Amalgam or composite resin? Factors influencing the choice of restorative material

Objectives

This study aimed to investigate the patient and tooth factors associated with selection of restorative material in direct posterior restorations in young adults from a population-based birth cohort.

Methods

A representative sample (n = 720) of all 5914 births occurring in Pelotas in 1982 were prospectively investigated, and posterior restorations were assessed in 2006, when the patients were 24 years old. Tooth-related variables (individual level) included restorative material (amalgam or composite), type of tooth, size of cavity, and estimated time in mouth. Data regarding demographic and socio-economic characteristics, oral health, and service utilization patterns during the life course were also assessed (contextual level).

Results

Logistic Regression Multilevel models showed that individuals who have accessed dental services by private insurance by age 15 [odds ratio (OR) = 1.66 (0.93–2.95)] and who had a higher dental caries index at age 15 (high DMFT tertile) [OR 2.89 (1.59–5.27)] presented more amalgam restorations in the posterior teeth. From tooth-level variables, the frequency of amalgams decreases with increasing number of surfaces enrolled in the cavity preparation (p < 0.001) and was almost 5 times greater in molars than in premolars.

Conclusions

The present findings suggest that variables related to type of dental service, dental caries (higher DMFT index), and cavity characteristics (tooth type, size) determine the choice of dentists for restorative materials. Other individual characteristics such as demographic and socioeconomic status have not influenced this choice.

Clinical significance

This is the first population-based study that assesses the determinant factors for the choice of dentists for composite or amalgam in posterior direct restorations, showing that, independently of socioeconomic and demographic characteristics, type of payment of dental services and clinical factors are associated with this choice.     

Colour stability,staining and roughness of silorane after prolonged chemical challenges

Objectives

To investigate the effect of prolonged chemical challenges on colour stability, staining susceptibility, and roughness of a silorane composite material when compared to methacrylate-based composites.

Methods

Initial colour and roughness were registered for specimens fabricated from methacrylate or silorane composites. Specimens were individually stored at 37 °C in 0.02 N citric acid, 0.02 N phosphoric acid, 75% ethanol or distilled water for 7, 14, 21 and 180 days, when new measurements were performed. A staining test was performed after the chemical challenge by immersion in coffee during 3 weeks at 37 °C. Colour changes were characterized using the CIEL*a*b* colour system. Data were submitted to analysis of variance for repeated measures, two-way analysis of variance and Tukey's multiple comparison test (α = 0.05).

Results

Colour changes on the methacrylate-based resins were considered acceptable (although significantly different) after immersion in water, citric acid, phosphoric acid or ethanol, but were unacceptable for the silorane composite immersed in ethanol for 180 days. The methacrylate-based resins stored in ethanol were significantly more stained by coffee than those stored in other media. The silorane composite demonstrated no staining, but increased roughness, when compared to the methacrylate-based resins.

Conclusions

No effect of the immersion solution was noticed on roughness of the investigated materials. Ethanol influenced colour stability and staining susceptibility differently for the methacrylate-based and silorane composites.

Clinical significance

The knowledge of how acids and solvents affect the properties of tooth-coloured restorative materials is one of the decision-making criteria for the selection of a restorative material.     

A New “Silver-Bullet” to treat caries in children – Nano Silver Fluoride: A randomised clinical trial

Background

Untreated dental caries in children remains a public health challenge in poor communities.

Objectives

This prospective controlled clinical trial investigated the effectiveness of a new anti-caries agent, Nano Silver Fluoride (NSF), applied once a year to arrest caries in children.

Methods

One hundred thirty decayed primary teeth were randomly divided into two groups: NSF as the experimental agent and water as the control group. Teeth were clinically diagnosed and treated by one masked examiner and followed up at seven days and five and 12 months by another calibrated examiner who was blinded to the type of treatment. The criteria of the ICDAS II were followed to determine the activity of lesion and the diagnosis of caries. The Pearson's chi-square test was used to compare the groups during different follow-up exams.

Results

At seven days, 81% of teeth in the NSF group exhibited arrested caries, whereas in controls, no teeth had arrested decay (p < 0.001) [PF, prevented fraction = 81%]. After five months, the NSF group had 72.7% with arrested decay, and the control group had 27.4% (p < 0.001) [PF = 62.5%]. At 12 months, 66.7% of the lesions treated with NSF were still arrested, while the control group had 34.7% remaining arrested (p = 0.003) [PF = 50%]. The number need to treat (NNT) at five months was two, and at 12 months, the number was three.Clinical Signi?cance: The NSF formulation is effective to arrest active dentine caries and not stain teeth.

Conclusions

NSF was demonstrated to be effective in arresting caries in children in poor communities.     

A 7-year randomized prospective study of a one-step self-etching adhesive in non-carious cervical lesions. The effect of curing modes and restorative material

Objective

The aim of this study was to evaluate the clinical retention of a one-step self-etching adhesive system (Xeno III) in Class V non-carious cervical lesions and the effect of restorative material and curing techniques on longevity of the restorations.

Materials and methods

A total of 139 Class V restorations were placed with the self-etching primer Xeno III and a resin composite (Tetric Ceram) or a poly-acid modified resin composite (Dyract AP) in non-carious cervical lesions without intentional enamel involvement. The materials were cured with a conventional continuous light, a soft-start or a pulse-delay curing mode. The restorations were evaluated at baseline, 6, 12, 18 and 24 months and then yearly during a 7 year follow-up with modified USPHS criteria. Dentine bonding efficiency was determined by the percentage of lost restorations.

Results

During the 7 years, 135 restorations could be evaluated. No post-operative sensitivity was reported by the participants. Overall relative cumulative loss rate frequencies for the adhesive system at 6 and 18 months and 7 years, independent of curing technique and restorative material, were 0.8%, 6.9% and 23.0%, respectively. The self-etching adhesive fulfilled at 18 months the full acceptance ADA criteria. Tetric Ceram showed at 7 years a 20.9% loss of retention and Dyract AP a 25.0% loss rate (Log rank p = 0.48). The loss rates for the 3 curing techniques: continuous, soft start and pulse delay were 17%, 27.9% and 24.4%, respectively (Log rank p = 0.52). No secondary caries was observed.

Significance

The single-step self-etching adhesive showed acceptable clinical long-time retention rates to dentine surfaces independent of restorative material and curing technique used.     

Quantitative light-induced fluorescence (QLF): A tool for early occlusal dental caries detection and supporting decision making in vivo

Objectives

This study reports the development and assessment of a novel method using quantitative light-induced fluorescence (QLF), to determine whether QLF parameters ΔF and ΔQ were appropriate for aiding diagnosis and clinical decision making of early occlusal mineral loss by comparing QLF analysis with actual restorative management.

Methods

Following ethical approval, 46 subjects attending a dental teaching hospital were enrolled. White light digital (WL) and QLF images/analyses of 46 unrestored posterior teeth with suspected occlusal caries were made after a clinical decision had already been taken to explore fissures operatively. WL and QLF imaging/analysis were repeated after initial cavity preparation. The type of restorative treatment was determined by the supervising clinician independent of any imaging performed. Actual restorative management carried out was recorded as fissure sealant/preventive resin restoration (F/P) or class I occlusal restoration (Rest.) thus reflecting the extent of intervention (=gold standard). All QLF images were analysed independently.

Results

The results showed statistically significant differences between the two treatment groups ΔF (p = 0.002) (mean 22.60 – F/P and 28.80 – Rest.) and ΔQ (p = 0.012) (mean 230.49 – F/P and 348.30 – Rest.).

Conclusions

ΔF and ΔQ values may be useful in aiding clinical diagnosis and decision making in relation to the management of early mineral loss and restorative intervention of occlusal caries.

Clinical significance

QLF has the potential to be a valuable tool for caries diagnosis in clinical practice.     

Fracture resistance and cuspal deflection of incompletely excavated teeth

Objectives

Incomplete excavation reduces the risk of pulpal complications, but doubts remain regarding the mechanical properties of incompletely excavated teeth. Remaining carious dentine is suspected to not sufficiently support the restoration and to reduce bond strengths between the tooth and the restoration, with effects possibly varying depending on the depth of the remaining caries lesion. This study investigated fracture resistance (FR) and cuspal deflection (CD) of premolars after leaving or removing demineralized dentine in vitro.

Methods

In 48 premolars, shallow and deep artificial lesions (depths [mean ± SD] of 64 ± 18 μm and 771 ± 176 μm) were created on pulpo-axial walls of standardised mesial-distal-occlusal cavities. Demineralized dentine was either removed or left before adhesively restoring the tooth (n = 12/group). Restored teeth were submitted to thermo-mechanical cycling. CD was subsequently measured at loads of 200 N and 400 N, and teeth submitted to occlusal-perpendicular loading until fracturing occurred.

Results

FR was not significantly different between teeth with or without remaining demineralized dentine regardless of the lesion depth (p > 0.30, t-test). Irrespective of the removal technique, teeth with deep lesions showed significantly decreased FR (p ≤ 0.001). In contrast, CD was significantly increased in teeth with remaining demineralized dentine compared with completely excavated teeth (p ≤ 0.05; Mann–Whitney test).

Conclusions

Remaining demineralized dentine did not significantly decrease the fracture resistance of premolars in vitro. Effects of increased cuspal deflection on restoration margins should be assessed. This study showed no indication that incomplete excavation increases the risk of non-pulpal complications.

Clinical significance

Incomplete caries removal seems suitable to treat especially deep lesions. Leaving demineralized dentine does not seem to affect the fracture resistance of incompletely excavated teeth regardless of the lesion depth.     

Micro-hardness and mineral loss of enamel lesions after infiltration with various resins: Influence of infiltrant composition and application frequency in vitro

Objectives

The aim of this in vitro study was to evaluate the influence of infiltrant composition and application frequency on micro-hardness and lesion progression after resin infiltration of artificial enamel lesions.

Methods

In each of 100 bovine enamel samples, three artificial caries lesions were created (pH = 4.95, 50 days). After etching two of the lesions (37% phosphoric acid) specimens were randomly allocated to five infiltrants (four experimental infiltrants with different monomer and solvent compositions and penetration coefficients, and one commercial infiltrant [Icon, DMG]). Lesions were then infiltrated and light-cured, and infiltration repeated afterwards for one of the lesions. Infiltrated samples were cut into halves, with one half being demineralised for further 50 days. Micro-hardness (VHN) and integrated mineral loss (ΔZ) were evaluated at baseline and after second demineralisation. Repeated measures ANOVA and paired t-tests were used to analyse influence of material composition and application frequency on micro-hardness and lesion progression (integrated mineral loss difference ΔΔZ).

Results

Resin infiltration significantly increased micro-hardness and reduced lesion progression compared to untreated artificial lesions (p < 0.05, t-test). Neither micro-hardness nor lesion progression were significantly influenced by material composition (p > 0.05, ANOVA). In contrast, twice application resulted in significantly increased micro-hardness and demineralisation resistance of infiltrated lesions (p < 0.05, ANOVA).

Conclusion

Resin infiltration significantly improves micro-hardness and demineralisation resistance of enamel lesions; these effects are significantly enhanced if resins are applied twice. Experimental resins did not outperform the commercial infiltrant.

Clinical significance

This in vitro study demonstrated that resin infiltration significantly increases both micro-hardness and demineralisation resistance of enamel caries lesions. Twice application of the infiltrant seems to increase these effects. In contrast, the composition of the infiltrant had no significant influence on investigated parameters.     

Comparison of Knoop and Vickers surface microhardness and transverse microradiography for the study of early caries lesion formation in human and bovine enamel

Objective

The aims of the present laboratory study were twofold: a) to investigate the suitability of Knoop and Vickers surface microhardness (SMH) in comparison to transverse microradiography (TMR) to investigate early enamel caries lesion formation; b) to compare the kinetics of caries lesion initiation and progression between human and bovine enamel.

Design

Specimens (90 × bovine and 90 × human enamel) were divided into six groups (demineralization times of 8/16/24/32/40/48 h) of 15 per enamel type and demineralized using a partially saturated lactic acid solution. SMH was measured before and after demineralization and changes in indentation length (ΔIL) calculated. Lesions were characterized using TMR. Data were analyzed (two-way ANOVA) and Pearson correlation coefficients calculated.

Results

ΔIL increased with increasing demineralization times but plateaued after 40 h, whereas lesion depth (L) and integrated mineral loss (ΔZ) increased almost linearly throughout. No differences between Knoop and Vickers SMH in their ability to measure enamel demineralization were observed as both correlated strongly. Overall, ΔIL correlated strongly with ΔZ and L but only moderately with the degree of surface zone mineralization, whereas ΔZ and L correlated strongly. Bovine demineralized faster than human enamel (all techniques).

Conclusions

Lesions in bovine formed faster than in human enamel, although the resulting lesions were almost indistinguishable in their mineral distribution characteristics. Early caries lesion demineralization can be sufficiently studied by SMH, but its limitations on the assessment of the mineral status of more demineralized lesions must be considered. Ideally, complementary techniques to assess changes in both physical and chemical lesion characteristics would be employed.     

Marginal integrity and secondary caries of selectively excavated teeth in vitro

Objectives

Selective caries removal involves sealing of carious dentine beneath restorations, which might decrease their marginal integrity and increase the susceptibility for secondary caries and microleakage. The present study compared these marginal characteristics of restorations in selectively and completely excavated teeth.

Methods

In 32 premolars, shallow and deep artificial lesions were created on pulpo-axial walls of mesial-distal-occlusal cavities, with mesial and distal margins located in enamel and dentine, respectively. Demineralised dentine was either removed or left before adhesively restoring the teeth (n = 8), which were then submitted to thermo-mechanical cycling. The integrity of gingivo-cervical margins was assessed using scanning electron microscopy. In half of each margin, caries was induced adjacent to restorations using a continuous-culture biofilm model, and resulting lesions were evaluated using transversal microradiography. The other half of each margin was used to assess microleakage.

Results

Integrity or microleakage of margins located in enamel did not differ significantly between groups, and bacterial biofilms did not induce distinct caries lesions in enamel. Dentinal margins in teeth with deep compared with shallow lesions showed a significantly higher proportion of marginal imperfections, gaps and microleakage (p ≤ 0.05, Mann–Whitney/χ²-test). In contrast, neither marginal integrity nor microleakage differed significantly between completely and selectively excavated teeth (p > 0.05). Dentinal mineral loss adjacent to restorations did not differ significantly between groups (p > 0.80).

Conclusions

The marginal characteristics of restorations were affected by the depth of sealed or excavated lesions, but not by the performed caries excavation. This study did not find selective excavation detrimental for restoration integrity in vitro.

Clinical significance

Selective excavation of deep lesions was shown to reduce pulpal risks, whilst leaving caries beneath restorations is feared to compromise the marginal characteristics of the subsequently placed restoration. Based on the present in vitro study, such assumptions cannot be supported.     

Effect of pit and fissure sealants on caries detection by a fluorescent camera system

Objective

The aim of this study was to evaluate the effect of sealant placement on the detection of caries by a fluorescent camera (FC), the Spectra caries detector.

Materials and methods

In a laboratory study, FC images and readings were obtained from 31 extracted teeth, before and following application of clear sealants (Shofu Clear or Delton unfilled), or opaque sealants (3M Clinpro or Delton FS). Teeth were then sectioned and examined for enamel or dentine caries. Using each tooth's true caries diagnosis, the sensitivity and specificity of the FC measurements in detecting dentine caries was calculated. In the clinical study, FC readings were obtained from 41 molars in children prior to and following application of clear sealants.

Results

Following application of Shofu or Delton unfilled there were reductions in the mean FC readings of 10% (p = 0.5) and 8.2% (p = 0.009), respectively. Application of two opaque sealants, 3M or Delton FS significantly reduced mean FC readings 16.2% and 20.8% (p < 0.5), respectively. Although the carious lesions could still be observed in FC images from teeth with opaque sealants there was a significant loss of sensitivity in detecting dentinal caries. Clear sealant application caused an insignificant loss of detection sensitivity. Following application of clear sealants to children's molars there was a small (4.01%) but significant (p < 0.01) reduction in FC readings recorded from these teeth.

Conclusions

The FC can detect caries under clear sealants with little loss of sensitivity. Although lesions can be seen through opaque sealants, loss of sensitivity precludes accurate lesion assessment.     

Penetration of amalgam constituents into dentine

Objectives

Amalgam restorations are replaced by adhesively placed composite resin restorations at an increasing rate. After the removal of amalgam dentine often shows marked dark discoloration that is attributed to the penetration of corrosion products from overlying amalgams. It is questioned whether penetration of metals into dentine affects the dentine as a substrate for adhesive procedures. This study has been performed to clarify the origin of dark discoloration of dentine by metals from amalgam with special regards to corrosion products.

Methods

A review of the literature has been performed using Medline database. As keywords dentine and amalgam, subsequently combined with penetration, interface, crevice, interaction, corrosion, were used. This was followed up by extensive hand search using reference lists of relevant articles.

Results

Data in the literature have been gathered from extracted amalgam filled teeth and from artificially aged amalgam filled teeth. Corrosion studies have been performed in vivo aged teeth as well as in vitro. Sn is the main element, followed by Zn and Cu, that is consistently found in dentine underneath amalgam, as well as in amalgam corrosion products and in marginal seal deposits. Penetration of elements from amalgam has only been observed in discolored and in demineralised dentine.

Conclusions

Darkly discolored dentine as found underneath amalgam restorations contains amalgam corrosion products and is demineralised. Therefore it must be considered a different substrate for clinical procedures than sound dentine.     

An ex vivo study of arrested primary teeth caries with silver diamine fluoride therapy

Objectives

This ex vivo study compared the physico-chemical structural differences between primary carious teeth biannually treated with silver diamine fluoride (SDF) and carious teeth without such treatment.

Method

Twelve carious primary upper-central incisors were collected from 6-year-old children. Six teeth had arrested caries after 24-month biannual SDF applications and 6 had active caries when there was no topical fluoride treatment. The mineral density, elemental contents, surface morphology, and crystal characteristics were assessed by micro-computed tomography (micro-CT), energy-dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Results

Micro-CT examination revealed a superficial opaque band approximately 150 μm on the arrested cavitated dentinal lesion. This band was limited in the active carious lesion. EDX examination detected a higher intensity of calcium and phosphate of 150 μm in the surface zone than in the inner zone, but this zone was restricted in the active cavitated dentinal lesion. SEM examination indicated that the collagens were protected from being exposed in the arrested cavitated dentinal lesion, but were exposed in the active cavitated dentinal lesion. TEM examination suggested that remineralised hydroxyapatites were well aligned in the arrested cavitated dentinal lesion, while those in the active cavitated dentinal lesion indicated a random apatite arrangement.

Conclusions

A highly remineralised zone rich in calcium and phosphate was found on the arrested cavitated dentinal lesion of primary teeth with an SDF application. The collagens were protected from being exposed in the arrested cavitated dentinal lesion.

Clinical significance

Clinical SDF application positively influences dentine remineralisation.     

Mineral distribution and CLSM analysis of secondary caries inhibition by fluoride/MDPB-containing adhesive system after cariogenic challenges

Objective

To evaluate the inhibition zone formation (IZ) and mineral distribution along the interface of adhesive systems either containing fluoride and antibacterial primer or not, after chemical and biological artificial caries challenges.

Methods

Forty-eight third molars were used. Artificial caries was developed with S. mutans in a 4 mm × 4 mm area of occlusal dentin surface. Carious dentin was removed and cavities were restored with Adper Scotchbond Multi-Purpose (SBM) and Clearfil Protect Bond (CPB) (n = 24). Samples were submitted to secondary caries development by chemical (C) (acidic gel) or biological (B) (S. mutans culture) methods for 5 days. Four groups were tested (n = 12): (1) SC (SBM + C); (2) SB (SBM + B); (3) CC (CPB + C); (4) CB (CPB + B). The IZ and outer lesion (OL) formations were analyzed by confocal laser scanning microscopy (CLSM). The distribution of calcium (Ca) and phosphorus (P) content along the interface was analyzed by micro X-ray fluorescence spectrometer by energy-dispersive (μEDX).

Results

The frequency of IZ formation and mean values of IZ thickness differed among the groups. The CC group presented the lowest OL depth. μEDX analysis showed that CPB had the highest mineral loss by the biological method, but the lowest mineral loss by the chemical method. SC and SB groups showed intermediate values of mineral loss.

Conclusion

The mineral loss along the dentin/restoration interface was affected by the artificial caries method, and hybrid layer formation by adhesive systems used. The adhesive system containing fluoride and antibacterial primer did not prevent secondary caries formation.     

Is non-cavitated proximal lesion sealing an effective method for caries control in primary and permanent teeth? A systematic review and meta-analysis

Objectives

The aim of this study was to perform a systematic review and meta-analysis on the effectiveness of sealing non-cavitated proximal caries lesions in primary and permanent teeth.

Data

Only controlled clinical trials and randomized controlled clinical trials that evaluated the effectiveness of sealing on non-cavitated proximal caries with a minimum follow-up of 12 months were included in the study. The primary outcome should be arrestment/progression of proximal caries evaluated by bitewing radiographs. A risk of bias evaluation based on the Cochrane Collaboration common scheme for bias was carried out for each study. The meta-analysis was performed on the studies considered low risk of bias and with pair-wise visual reading results through RevMan software.

Sources

A comprehensive search was performed in the Systematic Electronic Databases: Pubmed, Cochrane Library, Scopus, IBI Web of Science, Lilacs, SIGLE, and on website Clinical trials.gov, through until June 2013.

Study selection

From 967 studies identified, 10 articles and 3 studies with partial results were assessed for eligibility. However three articles were excluded and our final sample included 10 studies. According to the risk of bias evaluation, six studies were considered “high” risk of bias, and four “low” risk of bias. The forest plot of the meta-analysis showed low heterogeneity (I² = 29%) and a favourable outcome for the Infiltrant. The chance of caries progression when this technique was used was significantly lower (p = 0.002) compared with Placebo.

Conclusion

Our results suggest that the technique of sealing non-cavitated proximal caries seems to be effective in controlling proximal caries in the short and medium term. Further long-term randomized clinical trials are still necessary to increase this evidence.

Clinical significance

Contemporary dentistry is focused in minimally invasive approaches that prevent the destruction of sound dental tissues next to carious lesions. This paper searches for evidence of the efficacy of sealing/infiltrating non-cavitated proximal caries in arresting caries progression both in permanent and primary teeth.     

Validity of MicroCT for in vitro detection of proximal carious lesions in primary molars

Objective

This study aimed to validate the MicroCT for detection of proximal carious lesions in primary molars, using histology as the gold standard.

Methods

Forty-eight proximal surfaces of primary molars were examined. Two calibrated examiners conducted the examinations independently. Proximal surfaces were visually scored, using ICDAS. Bitewing radiographs, Micro-CT and histological analyses used caries scores: 0 = sound; 1 = outer enamel; 2 = inner enamel; 3 = not spread dentine; 4 = outer dentine; 5 = inner dentine. Axial and sagital images were used for Micro-CT analysis, whilst for histology, tooth sections (400 μm) were analyzed stereomicroscopically (×15).

Results

Inter-examiner agreement ranged from 0.87 to 0.93 kappa coefficient (k). Histological analysis revealed a frequency of sound tooth surfaces (18.8%) enamel carious lesions (E1) (48%) and dentine carious lesions (D1) (33.3%). MicroCT showed high correlation with histology (r_s0.88). At both diagnostic thresholds (E1 and D1), sensitivity and accuracy were higher for MicroCT. Inter-device agreement between MicroCT and histology was k = 0.81. No difference was found between MicroCT and histology as gold standards for detecting carious lesions using ICDAS.

Conclusion

MicroCT can be used as a gold standard for detecting carious lesions in proximal surfaces in primary molars.     

Novel protein-repellent dental adhesive containing 2-methacryloyloxyethyl phosphorylcholine

Objectives

Biofilms at tooth-restoration margins can produce acids and cause secondary caries. A protein-repellent adhesive resin can potentially inhibit bacteria attachment and biofilm growth. However, there has been no report on protein-repellent dental resins. The objectives of this study were to develop a protein-repellent bonding agent incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC), and to investigate its resistance to protein adsorption and biofilm growth for the first time.

Methods

MPC was incorporated into Scotchbond Multi-Purpose (SBMP) at 0%, 3.75%, 7.5%, 11.25%, and 15% by mass. Extracted human teeth were used to measure dentine shear bond strengths. Protein adsorption onto resins was determined by a micro bicinchoninic acid (BCA) method. A dental plaque microcosm biofilm model with human saliva as inoculum was used to measure biofilm metabolic activity and colony-forming unit (CFU) counts.

Results

Adding 7.5% MPC into primer and adhesive did not decrease the dentine bond strength, compared to control (p > 0.1). Incorporation of 7.5% of MPC achieved the lowest protein adsorption, which was 20-fold less than that of control. Incorporation of 7.5% of MPC greatly reduced bacterial adhesion, yielding biofilm total microorganism, total streptococci, and mutans streptococci CFU that were an order of magnitude less than control.

Conclusions

A protein-repellent dental adhesive resin was developed for the first time. Incorporation of MPC into primer and adhesive at 7.5% by mass greatly reduced the protein adsorption and bacterial adhesion, without compromising the dentine bond strength.

Clinical significance

The novel protein-repellent primer and adhesive are promising to inhibit biofilm formation and acid production, to protect the tooth-restoration margins and prevent secondary caries.     

Comparing two quantitative methods for studying remineralization of artificial caries

Objectives

To compare the detection of changes before and after remineralization of artificial enamel and dentin caries by microCT scanning, polarized light microscopy (PLM) and transverse microradiography (TMR).

Methods

Fourteen extracted premolars were cut into tooth blocks and painted with an acid-resistant varnish leaving one enamel and one dentin surface exposed. The tooth blocks were immersed into demineralizing solution for 4 days to produce artificial caries-like lesions and scanned by microCT. Then the 14 tooth blocks were randomly allocated into two groups. Seven tooth blocks in Group I were cut longitudinally through the exposed surface into 100–150 μm thick sections and microradiographs were taken. The other seven tooth blocks in Group II were left intact. All the tooth blocks and sections were then immersed into remineralizing solution for 5 days. PLM and TMR of the tooth sections in Group I were taken again. Depth of the lesion on the TMR was measured. Tooth blocks in Group II were scanned by microCT.

Results

Mean lesion depth in Group I reduced by 13.0% and 8.2% after remineralization for enamel and dentin, respectively (paired t-test, P < 0.001). In Group II, linear attenuation coefficient (LAC) of the region of interest (ROI) increased by 11.1% and 23.8% after remineralization for enamel and dentin lesions, respectively (paired t-test, P < 0.001).

Conclusion

Both microCT and microradiography are able to detect a change of similar magnitude in the artificial caries lesions after remineralization. MicroCT may be used to substitute TMR and PLM in in vitro studies about caries.     

Non-thermal atmospheric plasmas in dental restoration: Improved resin adhesive penetration

Objective

To investigate the influence of non-thermal plasma treatment on the penetration of a model dental adhesive into the demineralized dentine.

Methods

Prepared dentine surfaces were conditioned with Scotchbond Universal etchant for 15 s and sectioned equally perpendicular to the etched surfaces. The separated halves were randomly selected for treatment with an argon plasma brush (input current 6 mA, treatment time 30 s) or gentle argon air blowing (treatment time 30 s, as control). The plasma-treated specimens and control specimens were applied with a model adhesive containing 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA) and 2-hydroxyethyl methacrylate (HEMA) (mass ratio of 30/70), gently air-dried for 5 s, and light-cured for 20 s. Cross-sectional specimens were characterized using micro-Raman spectral mapping across the dentine, adhesive/dentine interface, and adhesive layer at 1-μm spatial resolution. SEM was also employed to examine the adhesive/dentine interfacial morphology.

Results

The micro-Raman result disclosed that plasma treatment significantly improved the penetration of the adhesive, evidenced by the apparently higher content of the adhesive at the adhesive/dentine interface as compared to the control. Specifically, the improvement of the adhesive penetration using plasma technique was achieved by dramatically enhancing the penetration of hydrophilic monomer (HEMA), while maintaining the penetration of hydrophobic monomer (BisGMA). Morphological observation at the adhesive/dentine interface using SEM also confirmed the improved adhesive penetration. The results further suggested that plasma treatment could benefit polymerization of the adhesive, especially in the interface region.

Conclusion

The significant role of the non-thermal plasma brush in improving the adhesive penetration into demineralized dentine has been demonstrated. The results obtained may offer a better prospect of using plasma in dental restoration to optimize adhesion between tooth substrate and restorative materials.     

The preventive effect of grape seed extract on artificial enamel caries progression in a microbial biofilm-induced caries model

Objectives

The aim of this study was to evaluate the effect of grape seed extract (GSE) on enamel caries lesion formation in an in vitro Streptococcus mutans biofilm model.

Methods

Enamel fragments were prepared from bovine incisors and divided into six treatment groups (n = 12): inoculated Brain Heart Infusion with 1% sucrose (BHIS), 1 mg/mL GSE, 2 mg/mL GSE, 3 mg/mL GSE, 10 ppm fluoride as NaF, and uninoculated BHIS. For biofilm formation, tooth fragments were incubated anaerobically in polystyrene 6-well tissue culture plates containing BHIS, the respective agents, and S. mutans (1 × 10⁵ CFU/mL) for 24 h at 37 °C. Culture medium was replaced with fresh BHIS and respective agents daily over a 7-day period. Following caries lesion formation, lesion depth (LD) and relative optical density (ROD) were determined by polarized light microscopy (PLM) and confocal laser scanning microscopy (CLSM), respectively, to evaluate lesion progression.

Results

LDs of the 2 mg/mL GSE group (122.86 ± 13.41 μm) and the 3 mg/mL GSE group (111.92 ± 11.39 μm) were significantly smaller than those of the 1 mg/mL GSE (198.33 ± 17.70 μm) and control groups (210.86 ± 15.50 μm) (p < 0.05). Compared with the 2 mg/mL and 3 mg/mL groups, the control and 1 mg/mL GSE groups showed significantly lower ROD values when depth was less than 200 μm, indicating greater mineral loss.

Conclusions

Dose-dependent GSE inhibits in vitro enamel caries formation due to its ability to suppress growth of S. mutans and the formation of bio?lm.

Clinical signi?cance

Grape seed extract may be a novel virulence-targeted natural antimicrobial agent for caries prevention.     

Dynamics of oral microbial community profiling during severe early childhood caries development monitored by PCR-DGGE

Objective

To monitor the longitudinal changes in oral microbial diversity of children with severe early childhood caries (S-ECC) compared to caries free (CF) controls.

Methods

Dental plaque samples of 12 children in each group at 8, 14, 20, 26 and 32 months of age were analysed. Total microbial genomic DNA was isolated from each sample, and PCR-denaturing gradient gel electrophoresis (DGGE) analyses were carried out.

Results

The number of bands was significantly higher in the CF group (18.17 ± 4.91 bands) than in the S-ECC group (14.54 ± 5.56 bands) at 32 months of age (P < 0.05). A total of 21 genera were identified in all subjects, and there were no significant differences between the two groups at genus level. DGGE profiles showed that most of the clusters were constructed from one individual over time in the both groups.

Conclusions

The onset of S-ECC is accompanied by a decrease in microbial diversity. The overall composition of the microbiota is highly similar within an individual over time.