Evaluating the relation of posterior occlusal plane to ala-tragal line according to age and sex

Safoura Ghodsi; Soroush Sef Omrani; Sara Mogharrabi; Sara Valizadeh

doi:10.3897/folmed.64.e68631

Abstract

Introduction: Occlusal plane orientation affects the esthetic, function, and success of removable or fixed prostheses. The most prevalent index for determination of this plane is the ala-tragus line while there are controversies in the exact location of tragus reference point.

Aims: This study aimed to determine the best point on tragus as the posterior reference of ala-tragal line in relation to occlusal plane according to age and sex.

Materials and methods: The study included 136 participants of both sexes who were randomly divided into three age groups: 20-35, 36-50, and older than 50. Fox plane was stabilized on incisal edge-occlusal table of maxillary teeth. A lateral photograph was obtained from each participant sitting in predetermined standard position. Using Auto-Cad software, three lines were traced from nasal ala base to superior, middle, and inferior borders of the tragus, and evaluated for being parallel to occlusal plane.

Results: The coordination between occlusal plane and ala was 20.5% for superior, 35.6% for middle, and 43.9% for inferior border of tragus. There was a significant difference in the relationship between sex and plane position (p=0.003), while the relationship between age and plane could not reach statistical significance (p=0.65). The results were analyzed using chi-square test, and ANOVA (p<0.05).

Conclusions: Ala-inferior border of tragus line was the most parallel, and ala-superior border of tragus line was the least parallel line to the occlusal plane. The parallelism between occlusal plane and ala-superior border was more prevalent in women, while the men demonstrated significantly more parallelism with inferior border of tragus.

Keywords

complete denture, dental prosthesis, jaw relation record, occlusal plane

Introduction

Edentulism is a pervasive problem all around the world.^[1] There are various treatment options available for partial or complete edentulism including fixed or removable prosthetic options.^[2] In all the treatment options, the occlusal plane orientation is one of the factors that affects the esthetics, function, and success of prosthesis^[3], and the major reference for maxillary teeth arrangement^[4]. The occlusal plane is defined as a hypothetical plane which coincides with the incisal edges of maxillary central incisors and mesiopalatal cusps of first maxillary molars.^[3] This plane helps in normal deglutition and respiration, supplies mechanical, esthetic, and phonetic needs^[5], and determines the position and angulation of teeth settlement for prosthetic rehabilitations. Different anatomical landmarks suggested to determine the correct position and orientation of occlusal plane include upper lip, lip commissures^[6], lateral borders of the tongue, retromolar pad^[7], hamular notch, incisal papilla, and parotid papilla.^[8,9] However, one of the most prevalent indices is the ala-tragus line^{[10, 11]}, which connects the auditory meatus to the ala of the nose^[4]. The confusing variations that exist in the ala-tragus line definition go mainly back to disagreement about the exact location of the posterior reference point.^{[12, 13]} Some authors believe the superior border of tragus is the correct posterior reference point^{[14, 15]}, while the others introduce middle^[16–18], or even inferior point as the correct posterior reference. ^[19] On the other hand, different studies show conflicting results regarding the relationship between occlusal plane and available indices (Table 1).^{[2, 4, 12, 13, 20-25]} Meanwhile, the relation between available occlusal plane of dentate patients and ala-tragus line could be the best guide to find the correct orientation of this questionable plane to be used in edentulous patients who missed the predetermined indices relationships.

Table 1.

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Review of the available literature on comparing parallelism of occlusal plane and Camper line

Author	Index for comparison	Parallelism percentage/ mean of angle	Results
Priest^[4]	Horizontal plane	+3.25	Both horizontal plane and ALT1 (superior border of tragus) were parallel to occlusal plane
	ALT1	+3.03
	ALT3	−4.09
Shettty^[20]	ALT1	12.1%	In a large number of subjects, the occlusal plane was parallel to ALT3.
	ALT2	24.7%
	ALT3	50.8%
Nayar^[2]	AT-S	5.8	No parallelism exists between the occlusal plane and the alatragus line, but AT-I was the most parallel line to the occlusal plane.
	AT-M	4.8
	AT-I	4
Quran^[21]	Camp I	2.1	The most common place for posterior reference point of ala-tragal line was the superior border
	Camp II	3.2
	Camp III	6.2
Hinducha^[12]	Superior	6.66%	The most common place for posterior reference point of ala-tragal line was the sub inferior and then the inferior border.
	Middle	19.05%
	Inferior	24.76%
	Above superior	3.82%
	Below inferior	30.48%
	Between superior and middle	6.66%
	Between middle and inferior	8.57%
Lahori^[22]	Sub inferior border		The most parallel line to the occlusal plane was ALT2 in Cl I and Cl II participants and ALT3 in Cl III ones.
	Inferior border
	Superior border
Sheikh^[23]	ALT1		There was a significant relationship between age and occlusal plane; inferior border in young adults and superior border in old people is the reference line.
	ALT2
	ALT3
Shigli^[13]	Superior		The most parallel line to OP was middle border and the least one was superior border.
	Middle
	Inferior
Chaturvedi^[24]	SA plane		There was not significant relationship between sex and occlusal plane. The inferior point marked on tragus is the most appropriate point for marking the ala-tragus line.
	MA plane
	IA plane
Kumar^[25]	AT₁	16.44±2.08	AT₃ (inferior border) was the most parallel line to the occlusal plane. There was no relationship between sex and occlusal plane
	AT₂	13.67±1.93
	AT₃	10.31±2.03

Aim

The present study aimed to determine which point of tragus plays the best role as the posterior reference of ala-tragus line according to the plane orientation in dentate patient, and evaluate if there are any differences according to age and sex. The null hypotheses were that the mid-tragus point was the best posterior index for ala-tragus line and there was no difference between different age and sex groups for the relation of occlusal plane and ala-tragus line.

Materials And Methods

The present descriptive epidemiological study was carried out on 136 participants each giving their informed consent prior to their inclusion in the study. The study protocol was registered and approved in institutional Ethics Committee (IR.JSUMS.REC.1395.483). The study was performed in full compliance with the ethical standards of the revised Helsinki Declaration, and the information and photographs we saved were confidential.

The participants were divided into 2 groups based on their sex. Each group was divided into three subgroups by age: young adults (20-35 years old), middle aged (36-50 years), and old aged (more than 50 years). The inclusion criteria included systemically healthy participant with class-I Angle classification of occlusion, without skin diseases, periodontal diseases, or bone problems; existence of enough posterior maxillary teeth to determine the occlusal plane without interfering supra-eruption or drift; and lack of any history of orthodontic treatments, orthognathic problems, and facial or temporomandibular joint surgery.

A sterilized Fox plane was held in touch with the incisal edge of maxillary central incisors and first molar palatal cusps while the head was stabilized in chin part of panoramic radiographic system, and the Frankfort plane was kept parallel with the horizontal plane. This adjustment was confirmed using a horizontal line traced on the wall behind the patient’s head. The Frankfort plane was kept parallel to the line by looking through the camera at the level of the mentioned line. Lateral photographs were taken from 1-meter distance, perpendicular to profile and at proper height for every participant. The position and distance of each patient’s head was adjusted by the fixed distance between the chin positioner of panoramic system and the camera. Afterwards, three lines were traced by Auto-cad software (Autodesk Inc., California, USA) connecting inferior border of ala to either inferior, middle, or superior border of tragus on each photograph (Fig. 1). Auto-cad data were analyzed by SPSS (SPSS Inc, Illinois, Chicago) using chi-square test, and one-way ANOVA test (p<0.05).

Figure 1.

Different tragus lines plan.

Results

The study was conducted with 136 participants, 81 men (58.9%) and 55 women (41.1%), with the mean age of 32.5 years (range 18-73 years). Table 2 summarizes the descriptive results on parallelism percentage of occlusal plane and ala-tragus line traced in different orientations. The occlusal plane showed higher percentage of parallelism with ala-tragus line traced to the inferior border of tragus in men. The highest percentage for parallelism in women was seen with superior border of tragus while this position showed the least percentage of parallelism in men. In other words, the parallelism between the occlusal plane and ala-superior border was more prevalent in women, while the men demonstrated significantly greater parallelism with the inferior border of tragus. The parallelism percentages were closer for different posterior border positions in women while the men showed more variations. Generally, inferior tragus border had higher percentages of parallelism and superior border had the least.

Table 2.

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Descriptive results for parallelism percentages

Different orientations of ala-tragus line	Parallelism percentage
Different orientations of ala-tragus line	Overall	Men	Women
Superior border (ALT1)	20.5%	11.7%	35%*
Middle point (ALT2)	35.6%	35.9%	34%
Inferior border (ALT3) *	43.9%	52.4%*	31%

Chi-square test showed a statistically significant difference for parallelism percentages in different genders (p=0.003). The relationship between age and occlusal plane was not statistically significant (p=0.65) (Fig. 2).

Figure 2.

Age group comparison of lines parallelism. ALT1: Ala to superior border of tragus line; ALT2: Ala to middle border of tragus line; ALT3: Ala to inferior border of tragus line.

Discussion

Finding the correct orientation of occlusal plane helps to gain an index pattern to arrange the artificial teeth in their natural positions, and consequently provides the best lip support, esthetic, and function in any type of prosthesis.

The present study investigated the relationship between occlusal plane and different ala-tragus orientations. The null hypotheses were partially rejected since there was significant difference for the occlusal plane orientation in the different sexes, and the results confirmed higher percentages for parallelism with ala-tragus line traced from inferior border of tragus compared to superior or middle border; the general results were in accordance with the results reported by Shetty et al.^[3], Nayar et al.^[2], Hindocha et al.^[12], Chaturvedi et al.^[24], and Kumar et al.^[25], while in opposition to the results obtained by Priest et al.^[4], Firas^[21], Lahori et al.^[22], Sheikh et al.^[23], and Shigli et al.^[13] The variations in the results of these studies could be attributed to race difference that calls for further studies, and using different index points in different race groups.

Considering the participant sex, the difference was also statistically significant (p=0.003); the superior border of tragus was preferred as posterior reference point in women, while the inferior border showed better results in men for tracing the ala-tragus line.

This study also evaluated the relationship between ala-tragal line and occlusal plane in different age groups and found no statistically significant difference (p>0.05). Kumar et al. reported no significant relationship between age and the angel between Camper (ala-tragal plane) and occlusal plane^[25]; however, Sheikh et al. reported significant differences between the ala-tragal line orientation and age.^[23] Their results suggested the inferior border of tragus as the preferred reference point in young adults while the middle point was preferred in aged individuals.

Occlusal plane redetermination should be based on dynamic functional requirements. The posterior occlusal plane in natural dentition is oriented to coordinate with temporomandibular joint, masticatory muscles, and dynamics of mastication. Static criteria help us to find the lost plane orientation resulting from posterior tooth loss. The determined plane could be used for complete or partial fixed or removable prostheses supported by either teeth or implants. However, different studies suggest possible effects of age, sex, and nationality on plane routine determinants. Comparison by considering only two determinants (age and gender) is one of the limitations of the present study that could be a subject for further study on other determinants. The controversies call for further extensive studies to register special criteria for selecting the best orientation compatible with all available structural and functional determinants.

Conclusions

Considering the limitation of present study, the following conclusion can be made:

The occlusal plane showed the highest percentage of parallelism with ala-tragus line traced from tragus inferior border (43.9%); the percentage was 35.6% for middle tragus line, and 20.5% for the line traced from superior border.
Comparing different lines orientations, the difference between parallelism percentage was statistically significant (p<0.05), and inferior border line showed significantly higher parallelism with occlusal plane.
Considering the participants’ sex, the difference was statistically significant (p=0.003); the application of superior border of tragus as posterior reference point is preferred in women, while the inferior border is suggested as reference in men for ala-tragus line.
Age has no statistically significant effect on the results obtained for the parallelism of ala-tragus (Camper) line with occlusal plane (p=0.65).

References

1. Ali Z, Baker SR, Shahrbaf S, et al. Oral health-related quality of life after prosthodontic treatment for patients with partial edentulism: A systematic review and meta-analysis. J Prosthet Dent 2019; 121(1):59–68.

2. Colvin J, Dawson DV, Gu H, et al. Patient expectation and satisfaction with different prosthetic treatment modalities. J Prosthodont 2019; 28(3):264–70.

3. Balaji SS, Bhat V. A comprehensive review on the errors that occur during ideal teeth arrangement for complete denture prosthesis. J Contemp Dent 2018; 19(5):624–7.

4. Priest G, Wilson MG. An evaluation of benchmarks for esthetic orientation of the occlusal plane. J Prosthodont 2017; 26(3):216–23.

5. Rahman MU, Dwivedi P, Tiwari RV, et al. Aesthetic in complete denture – a review. J Adv Med Dent Scie Res 2020; 8(1):187–9.

6. Hichy JC, Zarb GA, Bolender CL. Boucher’s prosthodontic treatment for edentulous patients. St. Louis: The C.V. Mosby Co; 1990.

7. Zarb GA, Bolender CL, Carlsson GE. Boucher’s prosthodontic treatment for edentulous patients. St Louis: Mosby; 1997.

8. Foley PF, Latta GH. A study of the position of the parotid papilla relative to the occlusal plane. J Prosthet Dent 1985; 53(1):124–6.

9. Tippashetty SK, Joshi S, Sajjan C, et al. Determining the occlusal plane using hamular notch incisive papilla plane evaluator: An in vivo study. J Indian Prosthodont Soc 2020; 20(1):61.

10. Fu PS, Hung CC, Hong JM, et al. Three‐dimensional analysis of the occlusal plane related to the hamular-incisive-papilla occlusal plane in young adults. J Oral Rehabil 2007; 34(2):136–40.

11. Shrestha L, Joshi SP. Reliable Ala-tragus line for the orientation of occlusal plane by cephalometry. J Nepalese Prosthodont Res 2018; 30;1(1):6–11.

12. Hindocha AD, Vartak VN, Bhandari AJ, et al. A cephalometric study to determine the plane of occlusion in completely edentulous patients: Part I. J Indian Prosthodont Soc 2010; 10(4):203–7.

13. Bondekar V, Wagh SB, Attal PN, et al. Evaluation of relation between occlusal plane and ala-tragus line with the help of cephalometry. J Adv Med Dent Sci Res 2015; 3(6):S43.

14. Glossary of prosthodontic terms. J Prosthet Dent 2005;94:10-92.

15. Boucher LJ. Boucher’s clinical dental terminology: A glossary of accepted terms in all disciplines of dentistry. 3rd ed. Zwemer TJ, editor. St Louis: The CV Mosby Co.: 1982.

16. Grant AA, Johnson W. An introduction to removable denture prosthetics. Churchill Livingstone; 1983.

17. Neill DJ. Complete denture prosthetics. Br John Wright Sons 1975: 72–3.

18. Spratley MH. A simplified technique for determining the occlusal plane in full denture construction. J Oral Rehab 1980; 7(1):31–3.

19. Karkazis HC, Polyzois GL. A study of the occlusal plane orientation in complete denture construction. J Oral Rehab 1987; 14(4):399–404.

20. Shetty S, Zargar NM, Shenoy K, et al. Position of occlusal plane in dentate patients with reference to the ala‐tragal line using a custom‐made occlusal plane analyzer. J Prosthodont 2015; 24(6):469–74.

21. Quran FA, Hazza’a A, Nahass NA. The position of the occlusal plane in natural and artificial dentitions as related to other craniofacial planes. J Prosthodont: Implant, Esthetic and Reconstructive Dentistry 2010; 19(8):601–5.

22. Lahori M, Nagrath R, Malik N. A cephalometric study on the relationship between the occlusal plane, ala-tragus and Camper’s lines in subjects with Angle’s class I, class II and class III occlusion. J Indian Prosthodont Soc 2013; 13(4):494–8.

23. Shaikh SA, Lekha K, Mathur G. Relationship between occlusal plane and three levels of ala tragus line in dentulous and partially dentulous patients in different age groups: A pilot study. J Clin Diagnostic Res 2015; 9(2):ZC39.

24. Chaturvedi S, Thombare R. Cephalometrically assessing the validity of superior, middle and inferior tragus points on ala-tragus line while establishing the occlusal plane in edentulous patient. J Adv Prosthodont 2013; 5(1):58–66.

25. Kumar S, Garg S, Gupta S. A determination of occlusal plane comparing different levels of the tragus to form ala-tragal line or Camper’s line: A photographic study. J Adv Prosthodont 2013; 5(1):9–15.