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Biomedical subjects

T M Graber

Publications and source records attributed to T M Graber.

At least 19 recordsLinked to original sources
PubMed1991

[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].

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.

Animals↗
PubMed1991

[The anatomical and physiological aspects in the treatment of temporomandibular joint disorders].

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.

Dental Occlusion↗
PubMed1991

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.

Adolescent↗
PubMed1991

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.

Animals↗
PubMed1990

Functional orthopedic magnetic appliance (FOMA) III--modus operandi.

An intraoral intermaxillary appliance has been developed for the treatment of Class III malocclusions that exhibit midface sagittal deficiency with or without mandibular excess. The functional orthopedic magnetic appliance (FOMA) III consists of upper and lower acrylic plates with a permanent magnet incorporated into each plate. The upper magnet is linked to a retraction screw. The upper magnet is retracted periodically (e.g., monthly) to stimulate maxillary advancement and mandibular retardation. The attractive mode neodymium magnets used in this study produced a horizontal force of 98 gm and a vertical force of 371 gm. Six female Macaca fascicularis monkeys were treated with FOMA IIIs. An additional three animals were treated with sham appliances. After 4 months of treatment, the following results were found: the growth pattern of the cranial base (saddle angle) was not altered; midfacial protraction did occur along a recumbent hyperbolic curve with a horizontal maxillary displacement and an anterosuperior premaxillary rotation; the cumulative protraction of the maxillary complex was initiated at the pterygomaxillary fissure with an additional contribution provided by other circummaxillary sutures (zygomaticomaxillary s., transverse s., premaxillary s.); and inhibition of mandibular length was minimal, but a tendency toward a vertical condylar growth pattern was observed. The interaction between sutural and condylar growth sites appeared biphasic, characterized by an immediate and rapid excitation of the circummaxillary sutures followed by a delayed and slow suppression of the condylar cartilage. Long-term animal and clinical FOMA III studies are recommended.

Animals↗
PubMed1989

Functional orthopedic magnetic appliance (FOMA) II--modus operandi.

A new functional appliance (FA) to correct Class II dentoskeletal malocclusions is introduced. The functional orthopedic magnetic appliance (FOMA) II uses upper and lower attracting magnetic means (Nd2Fe14B) to constrain the lower jaw in an advanced sagittal posture. In vitro, a special gauge transducer measured the magnetic attractive path and forces. In vivo, 13 prepubertal female Macaca fascicularis monkeys received facial implants and were treated for 4 months with the following appliances: conventional FA (four subjects), FOMA II (five subjects), a combined FOMA II + FA (two subjects), and sham (control) appliance (two subjects). The in vitro results showed the following: vertico-sagitally displaced upper and lower magnets attracted ultimately along an oblique line with a terminal horizonal slide to become fully superimposed; the functional performance improved when the magnetic interface acted as a magnetic inclined plane; and the magnetic force was able to guide and constrain the mandible toward the constructive protrusive closure position (CPCP) (1.2 mm, F = 570 gm) from levels below the habitual rest position (3 mm, F = 219 gm) and the electromyographic (EMG) relaxed position (8.5 mm, F = 45 gm). The in vivo results demonstrated the following: functional performance increased in FOMA II (22%) and in the combined FOMA II + FA (28%) over the conventional FA; mandibular length increased significantly in the treated animals (means = 2.83 +/- 0.70 mm) over the control animals (means = 0.43 +/- 0.08 mm); incisor proclination was lower in magnetic appliances (means = 4.57 +/- 1.76 degrees) than in the conventional FA (means = 8.75 +/- 1.85 degrees); mandibular elongation and condylar posterior inclination resulted from posterosuperior endochondral growth (increased cell proliferation and/or hyperplasia of functional chondroblasts) and by bony remodeling of the condylar neck (apposition posterior border, resorption anterior border), respectively; virtually no anterior displacement of the postglenoid spine (means = 0.19 +/- 0.68 mm) nor the articular eminence (means = 0.36 +/- 0.69 mm) was found. Increased lower posterior alveolar height (means = 1.71 +/- 0.82 mm) is a major impediment in the correction of excessive lower anterior facial height. The results of the study highly recommend the exploration of the clinical application of the FOMA II.

Activator Appliances↗
PubMed1989

Stability of magnetic versus mechanical palatal expansion.

Spatial stability following palatal expansion (PE) treatment was studied longitudinally on 8 Macaca fascicularis monkeys. The sample was divided into short-term and long-term groups. The four subjects in each group received: (1) an indirect screw (IS) PE appliance (F = 2035 g), (2) an indirect magnetic (IM) PE appliance (F = 258 g and 360 g), (3) a direct magnetic (DM) PE appliance (F = 258 g and 360 g) and (4) a sham appliance. The terms direct and indirect describe force transmission directly, via pinning to the palatal shelves or indirectly, via abutment teeth. Active treatment in the long-term group was followed by a 4 month retention phase and a 2 month relapse phase. The implant study indicated the transverse stability to be greatest in the skeletally borne appliance. Correspondingly, intercanine distance relapse was 53 per cent and 23 per cent for the IS and DM subjects, respectively. Intermolar expansion was significantly more stable than intercanine expansion due to selective activity of the circum-maxillary sutures (transverse suture) and root configuration. Sagittal advancement and vertical superior translation, which are controlled by selective activity of the premaxillary suture, were particularly apparent in the magnetic appliances with a low force PE regimen. Clinical implications suggest that the use of a low force PE regimen can be of substantial benefit in young skeletal Class III patients with transverse maxillary deficiency.

Animals↗
PubMed1987

Magnetic versus mechanical expansion with different force thresholds and points of force application.

The effects of force magnitude (high versus low) and point of force application (teeth versus direct palatal endosseous pins) on palatal expansion treatment were studied on four juvenile female Macaca fascicularis monkeys. Three subjects received one of the following appliances: (1) conventional type jackscrew maxillary plate bonded to the posterior teeth with a high force magnitude of 2033 g, (2) a similar tooth-borne appliance but with rare earth repulsive magnets having a low force of 258 g, or (3) a specially designed palatal acrylic appliance pinned directly to the palatal shelves also utilizing rare earth repulsive magnets with a low force of 258 g. A fourth animal, the control, received a passive sham appliance bonded to the abutment teeth. Spatial changes of dental markers and facial implants were studied radiographically. In the low force, magnetically induced appliances, treatment was longer (95 days for the palatally pinned appliance and 135 days for the bonded tooth-borne appliance). The force radiated superolaterally, dissipating in the zygomaticofrontal suture, and the overjet significantly increased because of the marked widening of the incisive and transverse sutures. With the conventional jackscrew high-force appliance bonded to the teeth, the treatment lasted 33 days. A diastema developed between the incisors and the force was transmitted superolaterally and then transmedially, thus causing fractures in the nasal complex and other iatrogenic sequelae. The palatally pinned magnetic appliance induced bodily tooth movement, the greatest increase in intermolar distance, and a superior repositioning of the maxillopalatine region. The latter two effects were caused by selective excitation of the transverse suture over the premaxillary suture. Symmetry decreased with remoteness from the point of application. These results suggest reduction of the conventional force by up to eightfold--a level supplied by the rare earth magnets. Extrapolating from these results, the slow palatal expansion regimen for the treatment of Class III malocclusions with maxillary transverse deficiency is preferred at an early age (not more than 6 years). In the event of a suture disorder, the use of direct forces to the palate might be considered.

Animals↗
PubMed1979

The use of muscle forces by simple orthodontic appliances.

Orthodontic appliances of simple construction have been described. They are valuable in intercepting the deforming action of perioral muscle function or malfunction. The same muscles that have the deforming potential may be enlisted to correct dental malocclusions. Early interception often prevents a problem of considerably greater magnitude at a later date.

Acrylic Resins↗