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

Buonocore Memorial Lecture 2023: Longevity of Dental Restorations or Longevity of Teeth: What Matters?

This paper aims to raise a discussion from the perspective of maintaining long-term oral health, posing a critical question: What holds greater significance for maintaining oral health, the longevity of restorations or teeth? This question explores the aspects that truly matter in ensuring sustained oral health throughout an individual's life. Restoration longevity is well-researched, and evidence shows several risk factors influencing longevity. The dentist's decision-making factor may be of utmost importance, and further studies are needed to investigate its relevance. The critical risk factors for restoration longevity are active pathology (high caries risk), less prominent parafunction, and extensive defects such as endodontic treatment. However, tooth longevity and the main risk factors for tooth loss are not well-researched. The evidence shows dental caries, and its sequelae, are the principal reasons for tooth loss. Patient-related risk factors, especially those associated with lifestyle and health choices, play a major role in the longevity of restorations and, more importantly, tooth longevity. To provide personalized dental care with maximum patient benefit, clinicians should identify and record potential risk factors, promoting a healthy lifestyle to ensure tooth and dentition longevity. Moreover, the evidence suggests that decision-making frameworks based on minimal intervention principles offer the best standard for clinical practice, promoting a longstanding healthy oral environment.

Current approaches to produce durable biomaterials: Trends in polymeric materials for restorative dentistry applications

Dental caries continues to be a public health issue, especially more evident in underserved populations throughout the U.S. Unfortunately, especially with an aging population, hundreds of thousands of resin composite restorations are replaced each year due to recurring decay and fracture. According to several cohort studies, the average life span of this type of restoration is 10 years or less, depending on the caries risk level of the patient and the complexity of the restorative procedure. Any new material development must depart from the simple restoration of form paradigm, in which the filling is simply inert/biocompatible. This review will discuss novel antibiofilm structures, based on a targeted approach specifically against dysbiotic bacteria. Biofilm coalescence can be prevented by using glycosyl transferase - GTF inhibitors, in a non-bactericidal approach. On the tooth substrate side, MMP-inhibiting molecules can improve the stability of the collagen in the hybrid layer. This review will also discuss the importance of testing the materials in a physiologically relevant environment, mimicking the conditions in the mouth in terms of mechanical loading, bacterial challenge, and the presence of saliva. Ultimately, the goal of materials development is to achieve durable restorations, capable of adapting to the oral environment and resisting challenges that go beyond mechanical demands. That way, we can prevent the unnecessary loss of additional tooth structure that comes with every re-treatment. CLINICAL SIGNIFICANCE: While proper restorative technique and patient education in terms of diet and oral hygiene are crucial factors in increasing the longevity of esthetic direct restorations, materials better able to resist and interact with the conditions of the oral environment are still needed. Reproducing the success of dental amalgams with esthetic materials continues to be the Holy Grail of materials development.

Survival rate of teeth adjacent and nonadjacent to dental implants: A retrospective cohort study

BACKGROUND

The aim of this retrospective study was to investigate the risk of tooth loss for teeth adjacent and nonadjacent to dental implants.

METHODS

A total of 787 patients with an average follow-up of 57.1 months were examined to define the tooth loss, cumulative survival rate, and odds ratio (OR) for teeth adjacent versus nonadjacent to implants. A multivariate logistic regression was employed to assess the association between dental history and various recorded etiologies of tooth loss among teeth adjacent to implants.

RESULTS

The incidence of tooth loss for teeth adjacent to implants was 8.1% at the tooth level and 15.1% at the patient level, while 0.7% and 9.5% at the tooth and patientlevel for teeth nonadjacent to implants. The 10-year cumulative survival rate for teeth adjacent to implants was 89.2%, and the primary etiology of tooth loss was root fracture (45.2%). The risk of tooth loss among teeth adjacent versus nonadjacent to implants was significantly higher (OR 13.15). Among teeth adjacent to implants, root canal-treated teeth had a significantly higher risk of tooth loss due to root fracture (OR 7.72), a history of existing restoration significantly increased the risk of tooth loss due to caries (OR 3.05), and a history of periodontitis significantly increased the risk of tooth loss due to periodontitis (OR 38.24).

CONCLUSION

The present study demonstrated that after patients received dental implant treatment, teeth adjacent to implants showed a 13.2-fold higher risk of tooth loss compared to teeth nonadjacent to implants, with the primary etiology being root fracture.

Applications of smart materials in minimally invasive dentistry - some research and clinical perspectives

OBJECTIVES

Dental caries is one of the most prevalent bacteria-induced non-communicable diseases globally. It is known to be the top oral health burden in both developing and developed nations. There is substantial literature on the disease process and there is still debate on the extent of caries removal needed and the adequacy of the materials available to restore the lost tooth structure. The current review discusses the disease process together with the contemporary management of the carious lesion and also presents substantial evidence on novel materials and techniques that make minimally invasive dentistry predictable.

METHODS

The written work presented shows the most relevant literature for the management of dental caries focusing on novel materials used in minimally invasive dentistry.

RESULTS

There is still much to learn about specific antimicrobial and caries prevention mechanisms of novel materials. Materials that respond to a single or a few stimuli remain "weakly intelligent" in the face of the complex microenvironment in the oral cavity. Engineered systems that combine artificial intelligence and chemical engineering, are expected to possess higher intelligence, self-healing capabilities as well as environmental adaptability, and may be future promising research directions.

SIGNIFICANCE

The targeted approach in managing dental caries will hopefully have a better clinical outcome. The strategies discussed are alternatives to the contemporary approach and will improve the clinical management.

Synergistic effects of bacteria, enzymes, and cyclic mechanical stresses on the bond strength of composite restorations

Predicting how tooth and dental material bonds perform in the mouth requires a deep understanding of degrading factors. Yet, this understanding is incomplete, leading to significant uncertainties in designing and evaluating new dental adhesives. The durability of dental bonding interfaces in the oral microenvironment is compromised by bacterial acids, salivary enzymes, and masticatory fatigue. These factors degrade the bond between dental resins and tooth surfaces, making the strength of these bonds difficult to predict. Traditionally studied separately, a combined kinetic analysis of these interactions could enhance our understanding and improvement of dental adhesive durability. To address this issue, we developed and validated an original model to evaluate the bond strength of dental restorations using realistic environments that consider the different mechanical, chemical, and biological degradative challenges working simultaneously: bacteria, salivary esterases, and cyclic loading. We herein describe a comprehensive investigation on dissociating the factors that degrade the bond strength of dental restorations. Our results showed that cariogenic bacteria are the number one factor contributing to the degradation of the bonded interface, followed by cyclic loading and salivary esterases. When tested in combinatorial mode, negative and positive synergies towards the degradation of the interface were observed. Masticatory loads (i.e., cycling loading) enhanced the lactic acid bacterial production and the area occupied by the biofilm at the bonding interface, resulting in more damage at the interface and a reduction of 73 % in bond strength compared to no-degraded samples. Salivary enzymes also produced bond degradation caused by changes in the chemical composition of the resin/adhesive. However, the degradation rates are slowed compared to the bacteria and cyclic loading. These results demonstrate that our synergetic model could guide the design of new dental adhesives for biological applications without laborious trial-and-error experimentation.

Effects of a Novel Magnetic Nanomaterial on Oral Biofilms

Dental caries is one of the most common oral chronic infectious diseases, and novel antibacterial materials must be developed to control plaque and inhibit formation of dental caries. Combining magnetic nanomaterials with antibacterial agents to decrease the formation of bacterial biofilm has been a hot topic in the biomedical field. The present study developed a novel magnetic nanomaterial chemically combined with dimethylaminododecyl methacrylate (DMADDM) and initially investigated its inhibiting effects on biofilms by using traditional caries-related bacteria and saliva flora models. The novel magnetic nanomaterials successfully loaded DMADDM according to thermogravimetric analysis, Fourier transform infrared spectroscopy, x-ray diffraction, vibrating sample magnetometry, scanning electron microscopy, and transmission electron microscopy results. Further, the novel nanoparticle Fe3O4@SiO2@DMADDM with concentration of 8 mg/mL could effectively reduce Streptococcus mutans biofilm and decrease the production of lactic acid. The 16S rDNA sequencing revealed that Fe3O4@SiO2@DMADDM could depress the proportion of caries-related bacteria in saliva-derived biofilm, such as Streptococcus, Veillonella, and Neisseria. Therefore, Fe3O4@SiO2@DMADDM is a novel effective antibacterial magnetic nanomaterial and has clinical potential in plaque control and dental caries prevention.

Antibacterial Dental Adhesive Containing Cetylpyridinium Chloride Montmorillonite

Oral bacteria cause tooth caries and periodontal disease. Much research is being conducted to prevent both major oral diseases by rendering dental materials' antimicrobial potential. However, such antimicrobial materials are regarded as 'combination' products and face high hurdles for regulatory approval. We loaded inorganic montmorillonite with the antimicrobial agent cetylpyridinium chloride, referred to below as 'CPC-Mont'. CPC-Mont particles in a 1, 3 and 5 wt% concentration were added to the considered gold-standard self-etch adhesive Clearfil SE Bond 2 ('CSE2'; Kuraray Noritake) to render its antibacterial potential (CSE2 without CPC-Mont served as control). Besides measuring (immediate) bonding effectiveness and (aged) bond durability to dentin, the antibacterial activity against S. mutans and the polymerization-conversion rate was assessed. Immediate and aged bond strength was not affected by 1 and 3 wt% CPC-Mont addition, while 5 wt% CPC-Mont significantly lowered bond strength and bond durability. The higher the concentration of the antimicrobial material added, the stronger the antimicrobial activity. Polymerization conversion was not affected by the CPC-Mont addition in any of the three concentrations. Hence, adding 3 wt% CPC-Mont to the two-step self-etch adhesive rendered additional antimicrobial potential on top of its primary bonding function.

Stability of the Dentin-Bonded Interface Using Self-Etching Adhesive Containing Diacrylamide after Bacterial Challenge

Purpose/Aim: Acrylamides are hydrolytically stable at pH lower than 2, and were shown to preserve bonded interface integrity with two-step, total etch adhesives. The objective of this study was to leverage those two characteristics in self-etching primers containing the acidic monomer 10-MDP and test the microtensile bond strength before and after incubation with S. mutans incubation. Materials and Methods: Acidic primers (10 wt % 10-methacryloyloxydecyl dihydrogen phosphate─10-MDP; 45 wt % N,N-diethyl-1,3-bis(acrylamido)propane─DEBAAP, or 2-hydroxyethyl methacrylate─HEMA; 45 wt %, glycerol-dimethacrylate─GDMA) and adhesives (DEBAAP or HEMA/10-MDP/UDMA 45/10/45 wt %) were made polymerizable by the addition of 0.2 wt % camphorquinone, 0.8 wt % ethyl-4-dimethylaminobenzoate, 0.4 wt % diphenyliodonium hexafluorophosphate, and 0.1 wt % butylhydroxytoluene. Nonsolvated materials were characterized for flexural strength (FS), modulus (E), toughness, water sorption/solubility (WS/SL), contact angle, and vinyl conversion (DC). Viscosity was evaluated after adding 20 and 40 vol % ethanol to the primer and adhesive, respectively. The experimental materials or Clearfil SE Bond (CC─commercial control) were used to bond a commercial composite (Filtek Supreme) to the flat surface of human dentin. Microtensile bond strength (MTBS) was tested in 1 mm2 sticks for the 5 primer/bond combinations: CC (Clearfil Bond Primer and Bond), HH (HEMA/HEMA), DD (DEBAAP/DEBAAP), HD (HEMA/DEBAAP), and DH (DEBAAP/HEMA). Prior to testing, sticks were stored in water or biofilm-inducing culture medium with S. mutans for 1 week. Confocal images and FTIR-ATR evaluation evaluated the hybrid layer of the adhesives. Results were analyzed using Student's t-test (WS, SL, DC, contact angle, FS, E, toughness), one-way ANOVA/Tukey's test for viscosity, and two-way ANOVA/Tukey's test for MTBS (95%). Results: HEMA-based materials had lower contact angle (p = 0.004), higher WS (p < 0.001), and similar SL values compared to DEBAAP (p = 0.126). FS (p = 0.171) and E (p = 0.065) dry values were similar, but after one week of water storage, FS/E dropped more significantly for HEMA materials. Dry and wet toughness was greater for DEBAAP (p < 0.001), but it also had the greatest drop (46%). Clearfil bonds had the highest viscosity, followed by DEBAAP and HEMA, respectively (p = 0.002). For the primers, HEMA had the lowest viscosity (p = 0.003). As far as MTBS, all groups tested in water were statistically different when compared with HH (p < 0.001). After storage in biofilm, DH had the highest MTBS value, being statistically different from HH (p = 0.002), CC (p = 0.015), and DD (p = 0.027). Conclusions: The addition of a diacrylamide and its association with HEMA in self-etching adhesive systems provided greater bonding stability after bacterial challenge.

Minimum intervention oral care: staging and grading dental carious lesions in clinical practice

Developmental staging of carious lesions is pivotal for appropriate ethical clinical decision-making in contemporary caries management. Accurate assessment of lesion extent/severity (staging) and activity (grading) allows practitioners to provide the most appropriate preventive advice and suitable interventions, enabling the implementation of evidence-based, person-focused, prevention-based, team-delivered and susceptibility-related phased minimum intervention oral care. Minimally invasive dentistry remains an important operative interventive option for cavitated lesions, but intervening at the right stage ensures patients are not started on an irreversible, destructive restorative cycle unnecessarily. This article provides an update on recommended practical methods for staging the extent/severity and grading the activity of dental carious lesions, especially for those clinical teams delivering primary care and needing to navigate remuneration systems.

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

OBJECTIVES

The purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites.

METHODS

The Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter.

RESULTS

Direct contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range.

SIGNIFICANCE

The addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

Preparation and antibacterial evaluation of silver-doped zirconia for enhanced dental restoration performance

Because of its superior strength, esthetic properties, and excellent biocompatibility, zirconia is preferred for dental prosthetic such as crowns and bridges. However, zirconia crowns and bridges are susceptible to secondary caries owing to margin leakage. Silver is a well-known antibacterial agent, making it a desirable additive to zirconia crowns and bridges for secondary caries prevention. This study focuses on imparting zirconia composite with antibacterial properties to enhance its protective capacity in dental restorations. We used the sol-gel method to dope Ag into zirconia. Silver-doped zirconia powders were prepared at Zr:Ag molar ratios of 100:0,100:0.1, 100:0.5, 100:1, 100:3, and 100:5 (respective samples denoted as Ag-0, Ag-0.1, Ag-0.5, Ag-1, Ag-3, and Ag-5) and were subjected to firing at various temperatures (400 °C-1000 °C). We performed x-ray diffraction to investigate the crystal phase of these powders and x-ray fluorescence and field emission scanning electron microscopy to analyze their elemental composition and surface morphology, respectively. Moreover, we performed spectrophotometry to determine theL*a*b* color values, conducted dissolution tests, and quantified the Ag content through inductively coupled plasma optical emission spectroscopy. In addition, we studied the antibacterial activity of the samples. Analyses of the samples fired at ⩽600 °C revealed a predominantly white to grayish-white coloration and a tetragonal crystal phase. Firing at ⩾700 °C resulted in gray or dark gray coloration and a monoclinic crystal phase. The Ag content decreased after firing at 900 °C or 1000 °C. Ag-0.5 and above exhibited antibacterial activity against bothEscherichia coliandStaphylococcus aureus. Therefore, the minimum effective silver-doped zirconia sample was found to be Ag-0.5. This study allows the exploration of the antimicrobial potential of silver-doped zirconia materials in dental applications such as prosthdontical lining materials, promoting the development of innovative restorations with protective capacity against secondary caries.

Antibacterial properties of mesoporous silica coated with cerium oxide nanoparticles in dental resin composite

Cerium oxide nanoparticles are known for their antibacterial effects resulting from Ce3+ to Ce4+ conversion. Application of such cerium oxide nanoparticles in dentistry has been previously considered but limited due to deterioration of mechanical properties. Hence, this study aimed to examine mesoporous silica (MCM-41) coated with cerium oxide nanoparticles and evaluate the antibacterial effects and mechanical properties when applied to dental composite resin. Cerium oxide nanoparticles were coated on the MCM-41 surface using the sol-gel method by adding cerium oxide nanoparticle precursor to the MCM-41 dispersion. The samples were tested for antibacterial activity against Streptococcus mutans via CFU and MTT assays. The mechanical properties were assessed by flexural strength and depth of cure according to ISO 4049. Data were analyzed using a t-test, one-way ANOVA, and Tukey's post-hoc test (p = 0.05). The experimental group showed significantly increased antibacterial properties compared to the control groups (p < 0.005). The flexural strength exhibited a decreasing trend as the amount of cerium oxide nanoparticle-coated MCM-41 increased. However, the flexural strength and depth of cure values of the silane group met the ISO 4049 standard. Antibacterial properties increased with increasing amounts of cerium oxide nanoparticles. Although the mechanical properties decreased, silane treatment overcame this drawback. Hence, the cerium oxide nanoparticles coated on MCM-41 may be used for dental resin composite.

Properties of a Dental Adhesive Containing Graphene and DOPA-Modified Graphene

Graphene is a promising biomaterial. However, its dispersion in aqueous medium is challenging. This study aimed to modify graphene nanoparticles with L-dopa to improve the properties of experimental dental adhesives. Adhesives were formulated with 0% (control), 0.25%, 0.5%, and 0.75% of graphene, modified or not. Particle modification and dispersion were microscopically assessed. Degree of conversion was tested by Fourier-transform infrared spectroscopy. Flexural strength and modulus of elasticity were evaluated by a 3-point flexural test. Bond strength was tested by shear. To test water sorption/solubility, samples were weighed during hydration and dehydration. Antibacterial activity was tested by Streptococcus mutans colony-forming units quantification. Cytotoxicity on fibroblasts was evaluated through a dentin barrier test. The modification of graphene improved the particle dispersion. Control presented the highest degree of conversion, flexural strength, and bond strength. In degree of conversion, 0.25% of groups were similar to control. In bond strength, groups of graphene modified by L-dopa were similar to Control. The modulus of elasticity was similar between groups. Cytotoxicity and water sorption/solubility decreased as particles increased. Compared to graphene, less graphene modified by L-dopa was needed to promote antibacterial activity. By modifying graphene with L-dopa, the properties of graphene and, therefore, the adhesives incorporated by it were enhanced.

Diagnostic Strategies for Restorations Management: A 70-Month RCT

We aimed to evaluate the impact of 2 visual diagnostic strategies for assessing secondary caries and managing permanent posterior restorations on long-term survival. We conducted a diagnostic cluster-randomized clinical trial with 2 parallel groups using different diagnostic strategies: (C+AS) based on caries assessment, marginal adaptation, and marginal staining aspects of the FDI (World Dental Federation) criteria and (C) based on caries assessment using the Caries Associated with Restorations or Sealants (CARS) criteria described by the International Caries Detection and Assessment System (ICDAS). The treatment for the restoration was conducted based on the decision made following the allocated diagnostic strategy. The restorations were then clinically reevaluated for up to 71 mo. The primary outcome was restoration failure (including tooth-level failure: pain, endodontic treatment, and extraction). Cox regression analyses with shared frailty were conducted in the intention-to-treat population, and hazard ratios (HRs) and 95% confidence intervals (95% CIs) were derived. We included 727 restorations from 185 participants and reassessed 502 (69.1%) restorations during follow-up. The evaluations occurred between 6 and 71 mo. At baseline, C led to almost 4 times fewer interventions compared with the C+AS strategy. A total of 371 restorations were assessed in the C group, from which 31 (8.4%) were repaired or replaced. In contrast, the C+AS group had 356 restorations assessed, from which 113 (31.7%) were repaired or replaced. During follow-up, 34 (9.2%) failures were detected in the restorations allocated to the C group and 30 (8.4%) allocated to the C+AS group in the intention-to-treat population, with no significant difference between the groups (HR = 0.83; 95% CI = 0.51 to 1.38; P = 0.435, C+AS as reference). In conclusion, a diagnostic strategy focusing on marginal defects results in more initial interventions but does not improve longevity over the caries-focused strategy, suggesting the need for more conservative approaches.

An In Vitro Validation of DIAGNOdent Versus Radiography for the Detection of Caries Underneath Different Types of Restorations

Objective This study aimed to assess the validity of DIAGNOdent as a diagnostic device for the detection of secondary dental caries underneath different types of restorations. Methods A total of 60 extracted human permanent molars were used in this experimental study (30 sound teeth and 30 teeth with proximal caries); 20 teeth (10 sound and 10 carious) were randomly allocated into one of three restoration groups: composite, amalgam, or resin-modified glass ionomer (RMGI). All teeth were examined using both KaVo DIAGNOdent Classic and digital radiographic sensors. Results In the composite-restored teeth, DIAGNOdent showed excellent sensitivity (90%) and specificity (90%). On the other hand, digital radiography had high sensitivity (80%) and poor specificity (20%). In amalgam-restored teeth, DIAGNOdent showed low sensitivity (30%) and excellent specificity (100%), while radiographs showed good sensitivity (70%) and low specificity (30%). In the RMGI-restored teeth, DIAGNOdent had excellent sensitivity (100%) and 70% specificity, while digital radiography had poor sensitivity (30%) and excellent specificity (90%). Conclusions DIAGNOdent showed superior results in detecting secondary caries lesions underneath composite and RMGI restorations when compared to digital radiography. On the other hand, radiography emerged as a preferable method for the detection of secondary caries underneath amalgam restorations. Based on our findings, DIAGNOdent can be used in dental clinics for the early diagnosis of hidden secondary caries underneath composite and RMGI restorations.

Mechanical Properties of Alkasite Material with Different Curing Modes and Simulated Aging Conditions

This study aimed to evaluate the micro-mechanical and macro-mechanical properties of self-cured and light-cured alkasite and to investigate how accelerated degradation in acidic, alkaline, and ethanol solutions affects the macro-mechanical properties of self-cured and light-cured alkasite. The specimens of the alkasite material (Cention Forte, Ivoclar Vivadent) were prepared according to the following three curing modes: (1) light-cured immediately, (2) light-cured after a 5-min delay, and (3) self-cured. Microhardness was tested before and after immersion in absolute ethanol to indirectly determine crosslink density, while flexural strength and flexural modulus were measured using a three-point bending test after accelerated aging in the following solutions: (1) lactic acid solution (pH = 4.0), (2) NaOH solution (pH = 13.0), (3) phosphate-buffered saline solution (pH = 7.4), and (4) 75% ethanol solution. The data were statistically analyzed using a two-way ANOVA and Tukey post hoc test. The results showed that the microhardness, flexural strength, and flexural modulus were significantly lower in self-cured specimens compared to light-cured specimens. A 5-min delay between the extrusion of the material from the capsule and light curing had no significant effect on any of the measured properties. A significant effect of the accelerated aging solutions on macro-mechanical properties was observed, with ethanol and alkaline solutions having a particularly detrimental effect. In conclusion, light curing was preferable to self-curing, as it resulted in significantly better micro- and macro-mechanical properties, while a 5-min delay between mixing the capsule and light curing had no negative effects.

Post-failure analysis of model resin-composite restorations subjected to different chemomechanical challenges

OBJECTIVE

The current study aimed to evaluate the effects of different combinations of chemical and mechanical challenges on the failure load, failure mode and composition of the resulting fracture surfaces of resin-composite restorations.

METHODS

Three resin composites were used to fill dentin disks (2 mm inner diameter, 5 mm outer diameter, and 2 mm thick) made from bovine incisor roots. The model restorations, half of which were preconditioned with a low-pH buffer (48 h under pH 4.5), were subjected to diametral compression with either a monotonically increasing load (fast fracture) or a cyclic load with a continuously increasing amplitude (accelerated fatigue). The load or number of cycles to failure was noted. SEM was performed on the fracture surfaces to determine the proportions of dentin, adhesive, and resin composite.

RESULTS

Both cyclic fatigue and acid preconditioning significantly reduced the failure load and increased the proportion of interfacial failure in almost all the cases, with cyclic fatigue having a more pronounced effect. Cyclic fatigue also increased the amount of adhesive/hybrid layer present on the fracture surfaces, but the effect of acid preconditioning on the composition of the fracture surfaces varied among the resin composites.

SIGNIFICANCE

The adhesive or hybrid layer was found to be the least resistant against the chemomechanical challenges among the components forming the model restoration. Increasing such resistance of the tooth-restoration interface, or its ability to combat the bacterial actions that lead to secondary caries following interfacial debonding, can enhance the longevity of resin-composite restorations.

Comparative Evaluation of Microhardness and Solubility of Different Combinations of Antibiotic Powders Added to Glass Ionomer Cement: An In Vitro Study

Introduction

The imbalance between remineralization and demineralization leads to the formation of secondary caries. Fluoride-releasing ability has been the characteristic property of glass ionomer cement (GIC), but it is uncertain if this property alone will be sufficient for the cessation of the growth of the organisms. Therefore, a restorative material with additional bacteriostatic properties needs to be introduced.

Aim

To evaluate the microhardness and solubility of the conventional GIC after adding different combinations of antibiotic powders.

Materials and methods

In this study, the three groups were conventional GIC (group I), GIC + metronidazole + ciprofloxacin (group II), and GIC + metronidazole + amoxicillin/clavulanic acid (group III). The concentration of the double antibiotic combination was maintained at 1.5% w/w. The antibiotic powders were added to the GIC and evaluated for microhardness and solubility of the specimens.

Results

The mean microhardness level of group II was the highest, which was statistically significant using analysis of variance (ANOVA) with a p-value of 0.022. The comparison of each group's solubility in different solutions was not statistically significant.

Conclusion

Along with the conventional properties of GIC, an additional therapeutic gain can also be obtained by incorporating various combinations of antibiotics, thereby arresting the progression of caries at the site of infection itself.

Clinical significance

This new approach shall help in community health programs, where treatment of a large population needs to be done within a short span of time and arrest the progression of caries activity in deep caries.

How to cite this article

Benson TL, Sogi S, Jain M, et al. Comparative Evaluation of Microhardness and Solubility of Different Combinations of Antibiotic Powders Added to Glass Ionomer Cement: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(6):619-624.

AI-Assisted Detection of Interproximal, Occlusal, and Secondary Caries on Bite-Wing Radiographs: A Single-Shot Deep Learning Approach

Tooth decay is a common oral disease worldwide, but errors in diagnosis can often be made in dental clinics, which can lead to a delay in treatment. This study aims to use artificial intelligence (AI) for the automated detection and localization of secondary, occlusal, and interproximal (D1, D2, D3) caries types on bite-wing radiographs. The eight hundred and sixty bite-wing radiographs were collected from the School of Dentistry database. Pre-processing and data augmentation operations were performed. Interproximal (D1, D2, D3), secondary, and occlusal caries on bite-wing radiographs were annotated by two oral radiologists. The data were split into 80% for training, 10% for validation, and 10% for testing. The AI-based training process was conducted using the YOLOv8 algorithm. A clinical decision support system interface was designed using the Python PyQT5 library, allowing for the use of dental caries detection without the need for complex programming procedures. In the test images, the average precision, average sensitivity, and average F1 score values for secondary, occlusal, and interproximal caries were obtained as 0.977, 0.932, and 0.954, respectively. The AI-based dental caries detection system yielded highly successful results in the test, receiving full approval from dentists for clinical use. YOLOv8 has the potential to increase sensitivity and reliability while reducing the burden on dentists and can prevent diagnostic errors in dental clinics.

Filler Mixed Into Adhesives Does Not Necessarily Improve Their Mechanical Properties

OBJECTIVES

To investigate the influence of filler type/loading on the micro-tensile fracture strength (μTFS) of adhesive resins, as measured 'immediately' upon preparation and after 1-week water storage ('water-stored').

METHODS

The morphology and particle-size distribution of three filler particles, referred to as 'Glass-S' (Esschem Europe), 'BioUnion' (GC), and 'CPC_Mont', were correlatively characterized by SEM, TEM, and particle-size analysis. These filler particles were incorporated into an unfilled adhesive resin ('BZF-29unfilled', GC) in different concentrations to measure the 'immediate' μTFS. After 1-week water storage, the 'water-stored' μTFS of the experimental particle-filled adhesive resins with the most optimum filler loading, specific for each filler type, was measured. In addition, the immediate and water-stored μTFS of the adhesive resins of three experimental two-step universal adhesives based on the same resin matrix but varying for filler type/loading, coded as 'BZF-21' (containing silica and bioglass), 'BZF-29' (containing solely silica), and 'BZF-29_hv' (highly viscous with a higher silica loading than BZF-29), and of the adhesive resins of the gold-standard adhesives OptiBond FL ('Opti-FL', Kerr) and Clearfil SE Bond 2 ('C-SE2', Kuraray Noritake) was measured along with that of BZF-29unfilled (GC) serving as control/reference. Statistics involved one-way and two-way ANOVA followed by post-hoc multiple comparisons (α<0.05).

RESULTS

Glass-S, BioUnion, and CPC_Mont represent irregular fillers with an average particle size of 8.5-9.9 μm. Adding filler to BZF-29unfilled decreased μTFS regardless of filler type/loading. One-week water storage reduced μTFS of all adhesive resins except BZF-21, with the largest reduction in μTFS recorded for BZF-29unfilled. Among the three filler types, the μTFS of the 30 wt% Glass-S and 20 wt% BioUnion filled adhesive resin was not significantly different from the μTFS of BZF-29unfilled upon water storage.

CONCLUSIONS

Adding filler particles into adhesive resin did not enhance its micro-tensile fracture strength but appeared to render it less sensitive to water storage as compared to the unfilled adhesive resin investigated.

The demineralization resistance and mechanical assessments of different bioactive restorative materials for primary and permanent teeth: an in vitro study

OBJECTIVES

This article examines the efficacy of two bioactive dental composites in preventing demineralization while preserving their mechanical and physical properties.

MATERIALS AND METHODS

The study compares Beautifil Kids and Predicta® Bioactive Bulk-Fill (Predicta) composites with conventional dental composite. Flexural strength and elastic modulus were evaluated using a universal testing machine. A pH-cycling model assessed the composites' ability to prevent dentin demineralization. Color stability and surface roughness were measured using a spectrophotometer and non-contact profilometer, respectively, before and after pH-cycling, brushing simulation, and thermocycling aging.

RESULTS

Beautifil Kids exhibited the highest flexural strength and elastic modulus among the materials (p < 0.05). Predicta demonstrated the highest increase in dentin surface microhardness following the pH-cycling model (p < 0.05). All groups showed clinically significant color changes after pH-cycling, with no significant differences between them (p > 0.05). Predicta exhibited greater color change after brushing and increased surface roughness after thermocycling aging (p < 0.05). While Beautifil Kids had higher surface roughness after pH-cycling (p < 0.05).

DISCUSSION/CONCLUSION

Bioactive restorative materials with ion-releasing properties demonstrate excellent resistance to demineralization while maintaining mechanical and physical properties comparable to the control group.

Enhanced remineralisation ability and antibacterial properties of sol-gel glass ionomer cement modified by fluoride containing strontium-based bioactive glass or strontium-containing fluorapatite

OBJECTIVES

This study aimed to compare two types of bioactive additives which were strontium-containing fluorinated bioactive glass (SrBGF) or strontium-containing fluorapatite (SrFA) added to sol-gel derived glass ionomer cement (SGIC). The objective was to develop antibacterial and mineralisation properties, using bioactive additives, to minimize the occurrence of caries lesions in caries disease.

METHODS

Synthesized SrBGF and SrFA nanoparticles were added to SGIC at 1 wt% concentration to improve antibacterial properties against S. mutans, promote remineralisation, and hASCs and hDPSCs viability. Surface roughness and ion-releasing behavior were also evaluated to clarify the effect on the materials. Antibacterial activity was measured via agar disc diffusion and bacterial adhesion. Remineralisation ability was assessed by applying the material to demineralised teeth and subjecting them to a 14-day pH cycle, followed by microCT and SEM-EDS analysis.

RESULTS

The addition of SrFA into SGIC significantly improved its antibacterial property. SGIC modified with either SrBGF or SrFA additives could similarly induce apatite crystal precipitation onto demineralised dentin and increase dentin density, indicating its ability to remineralise dentin. Moreover, this study also showed that SGIC modified with SrBGF or SrFA additives had promising results on the in vitro cytotoxicity of hASC and hDPSC.

SIGNIFICANT

SrFA has superior antibacterial property as compared to SrBGF while demonstrating equal remineralisation ability. Furthermore, the modified SGIC showed promising results in reducing the cytotoxicity of hASCs and hDPSCs, indicating its potential for managing caries.

Detection of caries around restorations on bitewings using deep learning

OBJECTIVE

Secondary caries lesions adjacent to restorations, a leading cause of restoration failure, require accurate diagnostic methods to ensure an optimal treatment outcome. Traditional diagnostic strategies rely on visual inspection complemented by radiographs. Recent advancements in artificial intelligence (AI), particularly deep learning, provide potential improvements in caries detection. This study aimed to develop a convolutional neural network (CNN)-based algorithm for detecting primary caries and secondary caries around restorations using bitewings.

METHODS

Clinical data from 7 general dental practices in the Netherlands, comprising 425 bitewings of 383 patients, were utilized. The study used the Mask-RCNN architecture, for instance, segmentation, supported by the Swin Transformer backbone. After data augmentation, model training was performed through a ten-fold cross-validation. The diagnostic accuracy of the algorithm was evaluated by calculating the area under the Free-Response Receiver Operating Characteristics curve, sensitivity, precision, and F1 scores.

RESULTS

The model achieved areas under FROC curves of 0.806 and 0.804, and F1-scores of 0.689 and 0.719 for primary and secondary caries detection, respectively.

CONCLUSION

An accurate CNN-based automated system was developed to detect primary and secondary caries lesions on bitewings, highlighting a significant advancement in automated caries diagnostics.

CLINICAL SIGNIFICANCE

An accurate algorithm that integrates the detection of both primary and secondary caries will permit the development of automated systems to aid clinicians in their daily clinical practice.

ORCA-EFCD consensus report on clinical recommendation for caries diagnosis. Paper I: caries lesion detection and depth assessment

OBJECTIVES

The aim of the present consensus paper was to provide recommendations for clinical practice considering the use of visual examination, dental radiography and adjunct methods for primary caries detection.

MATERIALS AND METHODS

The executive councils of the European Organisation for Caries Research (ORCA) and the European Federation of Conservative Dentistry (EFCD) nominated ten experts each to join the expert panel. The steering committee formed three work groups that were asked to provide recommendations on (1) caries detection and diagnostic methods, (2) caries activity assessment and (3) forming individualised caries diagnoses. The experts responsible for "caries detection and diagnostic methods" searched and evaluated the relevant literature, drafted this manuscript and made provisional consensus recommendations. These recommendations were discussed and refined during the structured process in the whole work group. Finally, the agreement for each recommendation was determined using an anonymous Delphi survey.

RESULTS

Recommendations (N = 8) were approved and agreed upon by the whole expert panel: visual examination (N = 3), dental radiography (N = 3) and additional diagnostic methods (N = 2). While the quality of evidence was found to be heterogeneous, all recommendations were agreed upon by the expert panel.

CONCLUSION

Visual examination is recommended as the first-choice method for the detection and assessment of caries lesions on accessible surfaces. Intraoral radiography, preferably bitewing, is recommended as an additional method. Adjunct, non-ionising radiation methods might also be useful in certain clinical situations.

CLINICAL RELEVANCE

The expert panel merged evidence from the scientific literature with practical considerations and provided recommendations for their use in daily dental practice.

Surface Degradation of Ion-releasing Restorative Materials With Cariogenic Challenge

This study examined the influence of cariogenic environments on the surface roughness of ion-releasing restorative materials (IRMs). Custom-made stainless steel molds with holes of 5 mm × 2mm were used to fabricate 60 disc-shaped specimens of each of the following materials: Activa Bioactive (AV), Beautifil Bulk Restorative (BB), Cention N (Bulk-fill) (CN), and Filtek Z350XT (FZ) (Control). Baseline surface roughness (Ra) measurements were obtained using an optical 3D measurement machine (Alicona Imaging GmbH, Graz, Austria). The specimens were then randomly divided into five subgroups (n=12) and exposed to 10 ml of the following mediums at 37°C: distilled water (DW), demineralization solution (DM), remineralization solution (RM), pH cycling (PC) and air (AR) (control). Ra measurements were again recorded after one week and one month, followed by statistical evaluations with two-way analysis of variance (ANOVA) to determine interactions between materials and mediums. One-way ANOVA and post hoc Games Howell tests were performed for intergroup comparisons at a significance level of 0.05. Mean Ra values ranged from 0.085 ± 0.004 (µm) to 0.198 ± 0.001 µm for the various material-medium combinations. All IRMs showed significant differences in Ra values after exposure to the aqueous mediums. The smoothest surfaces were observed in the AR for all materials. When comparing materials, AV presented the roughest surfaces for all mediums. All IRM materials showed increased surface roughness over time in all cariogenic environments but were below the threshold value for bacterial adhesion, except for AV 1-month post immersion with pH cycling. Therefore, besides AV, the surface roughness of IRMs did not deteriorate to an extent that it is clinically relevant.

Knowledge and attitude of dentists toward minimally invasive caries management in Almadinah Almunawwarah province, KSA

Objective

Over time, the management of dental caries has shifted towards minimally invasive dentistry (MID) and more conservative and evidence-based strategies. Although most dental schools have begun to incorporate MID caries management strategies in their curriculum; it has yet to be established whether these strategies are being implemented in everyday practice. In this study, we aimed to evaluate the knowledge and attitude of dentists working in Almadinah Almunawwarah province in KSA with regards to the implementation of MID in caries management.

Methods

This was a cross-sectional study which involved sending a self-administered and anonymous questionnaire to dentists practicing in both private and public clinics in Almadinah Almunawwarah, KSA. The questionnaire consisted of four sections: demographic data, dental education, clinical experience, and knowledge and attitude with regards to MID and the management of caries. For statistical analysis, we calculated simple descriptive statistics, including mean and frequency distributions; comparisons were performed using the Chi-squared test.

Results

A total of 130 dentists participated in the study; the majority of respondents were Saudi general dentists working in private dental clinics; there was a similar distribution of males and females and the age of the dentists ranged from 25 to 35 years. With regards to knowledge relating to selective caries removal (SCR), only 20% of subjects responded that SCR is based on lesion depth, while 74.6% reported that carious dentin consistency is important for SCR. Although 60% of respondents reported that they would assess a patient's risk of caries before commencing treatment, only 11.5% would perform risk assessment and non-surgical treatment in the first visit for caries management. Only 4.6% reported that they used the International Caries Detection and Assessment System (ICDAS) II criteria for the diagnosis of caries while 46.2% used the G.V. Black criteria. In addition, 53.8% of participants agreed that caries must be completely removed to prevent the progression of caries.

Conclusion

Dentists in Almadinah Almunawwarah province had reasonable levels of knowledge regarding the importance of MID in caries management. However, they did not fully implement certain concepts, such as caries risk assessment and the recently recommended criteria for the diagnosis of caries, in their everyday clinical practice.

Co-occurrence of dental caries and periodontitis: multilevel modelling approach

BACKGROUND

Previous studies reported varyingly positive, negative, or no relationships between caries and periodontitis. Therefore, the aim was to assess the potential co-occurrence of caries experience and periodontal inflammation on the same teeth.

METHODS

This cross-sectional study used data from the Lithuanian National Oral Health Survey. The study included a stratified random sample of 1405 individuals aged 34-78, recruited from 5 Lithuanian cities and 10 peri-urban/rural areas (response rate 52%). Information about sociodemographic (age, sex, education, residence), behavioral (sugar-containing diet, tooth brushing frequency, use of interdental care products, last dental visit, smoking) and biological (systemic disease, use of medication and xerostomia) determinants was collected using the World Health Organization (WHO) Oral Health Questionnaire for Adults supplemented with additional questions. Clinical data were recorded using the WHO criteria and collected by one trained and calibrated examiner. Dental caries status was recorded as sound, decayed, missing, filled surfaces. Subsequently for the analyses, status was recorded at a tooth-level as decayed- and filled-teeth (DT and FT) including proximal, buccal, and oral surfaces. Two measures were used for periodontal status. The probing pocket depth (PPD) was measured at six sites and recorded at a tooth level into the absence of PPD or presence of PPD ≥ 4 mm. Bleeding on probing (BOP) was measured at the same six sites and was recorded as either present or absent at a tooth-level. Univariable and multivariable 2-level random intercept binary logistic regression analyses were utilized.

RESULTS

Positive associations were found between DT and BOP (OR 1.42, 95% CI 1.20-1.67), FT and BOP (OR 2.07, 95% CI 1.82-2.23), DT and PPD (OR 1.38, 95% CI 1.15-1.67) and FT and PPD (OR 2.01, 95% CI 1.83-2.20).

CONCLUSIONS

Our findings add evidence for the co-occurrence of periodontal inflammation and caries on the same teeth. This suggests the need for increased emphasis on a transdisciplinary approach in designing oral health interventions that target dental caries and periodontal disease simultaneously. In addition, longitudinal studies exploring the co-occurrence of caries and periodontal disease at the same sites, taking into consideration the levels of both conditions and genetic variation, are warranted.

A low-shrinkage-stress and anti-bacterial adherent dental resin composite: physicochemical properties and biocompatibility

Polymerisation shrinkage and biofilm accumulation are the two main problems associated with dental resin composites (DRCs) that induce secondary caries, which can cause restoration failure. Polymerisation shrinkage can lead to microleakage gaps between the tooth and the DRCs, causing the aggregation of bacteria and development of secondary caries. Reducing the shrinkage stress (SS) and improving the resistance to bacterial adhesion have always been the focus of this field in modifying DRCs. A thiol-ene resin system can effectively reduce the polymerisation SS via its step-growth mechanism for delaying the gel point. Fluorinated compounds can reduce the surface free energies, thereby reducing bacterial adhesion. Thus, in this study, a range of mass fractions (0, 10, 20, 30, and 40 wt%) of a fluorinated thiol-ene resin system were added to a fluorinated dimethacrylate resin system/tricyclo decanedimethanol diacrylate to create a fluorinated methacrylate-thiol-ene ternary resin matrix. DRCs were prepared using the obtained ternary resin matrix, and their physical and chemical properties, effect on bacterial adhesion, and biocompatibility were investigated. The results demonstrated that the volumetric shrinkage and SS of the DRCs were reduced with no reduction in conversion degree even after the thiol-ene resin system was added. All DRC-based fluorinated resin systems exhibited an excellent anti-bacterial adhesion effect, as evidenced by the colony-forming unit counts, live/dead bacterial staining, and crystal violet staining tests against Streptococcus mutans (S. mutans). The genetic expressions associated with the bacterial adhesion of S. mutans were substantially affected after being cultured with fluorinated DRCs. All fluorinated DRCs demonstrated good biocompatibility through the in vitro cytotoxicity test and live/dead staining images of the L-929 cells. The above results illustrate that the DRCs based on the fluorinated methacrylate-thiol-ene resin matrix can be potentially applied in clinical practice due to their low SS and anti-bacterial adhesion effect.

Rapid detection of non-normal teeth on dental X-ray images using improved Mask R-CNN with attention mechanism

PURPOSE

Dental health has been getting increased attention. Timely detection of non-normal teeth (caries, residual root, retainer, teeth filling, etc.) is of great importance for people's health, well-being, and quality of life. This work proposes a rapid detection of non-normal teeth based on improved Mask R-CNN, aiming to achieve comprehensive screening of non-normal teeth on dental X-ray images.

METHODS

An improved Mask R-CNN based on attention mechanism was used to develop a non-normal teeth detection method trained on a high-quality annotated dataset, which can segment the whole mask of each non-normal tooth on the dental X-ray image immediately.

RESULTS

The average precision (AP) of the proposed non-normal teeth detection was 0.795 with an intersection-over-union of 0.5 and max detections (maxDets) of 32, which was higher than that of the typical Mask R-CNN method (AP = 0.750). In addition, validation experiments showed that the evaluation metrics (AP, recall, precision-recall (P-R) curve) of the proposed method were superior to those of the Mask R-CNN method. Furthermore, the experimental results indicated that proposed method exhibited a high sensitivity (95.65%) in detecting secondary caries. The proposed method took about 0.12 s to segment non-normal teeth on one dental X-ray image using the laptop (8G memory, NVIDIA RTX 3060 graphics processing unit), which was much faster than conventional manual methods.

CONCLUSION

The proposed method enhances the accuracy and efficiency of abnormal tooth diagnosis for practitioners, while also facilitating early detection and treatment of dental caries to substantially lower patient costs. Additionally, it can enable rapid and objective evaluation of student performance in dental examinations.

The preventive effect of glass ionomer cement restorations on secondary caries formation: A systematic review and meta-analysis

OBJECTIVE

The objective is to compare the preventive effect on secondary caries of glass ionomer cement (GIC) restorations with amalgam or resin-composite restorations.

METHODS

Two independent researchers conducted a systematic search of English publications in PubMed, Web of Science, Cochrane and Scopus. They selected randomized clinical trials comparing secondary caries incidences around GIC restorations (conventional GIC or resin-modified GIC) with amalgam or resin-composite restorations. Meta-analysis of the secondary-caries incidences with risk ratio (RR) and 95% confidence interval (95% CI) as the effect measure was performed.

RESULTS

This review included 64 studies. These studies included 8310 GIC restorations and 5857 amalgam or resin-composite restorations with a follow-up period from 1 to 10 years. Twenty-one studies with 4807 restorations on primary teeth and thirty-eight studies with 4885 restorations on permanent teeth were eligible for meta-analysis. The GIC restorations had a lower secondary caries incidence compared with amalgam restorations in both primary dentition [RR= 0.55, 95% CI:0.41-0.72] and permanent dentition [RR= 0.20, 95% CI:0.11-0.38]. GIC restorations showed similar secondary caries incidence compared with resin-composite restorations in primary dentition [RR= 0.92, 95% CI:0.77-1.10] and permanent dentition [RR= 0.77, 95% CI:0.39-1.51]. Conventional GIC restorations showed similar secondary caries incidence compared with resin-modified GIC-restored teeth in both primary dentition [RR= 1.12, 95% CI:0.67-1.87] and permanent dentition [RR= 1.63, 95% CI:0.34-7.84].

CONCLUSIONS

GIC restorations showed a superior preventive effect against secondary caries compared to amalgam restorations, and a similar preventive effect against secondary caries compared to resin-composite restorations in both primary and permanent teeth. [PROSPERO Registration ID: CRD42022380959].

Retrospective clinical study on the performance and aesthetic outcome of pressed lithium disilicate restorations in posterior teeth up to 8.3 years

OBJECTIVES

Evaluation of cumulative survival and complication rate of monolithic lithium disilicate inlays and partial crowns performed by supervised undergraduate students up to 8.3 years of clinical service.

MATERIALS AND METHODS

In this retrospective clinical study 143 lithium disilicate posterior restorations (IPS e.max Press) were examined according to the FDI criteria. A standardised questionnaire was used to determine patient satisfaction. The aesthetic outcome was evaluated by dentists and dental technicians using intraoral photographs. Data were descriptively analysed. Cumulative survival and success rates were calculated using Kaplan-Meier estimation.

RESULTS

The cumulative survival rate of lithium disilicate restorations was 97.5% after a mean service time of 5.9 years and 95.0% after 8.3 years. The cumulative success rate decreased from 94.4% after 5.9 years to 30.7% after 8.3 years. Repairs were required for 7 restorations (4.9%), and 5 (3.5%) were classified as failures. The results of the questionnaire indicate a high level of patient satisfaction. The subjective aesthetics were assessed more critically by dental technicians compared to dentists.

CONCLUSION

Lithium disilicate posterior restorations survived successfully up to 8.3 years when carried out by undergraduate students.

CLINICAL RELEVANCE

Pressed lithium disilicate glass ceramic inlays and partial crowns are reliable treatment options in posterior teeth.

Comparative evaluation on the effect of different cavity disinfectant nano gels; Chlorohexidine, Propolis, Liquorice versus Diode Laser in terms of composite microleakage (comparative in vitro study)

INTRODUCTION

The application of different cavity disinfectants is an essential step that eliminates bacteria after cavity preparation. However, some of these materials may affect restoration sealing ability.

AIM

This study aimed to assess the degree of microleakage at the tooth restoration interface after using different nano prepared cavity disinfectants versus Diode Laser.

MATERIALS AND METHODS

Three disinfectants were prepared on the nanoscale; Propolis, Liquorice and Chlorhexidine. A total of 40 extracted premolars with standard class V cavities were prepared on the facial surface. Teeth were divided into five groups according to the applied cavity disinfection protocol; no treatment, Chloehexidine, Propolis, Liquorice, and Diode Laser. After application of composite resin restoration, all teeth were subjected to thermocycling, afterwords the degree of microleakage was measured in micrometers. Data were analyzed by one-way analysis of variance (ANOVA) test, followed by Bonferroni's and Tukey's post hoc test.

RESULTS

The highest mean microlekage value was recorded in no treatment group, followed by Liquorice, Propolis. While Diode Laser group showed the lowest degree of microleakage.

CONCLUSION

Diode Laser cavity disinfectant has no negative effect on the restoration sealing ability. Nano prepared Propolis showed comparative results to nanoChloehexidine as both had low degree of microleakage.

Optimizing Dental Bond Strength: Insights from Comprehensive Literature Review and Future Implications for Clinical Practice

This review examines the modifying factors affecting bond strength in various bonding scenarios, particularly their relevance to the longevity of dental restorations. Understanding these factors is crucial for improving clinical outcomes in dentistry. Data were gathered from the PubMed database, ResearchGate, and Google Scholar resources, covering studies from 1992 to 2022. The findings suggest that for dentin-resin bonds, minimizing smear layers and utilizing MMP inhibitors to prevent hybrid layer degradation are essential. In the case of resin-resin bonds, reversing blood contamination is possible, but preventing saliva contamination is more challenging, underscoring its critical importance during clinical procedures. Additionally, while pretreatment on ceramics has minimal impact on bond strength, the influence of specific colorings should be carefully considered in treatment planning. This comprehensive review highlights that although established practices recognize significant bond strength factors, ongoing research provides valuable insights to enhance the clinical experience for patients. Once confirmed through rigorous experimentation, these emerging findings should be swiftly integrated into dental practice to improve patient outcomes.

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.

Efficient Photopolymerization of Dental Resin Composites Using the Photoluminescent Long Afterglow of Sr2MgSi2O7:Eu2+,Dy3

Dental curing light with blue emission acts as the excitation source for the photopolymerization of the dental composite resin to achieve dental repairing. However, the current repair methods still suffer from a low monomer conversion degree and incomplete resin curing. In this study, novel dental resin composites (DRCs) were prepared by combining Sr2MgSi2O7:Eu2+,Dy3+ (SMSED), a photoluminescent material with a blue long afterglow, and dental resin composites. The curing depth, double bond conversion, elastic modulus, compressive strength, water absorption and solubility, and cytotoxicity were investigated systematically. The results suggest that adding 1 wt % SMSED to dental resin composites can maximize the curing depth and double bond conversion rate of DRCs and reduce its water absorption capacity without affecting the mechanical properties and biological toxicity. This work explores the practical applications of SMSED in dental resin composites, which provides an important reference for further improving the effect of dental caries repair.

The clinical performance of bulk-fill versus the incremental layered application of direct resin composite restorations: a systematic review

OBJECTIVES

To systematically review the scientific evidence comparing the clinical effectiveness of bulk-fill versus incrementally layered conventional resin composites and to evaluate if one method offers clear merits with specific clinical outcomes.

MATERIALS AND METHODS

Using relevant mesh terms and pre-established eligibility criteria in PubMed, Embase, Scopus and Web of Science, a thorough scientific search was conducted with an end-date of 30.04.2023. Randomized controlled clinical trials that involved the direct comparison of Class I and Class II resin composite restorations applied using incremental layering techniques versus bulk-filled in permanent teeth with an observation period of at least six months were considered. To evaluate the bias risk of the finalized records, a revised version of the Cochrane risk-of-bias tool for randomized trials was implemented.

RESULTS

Out of the 1445 records determined, 18 eligible reports were chosen for qualitative analysis. Data obtained was categorized as per, the cavity design, the intervention, the comparator(s), the methods of success/failure assessment, the outcomes, and follow-up. Two studies demonstrated an overall low-risk of bias, fourteen studies raised some concerns, and two studies exhibited high-risk.

CONCLUSION

Bulk filled resin composite restorations demonstrated clinical outcomes similar to those of incrementally layered resin composite restorations within a review interval of 6 months to 10 years.

Recurrent caries models to assess dental restorations: A scoping review

OBJECTIVES

To review the literature on recurrent caries models used to evaluate restorative materials, compare reported methodology and parameters, and devise specific recommendations to be considered in future investigations.

DATA

The following were extracted: study design, sample characteristics, source of teeth, name of restorations compared including controls, recurrent caries model type, type of demineralizing and remineralizing solutions, type of biofilm used, methods to detect recurrent caries.

SOURCES

Literature searches were performed in OVID Medline, EMBASE, SCOPUS, and Cochrane Library.

STUDY SELECTION

For a study to be included, it had to examine dental materials for tooth restoration purposes only with a valid control group and evaluate restorative dental materials regardless of the form of the teeth caries model used or nature of the tooth structure used. A total of 91 studies were included. Most of the studies presented were in vitro. Human teeth were the main source of specimens utilized. Around 88% of the studies used specimens without an artificial gap, and 44% used a chemical model. S. mutans was the main bacterial species used in microbial caries models.

CONCLUSION

The findings of this review provided an insight into the performance of available dental materials assessed using different recurrent caries models, yet this review cannot be used as a guideline for material selection. Selecting the appropriate restorative material relies on several patient-related factors such as microbiota, occlusion, and diet that are not comprehensively taken into consideration in recurrent caries models and thus hinder reliable comparison.

CLINICAL SIGNIFICANCE

Due to the heterogenicity of variables among studies on the performance of dental restorative materials, this scoping review aimed to provide insights for dental researchers concerning the available recurrent caries models, testing methods used, and aspects of comparison between these materials including their characteristics and limitations.

Inhibition of Caries around Restoration by Ion-Releasing Restorative Materials: An In Vitro Optical Coherence Tomography and Micro-Computed Tomography Evaluation

The objective of this study was firstly to assess the demineralization inhibitory effect of ion-releasing restorations in enamel adjacent to restoration using a biofilm caries model and secondly to compare the effect to that in a chemical caries model. Fifty-six bovine incisors were filled with either Surefil one (SuO), Cention N (CN) (both ion-releasing materials), Ketac-Molar (GIC) or Powerfill resin composite (RC). The restored teeth were then randomly divided into 2 groups according to the used caries model (biofilm or chemical caries model). The micro-computed tomography (MicroCt) and optical coherence tomography (OCT) outcome measures used to evaluate demineralization inhibition effects were lesion depth, LD and increase in OCT integrated reflectivity, ΔIR, at five different depths. It was observed that all outcome measures of CN were statistically the same as those of GIC and conversely with those of RC. This was also the case for SuO except for LD, which was statistically the same as RC. When comparing the two caries models, LD of the biofilm model was statistically deeper (p < 0.05) than the chemical model for all four materials. In conclusion, CN and SuO have similar demineralization inhibitory effects as GIC, and the biofilm caries model is more discriminatory in differentiating demineralization inhibitory effects of ion-releasing restorative material.

Evaluation of Antibacterial Activity of a Bioactive Restorative Material Versus a Glass-Ionomer Cement on Streptococcus Mutans: In-Vitro Study

BACKGROUND

Dental caries management consists of both preventive and restorative approaches. Pediatric dentists can rely on many techniques and materials to restore decayed teeth, but a high failure rate is still observed, mainly due to secondary caries. New restorative bioactive materials combine the mechanical and aesthetic characteristics of resinous materials with the capability to remineralize and the antimicrobial properties of glass ionomers, thus counteracting the occurrence of secondary caries. The aim of this study was to assess the antimicrobial activity against Streptococcus mutans of a bioactive restorative material (ACTIVA™ BioActive-Restorative™-Pulpdent©) and a glass ionomer cement with silver particles added (Ketac™ Silver-3M©), using agar diffusion assay.

METHODS

Each material was formed into disks of 4 mm in diameter, and four discs of each material were placed on nine agar plates. The analysis was repeated seven times.

RESULTS

Both materials showed statistically significant growth inhibition properties against S. mutans (p < 0.05). The difference in the effectiveness of the two materials was not statistically significant.

CONCLUSION

Both ACTIVA™ and Ketac™ Silver can be recommended since both are similarly effective against S. mutans. However ACTIVA™, given its bioactivity and better aesthetics and mechanical properties compared to GICs, may provide better clinical performance.

Revised FDI criteria for evaluating direct and indirect dental restorations-recommendations for its clinical use, interpretation, and reporting

OBJECTIVES

The FDI criteria for the evaluation of direct and indirect dental restorations were first published in 2007 and updated in 2010. Meanwhile, their scientific use increased steadily, but several questions from users justified some clarification and improvement of the living document.

MATERIALS AND METHODS

An expert panel (N = 10) initiated the revision and consensus process that included a kick-off workshop and multiple online meetings by using the Delphi method. During and after each round of discussion, all opinions were collected, and the aggregated summary was presented to the experts aiming to adjust the wording of the criteria as precisely as possible. Finally, the expert panel agreed on the revision.

RESULTS

Some categories were redefined, ambiguities were cleared, and the descriptions of all scores were harmonized to cross-link different clinical situations with possible management strategies: reviewing/monitoring (score 1-4), refurbishment/reseal (score 3), repair (score 4), and replacement (score 5). Functional properties (domain F: fracture of material and retention, marginal adaptation, proximal contact, form and contour, occlusion and wear) were now placed at the beginning followed by biological (domain B: caries at restoration margin, hard tissue defects, postoperative hypersensitivity) and aesthetic characteristics (domain A: surface luster and texture, marginal staining, color match).

CONCLUSION

The most frequently used eleven categories of the FDI criteria set were revised for better understanding and handling.

CLINICAL RELEVANCE

The improved description and structuring of the criteria may help to standardize the evaluation of direct and indirect restorations and may enhance their acceptance by researchers, teachers, and dental practitioners.

Inorganic Compounds as Remineralizing Fillers in Dental Restorative Materials: Narrative Review

Secondary caries is one of the leading causes of resin-based dental restoration failure. It is initiated at the interface of an existing restoration and the restored tooth surface. It is mainly caused by an imbalance between two processes of mineral loss (demineralization) and mineral gain (remineralization). A plethora of evidence has explored incorporating several bioactive compounds into resin-based materials to prevent bacterial biofilm attachment and the onset of the disease. In this review, the most recent advances in the design of remineralizing compounds and their functionalization to different resin-based materials' formulations were overviewed. Inorganic compounds, such as nano-sized amorphous calcium phosphate (NACP), calcium fluoride (CaF₂), bioactive glass (BAG), hydroxyapatite (HA), fluorapatite (FA), and boron nitride (BN), displayed promising results concerning remineralization, and direct and indirect impact on biofilm growth. The effects of these compounds varied based on these compounds' structure, the incorporated amount or percentage, and the intended clinical application. The remineralizing effects were presented as direct effects, such as an increase in the mineral content of the dental tissue, or indirect effects, such as an increase in the pH around the material. In some of the reported investigations, inorganic remineralizing compounds were combined with other bioactive agents, such as quaternary ammonium compounds (QACs), to maximize the remineralization outcomes and the antibacterial action against the cariogenic biofilms. The reviewed literature was mainly based on laboratory studies, highlighting the need to shift more toward testing the performance of these remineralizing compounds in clinical settings.

Strong-field THz radiation-induced curing of composite resin materials in dentistry

Dental caries is listed as one of the three major non-communicable diseases by the World Health Organization, and its main treatment method is to restore it by filling it with resin. At present, the visible light-cure method has the problems of non-uniform curing and low penetration efficiency, which makes the bonding area easy to develop marginal leakages, thus leading to secondary caries and requiring repeated treatment. In this work, through the strong terahertz (THz) irradiation-weak THz detection technique, it is found that the strong THz electromagnetic pulses can accelerate the curing process of the resin, and the weak-field THz spectroscopy can be used to monitor this dynamic change in real time, which will greatly promote the potential application of THz technology in dentistry.

Investigation of Surface Layers on Biological and Synthetic Hydroxyapatites Based on Bone Mineralization Process

In this review, the current status of the influence of added ions (i.e., SiO₄^4-, CO₃^2-, etc.) and surface states (i.e., hydrated and non-apatite layers) on the biocompatibility nature of hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) is discussed. It is well known that HA is a type of calcium phosphate with high biocompatibility that is present in biological hard tissues such as bones and enamel. This biomedical material has been extensively studied due to its osteogenic properties. The chemical composition and crystalline structure of HA change depending on the synthetic method and the addition of other ions, thereby affecting the surface properties related to biocompatibility. This review illustrates the structural and surface properties of HA substituted with ions such as silicate, carbonate, and other elemental ions. The importance of the surface characteristics of HA and its components, the hydration layers, and the non-apatite layers for the effective control of biomedical function, as well as their relationship at the interface to improve biocompatibility, has been highlighted. Since the interfacial properties will affect protein adsorption and cell adhesion, the analysis of their properties may provide ideas for effective bone formation and regeneration mechanisms.

Long-Term Antibacterial Efficacy of Cetylpyridinium Chloride-Montmorillonite Containing PMMA Resin Cement

Despite being able to adhesively restore teeth, adhesives and cement do not possess any anticariogenic protection potential, by which caries recurrence may still occur and reduce the clinical lifetime of adhesive restorations. Several antibacterial agents have been incorporated into dental adhesives and cement to render them anticariogenic. Due to an additional therapeutic effect, such materials are classified as 'dental combination products' with more strict market regulations. We incorporated cetylpyridinium chloride (CPC), often used for oral hygiene applications, into montmorillonite (CPC-Mont), the latter to serve as a carrier for controlled CPC release. CPC-Mont incorporated into tissue conditioner has been approved by the Pharmaceuticals and Medical Devices Agency (PmontMDA) in Japan. To produce a clinically effective dental cement with the antibacterial potential to prevent secondary caries, we incorporated CPC-Mont into PMMA resin cement. We measured the flexural strength, shear bond strength onto dentin, CPC release, and the biofilm-inhibition potential of the experimental CPC-Mont-containing PMMA cement. An 8 and 10 wt% CPC-Mont concentration revealed the antibacterial potential without reducing the mechanical properties of the PMMA cement.

In vitro investigation of the impact of contemporary restorative materials on cariogenic bacteria counts and gene expression

OBJECTIVES

The aim of this study was to compare the antibacterial effect of different fluoride-containing and bioactive restorative materials, and their effect on the expression of specific biofilm-associated genes and therefore the caries process.

MATERIALS AND METHODS

The restorative materials utilized in this study included: 1. Filtek Z250, 2. Fuji II LC, 3. Beautifil II, 4. ACTIVA, and 5. Biodentine. For each material, disc-shaped specimens were prepared. The inhibitory effects against Streptococcus mutans, Lactobacillus acidophilus, and Leptotrichia shahii were tested. After incubation for 24 hours and 1 week, colony-forming units (CFUs) were enumerated. From the plates dedicated for biomass quantification and RNA purification, the target glucosyltransferase B (gtfB) and glucan-binding protein B (gbpB) genes were chosen for S. mutans. For L. acidophilus, a gene involved in exopolysaccharide synthesis (epsB) was chosen.

RESULTS

Except for Filtek Z250, all four materials showed statistically significant inhibitory effects on the biofilms of all three species. When biofilms were grown in the presence of the same four materials, the expression of S. mutans gtfB and gbpB genes, was significantly reduced. For L. acidophilus, the decrease in the expression of gtfB gene in the presence of ACTIVA was the highest change seen. The epsB gene expression also decreased. Compared to fluoride-releasing materials, bioactive materials had more inhibitory effect against L. acidophilus, both at 24 hours and 1 week.

CONCLUSIONS

Both fluoride releasing and bioactive materials exhibited a significant inhibitory effect on the biofilm growth. The expression of the targeted biofilm-associated genes was downregulated by both material groups.

CLINICAL SIGNIFICANCE

The findings from this study give insight into the antibacterial effect of fluoride-containing and bioactive materials which would help to reduce the chances for secondary caries and therefore increase the lifetime of dental restorations placed for patients.

Fluoride and Calcium Release from Alkasite and Glass Ionomer Restorative Dental Materials: In Vitro Study

This study evaluated the effect of pH and temperature on the ion (F^- and Ca²⁺) release of a resin-based material containing alkaline fillers and a self-setting high-viscous glass ionomer cement. Disks were prepared according to manufacturers' instructions for both materials: the EF group (Equia Forte HT filling, GC) and the CN group (Cention N, Ivoclar). Specimens were immersed in 50 mL buffer solution with three different pHs (4.8, 6.8, and 8.8), and stored at 0°, 18°, 37°, and 44 °C. After 24 h, 7 d, and 28 d, cumulative F^- and Ca²⁺ releases were analyzed by chromatography and mass spectrometry, and pH was measured. Both materials showed minimal changes in pH with final values after 28 d of 5.17 ± 0.56 for CN and 5.12 ± 0.24 for EF. In all experimental conditions, the percentages of ion release were higher for EF than for CF. In particular, both materials showed a significant difference in temperature in F^- release. Regardless of the pH values, the highest Ca²⁺ ion release was after 28 days, with a significant difference in temperature for CN and EF. Within the limit of this study, the temperature storage influenced ion release and the high-viscous glass ionomer showed the maximum values.

Antibacterial one-step self-etching dental adhesive with silver nanoparticles synthesized in situ

OBJECTIVES

The objective of this study is to value the long-term antibacterial capability and adhesive properties of one-step self-etching dental adhesive containing silver nanoparticles (AgNPs) synthesized in situ.

METHODS

One-step self-etching adhesives with various weight percentages of silver 2-ethylhezanoate (0%, 0.05%, 0.10%, and 0.20%) were obtained by in-situ synthesis; the sizes and distribution of the AgNPs in resin were observed. The antibacterial effects of dentin-resin specimens were assessed by various test methods after being aged for 1 week to 1 year. The microtensile bond strength (μTBS) and interfacial nanoleakage (NL) were evaluated using extracted human teeth after being aged for 1 day and 1 year.

RESULTS

Uniform distribution of AgNPs in resin was observed in all experimental groups, and the average size was 4.71 nm-4.81 nm. All groups containing AgNPs showed significant antibacterial differences from the control group (P<0.05) over the ageing of 1 year. Although the increase of concentration tended to improve antibacterial activity, significant differences were not observed between the 0.10% and 0.20% groups (P>0.05). No significant differences were observed between all experimental groups and the control group in μTBS testing and NL testing at 1-day and 1-year time points (P>0.05).

CONCLUSIONS

0.10% AgNPs synthesized in situ might be appropriate to impart a long-term antibacterial ability to the one-step self-etching adhesive, without affecting its adhesive performance.

CLINICAL SIGNIFICANCE

This study suggests that in-situ synthesis of AgNPs is an effective method to improve the antibacterial ability of dental adhesives with the potential to inhibit secondary caries.

Porcelain Veneers in Vital vs. Non-Vital Teeth: A Retrospective Clinical Evaluation

Nowadays, the ceramic veneer approach can be considered more predictable than direct composite veneer. To date, there is a lack of studies comparing the clinical performance of anterior veneers cemented on vital teeth (VT) and non-vital teeth (NVT). This longitudinal clinical study investigated the performance of ceramic veneers in VT or anterior NVT. A total of 55 patients were evaluated in the study. Two groups were defined based on the vitality status of the teeth (93 teeth-vital and 61 teeth-non-vital). The United States Public Health Service (USPHS) criteria were used to assess the clinical status. The data were evaluated statistically with the Mann-Whitney U test. All restorations were considered acceptable, and only one veneer in VT failed for the criteria of secondary caries. There were no statistically significant differences in any of the criteria evaluated (p ≤ 0.671). The ceramic veneers evaluated showed a satisfactory clinical performance both in VT and NVT.

Influence of Ionizing Radiation on Fluoride-Releasing Dental Restorative Materials

This study aimed to investigate the effects of radiotherapy on the mechanical, chemical, and surface properties of two recently introduced restorative dental materials (a glass hybrid and an alkasite), while two conventional restorative materials served as references. Material specimens of the experimental groups (irradiated) were compared to the specimens of the control groups that underwent the same preparation procedure but without irradiation. The experimental groups of restorative material specimens were irradiated with a total of 70 Gy over 35 days (2 Gy/day × 35 days), while the control groups received no treatment. The following properties were evaluated: surface microhardness (Vickers), surface roughness, color change, flexural strength, flexural modulus, material reliability, and infrared spectra. For the experimental groups, measurements were performed 24 h after specimen preparation, i.e., before radiotherapy and after the completion of the irradiation protocol. For the control groups, measurements were performed after the corresponding periods of no treatment. A statistically significant increase in microhardness (p = 0.001-0.004) and surface roughness (p = 0.013) was observed as a result of material aging/maturation in both the control and experimental groups. However, the only statistically significant difference between the control and experimental groups was observed in the discoloration of the conventional reference material (p < 0.001). In conclusion, no statistically significant negative effects of a therapeutic dose of radiotherapy on any of the tested properties of the alkasite and glass hybrid materials were observed, whereas only a minor negative effect of radiotherapy in terms of discoloration was found for a conventional resin composite that was used as a reference material.

Dental Composites with Magnesium Doped Zinc Oxide Nanoparticles Prevent Secondary Caries in the Alloxan-Induced Diabetic Model

Antibacterial restorative materials against caries-causing bacteria are highly preferred among high-risk patients, such as the elderly, and patients with metabolic diseases such as diabetes. This study aimed to enhance the antibacterial potential of resin composite with Magnesium-doped Zinc oxide (Mg-doped ZnO) nanoparticles (NPs) and to look for their effectiveness in the alloxan-induced diabetic model. Hexagonal Mg-doped ZnO NPs (22.3 nm diameter) were synthesized by co-precipitation method and characterized through ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The Mg-doped ZnO NPs (1, 2.5 and 5% w/w) were then evaluated for antibacterial activity using a closed system in vitro biofilm model. Significant enhancement in the antibacterial properties was observed in composites with 1% Mg-doped ZnO compared to composites with bare ZnO reinforced NPs (Streptococcus mutans, p = 0.0005; Enterococcus faecalis, p = 0.0074, Saliva microcosm, p < 0.0001; Diabetic Saliva microcosm, p < 0.0001). At 1−2.5% Mg-doped ZnO NPs concentration, compressive strength and biocompatibility of composites were not affected. The pH buffering effect was also achieved at these concentrations, hence not allowing optimal conditions for the anaerobic bacteria to grow. Furthermore, composites with Mg-doped ZnO prevented secondary caries formation in the secondary caries model of alloxan-induced diabetes. Therefore, Mg-doped ZnO NPs are highly recommended as an antibacterial agent for resin composites to avoid biofilm and subsequent secondary caries formation in high-risk patients.