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Biomedical subjects

P M Sinclair

Publications and source records attributed to P M Sinclair.

54 records · Page 3Linked to original sources
PubMed1987

An evaluation of combination second molar extraction and functional appliance therapy.

The purpose of this study was to examine the results of a treatment regimen involving the extraction of four second molars followed by a combination of sagittal, Bionator, and fixed appliance therapy. The pretreatment and posttreatment cephalometric and dental cast records of 30 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the Class II skeletal correction was achieved by a "headgear" effect inhibiting maxillary growth in conjunction with normal forward mandibular growth. No significant distal bodily movement or tipping of either maxillary or mandibular first molars was found. Significant increases were seen in maxillary arch length, maxillary intercanine and intermolar width, and mandibular intermolar width as a result of treatment. Maxillary third molar position tended to improve following second molar extraction; mandibular third molar changes were more variable.

Activator Appliances↗
PubMed1987

Effect of pulsed electromagnetic fields on orthodontic tooth movement.

The purpose of this study was to determine whether the application of a simple surgically noninvasive, pulsed electromagnetic field could increase both the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the electromagnetic field's effects on bony physiology and metabolism and to search for possible systemic side effects. Laterally directed orthodontic force was applied to the maxillary central incisors of a sample of 40 young male, Hartley guinea pigs (20 experimental, 20 control) by means of a standardized intraoral coil spring inserted under constricting pressure into holes drilled in the guinea pigs' two maxillary central incisors. During the experimental period, the guinea pigs were placed in specially constructed, plastic animal holders with their heads positioned in an area of uniform electromagnetic field. Control animals were placed in similar plastic holders that did not carry the electrical apparatus. The application of a pulsed electromagnetic field to the experimental animals significantly increased both the rate and final amount of orthodontic tooth movement observed over the 10-day experimental period. The experimental animals also demonstrated histologic evidence of significantly greater amounts of bone and matrix deposited in the area of tension between the orthodontically moved maxillary incisors. This increase in cellular activity was also reflected by the presence of significantly greater numbers of osteoclasts in the alveolar bone surrounding the maxillary incisors of the experimental animals. After a 10-day exposure to pulsed electromagnetic field, minor changes in serologic parameters relating to protein metabolism and muscle activity were noted. The results of this study suggest that it is possible to increase the rate of orthodontic tooth movement and bone deposition through the application of a noninvasive, pulsed electromagnetic field.

Alveolar Process↗
PubMed1986

Differential diagnosis and treatment planning for the adult nonsurgical orthodontic patient.

Increasing numbers of adult patients are seeking orthodontic care and some, despite significant skeletal malocclusions, elect not to have combined orthodontic-surgical treatment. The purpose of this article is to outline some of the diagnostic and therapeutic principles that can be used in the adult nonsurgical orthodontic patient. The importance of realistic goal setting in the face of compromised occlusions is emphasized. Diagnosis should include evaluation of all three dimensions and recognize the limitations of therapy in each dimension for the nongrowing patient. Periodontal considerations, extraction decisions, and retention regimens are of vital importance to the achievement and maintenance of an optimum result. Clinical records will demonstrate four commonly seen problems and their resolution.

Adolescent↗
PubMed1985

Bilateral congenital absence of maxillary lateral incisors: a craniofacial and dental cast analysis.

The dental casts and cephalometric records of forty-three patients exhibiting bilateral congenital absence of maxillary lateral incisors were evaluated to determine the nature and extent of any concurrent craniofacial and dental anomalies. The effects of bilateral orthodontic space closure were evaluated on a subsample of twenty-two cases. The data revealed normal dental arch length, arch width, overjet, and overbite, while significant tooth size discrepancies were found in several anterior and posterior teeth. Craniofacial deviations from normal included smaller maxillary length, smaller mandibular length, smaller anterior cranial base, and nasal bone. Vertical facial dimensions, both anterior and posterior, were significantly less, as was the mandibular plane angle. Soft-tissue examination revealed a 10 degrees greater nasiolabial angle, which was increased a further 5 degrees as a result of a mean incisor retraction of 1.5 mm during space closure. The craniofacial anomalies noted in the present sample were similar to those seen in persons with clefts and may reflect a common etiology related to a developmental disturbance during fusion of the facial processes in utero. In the treatment of patients with bilateral congenital absence of maxillary incisors, mechanotherapy designed to open the mandibular plane, increase the vertical dimension, and move the maxillary posterior teeth forward is recommended in order to prevent worsening the Class III tendency and to minimize maxillary incisor and upper lip retraction. Most cases will require significant mesiodistal reduction in tooth size in order to achieve an optimal occlusion.

Adolescent↗
PubMed1985

The effect of pulsating electromagnetic fields on condylar growth in guinea pigs.

The purpose of this study was to determine if a simple, noninvasive method could be developed for the application of pulsed electromagnetic fields that would lend itself to future clinical applications. Specifically, the modulation and control of condylar cellular metabolism and the stimulation of cellular proliferation were attempted in order to increase the amount of mandibular condylar growth. A pulsed electromagnetic field with a frequency of 100 hertz was applied for 8 hours per day to the mandibular condylar area of rapidly growing, male, Hartley guinea pigs. Ten guinea pigs were exposed for 10 days and a second group of 10 guinea pigs was exposed for 30 days. In addition, 5 guinea pigs were used as controls for each experimental period. During the experimental period the guinea pigs were placed in specially constructed, plastic animal holders with their heads positioned in an area of uniform magnetic field. After 10 days of pulsed electromagnetic field exposure, there were increases in vascularity, secretion of cartilagenous intercellular matrix, and woven-bone formation in the guinea pig condyle. After 30 days, there were continued but attenuated vascular and calcification responses with an increase noted in marrow hemopoietic elements. An increase in the number of osteoclasts was also noted after 10 days. This effect was transient and was not present at the end of the 30-day experimental period. The application of the pulsed electromagnetic field did not result in a significant increase in the overall anteroposterior or vertical size of the guinea pig mandible compared to controls. The results of this study suggest that it is possible to affect condylar cartilagenous and bony metabolism through the application of a noninvasive, pulsed electromagnetic field.

Animals↗
PubMed1985

The accuracy of computerized growth prediction in Class II high-angle cases.

This study was conducted to test the accuracy of a commercially available forecasting system in predicting the effects of growth and orthodontic treatment. The pretreatment cephalograms and wax bites of mandibular casts of thirty-three consecutively treated Class II patients with high mandibular plane angles, along with twenty-six criteria related to treatment preference, were submitted for analysis. All patients had already been treated on a nonextraction basis by a single practitioner using high-pull face-bow headgear. The computer-generated posttreatment predictions or visual treatment objectives (VTO's) were compared to the actual posttreatment cephalograms, using twenty-one linear and nine angular measurements. Fifteen of the thirty parameters evaluated showed statistically significant (P less than 0.01) differences between the actual posttreatment result and the computer prediction. The computer was found to be accurate in predicting the effects of growth and treatment on maxillary position and rotation, mandibular length, upper face height, and incisor positions. It was found to be inaccurate in predicting the effects of growth and treatment on maxillary length, mandibular rotation, lower anterior and posterior face heights, the horizontal and vertical positions of the molars, and over 50% of the soft-tissue parameters.

Adolescent↗
PubMed1985

Dentofacial maturation of untreated normals.

Cephalometric head films from a sample of 65 untreated normal persons were evaluated to determine the nature and extent of the normal dentofacial maturation process. Thirty-four parameters were examined in the mixed dentition (9 to 10 years), the early permanent dentition (12 to 13 years), and early adulthood (19 to 20 years). Results showed the importance of maxillary development, particularly in the vertical plane, as it was associated with the amount and direction of sagittal mandibular growth. "Late mandibular growth" was found to be a forward (bite-closing) rotation of the mandible that occurred after the cessation of vertical maxillary growth. Condylar growth amount and direction were influential in determining the degree of sagittal mandibular change. The degree of forward (bite-closing) mandibular rotation was strongly associated with the amount of both maxillary and mandibular molar eruption. Incisor positions were found to remain relatively constant, showing compensations for the amount and direction of skeletal growth. No correlations or predictions of clinical value were found between the cephalometric parameters examined and previously recorded dental-cast variables.

Adolescent↗
PubMed1983

Principles of orthodontic mechanics in orthognathic surgery cases.

In orthognathic surgery cases the treatment objectives, extraction patterns, and types of mechanics used are frequently the reverse of those used in conventional orthodontics. Thus, starting cases orthodontically and then, if unsuccessful, referring them for surgery often produces compromised results. Presurgical intra-arch objectives include positioning of the incisors in "ideal" positions, establishment of correct torque, and elimination of tooth-size discrepancies so as to permit the establishment of Class I canine and molar relationships after surgery. Presurgical objectives in the sagittal plane focus on removal of dental compensations. This may require the use of Class III elastics in Class II cases (and vice versa), thus allowing for maximal surgical correction of the underlying skeletal deformity. In the transverse plane, differentiation of skeletal from dental problems as well as identification of relative and absolute discrepancies should be carried out presurgically. Lateral corticotomies or segmental maxillary procedures should be used, depending on individual circumstances. Presurgical objectives in the vertical plane include maximizing the amount of presurgical orthodontic treatment carried out in open bites and minimizing the presurgical mechanics in deep bites. Encouragement of opening mandibular rotation at surgery while avoiding an increase in posterior face height contributes to stability. Orthodontic mechanics should not always include presurgical leveling of the curve of Spee and should actively avoid movements that may cause relapse tendencies. Careful attention to the use of surgical arch wires and splints during surgery and fixation, along with controlled elastic therapy and exercise programs after fixation, can greatly facilitate treatment.

Cephalometry↗
PubMed1983

Maturation of untreated normal occlusions.

The dental casts of 65 untreated normal occlusions were evaluated to determine the nature and extent of the developmental maturation process of the normal dentition. Six dental parameters were examined in the mixed dentition (9 to 10 years), early permanent dentition (12 to 13 years), and early adulthood (19 to 20 years). Results showed decreases in arch length and intercanine width; minimal overall changes in intermolar width, overjet, and overbite; and increases in incisor irregularity. Females showed more severe changes than males. The individual changes found were not correlated to changes in any of the other parameters measured. No associations or predictors of clinical value were found. The changes found in a sample of untreated normals were similar in nature but lesser in extent than postretention changes found in a sample of treated cases.

Adolescent↗
PubMed1980

Mercury levels in dental students and faculty measured by neutron activation analysis.

Samples of head hair, fingernails, and toenails were taken from 61 dental students and faculty members. The mercury levels were analyzed using a simple neutron activation analysis technique which proved to be easily applicable to large numbers. Significant results were found for the head hair and fingernail groups. There may be a correlation between the higher mercury levels and increased pressure of work, which might result in decreased standards of mercury hygiene.

Faculty, Dental↗
PubMedDate not supplied

Dentofacial growth and development.

Theoretical growth and development, and practical aspects are explored in an overview of how growth has been considered by investigators and clinicians during the past twenty years, to the beliefs held today. Diagnostic and treatment methods, where technical innovations are the most apparent, are considered in the context of classical orthodontic thinking. New diagnostic techniques will be introduced that will require changes in our basic understanding of growth and treatment. Orthodontics will continue to be integrated into total patient diagnosis and treatment.

Adolescent↗