Interest in the role of the microbiome in human health has burgeoned over the past decade with the advent of new technologies for interrogating complex microbial communities. The large-scale dynamics of the microbiome can be described by many of the tools and observations used in the study of population ecology. Deciphering the metagenome and its aggregate genetic information can also be used to understand the functional properties of the microbial community. Both the microbiome and metagenome probably have important functions in health and disease; their exploration is a frontier in human genetics.

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The human microbiome: at the interface of health and disease

The immediate bonding effectiveness of contemporary adhesives is quite favorable, regardless of the approach used. In the long term, the bonding effectiveness of some adhesives drops dramatically, whereas the bond strengths of other adhesives are more stable. This review examines the fundamental processes that cause the adhesion of biomaterials to enamel and dentin to degrade with time. Non-carious class V clinical trials remain the ultimate test method for the assessment of bonding effectiveness, but in addition to being high-cost, they are time- and labor-consuming, and they provide little information on the true cause of clinical failure. Therefore, several laboratory protocols were developed to predict bond durability. This paper critically appraises methodologies that focus on chemical degradation patterns of hydrolysis and elution of interface components, as well as mechanically oriented test set-ups, such as fatigue and fracture toughness measurements. A correlation of in vitro and in vivo data revealed that, currently, the most validated method to assess adhesion durability involves aging of micro-specimens of biomaterials bonded to either enamel or dentin. After about 3 months, all classes of adhesives exhibited mechanical and morphological evidence of degradation that resembles in vivo aging effects. A comparison of contemporary adhesives revealed that the three-step etch-and-rinse adhesives remain the 'gold standard' in terms of durability. Any kind of simplification in the clinical application procedure results in loss of bonding effectiveness. Only the two-step self-etch adhesives approach the gold standard and do have some additional clinical benefits.

http://www.endoexperience.com/documents/DeMunketalDurabiltyofadhesionJDR.pdf

A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results

Bonding to tooth tissue can be achieved through an "etch&rinse," "self-etch" or "glass-ionomer" approach. In this paper, the basic bonding mechanism to enamel and dentin of these three approaches is demonstrated by means of ultramorphological and chemical characterization of tooth-biomaterial interfacial interactions. Furthermore, bond-strength testing and measurement of marginal-sealing effectiveness (the two most commonly employed methodologies to determine "bonding effectiveness" in the laboratory) are evaluated upon their value and relevance in predicting clinical performance. A new dynamic methodology to test biomaterial-tooth bonds in a fatigue mode is introduced with a recently developed micro-rotary fatigue-testing device. Eventually, today's adhesives will be critically weighted upon their performance in diverse laboratory studies and clinical trials. Special attention has been given to the benefits/drawbacks of an etch&rinse versus a self-etch approach and the long-term performance of these adhesives. Correlating data gathered in the laboratory with clinical results clearly showed that laboratory research CAN predict clinical effectiveness. Although there is a tendency to simplify bonding procedures, the data presented confirm that conventional three-step etch&rinse adhesives still perform most favorably and are most reliable in the long-term. Nevertheless, a self-etch approach may have the best future perspective. Clinically, when adhesives no longer require an "etch&rinse" step, the application time, and probably more importantly, the technique-sensitivity are substantially reduced. Especially "mild," two-step self-etch adhesives that bond through a combined micromechanical and chemical interaction with tooth tissue closely approach conventional three-step systems in bonding performance.

Buonocore memorial lecture, adhesion to enamel and dentin: current status and future challenges

Oral diseases: a global public health challenge

Gram-positive bacteria possess a myriad of acid resistance systems that can help them to overcome the challenge posed by different acidic environments. In this review the most common mechanisms are described: i.e., the use of proton pumps, the protection or repair of macromolecules, cell membrane changes, production of alkali, induction of pathways by transcriptional regulators, alteration of metabolism, and the role of cell density and cell signaling. We also discuss the reponses of Listeria monocytogenes, Rhodococcus, Mycobacterium, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus, oral streptococci, and lactic acid bacteria to acidic environments and outline ways in which this knowledge has been or may be used to either aid or prevent bacterial survival in low-pH environments.

Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

Preface: An Editors' guide to reading the book List of Contributors Part I: The Disease Chapter 1 Clinical Cariology and Operative Dentistry in the Twenty-First Century (O Fejerskov and EAM Kidd) Chapter 2 Secretion and Composition of Saliva (B Nauntofte, JO Tenovuo and F Lagerlof) Chapter 3 The Oral Microflora and Biofilms on Teeth (PD Marsh and B Nyvad) Chapter 4 Chemical Interactions Between the Tooth and Oral Fluids Chapter 5 Clinical and Histological Manifestations of Dental Caries (O Fejerskov, B Nyvad and EAM Kidd) Part II: Diagnosis Chapter 6 Caries Diagnosis - 'A Mental Resting Place on the Way to Intervention' (V Baelum and O Fejerskov) Chapter 7 Clinical and Radiographic Diagnosis (EAM Kidd, I Mejare and B Nyvad) Chapter 8 Advanced Methods of Caries Diagnosis and Quantification (EH Verdonschot and B Angmar-Mansson) Chapter 9 Caries Epidemiology, with Special Emphasis on Diagnostic Standards (NB Pitts, O Fejerskov and FR von der Fehr) Part III: Prevention, Non-Operative and Operative Treatments Chapter 10 Prevention of Dental Caries and the Control of Disease Progression: Concepts of Preventive Non-Operative Treatment (EAM Kidd and O Fejerskov) Chapter 11 The Role of Oral Hygiene (B Nyvad) Chapter 12 The Role of Antimicrobials (AAa Scheie) Chapter 13 Clinical Use of Fluoride (R Ellwood and O Fejerskov) Chapter 14 The Role of Dietary Control (P Moynihan , P Lingstrom, AJ Rugg-Gunn and D Birkhed) Chapter 15 The Role of Operative Treatment (EAM Kidd and JP van Amerongen) Chapter 16 The Maze of Treatment Decisions (K Anusavice) Chapter 17 Caries Removal and the Pulpo-Dentinal Complex (EAM Kidd, O Fejerskov and IA Mjor) Chapter 18 Restoring the Tooth: 'The Seal is the Deal' (JP van Amerongen, CL Davidson, NJM Opdam, FJMRoeters and EAM Kidd) Part IV: Prognosis, Caries Control and Prediction Chapter 19 Prognosis for Caries and Restorations (I Majare and IA Mjor) Chapter 20 Caries Control for the Individual Patient (EAM Kidd and B Nyvad) Chapter 21 Caries Control for Populations (A Sheiham and O Fejerskov) Chapter 22 Caries Prediction (H Hausen) Index

Dental Caries: The Disease and its Clinical Management

Substantial pH fluctuations within the biofilm on the tooth surface are a ubiquitous and natural phenomenon, taking place at any time during the day and night. The result may be recordable in the dental tissues at only a chemical and/or ultrastructural level (subclinical level). Alternatively, a net loss of mineral leading to dissolution of dental hard tissues may result in a caries lesion that can be seen clinically. Thus, the appearance of the lesion may vary from an initial loss of mineral, seen only in the very surface layers at the ultrastructural level, to total tooth destruction. Regular removal of the biofilm, preferably with a toothpaste containing fluoride, delays or even arrests lesion progression. This can occur at any stage of lesion progression, because it is the biofilm at the tooth or cavity surface that drives the caries process. Active enamel lesions involve surface erosion and subsurface porosity. Inactive or arrested lesions have an abraded surface, but subsurface mineral loss remains, and a true subsurface remineralization is rarely achievable, because the surface zone acts as a diffusion barrier. The dentin reacts to the stimulus in the biofilm by tubular sclerosis and reactionary dentin.

http://www.endoexperience.com/documents/cariesandbiofilms.pdf

What constitutes dental caries? Histopathology of carious enamel and dentin related to the action of cariogenic biofilms.

This laboratory study of 100 occlusal surfaces investigated the reproducibility and accuracy of a visual ranked caries scoring system, an electronic caries scoring system (ECM) using a continuous conductance scale, and a radiographic ranked caries scoring system. Histological examination of the teeth served as a gold standard to validate the ability of each system to assess lesion depth and predict softened, demineralized dentine. After training, 3 examiners carried out each scoring system on two separate occasions. Kappa values for visual, ECM and radiographic ranked scoring systems showed good inter- and intra-examiner reproducibility levels and acceptable limits of agreement for ECM readings. When scoring systems were tabulated against histological scores there was a high correlation between the visual and ECM methods and lesion depth in both enamel and dentine, but radiographic examination could not detect enamel caries. When compared to the histological scoring, the Spearman correlation coefficients for the visual scoring ranged between 0.87 and 0.93, for the ECM between 0.80 and 0.85 and for the radiographic scoring system between 0.76 and 0.78. No tooth scored as visually sound had histological evidence of dentine caries. Soft dentine corresponded to demineralization involving the middle third of the dentine or more which was related to visual cavity formation or an ECM reading above 9 (score 3 or 4). The radiograph was an excellent predictor of soft dentine. In conclusion, the new visual system appears promising, but takes time to learn. The reproducibility and accuracy for the ECM is acceptable while radiographs miss early occlusal lesions.

Reproducibility and Accuracy of Three Methods for Assessment of Demineralization Depth on the Occlusal Surface: An in vitro Examination

Microleakage: a review.

Background
The management of dental caries has traditionally involved removal of all soft demineralised dentine before a filling is placed. However, the benefits of complete caries removal have been questioned because of concerns about the possible adverse effects of removing all soft dentine from the tooth. Three groups of studies have also challenged the doctrine of complete caries removal by sealing caries into teeth using three different techniques. The first technique removes caries in stages over two visits some months apart, allowing the dental pulp time to lay down reparative dentine (the stepwise excavation technique). The second removes part of the dentinal caries and seals the residual caries into the tooth permanently (partial caries removal) and the third technique removes no dentinal caries prior to sealing or restoring (no dentinal caries removal). This is an update of a Cochrane review first published in 2006.

Objectives
To assess the effects of stepwise, partial or no dentinal caries removal compared with complete caries removal for the management of dentinal caries in previously unrestored primary and permanent teeth.

Search methods
The following electronic databases were searched: the Cochrane Oral Health Group's Trials Register (to 12 December 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 11), MEDLINE via OVID (1946 to 12 December 2012) and EMBASE via OVID (1980 to 12 December 2012). There were no restrictions regarding language or date of publication.

Selection criteria
Parallel group and split-mouth randomised and quasi-randomised controlled trials comparing stepwise, partial or no dentinal caries removal with complete caries removal, in unrestored primary and permanent teeth were included.

Data collection and analysis
Three review authors extracted data independently and in triplicate and assessed risk of bias. Trial authors were contacted where possible for information. We used standard methodological procedures exacted by The Cochrane Collaboration.

Main results
In this updated review, four new trials were included bringing the total to eight trials with 934 participants and 1372 teeth. There were three comparisons: stepwise caries removal compared to complete one stage caries removal (four trials); partial caries removal compared to complete caries removal (three trials) and no dentinal caries removal compared to complete caries removal (two trials). (One three-arm trial compared complete caries removal to both stepwise and partial caries removal.) Four studies investigated primary teeth, three permanent teeth and one included both. All of the trials were assessed at high risk of bias, although the new trials showed evidence of attempts to minimise bias.

Stepwise caries removal resulted in a 56% reduction in incidence of pulp exposure (risk ratio (RR) 0.44, 95% confidence interval (CI) 0.33 to 0.60, P < 0.00001, I2 = 0%) compared to complete caries removal based on moderate quality evidence, with no heterogeneity. In these four studies, the mean incidence of pulp exposure was 34.7% in the complete caries removal group and 15.4% in the stepwise groups. There was also moderate quality evidence of no difference in the outcome of signs and symptoms of pulp disease (RR 0.78, 95% CI 0.39 to 1.58, P = 0.50, I2 = 0%).

Partial caries removal reduced incidence of pulp exposure by 77% compared to complete caries removal (RR 0.23, 95% CI 0.08 to 0.69, P = 0.009, I2 = 0%), also based on moderate quality evidence with no evidence of heterogeneity. In these two studies the mean incidence of pulp exposure was 21.9% in the complete caries removal groups and 5% in the partial caries removal groups. There was insufficient evidence to determine whether or not there was a difference in signs and symptoms of pulp disease (RR 0.27, 95% CI 0.05 to 1.60, P = 0.15, I2 = 0%, low quality evidence), or restoration failure (one study showing no difference and another study showing no failures in either group, very low quality evidence).

No dentinal caries removal was compared to complete caries removal in two very different studies. There was some moderate evidence of no difference between these techniques for the outcome of signs and symptoms of pulp disease and reduced risk of restoration failure favouring no dentinal caries removal, from one study, and no instances of pulp disease or restoration failure in either group from a second quasi-randomised study. Meta-analysis of these two studies was not performed due to substantial clinical differences between the studies.

Authors' conclusions
Stepwise and partial excavation reduced the incidence of pulp exposure in symptomless, vital, carious primary as well as permanent teeth. Therefore these techniques show clinical advantage over complete caries removal in the management of dentinal caries. There was no evidence of a difference in signs or symptoms of pulpal disease between stepwise excavation, and complete caries removal, and insufficient evidence to determine whether or not there was a difference in signs and symptoms of pulp disease between partial caries removal and complete caries removal. When partial caries removal was carried out there was also insufficient evidence to determine whether or not there is a difference in risk of restoration failure. The no dentinal caries removal studies investigating permanent teeth had a similar result with no difference in restoration failure. The other no dentinal caries removal study, which investigated primary teeth, showed a statistically significant difference in restoration failure favouring the intervention.

Due to the short term follow-up in most of the included studies and the high risk of bias, further high quality, long term clinical trials are still required to assess the most effective intervention. However, it should be noted that in studies of this nature, complete elimination of risk of bias may not necessarily be possible. Future research should also investigate patient centred outcomes.

Edwina Kidd

Papers

Dental Caries: The Disease and its Clinical Management

What constitutes dental caries? Histopathology of carious enamel and dentin related to the action of cariogenic biofilms.

Reproducibility and Accuracy of Three Methods for Assessment of Demineralization Depth on the Occlusal Surface: An in vitro Examination

Microleakage: a review.

Operative caries management in adults and children