Cinzia Fornai

Under the obstetrical dilemma hypothesis, sexual dimorphism in pelvic shape is a solution to accommodate high fetopelvic constraints. It is therefore unclear why chimpanzees display a human-like pattern of pelvic sexual dimorphism despite having easier births enabled by small neonates and capacious pelvic canals. Here we reassessed chimpanzee fetopelvic fit using three-dimensional simulations, revealing a similarly constricted midpelvis as in humans, with even narrower outlet dimensions. Geometric morphometric analyses confirm that female chimpanzees have larger pelvic canals than males despite a smaller body size and a morphology that maximizes pelvic dimensions favourable for parturition, particularly in smaller-bodied individuals. Together with evidence for increased neurological immaturity at birth relative to monkeys, our findings imply substantial obstetric constraints in chimpanzees and possibly other apes. We therefore propose that difficult birth did not arise abruptly in Homo with increasing encephalization but evolved gradually through a series of obstetric compromises from an already constricted birth canal shared across anthropoid primates. Specifically, we propose that obstetric selection pressures exacerbated incrementally with the stiffening of the symphysis that accompanied body size increase in hominoids, while subsequent adaptations to bipedalism shortened the ilium. The resulting contorted birth canal required obligatory fetal rotation, thus greatly increasing birth difficulty.

Morphological covariation within the modern human postcanine dentition remains an open field of study. Analysis of covariation patterns of the three-dimensional (3D) shape between different tooth types has been seldom conducted, but it is relevant for the advancement of human biology and evolution, as well as dental anthropology, phylogeny, and medicine. Here, we analysed 3D shape covariation of the postcanine dentition (excluding third molars), both within and between dental arches using geometric morphometrics (GM). Based on high-resolution (µCT) scans of 526 teeth from 136 individuals we found high pairwise correlation in tooth pairs within the dental arches (lower P3 and P4, r ₁ = 0.89; upper P3 and P4, r ₁ = 0.81; upper M1 and M2, r ₁ = 0.86). The correlation values between antagonists varied notably from the highest value detected between upper and lower M1s (r = 0.9), to the lowest between upper P4s and lower M1s (r = 0.58). Of all analysed tooth types, only the upper M1s showed moderate to high correlation in every pair analysis. Noticeably, unusually high covariation was detected between some of the tooth type pairs that do not articulate in a normal dentition (e.g., lower P3 and upper M2, r ₁ = 0.88). Furthermore, a relatively high covariation was found in the pairs of lower P4s and M1s (r ₁ = 0.79), and upper P4s and M1s (r ₁ = 0.77), which are the only tooth type pairs of the postcanine dentition belonging to different tooth classes (premolars and molars, respectively) and still serving similar masticatory functions. This study points to the fact that higher morphological integration seems to characterize teeth within the same dental arch rather than between antagonistic teeth. With this study, we provided an overview of pairwise correlations and strength of covariation between different tooth types. This information might inform future studies aimed at understanding developmental, phylogenetic, and functional aspects of the human postcanine dentition, including possible phenotype-genotype associations. However, with this study being the first one performed on a 3D sample of this size, we also report on obstacles and peculiarities that have been determined.

Varios aspectos del sistema craneomandibular deben ser investigados para profundizar nuestra comprensión de las causas próximas y evolutivas de las enfermedades orales más comunes en poblaciones humanas. Las poblaciones de América Central y América del Sur se ven afectadas por una elevada prevalencia de caries y, en general, padecen una salud bucodental deficiente. Por otra parte, tienen un acceso limitado a la atención sanitaria profesional, lo que hace aún más urgente la necesidad de centrar la investigación en estas regiones. Dada la naturaleza multifactorial de los determinantes que subyacen a las enfermedades bucodentales, y considerando la complejidad del sistema estomatognático, el trabajo interdisciplinar entre antropólogos, odontólogos, especialistas en dolor orofacial, entre otros, parece ser el más adecuado para llevar a cabo investigaciones que aborden las enfermedades bucodentales más comunes y sus posibles efectos funcionales y sociales en el individuo. Antropólogos y odontólogos comparten un interés común en el sistema craneomandibular, su variación morfológica y sus dolencias, y tradicionalmente han utilizado métodos similares para su investigación. Combinando los diferentes conjuntos de habilidades que poseen, estos profesionales podrían trabajar sinérgicamente para generar conocimientos relevantes que apoyen a las partes interesadas y puedan llegar a los responsables políticos de la atención de la salud bucodental. Su estrecha colaboración ayudaría a identificar los problemas de salud más relevantes, recopilar datos epidemiológicos y comprender sus implicaciones en el bienestar individual, respondiendo así a las necesidades de las poblaciones de estudio y cumpliendo la normativa ética local.

The stomatognathic structures act as a complex and integrated system, thereby accomplishing several essential functions of the body. Aside from participating in food digestion, they are key for respiration and swallowing and play a central role in social interaction and stress management. The lifeworks of Robert M. Ricketts (1920–2003), an American orthodontist, and Rudolf Slavicek (1928–2022), an Austrian prosthodontist, were centered on this understanding. Both were educated in the time of gnathology, functional dentistry, and cephalometry and were ready to challenge conventional knowledge and traditions, leading toward innovation. As untiring clinicians, researchers, and mentors, they were fully invested in the study of the stomatognathic system, considering its morphology, dynamics, growth patterns, evolution, and interactions with the body and mind. Based on their extensive knowledge of the masticatory system, they advanced dentistry both with theoretical notions and by implementing new diagnostic and therapeutic concepts, thus reinforcing the idea of dentistry as a medical discipline requiring interdisciplinary effort. Their heritage is represented by numerous publications, discoveries, and inventions that inspire the dental community to follow their exemplary approach to the individualized care of patients. Their knowledge and passion are further passed on through their students. As part of their legacy, they prepared the ground for new research aimed at fostering advancements in occlusion medicine, hence supporting education in oral health.

Myofascial pain diminishes the stomatognathic function and hinders clinical diagnosis. Therefore, initial pain reduction is crucial before definitive treatment. Here, the clinical validity of non-p...

Objectives The practice of premolar extraction in orthodontics is controversial for its potential detrimental effects on the stomatognathic system. However, the ways in which premolar extraction affects mandibular function are still poorly understood. The purpose of this study was to assess the influence of premolar extraction on mandibular kinematics by evaluating axiographic tracings. Materials and Methods Forty-five orthodontically treated patients with premolar teeth extraction were compared with 45 paired untreated controls, selected for the absence of malocclusions. Systematic three-dimensional axiographic recordings of the mandibular movements were performed for protrusive–retrusive movements and speech. The transversal deviations and length of the movements were recorded for both sides along with the rotation angle during speech. Statistical Analysis Differences between the axiographic variables were analyzed via the permutation test and Wilcoxon rank-sum test. Linear regression was performed to test whether axiographic parameters were predictive of group affiliation. Dot plots were used to explore the distribution of each of the axiographic outcomes, and isometric principal component analysis to assess the differences between the cumulative effects of premolar extraction on jaw motion. Results The mandibular lateral translation in protrusion–retrusion and speech, the amount of rotation as well as the length of mandibular movements during speech were significantly higher in the treated subjects than in the controls, while retral stability did not differ. The linear regression yielded significant results for the mandibular lateral translation in protrusion–retrusion. The isometric principal component analysis showed higher values of the axiographic variables for 11 out of 45 individuals in the study sample compared with the control group. Conclusions Premolar extraction altered mandibular kinematics in at least 25% of the cases within our sample, and the transversal discrepancy between protrusive and retrusive tracings was even predictive of group affiliation. These results support the notion that the routine practice of premolar extraction as part of the orthodontic treatment should be discouraged. It is compelling to perform further studies to assess whether a disrupted kinematics of the mandible is associated to temporomandibular disorders.

The recent review article by Zonnenberg, Türp and Greene ‘Centric relation critically revisited – What are the clinical implications’? opens an important debate by addressing topics of central relevance in Dentistry, namely the relationship between occlusion and the condyle‐to‐glenoid‐fossa position, and the need for diagnostic assessment and therapeutic alteration of the condylar position in orthodontic patients. Zonnenberg, Türp and Greene concluded that the mandibular condyle is correctly situated in most orthodontic patients. Thus, in their view, orthodontists can disregard this aspect during treatment, and rely on the plastic properties of the masticatory supporting structures, while aiming at finishing the cases in a good occlusal relationship.We think that this approach fails to consider that biological variation of the stomatognathic structures can also be pathological and that, as dental occlusion determines condylar relative position within the glenoid fossa, changes in the occlusion are likely to alter the original condylar‐to‐glenoid‐fossa relation. Hence, we claim that whenever the occlusal relationship must be changed, the clinician should carefully monitor the condyle position and the mandibular function to prevent possible iatrogenic effects.To advance the discourse on the topic, we invite Zonnenberg, Türp and Greene to clarify their definition of ‘average patient’ and their interpretation of ‘full‐mouth orthodontic and orthognathic treatment’, their understanding of ‘biologically acceptable condylar relationship’, their justification of maximum intercuspation as reference position, the extent to which they think it is safe to rely on the TMJ resilience, and finally their alternative to centric relation in the treatment of patients needing condylar repositioning.

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genusHomoand the increase in encephalization.