Carlos González-Cabezas

Protective Effect of the Dental Pellicle against Erosive Challenges in situ

The acquired dental pellicle helps prevent erosion, but the protection level is unknown. This in situ study tested whether a two-hour pellicle protects against different erosive challenges by orange juice. Subjects wore palatal appliances loaded with either enamel or dentin specimens. Pellicle was allowed to form, or not (control), on the surfaces of the specimens intra-orally for 2 hrs before the erosive challenges of 0 (control), 10, 20, and 30 minutes’ duration. Specimens were randomly removed from the appliances after each challenge. Percentage of surface microhardness change (%SMC) was determined for the enamel specimens, and that of mineral loss and lesion depth for the dentin specimens. Enamel specimens with the pellicle showed a significantly lower %SMC, only after the 10-minute challenge. No protection was found for dentin. It was concluded that the acquired pellicle reduced dental erosion, but that this effect was limited to the less severe erosive challenge on enamel surfaces.

Risk factors for incidence and severity of white spot lesions during treatment with fixed orthodontic appliances

INTRODUCTION The development of incipient caries, or white spot lesions (WSLs), is a significant clinical problem in orthodontics. The purpose of this study was to retrospectively determine the incidence and severity of WSLs by examining pretreatment and posttreatment digital photographs. METHODS A total of 332 consecutive finished patients from a university graduate orthodontic clinic were evaluated. Initial and final digital images were compared to assess WSLs. The facial surfaces of the anterior 8 maxillary teeth were analyzed. The percentage area of WSL per total facial tooth surface was calculated to control for magnification differences. Reliability of the method was assessed by comparison with direct clinical examination data. Patient and operator factors, and treatment complexity and outcomes were evaluated as predictors of WSL incidence and severity. RESULTS Agreement between direct clinical examination and digital photo data was excellent, with an intraclass correlation coefficient 0.88 and a 0.3% average difference between methods. The incidence of at least 1 WSL on the labial surface of the anterior 8 maxillary teeth was 36%. The order of incidence was lateral incisor (34%), canine (31%), premolar (28%), and central incisor (17%). CONCLUSIONS Risk factors for the development of incipient caries during orthodontic treatment were young age (preadolescent) at the start of treatment, number of poor hygiene citations during treatment, unfavorable clinical outcome score, white ethnic group, and inadequate oral hygiene at the initial pretreatment examination. The use of computer software to evaluate digital photos retrospectively is a valid method for assessing the incidence and severity of WSLs on the maxillary anterior incisors, canines, and premolars.

A New in vitro Model to Study the Relationship of Gap Size and Secondary Caries

Objectives: To investigate the relationship of gap size and secondary caries in a newly developed secondary caries microbial model that permits adjustment of the gap between the tooth and a restoration. Methods: Tooth-resin-matrix composite specimens were mounted on gap-model stages with a gap size of 50 or 500 µm in experiment 1, and 0, 25, 250, or 1,000 µm in experiment 2. They were attached to plastic Petri plates, gas-sterilized and then incubated in a microbial caries model (with Streptococcus mutans TH16 in 1% sucrose tryptic soy broth for 1 h, 4 times/day, and with a buffer solution for the rest of the day). After 8 days of incubation, tooth specimens were sectioned and stained overnight with a rhodamine B solution. Digital images taken under a confocal microscope were analyzed for lesion size at the outer surface lesion and wall lesion (WL). Results: Gap size was found to affect the development of dentin WL area in experiment 1 and enamel and dentin WL areas in experiment 2, with bigger lesions being observed in the wider gap group (p < 0.05). Conclusion: The findings of this study suggest that the size of the gap between tooth and restoration affects the development of secondary caries along the cavity wall.

Influence of the organic matrix on root dentine erosion by citric acid

This investigation was conducted in an attempt to clarify the role of the organic matrix in bovine dentine demineralisation by 1% citric acid. Dentine slabs (n = 15) were treated for 2 min with 10% sodium hypochlorite (NaOCl, a strong protein solvent), 2% glutaraldehyde (GDA, a protein fixative) or deionised water (DIW, as negative control) prior to each of 5 demineralisation periods of 30 min. The mineral loss (ΔZ), lesion depth (LD) and surface loss (SL) were determined after each period of demineralisation, by transverse microradiography. The NaOCl-treated group showed higher ΔZ and LD than the GDA- and DIW-treated groups. No differences between GDA and DIW groups were found. The ΔZ and LD profiles were explained by quadratic fits (r2 >0.80; p = 0.001) in all groups. SL was detected only in the NaOCl-treated group. The data suggested that the maintenance of the organic matrix in the lesion might be important to reduce the erosion progression rate.

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.

Influence of Fluoride Availability of Dentifrices on Eroded Enamel Remineralization in situ

Remineralization of eroded enamel by dentifrices containing similar sources/concentrations of fluoride was investigated in situ. Fifty-three subjects completed a double-blind crossover study with 3 randomly assigned dentifrice treatments: placebo (0 ppm F, PD); reference (1,450 ppm NaF, RD) and test (1,450 ppm NaF + 5% KNO3, TD). Fluoride availability for each dentifrice was analyzed in vitro by standard tests (1-min fluoride release rate and enamel fluoride uptake). The subjects wore palatal appliances holding bovine enamel specimens previously eroded in vitro. Surface microhardness was determined before and after the in vitro erosive challenge, after in situ remineralization and after a second in vitro erosive challenge. ANOVA and pairwise comparisons were performed (α = 0.05). TD was superior to RD in the fluoride release tests, but similar to RD in the enamel fluoride uptake test. The mean percent surface microhardness recovery was 21.9 (standard deviation 8.0) for PD, 28.6 (8.0) for RD and 36.0 (8.0) for TD. The mean percent relative erosion resistance change was –58.8 (12.7) for PD, –31.3 (12.7) for RD and –27.3 (12.6) for TD. Both fluoride-containing dentifrices provided superior remineralization (p < 0.001) and erosion resistance (p < 0.001) compared to PD. The percent surface microhardness recovery demonstrated by the TD was significantly greater than for the RD (p < 0.001). There was no significant difference (p = 0.073) between TD and RD in relative resistance to further erosive challenge. The results suggest that fluoride availability may be different in dentifrices with similar sources/concentrations of fluoride, providing different levels of remineralization of eroded enamel.

Evaluation of several techniques for the detection of secondary caries adjacent to amalgam restorations.

The objective of this study was to determine the ability of several techniques to detect natural secondary caries adjacent to proximal class II amalgam restorations. Two sites were selected and marked on each of 50 human extracted posterior teeth. Three examiners visually characterized each site independently for signs of demineralization (VI), ditching presence (VD), and color change, and utilized light-induced fluorescence (QLF), and infrared laser fluorescence (LF) techniques. The teeth were sectioned through the selected sites, and the severity of each lesion was determined by confocal laser scanning microscopy (CLSM) as the ‘gold standard’. Agreement among examiners was assessed using weighted kappa statistics and showed fair to moderate correlation with all techniques. Sensitivity, specificity, positive predictive value (PPV), negative predictive value and accuracy were determined by utilizing three arbitrary CLSM thresholds. Higher sensitivity was indicated by the QLF and LF than by VI. For PPV and accuracy, QLF and LF showed values higher or similar to VI. Low sensitivity was found for VD. The results obtained in this study suggest that LF and QLF may improve the ability to detect early secondary caries around amalgam restorations.

The Chemistry of Caries: Remineralization and Demineralization Events with Direct Clinical Relevance

Dental caries is a site-specific disease that undergoes many cycles of demineralization and remineralization during lesion development. Because of its developmental characteristics dynamics, the caries lesion can be arrested and even repaired at its early stages without operative intervention by increasing the net mineral gain during the demineralization and remineralization cycles. This result can be accomplished by reducing the effect of etiological factors such as cariogenic biofilms and diet, and increasing the efficacy of remineralizing agents such as saliva and fluoride.

The effect of brushing time and dentifrice quantity on fluoride delivery in vivo and enamel surface microhardness in situ

While the clinical anticaries efficacy of fluoride toothpaste is now without question, our understanding of the relation of fluoride efficacy to brushing time and dentifrice quantity is limited. The aim of this in situ study was to determine how differences in brushing time and dentifrice quantity influence (i) fluoride distribution immediately after brushing, (ii) clearance of fluoride in saliva, (iii) enamel fluoride uptake (EFU) and (iv) enamel strengthening, via the increase in surface microhardness. The study compared brushing times of 30, 45, 60, 120 and 180 s with 1.5 g of dentifrice containing 1,100 µg/g fluoride as sodium fluoride. In addition, 60 s of brushing with 0.5 g dentifrice was evaluated. A longer brushing time progressively reduced retention of dentifrice in the brush, thereby increasing the amount delivered into the mouth. A longer brushing time also increased fluoride concentrations in saliva for at least 2 h after the conclusion of brushing, showing that increased contact time promoted fluoride retention in the oral cavity. There was a statistically significant positive linear relationship between brushing time and both enamel strengthening and EFU. Compared to 0.5 g dentifrice, brushing with 1.5 g dentifrice more than doubled the fluoride recovered in saliva after brushing and increased EFU. In conclusion, the results of this preliminary, short-term usage study suggest for the first time that both brushing time and dentifrice quantity may be important determinants both of fluoride retention in the oral cavity and consequent enamel remineralization.

In-vitro evaluation of various treatments to prevent demineralization next to orthodontic brackets

INTRODUCTION One common negative side effect of orthodontic treatment with fixed appliances is the development of incipient caries lesions around brackets, particularly in patients with poor oral hygiene. Bio-available minerals from cement containing amorphous calcium phosphate (ACP) might facilitate remineralization and inhibit lesion development. Our objective was to compare the potential of ACP-containing resin cement, fluoride varnish, resin sealer, and MI Paste (GC America, Alsip, Ill) under similar in-vitro conditions to prevent incipient caries lesions next to brackets on teeth. METHODS One hundred extracted premolars were randomly allocated to 5 groups (n = 20). Brackets were bonded with ACP cement (Aegis-Ortho, Bosworth, Skokie, Ill), resin (Transbond XT [3M Unitek, Monrovia, Calif], control), or resin followed by application of fluoride varnish (Vanish, 3M, St Paul, Minn), resin sealer (Pro-seal, Reliance Orthodontic Products, Itasca, Ill), or casein phosphopeptide-ACP paste (MI Paste). All groups were cycled for 15 days in demineralization solution for 8 hours a day, rinsed, placed in artificial saliva (30 minutes), brushed, and stored overnight in artificial saliva. The extent of demineralization in each group was assessed by using quantitative light-induced fluorescence and confocal laser scanning microscopy. RESULTS Only the Pro-seal and Vanish groups showed significantly smaller lesions than the controls (Kruskal-Wallis test, P <0.05) for both quantitative light-induced fluorescence and confocal laser scanning microscopy measurements. Fluorescence loss of Aegis-Ortho was similar to Vanish; Aegis-Ortho, MI Paste, and the controls were not different from each other. CONCLUSIONS Both light-cured filled resin (Pro-seal) and fluoride varnish (Vanish) might prevent enamel demineralization next to orthodontic brackets exposed to cariogenic conditions, but the observed positive effects of Aegis-Ortho and MI Paste were not significant.