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Biomedical subjects

G F Currier

Publications and source records attributed to G F Currier.

At least 37 records · Page 2Linked to original sources
PubMed1992

An evaluation of the nasolabial angle and the relative inclinations of the nose and upper lip.

The purpose of this study was to develop a consistent and reproducible method of constructing a nasolabial angle that would also permit an evaluation of the relative inclination of the lower border of the nose and the upper lip, as well as their relationship to each other. Comparison of repeated individual measurements of soft tissue profile landmarks on 15 subjects, as completed by four orthodontists, revealed that the proposed method of constructing the nasolabial angle was consistent and reproducible by the same orthodontist and among different orthodontists. Normative data for the three nasolabial parameters were produced from a sample of 104 young white adults determined by the authors to have well-balanced faces. Mean and standard deviation values from this pooled sample demonstrated a lower border of the nose to Frankfort horizontal plane angle at 18 degrees +/- 7 degrees, upper lip to Frankfort horizontal plane angle 98 degrees +/- 5 degrees, and nasolabial angle 114 degrees +/- 10 degrees. No statistically significant difference was demonstrated between the values for men and women in this study, but the women did have a slightly larger nasolabial angle. A linear comparison of the three nasolabial parameters with six skeletal measurements revealed no significant relationship between the soft tissue profile of the nasolabial region and the underlying skeletal relationships.

Adult↗
PubMed1992

Fracture strengths of ceramic brackets subjected to mesial-distal archwire tipping forces.

This study tested the strength of ceramic orthodontic brackets subjected to mesial-distal tipping forces on five types of preadjusted, maxillary right central incisor ceramic twin brackets for both 0.018" and 0.022" slot sizes. Description of each bracket was by manufacturer's abbreviation-crystallinity-slot bracket, eg., AL-P-18, meaning Allure-polycrystalline-0.018" slot bracket. Thirty brackets of each type were used for a total of 300 brackets, each bonded to a porcelain denture tooth. A special apparatus was designed to hold the denture tooth, the wire, and the bracket in a standard position while an Instron machine applied a tipping force to the full size rectangular archwire at a distance of 7.0 mm lateral to the center of the bracket. The tipping force was applied until the bracket fractured. The fracture force, fracture angle, and fracture location were recorded. High fracture force values tended to accompany large fracture angles while low fracture force values tended to be associated with small fracture angles. The clinical significance was that the stronger ceramic brackets can be expected to withstand larger amounts of archwire tipping adjustments prior to bracket fracture. With the literature indicating the optimum force for tipping of maxillary incisors to be from 50 to 125 g, all the brackets are sufficiently strong to consistently withstand the suggested magnitude of archwire tipping forces. However, if excessive tipping forces were required by the clinician, ceramic brackets would be prone to fracture.

Ceramics↗
PubMed1991

Mandibular arch perimeter changes with lip bumper treatment.

The effects of lip bumper treatment on the mandibular arch were observed in 32 patients with late transitional and early permanent dentitions. Dental cast measurements were made for arch perimeter, arch length, and arch width. Cephalometric radiographs were used to determine labial tipping of the incisors and distal movement of the molars. Arch circumference increased in all patients, ranging from 0.7 mm to 8.8 mm, with an average of 4.1 mm. The mean increase in arch length was 1.2 mm and was largely attributed to anterior tipping of the mandibular incisors. Change in arch length was the most predictive variable for the increase in arch circumference. Passive changes in arch width were recorded, with a mean increase of 2.0 mm in the intercanine distance and 2.5 mm in the first premolar distance. Arch width increments contributed to the increase in arch circumference, but the increases in arch width were not found to be predictive of the change in arch circumference. Changes in either arch circumference or arch length were not related to the duration of treatment, age and sex of the patient, or the eruption status of the permanent second molars.

Activator Appliances↗
PubMed1991

Nonsurgical and interactive orthodontics.

Cephalometric radiographic evaluation needs to be supplemented with soft tissue analyses that assist in the proper mechanics. Radiographs remain prescriptive to alter therapy. Patient cooperation is directly related to understanding and applying learning principles that are essential for quality orthodontic care. Prescriptions and new wires continue to make treatment more efficient and exacting. The anomalies of the teeth profoundly affect tooth placement in the occlusion. The transverse plane is the first and most important plane of occlusion that needs early intervention. This plane is directly related to correction of the sagittal through vertical development. The scope of airway and function needs to supplement specific modalities of therapy. Functional appliances usually have significant dentoalveolar effects within the growth process. Individual variation remains the hallmark of human growth and development, with or without therapeutic intervention.

Child↗
PubMed1991

Pediatric orthodontics: where have we been? Where are we going?

Pediatric treatment planning is difficult for those doctors who observe their patients throughout the long period of childhood. Which changes are normal? Which will self-correct? How long should the therapy be? Which is the best, current modality of treatment? An understanding of cyclic patterns, a dentofacial orientation on an individual basis, problem-oriented treatment plans, and certain reasonably based protocols make this journey through the time of childhood and the current age of dentistry rather rewarding.

Adolescent↗
PubMed1990

An in vitro evaluation of bond strength of three glass ionomer cements.

The purpose of this study was to determine the bond strength of three commercially available glass ionomer cements when used to bond mesh-backed medium twin (0.130 inch) brackets to enamel surface. Three different enamel surface conditions, which included use of pumice, pumice and polyacrylic acid, and pumice followed by acidulated phosphate fluoride, were also tested to determine their effect on the bond strength. In addition, bond strength of one composite resin was compared with those of glass ionomer cements. The teeth were bonded with all the materials according to manufacturers' instructions. Each specimen was embedded in Super-Die with the bonded facial surface exposed. A surveyor was used to align the teeth in the stone uniformly for all specimens. A special bracket holder was used to hold the brackets precisely under the wings during debonding. An Instron universal testing machine was used to measure the force required for bond failure. To stimulate oral conditions, the direction of pull was so designed that it included an element of torsional stress along with tensile force. The findings indicate that a large variation existed between the bond strengths of all materials tested. The bond strength of glass ionomer cements was significantly less than that composite resin. However, the bond strength of at least one glass ionomer cement appears to be adequate for clinical use. The different surface preparation before bonding did not significantly affect the bond strengths of glass ionomer cements. Further investigation is required to test the bond strengths of glass ionomer cements clinically.

Acidulated Phosphate Fluoride↗
PubMed1990

A 3-year evaluation of skeletal stability of mandibular advancement with rigid fixation.

The postsurgical changes associated with mandibular advancements using the sagittal ramus osteotomy and rigid fixation were evaluated. This retrospective study was based on examination of lateral cephalometric radiographs of 19 individuals (16 females and 3 males) with a mean age of 26.6 years. These radiographs were evaluated presurgically, immediately postsurgery, and 3 years postsurgically (2 years, 9 months to 4 years, 5 months). The mean amount of sagittal surgical advancement was 6.7 +/- 2.3 mm, and the mean amount of postsurgical relapse was 1.3 +/- 2.0 mm, representing a 14% relapse of the original surgical advancement. However, individual variation in the amount and direction of movement of the mandible was found during the follow-up period. Postsurgical relapse was found to be related to the amount of surgical advancement. Linear-regression analysis between these two variables resulted in an R2 value of 0.448. Fourteen of the subjects relapsed in the posterior direction, with 2 relapsing more than 50% of the surgical advancement. Five of the subjects moved further anteriorly, with 1 advancing as much as 50% more than the original advancement. The findings of this study suggest that mandibular advancement with the sagittal ramus osteotomy and rigid fixation does not provide consistently stable postsurgical results. However, when compared with previously reported relapse studies using nonrigid fixation techniques, rigid fixation yielded superior results.

Adolescent↗
PubMed1990

Arch perimeter changes on rapid palatal expansion.

Relationships between changes in arch perimeter and arch width resulting from rapid palatal expansion with the Hyrax appliance were analyzed with the use of dental study casts of 21 adolescent patients. Photographs and measurements from the dental casts obtained before treatment and approximately 3 months after stabilization were used. Regression analysis indicated that changes in premolar width were highly predictive of changes in arch perimeter (r2 = 0.69) at approximately 0.7 times the premolar expansion. Without any orthodontic appliances attached to the mandibular teeth in 16 of the 21 patients, buccal uprighting of the posterior teeth was observed because of the redirection of occlusal forces. In addition, posterior movement of the maxillary incisors and buccal tipping of the anchor teeth were quantified. The prediction of arch perimeter change for a given amount of expansion is helpful in the treatment planning of rapid palatal expansion cases and may facilitate nonextraction orthodontic treatment.

Adolescent↗
PubMed1990

Load-deflection rate measurements of activated open and closed coil springs.

The purpose of this investigation was to provide load-deflection rate data for a variety of open and closed coil springs. Ten millimeter lengths of open and closed coil stainless steel and Cobalt-Chromium-Nickel (Co-Cr-Ni) alloys in combinations of 0.008, 0.009 and 0.010 inch wire sizes, and 0.030 and 0.032 inch lumen sizes were tested. Other groups included heat treated Co-Cr-Ni springs and springs of 15 and 20 millimeter lengths. Forces and activations were measured by a tension load cell with an Instron universal testing instrument. Stiffness increased dramatically with wire size and pitch angle of the coils. Stiffness decreased slightly with increased lumen size. Co-Cr-Ni closed coil springs were slightly stiffer than stainless steel, whereas stainless steel open coil springs were much stiffer than Co-Cr-Ni. Heat treatment increased the stiffness of Co-Cr-Ni coil springs. The length of the spring had a great effect on the load-deflection rate. A shorter spring is stiffer than a longer spring by an amount directly proportional to the ratio of the length of the longer spring to that of the shorter spring.

Chromium Alloys↗
PubMed1989

The skeletal stability of Le Fort I downfracture osteotomies with rigid fixation.

Twenty subjects receiving Le Fort I downfracture osteotomies stabilized with rigid fixation were studied for relapse. The analysis was based on longitudinal cephalometric radiographs taken within 2 weeks presurgically, 1 week postsurgically, and after a minimum period of 6 months postsurgically. Vertical and sagittal changes in the maxilla were evaluated in reference to the Frankfort horizontal plane. It was found that the mean postsurgical relapse was minimal and not significant. It was smaller than that reported for patients who had received stabilization of the maxilla with intraosseous and maxillomandibular wiring. It was concluded that the rigid fixation technique is dependable and yields stable postsurgical results in the maxilla.

Adolescent↗
PubMed1988

The longitudinal effects of growth on the Wits appraisal.

The longitudinal changes occurring between the ages of 4 and 24 years in the Wits appraisal and its component parts were evaluated in 40 persons. Contrary to what may have been believed previously, the Wits appraisal was not found to remain stable throughout the growth period. When the findings of the Wits appraisal were studied in individual subjects, there was a wide range of variation. Real changes in the Wits appraisal were found to be disguised clinically by the differential sagittal growth of pogonion in relation to B point, especially in male subjects. Furthermore, the appraisal was found to be affected profoundly by changes occurring in the angulation of the occlusal plane. It was concluded that if the Wits appraisal is to be used, it should be used in conjunction with other methods of assessment of apical base discrepancies and with due regard for the likely effects of changes in its component parts.

Adolescent↗
PubMed1988

The effect of a modified functional appliance on obstructive sleep apnea.

This study combined the use of cephalometrics and overnight polysomnographic monitoring to analyze the effects of a modified functional appliance on airway, sleep, and respiratory variables in patients with obstructive sleep apnea (OSA). Twelve patients without overt anatomic or pathologic evidence of obstruction were selected on the basis of an initial single night of polysomnographic monitoring, which confirmed the diagnosis of obstructive sleep apnea syndrome. The patients subsequently were fitted with a modified functional appliance designed to securely hold the mandible in an anterior-inferior position. A subsequent overnight polysomnographic study was obtained with each patient wearing the appliance. Lateral cephalometric radiographs with and without the appliance in place were also obtained. The mean vertical and horizontal changes in mandibular position while wearing the appliance were 8.49 mm and 2.28 mm, respectively. The findings indicate that 10 of the 12 patients had decreases in the rate of complete airway obstructions from a mean of 28.86 to 18.69 events per hour, and in the total apnea index from a mean of 53.81 to 35.99 events per hour. A reduction in the rate of obstructive events is attributed to the effect of the appliance on the oropharyngeal structures. Six cephalometric measurements are presented to provide a means of assessing effects of the appliance on the oropharynx and associated structures. The modified functional appliance is a conservative, successful treatment alternative that could benefit patients with obstructive sleep apnea syndrome.

Activator Appliances↗
PubMed1977

The child and the adolescent: new rights for an "old" minority.

The use of the learning model is a necessary prerequisite for rendering dental care to the child or adolescent. The awareness of the emotional needs of the child and adolescent and the ability of the doctor to handle them is a requirement for an individual to treat these persons. The treatment plan and methods of treatment are essential factors in the behavioral management of the child or adolescent. There is a normal range for grwoth, development, and maturation in which sequences, timing, and rates of changes are critical. A cross-sectional approach in rendering care is not appropriate in learning to work with children and adolescents. The doctor who renders the care for this age group should be well versed in certain aspects of behavior, as this will affect the treatment plan and methodology, but that doctor must also have the technical abilities to do the spectrum of services to which the patient is entitled. One without the other is a definite compromise for the patient. If the doctor does not further pursue additional assistance from his colleagues, the rights of the child or adolescent have been violated.

Adolescent↗