Dental Reduction Research Articles

From teeth to pad: tooth loss and development of keratinous structures in sirenians.

Sirenians are a well-known example of morphological adaptation to a shallow-water grazing diet characterized by a modified feeding apparatus and orofacial morphology. Such adaptations were accompanied by an anterior tooth reduction associated with the development of keratinized pads, the evolution of which remains elusive. Among sirenians, the recently extinct Steller's sea cow represents a special case for being completely toothless. Here, we used μ-CT scans of sirenian crania to understand how motor-sensor systems associated with tooth innervation responded to innovations such as keratinized pads and continuous dental replacement. In addition, we surveyed nine genes associated with dental reduction for signatures of loss of function. Our results reveal how patterns of innervation changed with modifications of the dental formula, especially continuous replacement in manatees. Both our morphological and genomic data show that dental development was not completely lost in the edentulous Steller's sea cows. By tracing the phylogenetic history of tooth innervation, we illustrate the role of development in promoting the innervation of keratinized pads, similar to the secondary use of dental canals for innervating neomorphic keratinized structures in other tetrapod groups.

Few dental indices in modern Bulgarian population from southern Bulgaria

AimThe aim of the present study is to evaluate the reduction of the distal teeth towards the medial ones in one functional dental group in southern Bulgarian population.Materials and methodsThe study included 232 Bulgarians aged 20–40 years. Mesiodistal dimensions of the teeth were measured by Dentistry Sliding Vernier Caliper and analyzed with SPSS 23.0. Four interdental indices were calculated: inter-incisive, premolar, upper, and lower molar indices.ResultsWe found a decrease in the percentage ratio of the lateral to the central incisors of people from the Bulgarian population compared to those dating from the Eneolithic period on the territory of Bulgaria. Furthermore, we found a reduction in the percentage ratio of the upper and lower second molars compared to the first ones. The biggest reduction in the percentage ratio (more than 6%) was found in the lower second premolars compared to the first ones, which is characteristic for southern Bulgarians.ConclusionThere was a dental reduction in all the distal members compared to the medial ones participating in one morphological dental group. As a result, we think that interdental indices can be used for explaining historical, cultural, and biological macro and microevolutionary processes and thus for understanding the origin, formation, contacts, and migration pathways of the different populations leading to ethnic variation of humanity. Therefore, they can be a reliable source of information in physiological anthropology.

Association of clinical, social and environmental variables with dental caries prevalence in adolescents from a Brazilian municipality supplied with fluoridated water

Abstract Background Although a trend towards dental caries reduction has been observed, further investigations on its pattern and development are still needed. Objective To investigate the influence of clinical, social and environmental variables on dental caries prevalence in adolescents from a Brazilian municipality supplied with fluoridated water in 2018. Method This study was conducted with a non-probabilistic sample of 277 adolescents aged 12 years of public schools in Nova Friburgo, state of Rio de Janeiro, Brazil. Clinical examinations were carried out by calibrated examiners to assess caries, periodontal disease, and fluorosis according to criteria of the World Health Organization (WHO). Semi-structured questionnaires were applied to record socio-environmental information. Results Individuals living in regions supplied with fluoridated water below the minimum required levels (OR=3.60, p=0.0006), with low income (OR=1.90, p=0.0444), presence of gingivitis (OR=3.36; p=0.0016), and whose reason for visiting the dentist was dental treatment (OR=2.41; p=0.0203) were more likely to have dental caries. A significant reduction (p<0.0001) in dental caries indexes was observed between 2012 and 2018. Conclusion Fluoridation of public water supply at unsuitable levels, as well as other social and clinical variables can influence the caries pattern in adolescents.

Third Molar Agenesis in Post-Medieval Chichester

Third molar agenesis is a dental anomaly that occurs in approximately 25% of people worldwide and results in the complete absence of one or more of the third molars in the dentition. A rise in the prevalence of congenitally absent third molars has been noted in modern populations, and it has been proposed as the final evolutionary step in the dental reduction of the human dentition. 
 Whilst much research has been conducted in modern cohorts, relatively little has been published on third molar agenesis in archaeological assemblages. A post-medieval assemblage from Chichester was visually and radiographically analysed to determine the prevalence of this anomaly. Third molars were measured to determine if there was an association between agenesis and size reduction. Prevalence of agenesis was found to be relatively high at 42.7% and 2 of 8 measurements were found to produce significant differences.
 Consequently, it can be said that high rates of third molar agenesis are not solely a modern phenomenon, as many prevalence rates in recent populations are lower. However, if we are to assess the significance of size differences in third molars of those with agenesis and those without, and to detect patterns within and between these groups, assemblages with larger sample sizes are needed. In order to better understand the trajectory and evolution of this anomaly, more archaeological assemblages must be examined.

Treatment of gunshot-related mandibular fracture with splint-guided reduction: Case report

Background/Aim: Gunshot injury-related mandibular fractures often have a complex pattern, characterized by comminution, bone loss, and soft-tissue avulsion. The management is difficult and varies between individual cases. Case Report: A 41-year-old male patient presented with marked swelling and ecchymosis in the left mandibular region. Intraorally, he had a deviated open bite on the left side. A unilateral comminuted mandibular fracture was diagnosed by panoramic radiograph and computed tomography. An acrylic dental splint-guided open reduction and internal fixation, including intermaxillary fixation through brackets and intermaxillary elastics, was planned. No complications were observed throughout the healing period, and healing at the fracture site was satisfactory. The occlusion returned to the pre-injury position and was stable. Conclusions: This case report shows that successful functional and esthetic results can be achieved with a strict patient-specific treatment protocol for a comminuted mandibular fracture due to gunshot injury.

Metal Artifact Reduction of Dental Fillings in Head and Neck CT Images

Introduction: The issue of metal artifact and its reduction is as old as the clinical use of computed tomography itself. When metal objects such as dental fillings, hip prostheses or surgical clips are present in the computed tomography (CT) field of view (FOV), make severe artifacts that reduce the image quality and accuracy of CT numbers. They can lead to unreliable clinical results due to inability in true tumor volume delineation and uncertainty in dose calculation of treatment planning software. So far, no generally accepted solution to this problem, especially for small size dental fillings, has been found. Herein, an approach is presented to reduce the dental filling artifacts in CT images of head and neck patients with multiple dental fillings. The proposed approach is compared with the commercial orthopedic metal artifact reduction (O-MAR) algorithm by Philips company. Materials and Methods: Our algorithm consists of six steps: 1) metallic object segmentation by thresholding, 2) obtaining the prior image by multi thresholding of the initial image, 3) normalization of the original image sinogram by prior image, 4) interpolation (replacing the affected projection data by previous slice unaffected projection data, 5) denormalization of the corrected sinogram and 6) application of a two dimensional adaptive filter to the final image. The forth step can be implemented by substitution of affected projections with opposite view projections. Both methods were tested and previous slice substitution was superior. Quantitative evaluation of the commercial and proposed algorithms was done in terms of peak signal-to-noise ratio (PSNR), signal-to- noise ratio (SNR) and structural similarity index (SSIM) on a CT image of a head and neck patient with four dental fillings. The posterior part of the head in original image was considered as the reference image. Also two uniform regions of interest (ROI) were considered in the image. ROI1 was posterior region of the head away from dental fillings, while ROI2 was restricted to the tongue region near to the dental fillings. Results: The PSNR, SNR, SSIM values obtained by the proposed method and O-MAR algorithm were 37.05, 36.13, 22.29, 21.37, 0.93 and 0.84, respectively. Using our approach, the standard deviation of CT numbers in ROI1 was 27 times less than the original image and 7% better than the commercial competitor. However, for ROI2 the commercial algorithm was 36% more successful in reduction of variations due to metal artifact. Conclusion: The proposed approach can be applied successfully for dental filling artifact reduction in head and neck patients. Although the performance of the commercial method was superior to ours in near dental regions, for the farther regions with more critical organs was vice versa. However, weighting the interpolation and adaptive filtering steps may result in even better results.

Illuminating the processes of microevolution: A bioarchaeological analysis of dental non-metric traits from Armenian Highland

Non-metric dental traits provide useful information for assessing temporal changes as well as for assessing biological relationships among living and ancient populations. Dental morphological traits were employed in this study as direct indicators of biological affinities among the populations that inhabited the Armenian Highland from the Late Chalcolithic-Early Bronze Age to Modern times. Sixteen morphological features in 2643 permanent adult teeth from 41 samples coming from 5 areas within the Armenian Highland were scored. Both Zubov’s standard protocol and Turner’s ASUDAS were employed. Given the paucity of odontological data for this area, this study contributes to the dental non-metric traits’ history of Armenian Highland and is a summary compilation and comparison of previously conducted work where non-metric traits were used in relation to dental reductions within the ancient Caucasus and Near East. The chronological sequence is considerable and spans from the Late Chalcolithic-Bronze Age to the Modern Age. It is suggested that offspring of ancient inhabitants of Armenian Highland continued to inhabit this area during the Late Iron Age, Classical/Late Antiquity, Middle Age and Modern period. This scenario indicates genetic continuity and gene flow between populations. Such a perspective is supported by the archaeological and molecular findings.

Cro-Magnon and Qafzeh - Vive La Differences

The obligatory use of cooking by the Mousterian occupants of the north temperate zone relaxed the forces of selection maintaining archaic tooth size and led to the reductions that shaped modern human face form from the Middle East to the Atlantic coast. The delay in the spread of cooking techniques accounts for the later onset of dental reduction to the south. The development and use of projectiles in the African Middle Stone Age led to gracilization and the earlier appearance of "modern" post-cranial and reflected cranial form in Africa. The subsequent adoption of the use of projectiles elsewhere was followed by gracilization and the appearance of "modern" post-cranial morphology. The craniofacial form of Cro-Magnon allies it with the living populations of northwestern Europe, specifically with the fringes in Scandinavia and England, but not with the European continent. Qafzeh represents the pattern still found in sub-Saharan Africa, particularly West Africa. Although the craniofacial configuration in both is "modern," the dentition of Qafzeh is archaic in size and form. Qafzeh is a logical representative of the ancestral form for sub-Saharan Africans but not for Cro-Magnon and subsequent Europeans.

Dental Reduction and Diet in the Prehistoric Ohio River Valley

Post-Pleistocene dental reduction has been documented around the globe. Dietary change is a common factor in many of the selectionist models explaining this reduction. The current study examines tooth size in the prehistoric Ohio River Valley of Indiana and Kentucky to determine if a dental reduction occurred from the Late Archaic to the Mississippian periods and, if so, to see if dietary shifts are associated with dental reduction. Data from 282 individuals are compiled from 21 sites that span from 5000 BC to AD 1400. These sites represent Late Archaic foragers, Early/Middle Woodland early horticulturalists, Late Woodland mixed-economy horticulturalists, and Mississippian agriculturalists. Previous studies have indicated that the diet became less abrasive through time in this region but became harder from the Late Archaic to the Early/Middle Woodland just to became softer again thereafter. Buccolingual diameters were taken for all suitable permanent teeth. Standard descriptive statistics, ANOVA, percent differences, and rate of change were calculated for each dental measurement to determine the degree of change between the various temporal groups. It was found that a dental reduction occurred in the Ohio River Valley that was more pronounced in females and in the maxillary molars. The general reduction in tooth size mirrors the reduction in dietary abrasiveness. By contrast, it does not seem to follow the course of dietary hardness.

Metric Analysis of Permanent and Deciduous Teeth from Bronze Age Tell Leilan, Syria

Between 1979 and 1989 the skeletal remains of 21 adults and 38 children, yielding 317 permanent and 134 deciduous teeth, were recovered at Tell Leilan, Syria, the site of a major urban center during the emergence of complex state society in northern Mesopotamia in the mid-third millennium BC. Tooth crown dimensions (faciolingual and mesiodistal diameters, total crown area, and molar crown area) are presented and the last two serve as the primary units of comparison for a diachronic interpretation of tooth size variation in the ancient Near East. Both permanent and deciduous dental data support the pattern of dental reduction since the Middle Paleolithic that has been documented for Asia and Europe. The total crown areas for the permanent and deciduous dental samples, 1189 mm2 and 497 mm2 respectively, place this archaeological population at the smaller end of the crown area scale for the Near East; smaller in size than nearby Paleolithic and Neolithic populations. Given the paucity of odontological data for this area, this study contributes to the odontometric history of Mesopotamia and as a summary compilation and comparison of previously conducted odontometric work as it relates to the phenomenon of dental reduction within the ancient Near East.

Dentine morphology of Atapuerca-Sima de los Huesos lower molars: Evolutionary implications through three-dimensional geometric morphometric analysis.

This study aims to explore the affinities of the Sima de los Huesos (SH) population in relation to Homo neanderthalensis, Arago, and early and contemporary Homo sapiens. By characterizing SH intra-population variation, we test current models to explain the Neanderthal origins. Three-dimensional reconstructions of dentine surfaces of lower first and second molars were produced by micro-computed tomography. Landmarks and sliding semilandmarks were subjected to generalized Procrustes analysis and principal components analysis. SH is often similar in shape to Neanderthals, and both groups are generally discernible from Homo sapiens. For example, the crown height of SH and Neanderthals is lower than for modern humans. Differences in the presence of a mid-trigonid crest are also observed, with contemporary Homo sapiens usually lacking this feature. Although SH and Neanderthals show strong affinities, they can be discriminated based on certain traits. SH individuals are characterized by a lower intra-population variability, and show a derived dental reduction in lower second molars compared to Neanderthals. SH also differs in morphological features from specimens that are often classified as Homo heidelbergensis, such as a lower crown height and less pronounced mid-trigonid crest in the Arago fossils. Our results are compatible with the idea that multiple evolutionary lineages or populations coexisted in Europe during the Middle Pleistocene, with the SH paradigm phylogenetically closer to Homo neanderthalensis. Further research could support the possibility of SH as a separate taxon. Alternatively, SH could be a subspecies of Neanderthals, with the variability of this clade being remarkably higher than previously thought.

Brain enlargement and dental reduction were not linked in hominin evolution

The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans.

A previously undescribed specimen reveals new information on the dentition of Sapeornis chaoyangensis

Here we describe the well-preserved skull of a juvenile specimen of Sapeornis, STM 16-18. Only the tail and hindlimb plumage of this specimen have been previously described. It preserves what we consider to be the complete dentition of Sapeornis with four premaxillary teeth, three maxillary teeth and two tiny dentary teeth on each side, the latter feature being previously unknown for this taxon. Based on a study of 71 specimens of Sapeornis preserving dentition, we infer the absence of dentary teeth in previously described specimens of Sapeornis is taphonomic, and consider the true dental formula of Sapeornis to be 4-3-2 (premaxillary teeth number – maxillary teeth number – dentary teeth number). Rostral to the dentary teeth, STM 16-18 preserves three shallow, empty aveoli. We hypothesize that this morphology captures an early stage in dental reduction and indicates that in at least some avian lineages, the loss of teeth was gradual.

A dental perspective on the taxonomic affinity of the Balanica mandible (BH-1)

The Middle Pleistocene represents a period of critical importance in human evolution, marked by encephalisation and dental reduction, and increasing diversification of temporally and spatially distributed hominin lineages in Africa, Asia and Europe. New specimens, especially from areas less well represented in the fossil record, can inform the debate on morphological changes to the skeleton and teeth and the phylogenetic course of human evolution during this period. The mandible from the cave of Mala Balanica, Serbia has recently been re-dated to at least 400 ka, and its well-preserved dentition presents an excellent opportunity to characterize molar crown morphology at this time period, and re-examine claims for a lack of Neandertal affinities in the specimen. In this study we employ microtomography to image the internal structure of the mandibular molars (focusing on the morphology of the enamel-dentine junction, or EDJ) of the BH-1 specimen and a comparative sample (n = 141) of Homo erectus sensu lato, Homo neanderthalensis, Pleistocene Homo sapiens, and recent H. sapiens. We quantitatively assess EDJ morphology using 3D geometric morphometrics and examine the expression of discrete dental traits at the dentine surface. We also compare third molar enamel thickness in BH-1 to those of H. neanderthalensis and both Pleistocene and recent H. sapiens, and document previously unreported morphology of the BH-1 premolar and molar roots. Our results highlight the reliability of the EDJ surface for classifying hominin taxa, indicate a primitive dental morphology for BH-1 molars, and confirm a general lack of derived Neandertal features for the Balanica individual. The plesiomorphic character of BH-1 is consistent with several competing models of Middle Pleistocene hominin evolution and provides an important regional and temporal example for reconstructing morphological changes in the mandible and teeth during this time period.

Morphometric analysis of Atapuerca-Sima de los Huesos lower first molars

The study of dental remains is a wealthy and stable source of information about taxonomical relations between extinct hominin species. Both morphological and metric dental features can be a reliable indicator of the underlying genotype of the individual/species under study. First lower molars (M1s) are the most stable teeth within the lower molar series. Since the last systematic metric analyses of the Atapuerca-Sima de los Huesos (SH) lower molars (Bermudez de Castro and Nicolas, 1995) the dental sample has substantially increased from 133 to over 533 specimens, so an updated assessment was necessary. Here, we analyze the absolute and relative proportions of the crown and the cusps of the SH M1s and we compare it against a large fossil simple including Australopithecus, Paranthropus, early Homo sapiens, Homo neanderthalensis, Homo heidelbergensis, Homo antecessor and Asian and African early Homo specimens, as well as a wide sample of contemporary Homo sapiens. Our study reveals that concerning M1s absolute size SH does not differ significantly from contemporary Homo sapiens. Homo antecessor M1s fall near to Asian Early and Middle Pleistocene Homo and differ from SH and H. sapiens. Regarding the relative cusp proportion we find three patterns: 1) a pattern that characterizes non-Homo specimens and some African Early Pleistocene Homo specimens (metaconid > protoconid > hypoconid > entoconid > hypoconulid), 2) a pattern that characterizes Early and Middle Pleistocene Homo from Asia and Europe including early Homo sapiens (protoconid > metaconid > hypoconid > entoconid > hypoconulid), 3) a pattern represented by contemporary Homo sapiens and Neandertals (protoconid > metaconid > entoconid > hypoconid > hypoconulid) and 4) an exclusive pattern for SH (pro > met = ent = hyp > hld). The SH protoconid is the largest from all the studied groups. Interestingly, this result matches previous observations by Martinon-Torres et al. (2013) regarding the protocone in SH upper first molars. We suggest that this may be an exclusive feature for this population. Molar size reduction in SH and contemporary Homo sapiens suggests a likely case of evolutionary parallelism. However, the cusp pattern variation differ between SH and contemporary Homo sapiens, suggesting that the evolutionary mechanisms of dental reduction in each group are different. Analysis of other dental classes may be necessary.

The effect of various methods of primary pathogenetic dental caries prevention on the mineral composition of the oral cavity in the oilfield workers of the north of the Tomsk region

The summary The effect of various methods of primary pathogenetic dental caries prevention of on the mineral composition of the oral cavity in oil workers of the North of the Tomsk region was surveyed. 120 oilfield workers of the North between the ages of 35 and 44 were surveyed, there being four survey groups: a control group, the first, the second and the third groups. In the control group, there was carried out no primary prevention. The first group was subject to deep fluoridation. In the second group immune correctors and antioxidants were prescribed. The third group received comprehensive prevention: deep fluoridation, immune correctors and antioxidants. The groups were surveyed both prior to carrying out prevention and one year after preventive measures taking. The survey revealed that the oilfield workers of the North having received no primary prevention, had a significant dental caries increase together with calcium and sodium saliva concentration decrease. In the first and second prevention groups, the reduction of increase caries ranged between 26.4% and 18.3%, the mineral composition of the oral fluid had not changed. Comprehensive prevention proved to be the most effective, dental caries growth reduction within the group being 49.6%. The effect was accompanied by an increase in the concentration of calcium and phosphorus in the oral fluid.

A efetividade das intervenções educativas em saúde bucal: revisão de literatura

Resumo Visando diminuir impactos negativos dos agravos bucais, intervenções educativas em saúde bucal têm sido propostas e avaliadas. Entretanto, a efetividade das iniciativas publicadas a partir de 2004 ainda não constituiu objeto de escrutínio acadêmico. Este trabalho objetivou revisar as intervenções educativas e estimar seu impacto sobre as condições de saúde bucal. Consultou-se a base de dados MEDLINE via PubMed, com termos livres e controlados, para identificar intervenções educativas publicadas no período de 2003 a 2013. Analisaram-se e sintetizaram-se qualitativamente os resultados dos estudos originais. Nos 37 estudos revisados, observou-se que as intervenções produziram resultados clínicos inconsistentes em curto prazo, incluindo a redução de placa bacteriana (melhor resultado [MR] -88,9%; pior resultado [PR] +29,7%), sangramento gengival (MR -77,8%; PR +72,2%) e menor incremento de cárie (MR -39,5%; PR +961,1%) e de cálculo dentário (+16,2%). Por sua vez, houve maior redução dos desfechos avaliados, quando os participantes receberam acompanhamento clínico intensivo, sugerindo que este é um aspecto importante das intervenções. De modo semelhante às revisões prévias da literatura, observou-se que as intervenções educativas para prevenção, controle ou redução de agravos bucais não apresentaram efeitos consistentes.

A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation

Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies.

Testing functional and morphological interpretations of enamel thickness along the deciduous tooth row in human children

The significance of a gradient in enamel thickness along the human permanent molar row has been debated in the literature. Some attribute increased enamel thickness from first to third molars to greater bite force during chewing. Others argue that thicker third molar enamel relates to a smaller crown size facilitated by a reduced dentin component. Thus, differences in morphology, not function, explains enamel thickness. This study draws on these different interpretive models to assess enamel thickness along the entire human deciduous tooth row. Average enamel thickness (AET), the area and proportion of crown enamel and dentin, and a crown size proxy are calculated for incisors, canines, and molars. Allometric scaling relationships are assessed within each tooth class, and then comparisons are undertaken along the row. Generally, AET was correlated with crown size and scaled with isometry, except for second molars which scaled with positive allometry. Mean AET increased along the row and was greater on molars, where bite forces are reported to be higher. Second molars combined the largest crown size with the thickest enamel and the smallest proportion of dentin, which is consistent with a reduction in the potential for cusp fracture under high bite forces. Resistance to wear may also account for some enamel thickness variation between tooth classes. Dental reduction did not explain the trend in AET from central to lateral incisors, or from first to second molars. The gradient in AET along the deciduous tooth row is partly consistent with a functional interpretation of enamel thickness.

The most basal beaked whaleNinoziphius platyrostris Muizon, 1983: clues on the evolutionary history of the family Ziphiidae (Cetacea: Odontoceti)

Ninoziphius platyrostris, from the late Neogene of Peru, is one of the best-known fossil beaked whales (Odontoceti: Ziphiidae), with a holotype including the skull with ear bones, mandibles, teeth, and postcranial elements. Furthermore, based on several characters, including a complete functional upper and lower dentition, it is usually considered as one of the most archaic ziphiids. However, the poorly preserved dorsal portion of the holotype skull has led to unresolved phylogenetic relationships. With the addition of two newly prepared skulls from the same Peruvian locality we redescribed N. platyrostris. In the light of recent ziphiid discoveries, an emended diagnosis of the species is proposed here. In our cladistic analysis Ninoziphius is the most basal stem ziphiid. Newly observed or reassessed morphological traits allow functional and ecological considerations. The morphology of the oral apparatus suggests that Ninoziphius was less specialized for suction feeding than most extant ziphiids. Tooth wear in the holotype may indicate benthic feeding. Although the vertebral column of Ninoziphius corresponds to less developed locomotor abilities for deep dives, its cranial morphology does not provide definitive arguments for an echolocation system less efficient than in deep diving extant ziphiids. Finally, the phylogenetic tree produced was used to detail the evolutionary history of several major ziphiid features (dental reduction, development of mandibular tusks, and increased body size).