Biomedical subjects

J A McNamara

Publications and source records attributed to J A McNamara.

At least 19 recordsLinked to original sources

PubMed1997

Early dentofacial features of Class II malocclusion: a longitudinal study from the deciduous through the mixed dentition.

A group of 25 untreated subjects with Class II malocclusion in the deciduous dentition (featuring the concomitant presence of distal step, Class II deciduous canine relationship, and excessive overjet) was compared with a control group of 22 untreated subjects with ideal occlusion (flush terminal plane, Class I deciduous canine relationship, minimal overbite, and overjet) at the same dentitional stage. The subjects were monitored during a 2 1/2-year period in the transition from the deciduous to the mixed dentition, during which time no orthodontic treatment was provided. Occlusal analysis of the Class II group in the deciduous dentition revealed an average interarch transverse discrepancy due to a narrow maxillary arch relative to the mandible. All occlusal Class II features were maintained or became exaggerated during the transition to the mixed dentition. The skeletal pattern of Class II malocclusion in the deciduous dentition typically was characterized by significant mandibular skeletal retrusion and mandibular size deficiency. During the period examined, cephalometric changes consisted of significantly greater maxillary growth increments and smaller increments in mandibular dimensions in the Class II sample. Moreover, a greater downward and backward inclination of the condylar axis relative to the mandibular line, with consequent smaller decrements in the gonial angle, were found in the Class II group, an indication of posterior morphogenetic rotation of the mandible in patients with Class II malocclusion occurring during the period examined. The results of this study indicate that the clinical signs of Class II malocclusion are evident in the deciduous dentition and persist into the mixed dentition. Whereas treatment to correct the Class II problem can be initiated in all three planes of space (e.g., RME, extraoral traction, functional jaw orthopedics), other factors such as patient cooperation and management must also be taken into consideration before early treatment is started.

Cephalometry↗

PubMed1997

Orthodontic treatment and temporomandibular disorders.

The relationship between orthodontic treatment and temporomandibular disorders (TMDs) has long been of interest to the practicing orthodontist, but only during the past decade have a significant number of clinical studies been conducted that have investigated this association. This interest in orthodontics and TMD in part was prompted in the late 1980s after litigation that alleged that orthodontic treatment was the proximal cause of TMD in orthodontic patients. This litigious climate resulted in an increased understanding of the need for risk management as well as for methodologically sound clinical studies. The findings of current research investigating the relation of orthodontic treatment and TMD can be summarized as follows: (1) signs and symptoms of TMD may occur in healthy persons; (2) signs and symptoms of TMD increase with age, particularly during adolescence, until menopause, and therefore TMDs that originate during orthodontic treatment may not be related to the treatment; (3) in general, orthodontic treatment performed during adolescence does not increase or decrease the chances of development of TMD later in life; (4) the extraction of teeth as part of an orthodontic treatment plan does not increase the risk of TMD; (5) there is no increased risk of TMD associated with any particular type of orthodontic mechanics; (6) although a stable occlusion is a reasonable orthodontic treatment goal, not achieving a specific gnathologic ideal occlusion does not result in signs and symptoms of TMD; and (7) thus far, there is little evidence that orthodontic treatment prevents TMD, although the role of unilateral posterior crossbite correction in children may warrant further investigation.

Humans↗

PubMed1997

Multiple linear regression as an analytical tool in cephalometric studies.

When the effect is studied of a factor like 'orthodontic therapy' on linear craniofacial growth, the concomitant consequence of age and gender on size cannot be ignored. The methodologically correct solution is division of the study group into smaller units, each of which is homogeneous with respect to age, gender, and therapy, and to compare these with matched controls. Yet, apart from matched controls being hard to find, this method of subdivision has the serious drawback that smaller groups decrease statistical power. A solution without the need to create sub-groups lies in the application of multiple linear regression analysis. It has been applied to biological data in other studies, but verification of the outcome has not been reported so far. Indeed, testing the mathematical assumptions underlying the regression model created unresolvable obstacles and, therefore, it was decided to perform verification by means of practical examples. Two separate tests for the applicability of the multiple linear regression method, on different data, with differing predictor sets, and with different control samples have been performed.

Adolescent↗

PubMed1997

Morphometry of the cranial base in subjects with Class III malocclusion.

The significance of the cranial base in the development of Class III malocclusion remains uncertain. The purpose of this study was to determine whether the form of the cranial base differs between prepubertal Class I and Class III subjects. Lateral cephalographs of 73 children of European-American descent aged between 5 and 11 years with Class III malocclusion were compared with those of their counterparts with a normal, Class I molar occlusion. The cephalographs were traced, checked, and subdivided into seven age- and sex-matched groups. Average geometries, scaled to an equivalent size, were generated based on 13 craniofacial landmarks by means of Procrustes analysis, and these configurations were statistically tested for equivalence. Bivariate and multivariate analyses utilizing 5 linear and angular measurements were undertaken to corroborate the Procrustes analysis. Graphical analysis, utilizing thin-plate spline and finite element methods, was performed for localization of differences in cranial base morphology. Results indicated that cranial base morphology differed statistically for all age-wise comparisons. Graphical analysis revealed that the greatest differences in morphology occurred in the posterior cranial base region, which generally consisted of horizontal compression, vertical expansion, and size contraction. The sphenoidal region displayed expansion, while the anterior regions showed shearing and local increases in size. It is concluded that the shape of the cranial base differs in subjects with Class III malocclusion compared with the normal Class I configuration, due in part to deficient orthocephalization, or failure of the cranial base to flatten during development.

Aging↗

PubMed1997

Orthodontic treatment and temporomandibular disorders: is there a relationship? Part 1: Clinical studies.

The relationship between orthodontic treatment and temporomandibular disorders (TMD) has long been of interest to the practicing orthodontist, but only during the last decade or so have a significant number of methodologically-sound clinical studies been conducted that have investigated this association. The aim of this paper is to critically review particularly those studies that have been published since 1989 and to answer the following questions: 1. Does orthodontic treatment with fixed or removable appliances lead to a greater incidence of TMD? 2. Does the extraction of premolars as part of an orthodontic treatment plan result in a greater incidence of TMD? 3. Does orthodontic treatment prevent or cure TMD? For this purpose, we conducted a MEDLINE search, complemented by a hand search in selected journals. We found 21 publications of studies related to the orthodontic-TMD interface. Based on these studies, the following statements can be made: 1. Orthodontic treatment performed during adolescence does not increase or decrease the chances of developing TMD later in life. There is no evidence of an elevated risk for TMD associated with any particular type of orthodontic mechanics. 2. The extraction of teeth as part of an orthodontic treatment plan does not increase the risk of TMD. 3. Thus far, there is no compelling evidence that orthodontic treatment prevents TMD, although the role of unilateral posterior crossbite correction in children may warrant further investigation. Likewise, there is no convincing evidence that TMD can be cured by orthodontic treatment.

Adolescent↗

PubMed1996

Measurement of Goldmann visual fields in older children who received cryotherapy as infants for threshold retinopathy of prematurity.

BACKGROUND: Cryotherapy administered to eyes with severe acute-phase (threshold) retinopathy of prematurity benefits retinal structure and visual acuity compared with the natural course of the retinopathy. OBJECTIVES: To determine the extent of peripheral field abnormalities in eyes with threshold retinopathy of prematurity that had retinal structure preserved by cryotherapy. METHODS: Kinetic perimetry was performed with a Goldmann perimeter by masked testers on patients in whom bilateral threshold retinopathy of prematurity developed and who had been randomly assigned to undergo cryotherapy in one eye and no cryotherapy in the fellow eye. With the V-4-e and the II-4-e targets, eight meridians were tested: 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, and 315 degrees. The median value of three presentations in each meridian was accepted as the extent in that meridian. RESULTS: Fourteen eyes (eight treated and six control) of eight patients (mean age, 9.9 years; range, 6 to 11 years) had adequate vision to undergo fields testing. Mean (+/-SE) extent of visual field for treated vs control eyes was 36 degrees +/- 3 degrees vs 46 degrees +/- 6 degrees for the II-4-e target and 49 degrees +/- 4 degrees vs 59 degrees +/- 6 degrees for the V-4-e target. This difference was consistent across all eight meridians for either target, and repeated-measures analysis of variance showed that cryotherapy was associated with smaller visual field extent for both target sizes (P=.08). CONCLUSION: The results of this small pilot study suggest that eyes that have retinal structure and acuity preserved by cryotherapy for severe acute-phase retinopathy of prematurity have slightly smaller visual fields than untreated eyes with severe acute-phase retinopathy of prematurity that had vision preserved.

Acute Disease↗

PubMed1996

Pattern dystrophy of the retinal pigment epithelium and geographic atrophy of the macula.

PURPOSE: Little information is available on the long-term course of pattern dystrophies, although some older individuals have been observed with macular atrophy. We sought to evaluate the evolution of symptoms, fundus changes, and physiologic findings by re-examining a family with pattern dystrophy after 20 years. METHODS: Four patients of seven initially examined were reevaluated 20 years later; two additional affected family members over age 60 were studied for the first time. Patients' current ages ranged from 38 to 73 years. Comprehensive ophthalmic examinations were supplemented with fluorescein angiography, dark adaptometry, color vision, electroretinography, and electrooculography. RESULTS: During the 20-year interval, visual acuity remained stable and 20/40 or better in all patients. One 62-year-old patient developed paracentral scotomas. All fundi showed evolution of pigmentary changes and increasing atrophy of pigment epithelium and choriocapillaris in the macula. Electro-oculograms were originally subnormal in all patients and changed very little. Electroretinograms, initially normal in two patients, became borderline or mildly subnormal and slightly reduced in the two patients first examined after age 60. CONCLUSIONS: Pattern dystrophy in this family was associated with minimal diminution of visual function during a 20-year interval. However, there was electroretinographic evidence of mild diffuse photoreceptor damage in the older patients, and geographic macular atrophy was prominent (suggesting a risk of vision loss in old age). Some cases of atrophic, age-related macular degeneration may represent an evolution of pattern dystrophy.

Adult↗

PubMed1996

Craniofacial structure of Japanese and European-American adults with normal occlusions and well-balanced faces.

The purpose of this study is to compare two groups of adults from different races who were selected on the basis of having normal ("ideal") occlusions and well-balanced faces. The lateral cephalometric radiographs of 54 Japanese adults (26 men and 28 women) were compared with a sample of 125 adults (44 men and 81 women) of European-American ancestry. The samples were chosen by orthodontists of the same racial background as the sample selected. Each lateral cephalogram was traced and digitized, and differences between cephalometric measurements between groups were analyzed with completely randomized t tests. In comparison to the European-American sample, the Japanese sample, in general, was smaller in anteroposterior facial dimensions and proportionately larger in vertical facial dimensions. The facial axis angle was more vertical in Japanese subjects, indicating a more downward direction of facial development. On average, the subjects in the Japanese sample were more protrusive dentally, with a more acute nasolabial angle and a greater tendency toward bilabial protrusion. These differences, evident even in groups with so-called "well-balanced faces", indicate that fundamental variation exists in the craniofacial structure of Japanese and European-Americans. The results of this study support the premise that a single standard of facial esthetics is not appropriate for application to diverse racial and ethnic groups.

Adult↗

PubMed1996

Orthodontic services provided by general dentists.

A survey was mailed to a stratified random sample of general dentists to determine the amount and nature of orthodontic treatment provided by general practitioners to their patients. The response to the survey was 75%, a rate considered excellent for this type of mailing. A large majority of the responding dentists (76.3%) provide orthodontic services to their patients, with 19.3% providing comprehensive orthodontic treatment. The percentage of time spent providing orthodontic services varied greatly among general dentists, with only a very few practitioners spending more than 50%. The number of patients under active treatment also varied widely, with only about 17% of those practitioners providing comprehensive treatment having more than 50 patients. A comparison of the three groups of practitioners showed that there was no relationship between the level of orthodontic involvement (none, limited, comprehensive) and the number of miles from orthodontic specialist or the pattern of referrals to orthodontists. Extrapolation of data from this study to the results of other investigations led to an estimate of the relative percentage of treatment provided by orthodontic specialists, pediatric dentists, and general practitioners. Almost two thirds of orthodontic patients are treated by orthodontic specialists, with pediatric dentists treating less than 4%. Slightly less than one third of all orthodontic patients appear to receive treatment from general practitioners.

Comprehensive Dental Care↗

PubMed1996

Three-dimensional diagnosis and management of Class II malocclusion in the mixed dentition.

Class II malocclusion is a commonly observed problem, occurring in about one third of the United States population. The numerous treatment approaches that have been advocated to treat this malocclusion presumably produce differing treatment effects within the skeletal, dentoalveolar, and soft tissue components of the face. In the first section of this article, the three-dimensional components of Class II malocclusion are described, with transverse maxillary discrepancy, mandibular skeletal retrusion, and increased lower anterior facial height observed as common findings in a mixed dentition sample of Class II subjects. Second, the literature concerning two seemingly diverse treatment methods (extraoral traction and functional jaw orthopedics) is reviewed in detail. Last, cephalometric data are presented from a retrospective clinical study and is used to evaluate the treatment effects produced by cervical traction and the FR-2 appliance of Fränkel in comparison with an untreated sample of mixed dentition Class II patients. The results of this study indicated that although both skeletal and dentoalveolar components of Class II, Division 1 malocclusion were altered in the Class I direction by either a facebow or a Fränkel appliance, these two appliance systems accomplished the correction in dramatically differing ways. Cervical traction affected the skeletal and dentoalveolar components of the maxilla and mandible, whereas the FR-2 appliance had less of an effect on maxillary and dentoalveolar components and a greater effect on mandibular length. Thus, these two treatment modalities produce decidedly different treatment effects in patients with Class II malocclusions.

Analysis of Variance↗

PubMed1995

The correction of interarch malocclusions using a fixed force module.

This article describes the use of a flexible force module (the Jasper Jumper) that can be incorporated into existing fixed appliances to correct various types of sagittal malocclusion. Essentially the spring mechanism described in this article is a modification of the original bite jumping mechanism of Herbst. The flexible spring module provides greater freedom of mandibular movement than is possible with the more rigid mechanism of the Herbst appliance. The facial musculature applies force through these modules to the anchor points to produce a variety of treatment effects. The treatment effects produced by the module mimic those previously described for the Herbst appliance and include posterior movement of the maxillary buccal segments and anterior movement of the mandible or mandibular dentition or both. Specifics of the clinical management of this modular system are discussed, including anchorage preparation and torque application, as well as the methods of anchoring, activating and reactivating the modules.

Activator Appliances↗

PubMed1995

The effect of bite-blocks with and without repelling magnets studied histomorphometrically in the rhesus monkey (Macaca mulatta).

The effect of bite-blocks with and without repelling magnets as proposed for the treatment of open bite was analyzed. Twelve male juvenile monkeys were divided into three groups of four. Group A was used as control, group B was given bite-blocks containing samarium cobalt disks, and group C received identical bite-blocks without active magnets. The monkeys were observed for 24 weeks before death. Histomorphometric evaluation was then performed on the molar roots, their periodontal tissues, the zygomaticotemporal suture, and the pterygomaxillary suture. The root surfaces of the molars in both the bite-block group and the magnetic group were characterized by pronounced resorption that sometimes was active and occasionally undergoing repair with bony tissue. The sutures also clearly reflected the effect of both appliances used, although more markedly in the cases of bite-blocks containing active magnets. The surface density expressing the sutural area, was increased significantly, possibly as an adaptation to the altered functional demand. The cellular activity of the sutural surfaces also was increased markedly in both appliance groups, reflecting an ongoing adaptation. A steady state had not been reached. The study demonstrated a widespread effect of the force developed by bite-blocks with and without magnets. The final quantity and the reversibility of the effect is not known, however. More long-term studies should be undertaken to obtain this information.

Adaptation, Physiological↗

PubMed1995

Maxillary adaptation to expansion in the mixed dentition.

This study presents the findings of 162 patients who underwent rapid maxillary expansion during the early mixed dentition. Maxillary changes were evaluated through the analysis of serial dental casts. Arch dimensions were measured pre-expansion, immediately post-expansion, and at yearly intervals until the eruption of the first premolars. The expansion was effected with an acrylic rapid maxillary expansion appliance bonded to the posterior teeth for 5 to 6 months. A simple retention protocol was used post-expansion. The average increase in transpalatal width was 5 to 6 mm. During the post-expansion period, most of the arch width increases were maintained. For example, 90.5% of the original expansion at the first permanent molars remained after the first year, with slightly less overall expansion (80.4%) evident at the end of the observation period (2.4 years postexpansion). Maxillary dental arches that initially were narrow tended to retain a greater percentage of the achieved expansion than those with initially wider arch dimensions. In addition, maxillae with initially more lingually-inclined molars tended to retain more expansion than maxillae with initially more facially-inclined molars. Palatal vault height decreased very slightly during treatment, but returned to pretreatment values one year after expansion and increased slightly during subsequent time intervals. The results of this study indicate that the majority of increased arch dimensions in patients produced by early orthopedic expansion of the maxilla are maintained at the end of the transitional dentition.

Adaptation, Physiological↗

PubMed1995

Arch dimensional changes in children with idiopathic short stature treated with recombinant growth hormone: a five-year study.

Recombinant human growth hormone (rhGH) increases stature when administered to non-GH-deficient idiopathic short statured children. The aims of this investigation were to determine pretreatment arch dimensions of short statured children (height > or = 2 S.D. below mean for age) and to evaluate their response to rhGH administration by measuring arch-dimensional changes over 5 years of rhGH treatment. Dental casts of 28 short subjects (22 male, 6 female) and of age/gender-matched controls of normal stature were analyzed using a digital imaging system. Four measures of arch width and one of arch depth were calculated for each maxillary and mandibular cast. Subjects receiving orthodontic care were eliminated from the study at the initiation of treatment. Z-scores were calculated to allow for pooling of data. Prior to rhGH treatment, all arch dimensions of the short statured subjects were smaller than the controls, with the exception of mandibular arch depth. Arch dimensions of the rhGH subjects did increase with the continued administration of rhGH. The control group also showed a significant trend for the arch dimensions to increase over time. The influence of rhGH treatment on arch dimensional changes over time remains equivocal based on the results of this investigation.

Adolescent↗

PubMed1995

Condylar adaptation after alteration of vertical dimension in adult rhesus monkeys, Macaca mulatta.

Remodeling in the cartilage of the mandibular condyle was investigated in young adult monkeys after an increase in vertical dimension of the midface through the use of a tooth-borne intraoral appliance. Six young adult male rhesus monkeys had bite-splints of 5 mm, 10 mm or 15 mm cemented to their maxillary dentition for 48 weeks. Five age- and sex-matched monkeys were used as controls. The thickness of the articular tissue and of the prechondroblastic and chondroblastic layers of the condylar cartilage in the superior, posterosuperior and posterior regions was measured from parasagittal sections of the temporomandibular joint (TMJ). It was found that articular tissue thickness was reduced in the superior region; the prechondroblastic layer, absent in control animals, was very distinctive (30-75 microns) in experimental animals; and there was a 62% increase in the thickness of the chondroblastic layer in the experimental animals. These findings indicate that chronic alteration of mandibular posture via increase in vertical dimension stimulates progressive remodeling of the mandibular condyle in young adult monkeys.

Adaptation, Physiological↗

PubMed1995

Occlusion, Orthodontic treatment, and temporomandibular disorders: a review.

A review of the current literature regarding the interaction of morphologic and functional occlusal factors relative to TMD indicates that there is a relatively low association of occlusal factors in characterizing TMD. Skeletal anterior open bite, overjets greater than 6 to 7 mm, retruded cuspal position/intercuspal position slides greater than 4 mm, unilateral lingual crossbite, and five or more missing posterior teeth are the five occlusal features that have been associated with specific diagnostic groups of TMD conditions. The first three factors often are associated with TMJ arthropathies and may be the result of osseous or ligamentous changes within the temporomandibular articulation. With regard to the relationship of orthodontic treatment to TMD, the current literature indicates that orthodontic treatment performed during adolescence generally does not increase or decrease the odds of developing TMD later in life. There is no elevated risk of TMD associated with any particular type of orthodontic mechanics or with extraction protocols. Although a stable occlusion is a reasonable orthodontic treatment goal, not achieving a specific gnathologically ideal occlusion does not result in TMD signs and symptoms. Thus, according to the existing literature, the relationship of TMD to occlusion and orthodontic treatment is minor. Signs and symptoms of TMD occur in healthy individuals and increase with age, particularly during adolescence; thus, TM disorders that originate during various types of dental treatment may not be related to the treatment but may be a naturally occurring phenomenon.

Adolescent↗

PubMed1994

Developing measures of patients' perceptions of orthognathic surgery.

Measurements of patients' perceptions of the benefits, costs, and risks of orthognathic treatment are needed to assess the utility of alternative treatments, and to assess and improve patient education to make informed decisions. A two-part study was conducted to develop and evaluate measures assessing patients' perceptions of the benefits and risks of orthognathic surgery in comparison to an orthodontics-only approach or no treatment. The first part of this study included 49 patients who had completed orthodontics and orthognathic surgery and 34 patients considering orthognathic surgery. All patients were asked to complete an open-ended telephone questionnaire about their perceptions of the benefits and risks of orthognathic surgery and of alternative options. Patients' answers were sorted into categories, and the second part of this study included a closed-form written questionnaire to assess the perceived likelihood of possible outcomes in each category. Reliability of the questionnaire was assessed using Cronbach's alpha coefficient of internal consistency reliability. Cronbach's alpha ranged from 0.74 to 0.91 when the instrument was used to assess either overall benefits or risks of orthognathic surgery, orthodontics only, or no treatment, indicating acceptable reliability for each of these uses. Subscales concerning more narrowly defined aspects of benefits and risks were less reliable than the overall scales.

Adult↗

PubMed1994

Cryotherapy for retinopathy of prematurity: a histopathologic comparison of a treated and untreated eye.

A female infant born at 28 weeks gestational age, weighing 570 g, developed retinopathy of prematurity (ROP) which progressed to threshold disease in one eye. Transscleral cryotherapy of the avascular peripheral retina resulted in complete clinical regression of the active ROP in that eye. The fellow eye continued to manifest subthreshold ROP. Histopathologic findings included a striking reduction of the cryotreated retina to a thin glial scar, with associated retinal pigment epithelium atrophy, denudation of Bruch's membrane, and extensive atrophy of the underlying choroidal vasculature, predominantly the choriocapillaris.

Atrophy↗