Introduction
Social and psychological concerns, improved function, appearance, and self- esteem encourages a patient to pursue Orthodontic treatment, for which extraction may or may not be needed. Conventionally Steiner Stick Analysis.1, 2, 3 or Tweed Head Plate correction4 is followed to decide extraction during fixed Orthodontic treatment for desirable treatment outcome. The accuracy of prediction by these methods need to be assessed. Steiner Stick Analysis discuss the predetermination of anteroposterior position of the upper and lower incisors based on the appraisal of changes in the ANB angle and the position of the bony chin (Pg) to NB at the end of the treatment. Once the appraisal of the changes in the ANB angle and the Pg-NB distance is put in place, the clinician can allude to a set of acceptable compromises for the incisor position to arrive at the so called ‘settled ‘position. Finally, the treatment goal is individualized as these estimated values may be modified for individuals.
This study was designed to compare predicted position and angulation of Maxillary and Mandibular incisor by Steiner Stick Analysis with the actual treatment outcome using Nemotech software.
Materials and Methods
Sample
Sample was taken from record files of our department consisting of pre and post treatment lateral cephalogram of 15 subjects with age ranging from 20- 22 years. Informed consent from the patient and Ethical committee approval from the etheical committee of Babu Banarsi Das college of Dental Sciences, BBDU, Lucknow was taken.
Armamentarium for the study
Material used for obtaining lateral cephalogram
Lateral cephalogram were taken from records file of the patient for whom cephalogram was taken from same machine in Department of Oral Medicine and Radiology.
Cephalostat machine: Planmeca proline XC cephalostat (Finland) machine were used to take digital lateral cephalograms of selected subjects. The exposure was set at 68KV, 5mA and exposure time was of 23 second. Pre and Post lateral cephalograms of each patient saved in CD-ROM were taken from the record files.
Nemoceph software: Nemoceph software (Dental studio version 6.0) was used to trace and analyze the lateral cephalogram uploaded on laptop.
Methodology
Methods of taking radiographs
Lateral cephalogram taken following standard protocol The lateral cephalograms were taken in natural head position with lips relaxed and teeth in centric occlusion. Subject was placed at a distance of 60 inches.(Figure 1). Soft copy of lateral cephalograms were transferred to a computer loaded with Planmeca software from where the digital lateral cephalograms were saved in bitmap files and taken in a CD ROM.
Transfer of soft copies of lateral cephalogram
The soft copies of all the lateral cephalograms were transferred to Nemotec software program (Dental studio-NX, version 6.0).(Figure 2)
Calibration of images
The images were calibrated by identifying two crosshairs 10 mm apart on lateral cephalogram using calibration tool of the software, both for pre and post treatment lateral cephalogram.
Identification of landmarks
The image enhancement feature of the software (basic an advanced cephalometric tools), like brightness, contrast adjustment and magnification were used to identify individual cephalometric landmarks as precisely as possible. The landmarks were marked with the help of mouse/cursor.
Following landmarks are used in the study (Figure 3)
Nasion (N): Most anterior point of the Nasofrontal suture in the midsagittal plane.
Point A: Deepest point in the midsaggital plane between the Anterior Nasal Spine and Prosthion.
Point B: Deepest point in the midsaggital plane between Infradentale and Pogonion. Most anterior point of the bony chin.
Following angular and linear parameters were measured on tracing with the help of the Nemotech software.(Figure 4)
Steiner Stick Analysis was done based on values as obtained for Steiner’s Analysis in pretreatment tracing on Nemotech Software.
Steiners Prediction was compared with post treatment outcome.(Figure 6)
Observation and Results
From Table 1, it was observed that there was no significant difference was seen in U1-NA distance in mm and angulation in degree compared from predicted to post treatment as p>0.05 for both when compared using Paired t test.
From Table 2, it was observed that there was no significant difference was seen in L1-NB distance in mm compared from predicted to Post treatment asp>0.05 for both when compared using Paired t test but significant increase in L1-Nb angulation in degree was seen from predicted to post treatment as p<0.05.
Table 1
Predicted steiner stick analysis (PSSA)and post treatment outcome comparison of U1-NA
Table 2
Predicted steiner analysis (PSSA) an post treatment outcome comparison of L1-NB
Discussion
Most of the studies have evaluated the accuracy of prediction in orthognathic surgery cases5, 6, 7, 8, 9 but few evaluated[13] the accuracy of prediction case who had undergone fixed orthodontic treatment alone. These studies evaluated accuracy of prediction of Steiner Stick Analysis,10 manual and computerized 11 VTO 12 or morphing tool of digital cephalometric software. Determination of the treatment goal for an individual patient is very critical. One has to predict the changes in ANB the Pg NB distance during changes. The result of the present study show that the accuracy in predicting the values of the four variables at the end of the treatment is limited. Though position and angulation of Maxillar incisor, position of Mandibular Incisor was overestimated by SSA, but difference was statistically non significant in predvious studies.Mandibular Incisor angulation was also overestimated and difference was statistically significant.(Figure 7).
Comparison with previous studies by Abdullah et al observed contrary result where U1-NA (linear in mm)and L1-NB (linear in mm)showed statistically significant difference between Steiner predicted value and actual post treatment outcome.Cangialosi et al 6 found predicted value for Mandibular incisor position and angulation appeared to be inaccurate and overated for growing subject.The prediction of the other angles between anatomical planes was significantly accurate, however predicted of the Anteroposterior position and angulation of incisor were least reliable. (Figure 8)
Sample et al compared manual and computerized VTO forecast in growing subject and found significant difference for position and angulation of Maxillary Incisor by manual VTO and post treatment but showed insignificant difference for Mandibular Incisor position and angulation.Similar to our study it was general trend of overestimation in studies by Abdullah et al and Sample et al.
Steiner Stick Analysis helped in determing amount of space requirement in particular case to correct Maxillary and Mandibular Incisor position and angulation. However, it did not consider soft tissue profile of the patient. The overestimation by Steiner Stick Analysis could be due to the fact that retraction might have been stopped once adequate changes in profile were achieved which might have been before achieving ideal hard tissue values of Steiner prediction.
Another limitation could be due to variability in orthodontic mechanics during the course of the treatment. Steiner Stick Analysis is quick, easy method of prediction possible on manual tracing and if used with careful correlation with soft tissue profile can help us in deciding amount of space required in orthodontic cases. Further, studies should aim at comparisons done in larger sample size.
