METHODS: Sixteen New Zealand white rabbits, 20 to 24 weeks old, were randomly divided into 4 experimental groups. Modified hyrax expanders were placed across their interfrontal sutures and secured with miniscrew implants located bilaterally in the frontal bone. The hyrax appliances were activated as follows: group 1 (control), 0.5-mm per day expansion for 12 days; group 2, 1-mm instant expansion followed by 0.5 mm per day for 10 days; group 3, 2.5-mm instant expansion followed by 0.5 mm per day for 7 days, and group 4, 4-mm instant expansion followed by 0.5 mm per day for 4 days. After 6 weeks of retention, sutural separation and sutural bone modeling were assessed by microcomputed tomography and quantified. Statistical analysis was performed using Kruskal Wallis and Mann-Whitney U tests and the Spearman rho correlation (P <0.05).
RESULTS: Median amounts of sutural separation ranged from 2.84 to 4.41 mm for groups 1 and 4, respectively. Median bone volume fraction ranged from 59.96% to 69.15% for groups 4 and 3, respectively. A significant correlation (r = 0.970; P <0.01) was observed between the amounts of instant expansion and sutural separation.
CONCLUSIONS: Pending histologic verifications, our findings suggest that the protocol involving 2.5 mm of instant expansion followed by 0.5 mm per day for 7 days is optimal for accelerated sutural expansion. When 4 mm of instant expansion was used, the sutural bone volume fraction was decreased.
Study design: The research was designed as a crossover, randomized control trial.
Materials and methods: Subjects comprised patients receiving fixed appliances at a teaching institution and indicated for VFRs. Post-treatment stone models were scanned with a structured-light scanner. A fused deposition modelling machine was used to construct acrylonitrile-butadiene-styrene (ABS)-based replicas from the 3D scanned images. VFRs were fabricated on the original stone and printed models. Analysis comprised independent t-tests and repeated measures analysis of variance.
Randomization: Subjects were allocated to two groups using Latin squares methods and simple randomization. A week after debond, subjects received either VFR-CV first (group A) or VFR-3D first (group B) for 3 months, then the interventions were crossed over for another 3 months.
Blinding: In this single-blinded study, subjects were assigned a blinding code for data entry; data were analysed by a third party.
Outcome measures: The primary outcome measured was oral health-related quality of life (OHRQoL) based on Oral Health Impact Profile-14 (OHIP-14). Secondary outcome was post-treatment stability measured using Little's Irregularity Index (LII).
Results: A total of 30 subjects (15 in each group) were recruited but 3 dropped out. Analysis included 13 subjects from group A and 14 subjects from group B. Group A showed an increase in LII (P < 0.05) after wearing VFR-CV and VFR-3D, whereas group B had no significant increase in LII after wearing both VFRs. Both groups reported significant improvement in OHRQoL after the first intervention but no significant differences after the second intervention. LII changes and OHIP-14 scores at T2 and T3 between groups, and overall between the retainers were not significantly different. No harm was reported during the study.
Conclusion: VFRs made on ABS-based 3D printed models showed no differences in terms of patients' OHRQoL and stability compared with conventionally made retainers.
Registration: NCT02866617 (ClinicalTrials.gov).
Materials and Methods: A randomized-controlled split-mouth study was conducted to compare the retention and the caries preventive effect of light-cured resin-based sealant (3M ESPE) and glass ionomer sealant (Fuji VII). The sealants were applied to either the right or the left lower mandibular molars (7-9 yrs of age) in 120 school children, based on the randomization process. They were recalled for assessment of clinical retention at intervals of 3, 6, and 12 months. The caries-preventive effect between the two materials was tested statistically by the McNemar's test for matched pairs, and the differences observed with regard to the retention of the materials was tested by Chi-square tests. The level of significance was set to be at P < 0.05.
Results: At the end of 12th month, sealant retention is found to be higher in the resin-based sealant group compared to the glass ionomer group. In the glass ionomer sealants placed, 101 (91%) were caries-free and 10 (9%) had caries. In the resin-based sealant, 105 (94.60%) had sound teeth and 6 (5.4%) had dental caries (P = 0.34).
Conclusion: The glass ionomer sealant was less retentive when compared to resin sealants. The caries incidence between the glass ionomer and resin-based sealants was not statistically significant.