INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)  
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue XI November 2025  
Distribution and Association of Lip Print Patterns with Dental  
Diastema in University of Port Harcourt Students  
Ibinabo Fubara Bob-Manuel, Gospel Uchechukwu Collins  
Faculty of Basic Medical Sciences, College of Health Sciences, University of Port Harcourt, Rivers State,  
Nigeria.  
DOI: https://dx.doi.org/10.51244/IJRSI.2025.12110025  
Received: 21 November 2025; Accepted: 28 November 2025; Published: 03 December 2025  
ABSTRACT  
Lip prints are unique patterns formed by the grooves on the labial mucosa and have been widely recognised as  
valuable tools in forensic identification and sex determination. Midline and other types of diastema, representing  
spacing between teeth, are also considered distinctive features in dental anthropology and forensic investigations.  
The present study aimed to examine the distribution of lip print patterns in relation to diastema types and to  
explore potential associations with sex. A cross-sectional study was conducted among 500 students of the  
University of Port Harcourt, comprising 301 females and 199 males. Lip prints were recorded and classified  
according to Suzuki and Tsuchihashi’s method into five types (I–V), while diastema was categorised as  
mandibular, maxillary, or combined. Data were analysed using descriptive statistics and chi-square tests to  
determine associations between variables. The results revealed that in females, type I lip print was most prevalent  
(68.44%), while in males, type II (48.74%) and type III (38.69%) predominated. Maxillary diastema was more  
common in both sexes, with mandibular diastema being rare. Chi-square analysis indicated a significant  
association between lip print type and diastema category in males (χ² = 21.321, p < 0.05), but not in females (χ²  
= 11.528, p > 0.05). Additionally, a significant relationship was observed between sex and lip print type (χ² =  
286.68, p < 0.05), confirming sexual dimorphism in lip patterns. In conclusion, lip prints demonstrate sex-  
specific distribution and, in combination with diastema patterns, may serve as reliable adjuncts for human  
identification and sex determination in forensic and anthropological contexts. These findings underscore the  
potential utility of cheiloscopy and dental morphology as complementary tools in forensic investigations.  
Keywords: Lip Prints, Diastema, Sex Determination, Cheiloscopy  
INTRODUCTION  
Accurate human identification is a crucial component of forensic science, especially in contexts involving mass  
casualties, criminal cases, and missing-person investigations. While conventional identifiers such as fingerprints,  
DNA, and dental records are widely utilised (1, 2), lip prints have received increasing interest as an additional  
biometric indicator. Cheiloscopy, the examination of lip-print patterns on the vermilion border, centres on the  
distinctive grooves and fissures that define each person (3, 2). Similar to fingerprints, lip prints feature unique  
ridge and furrow patterns, are established early in fetal development, mostly remain unchanged throughout one's  
life, and vary even among identical twins (4, 5). Due to their stability, permanence, and ease of collection, lip  
prints can serve as a dependable method for personal identification in forensic contexts, particularly when  
traditional evidence is compromised or unavailable.  
Diastema, or the gap between adjacent teeth, is a significant aspect in dentistry for both functional and aesthetic  
reasons (6). Maxillary midline diastema (MMD) refers to a gap that exceeds 0.5 mm between the erupted  
maxillary central incisors, measured from their mesial surfaces. It is among the known dental anomalies that can  
greatly impact an individual's oral health, aesthetics, and psychosocial well-being (7). Typically occurring  
between the upper central incisors, it can also be present in the lower jaw. Various factors can lead to this  
condition, including genetic predisposition, discrepancies between tooth size and jaw length, extra teeth, an  
abnormal upper labial frenum, and oral habits such as thumb-sucking or tongue thrusting (8). In many African  
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ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue XI November 2025  
communities, particularly among Nigerians, a maxillary midline diastema is prevalent, culturally accepted, and  
not necessarily addressed (9).  
Prior research has shown that there are notable variations in lip print types and diastema across different ethnic  
groups, age categories, and genders. Males generally possess longer and thicker lips compared to females (10,  
11, 7, 12). Research has underscored the importance of facial soft tissue landmarks in exploring occlusion, lip  
dynamics, and proportionality (13, 14).  
Despite advancements in forensic science and dental anthropology, there is a notable lack of information  
regarding the relationship between external morphological traits like lip prints and internal dental conditions,  
such as diastema, in Nigeria. This research aimed to assess the correlation between lip print patterns and the  
presence of diastema among the University of Port. Harcourt students.  
METHODOLOGY  
A cross-sectional, descriptive study design was employed to evaluate the association between lip-print patterns  
and the presence of diastema among undergraduate students at the University of Port Harcourt, Rivers State,  
Nigeria. A total of 500 students (301 females and 199 males), aged 16 to 30 years, were recruited. The sample  
size was calculated using Cochran's formula. Eligible participants had fully erupted anterior teeth and no history  
of orthodontic treatment or craniofacial trauma affecting the lips. Only subjects with the presence of a confirmed  
diastema were used; hence, students without a diastema were excluded. Students were drawn randomly from  
multiple faculties and departments to achieve balance by age and sex.  
Lip-print impressions were collected using dark-colored lipstick, strips of transparent cellophane tape, and white  
A4-sized bond paper. A magnifying hand lens was used for detailed examination. For diastema assessment, a  
mouth mirror and a millimetre ruler were used. Before recording, participants were asked to clean and dry their  
lips. Dark-colored lipstick was applied to the lips, and participants pressed their lips gently onto a strip of  
transparent cellophane tape; the tape was then transferred and affixed to a labelled area on white bond paper for  
permanent recording.  
Examination focused on the middle third of the lower lip. Lip prints were inspected with a magnifying hand lens  
and classified according to the Suzuki and Tsuchihashi system as follows: Type I, clear-cut vertical grooves;  
Type I prime, partial-length vertical grooves; Type II, branched grooves; Type III, intersected grooves; Type IV,  
reticular grooves; and Type V, undetermined patterns. Additionally, the oral anterior region was examined using  
a mouth mirror, and interdental spaces were measured with a millimetre ruler to determine the presence and  
location (maxillary or mandibular) of diastema.  
Figure 1: Suzuki and Tsuchihashi classification of lip prints (15)  
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ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue XI November 2025  
Each participant underwent an intraoral examination under natural daylight using a mouth mirror and a  
millimetre ruler. The presence of a diastema was recorded, with attention to its anatomical location in the dental  
arch: maxilla (upper jaw), mandible (lower jaw), or both. A gap of 0.5 millimetres or greater between adjacent  
anterior teeth was used to define a true diastema. A digital Vernier calliper was used to measure and confirm the  
presence of diastema. For this study, diastema was classified solely by its location within the dental arch  
(maxillary or mandibular).  
Recorded data were entered into Microsoft Excel and subsequently analysed using the Statistical Package for  
the Social Sciences, version 25. Descriptive statistics (frequencies and percentages) summarised categorical  
variables. Chi-square tests were used to evaluate associations between lip-print patterns and diastema type, with  
analyses stratified by sex where appropriate. A probability value less than 0.05 was considered statistically  
significant.  
Ethical approval for the study was obtained from the Research Ethics Committee of the University of Port  
Harcourt. Participation was voluntary, and informed consent was obtained from all participants. Participant  
confidentiality and anonymity were preserved throughout data collection and analysis.  
RESULTS  
The results of the study were presented in tables as follows:  
Table 1: Distribution of lip print patterns by diastema category among females.  
Lip Prints  
Types of Diastema  
Man. D  
Combined  
Max. D  
n(%)  
Total  
n(%)  
n(%)  
n(%)  
Type I  
-
52(25.24)  
5(21.74)  
4(30.77)  
4(19.05)  
13(34.21)  
78(25.91)  
154(74.76)  
18(78.26)  
9(69.23)  
16(76.19)  
24(63.16)  
221(73.42)  
206(68.44)  
23(7.64)  
13(4.32)  
21(6.98)  
38(12.62)  
301(100.00)  
Type II  
Type III  
Type IV  
Type V  
Total  
-
-
1(4.76)  
1(2.63)  
2(0.66)  
Man D= Mandibular Diastema; Max D= Maxillary Diastema; n= Sample Size; %= Percentage.  
The result shows that out of the 301 female participants, 73.42% exhibited maxillary diastema, 25.91% had  
combined (Maxillary and Mandibular) diastema, and only 0.66% had mandibular diastema. Lip print pattern  
analysis revealed that Type I was the most predominant among females, accounting for 68.44%.  
Table 2: Distribution of lip print pattern by type of diastema in males  
Lip Prints  
Types of Diastema  
Man. D  
n(%)  
Combined  
n(%)  
Max. D  
n(%)  
Total  
n(%)  
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)  
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue XI November 2025  
Type I  
1(10.00)  
2(20.00)  
24(24.74)  
22(28.57)  
3(42.86)  
1(12.50)  
52(26.13)  
7(70.00)  
73(75.26)  
55(71.43)  
4(57.14)  
10(5.03)  
97(48.74)  
77(38.69)  
7(3.52)  
Type II  
Type III  
Type IV  
Type V  
Total  
-
-
-
-
7(87.50)  
8(4.02)  
1(0.50)  
146(73.37)  
199(100.00)  
Man D= Mandibular Diastema; Max D= Maxillary Diastema; n= Sample Size; %= Percentage.  
The analysis revealed that of the 199 male participants, 73.37% presented with maxillary diastema, 26.13% had  
combined (Maxillary and Mandibular) diastema, and only 0.5% had mandibular diastema. The most common  
lip print pattern among males was Type II, accounting for 48.74% of the male sample.  
Table 3: Chi-square test of independence between lip Print Type and Diastema Category in Females.  
Lip Prints  
Types of Diastema  
Total  
ꭕ2  
p-  
Inference  
value  
Man. Combined Max. D  
D
df calculated Critical  
at α =0.05  
TYPE I  
TYPE II  
TYPE III  
TYPE IV  
TYPE V  
Total  
0
0
0
1
1
2
52  
5
154  
18  
9
206  
23  
8
11.528  
15.507  
p>0.05  
Not  
Significant  
4
13  
4
16  
24  
221  
21  
13  
78  
38  
301  
Man D= Mandibular Diastema; Max D= Maxillary Diastema; df= Degree of Freedom; X2= Chi-square value.  
The test result shows a calculated Chi-square value of 11.528 with eight degrees of freedom, compared against  
a critical value of 15.507 at a 0.05 significance level. Since the calculated value is less than the critical value,  
the result indicates that there is no statistically significant association between lip print type and the type of  
diastema among females. This implies that variations in female lip print patterns do not have a meaningful  
relationship with whether the diastema occurs in the maxilla, mandible, or both.  
Table 4: Chi-square test of independence between lip print type and diastema category in males.  
Lip Prints  
Types of Diastema  
Total  
ꭕ2  
p-  
Inference  
value  
Man. Combined Max.  
df calculated Critical  
D
D
at α  
=0.05  
TYPE I  
1
2
7
10  
8
21.321  
15.507  
p<0.05 Significant  
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)  
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue XI November 2025  
TYPE II  
TYPE III  
TYPE IV  
TYPE V  
Total  
0
0
0
0
1
24  
22  
3
73  
55  
4
97  
77  
7
1
7
8
52  
146  
199  
Man D= Mandibular Diastema; Max D= Maxillary Diastema; df= Degree of Freedom; X2= Chi-square value.  
The analysis reveals a calculated Chi-square value of 21.321 with eight degrees of freedom and a critical value  
of 15.507 at the 0.05 level of significance; hence, a significant association was observed.  
Table 5: Chi-square test of independence between sex and lip print type.  
Sex  
Lip Prints  
Tota  
l
ꭕ2  
p-value Inference  
Typ Type Type Type Typ  
df Calculate Critical  
e I  
II  
III  
IV  
e V  
d
at α  
=0.05  
Femal  
e
206  
23  
13  
21  
38  
301  
4
286.68  
9.488  
P<0.05 Significan  
t
Male  
Total  
10  
97  
77  
90  
7
8
199  
500  
216  
120  
28  
46  
df= Degree of Freedom; X2= Chi-square value.  
DISCUSSION  
The present study examined the distribution of lip print patterns in relation to the type of diastema among males  
and females. In females, type I lip print was the most prevalent (68.44%), followed by type V (12.62%) and type  
II (7.64%). Among males, type II was the most frequent (48.74%), followed by type III (38.69%) and type I  
(5.03%). These findings indicate a clear sexual dimorphism in lip print patterns, with type I dominating in  
females and type II in males. The chi-square analysis further confirmed a significant association between sex  
and lip print type (χ² = 286.68, p < 0.05), indicating that lip prints may serve as a reliable indicator for sex  
determination in forensic and anthropological contexts. These results align with prior findings by Jaber et al.  
(16), who reported that type I lip prints were predominant in females (36.5%) while type III and II were more  
common in males (30.2% and 29.9%, respectively), highlighting the potential of cheiloscopy as a tool for human  
identification.  
Regarding the relationship between lip print patterns and diastema, in females, type I lip print was most  
commonly associated with maxillary diastema (74.76%), while mandibular diastema was rare across all types.  
The chi-square test showed no significant association between lip print type and diastema category in females  
(χ² = 11.528, p > 0.05), suggesting that lip print patterns in females are largely independent of diastema type. In  
contrast, in males, type II and III lip prints were predominantly associated with maxillary diastema (75.26% and  
71.43%, respectively), and the chi-square test revealed a significant association (χ² = 21.321, p < 0.05). This  
indicates a potential predictive relationship between lip print type and diastema occurrence in males, which may  
reflect underlying genetic or developmental factors influencing both lip morphology and dental spacing.  
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The prevalence of diastema observed in this study also corresponds with earlier research on midline diastema.  
The majority of diastema cases in both sexes were maxillary, with mandibular diastema being relatively rare.  
This pattern is consistent with reports by Erfan et al. (17) and Modak et al. (18), who observed a higher frequency  
of maxillary midline diastema in comparison to mandibular. While Erfan et al. (17) reported a slightly higher  
prevalence in males, Modak et al. (18) noted a higher prevalence in females, which aligns with the current study’s  
findings showing more maxillary diastema in females. Additionally, Al-Zazai et al. (7) emphasised that gender  
differences exist in the aetiology and prevalence of diastema, with males exhibiting higher generalised spacing  
and females showing a higher incidence of specific types of diastema, such as maxillary midline diastema.  
The present findings also compare with previous studies on lip print patterns in broader populations. Paul et al.  
(15) and Sangam et al. (19) reported type II as the most common lip print overall, followed by type I, whereas  
in this study, type I predominated in females. This difference may be attributed to population-specific genetic  
factors and sample characteristics. Overall, these results reinforce the uniqueness of lip prints and their potential  
forensic utility, while highlighting the influence of sex and dental features, such as diastema, on lip print  
distribution. Future studies with larger and more diverse populations are recommended to further validate the  
observed associations and explore the underlying biological mechanisms linking lip morphology and dental  
spacing.  
CONCLUSION  
Based on the findings of this study, it can be concluded that lip print patterns exhibit clear sexual dimorphism,  
with type I being the most prevalent in females and type II and III being more common in males. Maxillary  
diastema was the predominant type in both sexes, while mandibular diastema was relatively rare. A significant  
association was observed between lip print type and diastema category in males, but not in females, suggesting  
potential sex-specific relationships between lip morphology and dental spacing. Overall, the results indicate that  
lip prints, in combination with diastema patterns, can serve as useful adjuncts for sex determination and human  
identification in forensic and anthropological investigations.  
Conflict of Interest Statement  
The authors declare that they have no known financial, personal, or institutional conflicts of interest that could  
have influenced the work reported in this study.  
Data Availability Statement  
The data supporting the findings of this study are available from the corresponding author upon reasonable  
request.  
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