Clinical application of magnets in orthodontics and biological implications: a review

Over the last decade magnets have been used in orthodontic and dentofacial orthopaedics and attempts have been made to evaluate the biological implications of magnets and magnetic fields during clinical application. This review aims to indicate the advantages and disadvantages of magnets in orthodontics and dentofacial orthopaedics over traditional techniques, and update related clinical experiences. The treatment of impacted teeth and Class II malocclusions by means of magnetic force is favoured and the correction of Class III and open bite malocclusions involving the use of magnets also appears promising. The advantages of magnets over traditional force delivery systems are: frictionless mechanics, when the magnets are in attractive configuration; predictable force levels, no force decay over time and less patient co-operation. However, the size of the magnets can increase the bulk of the appliance and three-dimensional control is limited when the magnets are in a repulsive configuration. In addition magnets used in vivo require a coating to prevent corrosion and the possible side effects of corrosive product

The drum spring (DS) retractor: a constant and continuous force for canine retraction

Although much research has been undertaken on the rate of tooth movement, with different hypotheses having been put forward, the concepts of threshold, light, heavy and optimal forces are not still clear. It has been stressed that an ideal orthodontic spring should have the ability to release a constant force throughout the entire range of its activation, but using traditional techniques applied initial force will decrease, depending on its deactivation due to the tooth movement and the physical properties of the force delivery system. The purpose of this study was to test the clinical use of a new and original spring, the drum spring (DS) retractor (developed in 1992), which applies a constant and continuous force without the need for reactivation, and to compare the effect of a constant and continuous force versus a continuous but diminishing force produced by a traditional pull coil (PC) retractor system on the rate of upper canine retraction. The clinical sample consisted of 15 patients with upper first premolar extractions. For each patient, the upper right canine was retracted by using a DS retractor applying a constant and continuous force of 50 g; the upper left canine was fitted with a conventional PC applying an initial force of 50 g, diminishing proportionally with the distal movement of the canine. In addition, each group was divided according to the age of each patient: eight patients (three males, five females) between 11.8 and 14.4 years of age (mean 13±1.2 years) represented the adolescent group, and seven patients (three males, four females) between 18.8 and 21.6 years of age (mean 18.2±1.9 years) representing the adult group. The experimental period started 1 week after the extraction of the first premolars. During this period no archwire was used, to avoid friction and force level changes, and the both springs were attached to a 6 mm hook fixed on the canine bracket to reduce tipping. The PC retractor was reactivated every 3 weeks whereas the DS retractor was left untouched over the entire experimental period. The study was continued until one of the two canines was completely retracted. The DS retractor was successful for space closure without any reactivation, and the continuous and constant force provided a more rapid canine movement than the continuous but diminishing force. Canine retraction occurred faster in adolescents than in adults. An entire field of clinical and research applications may be influenced by this new type of sprin

Light maxillary expansion forces with the magnetic expansion device. A preliminary investigation

An active maxillary magnetic expansion device (MED) was developed to be used clinically. The aim was to show the effects of light and continuous forces producing less traumatic stimulation of maxillary sutural growth than a conventional rapid maxillary expansion device. In this study, two different types of appliances were used on six patients between 7 years 4 months and 16 years 2 months: the first type was bonded, the other one used bands. For better appreciation, four implants were placed on each patient: two apically between central and lateral incisors, and two between second premolars and molars. A standardized radio-graphic technique was used to take occlusal radiographs, and postero-anterior and lateral headplates. The results varied according to the age and the appliance used. The skeletal effect with the banded MED was between 16 and 77 per cent, and for the bonded MED 0 and 25 per cent in comparison to the overall expansion. It seems that 250-500 g of continuous magnetic forces can produce dental and skeletal movements in a light force expansion concept, but further studies with larger samples are needed to make firm conclusion

A comparative assessment of the dentoskeletal effects of clear aligners vs miniplate-supported posterior intrusion with fixed appliances in adult patients with anterior open bite. A multicenter, retrospective cohort study.

INTRODUCTION This study aimed to retrospectively evaluate the dentoskeletal effects of clear aligners (Invisalign) vs miniplate-supported posterior intrusion (MSPI) and identify factors associated with posttreatment overbite in adults with anterior open bite. METHODS Twenty-nine patients treated with Invisalign and 24 with MSPI combined with full-fixed orthodontic appliances were included from 5 orthodontic practices. Pretreatment and posttreatment lateral cephalometric measurements were included as outcomes. Comparisons across groups and identification of final overbite predictors were assessed with regression modeling and machine learning techniques. RESULTS MSPI induced significantly greater maxillary molar intrusion (1.5 mm; 95% confidence interval [CI], 0.83-2.17; P <0.001), with subsequent reduction of anterior face height (ANS-Me) (-2.77 mm; 95% CI, -3.64 to -1.91; P <0.001), Mp-SN° (-1.95°; 95% CI, -2.77 to -1.12; P <0.001), and ANB° (-1.69°; 95% CI, -2.44 to -0.94; P <0.001) compared with Invisalign. MSPI resulted in a significantly larger increase in SNB° (0.94°; 95% CI, 0.23-1.65; P = 0.01) and point-Pog projection (2.45 mm; 95% CI, 1.12-3.77; P = 0.001). Compared with MSPI, Invisalign had a significantly greater increase in the distance of maxillary (1.05 mm; 95% CI, 0.38-1.72; P = 0.003) and mandibular (0.9 mm; 95% CI, 0.19-1.60; P = 0.01) incisal edges relative to their apical bases, with borderline greater lingual tipping of only the maxillary incisors (2.82°; 95% CI, -0.44 to 6.09; P = 0.09). Appliance type and initial overbite were significant final overbite predictors across all models. However, this difference was only evident in male patients (males [1.65; 95% CI, 0.99-2.32; P <0.001]; female [-0.04; 95% CI, -0.52 to 0.44; P = 0.87]). CONCLUSIONS Both appliances effectively improve overbite. MSPI applied the correction via molar intrusion and counterclockwise mandibular autorotation, whereas Invisalign via maxillary and mandibular incisor extrusion

A Patient with 22q11.2 Deletion Syndrome: Case Report

22q11 deletion is one of the most frequently encountered genetic syndromes. The phenotypic spectrum shows a wide variability. We report a boy who presented at age 11.9 years with seizures due to hypocalcemia as a result of hypoparathyroidism. FISH analysis revealed a heterozygote deletion at 22q11.2. Positive findings for the syndrome were delayed speech development due to velofacial dysfunction, recurrent croup attacks in early childhood due to latent hypocalcemia and mild dysmorphic features. The findings of this patient indicate that 22q11 deletion syndrome may present with a wide spectrum of clinical findings and that this diagnosis needs to be considered even in patients of older ages presenting with hypocalcemia

Repair of root resorption 2 to 16 weeks after the application of continuous forces on maxillary first molars in rats: a 2- and 3-dimensional quantitative evaluation.

INTRODUCTION: Root resorption is a side effect of orthodontic treatment that occurs with the removal of hyalinized tissue. Studies have shown that a reparative process in the periodontium begins when the applied orthodontic force is discontinued or reduced below a certain level. However, quantitative 3-dimensional evaluation of root resorption repair has not been done. The aim of this study was to quantitatively assess the 2- and 3-dimensional changes of root resorption craters after 2 weeks of continuous mesially applied orthodontic forces of 50 g on rat molars and 2- to 16-week retention periods. METHODS: We used 60 male Wistar rats (10 weeks old). Nickel-titanium closed-coil springs were used to apply 50-g mesial forces for 2 weeks to move the maxillary left first molars. The rats were randomly allocated to 6 groups. Those in the zero-week retention group were killed after force application. In the remaining 5 groups, the interdental spaces between the maxillary first and second molars were filled with resin to retain the molars. The molars were extracted after periods of retention from 2 and 16 weeks. The maxillary right molars were used as the controls. Mesial and distal roots (distobuccal and distopalatal) were examined by using scanning electron and 3-dimensional scanning laser microscopes. The surface area, depth, volume, and roughness of the root resorption craters were measured. RESULTS: The area, depth, and volume of the craters decreased gradually and showed similar trends over the retention time, approaching a plateau at the 12th week. After 16 weeks of retention, the volumes of the resorption craters of the distobuccal and distopalatal roots reached recovery peaks of 69.5% and 66.7%, respectively. Small pits on the mesial roots showed recovery of 62.5% at the 12th week. The healing patterns in distal roots with severe resorption and mesial roots with shallow resorption had no significant differences. CONCLUSIONS: The resorption and repair processes during the early stages of retention are balanced, and most of the reparative process occurs after 4 weeks of passive retention after the application of orthodontic force. Frequent orthodontic reactivations should be avoided to allow recovery and repair of root surface damage

The role of rapid maxillary expansion in the promotion of oral and general health

Rapid maxillary expansion (RME) is an effective orthopedic procedure that can be used to address problems concerned with the growth of the midface. This procedure also may produce positive side effects on the general health of the patient. The aim of the present consensus paper was to identify and evaluate studies on the changes in airway dimensions and muscular function produced by RME in growing patients. A total of 331 references were retrieved from a database search (PubMed). The widening of the nasal cavity base after midpalatal suture opening in growing patients allows the reduction in nasal airway resistance with an improvement of the respiratory pattern. The effects of RME on the upper airway, however, have been described as limited and local, and these effects become diminished farther down the airway, possibly as a result of soft-tissue adaptation. Moreover, limited information is available about the long-term stability of the airway changes produced by RME. Several studies have shown that maxillary constriction may play a role in the etiology of more severe breathing disorders such as obstructive sleep apnea (OSA) in growing subjects. Early orthodontic treatment with RME is able to reduce the symptoms of OSA and improve polysomnographic variables. Finally, early orthopedic treatment with RME also is beneficial to avoid the development of facial skeletal asymmetry resulting from functional crossbites that otherwise may lead to functional and structural disorders of the stomatognathic system later in life

3D effects of a bone-anchored intra-oral protraction in treating class III growing patient: a pilot study

Objectives: The aim of this prospective case series study is to assess the three-dimensional (3D) skeletal and soft tissue effects of the alternate rapid maxillary expansion and constriction (Alt-RAMEC) protocol in conjunction with a miniscrew-supported class III elastic wear in class III growing patients. Materials and methods: Fourteen consecutive participants (mean age 12.05 ± 1.09 years), who displayed class III malocclusions with retrognathic maxillae, were recruited. A cone beam computed tomography (CBCT) scan was acquired before commencing treatment (T1). All participants were treated with a tooth-bone-borne rapid maxillary expansion (hybrid MARME) appliance that was activated by the Alt-RAMEC protocol for 9 weeks. This was followed by full-time class III elastics, delivering 400 g/side, to protract the maxilla. When a positive overjet was achieved, protraction was ceased and a post-treatment CBCT scan (T2) was taken. The 3D analysis of pre- and post-treatment CBCT scans was blinded. The scans were registered on the anterior cranial base. The Euclidean distance between the two extracted surface models of the pre- and post-treatment scans was displayed as a color surface map. Results: All participants completed the intervention successfully. The majority of the participants showed protraction of the anterior maxillary region (71.4%) and in the zygomatic processes (64.2%). The maxilla significantly protracted (SNA 1.87° ± 1.06°; Vert.T-A 3.29 ± 1.54 mm), while the mandibular base significantly redirected posteriorly (SNB − 2.03° ± 0.85°, Vert.T-B − 3.43 ± 4.47 mm) and that was reflected on the ANB and Wits measurements. No adverse effects were observed. Conclusion: Class III elastics combined with the Alt-RAMEC activation protocol of the hybrid MARME appliance is an effective treatment method for mild/moderate class III malocclusions. A long-term follow-up and comparisons with other treatment modalities are required