Jaw Size Research Articles

Loss of the third upper premolar in Suncus murinus and its relation to jaw size

Musk shrew Suncus murinus (Linnaeus, 1766) has a very reduced P3, and it is often missing. Hanamura (1985), based on a sample from Okinawa Island, proposed that the high incidence in P3 loss was a distinguishing characteristic of musk shrew. However, while the Okinawa population lacked P3 in 26 of 95 individuals (27.4%), specimens from Taiwan showed no P3 loss. Thus, the high indicence of P3 loss is not one of distinguishing characteristic of musk shrews.

Linear and angular measurements of the mandible during maximal mouth opening

1. Wooten JW: Physiology of the temporomandibular joint. Oral Surg Oral Med Oral Patbol 21:543, 1966 2. Obwegeser HL, Farmand M, Al-Majali F, et al: Findings of mandibular movement and the position of the mandibular condyles during maximal mouth opening. Oral Surg Oral Med Oral Patbol 63:517, 1987 3. Sarnat BG, La&in DM: The Temporomandibular Joint (ed 3), Springfield, IL, Thomas, 1979, p 85 4. Madsen B: Normal variations in anatomy, condylar movements, and arthrosis frequency of the temporomandibular joint. Acta Radio1 Diagn 4:273, 1966 5. Or S, Ergen G: The assessment of temporomandibular subluxation by means of cephalometry. Am J Orthod 76:165, 1979 6. Thompson JR: A cephalometric study of the movement of the mandible. J Am Dent Assoc 28:750, 1941 7. Ingervall B: Variation of the range of movement of the mandible in relation to facial morphology in young adults. Stand J Dent Res 79:133, 1971 8. Landtwing K: Evaluation of the normal range of vertical mandibular opening in children and adolescents with special reference of age and stature. J Maxillofac Surg 6:157, 1978 9. Agerberg G: Maximal mandibular movement in children. Acta Odontol Stand 32: 147, 1974 10. Mezitis M, Rallis G, Zachariades N: The normal range of mouth opening. J Oral Maxillofac Surg 47:1028, 1989 11. Muto T, Kanazawa M: The relationship between maximal jaw opening and size of skeleton: A cephalometric study. J Oral Rehabil 23:22, 1996 12. Travel1 J: Temporomandibular joint pain referred from muscles of the head and neck. J Pro&et Dent 10:745, 1960 13. Agerberg G: On mandibular dysfunction and mobility. Ph.D. thesis, University of Umea, Sweden, 1974 14. Pullinger AG, Low SG, Tay D: Differences between sexes in maximum jaw opening when corrected to body size. J Oral Rehabil 14:291, 1987 15. Yamauchi K, Ito K, Suematsu H, et al: Sex difference of Japanese adult profile with normal occlusion on cephalometric roentgenograms. J Jpn Ortbod Sot 26:155, 1967 16. Ingervall B: Range of movement of mandible in children. Stand J Dent Res 78:311, 1970 17. Westling L, Helkimo E: Maximum jaw opening capacity in adolescents in relation to general joint mobility. J Oral Rehabil 19:485, 1992 18. Muto T, Kanazawa M: Positional change of the hyoid bone at maximal mouth opening. Oral Sur Oral Med Oral Path01 771451, 1994

Mandibular form and function in North American and European Adapidae and Omomyidae.

Previous experimental and comparative studies among a wide variety of primate and nonprimate mammals provide a unique source of information for investigating the functional and phylogenetic significance of variation in the masticatory apparatus of Eocene primates. To provide a quantitative study of mandibular form and function in Eocene primates, the scaling of jaw dimensions and the development of symphyseal fusion was considered in a broad sample of North American and European Adapidae and Omomyidae. Statistical analyses indicate a significant size-related pattern of symphyseal fusion across Eocene primates, with larger taxa often having a greater degree of fusion than smaller species; this trend is also evident at the family level. As adapids are mostly larger than omomyids and these taxa show allometry of symphyseal fusion, this may explain why no omomyids evince complete fusion. Controlling for jaw size, species with greater symphyseal fusion tend to have more robust jaws than those with a lesser amount of fusion. Upon further examination, a primary reason why adapids have more robust mandibles than omomyids is associated with the presence of taxa with fused symphyses, and thus more robust jaws, in the adapid sample, whereas no omomyids have fused symphyses. In addition, there is little indication of a dietary effect, as measured by molar shear-crest development, on symphyseal fusion. Moreover, as there is no correlation between molar shear-crest development and skull size, this also points to the absence of a size-related pattern of dietary preference underlying the allometry of symphyseal fusion. Based on the interspecific and ontogenetic allometry of symphyseal ossification in Eocene primates, jaw-scaling patterns are used to further examine the functional determinants of fusion in this group. This study indicates that greater dorsoventral shear during mastication is a more likely factor than lateral transverse bending ("wishboning") in the evolution of symphyseal fusion among "late-fusing" mammals like adapids and omomyids. Given that wishboning is an important functional determinant of symphyseal form in recent anthropoids, apparently the evolutionary development of marked wishboning occurs only in taxa that shift the timing of fusion to a growth stage preceding the onset of weaning (before adult masticatory patterns are fully developed) and perhaps first ossified the symphysis to counter elevated dorsoventral shear stress. As early anthropoids probably consisted of members varying interspecifically and ontogenetically in the degree of ossification, it is especially informative to analyze the adaptive setting in which anthropoid symphyseal fusion evolved from a similar primitive "prosimian" perspective. Finally, since taxa with fused symphyses are widely distributed across mammals, a similar analytical framework could be directed profitably at unraveling the functional and evolutionary significance of symphyseal fusion in other mammalian clades.

Variation in cohort mandible size as an index of roe deer (Capredus capreolus) densities and population trends

This paper examines the effects of increasing population density on the skeletal development of roe deer as indexed by variation in the size of the mandible. We tested for density‐dependence in total jaw length and minimum diastema height among cohorts in a single, intensively studied population in France. A strong relationship of average adult jaw length of both males and females with deer density in the year of birth of a given cohort was observed, and presumably reflects inadequate nutrition of juveniles at high population density. No such relationship was observed for the minimum diastema height which remained constant over the range of densities studied. This relationship was exploited to investigate population trends of roe deer in Britain. In nine populations, where equivalent data were available for between 16 and 28 separate cohorts, a consistent pattern of variation in cohort jaw size was observed, with a decrease in average total length, but not diastema height, towards the present. This trend is discussed in relation to changes in habitat structure in the coniferous forests of Britain. The utility of cohort jaw length as a management tool to index population trends of roe deer is highlighted.

Unequal competition between three-spined stickleback, Gasterosteus aculeatus, L., encountering sequential prey

Competition between pairs of stickleback was studied to investigate the effects of fish size and prey size on the feeding behaviour and competitive ability of the fish when single prey items were encountered sequentially. All the fish had a high probability of attacking the prey encountered. A fish with a high probability of being first to handle the prey had a high probability of ingesting it only when the prey was the smaller of the two prey sizes offered. With the larger prey, food gain was predicted not by the first to handle but by the jaw size of the fish. Encounter with a larger prey resulted in each fish attempting to capture it more often. This was due to the larger prey being visible for longer as it had to be manipulated before being swallowed. Even when prey were ingested and hence not visible, the unsuccessful competitor remained close by for approximately 7 s. The probability of eating any prey encountered was dependent on the phenotypic properties of the individual fish. A fast reacting fish with large jaws was able to reach its daily energy requirement regardless of the encounter rate with any prey size. Competitive ability was therefore a function of the fish, ability to reach the prey first, the capacity of the jaw apparatus to ingest the prey and prey encounter rate. When the pairs of fish encountered a high proportion of large prey, a generalist feeding strategy was the best option. The results can be applied to current foraging models, in particular to extending the sequential encounter model.

The relationship between maximal jaw opening and size of skeleton: a cephalometric study.

The purpose of this study was to investigate the correlation between maximal mouth opening and size of the skeleton. The subjects were dental students at the Dental School of the Health Sciences University of Hokkaido with no functional disorders of the masticatory system. The stature and maximal mouth opening were recorded in 29 males and 31 females. These subjects agreed to have a lateral cephalogram taken at the closed and maximal mouth opening positions. The correlations between the maximal mouth opening and the body height, mandibular length and mandibular angle were significant. The correlation between the maximal mouth opening and the movement of the condyle was also significant.

Relationship between congenital anodontism and jaw size.

Relationship between congenital anodontism and jaw size.

"Giant" tamarin from the Miocene of Colombia.

A nearly complete but badly crushed skull and mandible of Lagonimico conclucatus, gen. et sp. nov. is described from the La Victoria Formation, Colombia. The specimen is of middle Miocene age and dates from about 13.5 Ma. Features of the dentition suggest Lagonimico is a sister group to living Callitrichinae (Saguinus, Leontopithecus, Callithrix, and Cebuella). These features include having elongate compressed lower incisors, a reduced P2 lingual moiety, and the absence of upper molar hypocones. The new taxon also has autapomorphies, such as a relatively deep jaw, that rule it out of the direct ancestry of any living callitrichine. This animal is assigned to a new tribe of the callitrichine clade. The orbits of L. conclucatus are small, suggesting diurnal habits. Inflated, low-crowned (bunodont) cheek teeth with short, rounded shearing crests, as well as premolar simplification and M3 size reduction, suggest fruit- or gum-eating adaptations, as among many living callitrichines. Procumbent and slightly elongate lower incisors suggest this species could use its front teeth as a gouge, perhaps for harvesting tree gum. Estimates from jaw size suggest Lagonimico weighed about 1,200 g, about the size of Callicebus, the living titi monkey of South America. Judged from tooth size and jaw length, Lagonimico would have been slightly smaller than Callicebus, but still larger than Callimico or any living callitrichine. Therefore, many of the distinctive anatomical features of the callitrichine clade, sometimes explained by phyletic dwarfing, may have evolved at larger body size. Evolutionary size reduction may have occurred in parallel in callitrichines and Callimico.

Craniodental Allometry in the African Wild Cat, Felis lybica

Allometric relations of tooth size to jaw size and skull length were evaluated in Felis lybica . Tooth length and width were scaled to bimaxillary width, maxillo-alveolar length, mandibular length, and bigonial width, and to skull length. Females have less covariation between tooth size and jaw size than males. Maxillary canine size in males scaled positively allometric to skull length and near isometric to maxillary length. Upper canine size and skull size in females were not related. Maxillary postcanine teeth in males scale negatively, hence larger animals tend to have relatively smaller postcanine teeths. Lower canine size appears related to mandibular length only, scaling negatively in females and positively in males. Mandibular postcanines show little covariation with cranial characters; when correlated, the relationship is positively allometric or near isometry.

Tooth crown heights, tooth wear, sexual dimorphism and jaw growth in hominoids

The aim of this review is to bring together data that link tooth morphology with tooth function and tooth growth: We aim to show how the microanatomy of hominoid teeth is providing evidence about rates of tooth growth that are likely to be a consequence of both masticatory strategy and social behaviour. First, we present data about incisor and molar tooth wear in wild short chimpanzees that demonstrate how crown heights are likely to be related to relative tooth use in a broad sense. Following this we review recent studies that describe the microanatomy of hominoid tooth enamel and show how these studies are providing evidence about tooth crown formation times in hominoids, as well as improving estimates for the age at death of certain juvenile fossil hominids. Next, we outline what is known about the mechanisms of tooth growth in the sexually dimorphic canine teeth of chimpanzees and compare these patterns of growth with tooth growth patterns in the canines of three fossil hominids from Laetoli, Tanzania. Finally, we discuss how selection pressures that operate to increase or reduce the size of anterior teeth interact with jaw size. We argue that the space available to grow developing teeth in the mandibles of juvenile hominoids is determined by the growth patterns of the mandibles, which in turn reflect masticatory strategy. The consequences of selection pressure to grow large or small anterior teeth are likely to be reflected in the times at which these teeth are able to emerge into occlusion.

Alternate occlusal schemes

Comparative jaw size and the loss of function of the anterior determinants dictates establishing alternate types of occlusion. The chewing envelope and protrusive disocclusion are generally established by functioning anterior teeth. Dramatic changes in tooth morphology are dictated when the anterior teeth do not function. Bilateral balanced occlusion establishes guidance and support. When the mandible is much larger than the maxillae, a well-designed reverse occlusion will properly distribute the forces through the long axis of the teeth and provide a stable occlusal base. Bilateral balance and reverse occlusions are the recommended physiologic occlusions to use when a mandible disparity exists. Accurate reproduction of the posterior determinants is necessary. The arbitrary removal of balancing contacts can introduce imbalance, pain, lack of guidance, and serious compromise of an otherwise sound occlusion.

The fetal mandible measurement: an objective determination of fetal jaw size.

The sonographic diagnosis of micrognathia has been limited by the lack of an objective measurement of the fetal mandible. A cross-sectional study of 134 normal patients of known gestational age between 14 and 39 weeks' gestation was performed. Models to predict mandible length based on gestational age, biparietal diameter, head circumference or femur length were derived by least squares regression analysis. The 95% prediction limits were also derived. Utilization of these curves generated from a normal population should allow for a more sensitive and reproducible method to diagnose micrognathia in the fetus.

Effects of comparative jaw size on mandibular movement and occlusion

Comparative jaw size should be investigated as a fifth factor and determinant of occlusion. It has a direct effect on each component of occlusion. The loss of function of the anterior teeth generates profound changes in occlusion and mandibular movement alike. A hypothetical mandibular growth is used to show stable tooth-to-tooth relationships. These stable occlusions have been observed often and are functioning well in individual mouths. Guidance is a major factor in occlusion and when lost by nonfunction of the anterior teeth must be replaced to provide comfort and stabilization. Alternates to canine and anterior guidance are found in group function and bilateral balanced occlusions. Research is necessary to understand the full effect of comparative jaw size on occlusion and mandibular movement. Research will also provide answers to many perplexing questions.

Static intraspecific allometry of the dentition in Otolemur crassicaudatus

Adult static intraspecific allometry of tooth size was evaluated in a sample of 66 Otolemur crassicaudatus (34 male, 32 female). Tooth areas were calculated from mesiodistal and buccolingual measurements of canines and postcanine teeth of both arcades and were scaled to four viscerocranial measurements: bimaxillary width; maxillo-alveolar length; mandibular length and bigonial width. Individual tooth crown areas were also scaled to total skull length, body length and body weight. From the log-transformed analyses it is concluded that postcanine tooth size was unrelated to body length or weight, and poorly correlated to skull length or jaw size. Although viscerocranial size appears to be independent of body size, these measures are well correlated to skull length. It is shown that the longer the skull, the shorter and narrower the maxilla, and the longer and broader the mandible. Canines are shown to scale negatively allometric to skull length, hence, large animals will have relatively small canines.

Orthodontic treatment of the primary dentition for patients with clefts of lip, alveolus, and palate following presurgical orthodontics, labioplasty and palatoplasty

In spite of presurgical orthodontic treatment, after a labio- and palatoplasty in continuous uni- and bilateral clefts of the lip, alveolus bone, and palate, anomalies of the dental arch, occlusion, jaw size and position can appear. This is favoured in cases without adequate retention of the upper dental arch through intercuspidation of the lower dental arch. These anomalies should be treated. The treatment of the malposition of the primary teeth is not of concern, but the termination of the forced sagittal and transverse mandibular displacements and thereby the coordination of the growth of the upper and lower jaw, which depend on each other.

The occurrence of the eunicid polychaetesIphitime cuenotiFauvel andI. PaguriFage & legendre in crabs from the Scottish West Coast

Abstract During an investigation into the occurrence of various crab species in the Oban (West of Scotland) area, Iphitime cuenoti was found infesting the branchial cavity of Liocarcinus puber, L. corrugatus, L. depurator, Carcinus mamas, Cancer pagurus, Hyas araneus and Macropodia longirostris caught within, or on the sandy mud below, the Laminaria forest. The same crab species obtained from sandy habitats, and crabs peculiar to such a habitat (Portumnus latipes, Liocarcinus holsatus and Corystes cassivelaunus) did not harbour the polychaetes. Three or more worms were commonly found in each Liocarcinus host, the highest number recorded, in L. puber, comprising 9 adult and at least 98 juveniles, the latter being found between the gill lamellae. Over 90% of both L. puber and L. corrugatus were infested, 35% of L. depuratot, but less than 10% of any of the other species. The largest worms (up to 80 mm alcohol-preserved length) were found in L. puber and L. corrugatus. Worms were found to have either simple or slightly bifurcate branchiae, or multifurcate branchiae. Worms with simple branchiae rarely reached 40 mm in length, usually possessed jaws which exceeded 700 μm in length, and were never found to contain eggs. These are regarded as putative males, and histological evidence from three specimens confirms this suggestion. Only Iphitime with multifurcate branchiae were found to contain eggs, and were also the largest worms, but their jaw length was very variable, ranging from 0-1030 μm with little or no relationship to the length of the worm. The smallest worms, 3 mm in length, were found between the gill lamellae throughout the year, but mainly from December to August. In multiple infestations there appeared to be one dominant female which probably inhibited maturation of companion worms, and it is postulated that once this female vacates, there is a sequential maturation and spawning of subordinate worms. The greatest number of mature worms, and the largest worms, occurred during October and November, but because of the extended larval settlement period it is a matter of debate whether the worm is an annual, or has a more extended lifetime. Iphitime paguri was found occupying the apical whorl of4.6% of Buccinum undatum shells and 2.6% of Neptunea antiqua shells occupied by the hermit crab Eupagurus bernhardus. The worm is very fragile and, being rare, there is insufficient data to define its biology. The longest worm was 50 mm (alcohol- preserved length) and the largest jaw length 760 μm; there appeared to be an inverse relationship between length of worm and jaw size, and no worm over 25 mm had jaws larger than 250 μm. All ovigerous worms had small jaws. Nereis fucata was found in 2.6% of Neptunea antiqua and 7.1% of Buccinum undatum shells occupied by the hermit crab. It was not found associated with Iphitime paguri.

Population variation in tooth, jaw, and root size: a radiographic study of two populations in a high-attrition environment.

Radiographs were taken of the jaws of skeletal remains of two populations of different-phenotype Prehistoric Australians from Roonka and Early New Zealanders (Maoris). On these radiographs crown, root, and corpus size were measured. Corpus height was subdivided into alveolar bone height, defined as the bone superior to the mandibular canal, and basal bone height, defined as that inferior to the mandibular canal. Both between and within the two populations there was a significant and negative correlation between crown size and corpus height. The differences between the two populations in corpus height were associated with differences in alveolar bone height rather than basal bone height and support hypotheses associating continued eruption of adult teeth with growth of the alveolar bone. The findings also support previous studies that have shown only a low correlation between crown size, root size, and corpus height.

A water phantom controller for automated acquisition of linac beam parameters.

Three-dimensional water phantoms are routinely used when acquiring the data necessary to commission medical linear accelerators. A new water phantom controller has been developed at our institution that is unique in several aspects. The water phantom controller is based on an IBM XT compatible computer. This has been interfaced to an Artronix three-dimensional water phantom and a commercially available linac setup controller. Some of the unique features of the new controller are (i) its ability to perform three-dimensional coordinate transformations on the fly (this removes the need to level and align the water tank with the beam axes and greatly reduces setup time). (ii) Its ability to communicate with a device which can control the linac operating parameters (this allows the water phantom controller to adjust, for example, the jaw size of the accelerator as it acquires data). (iii) Its ability to output the acquired data in a number of modes, including screen display, hardcopy plot, or disk file that may be transferred to a central treatment planning computer). (iv) Its ability to digitally process the acquired data. This water phantom controller may be used to gather machine data in a highly automated manner, greatly reducing the time required to gather the desired data.

Allometric relations of teeth and jaws in man.

Static adult intraspecific allometry of jaws and teeth was investigated in a sample of 100 Negro crania. The relations between tooth area, postcanine surface, incisor surface, and four viscerocranial measures were examined separately for males and females. Our results indicate a marked lack of morphological integration between P-sets within the orofacial subregion and a similar lack of correspondence between jaw size and tooth size. Allometric analyses indicate that mandibular length scales negatively allometric to maxilloalveolar length and to bigonial width, that canine base area scales positively to upper and lower jaw length, and that all the other teeth scale negatively to jaw length. The postcanine surface area was found to be negatively allometric to the canine base area, which in turn scaled isometrically to incisor surface. Hence, any lengthening of the mandible will tend to be associated with a relative shortening of the maxilla, with relatively larger canines and a relative reduction of the cheek teeth.

Static intraspecific allometry of jaws and teeth in Cercopithecus aethiops

Adult static intraspecific allometry of jaw size and tooth area was evaluated in a sample of 100 Cercopithecus aethiops crania (50 male, 50 female). Tooth areas were calculated from mesiodistal and buccolingual measurements of all the teeth in both arcades and were scaled to four viscero‐cranial measurements: bimaxillary breadth, maxillo‐alveolar length, mandibular length and bigonial width. Allometric coefficients calculated for jaw dimensions alone indicate tighter viscerocranial integration in females than in males. A finding of note was that half of the variation in maxillo‐alveolar length may be accounted for by variation in mandibular length: females are isometric, males negatively allometric.A similar degree of allometric mosaicism was found when maxillary incisor size was scaled to maxillary length and width. In females, the relationship was negatively allometric, whilst incisor size in males was found to be unrelated to either. Negative allometry characterized the relationship of canine base area to jaw length in both sexes, with males additionally being positively allometric to mandibular width.The scaling of postcanine tooth areas to jaw length was characterized by a dichotomous pattern: males showed significant mandibular integration whilst females showed only significant maxillary integration. Compensatory tooth size interaction between maxillary canine base area and the summed incisor and postcanine areas was suggested by the significant negative allometric relation between them.