Journal of International Oral Health

REVIEW ARTICLE
Year
: 2021  |  Volume : 13  |  Issue : 6  |  Page : 533--538

Intermaxillary tooth-size ratios in Saudis: A systematic review


Sarah M Abuhassan1, Moshabab A Asiry2,  
1 College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
2 Division of Orthodontics, Department of Pediatric Dentistry and Orthodontics, College of Dentistry, King Saud University, Riyadh, Saudi Arabia

Correspondence Address:
Moshabab A Asiry
Division of Orthodontics, Department of Pediatric Dentistry and Orthodontics, College of Dentistry, King Saud University, Building No 3500, Riyadh 12372–7051.
Saudi Arabia

Abstract

Aim: The purposes of this study were to review all the studies that calculated the intermaxillary tooth-size ratios in Saudis, to review how gender and malocclusion groups influence tooth-size ratios, and to review the measurement methods for mesiodistal tooth width. Materials and Methods: MEDLINE, PubMed, Google Scholar, Saudi Dental Journal, and King Saud University Journal of Dental Sciences were searched for published studies reporting the intermaxillary tooth-size ratios of Saudis. No period of time for published studies was determined. The inclusion criteria were well-defined Saudi sample, reliable measurement method, and malocclusion classification determined for the study sample. Results: The searching process ended with five studies that met the final inclusion criteria. Gender and malocclusion groups are unlikely to have a significant influence on tooth-size ratios. Class III malocclusions cases have larger ratios. The anterior ratio and the overall ratio of Saudis seem not to be significantly different when compared with the Bolton results. Conclusion: All the studies that investigated tooth-size ratios in Saudis were conducted in major cities only. Until conducting more studies representing the overall population of Saudi Arabia, Bolton’s results can be used with caution for Saudi patients.



How to cite this article:
Abuhassan SM, Asiry MA. Intermaxillary tooth-size ratios in Saudis: A systematic review.J Int Oral Health 2021;13:533-538


How to cite this URL:
Abuhassan SM, Asiry MA. Intermaxillary tooth-size ratios in Saudis: A systematic review. J Int Oral Health [serial online] 2021 [cited 2022 Jan 26 ];13:533-538
Available from: https://www.jioh.org/text.asp?2021/13/6/533/331583


Full Text

 Introduction



Tooth-size ratio or Bolton’s analysis is a valuable diagnostic tool for assessing and managing tooth-size discrepancy. In 1958, Bolton calculated the tooth-size ratios for 55 patients with excellent occlusions.[1] The overall ratio was obtained by dividing the sum of mesiodistal width of the 12 mandibular teeth, the right first molar through the left first molar, by the sum of mesiodistal width of the 12 maxillary teeth, the right first molar through the left first molar. The anterior ratio was obtained by dividing the sum of mesiodistal width of the six mandibular anterior teeth by the sum of mesiodistal width of the six maxillary anterior teeth. Bolton found that an overall ratio of 91.3% and an anterior ratio of 77.2% were necessary for a good occlusion with normal overbite, normal overjet, and optimal posterior interdigitation.[1] Further, McLaughlin et al. reported that the coordination between the mesiodistal widths of the maxillary and mandibular teeth is an important factor in obtaining a good occlusion in the finishing stage of orthodontic treatment.[2] Therefore, tooth-size discrepancy should be recognized early during orthodontic examination and diagnosis stage. Dentition with tooth-size discrepancy can be managed by proximal stripping, extraction, or restorative solutions to gain the width balance between the maxillary and mandibular teeth.[3]

Numerous studies have calculated and compared the tooth-size ratios among different racial, malocclusion, and gender groups.[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18] There were controversies regarding the differences between these groups. Smith et al. reported that tooth-size ratios were significantly different among black, Hispanic, and white populations.[18] In addition, the overall and anterior ratios were significantly larger in males. On the contrary, Fernandes et al. did not find any significant gender and ethnic differences when they compared Bolton results with the findings among black, white, Afro-Mediterranean, and Japanese, except for the anterior ratio in Japanese patients.[13] Controversies were also found regarding the differences in tooth-size ratios between malocclusion classes. There was a statistically significant trend to larger anterior ratios in Class III malocclusion.[8],[19],[20],[21],[22] However, several studies revealed that no significant differences were found in tooth-size ratios between different malocclusion groups.[4],[5],[10],[23],[24],[25],[26],[27],[28]

The purposes of this study were to review all the studies that calculated the intermaxillary tooth-size ratios in Saudis, to review how gender and malocclusion groups influence tooth-size ratios, and to review the measurement methods for mesiodistal tooth width.

 Materials and Methods



MEDLINE, PubMed, and Google Scholar were searched up to October 29, 2020, for published studies reporting the intermaxillary tooth-size ratios of Saudi males and females. In addition, the Saudi Dental Journal, King Saud University Journal of Dental Sciences, and the reference list of selected articles were also searched for further studies. The following terms were used in the searching process: Saudi, tooth-size ratios, Bolton ratio, intermaxillary tooth width ratio, and mesiodistal tooth width. To identify potentially relevant studies, the initial searching process was performed by title. Initial inclusion criteria were studies quoting tooth-size ratios in Saudis.

The full text of these studies was then reviewed for (1) sample description, (2) determined malocclusion classification, and (3) reliable and reproducible measurement method. This process identified the articles ultimately selected in this review. Sample description was considered appropriate when the authors mentioned the sample type and specified the age range of the participants. In addition, gender and malocclusion diagnosis were identified for the study sample. The measurement method was considered adequate when the study described how the mesiodistal widths of teeth were measured, specified the device, and quantified the method in terms of reproducibility.

 Results



Ten studies were initially relevant to the review and then verified for eligibility [Figure 1]. Three studies were excluded because they reported the measurement of mesiodistal tooth widths, but not tooth-size ratios. The verification process revealed only seven of these 10 studies reporting the intermaxillary tooth-size ratios of Saudis (Alkofide and Hashim,[22] Hashim and Almurshid,[29] Al-Tamimi and Hashim,[30] Al SuIaimani and Afifi,[24] Al-Kawari et al.,[31] Asiry and Hashim,[32] and Alshahrani et al.[28]). After applying the final inclusion criteria, five studies remained. The study by Al-Kawari et al.[31] was excluded because they did not report the sample age and malocclusion classification. In addition, the study conducted by Hashim and Almurshid[29] was also excluded as they did not report the malocclusion classification for the subjects included in their sample.{Figure 1}

[Table 1] shows the studies selected in this review and their findings. No significant differences were detected in the overall ratio and anterior ratio between gender and malocclusion groups, except for the anterior ratio that was significantly greater in male cases of Class III malocclusion among the sample investigated by Alkofide and Hashim.[22] When the results of the selected studies were compared with Bolton’s results, there were no statistically significant differences regarding values of the anterior ratio and the overall ratio as reported by three of the selected studies.[29],[30],[32] On the contrary, Alkofide and Hashim found that a significant difference was found between the results of Saudis with different malocclusion classes and Bolton’s results.[22] Alshahrani et al.[28] reported that the anterior ratio for normal occlusion was statistically significantly greater than those of Bolton. A digitized or scanned cast measured by software was the measurement tool in two studies included in this review,[24],[28] while the other studies[22],[30],[32] used an electronic digital caliper to measure the mesiodistal tooth width on plaster cast. The authors of these studies measured the reproducibility of their methods by means of replicate measurements. All the results exhibited a high correlation between the first and second measurements.{Table 1}

 Discussion



The sample age range of the studies included in this review was 12–25 years. This age will provide the best sample for tooth-size measurements because early adulthood dentition has less alteration of mesiodistal width that might be caused by attrition, caries, or restorations.[33],[34] The measurement method in the selected studies relied on Ortho-1 software and electronic digital caliper to measure the mesiodistal tooth width on a digitized cast and plaster cast, respectively. The reproducibility of the method was tested in all studies, and the results exhibited a high correlation between the two measurements. Several studies have tested the accuracy of tooth width measurement using these devices.[35],[36],[37],[38],[39] The results concluded that the accuracy of the two methods is clinically acceptable and no statistically or clinically significant differences were found between them. However, Zilberman et al. reported that digital calipers on plaster models showed the highest accuracy and reproducibility, closely followed by OrthoCAD software.[38] In summary, both electronic digital calipers and digital model measuring techniques provide an easy and accurate method for mesiodistal tooth width measurement. The only advantage of digital model measuring techniques over digital calipers is the compatibility with 3D virtual model and the trend for paperless orthodontic clinics.

Significant gender differences in overall and anterior ratios were not found among Saudis in four of the selected studies. One study detected that anterior ratio in Class III malocclusion was significantly larger in males.[22] No significant gender differences in overall and anterior ratios were reported in several studies among Nigerian,[14] Yemeni,[4] Senegalese,[15] Japanese,[5] North Indian,[40] black South Africans,[16] Indian,[7] Brazilian,[21] Iranian,[10] Spanish,[12] Peruvian and Spanish,[11] Chinese,[41] Syrian,[25] Irish,[42] Turkish,[27] and black, white, Afro-Mediterranean, and Japanese.[13] However, gender differences in tooth-size ratios have been reported in the literature. Smith et al. concluded that population and gender groups influence intermaxillary tooth-size ratios.[18] They found larger overall and anterior ratios in males from black, Hispanic, and white populations. Uysal and Sari also reported larger overall ratios in males when compared with females in the Turkish population.[43] They explained this sexual dimorphism in the overall ratio by the relatively larger mandibular arch segments of men. However, these gender differences in both studies were small, less than 2%.

Three of the studies included in this review investigated the differences in intermaxillary tooth-size ratios between different malocclusion groups. All studies found no significant differences in the overall ratio and anterior ratio between Class I, Class II, and Class III malocclusions, except for the anterior ratio that was significantly greater in Class III malocclusion in the sample of one of the two studies.[22],[24] The statistically significant trend to larger anterior ratios in Class III malocclusion was also reported among Chinese, Iranian, and Brazilian.[19],[20],[21] Further, Wedrychowska-Szulc et al. reported that statistically significant differences in anterior ratio were observed for all malocclusion groups; the greatest difference was for males with Class III malocclusion.[8] On the contrary, Oktay and Ulukaya found no significant difference among the malocclusion groups in anterior ratio, but the differences in overall ratio was significant.[6] Uysal et al. found that all malocclusion groups showed statistically significantly higher overall ratios than the normal occlusion group among Turkish population.[34] On the other hand, several studies did not find significant differences in intermaxillary tooth-size ratios between different malocclusion groups.[4],[5],[10],[23],[24],[25],[26],[27] Endo et al. stated that “The probable reason for these different results might be population and malocclusion specific.”[5]

There were no statistically significant differences between the mean values of the anterior ratio and the overall ratio of Saudis and the Bolton mean values as reported by Hashim and Almurshid,[29] Al-Tamimi and Hashim,[30] and Asiry and Hashim.[32] On the contrary, Alkofide and Hashim found that a significant difference was found between the results of Saudis with different malocclusion classes and Bolton’s results.[22] In addition, Alshahrani et al.[28] reported that the anterior ratio for normal occlusion was statistically significantly greater than those of Bolton. Review of the literature reveals variations regarding whether original Bolton results represent different racial groups. Smith et al. reported significant differences in the overall and anterior ratios between whites, blacks, and Hispanics.[18] They recommended that population-specific standards are necessary for clinical assessments. Paredes et al.,[7] Subbarao et al.,[12] Uysal et al.,[40] and Sharma et al.[43] found that Bolton’s original data does not represent Spanish, Indian, Turkish, and North Indian populations, respectively. Statistically significant differences were found for the mean overall ratio (among Polish and black South Africans) and for the mean anterior ratio (among Japanese and Iranian) when compared with the original Bolton results.[5],[8],[16],[20] On the other hand, other studies concluded that Bolton’s original data represent Syrian, Nigerian, Yemeni, Senegalese, and Iranian.[4],[10],[14],[15],[25] In addition, Fernandes et al. investigated tooth-size ratios among black, white, Afro-Mediterranean, and Japanese.[13] They concluded that Bolton ratio can be applied to the investigated ethnic groups except for the anterior ratio in Japanese patients.

Although this review has reached its objectives, there were some limitations. First, few articles were yielded by searching the literature. This may be due to the restriction imposed by the inclusion criteria that limit the searching process to studies that have investigated Saudis. However, the strength of a review is reliant more on the quality of included studies than on their quantity. Second, all studies included in this review were conducted in Riyadh, Jeddah, and Abha cities, and no studies were performed in other cities and regions of Saudi Arabia. Therefore, this review might not represent the overall population in the country. It can be contended that the subjects are all Saudis having similar ethnic and environmental backgrounds. However, many Saudi cities are composed of different races. Third, samples in all the selected studies were categorized as patients attending orthodontic clinics, and no epidemiological samples were investigated. Such a sample type may or may not represent the overall population.

 Conclusion



The intermaxillary tooth-size ratios developed by Bolton can also be applied with caution to the Saudi population. Gender and malocclusion groups seem not to have a significant influence on tooth-size ratios. However, this review did not provide conclusive evidence about intermaxillary tooth-size ratios in Saudis because all the studies included were conducted in three cities only. Therefore, there is a great need for more studies to establish Saudi normative ratios based on a larger sample representing different parts of Saudi Arabia.

Acknowledgements

The authors gratefully acknowledge the College of Dentistry Research Center and Deanship of Scientific Research at King Saud University, Saudi Arabia for funding this research project.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Ethical policy and institutional review board statement

Not applicable.

Patient declaration consent

Not applicable.

Data availability statement

Data are available upon a valid request to the corresponding author.

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