Non-significant differences in the rugae shape between the two genders in the two studied groups were observed. These findings are partially in agreement with Azab et al., (2015) who found, in a study based on Egyptian sample, that the most frequent shape was the wavy shape (sinous shaped rugae in the current study), followed by the straight (line shaped rugae in the current study) and finally curved and circular shape rugae. The median values for the line, curve, and sinous shaped rugae were 1, 2, 3 rugae for Egyptian males and 2, 2, 3 rugae for Egyptian females.
The results of this study are inconsistent with Fahmi et al., (2001) who observed that Saudi males had significantly higher circular shaped rugae then Saudi females while other patterns were non-significantly different. Furthermore, ELamin et al., (2015) reported that Sudanese females possessed significantly greater sinous shaped rugae than the males.
Additionally, Gondivkar et al., (2011) showed that females had significantly greater sinuous shaped rugae than males among Indian populations. Furthermore, Saraf et al., (2011) demonstrated that circular type of rugae was significantly greater in males among Indian populations.
The conflict between the present study and some literature regarding the rugae shapes may be attributed to the racial differences or to the negligence of the rugae less than 5 mm. (secondary rugae) in some previous research but this study involved these small rugae. Secondary rugae (3-5 mm.) were as important as the primary ones in estimating different rugae shapes and counts. In this current study, all fragmentary rugae were considered as point shaped and were excluded from rugae shape analysis as they may be confused with artifacts.
Thomas and Kotze (1983) mentioned that although primary rugae had been more extensively studied than secondary and fragmentary rugae, the discrimination between humans was more dependent on the secondary and fragmentary rugae. Moreover, Kolude et al., (2016) revealed that secondary rugae were considered as superior to primary rugae in the field of identification.
Respecting the Egyptians in this present study, line shaped rugae were the most frequent rugae shape (76.67%), followed by curve shaped rugae (16.67%) and lastly sinous shaped rugae (6.66%). In the Malaysians, Curves (36.67%), sinouses (33.33%) and lines (30%) were the most frequent rugae shapes respectively. Circularly shaped rugae were the least frequent rugae pattern among both genders and both races, furthermore, none of the Malaysian males possessed this pattern of rugae. Significant results were observed among males and females. Malaysian males showed significantly greater curve shaped rugae, sinous shaped rugae and complexly shaped rugae than Egyptian males. Concerning the females, the Egyptians had significantly greater line shaped rugae while the Malaysians had significantly greater sinous shape rugae than the Egyptians.
The results of this current study partially agree with Abdellatif et al. (2011) who observed that both sexes of Egyptian and Saudi volunteers had insignificant differences regarding rugae shape. Surprisingly, they noted that Egyptians had significantly higher curve shaped rugae than Saudis who showed significantly higher sinous shaped rugae. The differences may be attributed to the different rugae patterns classifications used in each study. They consider cross linked, convergent and divergent rugae as separate rugae patterns which were not the same condition in this study. However and consisting with the current study, the curve, line and sinous shape rugae remained the most frequent rugae types while circularly shaped rugae were the least frequent shape among both Egyptians and Saudis.
This study coincides with Indian results as Shetty et al. (2005) observed that Indian males showed more curved rugae than Tibetan males while Tibetan females showed significantly greater sinous shaped rugae than Indian females. Also among Indians, Nayak et al., (2007) selected their volunteers from two geographically different regions (Southern and Western populations). Wavy, curved and straight rugae were the most common rugae shapes respectively among two groups of Indian populations although the relationship between sex and rugogram failed to be established as non-significant differences between both males and females regarding rugae shape were observed, they noticed that Southern Indians had significantly greater straight and curve shaped rugae than Western Indians. Variations in the rugae pattern even among the same race populations living in the different areas may be attributed to the fact that the formation of palatal rugae is a process of environmental and genetic backgrounds.
This study partially agrees with Paliwal et al., (2010) who observed that. In Indian populations, the most frequent rugae shapes were lines, curves, and sinouses, however, this study showed these patterns in a different arrangement. Paliwal et al., (2010) reported that wavy pattern (sinous shaped) followed by curved and lastly straight or line shaped rugae were the most frequent rugae patterns among Indian populations. Furthermore, they mentioned that Kerala populations had significantly greater sinous shaped rugae than Madhya Pradesh population who had more line shaped rugae.
The absence of circularly shaped rugae among Malaysian males in the current study coincides with Verma et al., (2014) who reported that circular rugae were absent in one Indian population while they constituted only 0.6% of the total rugae patterns in the other studied two populations.
Sivaraj (2013) considered the complexly shaped rugae as a strong positive identification tool thought to be more important than other rugae patterns. That was attributed to the fact that these bizarre shapes were almost unique and non-repeatable. This study agrees with this finding as Malaysian males showed significantly greater complex shaped rugae than the Egyptian males.
Regarding rugae direction in the present study, Egyptian males had a higher percentage of forwarding directed rugae (90%) than females (76.70%) while Malaysian females showed a higher percentage of forwarding directed rugae (80%) than the Malaysian males (66.70%). Variations in rugae direction among males and females of the same race were non-significant.
These results coincide with those obtained by Azab et al., (2015) as forwarding directed rugae were more frequent than backward directed rugae in Egyptian males and females. The results of this study are partially in agreement with Ahmed and Hamid (2015) results who observed the predominance of forwarding than backward directed rugae. However, they mentioned that Sudanese males had significantly greater forwarding directed rugae than the Sudanese females.
Gondivkar et al., (2011) & Jibi et al., (2011) noticed that forwarding directed rugae were more frequent than backward directed rugae and no significant differences were observed between Indian males and females regarding rugae direction.
The results of this study are compatible with results of Goyal and Goyal (2013) who found that forwardly directed rugae (48.3% in the males and 40.8% in the females) were more common than backwardly directed rugae (17.8% in the males and 19.6% in the females) among Rwandan populations. Additionally, non-significant differences between both sexes were noticed.
Regarding rugae direction, it was observed that forwarding directed rugae (83.30%) were more frequent than the backward directed ones (16.70%) among Egyptians. Forward directed rugae (73.30%) were more frequent than backward directed rugae (26.70%) among Malaysians as well. The Egyptian male showed significantly different distribution when compared with the Malaysian males. On the other hand, no significant differences were observed when the Egyptian females and Malaysian females were compared with each other.
The results of this study are partially in agreement with Reddy et al., (2014) who reported that forwardly directed rugae were more common among South Indians (90%) and North Indians (70%) than backwardly directed rugae (10% and 30%) for South and North Indians respectively while Chinese showed equal distribution of both types of rugae. In all conditions, these variations were not significant.
The significant racial differences among Egyptian and Malaysian males as regards to rugae direction in this study are different from Jibi et al., (2011) who reported non-significant differences between Muslims and Hindus regarding rugae direction.
Regarding the unification status in this study, divergent rugae were more frequent than convergent rugae. The divergent rugae were more frequent than convergent rugae among males and females in both Egyptian and Malaysian group with no significant differences.
The results of this study partially agree with the results obtained by Azab et al., (2015). The mean value of Egyptian males in the current study was 0.600 ± 0.621 divergent rugae which was the same (0.67 ± 0.78) as Azab et al., (2015) while the mean value of male was 0.200 ± 0.484 convergent rugae which was far from that (1.48 ± 1.42 convergent rugae) of Azab et al., (2015) as they noticed that convergent rugae were more frequent (mean value: 1.49 ± 1.56 rugae) than divergent rugae (mean value: 0.63 ± 0.77 rugae) among Egyptians. In all conditions, both studies observed that these variations were not significant. Moreover, Ibeachu et al., (2015) denied the impact of sex in unification status as they reported non-significant differences among Nigerian males and females.
The previous results of this study are inconsistent with Fahmi et al., (2001) who conducted their study among Saudis and found significant differences between different sexes. The mean values of convergent rugae were 15.1 ± 14.4 and 8.6 ± 12.4 in Saudi females and males respectively. Furthermore, ELamin et al., (2015) mentioned that the mean value of Sudanese male was 1.2 ± 1 convergent rugae which were significantly greater than the females (0.9 ± 1.1).
The results of this study regarding unification status are not in line with the Indian results. Saraf et al., (2011) observed that converging rugae were significantly greater in females (2 as a median value) than males of the same nationality (zero as a median value). Additionally, Bharath et al., (2011), Jibi et al., (2011) & Babu et al., (2013) conducted their study in India and concluded that males had significantly more convergent rugae than the females that showed a higher incidence of divergent rugae than the males. Chopra et al., (2013) reported that Indian females exhibited significantly greater divergent rugae count than the Indian males.
In this study, divergent rugae were more common than convergent rugae in both Egyptians and Malaysians. In Egyptian group, 42 divergent rugae were observed compared to 13 convergent rugae. Malaysian group possessed 42 divergent rugae while convergent rugae were 21 rugae. Moreover, this study revealed non-significant variations between both Egyptian and Malaysian races.
These findings are inconsistent with Abdellatif et al., (2011) who reported that diverging rugae were significantly higher in number among Saudi populations while converging rugae were significantly higher among Egyptians. Saudi populations possessed (27) divergent compared to (8) convergent ones while Egyptians had (15) and (23) divergent and convergent rugae respectively.
Results obtained in this study go in the same direction as those obtained by Reddy et al., (2014) who conducted their study among South and North Indians and among Chinese. All the three groups had more divergent rugae than convergent ones. They had 17 divergent rugae (56.7%) versus 4 convergent rugae (13.3%). Non-significant differences between both races were observed.
The variation in between this study and previous studies regarding the rugae unification status may be due to racial differences or due to different classifications used in each research. Most of the previous studies classified rugae patterns into three or four rugae patterns (line, curve, sinous and sometimes circular) and discarded angled shaped rugae from their classifications. They considered the convergent and divergent rugae as additional patterns (Chopra et al., 2013). Further studies with greater numbers of subjects are required to verify the findings in this study.