Tip, torque and rotation of maxillary molars during distalization using Invisalign: a CBCT study.

BACKGROUND: Desirable molar distalization by bodily movement is challenging and can be difficult to achieve. This study investigated changes in molar angulation (mesiodistal tipping), molar inclination (buccolingual torque) and rotation during distalization using clear aligner therapy (CAT). MATERIALS AND METHODS: This retrospective study included 38 cone beam computed tomographic images (CBCTs) taken for patients treated with molar distalization using CAT. The study evaluated pre- (T0) and post-treatment (T1) CBCTs of 19 adult patients (36.68 ± 13.50 years) who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization. Changes in maxillary molar tip, torque and rotation were measured for 61 molars (183 roots). Paired t-test was used to evaluate the differences between pre- and post-treatment readings. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC). RESULTS: Molar angulation did not show significant change after distalization (p = 0.158) however, there was significant increase in buccal molar inclination (p = 0.034) and mesiobuccal molar rotation (p < 0.001). CONCLUSION: Molar distalization of 2 mm did not cause significant molar tipping. Maxillary molars showed significant buccal inclination (increased torque) and mesiobuccal rotation after distalization.

Does maxillary sinus proximity affect molar root resorption during distalization using Invisalign? a CBCT study.

BACKGROUND: This study aimed to assess the correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption during molar distalization using clear aligner therapy (CAT). MATERIALS AND METHODS: Thirty-eight cone beam computed tomography scans (CBCTs) obtained pre- (T0) and post-treatment (T1) from 19 adult patients (36.68 ± 13.50 years), who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization, were evaluated in this study At least 22 h of aligner wear per day was a main inclusion criterion. Sinus proximity and changes in root lengths were measured for 61 molars (183 roots). Spearman coefficient analysis was used for assessing correlation between sinus proximity and root resorption. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by intraclass correlation coefficient (ICC). RESULTS: Spearman coefficient revealed no significant correlation between sinus proximity and molar root resorption for mesiobuccal, distobuccal or palatal roots (p = 0.558, p = 0.334, p = 0.931, respectively). CONCLUSION: There was no correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption.

Shear bond strength of metallic brackets bonded to enamel pretreated with CPP-ACP: a systematic review and meta-analysis of in vitro studies.

BACKGROUND: Development of white spot lesions (WSLs) is common among orthodontic patients. Several measures have been introduced to prevent and remineralize the lesions. Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is used for both prevention and remineralization. The effect of its application before bonding is controversial. This systematic review was conducted to investigate the most up to date available literature regarding the effect of CPP-ACP enamel pre-treatment on shear bond strength (SBS) of metallic orthodontic brackets. METHODS: A search was conducted in electronic databases (MEDLINE (via PubMed), Scopus, Cochrane Library, Web of Science and Google scholar (grey literature)) up to March 29th, 2023. The inclusion criteria included in vitro studies comparing the SBS of metal orthodontic brackets following pre-treatment of enamel using CPP-ACP versus control. The exclusion criteria included study types other than in vitro studies, studies conducted on non-human enamel, or studies using CPP-ACP in combination with another intervention. The included studies were analysed by two reviewers, independently. The risk of bias assessment was done using a modified risk of bias tool. A Meta-analysis was performed. I2 values and Q-test were used for assessment of heterogeneity. Results were displayed in forest plots with a random-effects model. Standardized mean difference, standard error (SE) and 95% confidence intervals were calculated for all studies. RESULTS: The search resulted in 76 articles. After duplicate removal and assessment for eligibility, 15 studies were included in the review. High statistical heterogeneity was found among the included studies using I2 values and Q-Test (I2 = 95.147%; Q = 288.456; df = 14; P < 0.001). The overall effect of CPP-ACP pre-treatment on the SBS of metal orthodontic brackets was not significant (Mean difference = 1.163 MPa, SE = 0.757, 95% CI = -0.321, 2.648, p value = 0.125). The use of CPP-ACP for prevention of WSLs did not significantly affect the SBS of brackets (Standardized mean difference = 1.009, SE = 0.884, 95% CI = -0.723, 2.740, p value = 0.254). No significant change was found when CPP-ACP was used for remineralization of WSLs (Standardized mean difference = 1.501, SE = 1.087, 95% CI = -0.630, 3.632, p value = 0.167). CONCLUSIONS: Within the limitations of the study, the evidence suggests that the use of CPP-ACP for either prevention or remineralization of WSLs before bonding does not affect the SBS of metal orthodontic brackets.

Dimensional changes of upper airway after slow vs rapid miniscrew-supported maxillary expansion in adolescents: a cone-beam computed tomography study.

BACKGROUND: To date, the effects of different activation rates of miniscrew-supported expanders on the airway have not been compared. Hence, the purpose of this retrospective study was to evaluate and compare the effects of slow and rapid miniscrew-supported maxillary expansion on the upper airway dimensions using cone-beam computed tomography (CBCT). METHODS: Data of 20 patients (Age 12 to 16 years old) treated using miniscrew-supported expanders at the Faculty of Dentistry, Alexandria University was collected. The patients were equally divided into two groups according to the activation protocol; slow maxillary expansion (SME): activation once every other day, and rapid maxillary expansion (RME): activation twice daily. CBCT scans obtained pre-expansion and 5 months post-expansion were used to evaluate the changes in the upper airway dimensions. Comparisons between the two time points within each group were done using paired samples t-test. SME and RME groups were compared using independent samples t-test. Significance level was set at p < 0.05. RESULTS: Both groups showed a significant increase in anterior, middle, and posterior nasal cavity width. SME resulted in significantly greater increase of the anterior nasal cavity width than RME (Mean difference between the groups, 2.64 mm; 95% CI, 0.83, 4.45; p = 0.007). The dimensions of the retropalatal and retroglossal airways did not change significantly in either group. Both groups resulted in a significant increase of maxillary width, palatal width, and inter-molar width. RME showed a significantly larger increase of inter-molar width than SME (Mean difference between the groups, - 2.44 mm; 95% CI, - 3.88, - 1.00; p = 0.002). CONCLUSIONS: The use of either a slow or rapid activation protocol is effective in expanding the nasomaxillary complex, with greater expansion achieved in the anterior section of the nasal cavity using the slow rate. However, the expander design employed in the current study does not affect the dimensions of the retropalatal or retroglossal airways.

Shear bond strength of metallic brackets bonded to enamel pretreated with Er,Cr:YSGG LASER and CPP-ACP.

BACKGROUND: Increased risk of enamel demineralization during and after orthodontic treatment raises the demand for better preventive measures including combinations of laser, CPP-ACP, and fluoride. The combination of Er,Cr:YSGG laser with CPP-ACP was proved to have a synergetic effect compared to each of them alone. Shear bond strength (SBS) of orthodontic brackets bonded to the enamel surface after being treated with preventive measures is critical. The aim of this study was to compare the SBS and failure mode of metallic brackets bonded to teeth with no pretreatment and pretreated enamel surface, either with Er,Cr:YSGG laser alone or combined with CPP-ACP. METHODS: Sixty sound extracted human premolar teeth were allocated randomly to 3 groups: In Group 1 (control), teeth were etched and bonded directly; in Group 2, laser pretreatment of the enamel surface was done followed by etching and bonding as in the control group; in Group 3, the enamel surface was lased then CPP-ACP was applied according to the manufacturer instructions, etched and bonded. SBS and Adhesive remnant index (ARI) were evaluated. RESULTS: No significant differences were found between the 3 groups neither in the SBS nor in the ARI scores. CONCLUSIONS: The use of combined Er,Cr:YSGG laser with CPP-ACP as a preventive measure before bonding orthodontic brackets does not endanger the bracket's bonding strength.