Canine impaction identified early with panoramic radiographs.
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Case-Control Studies↗
Biomedical subjects
R J Isaacson
Publications and source records attributed to R J Isaacson.
Development of supernumerary premolars in an orthodontic population.
Seven cases exhibiting supernumerary premolar development were detected during a 2-year period during the routine care of approximately 1,100 orthodontic patients. This 0.64% prevalence is more than twice as high as has been previously reported and represents an occurrence rate of 1 per 157 patients. This report describes the summary data for the cases detected and briefly reviews the available literature.
Adolescent↗
Tooth diameters and arch perimeters in a black and a white population.
This study was undertaken to test the hypothesis that a sample of black patients will have larger mesiodistal tooth diameters and larger dental arch perimeters than a corresponding sample of white patients. In this study, the black sample's mean canine, first and second premolar, and first molar mesiodistal diameters were significantly larger than those of the white sample. The dental arches of the black patients were significantly wider and deeper but did not show significantly more crowding. Gender and race differences did exist, but gender differences were controlled by sampling procedures. The black sample also had a larger mean MP-SN angle but this was not accompanied by the increased crowding and the narrower dental arches that had been reported associated with high-angle white samples.
Black People↗
Increase in arch perimeter due to orthodontic expansion.
A mathematical model was developed to compare quantitatively the effects of various types of orthodontic expansion on mandibular arch perimeter. Mandibular arch form was modeled with spline interpolation to fit a smooth curve between assigned molar, canine, and incisor positions. Starting with average arch dimensions, intermolar width, intercanine width, and midline arch length were increased individually and in combination in millimeter increments up to 5 mm, and the consequent changes in arch perimeter were measured. Increasing midline arch length by incisor advancement was nearly four times as effective in increasing arch perimeter as was molar expansion; canine expansion had an intermediate effect. Arch perimeter increments increased slightly with successive amounts of expansion for the molar, canine, and incisor. Combinations of molar-canine and canine-incisor expansion yielded results comparable to the total effects achieved by expansion of those teeth individually. Combined molar-canine expansion created increases in arch perimeter that were only slightly less than those generated by incisor advancement alone.
Cephalometry↗
Quantitation of rotational movements associated with surgical mandibular advancement.
Surgical mandibular advancement can be used to correct an anteroposterior and/or vertical malocclusion. The procedure of choice is often the bilateral sagittal split osteotomy (BSSO). By varying the amount of presurgical overbite correction, the rotational movement of the distal segment of the osteotomy can be controlled. Consequently, the malocclusion and the resultant vertical and anteroposterior facial form changes are predictably planned to produce both the desired occlusion as well as the optimal esthetic facial result. Opening rotation of the distal segment elongates the lower face height by varying amounts depending on the nature of the rotation. The amount and type of rotation can be determined and quantified by the technique presented in this paper, which is based on a geometric theorem used to determine the kinematic center of rotation of an object. This technique can shorten treatment time and produce more predictable results. The specific applications are: 1) treatment planning for individual patients, 2) uniform analyses of treatments and grouping of treatment types, and 3) development of more accurate computerized treatment planning programs.
Algorithms↗
Computers and cephalometrics.
Computers have been adapted to cephalometric data acquisition and analysis. Traditional cephalometric radiographs provide images that are entered into computers by converting them to digital data. Other non-ionizing radiation forms of energy, such as sound, light and magnetism, are now used to create images. Newer methods of data acquisition are emerging that convert objects directly to digital data for computer entry without going through intermediate analogue forms. The analysis of cephalometric data for diagnostic use is aided by computers, but the automated treatment planning application of computers is limited. This limitation is not a function of the computer, but a function of our inability to reliably predict absolute biologic changes in the face of biologic variability.
Cephalometry↗
Dental and skeletal contributions to occlusal correction in patients treated with the high-pull headgear-activator combination.
The purpose of this study was to examine dental and skeletal changes in patients treated with the high-pull headgear-activator combination. A group of 40 consecutively treated subjects with a Class II molar relationship and a minimum of 5 mm overjet was used for this study. The results showed that Class II correction often was achieved by distal repositioning of the maxillary teeth (mean, 0.07 mm) and mesial repositioning of the mandibular teeth (mean, 3.3 mm) with a wide range of variation. Correlation of maxillary molar repositioning with total interarch occlusal change showed a positive relationship; however, a weak correlation suggested that other variables were contributing factors, in addition to distal upper molar positioning. The change in mandibular molar position compared with the movement of pogonion strongly suggests that forward growth of the mandible is important to the correction of the Class II malocclusion. When total molar repositioning in the upper jaw was correlated with total molar repositioning in the lower jaw, a strong inverse correlation was found, indicating that upper molar movement parallels lower molar movement.
Activator Appliances↗
Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics.
Control of faciolingual tooth inclinations is obtained by using rectangular wire with third-order bends and standard edgewise brackets or by using a straight wire in a preadjusted appliance system. Ideal faciolingual inclinations have been determined previously by measuring facial surface contours relative to coronal long axes. This study evaluates faciolingual inclinations based on occlusal table inclinations relative to occlusal planes. The samples compared include untreated ideal occlusions and malocclusions in three different vertical skeletal growth patterns. Faciolingual inclinations of first molars and central incisors were measured relative to the occlusal plane and to selected cephalometric angular measurements. Statistical comparisons between groups revealed significant differences in the inclinations of the upper incisor relative to the occlusal plane (U1-OP) and the inclination of the occlusal plane relative to sella nasion (OP-SN). No statistically significant intergroup differences were found in the inclination of the lower incisor relative to the occlusal plane (L1-OP) or in the faciolingual inclinations of the maxillary and mandibular first molars. On the basis of the large intergroup differences in the mean angle between the occlusal plane and sella nasion (OP-SN), the use of straight-wire appliance therapy is discussed in terms of the potential for creating differential moments. Because differential moments may facilitate or hinder treatment goals, the practitioner must know the biomechanical sequelae resulting from occlusal plane-sella nasion variations, which differ from normative values when preadjusted brackets are used.
Adolescent↗
Biotechnical and other factors affecting orthognathic surgery.
Orthognathic surgery is a rapidly growing biotechnologic interaction involving alterations of facial form and dental occlusion. This article describes some of the important and complex psychological, sociological, ethical, and public policy issues involved. Advances in the latter issues are necessary for advancement of the field.
Adolescent↗
The morphology of canines in relation to preadjusted appliances.
The canine occupies the transition from anterior to posterior occlusion. Following orthodontic treatment the canine's incisal edge occlusion demonstrates the tip and torque present in the appliance that was used. The effective torque of the bracket, however, is influenced by the tooth morphology at the bracket's base. The morphology of the facial surface can be described by an angle formed between the tangent at the point of bracket placement and the long axis of the crown. In this study, tangent angles at four millimeters and five millimeters from the cusp tip of 100 maxillary and 70 mandibular canines were determined. There was a significant difference between tangent angles at the same location on different canine teeth and also at different locations on the same canine tooth. Proximal collum angles were also measured in this study and there was a significant negative proximal collum angle in maxillary canines and a significant positive proximal collum angle in mandibular canines. The presence of these normal biologic variables will either enhance or minimize the torque supplied by preadjusted appliances, depending on a combination of prescription used and biologic variable present.
Cuspid↗
Three biologic variables modifying faciolingual tooth angulation by straight-wire appliances.
The facial surface contours of 600 maxillary and mandibular teeth, including 50 of each type of tooth from central incisors to first molars, were measured. Facial contours present at the same location, facial contours from occlusal/incisal to gingival surfaces and the angle formed by the coronal and radicular long axes varied among teeth of the same type. The magnitude of the variation found was so great as to suggest that differences between patients or differences in height of bracket placement are greater than the differences between the standard torque prescriptions now used in orthodontics. No single point, including the coronal midpoint (LA point), was found to be constant among teeth of the same type. Variation in facial surface contour tended to be greater in the posterior teeth than in the anterior teeth. Future custom construction of brackets, adjusted to individual facial contour differences, will also require information regarding optimal tooth position in the head, including compensations necessary for variations in facial skeletal pattern.
Humans↗
Mechanics, growth, and class II corrections.
Growth of the orofacial region is quantitatively described by locating the center of mandibular rotation relative to the cranial base. The center of mandibular rotation is positioned by the ratio of vertical facial growth (AFH/PFH) and the direction of condylar growth. Appliance therapy is associated with changes in the means of both of these parameters. These changes reduce or stop favorable anterior mandibular rotation and redirect the mean condylar growth vector more posteriorly. When appliance therapy is stopped, these parameters return toward their resting values. The mean direction of the condylar growth vector became even more anteriorly directed after treatment than the pretreatment mean value. These data support the hypothesis that orthodontic appliances significantly alter the facial growth pattern and when they are stopped, the growth pattern tends to rebound to or beyond the pretreatment values.
Activator Appliances↗
Movement of the proximal and distal segments after mandibular ramus osteotomies.
Data was collected from 27 patients who were treated with various ramal surgical procedures. Movements of the proximal segment during and after surgery were frequently noted. If the proximal segment was moved from its preoperative position and fixed to the distal segment, occlusal relapse was visible shortly after release of maxillomandibular fixation. Proximal segments displaced during surgery and not fixed to the distal segment frequently returned to their preoperative positions during fixation or assumed positions of biologic equilibrium. In such cases, occlusal relapse was minimal or nonexistent.
Adolescent↗
Differential treatment planning for mandibular prognathism.
The treatment records of thirty-eight cases of mandibular prognathism treated by orthodontics means only (ORTHO) were evaluated. The pretreatment records of twenty cases of mandibular subapical esteotomy (SUB) and twenty cases of mandibular setback (SET) were evaluated for comparison and contrast with the pretreatment ORTHO records and with each other. Dental, skeletal, and soft-tissue parameters in the vertical and horizontal planes of space were recorded. Statistical analysis of means of parameters of the pretreatment records provided documentation of the discriminant variables in each of the following paired groups: ORTHO-SUB, ORTHO-SET, and SUB-SET. Analysis of the data as indicated above led to the following conclusions: 1. Three discriminant groups of mandibular prognathism of various degrees of severity were discernible when comparisons of treatment categories simulating clinical decisions were made. The ORTHO group was distinguished from the SUB group in the horizontal plane and, more strongly, in the vertical plane. The ORTHO group was distinguished from the SET group in the vertical plane and, more strongly, in the horizontal plane. The SUB group was distinguished from the SET group in the horizontal plane. 2. The physiologic developmental status of the patient should be carefully evaluated. 3. Anteroposterior dysplasias should be assessed relative to the cant of the mandibular plane. True denture base discrepancies can be noted relative to the occlusal plane. 4. Documentation of vertical dysplasias should include measurements of craniofacial divergence (SN-MP, FH-MP, and OP-MP). 5. In assessing the profile evaluation of the patient with mandibular prognathism, particular attention should be focused on facial contour angle (FCA), nasolabial angle (NLA), and relative lower lip protrusion (LLP). 6. Any numerical values obtained in the evaluation of the dental, skeletal, or soft-tissue characteristics of mandibular prognathism should be considered only as descriptive, diagnostic guides and not as components of a diagnostic formula.
Alveolar Process↗
Tooth-size discrepancy in mandibular prognathism.
A Bolton analysis of seventy-eight cases of Angle Class III malocclusion, twenty-six cases of Angle Class I malocclusion, and twenty-six cases of Angle Class II malocclusion was recorded. Frequency of excess mandibular tooth structure, magnitude of the excess, over-all ratios, and anterior segment ratios were computed and analyzed. Two clinical cases were presented to show the advantage of tooth-size harmony in mandibular prognathism. Analysis of the data as presented above suggests the following conclusions: 1. The frequency of mandibular tooth-size excess (over-all ratio) in this sample was greater in cases of mandibular prognathism than in Angle Class I and Angle Class II cases. 2. In those cases with mandibular tooth-size excess, there was a suggestion that the magnitude of the excess was greater in cases of mandibular prognathism than in Angle Class I and Angle Class II cases. 3. A tooth-size discrepancy analysis should be included as one part of the diagnostic records for mandibular prognathism.
Adolescent↗
Effects of rotational jaw growth on the occlusion and profile.
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Adolescent↗
Some effects of mandibular growth on the dental occlusion and profile.
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Alveolar Process↗