Dietary Consistency and Midline Sutures: A Study in Growing Pigs

Objectives: Previous studies have suggested that transverse facial growth is reduced in animals fed a soft diet, implying an effect on midline sutural growth. Sutural morphology, as well as growth rate, may reflect masticatory loading. The purpose of the present study was to test whether reduced masticatory function from a soft diet would retard midline suture growth and alter sutural morphology in growing pigs. Methods: 10 farm pigs and 10 minipigs, all male and divided between hard and soft diet groups, were given fluorochromic bone labels and sacrificed after 12 weeks. Undecalcified coronal sections of the interparietal, interfrontal, internasal and intermaxillary sutures, alternately stained with toluidine blue or mounted unstained, were evaluated for bone thickness and quantity, sutural complexity and sutural growth rate. After controlling for weight gain, differences between breed and dietary groups were evaluated for each suture location and for all locations considered together with linear regression models. Variables that did not satisfy linear regression model assumptions were analyzed using the Wilcoxon rank sum test. Results: Animals fed a soft diet were characterized by a slower rate of weight gain, significantly so for farm pigs (p=0.03). Few comparisons of individual sutures reached statistical significance, but when all locations were considered together, soft diet pigs of both breeds had significantly (p<0.001) less bone quantity and sutural thickness than their hard diet counterparts. Sutural growth rate could only be assessed in farm pigs, but was also found to be reduced with a soft diet (p=0.002) even after correction for weight gain. However, no difference in sutural complexity was detected. Conclusion: Restriction to a soft diet reduces midline suture growth and bone apposition in the growing pig, but does not alter sutural morphology. Supported by the UW Orthodontic Alumni Association, the American School of Prehistoric Research, and NIDCR award DE08513.