Light-curing process for clear aligners' attachment reproduction: comparison between two nanocomposites cured by the auxiliary of a new tool

A comparative in vitro study of different composite materials in terms of aligner attachment accuracy and surface roughness using different curing irradiances

BACKGROUND

To evaluate 4 different composite resins in terms of aligner attachment accuracy and surface roughness.

MATERIAL AND METHODS

160 premolars were divided into 4 groups (n=40): Group 1: GC Aligner Connect™; 2: GC Ortho Connect™; 3: 3M ESPE Filtek™ Z350 XT flowable; 4: 3M ESPE Filtek™ Z350 XT Universal. Each group was divided into 2 equal subgroups regarding curing irradiances (Power of 1000 mW/cm2 in subgroup A for 10s, and 3200 mW/cm2in B for 3s, VALO™ Cordless-LED Curing Light). The primary objective was to compare the realized attachments with those of the virtual with 3D Geomagic software. A contact surface profiler was used for roughness measurement (Ra) as the secondary aim. The data were analysed using the IBM SPSS 25.0. The significance level was set at p<0.05.

RESULTS

In subgroup A, the mean "excess" accuracy measurement of the 3M ESPE Filtek ™Z350 XT flowable resin was found to be higher than others. In subgroup B, the "excess" accuracy measurements of the 3M ESPE Filtek™Z350 XT flowable (0.24±0.07mm) and Universal (0.26±0.05mm) resins were significantly higher than those of the GC Aligner Connect™ resin (0.17±0.06mm), (p<0.05). According to the Ra measurements in subgroup A, the measurement of the GC Aligner Connect™ (1.75±1.09μm), GC Ortho Connect™ (0.99±1.04μm) and 3M ESPE Filtek™ Z350 XT flowable (1.33±1.16μm) resins were found to be higher than of the Universal resin (0.07±0.11μm), (p<0.05). In subgroup B, the Ra measurement of the GC Aligner Connect™ (1.74±1.81μm) was found to be higher than that of the 3M ESPE Filtek™ Z350 XT flowable (0.11±0.18μm) resin (p=0.010). Ra measurement observed for the 10-second curing factor for the 3M ESPE Filtek™ Z350 XT Flowable resin group was found to be significantly higher than for the 3-second curing factor (p<0.001).

CONCLUSION

In terms of "excess" value of accuracy, 3M ESPE Filtek™ Z350 XT flowable composite resin showed a higher value. The lowest surface roughness was observed for Universal restorative resin considering low power irradiation, while was observed for 3M ESPE Filtek™ Z350 XT flowable resin considering high power irradiation.

Wear resistance of orthodontic attachments: a comparative analysis of different composite resins in clear aligner therapy

OBJECTIVE

Clear aligner attachments play a crucial role in facilitating tooth movement in clear aligner treatments. This in-vitro study evaluates the wear of attachments made from 4 different composite resins during orthodontic therapy.

MATERIALS AND METHODS

The study included 32 extracted human premolar and molar teeth, divided into four groups based on the composite resin used: Flow Tain, Transbond XT, G-aenial Universal Flo, and Filtek Z350 XT. Horizontal rectangular attachments were bonded to the teeth, which underwent thermal cycling and tooth brushing to mimic clinical conditions. Micro-CT analysis measured volumetric and linear changes in attachment wear. Statistical analyses were conducted using the Wilcoxon Signed-Rank Test and Kruskal-Wallis test, followed by pairwise comparisons with the Mann-Whitney U Test.

RESULTS

All composite resins exhibited a significant decrease in attachment volume after aging. The greatest volume reduction was observed in the Transbond XT group, while the least reduction occurred in the G-aenial Universal Flo group. Significant differences were found in the occlusal and gingival thirds of the attachments, with Flow Tain showing the highest wear in all regions.

CONCLUSION

The study shows that the wear of orthodontic attachments is greatly influenced by the type of composite resin used. The results indicate that G-aenial Universal Flo composite resin may offer superior wear resistance, preserving attachment integrity more efficiently throughout orthodontic treatment than the other 3 composite resins.

CLINICAL RELEVANCE

The findings can assist clinicians in choosing composite materials that improve treatment effectiveness by preserving attachment integrity over time.

Accuracy Evaluation of Indirect Bonding Techniques for Clear Aligner Attachments Using 3D-Printed Models: An In Silico and Physical Model-Based Study

An inaccurate bonding procedure of the attachments related to clear aligner systems could influence the predictability of tooth movement The aim of this study was to compare the positioning reliability of horizontal and vertical orthodontic clear aligner attachments.

MATERIALS AND METHODS

A total of 70 horizontal and 70 vertical orthodontic clear aligner attachments were bonded to five upper and five lower experimental anatomically based acrylic resin models with 14 clinical crowns each. The experimental anatomically based acrylic resin models were randomly distributed to the following study groups: Group A-horizontal orthodontic clear aligner attachments (n = 70) (HORIZONTAL) and Group B-vertical orthodontic clear aligner attachments (n = 70) (VERTICAL). Afterward, the orthodontic clear aligner attachments were digitally planned using orthodontic planning software, and orthodontic templates were manufactured by thermoforming on 3D-printed models in trilayer glycol-modified polyethylene terephthalate. Both horizontal and vertical orthodontic clear aligner attachments were put through an intra-oral scan to obtain a postoperative digital image, and PAPver, PCPver, PMVver, AUver, Alver, PPMhor, PPDhor, PMVhor, AMhor and ADhor cephalometric parameters were analyzed using a t-test or a non-parametric Mann-Whitney-Wilcoxon test.

RESULTS

The results showed that all cephalometric parameters showed statistically significant differences (p < 0.05) between the accuracy of the indirect bonding technique for horizontal and vertical orthodontic clear aligner attachments, except for the PAPver (p = 0.6079) and PMVhor (p = 0.5001) cephalometric parameters.

CONCLUSIONS

The vertical orthodontic clear aligner attachments are more accurate than the horizontal orthodontic clear aligner attachments through the indirect bonding technique.

Esthetic comparison of two composites used for Invisalign's attachments bonding

Background

Esthetics is a factor of great importance for most patients undergoing treatment with Invisalign® aligners. When choosing a resin composite for the bonding of attachments required for the treatment, ideal characteristics such as low visibility and stain resistance of the material are essential to increase the overall perceived esthetics of the treatment. The objective of this article was to evaluate the esthetics of two resin composites used for attachment reproduction: the Transbond XT® from 3M® and the Tetric EvoCeram® from Ivoclar Vivadent®.

Material and Methods

An analytic, observational, longitudinal, and prospective study was done. Attachments were bonded on 51 patients, and a dental survey about esthetics was given 3 months after the bonding of attachments. The Student's t-test and 1-factor ANOVA tests were used, when the variables were normal, and the nonparametric alternative of the tests was used when they were not distributed normally.

Results

The results indicate that there are no statistically significant differences (p>.05) in the esthetic perception of attachments according to the type of composite used.

Conclusions

Even if some differences are observed between the resins, both Transbond XT® and Tetric EvoCeram® can be considered for attachments bonding from an esthetical point of view. Key words:Clear aligner therapy/Dental bonding/Orthodontic appliance/Dental Esthetics.

Surface wear and adhesive failure of resin attachments used in clear aligner orthodontic treatment

PURPOSE

This study evaluated adhesive and cohesive failures and the surface wear of attachments employed in clear aligner treatment (CAT) using three-dimensional (3D) superimposition.

METHODS

In all, 3D models of 150 teeth were obtained from intraoral scans from patients undergoing CAT with at least 4 months between each scan. Of the initial sample, 25 teeth were discarded, and 125 teeth were included in the study. Superimpositions of each individual tooth at the first and second time points were made using computer-aided design (CAD) software (Meshmixer; Autodesk, Mill Valley, CA, USA). Analyses were performed to compare surface wear and failures related to type of attachment (optimized/conventional), dental group (molars/premolars/anterior teeth), and arch (mandibular/maxillary). Mann-Whitney and Kruskal-Wallis statistical tests were applied with significance set at 5%.

RESULTS

More surface wear was observed in conventional attachments, mandibular and anterior teeth with statistical significance for surface wear on the distal surface of conventional attachments (p < 0.05). Cohesive failure was observed in 10% of attachments, occurring most frequently on optimized attachments and molar teeth. Adhesive failure was observed in 10% of the samples, more frequently on conventional attachments and posterior teeth.

CONCLUSION

Attachment type (conventional vs. optimized) was significantly correlated with surface wear on the distal surface of the attachment. Arch (mandibular or maxillary) and group of teeth (anterior or posterior) showed no correlation with surface wear. Failure, both adhesive and cohesive, correlated with attachment type and group of teeth, but not with the arch in which they were located.

Friction and wear behavior of a mechanical oscillating strip system used for interproximal enamel reduction: a quantitative and qualitative scanning electronic microscope evaluation

OBJECTIVES

To evaluate wear and friction properties of oscillating strips in order to validate the importance of a standardized interproximal enamel reduction (IPR) sequence to preserve their efficiency and lifetime.

MATERIALS AND METHODS

Fifteen complete oscillating IPR sequences were tested by means of tribological tests (Linear Reciprocating Tribometer, C.S.M. Instruments, Peseaux, Switzerland). Fifteen single 0.2-mm metallic strips underwent a long continuous cycle of 240 minutes. Strip surface roughness and waviness measurements were assessed by means of a contact probe surface profiler (TalySurf CLI 2000; Taylor Hobson, Leicester, UK) and TayMap software. Statistical analysis was performed with independent-samples t-test. Significance was at the P < .05 level. Scanning electronic microscopy analysis of strip surfaces was conducted with an FEI Quanta 200 (Hillsboro, Ore) in high vacuum at 30.00 kV.

RESULTS

Resin strips revealed a significant reduction in surface roughness (Ra, Rt, RDq) and a significant increase in waviness parameters (Wa, Wt). Rt and RDq values significantly decreased upon use of the metallic strips. Significantly higher values of Wa (+ 2.84 µm) and Wt (+0.1 µm) were observed only for the 0.2-mm metallic strips. Higher friction values were observed when the metallic strips were tested singularly rather than within the entire sequence. Lower Ra and Rt values were revealed when 0.2-mm metallic strips were tested up to 240 minutes.

CONCLUSIONS

The application of a standardized oscillating sequence allows for more efficient wear performance of the strips with a significant impact on their abrasive power and lifetime.