Purpose: Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics. Method: The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (f[subscript Rn]). The f[subscript Rn] were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing. Results: Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs. Conclusions: To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation.