Marginal integrity and secondary caries of selectively excavated teeth in vitro

Restorations performance after selective caries removal to soft dentine: 18-month follow-up of a controlled clinical trial

OBJECTIVE

This randomized controlled clinical trial aimed to evaluate the clinical performance of composite resin restorations placed after selective caries removal to soft dentin (SCRSD) or stepwise excavation (SW) over an 18-month period.

METHODS

Inclusion criteria were patients with permanent molars and/or premolars presenting deep caries lesions (≥50 % of the dentin thickness). Teeth were submitted to SCRSD (n = 76) or SW (n = 76). Evaluations were performed based on FDI (World Dental Federation) criterion. Survival analysis was performed to estimate the survival of restorations and its association with clinical variables and socio-demographic characteristics (adjusted Weibull regression model). The study was registered on Registro Brasileiro de Ensaios Clínicos (ReBEC 65ntbc).

RESULTS

The follow-up period ranged from 6 to 18 months (mean ± SD 16.3 ± 3.4 months). Patients' ages ranged from 9 to 55 years (mean ± SD 29 ± 10.5 years). A total of 135 teeth (SCRSD = 72; SW = 63) from 101 patients were evaluated. There were 4 failures in the SCRSD group (2 loss of restoration in need of replacement and 2 marginal fractures in need of repair) and 2 in the SW group (fracture in need of repair). The association between explanatory variables and restoration failure showed similar success rates for SW (99.4 %) and SCRSD (97.9 %) (p = 0.16). Patients presenting gingivitis (≥20 % of sites with gingival bleeding) had 8.50 times more risk for failure than those with <20 % of bleeding sites (p = 0.03).

CONCLUSION

This study showed that placing a composite resin restoration over soft dentin (after SCRSD) did not affect its clinical performance after 18 months.

CLINICAL SIGNIFICANCE

SCRSD is a feasible treatment option for the management of deep caries lesions in permanent teeth as it preserves tooth vitality and tooth structure without compromising restoration longevity.

Evaluation of the efficiency, trueness, and clinical application of novel artificial intelligence design for dental crown prostheses

OBJECTIVE

The unique structure of human teeth limits dental repair to custom-made solutions. The production process requires a lot of time and manpower. At present, artificial intelligence (AI) has begun to be used in the medical field and improve efficiency. This study attempted to design a variety of dental restorations using AI and evaluate their clinical applicability.

METHODS

Using inlay and crown restoration types commonly used in dental standard models, we compared differences in artificial wax-up carving (wax-up), artificial digital designs (digital) and AI designs (AI). The AI system was designed using computer calculations, and the other two methods were designed by humans. Restorations were made by 3D printing resin material. Image evaluations were compared with cone beam computed tomography (CBCT) by calculating the root mean squared error.

RESULTS

Surface truth results showed that AI (68.4 µm) and digital-designed crowns (51.0 µm) had better reproducibility. Using AI for the crown reduced the time spent by 400% (compared to digital) and 900% (compared to wax-up). Optical microscopic and CBCT images showed that AI and digital designs had close margin gaps (p < 0.05). The margin gap of the crown showed that the wax-up group was 4.1 and 4.3 times greater than those of the AI and digital crowns, respectively. Therefore, the utilization of artificial intelligence can assist in the production of dental restorations, thereby enhancing both production efficiency and accuracy.

SIGNIFICANCE

It is expected that the development of AI can contribute to the reproducibility, efficiency, and goodness of fit of dental restorations.

The Influence of Dental Virtualization, Restoration Types, and Placement Angles on the Trueness and Contact Space in 3D-Printed Crowns: A Comprehensive Exploration

The current digital dentistry workflow has streamlined dental restoration production, but the effectiveness of digital virtual design and 3D printing for restorations still needs evaluation. This study explores the impact of model-free digital design and 3D-printing placement angles on restorations, including single crowns and long bridges produced with and without casts. The restorations are 3D printed using resin at placement angles of 0°, 60°, and 90°. Each group of samples was replicated ten times, resulting in a total of 120 restorations. The Root Mean Square Error (RMSE) value was used to evaluate the surface integrity of the restoration. In addition, the contact space, edge gap, and occlusal space of restorations produced by different processes were recorded. The results indicate that there was no significant difference in the RMSE value of the crown group (p > 0.05). Changing the bridge restoration angle from 0° to 90° resulted in RMSE values increasing by 2.02 times (without casts) and 2.39 times (with casts). Furthermore, the marginal gaps in the crown group were all less than 60 μm, indicating good adaptation. In contrast, the bridge group showed a significant increase in marginal gaps at higher placement angles (p > 0.05). Based on the findings, virtual fabrication without casts does not compromise the accuracy of dental restorations. When the position of the long bridge exceeds 60 degrees, the error will increase. Therefore, designs without casts and parallel placement result in higher accuracy for dental restorations.

The Role of Bacterial, Dentinal, Salivary, and Neutrophil Degradative Activity in Caries Pathogenesis

Until recently, it was widely accepted that bacteria participate in caries pathogenesis mainly through carbohydrate fermentation and acid production, which promote the dissolution of tooth components. Neutrophils, on the other hand, were considered white blood cells with no role in caries pathogenesis. Nevertheless, current literature suggests that both bacteria and neutrophils, among other factors, possess direct degradative activity towards both dentinal collagen type-1 and/or methacrylate resin-based restoratives and adhesives, the most common dental restoratives. Neutrophils are abundant leukocytes in the gingival sulcus, where they can readily reach adjacent tooth roots or gingival and cervical restorations and execute their degradative activity. In this review, we present the latest literature evidence for bacterial, dentinal, salivary, and neutrophil degradative action that may induce primary caries, secondary caries, and restoration failure.

The state of oral health in patients with haemophilia in the Netherlands

INTRODUCTION

Previous studies show contradictory outcomes regarding dental, gingival and periodontal status in persons with haemophilia (PWH) compared to healthy controls. PWH may experience disease-specific barriers to access dental care due to their bleeding tendency, which may lead to delays in oral care and severe dental problems.

AIM

To determine the current subjective and objective oral health status in adult PWH.

METHODS

Randomly selected PWH of the Erasmus MC Haemophilia Treatment Center (HTC), Rotterdam, the Netherlands, were invited to participate. Data was collected using the Oral Health Impact Profile (OHIP-14NL) and personal interviews. A dentist used the DMFT index, the Dutch Periodontal Screening index (DPSI), plaque and bleeding index to score the dental status.

RESULTS

Forty-eight adult PWH were included in this study, 20 mild, 15 moderate-severe and 13 severe haemophilia with a mean age of 44.7. PWH scored low on the OHIP-14 questionnaire (median total score 1.0; IQR .0-3.0), indicating a high self-rating oral health status. The number of bleeding events, bleeding- and plaque index score was not statistically significant between patients with mild, moderate or severe haemophilia. The mean number of decayed, missing, and filled teeth (DMFT-score) was significantly lower in the group of patients with severe haemophilia (median 2.0) compared to mild haemophilia (median 16.0) (p = .04). Twenty-five patients (52.1%) reported to have encountered bleeding problems during or after dental interventions during their lifetime.

CONCLUSION

Dutch adult PWH A/B have good dental status and oral health status.

Secondary Caries Adjacent to Bulk or Incrementally Filled Composites Placed after Selective Excavation In Vitro

Objectives: selective caries excavation (SE) is recommended for deep carious lesions. Bulk fill composites (BF) may be considered to restore SE-cavities. We compared the susceptibility for secondary caries adjacent to BF versus incrementally filled composites (IF) in SE and non-selectively excavated teeth (NS) in vitro. Methods: in 72 extracted human premolars, artificial caries lesions were induced on pulpo-axial walls of standardized cavities. The lesions were left (SE) or removed (NS), and teeth were restored using two BF, GrandioSO x-tra/Voco (BF-Gra) and SDR/Dentsply (BF-SDR), and an IF, GrandioSO/Voco (IF-Gra) (n = 12/group for SE and NS). After thermo-mechanical cycling (5–55 °C, 8 days), teeth were submitted to a continuous-culture Lactobacillus rhamnosus biofilm model with cyclic loading for 10 days. Mineral loss (ΔZ) of enamel surface lesions (ESL), dentin surface lesions (DSL), and dentin wall lesions (DWL) was analyzed using transversal microradiography. Results: ΔZ was the highest in DSL, followed by ESL, and it was significantly lower in DWL. There were no significant differences in ΔZ between groups in DSL, ESL, and DWL (p > 0.05). Regardless of lesion location, ΔZ did not differ between SE and NS (p > 0.05). Conclusions: BF and IF both showed low risks for DWL (i.e., true secondary caries) after SE in vitro, and surface lesion risk was also not significantly different between materials. SE did not increase secondary caries risk as compared with NS. Clinical Significance: the risk of secondary caries was low after selective excavation in this study, regardless of whether bulk or incrementally filled composites were used

Secondary caries risk of different adhesive strategies and restorative materials in permanent teeth: Systematic review and network meta-analysis

OBJECTIVES

Secondary caries is a major long-term complication of dental restorations. Different adhesive strategies and restorative materials may affect secondary caries risk. We aimed to systematically review and synthesize the secondary caries risk of different adhesive strategies and restorative materials.

SOURCES

Medline via PubMed 01/2005-10/2019.

STUDY SELECTION

Randomized controlled studies with minimum 2 years follow-up, comparing different adhesive strategies and/or restorative materials in permanent teeth were included. Our outcome was the occurrence of secondary caries. Bayesian pairwise and network-meta-analysis were conducted.

DATA

We included 50 trials; 19 assessing secondary caries depending on different adhesive strategies, 31 on restorative materials. Studies were published between 2005 and 2017, largely of unclear risk of bias, and included a mean of 40 (range: 8-90) participants and 46 (range: 14-200) placed restorations. Mean follow-up was 43 (range: 24-180) months. Secondary caries was a rare event; the majority of studies did not find any lesions. Network meta-analysis found great uncertainty. 3-step etch-and-rinse adhesives showed the lowest risk of secondary caries, 2-step etch-and-rinse the highest. For restorative materials, resin-modified glass ionomer showed the lowest risk of secondary caries. Most resin composites showed similar risks.

CONCLUSION

Data from randomized trials comparing different adhesive strategies or restorative materials are extremely scarce. The differences between materials were limited over the observational period of the included studies. The yielded rankings should be interpreted with caution.

CLINICAL SIGNIFICANCE

Despite often claimed to be a major complication of restorations, there is surprisingly little data on secondary caries from randomized trials. Longer-term studies may be needed to identify differences in secondary caries risk between materials.

Influence of selective caries excavation on marginal penetration of class II composite restorations in vitro

Selective caries excavation may support pulp preservation. This in vitro study investigated the influence of selective removal of demineralized dentin on marginal integrity of composite restorations as determined by dye penetration. Dentinal caries-like lesions were produced in the approximal surfaces of 40 extracted human molars (ethylenediaminetetraacetate, 0.5 M, 96 h). The following test procedures were established: complete excavation, selective excavation, and caries-free control. Two class II cavities with enamel at the cervical margins were prepared per tooth and demineralization volume was determined by micro-computed tomography for the purpose of a stratified distribution to receive complete excavation or selective excavation. After complete or selective excavation (30 cavities each), adhesive composite restorations were placed. Cavities without demineralized dentin (20 cavities) served as control. The marginal integrity of restorations was evaluated by dye penetration with and without thermocycling or mechanical loading. Results were analyzed by non-parametrical statistical tests (Mann-Whitney U Test) with an α = 0.05 level of significance. Dye penetration did not differ significantly among completely excavated, selectively excavated, or undemineralized teeth, but was increased by thermocycling and mechanical loading in all experimental groups. Selective caries removal did not increase marginal penetration in class II restorations. The presence of remaining demineralized dentin surrounded by sound dentin did not impair marginal integrity of restorations with margins placed in sound enamel.

How to intervene in the caries process in adults: proximal and secondary caries? An EFCD-ORCA-DGZ expert Delphi consensus statement

OBJECTIVES

To provide consensus recommendations on how to intervene in the caries process in adults, specifically proximal and secondary carious lesions.

METHODS

Based on two systematic reviews, a consensus conference and followed by an e-Delphi consensus process were held with EFCD/ORCA/DGZ delegates.

RESULTS

Managing an individual's caries risk using non-invasive means (oral hygiene measures including flossing/interdental brushes, fluoride application) is recommended, as both proximal and secondary carious lesions may be prevented or their activity reduced. For proximal lesions, only cavitated lesions (confirmed by visual-tactile, or radiographically extending into the middle/inner dentine third) should be treated invasively/restoratively. Non-cavitated lesions may be successfully arrested using non-invasive measures in low-risk individuals or if radiographically confined to the enamel. In high-risk individuals or if radiographically extended into dentine, for these lesions, additional micro-invasive (lesion sealing and infiltration) treatment should be considered. For restoring proximal lesions, adhesive direct restorations allow minimally invasive, tooth-preserving preparations. Amalgams come with a lower risk of secondary lesions and may be preferable in more clinically complex scenarios, dependent on specific national guidelines. In structurally compromised (especially endodontically treated) teeth, indirect cuspal coverage restorations may be indicated. Detection methods for secondary lesions should be tailored according to the individual's caries risk. Avoiding false positive detection and over-treatment is a priority. Bitewing radiographs should be combined with visual-tactile assessment to confirm secondary caries detections. Review/refurbishing/resealing/repairing instead of replacing partially defective restorations should be considered for managing secondary caries, if possible.

CONCLUSIONS

An individualized and lesion-specific approach is recommended for intervening in the caries process in adults.

CLINICAL SIGNIFICANCE

Dental clinicians have an increasing number of interventions available for the management of dental caries. Many of them are grounded in the growing understanding of the disease. The best evidence, patients' expectations, clinicians' expertise, and the individual clinical scenario all need to be considered during the decision-making process.

Restorations after selective caries removal: 5-Year randomized trial

OBJECTIVE

To compare the survival of restorations placed in deep caries lesions after selective caries removal to soft dentin (SCRSD) over a 5-year period. A secondary aim was to investigate whether the material (amalgam or resin composite) affected the survival of restorations.

METHODS

This study used data derived from a multicenter randomized controlled clinical trial (Clinical trials registration NCT00887952). Inclusion criteria were: patients with permanent molars presenting occlusal or proximal deep caries lesions (≥1/2 of the dentin thickness on radiographic examination), positive response to a cold test, absence of spontaneous pain, negative sensitivity to percussion, and absence of periapical lesions. The teeth were randomized into SCRSD and restoration in a single visit or stepwise excavation (SW). Each of these groups was divided according to the filling material: amalgam (AM) or resin composite (RC). Survival analyses were performed to estimate therapy success rates over 5 years (adjusted Weibull regression model).

RESULTS

172 restorations were evaluated, 95 from SCRSD group and 77 from SW group, being 61 AMG and 111 RC. The 5-year survival analysis showed similar success rates for SW (76 %) and SCRSD (79 %) as well as for AM and RC (p > 0.05).

CONCLUSION

This study showed that, after a 5-year follow-up period, the presence of decayed tissue beneath restorations in deep caries lesions did not seem to affect restoration survival. Amalgam and resin composite restorations had similar survival rates, irrespective of the caries removal technique used - SCRSD or SW.

CLINICAL SIGNIFICANCE

Selective caries removal to soft dentin can be used in the management of deep caries to avoid pulp exposure and preserve tooth structure without affecting restoration longevity.

Secondary caries: what is it, and how it can be controlled, detected, and managed?

OBJECTIVES

To assess how to control, detect, and treat secondary caries. This review serves to inform a joint ORCA/EFCD consensus process.

METHODS

Systematic and non-systematic reviews were performed or consulted and narratively synthesized.

RESULTS

Secondary (or recurrent) caries is defined as a lesion associated with restorations or sealants. While the restorative material itself has some influence on secondary caries, further factors like the presence and size of restoration gaps, patients' caries risk, and the placing dentist's experience seem more relevant. Current detection methods for secondary caries are only sparsely validated and likely prone for the risk of over-detection. In many patients, it might be prudent to prioritize specific detection methods to avoid invasive overtreatment. Detected secondary caries can be managed either by repair of the defective part of the restoration or its complete replacement.

CONCLUSIONS

There is sparse data towards the nature of secondary caries and how to control, detect, and treat it.

CLINICAL SIGNIFICANCE

Despite often claimed to be a major complication of restorations, there is surprisingly little data on secondary caries. Longer-term studies may be needed to identify differences in secondary caries risk between materials and to identify characteristic features of progressive lesions (i.e., those in need of treatment).

Bonding of universal adhesive system to enamel surrounding real-life carious cavities

This study aimed to evaluate the bond strength of a universal adhesive system to enamel surrounding real-life carious cavities. Twenty-eight permanent molars (n = 7) with carious lesions in dentin were subjected to selective carious tissue removal to firm dentin and had their crowns sectioned longitudinally. A universal adhesive system (Single Bond Universal [SBU] used in either etch-and-rinse and self-etch strategies) was compared with an etch-and-rinse Adper Single Bond 2 (ASB) and a self-etch Clearfil SE Bond (CSE) adhesive systems (control systems). Adhesives were applied on the enamel, assumed demineralized, surrounding the cavity margins and on sound enamel (control substrate). Composite cylinders were built (0.72 mm2) and microshear bond strength (µSBS) test was performed after 24 h of water storage. The µSBS values (MPa) were analyzed using two-way ANOVA and Tukey's post hoc tests (α = 0.05). Bond strength values obtained in demineralized enamel surrounding carious cavity margins were significantly lower than that obtained in sound enamel (distant from carious cavity margins) (p = 0.035). The bonding strategy of the SBU did not influenced the bond strength values, which were higher than that obtained with ASB. CSE showed similar µSBS values to ASB and SBU in the self-etch mode. In conclusion, the bond strength to enamel assumed demineralized is lower than to sound enamel. The enamel surrounding carious cavities jeopardize the bonding of universal adhesive system. The bond strength of universal adhesive is similar, regardless to bonding strategy.

Tailored Dentistry: From "One Size Fits All" to Precision Dental Medicine?

Over the past 30 years and fueled by both a rapidly evolving understanding of dental diseases and technological advances in diagnostics and therapy, dentistry has been changing dramatically. Managing dental caries and carious lesions had, for nearly a century, encompassed only a small number of basic concepts that were applied to virtually all patients and lesions, namely, invasive removal of any carious tissue regardless of its activity or depth and its replacement with restorative materials (amalgams or crowns for most of the past) or tooth removal and prosthetic replacement. Grounded in a deeper understanding of the disease "caries," its management-aiming to control the causes of the disease, to slow down or alleviate existing disease, and, only as a last resort, to remove its symptoms using a bur or forceps-has become more complex and diverse. In parallel and at nearly unprecedented speed, our patients are changing, as mirrored by ongoing debates as to the demographic and, with it, the social future of most high-income countries. This article describes how these changes will have a profound future impact on how we practice dental medicine in the future. It will deduce, from both demographic and epidemiologic trends, why there is the need to apply not one but rather the whole range of existing evidence-based concepts in an individualized (personalized) manner, hence increasing the effectiveness and efficiency of dental management strategies, and also describe how these strategies should be tailored according not only to our patients (their age and risk profiles) but also to the specific tooth (or site or lesion).

Selective carious tissue removal using subjective criteria or polymer bur: study protocol for a randomised controlled trial (SelecCT)

INTRODUCTION

Selective (incomplete/partial) carious tissue removal is suitable for treating deep carious lesions in teeth with vital, asymptomatic pulps. In the periphery of a cavity, removal to hard dentin is performed, while in pulpo-proximal areas, leathery or soft dentin is left to avoid pulp exposure. As the decision of what contains 'soft' or 'leathery' dentin is subjective, using self-limiting burs which help to standardise the hardness of the remaining dentin, has been suggested to increase the reliability of carious tissue removal. The trial compares subjectively measured selective carious tissue removal in deep lesions in primary teeth with objectively measured selective removal with a self-limiting bur (Polybur, Komet).

METHODS AND ANALYSIS

A community-based single-blind clustered randomised controlled superiority trial nested into a larger evaluation is performed. Recruitment for this trial has been concluded. We have recruited 115 children aged 6-8 years with ≥1 vital primary molar with a deep dentin lesion. The unit of randomisation was the child, with all eligible molars per child treated identically. Treatment was performed in a mobile dental unit. Subjective and objective carious tissue removal was performed at random. Teeth were restored using glass ionomer cement (Equia Forte, GC). Our primary outcome will be the time until complications occur, evaluated via multilevel survival analysis. Secondary outcomes will be the time until extraction is needed, subjective satisfaction of the child with the treatment (measured using a Likert scale) and cost-effectiveness. Re-examination will be performed after 12, 24 and 36 months (the final examination is expected in 2020).

ETHICS AND DISSEMINATION

This trial has been approved by the Ethics Committee of the Health Sciences of the University of Brasília (CAAE 51310415.0.0000.0030). Trial results will be published in peer-reviewed journals and presented on conferences.

TRIAL REGISTRATION NUMBER

NCT02754466.

Toxic effects of four kinds of dental restorative materials on fibroblast HGF-1 and impacts on expression of Bcl-2 and Bax genes

The aim of this study was to investigate and discuss the toxic effect of four kinds of dental restorative materials on fibroblast HGF-1 and their impacts on the expression of B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax) genes. One hundred and ninety-two patients (240 diseased teeth), who received dental restoration in the Department of Stomatology of Xuzhou Stomatology Hospital from March 2014 to March 2015, were selected and randomly divided into four groups; namely, silver amalgam group, glass-ionomer cement group, nichrome group and novel nano-composite resin group, with 60 teeth in each group. The diseased teeth were restored. The fibroblast HGF-1 was incubated in the water extracts from the four kinds of materials and ordinary cell culture fluid (negative control). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to measure the levels of Bcl-2 and Bax. A flow cytometer was applied to detect cell apoptosis. RT-qPCR results showed that compared with those in the negative control group, the mRNA expression levels of Bcl-2 in the cells of silver amalgam group, glass-ionomer cement group and nichrome group were decreased, while those of Bax were upregulated (P<0.05). The mRNA expression of Bcl-2 in glass-ionomer cement group was the highest among these three groups; the mRNA expression of Bax in nichrome group was the highest of all groups. The western blotting results revealed the same tendency as those of RT-qPCR. The results via the flow cytometer showed that cell apoptosis in nichrome group, silver amalgam group and glass-ionomer cement group was increased significantly (P<0.05) compared with that in the negative control group. The novel nano-composite resin has no obvious toxic effect on cells, and its clinical application effect is better than that of traditional dental restorative materials, which is worthy of application and generalization in clinical practice.

Selective vs stepwise removal of deep carious lesions in primary molars: 12-Months results of a randomized controlled pilot trial

OBJECTIVES

For deep carious lesions, selective or stepwise carious tissue removal (SE, SW) seem advantageous compared with non-selective removal. For primary molars, there is insufficient evidence comparing SE against SW. This randomized pilot trial compared SE and SW over 12 months.

METHODS

A two-arm superiority trial was conducted comparing SE and SW in primary molars with deep lesions but without pulpal symptoms. We recruited 74 children (one molar/child) aged 3-9 years. In both groups, peripheral carious tissue removal was performed at T1 to hard dentin. In proximity to the pulp, leathery dentin was left followed by an adhesive compomer restoration. Blinded re-examination was performed after six months (T2). Molars allocated to SW were re-entered, removal to firm dentin carried out pulpo-proximally, and again restored. After another 6 months, all molars were re-examined (T3). Our primary outcome was success, defined as no restorative/endodontic complications (including pulp exposure) leading to reinterventions. Secondary outcomes included total treatment and opportunity costs. Patients', dentists' and parents' subjective assessments were recorded. This trial was registered (ClinicalTrials.gov/NCT02232828).

RESULTS

After 12 months a total of 72 children (36 SE, 36 SW) were analyzed. Three failures occurred (2 exposures in SW, 1 pulpal complication leading to extraction in SE) (p > 0.05). The subjective evaluation by patients, parents or dentists did not differ significantly. Combined treatment and opportunity costs were significantly higher in SW (mean;SD: 186;61 Euro) than SE (100;59) (p < 0.001).

CONCLUSIONS

The significantly increased costs for performing SW instead of SE in deep carious lesions in primary molars may not be justified.

CLINICAL SIGNIFICANCE

For primary molars with deep lesions, but vital pulps, SE was less costly at similar efficacy compared with SW. Dentists' decision-making should consider this alongside further clinical aspects.

Retentive strength and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent: An in vitro pilot study

STATEMENT OF PROBLEM

Information on the properties of a relatively new luting agent with a unique formulation (ceramic-reinforced calcium phosphate) is limited.

PURPOSE

The purpose of this in vitro study was to compare the retentive strengths and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent (CM) with a self-adhesive resin luting agent (RX) and to determine and compare the mode of failure of dislodged cemented copings.

MATERIAL AND METHODS

Forty extracted human molar teeth were prepared to receive zirconia copings. After cementation, the specimens were divided into 4 subgroups (n=10): CM A (axial loading), CM OA (off-axis loading), RX A (axial loading), and RX OA (off-axis loading). For each subgroup, 9 of the specimens received experimental treatment (thermocycling and dynamic loading), and the tenth received no experimental treatment. Eight copings were pulled off in a universal testing machine (MTS Insight; MTS). The ninth specimen was treated experimentally but was not pull tested. The marginal discrepancy and the dentin interface of the specimens that were not pull tested were analyzed with scanning electron microscopy and energy dispersion spectroscopy. The mode of failure of the dislodged copings was also subjectively evaluated.

RESULTS

The mean retentive strengths were 5.92 MPa for CM A, 5.81 MPa for CM OA, 5.75 MPa for RX A, and 5.69 MPa for RX OA. The marginal discrepancy recorded for both CM and RX ranged from 30 to 45 μm, (mean, 36 ±4.6 μm). Energy dispersion spectroscopy analysis showed the presence of calcium, phosphorus, silicon, and aluminum for the CM marginal discrepancy and the presence of aluminum in the dentinal tubules adjacent to the CM. Calcium and phosphorus were detected in lesser amounts adjacent to the RX marginal discrepancy. The mode of failure for CM was primarily adhesive to the tooth preparation, and, for RX, the failure mode was predominantly adhesive to the coping.

CONCLUSIONS

CM had statistically significantly higher mean retentive strength compared with RX. Subgroups loaded axially had statistically significantly higher retentive strengths compared with those loaded off axis.

Antibiofilm properties of model composites containing quaternary ammonium methacrylates after surface texture modification

OBJECTIVE

Investigate antimicrobial properties and surface texture of model composites with different concentration and alkyl chain length of quaternary ammonium monomers (QAS).

METHODS

Monomers derived from QAS salts with alkyl chain lengths of 12 carbons ((dimethylaminododecyl methacrylate) DMADDM) and 16 carbons (dimethylaminohexadecyl methacrylate-DMAHDM) were obtained from the reactions of their respective organo-halides with the tertiary amine 2-(dimethylamino)ethyl methacrylate (DMAEMA). DMADDM and DMAHDM were incorporated into model composite in concentrations of 5 or 10%, resulting the following groups: G12.5 (DMADDM 5%), G12.10 (DMADDM 10%), G16.5 (DMAHDM 5%), G16.10 (DMAHDM 10%) and GC (control). Biofilm viability, lactic acid production and surface roughness were analysed 24h after samples preparation (initial), repeated after toothbrush abrasion and after polishing simulation. Data were submitted to ANOVA and Tukey's test (p≤0.05).

RESULTS

The longer the molecular chain size of QAS and the higher its concentration (G16.10), the lower was the viability and the production of lactic acid by the biofilm. No differences were detected in initial roughness' measurements among groups. However, after abrasion, there was an increase of biofilm viability and lactic acid production. Composites containing QAS presented rougher surfaces compared to the CG. After polishing, biofilm viability and surface roughness were statistically similar for all groups. Nevertheless, DMAHDM at 10% showed reduction in lactic acid production.

SIGNIFICANCE

Chain length and concentration of QAS influenced biofilm development and production of lactic acid. Longer chains and higher concentrations of QAS promoted better antimicrobial properties. Changes in surface texture caused by abrasion, decreased antibiofilm properties.

Models of Caries Formation around Dental Composite Restorations

The main reason cited for the replacement of dental composite restorations is the recurrence of caries. Numerous models-both in vitro, with acid gels or bacterial biofilms, and in situ, with dental appliances-have been used to study caries formation around dental composites. The literature shows that many factors may affect caries formation, including marginal gap formation, gap size, the local chemical environment, the durability of the bonded interface, the extent of bacterial penetration, and the presence of mechanical loading. Studies have also shown that what have been called wall lesions may form independent of surface lesions, though not likely due to microleakage through very small gap spaces in the clinical situation. Gap size and mechanical loading have been shown to be related to lesion severity within in vitro models, but these results do not correspond exactly with those obtained from in situ studies using restorations in dental appliances. Though not conclusive, some in vitro models have shown that certain materials possessing antimicrobial characteristics may reduce the severity of lesion formation, suggesting possible pathways for developing new composite and adhesive materials for restorations with potentially enhanced longevity.

Association and comparison between visual inspection and bitewing radiography for the detection of recurrent dental caries under restorations

PURPOSE

The aim of the present study was to investigate, in posterior teeth, the association between the characteristics of the margins of a restoration visually inspected and the presence, under restorations, of recurrent or residual dental caries detected by radiographic examination. Furthermore, the agreement between visual inspection and radiographs to detect dental caries was assessed.

METHODS

Eighty-five permanent molars and premolars with resin restorations on the interproximal and/or occlusal faces, from 18 patients, were submitted for visual inspection and radiographic examination. The visual inspection involved the criteria of the International Caries Detection and Assessment System (ICDAS). Bitewing radiographs were used for the radiographic examination. Logistic regression was used to analyse the association between the characteristics of the margins of a restoration assessed by visual inspection (absence of dental caries, or early, established, inactive and active lesions) and the presence of recurrent caries detected by radiographs. Kappa coefficients were calculated for determining agreement between the two methods.

RESULTS

The Kappa coefficient for agreement between visual inspection and radiographic examination was 0.19. Established lesions [odds ratio (OR) = 9.89; 95% confidence interval (95% CI): 2.94-33.25; P < 0.05] and lesion activity (OR = 2.57; 95% CI: 0.91-7.27; P < 0.05) detected by visual inspection, were associated with recurrent or residual dental caries detected by radiographs. Restorations with established and active lesions at the margins had a greater chance of exhibiting recurrent or residual lesions in the radiographic examination.

CLINICAL SIGNIFICANCE

The present findings demonstrate that restorations with established and active lesions at the margins when visually inspected often require removal and retreatment.