Labial Side Research Articles

Augmented Corticotomy Combined With Accelerated Orthodontic Forces in Class III Orthognathic Patients: Morphologic Aspects of the Mandibular Anterior Ridge With Cone-Beam Computed Tomography

This study used cone-beam computed tomography to evaluate morphologic changes of the mandibular anterior ridge after using augmented corticotomy plus accelerated orthodontia to decompensate mandibular incisors in patients with surgical skeletal Class III. Fourteen patients (8 men, 6 women; mean age, 26.14 yr) with skeletal Class III were treated before orthognathic surgery with a technique that combined corticotomy, bone grafting, and accelerated orthodontic forces to decompensate the lower incisors. Three-dimensional cone-beam computed tomograms were taken before treatment (T0) and at the completion of presurgical orthodontic treatment (T1). Measurements of the amount of vertical alveolar bone changes and horizontal bone thickness at the midroot and root apex levels of the mandibular incisors were evaluated. All patients showed significant proclination of the mandibular incisors at T1. The mean alveolar bone thickness from T0 to T1 increased buccally at the midroot and apex levels, showing statistically significant horizontal bone augmentation at the labial side of the lower anterior mandibular teeth (P < .05). The mean amount of vertical bone change did not show any significant vertical loss of alveolar bone. This new combined technique provided adequate decompensation of the mandibular incisors by increasing horizontal bone thickness in the labial aspect of the mandibular anterior area, without any vertical bone loss. This approach decreases the risk of the typical periodontal complications associated with traditional orthodontics, such as marginal bone loss and gingival recession.

Effects of ultrasonic and high-speed air-driven devices on pulp–dentin reactions: An animal study

Background/purposeThe aim of this study was to evaluate the pulp–dentin response after pulp chamber perforation by ultrasonic and high-speed air-driven devices. Materials and methodsEighteen upper incisors from nine dogs were used in this study. We prepared Class V cavity (3 × 5 mm) at the labial side after anesthesia. The pulp was then exposed/perforated by either an ultrasonic or high-speed air-driven device. We evaluated the hemorrhage condition by stopping the bleeding with varying numbers of sponge pellets. Three observation time points were set: immediate, 1 week (1-wk), and 2 weeks (2-wk). Then, we evaluated the pulp–dentin response using scanning electronic microscopy (SEM) and histological examination. ResultsThe bleeding level caused by an ultrasonic device presented as either no bleeding or mild bleeding, and a high-speed air-driven bur caused worse bleeding conditions. The ultrasonic group showed better response in the immediate pulpal response. In 1 week, both methods presented no pulp necrosis, and those treated using the ultrasonic device presented with a regular odontoblastic layer under SEM observations. In the 2-wk group, both methods showed no pulp necrosis, whereas the high-speed device showed partial necrosis. SEM showed pulp tissue with lacerated wounds in those who had the high-speed device treatment. ConclusionWe conclude that the ultrasonic device causes less damage to the dental pulp tissue in comparison with the high-speed air-driven bur. Moreover, we expect that the ultrasonic device can be applied to vital pulp therapy—such as direct pulp capping, pulptotomy, or pulpectomy—due to its safe approach.

Differences in the gingival crevicular fluid composition between adults and adolescents undergoing orthodontic treatment

To investigate differences in the gingival crevicular fluid (GCF) composition between adolescent and adult patients undergoing orthodontic treatment with fixed appliances. Ten adolescents (14.4 ± 1.43) and 10 adults (28.5 ± 7.83) with Class I malocclusions and minor upper incisor crowding were allocated to two different age groups. Brackets were bonded only in the upper arch over the 20-week period of the experiment. Samples of GCF were collected from the labial sides of the upper incisors (experimental sites) and lower incisors (control sites) of each subject at five time points. Aliquots from diluted GCF were screened for the presence of receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), interleukin-1 (IL-1), interleukin-1 receptor antagonist (IL-1RA), and metalloproteinase-9 (MMP-9) using a microarray technique. The values were statistically analyzed. In adults, the ratio of IL-1 to IL-1RA decreased significantly (P = .033) in experimental sites 3 weeks after appliance placement and first archwire activation. In adolescents, the ratio of RANKL to OPG peaked 6 weeks after the insertion of the first rectangular archwire. This ratio peak found in adolescents was a consequence of a decrease in the mean concentration of OPG. No significant changes over time were observed in the concentration of MMP-9. This study demonstrates age trends in the GCF levels of IL-1, IL-1RA, RANKL, and OPG that may be used to track differences in tissue response between adults and adolescents undergoing orthodontic treatment.

Age determination of the Mongolian wild ass (Equus hemionus Pallas, 1775) by the dentition patterns and annual lines in the tooth cementum

Based on 440 skulls recently collected from two areas of the wild ass population in Mongolia, the time course of tooth eruption and replacement was investigated. The dentition pattern allows identification of age up to five years. We also conclude that annual lines in the tooth cementum can be used to determine the age in years for wild asses older than five years after longitudinal tooth sections were made with a low-speed precision saw. The first upper incisor proved to be most suitable for age determination, although the starting time of cement deposition is different between the labial and lingual sides of the tooth. The accurate age of the wild ass can be determined from the number of annual lines and the time before the first formation of the cementum at the respective side of the tooth.

Age‐related changes in maxillary and mandibular cortical bone thickness in relation to temporary anchorage device placement

The aim of this study was to investigate the correlation between alveolar bone cortical thickness (ABCT) and age in the maxillae and mandible in humans. This information could then be translated into clinical application with temporary anchorage devices (TADs) in orthdontics. Samples comprised 82 post-mortem CT datasets (41 males and 41 females) aged between 11 to 50 years, and were divided into five different age groups and gender. Alveolar ABCT was measured in the labial/buccal and palatal/lingual sides of the incisor, canine, premolar, molar and tuberosity/retromolar regions of the maxillae and mandible. Correlations between ABCT and age and gender were analysed with linear regression analysis. Strong correlation between ABCT and age was found for the maxilla on the labial side of the maxillary incisor region (p < 0.001). On the palatal aspect, significant correlations between ABCT and age were found in the maxillary incisor and maxillary premolar regions (p = 0.01 and p = 0.047 respectively). Significant correlation between ABCT and gender was found only at the buccal aspect of the maxillary molar region (p = 0.022). In the mandible, a statistically significant correlation between ABCT and age was found in the cortical bone of the labial side of the mandibular incisor region (p = 0.017). However, statistically significant negative correlation between ABCT and age was found in the mandibular canine region (p = 0.033). The only site to demonstrate a significant difference in change in ABCT with age between males and females was the lingual side of the retromolar region, in which female ABCT increased more than in males (slope = 0.015). There is minimal clinically significant correlation between ABCT and age at the alveolar bone level. Although investigations show statistically significant correlations, these may not be clinically significant as those regions are not ideal for anchorage reinforcement with TADs in orthodontic practice.

Vector-Controlled Alveolar Distraction Osteogenesis Using an Implant-Fixed Provisional Prosthesis

This is a case report of anterosuperior alveolar distraction using an implant-fixed provisional prosthesis. Osteotomy and placement of a distraction device were performed in a healthy 69-year-old woman. To avoid lingual inclination during the distraction period, the device's rod was buried in the labial side of a provisional prosthesis supported by posterior implants. The mandibular bone was obliquely distracted by 0.3 mm every 2 days. Implant insertion was performed, and a good prognosis was anticipated. Inclination is thought to be caused by soft tissue on the lingual side. Many reports propose methods to avoid inclination, but these methods require established support from the teeth and cannot be adapted for an edentulous case. The method reported here is useful for distraction osteogenesis because it can be adapted for edentulous cases.

Disruption of Wnt/β-catenin Signaling in Odontoblasts and Cementoblasts Arrests Tooth Root Development in Postnatal Mouse Teeth

Tooth development undergoes a series of complex reciprocal interactions between dental epithelium and the underlying mesenchymal cells. Compared with the study in tooth crown formation, little is known about the molecular mechanism underlying the development of tooth roots. In the present study, we conditionally knock out β-catenin gene (Ctnnb1) within developing odontoblasts and cementoblasts during the development of tooth roots, and observed rootless molars as well as incomplete incisors. Histological analyses revealed intact structure of molar crown and labial side of incisor, however, as for the molar roots and the lingual portion of incisor, the formation of dentin and periodontal tissues were greatly hampered. In situ hybridization experiments using probes of odontoblastic marker genes collagen type I, alpha 1 (Col1a1), osteocalcin (OC) and dentin sialophosphoprotein (Dspp) manifested striking undifferentiation of root odontoblasts in which Ctnnb1 was eliminated. Bromodeoxyuridine (BrdU) labeling and proliferating cell nuclear antigen (PCNA) immunohistochemical experiments also showed retarded proliferation of pre-odontoblasts in mutant mice. However, cell apoptosis was not affected. Additionally, a disrupted formation of cementoblasts, suggested by the absence of transcripts of bone sialoprotein (Bsp) in follicle mesenchyme, was also evident in mutant mice. Our study provides strong in vivo evidence to confirm that Wnt/β-catenin signaling is functionally significant to root odontogenesis and cementogenesis during the tooth root development.

Association of gingival biotype with the results of scaling and root planing

PurposeThe concept of gingival biotype has been used as a predictor of periodontal therapy outcomes since the 1980s. In the present study, prospective and controlled experiments were performed to compare periodontal pocket depth (PPD) reduction and gingival shrinkage (GSH) after scaling and root planing (SRP) according to gingival biotype.MethodsTwenty-five patients diagnosed with chronic periodontitis participated in the present study. The PPD and GSH of the labial side of the maxillary anterior teeth (from the right canine to the left canine) were evaluated at baseline and 3 months after SRP. Changes in the PPD following SRP were classified into 4 groups according to the gingival thickness and initial PPD. Two more groups representing normal gingival crevices were added in evaluation of the GSH. The results were statistically analyzed using the independent t-test.ResultsIn the end, 16 patients participated in the present study. With regard to PPD reduction, there were no significant differences according to gingival biotype (P>0.05). Likewise, sites with a PPD of over 3 mm failed to show any significant differences in the GSH (P>0.05). However, among the sites with a PPD of under 3 mm, those with the thin gingival biotype showed more GSH (P<0.05).ConclusionsPPD changes after SRP were not affected by gingival biotype with either shallow or deep periodontal pockets. GSH also showed equal outcomes in all the groups without normal gingival crevices. The results of SRP seem not to differ according to gingival biotype.

Unique features of pedicellate attachment of the upper jaw teeth in the adult gobiid fish Sicyopterus japonicus (Teleostei, Gobiidiae): Morphological and structural characteristics and development

Sicyopterus japonicus (Teleostei, Gobiidae), a hill-stream herbivorous gobiid fish, possesses an unusual oral dentition among teleost fishes on account of its feeding habitat. By using scanning electron microscopy, light microscopy, and transmission electron microscopy, including vital staining with tetracycline, we examined the development of the attachment tissues of the upper jaw teeth in this fish. The functional teeth of S. japonicus had an asymmetrical dentine shaft. The dentine shaft attached to the underlying uniquely shaped pedicel by means of two different attachment mechanisms. At the lingual base, collagen fiber bundles connected the dentine shaft with the pedicel (hinged attachment), whereas the labial base articulated with an oval-shaped projection of the pedicel (articulate attachment). The pedicel bases were firmly ankylosed to the crest of the thin flange of porous spongy bone on the premaxillary bone, which afforded a flange-groove system on the labial surface of the premaxillary bone. Developmentally, the pedicel and thin flange of spongy bone were completely different mineralized attachment tissues. The pedicel had a dual origin, i.e., the dental papilla cells, which differentiated into odontoblasts that constructed the internal surface of the pedicel, and the mesenchymal cells, which differentiated into osteoblasts that formed the outer face of the pedicel. A thin flange of spongy bone was deposited on the superficial resorbed labial side of the premaxillary bone proper, and later rapid bone remodeling proceeded toward the pedicel base. These unique features of pedicellate tooth attachment for the upper jaw teeth in the adult S. japonicus are highly modified teeth for enhancing the ability of individual functional teeth to move closely over irregularities in the rock surfaces during the scraping of algae.

Morphometric evaluation of changes in the alveolar bone and roots of the maxillary anterior teeth before and after en masse retraction using cone-beam computed tomography

To evaluate the morphometric changes in the alveolar bone and roots of the maxillary anterior teeth (MXAT) after en masse retraction with maximum anchorage (EMR-MA). The samples consisted of 37 female adult patients who had Class I dentoalveolar protrusion (CI-DAP) and were treated by extraction of the first premolars and EMR-MA. Using three-dimensional cone-beam computed tomography taken before treatment and after space closure, the maxillary central incisors (MXCI, N = 66), lateral incisors (MXLI, N = 69), and canines (MXC, N = 69) were superimposed using individual reference planes. After alveolar bone area (ABA), vertical bone level (VBL), root length (RL), root area (RA), and prevalence of dehiscence (PD) were measured at the cervical, middle, and apical levels, statistical analyses were performed. On the palatal side, ABA significantly decreased in all levels of MXAT (P < .001; middle of MXC, P < .01). MXCI and MXLI exhibited a greater decrease in the ratio of change in palatal ABA than did MXC (cervical, P < .01; middle and apical, P < .05; total, P < .001). Palatal/labial ABA ratios decreased in MXCI (cervical, middle, total, P < .001; apical, P < .05) and MXLI (cervical, P < .001; apical, P < .05). They showed greater amounts and ratios of change in VBL on the palatal side compared to the labial side (all P < .001). The palatal side showed more PD in the cervical area than did the labial side (MXCI and MXLI, P < .001; MXC, P < .01). Significant root resorption occurred in MXAT (RL and RA, all P < .001). During EMR-MA in cases with CI-DAP, ABA and VBL on the palatal side and RL and RA of MXCI and MXLI were significantly decreased.

The Use of Leukocyte- and Platelet-Rich Fibrin During Immediate Postextractive Implantation and Loading for the Esthetic Replacement of a Fractured Maxillary Central Incisor

I mplant-supported restoration of the maxillary anterior segment that is biologically, functionally, and esthetically acceptable following traumatic injuries in the maxillary anterior segment is always complex. Careful extraction of the fractured root, residual labial bone preservation, proper flap design, ideal positioning of the implant, appropriate softtissue contour, and the crown emergence are all important steps necessary to achieve a predictable, stable, functional, and esthetic success. However, healing of the tissues is always difficult to control and the development of new techniques and materials to improve these treatments is still necessary. The use of platelet concentrates is an interesting approach. Platelet concentrates for surgical use are widely used and continuously investigated in oral and maxillofacial surgery. The objective is to gather platelet growth factors and to inject them on a surgical site to stimulate the healing process. A significant percentage of the literature is focused on the platelet-rich plasma (PRP) families. PRP is a liquid platelet suspension often activated into a platelet-rich gel (like fibrin glues). Another technology called leukocyteand platelet-rich fibrin (L-PRF) allows for the preparation of strong fibrin membranes enriched with cells (activated platelets, leukocytes, circulating cells) and platelet growth factors. This autologous healing biomaterial is free of additives (no anticoagulant during blood harvest, no chemicals for activation), simple, inexpensive, and quick to prepare (15 minutes for all steps). This technique is specifically adapted to the practical needs in daily implant dentistry. Several articles have reported the use of these L-PRF membranes for the stimulation of bone and 1 Private practice, Turin, Italy. 2 Private practice, Ra’anana, Israel. 3 Clarion Research Group, Clarion, Penn. Department of Restorative Dentistry, State University of New York at Buffalo, Buffalo, NY. 4 LoB5 Unit, Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, South Korea. Department of Stomatology, Oral Surgery, and Dental and MaxilloFacial Radiology, School of Dental Medicine, University of Geneva, Geneva, Switzerland. * Corresponding author, e-mail: LoB5@mac.com DOI: 10.1563/AAID-JOI-D-12-CL.3802

Orientation and deformation of mineral crystals in tooth surfaces

Tooth enamel is the hardest material in the human body, and it is mainly composed of hydroxyapatite (HAp)-like mineral particles. As HAp has a hexagonal crystal structure, X-ray diffraction methods can be used to analyze the crystal structure of HAp in teeth. Here, the X-ray diffraction method was applied to the surface of tooth enamel to measure the orientation and strain of the HAp crystals. The c-axis of the hexagonal crystal structure of HAp was oriented to the surface perpendicular to the tooth enamel covering the tooth surface. Thus, the strain of HAp at the surface of teeth was measured by X-ray diffraction from the (004) lattice planes aligned along the c-axis. The X-ray strain measurements were conducted on tooth specimens with intact surfaces under loading. Highly accurate strain measurements of the surface of tooth specimens were performed by precise positioning of the X-ray irradiation area during loading. The strains of the (004) lattice plane were measured at several positions on the surface of the specimens under compression along the tooth axis. The strains were obtained as tensile strains at the labial side of incisor tooth specimens. In posterior teeth, the strains were different at different measurement positions, varying from tensile to compressive types.

Cortical and cancellous bone thickness on the anterior region of alveolar bone in Korean: a study of dentate human cadavers

PURPOSEThe cortical bone thickness on the anterior region is important for achieving implant stability. The purpose of this study was to examine the thickness of the cortical and cancellous bones on the anterior region of the maxilla and mandible.MATERIALS AND METHODSTwenty-five cadaver heads were used (16 male and 9 female; mean death age, 56.7 years). After the long axis of alveolar process was set up, it was measured in 5 levels starting from 2 mm below the cementoenamel junction (L1) at intervals of 3 mm. All data was analysed statistically by one-way ANOVA at the .05 significance level.RESULTSThe cortical bone thickness according to measurement levels in both the labial and lingual sides increased from L1 to L5, and the lingual side below L3 was significantly thicker than the labial side on the maxilla and mandible. In particular, the labial cortical bone thickness in the maxilla was the thinnest compared to the other regions. The cancellous bone thickness according to measurement levels increased from L1 to L5 on the maxilla, and on the mandible it was the thinnest at the middle level of the root.CONCLUSIONFor implant placement on the anterior region, a careful evaluation and full knowledge on the thickness of the cortical and cancellous bone are necessary, therefore, these results may provide an anatomic guideline to clinicians.

Multistage Bone-Charged Distraction Osteogenesis for Aesthetic Reconstruction of an Extensive Bone Deficiency in the Mandible

Alveolar and mandibular bone defects impair occlusion and affect the aesthetics of facial contouring, making it difficult to obtain a satisfactory outcome. Treatment with distraction osteogenesis (DO) is particularly difficult in cases in which the defective region extends to close to the inferior margin of the mandible. To overcome the limits of current DO, we developed a method as follows. In the first stage, a submucosal space necessary for bone grafting was prepared by soft tissue expansion through DO. In the second stage, an iliac corticocancellous bone was transplanted with its cancellous side in close contact with the new bone in the space formed on the labial side into this new space. In the third stage, the grafted bone was distracted. This technique requires time, but each surgery is of minimum invasiveness and does not leave a visible scar; use of this technique may expand the limited indication of current DO and dental implants.

A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina

BackgroundArgentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now, the Massospondylidae were the group of basal sauropodomorphs most widely spread around Pangea with a record in almost all continents, mostly from the southern hemisphere, including the only record from Antarctica.Methodology/Principal FindingWe describe here a new basal sauropodomorph, Leyesaurus marayensis gen. et sp. nov., from the Quebrada del Barro Formation, an Upper Triassic-Lower Jurassic unit that crops out in northwestern Argentina. The new taxon is represented by a partial articulated skeleton that includes the skull, vertebral column, scapular and pelvic girdles, and hindlimb. Leyesaurus is diagnosed by a set of unique features, such as a sharply acute angle (50 degrees) formed by the ascending process of the maxilla and the alveolar margin, a straight ascending process of the maxilla with a longitudinal ridge on its lateral surface, noticeably bulging labial side of the maxillary teeth, greatly elongated cervical vertebrae, and proximal articular surface of metatarsal III that is shelf-like and medially deflected. Phylogenetic analysis recovers Leyesaurus as a basal sauropodomorph, sister taxon of Adeopapposaurus within the Massospondylidae. Moreover, the results suggest that massospondylids achieved a higher diversity than previously thought.Conclusions/SignificanceOur phylogenetic results differ with respect to previous analyses by rejecting the massospondylid affinities of some taxa from the northern hemisphere (e.g., Seitaad, Sarahsaurus). As a result, the new taxon Leyesaurus, coupled with other recent discoveries, suggests that the diversity of massospondylids in the southern hemisphere was higher than in other regions of Pangea. Finally, the close affinities of Leyesaurus with the Lower Jurassic Massospondylus suggest a younger age for the Quebrada del Barro Formation than previously postulated.

Developmentally regulated expression of Sema3A chemorepellant in the developing mouse incisor

Objective. Semaphorin 3A (Sema3A) is an essential chemorepellant controlling peripheral axon pathfinding and patterning, but also serves non-neuronal cellular functions. Incisors of rodent are distinctive from molars as they erupt continuously, have only one root and enamel is present only on the labial side. The aim of this study is to address putative regulatory roles of Sema3A chemorepellant in the development of incisor innervation and formation. Materials and methods. This study analyzed expression of Sema3A mRNAs during embryonic and early post-natal stages of mouse mandibular incisor using sectional radioactive in situ hybridization. Results. Although Sema3A mRNAs were observed in condensed dental mesenchyme during the early bud stage, they were absent in dental papilla or pulp at later stages. Sema3A mRNAs were observed in the dental epithelium including the cervical loops and a prominent expression was also seen in alveolar bone. Interestingly, transcripts were absent from the mesenchymal dental follicle target area (future periodontal ligament) throughout the studied stages. Conclusion. The expression patterns of Sema3A indicate that it may control the timing and patterning of the incisor innervation. In particular, Sema3A appears to regulate innervation of the periodontal ligament, while nerve penetration into the incisor dental pulp appears not to be dependent on Sema3A. Moreover, Sema3A may regulate the functions of cervical loops and the development of alveolar bone. Future study with Sema3A deficient mice will help to elucidate the putative neuronal and non-neuronal functions of Sema3A in incisor tooth development.

Expression and characterization of c-Myb in prenatal odontogenesis

The transcription factor c-Myb is involved in the control of cell proliferation, survival and differentiation. As these processes accompany the morphogenesis of developing teeth, this work investigates the possible role of c-Myb during odontogenesis. Analysis of the expression of c-Myb in the monophyodont mouse was followed by similar analysis in a diphyodont species, the pig, which has a dentition more closely resembling that of the human. The distribution of c-Myb was correlated with the pattern of proliferation and apoptosis and the tooth phenotype of c-Myb mutant mice was also assessed. In the mouse, c-Myb expression was detected throughout prenatal development of the first molar tooth. Negative temporospatial correlation was found between c-Myb expression and apoptosis, while c-Myb expression positively correlated with proliferation. c-Myb-positive cells, however, were more abundant than the proliferating cell nuclear antigen positive cells, suggesting other roles of c-Myb in odontogenesis. In the minipig, in contrast to the mouse, there was an asymmetrical arrangement of c-Myb positive cells, with a higher presence on the labial side of the tooth germ and dental lamina. A cluster of negative cells was situated in the mesenchyme close to the tooth bud. At later stages, the number of positive cells decreased and these cells were situated in the upper part of the dental papilla in the areas of future cusp formation. The expression of c-Myb in both species was strong in the odontoblasts and ameloblasts at the stage of dentin and enamel production suggesting a possible novel role of c-Myb during tooth mineralization.

Effects of silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets

ObjectiveThe aim of this study was to evaluate the effects of tribochemical silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets.Material and MethodsTwenty debonded metal and 20 debonded ceramic brackets were randomly assigned to receive one of the following surface treatments (n=10 for each group): (1) sandblasting (control); (2) tribochemical silica coating combined with silane. Brackets were rebonded to the enamel surface on the labial and lingual sides of premolars with a light-polymerized resin composite. All specimens were stored in distilled water for 1 week and then thermocycled (5,000 cycles) between 5-55°C. Shear bond strength values were measured using a universal testing machine. Student's t-test was used to compare the data (α=0.05). Failure mode was assessed using a stereomicroscope, and the treated and non-treated bracket surfaces were observed by scanning electron microscopy.ResultsRebonded ceramic brackets treated with silica coating followed by silanization had significantly greater bond strength values (17.7±4.4 MPa) than the sandblasting group (2.4±0.8 MPa, P<0.001). No significant difference was observed between the rebonded metal brackets treated with silica coating with silanization (15±3.9 MPa) and the sandblasted brackets (13.6±3.9 MPa). Treated rebonded ceramic specimens primarily exhibited cohesive failure in resin and adhesive failure at the enamel-adhesive interface.ConclusionsIn comparison to sandblasting, silica coating with aluminum trioxide particles followed by silanization resulted in higher bond strengths of rebonded ceramic brackets.

Animal experiment of periodontal tissue remodeling in application of mini-implant anchorage for incisor intrusion

The aim of the present study is to observe the remodeling of periodontal tissue in application of miniimplant anchorage for incisor intrusion in dogs. Six adult male beagle dogs were used for the experiment. On the buccal site, a mini-implant was placed at the interalveolar septum between the maxillary second incisor and the third incisor on each side. The six maxillary incisors were connected together through the segmental wires and the individual bands were welded by brackets. An intrusive force (120 g) was applied by Ni-Ti coil spring on each side. An animal was sacrificed at the end of 0, 1, 3, 7, 14 and 30 days, respectively, after the activation. X-ray examination, HE staining and receptor activator of nuclear factor-kappa B ligand (RANKL) immunohistochemistry staining were performed afterwards. Then, we found that the periodontal tissue in apical area and crest of ridge remodeled most actively. In addition, the periodontal tissue on the buccal and the lingual sides also remodeled. In conclusion, the incisor teeth were not only intruded vertically but also showed rotation of the crown towards the labial side and the root towards the palatal side, by using mini-implants as anchorage. Besides, if the force applied was excessively large, it would cause apical root resorption. Key words : Anchorage, mini-implant, incisor intrusion, and receptor activator of nuclear factor-kappa B ligand (RANKL).

Wire load-deflection characteristics relative to different types of brackets

To test the hypothesis that the dimension of the bracket, both in labial and in lingual orthodontics, is a relevant parameter to determine the forces acting on the teeth, and that some wires commonly used in labial orthodontics (0.016"-diameter SS, TMA and Nitinol) are not suitable for the first phase of lingual treatment. An ideal dental cast was bonded with eight different brackets (Damon 3MX, Ovation, Time 2, Innovation and Smart Clip Clarity on the vestibular face; STB, Adenta Time and Innovation-L on the lingual). After photographic documentation, the interbracket distance was calculated for each type of bracket, using ImageJ software. The mean elasticity modulus of the tested wires was obtained from the review of the available literature. The theoretical wire load on every tooth was calculated mathematically at three different levels of deflection (0.5mm; 1.0mm and 1.5mm), on both the labial and lingual sides, for all types of bracket. The lingual arch in the anterior segment is always shorter than the vestibular arch. The different brackets, having different dimensions, have an influence on the interbracket distance, and, consequently, on the wire load. At large deflections, superelastic NiTi expresses light and continuous forces, which are significantly lower than the other examined alloys. The initial hypothesis was supported. Because of the reduced interbracket distance, the adoption of superelastic wires is required in lingual mechanics and with smaller diameter compared to labial mechanotherapy, in particular during the first phases of treatment. The use of a bracket with reduced mesiodistal dimensions can contribute to reduce the load on the teeth.