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Revista Facultad de Odontología Universidad de Antioquia

Print version ISSN 0121-246X

Rev Fac Odontol Univ Antioq vol.26 no.2 Medellín Jan./June 2015

 

ORIGINAL ARTICLES DERIVED FROM RESEARCH

 

SOME FACTORS ASSOCIATED TO COSMETIC DENTISTRY: A NEW APPROACH

 

 

Gerardo Becerra Santos1; Natalia Becerra Moreno2; Marcela Jiménez Arango2; Verónica María Medina Piedrahita2; Laura Cecilia Tamayo López2; Sandra L. Gómez3

 

1 DDM. Specialist in Comprehensive Dentistry of the Adult with a focus on Prosthodontics. Associate Professor, Universidad de Antioquia, Medellín, Colombia. Email:gerardob@une.net.co
2 Senior Dentistry Student. Universidad de Antioquia
3 DDM. Specialist in Orthodontics and Comprehensive Dentistry of the Adolescent. Master's degree in Epidemiology. Assistant Professor, Universidad de Antioquia, Medellín, Colombia

 

SUBMITTED: MAY 23/2013 - ACCEPTED: FEBRUARY 18/2014

 

Becerra G, Becerra N, Jiménez M, Medina VM, Tamayo LC, Gómez SL. Some factors associated to cosmetic dentistry: a new approach. Rev Fac Odontol Univ Antioq 2015; 26(2): 67-87.

 

 


ABSTRACT

INTRODUCTION: the purpose of this study was to determine the behavior of some factors influencing dental esthetics in male and female students of Universidad de Antioquia School of Dentistry (FOUA for its Spanish initials), aged 18 to 30 years.
METHODS:this was a descriptivetransversal study on 203 FOUA students. Direct measurements of the six maxillary anterior teeth were recorded with a digital Vernier caliper (Digimatic)® and the lower third of the face was photographed. The statistical analysis was conducted with SPSS 17. Descriptive measurements were obtained and a Student's t test was performed after testing normal distribution, in order to establish mean differences between the ideal proportions of lateral incisors.
RESULTS AND CONCLUSIONS: in males, the Facial Midline (FML) coincided with the Upper Teeth Line in 61.4% of the cases and both teeth lines coincided with each other in 38.6%. In females, the FML coincided with the Upper Teeth Line in 62.25% and both teeth lines coincided with each other in 31.1%. None of the subjects had the Golden Proportion between central and lateral upper incisors. The most prevalent Individual Tooth Ratio (ITR) range was the one over 80%. The average length of females' upper lip was 21.41 mm and the bottom lip 47.18 mm; in males, the upper lip measured 22.78 mm in average and the bottom lip 52.45 mm. In both sexes, the most frequent position of the upper lateral incisors' gingival margin was the incisal one.

Key words: cosmetic dentistry, incisor, gingiva.


 

 

INTRODUCTION

In recent years, clinicians have been using esthetic references resulting from studies carried out in foreign countries. These references have not been adjusted to the Colombian population and have been adopted as patterns for dental procedures.

Aesthetics is not an art neither a science but a mixture of both. Science is subjected to critical, objective analysis, while art includes subjective, romantic, and empathic components. It is hard to segregate cosmetic dentistry into separate units since all variables are interrelated and interdependent.1

The criteria established in the studies by Tjan and Miller2 in 1984 and Becerra et al3 in 2003 on the determinants of cosmetic dentistry should not be interpreted as rigid cosmetic standards because the highest frequency or percentage in the study population can be considered as a guideline to establish a typical or average smile.

According to Rüfenacht4 in 1990, maxillary central incisors are the most dominant teeth of the anterior sector, as their length range from 11 to 13 mm, with 12 mm in average. Lateral incisors are shorter in terms of their incisal-cervical dimensions, with an average length of 10 mm, which allows the free passage of the lower canine during protrusion movements. Maxillary canines are approximately 12 mm long, similar to the central incisors.4

Individual Teeth Proportion (ITP) is obtained by dividing the crown width (mesiodistal) by its length (gingival-incisal).5

In 1897, Black6 established that the ITP of the anterior maxillary teeth, defined as a percentage value, ranges from 72 to 80%, with 76% in average.

Sterrett et al7 reported a higher average proportion of 81%. They also showed that the largest dimensions in both directions (width and length) are more commonly found in males than females, and found out that the individual teeth proportion of central incisors and canines is virtually identical. The average width of maxillary central incisors ranges from 8.3 to 9.3 mm and their length ranges from 10.4 to 11.2 mm in teeth with no incisal attrition.

Chiche8 determined that, from an esthetical point of view, the most pleasant relationship in maxillary central incisors occurs when the mesiodistal diameter is between 75 and 80% in incisal-gingival length, in such a way that below 75% the tooth looks narrow and long and above 80% it looks wide and short.

Chu9 devised a gauge or tooth proportions indicator, known as Chu's T Bar, whose objective is to simultaneously measure the mesiodistal width and the cervical-incisal length of maxillary anterior teeth. These dimensions have a width/length ratio of approximately 78%.

On the other hand, some clinicians have accepted and implemented the principles of golden proportion in dentistry. This concept was initially mentioned by Lombardi5 and later developed by Levin.10

Central upper incisors are the widest teeth in the anterior sector, followed by canines and lateral incisors. When an observer stands in front of a patient, the apparent tooth size should become progressively smaller as he moves away from the midline. This apparent reduction in size would correspond to what is known as the Golden Proportions (0.618).10

In this specific context, the measurements made by Preston11 confirm the unreal nature of the "golden rule", as it was determined that, when strictly applied, this rule results in excessive "narrowing" of the maxillary arch and compression of the lateral segments.

In terms of estimation of the Facial Midline (FML) and its relationship with upper and lower teeth, and taking lip philtrum as a reference, Javaheri12 found out that in 70.4% of cases the FML coincides with the Upper Dental Midline.

Regarding gender, Miller et al13 found out that in 68.8% of males the FML coincides with the Upper Dental Midline, having lip philtrum as a reference, and that the two dental lines (upper and lower) coincide in 26.9% of cases. In 71.3% of females the FML coincides with the upper dental midline, and the two dental midlines coincide in 28.3% of cases.

Clinically, upper central incisors must be reasonably symmetrical. Studies have shown that the asymmetry between these two teeth is usually no greater than 0.3 to 0.4 mm in mesiodistal direction. Mavroskoufis and Ritchie14 showed that 14% of the subjects under study had completely identical central incisors, in 23% these two teeth were similar (with variations no greater than 0.2 mm in one or both dimensions) and 63% were different in the three dimensions (with variations over 0.2 mm in one of the dimensions).

Upper lateral incisors are the teeth with the most variations in shape, compared with central incisors. Variations in the mesial-distal direction can be up to 3.98 mm, which explains the extreme shape differences within the same individual. Therefore, reconstructions of the anterior sector must be based on the symmetry of both central teeth.15, 16

Lip length sets an inverse relationship with anterior teeth exposure. The upper lip, measured from the subnasal point to its lower edge, has an average length of 19 to 22 mm.17 If the upper lip is short (less than 18 mm), interlabial gap increases and the upper incisors are more exposed, but this is still a normal lower facial height—a situation that can be misperceived as vertical maxillary excess, when the lower facial height is actually increased.

From its upper edge to the chin, the lower lip measures 38 to 44 mm.17 An anatomically short lip is associated with Class II malocclusion and must be verified with cephalometric measurements of the lower-anterior dental height (lower-anterior incisal edge - hard tissue of chin). It is 40 ± 2 mm in females and 44 ± 2 mm in males. An anatomically long lower lip is usually associated with Class III malocclusions.17

The normal upper lip-lower lip proportion (ratio) is 1:2. Proportioned lips show harmonic length. Disharmonies indicate underlying dental-skeletal problems.17

Three gingival line patterns or morphologies can be identified. The first one is a winding pattern that occurs when the lateral incisor's gingival margin is incisal to the tangent between the margins of the central incisor and the canine. The second pattern occurs when the lateral incisor's gingival margin is apical to this tangent —which is indeed not very attractive from the esthetic point of view—. The third pattern corresponds to a straight line connecting the margins of the three abovementioned teeth and does not really compromise the appearance of the upper-anterior sector. These patterns can occur unior bi-laterally.18

In 1998, Ahmad19 maintained that symmetry in the gingival line of the right side and the left side in the anterior sector is esthetically pleasing and harmonious.

The present study attempted a biotechnical approach by using measurements, proportions, and symmetries in order to establish whether certain facial and dental factors define cosmetic parameters in the Colombian population.

 

METHODS

A descriptive-transversal study was conducted on 203 students from Universidad de Antioquia School of Dentistry (FOUA for its Spanish initials), aged 18 to 30 years, including males (90) and females (113) in an uneven proportion, taking into account that the total estimated population of FOUA was 562 students by the time of the survey. All subjects signed informed consent forms and the study was approved by the Ethics Committee.

Exclusion criteria included students with prosthetic restorations and extensive resin restorations in anterior teeth, facial birth defects or lip surgeries, skeletal discrepancies detectable from the clinical point of view, evident attrition in the anterior teeth, history of orthognathic surgery, and patients over 30 and under 18 years of age.

In order to achieve the proposed objectives, a representative sample was selected considering the following criteria:

A 5% sampling error and an estimated 95% confidence level, taking into account the estimated total population of FOUA students. The following esthetical referents were taken into account: LMF, upper and lower dental midlines, dental golden proportions, individual teeth ratios (width/length ratio), upper and lower lip length and its proportion, and the location of the lateral incisor's gingival margin with respect to the margins of central teeth and canines of each side.

Width and length measurements of the six maxillary anterior teeth of each subject were directly recorded with a digital Vernier caliper (Digimatic)®, which offers a simpler, more reliable interpretation of measurement values in comparison with conventional calipers. In addition, the same Vernier caliper (Digimatic)® was used to measure the upper lip from the subnasal point to its bottom edge, and the lower lip from its upper edge to the chin (soft tissue).

Finally, upper and lower dental midlines were observed and the deviation between them was measured with a periodontal probe.

In addition, three photographs were taken: one of the lower third of each patient's face on a "full smile" (a smile as wide as possible), another photo of teeth in occlusion, using lip separators, and a photograph of each patient's face showing a number previously assigned to them. The three photos were front view, using a tripod and positioning all patients in the same place in order to standardize the distance from which the photographs were taken. We used a Sony Cyber Shot DSC-HS camera, with a 7.20 CCD Super Had sensor, and a 36.0-432.0 lens 35 mm, optical 12x zoom. Once the photographs were transferred to a computer, the FML was marked out and related to the lower and upper dental midline. A tangent line was also drawn to the top of upper canines and central incisors in order to determine the position of the upper lateral incisor's gingival margin.

The gathered information was registered in a Windows Excel spreadsheet, and data analysis was conducted with the statistical program SPSS 17 (Statistical Package for the Social Sciences), which yielded the descriptive measurements. In addition, the corresponding normal distribution tests were carried out as well as the subsequent statistical tests to establish mean or median differences, depending on each case.

 

RESULTS

In this research project, the study population was analyzed with the intention of finding out patterns that define esthetic parameters or guidelines in order to establish clinical assessments that can be more frequently used in our population for a more appropriate patient management.

The study included 113 women and 90 men. 60.2% of women and 51.1% of men had orthodontic treatment. Of the total of both men and women, 56.2% had orthodontic treatment (figure 1).

By observing the FML coincidence with the upper teeth midline, we found out that there was coincidence in 43.5% of men with orthodontic treatment and in 61.4% of men without orthodontic treatment. Regarding upper and lower dental midlines, they coincided in 26.1% of men with orthodontic treatment and in 38.6% of men without orthodontic treatment. In women with orthodontic treatment, FML coincided with upper teeth line in 63.2% and in 62.2% without orthodontic treatment; upper and lower dental midlines coincided with each other in 23.5% of women with orthodontic treatment and in 31.1% of women without orthodontic treatment (table 1).

In general, of the total number of men, the upper midline coincided with the lower one in 32.2% of cases, and in women the result was 26.8%. Midline deviation to the right occurred in 27.8% of men and in 35.7% of women. Deviation to the left was present in 40% of men and 37.5% of women (table 2).

By analyzing the "golden proportions" (mesiodistal relationships between central and lateral upper incisors), mentioned by authors such as Moreira et al,20 Mahshid et al,21 and Murthy and Ramani,22 the present study found statistically significant differences between the golden proportions and those in the patients under study (p = 0.000). Moreover, differences in the actual measurements of the upper lateral incisors and the ones obtained following the golden proportions show a confidence level of 95%, ranging from 1.37 to 1.57 mm in the upper right lateral incisor and from 1.57 to 1.8 mm in the upper left lateral incisor (table 3).

The resulting width (mesiodistal) and length (gingivo-incisal) measurements of the six upper anterior teeth of both men and women were recorded on tables that show such measurements, and the minimum and maximum diameters were established with the respective percentiles per tooth in minimum, average, and maximum ranges (table 4, table 5 y table 6).

(table 4)

According to the ITP of upper central incisors (right and left), the most prevalent range found in both men and women was › 80%. Concerning the right upper central incisor, 80.5% of women and 93.3% of men were found in this range (› 80%). In terms of the upper left central incisor, 85.8% of women and 84.4% of men were found in this range (table 7).

With regard to average upper lip length, it was found to be 21.41 mm in females and lower lip was 47.18 mm. The proportion found among both lips was 1:2.2. In males, average upper lip length was 22.78 mm and lower lip was 52.45 mm. The proportion found among both lips was 1:2.3 (table 8).

Taking as a reference the position of the upper lateral incisor's gingival margin with respect to that of the canine and the upper central incisor, we found out that in both men and women, with or without orthodontic treatment, the most frequent position of the gingival margin was the incisal one, both on the right side and the left side. On the right side, it occurred in 70.8% of females and in 63.4% of males. On the left side it occurred in 69.0% of females and in 67.8% of males (table 9).

Finally, concerning the upper lateral incisor's gingival margin level which most often coincides between the right side and the left side in a single individual, we found out that in both men and women, with or without orthodontic treatment, the gingival margin position with the most coincidence was the incisal one for 48 men and 63 women, corresponding to 54.7% of the total sample. The straight marginal level was found in 13 men and 14 women, representing 13.3% of the sample, and the apical marginal level was found in 3 men and 0 women, corresponding to 1.5% of the sample. 30.5% of the studied individuals showed no coincidence between the position of the gingival margin of the right side and the left side in none of the sites (table 10).

 

DISCUSSION

This study showed that the FML coincides with the upper teeth line in 43.5% of men with orthodontic treatment and in 61.4% of men without orthodontic treatment. Regarding upper and lower dental midlines, they coincided in 26.1% of men with orthodontic treatment and in 38.6% of men without orthodontic treatment.

In women with orthodontic treatment, the FML coincides with the upper teeth midline in 63.2% of cases and in 62.2% of women without orthodontic treatment. Upper and lower dental midlines coincide in 23.5% of women with orthodontic treatment and in 31.1% of women without orthodontic treatment.

This study also showed that deviation to the right occurred in 35.7% of women and 27.8% of men, and left deviation in 37.5% of women and 40% of men.

In his study, Javaheri12 claims that the FML coincides with the upper dental midline in 70.4% of cases but he does not establish differences by sex and by the presence of orthodontic treatment. The upper dental midline coincides with the lower one in 27.8% of cases or, to put another way, upper and lower dental midlines do not coincide in 71.2% of cases.

Concerning gender, Miller et al13 showed that the FML coincides with the upper dental midline in 68.8% of men, taking lip-philtrum as a reference, and that both dental lines (upper and lower) coincide in 26.9% of the cases. In women, the FML coincides with the upper dental midline in 71.3% of cases, and both dental midlines coincide in 28.3% of cases.

When an observer stands in front of a patient, apparent tooth size should become progressively smaller as he moves away from the midline, and this apparent reduction in size would correspond to the "golden proportion" (0.618).

By analyzing the "golden proportion", Moreira et al20 determined that out of 260 students aged 18 to 30 years, 21 (11 women and 10 men) or 7.1% of the sample showed golden proportions in lateral upper incisors width when related to central incisors.

Mahshid et al21 evaluated individuals aged 18 to 30 years by measuring the apparent mesiodistal width of the six maxillary teeth in digital photographs, and their analysis yielded no golden proportions. In a study aimed at examining the "golden proportion", recurrent dental esthetics, and golden percentage in frontal standardized images of 56 dentistry students, Murthy and Ramani22 showed that the golden proportion does not exist in natural dentition.

The present study showed that none of the studied subjects had such proportions, taking into account that the width of the central teeth is considered to be 100% and that of the lateral teeth would correspond to 61.8%. It also showed that the difference between the actual measurements of upper lateral incisors and those obtained following the golden proportions range from 1.37 to 1.57 mm for the upper right lateral incisor and from 1.57 to 1.80 mm for the upper left lateral incisor. In other words, upper lateral incisors are narrower when the golden proportions are applied and when compared with the actual MD size of the same teeth.

The measurements made by Preston11 confirmed the unreal nature of the "golden rule", and his study showed some "over narrowing" of the maxillary arch and compression of the lateral segments when the golden rule is strictly applied.

The present study measured the mesiodistal diameter of the six upper anterior teeth in both men and women, establishing minimum, average, and maximum diameters with the respective percentiles for each tooth. If the tooth's mesiodistal diameter or the contralateral edentulous space is on or below percentile 20, it can be considered a small tooth, if is between 30 and 70, it is considered average, and above 70 is considered large.23

The results of the present study can be compared with the tables obtained by Sanin and Savara,23 who used plaster models to measure the mesiodistal diameter of all teeth, both upper and lower, with the exception of the third molar. These models corresponded to 51 men and 55 women of the University of Oregon School of Dentistry (USA). Their study refers to size and to teeth's discrepancies in mesiodistal width.

In terms of the mesiodistal diameter of anterior maxillary teeth, the results of the present study are very similar to those by Sanin and Savara.23

Sterrett et al7 showed that the average width of maxillary central incisors range from 8.3 to 9.3 mm and that the average length of a tooth with no incisal attrition ranges from 10.4 to 11.2 mm. In addition, the present study measured the gingivalincisal length of the six upper anterior teeth in men and women, establishing minimum, average, and maximum length with the respective percentiles for each teeth.

The study by Magne et al24 showed that central teeth width ranges from 9.10 to 9.24 mm and their length from 10.67 to 11.69 mm; lateral teeth width ranges from 7.07 to 7.38 mm and their length from 9.34 to 9.75 mm; and canines width ranges from 7.9 to 8.06 mm and their length from 9.90 to 10.83 mm.

To strictly establish ideal dental dimensions is difficult due to individual variations and to the amount of attrition of the incisal edge. As for ITR, it is obtained by dividing the crown's width (mesiodistal) by its length (gingival-incisal).5

In the present study, the most prevalent range of Individual Tooth Proportion of right and left upper central incisors in both men and women was › 80%. This study also found out that the average upper lip length in women is 21.41 mm and the lower lip 47.18 mm, the ratio between them being 1:2.2. In men, the average upper lip length is 22.78 mm and the lower lip 52.45, the ratio between them being 1:2.3.

Arnett and Bergman17 showed that, measured from the subnasal point to its lower edge, the upper lip is in average 19 to 22 mm in length, and the lower lip, measured from its top edge to the chin, measures between 38 and 44 mm. These authors claim that the normal upper lip-lower lip ratio is 1:2.

In 1998, Ahmad19 suggested that the gingival margins of the central incisor and the upper canine are located at the same level or slightly above the gingival margin of the lateral incisor. He also claimed that symmetry in the gingival line of the right side and the left side in the anterior sector is esthetically pleasing and harmonious.

The present study showed that in men and women, with or without orthodontic treatment, the most frequent position of the gingival margin is the incisal one, both on the right side and the left side. On the right side, it occurred in 70.8% of females and in 63.4% of males. On the left side it occurred in 69.0% of females and in 67.8% of males.

The upper lateral incisor's level of gingival margin with the most coincidence between the right side and the left side in a single individual was the incisal one. It occurred in 48 men (27 with orthodontic treatment and 21 without it) and in 63 women (44 with orthodontic treatment and 19 without it), which corresponds to 54.7% of the total sample. In 30.5% of the sample, the position of the gingival margin on the right side does not coincide with that of the left side in none of the sites.

Coincidence of the apical margins was found only in three men in the group without orthodontic treatment.

 

CONCLUSIONS

Taking into account the limitations of this study, the following conclusions can be drawn:

  • We found out that none of the subjects showed the golden proportions and that the upper lateral incisors are narrower from 1.37 to 1.80 mm when the golden proportion is applied and when compared with the actual MD size of the same teeth.

  • The most prevalent individual tooth proportion of the right and left upper central incisors in both men and women is › 80%.

  • The FML and the upper dental midline show 43.5% of coincidence in men with orthodontic treatment and 61.4% in men without it. For dental midlines, the coincidence was 26.1% in men with orthodontic treatment and 38.6% in men without it.

  • In women, the FML and the upper dental midline coincide in 63.2% of those with orthodontic treatment and in 62.2% of those without orthodontic treatment; dental midlines coincide in 23.5% of women with orthodontic treatment and 31.1% of those without orthodontic treatment.

  • The most frequent upper lateral incisor's position of the gingival margin was the incisal one, both in the right side and the left side in both sexes with or without orthodontic treatment, and the margin level that most commonly coincides between the two sides (right and left) of the same individual was the incisal.

  • In women, the average length of the upper lip was 21.41 mm and the lower lip was 47.18 mm, the ratio between them being 1:2.2. In men, the average length of the upper lip was 22.78 mm and the lower lip was 52.45 mm, the proportion between them being 1:2.3.

 

ACKNOWLEDGEMENTS

  • To the Polymer processing Laboratory, Polymer Material Group. Universidad de Antioquia. Coordinating Engineer: Diego H. Giraldo V. Tests performed by material engineers: Nadia Henao and Rubiela Montoya.

 

CONFLICTS OF INTEREST

The authors report not having any conflicts of interest.

 

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