Effect of TiF4 varnish on microbiological changes and caries prevention: in situ and in vivo models.

OBJECTIVE: The aim of this study was to evaluate microbiological changes, oral soft tissue toxicity, and caries-preventive effect of an experimental titanium tetrafluoride (TiF4) varnish compared with a commercially available fluoride varnish (NaF), using in situ and in vivo models. MATERIALS AND METHODS: The treatment groups were the following: TiF4 varnish (experimental varnish), Duraphat® (fluoride positive control), placebo varnish (no fluoride), and no treatment (negative control). The varnishes were applied once over the enamel surface using a microbrush. For the in vivo study, 48 Wistar rats were infected with Streptococcus sobrinus 6715, received a treatment, and were submitted to a cariogenic challenge. After 4 weeks, S. sobrinus, oral soft tissue toxicity, presence, and severity of caries were evaluated. For the in situ study, 12 volunteers took part in this randomized crossover, double-blind study performed in four phases of 14 days each. They used intraoral appliances containing four enamel specimens that received the varnish according treatment group. After 24 h, the varnish was removed and plaque accumulation was allowed. A 20% sucrose solution was dripped over the enamel blocks (10×/day for 5 min each). Total streptococci, S. mutans, Lactobacillus, Candida spp. counts, and presence of white spot lesions were evaluated. Lesion depth was also quantified by micro-CT. RESULTS: For the in vivo study, the fluoride (F-varnishes) showed a statistically significant reduction in the percentage of S. sobrinus compared to the negative control (p < 0.05). Toxicological analysis revealed no abnormalities in oral tissues of rats from all groups, and both F-varnishes reduced the number and severity of caries lesions, without significant differences (p < 0.05). No statistical differences in microbiological counts were seen for the in situ experiment (p > 0.05). However, the specimens treated with TiF4 exhibited lower percentage of white spot lesions and the lesion depth was significantly reduced by F-varnishes (p < 0.05). CONCLUSIONS: F-varnishes showed reduction in the percentage of S. sobrinus in vivo, no oral soft tissue toxicity, and a caries-preventive effect in vivo and in situ. CLINICAL RELEVANCE: NaF varnish is largely used due its capacity to form CaF2-like layer on enamel. Therefore, development of studies focused on other fluoride compounds such as a TiF4 varnish, which may have greater efficacy than NaF against tooth demineralization, is important.

Is the morphology and activity of the occlusal carious lesion related to the lesion progression stage?

OBJECTIVE: To investigate the relationship between degree of dentin demineralization with both lesion activity and morphology of the occlusal carious cavity. DESIGN: Occlusal sites (n=138) were identified by visual examination (Nyvad's scores 0-6) in 67 extracted teeth which were scanned in a high energy micro-CT. After 3D reconstruction, each stack was resliced in the mesio-distal direction and tooth mineral density (MD) was measured along a path from enamel to the deepest part of dentin in the slice showing the most severe carious involvement. Each site was classified in "open" or "closed" (if cavitated) depending on the morphology of the surrounding enamel walls as measured using micro-CT and as active or inactive in enamel or dentin by a clinical scoring system. RESULTS: Lesions showing dentin cavitation presented higher demineralization degree compared to non-cavitated, or enamel cavitated lesions. Inactive lesions presented lower demineralization degree compared to active lesions, although with a low effect size. According to the morphological aspect of the carious cavity, open enamel lesions showed lower dentin demineralization degree than closed lesion environments. CONCLUSION: Active lesions showed higher dentin demineralization degree than inactive ones, while lesions showing closed cavitation resulted in higher dentin demineralization degree only for enamel lesions. Including those parameters in treatment decisions may help to improve prognosis and increase effectiveness of the caries diagnostic systems in the clinical setting.

Comparison of canal transportation in simulated curved canals prepared with ProTaper Universal and ProTaper Gold systems.

OBJECTIVES: The purpose of this study was to assess the ability of ProTaper Gold (PTG, Dentsply Maillefer) in maintaining the original profile of root canal anatomy. For that, ProTaper Universal (PTU, Dentsply Maillefer) was used as reference techniques for comparison. MATERIALS AND METHODS: Twenty simulated curved canals manufactured in clear resin blocks were randomly assigned to 2 groups (n = 10) according to the system used for canal instrumentation: PTU and PTG groups, upto F2 files (25/0.08). Color stereomicroscopic images from each block were taken exactly at the same position before and after instrumentation. All image processing and data analysis were performed with an open source program (FIJI). Evaluation of canal transportation was obtained for two independent canal regions: straight and curved levels. Student's t test was used with a cut-off for significance set at α = 5%. RESULTS: Instrumentation systems significantly influenced canal transportation (p < 0.0001). A significant interaction between instrumentation system and root canal level (p < 0.0001) was found. PTU and PTG systems produced similar canal transportation at the straight part, while PTG system resulted in lower canal transportation than PTU system at the curved part. Canal transportation was higher at the curved canal portion (p < 0.0001). CONCLUSIONS: PTG system produced overall less canal transportation in the curved portion when compared to PTU system.

Stress and strain distribution in demineralized enamel: A micro-CT based finite element study.

Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D finite element analysis, stress, and strain patterns in sound and carious enamel after a simulated occlusal load. Micro-CT based models were created and meshed with tetrahedral elements (based on an extracted third molar), namely: a sound (ST) and a carious tooth (CT). For the CT, enamel material properties were assigned according to the micro-CT gray values. Below the threshold corresponding to the enamel lesion (2.5 g/cm(3) ) lower and isotropic elastic modulus was assigned (E = 18 GPa against E1 = 80 GPa, E2 = E3 = 20 GPa for sound enamel). Both models were imported into a FE solver where boundary conditions were assigned and a pressure load (500 MPa) was applied at the occlusal surface. A linear static analysis was performed, considering anisotropy in sound enamel. ST showed a more efficient transfer of maximum principal stress from enamel to the dentin layer, while for the CT, enamel layer was subjected to higher and concentrated loads. Maximum principal strain distributions were seen at the carious enamel surface, especially at the central fossa, correlating to the enamel cavity seen at the original micro-CT model. It is possible to conclude that demineralized enamel compromises appropriate stress transfer from enamel to dentin, contributing to the odds of fracture and cavitation. Enamel fracture over a dentin lesion may happen as one of the normal pathways to caries progression and may act as a confounding factor during clinical diagnostic decisions.

Quantitative Transportation Assessment in Simulated Curved Canals Prepared with an Adaptive Movement System.

INTRODUCTION: The aim of this study was to evaluate the ability of the Twisted File Adaptive (TF Adaptive; SybronEndo, Orange, CA) system in maintaining the original profile of root canal anatomy. The ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) and Twisted File (TF) (SybronEndo) systems were used as reference techniques for comparison. METHODS: Thirty simulated curved root canals manufactured in clear resin blocks were randomly assigned to 3 groups (n = 10) according to the instrumentation system: TF in rotary motion, TF in TF Adaptive motion, and ProTaper Universal. Color stereomicroscopic images from each block were taken exactly at the same position before and after instrumentation. All image processing and data analysis were performed with an open-source program (Fiji). Evaluation of canal transportation was obtained for 2 independent canal regions: straight and curved levels. Univariate analysis of variance and Tukey Honestly Significant Difference were used, and a cutoff for significance was set at alpha = 5%. RESULTS: Instrumentation systems significantly influenced canal transportation (P = .000). A significant interaction between instrumentation system and root canal level (P = .000) was also found as follows: at the straight part, TF and TF Adaptive systems produced similar canal transportation, which was significantly lower than for the ProTaper Universal system; at the curved part, TF resulted in the lowest canal transportation followed by TF Adaptive and ProTaper Universal systems. Canal transportation was higher at the curved canal parts (P = .00). CONCLUSIONS: The TF in rotary motion produced overall less canal transportation in the curved portion when compared with the others tested systems. The ProTaper Universal system showed the highest canal transportation.

Accumulated hard tissue debris produced during reciprocating and rotary nickel-titanium canal preparation.

INTRODUCTION: This study compared the amount of hard tissue debris produced after different apical enlargement with single-file reciprocating systems (WaveOne [Dentsply Maillefer, Baillaigues, Switzerland] and Reciproc [VDW, Munich, Germany]) and a conventional multifile rotary system (BioRaCe [FKG Dentaire, La-Chaux-de-Fonds, Switzerland]) using micro-computed tomographic imaging. METHODS: Thirty moderately curved mesial roots of mandibular molars presenting 2 independent root canals were selected and scanned at an isotropic resolution of 14.16 µm. The sample was assigned to 3 groups (n = 10) with respect to the root length and degree of curvature of the mesial root according to the system used for the root canal preparation: Reciproc, WaveOne, and BioRaCe. Second and third scans were taken after the root canals were prepared up to ISO sizes 25 and 40, respectively. The matched images of the mesial canals, before and after preparation, were examined from the furcation level to the apex to evaluate the amount of hard tissue debris (%). Data were statistically compared using a general linear model for repeated-measures with a significance level set at 5%. RESULTS: Instrumentation systems per se did not influence the amount of hard tissue accumulation (P > .05), whereas a significant reduction in the percentage of hard tissue debris was observed after sequential enlargement in all groups (P < .05). CONCLUSIONS: None of the systems yielded root canals completely free from packed hard tissue debris. The increased final apical size resulted in significantly less debris accumulation for both reciprocating and rotary systems.