Effect of carbamide peroxide on biomechanical properties of vacuum-formed retainers: A split-mouth randomized controlled trial.

OBJECTIVE: To investigate the effect of tooth whitening on biomechanical properties of vacuum-formed retainers (VFRs). METHODS: Using a split-mouth, randomised controlled trial design, thirty participants were randomly allocated to receive whitening on either the upper or the lower arch, using 10 % carbamide peroxide for two weeks. Biomechanical properties such as hardness, tensile strength, and surface roughness were assessed two weeks after whitening was completed. RESULTS: Tensile strength of the whitening arch (mean ± SD: 40.93 ± 3.96 MPa) was significantly lower than that of the control (47.40 ± 5.03 MPa) (difference 6.47 MPa, 95 % CI 4.51 - 8.42, p < 0.001). Hardness and internal roughness of the whitening arch (VHN = 14.63 ± 2.29 N/mm2 and Ra = 1.33 ± 0.35 µm, respectively) were significantly greater than those of the control (12.22 ± 1.86 N/mm2 and 0.96 ± 0.29 µm, respectively) (differences 2.41 N/mm2, 95 % CI 1.56 - 3.25, p < 0.001 and 0.37 µm, 95 % CI 0.23 - 0.51, p < 0.001, respectively). The whitening arch showed greater tooth colour change (ΔE = 6.00 ± 3.32) than the control (ΔE = 2.50 ± 1.70) (difference = 3.50, 95 % CI 2.43 - 4.56, p < 0.001). CONCLUSIONS: Based on this short-term study, marked tooth colour change was achieved by whitening with VFRs as the whitening trays, but this changed the VFRs' biomechanical properties, including a decrease in tensile strength and an increase in hardness and internal roughness. CLINICAL SIGNIFICANCE: The application of carbamide peroxide in VFRs may compromise their mechanical properties.

An orthodontic tooth brushing technique to enhance oral hygiene in patients wearing fixed orthodontic appliances: A randomized controlled trial.

BACKGROUND: An effective tooth brushing technique is essential in maintaining oral hygiene, especially for patients wearing fixed orthodontic appliances. Traditional tooth brushing techniques are mainly designed for the general population without orthodontic appliances, which may not account for the oral condition of orthodontic patients due to the increased biofilm formation. The aim of this study was to design an orthodontic tooth brushing technique and compare its effectiveness with the traditional modified Bass technique. METHODS: Sixty patients wearing fixed orthodontic appliances were included in this two-arm paralleling randomized controlled trial. Thirty patients were assigned to the modified Bass technique group and 30 patients were assigned to the orthodontic tooth brushing technique group. The orthodontic tooth brushing technique involved a biting motion on the head of toothbrush in order to place the toothbrush bristles behind the archwires and around the brackets. Plaque index (PI) and gingival index (GI) were used to assess oral hygiene. Outcome measurements were taken at baseline and 1 month after the intervention. RESULTS: The new orthodontic tooth brushing technique significantly reduced PI (average PI reduction = 0.42 ± 0.13), especially in the gingival (0.53 ± 0.15) and interproximal (0.52 ± 0.18) areas (p < 0.05 for all). No significant reduction was found for the GI (p > 0.05 for all). CONCLUSION: The new orthodontic tooth brushing technique showed a promising result in reducing PI in patients wearing fixed orthodontic appliances.

Prevalence of halitosis among young adults in Dunedin, New Zealand.

OBJECTIVES: To investigate the prevalence of halitosis in young adults. METHODS: Young adults (n = 372; mean age = 21.0 ± 2.6 years old, range = 18-30 years) in Dunedin, New Zealand, were recruited into the cross sectional study after providing informed consent. The prevalence of halitosis was determined using both objective measurements (parts per billion [ppb] volatile sulphur compounds [VSCs] in the exhaled air) and subjective measurements (self-reported halitosis questionnaire, tongue coating index, and organoleptic assessment). RESULTS: Volatile sulphur compounds measurements indicated that the prevalence of halitosis (values ≥140 ppb) was 31.2%; 25.6% of participants self-reported halitosis. The organoleptic assessment revealed that 14.3% of the participants had a score of ≥2. A positive correlation was found between the VSC measurements and organoleptic assessment (p < 0.05). No significant relationship was found between self-reported halitosis and either organoleptic assessment or VSC measurements. Self-reported dry mouth, smoking, oral hygiene index, DMFT index, and tongue coating score were significantly associated with the organoleptic assessment (p < 0.05). The self-reported dry mouth, mouth breathing and tongue coating score were significantly associated with the VSC scores (p < 0.05). CONCLUSION: Halitosis, as represented by VSC, was found in 31.2% of the participants. VSC scores and organoleptic assessment were positively correlated. There was no significant relationship between self-reported halitosis and either organoleptic assessment or VSC measurements.

Survival analysis of orthodontic retainers.

Objective: Retainers play a critical role in the long-term success of orthodontic treatment. The aims of this study were to evaluate the survival time of different retainers and to investigate the potential predictors of the retainer failures. Material and methods: A total of 591 retainers from 309 patients (between 2003 and 2014) were included in the study, including Hawley retainers (n = 199), vacuum-formed retainers (n = 34), lingual fixed retainers (n = 278), and the COMBO (a combination of two different retainers in the same arch; n = 80). Patient's demographics, retention procedures, time to failure (survival time), and reasons for failures were extracted from patient files. Failure of retainer was defined as any events after which the retainers needed to be replaced or repaired; loss of retainer was treated as a failure because the retainer could not fulfil its role. Survival analyses were performed to compare the survival time between different retainer groups. Results: The survival time was the longest for lingual fixed retainers (median 1604 days) and Hawley retainers (1529 days), followed by COMBO (258 days) and vacuum-formed retainers (105 days; overall P < 0.001). No statistical significance of survival time of lingual fixed retainers was found between maxilla (1497 days) and mandible (1604 days; P = 0.341), nor between different types of the COMBO (overall P = 0.078). These results were unchanged before and after adjusting for the age, gender, and socioeconomic status (SES) of the patients. The reasons for failures varied among different retainers: most failures of the Hawley retainers were 'lost' (52.0%), most failures of the lingual fixed retainers were debond (63.5%), and fracture was the most common cause of failure for both vacuum-formed retainers (43.5%) and the COMBO (41.9%). Conclusion: Lingual fixed retainers and Hawley retainers had the longest survival times, followed by the COMBO retainers and vacuum-formed retainers. The reasons of failure were mainly mechanical (debond and fracture) and patient-related (loss).