Cervical Abrasion, Sexual Dimorphism, and Anthropometric Tooth Dimension.

Introduction: The aim of this study was to analyze the anatomic crowns of the maxillary and mandibular dentition concerning the mesiodistal, buccolingual measurements which will be used to establish normative data as a part of comprehensive study being carried out to determine the depth of the cervical abrasion (CA) of the individuals by predicting the CA Index of Treatment Needs (CAITN) score. Materials and
Methods: A newly developed instrument termed as CAITN probe was used to measure CA of the tooth more quantitatively. The mesiodistal and buccolingual width of all the 14 maxillary and mandibular teeth from the right second permanent molar to the left second permanent molar of the study sample was measured. The ratio between buccolingual and mesiodistal measurements of each tooth of the maxillary and mandibular arch of the study sample (n=100) was also determined. Statistical analysis was performed using the SPSS 26.0 software.
Results: Descriptive statistics were calculated for each group independently. The statistical significance of the difference in mean in mesiodistal and buccolingual diameters between males and females was calculated using the t-test for independent samples with p < 0.05. The ratio was highest in the left second premolar (1.752) and least in the right central incisor (0.980) of the maxillary arch. Similarly, the ratio was highest in the left central incisor (1.723) and least in the left second molar (0.910) of the mandibular arch.
Conclusion: The present study was conducted as an initial step in the process of development of the novel tool or index enabling the dentists to organize the health-care needs of their patients by facilitating standardized identification of CA with objective measurements used for epidemiological or community purpose. Copyright:

INTRODUCTION

Cervical Abrasion (CA) is defined as a pathological condition caused by abrasive agents on the tooth surface or any objects placed frequently between or on theteeth. Tooth wear-attrition, abrasion, and erosion are considered non carious cervical lesions (NCCLs), discomfort, sensitivity, pain, and loss of tooth vitality.[1234] The etiology of cervical abrasion is multifactorialinvolving a complex interaction of various factors such as overzealous brushing technique, use of an abrasive agent. Other factors such as erosion and abfraction also contribute to varying degrees.[567] Literature reveals different forms of progression of the lesion such as shallow, concave, wedge shaped, notched, and irregular. Various unique indices had been in vogue to grade the CAs: Eccles index for dental erosion, Smith and Knight tooth wear index, and erosion index by Lussi and simplified tooth wear index of Bardsley. Similarly, Sawai et al. suggested a simple and logical system of classification CA based on morphological features. Other indices such as Larsen's system and Ryge and Snyder's system of grading tooth wear are said to be time-consuming and cumbersome.[48910]

These indices are based on qualitative and quantitative methods. No formal classification system of cervical abrasion index exists till date, due to lack of uniformity and clinical agreement between the various existing indices.[410] Furthermore, it is challenging to precisely replicate the morphological changes that make it arduous to compare such lesions among the diverse population; furthermore, clinically most of the deliberate indices do not seem to be sensitive to detect clinical changes associated with these lesions.[13] Consequently, it is vital to develop a fairly smooth grading system that helps to assess and quantify the severity of the clinical condition.

The purpose of this study was to analyze the anatomic crowns of the maxillary and mandibular dentition concerning the mesiodistal, buccolingual measurements. These measurements will be used to establish normative data as a part of comprehensive study being carried out to determine the depth of the CA of the individuals by predicting the CA Index of Treatment Needs (CAITN) score.

Variability of tooth sizes and sexual dimorphism of the crown are statistically significant in both the dentitions.[111213] Further, these anthropometric measurements are used for the best clinical interest for the future development of a new clinical index for CA and treatment need by using a specialized probe that is practical, reproducible, and scientifically sound, and less time-consuming. The present study was conducted as an initial step in the process of development of the novel tool enabling the dentists to organize the health-care needs of their patients by facilitating standardized identification of CA with objective measurements.

MATERIALS AND METHODS

The study sample was selected based on the inclusion criteria comprising of 50 males and 50 females (n=100) in the age range of 20-25 years. A sample size was estimated according to the “G*Power 3.1”, statistical power analysis software demonstrating a statistical power of 90% at 5% significance level. Ethical approval was obtained from the Institution Ethics Committee (SDC/Ph.D18/33), and written informed consent was obtained from all participating study subjects.

Selection criteria

The inclusion criteria of the study are those subjects with fully erupted teeth up to second molars having a; sound periodontium and noncarious, nonattrited teeth free from morphological and structural abnormalities, as well as intact and satisfactorily aligned maxillary and mandibular teeth with no history of orthodontic therapy and crown restorations. Informed consent was obtained from all the patients who were willing to participate in the study.

Armamentarium used in the study

CAITN probe – It is a newly developed instrument to measure CA of the tooth more quantitatively. The beak of the instrument is engaged either in buccopalatal or buccolingual direction and is locked to record the measurement (Indian Patency Right Application Number: 201941043211).[14] The measurements included the mesiodistal and buccolingual width of all the 14 maxillary and mandibular teeth from the right second permanent molar to the left second permanent molar of the study sample. Right and left symmetric teeth were measured, and the mean values of tooth crown size were calculated. The measurements were entered into an Excel (Microsoft, Seattle, Washington, USA) spreadsheet for calculation of descriptive statistics.

Mesiodistal diameter

The beaks of the CAITN probe were engaged into the cervical area below the contact points of teeth taken at maximum convexity of the tooth measured parallel to the occlusal plane, and a plane parallel to the vestibular surface was measured as the mesiodistal diameter.

Buccolingual diameter

The buccolingual diameter of the tooth was measured by engaging the beaks of the CAITN probe into the cervical area between the buccal and lingual surfaces of the crown at right angles to the occlusal plane.

Mouth mirror was used for retraction and also for better visibility as well as to avoid gingival piercing in the buccal and palatal marginal area of the gingiva. Both mesiodistal and buccolingual measurements obtained using CAITN probe reflected on the CAITN probe scale can be easily read and transferred to recording form.

All measurements were carried out by a single examiner to reduce random and systemic errors. The error analysis showed no statistically significant values (p > 0.05) in the measurement of initial and after 4 weeks in a randomly selected 20 subjects. Statistical analysis was performed using the Statistical Package for the Social Sciences (IBM SPSS Statistics for Windows, version 26.0). Descriptive statistics were calculated for each group independently. The statistical significance of the difference in mean in mesiodistal and buccolingual diameters between males and females was calculated using the t-test for independent samples with p < 0.05.

RESULTS

There is no significant difference in the mean age and standard deviation between males and females of the study sample. For each tooth, the mean, standard deviation, and variance of mesiodistal and buccolingual diameters were summarized for the males and females in Tables 1-4.

Table 1

Mesiodistal dimension of maxillary arch

	Side	Gender						Total			t	p
		Males			Females
		n	Mean	SD	n	Mean	SD	n	Mean	SD
Central incisor	Right	50	6.64	0.69	50	6.05	0.89	100	6.35	0.85	3.71	0.001**
	Left	50	6.20	0.65	50	6.16	0.58	100	6.18	0.61	0.33	0.75
Lateral incisor	Right	50	4.84	0.58	50	4.70	0.58	100	4.77	0.58	1.20	0.23
	Left	50	4.72	0.81	50	4.60	0.83	100	4.66	0.82	0.73	0.47
Canine	Right	50	5.25	0.45	50	5.21	0.43	100	5.23	0.44	0.45	0.65
	Left	50	5.15	0.89	50	5.05	0.86	100	5.10	0.87	0.57	0.57
First premolar	Right	50	4.90	0.74	50	4.78	0.62	100	4.84	0.68	0.89	0.38
	Left	50	4.80	0.63	50	4.78	0.55	100	4.79	0.59	0.17	0.87
Second premolar	Right	50	4.75	0.39	50	4.66	0.46	100	4.70	0.43	1.06	0.29
	Left	50	4.69	0.70	50	4.58	0.66	100	4.63	0.68	0.81	0.42
First molar	Right	50	7.77	0.42	50	7.68	0.33	100	7.73	0.38	1.19	0.24
	Left	50	7.52	0.54	50	7.49	0.56	100	7.51	0.55	0.27	0.79
Second molar	Right	50	7.49	0.68	50	7.12	0.59	100	7.30	0.66	2.90	0.005**
	Left	50	6.92	0.97	50	7.44	0.79	100	7.18	0.91	2.95	0.004**

**Highly significant. SD: Standard deviation

Table 4

Buccolingual dimension of mandibular arch

	Side	Gender						Total			t	p
		Males			Females
		n	Mean	SD	n	Mean	SD	n	Mean	SD
Central incisor	Left	50	5.52	1.09	50	5.06	1.13	100	5.29	1.13	2.07	0.04*
	Right	50	5.49	1.10	50	5.12	1.20	100	5.30	1.16	1.61	0.11
Lateral incisor	Left	50	5.80	1.16	50	5.32	1.04	100	5.56	1.12	2.18	0.03*
	Right	50	5.82	0.54	50	5.70	0.53	100	5.76	0.54	1.12	0.27
Canine	Left	50	7.23	1.02	50	6.83	0.97	100	7.03	1.01	2.01	0.05*
	Right	50	7.28	0.61	50	7.10	0.30	100	7.19	0.49	1.88	0.07
First premolar	Left	50	7.12	1.12	50	6.90	1.09	100	7.01	1.11	0.10	0.32
	Right	50	7.31	1.15	50	6.75	1.07	100	7.03	1.14	2.53	0.01**
Second premolar	Left	50	7.29	0.54	50	7.13	0.54	100	7.21	0.55	1.47	0.14
	Right	50	7.41	0.57	50	7.30	0.51	100	7.35	0.54	1.02	0.31
First molar	Left	50	9.10	1.11	50	8.75	1.01	100	8.93	1.07	1.65	0.10
	Right	50	9.21	1.21	50	8.65	1.09	100	8.93	1.18	2.43	0.02*
Second molar	Left	50	8.51	0.92	50	8.06	1.00	100	8.28	0.99	2.33	0.02*
	Right	50	8.71	1.09	50	8.56	1.21	100	8.64	1.15	0.65	0.51

*Significant, **Highly significant. SD: Standard deviation

Mesiodistal diameter in maxillary and mandibular teeth

The mean mesiodistal diameter of maxillary and mandibular teeth was greater in males than in females. When mesiodistal measurements of the maxillary and mandibular arch were compared as a function of gender, statistically significant differences were found in right maxillary central incisor, left maxillary first and second molar (p < 0.01) and in right mandibular second molar (p < 0.05). Mesiodistal measurements of the maxillary arch showed less variability than that of the mandibular arch and more variability was found in males than females [Tables 1 and 2]. The second premolars in the maxillary arch and first premolars in the mandibular arch showed less variability. The mean mesiodistal sizes of the first premolars are greater than that of the second premolar in maxillary and mandibular arch.

Table 2

Mesiodistal dimension of mandibular arch

	Side	Gender						Total			t	p
		Males			Females
		n	Mean	SD	n	Mean	SD	n	Mean	SD
Central incisor	Left	50	3.12	1.12	50	3.02	1.00	100	3.07	1.06	0.47	0.64
	Right	50	3.57	0.71	50	3.45	0.60	100	3.51	0.66	0.91	0.37
Lateral incisor	Left	50	3.66	0.61	50	3.55	0.60	100	3.60	0.60	0.91	0.37
	Right	50	3.73	0.74	50	3.71	0.85	100	3.72	0.79	0.13	0.90
Canine	Left	50	5.00	0.00	50	5.00	0.00	100	5.00	0.00	-	-
	Right	50	5.17	0.77	50	5.09	0.74	100	5.13	0.75	0.53	0.60
First premolar	Left	50	4.82	0.44	50	4.68	0.47	100	4.75	0.46	1.54	0.13
	Right	50	4.84	0.72	50	4.82	0.52	100	4.83	0.62	0.16	0.87
Second premolar	Left	50	4.70	0.84	50	4.70	0.91	100	4.70	0.87	0.00	1.00
	Right	50	4.86	0.64	50	4.72	0.57	100	4.79	0.61	1.15	0.25
First molar	Left	50	9.15	0.77	50	9.00	0.69	100	9.07	0.73	1.02	0.31
	Right	50	9.13	1.15	50	9.08	0.99	100	9.11	1.07	0.23	0.82
Second molar	Left	50	9.25	1.04	50	8.94	0.81	100	9.10	0.94	1.67	0.1
	Right	50	9.29	0.92	50	8.91	0.96	100	9.10	0.95	2.03	0.05*

*Significant, SD: Standard deviation

Buccolingual diameter in maxillary and mandibular teeth

The mean buccolingual diameters of maxillary and mandibular teeth were greater in males than in females. The buccolingual measurement of maxillary arch showed more variability and significant differences were found in 16, 31, 32, 33, 37, 44, and 46 (p < 0.05) between the groups, and males showed more variability than the females [Tables 3 and 4]. The first premolars have a larger buccolingual diameter than the second premolars in the maxillary arch, while in mandibular arch, the second premolars have greater buccolingual measurements. The first premolars in the maxillary arch and second premolars in the mandibular arch showed less variability.

Table 3

Buccolingual dimension of maxillary arch

	Side	Gender						Total			t	p
		Males			Females
		n	Mean	SD	n	Mean	SD	n	Mean	SD
Central incisor	Right	50	6.26	1.15	50	6.17	1.06	100	6.22	1.10	0.41	0.69
	Left	50	6.20	1.25	50	6.02	1.10	100	6.11	1.17	0.77	0.45
Lateral incisor	Right	50	5.66	1.24	50	5.56	1.01	100	5.61	1.13	0.44	0.66
	Left	50	5.26	0.69	50	5.20	0.53	100	5.23	0.62	0.48	0.63
Canine	Right	50	7.54	0.99	50	7.21	0.94	100	7.38	0.98	1.71	0.09
	Left	50	7.34	1.47	50	7.08	1.18	100	7.21	1.33	0.98	0.33
First premolar	Right	50	8.22	0.66	50	8.22	0.42	100	8.22	0.55	0.00	1.00
	Left	50	8.28	1.03	50	8.02	1.04	100	8.15	1.04	1.26	0.21
Second premolar	Right	50	8.28	0.99	50	7.94	1.20	100	8.11	1.11	1.54	0.13
	Left	50	8.31	1.28	50	7.91	1.31	100	8.11	1.31	1.54	0.13
First molar	Right	50	10.76	0.89	50	10.40	0.88	100	10.58	0.90	2.03	0.05*
	Left	50	10.50	0.95	50	10.44	1.21	100	10.47	1.09	0.28	0.78
Second molar	Right	50	10.34	1.36	50	10.30	1.15	100	10.32	1.25	0.16	0.87
	Left	50	10.12	1.15	50	10.10	0.97	100	10.11	1.06	0.09	0.93

*Significant. SD: Standard deviation

The ratio between buccolingual and mesiodistal measurements of each tooth of the maxillary and mandibular arch of the study sample (n=100) was calculated. The ratio was highest in the left second premolar (1.752) and least in the right central incisor (0.980) of the maxillary arch. Similarly, the ratio was highest in the left central incisor (1.723) and least in the left second molar (0.910) of the mandibular arch [Table 5].

Table 5

Frequency table for ratio between buccolingual and mesiodistal values of maxillary and mandibular arch

Ratio of	Side	n	Mean
			Maxillary arch	Mandibular arch
Central incisor	Right	100	0.980	1.510
	Left	100	0.989	1.723
Lateral incisor	Right	100	1.176	1.548
	Left	100	1.122	1.544
Canine	Right	100	1.411	1.402
	Left	100	1.414	1.406
First premolar	Right	100	1.698	1.455
	Left	100	1.701	1.476
Second premolar	Right	100	1.726	1.534
	Left	100	1.752	1.534
First molar	Right	100	1.369	0.980
	Left	100	1.394	0.985
Second molar	Right	100	1.414	0.949
	Left	100	1.408	0.910

DISCUSSION

NCCLs may occur due to the tooth structure loss forming clear cavities in the crown, root, or both. CA is usually noticed on the vestibular surface of the tooth resulting from the inappropriate brushing technique and use of abrasive agents for brushing.[1] In literature, the selection of ideal index for measurement of CA remains ambiguous. This is due to the availability of various indices and the lack of standardization in measuring the condition. Although many studies have been toiled on defining and describing the CA clinically, there is not one ideal index that can be used for clinical staging and monitoring the cervical lesions. The periodontal probe was used in few pioneer works of the past to determine and measure the abrasion.[4] Moreover, most of the indices currently in use are tooth wear indices which assess all the components such as abrasion, attrition, erosion, and abfraction using qualitative and quantitative methods.[9101516]

CAITN probe is a robust, standardized instrument used for recording CA with a fair gold standard comparison making it a reliable and easy to handle tool. The results of this study establish normative data for the mesiodistal and buccolingual dimensions of the whole dentition which may be used as a basis for future study of development of a new clinical index for determining the CA and its treatment needs.

In this study, the average mesiodistal and buccolingual measurements in a sample of 100 healthy subjects were obtained. The method generally described in anthropological and dental literature was used which is based on the work by Moorrees, to facilitate comparison of the present results with those of other studies.[17] An extensive review of literature reveals that several studies have been carried out to establish the tooth crown diameter by using Boley's gauge or conventional calipers.[18] However, the mean value of the right and left symmetric teeth (up to the second molars) obtained from the CAITN probe in the present study is a reliable and optimized measurement to serve as normative data for accurately determining the depth of the CA based on the CAITN score.

Odontometric studies are considered a useful tool in anthropological research and clinical practice. Dental traits such as tooth eruption, size, and shape of the tooth show minor differences among and within the diverse population and reflect the ongoing process of evolution.[19] Only a few studies are explored that assess buccolingual tooth diameter; it is now established that both the magnitude of sexual dimorphism in tooth size and the hierarchy of dimorphism values differ from those encountered in the mesiodistal crown diameters.[2021] Tooth crown diameter also serves as a valuable tool for sex differentiation which is attributed to the differences in hormonal balance, the effect of the Y chromosome in increased mitotic activity within the developing dental lamina, and the X chromosome is known to be involved in the enamel formation.[22] Canines are the most dimorphic in both the dentitions and central incisors were the least.[23]

Concerning gender differences, the present study recorded a mean size greater in males than in females for all the measurements studied. A statistically significant difference was observed in the mesiodistal crown size of 11, 26, 27, and 47 and buccolingual size of 16, 31, 32, 33, 37, 44, and 46. Concurrent studies reported a larger mesiodistal size in boys than in girls, but variability was not found in all molars.[1920] Margetts and Brown did not observe dimorphism in first mandibular molars, nor did Steigman et al. in second molars. Margetts and Brown noted that gender difference is more marked in permanent dentition than that of the primary dentition.[2425] Fearne and Brook did not find difference in any molars, and Yuen et al. observed that, although the mean size was greater, the difference was insignificant.[1126] Axelsson and Kirveskari used dental casts for crown measurements and reported significant dimorphism for maxillary molars, but not for mandibular molars.[27] Garn et al. and Kondo and Townsend stated that gender variability was greater for the buccolingual tooth diameter which is consistent with the results of our study.[2123] In contrast to the fact that mandibular canines show the greatest gender difference,[1923] our study result showed significant differences only in the buccolingual size of the left mandibular canine.

The relative sizes of the first and second molars are a source of considerable debate in the literature. The results of the study sample disclose that the mandibular central incisors have the least mesiodistal and buccolingual dimensions. Mesiodistal dimensions of the maxillary first molars and mandibular second molars were the greatest in the study sample, whereas the maxillary and mandibular first molars have the greatest buccolingual diameter. The buccolingual size of the maxillary arch exhibited greater variability among all the measurements.

The unique aspect of the present study is its linking of anatomic trait (labiolingual and mesiodistal) measurements to produce a standardized score or ratio. The severity levels or the depth of the CA lesions will then be determined in future studies by relating the standardized ratio to the anatomic trait of the specified case severities.

Limitations

The gender differences revealed from the study findings is solely based on the buccolingual and mesiodistal dimensions of the tooth, without considering the genetic, evolutionary, metabolic or hormonal factors. Future investigations should be directed toward these factors to clarify the etiology of sexual dimorphism in dental development.

CONCLUSION

This work investigated the anthropometric measurement of the anatomic crown of all the teeth in the maxillary and mandibular arch and established the mean mesiodistal and buccolingual measurements of each tooth in the whole dentition with special attention to developing a novel clinical index to determine CA and its treatment needs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.