Influence of posteruptive age of enamel on its susceptibility to artificial caries

Posteruptive Loss of Enamel Proteins Concurs with Gain in Enamel Hardness

Tooth enamel maturation requires the removal of proteins from the mineralizing enamel matrix to allow for crystallite growth until full hardness is reached to meet the mechanical needs of mastication. While this process takes up to several years in humans before the tooth erupts, it is greatly accelerated in in the faster developing pig. As a result, pig teeth erupt with softer, protein-rich enamel that is similar to hypomineralized human enamel but continues to harden quickly after eruption.Proteins, such as albumin, that bind to enamel crystals and prevent crystal growth and enamel hardening have been suggested as cause for hypomineralized human enamel that does not naturally harden after eruption. However, albumin is abundant in pig enamel. It is unclear whether fast posteruptive enamel hardening in pigs occurs despite the high protein content or requires a facilitated protein loss to allow for crystal growth. This study asked how the protein content in porcine enamel changes after eruption in relation to saliva. Based on previous data demonstrating the high albumin content in erupted porcine enamel, we hypothesize that following pre-eruptive maturation, enamel and saliva derived enzymes facilitate protein removal from porcine enamel after eruption. We analyzed enamel and the saliva proteome at three critical timepoints: at the time of tooth eruption, 2 weeks after eruption, and enamel 6 weeks after eruption. We used only fourth deciduous premolars and saliva samples from animals sacrificed at the respective time points to determine the organic content in tooth enamel, saliva, and saliva proteins within enamel. We found a decrease in the number of proteins and their abundancy in enamel with posteruptive time, including a decrease in serum albumin within enamel. The rapid decrease in the first two weeks is in line with previously reported rapid increase in mineral density of porcine enamel after eruption. In addition to the enamel proteases KLK-4 and MMP-20, we identified serine-, cysteine-, aspartic-, and metalloproteases. Some of these were only identified in enamel, while almost half of the enzymes are in common with saliva at all timepoints. Our findings suggest that the fast posteruptive enamel maturation in the porcine model coincides with saliva exchange and influx of saliva enzymes into porous enamel.

Assessment of changes in enamel colour following fixed orthodontic therapy using an advanced spectrophotometer: An in vivo study

BACKGROUND

Any manipulation of the surface of natural teeth may result in a variation of their colour. The fixed orthodontic treatment (FOT) is one such procedure which alters the enamel surface during the procedure.

OBJECTIVE

To clinically evaluate the colour changes in teeth associated with comprehensive FOT (to compare the changes in test and control groups) and to determine the relationship of age and gender on enamel colour due to FOT by using an advanced spectrophotometer.

METHODS

The selection of sixty patients for the study was done randomly and among these thirty patients who underwent the FOT as the case group, the other thirty patients who did not need FOT, were the control group. The recordings of spectrophotometric data were done in a standardized manner for all patients in the labial circular region of every anterior tooth, following debonding and cleaning operations, and before bracket bonding. The Commission Internationale de l'Eclairage's L*, a*, and b* (lightness, red/green, and blue/yellow) tooth-type characteristics were used to measure color, and the associated color differences (DE) between the groups were computed. One-way ANOVA (a < 0.05) and the paired t-test were used to evaluate any changes in these color characteristics.

RESULTS

Fixed orthodontic treatment is associated with changes in colour parameters. L* values decreased (P< 0.001), while a* and b* values increased (P< 0.001) at the end of treatment. All measured tooth types showed significant colour change (DE); their mean differences ranged from 1.64 to 2.96 DE units.

CONCLUSIONS

Fixed orthodontics can change the natural colour of teeth. The CIE colour parameters L*, a*, and b* of natural teeth showed statistically significant differences after debonding the orthodontic appliances. The L* values decreased making the teeth look darker. The adolescent and male patients had more tooth colour changes than the adult and female groups.

Prevalence of Dental Caries in Schoolchildren from the Galapagos Islands: ESSO-Gal Cohort Report

Objective

Dental caries remains a prevalent disease worldwide. Several epidemiological studies have shown that it affects the oral health of the pediatric population, and the Galapagos population in Ecuador is no exception. The aim of this study was to determine the prevalence of dental caries and its association, based on baseline information from the Galapagos Oral Health Study (ESSO-Gal), in children of the Galapagos Islands, Ecuador.

Methods

A cross-sectional study was conducted involving 804 children aged 2-11 years. The prevalence of dental caries was assessed using the International Caries Detection and Assessment System (ICDAS II) criteria, while the presence of dental biofilm was assessed using the Silness-Löe index. Descriptive statistics, including frequency analysis and measures of central tendency and dispersion, were performed. Inferential statistical analyses were conducted to identify associations between variables. Statistical analyses were performed using the SPSS version 25.0 statistical program.

Results

The caries prevalence rates based on ICDAS II codes 1-6, 1-2, and 3-6 were 98.01%, 96.9%, and 85%, respectively. A statistically significant difference was observed among the different islands regarding the cutoff point for ICDAS II codes 3-6 (p ≤ 0.001). Participants aged 6-11 years had the highest caries prevalence.

Conclusions

The results show a high prevalence of dental caries among children in the Galapagos Islands, which increases with age. Contrary to expectations, the study did not find a significant correlation between the severity of dental caries and the presence of dental biofilm.

Comparative analysis of DNA preservation in permanent and deciduous teeth of adults and non-adults: Implications for archaeological and forensic research

This study investigates the preservation of DNA in different categories of teeth, including permanent and deciduous, fully developed and not fully developed, in both adults and non-adults. Teeth were sampled from a modern-era cemetery in Ljubljana, Slovenia. DNA extraction was performed using a full demineralisation protocol. DNA quantity and quality were assessed using qPCR analyses, and autosomal STR typing was conducted to verify genetic profiles. Results revealed significant differences in DNA preservation among various tooth categories. Fully developed permanent teeth of adults exhibited the highest DNA yields, attributed to their fully developed roots and thicker cementum, which is rich in DNA. Deciduous teeth, with thinner enamel and cementum, showed lower DNA preservation regardless of developmental stage. Non-adult teeth generally yielded less DNA compared to adults, even when considering only fully developed permanent teeth, indicating factors beyond developmental stage. These findings suggest that, in archaeological and forensic contexts, researchers should prioritize fully developed permanent teeth for DNA analysis due to their superior preservation. Additionally, this study underscores the importance of considering tooth type and developmental stage when selecting samples for genetic analysis in cases where petrous bone is unavailable, expanding our understanding of DNA preservation in human remains.

Microleakage, microgap, and shear bond strength of an infiltrant for pit and fissure sealing

Objectives

This study aimed to evaluate the potential clinical application of an infiltrant with different etchants as pit and fissure sealants and to compare them with a conventional resin-based sealant.

Materials and methods

Seventy-five molars were randomly divided into three groups (n = 25): phosphoric acid etchant + conventional resin-based sealant (Group A); 15% hydrochloric acid etchant + infiltrant (Group B); phosphoric acid etchant + infiltrant (Group C). Fifteen teeth in each group were subjected to pit and fissure sealing procedures. After 500 thermocycling and methylene blue dye penetration, ten specimens were sectioned and the pencentages of dye penetration were measured under a stereomicroscope. Another five teeth in each group were sectioned and the microgaps between materials and enamel surface were measured using electron microscope scanning. Ten teeth in each group were used to measure shear bond strength and the failure mode was analyzed.

Results

The results showed that infiltrant exhibited significantly less microleakage and microgap than resin-based sealant, no matter which echant was used. Although there was no significant difference betweern the three groups, infiltrant applied with 15% hydrochloric acid etching showed higher shear bond strength than resin-based sealant etching with 35% phosphoric acid.

Conclusions

The infiltrant has significant advantages in reducing the degree of microleakage and microgap. Moreover, the infiltrant could achieve the same bonding strength as conventional resin-based sealant. Although, manufacturers do not currently recommend the infiltrant for fissure sealing, the potential clinical application would be an off-label use.Clinical relevance This report provides a theoretical basis for the potential clinical application of the infiltrant as a pit and fissure sealant, and provides a new perspective for selecting pit and fissure sealants.

Amyloid-Mediated Remineralization in Pit and Fissure for Caries Preventive Therapy

The pits and fissures of teeth have high caries susceptibility, and sealing these areas is considered as an effective method to prevent caries. However, long-term caries prophylaxis cannot be maintained because of the negative effects derived from the technical sensitivity and disadvantages of sealing materials. Herein, a new strategy is proposed to occlude fossae by amyloid-mediated biomimetic remineralization. In contrast to conventional inward blocking from the outside of fossae, amyloid-mediated biomimetic mineralization delivers an amyloid-like protein nanofilm into the deepest zone of the fossae and induces the formation of remineralized enamel inside. Such assembly from lysozyme conjugated with poly (ethylene glycol) enriches the interface with strongly bonded ionsand directs in situ nucleation to achieve enamel epitaxial growth. Not only is the structure of the enamel-like crystalline hydroxyapatite layer but also its mechanical stability is similar to that of natural enamel. Furthermore, the layer shows good biocompatibility and antibacterial properties. On the basis of the findings, it is demonstrated that amyloid-like protein aggregation may provide an enamel remineralization strategy to modify the current clinically available methods of pit and fissure sealing and shows great promise in preventing caries.

Comparative Assessment of Retention and Caries Protective Effectiveness of a Hydrophilic and a Conventional Sealant-A Clinical Trial

Sealants are highly efficient and the most secure method for the prevention of caries lesions from pits and fissures in recently erupted permanent teeth. The aim of this study is to clinically assess and compare the retention and evolution of caries of a moisture-tolerant resin-based sealant with a conventional hydrophobic resin-based sealant. Material and method: We have included in the study 28 children with between 6 and 8 years old. For each child we sealed 4 permanent molars (a total of 112 teeth). The study group was divided into two subgroups: the Embrace Group—consisting of 56 first permanent molars that underwent dental sealing with moisture-tolerant resin-based fissure sealant (Embrace™ WetBond™ Pulpdent, Watertown, MA, USA) and the Helioseal Group—represented by the same number of 56 first permanent molars that were sealed with conventional hydrophobic resin-based sealant (Helioseal F™, Ivoclar Vivadent Schaan, Liechtenstein). The retention and the incidence of new carious lesions of each sealant were assessed clinically at 6, 12, 18, and 24 months. Results: The 12-month follow-up assessment showed perfect integrity in 50 molars (89.28%) sealed with moisture-tolerant resin-based material (Embrace Group), and in 51 molars (91.07%) with conventional resin-based sealant (Helioseal Group). At the 24-month recall, the retention was maintained in 44 molars (78.57%) in the Embrace Group and in 45 molars (80.35%) in the Helioseal Group, respectively. The follow-up assessments showed no statistically significant differences (p > 0.5) between the two materials regarding sealant retention. First evidence of new carious lesions was present at 12 months on two molars sealed with Embrace WetBond and on one molar sealed with Helioseal. At the 24-month evaluation, the prevalence of caries in the Embrace Group was 7.14% (four caries) and 3.56% (two caries) in the Helioseal Group. Moreover, there were no statistically significant differences (p > 0.05) between the two materials regarding new caries development at any of the follow-up assessments. Conclusions: Moisture-tolerant resin-based sealant was effective in terms of retention and caries prevention.

Development and Feasibility Testing of CATCH Healthy Smiles, an Oral Health Promotion Intervention for Prevention of Dental Caries Among Elementary School Children

BACKGROUND

We present results of the development and feasibility testing of CATCH Healthy Smiles, a school-based oral health program, among children in grades K-2 in Houston, Texas.

METHODS

Study design was cross-sectional (N = 2 schools; N = 125 parent-child dyads; 31 kindergarteners, 42 first graders, and 52 second graders). CATCH Healthy Smiles program was implemented by trained school teachers in the 2016-2017 school year. Trained dentists conducted dental assessments to measure dental caries increment score (d3mfs). Parent-reported 24-hour dietary recalls and surveys assessed child and parent behavioral, environmental, and psychosocial factors. Logistic regression analysis assessed factors associated with caries experience adjusting for covariates.

RESULTS

Of the 113 children with complete dental assessments, 54% children in grade K, 62% in first grade, and 73% in second grade had caries experience. Children with caries experience had a higher body weight (AdjOR = 1.13, 95% confidence interval [CI]: 1.02-1.29), were less likely to be girls (AdjOR = 0.22, 95% CI: 0.05-0.82), had greater odds of difficulty drinking hot or cold beverages because of dental problems (AdjOR = 13.13, 95% CI: 1.09-275.14), greater frequency of consuming sugar-sweetened beverages (AdjOR = 11.53, 95% CI: 2.10-87.19), greater odds of receiving government assistance (AdjOR = 14.62, 95% CI: 2.74-119.81), and lower odds of seeing a dental provider (AdjOR = 0.11, 95% CI: 0.02-0.45). Process evaluation showed that 100% of the CATCH Healthy Smiles lessons and activities were taught in the two schools with a high degree of program fidelity and acceptability across the schools, children, and parents.

CONCLUSIONS

These data will be used to conduct a subsequent fully powered cluster randomized controlled trial.

Aging and Senescence of Dental Pulp and Hard Tissues of the Tooth

The ability to consume a meal using one's own teeth influences an individual's quality of life. In today's global aging society, studying the biological changes in aging teeth is important to address this issue. A tooth includes three hard tissues (enamel, dentin, and cementum) and a soft tissue (dental pulp). With advancing age, these tissues become senescent; each tissue exhibits a unique senescent pattern. This review discusses the structural alterations of hard tissues, as well as the molecular and physiological changes in dental pulp cells and dental pulp stem cells during human aging. The significance of senescence in these cells remains unclear. Thus, there is a need to define the regulatory mechanisms of aging and senescence in these cells to aid in preservation of dental health.

Susceptibility of Dental Enamel of Different Ages to Caries-Like Lesion Development

This study investigated the impact of estimated age, anatomical location, and the presence of wear facets on the susceptibility of enamel to develop caries-like lesions. Extracted human premolars (n = 261) had their age estimated between 10 and 93 years old, using established forensic methods. Specimens of enamel (4 × 4 mm) were prepared from the middle of the buccal surfaces, preserving the outer surface layer. The central area of the block (4 × 1 mm) was protected with nail polish and used as an internal control. The specimens were demineralized for 8 days (with 0.1 M acetic acid, 1.28 mM Ca, 0.74 mM Pi, and 0.03 µg F/mL, pH 5.0), to simulate caries-like lesion development. They were then scanned individually using microtomography, and digital 2D images were used to calculate the outcomes of integrated mineral concentration loss (ΔZ in µm/g/cm3) and lesion depth (LD in µm) at 3 locations, i.e., the cervical, middle, and occlusal thirds. The presence of natural surface wear facets was considered in the analysis. Data were evaluated using a linear mixed-effects models (α = 0.05). ΔZ increased significantly as a function of estimated tooth age at all 3 locations, and this increase was greater after the age of 30 years (p < 0.001), when a higher ΔZ was found in the occlusal third than in the middle and cervical thirds (p < 0.001). LD increased only in the occlusal third before the age of 30 years (p = 0.039) and this increase was significantly greater after 30 years at all 3 locations (p < 0.01), with no differences among them (p > 0.15). The presence of wear facets significantly increased ΔZ and LD (p < 0.001 for both). Overall, we concluded that the susceptibility of enamel to developing caries-like lesions increased with estimated dental age. This effect was more pronounced after the estimated age of 30 years and in the presence of natural tooth wear facets.

Study protocol of the cost-effectiveness comparison of two preventive methods in the incidence of caries: A randomized, controlled clinical trial

INTRODUCTION

Dental caries is the most frequent oral disease worldwide and the main cause of tooth loss in children and young adults. One of the most frequently affected areas is the occlusal surfaces of the first permanent molars (FPM) due to their morphological complexity. At present, several preventive treatments can reduce the incidence of this disease in school populations. In Mexico, the most commonly used technologies are those derived from some presentation of fluoride; on the other hand, research on this topic has been limited.

OBJECTIVE

To determine the cost-effectiveness of two different methods for preventing the incidence of caries on the FPM of schoolchildren (6-8 years of age) from public primary schools.

MATERIAL AND METHODS

This is a randomized experimental design. Participants will be assigned to two treatment groups of 114 each. In the first group, pit and fissure sealants will be applied, whereas the second group will receive a fluoride varnish. The work will be carried out in schoolchildren that attend public elementary schools in the state of Hidalgo, Mexico. The result variable will be the incidence of caries and the total cost of each of the interventions will be calculated in order to calculate the intervention's cost-effectiveness.

CONCLUSION

This work will allow us to compare the cost-effectiveness of the pit and fissure sealants and the fluoride varnish in order to determine which offers the best results.

Pit and Fissure Sealants-A Comprehensive Review

Even in the 21st century, dental caries is considered a global burden, severely upsetting the health and quality of life of those affected. Apart from the usage of fluoride and regular oral hygiene, one of the most important prophylactic approaches against the occurrence of caries is the sealing of pits and fissures. However, the rapid progress of new materials and applications for sealing pits and fissures also raises new questions about their correct application. Recent literature on pit and fissure sealing, caries prevention, as well as caries risk assessment for both children and adults was reviewed. This report provides a general overview of pit and fissure sealing, the materials used for sealing occlusal surfaces, as well as indications and possible side effects. The conclusions are that sealing pit and fissures of primary and permanent teeth is an effective method for preventing and arresting caries. However, regular checkups must be conducted to avoid advanced tooth decay attributable to leakages in the sealing.

Minimally invasive resin infiltration of arrested white-spot lesions: a randomized clinical trial

BACKGROUND

The authors conducted a randomized, single-masked clinical trial involving patients who had completed orthodontic treatment to assess changes in the appearance of white-spot lesions (WSLs) that were treated with resin infiltration.

METHODS

The authors divided affected teeth into control and treatment groups. In the treatment group, they restored teeth with WSLs by using resin infiltration. They evaluated changes in WSLs photographically by using a visual analog scale (VAS) (0 = no change, 100 = complete disappearance) and area measurements (in square millimeters). The authors analyzed the data by using two-way analysis of variance.

RESULTS

The mean VAS ratings for treated teeth demonstrated marked improvement relative to that for control teeth immediately after treatment (67.7 versus 5.2, P < .001) and eight weeks later (65.9 versus 9.2, P < .001). The results for treated teeth showed a mean reduction in WSL area of 61.8 percent immediately after treatment and 60.9 percent eight weeks later, compared with a -3.3 percent change for control teeth immediately after treatment and a 1.0 percent reduction eight weeks later.

CONCLUSIONS

Resin infiltration significantly improved the clinical appearance of WSLs, with stable results seen eight weeks after treatment.

PRACTICAL IMPLICATIONS

Resin infiltration, a minimally invasive restorative treatment, was shown to be effective for WSLs that formed during orthodontic treatment.

Caries process on occlusal surfaces: evolving evidence and understanding

Management of the caries process on occlusal surfaces of permanent molars has proven a major challenge. The onset of caries on these surfaces takes place soon after their eruption, and the permanent first molars, followed by the second molars, remain the sites in the dentition which show the highest caries prevalence. This paper is structured in the form of questions and answers in which traditional concepts of caries susceptibility of occlusal surfaces are appraised and confronted with the current evidence. Then, research studies examining the role of biological determinants on the development and arrest of occlusal caries in young permanent teeth are discussed. Finally, the contribution of these studies in terms of developing the available scientific evidence and our understanding of the caries process on occlusal surfaces is analyzed. The current evidence does not support the concept that the early onset and high prevalence of occlusal caries in young permanent teeth are due to a particularly low inherent resistance of the occlusal surface or due to the presence of inaccessible fissure-like structures on these surfaces. Evidence is provided to show that the most influential biological determinants of the development and arrest of occlusal caries are thick plaque accumulation on the groove-fossa system and the stage of tooth eruption limiting mechanical oral function. Consequently, active occlusal lesions are significantly more prevalent in erupting than in fully erupted teeth. The major contribution of this review is to provide updated knowledge about the biological principles determining the development and arrest of caries on occlusal surfaces of erupting teeth.

Shear bond strength of orthodontic attachments bonded to impacted teeth under in vivo and in vitro conditions

OBJECTIVES

To evaluate and compare the shear bond strength (SBS) of stainless steel and gold-plated attachments to impacted lower third molars in vivo and in vitro with a light-cured orthodontic resin.

SETTING AND SAMPLE POPULATION

Sixteen patients with bilaterally full soft tissue impaction of lower third molars were recruited on a voluntary basis from an oral and maxillofacial surgery department.

MATERIALS AND METHODS

A split-arch technique was used. Following surgical exposure of the crown, the tooth was luxated but not extracted. Then, two attachments (one stainless steel button and one gold-plated eyelet) were bonded to the labial enamel surface of the loosened tooth. Five minutes later, the luxated tooth was removed from its socket. In each patient, the impacted tooth on the other side was extracted, and attachments were bonded in vitro. The SBSs of the attachments were evaluated. For comparison, analysis of variance and multiple range tests were used (α = 0.05).

RESULTS

Statistically significant differences were evident in attachment adhesion to the impacted tooth surfaces among the four groups (p < 0.001). Superior SBS values were obtained for stainless steel button groups bonded in vitro. The mean bond strengths of the groups bonded in vitro were better than those of the same groups bonded in vivo.

CONCLUSIONS

Although the in vitro-bonded groups showed higher SBS values, adequate bond strength is possible with stainless steel buttons bonded in vivo.

Influence of CO2 (10.6 μm) and Nd:YAG laser irradiation on the prevention of enamel caries around orthodontic brackets

One possible undesirable consequence of orthodontic therapy is the development of incipient caries lesions of enamel around brackets. The aim of this study was to compare the effects of CO2 (λ = 10.6 μm) and Nd:YAG (λ = 1,064 nm) lasers associated or not with topical fluoride application on the prevention of caries lesions around brackets. Brackets were bonded to the enamel of 65 premolars. The experimental groups (n = 13) were: G1--application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2--Nd:YAG laser irradiation (0.6 W, 84.9 J/cm(2), 10 Hz, 110 μs, contact mode); G3--Nd:YAG laser irradiation associated with AFP; G4--CO2 laser irradiation (0.5 W, 28.6 J/cm(2), 50 Hz, 5 μs, and 10 mm focal distance); and G5--CO2 laser irradiation associated with AFP. Quantitative light-induced fluorescence was used to assess enamel demineralization. The data were statistically compared (α = 5%). The highest demineralization occurred in the Nd:YAG laser group (G2, 26.15% ± 1.94). The demineralization of all other groups was similar to that of the control group. In conclusion, CO2 laser alone was able to control enamel demineralization around brackets at the same level as that obtained with topical fluoride application.

Common SNPs of AmelogeninX (AMELX) and dental caries susceptibility

Genetic approaches have shown that several genes could modify caries susceptibility; AmelogeninX (AMELX) has been repeatedly designated. Here, we hypothesized that AMELX mutations resulting in discrete changes of enamel microstructure may be found in children with a severe caries phenotype. In parallel, possible AMELX mutations that could explain resistance to caries may be found in caries-free patients. In this study, coding exons of AMELX and exon-intron boundaries were sequenced in 399 individuals with extensive caries (250) or caries-free (149) individuals from nine French hospital groups. No mutation responsible for a direct change of amelogenin function was identified. Seven single-nucleotide polymorphisms (SNPs) were found, 3 presenting a high allele frequency, and 1 being detected for the first time. Three SNPs were located in coding regions, 2 of them being non-synonymous. Both evolutionary and statistical analyses showed that none of these SNPs was associated with caries susceptibility, suggesting that AMELX is not a gene candidate in our studied population.

Argon and Nd:YAG lasers for caries prevention in enamel

OBJECTIVE

The aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries.

BACKGROUND DATA

It is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface.

MATERIALS AND METHODS

Twenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250 mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 °C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 μm thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n=11). Data were analyzed by ANOVA and Tukey's test (p<0.05).

RESULTS

Means followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days).

CONCLUSIONS

The argon laser was more effective for caries preventive treatment than Nd:YAG laser, showing a smaller demineralization area in enamel.

The caries environment: saliva, pellicle, diet, and hard tissue ultrastructure

The pathogenicity of the dental biofilm is modified by salivary and dietary factors, as well as by the characteristics of the tooth structure. The composition of the acquired pellicle can modify the mineral homeostasis of the tooth surfaces and the attachment of bacteria for the development of the biofilm. The substitution of sucrose from the diet by other less cariogenic sugars and/or sugar substitutes can contribute to reducing the pathogenicity of the biofilm. Saliva clears, dilutes, neutralizes, and buffers acids produced by the biofilm. In addition, saliva provides the biofilm/tooth structure with Ca(2+) PO(4)(3-) and F(-) ions, which can positively affect the equilibrium between demineralization-remineralization toward the remineralization and modify the susceptibility of the tooth structure to caries progression.

The chemistry of caries: remineralization and demineralization events with direct clinical relevance

Dental caries is a site-specific disease that undergoes many cycles of demineralization and remineralization during lesion development. Because of its developmental characteristics dynamics, the caries lesion can be arrested and even repaired at its early stages without operative intervention by increasing the net mineral gain during the demineralization and remineralization cycles. This result can be accomplished by reducing the effect of etiological factors such as cariogenic biofilms and diet, and increasing the efficacy of remineralizing agents such as saliva and fluoride.

Effects of fluoride treatment on phosphoric acid-etching in primary teeth: an AFM observation

The aim of this study was to examine the effect of fluoride application on 37% phosphoric acid-etching by atomic force microscopy (AFM) in primary tooth samples based on a clinical protocol used in a pediatric dental hospital. Enamel samples were prepared from 36 exfoliated and non-carious primary teeth. Primary tooth samples were randomly assigned to one of the four groups based on the timing of acid-etching with 37% phosphoric acid after an acidulated phosphate fluoride (APF) pre-treatment. Group 1 received no fluoride application, Group 2 was pre-treated with fluoride and then received acid-etching 2 weeks later. One week separated the fluoride treatment and the acid-etching in Group 3, while Group 4 received acid-etching immediately after the fluoride treatment. The vestibular enamel surfaces of each primary tooth sample were scanned in air at a resolution of 512 x 512 pixels and a scan speed of 0.8 line/s. On the enamel surfaces of the primary teeth after APF pre-treatment, debris were observed although the teeth were smoother than they were prior to APF. As a result, it was concluded that APF treatment is responsible for decreased primary tooth surface roughness. The enamel surfaces etched for 20s showed that acid-etching was effective not only in removing scratches and debris, but also for evaluating enamel rod characteristics. Primary tooth enamel surfaces after etching showed minute structures caused by the decreased hydroxyapatite nanoparticle space, compared to those before etching. Also, acid-etching showed significantly increased roughness effects (p<0.0001, n=9). Finally, as more time elapsed after APF pre-treatment, the roughness was decreased to a lesser degree (p=0.005, n=9). We suggest that primary teeth etching 2 weeks after APF pre-treatment used clinically in pediatric hospitals may be effective to obtain properly etched enamel surfaces.

In vitro cariostatic effects of various iron supplements on the initiation of dental caries

Previous animal and laboratory studies have shown the possible cariostatic effect of iron. The purpose of this study was to in vitro study the effect of different concentrations of four iron supplements on the initiation of dental caries.

MATERIALS AND METHODS

Four products of iron supplements were used namely fre-in-sol, ferotonic, feromin and ferose. Two hundred extracted teeth were distributed randomly into 10 groups. Eight groups were from the four iron products in two concentrations (100% and 50%) in addition to the positive and negative control groups. Mutans streptococci bacteria (6715) grown in Todd Hewitt Broth were used. Assessment of decalcification and cavitation was done daily for 60 days.

RESULTS

It showed that different iron - supplement products play cariostatic effect in the initiation of the dental caries. With the exception of 100% and 50% ferose, both 100% and 50% concentrations of all supplements have cariostatic effect. The mean dates for decalcification varied with lowest for the positive control (12.2 days) and the highest was for 50% feromin. Cavitation was seen in the positive control and 100% ferose groups with mean on the first day of cavitation of 57 days.

CONCLUSION

It was concluded that iron may have cariostatic effect on the in vitro development of dental caries in human teeth.

Caries, gender and socio-economic change in the Xavante Indians from Central Brazil

BACKGROUND

The oral health conditions of indigenous peoples in Amazonia are closely associated with ecological and dietary changes related to interaction with non-Indians.

AIM

The study investigated the incidence of caries in an indigenous community from Central Brazil focusing on gender differences.

SUBJECTS AND METHODS

The research was conducted among the Xavante Indians and was based on longitudinal data collected in two surveys (1999 and 2004). The study included 128 individuals, 63 (49.2%) males and 65 (50.8%) females, divided in four age brackets (6-12, 13-19, 20-34, 35-60 years of age). The DMFT (decayed, missing and filled teeth) index and incidences (difference between 1999 and 2004) were calculated for each individual. The proportion of incidence was also calculated. Differences in caries risk between gender and age brackets were compared by parametric and non-parametric tests.

RESULTS

There were statistically significant differences in relation to caries incidence between age brackets and gender. The greatest incidence was observed in the 20-34 age bracket, which presented 3.30 new decayed teeth, twice the risk of the 6-12 age bracket (p<0.01), chosen as reference. While females in most age groups did not show higher risk for caries when compared to males, there was a 4.04-fold risk in the 20-34 age bracket (p<0.01).

CONCLUSION

It is concluded that factors related to the social functions of each sex (gender issues) and differential access to information, health services, and education may help to understand the differences observed in the incidence of caries.

In vivo enamel fluid movement

The aim of this study was to visualize fluid movement through dental enamel in vivo. Fifty permanent upper central incisors, from subjects aged 10-70 yr, and 5 permanent central just-erupted incisors, from subjects aged 6-7 yr, were included in the study. An impression was obtained by vinyl polyxiloxane, and replicas were then obtained by polyether impression material. The hydrophobic vinyl polyxiloxane material yielded a morphological image in situ of outward fluid flow through tooth enamel. The study confirmed in vivo that enamel is a permeable substrate, as shown by the presence of droplets on its surface, and demonstrated that age and enamel permeability are closely related. Samples from subjects of different ages showed a decreasing number and size of droplets with increasing age: freshly erupted permanent teeth showed many droplets covering the entire enamel surface. Droplets in permanent teeth were prominent along enamel perikymata.

Bonding properties of newly erupted and mature premolars

INTRODUCTION

The purpose of this study was to determine whether there were differences in bond strength between mature and newly erupted teeth when using both conventional and self-etching primer techniques for bonding orthodontic appliances. The nature of adhesive bond failure among the groups was also compared by using the adhesive remnant index (ARI).

METHODS

Premolars were collected, randomly divided, and bonded with either the conventional or the self-etching technique. Brackets were debonded on a testing machine with a shear-testing device. Bond strengths were compared with ANOVA and the Weibull analysis.

RESULTS

There were no statistically significant differences in bond strength values between the conventional etching and the self-etching primer groups or between newly erupted and mature teeth. ARI scores differed between mature and newly erupted teeth. Newly erupted teeth had more adhesive failures, and mature teeth had more cohesive bond failures at the enamel-composite resin interface.

CONCLUSIONS

Based on these results, bond strength does not appear to be affected by the posteruptive enamel maturation process.

The effect of a needs-related caries preventive program in children and young adults - results after 20 years

The risk for caries development in children varies significantly for different age groups, individuals, teeth, and surfaces. Thus from a cost-effectiveness point of view, caries preventive measures must be integrated and based on predicted risk from age group down to individual tooth surfaces. Based on this philosophy and experiences from continuously ongoing research on evaluating and reevaluating separate and integrated caries preventive measures, as well as methods for prediction of caries risk, a needs-related caries preventive program was introduced for all 0-19-year-olds in the county of Värmland, Sweden, in 1979. The goals for the subjects following the program from birth to the age of 19 years were: 1. To have no approximal restorations. 2. To have no occlusal amalgam restorations. 3. To have no approximal loss of periodontal attachment. 4. To motivate and encourage individuals to assume responsibility for their own oral health. The effect of the program is evaluated once every year on almost 100% of all 3-19-year-olds in a computer-aided epidemiologic program from 1979. Most of the individualized preventive program was carried out by dental hygienists or prophy dental assistants at clinics in the elementary schools. During the 20-year period the percentage of caries-free 3-year-olds increased from 51% to 97%. In 1999 as many as 86% of the 12-year-olds were caries free. Caries incidence was reduced more than 90% in all age groups. More than 90% did not develop any new caries lesions in 1999. As a consequence, caries prevalence was dramatically reduced. In 12- and 19-year-olds, the mean number of Decayed and Filled Surfaces (DFS) per individual was reduced from 6 to 0.3 and from 23 to 2 respectively. In 19-year-olds the mean number of approximal DFS was <1, and only 0.5 had to be filled. The mean number of occlusal DFS was <1. Since 1995 we have not been allowed to use amalgam in 1-19-year-olds in Sweden. As an effect of our high quality plaque program, approximal attachment loss was prevented, and by efficient education in self-care based on self-diagnosis, needs-related self-care habits were established. Thus it can be concluded that nearly 100% of our goals had been achieved.

First molar eruption related to plaque acidogenicity in children of different socio-economic status

OBJECTIVE

The aim of this study was to evaluate the association between the eruption stage of the lower first permanent molar and dental plaque acidogenicity. Socio-economic status (SES), gender, and oral hygiene condition were also variables considered.

MATERIAL AND METHODS

230 children between 6 and 8 years of age were recruited from one public and one private primary school with different SES in Lima, Peru. Clinical examinations were performed to assess lower first permanent molar eruption stage, plaque acidogenicity, and oral hygiene condition. Bivariate associations were analyzed through chi-square tests and the variable interactions were analyzed through a hierarchical log-linear analysis with backward elimination.

RESULTS

21.8% of the population had highly acidogenic plaque, 34.3% acidogenic plaque, and 43.9% non-acidogenic plaque. Of the lower first permanent molars, 46.1% were fully erupted, whereas 53.9% were partially erupted. According to the final log-linear model, children with fully erupted molars and non-acidogenic plaque are less frequent in low than in high SES. Also, the frequency of children with partially erupted molars and acidogenic to highly acidogenic plaque is higher in males than in females. Finally, fully erupted molars and non-acidogenic plaque are more frequent in children with good hygiene than in children with moderate to poor hygiene.

CONCLUSIONS

Association between eruption stage of the lower first permanent molar and plaque acidogenicity was not significant in a bivariate context. However, in a multivariate context, socio-economic status, oral hygiene condition, and gender had an impact on the association between the two main variables.

Time-dependent decrease and seasonal variation of the porosity of recently erupted sound dental enamel in vivo

Recently erupted teeth are more sensitive to dental caries than teeth that have remained free from caries lesions for a few years after eruption. It has been hypothesized that this may be ascribed to differences in enamel porosity. The objective of the present work was to assess the time-dependence of electrical conductance, as an indication of porosity, of occlusal enamel in recently erupted permanent molar teeth. Fifty children aged 5-15 years of age, receiving regular dental care at six-month intervals, participated in the study when their first molar teeth (in 5- to 6-year-olds) or their second molar teeth (in 11- to 15-year-olds) had not been exposed to the oral environment for more than six months. On the first semi-annual check-up after eruption of a first or second molar, baseline diagnostic measurements, i.e., visual inspection and electrical conductance measurements (ECMs), were made at three or four pre-defined sites in the fissures. Subsequently, data collection was repeated every six months for three years. Sites were excluded from ECMs when a caries lesion was observed at a site by visual inspection. After 36 months, there were 257 sites in teeth considered sound upon visual examination. The ECM values of these sound sites showed a clear decrease with time after the first examination. The conductance decreased on average from 0.13 (Momega)(-1) to 0.059 (Momega)(-1). Since the conductance is assumed to be proportional to the porosity of the enamel, the latter decreased by a factor of 2.2 over the 36-month period. The results furthermore indicated a higher conductance for maxillary than for mandibular enamel. Almost all sites in that sample appeared to be in teeth that were observed for the first time during the months September to December. Electrical conductance, and therefore enamel porosity, of the sites showed a periodic variation with season of observation: In the fall, the conductance was higher than in the spring. This implies that a dentist should be more prudent in the fall than in the spring when indicating restorative treatment of an incipient caries lesion.

Amalgam restoration and in vitro caries formation

Black's class I classic cavity preparations were completed in 124 extracted intact human premolars, of which 120 were restored with one of two silver amalgams, five different base combinations, and with or without cavity varnish. This resulted in 20 different restoration combinations. The other four teeth remained unrestored. Aging for 3 months and 1 year in 1% NaC1 at 20 degrees C followed. After aging, 80 of the restored teeth and the four unrestored teeth were subjected to an in vitro bacterial challenge for 36 days. The other 40 specimens were placed in an acidified (pH 4.0) broth for the same length of time. Sections were prepared for polarized light microscopy, and outer wall and dentin carious lesions were measured. The results were evaluated with one-way ANOVA and Tukey's Student range test with a critical level of statistical significance of p < 0.05 and p < 0.005. Lesions produced by bacterial challenge were significantly smaller than those formed by acidified broth. Aging time and varnish did not significantly influence lesion size. Low copper amalgam, a calcium hydroxide paste base, and restoration per se significantly reduced lesion size. Reproducible measurement of wall lesion length was not possible. Secondary caries lesion size can be minimized by judicious selection of restoration material combinations.

Reactivity of young and old human enamel to demineralization

The aim of this study was to determine the susceptibility of newly erupted and old permanent teeth to artificial, caries-like attacks. Two groups of caries-free teeth were used. Group 1 consisted of 38 teeth extracted for orthodontic reasons (9-12-yr-old children); group 2, of 40 teeth extracted for periodontal reasons (45-65-yr-old patients). After thorough cleaning, a test window was isolated on the incisal two-thirds of the buccal surface. After demineralization with 6% HEC gel at pH 4.9 for 8 days, longitudinal ground sections were prepared for imbibition studies in polarized light and for secondary ion mass spectrometry (SIMS). In the young teeth, the lesions appeared to be uniform in their extension in the enamel, whereas the old teeth showed less marked and thinner surface zones and greater depth of the positively birefringent body of the lesion. Polarized light microscopy and SIMS data support the hypothesis that there are different enamel pathways in the initiation of the natural carious process.