Assessment of preparation time and 1-year Invisalign aligner attachment survival using flowable and packable composites

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.

Innovative use of the snowplow technique in orthodontics: Evaluation of its effect on the accuracy and manipulation time in clear aligner attachment reproduction

OBJECTIVE

In this study, we evaluated the effectiveness of the snowplow technique, commonly used in restorative dentistry, in clear aligner therapy, focusing on manipulation time and the accuracy of attachment-shape transfer from the 3D-designed model (i.e., attachment-reproduction accuracy).

METHODS

Rectangular, ellipsoidal, and customized attachments were placed on the first premolar teeth, and different attachment-reproduction methods were evaluated. The study groups included high-viscosity (HV) and low-viscosity (LV) composites, as well as two variations of the snowplow techniques (S1 and S2). The manipulation time was recorded, and a highly detailed 3D comparison methodology (sigma, arithmetic mean, and deviation label) was used to assess attachment-reproduction accuracy.

RESULTS

Manipulation time differed significantly across all groups, with the LV group exhibiting the shortest time, followed by the S1 group (p < .001). For surface deviation, the S1 group demonstrated the lowest sigma values, particularly for rectangular attachment designs (p < .001).

CONCLUSIONS

Using the LV composite allowed the shortest application time, while the S1 technique required less manipulation time than did the HV composite. The S1 technique also achieved superior attachment accuracy, making it an effective technique for reproducing attachments with intricate surface details.

CLINICAL SIGNIFICANCE

The improved accuracy facilitated by the S1 technique may positively influence clinical outcomes by enhancing successful execution of planned tooth movements, thereby potentially improving the overall efficacy of clear aligner therapy.

Wear volumes of flowable and sculptable resin composite attachments and their correlation with retentive force of clear aligners: a laboratory study

BACKGROUND

Aligner attachment integrity is important for clear aligner retention and overall treatment efficacy. This study aimed to evaluate the wear volume of clear aligner attachments and the retentive force change of clear aligners over a simulated 24-week insertion/removal period, along with their correlation.

METHODS

Attachments made from Tetric N-Flow (flowable), Beautifil Injectable X (flowable), or Filtek™ Z350 XT (sculptable) resin composites (n = 6 each) were bonded to the first premolars of maxillary dental resin models. Each model underwent a simulated 3-cycle daily insertion and removal of 12 clear aligners, with each aligner tested for 14 days, using a universal testing machine. Attachment wear volume was quantified through 3D scanning and superimposition. Average daily retentive force of aligners was measured. Data were analyzed using mixed-design ANOVA to evaluate differences in retentive force and wear volume among composites, and Pearson's correlation to assess the relationship between wear and retentive force change. Statistical significance was set at p < 0.05.

RESULTS

Significant attachment wear was observed primarily in gingival regions, without significant differences in wear volume among the three composites. Retentive force decreased significantly from days 1 to 2 and continued to decline until day 14 (p < 0.01), without significant differences in retentive force among aligners nor composite types. No significant correlation was found between attachment wear volume and the retentive force difference between the 1st and 12th aligners.

CONCLUSIONS

Despite reductions in attachment volume across all three composites over the 24-week period, no significant change in mean retentive force among aligners was observed. The tested composites demonstrated comparable wear resistance during repeated aligner insertion and removal over 24-week, with stable aligner retentive force, supporting their feasibility for use in clear aligner therapy.

Effects of curing lights on polymerization shrinkage of composite attachments in clear aligner treatment: A microcomputed tomography study

INTRODUCTION

This study aimed to investigate the polymerization shrinkage of composite attachments and changes in attachment templates during bonding in clear aligner treatments.

METHODS

A total of 24 extracted teeth were divided into 4 groups, and plaster models were digitized. Attachment templates were produced with beveled attachments on premolars and rectangular attachments on molars. Polymerizations used a halogen curing light (800 milliwatts per square centimeter [mW/cm2] for 20 seconds) and light-emitting diode (LED) curing light in 3 modes (1000 mW/cm2 for 20 seconds, 1000 mW/cm2 for 10 seconds, and 3200 mW/cm2 for 3 seconds). The curing distance was 5 mm, and temperature changes were recorded with a thermal camera. Microcomputed tomography scanning measured volumetric and linear attachments before and after polymerization. Statistical analyses employed a 1-way analysis of variance with Bonferroni corrected Tukey post-hoc for multiple comparisons and the Kruskal-Wallis test for temperature change.

RESULTS

Significant differences (P <0.001) were found in temperature among curing lights. The highest temperature was in the LED unit-extra mode, and the lowest was in the halogen curing unit. The LED unit for 20 seconds caused the highest temperature change. A significant difference (P = 0.048) in occlusal attachment length was found between the LED unit for 20 seconds and the LED unit-extra mode. Polymerization resulted in increased attachment template thickness across all groups, with significant changes noted in the halogen unit, LED unit for 20 seconds, and LED unit-extra mode.

CONCLUSIONS

Temperature generated during polymerization varied between halogen and LED curing lights. Significant differences were found in attachment length at the occlusal level and template thickness postpolymerization. Preferences in attachment bonding protocols may affect the clinical precision of clear aligner treatments.

Effectiveness of palatal anchorage device (PAD) for maxillary anterior retraction with clear aligners using finite element study

The palatal anchorage device (PAD) is commonly used in fixed appliance for anchorage, but the biomechanics of PAD in patients treated with clear aligners(CAs)remains poorly understood, especially in its elastic mode and force magnitude. This study aimed to assess the biomechanical effects of using PAD for retraction during clear aligner treatment (CAT) with the extraction of two maxillary first premolars. Four finite element models were created: (1) Incisors retraction (IR) with active contraction of the clear aligner only; (2) IR with PAD using different forces (50,75,100 g) or not; (3) PAD without IR (forces of 50,75,100 g), and (4) Different elastic directions (D1, D2, D3) from aligner to PAD without IR. IR caused lingual tipping and extrusion of the central incisors, as well as mesial and buccal tipping of the first molar. PAD during IR provided strong anchorage for the first molar, with elastics slightly increasing the lingual tipping and extrusion of the central incisors. Elastics applied to the U-shaped arch led to central incisor intrusion and reduced lingual retraction. The highest stress was observed on the mesial attachment of the canine. PAD effectively reinforced posterior anchorage in CAT, while anterior positioning facilitated anterior teeth intrusion. The biomechanical importance of the canine's mesial attachments in maxillary teeth treatment planning was highlighted.

The effect of surface treatment and thermal aging on the bonding of clear aligner attachments to provisional resin-based material: shear bond strength analysis

Objectives

The aim of this study is to evaluate the effect of different surface treatments on the shear bond strength (SBS) of clear aligner attachments bonded to Bis-acryl provisional crowns.

Methods

120 cylindrical bisacrylic composite material (ProTemp type) specimens were prepared and divided into six groups (n = 20) based on surface treatment, control: (no treatment); super coarse grit diamond bur, carbide bur, alumina-blasting, non-thermal plasma treatment, and Er:YAG laser treatment. The features of treated surfaces were examined using scanning electron microscopy (SEM). A flowable composite resin (Transbond XT; 3M Unitek) was bonded to the specimens forming the attachment. Half of specimens were subjected to thermal cycling (5,000 cycles). SBS was measured before and after thermal cycling. Each specimen was loaded at the attachment/resin interface at a speed of 0.5 mm/min until failure. The nature of the failure was analyzed using the composite remnants index (CRI). Two-way ANOVA and Tukey HSD were used for data analysis α =  0.5. For CRI scores analysis, Kruskal-Wallis test and Dunn's multiple comparison were used as post-hoc test.

Results

SEM analysis showed that all surface treatments altered surface properties and increase surface bonding area. The specimens treated with plasma, Er:YAG laser, and alumina-blasting had higher SBS values before and after thermal cycling. In comparison to control plasma, Er:YAG laser, and alumina-blasting showed a significant increase in SBS (P < 0.001) while carbide and diamond bur groups showed no significant differences (P > 0.05). Thermal cycling significantly decreased the SBS of control, carbide bur, diamond bur, and Er:YAG laser while no significant effect of alumina-blasting and plasma group. Er:YAG laser and plasma groups significantly exhibited more dominance for scores 2 and score 3 and the absence of score 0.

Conclusion

Alumina-blasting, Er:YAG laser, or non-thermal plasma surface treatments increased the shear bond strength between clear aligner attachments and resin-based restorations.

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.

Loss of attachments in patients during orthodontic therapy with clear aligners: A prospective clinical study

OBJECTIVE

This study aimed to assess the loss rate of attachments and investigate its probable influencing factors in patients during orthodontic therapy with clear aligners.

MATERIALS AND METHODS

A total of 55 patients treated with clear aligners were enrolled in this prospective clinical study. The loss rate of attachments was evaluated after a 6-month follow-up since the initial bonding was finished. The attachment survival curves were gone through Kaplan-Meier estimates. The Cox regression model with shared frailty was conducted to evaluate the hazard ratios (HRs) for the following factors, including sex, age, dental malocclusion, vertical skeletal pattern, anterior overbite, operators, tooth extraction, attachment amount, arch, tooth position and attachment type.

RESULTS

There were a total of 47 patients (14 males and 33 females; and mean age: 26.77 ± 8.45) in which 722 attachments were involved in the final analysis. During the 6-month follow-up, 99 attachments were lost by 40 participants. The overall loss rate was 13.7%. The loss of attachments was more common in the early months of therapy. During the first 2 months, 71 attachments were lost. The loss rate of attachments was not significantly affected by sex, age, dental malocclusion, vertical skeletal pattern, anterior overbite, operators, tooth extraction, attachment amount and attachment type (P > 0.05). The loss rate of mandibular attachments was 1.8 times that of maxillary attachments (HR = 1.8; 95% CI: 1.2-2.8; P = 0.009). The loss rate of molar attachments was 5.5 times that of incisor attachments (HR = 5.5; 95% CI: 1.6-19; P = 0.007).

CONCLUSION

During the first 6 months, the overall loss rate of attachments was 13.7%. In the early months of therapy, loss of attachments was more common. The loss rate decreased as treatment time increased. Loss of attachments was significantly affected by arch and tooth position, with higher loss rates in the mandibular arch and molars. Besides, loss of attachments was not affected by sex, age, dental malocclusion, vertical skeletal pattern, anterior overbite, operators, tooth extraction, attachment amount and attachment type.

An In Vitro Study of the Abrasive Potential of Various Toothbrushes on the Surface of Aligner Attachments

Background Attachments play a vital role in aligner-led orthodontic therapy, first passively through retention of the appliance and secondly, through bringing about tooth movement, by virtue of its active surfaces, to achieve treatment goals. Additionally, irregularities on the surface of attachments attract plaque adhesion. Thus the effect of brushing with different toothbrushes on the surface of attachments is an important factor to study. This would allow clinicians to better advise patients who are undergoing aligner therapy. Four types of brushes are available commercially, namely hard, medium, soft, and ultra-soft. This study analyses the interaction between the kind of toothbrush used and the wear of the surface of the aligner attachment, to understand the impact of a toothbrush on the attachment. Aim To observe the surface wear and change in the shape of the aligner attachment on brushing with four varying hardness of toothbrush bristle (ultra-soft, soft, medium, and hard) over six months to three years. Material and methods One attachment was bonded to the buccal surface of extracted premolars. One tooth with attachment was subjected to SEM analysis and the rest were divided into four groups of five teeth each, based on the type of toothbrush to be used. Brushing with hard, medium, soft, and ultra-soft toothbrushes was carried out in a brushing simulator in two cycles simulating six months, one year, 18 months, and three years of brushing. A contact profilometer was used to evaluate surface roughness before and after brushing and pre- and post-surface roughness values were compared to quantitate changes after which SEM analysis was carried out for qualitative assessment of the surface of the samples. The Shapiro-Wilks test was applied to evaluate the normality of the data, followed by the one-way ANOVA, and statistical significance was applied at p<0.05. Results At six months, the samples brushed with the medium toothbrush showed the least surface roughness (0.2±0.192) and those brushed with the ultra-soft toothbrushes showed the highest surface roughness (1.9±0.159). At one year, the samples brushed with the soft toothbrush showed the least surface roughness (0.46 ±0.31) and those brushed with the ultra-soft toothbrushes showed the highest surface roughness (2.12 ±0.12). At the 1.5-year point, the surface roughness of the samples was lowest in the ultra-soft toothbrush group (0.43±0.39) and the highest in the soft toothbrush group (1.6± 0.41). At the three-year point, the surface roughness of the samples was lowest in the ultra-soft toothbrush group (0.28 ± 0.17) and the highest in the medium toothbrush group (1.6 ± 0.31). Conclusion Ultra-soft toothbrushes have a high abrasive potential, as seen by higher surface roughness values over six months and one year. Morphometric changes were the most noticeable for attachments brushed by hard-bristled toothbrushes and medium-bristled brushes.

Surface wear of attachments in patients during clear aligner therapy: a prospective clinical study

BACKGROUND

This prospective clinical study aimed to quantitatively evaluate the surface wear of attachments and investigate the associated risk factors. Additionally, the wear values and regions of three types of commonly used attachments were explored.

METHODS

Participants were recruited from the population of patients who received clear aligner therapy from October to December 2022. Intraoral scanning was performed on eligible participants before treatment (T0), immediately after initial bonding of attachments (T1), and at 2 months (T2), 4 months (T3), 6 months (T4), and 8 months (T5) after starting treatment. The attachment volume, average depth and regions of attachment wear were measured using superimposed digitized models. The Kruskal-Wallis test was performed to compare data between multiple groups. Multiple linear regression analyses were performed to evaluate risk factors for the volume of attachment wear.

RESULTS

A total of 47 patients with 617 attachments were included. As treatment time increased, the attachment volume decreased significantly (P = 0.003). The initial attachment volume was positively related to the volume of attachment wear (β = 0.527, P < 0.001). The volume of attachment wear was significantly greater in females than in males (β = 0.147, P = 0.020) and in optimized attachments than in conventional attachments (β = 0.308, P < 0.001). The wear of 3-mm rectangular attachments progressed from edges to buccal surfaces, with the deepest wear at corners of gingival edges; the wear of the optimized attachments was primarily located on surface ridges. The wear volume ratio of the optimized root control attachments was significantly greater than that of the 3-mm rectangular attachments at T3 (P = 0.011), T4 (P < 0.001), and T5 (P < 0.001).

CONCLUSIONS

The volume of attachment wear increased gradually with treatment time. Sex, attachment type, and initial attachment volume were risk factors for the volume of attachment wear. The deepest wear regions of 3-mm rectangular attachments were at the corners of gingival edges, while the deepest wear regions of optimized attachments were at surface ridges. Four months after treatment, optimized root control attachments showed more relative wear than 3-mm rectangular attachments.

Comparison of the bond strength of five different composites used in the production of clear aligner attachments

AIM

The aims of this study were to measure and compare shear bond strength (SBS) and manipulation time (MT) among five different composite resins (CR; two flowable and three highly viscous) which are used in the production of clear aligner attachments.

MATERIAL AND METHODS

This in vitro experiment study comprised of 150 extracted premolars which were divided into 5 equal groups. Predictor variables were CRs; Tetric Evo Ceram (Ivoclar VivadentAG, Liechtenstein) (Group 1), Tetric NCeram; (Ivoclar VivadentAG, Liechtenstein) (Group 2), Tetric N-Flow (GC Dental Products, Tokyo, Japan) (Group 3), G-aenial Universal Injectable (GC Dental Products, Tokyo, Japan) (Group 4), GC Aligner Connect (GC Dental Products, Tokyo, Japan) (Group 5), respectively. Outcome variables were; SBS and MT for each CR attachment in each group of teeth. Oneway ANOVA was used to compare the groups. Levene's test was used to determine variance homogeneity. In terms of variance homogeneity, Bonferroni tests were used as a post-hoc test for multiple group comparisons.

RESULTS

SBS was statistically different between study groups (p < 0.001). Average SBS values ​​are found to be 16.6 ± 3.6 MPa for Tetric Evo Ceram; 20.7 ± 5.4 MPa for Tetric NCeram; 21.0 ± 4.0 MPa for Tetric N-Flow; 18.9 ± 5.0 MPa for G-aenial Universal Injectable; and 17.4 ± 3.5 MPa for GC Aligner Connect. The values ​​in the Tetric Evo Ceram group were significantly lower than the Tetric N-Ceram group (p = 0.004) and the Tetric N-Flow group (p = 0.001). Mean value of shear bond strength in the GC Aligner connect group were significantly lower than in the Tetric N-Ceram group (p = 0.047) and in the Tetric N-Flow group (p = 0.017). Flowable composite had a significantly shorter manipulation time than the high viscous one; mean 1,08 ± 0,22 min to mean 4,57 ± 0,51 min, respectively.

CONCLUSION

Although SBSs of CRs tested in the study was found to be statistically different, they all quite exceeded the accepted clinically sufficient value of 6-8 MPa. Besides, flowable composite required substantially less time to manipulate than the high viscosity composite.

Effect of clear aligner attachment design on extrusion of maxillary lateral incisors: A multicenter, single-blind randomized clinical trial

INTRODUCTION

Extrusion of maxillary lateral incisors during aligner treatment is a difficult movement to achieve accurately. Despite recommendations regarding attachment design, few studies and no prospective trials compare predictability among attachments. This study aimed to compare the efficacy between optimized and horizontal attachment designs for achieving maxillary lateral incisor extrusion during clear aligner treatment.

METHODS

The study included maxillary lateral incisors in 3 orthodontic practices requiring at least 0.3 mm of extrusion during the first series of 20-25 aligners in patients aged ≥16 years who were scheduled to begin clear aligner treatment (Invisalign; Align Technology, San Jose, Calif). Teeth were randomly assigned to receive optimized (O), rectangular horizontal nonbeveled (H), rectangular horizontal incisally-beveled (HIB), or rectangular horizontal gingivally-beveled (HGB) attachments. After the first series, a blinded evaluator measured extrusion using superimpositions with initial and predicted models. Linear models determined the difference in the predicted extrusion percentage achieved on the basis of attachment design. Other covariates were patient age, sex, number of trays, and self-reported compliance.

RESULTS

Forty patients (74 teeth) were enrolled, and 38 patients (71 teeth) completed the study. Intraexaminer and interexaminer reliability for extrusion measurements was high (intraclass correlation coefficient, 0.985 and 0.991, respectively). The achieved extrusion was significantly less than predicted (mean, 73%; P <0.0001). The average achieved extrusion was 62%, 79%, 78%, and 78% for O, H, HIB, and HGB attachments, respectively, with H significantly more effective than O (P = 0.0403). Horizontal attachments (H, HIB, and HGB combined) were significantly more effective than O attachments (P = 0.0060), with an average difference in achieved extrusion of 14% of the predicted amount (95% confidence interval, 4-23; estimated 76% vs 62%). Horizontal attachments were an estimated 22% more effective than O attachments for extruding maxillary lateral incisors.

CONCLUSIONS

Horizontal attachments are more effective than O attachments for predicted maxillary lateral incisor extrusion between 0.3 and 2.5 mm. The 3 horizontal attachment designs evaluated performed similarly for achieving predicted extrusion.

TRIAL REGISTRATION

This randomized clinical trial was registered and reported at clinicaltrials.gov (NCT04968353).

PROTOCOL

The protocol was not published before trial commencement.

FUNDING

This study was funded in part by the Alexander Fellowship of the Virginia Commonwealth University School of Dentistry, the Southern Association of Orthodontists, and the Virginia Orthodontic Education and Research Foundation. No funding source influenced the study design, the collection, analysis or interpretation of data, writing of the report, or the decision to submit the article for publication.

Evaluation of the Clinical Variables Affecting Attachment Reproduction Accuracy during Clear Aligner Therapy

BACKGROUND

The purpose of this study was to evaluate some of the clinical variables that influence the accuracy of reproducing the planned attachment shape. The following clinical variables were considered: the template material, type of composite, and pressure application on the template during attachment curing.

METHODS

In this study, the evaluated materials for the thermoplastic transfer template construction are Erkolen 0.8 (polyethylene: PE) and Erkodur 0.8 (polyethylene terephthalate glycol-PET-G), and two types of composite resins: Enaflow (light-curing low-viscosity composite resin) and Enamel plus dentina HRI (light-curing high-viscosity composite resin). Two different light-curing lamps were used: Valo cordless color with no pressure and push light pressure (SCS). The 26 models included in the study were imported into the 3 Shape Ortho System 2022 (ver. 85.0.20 3 Shape, Denmark), and attachments were virtually placed on the dental elements of the first premolar and on both sides of the first upper molars. The accuracy of the attachment reproduction was evaluated through linear and angular evaluations against the reference model (MCAD). Three physical models were obtained: model A (MA), which was printed with attachments; model B (MB) with attachments made with a PE template; and model C (MC) with attachments made with a PET-G template.

RESULTS

The results showed statistically significant differences (p < 0.05) between the PE and PET-G templates with greater precision using the PET-G template. Statistically significant differences (p < 0.05) were found among the high-viscosity composite and low-viscosity composite with pressure curing.

CONCLUSIONS

In light of the obtained data, using a PET-G template is recommended. The pressure application during composite curing reduces the reproduction accuracy with a low-viscosity composite.

Treatment planning protocols with the Invisalign appliance: an exploratory survey

OBJECTIVES

To investigate the changes made by orthodontists to the initial digital treatment plan (DTP) regarding the Invisalign appliance provided by Align Technology until acceptance of the plan by the orthodontist.

MATERIALS AND METHODS

The DTPs of subjects who underwent treatment with the Invisalign appliance and satisfied inclusion criteria were assessed to determine the number of DTPs and changes regarding prescription of aligners, composite resin (CR) attachments, and interproximal reduction (IPR) between the initial DTP and the accepted plan. Statistical analyses were calculated via GraphPad Prism 9.0 (GraphPad Software Inc., La Jolla, Calif).

RESULTS

Most of the 431 subjects who satisfied inclusion/exclusion criteria were female (72.85%). More DTPs were required for subjects who had orthodontic extractions (median [interquartile range; IQR]: 4 [3, 5]) compared with those who did not (median [IQR]: 3 [2, 4], P < .0001). The median (IQR) overall number of aligners prescribed in the accepted DTP (30 [20, 39]) was greater than the initial DTP (30 [22,41], P < .001). The number of teeth used for CR attachments increased from the initial to the accepted DTP (P < .001). More CR attachments were observed in extraction treatment DTPs with a prescribed 2-week aligner change protocol compared with nonextraction treatment (P < .0001). The number of contact points with prescribed IPR increased between initial and accepted DTPs (P < .0001).

CONCLUSIONS

Significant changes regarding DTP protocols were observed between the initial and accepted DTPs and between nonextraction and extraction-based CAT.

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

BACKGROUND

Attachments' configuration play an important role during Clear Aligner Treatment (CAT) for aligner retention and control of movements planned. The aims were to compare the macroscopic morphology of attachments reproduced with flowable (FNC) and conventional (CNC) composites and the effects on them of two light-guide tips with different dimensions.

METHODS

4 resin casts derived from the initial scan of the same patient were obtained. 10 vestibular attachments were replaced on both upper and lower arches of each model with CNC (Models A, B) and FNC (Models C, D). Each composite was cured by means of the same LED lamp with both regular light-guide (Models A, B) and push and light tool® (Models C, D). The 80 attachments were qualitative analyzed by means of a digital stereo microscope. Surface roughness and waviness measurements were assessed by contact probe surface profiler (TalySurf CLI 2000; Taylor Hobson, Leicester, United Kingdom). Statistical analysis was performed with independent samples t-tests. Significance was established at the P < 0.05 level.

RESULTS

Model A showed lower values of surface roughness (Ra - 1.41 µm, Rt - 3.46 µm) and waviness (Wa - 2.36 µm, Wt - 10.95 µm) when compared with Model C. Significant reduction of waviness (Wa - 3.85 µm, Wt - 4.90 µm) was observed on Model B when compared with Model D. Significant increase of roughness and waviness parameters (Ra 3.88 µm, Rt 21.07, Wa 2.89 µm, Wt 14.74 µm) was found when CNC sample (Model A) was cured with regular light-guide tip. Higher values (Ra 2.33 µm, Rt 24.07 µm, Wa 1.67 µm, Wt 20.79 µm) were observed after regular light-guide tips curing on FNC sample (Model C).

CONCLUSIONS

CNC resins determine more regular surfaces of attachments profiles. The additional use of a smaller light- guide of the LED push and light tool® allows to improve the macroscopic morphology of the attachments and to maximize light irradiance delivering by enhancing the polymerization process and the integrity of the features during the treatment.