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The local thickness described by Hildebrand and Rüesgsegger can characterize a 3D binary image of a complex structure such as a bone, a cell, or a paper fiber [1]. Such images are available from, for example, micro-computed tomography [2]. Let 3 R W be the structure. The local thickness at point W p is the diameter of the largest sphere that contains p and is completely inside the structure.The problem is to transform the 3D binary image into the 3D local thickness image.Several steps to are given in [1]. The first is a Euclidean distance transformation (EDT) The distance map at W q , ( ) q D map , is the distance from q to the nearest background point. The sphere of radius ( ) q D map centered at q is completely inside the structure. If p is within this sphere, then the local thickness at p, ( ) p τ , is at least ( ) q D map . Points q are scanned to find ( ) p τ by maximizing this bound. A further simplification is to first remove many of the points whose spheres of radius ( ) q D map are completely contained within the corresponding spheres of other points. Removing all of the redundant points would produce the distance ridge (DR) which is related to the skeleton and the medial axis [1, 4].A 3D local thickness procedure has been implemented in Java as a plugin for ImageJ [5]. The EDT uses the fast algorithm given by Saito and Toriwaki [6]. The DR computation is a simplified form of a template scheme [7]. Care was taken to optimize the use computational resources. No temporary 3D buffers are required. A related implementation in C was given previously by Coeurjolly [8]

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The condensable composites differed significantly in their mechanical properties. This study suggested that, besides the filler content level and filler size, other factors like matrix-filler interactions highly influence the fracture and wear behavior of the materials.

Aim The aim of the present randomized, controlled trial was to compare the impact of the regular use of a fluoride‐free microcrystalline hydroxyapatite (HAP) dentifrice and a 1400 ppm fluoride control dentifrice on caries progression in 150 highly caries‐active orthodontic patients. Methods The primary outcome was the occurrence of lesions with International Caries Detection and Assessment System (ICDAS) ≥code 1 on the vestibular surfaces of teeth 15‐25 within 168 days after fixation of orthodontic brackets. Secondary outcomes were lesion development ICDAS ≥code 2, the plaque index, and the gingival index. Results In total, 147 patients were included in the intent‐to‐treat (ITT) analysis; 133 finished the study per protocol (PP). An increase in enamel caries ICDAS ≥code 1 was observed in 56.8% (ITT) and 54.7% (PP) of the HAP group participants compared with 60.9% (ITT) and 61.6% (PP) of the fluoride control group. Non‐inferiority testing (ITT and PP) demonstrated the absence of a significant difference between the groups. No significant differences in secondary outcomes were observed between the groups. Conclusion In highly caries‐active patients, the impact of the regular use of a microcrystalline HAP dentifrice on caries progression is not significantly different from the use of a 1400 ppm fluoride toothpaste (ClinicalTrials.gov: NCT02705456).

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The present study was designed to evaluate the surface roughness and the gloss of current composites before and after toothbrush abrasion. We assessed forty dimensionally standardized composite specimens (n=8/group) from five composites: two nanohybrids (i.e., IPS Empress Direct Enamel and IPS Empress Direct Dentin), two microhybrids (i.e., Clearfil AP-X and Filtek Z250) and one organically modified ceramics (Admira). All of the specimens were polished with 4000-grid silicon carbide papers. Surface roughness was measured with a profilometer and gloss was measured with a glossmeter before and after powered toothbrush abrasion with a 1:1 slurry (dentifrice/tap water) at 12,000 strokes in a toothbrush simulator. There was a significant increase in the surface roughness and a reduction in gloss after toothbrush abrasion in all of the composites except Clearfil AP-X (p<0.05). Simple regression analysis showed that there was not an association between the surface roughness and the gloss (R 2 =0.191, p<0.001).

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