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Treatment of ectopic mandibular second molar with titanium miniscrews.

The use of a Cizeta titanium miniscrew (Cizeta Surgical, Bologna, Italy) for treating an impacted mandibular second molar is presented in this report. The surgical procedure for placing the miniscrew and the subsequent orthodontic management are described, including orthodontic traction with a nickel-titanium closed-coil spring exerting 50 g of force. We concluded that the titanium miniscrew for skeletal anchorage is effective in treating deeply impacted mandibular second molars.

Adult↗

Influence of orthodontic derotation and extrusion on pulpal and periodontal condition of autotransplanted immature third molars.

The aim of this study was to determine the influence of orthodontic treatment on the pulpal and periodontal condition of 91 transplanted immature third molars. In patients with atrophy of the alveolar process or unfavorable root morphology, transplants had to be placed in extreme rotated or infraoccluded positions. After 3 to 6 months, these transplants were derotated (45 degrees to 90 degrees) to a correct position in the dental arch (derotation group; n = 28) or extruded to the occlusal plane (extrusion group; n = 21). Finally, approximal spaces were closed in both groups. A sample of 42 transplanted third molars with no orthodontic treatment need served as the control group. All transplants were followed clinically and radiologically for a mean period of 4.0 years. With respect to pulpal and periodontal conditions, no significant differences were observed between the control and the extrusion group. In contrast, compared with the control group, transplants in the derotation group had a significantly poorer pulpal and periodontal condition. In the derotated transplants, a significant correlation was detected between pulp necrosis and orthodontic treatment of multi-rooted transplants. This study indicates that orthodontic extrusion and minor lateral movements of autotransplanted immature third molars, as well as rotation of single-rooted third-molar transplants, represent no additional risk to transplant survival. In contrast, rotation of multi-rooted transplants seems to initiate later severance of the vascular and nerval supply to the pulp.

Adolescent↗

Physical properties of root cementum: Part 5. Volumetric analysis of root resorption craters after application of light and heavy orthodontic forces.

BACKGROUND: In previous studies on root resorption, resorption was quantified by making histologic cuts or by surface area measurements of resorption craters. The aims of this study were to evaluate the effects of orthodontic force magnitude on root resorption craters with volumetric measurements and also to identify the sites that might be predisposed to resorption. METHODS: After an experimental time of 28 days, 36 human premolars previously divided into light-force (25 g) and heavy-force (225 g) groups were extracted and prepared for scanning electron microscope imaging. Pairs of stereo images were taken, and 3-dimensional quantitative volumetric analysis was performed with commercial software. RESULTS AND CONCLUSIONS: The mean volume of the resorption crater in the light-force group was 3.49-fold greater than in the control group; the mean volume of the resorption crater in the heavy-force group was 11.59-fold greater than in the control group ( P < .001). The heavy-force group had 3.31-fold greater total resorption volume than the light-force group ( P < .001). Buccal cervical and lingual apical regions had significantly more resorption craters than the other regions ( P < .001). There was more resorption by volume in the heavy-force group compared with the light-force group and controls. Although more resorption was recorded in the light-force group, the difference in the amount of resorption between the light-force and control groups was not statistically significant. There was significantly more resorption on the buccal cervical and lingual apical regions of the root surfaces than on the other regions, suggesting that high-pressure zones might be more susceptible to resorption after 28 days of force application.

Adolescent↗

Physical properties of root cementum: Part 3. Hardness and elastic modulus after application of light and heavy forces.

BACKGROUND: The aims of this investigation were to evaluate the hardness and elastic modulus of untreated human premolar cementum and to investigate the changes after application of light and heavy orthodontic forces. METHODS: Thirty-six maxillary and mandibular first premolars were collected from 16 prospective orthodontic patients. The patients were assigned to 1 of 2 groups. Group I (light force) consisted of 8 subjects (4 male, 4 female, mean age 14.8 years) who had 25 g of buccally directed orthodontic force applied to the first premolars on 1 side. Group II (heavy force) consisted of 9 subjects (7 male, 2 female, mean age 13.8 years) who had 225 g of buccally directed orthodontic force applied to first premolars on 1 side. Contralateral premolars served as the control in both groups. The force was applied for 4 weeks; then each first premolar was extracted and stored in deionized water. Physical properties were tested on unprepared cementum on buccal and lingual surfaces at the cervical, middle, and apical thirds with an ultra-micro-indentation system. RESULTS: Mean (+/- standard deviation) hardness of the untreated cementum at the cervical, middle, and apical thirds, respectively, was 0.25 +/- 0.09 GPa, 0.24 +/- 0.07 GPa, and 0.18 +/- 0.06 GPa on the buccal surface and 0.24 +/- 0.08 GPa, 0.24 +/- 0.06 GPa, and 0.21 +/- 0.06 GPa on the lingual surface. Mean elastic modulus at the cervical, middle, and apical thirds, respectively, was 4.4 +/- 2.4 GPa, 3.4 +/- 2.0 GPa, and 2.4 +/- 1.8GPa on the buccal surface and 3.8 +/- 2.1 GPa, 3.2 +/- 1.4 GPa, and 2.4 +/- 1.5 GPa on the lingual surface. CONCLUSIONS: The mean hardness and elastic modulus of untreated human premolar cementum gradually decreased from cervical to apical regions of the buccal and lingual surfaces. A similar decrease was observed in the experimental teeth of light-force and heavy-force groups. There were no statistically significant differences between the control and experimental teeth; this is probably due to large intraindividual variation.

Adolescent↗

Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine.

BACKGROUND: Resorption of maxillary incisor roots because of an impacted canine is a well-recognized phenomenon that occurs in a surprisingly high proportion of patients with impacted canines. In this retrospective study, we studied a sample of patients in whom the resorption was particularly severe. METHODS: The sample consisted of 11 patients (age, 11.8 +/- 1.2 years) with 20 severely resorbed maxillary incisors. The amount of resorption was measured at the outset (T1), when the impacted canine was distanced from the incisor root area (T2), at the completion of the orthodontic treatment (T3), and at a follow-up appointment at least 1 year posttreatment (T4). RESULTS: A 17.2% increase in the crown/root ratio occurred due to aggressive continued resorption between T1 and T2. The resorption rate reduced to an almost insignificant level, despite continued and often appreciable orthodontic movement of the resorbed teeth from T2 to T3. CONCLUSIONS: Patients with impacted canines should be screened for resorption and the impacted tooth treated as soon as possible. The resorption process can be halted and the affected tooth moved orthodontically without further risk of resorption. In the long term, with early treatment, even severely resorbed teeth do not suffer from increased mobility or discoloration and might not require splinting.

Child↗

Orthodontic treatment of a traumatically intruded tooth with ankylosis by traction after surgical luxation.

This report presents the treatment of a patient with anterior crossbite and displacement of ankylosed maxillary and mandibular right lateral incisors. The maxillary lateral incisor, which was traumatically intruded, was successfully treated with 2 surgical luxations followed by orthodontic traction. The mandibular lateral incisor, which was avulsed and replanted, experienced replacement root resorption during orthodontic treatment and was ultimately extracted. Two years after active orthodontic treatment, the occlusal results were considered satisfactory.

Cephalometry↗

Influence of force systems on archwire-bracket combinations.

Orthodontic forces and couples are presented for the 3 principal directions and planes by using simplified free-body diagrams, equilibrium principles, and equivalent force systems. These simplified free-body diagrams show only the forces and couples applied by the practitioner to a single tooth or a group of teeth-minus any frictional effects associated with appliances. By using equilibrium principles, these forces and couples are resisted by each root in an equal but opposite manner. When an equivalent force system is produced at the center of resistance, the simplified free-body diagram requires only 1 force and 1 couple at the center of resistance of a tooth or a group of teeth because the reactions are the same but opposite in magnitude. This approach not only is much easier to comprehend but also facilitates the conceptualization of tooth mechanics with regard to centers of rotation. Specific examples of this approach include cases in which a tooth is labially or lingually displaced, intruded or extruded, bodily translated, or bodily rotated, as well as the combined effects of translation and rotation with and without auxiliary appliances or friction.

Biomechanical Phenomena↗

Anchorage quality of deciduous molars versus premolars for molar distalization with a pendulum appliance.

PURPOSE: The aim of this study was to assess dental anchorage qualities when the pendulum appliance is used for distal molar movement. MATERIAL: Thirty adolescents in various dentition stages received a modified pendulum appliance with a distal screw and a specially preactivated pendulum spring for bilateral molar distalization in the maxilla. The subjects were subcategorized into 3 groups of 10 according to the dental anchorage used: deciduous molars, premolars and deciduous molars, or only premolars. Dentoalveolar effects and side effects in the anchorage unit and in the molar area were determined by cephalometric analysis. RESULTS: Statistical analysis of the measurements showed significant differences between groups in the extent of molar distalization and the resulting incisor protrusion. Distal tipping of the 6-year molars was significantly less severe (2.3 degrees +/- 1.58 degrees to the palatal plane and 2.55 degrees +/- 1.52 degrees to the anterior cranial base) in patients with premolar anchorage than in those with deciduous molar anchorage (6.15 degrees +/- 3.42 degrees and 6.35 degrees +/- 3.46 degrees ). Incisor protrusion was significantly more pronounced in patients with deciduous molar anchorage (2.75 +/- 1.4 mm) than in the other 2 groups (1.65 +/- 0.82 mm, mixed deciduous molar and premolar anchorage, and 1.75 +/- 0.75 mm, premolar anchorage). Additionally, incisor protrusion was translatory compared with controlled tipping in subjects with deciduous molar anchorage or premolar and deciduous molar anchorage. CONCLUSIONS: Deciduous molars and premolars can be used for anchorage for molar distalization with a pendulum appliance; however, anchorage with premolars only results in the least pronounced dentoalveolar side effects. The anchorage quality of deciduous molar and mixed deciduous molar/premolar anchorage is limited.

Adolescent↗

Molar distalization with pendulum appliances in the mixed dentition: effects on the position of unerupted canines and premolars.

INTRODUCTION: The pendulum appliance allows for rapid molar distalization without the need for patient compliance. Its efficiency has been confirmed in a number of clinical studies. However, the potential interactions and positional changes between the deciduous molars used for dental anchorage and the erupted and unerupted permanent teeth have yet to be clarified when this appliance is used for molar distalization in the mixed dentition. METHODS: Twenty-nine patients in the mixed dentition each received a modified pendulum appliance with a distal screw and a preactivated pendulum spring for bilateral distalization of the maxillary molars. The patients were divided into 4 groups based on dentition stages: patient group 1 (PG 1, n = 10) was in the early mixed dentition; patients had resorption of the distal root areas of the deciduous molars being used for dental anchorage, and the unerupted premolars were located at the distal margin of the deciduous molar root region. Based on radiographs taken before placement of the pendulum appliance, patient group 2 (PG 2, n = 10) was diagnosed as having a central location of the unerupted premolars. In the third group (PG 3, n = 4), the first premolars were already erupted and could be integrated into the dental anchorage, but the canines were not yet erupted. In the fourth group (PG 4, n = 5), the first premolars and both canines were fully erupted. RESULTS: Statistical analysis of the measured results showed significant differences in the side effects between PG 1 and PG 2. In patients being treated with pendulum appliances, the anchorage quality of the deciduous molars that were already partially resorbed in the distal root area was comparatively reduced. Consequently, the mesial drift of the deciduous molars and incisors was increased, without impairing the extent and quality of the molar distalization. Anchorage loss in the supporting area had no direct impact on the sagittal position of the unerupted premolars in the early mixed dentition. CONCLUSIONS: If permanent teeth have already started to erupt in the supporting area, additional space restrictions should be avoided in patients with critical topography, especially if there is little space for the unerupted canines. At this stage of the mixed dentition, premolar extraction or augmentation of the supporting area with extraoral headgear offers a therapeutic alternative to intraoral distalization appliances with exclusively dental anchorage.

Analysis of Variance↗

Correction of a canted occlusal plane with miniscrews in a patient with facial asymmetry.

The inability of orthodontists to change the cant of the maxillary occlusal plane without surgical intervention is a limitation of orthodontic treatment. LeFort I osteotomy with asymmetric maxillary impaction is often used to correct this problem. However, canting caused by extruded teeth can be corrected easily with normal orthodontic appliances and skeletal anchorage. The correction occurs through intrusion of the extruded teeth on 1 side of the maxilla, thereby avoiding a more aggressive surgical approach. A 22-year-old Korean man with facial asymmetry and mandibular prognathism treated in this manner showed the possibility of correcting occlusal plane canting with miniscrews.

Adult↗

Congenitally missing mandibular second premolars: clinical options.

INTRODUCTION: Congenital absence of mandibular second premolars affects many orthodontic patients. The orthodontist must make the proper decision at the appropriate time regarding management of the edentulous space. These spaces can be closed or left open. IMPLICATIONS: If the space will be left open for an eventual restoration, the keys during orthodontic treatment are to create the correct amount of space and to leave the alveolar ridge in an ideal condition for a future restoration. If the space will be closed, the clinician must avoid any detrimental alterations to the occlusion and the facial profile. SIGNIFICANCE: Some early decisions that the orthodontist makes for a patient whose mandibular second premolars are congenitally missing will affect his or her dental health for a lifetime. Therefore, the correct decision must be made at the appropriate time. PURPOSE: In this article, we present and discuss various treatment alternatives for managing orthodontic patients with at least 1 congenitally missing mandibular second premolar.

Adolescent↗

CMT-3 inhibits orthodontic tooth displacement in the rat.

OBJECTIVE: Orthodontic tooth movement requires extensive remodeling of the periodontal ligament (PDL) and the alveolar bone. Osteoclasts resorb bone, allowing teeth to migrate in the direction of the force. Matrix metalloproteinases (MMPs) are able to degrade the extracellular matrix of the periodontal tissues. Chemically modified tetracyclines (CMTs) can inhibit MMPs, but lack antimicrobial activity. We hypothesize that CMT-3 will decrease the rate of orthodontic tooth movement in the rat. DESIGN: Eighteen Wistar rats received a standardized orthodontic appliance at one side of the maxilla. During 14 days, three groups of six rats received a daily dose of 0, 6 or 30mg/kg CMT-3, and tooth displacement was measured. Thereafter, osteoclasts were counted on histological sections using an ED-1 staining. Multi- and mononuclear ED-1-positive cells in the PDL were also counted. In addition, sections were stained for MMP-9. RESULTS: CMT-3 significantly inhibited tooth movement (p=0.03) and also decreased the number of osteoclasts at the compression sides in the 30mg/kg group (p<0.05). Significantly more mono- than multinuclear ED-1-positive cells were present in the PDL, but no significant differences were found between the dosage groups. Osteoclasts in the 30mg/kg group seemed to contain less MMP-9 than in the control. CONCLUSIONS: CMT-3 inhibits tooth movement in the rat, probably by reducing the number of osteoclasts at the compression side. This might be due to induction of apoptosis in activated osteoclasts or reduced osteoclast migration. Reduced MMP activity by CMT-3 might also directly inhibit degradation of the organic bone matrix.

Alveolar Process↗