Tooth wear and bruxism: A scoping review

OBJECTIVE

This study presents a scoping review to determine the association between tooth wear and bruxism.

DATA

A protocol was developed a priori (Open Science Framework (DOI 10.17605/OSF.IO/CS7JX)). Established scoping review methods were used for screening, data extraction, and synthesis. Risk of bias was assessed using JBI tools. Direct associations between tooth wear and bruxism were assessed.

SOURCES

Embase, SCOPUS, Web of Science, Cochrane, and PubMed were searched.

STUDY SELECTION

Any clinical study containing tooth wear and bruxism assessment done on humans in any language was included. Animal, in-vitro studies and case reports were excluded.

CONCLUSIONS

Thirty publications reporting on the association between tooth wear and bruxism were included. The majority of publications were cross-sectional studies (90%) while only three were longitudinal (10%). Eleven papers assessed definitive bruxism for analysis (instrumental tools), one paper assessed probable bruxism (clinical inspection with self-report) and eighteen assessed possible bruxism (self-report). Of the eleven papers assessing definitive bruxism, eight also reported outcomes of non-instrumental tools. Tooth wear was mostly scored using indexes. Most studies reported no or weak associations between tooth wear and bruxism, except for the studies done on cervical tooth wear. When bruxism assessment was done through self-report, more often an association was found. Studies using multivariate analyses did not find an association between tooth wear and bruxism, except the cervical wear studies. Evidence shows inconclusive results as to whether bruxism and tooth wear are related or not. Therefore, well-designed longitudinal trials are needed to address this gap in the literature.

CLINICAL SIGNIFICANCE

Based on the evidence, dental clinicians should not infer bruxism activity solely on the presence of tooth wear.

ORCA-EFCD consensus report on clinical recommendations for caries diagnosis. Paper II: caries lesion activity and progression assessment

INTRODUCTION

This consensus paper provides recommendations for oral health professionals on why and how to assess caries activity and progression with special respect to the site of a lesion.

METHODS

An expert panel was nominated by the executive councils of the European Organization for Caries Research (ORCA) and the European Federation of Conservative Dentistry (EFCD). The steering committee built three working groups that were asked to provide recommendations on 1) caries detection and diagnostic methods, 2) caries activity and progression assessment and 3) obtain individualized caries diagnoses. The experts of work group 2 phrased and agreed on provisional general and specific recommendations on caries lesion activity and progression, based on a review of the current literature. These recommendations were then discussed and refined in a consensus workshop followed by an anonymous Delphi survey to determine the agreement on each recommendation.

RESULTS

The expert panel agreed on general (n=7) and specific recommendations (n=6). The specific recommendations cover coronal caries on pits and fissures, smooth surfaces, proximal surfaces, as well as root caries and secondary caries/ caries adjacent to restorations and sealants (CARS). 3/13 recommendations yielded perfect agreement.

CONCLUSION

The most suitable method for lesion activity assessment is the visual-tactile method. No single clinical characteristic is indicative of lesion activity; instead, lesion activity assessment is based on assessing and weighing several clinical signs. The recall intervals for visual and radiographic examination need to be adjusted to the presence of active caries lesions and recent caries progression rates. Modifications should be based on individual patient characteristics.

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.

Inter- and intra-variability in tooth wear progression at surface-, tooth- and patient-level over a period of three years: A cohort study: Inter- and intra-variation in tooth wear progression

OBJECTIVE

To explore the variability of tooth wear progression at the surface-, tooth- and patient-level over a period of three years three years using in vivo 3D-measurements of full dentitions amongst patients with moderate to severe tooth wear and without demand for restorative rehabilitation.

METHODS

Fifty-five eligible patients with moderate to severe tooth wear had intra-oral scans taken using either the 3 M True Definition Intraoral Scanner or the 3 M Lava Chairside Oral Scanner. The maximum height loss (µm) per cusp/incisal/palatal surface at unrestored surfaces was measured using the 3D Wear Analysis (3DWA)-protocol with Geomagic Qualify, resulting in sixty-four measurements per dentition. Data was visualized using box plots. Correlation was calculated between tooth wear progression rates of different tooth types and surfaces.

RESULTS

Thirty patients with scans at intake and after three years were included (38 ± 8 years, 77% M, 23% F). Mean observation time was 3.1 ± 0.2 years. Surface measurements (N = 1,615) showed a high deviation and a high number of outliers at all surfaces, indicating large variability amongst the surfaces, tooth types and patients with tooth wear progression rates. Correlations between regions were very low: anterior-molar region -0.219, anterior-premolar region 0.116 and premolar-molar region 0.113. Correlations between the surfaces of molars were also low (between 0.190 and 0.565).

CONCLUSIONS

In a group of patients with moderate to severe tooth wear, large differences in wear progression were found within and amongst patients. Tooth wear progression is therefore highly individualized and can be very localized.

CLINICAL SIGNIFICANCE

This study confirms the necessity of individual management of patients with moderate to severe tooth wear. Effective monitoring of tooth wear is important when deciding the timing and need for restorative intervention.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04790110.

Systematic review and meta-analysis of diagnostic studies of proximal surface caries

AIM

This systematic review and meta-analysis aimed to assess the diagnostic accuracy and reliability of commonly used caries detection methods for proximal caries diagnostics. Visual examination (VE), bitewing radiography (BWR), laser fluorescence (LF), and fibre-optic transillumination (FOTI) were considered in detail.

MATERIAL AND METHODS

PRISMA guidelines for the reporting of systematic reviews and meta-analyses were applied. The mnemonic PIRDS (problem, index test, reference test, diagnostic and study type) concept was used to guide the literature search. Next, studies that met the inclusion criteria were stepwise selected and evaluated for their quality with a risk of bias (RoB) assessment tool. Studies with low/moderate bias and sufficient reporting were considered for meta-analysis. The pooled sensitivity (SE), specificity (SP), diagnostic odds ratio (DOR), and area under the ROC curve (AUC) were calculated.

RESULTS

From 129 studies meeting the selection criteria, 31 in vitro studies and five clinical studies were finally included in the meta-analysis. The AUC values for in vitro VE amounted to 0.84 (caries detection) and 0.85 (dentin caries detection). BWR ranged in vitro from 0.55 to 0.82 (caries detection) and 0.81-0.92 (dentin caries detection). LF showed higher AUC values for overall caries detection (0.91) and dentin caries detection (0.83) than did other methods. Clinical data are limited.

CONCLUSION

The number of diagnostic studies with low/moderate RoB was found to be low and indicates a need for high-quality, well-designed caries diagnostic studies.

CLINICAL RELEVANCE

BWR and LF showed good diagnostic performance on proximal surfaces. However, because of the low number of includable clinical studies, these data should be interpreted with caution.

Systematic review and meta-analysis of diagnostic methods for occlusal surface caries

AIM

This systematic review and meta-analysis aimed to assess the diagnostic performance of commonly used methods for occlusal caries diagnostics, such as visual examination (VE), bitewing radiography (BW) and laser fluorescence (LF), in relation to their ability to detect (dentin) caries under clinical and laboratory conditions.

MATERIALS AND METHODS

A systematic search of the literature was performed to identify studies meeting the inclusion criteria using the PIRDS concept (N = 1090). A risk of bias (RoB) assessment tool was used for quality evaluation. Reports with low/moderate RoB, well-matching thresholds for index and reference tests and appropriate reporting were included in the meta-analysis (N = 37; 29 in vivo/8 in vitro). The pooled sensitivity (SE), specificity (SP), diagnostic odds ratio (DOR) and areas under ROC curves (AUCs) were computed.

RESULTS

SP ranged from 0.50 (fibre-optic transillumination/caries detection level) to 0.97 (conventional BW/dentine detection level) in vitro. AUCs were typically higher for BW or LF than for VE. The highest AUC of 0.89 was observed for VE at the 1/3 dentin caries detection level; SE (0.70) was registered to be higher than SP (0.47) for VE at the caries detection level in vivo.

CONCLUSION

The number of included studies was found to be low. This underlines the need for high-quality caries diagnostic studies that further provide data in relation to multiple caries thresholds.

CLINICAL RELEVANCE

VE, BW and LF provide acceptable measures for their diagnostic performance on occlusal surfaces, but the results should be interpreted with caution due to the limited data in many categories.

Identifying and Avoiding Risk of Bias in Caries Diagnostic Studies

Caries diagnostic studies differ with respect to their design, included patients/tooth samples, use of diagnostic and reference methods, calibration, blinding and data reporting. Such heterogeneity makes comparisons between studies difficult and could represent a substantial risk of bias (RoB) when it is not identified. Therefore, the present report aims to describe the development and background of a RoB assessment tool for caries diagnostic studies. The expert group developed and agreed to use a RoB assessment tool during three workshops. Here, existing instruments (e.g., QUADAS 2 and the Joanna Briggs Institute Reviewers' Manual) influenced the hierarchy and phrasing of the signalling questions that were adapted to the specific dental purpose. The tailored RoB assessment tool that was created consists of 16 signalling questions that are organized in four domains. This tool considers the selection/spectrum bias (1), the bias of the index (2) and reference tests (3), and the bias of the study flow and data analysis (4) and can be downloaded from the journal website. This paper explores possible sources of heterogeneity and bias in caries diagnostic studies and summarizes the relevant methodological aspects.

Dental caries and periodontal diseases in the ageing population: call to action to protect and enhance oral health and well-being as an essential component of healthy ageing - Consensus report of group 4 of the joint EFP/ORCA workshop on the boundaries between caries and periodontal diseases

BACKGROUND

Over the last two decades, progress in prevention and treatment of caries and periodontal diseases has been translated to better oral health and improved tooth retention in the adult population. The ageing population and the increasing expectations of good oral health-related quality of life in older age pose formidable challenges to clinical care and healthcare systems.

AIMS

The objective of this workshop was to critically review scientific evidence and develop specific recommendations to: (i) prevent tooth loss and retain oral function through prevention and treatment of caries and periodontal diseases later in life and (ii) increase awareness of the health benefits of oral health as an essential component of healthy ageing.

METHODS

Discussions were initiated by three systematic reviews covering aspects of epidemiology of caries and periodontal diseases in elders, the impact of senescence on caries and periodontal diseases and the effectiveness of interventions. Recommendations were developed based on evidence from the systematic reviews and expert opinion.

RESULTS

Key messages included: (i) the ageing population, trends in risk factors and improved tooth retention point towards an expected increase in the total burden of disease posed by caries and periodontal diseases in the older population; (ii) specific surveillance is required to monitor changes in oral health in the older population; (iii) senescence impacts oral health including periodontitis and possibly caries susceptibility; (iv) evidence indicates that caries and periodontal diseases can be prevented and treated also in older adults; (v) oral health and functional tooth retention later in life provides benefits both in terms of oral and general quality of life and in terms of preventing physical decline and dependency by fostering a healthy diet; (vi) oral healthcare professionals and individuals should not base decisions impacting tooth retention on chronological age but on level of dependency, life expectancy, frailty, comfort and quality of life; and (vii) health policy should remove barriers to oral health care for vulnerable elders.

CONCLUSIONS

Consensus was reached on specific actionable priorities for public health officials, oral healthcare professionals, educators and workforce planners, caregivers and relatives as well as for the public and ageing patients. Some priorities have major implications for policymakers as health systems need to adapt to the challenge by systemwide changes to enable (promote) tooth retention later in life and management of deteriorating oral health in increasingly dependent elders.

Impact of Oral Side Effects from Conditioning Therapy Before Hematopoietic Stem Cell Transplantation: Protocol for a Multicenter Study

Background

The oral cavity is a common site of complications related to the cytotoxic effect of high-dose chemotherapy and radiation therapy. Considering our limited understanding of the burden of illness in the oral cavity from various cytotoxic therapies, it is difficult to produce evidence-based, preventive and management protocols. A prospective multicenter study is necessary to collect data on the burden of illness from various cytotoxic regimens.

Objective

The objectives of this prospective international observational multicenter study in hematopoietic stem cell transplant (HSCT) patients are to establish the nature, incidence and temporal relationship of oral complications related to conditioning regimens (chemotherapy with or without total body irradiation), stem cell transplantation and the immunologic reactions (mainly graft-vs-host-disease) that may follow, and to determine what subjective and objective oral complications related to treatment can predict negative clinical and economic outcomes and reduced quality of life.

Methods

Adult patients at six study sites receiving full intensity conditioning, reduced intensity conditioning or nonmyeloablative conditioning, followed by autologous or allogeneic hematopoietic stem cell infusion, are included. A pre-treatment assessment includes medical conditions, planned chemo- and radiation therapy regimen, medications, allergies, social history, patient report of oral problems, dental history, subjective oral complaints, objective measures of oral conditions, current laboratory values, dental treatment recommended and untreated dental disease. Starting 1-3 days after hematopoietic stem cell infusion, a bedside assessment is completed 3 days per week until resolution of neutropenia. A patient questionnaire is also completed during hospitalization. Beyond this time, patients with continued oral mucositis or other oral problems are followed 1 day per week in an inpatient or outpatient setting. Additional visits for urgent care for acute oral problems after hospitalization are documented. Autologous transplant patients are being followed up at 100 days (SD 30 days) and at 1 year (SD 30 days) post-transplantation to identify any long-term side effects. Patients treated with allogeneic transplantation are being followed at 100 days (SD 30 days), 6 months (SD 30 days), and 12 months (SD 30 days). The follow-up assessments include cancer response to therapy, current medical conditions, medications, subjective and objective oral findings, quality of life measures and laboratory values. The targeted enrollment is 254 patients who have received HSCT.

Results

A total of 260 participants have been enrolled, with 233 (91%) who have received HSCT. We anticipate enrollment of 20-30 additional participants to obtain the sample size of 254 enrolled participants who have received HSCT.

Conclusions

The results of the ongoing prospective study will provide a unique dataset to understand the impact of oral complications on patients undergoing HSCT and provide needed evidence for guidelines regarding the management of this patient cohort.

Bonding effectiveness of composite-dentin interfaces after mechanical loading with a new device (Rub&Roll)

This study evaluated the effect of mechanical loading with a new device on the microtensile bond strength (µTBS) of adhesive systems to dentin. Forty molars were divided according to adhesive systems: self-etch (Clearfil^TM SE Bond -CSE) and etch-and-rinse (Adper Scotchbond^TM 1XT -ASB); and to aging (n=5): control; MC1-250,000; MC2-500,000; and MC3-750,000 mechanical cycles. Microtensile bond strength was measured and fracture modes were analyzed. Data for µTBS were subjected to Kruskal-Wallis and post hoc tests (p<0.05). Mechanical loading (p<0.001) and adhesive systems (p=0.024) affected µTBS values. The adhesive systems showed a similar behavior, except in the MC3 group, which the self-etch CSE showed the highest µTBS. The new device promotes a decreasing of µTBS as the number of cycles increased. Difference between materials was observed only after 750,000 mechanical cycles.

Failed bonded interfaces submitted to microcosm biofilm caries development

OBJECTIVES

This study aimed to evaluate the dentin wall carious lesion development of different composite-dentin interfaces in the presence of two adhesive bonding materials in the gaps, using a microcosm biofilm model.

METHODS

Dentin samples were prepared (10.4mm(2)) and restored with a composite resin using two adhesive systems (etch-and-rinse and self-etch techniques). Different conditions with respect to composite-dentin interfaces were produced with a 200μm gap: failed bonded without ageing or after mechanical ageing, or non-bonded with or without the presence of adhesive material on the dentin wall. For cariogenic challenge, specimens were subjected to a biofilm microcosm model for 14days to create caries-like wall lesions. Before and after caries development, transverse wavelength-independent microradiography images were taken, and lesion depth and mineral loss were measured. Data were analysed with linear regression models (p<0.05).

RESULTS

The composite-dentin interface conditions significant influenced the caries development: lesion development was reduced by the presence of the adhesive material on dentin wall, while lesion development was increased by the mechanical ageing (p=0.019). There was no difference between the adhesive materials (p values>0.05).

CONCLUSION

Different composite-dentin interfaces influence wall lesion development in gaps, with the interfaces submitted to ageing showing less carious protection than those interfaces with the presence of adhesive covering the dentin.

CLINICAL SIGNIFICANCE

The presence of adhesive bonding material in the gaps plays a role on the wall caries lesion development.

Crown vs. composite for post-retained restorations: A randomized clinical trial

OBJECTIVES

This randomized clinical trial compared the survival of composite resin restorations and metal-ceramic crowns on endodontically treated teeth that received a glass fiber post using 2 different cementation methods.

METHODS

Forty-seven patients (age 42.5 ± 11.5) with fifty-seven endodontically treated teeth with extensive coronal damage but always with one intact surface were randomly allocated according to the type of coronal restoration: metal-ceramic crown or composite resin. In case of crown restoration, a core buildup was performed with microhybrid composite resin. The dentin bonding agent and composite resin used were the same for both direct and indirect restorations. Descriptive analysis was performed using FDI clinical criteria and survival of restorations/teeth analyzed using Kaplan-Meier statistics and log-rank tests.

RESULTS

57 restorations (30 composite resin and 27 crowns) were made in 47 patients. The recall rate was 100% and follow up time ranged between 1 and 5 years. One tooth was extracted 11 months post-restoration due to root fracture (composite group). Eight composite restorations and one crown had reparable failures, all due to secondary caries or restoration fracture. The overall annual failure rate (AFR) was 0.92% after 50 months for success of the restorations, with 1.83% for the composite group and 0.26% for the metal-ceramic crown group. The log-rank test showed no difference for survival according to the type of restoration (p=0.344). However, for success rates, metal-ceramic crowns demonstrated better performance (p=0.022).

CONCLUSIONS

Indirect restorations provided higher acceptable clinical performance and lower need for re-intervention, but both types of restorations presented good survival rates. (NCT01461239).

CLINICAL SIGNIFICANCE

When endodontically treated teeth with at least one intact surface must be restored, composite resin restorations and metal-ceramic crows are acceptable alternatives to achieve good survival and success rates.

Effect of Remaining Cavity Wall, Cervical Dentin, and Post on Fracture Resistance of Endodontically Treated, Composite Restored Premolars

PURPOSE

The aim of this study was to examine the effect of remaining buccal cavity wall, remaining cervical tissue, and post on the fracture strength of endodontically treated restored premolars.

MATERIALS AND METHODS

Teeth were randomly allocated to 10 experimental groups (n=10) according to cavity design and presence or absence of post or to a control group. After thermal and mechanical aging, ramped loading until fracture was performed.

RESULTS

A high cervical outline (417 N) and the presence of a post (189 N) increased fracture strength, but both factors together had an antagonistic effect of -218 N, resulting in a higher strength of not 606 N (417+189) but 388 N. The risk of catastrophic failure increased (OR=3.17) when a post was present.

Survival of Restored Endodontically Treated Teeth in Relation to Periodontal Status

Abstract The aim of the present study was to investigate the success and survival of restored endodontically treated teeth (ETT) in a general practice environment related to periodontal parameters. Data from 360 restored ETT treated between 2000 and 2011 were collected. Dates of interventions like restorations, repairs, replacements and extractions were recorded. Additionally, general information about patients and dentitions as well as periodontal status was recorded. Success was analyzed using Kaplan-Meier statistics and a multivariate Cox regression analysis was performed to assess variables influencing success and survival. After a mean observation time of 4.34 years (range 0.6 - 11.6 years), 19 teeth were extracted and 27 restorations needed repair or replacement. According to the Cox regression, increasing maximum pocket depth of the tooth resulted in a higher risk for failure (p=0.012). In conclusion, periodontal pocket depth was found to be a significant factor in the survival of restored ETT.

Consensus Report of the European Federation of Conservative Dentistry: Erosive tooth wear – diagnosis and management

OBJECTIVE

Due to an increased focus on erosive tooth wear (ETW), the European Federation of Conservative Dentistry (EFCD) considered ETW as a relevant topic for generating this consensus report.

MATERIALS AND METHODS

This report is based on a compilation of the scientific literature, an expert conference, and the approval by the General Assembly of EFCD.

RESULTS

ETW is a chemical-mechanical process resulting in a cumulative loss of hard dental tissue not caused by bacteria, and it is characterized by loss of the natural surface morphology and contour of the teeth. A suitable index for classification of ETW is the basic erosive wear examination (BEWE). Regarding the etiology, patient-related factors include the predisposition to erosion, reflux, vomiting, drinking and eating habits, as well as medications and dietary supplements. Nutritional factors relate to the composition of foods and beverages, e.g., with low pH and high buffer capacity (major risk factors), and calcium concentration (major protective factor). Occupational factors are exposition of workers to acidic liquids or vapors. Preventive management of ETWaims at reducing or stopping the progression of the lesions. Restorative management aims at reducing symptoms of pain and dentine hypersensitivity, or to restore esthetic and function, but it should only be used in conjunction with preventive strategies.

CONCLUSIONS

Effective management of ETW includes screening for early signs of ETW and evaluating all etiological factors.

CLINICAL RELEVANCE

ETW is a clinical condition, which calls for the increased attention of the dental community and is a challenge for the cooperation with other medical specialities.

Estimated prevalence of erosive tooth wear in permanent teeth of children and adolescents: an epidemiological systematic review and meta-regression analysis

OBJECTIVES

The main purpose of this systematic review was to estimate the prevalence of dental erosion in permanent teeth of children and adolescents.

METHODS

An electronic search was performed up to and including March 2014. Eligibility criteria included population-based studies in permanent teeth of children and adolescents aged 8-19-year-old reporting the prevalence or data that allowed the calculation of prevalence rates of tooth erosion. Data collection assessed information regarding geographic location, type of index used for clinical examination, sample size, year of publication, age, examined teeth and tissue exposure. The estimated prevalence of erosive wear was determined, followed by a meta-regression analysis.

RESULTS

Twenty-two papers were included in the systematic review. The overall estimated prevalence of tooth erosion was 30.4% (95%IC 23.8-37.0). In the multivariate meta-regression model use of the Tooth Wear Index for clinical examination, studies with sample smaller than 1000 subjects and those conducted in the Middle East and Africa remained associated with higher dental erosion prevalence rates.

CONCLUSIONS

Our results demonstrated that the estimated prevalence of erosive wear in permanent teeth of children and adolescents is 30.4% with high heterogeneity between studies. Additionally, the correct choice of a clinical index for dental erosion detection and the geographic location play an important role for the large variability of erosive tooth wear in permanent teeth of children and adolescents.

CLINICAL SIGNIFICANCE

The prevalence of tooth erosion observed in permanent teeth of children and adolescents was considerable high. Our results demonstrated that prevalence rate of erosive wear was influenced by methodological and diagnosis factors. When tooth erosion is assessed, the clinical index should be considered.

The influence of different restorative materials on secondary caries development in situ

OBJECTIVES

The effect of direct restorative materials on caries lesion formation was investigated with an 8-week in situ study with split-mouth design, testing the hypothesis that no difference in mineral loss next to a restoration would be found between different composite-based-materials and amalgam.

METHODS

Six groups (n=18) of restored dentine samples were prepared using amalgam, a microhybrid, a nanohybrid and a silorane composite. The composites were adhesively bonded with systems with or without an antibacterial monomer (Clearfil-SE-Protect, Clearfil-SE-bond, respectively), except for the silorane group (Silorane-System-Adhesive). Non-restored dentine samples were used as control (primary caries). Samples were inserted into slots, in lower prosthesis especially made for the experiment. Subjects were instructed to dip the lower prosthesis in a sucrose solution 4 times per day. At baseline and 8 weeks, samples were radiographed extra-orally and the integrated mineral loss was calculated. Data were statistically analyzed using multiple linear regression with a multilevel model (p=0.05).

RESULTS

Nine subjects were selected, and only outer lesions were observed. The hypothesis was partially rejected, as the microhybrid composite bonded with the antibacterial system and the nanohybrid composite presented statistically significant lower mineral loss compared to amalgam. Also, no significant differences were seen for these groups compared to control.

CONCLUSION

Within the limits of this study, the restorative material may influence outer lesion progression. Amalgam was not found to be related to lower secondary caries progression in dentine compared to composite-based materials after 8 weeks in situ.

CLINICAL SIGNIFICANCE

Although patient factors play a major role in caries progression, the restorative material may affect outer secondary lesion progression.

Comparison between visual clinical examination and the replica method for assessments of sealant retention over a 2-year period

To compare the levels of agreement and the survival rates of sealant retention for different sealing materials over a 2-year period assessed using the visual clinical examination and replica methods, sealant retention data were obtained by visual clinical examination and from replicas of the same sealed tooth at baseline and at 0.5-, 1- and 2-year evaluation points in 407 children and were compared for agreement using kappa coefficients. Survival curves of retained sealants on occlusal surfaces were created using modified categorisation (fully retained sealants and those having all pits and fissures partly covered with the sealant material versus completely lost sealants that included pit and fissure systems that had ≥1 pit re-exposed) according to the Kaplan-Meier method. The kappa coefficient for the agreement between both assessment methods over the three evaluation time points combined was 0.38 (95% confidence interval (CI): 0.35-0.41). More sealant retention was observed from replicas than through visual clinical examination. Cumulative survival curves at the three evaluation times were not statistically significantly higher when assessed from replicas (P=0.47). Using the replica method, more retained sealant material was observed than through visual clinical examination during the 2-year period. This finding did not result in a difference in the survival rates of sealants assessed by the two assessment methods. When replicas cast in die stone are used for assessing sealant retention, the level of reliability of the data is higher than that of data obtained through the commonly used visual clinical examination, particularly if such assessments are conducted over time.

A practice-based study on the survival of restored endodontically treated teeth

INTRODUCTION

This retrospective study evaluated the survival of endodontically treated teeth (ETTs) and investigated factors influencing restoration and tooth survival.

METHODS

Data from 795 ETTs were recorded, and success (restoration still intact) and survival (restoration intact or failed/repaired/replaced and tooth still in situ) were analyzed using Kaplan-Meier statistics. A multivariate Cox regression analysis was performed to assess the variables influencing success and survival.

RESULTS

At the end of the observation period (mean observation time = 4.48 years), 45 teeth had been extracted (annual failure rate for survival = 1.9% at 9.6 years) and 114 restorations had received a restorative follow-up treatment (annual failure rate for success = 4.9% at 9.6 years).

CONCLUSIONS

ETTs showed acceptable survival and success in the long-term. Variables showing significant influence on survival were the number of teeth in the dentition and the presence of decay at the moment the patient entered the practice.

Effectiveness of two new types of sealants: retention after 2 years

The hypotheses tested were: survival rate of fully and partially retained glass-carbomer sealants is higher than those of high-viscosity glass-ionomer, with and without energy supplied, and that of resin composite; survival rate of fully and partially retained sealants of high-viscosity glass-ionomer with energy supplied is higher than those without energy supplied. The randomized clinical trial covered 407 children, with a mean age of 8 years. The evaluation took place after 0.5, 1 and 2 years. Survival of sealant material in occlusal and in smooth surfaces, using the traditional categorization (fully and partially retained versus completely lost sealants) and the modified categorization (fully and more than 2/3 of the sealant retained versus completely lost sealants), were dependent variables. The Kaplan-Meier survival method was used. According to both categorizations of partially retained sealants, the survival of completely and partially retained resin composite sealants in occlusal and in smooth tooth surfaces was statistically significantly higher, and those of glass-carbomer sealants lower, than those of sealants of the other three groups. There was no statistically significant difference in the survival rates of completely and partially retained high-viscosity glass-ionomer sealants with and without energy supplied in occlusal and in smooth surfaces. After 2 years, glass-carbomer sealant retention was the poorest, adding energy to high-viscosity glass-ionomer sealant did not increase the retention rate and resin composite sealants were retained the longest. We suggest the use of the modified categorization of partially retained sealants in future studies. It seems not necessary to cure high-viscosity glass-ionomer sealants. The use of glass-carbomer sealants cannot be recommended yet.

Bonding polycarbonate brackets to ceramic: effects of substrate treatment on bond strength

This study evaluated the effects of 5 different surface conditioning methods on the bond strength of polycarbonate brackets bonded to ceramic surfaces with resin based cement. Six disc-shaped ceramic specimens (feldspathic porcelain) with glazed surfaces were used for each group. The specimens were randomly assigned to 1 of the following treatment conditions of the ceramic surface: (1) orthophosphoric acid + primer + bonding agent, (2) hydrofluoric acid gel + primer + bonding agent, (3) tribochemical silica coating (silicon dioxide, 30microm) + silane, (4) airborne particle abrasion (aluminum trioxide, 30microm) + silane, and (5) airborne particle abrasion (aluminum trioxide, 30microm) + silane + bonding agent. Brackets were bonded to the conditioned ceramic specimens with a light-polymerized resin composite. All specimens were stored in water for 1 week at 37 degrees C and then thermocycled (1000 cycles, 5 degrees C to 55 degrees C, 30 seconds). The shear bond strength values were measured on a universal testing machine at a crosshead speed of 1 mm/min. Brackets treated with silica coating with silanization had significantly greater bond strength values (13.6 MPa, P =.01) than brackets treated with orthophosphoric acid (8.5 MPa). There was no significant difference (P =.97) between the bond strengths obtained after airborne abrasion with aluminium trioxide particles followed by silanization (12 MPa) and hydrofluoric acid application (11.2 MPa) (ANOVA and Tukey test). Although brackets conditioned with orthophosphoric acid exhibited only adhesive failures of the luting cement from the ceramic surface, other conditioning methods showed mixed types of failures. Airborne particle abrasion with aluminium trioxide or silica coating followed by silanization gave the most favorable bond strengths. The types of failures observed after debonding indicated that the critical parameter was the strength of the adhesive joint of the luting cement to both the bracket and the ceramic.

Effect of drying time of 3-methacryloxypropyltrimethoxysilane on the shear bond strength of a composite resin to silica-coated base/noble alloys

OBJECTIVES

In this in vitro study, the effect of various drying (surface reaction) times of a commercial silane, other than that recommended by the manufacturer (at least 5 min), on the bond strength between the resin composite and silica coated base and noble alloys was evaluated.

METHODS

A total of 112 disc specimens (9 mm diameter and 0.5 mm thickness) were cast out of two types of alloy designed for ceramic firing, one of which was a noble (Degunorm) (gold-silver-platinum) and the other a base alloy (Wiron 99) (nickel-chromium-molybdenum). The specimens were assigned to two main groups according to each alloy type. These two main groups were further divided into seven subgroups, having eight specimens each. The specimens of both alloy types were air-abraded with 30 microm silica (SiO2) coated alumina (Al2O3) (CoJet-Sand, ESPE, Seefeld, Germany). The conditioned surfaces were coated with 3-methacryloxypropyltrimethoxysilane (MPS) and were allowed to react and dry for 1, 2, 3, 4, 5, 6, and 7 min, respectively, before the opaquer was applied. Immediately after the waiting periods for the silane to dry, first opaquer and then resin composite were applied. After storage in water for 30 days at 37 degrees C and thermocycling (5000 cycles, 5-55 degrees C), shear tests were performed using the universal testing machine at a crosshead speed of 0.5 mm/min.

RESULTS

Analysis of data showed no significant difference in bond strength for any silane drying and reaction period for both base and noble alloys between 1 and 7 min (ANOVA, P = 0.05) (Degunorm: 5.8 - 7.4 MPa and Wiron 99: 7.2 - 10.2 MPa, respectively). Bond strengths of resin composite to base alloys were significantly higher than those to noble alloys at 2, 3 and 5 min (P = 0.0045, P = 0.05, P = 0.002, respectively).

SIGNIFICANCE

In order to optimize the flow of laboratory work, the silane solution drying time might be reduced to 1 min for both base and noble alloys.

[Is Dutch swimming pool water erosive?]

Etiological factors in the development of dental erosion are usually listed as dietary acids, for instance in soft drinks and fruit juices, and intrinsic acid exposure due to gastro-intestinal disease or frequent vomiting. Quite often the list of causes in reviews and textbooks also includes frequent swimming. This paper evaluates the evidence behind this erosion etiology. The main disinfection techniques using gas chlorination and sodium hypochlorite are described, and their relative risk for development of low pH water is discussed. In the Netherlands only the relatively safe sodium hypochlorite method is used, and the quality of the water in public swimming pools is monitored monthly by independent test laboratories. Data for 2001 from such a test laboratory show that the percentage of low-pH results is very low (0.14%). It is concluded that the risk of dental erosion from frequent swimming in acidic pool water is probably negligible in the Netherlands.

[Caries diagnosis: the lesions are central]

In this paper two new visual scoring systems are described, aimed at estimating both depth and activity of occlusal lesions. Their validity is acceptable for lesion depth estimation. However, the validity of the activity estimate is to be questioned. Both for approximal enamel and dentine lesions as for deep dentinal occlusal lesions, bite-wing radiographs are still useful for evaluation of new lesions and lesion progression. Many quantitative caries diagnostic methods are being developed, but to this date none of them has been shown to be reliably applicable in lesion monitoring. The evaluation of caries risk factors is primarily useful for selecting preventive treatment options. Other caries prediction-tests than those based on the present caries lesions are of little value. The main disadvantage of such prediction models is that they are usually limited to application in children, where caries is a disease that affects all ages.

Caries detection methods: can they aid decision making for invasive sealant treatment?

The decision to place sealants is a difficult one, and it has been suggested that in a low risk population it may be efficient to wait until caries is detected in the fissure. An invasive sealant technique with fissure preparation may then be indicated. The diagnostic method used in the indication of such a procedure should accurately detect both dentine caries and sound fissures: high sensitivity for dentine caries (at D3 threshold) with high specificity for enamel caries (at D1 threshold). The aims of this study were to assess the diagnostic performance of selected diagnostic methods at normal cut-offs for traditional dentine caries detection and at reduced cut-offs in relation to the desired performance mentioned above, and to assess whether fissure opening allows for accurate visual detection of dentinal caries. Data were obtained from 230 occlusal sites of 101 extracted human molar teeth. Diagnostic methods used on the entire sample were: visual inspection, electrical conductance measurements and laser fluorescence measurements. The sample was then divided into two groups. Group 1 was subjected to visual inspection after application of a dye. Group 2 was subjected to visual inspection after fissure opening only, and after subsequent dye application. Validation was performed by histological investigation. The results with cut-offs normally used in dentine caries detection were roughly in accordance with the literature, except for laser fluorescence. The sensitivity of visual inspection for dentinal caries (D3) was 17% before and 70% after fissure opening. Using reduced cut-offs, a 100% sensitivity (D3) was achieved with 2 methods, but this also resulted in 63 or 87% false positive diagnoses of sound surfaces. Visual inspection and electrical methods both showed a moderate to high sensitivity (D3) with a higher than 50% specificity (D1). It was concluded that visual inspection and electrical methods at reduced cut-offs may aid the indication of invasive sealant treatment. The visual detection of dentinal caries is substantially increased, but not perfect after fissure opening.

Relationship between mineral distributions in dentine lesions and subsequent remineralization in vitro

Though the mineral distribution of the dentine carious lesion varies largely from tooth to tooth and from patient to patient, there are two main distribution profiles that characterize natural carious lesions in dentine. These profiles include softened and subsurface lesion types. The mineral distribution relationship between the starting profile and the profile after remineralization is not known. In order to study the relational aspects, we have produced demineralized dentine samples in vitro with mineral profiles similar to those of typical natural carious lesions, and subsequently remineralized the samples in a remineralizing solution with various fluoride concentrations (0, 2 and 10 ppm F). The mineral distributions were obtained by using an improved microradiographic technique. In addition, the nature of deposited mineral was analyzed by diamond-coupled total internal reflectance spectroscopy. Definite relationship was observed between the original lesion mineral distribution and the mineral distributions following remineralization. The amount of mineral present in approximately the first 50 microm of the lesion influenced the overall mineral profile after remineralization, possibly through influencing ion transport. If the amount was high (> approximately 10 vol%), the deposited mineral was confined to the surface (0-50 microm). The original mineral at those depths acted like a nucleus of mineral regrowth when the amount of residual mineral was intermediate, and like a transport barrier when the surface layer was well mineralized. If a surface barrier was not present, mineral was deposited at deeper depths in the lesion. Fluoride effect on dentine remineralization was dependent on the original mineral content and its distribution in the lesion. Although a high concentration of fluoride was very effective in low-mineral lesions, it produced hyperremineralization on well-mineralized subsurface lesions so that it prevented effective remineralization especially in deeper lesions.

Developments in caries diagnosis and their relationship to treatment decisions and quality of care. ORCA Saturday Afternoon Symposium 1997

This symposium report evaluates the achievements made in caries diagnostic research since the previous symposium held in 1992. The symposium aimed at presenting the state of the art of caries diagnostic methods, on presenting the links between caries diagnosis and subsequent treatment decisions and their effect on the treatment outcomes, particularly the quality of dental care. The variation among dentists in diagnosing (small) caries lesions and in treatment decision making is considerable. This has been explained by the imperfection of caries decision making tests, but also by making incorrect treatment decisions due to incorrect or partial understanding of diagnostic test parameters. Meta-analyses into the performance of caries diagnostic tests revealed that the available quantitative methods are very promising. It was concluded that these methods had high correlations with lesion depth. They were considered suitable to monitor small changes in lesions. Many obstacles have been experienced in attempting to transfer the outcomes of diagnostic research into clinical practice and it was concluded that caries diagnosis researchers should co-operate with manufacturers to introducing valid new diagnostic tools to the market. Main research priorities for the coming 10 years are to conduct cost-effectiveness and cost-utility studies of caries diagnostic tools, to continue to review the performances of diagnostic tests, to transfer diagnostic knowledge and experience to the general practitioners particularly by constructing evidence-based clinical guide-lines, to study the relationship between diagnosis and treatment decision, and to assess the effect of diagnostic and treatment decisions on the outcome of care.

Electrical methods in occlusal caries diagnosis: An in vitro comparison with visual inspection and bite-wing radiography

The aim of this study was to compare in vitro diagnostic performance of three electrical methods for occlusal caries diagnosis with that of visual inspection and bite-wing radiography. One hundred and seven extracted molar and premolar teeth were subjected to the diagnostic methods by 2 operators and subsequently sectioned for histological validation. Electrical measurements were made at site level and at surface level using two different instruments. The diagnostic parameters calculated from the results were: sensitivity, specificity, diagnostic accuracy at a theoretical caries prevalence of 10% and area under the ROC curve. The electrical methods and bite-wing radiography showed higher sensitivity and lower specificity than visual inspection. Diagnostic accuracy was significantly lower for bite-wing radiography and one electrical method than for visual inspection. Overall diagnostic performance of two electrical methods was superior.

Surface-specific electrical occlusal caries diagnosis: reproducibility, correlation with histological lesion depth, and tooth type dependence

Electrical conductance measurements are being used experimentally for occlusal caries detection. Recently, it was suggested to cover the fissure system with a conducting medium, resulting in a surface-specific measurement. It was the aim of this study to determine in vitro the reproducibility of this modified technique for occlusal caries in posterior teeth, to determine for a large study sample the correlation between the electrical measurements and histological lesion depth, and to evaluate the difference between results for premolars and molars. For the reproducibility determination, surface-specific electrical resistance measurements were made using a sample of 68 posterior teeth. Eight operators performed measurements on all teeth, and repeated measurements on 24 teeth. The validity study included the previous sample and the collected samples from two more studies, resulting in a total sample of 325 posterior teeth. One operator had performed electrical resistance measurements on all teeth in the sample. Reproducibility was good: mean Pearson's correlation coefficient 0.89 (+/-0.05) for interexaminer correlation, and 0.86 (+/-0.12) for intra-examiner correlation, using log (resistance) as the result parameter. The correlation coefficient between log(resistance) and histological lesion depth for the large sample was -0.78 for all teeth, -0.64 for premolars, and -0.73 for molars. The regression line for molars was located below the regression line for premolars: at a hypothetical histology score of 2.5 (a dentine caries threshold) the estimated resistance threshold would be 507 kOmega for premolars, and 233 kOmega for molars. Converted to Electronic Caries Monitor (ECM) readings, the difference is about 1.4 on the ECM scale. It was concluded that the in vitro reproducibility of the described surface-specific method for electrical resistance measurement is very good, even for inexperienced operators. The correlation between measurements and histological lesion depth is moderate to good. The method is sensitive to electrode area differences, which will result in different clinical cut-offs for caries diagnosis in premolar and molar teeth.

Temperature dependence of the electrical resistance of sound and carious teeth

Temperature variations are expected to influence measurement error in electrical resistance of teeth. It was the aim of this study to determine the changes in electrical behavior of extracted human teeth due to temperature changes in the range of room temperature to intra-oral temperature. Nine extracted teeth were selected, and the occlusal or an approximal surface was chosen for measurement. Carious involvement of the surfaces ranged from sound to cavitated. Electrical impedance spectroscopy sweeps in a frequency range of about 100 kHz to 10 Hz were completed at selected temperatures between 22 degrees C and 40 degrees C. After fitting the data to equivalent circuits that yielded parameter values for components of the equivalent circuit, we calculated the dc bulk resistance (Rh). The temperature dependence of Rb of the surfaces with different carious involvement was very similar, and the mean drop of Rb from 20 to 35 degrees C was 45% (SD 2%). It was concluded that the electrical resistance of sound and carious tooth surfaces is inversely related to temperature.

Ultrasonic measurement of enamel thickness: a tool for monitoring dental erosion?

OBJECTIVES

Wear of dental hard tissues, e.g. dental erosion, is reported to be a growing problem. A non-destructive measurement of enamel layer thickness would provide the opportunity for both early diagnosis, and longitudinal measurement of progressive enamel loss. It was the aim of this study to investigate the potential of ultrasonic pulse-echo measurements for the enamel thickness measurement.

METHODS

Nine extracted human incisor teeth were selected and stored in physiological saline. Mesial and distal tooth parts were removed, resulting in a central tooth slice of about 2 mm thickness. Where possible three buccal, and one palatal measuring sites were selected and indicated by pencil marks on one of the section planes. Ultrasonic pulse-echo measurements were made at each site using a Panametrics 25DL thickness gauge (Panametrics, Waltham, MA, USA), using a perspex delay line transducer (15 MHz) and glycerine coupling medium. Ultrasonic measurements were validated by measuring the thickness of the enamel layer at the marked side of the tooth slices with a light stereomicroscope at 120 x magnification. Two observers performed independent measurements.

RESULTS

Limits of agreement for measurements by two observers (n = 42) were -0.09 and 0.09 mm. Measurements performed at 21 degrees C and 34 degrees C were not significantly different, as analysed by paired Student's t-test (p = 0.19). Pearson's correlation coefficient between ultrasonic and microscopic measurements was 0.90. Analysis of all measurements from both observers at both temperatures yielded a sound velocity in enamel of 6.5 x 10(3) m/s (standard error 0.1 x 10(3) m/s).

CONCLUSIONS

It was concluded that the ultrasonic measurement of the enamel thickness is feasible without enamel preparation.

Effects of alternating and direct electrical current application on the odontoblastic layer in human teeth: an in vitro study

AIM

The aim of this study was to investigate the influence of a low intensity alternating current on the odontoblasts and odontoblast layer and compare this with the effects of a direct current.

METHODOLOGY

Teeth extracted for orthodontic reasons were immersed in physiological saline stabilized with thymol crystals. Within 1 h of extraction, an alternating or direct current was applied on the crown in the direction of the apex of the tooth for 120-360 s. The current doses were 12, 30, 60, 600, 1800, 3600, 7200, 24,000 and 144,000 microC. The teeth were fixed in Bouin or Baker fluids, the pulps removed, dehydrated and immersed in paraffin, then sectioned, stained with haematoxylin and eosin, and studied under a light microscope.

RESULTS

Neither direct nor alternating current, similar to that applied in electrical caries diagnosis caused histological changes in the odontoblasts.

CONCLUSIONS

There was no difference between direct and low intensity alternating current in the response of the odontoblast.

Effect of exposure time on in vitro caries diagnosis using the Digora system

The aim of this study was to determine the in vitro diagnostic performance for approximal caries and occlusal dentine caries diagnosis of the Digora system for digital radiography in relation to the exposure time. Radiographs were made of 220 extracted human posterior teeth and cuspids at exposure time levels of 3%, 6%, 10%, 20%, and 78% of the exposure time needed for E-speed film (image sets I, II, III, IV, and V, respectively). The image sets were put in random order (III, I, IV, II, V) and assessed independently by 3 observers using a 5-point confidence scale. True caries status was determined histologically after sectioning of the teeth. Evaluated parameters were: interexaminer kappa, sensitivity, specificity, Dz3/4 (the distance of one operating point to the diagonal in the ROC domain) and area under the ROC curve. The Spearman correlation coefficients between the parameters and both exposure time and order of viewing of the sets were calculated. For approximal surfaces, the ranges of mean parameter values were: sensitivity 26-33%, specificity 93-95%, Dz3/4 0.63-0.84, area 0.61-0.69. For occlusal surfaces, the ranges were: sensitivity 52-60%, specificity 91-95%, Dz3/4 1.03-1.34, area 0.79-0.87. Out of 24 pairwise comparisons between sets V and I, 5 were significant. Out of 24 comparisons between set V and II, only 2 were significant. It was concluded that diagnostic performance is unlikely to be impaired for an exposure time as short as 6% of E-speed film exposure. When reducing the exposure time to 3% of E-speed film exposure, caries diagnosis may be impaired.

Wavelength-dependent fibre-optic transillumination of small approximal caries lesions: the use of a dye, and a comparison to bitewing radiography

The mere detection of caries lesions is insufficient for optimal treatment decision-making. Hence, the aim of this study was to investigate whether quantitative information about approximal lesion depth can be obtained from a technique based on the wavelength dependency of light propagation and additional use of a dye. Another aim was to compare the diagnostic performance of the optical technique and bitewing radiography. Measurements were performed on 33 extracted premolar teeth. Twelve proximal surfaces had white-spot, and 17 had discoloured small lesions. Four surfaces were sound. The teeth were transilluminated with a single glass fibre at the approximal surface before and after dye application. The occlusal surface was imaged with a CCD camera. Light in the blue and red part of the electromagnetic spectrum was selected using Schott glass filters. Average decadic optical thickness differences, delta bl-rd tau eff, were estimated and plotted as a function of normalised lesion depth, dhist, established from histological validation by two observers. The Spearman rank correlation was rs (delta bl-rd tau eff, dhist) = 0.87 (95% confidence interval, CI: 0.74-0.94). A marked increase in average decadic optical thickness in the blue part of the electromagnetic spectrum, delta dye tau eff, was observed for those lesion that, upon direct visual inspection of the approximal surface, clearly showed dye uptake. Bitewing radiographic depth ratings of two observers were plotted as a function of dhist. The correlations were rs (dRA,1, dhist) = 0.62 (95% CI: 0.34-0.80), rs (dRA,2, dhist) = 0.75 (95% CI: 0.54-0.87), and between the observers rs (dRA,1, dRA,2) = 0.44 (95% CI: 0.10-0.69). The p values of rs (delta bl-rd tau eff, dhist) -rs (dRA1,1, dhist) and rs (delta bl-rd tau eff, dhist) -rs (dRA,2, dhist) were p1 = 0.01 and p2 = 0.08, respectively. It was concluded that quantitative information about lesion depth can be obtained optically. The dye penetrates into only a limited number of caries lesions, in which cases dye uptake is detectable in transillumination geometry. Under laboratory circumstances the optical technique performs as well as bitewing radiography in the diagnosis of small approximal caries lesions.

Impedance spectroscopy of teeth with and without approximal caries lesions--an in vitro study

Caries diagnosis by the measurement of electrical resistance is hampered by polarization effects when dc or single-low-frequency ac currents are used. Electrical impedance spectroscopy, measuring impedance over a large range of frequencies, will provide more detailed information about the electrical characteristics of teeth. It was the aim of this study (a) to characterize the complex impedance behavior of whole extracted teeth, measured at the approximal surface, and (b) to identify parameters of the complex impedance behavior of the teeth which would be useful in distinguishing between degrees of carious involvement. Thirty-nine extracted premolar teeth with 59 unrestored and undamaged (excepting caries) approximal surfaces were selected. The tooth surfaces were divided into three groups according to their macroscopic appearance: sound (group S, n = 16), white- or brown-spot lesion present (group L, n = 33), or cavitated (group C, n = 10). The teeth were inserted into a jig which allowed for counter-electrode contact via a conducting gel. The working electrode consisted of a carbonated fiber material. Electrical impedance measurements were performed over a maximum range of about 1 MHz to 0.1 Hz. We analyzed electrical impedance data by fitting equivalent circuits. Fit was evaluated numerically and visually. The complex impedance spectra divided naturally into three groups which corresponded almost perfectly with the classifications of S,L, and C. The groups differed most in the dc resistance (Rdc), as calculated from the impedance parameters. Mean Rdc for groups S, L, and C were 68 M omega, 5.9 M omega, and 321 k omega, respectively. These means were significantly different from each other (log-transformed data, ANOVA, p < 0.001; Tukey multiple comparisons, p < 0.001). It is concluded that the in vitro performance of electrical impedance spectroscopy in differentiating among sound, non-cavitated carious, and cavitated approximal tooth surfaces is excellent.

The influence of simulated clinical handling on the flexural and compressive strength of posterior composite restorative materials

OBJECTIVES

The aim of this study was to investigate the influence of clinical handling on the flexural and compressive strengths of two commercially available posterior composites.

METHODS

Since the manufacturing of test specimens in a truly clinical situation presents many problems, an in vitro model was developed, consisting of a phantom-head set-up in a clinical operatory. Two composite materials, recommended for use in posterior teeth, were used: P50 APC (3M Dental Products) and Herculite XRV (Kerr, Dental Manufacturing). Beam specimens for 3-point bending tests of both materials and cylindrical specimens for compression test of P50 were made both under ideal laboratory circumstances and under simulated clinical circumstances.

RESULTS

The difference in mean flexural strength between laboratory prepared and the quasi-clinically prepared specimens was highly significant for both the specimens handled in a clinical manner was 15% of the flexural strength of the P50 specimens made under laboratory conditions, and the difference for Herculite XRV was 29%. No difference in compressive strength could be shown between the laboratory-fabricated and the quasi-clinically made specimens of P50.

SIGNIFICANCE

The relative flexural strength of composite materials in a clinical situation may differ significantly from that predicted from mechanical properties measured in vitro.

Detection of dental decay and its extent using a.c. impedance spectroscopy

Dental caries (decay), the most prevalent of diseases, represents a health problem of immense proportions. It principally affects posterior (back) teeth on occlusal (biting) and approximal (adjacent contacting) surfaces. Caries starts as a subsurface demineralization of enamel, may progress to the underlying dentine and, eventually, to cavitation of the surface. Accurate diagnosis before cavitation would permit targeted preventive treatment, thereby significantly improving dental health and reducing the need for expensive drilling and filling. Inaccessibility of caries initiation sites and recent changes in lesion morphology contribute to the relatively poor accuracy of conventional diagnostic methods. Among alternative techniques, measurements of electrical resistance have shown the most promise. Here we describe a new experimental technique that demonstrates an outstanding 100% correlation between a.c. impedance measurements of whole teeth and the actual extent of approximal caries in vitro. Only relatively minor modifications should be required to transfer the technique to in vivo applications.

[Quality control of intra-oral radiographs]

This paper deals with the different stages in the process of making intra-oral radiographs and the factors which influence their quality: the X-ray equipment, operator technique, and processing and film variables. Common errors at each stage are discussed and suggestions for quality assurance measures are given.

Mechanical longevity estimation model for post-and-core restorations

OBJECTIVES

The aim of this study was to integrate existing knowledge of in vitro strength of post-and-cores and masticatory loading to arrive at longevity estimates for post-and-core restorations when subjected to clinically relevant loads.

METHODS

A biomechanical model was developed to predict the in vivo longevity. This method was applied to direct post-and-core restorations with amalgam or composite cores. Both experimental laboratory strength values and theoretical clinical strength values were used in the model. The restorations made in the laboratory were assumed to be of a higher quality than clinically made restorations, due to factors such as ease of manipulation, absence of saliva, etc. Both a high and low level of average masticatory loading were considered. The model was used to estimate the probability of mechanical failure before 5 X 10(6) load cycles (5 to 15 years) for all combinations of load range and manufacturing quality.

RESULTS

The calculated failure probability was effectively zero for most combinations except for a clinical quality core subjected to loads in the high range. There the probability of mechanical failure before 5 X 10(6) cycles was estimated to be 2 X 10(-5) for amalgam and 5 X 10(-5) for composite cores. These results agree with the overall observed clinical failure rate of about 1% per year for post-and-core restorations.

SIGNIFICANCE

The mechanical properties of the post-and-core restorations were adequate for clinically relevant loading conditions.

Validity of electrical conductance measurements in evaluating the marginal integrity of sealant restorations

The use of sealants and sealant restorations has increased considerably over the past 10 years, and with it increased the problem of detecting secondary caries and marginal (micro)leakage. It was the purpose of this study to investigate the validity of electrical conductance measurements (ECMs) in diagnosing marginal leakage into dentine of sealants and sealant restorations. Ninety extracted premolar teeth were divided into three groups. Initial ECMs, denoted 'baseline ECMs', were conducted in all three groups by placing the probe tip of an Electronic Caries Monitor in the occlusal fissure which was filled with a dentifrice. The ECMs were divided by the area, yielding ECM/mm2 values. In group A 30 teeth were treated to receive 'nonleaking sealants'. In the 30 teeth of group B a narrow groove was cut at the occlusal surface reaching the dentine and restored by the application of a sealant without etching of the adjacent enamel to create a high probability of marginal leakage. The samples in group C received the same treatment as those in group B, but in this group the enamel was etched to reduce the probability of marginal leakage. The ECMs subsequently conducted were denoted 'sealed/restored ECMs'. Teeth in groups B and C were thermocycled 700 times (4-67 degrees C) to provoke leakage, after which ECMs were conducted (denoted 'ECMs after thermocycling'). The teeth were immersed in fuchsin for 24 h and cut along the fissure system to validate marginal leakage. The electrical conductance decreased significantly from baseline to the sealed/restored stage in all groups (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical conductance and electrode area on sound smooth enamel in extracted teeth

Electrical conductance measurements are being used experimentally to diagnose caries. Current equipment, e.g. the electronic caries monitor (ECM), uses a probe to scan occlusal fissures. For full-mouth examination this method is rather time-consuming. A method with which only one measurement is needed for an entire (occlusal) surface would be preferable. However, the enlargement of the area being measured will influence the conductance. It was the purpose of this study to investigate the relationship between the electrical conductance of human teeth and the enamel electrode area, and to compare the range of results of surface measurements with those of the scanning method. Twenty-five sound extracted teeth were selected for the study. The reference electrode of the ECM was connected to the roots. The buccal surface was blotted dry, and a coloured dentifrice was syringed in increments onto the surface. After each increment the surface was photographed together with a metric reference, a conductance measurement was performed by holding the ECM probe tip in the dentifrice, and the ECM reading was recorded. For each tooth between 5 and 10 increments were applied and measured. The photographs were digitised and the electrode areas were calculated. A least squares curve fitting procedure yielded a linear relationship between conductance and electrode area (0.88 < or = R2 < or = 1.0, mean R2 = 0.97). For most teeth the threshold for dentinal caries as used for scanning ECM measurements (ECM reading = 6.00) was reached only when the electrode area exceeded 12 mm2. For 6 teeth this conductance was already reached between 5 and 12 mm2.(ABSTRACT TRUNCATED AT 250 WORDS)

[Diagnosis of primary caries. Current techniques and their consequences for treatment]

The decline in caries prevalence in The Netherlands has incited dentists to focus their attention to the detection of small carious lesions rather than large cavities. The diagnosis of primary caries is, however, still predominantly being accomplished by the traditional diagnostic methods, used in the high caries prevalence era. Today's appearance and behaviour of caries lesions have led to the situation that incipient enamel lesions, dentinal caries and cavities are frequently missed during routine recall examinations. There is increasing concern with the occurrence of large caries lesions underneath visually intact enamel. These problems have induced diagnostic research aimed at developing and evaluating new caries diagnostic methods and some of them are already used in general practice. Visual inspection and bitewing radiography, however, still constitute the most important methods in the diagnosis of primary caries. The results from these examinations are used to classify an individual's caries risk, to monitor the progression of existing caries lesions, and to aid preventive or restorative treatment decision making.

Failure behaviour of fatigue-tested post and cores

Evaluation of the long-term behaviour of restorations in clinical trials can be time-consuming. A partial alternative to the clinical trial can be found in mechanical fatigue testing. The aim of this study was to evaluate the failure behaviour of post and core restored teeth when subjected to cyclic mechanical loading and to compare it with quasistatic failure. Eighty seven premolar teeth were restored with a titanium alloy post and an amalgam or composite core. Five to 21 days after restoration, the specimens were subjected to cyclic loading (frequency 5 Hz), at an angle of 45 degrees to the long axis of the tooth. The load levels were 50, 60, 65 and 70% of mean quasistatic failure loads. The specimens were divided into three groups according to their survival time: short (S) (< 10(4) cycles), intermediate (I) (10(4) < or = life < 10(5) cycles) and long (L) (> or = 10(5) cycles). For both core materials failure behaviour changed after approximately 10(5) cycles, and the change was most marked for the composite group. Catastrophic fatigue failure consisted of core fracture in the amalgam group (three times) and of post fracture in the composite L group (four times). Three post fractures occurred at a site theoretically predisposed to fatigue failure. It was concluded that fatigue failure characteristics of post and core restorations may be very different from those of quasistatic failure. Therefore, in addition to quasistatic tests, fatigue tests are necessary, covering at least 10(5) load cycles.

[The restoration of endodontically treated teeth. A literature study of the mechanical behavior of post-core restorations]

Rapid developments in dental health and science have resulted in an increasing number of teeth receiving post and core restoration. The dentist can choose from a wide range of restoration-modalities. Success or failure of these restorations largely depends on their ability to meet functional demands. This article presents a review of the literature on the mechanical behaviour of post-core restorations, as it is determined by functional forces, shape of the tooth and restoration and properties of the materials the construction encorporates. Some attention is drawn to the importance of failure characteristics in view of re-restoration possibilities. As a conclusion some guide-lines for the use of post and core restorations in the general dental practice are formulated.

Finite element analysis of quasistatic and fatigue failure of post and cores

Finite element (FE) analysis of the mechanical behaviour of materials and structures facilitates the investigation of their internal stress distributions. However, the validity of the model is not always ascertained. In this study a three-dimensional (3D) FE model was developed, representing a laboratory set-up of direct post and core restored upper premolars. These restorations, using either composite or amalgam for core material, have been the subject of study in previous quasistatic and fatigue strength tests. The aim of this study was to validate the FE model for prefailure and failure modelling, by comparing the computational results with the laboratory observations and failure results. Two failure criteria were selected for investigation: Modified Von Mises and Drücker-Prager equivalent stress. Four model variations were carried out, representing different conditions at the core-tooth interface. Prefailure modelling was found to be adequate. The calculated failure results could only partly be fitted to the quasistatic tests. The best fit was effected with a model using partial bonding of the core, for the composite core. Fatigue failure was reproduced somewhat better by a model using no bonding at all, again to a higher degree for the composite core. Calculations of post stress using a model simulating increased core mobility supported an observation made previously (M. C. D. N. J. M. Huysmans et al., in press; Int. Endodont. J. XX, XXX-XXX), implying that a composite core raises the demands made on the post. The conclusion is made that validation of FE calculations is essential. A 3D model as presented here shows a satisfactory fit to fatigue data but not to quasistatic results.(ABSTRACT TRUNCATED AT 250 WORDS)

The Weibull distribution applied to post and core failure

In this study, data on initial failure loads of direct post and core-restored premolar teeth were analyzed using the Weibull distribution. Restorations consisted of a prefabricated titanium alloy post, and an amalgam, composite or glass cermet core buildup in human upper premolar teeth. The specimens were subjected to compressive forces until failure at angles of 10, 45 and 90 degrees to their long axis. The two- and three-parameter Weibull distributions were compared for applicability to the failure load data. For estimation of the parameters of the two-parameter distribution: sigma 0 (reference stress) and m (Weibull modulus), linear regression was used. In this distribution, it is assumed that the third parameter, sigma u (cut-off stress), equals 0. The Maximum Likelihood (MLH) method was used to estimate all three parameters. It was found that the choice of distribution has a strong influence on the estimated values and that the three-parameter distribution is best fitted for the failure loads in this study. Comparisons were made between the failure probability curves as found by MLH estimation for the different core materials and loading angles. The results indicated that the influence of loading angle on the failure mechanism was stronger than that of core material.