed using a standard scheme, under magnification (x20). Data were submitted to statistical analysis using nonparametric Kruskal-Wallis test.

RESULTS

Groups A and C exhibited similar leakage patterns, and both demonstrated less leakage values than group B (P < 0.05).

CONCLUSIONS

It was concluded that bleaching with sodium perborate and hydrogen peroxide increases microleakage; short-term use of a calcium hydroxide medicament did not increase microleakage.

Clinical and radiographic evaluation of pulpotomies performed under intrapulpal injection of anaesthetic solution

AIM

The purpose of this study was to evaluate clinically and radiographically pulpotomies carried out under intrapulpal injection of anaesthetic solution.

METHODOLOGY

Forty-one permanent mandibular molar teeth presenting with deep carious lesions and/or exposed pulps, with or without periapical changes on radiographic examination, were treated with pulpotomy and dressed with calcium hydroxide. The teeth were divided into three groups. Group A consisted of 15 teeth, where intrapulpal anaesthesia was administered by a slow injection of lidocaine hydrochloride 2%. Group B, with 14 teeth, where intrapulpal anaesthesia was obtained with lidocaine hydrochloride 2% with adrenaline 1:100,000. Group C consisted of 12 teeth in which anaesthesia was performed with a mandibular block using prilocaine hydrochloride 3% with felypressin 1: 100,000. Healing was evaluated using clinical and radiographic criteria: dentine barrier formation, absence of clinical symptoms and resolution of periapical involvement.

RESULTS

After an observation time of 6-8 weeks (postoperative control) and 24-32 weeks (intermediate control), healing occurred in 13 teeth from group A (87%), in 11 teeth from group B (79%) and in 10 teeth from group C (83%). No statistical difference was demonstrated between the three groups (Fisher's exact test).

CONCLUSIONS

Based on the methodology adopted, intrapulpal injection of anaesthetic solution did not impair healing in pulpotomized teeth.

Microleakage in amalgam restorations: influence of cavity cleanser solutions and anticariogenic agents

This study evaluated in vitro the influence of five solutions used to treat cavity preparations on microleakage of amalgam restorations. Seventy-two standard Class V cavities were prepared in buccal and lingual surfaces of 36 recently extracted human third molars. The cervical wall was located in cementum and the occlusal wall was located in enamel. Specimens were randomly divided into six groups (n=12) according to the solution employed to treat the cavities: Group I-2.5% sodium hypochlorite; Group II-Calcium hydroxide solution; Group III-1.23% Acidulated phosphate fluoride; Group IV-2% digluconate of chlorhexidine; Group V-anionic detergent solution (1.25% sodium lauryl sulfate) and Group VI-control group. The solutions were applied for one minute, followed by washing and drying. Two coats of copal varnish were applied in each cavity. The cavities were filled with capsuled amalgam GS-80 (SDI). After finishing and polishing, the specimens were submitted for thermal cycling followed by immersion in methylene blue. Then, the specimens were sectioned and microleakage was evaluated based on a standard ranking under magnification (40x). Data were subjected to statistical analysis using non-parametric tests. Results of the study concluded that leakage was higher in cementum than enamel (p<0.01). The substances employed have no influence on microleakage except for sodium hypochlorite, which increased leakage values in enamel (p<0.05).

Influence of different restorative techniques on microleakage in Class II cavities with gingival wall in cementum

This study compared marginal leakage of Class II cavities with gingival margin in cementum using different techniques. Twenty-four recently extracted third molars were used. Proximal standard box cavities were prepared in both mesial and distal surfaces. The gingival margin was located apical to the cemento-enamel junction. All the preparations and restorations were performed by the same operator. Standard cavities were randomly divided into three groups (n = 16) and restored as follow: Group 1-light-cured composite resin; Group 2-self-cured composite resin + light-cured composite resin and Group 3-amalgam + light-cured composite resin. After polishing, the teeth were thermocycled and their gingival margins exposed to dye. Specimens were sectioned and leakage scores observed in accordance with a standard ranking. Data were subjected to statistical analysis (Kruskal-Wallis). Results showed that the amalgam/resin composite combination demonstrated the least leakage.

Pulp response and cytotoxicity evaluation of 2 dentin bonding agents

OBJECTIVE

This study evaluated the biocompatibility of two dentin bonding agents (Clearfil Liner Bond 2 and Scotchbond Multi-Purpose) applied in human dental pulps and cell cultures.

METHOD AND MATERIALS

In vivo: Twenty human third molars that were scheduled for extraction were used. After cavity preparation, pulp exposure was achieved with a carbide bur. Hemorrhage control was obtained with saline solution. In 16 teeth, adhesive pulp capping was performed and the cavities were sealed with resin composite. In the control group (n = 4), pulps were capped with Ca(OH)2 and the cavities were sealed with IRM. Teeth were extracted 30 or 90 days following treatment and prepared for histological examination and bacterial detection. In vitro: materials were applied in Petri dishes, where NIH-3T3 cells were plated. The cells were counted 2, 4, and 6 days after plating to obtain the growth curves and to determine cell viability. All data were submitted to statistical analysis.

RESULTS

In vivo: Dentin bridge formation was seen in all teeth capped with Ca(OH)2, without an inflammatory response. Mild inflammatory responses and dentin bridge formation after 90 days were observed in 50% of specimens treated with Liner Bond 2. Pulps treated with Scotchbond Multi-Purpose presented mild to severe inflammatory response, and no mineralized tissue formation was detected. Bacteria were not disclosed in any specimen. In vitro: The cytotoxicity was similar between the two bonding agents, and both had statistically higher cytotoxic effects (P < 0.002) than Ca(OH)2.

CONCLUSION

Ca(OH)2 produced pulp healing in all teeth and exhibited lower cytotoxic effects than both adhesive systems; however, pulp healing was also observed under Liner Bond 2.

Tensile bond strength of two dentin adhesive systems

The tensile bond strength of one third-generation (XR Bond) and one fourth-generation (Optibond) adhesive system to dentin was compared. The influence of acid etching of dentin on the bond strength in the XR Bond system was also evaluated. In addition, two kinds of curing (photo and dual) of the Optibond system were evaluated. The Optibond system showed a statistically significant higher tensile bond strength to dentin than the XR Bond system. Etching of the dentin before application to XR Bond did not significantly improve the bond strength to dentin. Both photo and dual curing showed similar bond strengths two hours and seven days after sample preparation.

Dyes for caries detection influence sound dentin bond strength

This study evaluated the influence of caries-detection dyes on the in vitro tensile bond strength of adhesive materials to sound dentin. Caries-free human molars were ground to expose superficial dentin. Two dyes (a commercial 0.5% basic fuchsin in propylene glycol and Cari-D-Tect) were applied to sound dentin and rinsed. Subsequently, the dentin was etched with phosphoric acid (35%) and rinsed, leaving a moist dentin surface. The adhesive (Prime & Bond 2.0) was applied in two layers and light cured. A composite (TPH Spectrum), a compomer (Dyract), and a hybrid ionomer (Advance) were used to prepare the bond-strength specimens with a 3-mm-in-diameter bonding area. Control groups were made without use of dyes. Six specimens were prepared for each group. After 24 hours in distilled water, tensile bond strength (MPa) was measured using a testing machine. Analysis of variance was used to evaluate the data. Without dyes, bond strengths of TPH Spectrum and Dyract with Prime and Bond 2.0 were similar and both values were significantly (P < 0.05) higher than that of Advance with Prime & Bond 2.0. Dyes for caries detection reduced the bond strength of TPH Spectrum and Dyract but not Advance when used with Prime and Bond 2.0.