Shear bond strength of orthodontic brackets bonded to different ceramic surfaces.

This study was undertaken to measure the shear bond strength (SBS) of stainless steel brackets bonded to different ceramic surfaces, to compare the SBS of the different ceramics with each other and with conventional ceramo-metal porcelains, and to determine the mode of failure for each group following debonding. A total of 60 ceramic crowns were constructed on extracted teeth and divided into three equal groups as follows: In-Ceram ceramic crowns, IPS-Impress ceramic crowns, and conventional ceramo-metal porcelain. Standard edgewise metal premolar brackets were bonded to the prepared porcelain surfaces. After bonding, all samples were tested in shear mode on an Instron universal testing machine. Statistical analysis was undertaken using analysis of variance, LSD, and chi-squared tests. The results showed that the SBS for the ceramo-metal and the In-Ceram groups were comparable, with mean values of 80.54 +/- 13.44 N and 78.87 +/- 13.47 N, respectively. The IPS-Impress group showed the weakest SBS which averaged 67.40 +/- 8.99 N. This was significantly lower than that of the conventional ceramo-metal porcelain (P < 0.001) and the In-Ceram surface (P < 0.01). The mode of failure in the ceramo-metal group was between the porcelain surface and adhesive and in the other two ceramic groups, between the brackets and adhesive (P < 0.001). The SBS of orthodontic brackets to the three tested ceramic surfaces were adequate for orthodontic use.

Relationship between tooth irregularity and periodontal disease in children with regular dental visits.

OBJECTIVES: The aim of this study was to investigate any association between irregular teeth and periodontal breakdown among children who attend dental clinics regularly. METHODS: The subjects were 80 children (39 females and 41 males) with a mean age of 12.38 +/- 0.75 years. Each subject had an alginate impression in the mandibular arch, periapical radiographs for the lower incisor teeth and clinical examination for periodontal health. Plaque accumulation, gingival condition and probing depth, bone level and status of lower incisor teeth contact areas were recorded. Spearman correlation test was used to observe any relationship between the clinical variables. RESULTS: The average probing depth, gingival index and plaque index scores in the subjects studied were 1.3 +/- 0.25, 0.99 +/- 0.28 and 1.17 +/- 0.52 respectively. The average number of sites with labiolingual displacement with mesiodistal overlap was 1.81 +/- 1.30 and those without mesiodistal overlap was 1.39 +/- 1.10. The average number of contact areas with spacing was 0.59 +/- 1.23. The correlation observed between irregularity and periodontal health indicated no association between the number and type of displacement and plaque accumulation, gingivitis, attachment loss and alveolar bone level. CONCLUSION: There was no association between irregularity of teeth and periodontal diseases in presence of good oral hygiene.

Evaluation of shear bond strength with different enamel pre-treatments.

The purpose of this study was to investigate the shear bond strengths of two adhesives, Panavia-21 and a composite resin (Transbond XT), with different enamel pre-treatments, acid etching (37 per cent phosphoric acid) and grit blasting (50 microm aluminium oxide particles). The mode of bond failure was also assessed using the modified adhesive remnant index (ARI). Ninety freshly extracted non-carious human premolar teeth were randomly divided into the following groups: (1) Transbond XT, acid-etched enamel surface; (2) Panavia-21, acid-etched enamel surface; (3) Transbond XT, grit-blasted enamel surface; (4) Panavia-21, grit-blasted enamel surface; (5) Transbond XT, acid-etched enamel surface with grit-blasted brackets; (6) Panavia-21, acid-etched enamel surface with grit-blasted brackets. All groups had stainless steel brackets bonded to the buccal surface of each tooth. An Instron universal testing machine was used to determine the shear bond strengths at a crosshead speed of 0.5 mm/second. Statistical analysis was undertaken using analysis of variance and the Tukey test. The mean bond strength values were as follows: group 1, 135.7 +/- 23.0 N; group 2, 181.5 +/- 18.4 N; group 3, 38.4 +/- 27.5 N; group 4, 59.1 +/- 24.1 N; group 5, 106.7 +/- 21.5 N; group 6, 165.3 +/- 21.4 N. Panavia-21 with the acid-etched enamel surface had a significantly higher shear bond strength than the other groups (P < 0.001). This was followed by the composite group with the acid-etched enamel surface. This group differed significantly from the composite and Panavia-21 groups with the grit-blasted tooth surface (P < 0.001) and from the composite and Panavia-21 groups with the acid-etched enamel surface and grit-blasted brackets (P < 0.01). The current findings indicate that Panavia-21 is an excellent adhesive and produces a bond strength that is clinically useful. Enamel surface preparation using grit blasting alone results in a significantly lower bond strength and should not be advocated for clinical use.

Uvulo-glosso-pharyngeal dimensions in subjects with beta-thalassaemia major.

The purpose of this study was to investigate cephalometrically the uvulo-glosso-pharyngeal dimensions in subjects with beta-thalassaemia major. The subjects were 15 thalassaemic patients (eight males, seven females) with a mean age of 14.13 +/- 1.06 years. The variables measured on the lateral cephalograms were tongue height and length, soft palate length and thickness, superior, middle and inferior pharyngeal airway space, and hyoid bone position. The thalassaemic group was compared with a normal control group matched for sex and age using a t-test. The results showed that thalassaemic patients had a smaller tongue size (length P < 0.05, height P < 0.001), shorter soft palate (P < 0.001), smaller upper (P < 0.001) and middle (P < 0.05) pharyngeal airway spaces, and a shorter vertical pharyngeal length (P < 0.05). The hyoid bone in thalassaemic patients was closer to the mandibular plane (P < 0.001).