Skeletal anchorage via temporary anchorage devices (TADs) is a fast growing technique used in orthodontic treatment. The bone density in the anterior palate provides a good condition for primary stability of the orthodontic miniscrew. An intraoral scan and a lateral cephalogram can be used to create a combined model for planning miniscrew placement either into the midpalatal suture or parasutural. The TADs can be placed virtually into the anterior palate. Their position and insertion depth can be reviewed and, if necessary, the TADs can be repositioned. There are different ways to fabricate the surgical guide based on the 3D-printed positioning model. Instead of 3D printing the model and manufacturing the surgical guide with it, it is possible to design the guide within the software and print it directly without using an actual printed model.

Background/Objectives: This ex vivo study aimed to evaluate the diagnostic performance of ultra-low-dose (ULD) cone-beam computed tomography (CBCT) protocols in detecting vestibular bone defects for immediate implant planning, using intraoral scan (IOS) data as a reference. Methods: Four CBCT protocols (ENDO, A, B, C) were applied to four dried human skulls using a standardized setup and a single CBCT unit (Planmeca ProMax® 3D Mid, Planmeca Oy, Helsinki, Finland). All scans were taken at 90 kV, with varying parameters: (1) ENDO (40 × 50 mm, 75 µm, 12 mA, 80-120 µSv, 15 s), (2) A (50 × 50 mm, 75 µm, 9 mA, 20-40 µSv, 5 s), (3) B (100 × 60 mm, 150 µm, 7.1 mA, 22-32 µSv, 5 s), and (4) C (100 × 100 mm, 200 µm, 7.1 mA, 44 µSv, 4 s). Vestibular root surfaces of single-rooted teeth (FDI regions 15-25 and 35-45) were digitized via IOS and exported as STL files. CBCT datasets were superimposed using 3D software (Blender 2.79), and surface defects were measured and compared using one-sample t-tests and Bland-Altman analysis. The level of significance was set at p < 0.05. Results: A total of 330 vestibular surfaces from 66 teeth were analyzed. Compared to the IOS reference, protocols ENDO and A showed minimal differences (p > 0.05). In contrast, protocols B and C exhibited statistically significant deviations (p < 0.05). Protocol B demonstrated a mean difference of -0.477 mm2 with limits of agreement (LoA) from -2.04 to 1.09 mm2 and significant intra-rater variability (p < 0.05). Protocol C revealed a similar mean deviation (-0.455 mm2) but a wider LoA (-2.72 to 1.81 mm2), indicating greater measurement variability. Overall, larger voxel sizes were associated with increased random error, although deviations remained within clinically acceptable limits. Conclusions: Despite statistical significance, deviations for protocols B and C remained within clinically acceptable limits. ULD CBCT protocols are, thus, suitable for evaluating vestibular bone defects with reduced radiation exposure.

AIM:The objective of the present study was to evaluate OccluSense's reliability against conventional articulating films in assessing static occlusion. The study also aimed to identify possible limitations and influencing factors when using this device to assess static occlusion. MATERIALS AND METHODS:The experimental study utilized 20 epoxy resin typodont models representing various occlusal discrepancies. These were mounted in a CP Artex articulator, and static occlusion was assessed in maximum intercuspal position using Shimstock foil as the gold standard. The digitally generated occlusograms by OccluSense were compared with conventional occlusal indicators, including 40-µm articulating paper (AP) and 12-µm articulating foil (AF). Intrarater reliability was assessed using Cohen's kappa coefficient (κ). RESULTS:AP and AF showed high reliability, with κ values of 0.94 and 0.93, respectively, indicating almost perfect agreement with the gold standard. In contrast, OccluSense demonstrated an overall reliability of κ = 0.22, signifying fair agreement. Notably, significant discrepancies in κ values were observed among different malocclusions, with deep bite exhibiting the lowest reliability at κ = 0.02, representing poor agreement (P 0.05). CONCLUSION:OccluSense is less reliable compared to traditional methods, such as AP, for assessing static occlusion. Its limitations are particularly evident in patients with deep bite, making it unsuitable as a standalone tool at the present time.

BACKGROUND:There are little scientific data on fully automated Peer Assessment Rating (PAR); this study compares a number of PAR scoring methods to assess their reliability.OBJECTIVES:This investigation evaluated PAR scores of plaster, 3D printed, and virtual digital models scored by specialist orthodontists, dental auxiliaries, undergraduate dental students,and using a fully automated method.MATERIALS AND METHODS:Twelve calibrated assessors determined the PAR score of a typodont and this score was used as the gold standard. Measurements derived from a plaster model, a 3D printed model, and a digital model, were compared. A total of 120 practitioners (specialist orthodontists, dental auxiliaries, and undergraduate dental students, n = 40 each) scored the models (n = 10) per group. The digital models were scored twice, using OnyxCeph (OnyxCeph) and OrthoAnalyzer (3Shape). The fully automated PAR scoring was performed with Model+ (Carestream Dental).RESULTS:Neither type of model (P = 0.077), practitioner category (P = 0.332), nor interaction between the two (P = 0.728) showed a statistically significant effect on PAR scoring. The mean PAR score and standard deviation were comparable for all models and groups except the automated group, where the standard deviation was the smallest (SD = 0). Overall, the greatest variation was observed for weighted overjet and contact point displacements.CONCLUSIONS:PAR scoring using plaster, 3D printed, and digital study models by orthodontists, dental auxiliaries, dental students, and a fully automated method produced very similar results and can hence be considered equivalent. Automated measurements improve repeatability compared with all groups of practitioners, but this did not reach the significance level.

Objective. The purpose of this study was to evaluate the impact of thyroid gland shielding on radiation doses in dental cone beam computed tomography (CBCT) with small and medium fields of view (FOVs). Study Design. Six CBCT protocols were investigated by exposing an adult anthropomorphic male phantom head without and with thyroid shielding, using 4 small (4 x 5 cm) and 2 medium (10 x 6 cm) FOVs. Twenty metal oxide semiconductor field-effect transistor dosimeters were placed in the phantom head to measure absorbed doses and calculate equivalent doses at 11 sites. Effective doses were calculated based on the tissue weighting factors in International Commission on Radiological Protection Publication 103. The data were analyzed using the independent samples t test. Results. Thyroid gland shielding led to significant equivalent dose reductions in many tissues for all protocols. Equivalent dose reductions to the thyroid were significant in all 6 protocols (P <=.037). Significant reduction depended on the FOV and ranged between 24.5% and 42.6% for the thyroid gland and 4.9% and 34.5% for other tissues and organs. Effective doses were significantly lower in all protocols (P <=.016). Conclusions. Thyroid gland shielding protects the thyroid gland and other organs and should be utilized with all CBCT examinations where feasible.

Dose reduction achieved by downsizing the field of view (FOV) in CBCT scans has brought no benefit for pediatric orthodontics, until now. Standard 2D or 3D full-size cephalometric analyses require large FOVs and high effective doses. The aim of this study was to compare a new 3D reduced-FOV analysis using the Frankfurt horizontal (FH) plane as reference plane with a conventional full-size analysis using the Sella-Nasion (S-N) plane as reference plane. Thirty-eight CBCT data sets were evaluated using full- and reduced-FOV analysis. The measurements of a total of 20 skeletal and dental standard 3D full-size variables were compared with the measurements of 22 corresponding 3D reduced-FOV variables. Statistical analysis was performed to prove mathematic relation between standard and alternative variables. Regression analyses were carried out. Coefficients of determination (R2) between 0.15 and 0.95 (p < 0.001–0.055) were described. All variables showed obvious relations of different strength except for SNA and its alternative Po_R-Or_R-A (°) (R2 = 0.15, p = 0.055), but a second variable Ba_A (mm) showed stronger relation (R2 = 0.28, p = 0.003). All standard variables related to the reference plane S-N could be described with alternative variables related to the FH. Further research should define more reliable landmarks for coordinate systems and reference points. Minimized large FOVs meet the demand of 3D cephalometric analyses and enable the application of CBCT scans in pediatric orthodontic patients in many specific indications. Dose reduction is accompanied by increasing access to all the advantages of 3D imaging over 2D imaging.

INTRODUCTION:This study aimed to determine the identifiability and measurement accuracy of defined bony defects of the temporomandibular joint (TMJ) in cone-beam computed tomographies, depending on different milliampere-second (mAs)-reduced protocols. METHODS:Defined artificial defects were prepared on 30 condyles from 15 intact pig heads, with a maximum of surrounding soft tissue preserved. Three-dimensional imaging was performed using ProMax 3D Mid (Planmeca, Helsinki, Finland). The scan protocol with maximum resolution and without mAs-reduction was defined as control. Twenty-six mAs-reduced imaging protocols were analyzed by 1 examiner regarding the protocol-specific measurement accuracy. Defect depth (DD) was divided into 3 categories: I, <2 mm; II, 2-3 mm; and III, >3 mm. The protocol-specific sensitivity and specificity were evaluated in relation to localization and defect size as determined from the results of 3 examiners. RESULTS:There was a significant difference from the control protocol in DD measurement in 8 mAs-reduced protocols, P <0.001-0.027. In most protocols, there was no significant difference in measurement accuracy concerning defect size and localization. The mean sensitivity reached values between 93.3% and 98.6% and differed significantly among protocols (P = 0.002). The mean specificity amounted to 97.0%-98.1% and did not differ among protocols (P = 0.462). The specificity of DD III (99.1%) was higher than DD I (97.7%) and DD II (97.1%). There was a significant difference in specificity and sensitivity concerning defect localization (P <0.001). CONCLUSIONS:This study showed that mAs-reduced cone-beam computed tomographies protocols are suitable for the analysis of defined osseous TMJ defects. When 3-dimensional TMJ imaging is indicated because of potential erosive defects, validated mAs-reduced scan protocols should be applied instead of high-definition protocols.

STATEMENT OF PROBLEM:Intraoral scanners (IOSs) are based on light-optical imaging methods. However, little is known about whether the ambient light in dental practices influences the accuracy and scanning time of the IOS.PURPOSE:The purpose of this in vitro study was to investigate the influence of different illuminations on the accuracy of 4-unit and complete-arch scans of 6 IOSs. In addition, the required scanning time was evaluated.MATERIAL AND METHODS:A reference structure was attached to the first premolars (P) and second molars (M) in both quadrants (L/R) of a maxillary model. The resulting measured distances were M1-P1, M2-P2, P1-P2, and M1-M2. The investigation included 6 IOSs: TRIOS 3 (TRI), Cerec Omnicam (OC), iTero Element (ITE), CS 3600 (CS), Planmeca Emerald (EME), and GC Aadva (AAD). With each IOS, 17 scans at different illuminances (100, 500, 1000, and 5000 lux) were performed (N = 408). The precision and trueness for all distances were determined, and the scanning time was recorded. For statistical analyses, the Levene tests (precision) and 1-way analysis of variance with the post hoc Tukey honestly significant difference and Games-Howell tests (trueness) were calculated.RESULTS:Illuminance significantly influenced the trueness of 4-unit scans for OC, EME, and AAD. TRI, OC, ITE, and CS demonstrated comparable results. AAD (>96 ±22 μm; 1000 lux) and EME (>248 ±88 μm; 500 lux) revealed greater deviations. For complete-arch scans, illuminance did not influence TRI and AAD, but significant variations were detected for ITE, CS, EME, and AAD. The least deviations were achieved with TRI and OC. The scanning time was extended for all IOSs except ITE at more than 500 lux. The shortest scanning times with OC and EME were recorded at 100 lux; with TRI, CS, and AAD at 500 lux; and with ITE at both 100 and 5000 lux. At all illuminances, the fastest scans were obtained with TRI.CONCLUSIONS:Ambient light was found to influence the accuracy and scanning time of IOSs. This influence varies depending on the device. For 4-unit scans, the effect was not clinically relevant, but for complete-arch scans, accuracy and scanning time can be improved with appropriate lighting.

STATEMENT OF PROBLEM:Reliable studies comparing the accuracy of complete-arch casts from 3D printers are scarce.PURPOSE:The purpose of this in vitro study was to investigate the accuracy of casts printed by using various extrusion- and photopolymerization-based printers.MATERIAL AND METHODS:A master file was sent to 5 printer manufacturers and distributors to print 37 identical casts. This file consisted of a standardized data set of a maxillary cast in standard tessellation language (STL) format comprising 5 reference points for the measurement of 3 distances that served as reference for all measurements: intermolar width (IMW), intercanine width (ICW), and dental arch length (AL). The digital measurement of the master file obtained by using a surveying software program (Convince Premium 2012) was used as the control. Two extrusion-based (M2 and Ultimaker 2+) and 3 photopolymerization-based printers (Form 2, Asiga MAX UV, and myrev140) were compared. The casts were measured by using a multisensory coordinate measuring machine (O-Inspect 422). The values were then compared with those of the master file. The Mann-Whitney U test and Levene tests were used to determine significant differences in the trueness and precision (accuracy) of the measured distances.RESULTS:The deviations from the master file at all 3 distances for the included printers ranged between 12 μm and 240 μm (trueness), with an interquartile range (IQR) between 17 μm and 388 μm (precision). Asiga MAX UV displayed the highest accuracy, considering all the distances, and Ultimaker 2+ demonstrated comparable accuracy for shorter distances (IMW and ICW). Although myrev140 operated with high precision, it displayed high deviations from the master file. Similarly, although Form 2 exhibited high IQR, it did not deviate significantly from the master file in the longest range (AL). M2 performed consistently.CONCLUSIONS:Both extrusion-based and photopolymerization-based printers were accurate. In general, inexpensive printers were no less accurate than more expensive ones.

The aim of this study was to compare the accuracy of six intraoral scanners as regards clinically relevant distances using a new method of evaluation. An additional objective was to compare intraoral scanners with the indirect digitization of model scanners. A resin master model was created by 3D printing and drilled in five places to reflect the following distances: intermolar width (IMW), intercanine width (ICW), and arch length (AL). To determine a gold standard, the distances were measured with a coordinate measuring instrument (Zeiss O-Inspect 422). The master model was scanned 37 times with the following intraoral scanners: Apollo DI (Sirona), CS 3500 (Carestream Dental), iTero (Cadent), PlanScan (Planmeca), Trios (3Shape), and True Definition (3M Espe), and indirectly digitized with the OrthoX Scan (Dentaurum). The digital models were then measured, and deviations from the gold standard calculated. Significant differences were found between the devices. Among the intraoral scanners, Trios and iTero showed the most accurate results, although CS 3500, True Definition, and Apollo DI achieved comparable results. PlanScan demonstrated the highest deviations from the gold standard, and presented a high standard deviation (SD). Direct digitization revealed comparable (and, in fact, slightly higher) accuracy than indirect digitization. Both indirect digitization and most of the intraoral scanners were therefore demonstrated to be suitable for use in the orthodontic office, with the exception of PlanScan, which did not meet the demands of individual orthodontic treatment.

Plaster casts can be digitized with desktop scanners, intraoral scanners, and recently also with cone beam computed tomography (CBCT). The aim of this study was to investigate the accuracy of five different CBCT devices digitizing a plaster cast. A study cast serving as a patient was made using the double mix impression technique, and the impression was poured out with plaster. On the resulting plaster cast, arch length (AL), intermolar width (IMW), and intercanine width (ICW) were measured by a coordinate measuring machine (CMM) (Zeiss O-Inspect 422). The patient cast was then scanned by five CBCT devices - CS 9300, CS 9300 Select, CS 8100 3D (all Carestream), Promax 3D Mid (Planmeca), and Whitefox (Acteon) - in eight scan modes. For each CBCT device, 37 scans were performed. The resulting DICOM data were exported as stereolithographic (STL) data and linearly measured using Convince Premium 2012 (3Shape) software. All measurements were compared to the reference master values of the patient cast. The accuracy measurements showed significant differences among the CBCT devices. The highest accuracy was achieved by Whitefox (IMW: mean ± standard deviation (SD): 5.5 ± 5.7 µm) and CS 9300 (IMW: -15 ± 7.4 µm). Comparable results with less accuracy were shown by CS 8100 3D (IMW: -81.2 ± 7.4 µm) and CS 300 Select (IMW: -82.2 ± 6.6 µm). Significantly lower accuracy was shown by Promax 3D Mid (IMW: -126.1 ± 4.8 µm). Some CBCT devices are suitable for the digitization of plaster casts and show very good clinical accuracy. Dental offices equipped with CBCT devices could digitize plaster casts without the need for additional devices.

Objetivo: el objetivo principal de este estudio fue comparar la precision y la rentabilidad en tiempo de un flujo de trabajo de digitalizacion indirecta y directa con las de una impresora tridimensional (3D) para identificar el metodo mas idoneo para el uso en ortodoncia. Materiales y metodos: se midio un modelo maestro con un instrumento de medicion de coordenadas. Las distancias medidas fueron la anchura intercanina, la anchura intermolar y la longitud de la arcada dental. Se tomaron 64 escaneados con cada uno de los escaneres desktop R900 y R700 (3Shape), escaner intraoral TRIOS Color Pod (3Shape) y la unidad de tomografia computarizada de haz conico (TCHC) Promax 3D Mid (Planmeca). Todos los escaneados se midieron con el correspondiente software. Se selecciono un escaneado y se imprimio tres veces en la impresora D35 estereolitografica 3D (Innovation MediTech). Los modelos impresos se volvieron a medir con los instrumentos de medicion de coordenadas. Resultados: los resultados mas precisos se obtuvieron con el R900. Los escaneres intraorales R700 Y TRIOS mostraron resultados equivalentes. La renderizacion 3D con la unidad de TCHC Promax 3D Mid mostro una precision significativamente superior en cuanto a los modelos dentales, en comparacion con las impresiones dentales. La impresion 3D ofrecio un nivel significativamente superior de desviacion en comparacion con la digitalizacion con los escaneres desktop o un escaner intraoral. El tiempo en consulta requerido para las impresiones digitales fue un 27 % mas prolongado que para las impresiones convencionales. Conclusion: las impresiones convencionales, el vaciado de modelos y la digitalizacion opcional con escaneres desktop sigue siendo el proceso de flujo de trabajo recomendado. Para las exigencias ortodonticas, los escaneres intraorales constituyen una alternativa util para los escaneos de arcada completa. Para el uso en prostodoncia, el rango de escaneado debe ser inferior a un cuadrante y tres dientes adicionales.

OBJECTIVE To quantify treatment-related changes in peridental bone height and thickness in orthodontic patients. MATERIALS AND METHODS Cone-beam computed tomographs (CBCTs) of 43 patients (24 female, 19 male; mean age: 25 years, 5 months) who underwent orthodontic treatment with multibracket appliances for at least 1 year were chosen for retrospective evaluation. Dehiscence depth and changes in bone width and tooth inclination were determined for 954 teeth. RESULTS There was a significant decrease in peridental bone height (dehiscence; -0.82 ± 1.47 mm) and bone thickness (-0.56 ± 0.7 and -0.69 ± 0.9 mm at 5 mm and 10 mm apical to the CEJ, respectively) during treatment (P < .001). A significantly greater dehiscence depth with increased vertical bone loss occurred in patients older than 30 years. In patients <30 years old, approximately 20% of the teeth showed defect depths >2 mm before treatment. In 90% of these patients, at least one tooth was affected. The maxillary canines and all mandibular teeth showed a higher risk for vestibular bone loss. Treatment changes in tooth inclination were correlated with horizontal bone loss. CONCLUSIONS Based on these results, it seems reasonable to recommend that peridental bone in orthodontic patients older than 30 be evaluated on a routine basis due to the risk of increased vertical bone loss. Ninety percent of patients younger than 30 showed reduced bone height (dehiscence) of the periodontium of at least one tooth.

OBJECTIVE:The primary objective of this study was to compare the accuracy and time efficiency of an indirect and direct digitalization workflow with that of a three-dimensional (3D) printer in order to identify the most suitable method for orthodontic use.METHOD AND MATERIALS:A master model was measured with a coordinate measuring instrument. The distances measured were the intercanine width, the intermolar width, and the dental arch length. Sixty-four scans were taken with each of the desktop scanners R900 and R700 (3Shape), the intraoral scanner TRIOS Color Pod (3Shape), and the Promax 3D Mid cone beam computed tomography (CBCT) unit (Planmeca). All scans were measured with measuring software. One scan was selected and printed 37 times on the D35 stereolithographic 3D printer (Innovation MediTech). The printed models were measured again using the coordinate measuring instrument.RESULTS:The most accurate results were obtained by the R900. The R700 and the TRIOS intraoral scanner showed comparable results. CBCT-3D-rendering with the Promax 3D Mid CBCT unit revealed significantly higher accuracy with regard to dental casts than dental impressions. 3D printing offered a significantly higher level of deviation than digitalization with desktop scanners or an intraoral scanner. The chairside time required for digital impressions was 27% longer than for conventional impressions.CONCLUSION:Conventional impressions, model casting, and optional digitization with desktop scanners remains the recommended workflow process. For orthodontic demands, intraoral scanners are a useful alternative for full-arch scans. For prosthodontic use, the scanning scope should be less than one quadrant and three additional teeth.

OBJECTIVE:The purpose of this study was to evaluate the accuracy of full-arch scans using 11 different cast scanners.METHOD AND MATERIALS:Dental arch length (AL), intermolar width (IMW), and intercanine width (ICW) of the reference plaster casts were measured using a coordinate measuring machine (Zeiss O-Inspect 422). The master cast was subsequently scanned 37 times using 11 desktop scanners (3Shape R500, 3Shape R700, 3Shape R1000, 3Shape R2000, Medianetx grande, Medianetx colori, DentaCore CS ULTRA, Dentaurum OrthoX, Maestro 3D, Imetric IScan D104i, GC Aadva Lab Scan). Using the software Convince Premium 2012 (3Shape), AL, IMW, and ICW were measured on the digital models and compared to the reference plaster cast.RESULTS:The accuracy of the cast scanners differed significantly. The most accurate measurements were given by the cast scanners 3Shape R700 (ICW: 7.4?±?5.9?µm) and Imetric IScan D104i (ICW: 9.1?±?4.9?µm). The cast scanners 3Shape R1000 (ICW: 11.2?±?3.4?µm) and GC Aadva Lab Scan (ICW: 13.8?±?8.1?µm) yielded comparable measurements. DentaCore (ICW: 26.6?±?7.5?µm) and Dentaurum OrthoX (ICW: 31.1?±?24?µm) were significantly less accurate.CONCLUSION:Almost all scanners demonstrated a level of accuracy so high that further improvement would not provide additional benefit for use in orthodontics. Advancement of the scanners should focus primarily on reducing time and cost. For prosthodontic use, the scanners with the highest accuracy are recommended.

OBJECTIVE To determine the bone thickness in the anterior palate and to test whether there is any dependency between bone thickness and patient's age or gender and whether there is any difference between left and right sides. MATERIALS AND METHODS Cone beam computed tomographic (CBCT) evaluations (n  =  431; 229 females, 202 males) of healthy orthodontic patients aged 9-30 years were selected from the database of the imaging center network Mesantis. In each CBCT image, palatal bone thickness was determined as the median and 2, 4, 6, and 8 mm paramedian bilaterally. Bone height was measured perpendicularly to the bony surface at 10, 12, 14, 16, 18, and 20 mm from the cementoenamel junction of the maxillary central incisor in the sagittal plane. RESULTS The greatest bone thickness was found in the lateral anterior palate. Palatal bone thickness of male patients was on average 1.2 mm greater than that of females. Bone height of 9-13-year-olds was less than that of older patients. No difference could be determined between the left and right side. CONCLUSIONS The lateral anterior palate offers the greatest bone thickness. Because there is considerable variation of bone thickness between individuals, a CBCT evaluation is recommended if maximum screw length is to be used.

INTRODUCTION:The aim of this study was to compare the presence of alveolar defects (dehiscence and fenestration) in patients with Class I and Class II Division 1 malocclusions and different facial types.METHODS:Seventy-nine Class I and 80 Class II patients with no previous orthodontic treatment were evaluated using cone-beam computed tomography. The sample included 4319 teeth. All teeth were analyzed by 2 examiners who evaluated sectional images in axial and cross-sectional views to check for the presence or absence of dehiscence and fenestration on the buccal and lingual surfaces.RESULTS:Dehiscence was associated with 51.09% of all teeth, and fenestration with 36.51%. The Class I malocclusion patients had a greater prevalence of dehiscence: 35% higher than those with Class II Division 1 malocclusion (P <0.01). There was no statistically significant difference between the facial types.CONCLUSIONS:Alveolar defects are a common finding before orthodontic treatment, especially in Class I patients, but they are not related to the facial types.

Introduction White spots (WS) related to orthodontic treatment are severe cariologic and cosmetic complications, but they are shown to be partially reduced by remineralization or abrasion in short-term follow-ups. In this prospective study, we quantitatively analyzed changes in WS in general and in treatment-related white spot lesions (WSL) during orthodontic treatment and at a 12-year follow-up after treatment. In addition, we quantitatively compared the effects of an acrylic bonding material vs a glass ionomer cement (GIC) on WSL. Methods Sum areas of WS and WSL were calculated on scans of standardized photos of the vestibular surfaces of 4 teeth in consecutive orthodontic patients (median treatment time, 1.7 years) bonded with the 2 materials in a split-mouth design. Comparisons were made in 59 patients before treatment (BF), at debonding (T0), at 1 year (T1), and at 2 years (T2), and in 30 patients at a 12-year follow-up (T3) with the Friedman test followed by pairwise comparisons with the Wilcoxon matched-pairs signed rank test. Differences of the effects of acrylic vs GIC on the sum areas of WSL were tested for each observation period with the Mann-Whitney U test. Results Increases in the sum areas of WS and WSL from BF to T0 (P <0.001) were followed by significant decreases at T1 (P <0.001) and T2 (P <0.01 for WS; P <0.001 for WSL). Significant changes were also found in the sum areas for WS at T3 compared with T2 (P <0.01), but not for WSL (P = 0.328). The sum areas of WS and WSL at T3 did not return to BF levels (P <0.001). Sum areas of WSL were higher for surfaces bonded with acrylic compared with GIC for each observation period from BF to T2 (P >0.001), and from T2 to T3 (P >0.05). Conclusions Although significantly reduced during the 12-year follow-up and significantly lower with the GIC than the acrylic material at bonding, WSL are a cariologic and cosmetic problem for many orthodontic patients.