Learning to spell is a challenging process, especially for young learners, in part because it relies on multiple aspects of linguistic knowledge, primarily phonological and morphological. However, alongside these universals, there are significant writing system specifics, namely, language-specific and script-specific factors that may also challenge young readers and writers (Daniels and Share, 2018). The current study focuses on the impact of four distinctive visual-orthographic features of the Arabic abjad on spelling, namely, (i) the similarity of many basic letter-forms, (ii) allography (the positional variants of the letter forms), (iii) ligaturing (the joining of letters), and (iv) non-linearity (extra-linear diacritic-like signs used to mark consonantal, short vowel and morpho-syntactic distinctions). We examined the distribution of visual-orthographic spelling errors across three grade levels as well as the developmental changes in these errors. We predicted that these errors would account for a significant proportion of children's spelling errors. Ninety-six Arabic-speaking pupils from three elementary grades (1st, 2nd, 4th grades) were presented with a sequence of six pictures and asked to write a story or several sentences about the events depicted. All spelling errors were analyzed and categorized according to two types of categories: six visual-orthographic categories and six additional categories that relate to the more traditional error types (e.g., phonological). The results showed that the visual-orthographic category was the second most common error category across the three grade levels, accounting for over one quarter of all spelling errors. Ligaturing and letter shape formation errors emerged as the two most prevalent types of errors in this category. These findings clearly demonstrate that visual-orthographic features of the Arabic abjad pose significant challenges in learning to spell.
A marginal fit of all-ceramic crowns is a prerequisite for the long-term clinical success of a dental restoration. Few in vivo studies have investigated the effect of the film thickness of various luting agents on vertical discrepancy. This in vivo study evaluated the influence of three luting cements on the occlusal vertical discrepancy of milled crowns using a complete digital workflow. Forty-three patients treated in a students’ clinic in Tel-Aviv University with 45 single posterior digitally prepared monolithic crowns were included in the study. The crowns were randomly divided into three groups using different resin luting agents: self-adhesive resin cement, resin-modified glass ionomer cement and adhesive resin cement. The crowns were intra-orally scanned before and after cementation. The two standard tessellation language (STL) files for each crown were superimposed using digital software, and between four and six measurements were made at the occlusal surface to demonstrate the occlusal and marginal discrepancies. One-way ANOVA (α = 0.05) was used. The vertical occlusal discrepancy ranged from 2 to 38 μm. The mean vertical discrepancy values were (µm): self-adhesive resin = 12.93 ± 4.74, resin-modified glass ionomer = 19.05 ± 4.60 and adhesive resin = 13.69 ± 5.17. There were significant differences between resin-modified and self-adhesive cement groups (p = 0.004), and between resin-modified and adhesive resin cement groups (p = 0.013). Distal marginal ridge measurements were significantly different between resin-modified glass ionomer cement and self-adhesive resin cement group (p < 0.001) and the adhesive resin cement group (p = 0.021). There were no significant differences between the discrepancy values at the two measurement points in the self-adhesive cement group (p = 0.377), nor the resin-modified glass ionomer group (p = 0.388), or the adhesive resin cement group (p = 0.905). The cementation procedure with various resin cements results in occlusal vertical discrepancies within standard clinical acceptability. Resin-modified glass ionomer cement produced more vertical discrepancy than adhesive and self-adhesive resin cements did.
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