Evaluation of magnetic resonance imaging artifacts caused by fixed orthodontic CAD/CAM retainers-an in vitro study.

OBJECTIVES: Magnetic resonance imaging (MRI) image quality can be severely impaired by artifacts caused by fixed orthodontic retainers. In clinical practice, there is a trend towards using computer-aided design/computer-aided manufacturing (CAD/CAM) retainers. This study aimed to quantify MRI artifacts produced by these novel CAD/CAM retainers. MATERIAL AND METHODS: Three CAD/CAM retainers and a stainless-steel retainer ("Twistflex"; clinical reference standard) were scanned in vitro at 3-T MRI using a high-resolution 3D sequence. The artifact diameters and three-dimensional artifact volumes (AV) were determined for all mandibular (AVmand) and maxillary (AVmax) retainers. Moreover, the corresponding ratio of artifact volume to retainer volume (AV/RVmand, AV/RVmax) was calculated. RESULTS: Twistflex caused large artifact volumes (AVmand: 13530 mm3; AVmax: 15642 mm3; AV/RVmand: 2602; AV/RVmax: 2235). By contrast, artifact volumes for CAD/CAM retainers were substantially smaller: whereas artifact volumes for cobalt-chromium retainers were moderate (381 mm3; 394 mm3; 39; 31), grade-5 titanium (110 mm3; 126 mm3; 12; 12) and nickel-titanium (54 mm3; 78 mm3; 12; 14) both produced very small artifact volumes. CONCLUSION: All CAD/CAM retainers caused substantially smaller volumes of MRI artifacts compared to Twistflex. Grade-5 titanium and nickel-titanium CAD/CAM retainers showed the smallest artifact volumes. CLINICAL RELEVANCE: CAD/CAM retainers made from titanium or nickel-titanium may not relevantly impair image quality in head/neck and dental MRI. Artifacts caused by cobalt-chromium CAD/CAM retainers may mask nearby dental/periodontal structures. In contrast, the large artifacts caused by Twistflex are likely to severely impair diagnosis of oral and adjacent pathologies.

OCT evaluation of orthodontic surface sealants: a 12-month follow-up randomized clinical trial.

OBJECTIVES: The aim of this single-center randomized controlled trial (NCT03753256) was to assess orthodontic surface sealant layer thickness and integrity in vivo during a 12-month follow-up by optical coherence tomography (OCT). MATERIALS AND METHODS: Using a split-mouth design, quadrants of 20 patients treated with fixed orthodontic appliances were included. Quadrants were randomly assigned to the sealants Pro Seal® (PS) or Opal® Seal™ (OS). OCT scans were performed immediately after the application of the sealants and after 3, 6, 9, and 12 months. Sealant layer thicknesses and their integrity were determined at 5 regions of interest (ROIs) known for high risks of demineralization. Sealant integrity loss was determined using a self-developed scale. RESULTS: A total of 16 patients successfully completed the study. The studied sealants showed significant differences in initial layer thickness. Mean layer thickness was significantly lower for PS (67.8 µm, (95% CI, 56.1-79.5)) than for OS (110.7 µm, (95% CI, 97.3-124.1)). Layer thickness loss was significant after 3 months for PS and after 6 months for OS. Sealant integrity was compromised in more than 50% of the ROIs already after 3 months for both sealants. CONCLUSIONS: Patients treated with fixed orthodontic surface sealants lost the integrity of the protective layer in more than 50% of cases after 3 months, and the layer thickness of the sealants was significantly reduced after 3-6 months. CLINICAL RELEVANCE: The protective effect against demineralization lesions of orthodontic sealants in patients treated with fixed appliances appears to be limited in time. Further preventive measures should be investigated. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03753256).

Discoloration of surface sealants by plaque disclosing solution.

PURPOSE: Surface sealants are widely used as a prevention strategy and are indicated for young patients with insufficient oral hygiene who also need plaque removal by professional tooth cleaning. The aim of this study was to evaluate discoloration of surface sealants by plaque disclosing solutions and to test to what extent this discoloration can be reduced again by professional tooth cleaning. METHODS: In all, 96 extracted lesion-free human teeth were randomly assigned to treatment with either Pro Seal® (PS; Opal Orthodontics, South Jordan, UT, USA) or Opal®Seal™ (OS; Reliance Orthodontic Products, Itasca, IL, USA). Color evaluations after application of the plaque disclosing solution Mira-2-Ton® (Hager & Werken, Duisburg, Germany) were performed using a clinical spectrophotometer. Staining and polishing were repeated once. Color differences (∆E) above 3.77 were regarded as clinically relevant. RESULTS: All sealants showed high, clinically relevant ∆E values after the first staining. Polishing led to significantly decreased ∆E values on PS-treated teeth; however, the median ∆E value remained above the clinically relevant threshold. Polishing on OS-treated teeth only slightly reduced ∆E values. After professional tooth cleaning both PS and OS showed clinically relevant ∆E values. CONCLUSION: Surface sealants show clinically relevant discoloration after exposure to plaque disclosing solution under in vitro conditions. Such discolorations could not be removed by professional tooth cleaning. Thus, in clinical practice, plaque disclosing solutions might cause esthetic deficits in surface sealant-treated teeth. The impact of plaque disclosing solutions under clinical conditions (e.g., in the presence of saliva and by various aspects of a person's nutrition) should be investigated in clinical studies.

In vivo reliability of 3D cephalometric landmark determination on magnetic resonance imaging: a feasibility study.

OBJECTIVE: 3D cephalometric analysis performed on cone-beam or multi-slice computed tomography (CBCT, MSCT) has superior diagnostic value compared to 2D cephalometry based on radiographs. However, this comes at the expense of increased radiation risks for the predominantly young patients. Magnetic resonance imaging (MRI) has the potential to overcome this diagnostic dilemma but has not been established for 3D cephalometry so far. Since landmark reliability forms the basis for 3D cephalometry, we evaluated the in vivo reliability of established 3D landmarks using MRI. MATERIALS AND METHODS: Sixteen orthodontic patients underwent MRI at 3 Tesla using a 0.5 mm 3D sequence. On each MRI scan, 44 cephalometric landmarks were determined. Image analysis was performed twice by two independent observers. Intra- and inter-rater agreement was assessed by mean measurement errors and intraclass correlation coefficients (ICCs). Measurement errors were calculated as Euclidean distances and distances for x-, y-, and z-coordinates. RESULTS: Overall, MRI-based 3D cephalometric landmarks revealed a high reliability comparable to prior in vivo studies using CBCT/MSCT. Intra- and inter-rater ICCs were consistently higher than 0.9. Intra-rater comparisons showed mean measurement differences (ranges) of 0.87 mm (0.41-1.63) for rater I and 0.94 mm (0.49-1.28) for rater II. Average inter-rater difference was 1.10 mm (0.52-2.29). Distinct differences in reliability between the various landmarks were observed, corresponding well with the landmarks' specific shapes. CONCLUSIONS: The present study demonstrates that MRI enables reliable determination of 3D cephalometric landmarks in vivo. CLINICAL RELEVANCE: This study emphasizes the potential of MRI to perform treatment planning and monitoring in orthodontics as well as oral and maxillofacial surgery without radiation exposure.

Abrasion of Pro Seal® and Opal® Seal™ by professional tooth cleaning protocols: results from an in vitro study and a randomized controlled trial.

BACKGROUND: The integrity of orthodontic surface sealants after professional tooth cleaning (PTC) has previously only been evaluated in vitro. Recently, we have shown that optical coherence tomography (OCT) can successfully be used for the longitudinal assessments of sealant thickness in vitro and in vivo. OBJECTIVES: Thus, the aim of the present study was to assess the sealant thickness after PTC in vitro and in vivo by OCT. TRIAL DESIGN: Single-centre four-arm parallel-group randomized controlled trial. METHODS: Ninety-six extracted human teeth were randomly assigned to the surface sealants Pro Seal® (PS) and Opal® Seal™ (OS) and to PTC protocols: (1) polishing with brush and prophy paste (Cleanic®) or (2) erythritol air-polishing. Sealant thickness was assessed by OCT immediately after application (baseline), after thermocycling and after polishing for totals of 5, 10, 15, 30, 60, 90, and 120 seconds. Additionally, a clinical trial was conducted. Therefore, using a split-mouth design, quadrants of 20 patients and PTC protocols were randomized by an external randomization centre using computer generated tables to assign the surface sealants and PTC protocols. Sealant thicknesses were analysed at baseline, before and after PTC. Due to the optical properties of sealants, a complete blinding was not feasible. RESULTS: In vitro both sealants revealed significant layer thickness losses after both PTC protocols. PS lost 0.77 µm/s [95% CI (confidence interval): 0.67, 0.87] from air-polishing and 0.43 µm/s (95% CI: 0.37, 0.49) from polishing with brush while OS lost 0.44 µm/s (95% CI: 0.32, 0.55) from air-polishing and 0.79 µm/s (95% CI: 0.68, 0.89) from polishing with brush of layer thickness. Sealant thickness loss of was significantly higher after erythritol air-polishing for PS and after polishing with brush for OS. The results of a concurrent randomized controlled trial (RCT) were comparable to those achieved in the in vitro part of this study. LIMITATIONS: Long-term surface sealant abrasion should be validated by additional RCTs. CONCLUSIONS: For PTC on surface sealant treated teeth, low abrasive protocols should be used. Air-polishing should be avoided on PS protected teeth and polishing with brush on OS treated teeth. TRIAL REGISTRATION: ClinicalTrials.gov NCT03753256.

In vivo comparison of MRI- and CBCT-based 3D cephalometric analysis: beginning of a non-ionizing diagnostic era in craniomaxillofacial imaging?

OBJECTIVES: To evaluate whether magnetic resonance imaging (MRI) can serve as an alternative diagnostic tool to the "gold standard" cone-beam computed tomography (CBCT) in 3D cephalometric analysis. METHODS: In this prospective feasibility study, 12 patients (8 males, 4 females; mean age ± SD, 26.1 years ± 6.6) underwent 3D MRI and CBCT before orthognathic surgery. 3D cephalometric analysis was performed twice by two independent observers on both modalities. For each dataset, 27 cephalometric landmarks were defined from which 35 measurements (17 angles, 18 distances) were calculated. Statistical analyses included the calculation of Euclidean distances, intraclass correlation coefficients (ICCs), Bland-Altman analysis, and equivalence testing (linear mixed effects model) with a predefined equivalence margin of ± 1°/1 mm. RESULTS: Analysis of reliability for CBCT vs. MRI (intra-rater I/intra-rater II/inter-rater) revealed Euclidean distances of 0.86/0.86/0.98 mm vs. 0.93/0.99/1.10 mm for landmarks, ICCs of 0.990/0.980/0.986 vs. 0.982/0.978/0.980 for angles, and ICCs of 0.992/0.988/0.989 vs. 0.991/0.985/0.988 for distances. Bland-Altman analysis showed high levels of agreement between CBCT and MRI with bias values (95% levels of agreement) of 0.03° (- 1.49; 1.54) for angles and 0.02 mm (- 1.44; 1.47) for distances. In the linear mixed effects model, the mean values of CBCT and MRI measurements were equivalent. CONCLUSION: This feasibility study indicates that MRI enables reliable 3D cephalometric analysis with excellent agreement to corresponding measurements on CBCT. Thus, MRI could serve as a non-ionizing alternative to CBCT for treatment planning and monitoring in orthodontics as well as oral and maxillofacial surgery. KEY POINTS: • Clinically established 3D cephalometric measurements performed on MRI are highly reliable and show an excellent agreement with CBCT (gold standard). • The MRI technique applied in this study could be used as a non-ionizing diagnostic tool in orthodontics as well as oral and maxillofacial surgery. • Since most patients benefiting from 3D cephalometry are young in age, the use of MRI could substantially contribute to radiation protection and open up new possibilities for treatment monitoring.

Demineralization detection in orthodontics using an ophthalmic optical coherence tomography device equipped with a multicolor fluorescence module.

OBJECTIVES: Demineralizations such as white spot lesions are among the most prevalent side effects during orthodontic treatment. Fluorescence devices, including quantitative light-induced fluorescence (QLF), exploiting the intrinsic fluorescence of enamel and teeth and most recently optical coherence tomography (OCT) were introduced for early demineralization detection. In addition to near-infrared OCT scanning, multicolor modules allow for imaging with different laser wavelengths and the detection of reflective- and fluorescent light. The aim of this study was to evaluate a modified multicolor ophthalmic OCT device for the detection of early carious lesions in vitro and in vivo. MATERIALS AND METHODS: Twenty-seven extracted lesion free human teeth were randomly assigned to three different demineralization protocols. Carious lesion detection was performed using macrophotography, OCT, and reflectance/fluorescence imaging using green laser and blue laser light. In addition, teeth of 5 orthodontic patients were OCT scanned, and fluorescence imaging using blue laser light was performed to assess demineralization after orthodontic therapy. RESULTS: Both in vitro and in vivo, OCT allowed for precise determination of lesion depth and enamel loss. Fluorescence imaging using blue laser light was most sensitive for the detection of early demineralization in vitro and in vivo. However, established and severe demineralizations were also reliably detected by macrophotography in vitro and in vivo. CONCLUSION: Demineralization can be detected with high sensitivity using blue fluorescence imaging with multicolor OCT devices. CLINICAL RELEVANCE: In the future, OCT fluorescence imaging might be considered for longitudinal monitoring of dental hard tissue during orthodontic treatment in clinical trials.

Comparison of crevicular fluid cytokine levels after the application of surface sealants : A randomized trial.

PURPOSE: Surface sealants are widely used in orthodontic practice to avoid enamel decalcifications in patients treated with fixed orthodontic appliances. While their clinical benefit was tested in several studies, their biocompatibility has been evaluated to a lesser extent. Therefore, the aim of this randomized prospective study was to evaluate possible adverse biological effects of three commonly used surface sealants and a bonding primer on gingival tissues by analysing cytokines in crevicular fluid of orthodontic patients after the application of surface sealants. METHODS: A single centre parallel trial was conducted. Using a split-mouth design quadrants of 15 patients requiring orthodontic treatment with fixed appliances were randomized to one of three commonly used surface sealants (Pro Seal®, Opal®Seal™, Protecto®CaF2Nano) and a bonding primer (Transbond™ XT). Interleukin (IL)-8 and IL-10 levels in crevicular fluids of the individual quadrants were assessed at four different time points (before application, and at 30, 60 and 90 min after application). RESULTS: In all, 60 quadrants of 15 patients were randomized (Pro Seal® n = 15, Opal®Seal™ n = 15, Protecto®CaF2Nano n = 15, Transbond™ XT n = 15) and analysed. No significant changes for IL-8 or IL-10 levels in crevicular fluid after the application of surface sealants or bonding primer were detected. However, interpatient variability was high. No further clinical side effects were detected. CONCLUSIONS: Commonly used pre-bonding surface sealants (Pro Seal®, Opal®Seal™) do not appear to have a significant impact on inflammatory cytokines levels of crevicular fluid and do not appear to contribute to sensitization or hypersensitivity events.

Accuracy of patient-specific implants and additive-manufactured surgical splints in orthognathic surgery - A three-dimensional retrospective study.

INTRODUCTION: Because of the many limitations of conventional surgery planning for the treatment of orthognathic deformities, as well as advancements in computer-assisted planning, there is an urgent need for technical devices that transfer the surgical plan into the operating theatre. In this regard, additive-manufactured, patient-specific implants (PSI) and additive-manufactured interocclusal splints represent promising approaches. The aim of this retrospective study was to compare the accuracy of these two devices, with regard to preoperative virtual treatment planning for maxillary Le-Fort I advancement surgery using IPS CaseDesigner®, and based on a new analysis method without the use of landmarks. MATERIALS AND METHODS: A retrospective evaluation of 18 class III patients (n(PSI) = 9; n(splint) = 9), who had undergone virtually planned orthognathic surgery (including maxillary Le Fort I advancement), was performed. The preoperative treatment plan and the postoperative outcome were combined to calculate the translational and rotational discrepancies between the 3D planning and the actual surgical outcome. RESULTS: For the PSI and splint groups the accuracy of left/right positioning was 0.51 mm ± 0.48 and 1.11 mm ± 1.32 respectively. The accuracy of anterior/posterior positioning was 0.39 mm ± 0.26 and 1.42 mm ± 0.87, and that of up/down-positioning was 0.44 mm ± 0.31 and 0.62 mm ± 0.47. The rotational discrepancies were less than 2° in both groups. CONCLUSION: The findings demonstrate that both PSI and splint approaches can accurately transfer the virtual planning into the operating theatre. However, PSIs show an overall higher accuracy, especially for anterior/posterior translational movement (p < 0.002).

Effects of staining and polishing on different types of enamel surface sealants.

OBJECTIVE: To assess surface discoloration of four enamel sealants based on different chemical compositions after exposure to artificial aging and staining solutions. Furthermore, their cleanability after polishing will be evaluated. MATERIALS AND METHODS: Selected sealants were a composite resin-based sealant with fillers (Pro Seal), a composite resin-based sealant without fillers (Light BondSealant), a resin-modified glass ionomer-based sealant (ClinproXT Varnish) and a silicon-based sealant (Protecto). Natural teeth served as medium. Immersion solutions were water, juice, tea, and turmeric. In a standardized setting, all samples were measured seven times with a spectroradiometer (Photoresearch PR670) at baseline, after thermocycling; 7 days; 2 and 4 weeks of immersion; and after finally polishing. RESULTS: Thermocycling had no significant effect on color stability. After exposure to staining solutions, all sealed surfaces showed significant color changes. Color change predominately occurred for all sealants in the first week of staining (P ≤ .01). Best resistance to staining decreased as follows: Protecto > Light Bond Sealant > ProSeal > Clinpro XT Varnish. Surface cleaning by polishing significantly reduced the color change. CONCLUSION: Sealed enamel surfaces are prone to discoloration, which is most prominent in filled composite and glass-ionomer-based sealants. Staining can be reduced by polishing; however, in this in vitro setting the original color could not be restored. CLINICAL SIGNIFICANCE: Enamel sealants might exert adverse effects in terms of discoloration. This should be taken into consideration by clinicians and patients, particularly when sealants are applied in esthetically critical areas.

3D cephalometric analysis using Magnetic Resonance Imaging: validation of accuracy and reproducibility.

The aim of this study was to validate geometric accuracy and in vivo reproducibility of landmark-based cephalometric measurements using high-resolution 3D Magnetic Resonance Imaging (MRI) at 3 Tesla. For accuracy validation, 96 angular and 96 linear measurements were taken on a phantom in 3 different positions. In vivo MRI scans were performed on 3 volunteers in five head positions. For each in vivo scan, 27 landmarks were determined from which 19 angles and 26 distances were calculated. Statistical analysis was performed using Bland-Altman analysis, the two one-sided tests procedure and repeated measures one-way analysis of variance. In comparison to ground truth, all MRI-based phantom measurements showed statistical equivalence (p < 0.001) and an excellent agreement in Bland-Altman analysis (bias ranges: -0.090-0.044°, -0.220-0.241 mm). In vivo cephalometric analysis was highly reproducible among the five different head positions in all study participants, without statistical differences for all angles and distances (p > 0.05). Ranges between maximum and minimum in vivo values were consistently smaller than 2° and 2 mm, respectively (average ranges: 0.88°/0.87 mm). In conclusion, this study demonstrates that accurate and reproducible 3D cephalometric analysis can be performed without exposure to ionizing radiation using MRI.

Assessing abrasion of orthodontic surface sealants using a modified ophthalmic optical coherence tomography device.

OBJECTIVE: Optical coherence tomography (OCT) is a clinical standard in ophthalmology. Currently, its application in dentistry is gaining increasing interest. In this study, we tested the possibility to use a modified commercially available spectral domain OCT (SD-OCT) to assess the layer thickness of orthodontic surface sealants. MATERIALS AND METHODS: Reference samples of surface sealants for calibration and repeatability testing were measured using a micrometer screw. SD-OCT measurements were compared with micro-CT and light microscopic analyses. After validating the calibration of the SD-OCT, surface sealant layer thickness after aging (thermo cycling) and simulation of professional tooth cleaning (PTC) was assessed using the SD-OCT on 45 extracted teeth assigned to three test groups (n = 15 each): Light Bond™ Sealant, Pro Seal®, and Opal® Seal. RESULTS: SD-OCT showed excellent repeatability and accuracy for measurements of surface sealant layer thickness. Compared with micro-CT, SD-OCT showed better accordance with the reference measurements. The analysis of surface sealants after thermo cycling and PTC revealed poor resistance of Light Bond after only aging and demonstrated substantial wear of all sealants after aging and PTC. CONCLUSION: Imaging using commercially available ophthalmic SD-OCT might represent a suitable non-invasive methodology for longitudinal assessments of surface sealant layer thickness in vitro and in vivo. CLINICAL RELEVANCE: SD-OCT might be a suitable non-invasive method for longitudinal assessments of surface sealant durability in clinical trials.

Surgery-first approach in orthognathic surgery: Psychological and biological aspects - A prospective cohort study.

INTRODUCTION: The aim of this pilot study was to investigate psychological and biological changes after application of a surgery-first orthognathic treatment approach. METHODS: A prospective cohort study of 9 patients (6 women and 3 men; mean age 26.7 years) suffering from skeletal Class II and III deformities was conducted. Skeletal changes from pre-to post-treatment were analyzed based on data acquired by use of cone-beam computed tomography (CBCT). Psychological changes were analyzed using the orthognathic quality of life (OQLQ) questionnaire, Sense of Coherence 29-item scale (SOC-29) and longitudinal day-to-day questionnaire. For biological evaluation, concentrations of IL-1 ß, IL-6, TGF ß 1-3, MMP-2 and VEGF were assessed in crevicular fluid by bead-based multiplex assays at one preoperative and various postoperative time points. RESULTS: A significant improvement (P = 0.015) in quality of life, as measured with the OQLQ, was observed between baseline and 3 months post-surgery. The most affected dimensions were: facial aesthetics (p = 0.022), oral function (p = 0.051) and social aspects (p = 0.057). Sense of coherence (SOC) significantly improved after treatment by 9 points (P = 0.029). Despite the significant improvement in OQLQ and SOC during the course of the study, the personal experience of appearance varied distinctly in course and intensity. In accordance with the temporal pattern of fracture healing, the analysis of crevicular fluid revealed an increase in pro-resorptive factors (IL-1 ß, IL-6 and MMP-2) at early postoperative time points, while remodeling factors (members of the TGF-ß superfamily) were detected at later postoperative time points. CONCLUSIONS: Orthognathic treatment using the surgery-first approach has a positive impact on patient's psychosocial status. Accelerated tooth movement after surgery might, to a certain extent, be due to elevated levels of bone remodeling factors with overlapping functions during fracture healing and tooth movement.

Lateral cephalometric analysis for treatment planning in orthodontics based on MRI compared with radiographs: A feasibility study in children and adolescents.

OBJECTIVE: The objective of this prospective study was to evaluate whether magnetic resonance imaging (MRI) is equivalent to lateral cephalometric radiographs (LCR, "gold standard") in cephalometric analysis. METHODS: The applied MRI technique was optimized for short scanning time, high resolution, high contrast and geometric accuracy. Prior to orthodontic treatment, 20 patients (mean age ± SD, 13.95 years ± 5.34) received MRI and LCR. MRI datasets were postprocessed into lateral cephalograms. Cephalometric analysis was performed twice by two independent observers for both modalities with an interval of 4 weeks. Eight bilateral and 10 midsagittal landmarks were identified, and 24 widely used measurements (14 angles, 10 distances) were calculated. Statistical analysis was performed by using intraclass correlation coefficient (ICC), Bland-Altman analysis and two one-sided tests (TOST) within the predefined equivalence margin of ± 2°/mm. RESULTS: Geometric accuracy of the MRI technique was confirmed by phantom measurements. Mean intraobserver ICC were 0.977/0.975 for MRI and 0.975/0.961 for LCR. Average interobserver ICC were 0.980 for MRI and 0.929 for LCR. Bland-Altman analysis showed high levels of agreement between the two modalities, bias range (mean ± SD) was -0.66 to 0.61 mm (0.06 ± 0.44) for distances and -1.33 to 1.14° (0.06 ± 0.71) for angles. Except for the interincisal angle (p = 0.17) all measurements were statistically equivalent (p < 0.05). CONCLUSIONS: This study demonstrates feasibility of orthodontic treatment planning without radiation exposure based on MRI. High-resolution isotropic MRI datasets can be transformed into lateral cephalograms allowing reliable measurements as applied in orthodontic routine with high concordance to the corresponding measurements on LCR.

Inhibition of AXUD1 attenuates compression-dependent apoptosis of cementoblasts.

OBJECTIVES: Root resorptions are common undesirable side effects of orthodontic treatment. In most patients, these defects are repaired by cementoblasts. However, in 1-5 % of patients, the repair fails. The repair mechanism is not well understood. Apoptosis of cementoblasts might contribute to an impaired repair of root resorptions induced by orthodontic forces. MATERIALS AND METHODS: To gain insight into putative molecular pathways leading to compression-induced apoptosis of human primary cementoblasts (HPCBs), three independent cell populations were subjected to compressive loading at 5, 20, and 30 g/cm2 for 1, 6, and 10 h. The mRNA expression of AXUD1, a novel pro-apoptotic gene, was monitored by quantitative reverse transcription PCR (qRT-PCR). To identify a possible function in compression-dependent apoptosis, AXUD1 was silenced in cementoblasts using an siRNA approach. Apoptosis of cementoblasts was measured by annexin V staining and flow cytometry. The phosphorylation of c-Jun-N-terminal kinases (JNKs) was investigated by Western blotting. RESULTS: AXUD1 was significantly induced in a time- and force-dependent manner. The rate of apoptotic HPCBs increased by 20-40 % after 10 h of compression (30 g/cm2). Phosphorylation of JNKs was detected after 10 h at 30 g/cm2. SiRNA-mediated knockdown of AXUD1 led to decreased phosphorylation of JNKs and reduced apoptosis rates in compressed HPCBs. CONCLUSIONS: Compression-induced apoptosis of HPCBs is mediated by AXUD1 via a JNK-dependent pathway. CLINICAL RELEVANCE: AXUD1-dependent apoptosis of human cementoblasts might contribute to an impaired repair of root resorptions during orthodontic tooth movement. Further studies are needed to develop treatment strategies aiming to minimize root resorption during orthodontic tooth movement.

Efficiency of powered systems for interproximal enamel reduction (IER) and enamel roughness before and after polishing-an in vitro study.

OBJECTIVE: This aims to evaluate the efficiency of three different powered interproximal enamel reduction (IER) systems and to assess enamel roughness before and after polishing using different polishing times. MATERIAL AND METHODS: Four metal strips of the G5 ProLign Set (swissdentacare, SDC, Grancia, Switzerland), four segmental discs of the ASR-Set 4594 and two sonic tips of the SonicLine Set (both Gebr. Basseler GmbH & Co. KG, Komet, Lemgo, Germany) were evaluated. Human extracted incisors served as the medium. Enamel reduction was determined in five intervals of 15 s each. Polishing was performed for 15 and 30 s using the manufacturers' recommended polishing systems. Enamel roughness (Ra) was quantitatively assessed by confocal laser scanning microscopy (CLSM). RESULTS: Significant differences in terms of enamel reduction were found among the working ends of all tested systems. The time needed to remove 0.1, 0.2 and 0.3 mm of enamel was determined. Surface analysis showed significantly higher mean Ra values for nine out of ten working ends before polishing. This was still the case for five working ends after 15 s and for two after 30 s of polishing. CONCLUSION: The graining and the system used have a significant influence on enamel reduction. The time needed for polishing depends on the last working end used; a polishing time of 30 s is not always appropriate. CLINICAL RELEVANCE: Knowledge about the cutting efficiency of powered IER working ends might help the clinician to estimate better the amount of enamel reduction during the stripping process.

One-stage tooth-borne distraction versus two stage bone-borne distraction in surgically assisted maxillary expansion (SARME).

OBJECTIVE: To evaluate and compare the effects of tooth-borne and bone-borne distraction devices in surgically assisted maxillary expansion (SARME) on dental and skeletal structures. STUDY DESIGN: A sample of 33 skeletally mature patients with transverse maxillary deficiencies was examined with cone beam computed tomography (CBCT) before and 3 months after surgery. Fourteen patients were treated with tooth-borne devices and 19 patients with bone-borne devices. RESULTS: Dental crown expansion in the first premolars did not differ significantly between the two groups, and median expansion was 5.55 mm (interquartile range [IQR] 5.23) in the tooth-borne device group and 4.6 mm (IQR 3.4) in the bone-borne device group. In the first molars, crown expansion and lateral tipping were significantly greater in the tooth-borne device group (P ≤ .02). The median skeletal nasal isthmus increase was significantly more in the bone-borne device group at 3.0 mm than in the tooth-borne device group at 0.98 mm (P ≤ .02). CONCLUSIONS: Both tooth-borne and bone-borne devices are effective treatment modalities to correct maxillary transverse deficiencies. Bone-borne devices produced greater widening of the skeletal nasal floor and fewer dental side effects in the first molars.

Biological evaluation of enamel sealants in an organotypic model of the human gingiva.

OBJECTIVES: Various sealant materials have been suggested to decrease decalcification during orthodontic treatment. However, only a few in vitro studies on the cytotoxicity of resinous pit and fissure sealants have been published, and to the best of our knowledge no similar studies are available for the enamel sealants used in orthodontics. Therefore, we aimed to characterize the possible adverse effects of enamel sealants, especially on the gingival epithelium. METHODS: Organotypic cultures of the human gingival mucosa were used to assess the possible impact of six enamel sealants. Differentiation and apoptosis were determined by immunofluorescent staining. The pro-inflammatory cytokines IL-1ß and IL-6 were quantified by ELISA. Cytotoxicity was measured using MTS assays in monolayer cultures of human gingival fibroblasts. Leaching of monomers from enamel sealants was quantified using HPLC. RESULTS: The differentiation of the organotypic gingival mucosa remained unaffected. All under-cured and several standard-cured sealants (Light Bond™ Sealant, Light Bond™ Filled Sealant, and L.E.D. Pro Seal®) significantly induced apoptosis in the organotypic model. Light Bond™ Sealant, Light Bond™ Filled Sealant, and L.E.D. Pro Seal® caused a significant induction of pro-inflammatory cytokines. Reducing curing time had an influence on cytotoxicity in monolayer cultures of primary human oral cells. All resin-based sealants leached monomers. SIGNIFICANCE: Enamel sealants might exert adverse effects on the gingival epithelium. Due to the vicinity of the enamel sealant to the gingival epithelium, and the large surface area of applied sealants, these materials should be carefully applied and sufficiently cured.

Gene expression profile of compressed primary human cementoblasts before and after IL-1ß stimulation.

OBJECTIVES: Root resorptions due to a reduced repair function of cementoblasts are common side effects during orthodontic tooth movement (OTM). The mechanisms, which lead to an impaired cementoblast function, are not fully understood. Therefore, we aimed to investigate changes in the gene expression of cementoblasts during mechanical stimulus under inflammatory conditions. MATERIALS AND METHODS: Human primary cementoblasts (HPCB) were exposed to compression for 6 h or stimulation with IL-1ß for 96 h and subsequent 6 h compression. Genome-wide expression analysis was performed using microarray analysis. Prominent gene expression alterations (COX2, AXUD1, FOSB, CCL2, IFI6, and PTGES) were verified by quantitative RT-PCR (qRT-PCR) in two HPCB populations. A caspase 3/7 activity assay was used to determine caspase-3 and caspase-7 activity in stressed cells. RESULTS: Gene expression cluster analysis revealed apoptosis as an important process induced under both conditions. Apoptosis (pro- and anti-apoptotic) related gene expression was most relevant after pro-inflammatory stimulation and compression. qRT-PCR analysis confirmed significant up-regulation of COX2, AXUD1, and FOSB in both HPCB populations after compression, while selected genes significantly increased after pro-inflammatory stimulation and compression. Compression of cementoblasts increased caspase. The combination of pro-inflammatory stimulation and compression led to a slightly smaller increase of caspase activity. CONCLUSIONS: Gene ontology analysis showed that compressed HPCB up-regulate genes that are associated with apoptosis. Combining compression with a pro-inflammatory stimulus (IL-1ß) augmented the positive regulation of apoptosis-related pathways. The induction of apoptosis related gene expression (pro- and anti-apoptotic genes) in cementoblasts suggests an involvement of apoptosis in cementoblast regulation during OTM. CLINICAL RELEVANCE: As apoptosis is induced in HPCB after compression and inflammation, it is conceivable that HPCB cell death might contribute to root resorptions due to a loss of repair activity of cementoblasts. Further studies should be conducted to clarify the implication of the identified genes on root resorptions in order to develop therapeutic strategies to prevent a shortening of roots.