3.2. COMPARACIÓN [SUPERTEL]
4.2.1. NIVEL DE SEÑAL [2] [L1]
Macaques, baboons, great apes and humans share a general order of permanent tooth mineralization: M l, II, 12, C, P3, P4, M2 and M3 (Swindler & Meekins 1991). Within this, the least stable mineralization sequence is P4 and M2. While these teeth typically begin to mineralize in this order, M2 often
completes subsequent developmental stages, such as crown completion and emergence before, or in tandem with, P4 (Swindler & Meekins 1991). In the pig-tailed macaque, M2 and P4 usually develop in tandem, although the molar may develop before the premolar, or, less frequently, after it (Swindler et al. 1982). The histological study of crown mineralization conducted by Dirks and colleagues (2002) on four baboons included two females, 73261 and 73436, that shared identical permanent tooth initiation sequences (Mi U I2 C P3 M2 P4 M3), where M2 initiated growth before P4. In these monkeys, as is the case in great apes, crown initiation sequences differed from crown completion sequence. The latter sequence differed between the above two female baboons (Mi M2 P3 [li P4] I2 C M3 in the first female and Mi UI2 [P3 P4 M2] C M3
in the second female) (Dirks et al. 2002). From their radiographic study of twenty baboons, Swindler and Meekins (1991) observed yet different crown completion sequences for Papio cynocephalus. These differences involved the earlier completion of both incisors, and the rather later completion of the second molar (Swindler & Meekins 1991). The P4 M2 sequence polymorphism occurred most frequently in humans, followed by (M2 P4) and, least frequently, by M2 P4 (Swindler et al. 1982). These sequence polymorphisms varied in frequency between taxa, and may indeed be shared among all higher primates, as well. However, Winkler et al. (1996) noted that, in the orang-utan, there appeared to be close parallels between the developmental stages of P4/4 and M2/2. Both teeth began to calcify at about the same time, and later, emerged in rapid succession (Winkler etal. 1996).
In their study of the crab-eating macaque, Bowen and Koch (1970) found that mineralization times of the permanent teeth were remarkably constant in the incisor, P4 and M2 teeth. These teeth began to mineralize at about 5 months (I) and 15 months (P4, M2), respectively (Bowen & Koch 1970). Crown completion times of M2, P4, II, 12, and M l were also remarkably consistent, and ranged from 11 months for the incisors to 27 months for the premolars and second molars (Bowen & Koch 1970). In the rhesus macaque, initial mineralization of the lower M2 occurred at just under or, in some cases, at approximately one year (Swindler 1962). In the baboon, ranges of M l crown completion were broader than those of crown initiation, encompassing 2 0 2 to
1991). The mean age that M l completed development was 2.4 years (Swindler & Meekins 1991). While the second molar was among the last teeth to mineralize, the third molar and canine were the final teeth to begin mineralization and complete development (Swindler & Meekins 1991).
In a dental study of baboons (Papio; one anubis hybrid, the other hamadryas-like), Dirks and colleagues (2002) found that daily enamel formation rates increased from the enamel dentine junction (EDJ) to the enamel surface, suggesting that tooth crowns formed at increasingly accelerated rates over time. Despite accelerated mineralization rates, the findings of Dirks et al. (2002) differed from those of Swindler and Meekins (1991), where baboon teeth demonstrated significantly shorter crown mineralization periods. Dirks et al. (2002) calculated the mean duration of M l crown formation for their baboon sample as 1.41 years, 0.5 to 0.7 years longer than the mean periods (for both males and females) registered by Swindler and Meekins (1991). In the same monkeys, the incisor and third molar crowns completed formation one year later, the premolar and second molar crowns 0.5 to 0.7 years later, and the canine crowns almost two years later than the top ages given by Swindler and Meekins (1991). These top ages, all from male baboons, were 2.33 (II, 12), 4.71 (M3), 2.47 (P3, P4), 1.13 (M l), and 2.64 (M2) years (Swindler & Meekins 1991). However, onsets of mineralization for every tooth but P4, M2 and M3 were within the ranges assessed by Swindler and Meekins (1991), most of which exceeded five months. Mineralization of the fourth premolar and second and third molars began after 0.95, 0.9, and 2.2 years of age, respectively, but no later than one year subsequent to these ages (Swindler & Meekins 1991).
Swindler and Meekins (1991) found that events in lower molar development occurred at “practically the same chronological time” in macaques (M. nemesthna) and baboons (P. cynocephalus). Swindler and Beynon (1993) noted that Theropithecus, a cercopithecid closely related to Papio, was rather similar to Papio and Macaca in “relative sequence and perhaps timing of ontogenetic events”. Development of the first permanent molars began slightly earlier in the baboon (Papio cynocephalus) than in the rhesus macaque, prior to 120 days In utero (Swindler & Meekins 1991). With the exception of M3, baboon permanent teeth took longer to develop than those of macaques
(Swindler & Meekins 1991). Indeed, Swindler and Beynon (1993) concluded that crown length “determines the overall period of crown formation”. It is interesting that, although the third molar crown is the longest among the permanent teeth of the baboon, this tooth formed faster in this animal than in the smaller-bodied macaque. Differences in rates of molar development among gibbons, siamangs, and baboons, which were relatively slower in the monkey, manifested themselves in variations in developmental rates of different molar teeth, or parts of these teeth (Dirks 1998).