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 Table of Contents  
Year : 2020  |  Volume : 12  |  Issue : 7  |  Page : 24-29

Age-related changes in tooth dimensions in adults in Shiraz, Iran

1 Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran
2 Department of Anatomy, Iranshahr University of Medical Sciences, Iranshahr, Iran

Date of Web Publication17-Jan-2020

Correspondence Address:
Dr. Rashin Giti
Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Qasrodasht Street, Qomabad Avenue, Shiraz.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jioh.jioh_148_19

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Aims and Objectives: This study aimed to determine the biometric dimensions of three human permanent teeth in the occlusal/incisal-cervical and apical, buccolingual, and mesiodistal directions, and its relationship with age in adults in Shiraz, Iran. Materials and Methods: The samples included 50 upper canines, 50 maxillary first premolars, and 50 maxillary second molars, extracted from patients aged 25–55 years. Total length, crown labial surface length, crown palatal surface length, crown mesiodistal width, root length, and some other biometrical characteristics of the teeth were measured by using a Vernier caliper with 0.05-mm accuracy. The samples were divided into two age groups: patients aged below 45 years (younger adults group), and those aged over 45 years (older adults group). The data were analyzed by using independent t-test. P < 0.05 was considered as the significance level. Results: Most parameters such as the total length, crown mesiodistal and labiopalatal width, as well as the root length decreased in older adults group in all the three tested permanent teeth. Conclusion: During a lifetime, the crown length, mesiodistal, and buccolingual dimensions seem to decrease because of the physiological and pathological tooth wear. The tooth wear in a mesiodistal dimension is more frequent in posterior teeth than in the anterior ones.

Keywords: Aging, Tooth Dimensions, Tooth Shape, Tooth Size, Tooth Wear

How to cite this article:
Farzin M, Giti R, Heidari E. Age-related changes in tooth dimensions in adults in Shiraz, Iran. J Int Oral Health 2020;12, Suppl S1:24-9

How to cite this URL:
Farzin M, Giti R, Heidari E. Age-related changes in tooth dimensions in adults in Shiraz, Iran. J Int Oral Health [serial online] 2020 [cited 2020 Sep 27];12, Suppl S1:24-9. Available from:

  Introduction Top

Differences in size, shape, arrangement, and wear pattern of the teeth have long been of great interest to physical anthropologists.[1] Throughout the life, the teeth are exposed to different risk factors such as abrasive habits and diets, which can cause attrition, abrasion, abfraction, and erosion, all described in a general term as “tooth wear.”[2],[3],[4],[5]

Tooth wear can be physiological (normal) or pathological; they should be differentiated.[6] Premature tooth wear often causes hypersensitivity, aesthetic, and psychological problem; severe cases may even lead to loss of the tooth vitality.[7],[8] Evidence has proven the tooth wear to be a common condition, which increases with aging within the permanent dentition.[9],[10] Regardless of the physiological or pathological nature of the tooth wear, early interventions are necessary to prevent the problem exacerbation and the need for broad prosthetic restorations.[7] Remodeling of the dentoalveolar hard tissue is also triggered by occlusal and proximal dental wear, aging, pathologies, and trauma. The mechanism of remodeling maintains masticatory function.[11],[12]

In the near future, the population of elderly people will be far larger than ever before; subsequently, prevention and treatment of severe tooth wear will be a rising problem. Moreover, the inherent differences in tooth morphology, which are related to the tooth shape, size, and position in the dental arch, can greatly affect the aesthetic and the tendency for plaque accumulation. The latter is the leading factor in initiation and progression of caries and periodontal diseases.[13] Little information is available about tooth dimension and tooth wear and the contributing factors in the general population. Moreover, the comparability of the study results is limited due to the variety of assessment indices. Some studies have reported that factors such as age, ethnicity,[14] genetics,[15] sex,[16] environmental condition, and secular trend[17],[18] can influence the tooth morphology in different populations. However, the extent of effect of these factors is unclear.

Schierz et al.[19] found that aging increased the occlusal tooth wear scores and dentine exposure in the adult population of Germany. Another study on the United States population found that the extent and type of tooth wear was related to age and location of the teeth; the dentists managed different types of tooth wear with dissimilar methods in that population.[3] Despite the importance of tooth size and tooth wear, and the need for preventive and early treatments to gravel the progression of tooth wear, there is not enough published information about the age-related changes of tooth size in the Iranian population. Thus, the aim of this study was to evaluate the biometrical characteristics of three permanent teeth of adult patients of different ages in Shiraz, Southern Iran. The null hypothesis was that aging would not affect the tooth dimensions in this population.

  Materials and Methods Top

This cross-sectional study was performed on 150 permanent teeth including 50 upper canines, 50 maxillary first premolars, and 50 maxillary second molars, divided into two age groups of 25–45 years (younger adults group) and 46–55 years (older adults group) for both male and female (n = 25 per group). The teeth were selected from those extracted from patients referring to School of Dentistry, Shiraz University of Medical Sciences, during a one-year period (2018–2019). Informed consent was obtained from all patients, and the study was approved by the Ethics Committee of Shiraz University of Medical Sciences (No. 0457/18-19). The inclusion criteria were being aged 25–55 years, and having the teeth extracted for orthodontic purposes or periodontal treatments. The teeth with carious lesions were excluded from the study.

The teeth were rinsed with distilled water and fixed in 10% buffered formalin. Biometrical characters of the teeth, such as the total length, crown labial surface length, crown palatal surface length, crown mesiodistal width, crown labiopalatal width, and root length, were measured by using a Vernier caliper (Mini Electronic Caliper, INSIZE, Suzhou, China) with 0.05-mm accuracy.

The total tooth length was measured between the highest points of the crown and the root along the center of the cervical margin. The crown length and the root length were recorded from the center of cervical margin to the highest points of the crown and the root in each labial and palatal surface [Figure 1] and [Figure 2]. The crown palatal surface length of canine was measured from the highest point of linguoincisal line angle to the center of cervical margin on the palatal surface. The mesiodistal and labiopalatal width were measured from the most prominent points on each surface to the other one [Figure 3] and [Figure 4].
Figure 1: The lengths were measured between the highest points of the crown and the root along the center of the cervical margin

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Figure 2: (A) Mesiodistal width of the crown was measured between the most prominent points of each surface. (B) Labiopalatal width of the crown was measured between the most prominent points of each surface

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Figure 3: Total length of the first premolar teeth in older adults group (A) and younger adults group (B)

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Figure 4: Crown labiopalatal width of canine teeth in older adults group

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Statistical analysis: The statistical analyses were performed by using the Statistical Package for the Social Sciences (SPSS) software, version 17.0 (SPSS, Chicago, Illinois). Independent t-test was used to compare the mean values between the two age groups for the three types of permanent teeth. P < 0.05 was considered as the significance level.

  Results Top

[Table 1] represents the mean ± standard deviation (SD) of all measured dimensions of the upper canine permanent teeth in both age groups. The results of independent t-test showed that the mean values of the total length, crown labial surface length, and root length in older adults group were significantly lower than that in younger adults group (P < 0.05). The mean ± SD of all the measured dimensions of the maxillary first premolar teeth are listed in [Table 2], showing significant reduction in the total length, crown palatal surface length, crown labiopalatal width, and root length in older adults group (P < 0.05). However, the reduction of crown labial surface length (P = 0.1) and crown mesiodistal width (P = 0.3) in the maxillary first premolar was not statistically significant.
Table 1: Comparison of the mean ± standard deviation (SD) of the measured dimensions (mm) in human maxillary canine between the two age groups (patients <45 and >45 years)

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Table 2: Comparison of the mean ± standard deviation (SD) of the measured dimensions (mm) in human maxillary first premolar between the two age groups (patients <45 and >45 years)

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[Table 3] shows the mean ± SD of all measured dimensions in the second maxillary molar teeth. All measurements had decreased in older adults group. The differences were statistically significant for total length, crown labial surface length, crown palatal surface length, crown mesiodistal width, and root length (P < 0.05). However, the reduction in the crown labiopalatal width value was not statistically significant (P = 0.21).
Table 3: Comparison of the mean ± standard deviation (SD) of the measured dimensions (mm) in human maxillary second molar between the two age groups (patients <45 and >45 years; n = 25 per group)

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  Discussion Top

The null hypothesis was rejected based on the evidence, which showed that the reduction of crown size could happen as a result of aging. The three tooth dimensions of total length, crown labial surface length, and crown palatal surface length decreased in the older adults group for the three tested permanent teeth. But, the dimensional decrease was not significant for crown palatal surface length in canine and crown labial surface length in the first premolar.

Generally, different factors such as bruxism, sex,[20] habits, and crowding[4],[5],[10] can induce the loss of non-carious tooth structure (including attrition, abrasion, and erosion). Different authors reported age as a dominant factor for occlusal tooth wear, and detected a negative relationship between the age and crown length.[19],[21],[22] Bartlett and O’Toole[14] found that aging increased the rate of occlusal and incisal tooth wear. Schierz et al.[19] showed the age-related linear progress in tooth wear in a German population. In a study by Pontes and Prietsch,[23] the individuals older than 40 years reported a higher prevalence of sleep bruxism and tooth wear, although the prevalence of these two factors were not significantly different between the sexes in the population of Rio Grande, Brazil. These studies were comparable with the results of this study, which found that the tooth wear increased in the older adults group (>45 years old). However, Seligman et al.[24] noted no statistically significant difference between the age groups. Their different findings could be related to the limited age range of 20–40 years, whereas the age range in this study was 25–55 years.

As tooth wear is not reversible, undoubtedly severer tooth wear is found in the elderly population. The higher rate of the second molar wear in this study would be attributed to mastication of more fibrous and hard food with the posterior teeth.[25] In line with this study, Masotti et al.,[26] who studied Italian population, detected significantly different wear directions between the anterior (oblique and flat) and posterior (oblique and concave) teeth in both sexes. Moreover, significant age-related differences were observed in wear direction and level in the incisors, canines, and premolars, the wear being significantly higher in the older age group. Surprisingly, Schierz et al.[19] noticed more tooth wear in the anterior teeth due to the lack of effective anterior guidance.

This study found the reduction of crown length to be higher in the palatal surface of the maxillary first premolar (crown palatal surface length) than the labial surface (crown labial surface length). The reason might be the higher wear of functional cusp (palatal cusp) compared with the nonfunctional cusp (buccal cusp) during different functional activities. Littleton[27] documented the rapid advancement of dental wear during the life, but no difference was observed between the sexes regarding the wear pattern in the population of South Australia. Although disproportionate anterior wear occurred among the juveniles and young adults, by middle adulthood, the pattern was less variable and more involved the premolars. Old adults had a much flatter pattern of wear in that population. Our findings also revealed reduction in tooth size in mesiodistal and buccolingual dimensions of all the studied permanent teeth; however, they were not significant for canine, crown mesiodistal width in premolar, and crown labiopalatal width in the second molar. Tooth wear was found to happen not only in an occluso-cervical but also in mesiodistal dimension.[28],[29]

According to Sarig et al.,[30] the environmental factors had more effect than the genetics on the reduction of mesiodistal and buccolingual dimensions of the teeth. They found the proximal attritional facets to have increased by aging, which was consistent with this study.

This study found that the crown mesiodistal width mainly decreased for the second molar in the adults of older age. Another study showed that the proximal tooth wear chiefly affected the posterior teeth due to the mesial drift of the arches, as well as masticating harder foods with the posterior teeth rather than the anterior ones.[11]

In this study, reduction was also observed in the labio-palatal width; however, it was solely significant for the first premolar. Bartlett et al.[31] found a considerable correlation between the buccolingual tooth erosion and acid reflux, recurrent vomiting, aggressive toothbrushing, use of abrasive toothpastes, residence in rural areas, and acidic intakes. They also detected a moderate increase in tooth wear in the buccolingual dimension with age,[31] which was detectable despite the limited age range. It was in agreement with the results of this study.

The higher prevalence of labiopalatal tooth wear in the first premolar can be related to its lower enamel thickness compared with the other tested teeth in this study, and also chewing the hard foods with the premolar teeth. It was found that positioning of the food bolus during mastication depends on the consistency of food; that is, the tougher the food is, the greater the individual’s preference would be for using the premolar region.[32] Another reason may be the easier accessibility of premolars for brushing and the higher exposure to abrasive toothpastes.[31]

Another considerable finding of this study was the significant decrease of root length in all the three permanent teeth with aging. Moyers[33] reported that 90% of all teeth revealed evidence of idiopathic root resorption throughout the life. He also announced most of the resorption to be mild and restricted to the apical blunting, but almost 10% of them showed resorption of 2–4 mm.

Kaya et al.[34] evaluated the effect of aging on the dimensions of upper incisor root canals by using cone-beam computerized tomography. They found that the root length did not change with aging, whereas the pulp width did.

On the contrary, another study reported age-related deposition of cementum throughout the life, which was meant to compensate for the tooth wear and remodeling. That study also observed that the apices of all teeth looked rounded as a result of continued cementum deposition.[35] It contrasted the finding of this study. Seemingly, there is not a single factor responsible for the root resorption or cementum apposition during the life, and they can happen in different manners in each single individual.

The limitation of this study was evaluation of the tooth dimensions in only three permanent teeth (one anterior and two posterior) in two age groups. Further studies are suggested to investigate the age-related changes in the dimensions of other permanent teeth.

Within the limitations of this study, it was concluded that the crown length decreases due to the physiological and pathological tooth wear during the life. Moreover, the root length can decrease due to resorption. The mesiodistal and buccolingual dimensions of the teeth partly decrease with aging because of the proximal tooth wear and perhaps aggressive toothbrushing. Finally, this study concluded that the tooth wear in a mesiodistal dimension occurs more in posterior teeth rather than the anterior ones.


We would like to thank Dr. Farhad Mohammadi for his precious help with the statistical analyses, and Ms. Farzaneh Rasouli for proofreading and English editing of the manuscript.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3]


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