Prevention of orthodontic enamel demineralization: a systematic review with meta‐analyses

Aim of this systematic review was to assess the efficacy of preventive interventions against the development of white spot lesions (WSLs) during fixed appliance orthodontic treatment. Nine databases were searched without limitations in September 2018 for randomized trials. Study selection, data extraction and risk of bias assessment were done independently in duplicate. Random-effects meta-analyses of mean differences (MDs) or relative risks (RRs) with their 95% confidence intervals (CIs) were conducted, followed by sensitivity analyses, and the GRADE analysis of the evidence quality. A total of 24 papers (23 trials) were included, assessing preventive measures applied either around orthodontic brackets (21 trials; 1427 patients; mean age 14.4 years) or molar bands (2 trials; 46 patients; age/sex not reported). Active patient reminders were associated with reduced WSL incidence on patient level compared to no reminder (3 trials; 190 patients; RR: 0.4; 95% CI: 0.31-0.64; Number Needed to Treat [NNT]: 3 patients), flat surface sealants were associated with reduced WSL incidence on tooth level than no sealant (5 trials; 2784 teeth; RR: 0.8; 95% CI: 0.63-0.95; NNT: 33 teeth), and fluoride varnish was associated with reduced WSL severity on tooth level (2 trials; 1160 teeth; MD: -0.32 points; 95% CI: -0.44 to -0.21 points). However, the quality of evidence was low according to GRADE, due to risk of bias. Some evidence indicates that active patient reminders and flat surface sealants or fluoride varnish around orthodontic brackets might be associated with reduced WSL burden, but further research is needed. Keywords: adverse effects; clinical trials; dental caries; evidence-based medicine; fixed appliances; systematic review

Developing Optical Coherence Tomography for the Quantitative Study of Erosive and Carious Lesions in Dental Enamel in vitro

PhDOptical Coherence Tomography (OCT) is an imaging technique that uses near infra-red light to non-invasively form cross-sectional images of specimens, in a similar way to ultrasound and RADAR. A number of research groups have used OCT to study natural and artificial carious lesions and to some extent erosive lesions. For this, a variety of in vitro models have been used. However, the exact mechanism by which these demineralised enamel lesions affect the OCT measurements is not fully understood. This remains a barrier to its adoption as both an analytical laboratory tool and a widespread technique in clinical dentistry. Therefore, the aim of this thesis was to develop an understanding of how different demineralised enamel lesions manifest in OCT measurements. This is necessary for the technique to become useful as an in vivo clinical measurement and imaging system. Consequently, this study was carried out in a controlled laboratory environment for which a novel specimen holder was designed. This mitigated against specimen movement and maintained specimen hydration, which can be a source of uncertainty in the measurements. A custom-built OCT microscope was used for this work, which enabled automation of experiments and continuous time-lapse OCT imaging over time periods of hours to several days. This enabled bovine enamel demineralisation dynamics to be captured during in vitro caries and erosion formation. The stability of the system also enabled direct comparison between the OCT measurements of the optical properties of different demineralisation models. To achieve these measurements, the OCT system was carefully characterised and compared to established profilometry measurements. Interestingly, this revealed that the experimental protocol used to obtain lesions for profilometry was not to be representative of the lesions formed and measured by OCT. This is an important point when interpreting OCT data in light of other techniques. A novel method of analysis was developed that uses longitudinal OCT image correlation to quantify early stage surface softening during erosion. By using OCT volumetric data, this technique was able to measure sub-resolution changes at the specimen surface. Early results also indicate sensitivity to remineralisation. This thesis shows that OCT is sensitive to different demineralisation models produced and measured under controlled conditions. New method of handling the data can observe changes not previously seen in OCT. However, further work is still required to understand the underlying physical changes that lead to this sensitivity in OCT.BBSRC and GSK - BBSRC Industrial CASE award BB/K501190/1)

The Interfacial Integrity Of Dental Restorations: Exploring The Effect Of Oral Biofilms, Mechanical Challenges, And Antimicrobial Treatments

University of Minnesota Ph.D. dissertation.May 2016. Major: Oral Biology. Advisor: Joel Rudney. 1 computer file (PDF); xii, 197 pages.Better tools to study the interfacial integrity of dental composites and the factors associated with its eventual breakdown are needed. The initial work focused on the optimization of techniques to study leakage and bond strength. We developed a method for 3D quantification of leakage around dental restorations by using silver nitrate infiltration, micro-CT and image subtraction, overcoming previous limitations of this technique. Also, a new variant of the Brazilian Disk Test specimen was developed for testing dentin-composite bond strength. This novel test provided several advantages including: zero premature failure, simpler testing procedures, a consistent failure mode involving the adhesive interface, and reduced variation in the measurements. We also developed a model to investigate the role of oral biofilms on the degradation of the adhesive interface. Our results suggested that oral biofilms in the presence of sucrose led to active degradation of the adhesive interface. Furthermore, we studied the combined effect of mechanical and biofilm challenge on the interfacial integrity of dental restorations. The results showed that when specimens are subjected to both challenges, a greater reduction in fracture strength is seen compared to the effects of fatigue and biofilm alone, demonstrating the additive effect of both. Again, the presence of biofilm showed a substantial effect in the degradation of the adhesive interface, which was significant in the presence of sucrose. The effect of fatigue was much less pronounced. Antimicrobial containing adhesives are used to prevent the breakdown of the adhesive interface. In the final part of this project, a multispecies oral biofilm/culture model was developed to test the effectiveness of commercially available MDPB-containing adhesive system. We found that the polymerized antimicrobial adhesive reduced biofilm formation and metabolic activity when tested in a closed multispecies biofilm model; however complete inhibition of oral biofilm formation was not observed. The presence of sucrose in the media abolished the antimicrobial effect seen under basal growing conditions. In addition, the polymerized MDPB-containing adhesive failed to inhibit multispecies oral biofilm formation in the absence and presence of sucrose when tested in a Drip Flow Reactor

Nanostructural Materials with Rare Earth Ions: Synthesis, Physicochemical Characterization, Modification and Applications

This Special Issue of "Nanostructural Materials with Rare Earth Ions: Synthesis, Physicochemical Characterization, Modification and Applications" is related to studies of nanometer-sized materials doped and co-doped with rare earth ions and the creation of periodically ordered nanostructures based on single nanoparticles. A small particle size implies a high sensitivity and selectivity. These new effects and possibilities are mainly due to the quantum effects resulting from the increasing ratio of surface-to-volume atoms in low-dimensional systems. An important factor in this context is the design and fabrication of nanocomponents displaying new functionalities and characteristics for the improvement of existing materials, including photonic materials, conductive materials, polymers and biocomposites. With this concept in mind, the aim of the Special Issue is to publish research on innovative materials and their applications.Topics to be covered in this Special Issue include, but are not limited to, the following: Technology and applications of nanomaterials with rare earth ions; Advanced physicochemical properties, characterization and modification of nanomaterials with rare earth ions; Novel active materials, especially organic and inorganic materials, nanocrystalline materials, nanoceramics doped and co-doped with rare-earth ions with bio-related and emerging applications; Magnetic properties of nano-sized rare-earth compounds; Applications of nano-sized rare-earth-doped and co-doped optical materials