Effects of diabetes on tooth movement and root resorption after orthodontic force application in rats

OBJECTIVE

To investigate the effects of diabetes on orthodontic tooth movement and orthodontically induced root resorption in rats.

SETTING AND SAMPLE POPULATION

Twenty-three 10-week-old male Sprague-Dawley rats divided into control (n = 7), diabetes (n = 9), and diabetes + insulin (n = 7) groups.

MATERIALS AND METHODS

Diabetes was induced by administering a single intraperitoneal injection of streptozotocin. Rats with a blood glucose level exceeding 250 mg/dl were assigned to the diabetes group. Insulin was administered daily to the diabetes + insulin group. A nickel-titanium closed-coil spring of 10 g was applied for 2 weeks to the maxillary left first molar in all rats to induce mesial tooth movement. Tooth movement was measured using microcomputed tomography images. To determine the quantity of root resorption, the mesial surfaces of the mesial and distal roots of the first molar were analyzed using both scanning electron microscopy and scanning laser microscopy.

RESULTS

After 2 weeks, the amount of tooth movement in the diabetic rats was lower than that in the control rats. Root resorption was also significantly lower in the diabetic rats. These responses of the rats caused by diabetes were mostly diminished by insulin administration.

CONCLUSIONS

Diabetes significantly reduced orthodontic tooth movement and orthodontically induced root resorption in rats. The regulation of blood glucose level through insulin administration largely reduced these abnormal responses to orthodontic force application.

Clinical guidelines for oral appliance therapy in the treatment of snoring and obstructive sleep apnoea

The purpose of this review is to provide guidelines for the use of oral appliances (OAs) for the treatment of snoring and obstructive sleep apnoea (OSA) in Australia. A review of the scientific literature up to June 2012 regarding the clinical use of OAs in the treatment of snoring and OSA was undertaken by a dental and medical sleep specialists team consisting of respiratory sleep physicians, an otolaryngologist, orthodontist, oral and maxillofacial surgeon and an oral medicine specialist. The recommendations are based on the most recent evidence from studies obtained from peer reviewed literature. Oral appliances can be an effective therapeutic option for the treatment of snoring and OSA across a broad range of disease severity. However, the response to therapy is variable. While a significant proportion of subjects have a near complete control of the apnoea and snoring when using an OA, a significant proportion do not respond, and others show a partial response. Measurements of baseline and treatment success should ideally be undertaken. A coordinated team approach between medical practitioner and dentist should be fostered to enhance treatment outcomes. Ongoing patient follow-up to monitor treatment efficacy, OA comfort and side effects are cardinal to long-term treatment success and OA compliance.

The biology of TMJ growth modification: a review

Several studies have indicated a positive response of the temporomandibular joint (TMJ) to mandibular advancement, while others have reported that TMJ adaptive responses are non-existent and negligible. Controversy continues to grow over the precise nature of skeletal changes that occur during mandibular growth modification, due to an apparent lack of tissue markers required to substantiate the precise mechanism by which this is occurring. However, evidence suggests that orthopedic forces clinically modify the growth of the mandible. To further our knowledge about the effect of orthopedic treatment on the TMJ, it is necessary that we understand the biologic basis behind the various tissues involved in the TMJ's normal growth and maturation. The importance of this knowledge is to consider the potential association between TMJ remodeling and mandibular repositioning under orthopedic loading. Considerable histologic and biochemical research has been performed to provide basic information about the nature of skeletal growth modification in response to mandibular advancement. In this review, the relevant histochemical evidence and various theories regarding TMJ growth modification are discussed. Furthermore, different regulatory growth factors and tissue markers, which are used for cellular and molecular evaluation of the TMJ during its adaptive response to biomechanical forces, are underlined.

Dissecting the role of the S1P/S1PR axis in health and disease

Sphingosine-1-phosphate (S1P) is a pleiotropic sphingophospholipid generated from the phosphorylation of sphingosine by sphingosine kinases (SPHKs). S1P has been experimentally demonstrated to modulate an array of cellular processes such as cell proliferation, cell survival, cell invasion, vascular maturation, and angiogenesis by binding with any of the five known G-protein-coupled sphingosine 1 phosphate receptors (S1P1-5) on the cell surface in an autocrine as well as a paracrine manner. Recent studies have shown that the S1P receptors (S1PRs) and SPHKs are the key targets for modulating the pathophysiological consequences of various debilitating diseases, such as cancer, sepsis, rheumatoid arthritis, ulcerative colitis, and other related illnesses. In this article, we recapitulate these novel discoveries relative to the S1P/S1PR axis, necessary for the proper maintenance of health, as well as the induction of tumorigenic, angiogenic, and inflammatory stimuli that are vital for the development of various diseases, and the novel therapeutic tools to modulate these responses in oral biology and medicine.

Effects of mechanical stimuli on adaptive remodeling of condylar cartilage

Trabecular bone has been shown to be responsive to low-magnitude, high-frequency mechanical stimuli. This study aimed to assess the effects of these stimuli on condylar cartilage and its endochondral bone. Forty female 12-week-old C3H mice were divided into 3 groups: baseline control (killed at day 0), sham (killed at day 28 without exposure to mechanical stimuli), and experimental (killed following 28 days of exposure to mechanical stimuli). The experimental group was subjected to mechanical vibration of 30 Hz, for 20 minutes per day, 5 days per week, for 28 days. The specimens were analyzed by micro-computed tomography. The experimental group demonstrated a significant decrease in the volume of condylar cartilage and also a significant increase in bone histomorphometric parameters. The results suggest that the low-magnitude, high-frequency mechanical stimuli enhance adaptive remodeling of condylar cartilage, evidenced by the advent of endochondral bone replacing the hypertrophic cartilage.

Cephalometric evaluation of condylar and mandibular growth modification: a review

OBJECTIVE

Based on a wealth of orthodontic archives, this work aims to review the cephalometric analysis systems that can identify the changes in condylar and mandibular position as well as growth direction in response to bite jumping therapy.

DESIGN

Numerous cephalometric approaches were screened to testify their feasibility and reliability in accurately depicting the growth modification of the condyle and the mandible. The critical assessment of the working mechanisms of these cephalometric methods was elaborated to help build up the rationale and justification for their clinical use.

RESULTS

1) The changes in condylar and mandibular size, position and growth direction can be identified by using lateral cephalograms with closed-mouth or open-mouth posture. 2) With superimposition methods where the anatomical structures for superimposition registration must be stable and reproducible, the growth modification of the condyle and the mandible between two time-points is qualitatively demonstrated in a diagram if reference lines are not constructed. The growth modification can be quantitatively identified if the reference lines are created. 3) With non-superimposition methods, the size and position of the condyle and the mandible are separately identified for each time-pint by relating them to the stable reference structures. The growth modification between two time-pints is evaluated by comparing the two separate measurements.

CONCLUSION

The application of a standardized and well designed cephalometric evaluation system may reduce the bias that attribute to the arbitrariness of the clinical effects of bite jumping functional appliances.

Validation of two-dimensional measurements of root resorption craters on human premolars after 28 days of force application

The aims of this study were to develop a three-dimensional (3D) mathematical model of a typical root resorption crater and to correlate two-dimensional (2D) surface area measurements to 3D volumetric measurements of root resorption craters created under light and heavy orthodontic forces. Data were obtained from a previous study of 36 first premolars from 16 subjects requiring extraction of these teeth as part of their orthodontic treatment. Buccal tipping forces of 25 or 225 g were applied for an experimental period of 28 days. After extraction, the samples were prepared for scanning electron microscopy (SEM) imaging, image processing and analysis. Surface area (2D) and volumetric (3D) measurements of all craters were obtained. A mathematical analysis of the 2D/3D relationship enabled the determination of an appropriate digital model for the shape, type and dimensions of resorption craters, which was also able to distinguish between a 'hemispheric' model versus a 'layered' model of craters. The results demonstrated that 2D and 3D measurements were strongly correlated (r = 0.991**). Within the light and heavy force groups, the measurements were also strongly correlated (r = 0.978** and r = 0.994**, respectively). For a 28 day experimental period, 2D measurements of root resorption craters were found to be as reliable as 3D measurements.

Exploring the third dimension in root resorption

OBJECTIVE

To review and investigate the validity of various 2D quantitative measurement techniques, and to explore the third dimension of root resorption.

DESIGN

A review of the literature involving various quantitative evaluation of root resorption.

RESULTS

Quantitative evaluation of resorption using radiographs has proven to be highly inaccurate because of magnification errors and their inability to be readily repeated and reproduced. Studies using histology sections of samples have proven to be laborious and technique sensitive. Inherent parallax errors and loss of material in data transfer have denied the true understanding of this 3D event.

CONCLUSION

With the evolution in computing technology and digital imaging, the vision of evaluating the extent of root resorption in 3D has materialized. It was demonstrated that 3D volumetric quantitative evaluation of root resorption craters was feasible and its accuracy and repeatability was high.

Root resorption and its association with alterations in physical properties, mineral contents and resorption craters in human premolars following application of light and heavy controlled orthodontic forces

OBJECTIVES

To study the effect of different orthodontic force levels on cementum, investigating from the point of view of its physical properties, alterations in the mineral components, type and location of the resorption craters and the exploration in 3D of space.

DESIGN

In vivo human premolars subjected to heavy and light forces were employed for this study. After a period of movement they were analyzed for hardness and elasticity. Also, the mineral composition measuring Ca, P and F of the cementum root surface was investigated. A new method for volumetric analysis of resorption craters was developed.

RESULTS

There were no significant differences for hardness and elastic modulus between the light and heavy force groups and no significant effects for different tooth positions. Significant inter-individual variation in the Ca, P and F concentrations was noted. Force-related data showed that mean volume of the resorption crater in light-force group was 3.49-fold greater than the control group, and the heavy-force group 11.59-fold more than control group. The heavy force group had 3.31-fold greater total resorption volume then light force group. Buccal cervical and lingual apical regions demonstrated significantly more resorption craters than the other regions. The 2D measurements were strongly correlated to 3D measurements.

CONCLUSION

The application of light and heavy forces did not show any statistically significant differences in hardness and elastic modulus when compared with untreated teeth. The inconsistent increase or decrease of Ca, P and F contents between control and experimental teeth at sites of compression and tension were difficult to explain. There was more resorption by volume in the heavy force group as compared with the light group and controls. Our data also suggested that the high-pressure zones might be more susceptible to resorption after 28 days of force application.

Cephalometric norms for the Chinese: a compilation of existing data

The intention of this paper is to compile Chinese cephalometric norms for a more objective orthodontic diagnosis of Chinese patients so that their orthodontic treatment may be better planned. Studies on cephalometric norms of Chinese and subjects of Chinese descent were reviewed. Some important studies were available only in the Chinese journals and they were especially procured and translated for this purpose. A normal range of anteroposterior apical base differences, concomitant nterincisal inclinations and locations, were derived from different Chinese groups and were tabulated. The differences between Chinese and Caucasian norms are discussed. A distinctive craniofacial and dental pattern of the people of Chinese origin was found and is reflected in the cephalometric measurements. Compared with Caucasian norms, Chinese norms have skeletal, dental and soft-tissue variations. The Chinese have a shorter cranial base and a larger ANB. The Chinese dentition demonstrates greater bimaxillary-alveolar protrusion, with a decreased interincisal angle. The Chinese soft-tissue profile shows a less prominent nose, with a less obtuse nasolabial angle, and more protrusive lips.

Varying treatments of Class II malocclusions: two case reports

Two female patients, JH aged 13 years 5 months and CN, aged 13 years 10 months, presented at the Sydney University Orthodontic Clinic, Australia. Patient JH complained that her lower teeth were "too far back behind her top teeth". She was treated using the Speed Appliance. Patient CN complained that her teeth were "crooked". The main point of interest of her case is the mechanics used following the extraction of her four first molar teeth. Both patients were keen to improve their appearance.

Profile of orthodontic services provided in private practice by general practitioners and specialist orthodontists for an insured population

In Australia, the proportion, volume and type of orthodontic care provided by general practitioners and orthodontists are largely unknown. The overall objective of this study was to create a profile of orthodontic services provided by general practitioners and orthodontists for a cohort of insured patients using private practices in New South Wales, Australia, from 1st January 1992 to 31st December 1995. Data were derived from claims records submitted by members of a health insurance fund for rebates for fees paid to private practitioners for orthodontic services they received during the study period. Distribution of the volume and type of service provided by general practitioners and orthodontists was compared using the Chi-squared test. Statistical significance was taken at the 5 per cent level. Orthodontic services were provided predominantly by orthodontists (80%). Fixed orthodontic treatment was provided almost exclusively (91%) by orthodontists. The majority of removable appliance services was provided by general practitioners. Orthodontists provided more orthodontic services in the capital city and other metropolitan areas, whereas general practitioners provided more orthodontic services in rural areas. Orthodontists provided more services to members in the highest socio-economic group, whereas general practitioners provided more services to members in the lowest socio-economic group.

Finishing occlusion in Class II or Class III molar relation: therapeutic Class II and III

The most frequent extraction regime consists of the removal of upper and lower premolars. Depending on anchorage requirements, camouflage treatment options, surgical intervention, or the absence of teeth in only one arch, it may become necessary to finalize the occlusion with a one-dental-unit discrepancy between the upper and lower dental arches. Guidelines are presented for finishing occlusions in Class II or Class III molar relation.

Physical properties of root cementum: Part I. A new method for 3-dimensional evaluation

Cementum is a nonuniform connective tissue that covers the roots of human teeth. Investigation of the physical properties of cementum may help in understanding or evaluating any possible connection to root resorption. A variety of engineering tests are available to investigate these properties. However, the thickness of the cementum layer varies, and this limits the applicability of these techniques in determining the physical properties of cementum. Hardness testing with Knoop and Vickers indentations overcame some of these limitations, but they prohibited the retrieval and retesting of the sample and therefore the testing was restricted to one area or section of the tooth. Another limiting factor with the existing techniques was the risk of artifacts related to the embedding material such as acrylic. A new method to investigate the physical properties of human premolar cementum was developed to obtain a 3-dimensional map of these properties with the Ultra Micro Indentation System (UMIS-2000; Commonwealth Scientific and Industrial Research Organization, Campbell, Australia). UMIS-2000 is a nano-indentation instrument for investigation of the properties of the near-surface region of materials. Premolars were harvested from orthodontic patients requiring extractions and then mounted on a newly designed surveyor that allowed sample retrieval and 3-dimensional rotation. This novel method enabled the quantitative testing of root surface cementum, on all 4 root surfaces, extending from the apex to the cementoenamel junction at 60 different sites.

A randomized, controlled study of a mandibular advancement splint for obstructive sleep apnea

Although there is increasing interest in the use of oral appliances to treat obstructive sleep apnea (OSA), the evidence base for this is weak. Furthermore, the precise mechanisms of action are uncertain. We aimed to systematically investigate the efficacy of a novel mandibular advancement splint (MAS) in patients with OSA. The sample consisted of 28 patients with proven OSA. A randomized, controlled three-period (ABB/BAA) crossover study design was used. After an acclimatization period, patients underwent three polysomnographs with either a control oral plate, which did not advance the mandible (A), or MAS (B), 1 wk apart, in either the ABB or BAA sequence. Complete response (CR) was defined as a resolution of symptoms and a reduction in Apnea/Hypopnea Index (AHI) to < 5/h, and partial response (PR) as a > or = 50% reduction in AHI, but remaining > or = 5/h. Twenty-four patients (19 men, 5 women) completed the protocol. Subjective improvements with the MAS were reported by the majority of patients (96%). There were significant improvements in AHI (30 +/- 2/h versus 14 +/- 2/h, p < 0.0001), MinSa(O(2)) (87 +/- 1% versus 91 +/- 1%, p < 0.0001), and arousal index (41 +/- 2/h versus 27 +/- 2/h, p < 0.0001) with MAS, compared with the control. The control plate had no significant effect on AHI and MinSa(O(2)). CR (n = 9) or PR (n = 6) was achieved in 62.5% of patients. The MAS is an effective treatment in some patients with OSA, including those patients with moderate or severe OSA.

The effects of low level laser irradiation on osteoblastic cells

Low level laser therapy has been used in treating many conditions with reports of multiple clinical effects including promotion of healing of both hard and soft tissue lesions. Low level laser therapy as a treatment modality remains controversial, however. The effects of wavelength, beam type, energy output, energy level, energy intensity, and exposure regime of low level laser therapy remain unexplained. Moreover, no specific therapeutic window for dosimetry and mechanism of action has been determined at the level of individual cell types. The aim of this study was to investigate the effects of low level laser irradiation on the human osteosarcoma cell line, SAOS-2. The cells were irradiated as a single or daily dose for up to 10 days with a GaAlAs continuous wave diode laser (830 nm, net output of 90 mW, energy levels of 0.3, 0.5, 1, 2, and 4 Joules). Cell viability was not affected by laser irradiation, with the viability being greater than 90% for all experimental groups. Cellular proliferation or activation was not found to be significantly affected by any of the energy levels and varying exposure regimes investigated. Low level laser irradiation did result in a heat shock response at an energy level of 2 J. No significant early or late effects of laser irradiation on protein expression and alkaline phosphatase activity were found. Investigation of intracellular calcium concentration revealed a tendency of a transient positive change after irradiation. Low level laser irradiation was unable to stimulate the osteosarcoma cells utilised for this research at a gross cell population level. The heat shock response and increased intracellular calcium indicate that the cells do respond to low level laser irradiation. Further research is required, utilising different cell and animal models, to more specifically determine the effects of low level laser irradiation at a cellular level. These effects should be more thoroughly investigated before low level laser therapy can be considered as a potential accelerator stimulus for orthodontic tooth movement.

Effects of static magnetic and pulsed electromagnetic fields on bone healing

The purpose of the present study was to evaluate the healing pattern of an experimentally induced osteotomy in Hartley guinea pigs in the presence of static magnetic and pulsed electromagnetic fields. The sample consisted of 30 Hartley guinea pigs 2 weeks of age divided into 3 groups: pulsed electromagnetic, static magnetic, and control. An osteotomy was performed in the mandibular postgonial area in all groups under general anesthesia. During the experimental period of 9 days, the animals were kept in experiment cages 8 hours per day, the first two groups being in the presence of pulsed electromagnetic and static magnetic field, respectively. Based on histologic results, both static and pulsed electromagnetic fields seemed to accelerate the rate of bone repair when compared to the control group. The osteotomy sites in the control animals consisted of connective tissue, while new bone had filled the osteotomy areas in both magnetic field groups.

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 products.

The drum spring (DS) retractor: 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 the 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 spring.

Distal molar movement using the pendulum appliance. Part 1: Clinical and radiological evaluation

Intra-arch distal molar movement techniques have recently assumed an important role in clinical orthodontics. In this study, the dental and skeletal effects of the pendulum appliance, applying 200 to 250 g of force to the molars in 13 patients (age range 8 years to 13 years 5 months) were evaluated by means of cephalometric radiographs. The results showed that the pendulum appliance moved the molars distally without creating dental or skeletal bite opening and with little incisor anchorage loss. However, important molar tipping should be taken into consideration when using this appliance.

Distal molar movement using the pendulum appliance. Part 2: The effects of maxillary molar root uprighting bends

A clinical study was recently undertaken to evaluate the dental and skeletal effects of the pendulum appliance (PA). In the present study, the appliance was modified by incorporating an uprighting bend into the distalizing spring during the second phase of treatment to avoid excessive distal tipping of the maxillary molars. The sample consisted of 20 patients: 8 females and 12 males, mean age 13.11 +/- 1.10 years. Eight of the patients were subjected to a slow rate of maxillary expansion. Measurements were obtained from cephalometric headfilms prior to (T1) and the day of removal (T2) of the PA. Treatment changes were analyzed and compared with the previous study. The PA with uprighting bends led to reduced molar tipping without significantly changing the effects of the PA, with the exceptions of 0.62 mm more anchorage loss of the maxillary incisor edge and increased treatment time. There was no significant difference in anchorage loss between the patients with and without maxillary expansion.

The effects of samarium-cobalt magnets and pulsed electromagnetic fields on tooth movement

The purpose of this study was to determine whether the application of either samarium cobalt magnets or pulsed electromagnetic fields could increase the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the effect of a magnetic field on bony physiology and metabolism and to monitor for possible systemic side effects. Fifteen grams of laterally directed orthodontic force were applied to move the maxillary central incisors of a sample of 18 young male Hartley guinea pigs divided into three groups: group 1, an orthodontic coil spring was used to move the incisors; group 2, a pair of samarium-cobalt magnets provided the tooth moving force; and group 3, a coil spring was used in combination with a pulsed electromagnetic field. The results showed that both the static magnetic field produced by the samarium-cobalt magnets and the pulsed electromagnetic field used in combination with the coil spring were successful in increasing the rate of tooth movement over that produced by the coil springs alone. The mechanism producing this effect appears to have involved a reduction in the "lag" phase often seen in orthodontic tooth movement. Both magnetically stimulated groups also showed increases in both the organization and amount of new bone deposited in the area of tension between the orthodontically moved maxillary incisors.

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 radiographic 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 conclusions.

Magnetic activator device II (MAD II) for correction of Class II, division 1 malocclusions

A magnetically active, two-piece (upper and lower), functional orthopedic appliance has been developed, magnetic activator device (MAD) for the correction of Class II malocclusions. The magnetic forces are used to give freedom of mandibular movement and to allow for continuous functioning of the orofacial muscles when the appliance is worn. Samarium cobalt (Sm2Co17) magnets are incorporated on the buccal aspects of the upper and lower appliances. Magnetic forces ranging from 150 to 600 gm per side have been used on patients, and it seems that the skeletal versus dental response depends on the intensity of the magnetic force used. A force of 300 gm, when the magnets are in contact, on each side has been found to be an appropriate value in patients age 7 to 12 years. The use of this less bulky design rather than a traditional orthopedic appliance, along with the freedom of function it permits, has enabled patients to wear the appliance nearly 24 hours in most cases.