Browsing by Author "Department of Cariology, Operative Dentistry and Dental Public Health, School of Dentistry"
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Item Characteristics of Methylcellulose Acid Gel Lesions Created in Human and Bovine Enamel(Karger, 2013-01) Lippert, Frank; Butler, A.; Lynch, R. J. M.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryAcid gel caries lesions were created in 3,100 human and bovine enamel specimens and studied with transverse microradiography. Small, significant differences were found. Human enamel lesions were found to be less demineralized, shallower, had a higher ratio of integrated mineral loss (ΔZ) to lesion depth (L), a lower degree of surface zone mineralization (SZmax) and showed less variability than those in bovine enamel. SZmax showed the highest variability. Between tissues, L differed the most, ΔZ the least. Biological variation within bovine enamel is perhaps not only bigger than previously assumed, it may also overshadow any structural and chemical differences between tissues.Item Comparison of Knoop and Vickers Surface Microhardness and Transverse Microradiography for the Study of Early Caries Lesion Formation in Human and Bovine Enamel(Elsevier, 2014-07) Lippert, Frank; Lynch, R. J. M.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryObjective The aims of the present laboratory study were twofold: a) to investigate the suitability of Knoop and Vickers surface microhardness (SMH) in comparison to transverse microradiography (TMR) to investigate early enamel caries lesion formation; b) to compare the kinetics of caries lesion initiation and progression between human and bovine enamel. Design Specimens (90 × bovine and 90 × human enamel) were divided into six groups (demineralization times of 8/16/24/32/40/48 h) of 15 per enamel type and demineralized using a partially saturated lactic acid solution. SMH was measured before and after demineralization and changes in indentation length (ΔIL) calculated. Lesions were characterized using TMR. Data were analyzed (two-way ANOVA) and Pearson correlation coefficients calculated. Results ΔIL increased with increasing demineralization times but plateaued after 40 h, whereas lesion depth (L) and integrated mineral loss (ΔZ) increased almost linearly throughout. No differences between Knoop and Vickers SMH in their ability to measure enamel demineralization were observed as both correlated strongly. Overall, ΔIL correlated strongly with ΔZ and L but only moderately with the degree of surface zone mineralization, whereas ΔZ and L correlated strongly. Bovine demineralized faster than human enamel (all techniques). Conclusions Lesions in bovine formed faster than in human enamel, although the resulting lesions were almost indistinguishable in their mineral distribution characteristics. Early caries lesion demineralization can be sufficiently studied by SMH, but its limitations on the assessment of the mineral status of more demineralized lesions must be considered. Ideally, complementary techniques to assess changes in both physical and chemical lesion characteristics would be employed.Item Contribution of prosthetic treatment considerations for dental extractions of permanent teeth(2016-07) Fernández-Barrera, Miguel Ángel; Medina-Solís, Carlo Eduardo; Casanova-Rosado, Juan Fernando; Mendoza-Rodríguez, Martha; Escoffié-Ramírez, Mauricio; Casanova-Rosado, Alejandro José; Navarrete-Hernández, José de Jesús; Maupome, Gerardo; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryBackground. Tooth loss is an easily identifiable outcome that summarizes a complex suite of factors in an individual’s history of dental disease and its treatment by dental services over a lifetime. Assessment of overall tooth loss data is essential for epidemiologically evaluating the adequacy of dental care provided at a systems level, as well as for placing in context tooth loss for non-disease causes. For example, when derived from prosthetic treatment planning, the latter may unfortunately lead to some teeth being extracted (pulled) for the sake of better comprehensive clinical results. The objective of the present manuscript was to identify the contribution to overall tooth loss, by extraction of permanent teeth because of prosthetic treatment reasons. Material and Methods. A cross-sectional study included sex, age, total number of extractions performed by subject, sextant (anterior vs. posterior), group of teeth (incisors, canines, premolars and molars), upper or lower arch, and the main reason underlying extraction (extraction for any reason vs. prosthetic treatment), in patients 18 years of age and older seeking care at a dental school clinic in Mexico. A multivariate logistic regression model was generated. Results. A total of 749 teeth were extracted in 331 patients; 161 teeth (21.5% of total) were extracted for explicit prosthetic treatment indications. As age increased, the likelihood of having an extraction for prosthetic reasons increased 3% (OR = 1.03, p < 0.001). Women (OR = 1.57, p < 0.05) were more likely to be in this situation, and molars (OR = 2.70, p < 0.001) were most at risk. As the total number of extractions increased, the risk of having an extraction for prosthetic reasons decreased (OR = 0.94, p < 0.05). Conclusions. A significant amount (21.5%) of the extractions of permanent teeth were performed for prosthetic reasons in this dental school clinical environment; age, sex, type of tooth, and the total number of extractions moderated such pattern.Item Dose-Response Effects of Zinc and Fluoride on Caries Lesion Remineralization(Karger, 2012-02) Lippert, Frank; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryThe present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0–153 µmol/l) and fluoride (1.1 or 52.6 µmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 µmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 µmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8–15.3 µmol/l. At 76.5 and less so at 153 µmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 µmol/l fluoride, but enhanced remineralization at 52.6 µmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.Item Effect of Enamel Caries Lesion Baseline Severity on Fluoride Dose-Response(Hindawi, 2017) Lippert, Frank; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryThis study aimed to investigate the effect of enamel caries lesion baseline severity on fluoride dose-response under pH cycling conditions. Early caries lesions were created in human enamel specimens at four different severities (8, 16, 24, and 36 h). Lesions were allocated to treatment groups (0, 83, and 367 ppm fluoride as sodium fluoride) based on Vickers surface microhardness (VHN) and pH cycled for 5 d. The cycling model comprised 3 × 1 min fluoride treatments sandwiched between 2 × 60 min demineralization challenges with specimens stored in artificial saliva in between. VHN was measured again and changes versus lesion baseline were calculated (ΔVHN). Data were analyzed using two-way ANOVA (). Increased demineralization times led to increased surface softening. The lesion severity×fluoride concentration interaction was significant (). Fluoride dose-response was observed in all groups. Lesions initially demineralized for 16 and 8 h showed similar overall rehardening (ΔVHN) and more than 24 and 36 h lesions, which were similar. The 8 h lesions showed the greatest fluoride response differential (367 versus 0 ppm F) which diminished with increasing lesion baseline severity. The extent of rehardening as a result of the 0 ppm F treatment increased with increasing lesion baseline severity, whereas it decreased for the fluoride treatments. In conclusion, lesion baseline severity impacts the extent of the fluoride dose-response.Item Effect of Fluoride, Lesion Baseline Severity and Mineral Distribution on Lesion Progression(Karger, 2012) Lippert, Frank; Butler, A.; Lynch, R. J. M.; Hara, Anderson T.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryThe present study investigated the effects of fluoride (F) concentration, lesion baseline severity (ΔZbase) and mineral distribution on lesion progression. Artificial caries lesions were created using three protocols [methylcellulose acid gel (MeC), hydroxyethylcellulose acid gel (HEC), carboxymethylcellulose acid solution (CMC)] and with low and high ΔZbase groups by varying demineralization times within protocols. Subsequently, lesions were immersed in a demineralizing solution for 24 h in the presence of 0, 1, 2 or 5 ppm F. Changes in mineral distribution characteristics of caries lesions were studied using transverse microradiography. At baseline, the protocols yielded lesions with three distinctly different mineral distributions. Secondary demineralization revealed differences in F response between and within lesion types. In general, lowΔZ lesions were more responsive to F than highΔZ lesions. LowΔZ MeC lesions showed the greatest range of response among all lesions, whereas highΔZ HEC lesions were almost unaffected by F. Laminations were observed in the presence of F in all but highΔZ HEC and CMC lesions. Changes in mineral distribution effected by F were most pronounced in MeC lesions, with remineralization/mineral redeposition in the original lesion body at the expense of sound enamel beyond the original lesion in a dose-response manner. Both ΔZbase and lesion mineral distribution directly impact the F response and the extent of secondary demineralization of caries lesions. Further studies – in situ and on natural white spot lesions – are required to better mimic in vivo caries under laboratory conditions.Item Effect of Lesion Baseline Severity and Mineral Distribution on Remineralization and Progression of Human and Bovine Dentin Caries Lesions(Karger, 2015-10) Lippert, Frank; Churchley, David; Lynch, Richard J.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryThe aims of this laboratory study were to compare the effects of lesion baseline severity, mineral distribution and substrate on remineralization and progression of caries lesions created in root dentin. Lesions were formed in dentin specimens prepared from human and bovine dentin using three protocols, each utilizing three demineralization periods to create lesions of different mineral distributions (subsurface, moderate softening, extreme softening) and severity within each lesion type. Lesions were then either remineralized or demineralized further and analyzed using transverse microradiography. At lesion baseline, no differences were found between human and bovine dentin for integrated mineral loss (ΔZ). Differences in mineral distribution between lesion types were apparent. Human dentin lesions were more prone to secondary demineralization (ΔΔZ) than bovine dentin lesions, although there were no differences in ΔL. Likewise, smaller lesions were more susceptible to secondary demineralization than larger ones. Subsurface lesions were more acid-resistant than moderately and extremely softened lesions. After remineralization, differences between human and bovine dentin lesions were not apparent for ΔΔZ although bovine dentin lesions showed greater reduction in lesion depth L. For lesion types, responsiveness to remineralization (ΔΔZ) was in the order extremely softened > moderately softened > subsurface. More demineralized lesions exhibited greater remineralization than shallower ones. In summary, some differences exist between human and bovine dentin and their relative responsiveness to de- and remineralization. These differences, however, were overshadowed by the effects of lesion baseline mineral distribution and severity. Thus, bovine dentin appears to be a suitable substitute for human dentin in mechanistic root caries studies.Item Effect of toothbrushing duration and dentifrice quantity on enamel remineralisation: An in situ randomized clinical trial(Elsevier, 2016-12) Creeth, J. E.; Kelly, Sue A.; González-Cabezas, Carlos; Karwal, R.; Martinez-Mier, Esperanza A.; Lynch, R. J. M.; Bosma, M.; Zero, Domenick T.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryObjectives The influence of toothbrushing duration and dentifrice quantity on fluoride efficacy against dental caries is poorly understood. This study investigated effects of these two oral hygiene factors on enamel remineralisation (measured as surface microhardness recovery [SMHR]), enamel fluoride uptake (EFU), and net acid resistance (NAR) post-remineralisation in a randomized clinical study using an in situ caries model. Methods Subjects (n = 63) wore their partial dentures holding partially demineralised human enamel specimens and brushed twice-daily for two weeks, following each of five regimens: brushing for 120 or 45 s with 1.5 g of 1150 ppm F (as NaF) dentifrice; for 120 or 45 s with 0.5 g of this dentifrice; and for 120 s with 1.5 g of 250 ppm F (NaF) dentifrice. Results Comparing brushing for 120 s against brushing for 45 s, SMHR and EFU increased by 20.0% and 26.9% respectively when 1.5 g dentifrice was used; and by 22.8% and 19.9% respectively when 0.5 g dentifrice was used. Comparing brushing with 1.5 g against brushing with 0.5 g dentifrice, SMHR and EFU increased by 35.3% and 51.3% respectively when brushing for 120 s, and by 38.4% and 43.0% respectively when brushing for 45 s. Increasing brushing duration and dentifrice quantity also increased the NAR value. The effects of these two oral hygiene factors on SMHR, EFU, and NAR were statistically significant (p < 0.05 in all cases). Conclusion Brushing duration and dentifrice quantity have the potential to influence the anti-caries effectiveness of fluoride dentifrices. Study NCT01563172 on ClinicalTrials.gov. Clinical significance The effect of two key oral hygiene regimen factors – toothbrushing duration and dentifrice quantity – on fluoride’s anticaries effectiveness is unclear. This 2-week home-use in situ remineralisation clinical study showed both these factors can influence fluoride bioactivity, and so can potentially affect fluoride’s ability to protect against caries.Item Effects of fluoride concentration and temperature of milk on caries lesion rehardening(Elsevier, 2012-10) Lippert, Frank; Martinez-Mier, Esperanza A.; Soto-Rojas, Armando E.; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryObjectives The aim of the present in vitro study was to investigate the effects of fluoride concentration and temperature of milk on caries lesion rehardening under pH cycling conditions. Methods Incipient caries-like lesions were formed in human enamel specimens, characterized using Vickers surface microhardness (VHN) and assigned to seven treatment groups (n = 18 per group): fluoride was tested at five levels (0, 2.5, 5, 10, 20 mg/l, all 22 °C) and milk temperature at three levels (4, 22, 60 °C), but only for 10 mg/l F. Lesions were pH cycled for 15d (4×/daily 10 min milk treatments, 1×/daily 4 h acid challenge, remineralization in human/artificial saliva mixture). VHN of specimens were measured again and changes from lesion baseline were calculated. Subsequently, enamel fluoride uptake (EFU) was determined using the micro drill technique. Results Lesions responded to fluoride in a dose–response manner with higher fluoride concentrations resulting in more lesion rehardening (20 > 10 ≥ 5 ≥ 2.5 > 0 mg/l F). Furthermore, fluoridated milk at 60 °C was found to be more efficacious than at 4 °C (60 ≥ 22 > 4 °C). EFU results were similar (20 > 10 > 5 > 2.5 ≥ 0 mg/l F; 60 > 22 ≥ 4 °C). Conclusions Both fluoride concentration and milk temperature are likely to contribute to the anti-caries potential of fluoridated milk.Item The Effects of Fluoride, Strontium, Theobromine and their Combinations on Caries Lesion Rehardening and Fluoridation(Elsevier, 2017-08) Lippert, Frank; Department of Cariology, Operative Dentistry and Dental Public Health, School of DentistryObjective The aim was to investigate the effects of fluoride, strontium, theobromine and their combinations on caries lesion rehardening and fluoridation (EFU) under pH cycling conditions. Design Human enamel specimens were demineralized at 37 °C for 24 h using a pH 5.0 solution containing 50 mM lactic acid and 0.2% Carbopol 907 which was 50% saturated with respect to hydroxyapatite. Lesions were assigned to nine treatment groups (n = 16) based on Knoop surface microhardness indentation length. Treatment aqueous solutions were: placebo, 11.9 mM sodium fluoride (F), 23.8 mM sodium fluoride (2 × F), 1.1 mM strontium chloride hexahydrate (Sr), 1.1 mM F theobromine, Sr + theobromine, F + Sr, F + theobromine, F + Sr + theobromine. Lesions were pH cycled for 5d (daily protocol: 3 × 1min-treatment; 2 × 60min-demineralization; 4 × 60 min & overnight-artificial saliva). Knoop indentation length was measured again and%surface microhardness recovery (%SMHr) calculated. EFU was determined using the acid-etch technique. Data were analysed using ANOVA. Results Model showed fluoride dose-response for both variables (2 × F > F > placebo). For%SMHr, F + Sr+/−theobromine resulted in more rehardening than F, however less than 2 × F. F + theobromine was similar to F. For EFU, F + Sr was inferior to F, F + theobromine and F + Sr + theobromine which were similar and inferior to 2 × F. In absence of fluoride, Sr, theobromine or Sr + theobromine were virtually indistinguishable from placebo and inferior to F. Conclusions It can be concluded that a) strontium aids rehardening but not EFU and only in presence of fluoride; b) theobromine does not appear to offer any anti-caries benefits in this model; c) there are no synergistic effects between strontium and theobromine in the presence or absence of fluoride.