Mandibular cortical bone remodeling characteristics in patients with extraction: A cone-beam computed tomography study.

INTRODUCTION: This study evaluated the labial and lingual cortical bone remodeling characteristics of mandibular central incisors after retraction, which remain controversial among orthodontists. METHODS: Cortical bone remodeling and central incisor movement of 33 patients (aged 23.64 ± 4.30 years) who underwent mandibular first premolar extraction and incisor retraction at the crestal (S1), midroot (S2), and apical (S3) levels were analyzed using superimposed cone-beam computed tomography images on the basis of voxel-based registration of the mandibular stable region. Multivariate linear regression was used to explore the relationships between labial bone remodeling/tooth movement (BT) ratios and factors such as the ANB angle, mandibular plane angle (Mp-SN), and incisor movement patterns. The patients were divided into 4 groups according to the lingual cortical bone remodeling condition and the relationship between posttreatment incisor roots and the original lingual cortical bone border. At the 3 levels (S1, S2, and S3), the classifications of cortical bone remodeling of the mandibular incisors were calculated; t tests were used to compare the amount of labial and lingual bone remodeling, BT ratios, and lingual bone remodeling/root over the original border (BRo) ratios. RESULTS: The mean labial BT ratios at all 3 levels were close to 1. Multivariate linear regression indicated that the tooth movement pattern negatively correlated with the BT ratio at the S2 and S3 levels (P <0.05). Lingual bone apposition occurs when the root penetrates the original lingual cortical bone border in most patients. BRo ratios can more accurately reflect the inherent remodeling ability of the lingual cortical bone than BT ratios. The mean lingual BRo ratios were (1) S1 level: mandibular left central incisor (T31), 0.87 ± 0.25 and mandibular right incisor (T41), 0.86 ± 0.25; (2) S2 level: T31, 0.81 ± 0.12 and T41, 0.80 ± 0.22; and (3) S3 level: T31, 0.76 ± 0.20 and T41, 0.83 ± 0.26. There was no significant difference between labial BT ratios and lingual BRo ratios at the S2 and S3 levels. CONCLUSIONS: The amount of labial cortical bone resorption caused by mandibular incisor retraction showed varied relationships with the amount of tooth movement. Bodily retraction may decrease the labial BT ratios at the S2 and S3 levels. Active lingual cortical bone apposition occurred when the roots penetrated the original lingual border and exhibited strong remodeling ability.

Inclination of mandibular incisors and symphysis in severe skeletal class III malocclusion.

OBJECTIVE: The aim of this study was to systematically explore the inclination of the lower central incisor and symphysis in alveolar bone in severe skeletal class III patients. MATERIALS AND METHODS: A total of 198 severe skeletal class III patients (ANB ≤ -4°) who underwent combined orthodontic and orthognathic treatment were divided into three groups based on the mandibular plane angle (MP-SN). Pretreatment lateral cephalograms were analysed and compared among the three groups. We also assessed cone-beam computed tomography (CBCT) images of 11 samples to investigate the reliability of the cephalometric analysis. RESULTS: ANOVA showed no statistically significant differences in the angle between the long axis of the mandibular symphysis and the long axis of the lower central incisor (MIA) among the low-angle, normal-angle and high-angle groups (P > 0.05), while significant differences were found in the angle between the axis of the lower incisor and the mandibular plane (IMPA) among the three groups (P < 0.001). The mean IMPA decreased with increasing MP-SN in the 198 patients. The mean MIA in the low-angle and normal-angle groups was 3.70° and 3.52°, respectively, while the value (2.33°) was smaller in the high-angle group. Paired-samples t test showed no statistically significant differences between the cephalometric and CBCT measurements of the MP-SN, the angle between the mandibular plane and the Frankfort plane (FH-MP) and the MIA (P > 0.05). CONCLUSIONS: In severe skeletal class III patients, the long axis of the lower central incisor was highly consistent with the long axis of the mandibular symphysis, which was more obvious in the high-angle subjects. The MIA reflects the physiological inclination of the lower central incisor better than the IMPA.

Maxillary cortical bone remodeling characteristics in extraction patients: A cone-beam computed tomography study.

INTRODUCTION: This study aimed to evaluate labial and palatal cortical bone remodeling (BR) characteristics and related aspects of maxillary incisors after retraction, as these aspects are still controversial among orthodontists. METHODS: Cortical BR and incisor movement of 44 patients (aged 26.18 ± 4.71 years) who underwent maxillary first premolar extraction and incisor retraction were analyzed using superimposed cone-beam computed tomography images. Labial BR/tooth movement (BT) ratios at the crestal, midroot (S2), and apical (S3) levels were compared using the Friedman test and pairwise comparisons. Multivariate linear regressions were used to explore the relationships between the labial BT ratio and several factors, including age, ANB angle, mandibular plane angle, and incisor movement patterns. According to the type of palatal cortical BR observed, the patients were divided into 3 groups: type I (no BR without root penetration of the original palatal border [RPB]), type II (BR with RPB), and type III (no BR with RPB). Student's t test was used to compare the type II and III groups. RESULTS: The mean labial BT ratios at all levels were <1.00 (0.68-0.89). This value at the S3 level was significantly smaller than that at the crestal and S2 levels (P <0.01). Multivariate linear regression indicated that the tooth movement pattern negatively correlates with the BT ratio at S2 and S3 levels (P <0.01). Type I was noted in 40.9% of the patients, and similar proportions exhibited type II (29.5%, 25.0%) or type III remodeling (29.5%, 34.1%). The retraction distance of the incisors in type III patients was significantly larger than in type II patients (P <0.05). CONCLUSIONS: The amount of cortical BR secondary to maxillary incisor retraction is less than the tooth movement. Bodily retraction may lead to lower labial BT ratios at the S3 and S2 levels. Roots penetrating the original border of the cortical plate are necessary for palatal cortical BR initiation.

Functional Surface Coatings on Orthodontic Appliances: Reviews of Friction Reduction, Antibacterial Properties, and Corrosion Resistance.

Surface coating technology is an important way to improve the properties of orthodontic appliances, allowing for reduced friction, antibacterial properties, and enhanced corrosion resistance. It improves treatment efficiency, reduces side effects, and increases the safety and durability of orthodontic appliances. Existing functional coatings are prepared with suitable additional layers on the surface of the substrate to achieve the abovementioned modifications, and commonly used materials mainly include metal and metallic compound materials, carbon-based materials, polymers, and bioactive materials. In addition to single-use materials, metal-metal or metal-nonmetal materials can be combined. Methods of coating preparation include, but are not limited to, physical vapor deposition (PVD), chemical deposition, sol-gel dip coating, etc., with a variety of different conditions for preparing the coatings. In the reviewed studies, a wide variety of surface coatings were found to be effective. However, the present coating materials have not yet achieved a perfect combination of these three functions, and their safety and durability need further verification. This paper reviews and summarizes the effectiveness, advantages and disadvantages, and clinical perspectives of different coating materials for orthodontic appliances in terms of friction reduction, antibacterial properties, and enhanced corrosion resistance, and discusses more possibilities for follow-up studies as well as for clinical applications in detail.

Advances in orthodontic clear aligner materials.

Rapid technological improvements in biomaterials, computer-aided design (CAD) and manufacturing (CAM) have endorsed clear aligner therapy (CAT) as a mainstay of orthodontic treatment, and the materials employed for aligner fabrication play an all-important role in determining the clinical performance of clear aligners. This narrative review has attempted to comprehensively encompass the entire gamut of materials currently used for the fabrication of clear aligners and elucidate their characteristics that are crucial in determining their performance in an oral environment. Historical developments and current protocols in aligner fabrication, features of contemporary bioactive materials, and emerging trends related to CAT are discussed. Advances in aligner material chemistry and engineering possess the potential to bring about radical transformations in the therapeutic applications of CAT; in the absence of which, clear aligners would continue to underperform clinically, due to their inherent biomechanical constraints. Finally, while innovations in aligner materials such as shape memory polymers, direct three-dimensional (3D) printed clear aligners and bioactive materials combined with clear aligner materials are essential to further advance the applications of CAT; increased awareness of environmental responsibilities among aligner manufacturers, aligner prescribing clinicians and aligner users is essential for better alignment of our climate change goals towards a sustainable planet.

Preparation and Characterization of a Polyetherketoneketone/Hydroxyapatite Hybrid for Dental Applications.

Here, we developed a new synthetic method for the production of a new class of polymeric inorganic hybrid biomaterial that has potential for dental implant applications and, in general, other orthopedic applications owing to its excellent mechanical properties and biomechanical compatibility. The new hybrid biomaterial is a composite consisting of polyetherketoneketone (PEKK) and hydroxyapatite (HA). This hybrid material boasts several unique features, including its high HA loading (up to 50 wt%), which is close to that of natural human bone; the homogeneous HA distribution in the PEKK matrix without phase separation; and the fact that the addition of HA has no effect on the molecular weight of PEKK. Nanoindentation analysis was used to investigate the mechanical properties of the composite, and its nano/microstructure variations were investigated through a structural model developed here. Through nanoindentation technology, the newly developed PEKK/HA hybrid biomaterial has an indentation modulus of 12.1 ± 2.5 GPa and a hardness of 0.42 ± 0.09 GPa, which are comparable with those of human bone. Overall, the new PEKK/HA biomaterial exhibits excellent biomechanical compatibility and shows great promise for application to dental and orthopedic devices.

Mechanical Properties and Biocompatibility of Ti-doped Diamond-like Carbon Films.

A series of Ti/Ti-diamond-like carbon (Ti-DLC) films was deposited onto monocrystalline Si substrates by dual-magnetron sputtering. The mechanical properties, chemical composition, and microstructure of the films were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and nanoindentation. The biocompatibility of the Ti-DLC films was evaluated via cell viability testing. The TiC phase was formed at a Ti content of 4.43 atom %, and the surface roughness gradually increased as the Ti content increased. Ti-DLC films with 17.13 atom % Ti exhibited superior adhesion strength and surface hardness. The optical densities (ODs) of the different Ti-DLC films were similar, indicating that the films exhibit biocompatibility regardless of the Ti content. Overall, doping DLC films with Ti provides a better film for medical applications, as it improves the mechanical properties, as evidenced by the elastic modulus, hardness, adhesion strength, and surface roughness of the coating, and maintains ideal biocompatibility.

Biological Safe Gold Nanoparticle-Modified Dental Aligner Prevents the Porphyromonas gingivalis Biofilm Formation.

Oral microbiology could directly influence overall health. Porphyromonas gingivalis (P. gingivalis) is a highly pathogenic bacterium that causes periodontitis and other related systematic diseases, including Alzheimer's disease. Orthodontic devices (e.g., invisalign aligner) is commonly used in populations with periodontitis who are also at a high risk of systematic diseases. In this study, newly explored antibacterial 4,6-diamino-2-pyrimidinethiol-modified gold nanoparticles (AuDAPT) were coated onto aligners. The coated aligners showed favorable antibacterial activity against P. gingivalis. In the presence of the coated aligner, the number of planktonic cells was decreased, and biofilm formation was prevented. This material also showed favorable biocompatibility in vivo and in vitro. This study reveals a new method for treating oral P. gingivalis by coating aligners with AuDAPT, which has typical advantages compared to other treatments for both periodontitis and related systematic diseases.

Gold Nanoclusters-Coated Orthodontic Devices Can Inhibit the Formation of Streptococcus mutans Biofilm.

Oral health is an issue that has attracted increasing attention recently. Poor oral hygiene may induce the formation of oral biofilm on orthodontic devices, and cause gingivitis and dental caries. Here, we present a strategy for modifying orthodontic devices (e.g., invisalign aligner) with quaternary ammonium (QA)-modified gold nanoclusters (QA-GNCs) as an antibiotic reagent to prevent bacterial contamination and biofilm formation. The QA-GNCs-coated aligner can efficiently inhibit the adhesion of cariogenic pathogenic Streptococcus mutans and the formation of biofilm. Moreover, the antibacterial activity of the coated QA-GNCs can be maintained for at least 3 months and after repeated usage (>3 cycles). Furthermore, the QA-GNCs coating shows excellent biosafety confirmed by the cell viability test, the hemolysis assay, and animal experiments. Our strategy for antibacterial coating has the advantages of broad applications, low cost, good stability, high antibacterial efficiency, good biocompatibility, and low risk of antibiotic contamination, which could be particularly useful in preventing infections involving implantable medical devices or wearable electronics.

Combining situ-morcellation with continuous-fill-mattress suture in laparoscopic myomectomy: A surgical approach of choice for patients with large uterine fibroids.

BACKGROUND: To investigate the efficacy and advantage of combining situ-morcellation with continuous-fill-mattress suture compared with conventional morcellation and suture in laparoscopic myomectomy. METHODS: One hundred sixteen patients who underwent laparoscopic myomectomy from March 2014 to October 2016. INTERVENTIONS: Patients were divided into combining situ-morcellation with continuous-fill-mattress suture group (n = 62) and conventional group (n = 54), and subsequent statistical analysis the clinical data of the 2 groups. RESULTS: The combining situ-morcellation with continuous-fill-mattress suture group shows significantly decrease of surgery time, incision size, blood loss, postoperative drainage volume and time, postoperative vent time, hospital stay and the loss of hemoglobin value. Moreover, there is significant significance between the 2 groups in the surgery time (P = .018), the postoperative drainage volume (P = .000), and the loss of hemoglobin value (P = .000). CONCLUSIONS: The combining situ-morcellation with continuous-fill-mattress suture shows significant advantages in shortening surgery time and reducing blood loss compared with conventional group in laparoscopic myomectomy.

Surface Chemistry of Nanoscale Mineralized Collagen Regulates Periodontal Ligament Stem Cell Fate.

The interplay between stem cells and their extracellular microenvironment is of critical importance to the stem cell-based therapeutics in regenerative medicine. Mineralized collagen is the main component of bone extracellular matrix, but the effect of interfacial properties of mineralized collagen on subsequent cellular behaviors is unclear. This study examined the role of surface chemistry of nanoscale mineralized collagen on human periodontal ligament stem cell (hPDLSC) fate decisions. The intrafibrillarly mineralized collagen (IMC), fabricated by a biomimetic bottom-up approach, showed a bonelike hierarchy with nanohydroxyapatites (HAs) periodically embedded within fibrils. The infrared spectrum of the IMC showed the presence of phosphate, carbonate, amide I and II bands; and infrared mapping displayed uniform and higher spatial distribution of mineralization in the IMC. However, the distribution of the phosphate group differed far from that of the amide I group in the extrafibrillarly mineralized collagen (EMC), in which flowerlike HA clusters randomly depositing around the surface of the fibrils. Moreover, a large quantity of extrafibrillar HAs covered up the C═O stretch and N-H in-plane bend, resulting in substantial reduction of amide I and II bands. Cell experiments demonstrated that the hPDLSCs seeded on the IMC exhibited a highly branched, osteoblast-like polygonal shape with extended pseudopodia and thick stress fiber formation; while cells on the EMC displayed a spindle shape with less branch points and thin actin fibril formation. Furthermore, the biocompatibility of EMC was much lower than that of IMC. Interestingly, even without osteogenic induction, mRNA levels of major osteogenic differentiation genes were highly expressed in the IMC during cultivation time. These data suggest that the IMC with a similar nanotopography and surface chemistry to natural mineralized collagen directs hPDLSCs toward osteoblast differentiation, providing a promising scaffold in bone tissue regeneration.

Effects of bracket design on critical contact angle.

OBJECTIVE: To explore how the position of the bracket slots relative to the archwire influences the friction between them, and how bracket design affects the critical contact angle (θc). MATERIALS AND METHODS: Two kinds of stainless steel archwires (0.016 and 0.019 × 0.025-inch) were tested against four kinds of brackets (Transmission Straight Archwire bracket, Domestic MBT bracket, Tip-Edge Plus bracket, and BioQuick self-ligation bracket) in the dry state. Resistance to sliding (RS) was measured as an increase in contact angle (θ). The value of θc was calculated by two linear regression lines. RESULTS: Friction remained stable when θ < θc, then increased linearly when θ > θc. The θc values of the Tip-Edge Plus bracket and Transmission Straight Archwire bracket were significantly larger than those for the Domestic MBT bracket and BioQuick self-ligation bracket. CONCLUSIONS: The relationship between the archwire and bracket slot significantly affects the resistance to sliding. The "edge-off" structure of the Tip-Edge Plus bracket and Transmission Straight Archwire bracket could help to increase the θc value, and to expand the passive configuration range.

Changes in the surface roughness and friction coefficient of orthodontic bracket slots before and after treatment.

In this study, we tested the surface roughness of bracket slots and the friction coefficient between the bracket and the stainless steel archwire before and after orthodontic treatment. There were four experimental groups: groups 1 and 2 were 3M new and retrieved brackets, respectively, and groups 3 and 4 were BioQuick new and retrieved brackets, respectively. All retrieved brackets were taken from patients with the first premolar extraction and using sliding mechanics to close the extraction space. The surface roughness of specimens was evaluated using an optical interferometry profilometer, which is faster and nondestructive compared with a stylus profilometer, and provided a larger field, needing no sample preparation, compared with atomic force microscopy. Orthodontic treatment resulted in significant increases in surface roughness and coefficient of friction for both brands of brackets. However, there was no significant difference by brand for new or retrieved brackets. These retrieval analysis results highlight the necessity of reevaluating the properties and clinical behavior of brackets during treatment to make appropriate treatment decisions.