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Difference between revisions of "Influence of the Text Neck Posture on the Static Dental Occlusion"
Influence of the Text Neck Posture on the Static Dental Occlusion (view source)
Revision as of 15:01, 10 June 2023
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==== Examination Procedure ==== | ==== Examination Procedure ==== | ||
At the beginning of the procedure, we explained the different steps of the examination to our subjects without giving any details about the purpose or hypotheses of the research. The images in Figure 2 and Figure 3 present one of the examiners as she demonstrates the NHP (Figure 2) and the TNP (Figure 3) to the study subjects. | At the beginning of the procedure, we explained the different steps of the examination to our subjects without giving any details about the purpose or hypotheses of the research. The images in Figure 2 and Figure 3 present one of the examiners as she demonstrates the NHP (Figure 2) and the TNP (Figure 3) to the study subjects. | ||
[[File:Stoica 2a.jpeg|center|thumb|500x500px|Figure 2: ('''a''') Measurement of the neck flexion angle with a manual goniometer in NHP; ('''b''') T-Scan registration in NHP.]] | [[File:Stoica 2a.jpeg|center|thumb|500x500px|'''Figure 2:''' ('''a''') Measurement of the neck flexion angle with a manual goniometer in NHP; ('''b''') T-Scan registration in NHP.]] | ||
[[File:Stoica 3.jpeg|center|thumb|500x500px|Figure 3: ('''a''') Measurement of the neck flexion angle with a manual goniometer in TNP; ('''b''') T-Scan registration in TNP.]] | [[File:Stoica 3.jpeg|center|thumb|500x500px|'''Figure 3:''' ('''a''') Measurement of the neck flexion angle with a manual goniometer in TNP; ('''b''') T-Scan registration in TNP.]] | ||
Further on, the subjects were instructed on how to adopt an NHP. Then they were asked to text for 60 s on their mobile phones, in order to relax and get accustomed to the TNP. For most of them, the mandible went into the postural position (with the freeway space between the dental arches) during texting, but each one of them swallowed at some point in MI, which was the position we followed in our research. The data from the dental literature showed a mean spontaneous swallowing frequency of 0.98 swallows/minute for healthy young subjects.<ref>Bulmer J.M., Ewers C., Drinnan M.J., Ewan V.C. Evaluation of spontaneous swallow frequency in healthy people and those with, or at risk of developing, dysphagia: A review. Gerontol. Geriatr. Med. 2021;7:23337214211041801. doi: 10.1177/23337214211041801.</ref> | Further on, the subjects were instructed on how to adopt an NHP. Then they were asked to text for 60 s on their mobile phones, in order to relax and get accustomed to the TNP. For most of them, the mandible went into the postural position (with the freeway space between the dental arches) during texting, but each one of them swallowed at some point in MI, which was the position we followed in our research. The data from the dental literature showed a mean spontaneous swallowing frequency of 0.98 swallows/minute for healthy young subjects.<ref>Bulmer J.M., Ewers C., Drinnan M.J., Ewan V.C. Evaluation of spontaneous swallow frequency in healthy people and those with, or at risk of developing, dysphagia: A review. Gerontol. Geriatr. Med. 2021;7:23337214211041801. doi: 10.1177/23337214211041801.</ref> | ||
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The distribution, force, and timing of occlusal contacts were analyzed in MI and in static intercuspation. The latter was defined by Kerstein as the moment of the last tooth contact during the closure of the mouth, which is marked as the Bline on the registration. It is different from the MI, which appears later.<ref name=":6" /><ref name=":7">Kerstein R.B., Grundset K. Obtaining measurable bilateral simultaneous occlusal contacts with computer-analyzed and guided occlusal adjustments. Quintessence Int. 2001;32:7–18. </ref><ref name=":8">Kerstein R.B. Handbook of Research on Clinical Applications of Computerized Occlusal Analysis in Dental Medicine. 1st ed. IGI Global; Hershey, PA, USA: 2015. T-Scan 8 recording dynamics, system features and clinician user skills; pp. 95–151. </ref> The maximum intercuspation was analyzed in the maximum area frame of the registration (MA). In an ideal occlusion, the MA frame is also the frame where the ''maximum movie force'' (MMF) occurs. | The distribution, force, and timing of occlusal contacts were analyzed in MI and in static intercuspation. The latter was defined by Kerstein as the moment of the last tooth contact during the closure of the mouth, which is marked as the Bline on the registration. It is different from the MI, which appears later.<ref name=":6" /><ref name=":7">Kerstein R.B., Grundset K. Obtaining measurable bilateral simultaneous occlusal contacts with computer-analyzed and guided occlusal adjustments. Quintessence Int. 2001;32:7–18. </ref><ref name=":8">Kerstein R.B. Handbook of Research on Clinical Applications of Computerized Occlusal Analysis in Dental Medicine. 1st ed. IGI Global; Hershey, PA, USA: 2015. T-Scan 8 recording dynamics, system features and clinician user skills; pp. 95–151. </ref> The maximum intercuspation was analyzed in the maximum area frame of the registration (MA). In an ideal occlusion, the MA frame is also the frame where the ''maximum movie force'' (MMF) occurs. | ||
The first analyzed occlusal parameter was ''occlusion time'' (OT)—Figure 4b and Figure 5b—defined by Kerstein as the elapsed time (in seconds) measured from the first occlusal contact (A line) until the last tooth contact in static intercuspation (B line) during mouth closure.<ref name=":7" /><ref name=":8" /> The T-Scan III system was set at a normal OT value of under 0.3 s (“within range”); the “borderline range” was 0.3 to 0.5 s.<ref name=":6" />{{Bib}} | The first analyzed occlusal parameter was ''occlusion time'' (OT)—Figure 4b and Figure 5b—defined by Kerstein as the elapsed time (in seconds) measured from the first occlusal contact (A line) until the last tooth contact in static intercuspation (B line) during mouth closure.<ref name=":7" /><ref name=":8" /> The T-Scan III system was set at a normal OT value of under 0.3 s (“within range”); the “borderline range” was 0.3 to 0.5 s.<ref name=":6" /> | ||
[[File:Stoica 4.jpeg|center|thumb|500x500px|'''Figure 4:''' MA frame of the T-Scan registration of MC subject in NHP: ('''a''') two-dimensional (2D) view with the distribution of the occlusal force between the left and the right side of the arch; ('''b''') graph of the % of the total force in time, with %MMF, OT, OTB, and MAT (0.7 s).]] | |||
[[File:Stoica 5.jpeg|center|thumb|500x500px|'''Figure 5:''' MA frame of the T-Scan registration of MC subject in TNP: ('''a''') 2D view with the distribution of the occlusal force between the left and the right side of the arch; ('''b''') graph of the % of the total force in time, with %MMF, OT, OTB, and MAT (1.25 s).]] | |||
In the MA frame (MI), the following aspects were investigated (Figure 4 and Figure 5): | |||
* (i) ''Distribution of the occlusal force'' between the left and right SSS side of the arch (Figure 4a and Figure 5a). The ideal occlusion has 50% of the occlusal force on each side, but the T-Scan III System Manual states that a distribution of 53% to 47% of the occlusal force can be considered within the normal range.<ref name=":6" /> Based on these values, we ''calculated the asymmetry index of the occlusal force''(AOF) according to the formula:<ref>Wang C., Yin X. Occlusal risk factors associated with temporomandibular disorders in young adults with normal occlusions. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. 2012;114:419–423. doi: 10.1016/j.oooo.2011.10.039. </ref> '''AOF (%) = [(occlusal force on the right side−occlusal force on the left side)/total occlusal force] × 100''' AOF has normal values ranging from 0 to 6%. | |||
* (ii) ''Percent of the maximum movie force'' (%MMF)—Figure 4b and Figure 5b. In an ideal occlusion, the MA frame is the frame with the largest area of tooth contact, but also the frame with the MMF. | |||
* (iii) ''Time elapsed from the last occlusal contact in static intercuspation till MI'' (MAT-OTB). It describes the time that passes till the slopes of the guiding cusps bring the mandible into MI. This parameter was calculated by subtracting the OTB value from the MAT value. Both values are displayed by the T-Scan software (Figure 4b and Figure 5b). | |||
Statistical processing was performed using the SPSS 17.0 software package. Descriptive statistics were calculated for several continuous variables: OT, AOF, %MMF, and MAT-OTB. The comparisons between the two paired numerical series were performed using the non-parametric Wilcoxon Signed Ranks Test. The results were considered significant for a value of ''p'' < 0.05. The correlations between variable pairs were made by calculating the Spearman’s correlation coefficient, since they did not have a normal distribution. The correlations were considered significant for a value of ''p'' < 0.05, as well. | |||
=== Results === | |||
The demographic characteristics of the study group are presented in Table 1. | |||
{| class="wikitable" | |||
|+ | |||
| | |||
= Table 1 = | |||
Demographic characteristics of the study group. | |||
{| class="wikitable" | |||
! colspan="1" rowspan="1" |Variable | |||
! colspan="2" rowspan="1" |Characteristics | |||
|- | |||
| colspan="1" rowspan="2" |'''Gender—''n'' (%)''' | |||
| colspan="1" rowspan="1" |Male | |||
| colspan="1" rowspan="1" |4 (21.1%) | |||
|- | |||
| colspan="1" rowspan="1" |Female | |||
| colspan="1" rowspan="1" |15 (78.9%) | |||
|- | |||
| colspan="1" rowspan="1" |'''Age''' | |||
| colspan="2" rowspan="1" | | |||
|- | |||
| colspan="1" rowspan="1" |Mean (standard deviation) | |||
| colspan="2" rowspan="1" |21.32 (0.95) | |||
|- | |||
| colspan="1" rowspan="1" |Median (interquartile range) | |||
| colspan="2" rowspan="1" |21.00 (1.00) | |||
|} | |||
|} | |||
The values of the OT were 1.34 ± 1.84 s in NHP and 1.32 ± 1.8 s in TNP, while the difference between the two head and neck positions was small and not statistically significant (''p'' = 0.658), as presented in Table 2. The values of the AOF were 14.88 ± 10.39% in NHP and 18.04 ± 12.83% in TNP; the increase in AOF in TNP was not statistically significant (''p'' = 0.344)—Table 2. The values of the MAT-OTB were 2.08 ± 1.82 s in NHP and 1.45 ± 2.3 s in TNP. Therefore, the decrease in MAT-OTB in TNP was not statistically significant (''p'' = 0.117)—Table 2. The values of the %MMF were 97.5 ± 2.83% in NHP and 96.31 ± 3.17% in TNP; the difference between the two head and neck positions was small and not statistically significant (''p'' = 0.251). The fact that the studied parameters’ variations between the two head and neck positions were not statistically significant could be due to the choice of the NHP as the starting position of our T-Scan study. Adding 30° to the neck flexion angle measured in NHP could have brought the handle and the power cable of the T-Scan into an inappropriate position, leading to the collection of TNP parameter values that were not conclusive in some subjects. | |||
{| class="wikitable" | |||
|+ | |||
| | |||
= Table 2 = | |||
Descriptive statistics and ''p'' values obtained from the applied Wilcoxon Signed Ranks Test. | |||
{| class="wikitable" | |||
! colspan="1" rowspan="1" |Variable | |||
! colspan="1" rowspan="1" |Mean ± Standard Deviation | |||
! colspan="1" rowspan="1" |Median (Interquartile Range) | |||
! colspan="1" rowspan="1" |''p'' 1 | |||
|- | |||
| colspan="1" rowspan="1" |OTN | |||
| colspan="1" rowspan="1" |1.34 ± 1.84 | |||
| colspan="1" rowspan="1" |0.41 (1.22) | |||
| colspan="1" rowspan="2" |0.658 | |||
|- | |||
| colspan="1" rowspan="1" |OT30 | |||
| colspan="1" rowspan="1" |1.32 ± 1.8 | |||
| colspan="1" rowspan="1" |0.45 (1.39) | |||
|- | |||
| colspan="1" rowspan="1" |AOFN | |||
| colspan="1" rowspan="1" |14.88 ± 10.39 | |||
| colspan="1" rowspan="1" |10.8 (21.2) | |||
| colspan="1" rowspan="2" |0.344 | |||
|- | |||
| colspan="1" rowspan="1" |AOF30 | |||
| colspan="1" rowspan="1" |18.04 ± 12.87 | |||
| colspan="1" rowspan="1" |17.1 (16.4) | |||
|- | |||
| colspan="1" rowspan="1" |MMFN | |||
| colspan="1" rowspan="1" |97.5 ± 2.83 | |||
| colspan="1" rowspan="1" |98.3 (2.3) | |||
| colspan="1" rowspan="2" |0.251 | |||
|- | |||
| colspan="1" rowspan="1" |MMF30 | |||
| colspan="1" rowspan="1" |96.31 ± 3.17 | |||
| colspan="1" rowspan="1" |97.7 (4.9) | |||
|- | |||
| colspan="1" rowspan="1" |MAT-OTBN | |||
| colspan="1" rowspan="1" |2.08 ± 1.82 | |||
| colspan="1" rowspan="1" |1.95 (2.76) | |||
| colspan="1" rowspan="2" |0.117 | |||
|- | |||
| colspan="1" rowspan="1" |MAT-OTB30 | |||
| colspan="1" rowspan="1" |1.45 ± 2.3 | |||
| colspan="1" rowspan="1" |0.85 (1.28) | |||
|} | |||
1 Statistically significant ''p'' < 0.05. | |||
|} | |||
Although NHP was inappropriate as a starting point to simulate the TNP in our T-Scan study, the recordings made in that position revealed some significant and useful results. Thus, the mean value of the AOF was 14.88 ± 10.39% in NHP. Perfect symmetry of the occlusal force in MI was not found in any subject, nor in the NHP. Instead, we found an AOF less than or equal to 6% in four subjects with NHP (i.e., subject number 15, 16, 17, and 19; 21.05%). All other subjects had AOF values above 6%, which indicate an unbalanced distribution of the occlusal forces between the right and left side of the dental arches in NHP. The actual distribution of occlusal forces between the left and right side of the arch in each subject can be observed in Supplementary Material Table S1. | |||
The mean value of the OT was 1.34 ± 1.84 s in NHP. Bilateral simultaneous occlusal contacts in static intercuspation are generally associated with an OT under 0.2 s <ref name=":7" /><ref name=":8" /> or 0.3 s.<ref name=":6" /> In NHP, we found an OT below 0.3 s in only four subjects (i.e., subject number 7, 8, 17, and 19; 21.05%). All other subjects had OT values above 0.3 s, which revealed a lack of simultaneity of the occlusal contacts in static intercuspation. The OT values of all subjects can be viewed in Supplementary Material Table S1. | |||
The correlation between OT and AOF was significant, direct, and strong in NHP (Spearman’s rho = 0.724, ''p'' < 0.001)—Figure 6. An increased OT was associated with an increased AOF. The lack of simultaneity of the occlusal contacts in static intercuspation (as concluded from high OT values), associated with an unbalanced distribution of the occlusal forces between the right and left side of the dental arches in MI (high AOF values), point to an unstable static occlusion in NHP. | |||
{{Bib}} | |||