Chapter 9.4: Operative Treatment and Monitoring of Coronal Caries in Daily Practice.

After the caries lesion reaches a certain extent of tooth structure loss, a restoration is often needed to repair the defect. Operative interventions in cariology aim to aid biofilm removal and lesion arrest by cavity sealing, avoid pulpal damage, and restore form, function, and esthetics. There are no clear evidence-based parameters to determine the most appropriate treatment option for each clinical situation. Despite of this, direct composite resins have been the preferable restorative treatment. Scientific literature shows that composites and adhesive strategies play a minor role in treatment success. Patient-related risk factors (mainly those associated with lifestyle and health choices), in addition to the dentist's decision-making process, play a significant role in longevity of the restorations, which tend to fail for the same reasons that lead to the need for restoration (dental caries, tooth/restoration fracture, and esthetics). Therefore, monitoring old restorations in clinical service, even if those present clear signs of degradation, is possible and reasonable within the concept of minimal intervention in dentistry. Unnecessary reinterventions are harmful and costly to health systems, and the clinician's efforts must be directed to eliminating or reducing the etiological factors that can cause the restoration to fail. Thus, patient risk factors assessment is a crucial point in monitoring restorations. Clinician should - whenever possible - postpone operative reinterventions, monitoring the etiological factors that may compromise the restoration's longevity. Also, when operative reintervention is necessary, refurbishment, polishing, and repair should be prioritized over replacement.

Clinical performance of posterior resin composite restorations after up to 33 years.

OBJECTIVES: This retrospective study evaluated the performance of posterior composites after up to 33 years of clinical service and investigated factors associated with the risk of failures over time including patient- and tooth-related variables. METHODS: Patients who received at least one Class I or Class II direct composite restoration in a private office in 1986-1992 and had follow-up appointments were included. Failures and interventions over time were investigated using the dental records. A follow-up clinical recall was carried out in 2020. Two scenarios were considered: restorations that did not require any intervention (success) or restorations that were repaired and still functional (survival). Multivariate Cox regression analyses and Kaplan-Meier curves were performed using success and survival rates (p < 0.05). RESULTS: One hundred patient records and 683 restorations were included. A total of 353 failures were reported (success rate= 48%). Main reasons for failure were fracture and secondary caries. Most interventions after failures were repairs. Replacements were registered in 183 cases (survival rate= 73%). Annual failure rates were below 2.5% (success) and 1.1% (survival). Larger restorations and maxillary molars had higher failure risks. No significant differences in success rates among different resin composites was observed. A typical observation in this sample of restorations was the presence of moderate to advanced signs of aging, including marginal and surface staining, wear, chipping, changes in anatomical shape and translucency. Clearly aged restorations were still clinically satisfactory. SIGNIFICANCE: This long-term, practice-based study indicates that resin composites can be used to restore posterior teeth with a long-lasting durability.

Email Vs. Instagram Recruitment Strategies For Online Survey Research.

In this study, we describe a method for reaching a target population (i.e., dentists practicing in Brazil) to engage in survey research using traditional e-mail invites and recruitment campaigns created on Instagram. This study addresses methodological aspects and compares respondents reached by different methods. A pre-tested questionnaire was used and participants were recruited for 10 days via a source list of email addresses and two discrete Instagram organic open campaigns. A total of 3,122 responses were collected: 509 participants were recruited by email (2.1% response rate) and 2,613 by the two Instagram campaigns (20.7% and 11.7% conversion rates), respectively. Response/min collection rates in the first 24 h ranged between 0.23 (email) and 1.09 (first campaign). In total, 98.8% of all responses were received in the first 48 h for the different recruitment strategies. There were significant differences for all demographic variables (p< 0.001) between email and Instagram respondents, except for sex (p=0.37). Instagram respondents were slightly older, had more professional experience (years in practice), and a higher graduate education level than email respondents. Moreover, most email and Instagram respondents worked in the public sector and private practice, respectively. Although both strategies could collect responses from all Brazilian regions, email responses were slightly better distributed across the five territorial areas compared to Instagram. This study provides evidence that survey recruitment of a diverse, large population sample using Instagram is feasible. However, combination of email and Instagram recruitment led to a more diverse population and improved response rates.

Email vs. instagram recruitment strategies for online survey research

Abstract In this study, we describe a method for reaching a target population (i.e., dentists practicing in Brazil) to engage in survey research using traditional e-mail invites and recruitment campaigns created on Instagram. This study addresses methodological aspects and compares respondents reached by different methods. A pre-tested questionnaire was used and participants were recruited for 10 days via a source list of email addresses and two discrete Instagram organic open campaigns. A total of 3,122 responses were collected: 509 participants were recruited by email (2.1% response rate) and 2,613 by the two Instagram campaigns (20.7% and 11.7% conversion rates), respectively. Response/min collection rates in the first 24 h ranged between 0.23 (email) and 1.09 (first campaign). In total, 98.8% of all responses were received in the first 48 h for the different recruitment strategies. There were significant differences for all demographic variables (p< 0.001) between email and Instagram respondents, except for sex (p=0.37). Instagram respondents were slightly older, had more professional experience (years in practice), and a higher graduate education level than email respondents. Moreover, most email and Instagram respondents worked in the public sector and private practice, respectively. Although both strategies could collect responses from all Brazilian regions, email responses were slightly better distributed across the five territorial areas compared to Instagram. This study provides evidence that survey recruitment of a diverse, large population sample using Instagram is feasible. However, combination of email and Instagram recruitment led to a more diverse population and improved response rates.

Resumo Neste estudo, descrevemos um método para atingir uma população-alvo (dentistas atuando no Brasil) para se engajar em pesquisa do tipo enquete (survey) utilizando convites tradicionais por e-mail e campanhas de recrutamento criadas no Instagram. Este estudo aborda aspectos metodológicos e compara as pessoas entrevistadas alcançadas por diferentes métodos. Foi utilizado um questionário pré-testado e os(as) participantes foram recrutados(as) por 10 dias por meio de uma lista de endereços de e-mail e duas campanhas abertas orgânicas independentes no Instagram. Foram coletadas 3122 respostas: 509 participantes foram recrutados(as) por e-mail (taxa de resposta 2,1%) e 2613 pelas duas campanhas do Instagram (taxas de conversão 20,7% e 11,7%), respectivamente. As taxas de coleta de resposta/min nas primeiras 24h variaram entre 0,23 (e-mail) e 1,09 (primeira campanha). No total, 98,8% das respostas foram recebidas nas primeiras 48h para as diferentes estratégias de recrutamento. Houve diferenças significativas para todas as variáveis demográficas (p<0,001) entre recrutados(as) por e-mail e Instagram, com exceção de sexo (p=0,37). As pessoas recrutadas via Instagram eram um pouco mais velhas, tinham mais experiência profissional (anos na prática) e nível de pós-graduação superior às entrevistadas por e-mail. Além disso, a maioria dos entrevistados por e-mail e Instagram trabalhava no setor público e na prática privada, respectivamente. Embora ambas estratégias tenham sido capazes de coletar respostas de todas as regiões brasileiras, as respostas por e-mail foram ligeiramente melhor distribuídas nas cinco áreas territoriais em comparação ao Instagram. Este estudo fornece evidências de que o recrutamento de uma amostra de população diversificada e grande usando o Instagram é viável. No entanto, a combinação de e-mail e Instagram no recrutamento levou a uma população mais diversificada e melhores taxas de resposta.

COVID-19 challenges to dentistry in the new pandemic epicenter: Brazil.

A nationwide survey of dentists was carried out in Brazil, a new pandemic epicenter, to analyze how dental care coverage has been affected in public versus private networks, changes in routine and burdens, and how local prevalence of COVID-19 affects dental professionals. Dentists were recruited via email and Instagram®. Responses to a pre-tested questionnaire were collected May 15-24, 2020. COVID-19 case/death counts in the state where respondents work was used to test associations between contextual status and decreases in weekly appointments, fear of contracting COVID-19 at work, and current work status (α = 0.05). Over 10 days, 3,122 responses were received (response rate ~2.1%) from all Brazilian states. Work status was affected for 94%, with less developed regions being more impacted. The pandemic impact on clinical routine was high/very high for 84%, leading to varied changes to clinic infrastructure, personal protective equipment use, and patient screening, as well as increased costs. COVID-19 patients had been seen by 5.3% of respondents; 90% reported fearing contracting COVID-19 at work. Multilevel models showed that greater case and death rates (counted as 1000 cases and 100 deaths per million inhabitants) in one's state increased the odds of being fearful of contracting the disease (18% and 25%). For each additional 1000 cases/100 deaths, the odds of currently not working or treating only emergencies increased by 36% and 58%. The reduction in patients seen weekly was significantly greater in public (38.7±18.6) than in private clinics (22.5±17.8). This study provides early evidence of three major impacts of the pandemic on dentistry: increasing inequalities due to coverage differences between public and private networks; the adoption of new clinical routines, which are associated with an economic burden for dentists; and associations of regional COVID-19 incidence/mortality with fear of contracting the disease at work.

Treatment options for large posterior restorations: a systematic review and network meta-analysis.

BACKGROUND: The best treatment option for large caries in permanent posterior teeth is still a matter of uncertainty in dental literature. The authors conducted a network meta-analysis to address the challenges related to rehabilitation of these teeth. TYPES OF STUDIES REVIEWED: The authors selected prospective and retrospective studies that compared at least 2 different treatment alternatives for permanent teeth with a minimum of 5 years of follow-up. The authors searched databases from MEDLINE, Scopus, Cochrane Library, and Web of Science in October 2019 without language or year of publication restrictions. RESULTS: From 11,263 studies identified, 43 studies fulfilled the eligibility criteria and were included in the final review. Only 13 studies were randomized controlled trials and were classified as low risk of bias. Gold (annual failure rate of 0.29%) and metal ceramic (annual failure rate of 0.52%) crowns performed better for indirect restorations and direct resin composite performed better for direct restorations (annual failure rate of 2.19%). The most substantial comparisons were between feldspathic and glass ceramics, followed by direct resin composite and amalgam; there were no statistically significant differences between these interventions. Results of the pairwise meta-analysis showed mainly glass ionomer as significantly more prone to failure than amalgam and direct composite resin. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Reference standard direct and indirect materials except for glass ionomer can be used for restorations of large posterior caries.

Aging Reduces the Anticaries Effect of Antibacterial Adhesive - An In Vitro Biofilm Study.

PURPOSE: This in vitro study investigated whether aging different restorative materials influences secondary caries development using a short-term in vitro biofilm model, hypothesizing that the antibacterial adhesive employed may lose its effect over time. MATERIALS AND METHODS: Sixty enamel-dentin blocks were divided into 6 groups with n = 10 per group. The groups were restored with three different restorative materials, of which each sample contained an artificial gap: composite with conventional adhesive (CCA; negative control), composite with an antibacterial adhesive (CAA), and amalgam (A; positive control). Half of the groups were prepared fresh and half of the groups were submitted to an aging protocol consisting of water storage, thermocycling, storage in human saliva, and storage in 0.9% saline solution. All specimens were subjected to an intermittent 1% sucrose biofilm model for 20 days to create artificial caries lesions. Lesion progression in the enamel and dentin next to the different materials was measured as lesion depth (LD) and mineral loss (ML), using transverse wavelength independent microradiography (T-WIM). Regression analysis was used to evaluate the effect of aging on LD and ML per restorative material, corrected for gap size. RESULTS: In the amalgam group, aging led to shallower lesions and less mineral loss. Fresh amalgam samples showed an average lesion depth of 156.65 ± 39.18 µm at wall dentin locations. Aged amalgam samples had an average lesion depth of 73.42 ± 73.50 µm. Fresh CAA samples showed lower average surface mineral loss values (9104 ± 2631 µm•vol%) than did fresh CCA samples (13166 ± 4769 µm•vol%). After aging, this effect was absent, and the average mineral loss in the CAA group was 13382 ± 5586 µm•vol%, while in the CCA group it was 15518 ± 9283 µm•vol%. CONCLUSION: Aging can influence secondary caries development either positively or negatively depending on the kind of restorative material. Antibacterial adhesives may lose their effectiveness over time.

Impact of a diagnostic workshop on undergraduate teaching-learning process for the diagnosis and management of tooth restorations-A randomised controlled study.

OBJECTIVE: The aim of this study was to investigate the impact of a diagnostic workshop on undergraduate teaching-learning process for the diagnosis and management of tooth restorations. METHODS: The first stage of the study was a randomised controlled study with two parallel groups: lecture (L) and lecture coupled with a diagnostic workshop (LW). A pool of cases of tooth restorations including secondary caries and marginal defects was used for training. Theoretical knowledge, perception about the activity and practical abilities were evaluated. The second stage of the study assessed students' theoretical knowledge retention six months following intervention. All students included in the first stage of the study were exposed to LW. Hence, a new control group of students not exposed to LW was selected. One-way analysis of variance, Fisher's exact test, Kruskal-Wallis test and multilevel regression analysis were used as part of statistical analysis. RESULTS: The LW group had greater scores for the assignment of lesion severity and activity, presence of marginal defect and treatment indication than the L group (P < 0.05). Multilevel regression analysis showed a positive impact of the workshop diagnosis in the correct assessment of lesion activity (P = 0.03). There was no statistical difference between the LW and L groups in students' perception of the activity. The LW group showed greater knowledge retention after six months than the L group (P = 0.027). CONCLUSION: Lecture coupled with diagnostic workshop improved students' practical skills of diagnosis restorations and knowledge retention in the six months following intervention.

Impact of individual-risk factors on caries treatment performed by general dental practitioners.

OBJECTIVE: This prospective study investigated how individual patient risk factors impacted non-operative and operative treatment decisions in a dental practice-based research network in The Netherlands. METHODS: Data from were collected from 11 dental practices, whose patients visited the practice at least once during the observation period (January 2015 to September 2017). Descriptive analysis was performed, followed by multiple logistic regression. RESULTS: The records of 39,690 patients were analyzed. Approximately one-half of the population (n = 21,056) underwent a restoration procedure during the observation period, of which 5981 (28.4%) were classified with fair oral hygiene, and 5341 (25.4%) with a high risk for caries. The population without restorative intervention (n = 18,634) consisted mainly of patients with good oral health (n = 5132 [27.5%]) and low risk for caries (n = 7792 [41.8%]). A high risk for caries was associated with a greater chance of preventive instruction (odds ratio [OR] 1.60), applications of topical fluoride (OR 1.20) or sealants (OR 1.39), and restorative interventions (OR 5.72). There was wide variation among practices regarding the treatment provided. CONCLUSION: Of the 11 general dental practices that participated in this study, there was a higher chance of patients with a high risk for caries to receive preventive instructions, and professionally applied topical fluoride and sealants in the majority of practices promoting a personalized treatment approach to patients with caries. CLINICAL SIGNIFICANCE: A more personalized treatment approach for patients with caries was associated with a higher prevalence of high caries risk patients in the majority of practices. More studies, however, are needed to investigate whether general dental practitioners consider the assessment of individual patient risk factors in planning personalized treatment strategies.

Chlorhexidine, a Matrix Metalloproteinase Inhibitor and the Development of Secondary Caries Wall Lesions in a Microcosm Biofilm Model.

This study investigated the role of a matrix metalloproteinase (MMP) inhibitor (CHX 2%) in the development of secondary caries wall lesions in different interface conditions with small (run 1) and wider gaps (run 2). Dentin discs were restored and pretreated with or without CHX 2%. In run 1, interfaces were made with gaps of 30, 60, or 90 µm. Interfaces with composite placed directly onto the dentin were either bonded (Adper Single Bond 2) or not bonded. In run 2, interfaces were made with gaps of 100 µm, with or without adhesive on the composite side (CLEARFIL SE Bond). Interfaces were either bonded or not bonded, as in run 1. Microcosm biofilms were grown on dentin-composite samples for 14 days. Caries lesion outcomes were analyzed by transversal wavelength-independent microradiography at 3 locations: the outer surface, and the interface wall at a distance of 200 and 500 µm from the gap entrance. Linear regression analyses showed that pretreatment with MMP inhibitor did not influence progression of the wall lesion at any location (p ≥ 0.218). Interfaces with intentional gaps showed positive and significant effect on the wall lesion progression at 200 µm from the gap entrance (p ≤ 0.005). A small trend of increase in wall lesion development was observed at the 200-µm location when bonding was present on the composite side. In conclusion, the dentin pretreatment with CHX 2% was not able to slow down the development of secondary caries wall lesions in small and wide gaps in this biofilm model.

Is composite repair suitable for anterior restorations? A long-term practice-based clinical study.

OBJECTIVES: This study investigated the impact in survival, when repair is seen as failure or not, in anterior composite restorations with a retrospective 15-year follow-up study. MATERIALS AND METHODS: Data was collected from patients' files of a private dental practice, including patients with direct composite restorations placed in anterior teeth (class III, class IV, or veneer) between January 1994 and December 2009. Data were analyzed considering or not repair as failure. Statistical analysis was performed with log rank test, Kaplan-Meier, and Cox regression (p < .05). RESULTS: One hundred forty-four patients' files were included, with 634 restorations. At 15 years, Class III / IV restorations showed 69% survival and 2.4% annual failure rate (AFR) when repair was not considered as failure, and 64% and 2.9% AFR, respectively, when repair was seen as failure. For direct veneers, at 5 and 10 years of follow-up, survival dropped from 85% to 74% and from 52% to 38% respectively, when repair was considered as failure. In general, restorations placed in the upper jaw showed increased risk for failure compared to the lower jaw (p < .01), and restorations in central incisors presented a higher risk for failure compared to canines (p < .01). CONCLUSION: Composite repair seems a suitable alternative for class III, class IV, and veneer restorations since it was able to increase the survival of restorations performed in anterior teeth. CLINICAL RELEVANCE: Composite repair for anterior restorations is a suitable restorative treatment option and presents benefits over replacement, including the preservation of sound tooth structures, reduced clinical chair time, and patient anxiety.

Chemical hygiene protocols for complete dentures: A crossover randomized clinical trial.

STATEMENT OF PROBLEM: Clinical evidence on the best chemical protocol for the disinfection and removal of biofilm from complete dentures is lacking. PURPOSE: The purpose of this crossover randomized clinical trial was to assess the effectiveness of various chemical hygiene clinical protocols in reducing the microbial viability of biofilm formed on complete dentures. MATERIAL AND METHODS: In this triple-blind (participants, dentist, and outcome evaluator) study, complete denture wearers without candidiasis were randomly divided into 4 groups (n=40) according to the chemical hygiene protocol: water (placebo), 0.5% sodium hypochlorite solution, 0.12% chlorhexidine gluconate solution, and 5% sodium bicarbonate solution. The biofilm formed on the palate intaglio and denture teeth was collected and assessed in each experimental phase for quantitative microbial viability at the seventh and 14th day after using the chemical protocol. RESULTS: Two participants were lost. Data were analyzed by MANOVA and Tukey HSD tests. Soaking dentures was not effective in decreasing Candida albicans, C. non-albicans, and lactobacillus counts. The use of sodium hypochlorite and chlorhexidine decreased total microorganisms and Streptococcus mutans counts for both palate and teeth compared with water and sodium bicarbonate. The intaglio of the dentures always presented higher microbial counts than did the denture teeth. CONCLUSIONS: The use of sodium hypochlorite and chlorhexidine and mechanical cleansing with a toothbrush decreased microbial viability in healthy complete denture wearers.

Decision-making of general practitioners on interventions at restorations based on bitewing radiographs.

OBJECTIVE: The aim of this study was to compare decision-making based on bitewing analysis of restored proximal surfaces by general dental practitioners (GDPs) with diagnossis and clinical decisions made by experts in cariology and restorative dentistry. METHODS: This practice-based study used a database of 7 general dental practices. Posterior bitewing radiographs were selected from the electronic patient files of patients, and 770 cases of proximal restored surfaces were selected. Fifty percent of the cases which lead to the restorative decision, and the other half were cases decided for monitoring by the GDPs. Three experts performed radiographic assessment. The outcome variables were agreement of diagnosis and decision of treatment. Cohen's kappa statistic was used. RESULTS: For the experts, moderate to substantial intraexaminer agreement was observed for the diagnostic criteria, and kappa values of 0.77, 0.79, and 0.88 were obtained for each expert regarding the treatment assignment. Agreement between GDPs and the majority of experts for secondary caries varied between 67 and 83%. One hundred seventy-three out of 385 cases that were treated by GDPs were decided for monitoring by the experts, while 8 cases that were decided for monitoring by the GDPs were decided for treatment. The agreement between experts and GDPs was moderate for secondary caries detection, and fair for treatment decision. CONCLUSION: The GDPs tend to have a less conservative approach regarding the decision to intervene or not concerning the reassessment of restorations, showing moderate agreement with the experts for secondary caries detection and fair agreement regarding the treatment decision. CLINICAL SIGNIFICANCE: This study highlights that GDPs tend to have a less conservative approach to the decision to intervene or not in posterior restorations, compared to experts in cariology and restorative dentistry. Efforts should be made to reduce these differences based on minimally invasive dentistry.

Clinical relevance of studies on the visual and radiographic methods for detecting secondary caries lesions - A systematic review.

OBJECTIVE: Accuracy studies should associate the diagnostic criteria and outcomes collected to the treatment decision for patients to be considered clinically relevant. This systematic review performed a critical evaluation of the clinical relevance of accuracy studies on the visual and radiographic methods for secondary caries detection, and other aspects. SOURCE: The search was conducted in PubMed, SCOPUS and ISI Web of knowledge databases. STUDY SELECTION: Accuracy studies assessing clinical and/or radiographic method for evaluation of secondary caries were included. The systematization of the diagnostic criteria, lesion activity assessment and differential diagnosis of secondary caries from factors that can lead to misinterpretations were assessed. Clinical relevance was evaluated by the report of aspects related to: link to treatment decision, evaluation of patient-centered outcomes, establishment of thresholds for non-operative and operative treatment, lesion activity assessment, and reference method. Risk of bias was also assessed. A descriptive analysis was performed. DATA: Following eligibility criteria, 19 articles of the 3089 searched were reviewed. Different diagnostic criteria were reported, mainly for the visual inspection. The use of a standardized diagnostic system, lesion activity assessment and differential diagnosis were described by a limited number of studies. Approximately half of the studies reported association of diagnosis and treatment. Enamel lesions were evaluated radiographically in 28.6% of studies, and visually in 69.2%. Visual diagnosis was more relevant in relation to the operative treatment decision. Patient-centered outcomes were not investigated. CONCLUSION: The majority of studies fails to present clinical relevance and report of patient-centered outcomes.

Validation of assessment of intraoral digital photography for evaluation of dental restorations in clinical research.

OBJECTIVES: The aim of this study was to investigate the validity of assessment of intraoral digital photography in the evaluation of dental restorations. METHODS: Intraoral photographs of anterior and posterior restorations were classified based on FDI criteria according to the need for intervention: no intervention, repair and replacement. Evaluations were performed by an experienced expert in restorative dentistry (gold standard evaluator) and 3 trained dentists (consensus). The clinical inspection was the reference standard method. The prevalence of failures was explored. Cohen's kappa statistic was used. Validity was accessed by sensitivity, specificity, likelihood ratio and predictives values. RESULTS: Higher prevalence of failed restorations intervention was identified by the intraoral photography (17.7%) in comparison to the clinical evaluation (14.1%). Moderate agreement in the diagnosis of total failures was shown between the methods for the gold standard evaluator (kappa = 0.51) and consensus of evaluators (kappa = 0.53). Gold standard evaluator and consensus showed substantial and moderate agreement for posterior restorations (kappa = 0.61; 0.59), and fair and moderate agreement for anterior restorations (kappa = 0.36; 0.43), respectively. The accuracy was 84.8% in the assessment by intraoral photographs. Sensitivity and specificity values of 87.5% and 89.3% were found. CONCLUSIONS: Under the limits of this study, the assessment of digital photography performed by intraoral camera is an indirect diagnostic method valid for the evaluation of dental restorations, mainly in posterior teeth. This method should be employed taking into account the higher detection of defects provided by the images, which are not always clinically relevant.

Minimal Gap Size and Dentin Wall Lesion Development Next to Resin Composite in a Microcosm Biofilm Model.

This in vitro study investigated the development of dentin wall lesions next to resin composite containing very small gap sizes using an in vitro biofilm model, and evaluated whether a relevant threshold for the gap size could be established. Microcosm biofilms were grown for 14 days within small interfacial gaps between dentin-resin composite discs under intermittent cariogenic challenge. The factor under study was gap size: samples were either restored with composite resin without adhesive procedure (no intentional gap; no bonding [NB] group) or with intentional gaps of 30, 60, or 90 µm, or with complete adhesive procedure (no gap; bonding [B] group). Secondary caries wall lesion progression was measured in lesion depth (LD) and mineral loss (ML) using transversal wavelength independent microradiography at 3 locations: outer surface lesion and wall lesions at 200 and 500 µm distance from gap entrance. Results from linear regression analysis showed that the presence of an intentional gap (30, 60, and 90 µm) affected the secondary caries progression at 200 µm from the gap entrance (p ≤ 0.013). The NB group did not show significant wall lesion development (ML and LD, p ≥ 0.529). At 500 µm distance almost no wall caries development was observed. In conclusion, dentin wall lesions developed in minimal gap sizes, and the threshold for secondary wall lesion development was a gap of around 30 µm in this microcosm biofilm model.

Bonding Efficacy and Fracture Pattern of Adhesives Submitted to Mechanical Aging with the Rub&Roll Device.

PURPOSE: To evaluate the effect of water storage and cyclic loading on the microtensile bond strength (µTBS) and fracture pattern of adhesives to dentin. MATERIALS AND METHODS: Midcoronal dentin surfaces (n = 36) were prepared and composite restorations were built up using two adhesives (self-etch and etch-and-rinse). The specimens were randomly divided into 3 groups according to the aging conditions (n = 6): 1. CONTROL: storage in water for 24 h (CO); 2. water storage: storage in water for 6 months (WS); 3. mechanical loading: 750,000 mechanical cycles (ML) using the Rub&Roll loading device. Specimens were sections into beams and the µTBS was tested. Fracture patterns were analyzed using stereomicroscopy and fractographic analysis was performed using SEM. µTBS data (n = 53-72 specimens) were subjected to two-way ANOVA and Tukey's post-hoc test. The chi-squared test was used to compare the distribution of failure modes (p < 0.05). RESULTS: Aging conditions and adhesives significantly affected µTBS (p < 0.01). The CO group showed no difference between materials and had highest µTBS. After WS, the self-etch adhesive showed higher µTBS than did the etchand- rinse adhesive. ML resulted in lower µTBS for both adhesives. Materials (p < 0.01) and aging (p < 0.01) significantly influenced the distribution of failure modes. SEM analysis showed that specimens submitted to WS or ML showed features of degradation and fatigue at the fractured interface, depending on the adhesive. CONCLUSION: Mechanical loading had a negative effect on the bonding efficacy of both adhesives and influenced the fracture pattern, with specimens presenting a different fracture surface from that observed in water-stored specimens.

Failed bonded interfaces submitted to microcosm biofilm caries development.

OBJECTIVES: This study aimed to evaluate the dentin wall carious lesion development of different composite-dentin interfaces in the presence of two adhesive bonding materials in the gaps, using a microcosm biofilm model. METHODS: Dentin samples were prepared (10.4mm(2)) and restored with a composite resin using two adhesive systems (etch-and-rinse and self-etch techniques). Different conditions with respect to composite-dentin interfaces were produced with a 200µm gap: failed bonded without ageing or after mechanical ageing, or non-bonded with or without the presence of adhesive material on the dentin wall. For cariogenic challenge, specimens were subjected to a biofilm microcosm model for 14days to create caries-like wall lesions. Before and after caries development, transverse wavelength-independent microradiography images were taken, and lesion depth and mineral loss were measured. Data were analysed with linear regression models (p<0.05). RESULTS: The composite-dentin interface conditions significant influenced the caries development: lesion development was reduced by the presence of the adhesive material on dentin wall, while lesion development was increased by the mechanical ageing (p=0.019). There was no difference between the adhesive materials (p values>0.05). CONCLUSION: Different composite-dentin interfaces influence wall lesion development in gaps, with the interfaces submitted to ageing showing less carious protection than those interfaces with the presence of adhesive covering the dentin. CLINICAL SIGNIFICANCE: The presence of adhesive bonding material in the gaps plays a role on the wall caries lesion development.

Behavior of failed bonded interfaces under in vitro cariogenic challenge.

OBJECTIVE: This in vitro study aimed to compare dentin wall caries development at different composite-dentin interfaces. METHODS: Dentin samples (10.4 mm(2)) were restored with composite resin using two adhesive systems (etch-and-rinse and self-etch techniques). Different composite-dentin interfaces with gaps were produced: (a) failed bonded, which were fractured at interface after being submitted to aging protocols (no aging, mechanical loading or water storage); (b) non-bonded interfaces, both without any adhesive material or with adhesive material applied only on the dentin. Adhesively fractured and non-bonded samples were subjected to a lactic acid gel (pH=5) caries model with a continuous opening/closing movement of the interfacial gap for 10 days. Transverse wavelength-independent microradiographs were taken, and lesion depth and mineral loss were measured. Data were analyzed with linear mixed-effects regression models. RESULTS: Caries development differed among the composite-dentin interfaces (p<0.001). The non-bonded interface with adhesive material on the dentin showed less lesion depth than the failed bonded groups, while the non-bonded interface without adhesive on dentin showed the deepest wall lesions. Difference between the adhesive systems was observed only in the non-bonded groups (p=0.003), with the self-etch adhesive applied on the dentin showing more severe lesions. Samples broken after mechanical loading aging showed deeper lesions than those broken after water storage (p<0.001). SIGNIFICANCE: Composite-dentin interfaces failed after aging presented different demineralization from interfaces that were never bonded, indicating that the restorative treatment changes the tissue in a way relevant to secondary caries development.

Influence of the Inoculum Source on the Cariogenicity of in vitro Microcosm Biofilms.

This study investigated the cariogenic potential of biofilms originating from different types of inoculum (saliva and dental plaque) from caries-active and caries-free individuals. Ten volunteers were selected from each caries condition for the paired collection of saliva and dental plaque. Microcosm biofilms were grown in triplicate from each inoculum on enamel specimens in 24-well plates under cariogenic challenge. After 10 days, the biofilms were collected for analysis of outcome variables: percentage of surface hardness change (%SHC) and microbiological composition of biofilms. Statistical analysis was performed using the t test, the linear multivariate analysis model and Pearson's correlation coefficients (α = 0.05). A comparative analysis between microbiological baseline data showed higher counts of mutans streptococci in plaque samples within caries-active individuals; a comparative analysis of colony-forming unit (CFU) counts between individuals with different caries status showed higher counts of acid-tolerant microorganisms and mutans streptococci in dental plaque and of acid-tolerant microorganisms in saliva. After 10 days of biofilm growth, the CFU values for total microorganisms, lactobacilli, mutans streptococci and acid-tolerant bacteria, as well as for SHC, were not statistically significant, considering the type of inoculum and caries condition (p > 0.05). A positive correlation was found for %SHC and CFU counts of acid-tolerant bacteria (r = 0.406) and lactobacilli (r = 0.379). Under the limits of this study, the cariogenic potential of biofilms, formed under identical conditions in vitro, is similar, regardless of baseline differences between the source and type of inoculum.