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Full Length Article
Occlusal Development and Masseter Activity in Alpacas (Lama pacos)
Version of Record online: 6 NOV 2009
Copyright © 2009 Wiley-Liss, Inc.
The Anatomical Record
Volume 293, Issue 1, pages 126–134, January 2010
How to Cite
Williams, S. H., Sidote, J. and Stover, K. K. (2010), Occlusal Development and Masseter Activity in Alpacas (Lama pacos). Anat Rec, 293: 126–134. doi: 10.1002/ar.21016
- Issue online: 28 DEC 2009
- Version of Record online: 6 NOV 2009
- Manuscript Accepted: 10 JUL 2009
- Manuscript Received: 2 MAR 2009
- National Science Foundation. Grant Numbers: IOB-0520855, BCS-0241652
- tooth eruption;
Tooth eruption and the development of occlusion are significant ontogenetic changes in the masticatory apparatus of mammals. Here, we test the hypothesis that changes in masseter activity are correlated with increased occlusal contacts at major stages of dental development in the alpaca, Lama pacos. We compare electromyographic data from the superficial and deep masseter in infant and juvenile alpacas prior to and following m1 occlusion and from adults with full permanent dentitions. The pre-m1 and post-m1 occlusion groups exhibit similar masseter activity durations, chewing cycle durations, and with the exception of the balancing-side deep masseter, similar timing differences between the jaw muscles. On average, the balancing-side deep masseter fires significantly later in the post-m1 occlusion group. The m2–m3 group exhibits significantly longer chewing cycle length and an even later firing balancing-side deep masseter. Increased occlusion is also associated with an increase in the relative amount of working-side superficial and deep masseter muscle activity when compared with the balancing side muscles. Although the development of occlusal relations in infant and juvenile alpacas are associated with minor changes in masseter activation patterns, additional molar occlusal contacts increase chewing cycle duration resulting in concomitant changes in masseter recruitment patterns. Currently, we cannot rule out that musculoskeletal development influences masseter activity as demonstrated in other mammals. However, the data presented here indicate that alpacas have a relatively delayed onset of the adult motor pattern that may be correlated with changes in occlusal relations due to tooth eruption. Anat Rec, 2010. © 2009 Wiley-Liss, Inc.