Long-term application of chincup force alters the morphology of the dolichofacial Class III mandible.

The conventional orthopedic Milwaukee brace exerts a large and continuous force that induces malocclusion and a significant deformation of the mandible. Our previous chincup study examined its use in moderately severe mandibular prognathism without retrusion of the maxilla. The orthopedic force was approximately 500 g at the center of chin and was applied during sleep for 6 to 24 months. For mandibular prognathism subjects (means, 1.0 degrees and -1.3 degrees of ANB angle in the prepubertal and pubertal subjects), the resultant changes were maintained after retention. However, research reported that the changes obtained during chincup treatment (average, 4 (1/2) years' use) were often not maintained in severe skeletal Class III malocclusion. The aim of this clinical study was to investigate the immediate and long-term effects of prolonged use (mean, 7 years 2 months) of chincup appliances in subjects with dolichofacial Class III mandibles. Thirty-six female subjects with severe skeletal Class III malocclusions, associated with large gonial angles, were selected from the dental records of a private clinic. At posttreatment (T1, 65 months' duration) and postretention (T2, 56 months after T1), Ar-Me and Wits appraisal cephalometric parameters were significantly different (P <.01) between patients and control subjects (n = 230). Furthermore, the Go-Me parameter in treated subjects was longer than that of the controls at T0 but became significantly shorter at T2 (P <.01). Treatment was associated with a finding that the Ar-Go parameter increased less than the controls at T2. Our results indicate that long-term use of the chincup appliance (>5 years) is effective in subjects with severe skeletal Class III abnormality.

The effectiveness of protraction face mask therapy: a meta-analysis.

This study examined the effectiveness of maxillary protraction with orthopedic appliances in Class III patients. A meta-analysis of relevant literature was performed to determine whether a consensus exists regarding controversial issues such as the timing of treatment and the use of adjunctive intraoral appliances. An initial search identified 440 articles relating to Class III malocclusion. Among those articles, 11 studies in English and 3 studies in foreign languages met the previously established selection criteria. Data from the selected studies were categorized by age and appliance groups for the meta-analysis. The sample sizes were comparable between the groups. The statistical synthesis of changes before and after treatment in selected cephalometric landmarks showed no distinct difference between the palatal expansion group and nonexpansion group except for 1 variable, upper incisor angulation, which increased to a greater degree in the nonexpansion group. This finding implies that more skeletal effect and less dental change are produced in the expansion appliance group. Examination of the effects of age revealed greater treatment changes in the younger group. Results indicate that protraction face mask therapy is effective in patients who are growing, but to a lesser degree in patients who are older than 10 years of age, and that protraction in combination with an initial period of expansion may provide more significant skeletal effects. Overall mean values and corresponding standard deviations for the studies selected can also be used to estimate mean treatment effects expected from the use of protraction face mask.

Reaction of the pterygomaxillary fissure and the condylar cartilage to intermaxillary Class III magnetic mechanics.

The skeletal reaction to Class III intermaxillary magnetic mechanics was previously found to affect two target areas, the pterygomaxillary fissure (PMF) and the condylar cartilage. The objectives of this study were to analyze, radiographically and histologically, the response of these tissues to Class III intermaxillary functional orthopedic magnetic appliance (FOMA III), and to postulate possible models of their dichotomous biomechanism. Nine Macaca fascicularis monkeys received periodic administration of vital bone procion dye and were treated for 4 months with FOMA III (6 subjects) and sham appliance (3 subjects). The PMF (the target area of the midfacial complex) demonstrated a decreased skeletal reaction in inferosuperior and lateromedial directions. Cephalometrically, the lowermost PMF point was displaced inferiorly 1.98 +/- 1.74 mm and 0.42 +/- 0.38 mm and anteriorly 1.42 +/- 0.96 mm and 0.58 +/- 0.38 mm in the treated and control groups, respectively. The displacement of the uppermost PMF point, compared with the lowermost point, was three to five times lower. Histologically, two modes of response were found; first, a sutural response (disarticulation and osteogenesis) of the palatomaxillary and pterygopalatine sutures, which was distinctive of the lateral PMF aspect, and second, a dentosutural response, which was characteristic of the medial PMF aspect (bony microfractures between the third molar germ and the maxillary tuberosity in conjunction with mild sutural response). In the mandible, a discrepancy was found between the histologic and the cephalometric findings. Radiographically, mandibular length was unaffected after 4 months of treatment, and the distance condylion-pogonion was equally increased in the treated (0.75 +/- 0.78 mm) and the control animals (0.77 +/- 0.32 mm). Histologically, however, the condylar cartilage demonstrated increased osteoclastic activity at the zone of endochondral ossification and a decreased apposition rate at the adjacent bony trabeculae. Conceivably, the two target areas (PMF sutures versus condylar cartilage) demonstrate two diverse time-related responses that are either unrelated or interrelated to each other. An unrelated tissue response suggests that tissue stimulation (sutural) is always superior to tissue suppression (condylar). Another possible unrelated tissue reaction implies diverse response velocity (high sutural, low condylar). An interrelated mechanism suggests that an applied force will dissipate initially at the less resistant target area (sutures), and will subsequently affect the more resistant target area (condyle) once the sutural resistance exceeds a certain threshold. The fact that no pathologic change was found in the condylar cartilage encourages a long-term use of the FOMA III appliance, initiating treatment at an early skeletal age.

Repair process of external root resorption subsequent to palatal expansion treatment.

The repair process of external root resorption (ERR) and the role of retention mechanics in enhancing ERR repair were studied on eight Macaca fascicularis monkeys that were divided equally into short- and long-term groups. Six monkeys received palatal expansion appliances, and two received sham appliances. The short-term group received active treatment. The long-term group received additional retention (4 months) and relapse (2 months) treatment periods with biweekly injections of individual vital dye per phase, i.e., procion red H-8B and violet H-3R (80 mg/kg B.W.), respectively. Histomorphologic examinations included scanning electron microscopy, light, and ultraviolet microscopy. The short-term group demonstrated penetrated resorption with pulp exposure at sites with initial deficiency of the protecting odontoblastic layer (apical zone, nutrition canal). The long-term group showed two forms of ERR repair: (1) Nonfunctional retarded repair cementum, comprised of overlapped incremental lines and deprived of extrinsic fibers, was delineated in severe pulp exposure. The pulp/dentin complex showed intense incorporation of procion dye in the dentinal tubuli, conceivably related to a defense response in the form of sclerotic dentin. (2) Functional rapid repair cementum, comprised of discriminated incremental lines mainly of mixed cellular cementum, with a consistent pattern of five sequential phases: the lag phase (14 to 28 days), the incipient phase (14 days), the peak phase (14 to 28 days), the steady phase (42 to 56 days) and the retreating phase (70 days). Sharpey's fibers at functional ERR sites were scarce, never emerging from the dentinocemental junction, and not developing into principal fibers. The pulp/dentin complex showed an increase in pulp stones but no formation of tertiary dentin. The apical area responded by hypercementosis in the form of apical occlusion and a displaced pulp canal. The application of a fixed retention device is recommended in light of accelerated apposition of repair cementum during the retention period. However, increased formation of Sharpey's fibers during the relapse period might suggest a restricted duration in splinting therapy.

Rare earth magnets and impaction.

Aberration in the eruption process was found to be a prime etiologic factor in inducing impaction. Thus an ideal treatment approach should attempt to mimic the normal eruption modus. However, conventional traction methods have been found to be associated with gingiva inflammation, bone recession, reduced attached gingiva, periodontal pockets, exposed cementoenamel junction, and root resorption of the impacted and adjacent teeth. These side effects are the result of premature exposure of the impacted tooth to the oral cavity through a nonself-cleansing pathway and an uncontrolled force system. The present study introduces a new, magnetic attraction system, with a magnetic bracket bonded to an impacted tooth and an intraoral magnet linked to a Hawley type retainer. Vertical and horizontal magnetic brackets were designed, with the magnetic axis magnetized parallel and perpendicular to the base of the bracket, respectively. The vertical type is used for impacted incisors and canines, and the horizontal magnetic bracket is applied for impacted premolars and molars. A three-dimensional analysis of the magnetic force system, by means of the OMSS apparatus, found the small magnetic bracket combined with a large pole surface area of the intraoral magnet to exhibit the most efficient convergent guidance. For this report the magnetic eruption device was examined on one animal subject and four patients. The Nd2Fe14B magnets were coated with parylene and/or encapsulated in stainless steel housings. In deep impaction, the magnetic bracket was cold-sterilized before surgery, and the surgical mucoperiosteal flap was then sutured over the bonded magnetic bracket. Attraction was initiated 1 to 2 weeks after healing. Thus tooth emergence into the oral cavity replicated normal eruption conditioning. The system operated at an attractive force level of 0.2 to 0.5 N. Adjustment was accomplished by temporarily interposing a magnetic spacer between the two magnetic units. No side effects were observed in this restricted number of treated cases, and treatment time was reduced. The study recommends the application of magnets in the treatment of impaction on the grounds of less invasive surgical procedure, effective attractive forces at short distances, and controlled spatial guidance.

[The causes of and repair procedures in external root resorption following palatal suture expansion with magnetic and conventional dilators. Experimental animal research on Macaca fascicularis monkeys]. / Ursachen und Reparaturvorgänge der externen Wurzelresorption nach Gaumennahterweiterung mit magnetischen und konventionellen Dehnapparaten. Tierexperimentelle Untersuchung an Macaca-fascicularis-Affen.

Eight Macaca fascicularis monkeys received rapid maxillary expansion with conventional and magnetic appliances. The histomorphometric analysis (SEM) showed increased external root resorption (ERR) in: multirooted teeth, buccal root surfaces, mesiobuccal roots and apical zones. ERR is determined by the impulse, the decrease in the periodontal width and the extent of mineralization of adjacent hard tissues. The microscopic examinations of light, UV and SEM defined two types of cellular cement in ERR areas: a) unfunctional repair cement (slow type), b) functional repair cement (rapid type). The first was characterized by the absence of Sharpey's fibers and by overlapped incremental lines, the second by the formation of new Sharpey's fibers and discriminated incremental lines. These incremental lines indicate five sequential phases with diverse rates of cement apposition, i.e. lag-, incipient-, peak-, steady-, and retreating phase. Therefore, the study recommends the application of a fixed retainer immediately subsequent to rapid maxillary expansion which is followed by an intermittent retention appliance.

[The anatomical and physiological aspects in the treatment of temporomandibular joint disorders]. / Anatomische und physiologische Aspekte bei der Behandlung von Kiefergelenkstörungen.

The specialty of orthodontics and its relationship to TMJ problems is in the thick of controversy. Several anatomic and physiologic aspects are discussed so as to improve the understanding of the multi-faceted problems. The use of this biologically-based information is likely to make therapy more successful. From a therapeutic point of view, it is incumbent on the dentist to institute early preventive or interceptive procedures.

Determinants controlling iatrogenic external root resorption and repair during and after palatal expansion.

The mechanisms controlling iatrogenic external root resorption (ERR) and repair were studied on 8 Macaca fascicularis monkeys. The animals were divided into short-term and long-term groups, and were treated with jackscrew, magnetic and sham palatal expansion appliances. Scanning electron microscopy morphometric analysis found major evidence of ERR in the tooth-borne jackscrew appliance, in the long-term group, in the maxillary premolars, on the buccal and furcation root surfaces, on the mesiobuccal root, and in the apical zone. Correspondingly, the ERR mechanism is controlled by the impulse (F. delta t) and the critical barrier of the periodontal ligament as primary determinants and by the environmental density as a secondary determinant. ERR is initially regulated by the force component of the impulse and, with increased duration, by the time component of the impulse. The impairment/repair dynamics were found to be regulated by three principles: ERR level of irreversibility, delayed resorption response and jiggling.