Comparing bite force in untreated and orthodontically treated non- extraction cases with MBT appliance and self ligation technique using T-scan

Abstract

Aim

Aim of this cross sectional study was to compare the bite force and the individual tooth load among three groups of patients: cases finished with the Self ligation appliance (Damon-Q®, 0.022”X0.028” prescription) cases finished with the MBT (McLaughlin, Bennett and Trevisi) appliance system (0.022”X0.028”prescription) and orthodontically untreated cases using T-Scan® 9.0 version.

Material & methods

A sample size of sixty non-extraction cases were divided equally into three groups – Group 1: patients treated with Self-ligation appliance (Damon Q®), Group 2: cases treated with the MBT prescription and Group 3: untreated subjects with Class I canine and molar relationship who were used as the control group. The bite force and distribution of force was measured on the right and left side as well as individual tooth loads were measured using the T-Scan® 9.0 device and inter-and intra-group comparisons made using Paired t-Test, ANOVA and Chi-square test.

Result

The bite forces were balanced on both the sides in cases treated with Self-ligation and MBT appliance. The Self-ligation finishes were marginally better than the MBT group but the difference was statistically insignificant.

Conclusion

Orthodontically treated individuals had a better (or more even) bite force distribution compared to untreated participants.

Graphical abstract

1. Introduction

The goal of the orthodontic treatment is to improve the patient's life by enhancing jaw function and Dento-facial aesthetics. Most of the orthodontists have stated that the goal of orthodontic treatment is to mainly improve the masticatory function.¹ But no standard assessment is routinely performed before or after the treatment, to determine whether any improvement occurred in the chewing efficiency or not.

The conventional methods used to assess occlusion using an articulating paper cannot give the information on the sequence, time and intensity of the bite force.² Several studies have shown that premature contacts and occlusal interferences cause a change in the functional activity of the masticatory muscles.^2,3

Tek-scan (T-Scan® system; Sentek Crop, Boston, Massachusetts,USA)⁴ developed the T-Scan® system, in 1987, to overcome the challenges of using such less accurate methods for occlusal analysis.⁵ It helps to record distribution of force around the arch, the timing, presence of interferences and balance of forces between the left to right or front to back at any point of closure. This device helps the clinician to dynamically visualize the patient's bite at the beginning, during and after treatment. Hence, it is a great tool with applications in orthodontics, in loading implants, balancing splints, etc. Its accuracy and the extent of information, led to a decision to use this new evaluative tool to study the occlusion achieved following orthodontic treatment. The T-Scan® 9.0 version used in the study is the newer version of the software launched in 2015. The version has the ability to portray contact forces directly on contact locations as well as improved handling and better views of upper and lower arches.

The aim of this cross sectional study was to determine and compare the bite force and the individual tooth load among three groups of patients: cases finished with the Self ligation appliance, cases finished with the MBT (McLaughlin, Bennett and Trevisi) appliance system (0.022”X0.028” prescription) and orthodontically untreated cases.

2. Materials and method

The study comprised of a sample size of 60 patients equally divided into three groups; Group 1: the Self ligation appliance (Damon-Q®), Group 2: the MBT appliance system and Group 3: Orthodontically untreated cases.

Patients having mild crowding with Angle's Class I molar relation, fully erupted 2 nd Molars in both arches for orthodontically untreated cases and patients who have completed orthodontic treatment either by Self ligation appliance or by MBT appliance system were included in the study. All cases were treated by a single experienced operator and were blinded before further analysis. Patients with temporomandibular dysfunction, dentinal hypersensitivity and occlusal restorations were excluded from the study. A computer with pre-installed T-Scan® 9.0 occlusal diagnostic system software along with the evolution handle, the sensor support, the sensors, and set of diagnostic instruments were used.

2.1. Scan procedure

The individual was oriented to sit down on the dental chair in a way that the Camper's plane (a plane running from the tip of the anterior nasal spine (acanthion) to the center of the bony external auditory meatus on the right and left sides) and the bi-pupillary line are parallel to the floor. T-Scan® 9.0 assembly was set up by connecting the handle's USB cable connector to the USB port of the computer, selected sensor support is inserted into the handle and the sensor is slided into the device. On the computer screen, the details of the new patient were added and a new scan was opened. Patient was asked to close firmly on the sensor in habitual maximum inter-cuspation, as it is interposed between the arches. After all the required movements were performed, the scan which was recorded was assessed independently by an operator. The forces in 2D and 3D were viewed, along with force graph and timing. The colour of the bars as per the graph on the T-Scan® 9.0 starts from the minimum forces depicted by dark blue color, light blue color, green color and yellow color whereas moderate forces are depicted by orange color and brown colours. The highest abnormal forces are depicted by red and pink colours (Fig. 1). These colour coded bars were taken individually and all the three groups were assessed in them to determine whether the forces present are high, medium or low. Also, a 2 min movie format on the screen showing movements from the maximum inter-cuspation to the dis-occlusion of both the arches was played to study the individual's scan in detail" for better understanding.

Fig. 1.

Bite scans of three groups.

3. Results

Paired t-test was applied to compare the bite forces on the right and the left side in cases treated with the Self ligation system, the mean values on the right side- 50.85% ± 2.79% and on the left side- 49.21% ± 2.75%, showing statistically non – significant difference(Table 1).

Table 1.

Group 1: Self ligation system.

	Mean	Std. Deviation	Std. Error Mean	Mean difference	t-test value	p-value
BITE FORCE ON RIGHT SIDE	50.85%	2.79%	0.62%	1.64%	1.325	0.201
BITE FORCE ON LEFT SIDE	49.21%	2.75%	0.61%

Paired t-test ^# Non-significant difference.

1.Table 1: Paired-t-Test was used to compare the Bite force on the Right and the Left side in Group 1: Self Ligation System.

Paired t-test was conducted to compare the bite forces on the right and the left side in cases treated with the MBT appliance system, mean values on the right side- 51.92% ± 4.45% and on the left side- 48.08% ± 4.45%, showing a statistically non – significant difference.

Paired t-test was conducted to compare the bite forces on the right and the left side in cases which were orthodontically untreated, values on the right side- 44.71% ± 4.57% and on the left side- 55.04% ± 4.66%, showing statistically significant difference (Table 3).

Table 3.

Group 3:Orthodontically untreated.

	Mean	Std. Deviation	Std. Error Mean	Mean difference	t-test value	p-value
BITE FORCE ON RIGHT SIDE	44.71%	4.57%	1.02%	−10.33%	−12.278	<0.001***
BITE FORCE ON LEFT SIDE	55.04%	4.66%	1.04%

Paired t-test *** Very Highly significant difference.

3.Table 3: Paired-t test was used to compare the Bite force on the Right and the Left side in Group 3: Orthodontically Untreated cases.

The mean bite force on the right side was compared between Self Ligation system, MBT appliance system and orthodontically untreated cases using the One–way ANOVA Test. The cases treated with Self-ligation system showed the value of 50.85% ± 2.79%, cases treated with MBT appliance system had 51.92% ± 4.45%, and orthodontically untreated cases had value of 44.71% ± 12.30%. This showed that the Self-ligation system had more balanced forces towards 50% as compared to the cases treated with the MBT system; the untreated cases had the most unbalanced forces. The findings of results had a high statistical significance (GRAPH 1).

Graph 1.

Comparison of the Bite Force on the right side between the three groups, Group1: Self Ligation system, Group2: MBT Appliance system and Group3: Orthodontically untreated cases.

One–way ANOVA Test was used to compare the mean bite force on the left side between Self-ligation system, MBT appliance system and orthodontically untreated cases. The cases treated with Self-ligation system showed the value of 49.21% ± 2.75%, cases treated with MBT appliance system had 48.08% ± 4.45%, and orthodontically untreated cases had a value of 55.04% ± 11.92%. This showed that the Self-ligation system had more balanced forces towards 50% as compared to the MBT appliance system and the untreated cases had the most unbalanced forces. The findings of results had a high statistical significance (GRAPH 2).

Graph 2.

Comparison of the Bite Force on the left side between the three groups, Self Ligation system, MBT Appliance system and Orthodontically untreated cases.

The Chi–Square test was applied between the three groups based on all the different colour coded bars on the T-Scan® 9.0 (GRAPH 3). Initially the three groups were assessed under the highest force levels, i.e., the Pink colour coded bars on the T-Scan® 9.0 graph. The pink coloured bars were absent in Group 1, but were present in 4 cases of total samples of Group 2 and were present in 8 cases of Group 3. This showed that the high forces were absent in Group 1.

Graph 3.

Comparison between the three groups, Group1: Self Ligation system, Group2: MBT Appliance system and Group3: Orthodontically Untreated cases based on the complete force level scale depicted by color coded bars on the T- Scan graph.

This was followed by the next colour on the force level scale i.e., red color coded bars. The red coloured bars were completely absent in both the Group 1 and the Group 2, showing that there was no high forces present in individual tooth load. But 50% of total cases of Group 3 had an appearance of the red colour coded bars.

The third colour orange indicates higher force levels of abnormal force but comparatively less than the first two colour bars (red and pink). During their assessment, orange bars were absent in both Group 1 and Group 2 but were present in Group 3.

The next colour assessed was the brown colour coded bars for the medium level of forces. It was seen that they were also present in maximum numbers in Group 3 but were completely absent in both Group 1 and Group 2.

The medium forces lower to the brown coloured bars are yellow and green, in the same sequence. Results showed that the yellow coloured bars were present in all the three groups and the green coloured bars were only present in Group 1 and Group 2 but were absent in Group 3.

4. Discussion

The occlusion or bite of individuals as well as animals are of interest from an anthropological perspective. Various methods have been used to study the bite forces or the chewing efficiency. The gnathodynamometer was used by Yildirim E and De Vincenzo⁶ to measure the closing force of patients of diverse skeletal types i.e. closed bite versus open bite groups. Individual tooth measurements could not be made but they concluded that a significant relationship existed between muscle force and skeletal type.

Atkinson HF and Shepherd RW⁷ incorporated strain gauges in selected teeth in artificial dentures and used oscilloscope to indicate the forces developed during chewing. Their results showed significant forces were not developed until the teeth were almost in contact and that after contact, the force increased without further movement being detected. A miniature bite force recorder was used by Ingervall B and Minder C⁸ to measure the bite force on the first molars. The generated forces were further corelated with the inclination of the mandible, size of the gonial angle, the correlations implied a large bite force with a small mandibular inclination and gonial angle. Kerstein RB⁹ confirmed that articulating paper mark size is understood to be non-descriptive of occlusal loads. According to them, many different sized marks can represent the same load, and equal sized marks do not represent similar loads. They stressed that, with a reported reliability between mark size and applied occlusal load of only 21%, choosing the paper marks to occlusally adjust, based upon their relative size and operator-subjective assessment of those various sizes, is tantamount to clinical guessing.

Serra CM and Manns AE¹⁰ compared the maximum voluntary bite force using a digital occlusal force gauge (GM10 Nagano Keiki, Japan) between different opponent teeth, employing semi-hard or soft bite surfaces and concluded that soft surface induces greater activation of elevator musculature, while a hard one induces inhibition more promptly. Thus, soft bite surfaces were recommended for higher reliability in maximum voluntary bite force recordings. These conventional methods cannot give the information on the sequence, time and intensity of bite force.³

The T-Scan® 9.0 helps to record distribution of force around the arch, the timing, presence of interferences, and balance of forces left to right or front to back at any point of closure. Flanagnan D et al.¹¹ used the Tek-scan to measure patient bite force as a diagnostic aid in determining dental implant size, number of implants, and prosthetic design for restoring partial edentulism. The accuracy of this device coupled with its’ ability to record measurement of forces exerted by individual teeth compelled the use of this relatively newer technology for this study.

In order to standardize the cases selected in the treated group, cases treated by a single experienced, clinician well versed in the use of both the MBT and the Self-ligation (Damon Q) appliance were selected. All the cases had been treated non-extraction and presented with no prosthetic replacements or major restorative work on the occlusal surfaces. This was done to aid uniformity of the selected samples. Equal number comprising of twenty patients each were taken from a random pool of finished cases into each group. These cases were blinded and the T-scan® was used to measure the bite forces. This was followed by individual group and inter-group comparisons based on the forces present on the right and the left sides of the dental arch and the individual tooth load exerted by each sample in all the three groups.

When the bite forces on the right side and left sides of all the three groups were compared individually, the Group 1 and Group 2 values on the right and left sides were around 50% (on each side) indicating that the occlusal forces were balanced on both the sides of dental arch (Table 1, Table 2). The Group 1 values were better as compared to Group 2 but were not statically significant. Whereas in Group 3 (Table 3) the bite forces appeared to be greater on the left side as compared to the right side. This indicated that the forces were not balanced in Group 3 between the right and the left sides.

Table 2.

Group 2: MBT Appliance system.

	Mean	Std. Deviation	Std. Error Mean	Mean difference	t-test value	p-value
BITE FORCE ON RIGHT SIDE	51.92%	4.45%	0.99%	3.84%	1.931	0.069
BITE FORCE ON LEFT SIDE	48.08%	4.45%	0.99%

Paired t-test ^# Non-significant difference.

2.Table 2: Paired-t-Test was used to compare the Bite forces on the Right and the Left side in Group 2: MBT Appliance System.

This is an important observation since it helps us to conclude that the orthodontic treatment leads to better distribution of the bite forces between the right and left sides of treated cases as compared to orthodontically untreated cases.

When the bite forces on the left side were compared in all three groups individually, it was again seen that the values of Group 1 which were more towards the balance forces of 50% having the value of 49.21%, Group 2 had 48.08% and the Group 3 had 55.04% of bite force on the left side. Group 3 had the highest amount of bite forces on the left side (greater than the balanced forces of 50%), whereas the Group 1 and Group 2 are more towards the balance force of 50% (Graph 1).

Thus it could be concluded that the bite forces on the right side in Group 1 were more towards balanced forces that is 50% and the Group 3 has less amount of force among all three groups on the right side (Graph 2).

When the individual tooth loads were assessed depending on the colour of the bars depicting the force levels from highest to medium to low (Graph 3, Fig. 1). The results based on the force level scale ranged from highest to lowest according to the colour coded graphs present on the T-Scan® 9.0 showed that the most balanced occlusion, with no abnormal high forces on the any individual tooth, was the Group 1. The highest amounts of abnormal high forces were present in Group 3.

This appears to be the first study of its kind using the T-Scan® 9.0. The T-Scan® 9.0 appears to be an important tool to access the finished results achieved following the orthodontic appliance therapy.

5. Conclusion

• 1)The bite forces in the orthodontically untreated cases were most unequally divided between the left and the right side as compared to the cases finished using the MBT or Self-ligation (Damon Q®) appliance. The cases finished using the Self-ligation (Damon Q®) appliance gave the most favorable distribution of forces between the right and the left sides.
• 2)On comparing the individual tooth load in all the three groups, high to medium forces were seen most often in orthodontically untreated cases and rarely seen in cases treated by the MBT appliance and never in the self-ligation (Damon Q®) group.

Limitations of the study

The study is a cross sectional study therefore we can go for a prospective study to see the changes in bite force distribution during different stages of the orthodontic treatment as well as we can increase the number of cases to further draw some more conclusive evidence.