Indian Journal of Dental Research

ORIGINAL RESEARCH
Year
: 2011  |  Volume : 22  |  Issue : 3  |  Page : 376--380

Evaluation of buccolingual inclination of posterior teeth in different facial patterns using computed tomography


Suomo Mitra1, MS Ravi2,  
1 Department of Orthodontics, Buddha Institute of Dental Sciences, Patna, Bihar, India
2 A.B.Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore, India

Correspondence Address:
M S Ravi
A.B.Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore
India

Abstract

Background and Objective: Buccolingual inclination of teeth is an essential factor in establishing good occlusion. The objective of this study was to evaluate the buccolingual inclination of molar teeth in different vertical skeletal patterns by using computed tomography scans. Materials and Methods: Coronal section of the jaws obtained from computed tomograms were used to measure the buccolingual inclination of the long axis of the molars relative to their skeletal base. Forty male adult individuals with class I dental occlusion were selected. They were classified as short (Group 1), average (Group II), and long faced (Group III) as per their skeletal patterns measured by GoGn-SN, FH-MP, Y-axis and facial height index in cephalograms. Statistical Analysis: ANOVA and Tukey HSD tests were applied to calculate if there were any significant differences in the mean molar inclination between the groups. Pearson«SQ»s coefficients of correlation were calculated between the facial parameters and tooth inclination. Results: The differences in the mean molar inclination between the short, average, and long faced groups is significant for mandibular 1 st and 2 nd molars and maxillary 2 nd molars. Conclusion: Variations in mean molar inclination values are observed between short, average, and long faced groups.



How to cite this article:
Mitra S, Ravi M S. Evaluation of buccolingual inclination of posterior teeth in different facial patterns using computed tomography.Indian J Dent Res 2011;22:376-380


How to cite this URL:
Mitra S, Ravi M S. Evaluation of buccolingual inclination of posterior teeth in different facial patterns using computed tomography. Indian J Dent Res [serial online] 2011 [cited 2020 Apr 3 ];22:376-380
Available from: http://www.ijdr.in/text.asp?2011/22/3/376/87056


Full Text

Proper torque for anterior and posterior teeth is essential to achieve optimal aesthetics and also to establish functional occlusion devoid of occlusal interferences on excursive movements of the mandible. [1] Several investigators have attempted to establish norms for torque values of teeth [2],[3]

Several investigators [4],[5] have found torque values, particularly those of posterior teeth, to have a wide dispersion. Few authors have reported the buccal inclination of the crown in long faces, while few others have reported the opposite tendency. [6],[7]

The objective of the present study was to evaluate the buccolingual inclination of posterior teeth in different vertical facial patterns using the long axis of the tooth as the measuring parameter by using computed tomography.

 Materials and Methods



Forty CT head scans of the male adults having full complement of teeth with Class I occlusion, minimal or no dental discrepancies and with no prior history of orthodontic or orthognathic surgery treatment are selected from the hospital records.

The CT scans had been done with contiguous 1 mm slice thickness at 120 kV, 100 mA, FOV 19.6, window width 350, level 40 on CT/e spiral CT machine (GE Medical Systems, USA) [Figure 1] and [Figure 2].{Figure 1}{Figure 2}

Lateral cephalograms of the selected subjects were made under standardized conditions with the Frankfort horizontal plane kept parallel to the floor.

The cephalometric measurements carried out were GoGn-SN; SGn-FH; GoMe-FH; posterior facial height (PFH); anterior facial height (AFH); and facial height index (FHI) [Figure 3].{Figure 3}

The angular measurements and FHI were used as the indicators of skeletal pattern. Grouping of subjects was done based on their rank order in each of the four parameters as follows.

[INLINE:1]

Computed tomography

The scans were reformatted for sections of the mandible obtained at a plane passing through the midpoint between the roots at one-third of the root length. A plane parallel to this was then passed through the mesial roots in case of mandibular molars and mesiobuccal roots in the case of maxillary molars to obtain the coronal section image [Figure 4] and [Figure 5]. [8] The tooth inclination measured as the angle between the base line (line drawn between right and left inferior border of the mandibular section; palatal plane in the maxillary section) and the tooth axis (line drawn through the central fossa and middle of the root width at one-third of the root length from the apex). The measurement was recorded for first and second molars of both jaws [Figure 6], [Figure 7], [Figure 8] and [Figure 9].{Figure 4}{Figure 5}{Figure 6}{Figure 7}{Figure 8}{Figure 9}

Analysis of variance (ANOVA) showed differences in the mean molar inclination angles between the groups. Tukey HSD test was done for multiple comparisons between the groups. Pearson's coefficients of correlation were calculated between the skeletal parameters and the mean inclination angle of each tooth.

 Results



The mean buccolingual inclination of lower 1 st and 2 nd molars and upper 2 nd molars showed a significant increase from short-faced individuals to long-face individuals. A very highly significant positive corelation was seen between GoGn-SN, SGn-FH and FH-MP, and lower and upper 2 nd molar inclinations. A significant negative corelation was seen between FHI and the inclination of these teeth [Table 1], [Table 2], [Table 3], [Table 4] and [Table 5].{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}

 Discussion



An understanding of the buccolingual inclination of the teeth is important for their proper positioning with respect to the skeletal base. The buccolingual inclination of incisors has been studied extensively by using lateral cephalograms, which allow convenient visualization of the long axis of the incisor tooth and its relationship to the skeletal base. However, CT scans are required to visualize the long axis of posterior teeth. [6]

In the present study, coronal sections of CT scans of mandible and maxillae were used to measure the inclination of the long axis of the molar as suggested by Tsumori et al., [6] and Masumoto et al. [7]

The results of the present study indicated that teeth are more lingually inclined in the short-faced group than in the long faced. This finding is in agreement with Tsumori et al. [6] Similar findings were also reported by Ross et al. [8] However, the finding does not concur with those of Janson et al. [9] and Masumoto et al., [7] who had found no significant differences in lowermolar inclination between short- and long-face individuals.

The maxillary 2 nd molars showed a significant buccal inclination in long faced individuals. This finding is in agreement with Ross et al. [8] and Janson et al. [9]

The wide range of molar inclinations found in different vertical skeletal patterns suggest a need for reassessment of the torque prescriptions. The concept of "one appliance fits all" defies the normal biologic variation among orthodontic patients.

However, further study in different skeletal and dental malocclusions in various racial groups would be required for establishing the torque values.

 Conclusion



Variations in mean molar inclination values are observed between short, average, and long-faced groups. The mandibular 1 st and 2 nd molars and maxillary 2 nd molars are more buccally inclined in the long-faced group than in the short-faced individuals.

 Acknowledgments



The authors would like to thank Dr. S. K. Sharma, Director, Eko X-Ray and Imaging Institute, Kolkata., Prof. Dr. B. Rajendra Prasad, Dean and Principal, A. B. Shetty Dental College, Mangalore, Prof. Dr. Krishna Nayak U.S, HOD, Orthodontics, A. B. Shetty Dental College, Mangalore and Dr. M. S. Kotian, Associate Professor, Department of Community Medicine, Kasturbha Medical College, Mangalore, for their technical and academic help and support.

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