Survival and success of composite resin restorations in endodontically treated maxillary incisors with minimal structure loss

The primary aim of this study was to evaluate the clinical performance of nanofilled composite resin restorations in traumatized, endodontically treated maxillary incisors with structural loss of 40% or less. The performance of the restorations was assessed in terms of longevity (survival) and esthetics (success) over a 20-month period. The secondary objective was to employ a novel digital method to quantify preoperative tooth structure loss. Sixty-one fractured maxillary incisors in 55 patients were included in the study. The teeth were photographed with a digital single-lens reflex camera equipped with a macro ring flash. The amount of lost tooth structure was calculated with digital photography software. The teeth were restored with a nanohybrid composite resin and self-etching adhesive system bonding agent. To assess esthetics, color change in the blue-yellow axis (Δb*) of the composite resin restoration was evaluated digitally with the Commission Internationale de l'Eclairage (CIE) L*a*b color system. The Wilcoxon signed-rank test was used to assess Δb*, and a Kaplan-Meier survival analysis was used to assess the longevity of the restorations. The study findings showed a statistically significant difference between pretreatment and posttreatment b* values (P < 0.05), but the difference was too small to be clinically perceptible to the human eye. A total of 5 restorations (9.8%) failed. The remaining restorations survived for a mean (SD) period of 18.6 (4.4) months. The log-rank test did not show any significant association between the amount of residual tooth structure and success of the restoration. The results of this study showed that use of direct composite resin restorations in endodontically treated maxillary incisors resulted in acceptable survival and success rates. Trial registration: Clinical Trial Registry of India No. CTRI/2020/01/023019.

Investigation of the esthetic outcomes of white spot lesion treatments

Objective

The present study compared the ability of bleaching, resin infiltration and microabrasion to restore the appearance of existing white spot lesions (WSL) on tooth surfaces as close as possible to that of the original healthy enamel.

Materials and Methods

Sixty extracted human teeth with WSL were randomly assigned to three treatment groups (20/group). Prior to treatment, the colour of the surrounding healthy enamel and the WSL were measured as the baseline and pre-treatment (PreRX) colours respectively using spectrophotometer based on CIE L*A*B. The L-value was used for the statistical comparison. WSLs in each group were treated respectively by bleaching, infiltration or microabrasion following the manufacturer's instructions. Colour measurement was repeated after treatment. Both intragroup and intergroup comparisons were performed using ANOVA followed by Tukey's multiple comparison test (α=0.05).

Result

In all groups the mean L-values were significantly higher in PreRX WSL (P < 0.01; Tukey) compared to baseline (sound enamel). After treatment the difference in mean L-value between baseline and WSL increased significantly (P < 0.01, Tukey) in Bleaching and Microabrasion groups by 1.4% and 1% respectively, but decreased in Infiltration group by 3.4%. Thus resin infiltration decreased the L-value of the WSL, bringing it closer to the L-value of the sound enamel while bleaching and microabrasion increased the L-value.

Conclusions

Among the three treatment modalities investigated in this study, resin infiltration was the most effective in masking the WSLs.

Remineralisation - the buzzword for early MI caries management

Minimal intervention (MI) dentistry aims to preserve dental tissues first and restore only when indicated, thus remineralisation of initial (non-cavitated) caries lesions, an integral part of caries management, is an essential treatment strategy in MI. With this understanding, dental practitioners are increasingly embracing the principle of non-operative treatment of initial caries lesions. The purpose of this review was to summarise the most recent literature published in non-operative management of dental caries. Three electronic databases (MEDLINE, EMBASE, Cochrane CENTRAL) were searched, and clinical studies, systematic reviews and meta-analysis were included. This report outlines the strategies and numerous therapeutic materials available to aid in arrestment/remineralisation of initial caries lesions on root and coronal surfaces. However, the level of evidence of effect is variable, as well as the availability in different parts of the world. Options available to practitioners will vary when placing emphasis on the level of evidence supporting them. Strong clinical evidence support the effectiveness of pits/fissure sealants for therapeutic management of active initial caries on occlusal surfaces, and fluoride varnishes for remineralisation of caries lesions on root and coronal smooth surfaces, including proximal surfaces. Other materials formulated to enhance the effectiveness of any chosen remineralisation strategy were discussed. However, it is absolutely necessary that all caries remineralisation treatment be complemented with general behavioural modification in oral health through motivational interviewing directed towards change in oral hygiene to control plaque, dietary attitude modification to reduce the frequency of intake of fermentable sugars, and establishment of risk-based recall visits.

Remineralization of artificial enamel lesions by theobromine

OBJECTIVE

This study investigated the remineralization potential of theobromine in comparison to a standard NaF dentifrice.

METHODS

Three tooth blocks were produced from each of 30 teeth. Caries-like lesion was created on each block using acidified gel. A smaller block was cut from each block for baseline scanning electron microscopy imaging and electron-dispersive spectroscopy (EDS) analysis for surface Ca level. A tooth slice was cut from each lesion-bearing block for transverse microradiography (TMR) quantification of baseline mineral loss (Δz) and lesion depth (LD). Then baseline surface microhardness (SMH) of each lesion was measured. The three blocks from each tooth were assigned to three remineralizing agents: (1) artificial saliva; (2) artificial saliva with theobromine (0.0011 mol/l), and (3) NaF toothpaste slurry (0.0789 mol/l F). Remineralization was conducted using a pH cycling model with storage in artificial saliva. After a 28-day cycle, samples were analyzed using EDS, TMR, and SMH. Intragroup comparison of pre- and posttest data was performed using t tests (p < 0.05). Intergroup comparisons were performed by post hoc multistep comparisons (Tukey).

RESULTS

SMH indicated significant (p < 0.01) remineralization only with theobromine (38 ± 32%) and toothpaste (29 ± 16%). With TMR (Δz/lD), theobromine and toothpaste exhibited significantly (p < 0.01) higher mineral gain relative to artificial saliva. With SMH and TMR, remineralization produced by theobromine and toothpaste was not significantly different. With EDS, calcium deposition was significant in all groups, but not significantly different among the groups (theobromine 13 ± 8%, toothpaste 10 ± 5%, and artificial saliva 6 ± 8%).

CONCLUSION

The present study demonstrated that theobromine in an apatite-forming medium can enhance the remineralization potential of the medium.

Tooth-surface-specific effects of xylitol: randomized trial results

The Xylitol for Adult Caries Trial was a three-year, double-blind, multi-center, randomized clinical trial that evaluated the effectiveness of xylitol vs. placebo lozenges in the prevention of dental caries in caries-active adults. The purpose of this secondary analysis was to investigate whether xylitol lozenges had a differential effect on cumulative caries increments on different tooth surfaces. Participants (ages 21-80 yrs) with at least one follow-up visit (n = 620) were examined at baseline, 12, 24, and 33 months. Negative binomial and zero-inflated negative binomial regression models were used to estimate incidence rate ratios (IRR) for xylitol's differential effect on cumulative caries increments on root and coronal surfaces and, among coronal surfaces, on smooth (buccal and lingual), occlusal, and proximal surfaces. Participants in the xylitol arm developed 40% fewer root caries lesions (0.23 D2FS/year) than those in the placebo arm (0.38 D2FS/year; IRR = 0.60; 95% CI [0.44, 0.81]; p < .001). There was no statistically significant difference between xylitol and control participants in the incidence of smooth-surface caries (p = .100), occlusal-surface caries (p = .408), or proximal-surface caries (p = .159). Among these caries-active adults, xylitol appears to have a caries-preventive effect on root surfaces (ClinicalTrials.gov NCT00393055).

Clinical evaluation of an enhanced white light and fluorescence device for early detection of caries lesions

OBJECTIVE

Sensitivity of a device based on Fluorescence Imaging with Reflectance Enhancement (FIRE) in detecting a potential incipient lesion (PIL) was compared with visual examination to demonstrate non-inferiority to it.

METHODS

Visual examination (VE) and an investigational device (ID) were used to detect PIL (actual incipient caries [AIC] and hypomineralization). Seventeen subjects satisfied data analysis criteria. Two-hundred and seventy-seven AIC and 367 hypomineralizations reached VE consensus. Ground truth was generated from consensus VE results and image information from enhanced white light (eWL) and FIRE images. Data from VE and ID in Still Image (IDSM) and Video (IDVM) modes were evaluated against ground truth.

RESULTS

Overall sensitivity of VE, IDSM, and IDVM evaluated against ground truth were 0.94, 0.884, and 0.848, respectively, for Actual Incipient Caries (AIC) detection, and 0.95, 0.916, and 0.883, respectively, for PIL detection. Sensitivity of ID in both modes was > 90% that of VE, thus demonstrating non-inferiority of IDSM and IDVM to VE.

CONCLUSION

The investigated eWL and fluorescence device is clinically effective and at least as good as expert VE in detecting PIL. An enhanced white light device with FIRE technology can be used, in Video or Still Image Detection modes, as an aid to caries diagnosis.

In situ remineralization of early caries by a new high-fluoride dentifrice

The present study evaluated the ability of a high-fluoride dentifrice containing tricalcium phosphate to remineralize white spot lesions and inhibit lesion formation. Three demineralized enamel blocks and three healthy blocks (cut from a group of 30 molars), were exposed in pairs (one demineralized, one sound) via an appliance worn by 30 adults in a three-phase crossover study lasting 28 days per phase. The pairs were exposed to three dentifrices: one contained 5,000 ppm fluoride with tricalcium phosphate, one contained 5,000 ppm fluoride alone, and one contained no fluoride at all. Lesion status was analyzed using surface microhardness and transverse microradiography. Surface microhardness showed that the two dentifrices containing fluoride significantly inhibited enamel demineralization (p < 0.05) and significantly remineralized white spot lesions (p < 0.05), while the fluoride-free dentifrice did not. The results indicate that combining fluoride with tricalcium phosphate could provide more anti-caries benefits compared to using fluoride alone.

A survey on education in cariology for undergraduate dental students in Europe

The aim of the survey was to collect relevant information about education in cariology for dental undergraduate students in Europe. The ORCA/ADEE cariology curriculum group prepared a questionnaire that was mailed in 2009 to 179 European dental schools. One hundred and twenty-three dental schools (72%) from 32 countries completed and returned the questionnaires. In most of these schools, education in cariology is delivered by at least two different units. The units mainly involved are Paediatric Dentistry, Conservative Dentistry, Restorative Dentistry or Operative Dentistry. Theoretical education in cariology is delivered by practically all responding dental schools, and in 96% of these schools, it starts within the first 3 years. Pre-clinical exercises are offered by 98% of the schools starting mainly in the third or fourth year. In 97% of the schools, clinical exercises are carried out, and this occurs mainly in the fourth and fifth year. In nearly all dental schools (88%), education in cariology comprises not only caries but also dental erosion and non-erosive wear. The vast majority of the responding dental schools (89%) supported the idea of developing a European Core Curriculum in Cariology.

Remineralization of early caries by a nano-hydroxyapatite dentifrice

OBJECTIVE

The purpose of this randomized, double-blind, crossover, in situ study was to evaluate the efficacy of nano-hydroxyapatite (nHAP) dentifrices on caries remineralization and demineralization inhibition.

METHODS

Three demineralized enamel blocks (A,B,C) and one healthy block (D), cut from each of 30 molars, were exposed respectively to dentifrices of A) 5% nHAP, B) 10% nHAP, C) 1100 ppm fluoride, and D) 10% nHAP via an intra-oral appliance worn by 30 adults in this four-phase study lasting 28 days per phase. Baseline and post-test mineral loss (delta Z) and lesion depth (LD) were quantified using microradiography.

RESULTS

Pair-wise comparison (baseline versus test) demonstrated significant (p < 0.001) reductions in delta Z and LD in A, B, and C. ANOVA showed no significant differences among the three products in percent mineral gain. No demineralization occurred in the sound enamel specimens exposed intra-orally while using 10% nHAP.

CONCLUSION

nHAP dentifrice caused remineralization comparable to a fluoride dentifrice, and inhibited caries development, thus suggesting that an nHAP dentifrice can be an effective alternative to fluoride toothpaste.

Recall, reassessment and monitoring

A recall system is a continuing care regime which provides opportunities to reassess and monitor the oral health of patients and to inform future treatment planning. There is some evidence that recall visits have a positive impact on the natural and functional dentition. Unfortunately, there is a general paucity of reliable evidence about the timing of recall visits despite the widely adopted 6-month interval. In response to political, professional and patient uncertainty, the UK National Institute of Health and Clinical Excellence (NICE) convened a guideline development group to consider both best evidence and best practice in this field. The NICE issued a guidance document in 2004 recommending that the individual risk status should determine the patient's recall interval. The recommendations cover risk factors such as caries incidence and restorations; periodontal health and tooth loss, patients' well-being, general health and preventive habits, pain and anxiety. Methods and tools to facilitate and standardize the collection of risk information are currently being developed and/or collated by the Scottish Dental Clinical Effectiveness Programme. The selection of a recall interval is a multifaceted and complex decision involving the judgement of both clinician and patient. More research is needed into the rate of progression of oral diseases and the impact of recall on oral health and quality of life. Nevertheless, the NICE guidance is based on the best available evidence, and it should be used to determine personalized variable time intervals to assess, reassess and monitor the oral health and caries status of patients.

Dental erosion: possible approaches to prevention and control

OBJECTIVES

To discuss the key elements for establishment of a preventive programme for dental erosion.

DATA AND SOURCES

The data discussed are primarily based on published scientific studies and reviews from case reports, clinical trials, epidemiological, cohort, animal, in vitro and in vivo studies. References have been traced manually or by MEDLINE.

STUDY SELECTION

The aetiology, pathogenesis and modifying factors of dental erosion were reviewed. Strategies to either prevent the occurrence or limit the damage of dental erosion or protect the remaining tooth tissues from further erosive destruction were reviewed and discussed. These includes: (A) measures to (1) enhance remineralisation and acid resistance of enamel surface softened by erosive challenge, (2) reduce the erosive potential of acidic products, (3) enhance salivary flow, (4) protect and restore erosively damaged tooth, and (5) provide mechanical protection against erosive challenge. (B) Health education geared towards (1) diminution of frequency of intake of dietary acids, and (2) change of habits and lifestyles that predispose teeth to erosion development.

CONCLUSIONS

It may be easier to gain patients' compliance with the advice that immediately following an acidic challenge, a remineralising agent, such as fluoride mouthrinses, fluoride tablets, fluoride lozenges or dairy milk, should be administered to enhance rapid remineralisation of the softened tooth surface as well as serve as a mouth refresher, or an alternative, a neutralising solution should be used. Effective counselling on erosion preventive regimes should involve all healthcare personnel, dentists, doctors, pharmacist, nurses/hygienists and clinical psychologists.

Influence of abrasion in clinical manifestation of human dental erosion

The influence of abrasion from oral soft tissues on softened enamel lesion remineralization and erosion development was investigated. Using orange juice, softened enamel lesions were produced on 20 human premolars assigned randomly to 10 volunteers. Sections used as control and two test slabs were cut from each tooth. One of the two slabs from each tooth had an appliance built on it, which protected the lesion from abrasion. The two slabs (with/without appliance) were bonded to the palatal surfaces of upper right and left lateral incisor teeth of the participants who chewed sugar-free gum four times daily. After 28-day intra-oral exposure, mineral loss (Delta Z) and lesion depth (ld) in both control and test samples were quantified using transverse microradiography, and the data was analysed by paired t-test. Delta Z was significantly lower in lesions with appliance (protected), but higher in lesions without appliance (unprotected) when compared with control (unexposed). Similar pattern was observed with lesion depth. In unprotected slabs the lesions were abraded resulting in eroded enamel lesions. It was concluded that erosion observed clinically is the combined effect of demineralization of the tooth surface by an erosive agent and abrasion of the demineralized surface by surrounding oral soft tissues and through food mastication. Abrasion from oral soft tissues can contribute to site-specificity of dental erosion.

Use of optical coherence tomography for assessment of dental caries: quantitative procedure

A method for quantitative assessment of dental caries using optical coherence tomography (OCT) was demonstrated. Development of caries lesions in 15 bovine teeth, by demineralization in acidic buffer solution, was quantitatively assessed daily for 3 days, using OCT. An OCT system which can collect A-scans (depth versus reflectivity curve), B-scans (longitudinal images) and C-scans (transverse images at constant depth) was used. While the B- and C-scans qualitatively described the lesion detected, the A-scan which showed the depth (mm) resolved reflectivity (dB) of the tooth tissue was used for the quantitative analysis. After a simple normalization procedure to determine the actual depth the light travelled into the tooth tissue, the area (R) under the A-scan was quantified as a measure of the degree of reflectivity of the tissue. The result showed that R (dB mm) decreased with increasing demineralization time. The percentage reflectivity loss (R%) in demineralized tissue, which related to the amount of mineral loss, was also calculated, and it was observed that R% increased with increasing demineralization time. It was concluded that with the above procedure, OCT could quantitatively monitor the mineral changes in a caries lesion on a longitudinal basis.

Enamel demineralization in situ with various frequencies of carbohydrate consumption with and without fluoride toothpaste

There is little information in the literature on the relationship among the frequency of carbohydrate consumption, the use of fluoride toothpaste, and enamel demineralization. The aim of this investigation was to compare the extent of demineralization of enamel slabs in situ, with a sugar-based solution, consumed in constant amounts but with various frequencies in subjects both with and without the use of fluoride (F) toothpaste. Eight subjects wore removable mandibular appliances carrying an enamel slab cut from white-spot lesions. The subjects were required to drink 500 mL of a 120-gm/L sugar solution either once, 3, 5, 7, or 10 times/day for 30 sec on each occasion, for a period of 5 days while brushing their teeth twice daily with either a F (1450 ppm NaF) or a F-free toothpaste. Mineral analysis revealed that when the subjects used a F toothpaste, net demineralization was evident only with the seven- and 10-times/day regime (ns). When F-free toothpaste was used, statistically significant demineralization was observed when the frequency exceeded 3 times/day. This study demonstrates the importance of F-containing toothpaste in enamel re-/demineralization by varying the frequency of carbohydrate challenge

Eroded enamel lesion remineralization by saliva as a possible factor in the site-specificity of human dental erosion

The composition and flow of saliva, which determine its functions, vary within intraoral sites and among individuals. Also, the susceptibility to tooth erosion reportedly varies among individuals and within the dental arches. A possible effect of saliva on early-eroded lesions may be a contributory factor. The aims here were firstly to determine the remineralization of eroded enamel lesions by saliva, and secondly to investigate any variation of this remineralization within the dental arches and among individuals. Early enamel erosion was produced on human premolars using orange juice. Control sections and two test slabs were cut from each tooth. The two slabs from the same lesion were bonded with composite resins to the palatal surface of upper right lateral incisor teeth and the lingual surface of the lower right lateral incisor teeth of volunteers, who then chewed a sugar-free gum four times daily. After 28-day intraoral exposure, mineral loss (DeltaZ) and lesion depth (ld) were quantified using microradiography and the data analysed by paired t-test (n=10, alpha=0.05). Mean DeltaZ was significantly lower in the group of slabs positioned palatally (P<0.001) and lingually (P<0.001) when compared with the control group, and in the lingually placed group when compared with the palatally positioned (P<0.01). A significantly lower ld was observed in the group of slabs positioned palatally (P<0.05) and lingually (P<0.001) when compared with the control group, and in the lingually positioned group when compared with the palatally placed (P<0.05). It was concluded that saliva can remineralize early enamel erosion, and that the degree of remineralization varies within intraoral sites and may be responsible for the differing susceptibility to erosion within the dental arches.

In vitro remineralisation of eroded enamel lesions by saliva

OBJECTIVES

It is speculated that saliva, with its mineral content, may possess a reparative effect on an early erosion which is characterised by softened surface and slight subsurface demineralisation in addition to a crater. This study aimed to determine the possible remineralisation of early enamel erosion by saliva.

METHODS

Eroded lesions were produced in bovine incisors by 1-h immersion in orange juice. Control sections and three experimental slabs were produced from each tooth. The three slabs were assigned randomly to one of three remineralising agents: clarified natural saliva (NS), artificial saliva (AS) and remineralising solution (RS). All solutions had a pH of 7.2, a fluoride concentration of 0.022 ppm, and were changed daily. NS was collected daily from the same individual at the same time of day. The specimens were exposed to their respective remineralising agents for 28 days. Using microradiography and image analysis, the mineral loss (Delta z) and lesion depth (ld) were quantified in sections cut from the control and experimental slabs.

RESULTS

A significant (p<0.001) amount of mineral was gained following exposure to each remineralising agent. Significantly less Delta z and ld were observed for the experimental groups compared with the control group (p<0.001; paired t-test). This effect was greatest with RS and least with AS. Inter-group comparison (Duncan multiple tests) showed no significant difference in Delta z among the experimental groups, however ld was significantly higher for AS (p<0.001) compared with RS and NS, and no difference was observed between RS and NS.

CONCLUSION

Saliva as well as remineralising solutions can remineralise early enamel erosion.

Efficacy of sterilisation methods and their effect on enamel demineralisation

The aim of this project was to determine the effectiveness of sterilisation methods for dental enamel for use in intra-oral cariogenicity tests, and their possible effect on the degree of demineralisation of enamel. Bovine incisors were cut vertically into five portions and each assigned to one of five groups. Group 1 was used as a control while the other four groups were subjected, respectively, to gamma irradiation ( congruent with 25kGy), steam autoclaving (121 degrees C for 15 min), sodium hypochlorite (12% w/v for 24h) and povidone-iodine (7.5% w/v for 24h). Total viable counts of microorganisms remaining following sterilisation of the specimens were performed following incubation of the specimens for 24h at 37 degrees C. Caries-like lesions were produced in each specimen using an acidic buffer solution (pH4.5). Sections were cut from each specimen, ground to 80-microgram thickness, and microradiographed. Mineral loss and lesion depth were quantified using transverse microradiography. Statistical analysis was by ANOVA. Dunnett's and Tukey's tests. Microbial growth (Staphylococcus aureus and bacilli) was observed only in control specimens in both brain heart infusion broth and on blood agar plates. The sterilisation methods affected the enamel surface as follows: gamma irradiation (cream discolouration), NaOCl (bleaching), and povidone-iodine (white spot-like lesion). Compared with the control, there was no significant difference in mineral loss and lesion depth with any of the groups, but the numerical values of mineral loss and lesion depth in groups can be ranked as follows: gamma irradiation <povidone-iodine <control <autoclave <NaOCl. In conclusion, the four sterilisation methods were all effective to sterilise enamel, but gamma irradiation proved the most acceptable method for enamel to be used in cariogenicity tests having the least adverse effect.

Use of transverse microradiography to quantify mineral loss by erosion in bovine enamel

The aim of the present study was to develop transverse microradiography (TMR) in order to quantitatively assess the influence of artificial saliva and orange juice on the erosion of bovine enamel. Bovine incisors were sectioned sagittally into two equal halves. Each half was coated with acid-resistant nail varnish except for a rectangular enamel window on the labial surface of the tooth. While both halves of each tooth were immersed in pure orange juice 6 times daily for a period of 5 min at each occasion making a total of 30 min per day, one half was stored in artificial saliva and the other half in deionized distilled water between exposures to orange juice and for the remaining 12 h overnight, for 24 days making a total of 12 h of exposure to orange juice. Sections bearing intact and eroded enamel surfaces were cut from each specimen and ground to 80 microm thickness, and TMR of the sections was made. Mineral loss was quantified from the microradiographs using two-step image analysis. Mineral loss was significantly greater in those specimens cycled in orange juice and de-ionized distilled water. TMR was used successfully to quantify the mineral loss by erosion in vitro, and it is envisaged that it will be useful for specimens used in intra-oral appliances during in situ trials. Artificial saliva saturated with respect to calcium and phosphate salts can possibly remineralize an erosive lesion and may reduce the degree of erosion.

Thickness of acquired salivary pellicle as a determinant of the sites of dental erosion

Dental erosion shows a typical distribution pattern within the dental arches. Tooth protection from erosion by salivary pellicle has been shown in vitro, but the hypothesis that pellicle may differ quantitatively at sites of erosion has not been investigated. This study aimed to determine the thickness of acquired salivary pellicle within the dental arches, investigate the possible relationship of this thickness to the distribution and severity of erosion within the arches, and confirm the protective effect of pellicle against dental erosion. Eight enamel blocks were produced from each of 5 bovine incisors assigned to five volunteers. Each block was further cut into 2 slabs, producing control and experimental slabs. Pellicle developed on experimental slabs located on 8 intra-oral sites after 1 hr of exposure was stained by "sheep anti-human IgGAM-FITC". Slabs were then visualized, and pellicle thickness measured, by confocal laser scanning microscopy. Eroded enamel lesions were produced in experimental and control slabs by means of pure orange juice. The degree of erosion was quantified by transverse microradiography. Pellicle thickness varied significantly within the dental arches and among individuals. An inverse relationship (r = -0.96, p<0.001) was observed between the degree of erosion and pellicle thickness. Significant differences in erosion were observed between slabs with and those without pellicle. This study has shown that the thickness of acquired salivary pellicle varies within the dental arches, which may be responsible for the site-specificity of dental erosion, and that pellicle does protect the teeth from erosion.

The use of gamma irradiation for the sterilization of enamel for intra-oral cariogenicity tests

The dose of gamma irradiation sufficient to sterilize enamel samples to be used for intra-oral cariogenicity tests (ICT) without alteration to the structure or solubility of the enamel was determined. Each bovine incisor used was cut vertically into eight portions and each portion assigned to one of eight groups. Group 1 was used as control while other groups were subjected to respective doses of gamma irradiation from a cobalt-60 source. Following sterilization, both control and experimental groups were incubated in nutrient broth for 7 days at 37 degrees C under aerobic and anaerobic conditions. Caries-like lesions were subsequently produced in each specimen using acidic buffer solution, and mineral loss quantified using transverse microradiography. Data were analysed statistically. There was no significant difference in mineral loss between the control and experimental groups, but the numerical value of mineral loss was lower in groups irradiated with> 4080 Gy, in addition to full sterilization and enamel discoloration to cream colour observed in these groups. Microbial growth was observed in the control group and in groups irradiated with <4080 Gy but no discoloration. With 4080 Gy full sterilization without discoloration was observed. It was concluded that 4080 Gy of gamma irradiation is optimal for sterilization of enamel samples for use in ICT.

Factors influencing the development of dental erosion in vitro: enamel type, temperature and exposure time

The influence of temperature, duration of exposure, and enamel type on the development and progression of dental erosion has been determined. Three experiments were devised as follows. Eroded lesions were produced on enamel samples with orange juice: (1) at different temperatures; (2) for different lengths of time; and (3) on bovine permanent, human deciduous and human permanent enamel. Lesion parameters (mineral loss and lesion depth) were quantified using transverse microradiography. Both lesion parameters were significantly lower at 4 degrees C when compared with 20 degrees C and 37 degrees C, and at 20 degrees C when compared with 37 degrees C. Lesion parameters increased significantly as the length of exposure increased, and were positively correlated (r=0.98, P<0.05) to the exposure time. Both parameters were significantly greater in bovine enamel than human permanent and deciduous enamel, and in human deciduous than permanent enamel. Lesion progression, as measured by mineral loss, was in the ratio 2.0:1.5:1.0 for bovine:human deciduous:human permanent, and by lesion depth, 1.7:1. 3:1.0. In conclusion, the erosiveness of orange juice was less pronounced at a lower temperature, and increased with an increased exposure time. Erosion progressed twice as fast in bovine permanent than in human permanent enamel, and 1.5 times more rapidly in human deciduous than in permanent enamel.

Caries inhibiting and remineralizing effect of xylitol in vitro

This study aimed to determine the effect of xylitol on the development and remineralization of caries in vitro, and to compare this effect with that of fluoride alone and in combination. Two experiments were devised. In experiment 1, bovine incisors were each sectioned into 4 portions which were randomly assigned to 4 demineralizing agents: A) acidic buffer (x), B) x + 0.5 ppm fluoride, C) x + 20% xylitol, and D) x + 20% xylitol + 0.5 ppm fluoride. Caries-like lesions were produced in specimens. In experiment 2, carious lesions were produced in teeth. Five lesion-bearing slabs were cut from each tooth. While one was reserved as control (UN), others were randomly assigned to 4 remineralizing agents: 1) artificial saliva (y), 2) y + 0.05 ppm fluoride, (3) y + 20% xylitol, and 4) y + 20% xylitol + 0.05 ppm fluoride. Mineral loss (delta Z) and lesion depth (ld) were quantified after 4-week remineralization. In experiment 1, numerical values of delta Z and ld observed can be ranked as A > C > B > D. These differences were significant only in B and D when compared with A for delta Z, but not between any group for ld. In experiment 2, the numerical values of delta Z and ld for control UN (unremineralized) and remineralized groups (1-4) ranked as UN > 3 > 4 > 1 > 2. Compared with UN, this difference was significant in all groups with ld, but not in any group with delta Z. We concluded that tolerable levels of xylitol alone may not show a significant caries inhibiting and remineralizing effect, but may act as a caries inhibitor additively with fluoride.

Techniques for the production of dental eroded lesions in vitro

This project firstly demonstrated an in vitro technique for the production of eroded lesions which simulates the in vivo conditions, and secondly evaluated the influence of salivary parameters on the degree of erosion in vitro. Teeth were sectioned sagitally into three equal portions. The portions were randomly assigned to one of three experimental groups (A, B and C). Lesions were produced by cycling the teeth between orange juice and either artificial saliva (A) or water (B) for a total period of 12 h, or by a single 12 h immersion in orange juice (C). Sections were prepared from each specimen and mineral loss was quantified using transverse microradiography. Mineral loss was significantly lower in group A compared with B and C. Greatest mineral loss was observed in B though not significant when compared with C. The present technique mimics the in vivo conditions with the saliva reducing the degree of erosion and possibly remineralizing the lesions.

Factors affecting the development of carious lesions in bovine teeth in vitro

This study aimed to determine the effect of temperature, duration of exposure, position on enamel surface, and type of demineralization solution on the production of caries-like lesions in bovine enamel in vitro, and to establish the conditions for the formation of artificial caries in bovine enamel. Caries-like lesions were produced in incisal, middle and cervical sites on enamel samples, with either an acidified hydroxyethylcellulose gel system or a partially saturated acidic buffer solution at either 20 degrees C or 37 degrees C for 3, 4, or 5 days. Lesion variables (mineral loss/lesion depth) were quantified. Regular subsurface lesions were produced in all specimens in acidic buffer solution within 3 days at either temperature. In gel, caries-like lesions were produced in 62% of the specimens at 37 degrees C and in 49% at 20 degrees C, while the remaining specimens were either eroded or softened. Mineral loss and lesion depth were significantly greater with buffer than with gel, and with increased length of exposure in either solution. There were no significant differences in either variable with position or temperature in either solutions, though numerically both variables were greater at the cervical site, and at 37 degrees C in either solution. It was concluded that caries-like lesions can be consistently produced in bovine enamel with a partially saturated acidic buffer solution at 20 degrees C or 37 degrees C within 3 days.

The influence of xylitol and fluoride on dental erosion in vitro

The aim was to determine the effect of xylitol, fluoride and xylitol/fluoride combined on the erosion of dental enamel by pure orange juice in vitro. Freshly extracted bovine incisors were sectioned vertically into four equal portions. Each portion was then coated with an acid-resistant nail varnish except for an enamel window on the labial surface of the tooth. These were then divided into four groups with each group containing one portion of each tooth selected randomly. Four erosive agents were prepared as follows: (A) pure orange juice only; pure orange juice plus either (B) xylitol (25% w/v) or (C) fluoride (0.5 parts/10(6)) or D) xylitol/fluoride (25% and 0.5 parts/10(6) respectively). Each group was assigned to one of the erosive agents and immersed six times daily for a period of 5 min on each occasion and stored in artificial saliva between exposures and for 12 hr overnight, for 24 days making a total of 12 hr of exposure to the assigned erosive agent. Sections were cut from each enamel specimen ground to a thickness of 80 microns and microradiographed. Mineral loss was quantified by a two-step image analysis. Mineral loss was significantly lower (p < 0.05) in group D (xylitol/fluoride) only when compared with group A (pure orange juice only). The numerical values of mineral loss could be ranked as follows: group D < group C < group B < group A. It was concluded that xylitol and fluoride have an additive effect in the reduction of dental erosion by pure orange juice in vitro.