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Biomedical subjects

T M Graber

Publications and source records attributed to T M Graber.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1982

Postpharyngeal lymphoid tissue in Angle Class I and Class II malocclusions.

Opinions differ with regard to the relationship of adenoids and type of malocclusion. To study this possible relationship, xeroradiographic lateral cephalograms were made of eighty Class I (Angle) and sixty-four Class II, Division 1 (Angle) malocclusions to obtain reliable measures of the epipharyngeal lymphoid tissue, the nasopharyngeal airway, the nasopharynx, and certain cephalometric landmarks. Xeroradiographic cephalograms provide superior visualization with edge-enhancement effect for both soft and hard tissues. Electronic digitization and a comprehensive computer analysis were used to assess the head films. Significant differences were found for some of the linear and angular cephalometric criteria between the two malocclusion categories. A sexual dimorphism was observed. These skeletal and dental differences were anticipated in this mixed malocclusion sample, as prior cephalometric studies which compare different classes of malocclusion have shown. Airway space did not appear to vary with the type of malocclusion. Some low-level correlations were found between the size of the nasopharyngeal area and certain skeletal characteristics. These correlations depended on both the malocclusion type and the sex of the individual. The lateral, two-dimensional cephalogram does not seem to offer satisfactory information relating the nasopharyngeal area to Class I or to Class II, Division 1 malocclusions.

Cephalometry↗
PubMed1980

Occlusal splints.

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Dental Occlusion, Traumatic↗
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↗