Indian Journal of Dental Research

ORIGINAL RESEARCH
Year
: 2013  |  Volume : 24  |  Issue : 4  |  Page : 523-

Reliability of the frontal sinus index as a maturity indicator


Ajinkya A Patil1, Ameet V Revankar2,  
1 Department of Orthodontics and Dentofacial Orthopedics, Bharthi Vidyapeeth University, Sangli, Maharashtra, India
2 Department of Orthodontics and Dentofacial Orthopedics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad, Karnataka, India

Correspondence Address:
Ameet V Revankar
Department of Orthodontics and Dentofacial Orthopedics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad, Karnataka
India

Abstract

Aim: The aim of this study was to compare the reliability of frontal sinus as a skeletal maturity indicator in males and females. Setting and Sample Population: Lateral cephalograms of 75 males and 75 females, both in pre- and post-pubertal stages of development as determined by Middle phalanx of the third finger (MP3) radiographs. Materials and Methods: Lateral cephalograms were analyzed for frontal sinus maturity. Maximum height, maximum width and height to width ratio of the sinus were calculated. The mean height to width ratio of the sinus at respective MP3 stages were tabulated and subjected to statistical analysis to determine the correlation. Correlation at different MP3 stages between males and females was also determined. Results: Statistically significant differences were observed between the mean values of F and FG along with F and I stage in males, significant difference between the values of FG stage among males and females were also observed. Conclusion: Based on statistical and direct comparison of raw data, study concludes that frontal sinus is not reliable as a sole criterion for prediction of skeletal maturity.



How to cite this article:
Patil AA, Revankar AV. Reliability of the frontal sinus index as a maturity indicator.Indian J Dent Res 2013;24:523-523


How to cite this URL:
Patil AA, Revankar AV. Reliability of the frontal sinus index as a maturity indicator. Indian J Dent Res [serial online] 2013 [cited 2022 Aug 17 ];24:523-523
Available from: https://www.ijdr.in/text.asp?2013/24/4/523/118372


Full Text

Growth is a critical variable in orthodontic diagnosis and treatment planning. Prior knowledge of the amount along with rate, timing and direction of growth would be extremely useful in forecasting treatment outcome. Indicators of skeletal age are more informative than the chronological age for clinical decisions regarding use of orthopedic extra oral appliances, functional appliances and orthognathic surgery.

Many skeletal maturity indicators have been proposed over the previous decades. However, in the current era of radiation awareness use of the ephiphyseal development of the middle phalanx of the third finger (MP3) radiograph is advisable instead of hand and wrist radiographs for growth assessment. [1],[2],[3],[4] Researchers took a step further when they eliminated the need for additional radiographs using the cervical vertebrae, [5],[6] seen in the lateral cephalogram for growth assessment. Although the frontal sinus, also seen on the lateral cephalogram was mentioned to be a suitable indicator by Ruf and Pancherz, [7] their study was restricted to males with a relatively small sample size and required 2 cephalograms at 1 or 2 year intervals.

Thus, it was felt necessary to evaluate the suitability of the frontal sinus as a maturity indicator from a single cephalogram. This was carried out by correlating sinus parameters width, height and sinus index (height/width ratio) as evaluated in the sagittal plane with the MP3 radiograph, which by far is the most established skeletal maturity indicator in both sexes.

Hence, the present study was undertaken with the following objectives:



To determine whether cross-sectional frontal sinus parameter "sinus index"(height/width ratio), which we developed could be correlated to skeletal maturity levels demonstrated by MP3 radiographs.

Compare the reliability of frontal sinus index as a skeletal maturity indicator in males and females.

Why the sinus index?

The frontal sinus enlargement takes place as an adaptive mechanism to keep pace with the sagittal increase in the nasomaxillary complex. [8] In order to do the assessment from a single cephalogram, it was decided to consider both height width dimension of the frontal sinus in the form of an index termed the "sinus index" being the height to width ratio. This was carried out on the basis that the sagittal increase of the face occurs earlier, whereas the increase in the height continues beyond the pubertal growth spurt. [9] Hence, the hypothesis of ascertaining, whether the "sinus index" could be a better indicator of the sinus maturity was arrived at since width and height measurements alone are bound to differ considerably in individuals with different head sizes. [10] Furthermore, because of the inherent shortcomings of cephalometry, such as magnification, ratios are always more reliable than individual absolute measurements. [11]

 Materials and Methods



Sample selection

A retrospective cross-sectional study was planned. MP3 radiographs and lateral cephalograms of 75 males and 75 females; both in the pre- pubertal and post-pubertal stages of development as determined by MP3 radiographs were randomly selected.

Assessment of skeletal maturation using MP3 radiograph as an indicator

The five different stages of MP3 were evaluated from the radiographs as described by Hägg and Taranger. [12] The scores imparted were F, FG, G, H, and I corresponding to the relationship of the epiphysis to the metaphysis as seen on the MP3 radiograph.

Assessment of frontal sinus as seen on the lateral cephalogram

The radiographs were taken in the same cephalostat with the subjects looking straight ahead with the Frankfort Horizontal plane parallel to the floor. The film source distance was 5 feet 2 inches and distance between film and subject's mid sagittal plane was 6 inches.

On the lateral cephalogram, frontal sinus analysis was performed. Each radiograph was manually traced on a 0.003 inch lacquered polyester acetate paper using a 0.3 inch lead pencil, by a single operator. The cephalogram was oriented with the nasion-sella line horizontally. The peripheral border of the frontal sinus as seen on the lateral cephalogram was traced. The highest (SH) and lowest (SL) points of sinus extension were marked, [13] [Figure 1]. The maximum height was obtained by connecting these points. The maximum width of sinus was assessed perpendicular to this interconnecting line [Figure 1].{Figure 1}

The ratio of maximum height to width of the frontal sinus (i.e., sinus index) was calculated. The scores obtained were tabulated with the respective MP3 stage for each patient and subjected to statistical analysis. Thirty five cephalograms, which presented with radio opacity in the region of frontal sinus were rejected and out of 115 cephalogram scores of only 100 were considered, eliminating the remaining 15 for the sake of equal distribution in both the sexes at each MP3 stage.

Statistical analysis

The method error was calculated using Dahlberg's formula, [14] by repeating the tracings and was not statistically significant, for any of the variables. The data were analyzed with SPSS software (version 16.0, SPSS, Chicago, III). The sinus index was compared at different MP3 stages using one way ANOVA test in both sexes. The means and standard deviations were compared using t-test. To test the significance of particular pairs of means "Tukeys honest significant difference test" was performed.

 Results



At each individual MP3 stage, the sinus index values apparently varied from individual to individual [Table 1] and [Table 2]. Hence, the hypothesis that a specific skeletal stage corresponded to a specific sinus index value was rejected. However, statistical analysis was performed on the data to derive any other implication as detailed below.{Table 1}{Table 2}

The mean maximum height, width, and sinus index obtained from the frontal sinus analysis at the respective MP3 stages, in both the sexes, was tabulated [Table 1] and [Table 2]. The mean and standard deviation at various MP3 stages for males and females have been tabulated in [Table 3]. The sinus index was compared at different MP3 stages using one-way ANOVA test in both the sexes [Table 4] and [Table 5]. The readings were statistically significant for the male group at 0.0004 level of significance.{Table 3}{Table 4}{Table 5}

Furthermore, the value of the mean and standard deviations of the sinus index at all stages was compared between males and females using the t-test [Table 6]. Significant difference was observed between the values at FG stage among males and females.

To test the significance of particular pairs of means of the sinus "Tukeys honest significant difference test" was performed. Significant difference between the mean values of F and FG stage along with F and I stage was noted in males [Table 7].{Table 6}{Table 7}

Interpretation from tabulated data

The inference derived from the statistical tests as well as a direct comparison of the data is as follows:

The frontal sinus width gradually increases through MP3 stages F to H and at stage I, the increase in sinus height in more than the width in both sexes.However, the width increase is more marked in boys throughout the stages especially so at FG stage [Figure 2].{Figure 2}Comparatively the sinus index in females is more than of males at all MP3 stages except for F stage.Comparatively the sinus index is same at FG, G, and H stage in females.The maximum height, width, and the sinus index is more in males at F stage.Height of the sinus is more at all MP3 stages in males except for G stage.Height of the sinus is comparatively the same in males and females at G stage.Width of the sinus is more at all MP3 stages in males.Minimal difference is noted in the measurements of mean height to width ratio in males at FG, G, H, and I stage.Taking into consideration the maximum height and width of sinus in both sexes, it is observed that the sinus size is larger in males.

 Discussion



A number of indicators have been documented in the literature to assess skeletal growth. Abdel-Kader, [1] proposed MP3 radiograph alone on a dental film in order to reduce radiation exposure. Ruf and Pancherz, [7] have shown that the enlargement in the width of the frontal sinus can be considered as one of the skeletal maturity indicators in males. However, the method suggested by them requires at least two cephalograms taken at intervals 1 or 2 years apart. By their own admission, two such cephalograms are seldom available at the beginning of treatment.

The present study; however, is conducted in both males and females using a single cephalogram available at the beginning of treatment alone. The maximum height of the frontal sinus along with the maximum width was taken into consideration, and the sinus index was calculated and compared to the MP3 stage of each individual.

The results of our study reveal that prediction potential using this cross-sectional sinus index technique is low. Probably the sample size was not adequate enough to reveal a statistical difference if at all present.

If chronological age was compared along with the MP3 radiograph the results could have been useful from the age estimation point of view.

Rossouw et al.[15] studied skeletal growth pattern on a mixed sample consisting of 53 adult skeletal Class I and 50 adult skeletal Class III cases, surface area of frontal sinus was examined to assess the abnormal mandibular growth. Their study concluded that the frontal sinus can be used as an additional indicator for predicting mandibular growth. In contrast, our study checks the validity of the frontal sinus as a skeletal maturity indicator by observing the sinus index. Though direct comparison of frontal sinus with mandibular length is not a part of our study, it is noticed that no significant correlation exists between the sinus index and MP3 stages, which by far is the most established skeletal maturity indicator.

 Conclusions



None of the parameters of frontal sinus analysis could be significantly correlated with the individual stages of MP3 development. Hence, at this juncture, the use of this indicator as the sole criteria for assessing the maturational status using cross sectional data is questionable.For routine pretreatment orthodontic diagnostic procedure the MP3 method should be considered more reliable.

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