M.H. van der Veen

Caries Prevalence Measured with QLF after Treatment with Fixed Orthodontic Appliances: Influencing Factors

Caries prevalence on the buccal surfaces of teeth in orthodontic patients was determined with QLF and visual examination immediately after removal of fixed appliances. The number of lesions found by QLF far outnumbered that found by visual examination, but the distribution pattern was similar. 97% of all subjects and on average 30% of the buccal surfaces in a person were affected. On average, in males 40% of surfaces and in females 22% showed white spots (p < 0.01). Caries prevalence was lower (p < 0.01) in incisors and cuspids than in molars and premolars. A positive correlation with caries prevalence was found for the bleeding scores 6 weeks after debonding and lactobacillus counts before debonding. Mutans streptococci counts, age, treatment duration, socioeconomic status and dietary habits showed no correlation with caries prevalence.

Caries outcomes after orthodontic treatment with fixed appliances: do lingual brackets make a difference?

Orthodontic treatment with fixed appliances is considered a risk factor for the development of white spot caries lesions (WSL). Traditionally, brackets are bonded to the buccal surfaces. Lingual brackets are developing rapidly and have become more readily available. Buccal surfaces are considered to be more caries prone than lingual surfaces. Furthermore, lingual brackets are shaped to fit the morphology of the teeth and seal almost the entire surface. In the present study we tested the hypothesis that lingual brackets result in a lower caries incidence than buccal brackets. We tested this hypothesis using a split-mouth design where subjects were allocated randomly to a group receiving either buccal or lingual brackets on the maxillary teeth and the alternative bracket type in the mandible. The results indicate that buccal surfaces are more prone to WSL development, especially when WSL existed before treatment. The number of WSL that developed or progressed on buccal surfaces was 4.8 times higher than the number of WSL that developed or progressed on lingual surfaces. When measured using quantitative light-induced fluorescence (QLF), the increase in integrated fluorescence loss was 10.6 times higher buccally than lingually. We conclude that lingual brackets make a difference when caries lesion incidence is concerned.

The Validity and Repeatability of Three Light–Induced Fluorescence Systems: An in vitro Study

New optical systems are being developed that aim to determine the extent of demineralization in enamel. In our laboratory we have compared three such systems: a ring illuminator equipped with a laser, a beam splitter also equipped with a laser and an intra–oral camera equipped with a white–light arc lamp. The aim of the study was to compare the ability of the different optical systems to detect small enamel lesions with microradiographic analysis and to determine the repeatability of these systems. Forty human enamel specimens (3mm in diameter) were mounted in acrylic and polished. The specimens were kept moist throughout the study. Each specimen of the four groups was individually exposed to 14 ml of Carbopol demineralizing solution for 24, 48, 72 and 96 h, respectively. The mineral loss of the 40 specimens was assessed with blue–violet light– induced fluorescence. Each image was captured with a video camera and analysed with dedicated software. The measurements were repeated 3 times with complete shut–down of the system in between the measurements. The same measurements were performed with the ring illuminator, the beam splitter and the arc lamp. The specimens were then cut into thin sections and analysed with microradiography. Similar high correlations between microradiography and the light–based analysis systems were found for the beam splitter and the clinical caries camera set–up. The repeatability was best for the beam splitter set–up. This indicates that the light–induced fluorescence measurement technique can be used in different configurations and that the repeatability of the measurements is influenced by the physical stability of the set–up.

Red autofluorescence of dental plaque bacteria

Red autofluorescence of plaque and its relation to fluorescence of a single species in the biofilm was studied. Fluorescence images of non-disclosed and disclosed plaque of 28 first-year students were captured. The plaque samples were assessed by culture methods and studied for red autofluorescence. Species capable of producing red autofluorescence were cultivated from subjects with and without red plaque autofluorescence. Red autofluorescence was observed from Actinomyces odontolyticus, Prevotella intermedia and from Porphyromonas gingivalis and Peptostreptococcus micros grown together. The microbial findings indicated that the intrinsic characteristics of the mature biofilm itself are more responsible for the red autofluorescence than the characteristics of the single species.

Detection of Early Interproximal Caries in vitro Using Laser Fluorescence, Dye–Enhanced Laser Fluorescence and Direct Visual Examination

This in vitro study evaluated the use of laser fluorescence (LF) for the detection of early interproximal carious lesions and whether the detection could be enhanced using a fluorescent dye (DELF). Direct visual examination (DV) was used for comparison. Eighty extracted teeth were used, arranged in 20 blocks, each block having 2 premolars and 2 molars, lined up in a simulated sextant situation. After cleaning with a microabrasion kit, a subcontact window on half of the surfaces (60) was exposed to Carbopol white–spot solution for 5 days. The teeth were remounted in stone and examined by three independent examiners. For LF and DELF an argon laser was used (mixed wavelength of 488 and 514 nm) viewed through glasses (excluding wavelength <520 nm). For DELF a sodium fluorescein dye (0.075%) was applied before examination. A clinical examination light was used for DV. The approximal surfaces were scored for lesion presence or absence. To verify lesion presence, the subcontact area was cut perpendicularly to the surface, stained with rhodamine B, and images were taken using a confocal microscope. The images were analyzed using a histogram program for lesion depth and image area. Lesions were present in 62 out of 120 approximal surfaces, with an average depth of 60 μm (range 17–190 μm). Sensitivity ranges for LF, DELF and DV were 56–74, 61–79 and 58–74%, and specificity ranges 67–78, 86–98 and 83–97%, respectively. With this model DELF compared favorably with DV and LF in sensitivity, but specificity was better for DELF and DV than for LF.

Bacterial composition and red fluorescence of plaque in relation to primary and secondary caries next to composite : an in situ study

BACKGROUND/HYPOTHESIS Secondary caries has been suggested as the main reason for restoration replacement. We hypothesized that more caries-associated bacteria are found on composite resin restoration material, compared to sound tooth tissue. METHODS Both restored and unrestored dentin and enamel samples were placed in a full denture of eight subjects for 20 weeks. The microbiological composition of approximal plaque and the association between caries-associated bacteria and red autofluorescence of dental plaque was studied. Every 4 weeks the specimens were microradiographed using transversal wavelength independent microradiography (T-WIM). After 1 and 20 weeks red fluorescence pictures and plaque samples were taken. Samples were cultured for total anaerobic counts, mutans streptococci, lactobacilli, candida and Actinomyces odontolyticus. RESULTS Lesion depth in the dentin and enamel was positively associated with lactobacilli, and lesion depth in dentin was positively associated with A. odontolyticus, whereas no association was found between mutans streptococci and lesion depth. The red-fluorescent bacteria A. odontolyticus and lactobacilli did not correlate with red-fluorescent plaque, indicating that red fluorescence is probably not caused by a single species of these bacteria. After 20 weeks, a higher proportion of combined mutans streptococci and lactobacilli was found on restored tissue compared to non-restored tissue (P = 0.04). CONCLUSION The higher proportion of caries-associated bacteria on restored tissue indicates that the ecology on the surface of primary lesions differs from that on lesions next to composite, and that secondary caries next to composite may differ from the primary caries process.

In vitro quantitative light-induced fluorescence to measure changes in enamel mineralization

A sensitive, quantitative method for investigating changes in enamel mineralization of specimens subjected to in vitro or in situ experimentation is presented. The fluorescence-detecting instrument integrates a Xenon arc light source and an object positioning stage, which makes it particularly suitable for the nondestructive assessment of demineralized or remineralized enamel. We demonstrate the ability of in vitro quantitative light-induced fluorescence (QLF) to quantify changes in mineralization of bovine enamel discs that had been exposed in vitro to a demineralizing gel (n=36) or biofilm-mediated demineralization challenges (n=10), or were carried in situ by three volunteers during a 10-day experiment (n=12). Further experiments show the techniques value for monitoring the extent of remineralization in 36 specimens exposed in vitro to oral multispecies biofilms and document the repeatability of in vitro QLF measurements (n=10) under standardized assay conditions. The validity of the method is illustrated by comparison with transversal microradiography (TMR), the invasive current gold standard for assessing experimental changes in enamel mineralization. Ten discs with 22 measurement areas for comparison demonstrated a positive correlation between TMR and QLF (r=0.82). Filling a technological gap, this QLF system is a promising tool to assay in vitro nondestructively localized changes in mineralization of enamel specimens.

The Influence of Mineral Loss on the Auto-Fluorescent Behaviour of in vitro Demineralised Dentine

The aim of this study is to investigate the influence of demineralisation on the fluorescent properties of dentine. The fluorescence emission at 529 nm due to 515 nm excitation of in vitro demineralised lesions was determined with a micro-Raman spectroscope as a function of location. Results were compared with the mineral loss profiles of the same lesions measured by microradiography. The root surfaces of 6 in vitro demineralised human third molars (lactic acid CMC gel, pH 5; six groups: 0,4,7,14,18 and 21 days) were used in the experiment. Thin slices of ± 130 μm were cut perpendicular to the tooth axis. The fluorescence scans corresponded to mineral loss profiles. Confocal microscope images showed increasing fluorescence with increasing mineral loss. From these results it is concluded that this mineral loss causes an increase in auto-fluorescence by a factor of at least 10, therefore the chromophore causing this green fluorescence must be organic in nature. De-quenching or modification of this fluorophore due to the demineralisation process is probably the cause for the increase of the green fluorescence.

Optimal Camera and Illumination Angulations for Detection of Interproximal Caries Using Quantitative Light-Induced Fluorescence

The aim of the study was to find the optimal illumination and camera angulations for interproximal use of quantitative light-induced fluorescence (QLF). A multiaxis optical bench was developed and interproximal tooth assemblies were investigated using a modified version of QLF. Extracted human premolars without caries (n = 8) and with interproximal D1, D2 and D3 caries (n = 20) were selected. Tooth-pair models without caries and with interproximal caries of matching size, location, and shape were imaged with varying camera and illumination directions from buccal (0°) to occlusal (90°) to lingual (180°) in steps of 30° using a PC and framegrabber and examined for observed presence. Interproximal lesions could be detected in all teeth, but observed presence was dependent on camera angulation (p < 0.05), rather than on illumination angulation (p = 0.32). No caries could be detected with the camera in the 90° position.

The influence of drying on quantitative laser fluorescence and optical pathlengths in incipient natural caries lesions.

Drying effects in 14 natural lesions were studied with quantitative light-induced fluorescence and optical pathlength spectroscopy. Results were compared with clinical judgments of the lesion surface and microradiographical characterizations of the lesions. Relative fluorescence and average pathlength decreased as a function of drying time with a decay time ranging from 35.5 to <1 min. Depth and mineral loss correlated with average pathlength total changes (r = –0.79/–0.60, respectively) and poorly with total fluorescence changes (r 0.3). The decay time of the drying process for the relative fluorescence correlated well with a theoretical model based on water diffusion in lesion and surface layer, but only for large decay times. Clinical judgments could not be related to the surface layer properties or the changes in the average pathlength, but were weakly related to the changes in the relative fluorescence. We conclude that (i) fluorescence effects are mostly due to the screening by the lesion of the fluorescence from the dentin and enamel-dentin junction; (ii) water evaporation in lesions conforms to the diffusion laws only in large lesions with low surface layer penetrability; (iii) the evaporation process is controlled by the surface layer only for small surface penetrabilities (≈ 0.1 vol% µm–1).