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The present systematic review was done to assess the available literatures on changes in the number of occlusal contacts (NOC), occlusal contact surface areas, and occlusal force distribution (OFD) with vacuumformed retainers (VFRs) or clear overlay retainers during retention and to compare them with other retainers. Six electronic databases (Web of Science, Scopus, PubMed, Cochrane Library, Lilacs, and Google Scholar) were searched. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) reporting on occlusal contact changes with VFRs were included. A total of nine articles were included in this review: three RCTs, five prospective controlled trials (PCTs), and one CCT. The Cochrane risk of bias tool and ROBINS-I tool were used for risk of bias assessment. The three RCTs showed moderate risk of bias, and out of five CCTs, four showed low risk of bias, and one showed moderate risk of bias. One CCT showed a low risk of bias in the ROBINS-I tool. Two out of four studies reported improved occlusal surface area (OSA) with VFRs when assessed at the end of six months and 12 months; one out of four studies reported improved NOC; and one study reported a decrease in OFD anteriorly and an increase in OFD posteriorly after two months of retention. On comparison between the groups, the other retainer groups showed more NOCs compared to VFRs. The limited available evidence suggests an increase in OSA and no change in NOCs and OFD with VFRs during retention. No significant differences between VFRs and other retainers for OSA and OFD were noted, and more NOCs were noted for other retainer groups.
The present systematic review was done to assess the available literatures on changes in the number of occlusal contacts (NOC), occlusal contact surface areas, and occlusal force distribution (OFD) with vacuumformed retainers (VFRs) or clear overlay retainers during retention and to compare them with other retainers. Six electronic databases (Web of Science, Scopus, PubMed, Cochrane Library, Lilacs, and Google Scholar) were searched. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) reporting on occlusal contact changes with VFRs were included. A total of nine articles were included in this review: three RCTs, five prospective controlled trials (PCTs), and one CCT. The Cochrane risk of bias tool and ROBINS-I tool were used for risk of bias assessment. The three RCTs showed moderate risk of bias, and out of five CCTs, four showed low risk of bias, and one showed moderate risk of bias. One CCT showed a low risk of bias in the ROBINS-I tool. Two out of four studies reported improved occlusal surface area (OSA) with VFRs when assessed at the end of six months and 12 months; one out of four studies reported improved NOC; and one study reported a decrease in OFD anteriorly and an increase in OFD posteriorly after two months of retention. On comparison between the groups, the other retainer groups showed more NOCs compared to VFRs. The limited available evidence suggests an increase in OSA and no change in NOCs and OFD with VFRs during retention. No significant differences between VFRs and other retainers for OSA and OFD were noted, and more NOCs were noted for other retainer groups.
Purpose Aim of the present study was to assess the relative distribution of occlusal forces after orthodontic treatment and during the first 3 months of the retention phase using a computerized occlusal analysis system (T-Scan, Tekscan Inc., Norwood, MA, USA). Materials and methods A total of 52 patients were included in this prospective cohort study and underwent analysis of occlusal forces on the level of tooth, jaw-half, and -quadrant during a 3-month period. Furthermore, differences between three retention protocols (group I: removable appliances in both jaws; group II: fixed 3–3 lingual retainers in both jaws; group III: removable appliance in the maxilla and fixed 3–3 lingual retainer in mandible) were assessed with Wilcoxon signed-rank tests at 5%. Results Directly after debonding, measured forces distribution were similar to published references for untreated samples. In the following, no significant difference was found between retention protocols II and III with regard to the asymmetry of the anterior occlusal forces. Both groups maintained an asymmetric force distribution in the anterior segment during the study period. There was also no difference between groups II and III in the distribution of occlusal forces for the posterior segments. Both retention concepts kept the symmetrical distribution of occlusal forces stable over the observation period. The retention concept of group I demonstrated a symmetrical distribution of occlusal forces in the anterior segment after debonding and this remained stable during the 3‑month period. In the posterior segment, no improvement of the initially asymmetric masticatory force distribution could be observed. Conclusions All three studied retention protocols showed stability in retaining their original symmetrical or asymmetrical occlusal force distribution posteriorly/anteriorly during the 3‑month observation period. Therefore, an even distribution of occlusal forces should be the aim of the finishing phase, as no relative benefit of any single retention scheme in terms of post-debond improvement during the retention phase was seen.
Aims: The aim of this in vitro study was to evaluate the color changes in the retainers by different manufacturers (Essix ACE, Forestadent, Leone, and Bioart) after exposure to various beverage solutions (coke, tea, coffee, and artificial saliva) and also to assess the stain removal potential of different cleansing agents [listerine (L) and retainer brite (RB)]. Materials and Methods: A total of 320 specimens (80 samples in each group) of thermoformed retainers from four different manufacturers were tested. All retainers were thermoformed and were immersed in different beverages (black tea, coffee, and cola) and artificial saliva as a control group for 7 and 14 days. These were then cleaned by either L or RB crystals. The color changes (ΔE) in several retainers were assessed following a 7-day exposure (T1–T0), a 14-day exposure (T2–T0), and following cleaning (T3–T1 and T3–T2). The CIELAB color space approach was utilized to obtain the ΔE measurements. To statistically evaluate the data, t test, analysis of variance, Tukey’s range test, and Levene’s test were employed. Results: On intragroup comparison, all groups were stained by tea with significant differences at 7 and 14 days (P < 0.05). Significant differences in color change after cleaning by L at the 7-day interval (P < 0.05) were noted in group A for immersion in cola. No significant difference was noted for groups B and C (P > 0.05). Significant differences in color change after cleaning with RB for tea stains in group D (P < 0.05) were noted. Significant intergroup differences in staining were noted for tea at 7- and 14-day intervals (P < 0.05) with maximum staining in group D. For coffee, significant intergroup differences were noted with maximum staining in group A (P < 0.05) at both 7- and 14-day intervals. Significant intergroup differences in cleaning were noted at the 12- h interval in group A for tea stains by RB (P < 0.05) and cola stains by L (P < 0.05). Conclusions: Tea exhibited the greatest staining potential among all staining agents at 7-and 14-day intervals for Forestadent, Leone, and Bioart retainers, while coffee stained Essix ACE retainers the most. Among the four different retainer brands, Bioart exhibited the least staining with the various staining agents at 7- and 14-day intervals. RB eliminated tea stains better, whereas cola and coffee stains were better removed by L.
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