Occlusal Vertical Dimension and Its Association with Length of Thumb: An Original Research.

Introduction: Establishing an accurate vertical dimension at occlusal (VDO) is a challenge. Hence, we aim to find the association between the VDO and the Thumb Length (TL). Materials and
Methods: We piloted an observational study by evaluating the VDO and the TL among the Dravidian and Aryan ethnicities with 200 volunteers. The comparisons were made applying the "linear regression analysis" to find the correlation of both.
Results: We observed that a strong and positive relation was established for the two parameters of VDO and TL for both the ethnicities.
Conclusion: We can suggest from our study that the thumb length can be used as an aid for the occlusal vertical dimension estimation. Copyright:

INTRODUCTION

The prosthetic rehabilitation of the dentition is a challenge to the prosthodontist. There are various modalities for the accurate measurement of the factors that are a prime requisite for the rehabilitation of the lost dentition. One of the main factors that impact the output is the vertical dimension. This is again classified as two, i.e., when at rest and at occlusion. Occlusal vertical dimension (VDO) is very important for the calculation of the height of the final prosthesis at function. Various methods have been proposed to measure the VD.[123] However, they are inherent to few disadvantages and inaccuracies.

The phalanges of the hands are one of the markers of age. There are a trickle of studies done to associate the thumb length with that of the facial height.[456] Hence, in our study, we aim to find the association between the VDO and the length of the thumb (TL).

MATERIALS AND METHODS

We conducted an observational study among 200 participants, with 100 in each group. The ethics clearance and the participant consent were obtained for the study. We included the participants from North and South India, thus comparing the Aryan and the Dravidian ethnicities. We included only the subject with no medical conditions and between the ages of 20 and 40 years, to avoid any age-related degenerative changes. We excluded any other malocclusal cases which may impact the altered VDO. Based on the method of Kumar et al.,[2] the TL was measured. The VDO was measured with Boley's gauge and Vernier calipers using the “ala-tragus line” as measured for the routine prosthodontic procedures. We also calculated two other parameters: the “rima oris to the pupil of the eye (RE)” and the distance from “the lateral border of the outer canthus to the tragus of the ear computed tomography (CT).” The comparisons were made using “Pearson's product-moment correlation coefficient and linear regression analysis.”

RESULTS

We observed that there was no significant variation of genders and age among the groups. The mean age was 31 ± 0.5 years. The mean TL, VDO, RE, and CT for the groups are shown in Table 1. The Dravidians showed greater VDO, TL, and CT than Aryans, while the RE was shorter. When the genders were compared for all the four variables, the significant variation was seen with men having larger dimensions than women in both the ethnicities. A strong and positive correlation was seen for the parameter of the TL that was seen in both the sexes and ethnicities.

Table 1

Comparison of the parameters between ethnicities

Parameters	Mean±SD		P
	Aryan	Dravidians
VDO	63.61±4.41	66.92±5.01	<0.001
TL	57.51±4.32	59.08±4.68	<0.001
RE	65.73±4.70	61.28±5.53	<0.001
CT	69.17±4.04	70.17±4.86	0.012

SD: Standard deviation, VDO: Vertical dimension at occlusal, TL: Thumb length, RE: Rima Oris to Eye, CT: Computed tomography

The TL can be used to measure the VDO using the following formulas after the association was established between TL and VDO using the “univariable linear regression analysis” [Table 2].

Table 2

Thumb length (independent variable) and vertical dimension (dependent variable) association shown by the “univariable linear regression analysis”

Population	R (TL)*	R 2	Adjusted R2	SE	B	P
Sample size=100	0.871*	0.762	0.761	2.448	8.197 0.961	<0.001
Aryans=50	0.825*	0.682	0.680	2.824	14.800 0.882	<0.001
Dravidians=50	0.942*	0.890	0.881	1.479	7.391 0.978	<0.001

TL: Thumb length, SE: Standard error, *: P>0.05

”Whole population, VOD = 9.197 + 0.962 × TL

Aryan population, VOD = 14.801 + 0.844 × TL

Mongoloid population, VOD = 7.392 + 0.977 × TL.”

DISCUSSION

Our findings suggest a strong relation between the TL and the VDO. We also found a significant relation between the other two parameters (RE and CT) to the TL. The optimal VDO at occlusion is a prime requisite for the construction of the prosthesis that can be a partial or complete denture. Since there are no accurate methods for the exact calculation of the VDO, we have endeavored to find the association of the VDO and the length of the thumb among the Aryans and Dravidians. We observed that the TL had a positive relation with the VDO at occlusion along with other commonly used parameters of RE and CT. We also noted higher values for men than women. This is in accord with the previous studies.[345678] However, these studies did not compare between the ethnicities, which was unique in our study.

Few limitations were recorded in our study. The sample size was small. The findings cannot be generalized to the other ethnic groups since we compared only two races.

CONCLUSION

Within the limitations of the study, a strong association between the length of the thumb and the occlusal VD was seen. A strong and positive correlation was seen for these parameters among the Dravidians than the Aryans. Further studies with different races and ethnicities are suggested.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.