Tunable polymer-peptide hybrids for dentin tissue repair

OBJECTIVES

This study targets to assess the remineralization capability of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs).

METHODS

Dentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanohardness, Masson's trichrome staining microscopy, and Raman analysis.

RESULTS

Dentin surfaces treated with TDg-NPs and load cycled produced higher nanohardness than the rest of the groups at the hybrid layer. At the bottom of the hybrid layer, all samples treated with TDg-NPs showed higher nanohardness than the rest of the groups. Active remineralization underneath the hybrid layer was detected in all groups after TDg application and load cycling, inducting new dentinal tubuli formation. After thermocycling, remineralization at the hybrid layer was not evidenced in the absence of NPs. Raman analysis showed increase mineralization, enriched carbonate apatite formation, and improved crosslinking and scaffolding of the collagen.

CONCLUSIONS

Mechanical loading on the specimens obtained after TDg-NPs dentin infiltration inducts an increase of mineralization at the resin/dentin interface, indicating remineralization of peritubular and intertubular dentin with augmented crystallographic maturity in crystals. Enriched collagen quality was produced, generating an adequate matrix organization to promote apatite nucleation, after tideglusib infiltration.

CLINICAL SIGNIFICANCE

At the present research, it has been proved the creation of reparative dentin, at the resin-dentin interface, after tideglusib dentin infiltration. Chemical stability, to favor integrity of the resin-dentin interface, is warranted in the presence of the TDg-NPs in the demineralized dentin collagen.

Perceptions of dental students, dental faculty, practicing dentists and industry dental professionals on the acquisition of dental competencies and clinical skills in the Dominican Republic

INTRODUCTION

This study gathered perceptions from four stakeholder groups in the Dominican Republic (DR) regarding acquiring professional dental competencies and clinical skills.

MATERIALS AND METHODS

Researcher-created surveys covering core dental competencies and clinical skills were distributed to stakeholder groups associated with nine different DR dental programs. Respondents included 153 undergraduate dental students, 153 dental faculty members, 108 practicing dentists (who had graduated in the past 5 years) and 42 industry professionals (who hire and supervise dentists). Data were examined using descriptive statistics, univariate ANOVA and multiple linear regressions.

RESULTS

Dental school students and recent graduates now practicing dentists in the DR reflected moderate to solid confidence that they had learned most of the dental skills and competencies covered in the survey. Industry professionals were a bit less confident overall, while dental faculty offered the lowest scores, although those were often still in the moderately confident range. ANOVAs revealed significant differences when broken down by individual university dental programs. Regressions also revealed that individual university dental programs significantly predict confidence that dental skills and competencies were achieved.

CONCLUSION

Data show that DR's dental stakeholder groups generally felt optimistic about the learning occurring. However, the lower mean scores and higher standard deviations from faculty responses raise concern, as do the significant differences between individual dental programs and the dental program itself a significant predictor. Further review of programs is needed, and a national set of dental competencies should be considered in this country.

Effect of doxycycline doped nanoparticles on osteogenic/cementogenic and anti-inflammatory responses of human cells derived from the periodontal ligament

OBJECTIVES

This work aimed to evaluate if doxycycline-doped polymeric nanoparticles possessed any anti-inflammatory effect and promote osteogenic/cementogenic differentiation of stem cells from human periodontal ligament (PDLSCs).

METHODS

The polymeric nanoparticles (NPs) were produced by a polymerization/precipitation process and doped with doxycycline (Dox-NPs). PDLSCs were cultured in the presence or absence of the NPs under osteogenic medium or IL-1β treatment. Cells' differentiation was assessed by gene expression analysis of osteogenic/cementogenic markers alkaline phosphatase (ALP) and Runt-related transcription factor 2 (RUNX2). An anti-inflammatory effect was also ascertained by analyzing IL-1β gene expression. Adipogenic and chondrogenic differentiation was used to confirm the multipotency of PDLSCs.

RESULTS

Gene expression of ALP and RUNX2 in PDLSCs was significantly upregulated by the osteogenic medium (ALP: p<0.001; RUNX2: p = 0.005) while Dox-NPs further enhanced ALP gene expression of PDLSCs treated with the osteogenic medium. Furthermore, Dox-NPs suppressed the up-regulation of IL-1β when cells were subjected to an inflammatory challenge.

CONCLUSIONS

Dox-NPs enhanced PDLSCs differentiation into osteoblasts/cementoblasts lineages while providing an anti-inflammatory effect.

CLINICAL SIGNIFICANCE

Due to their biocompatibility as well as anti-inflammatory and osteogenic/cementogenic effects, Dox-NPs are potential candidates for being used in periodontal regeneration.

A Systematic Review and Meta-Analysis of Systemic Antibiotic Therapy in the Treatment of Peri-Implantitis

Research has been conducted into the advantages of the systemic administration of antibiotics. The aim of this systematic review and meta-analysis was to assess the efficacy of systemic antibiotic administration in the treatment of peri-implantitis in terms of bleeding on probing (BoP) and probing pocket depth (PPD). Literature searches were performed across PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) to identify randomized controlled trials and observational clinical studies. After peri-implantitis treatment, PPD was reduced by 0.1 mm (p = 0.58; IC 95% [-0.24, 0.47]), indicating a non-significant effect of antibiotic administration on PPD. The BoP odds ratio value was 1.15 (p = 0.5; IC 95% [0.75, 1.75]), indicating that the likelihood of bleeding is almost similar between the test and control groups. Secondary outcomes were found, such as reduced clinical attachment level, lower suppuration and recession, less bone loss, and a reduction in total bacterial counts. In the treatment of peri-implantitis, the systemic antibiotic application reduces neither PPD nor BoP. Therefore, the systemic administration of antibiotics, in the case of peri-implantitis, should be rethought in light of the present results, contributing to address the problem of increasing antibiotic resistance.

Zn-containing Adhesives Facilitate Collagen Protection and Remineralization at the Resin-Dentin Interface: A Narrative Review

This is a narrative review of the literature assessing the potential effectiveness of doping dentin polymeric adhesives with zinc compounds in order to improve bonding efficacy, remineralization and protection against degradation. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI and Web of Science. Through our search, we found literature demonstrating that Zn-doped dentin adhesives promote protection and remineralization of the resin-dentin interfaces. The increased bioactivity has also facilitated dentinal tubules' occlusion by crystals' precipitation contributing to improved sealing efficacy of restorations. Loading dentin adhesives with zinc gives rise to an increase of both crystallinity of mineral and crosslinking of collagen. The main role of zinc, in dentin adhesives, is to inhibit collagen proteolysis. We concluded that zinc exerts a protective effect through binding at the collagen-sensitive cleavage sites of matrix-metalloproteinases (MMPs), contributing to dentin matrix stabilization. Zinc may not only act as a MMPs inhibitor, but also influence signaling pathways and stimulate metabolic effects in dentin mineralization and remineralization processes. Zn-doped adhesives increase the longevity of dentin bonding through MMPs inhibition. Zn poses a remineralization strategy in demineralized dentin.

Cariology consensus for undergraduates at dental schools in the Caribbean region

AIM

To obtain a consensus on the domains of cariology for undergraduates in dental schools in the Caribbean.

MATERIALS AND METHODS

Dental school deans from the Dominican Republic (DR) and Puerto Rico (PR) were invited to participate. Afterwards, 24 cariology faculty members from the dental schools in the DR received a 40-h workshop on the current understanding of dental caries. Then, representatives from participating dental schools in the DR and PR were divided into six groups and tasked with exploring the cariology domains described in the European and Colombian consensus. For each domain, the competencies in what the dental student, upon graduation, would have to (1) be proficient in, (2) have knowledge of, (3) and be familiar with were described. Two cariology consensus meetings to work on the domains and suggest changes for the Caribbean region were done, and representatives from the DR and PR agreed on a cariology consensus. For the second stage, Caribbean English-speaking countries were invited to participate in the consensus. Meetings were held with representatives from dental schools in Trinidad and Tobago (TT) and Jamaica (J) to include their suggestions on each consensus domain.

RESULTS

A total of 15 dental schools (DR = 12; PR = 1; TT = 1; and J = 1) participated; they agreed on a new consensus considering the realities of the Caribbean participating countries.

CONCLUSION

A cariology consensus for undergraduates was achieved for 15 dental schools in the Caribbean region. This accomplishment will promote a shift for the Caribbean dental schools' graduates towards a current understanding of dental caries.

Effect of Cervical Lesions on Fracture Resistance and Failure Mode of Maxillary Central Incisors Restored with Fiber Posts and Complete Crowns

PURPOSE

To investigate the effect of a cervical cavity extending 1 mm apical to the cemento-enamel junction (CEJ) on fracture resistance and failure mode of maxillary central incisors that have been treated endodontically, present with complete and incomplete ferrules, and are restored with and without a fiber post.

METHODS AND MATERIALS

50 intact human maxillary central incisors were divided into five groups (n=10): CG (control group) 6-mm fer-rule height, no cervical cavity, and without post; (CO) 6-mm ferrule height without post, with a cervical cavity (access to root canal and cervical cavity restored with composite resin), cervical cavity; and post with ferrule heights of 1 mm (CP1), 2 mm (CP2), and 6 mm (CP6) restored with fiberglass post and composite resin core. After complete metal crowns were cemented on all specimens, they were subjected to thermal cycling (6000 cycles, 5°C/55°C), followed by immediate testing of fracture resistance. After failure, the specimens were sectioned buccolingually to evaluate and identify the mode of failure. The data were analyzed with an analysis of variance (ANOVA) and the Student-Newman-Keuls multiple comparison tests (α =0.05).

RESULTS

A 1-mm ferrule height (CP1) fracture resistance was significantly lower (531±125 N) compared to the 6-mm ferrule height (CP6) (769±175 N) (p<0.05). With respect to the groups with similar residual dentin, with and without a cervical cavity, CG (667±119 N) and CO (668±119 N), the presence of a post (CP6) increased the resistance to fracture, although no statistically significant difference was demonstrated. Partial decementation was observed in all specimens of CG and CP6, in nine of CP1 and CP2, and in three in CO. Root fractures occurred in 23 specimens. The root surface was exposed 2 mm below the CEJ to simulate bone level. Propagation of subosseous cracks occurred in four specimens in CG and CP2, in seven specimens in CP6, in two specimens in CP1, and in six specimens in CO. All were considered catastrophic failures.

CONCLUSIONS

Within the limitations of this study it is suggested that, when restoring an endodontically treated maxillary central incisor that has a cervical lesion and needs to be restored with a complete crown, a fiber post is cemented to improve fracture resistance.

Stopping the COVID-19 pandemic in dental offices: A review of SARS-CoV-2 transmission and cross-infection prevention

Due to the essential role of dentists in stopping the COVID-19 pandemic, the purpose of this review is to help dentists to detect any weaknesses in their disinfection and cross-contamination prevention protocols, and to triage dental treatments to meet the needs of patients during the pandemic. We used PRISMA to identify peer-reviewed publications which supplemented guidance from the center for disease control about infection control and guidelines for dentists. Dentists must triage dental treatments to meet the needs of patients during the pandemic. The ongoing pandemic has changed the practice of dentistry forever, the changes make it more cumbersome, time-consuming, and costly due to the possible pathways of transmission and mitigation steps needed to prevent the spread of COVID-19. Dental chairside rapid tests for SARS-CoV-2 are urgently needed. Until then, dentists need to screen patients for COVID-19 even though 75% of people with COVID-19 have no symptoms. Despite the widespread anxiety and fear of the devastating health effects of COVID-19, only 61% of dentists have implemented a change to their treatment protocols. As an urgent matter of public health, all dentists must identify the additional steps they can take to prevent the spread of COVID-19. The most effective steps to stop the pandemic in dental offices are to; vaccinate all dentists, staff, and patients; triage dental treatments for patients, separate vulnerable patients, separate COVID-19 patients, prevent cross-contamination, disinfect areas touched by patients, maintain social distancing, and change personal protective equipment between patients.

Salivary parameters and oral health status amongst adolescents in Mexico

Background

In the last years an increased interest in the use of salivary parameters in connection with caries experience and caries prediction has been shown. In schoolchildren investigations are known, where the relationship between caries prevalence and salivary parameters has been assessed, but in the adolescent population studies are scarce. The aim of the study was evaluate of the association among salivary parameters, oral health status and caries experience in adolescents in Mexico.

Methods

A cross-sectional study was conducted on 256 (DMFT≥5) and 165 (DMFT< 5) 12-to- 14-year-old adolescents. From all the adolescents, unstimulated mid-morning saliva samples were collected, after which the salivary flow rate was calculated, and the salivary pH and buffer capacity was measured. The caries was evaluated via the application of the DMFT score. Clinical variables such as oral hygiene and dental calculus were examined in the adolescent’s oral cavity. The adolescents provided data on their personal characteristics by completing a questionnaire, while socioeconomic data were collected from their parents. Descriptive, bivariate and logistic regression model analyses were performed.

Results

The prevalence of caries was 61.1% (DMFT≥5) in permanent dentition, with 72.7% of subjects presenting poor oral hygiene. The mean levels of salivary flow rate, pH, and buffer capacity was significantly lower (p < 0.05) in adolescents with caries score of DMFT≥5 than in those with caries score of DMFT < 5. Salivary flow and buffer capacity were higher in boys than in girls. The logistic regression model applied showed that adolescents with a salivary flow rate < 1 ml per min were more likely to present caries [OR = 1.58 (CI95% 1.04–2.40); p = 0.033] than adolescents with a flow rate ≥ 1 ml per-min, and that, for each unit of increased pH, the probability of presenting caries reduced by 76% [OR = 0.24 (CI95% 0.10–0.55); p = 0.001].

Conclusion

Significant association was found in salivary flow rate, pH and buffer capacity in adolescents with caries (DMFT≥5). In addition to differences of these parameters by sex, the results suggest saliva parameters may act as indicators of caries in adolescents.

Differential Biodegradation Kinetics of Collagen Membranes for Bone Regeneration

Native collagen-based membranes are used to guide bone regeneration; but due to their rapid biodegradation, this treatment is often unpredictable. The purpose of this study was to investigate the biodegradability of natural collagen membranes. Three non-cross-linked resorbable collagen barrier membranes were tested: Derma Fina (porcine dermis), Evolution Standard (equine pericardium) and Duo-Teck (equine lyophilized collagen felt). 10 × 10 mm² pieces of membranes were submitted to three different degradation procedures: (1) hydrolytic degradation in phosphate buffer solution, (2) enzyme resistance, using a 0.25% porcine trypsin solution, and (3) bacterial (Clostridium histolyticum) collagenase resistance test. Weight measurements were performed with an analytic microbalance. Thickness was measured with a digital caliper. Membranes were analyzed at different time-points, up to 21 d of immersion. A stereomicroscope was used to obtain membranes’ images. ANOVA and Student Newman Keuls were used for mean comparisons (p < 0.05), except when analyzing differences between time-points within the same membrane and solution where pair-wise comparisons were applied (p < 0.001). Derma Fina attained the highest resistance to all degradation challenges. Duo-Teck was the most susceptible membrane to degradation, complete degradation occurred as soon as 8 h. The bacterial collagenase solution performed as the most aggressive test as all membranes presented 100% degradation before 21 d.

Effect of Ferrule Location with Varying Heights on Fracture Resistance and Failure Mode of Restored Endodontically Treated Maxillary Incisors

PURPOSE

To investigate the effect of the location of a partial ferrule on 2 walls and the influence of ferrule height variations on remaining walls, fracture resistance, and failure mode of maxillary incisors endodontically treated and restored with fiber posts.

MATERIALS AND METHODS

Sixty intact human maxillary central incisors were divided into 6 groups (n = 10): no ferrule (NF), 2-mm ferrule (CF2), absence of lingual wall and 1 proximal wall with remaining walls' height, 1 mm (IF1), 2 mm (IF2), 3 mm (IF3), and 4 mm (IF4). They were restored with a fiberglass post and composite resin core. Complete metal crowns were then cemented on all specimens. Completed specimens were subjected to thermal cycling (6000 cycles, 5°C/55°C) followed by the immediate testing of fracture resistance. After failure, the specimens were sectioned buccolingually and evaluated to identify the mode of failure. The data were analyzed with an ANOVA and the Student-Newman-Keuls multiple comparison tests (α = 0.05).

RESULTS

An incomplete ferrule (IF2) with the lingual wall missing and 1 proximal wall had a fracture resistance of 494 ± 137 N, which was significantly less that of a complete ferrule (CF2) (707 ± 162 N, p = 0.002). An increase of 3 to 4 mm in height of the remaining walls had negligible influence on the fracture resistance: 514 ± 117 N (IF3), 557 ± 177 N (IF4). Partial decementation was observed in all specimens of IF3 and IF4, in 9 of IF1 and IF2, in 6 in NF, and in 3 in CF2. Root fractures occurred in 7 specimens, 4 in CF2, 1 in IF1, 1 in IF2, and 1 in IF4. Cracks under the cemento-enamel junction occurred in 4 specimens (NF and IF1), in 5 (IF2 and IF3), and in 6 (CF2 and IF4) and were considered catastrophic failures.

CONCLUSIONS

Specimens with a complete ferrule of 2 mm height were more resistant to fracture than specimens with 2 mm height and absence of the lingual wall and 1 proximal wall. A 3 or 4 mm wall height increase was associated with an insignificant increase in fracture resistance and cannot compensate for the absence of the lingual wall and 1 proximal wall.

Silver-loaded nanoparticles affect ex-vivo mechanical behavior and mineralization of dentin

Background

The aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin.

Material and Methods

Treated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used.

Results

Dentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta values after 7 days of storage. Dentin treated with undoped-NPs achieved the lowest nanoroughness and the greatest collagen bandwidths among groups. Crystals were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with undoped-NPs. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Ag-NPs at 310 plane. Polyhedral, block-like, hexagonal or plate-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Ag-NPs, after 7 d. Polyhedral or rounded/drop-like, and polymorphic in strata crystal apatite characterized the minerals when undoped-NPs were used, with more crystalline characteristics after 7 d than that found when Ag-NPs were applied. Ag-NPs application did not improve the mechanical performance of dentin and did not produce dentin remineralization. However, energy was dissipated through the dentin without showing stress concentration; contrary was occurring at dentin treated with undoped-NPs, that provoked bridge-like mineral deposits at the dentin surface.

Conclusions

Ag-NPs application did not enhance the mechanical properties of cervical dentin, though the energy dissipation did not damage the dentin structure. Remineralization at dentin was not produced after Ag-NPs application, though improved crystallinity may lead to increase stability of the apatite that was generated at the dentin surface.

Key words:Dentin, mechanical, mineralization, roughness, silver, viscoelastic.

Modified Polymeric Nanoparticles Exert In Vitro Antimicrobial Activity Against Oral Bacteria

Polymeric nanoparticles were modified to exert antimicrobial activity against oral bacteria. Nanoparticles were loaded with calcium, zinc and doxycycline. Ions and doxycycline release were measured by inductively coupled plasma optical emission spectrometer and high performance liquid chromatography. Porphyromonas gingivalis, Lactobacillus lactis, Streptoccocus mutans, gordonii and sobrinus were grown and the number of bacteria was determined by optical density. Nanoparticles were suspended in phosphate-buffered saline (PBS) at 10, 1 and 0.1 mg/mL and incubated with 1.0 mL of each bacterial suspension for 3, 12, and 24 h. The bacterial viability was assessed by determining their ability to cleave the tetrazolium salt to a formazan dye. Data were analyzed by ANOVA and Scheffe’s F (p < 0.05). Doxycycline doping efficacy was 70%. A burst liberation effect was produced during the first 7 days. After 21 days, a sustained release above 6 µg/mL, was observed. Calcium and zinc liberation were about 1 and 0.02 µg/mL respectively. The most effective antibacterial material was found to be the Dox-Nanoparticles (60% to 99% reduction) followed by Ca-Nanoparticles or Zn-Nanoparticles (30% to 70% reduction) and finally the non-doped nanoparticles (7% to 35% reduction). P. gingivalis, S. mutans and L. lactis were the most susceptible bacteria, being S. gordonii and S. sobrinus the most resistant to the tested nanoparticles.

Effect of body weight and behavioural factors on caries severity in Mexican rural and urban adolescents

OBJECTIVES

To investigate if, in Mexican adolescents, body weight and caries severity are associated, and if this association differs between rural and urban populations.

METHODS

Adolescents from the rural area of Tepancan and the city of Veracruz were enrolled. Caries was recorded using the International Caries Detection and Assessment System and the body mass index (BMI) was calculated. Oral habits (toothbrushing, flossing, dental check-ups) and dietary patterns (sweets intake) were assessed. A dummy variable between BMI and living area (BMI/Area) was generated. Data were analysed using STATA and a multinomial logistic regression model was run, using caries severity as the dependent variable.

RESULTS

Four-hundred and sixty-four subjects, 12-15 years of age, participated (rural = 240; urban = 224). The BMI and area of residence were significantly associated (χ² = 12.59, P < 0.01). Area was also associated with caries severity (χ² = 24.23, P < 0.01), with the highest number of caries in dentine recorded in participants from the rural area. The dummy variable BMI/Area was related to caries severity (χ² = 27.47, P < 0.01): overweight adolescents with caries in dentine were most frequently found in the rural area. A higher prevalence of caries in enamel and a lower prevalence of caries in dentine (P < 0.01) were recorded in adolescents from the urban area, where better oral habits, but higher sweets intake (P = 0.04), were encountered. According to the multinomial logistic regression model, BMI/Area was significantly associated with caries severity (P < 0.01).

CONCLUSIONS

Overweight was not associated with caries severity in the overall population, but it became a statistically significant risk indicator in adolescents living in the rural area.

The Use of Resin-based Composite in Children: An Update

Resin-based composites are an integral component of contemporary pediatric restorative dentistry. They can be utilized effectively for preventive resin restorations, moderate Class II restorations, Class III restorations, Class IV restorations, Class V restorations, and strip crowns. Tooth isolation to prevent contamination is a critical factor, and high-risk children may not be ideal candidates for resin-based composite restorations. Important factors to consider during composite placement are isolation, polymerization shrinkage, and extent of restoration. When utilized correctly, resin-based composites can provide excellent restorations in the primary and permanent dentition. The purpose of this paper was to update previous publications that addressed the use of resin-based composites in children with accepted recommendations through a Pediatric Restorative Dentistry Consensus Conference.

Dentin-enamel adhesives in pediatric dentistry: an update

Adhesives and composite technology have made composite resins and polyacid-modified resin-based composites (compomers) very popular as materials to restore primary and permanent anterior and posterior teeth. More conservative preparations can be performed that maintain more tooth structure due to the adhesive properties of the adhesives used with composites and compomers. Meticulous care in the placement of adhesives and, subsequently, resin-based composites and compomers is necessary to produce long-term satisfactory results. The purpose of this paper is to update the current status in regards to dentin-enamel adhesives in primary teeth.

Inhibitory effects of a cured antibacterial bonding system on viability and metabolic activity of oral bacteria

OBJECTIVES

To evaluate the antimicrobial efficacy of Clearfil SE Protect (CP) and Clearfil SE Bond (CB) after curing and rinsed against five individual oral microorganisms as well as a mixture of bacterial culture prepared from the selected test organisms.

METHODS

Bacterial suspensions were prepared from single species of Streptococcus mutans, Streptococcus sobrinus, Streptococcus gordonii, Actinomyces viscosus and Lactobacillus lactis, as well as mixed bacterial suspensions from these organisms. Dentin bonding system discs (6 mm×2 mm) were prepared, cured, washed and placed on the bacterial suspension of single species or multispecies bacteria for 15, 30 and 60 min. MTT, Live/Dead bacterial viability (antibacterial effect), and XTT (metabolic activity) assays were used to test the two dentin system's antibacterial effect. All assays were done in triplicates and each experiment repeated at least three times. Data were submitted to ANOVA and Scheffe's f-test (5%).

RESULTS

Greater than 40% bacteria killing was seen within 15 min, and the killing progressed with increasing time of incubation with CP discs. However, a longer (60 min) period of incubation was required by CP to achieve similar antimicrobial effect against mixed bacterial suspension. CB had no significant effect on the viability or metabolic activity of the test microorganisms when compared to the control bacterial culture. CP was significantly effective in reducing the viability and metabolic activity of the test organisms.

SIGNIFICANCE

The results demonstrated the antimicrobial efficacy of CP both on single and multispecies bacterial culture. CP may be beneficial in reducing bacterial infections in cavity preparations in clinical dentistry.

Randomized clinical trial of adhesive restorations in primary molars. 18-month results

PURPOSE

To evaluate the clinical performance of adhesive restorations of resin composite and resin-modified glass-ionomer cements in primary molars.

METHODS

This randomized clinical trial included subjects (5-9 year-old children) selected at two university centers (UFRGS and UNIFRA). The sample consisted of 132 primary molars presenting active cavitated carious lesions (with radiographic involvement of the inner half of the dentin), located on the occlusal and occlusal-proximal surface. The sample was randomly divided into three groups, according to the restorative material: (G1) universal restorative system (Adper Single Bond 2 system and Filtek Z350); (G2): Resin-modified glass-ionomer cement (Vitremer); and (G3): Low shrink restorative system (Filtek P90). The restorations were clinically and radiographically followed every 6 months for up to 18 months using the USPHS modified criteria for clinical evaluation. Survival estimates for restoration longevity were evaluated using the Kaplan-Meier method. Log-rank test (P< 0.05) was used to compare the differences in the success rate according to the type of the restorative material.

RESULTS

The type of restorative material used did not influence the longevity of the restorations. After clinical follow-up, there was no statistical difference in the rates of success for the three materials used to restore active cavitated carious lesions in primary molars. The survival rates for the follow-up were similar regarding the number of restored surfaces and the caries removal technique (partial or complete). Mean estimated time of survival was 17.2 months (95% CI: 16.7-17.7). Estimated survival rates of the restorations were 100%, 98%, 88% and 65% at 1, 6, 12 and 18 months of clinical evaluations, respectively.

Effect of temperature on the mass and color stability of additional photoinitiatorcontaining composite resins

The purpose of this study was to evaluate how the temperature affects the stability of polymerized additional photoinitiator-containing composite resins. Five resin products were light-cured using a quartz-tungsten-halogen, and single and dual emission peaks lightemitting diodes. The degree of conversion (DC) and water sorption, solubility, and color change of the specimens were evaluated after immersion in the solutions of different temperatures (4, 37, and 60ºC) for 14 days. On the top surface, the light-curing units had no significant influence on DC of the tested specimens. On the bottom surface, the influence was inconsistent. As the solution temperature increased, water sorption also consistently increased in all specimens, whereas solubility changed inconsistently. Water sorption and solubility had a high linear correlation only at low temperature solution. Color change of the specimens was similar, mostly slight, and statistically inconsistent regardless of solution temperature. The restored composite resins are needed to avoid contact with hot solutions for durable dental restoration.

Fluoride dentifrice containing xylitol: in vitro root caries formation

PURPOSE

To evaluate the effects of experimental xylitol dentifrices with and without fluoride on in vitro root caries formation.

METHODS

Root surfaces from caries-free human permanent teeth (n = 10) underwent debridement and a fluoride-free prophylaxis. The tooth roots were sectioned into quarters, and acid-resistant varnish was placed with two sound root surface windows exposed on each tooth quarter. Each quarter from a single tooth was assigned to a treatment group: (1) No treatment control; (2) Aquafresh Advanced (0.15% F = 1,150 ppm F); (3) Experimental xylitol dentifrice without fluoride (0.45% xylitol); and (4) Diamynt fluoride dentifrice with xylitol (0.83% sodium monofluorophosphate = 1,100 ppm F and 0.20% xylitol). Tooth root quarters were treated with fresh dentifrice twice daily (3 minutes) followed by fresh synthetic saliva rinsing over a 7-day period. Controls were exposed twice daily to fresh synthetic saliva rinsing daily over a 7-day period. In vitro root caries were created using an acidified gel (pH 4.25, 21 days). Longitudinal sections (three sections/tooth quarter, 60/group) were evaluated for mean lesion depths (water inhibition, polarized light, ANOVA, DMR).

RESULTS

Mean lesion depths were 359 +/- 37 microm for the control Group; 280 +/- 28 microm for Aquafresh Advanced; 342 +/- 41 microm for the experimental xylitol dentifrice without fluoride; and 261 +/- 34 microm for Diamynt. Aquafresh Advanced and Diamynt had mean lesion depths significantly less than those for the no treatment control and the experimental xylitol without fluoride dentifrice (P< 0.05). There were minimal non-significant differences in mean lesion depths between Aquafresh Advanced and Diamynt (P > 0.05).

Effect of energy density on low-shrinkage composite resins: diode-pumped solid state laser versus quartz-tungsten-halogen light-curing unit

OBJECTIVE

The purpose of the present study was to evaluate the effect of energy density on the polymerization of low-shrinkage composite resins.

BACKGROUND DATA

The number of photons needs to initiate the polymerization process can be controlled by light intensity and curing time through the form of energy density.

MATERIALS AND METHODS

For the study, two methacrylate-based (Premise [PR] and Venus Diamond [VE]) and one silorane-based (Filtek LS [LS]) composite resins were light cured using a quartz-tungsten-halogen (QTH) light-curing unit (LCU) and a 473 nm diode-pumped solid state (DPSS) laser. Degree of conversion (DC), microhardness, refractive index, and polymerization shrinkage were evaluated under different energy densities. Through the study, the feasibility of DPSS laser as a light source was tested as well.

RESULTS

LS showed the highest DC and refractive index both on the top and bottom surfaces, and the least polymerization shrinkage among the tested specimens. For the same or similar energy density, QTH and DPSS showed insignificant DC difference (p>0.05). On the other hand, for microhardness, except for one case at the bottom surface, QTH and DPSS showed significant difference (p<0.001). DPSS generated slightly lower polymerization shrinkage than that by QTH.

CONCLUSIONS

DC, microhardness, refractive index, and polymerization shrinkage were linearly correlated with energy density. In most cases, there was a strong linear correlation among DC, mirohardness, and refractive index. The DPSS laser of 473 nm could polymerize low-shrinkage composite resins to the level that was achieved by the conventional QTH unit.

Six-month evaluation of ART one-surface restorations in a community with high caries experience in Brazil

The aim of this study to evaluate the success rate in one-surface ART restorations placed in permanent molars using a glass ionomer cement especially developed for ART in a community with high caries experience; to evaluate the operator influence on its success, post-operative sensitivity and technique acceptance by patients. Prior to placement of the restorations, the Gingival Bleeding Index, Visible Plaque Index, DMFT, dmft indices and treatment needed were assessed. One hundred and fifty five one-surface restorations were placed in permanent molars of school children, according to the WHO ART manual, 1997. After 6 months, the success rate was verified clinically and by slides. At baseline, the mean DMFT was 2.56 (±1.08) and the mean dmft, 2.53 (±2.33). Operators A and B have placed 102 and 53 ART restorations respectively. The mean time of placement was 16 minutes and 25 seconds to operator A and 14 minutes and 43 seconds to operator B. At 6-month follow up, 152 ART restorations were evaluated and 97.3% were assessed to be successful. Two restorations were excluded from the sample because the ART restorations were replaced by amalgam fillings. Only 4 restorations have failed, in which 2 due to caries, 1 due to fistula presence and the other because the restoration was lost. Four patients reported postoperative sensitivity. At this study period, ART treatment seems to be suitable for its purpose. Further evaluations are necessary to the new glass ionomer cements especially developed for ART technique provided good results at 6-month follow up in a community with high DMFT and dmft indices. The success rate for one-surface cavities in permanent molars was 97.3%, and the studied indices seemed to have no influence in this early evolution period.

Caries activity and the presence of adjacent caries lesions on resin composite restorations in primary teeth

PURPOSE

To clinically evaluate the status of caries lesions adjacent to restorations (AdjCL) in primary molars, and its relationship to the child's carious activity and marginal restoration integrity.

METHODS

Three independent examiners (trained, calibrated and blinded) evaluated 64 randomly selected restorations (occlusal and occluso-proximal) by the AdjCL status (kappa = 0.844), the restoration marginal integrity (kappa = 1) and the radiographic presence of lesions in the occlusal restoration margins (kappa = 1). One of the examiners also evaluated the child's carious activity (kappa = 1). The variables were related to the outcome through Chi-square and Fisher's Exact analysis (alpha = 5%).

RESULTS

A prevalence of 40.63% AdjCL (88.46% inactive) was seen, with no significant association to the child's carious activity (P = 0.23). The association of the absence of AdjCL and the presence of marginal integrity was statistically significant (P = 0.013). Also, the presence of AdjCL occurred especially around older restorations (P = 0.044).

The effect of some fluids on surface oxidation and amount of released iron of stainless steel endodontic files

Endodontic files come in contact with blood, infected pulp tissue, and irrigating solutions during root canal therapy. Some instruments such as stereomicroscopy and scanning electron microscopy are used to observe corrosion of endodontic files which are complicated and dependent on preparation methods. Having knowledge of the corrosion and ion release of endodontic files can help in drawing firm deductions as to which files would perform better in the clinical scenario. Therefore, we have used energy dispersive X-ray analysis and an atomic absorption spectrophotometer to track oxygen on the surface and iron in the exposed media to observe the oxidative rate of the media. In this study, corrosion by blood was higher than other biological fluids, but less than with sodium hypochlorite (NaOCl). Observations of energy dispersive X-ray analysis and atomic absorption spectrophotometer results demonstrated that after exposure the amount of oxygen on the surface and surrounding areas increased. Therefore, the files should be rinsed as soon as possible during and after use to hinder the oxidation rate, but blood may produce a different behavior and it might be considered as a decreased risk of broken stainless steel files remaining in the root canal after treatment.

Determining efficacy of monitoring devices on ceramic bond to resin composite

Objectives: This paper aims to assess the effectiveness of 3D nanoroughness and 2D microroughness evaluations, by their correlation with contact angle measurements and shear bond strength test, in order to evaluate the effect of two different acids conditioning on the bonding efficacy of a leucite-based glass-ceramic to a composite resin. Study Design: Ceramic (IPS Empress) blocks were treated as follows: 1) no treatment, 2) 37% phosphoric acid (H3PO4), 15 s, 3) 9% hydrofluoric acid (HF), 5 min. Micro- and nano-roughness were assessed with a profilometer and by means of an atomic force microscopy (AFM). Water contact angle (CA) measurements were determined to assess wettability of the ceramic surfaces with the asixymetric drop shape analysis contact diameter technique. Shear bond strength (SBS) was tested to a resin composite (Z100) with three different adhesive systems (Scotchbond Multipurpose Plus, Clearfil New Bond, ProBOND). Scanning electron microscopy (SEM) images were performed. Results: Nanoroughness values assessed in 50x50 μm areas were higher for the HF group, these differences were not detected by profilometric analysis. HF treatment created the nano- roughest surfaces and the smallest CA (p<0.05), producing the highest SBS to the composite resin with all tested adhesive systems (p<0.05). No differences existed between the SBS produced by the adhesive systems evaluated with any of the surface treatments tested. Conclusions: Nano-roughness obtained in a 50x50 µm scan size areas was the most reliable data to evaluate the topographical changes produced by the different acid treatments on ceramic surfaces.

Key words:Dental ceramic, acid etching, bonding efficacy, resin composite, adhesive systems, contact angle, roughness.

Shear bond strength evaluation of bonded molar tubes on fluorotic molars

OBJECTIVE

To study the shear bond strength (SBS), sites of failure, and micromorphology of bonded molar tubes used on teeth affected by dental fluorosis.

MATERIALS AND METHODS

This in vitro study included 140 first molars classified according to Dean's index for dental fluorosis. Samples were divided into seven groups: (1) healthy teeth etched for 15 seconds, (2) teeth with moderate fluorosis (MOF) etched for 15 seconds, (3) teeth with MOF etched for 150 seconds, (4) teeth with MOF microabrasion etched for 15 seconds, (5) teeth with severe fluorosis (SEF) etched for 15 seconds, (6) teeth with SEF etched for 150 seconds, and (7) teeth with SEF microabrasion etched for 15 seconds. All samples were incubated and were then submitted to the SBS test and evaluated with the modified adhesive remnant index (ARI) and analyzed by using a scanning electronic microscope.

RESULTS

The SBS mean value for healthy enamel was 20 ± 10.2 MPa. For the group with MOF, the etched 150-second mean value was the highest (19 ± 7.6 MPa); for the group with SEF treated with microabrasion and etched for 15 seconds, the mean value was (13 ± 4.1 MPa). Significant differences (P ≤ .05) were found in the ARI between healthy and fluorosed groups.

CONCLUSIONS

Fluorotic enamel affects the adhesion of bonded molar tubes. The use of overetching in cases of MOF and the combination of microabrasion and etching in SEF provides a suitable adhesion for fixed appliance therapy.

Laboratory enamel fluoride uptake from fluoride products

PURPOSE

To evaluate the fluoride concentration in enamel after the use of different fluoride products and 48 hours after the cessation of fluoride use.

METHODS

16 enamel slabs were divided and treated for 15 days as following: Group A, with an amine fluoride toothpaste and mouthrinse (1400 and 250 mg/L(-1), respectively); Group B, with an amine fluoride toothpaste (1400 mg/L(-1)) and mouthrinse without fluoride; Group C, with a sodium fluoride toothpaste (1400 mg/L(-1)) and mouthrinse (250 mg/L(-1)). Chemical biopsy and multiple means were used to determine fluoride concentration. The data were statistically analyzed using the two-way ANOVA and Tukey HSD tests (P<0.05).

RESULTS

After 15 days of fluoride product use, Group A samples had the highest fluoride uptake (0.19 microg mm(-2)) (P<0.05). 48 hours after the interruption of fluoride product usage, a higher fluoride concentration was found in Group A samples. Although all fluoride products led to an enamel uptake, amine fluoride products promoted the most effective long-term uptake.

Microbiological analysis of gingivitis in pediatric patients under orthodontic treatment

AIM

The aim of this study was to determine the relationship between gingival inflammation and changes in bacteria of the gingival sulcus in children in orthodontic treatment with brackets.

STUDY DESIGN

this prospective study assessed gingival and plaque index of two groups: children with brackets (Group 1) and without brackets (Group 2). The sample was selected from patients treated at the Faculty of Dentistry, Complutense University of Madrid, Spain. Microbiological assessment was performed in every child and all data were statistically analysed.

RESULTS

Group 1 showed significantly higher microbiological values and the difference was greater in lower teeth. Comparing the total plaque percentage, it was significantly higher in Group 1.

STATISTICS

there was no significant correlation between gingival and plaque indexes in any group. No significant correlation was found between plaque index and bacteria.

CONCLUSION

Children using brackets showed significantly higher gingival and plaque indices than children without brackets. No direct relationship was found between the increase in gingival and plaque indices and the presence and quantity of bacteria; therefore it was not possible to identify specific bacteria as responsible for the high gingival index in patients with brackets.

Dentin protection by a primer-less adhesive technique

PURPOSE

To identify the remaining demineralized dentin (the permeable layer that allows leakage) when using primer-less wet bonding with a total etching period of 10 to 60 seconds compared with contemporary resin adhesives.

METHODS

Extracted human molars were selected and Class V cavities were prepared on the axial surfaces at the CEJ, providing margins in enamel and dentin for leakage testing using a basic dye (n = 10). Seven groups of conditioned teeth [1-1 etched for 10, 30, and 60 seconds (primer-less wet), All-Bond 2 and Single-Bond 2 (wet), AQ-Bond (self-etched), Super-Bond C&B (dry)] were used as bonding systems for resin composite restoration. All specimens were stored in water at 37 degrees C for 24 hours before soaking in a 0.5% basic fuchsin solution for 24 hours. The distance of dye penetration was measured using stereomicroscopy.

RESULTS

No leakage at the enamel- and dentin-resin interfaces was found for all etching periods of 1-1 primer-less, Super-Bond C&B, and AQ-Bond specimens. However, leakage was observed at dentin margins in two wet with primer systems, All-Bond 2 (1.31 +/- 1.39 mm) and Single-Bond 2 (0.37 +/- 0.28 mm), which required phosphoric etching to remove a weak smear layer on prepared dentin.

Effects of polishing on surface roughness, gloss and color of surface reaction type pre-reacted glass-ionomer filled resin composite

PURPOSE

To evaluate the effects of polishing on surface roughness, gloss and color of different shades of surface reaction type pre-reacted glass-ionomer (S-PRG) filled nano-hybrid resin composite.

METHODS

Resin disks of 15 mm diameter and 2 mm thickness and final polish with 1000-grit SiC paper, super fine cut diamond (FG) point, silicon (MFR) point and Super-Snap mini-disk red (SNAP) were made with Beautifil II shades: A2, A20, Inc). One week after curing, the surface roughness, gloss and color were measured. Data was analyzed with ANOVA and Fisher's PLSD with alpha= 0.05

RESULTS

For all shades, the order of roughness (Ra) ranked according to groups of 1000-grit SiC > FG > MFR > SNAP with significant differences among all groups. For all shades, the order of gloss ranked according to groups of SNAP > MFR > FG > 1000-grit SiC with significant differences among the groups except for between MFR and FG without significant difference. The influence of the surface roughness on color differed among the polishing groups and shades. However, the values of the color differences (deltaE*ab) between the polishing groups of all shades were imperceptible to the naked eye.

Influence of tooth preparation burs on the roughness and bond strength of adhesives to human dentin surfaces

PURPOSE

To characterize the surface roughness of human dentin prepared with different rotary instruments and its influence on the micro-tensile bond strength (microTBS) of self-etch adhesives.

METHODS

Dentin surfaces were created from mid-coronal sound dentin in extracted, human third molars. The teeth were ground with high-speed diamond, tungsten carbide finishing, and cross-cut carbide rotary instruments. Morphological changes obtained were investigated with a surface texture analyzer. Two additional specimens from each group were treated and prepared for scanning electron microscopy. Resin composite (Z 100) was bonded to the surfaces using Optibond FL (control), Adper Prompt L-Pop (strong), Clearfil SE Bond (mild), or Clearfil S3 Bond (ultra-mild). Rectangular micro-specimens were prepared using the slow-speed diamond saw and tested in tensile to determine the microTBS. The data were analyzed with one-way analysis of variance and Tukey's HSD test (alpha= 0.05).

RESULTS

Surface preparation resulted in significant differences for surface topography and micro-tensile bond strength (P< 0.001). The cross-cut carbide burs had significantly higher mean roughness readings (SD) for all parameters: Ra [8.6 (1.9) microm], Rq [10.9 (2.2) microm], and Ry [41.1 (2.1) microm], except for the mean Rz [12.1 (3.1) microm] value, which was recorded for diamonds. The other roughness parameters for the diamond rotary instruments were intermediate. Dentin surfaces completed with tungsten carbide finishing burs produced a smoother surface Ra [1.2 (0.5) microm)] Rq ([1.6 (0.6) microm], Ry [6.4 (2.6) microm)] and Rz [1.9 (0.6) microm)]. The etch-and-rinse adhesive (OptiBond FL) yielded high micro-tensile values (58.1-68.3 MPa), irrespective of the rotary instruments used. The micro-tensile bond strength values were comparable for self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond, Clearfil S3 Bond) irrespective of the burs used. The microTBS values were significantly higher with tungsten carbide finishing burs and smooth dentin surfaces.

Noncarious cervical lesions (NCCL)--a clinical concept based on the literature review. Part 2: restoration

PURPOSE

To present an updated knowledge on the restorative options and their performance in the particular environment of non-carious cervical lesions (NCCL).

METHODS

Evidence-based support for a proper restoration of NCCL was searched. For this purpose, literature over the last 10 years available in the MEDLINE database was reviewed. Previous systematic reviews, meta-analysis and clinical trials as randomized clinical trials with a testing period of minimum 1 year were selected.

RESULTS

Until recently, glass-ionomer-based materials were considered the treatment of choice in most of the NCCL, although consistent improvements are still required. Today, based on the excellent esthetic properties and the good clinical performance, there is a general indication to use composite in NCCL. Clinical behavior was found to be highly product-dependent. The choice of an adhesive with tested efficiency is decisive for the retention and marginal adaptation, whereas differences in flexibility were not found to be clinically important. A periodontal-esthetic approach was suggested by combining the surgical root coverage with the correction of the emergence profile by composite.

Influence of DPSS laser on polymerization shrinkage and mass change of resin composites

OBJECTIVES

This study evaluated the effectiveness of the diode-pumped solid state (DPSS) laser as a light source for light-curing dental resin composites.

BACKGROUND DATA

A DPSS laser of 473  nm may be useful because of its match with the absorption peak of camphorquinone (CQ), the photoinitiator.

MATERIALS AND METHODS

A DPSS laser (LAS) of 473  nm and a quartz-tungsten-halogen (QTH) light-curing unit (OP) were used as the light sources for light curing six different resin composites (four nanocomposites and two hybrid composites). Polymerization shrinkage and mass change (water sorption and solubility) were measured during and after light curing to determine the degree of polymerization. Mass change was evaluated by following the ISO 4049 standard.

RESULTS

According to the evaluation, the specimens light cured using LAS showed similar maximum polymerization shrinkage (12.3∼18.1  μm for LAS; 13.2∼16.2  μm for OP) and water sorption (11.4∼24.1  μg/mm(3) for LAS; 11.3∼22.8  μg/ mm(3) for OP) to the cases light cured using OP. The specimens light cured using LAS showed a significantly higher solubility than the cases light cured using OP (2.4∼6.6  μg/ mm(3) for LAS; 0.8∼1.6  μg/ mm(3) for OP). However, the maximum water sorption and solubility obtained from the specimens were lower than the values permitted by the ISO 4049 standard.

CONCLUSIONS

The results may suggest that the DPSS laser with an emission wavelength of 473  nm can be used as a light source for light-curing dental resin composites.

Clinical study of Mineral Trioxide Aggregate in primary molars. Comparison between Grey and White MTA--a long term follow-up (84 months)

OBJECTIVES

The aim of the present study was to conduct a clinical and radiographic long-term evaluation of pulpotomy in temporary molars performed with Grey and White Mineral Trioxide Aggregate (MTA) and compare the results of Grey and White MTA pulpotomies in a sample of 233 primary molars with a maximum follow-up period of 84 months.

METHODS

The sample was selected from patients treated at the Department of Pediatric Dentistry, Faculty of Dentistry, Complutense University of Madrid, Spain. This prospective study included first and second primary molars treated with pulpotomy with Grey or White MTA, controlled for a maximum follow-up period of 84 months. Statistical analysis of clinical and radiographic findings was completed using ANOVA (P<0.05).

RESULTS

Follow-up evaluations, performed every 6 months, revealed that only 2 molars treated with White MTA presented abscess and pathological mobility. Radiographic examination of the 210 molars revealed unfavourable pulp response in only 6 molars (internal or furcation root resorption), without statistically significant differences between Grey and White MTA. Two radiological findings were noticed: dentine bridge formation and partial or total root canal stenosis. Grey MTA induced a higher percentage of dentine bridges with statistically significant differences (P<0.05), and a higher percentage of pulp canal stenosis, without a statistically significant difference.

CONCLUSIONS

Grey and White MTA presented high levels of clinical and radiographic success. Although the present study showed evidence of a very good biologic response with both types of MTA, Grey MTA showed significantly higher number of dentine bridge formation than White MTA.

Effect of light-curing units on the thermal expansion of resin nanocomposites

PURPOSE

To examine the thermal expansion of resin nanocomposites after light-curing using different light-curing units.

METHODS

Four different resin nanocomposites and four different light-curing units [quartz-tungsten-halogen (QTH), light emitting diode (LED), laser, and plasma arc] were chosen. Metal dies were filled with resin to make specimens and light-cured. The light intensity and light-curing time of the QTH and LED light-curing units were 1000 mW/cm2 and 40 seconds, 700 mW/cm2 and 40 seconds for the laser, and 1600 mW/cm2 and 3 seconds for the plasma arc. The coefficient of thermal expansion (CTE) was evaluated using a thermomechanical analyzer (TMA) at temperatures ranging from 30-80 degrees C.

RESULTS

The CTE of the resin nanocomposites tested ranged from 28.5 to 65.8 (x 10(-6)/ degrees C), depending on the product and type of light-curing unit used. Among the specimens, Grandio showed the lowest CTE. The specimens cured using the plasma arc unit (Apollo 95E) showed the highest CTE. There was a linear correlation between the CTE and filler content (vol%) (R: -0.94-0.99 depending on the light-curing unit). The results may suggest a careful selection of the light-curing unit because there was more expansion in the specimens cured using the plasma arc unit than those cured by the other units.

Effect of an 8.0% arginine and calcium carbonate in-office desensitizing paste on the shear bond strength of composites to human dental enamel

PURPOSE

To evaluate the effect of 8.0% arginine and calcium carbonate, in-office desensitizing paste (Colgate Sensitive Pro-Relief Desensitizing Paste) on the shear bond strength of composites to human dental enamel.

METHODS

Two resin composites (Filtek Supreme, Premise) and human dental enamel were used. 16 samples per composite were prepared. Caries-free extracted human molars, not older than 3 months, and stored in distilled water were used for this portion of the experiment. Buccal and lingual surfaces were polished with high polishing pastes to create a uniform flat surface area to which the cylindrical composite samples were bonded. After polishing, the samples were rinsed in tap water and stored at 100% relative humidity. The resin composites were used to form cylindrical samples 3 mm x 1.6 mm, which were light-cured with a Demetron curing light according to the manufacturers' instructions. For each composite, 32 surfaces were used; 16 were a control group with the enamel polished with a water slurry of flour of pumice. The experimental group had the enamel polished with the 8.0% arginine and calcium carbonate desensitizing paste, using disposable latex free prophy cups with a slow speed hand piece at 3,000 rpm using moderate to light pressure, according to manufacturer's instructions. The composite cylinders were bonded to the enamel with their respective etching agents and adhesives and left in distilled water for 48 hours, after which the samples were sheared with an Instron testing machine at 0.5 mm/minute. After shearing, all samples were analyzed with a stereo microscope to evaluate failure pattern (failure at the enamel surface, failure at the composite surface, or mixed failure, at both enamel and composite surfaces). SEM images of selected surfaces were made to depict the overall morphology of the surface of dental materials used after 8.0% arginine and calcium carbonate desensitizing paste, application and shear strength tests. ANOVA and Student-Newman-Keuls tests (P < 0.05) were used to evaluate the difference among the groups.

RESULTS

The 8.0% arginine and calcium carbonate desensitizing paste did not have a significant effect on the shear bond strength of the composites tested to enamel.

Direct and transdentinal antibacterial activity of chlorhexidine

PURPOSE

To evaluate the antibacterial effect of different chlorhexidine (CHX) concentrations against Streptococcus mutans using the agar-diffusion method with and without human dentin discs placed between the bacteria and the test substances.

METHODS

For the direct application (agar-well technique), a base layer containing 15 mL of BHI agar and 300 microL of S. mutans inoculum (10(9) cfu/mL) was prepared in Petri dishes. Six wells per dish were made at equidistant points and immediately filled with CHX gels (0.12%, 0.2%, 1% and 2%), 35% phosphoric acid and pure natrosol (n = 6 wells/substance). Paper discs soaked in sterile distilled water served as control group (n = 6). For the indirect application (transdentinal diffusion), 0.2 mm- and 0.5 mm-thick human dentin discs (36 discs/thickness) had the hydraulic conductance determined, which allowed the homogeneous allocation of them to the experimental and control groups. The discs were placed at equidistant points on the Petri dishes containing BHI with the S. mutans inoculum (six discs per dish; one per substance) with the pulpal side in contact with the bacteria. In the discs treated with CHX gels, dentin surface was etched with H3PO4 and rinsed with distilled water before CHX gel application for 1 minute. After both direct and indirect application, the dishes were incubated for 24 hours and the bacterial growth inhibition zones formed around the wells and dentin discs were measured. Data were analyzed statistically by the non-parametric Kruskal-Wallis and Mann-Whitney tests at 5% significance level.

RESULTS

In the direct test, all CHX concentrations presented a dose-dependent antibacterial activity against S. mutans. In the indirect test, there were statistically significant differences (P < 0.05) among all groups and the largest microbial growth inhibition zones were observed when 2% CHX was applied on 0.2 mm-thick discs (P < 0.05). It was concluded that all evaluated CHX gels exhibited both direct and transdentinal antibacterial activity against S. mutans. This effect of CHX was strongly influenced by the CHX concentration as well as the dentin barrier thickness.

Evolution of apical formation on immature necrotic permanent teeth

PURPOSE

To evaluate the evolution of apical formation on 28 necrotic immature permanent teeth treated with calcium hydroxide at different stages of root development.

METHODS

Apical formation in 28 necrotic incisors was carried out (27 upper and one lower incisors), in children between the ages of 6 and 13 years old (11 males, 10 females). Following anesthesia and rubber dam isolation, the chamber was opened and the coronal and root pulp tissue was removed. Next, after measuring the canal, the root canal was irrigated with 5% sodium hypochlorite. Once the canal was dried, it was filled with the CaOH2 powder mixed with physiologic saline solution to a dense consistency but malleable. This paste was compressed into the canal using a cotton pellet. The canal was completely filled up to the apex. Finally, the cavity opening was sealed with zinc oxide-eugenol (IRM) and glass-ionomer (Vitrebond). Follow-up appointments were made every 3 months in order to evaluate the evolution of the periapical radiolucency and the formation of the apical barrier.

RESULTS

The duration of the apical induction was 8.6 +/- 5.36 months. Increase or lack of growth in the length of the root canal and the type of root end closing was as follows: cementoid tissue (85.72%); osseous tissue (14.28%), with a 100% overall success rate. The evolution of these teeth was monitored over a 2-year period with re-infections occurring in 7.1 percent of the cases.

Comparison of fracture resistance of bonded glass fiber posts at different lengths

PURPOSE

To evaluate in vitro the fracture resistance of quartz fiber posts for three different dowel lengths.

METHODS

30 single-rooted human premolars with similar root length and diameter were endodontically treated and randomly divided into three experimental groups (n = 10) according to the post space depth created: (1) 5 mm; (2) 7 mm; (3) 9 mm. Quartz fiber posts (Endo Light post) were cemented using a dual cured resin cement with its adhesive system (Prime & Bond NT + Fluorocore 2). After 24 hours, specimens were embedded in acrylic resin and loaded under continuous compressive force at the extruding coronal part of the post (45-degree angle) to the long tooth axis (crosshead speed: 0.75 mm/minute). Forces at fracture (Newtons) were recorded. One-way ANOVA and Tukey tests were used for the statistical analysis (P < 0.05).

RESULTS

Mean strength values (SD) were: (1) 40.52 (3.14); (2) 41.68 (5.31); (3) 44.88 (6.77), respectively. No statistically significant differences were found among the groups.

Resin composite polyethylene fiber reinforcement: effect on fracture resistance of weakened marginal ridges

PURPOSE

To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite on the fracture resistance of weakened marginal ridges in molar teeth.

METHODS

50 sound extracted human mandibular molars were used. Specimens were divided into five groups (n = 10). Group 1: served as a control for comparison; Group 2: Class I cavity preparation with resin composite (Prodigy); Group 3: Class I cavity preparation with polyethylene ribbon fiber (Ribbond) and resin composite. Group 4: Class II cavity preparation with resin composite restoration; Group 5: Class II cavity preparation with polyethylene woven fiber and resin composite. Specimens were stored in 100% humidity at 37 degrees C for 7 days. Compressive loading of the teeth was performed with a universal testing machine at a cross-head speed of 0.5 mm/minute until failure. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha = 0.05).

RESULTS

Reinforcement with polyethylene fiber resulted in significant differences for fracture resistance (P < 0.001). Mean fracture resistance (SD) was [1737.4 (84.8) N] for control group. Among the experimental groups, the highest mean fracture resistance (SD) [1543.8 (71.1) N] was associated with Class I cavity preparation with polyethylene fiber and resin composite. The lowest mean fracture resistance (SD) [869.2 (91.7) N] was recorded for Class II cavity preparation with conventional resin composite.

Indirect pulp treatment in primary teeth: 4-year results

PURPOSE

To evaluate clinical and radiographic outcomes of indirect pulp treatment (IPT) in primary molars after long-term function (up to 60 months).

METHODS

Teeth with deep carious lesions without signs and symptoms of irreversible pulpitis were divided by random allocation into two groups, according to the capping material utilized over demineralized dentin: experimental group (1): self-etching adhesive system (Clearfil SE Bond); and control group (2): calcium hydroxide liner (Dycal). Both groups were filled with resin composite (Z250) and submitted to a clinical and radiographic monitoring period until exfoliation.

RESULTS

After the follow-up period (up to 60 months), no statistical difference was found between groups (P= 0.514). The overall success rate reached 78%. The failures occurred after the first year period recall.