Pseudoelasticity and thermoelasticity of nickel-titanium alloys: a clinically oriented review. Part I: Temperature transitional ranges.

The purpose of this review was to organize a systematic reference to help orthodontists evaluate commonly used orthodontic nickel-titanium alloys. Part I of the article reviews the data available in the literature regarding the temperature transitional ranges of the alloys. The thermomechanical behavior of these compounds is, in fact, strictly dependent on the correlation between the temperature transitional range and the oral temperature range. Part II of the article will focus on the mechanical characteristics of the alloys, such as the magnitude of the forces delivered and its correlations with temperature transitional range and oral temperature.

Pseudoelasticity and thermoelasticity of nickel-titanium alloys: a clinically oriented review. Part II: Deactivation forces.

The purpose of this review was to organize a systematic reference to help orthodontists evaluate commonly used orthodontic nickel-titanium alloys. Part I of the article reviewed the data available in the literature regarding the temperature transitional ranges of the alloys. The thermomechanical behavior of these compounds is, in fact, strictly dependent upon the correlation between the temperature transitional range and the oral temperature range. Part II focuses on the mechanical characteristics of the alloys, such as the magnitude of the forces delivered and correlations with the temperature transitional range and oral temperature.

Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans.

The purpose of the study was to establish normative data on the mesiodistal crown dimensions of Americans of Dominican background. The Bolton tooth size analysis was performed on a sample of 54 Dominican Americans. The mean, range and standard deviation were calculated for the size of the teeth, and a coefficient of variation was obtained for the tooth size ratio. A 2-sample t-test was used to test for the statistical difference between means. In general, the values obtained for the Dominican American sample closely resembled previous data available for the African American population. The tooth size ratios obtained were compared to the Bolton ratios. The overall ratio was found to be 91.3, equivalent to the Bolton overall ratio, whereas the anterior ratio was 78.1, larger than the 77.1 Bolton ratio. The frequency of tooth size discrepancy outside 2 standard deviations from the Bolton mean was also calculated. An overall tooth size discrepancy was found in 11% of our sample, and 28% of the sample presented an anterior tooth size discrepancy.

A new approach determining the sagittal interjaw relationship: the bisecting plane analysis.

BACKGROUND: Assessment of the sagittal interjaw relationship has for long time been dependent upon the relative positions, either to reference lines outside the jaw itself or, in some cases, the position was dentally determined. The present study developed a line bisecting the upper and lower jaws for a better approach to the assessment of orthopedic sagittal interjaw relationships. METHODS: One hundred and ten randomly selected samples were used to make a comparison between bisecting plane (BSP) and functional occlusal plane (FOP) in terms of their accuracy in determining sagittal interjaw relationships. The "gold standard" for comparison was obtained through clinical comprehensive classification (CCC). RESULTS: The BSP method was found to provide a better assessment of the sagittal interjaw relationship than the FOP method. Tests of chance-expected correction proportions were taken for both methods with CCC. A higher kappa value for the BSP method (0.659) was obtained than for the FOP (0.477). CONCLUSIONS: Bisecting (BS) plane is an alternative reference plane for judging a skeletal sagittal interjaw relationship. The compliance with the clinical evaluation makes it a possible option when the orthopedic interjaw relationship needs to be critically determined for jaw rotation cases.

Reliability of computer-generated prediction tracing.

The reliability of a commercially available computer prediction program (Quick Ceph II) was evaluated using pretreatment and posttreatment cephalograms of 30 patients who were treated during an active period of growth. The computer prediction was compared with the actual treatment result, and the growth forecast with the computer program was compared with the growth forecast using a manual method. Using paired student's t-tests, predictions for 5 of the 10 variables measured were found to be statistically reliable. Comparing the relative accuracy of growth prediction in terms of absolute values, the computer came closer to the actual result in four of the nine variables, while the manual method came closer in three variables. Predictions for the other two variables were virtually the same using both methods. The manual method of prediction was sufficient to give a reasonably good graphic representation of growth changes to create a VTO. However, the computer offers the added advantages of quicker access to information and somewhat greater accuracy in producing the tracing, as well as its use in patient education.

An evaluation of growth changes and treatment effects in Class II, Division 1 malocclusion with conventional roentgenographic cephalometry and finite element method analysis.

Conventional methods of roentgenographic cephalometry will yield differences in interpretation of growth or treatment changes depending on which methods of superimposition are used. The finite element method of analysis has been reported to have significant advantages since it does not require a reference frame to describe the changes that have taken place. This article describes the growth of a patient with a Class II, Division 1 malocclusion during approximately 2 years of orthodontic treatment with the use of conventional cephalometric growth and static analyses, as well as the finite element method. Thirty cephalometric points were digitized on the pretreatment and the posttreatment lateral cephalograms of a patient undergoing orthodontic treatment between the ages of 10 and 12 years. The finite element method provided a reference frame invariant description of the size, shape, change, and rotation of each of the 12 finite elements representing different anatomic structures.

A cephalometric appraisal of edgewise Class II nonextraction treatment with extraoral force.

The purpose of this study was to determine the treatment effects of nonextraction edgewise therapy combined with cervical headgear on Class II, Division 1 malocclusions. Data from a sample of 43 treated patients with a mean age of 11 years 11 months and a mean treatment time of 2 years 8 months were recorded. A cephalometric appraisal was done and the initial and final measurements of points, lines, and angles based on accepted cephalometric analyses were compared. Student's t test for paired cases was used to evaluate the significance of all measurement changes. The significant findings were as follows: the inhibition of forward growth of the maxilla, downward tipping of the anterior part of the palate, reduction of flaring of the maxillary incisors, reduction of the facial convexity, and extrusion and mesial movement of maxillary and mandibular first molars. The overall results tend to indicate the efficacy of this treatment modality in the treatment of the Class II, Division 1 malocclusion.

A cephalometric appraisal of nonextraction Begg treatment of Class II malocclusions.

Initial and final cephalometric evaluations are compared in a sample of 42 patients with Class II malocclusions treated in a nonextraction manner with the Begg appliance. The sample was analyzed as a group. Subgroups of patients with Division 1 and Division 2 characteristics were analyzed separately. To depict skeletal and dental changes, measurements were made using the sella nasion, palatal, and mandibular planes as reference planes. The findings show that on the average: The upper first molar maintained its anteroposterior position at the same time that SNA was reduced. This suggests a restriction of anterior maxillary growth. The mandibular first molar moved forward by 1.2 mm. Part of this change was attributed to anchorage consumption. Vertical changes in both the maxilla and the mandible were found to be within the normal range. No significant change in occlusal or mandibular plane angles was observed except for the Division 1 subgroup in whom a mild increase in the mandibular plane angle was observed.

Skeletal morphologic features of anterior open bite.

Lateral cephalograms of sixty patients with open bite and sixty untreated subjects who were determined clinically to have Class I normal occlusions were studied. The following six values were recorded: (1) ratio of posterior to anterior face height, (2) ratio of upper to lower face height, (3) Sn GoGn angle, (4) gonial angle, (5) SN-PP angle, and (6) PP-GoGn angle. Results were compared with previous studies. The constancy of the ratios and angles with age was tested and an attempt was made to separate the open-bite sample into skeletal and dentoalveolar groups. Results were generally consistent with those reported previously, except for the Sn PP angle, which was not significantly different from the normal group. In the open-bite sample the study showed a decrease in the ratio of PFH/AFH, a decrease in the ratio of UFH/LFH, and an increase in the other angles measured. Upon further division of the sample into mixed- and permanent-dentition groups, it was found that the angles and ratios remained relatively constant with age. An attempt to divide the open-bite sample into skeletal and dentoalveolar groups resulted in more extreme values for all the measurements made. The difficulty in differentiating between the two groups and the variability of dentoskeletal patterns in open bite is discussed.

Management of a maxillary central incisor impacted by a supernumerary tooth.

Supernumerary teeth in the maxillary midline are common and can present both esthetic and pathologic problems that can be extremely difficult to solve. Early detection of the mesiodens is most important if such complications are to be avoided. This case required both surgical and orthodontic treatment to bring an unerupted, impacted maxillary central incisor into position. Using a combination of conservative surgical treatment and careful orthodontic management, the tooth was brought into good position in the dental arch and injury to root structure and surrounding oral tissues was avoided.

A cephalometric evaluation of hard- and soft-tissue changes during the third stage of Begg treatment.

This study examined the effect of lingual root torque during the third stage of Begg treatment upon the maxillary central incisor, hard-tissue Point A, and soft-tissue Point A. Lateral cephalograms were taken, at the beginning and end of Stage III, of eighteen patients undergoing Begg treatment. Linear and angular measurements were made in an attempt to find the anteroposterior changes which occurred in the above structures as well as the superior-inferior changes which occurred in the maxillary first molar and the maxillary central incisor. It was found that the apex of the maxillary incisor, Point A, and soft-tissue Point A moved posteriorly a significant amount following Stage III mechanics. Also, the incisal edge of the maxillary central incisor moved anteriorly and extruded significantly. Weak correlations between hard- and soft-tissue changes may be due to changes in thickness of the upper lip related to growth and to growth of the nose.