Color changes induced by fluoride on nickel-titanium orthodontic wires / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To observe the color changes of nickel-titanium (Ni-Ti) orthodontic wires induced by fluoride.</p><p><b>METHODS</b>Each 40 samples of 4 kinds of nickel-titanium orthodontic wires (IMD, SL, TP, YY) were put into artificial saliva with sodium fluoride at different F concentrations (0.05%, 0.10%, 0.15%) and artificial saliva, separately. Dislodged the species and immersed them into artificial saliva with sodium fluoride for 3 minutes, then washed them with deionized water, and put back to artificial saliva, this course should be repeated 3 times per day. The whole immersion test lasted for 28 days. The color and micro-morphous changing were observed.</p><p><b>RESULTS</b>The color changes came to be more serious as the F- concentration growing (P < 0.05). At the same F- concentration, the color changes of IMD and YY were higher than SL and YP (P < 0.01), while there were no significant difference between IMD and YY, SL and TP (P > 0.05).</p><p><b>CONCLUSION</b>Fluoride can change the color of Ni-Ti wire. Different Ni-Ti wires get different changes at the same F- concentration.</p>

Correlation analysis on the malocclusion and articulation of skeletal angle III malocclusion in mixed dentition / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of skeletal Class III malocclusion in mixed dentition on speech articulation and to look for which factors lead to the speech errors.</p><p><b>METHODS</b>Thirty-eight children with skeletal Angle Ill malocclusion in mixed dentition were selected as a sample group and 40 children with normal occlusion in mixed dentition as a control group. Two phoneticians evaluated their articulations and wrote down error phonemes respectively. The correlation analysis was undertaken between the number of errors and the measurements of patients' cephalometry.</p><p><b>RESULTS</b>The number of errors were correlated significantly with overbite, UI-LI, OBJ (OB+OJ) and TD-PW.</p><p><b>CONCLUSION</b>There is articulatory malfunction in the majority of skeletal Angle III malocclusion patients in mixed dentition. Articulatory malfunction is related to the position of incisors and the tongue.</p>

Influence of different porcelain surface treatment method on the bonding of metal brackets to porcelain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the influence of different porcelain surface treatment methods on the shear bond strength of metal brackets bonded to porcelain.</p><p><b>METHODS</b>80 porcelain facets were divided randomly into two groups according to different adhesive material that was used to bond metal brackets. Adhesive material were Jing-Jin enamel adhesive and light-cured composite resin. Each group was further divided into 4 subgroups according to different surface treatment methods, which were acid etching with 37% phosphoric acid (H3PO4), acid etching with 9.6% hydrofluoric acid (HF), deglazing by grinding and silanating the porcelain surface. All specimens were stored in 37 degrees C water for 24 hours and then the shear bond strength and the porcelain fracture after debonding was determined. The porcelain surfaces after HF etching, H3PO4 etching and deglazing by grinding were examined by scanning electron microscopy respectively.</p><p><b>RESULTS</b>The shear bond strengths in the HF etching groups, the deglazing groups and the silanating groups were much greater than that in the phosphoric etching groups (P < 0.01). Adequate orthodontic bonding strength was achieved both when bonded with light-cured composite resin after deglazing by grinding and when bonded with either of these adhesives after HF etching or surface silanating. There were no differences in the rates of porcelain fractures among groups (P > 0.05).</p><p><b>CONCLUSION</b>HF etching, deglazing by grinding and silanating can all increase the shear bond strength between metal bracket and porcelain. Surface silanating of porcelain is a better surface treatment when metal brackets bonded to porcelain.</p>

A statistic analysis on absence of third molar germs in orthodontic patients / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To examine the absence of the third molar germs in orthodontic patients and to evaluate the relationship between third molar germs and malocclusion.</p><p><b>METHODS</b>The subjects comprised 234 patients (male 92, female 142) from the orthodontic clinic whose ages were 14-18. The assessments of the third molar germs were made from panoramic radiographs, and the assessments of ANB angle were made from lateral cephalograms. All the data were analyzed by statistic chi2 test.</p><p><b>RESULTS</b>The percentage of male who missed one or more third molar gems (37.0%) was higher than that of female (24.6%). There was no significant difference between the absent frequencies of third molar germs on left and right sides in either maxilla or mandible. The absent percentage of third molar germs in skeletal III subjects was higher than those in both skeletal class I and II subjects. The absent difference of third molar germs was in upper arches (P < 0.05), but not in lower arches (P > 0.05). There was no significant difference in absent percentage of third molar germs between skeletal class I and II subjects.</p><p><b>CONCLUSION</b>Male patients have higher absent frequencies of third molar germs than female ones. Skeletal class III patients have higher absence of third molar germs in upper jaws than skeletal class I and II patients.</p>