Variation In Number Of Teeth Research Articles

Molar Incisor Hypomineralisation as a Dental Caries Risk Factor - Is It True?

The development of the human dentition is susceptible to disruption owing to its intricate and delicate nature, encompassing variations in tooth number, anatomical configuration, and the characteristics of enamel, dentine, and cementum. This chapter will specifically address the prevalent defect of molar incisor hypomineralisation (MIH), which can impose a significant treatment burden on individuals. MIH is linked to deleterious alterations in the properties of affected enamel, which can lead to rapid enamel breakdown and carious lesion formation in those at a heightened caries risk. In addition, MIH is associated with tooth sensitivity, dental anxiety, difficulty eating, aesthetic concerns, and negative influence during the child's psychological growth, especially when the MIH is severe. Regarding dental caries, it is essential to note that MIH does not directly increase the risk of caries. However, MIH can alter the way the caries process manifests by creating niches where biofilm can accumulate, complicating oral cleaning efforts. Additionally, MIH adversely modifies the physicochemical properties of enamel, influencing how this "hardest of tissues" responds to cariogenic challenges.

Chapter 4: Development Defects of Enamel and Dentine and Coronal Caries.

The development of the human dentition is prone to disruption due to its delicate and complex nature - including variations in tooth number and anatomical form and in the characteristics of enamel, dentine, and cementum. This chapter will focus on developmental defects of dental enamel (DDE) and dentine (DDD), which can be associated with considerable treatment burden on an individual, often related to the change in dental hard tissue characteristics in those at increased caries risk. DDE are prevalent and can be related to genetic conditions such as amelogenesis imperfecta and environmental challenges such as direct physical trauma to the developing tooth or systemic insults during the different phases of amelogenesis. Phenotypical variability can be great, making diagnosis difficult in many cases. There are two major enamel defects - the quantitative defect of hypoplasia and the qualitative defect of hypomineralization. DDDs are less prevalent than DDEs, with two major DDD types: dentinogenesis imperfecta and dentine dysplasia. The main features of the DDDs are enamel fracture exposing the dentine and subsequent wear, with enlarged pulp spaces in some variants. The appearance may be affected, with bulbous teeth and grey-blue to brown opalescent colouring. With respect to dental caries, developmental defects of the teeth, in themselves, do not cause caries risk; however, they can change the manifestation of the disease due to creating niches for biofilm accumulation and thereby increasing cleaning difficulty and changing the physical and chemical characteristics of dental hard tissues and how they react to cariogenic challenges.

Palatal rugae morphology is associated with variation in tooth number

This observational study compared palatal rugae morphology in adolescent subjects with normal tooth number and tooth agenesis. Maxillary dental study casts were used to compare rugae number, length and shape. Each study group contained 60 subjects (30 females and 30 males) mean age 13.4 (SD, 1.55) in control and 13.56 (SD, 1.54) years in tooth agenesis groups (p = 0.576). Mean number of missing tooth units in the tooth agenesis group was 2.1. Mean number of primary rugae in the whole sample was 4.35 (SD, 0.98) on the right and 4.33 (SD, 0.92) on the left with no significant differences (p = 0.236 and p = 0.404, respectively). However, the number of secondary rugae on the left (p = 0.006) and fragmentary rugae on the right (p = 0.004) was significantly increased in the tooth agenesis group. The shape of left primary rugae 2 and 3 also differed between groups, tending towards a wavy pattern in the control group and curved in the tooth agenesis group (p = 0.012 and p = 0.004, respectively). In addition, primary rugae 3 was more convergent (p = 0.008) whilst left primary rugae 3 and 5 were orientated in an antero-posterior direction (p = 0.04 for both rugae) in the tooth agenesis group. Subgroup analysis also identified significant associations between patterns of tooth agenesis and rugae number, in addition to shape of primary rugae. The identification of significant differences in rugae pattern between subjects with normal tooth number and agenesis suggests potential commonality in signal pathway disruption during establishment of these structures.

The large X-effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura.

Genetic studies of secondary sexual traits provide insights into whether and how selection drove their divergence among populations, and these studies often focus on the fraction of variation attributable to genes on the X‐chromosome. However, such studies may sometimes misinterpret the amount of variation attributable to the X‐chromosome if using only simple reciprocal F1 crosses, or they may presume sexual selection has affected the observed phenotypic variation. We examined the genetics of a secondary sexual trait, male sex comb size, in Drosophila subobscura. This species bears unusually large sex combs for its species group, and therefore, this trait may be a good candidate for having been affected by natural or sexual selection. We observed significant heritable variation in number of teeth of the distal sex comb across strains. While reciprocal F1 crosses seemed to implicate a disproportionate X‐chromosome effect, further examination in the F2 progeny showed that transgressive autosomal effects inflated the estimate of variation associated with the X‐chromosome in the F1. Instead, the X‐chromosome appears to confer the smallest contribution of all major chromosomes to the observed phenotypic variation. Further, we failed to detect effects on copulation latency or duration associated with the observed phenotypic variation. Overall, this study presents an examination of the genetics underlying segregating phenotypic variation within species and illustrates two common pitfalls associated with some past studies of the genetic basis of secondary sexual traits.

Mild hypodontia is associated with smaller tooth dimensions and cusp numbers than in controls

ObjectiveThe associations seen clinically between variations in tooth number, size and shape reflect the repetitive genetic interactions occurring between the epithelium and mesenchyme during the initiation and morphogenetic stages of the Complex Adaptive System that is dental development. The aim of this study was to investigate the clinical relationship further by comparing multiple crown parameters, including cusp numbers, between patients with mild hypodontia and controls in a Romanian sample. DesignDigital images of dental casts of the permanent dentition from 28 patients with mild hypodontia and 28 controls were used. Measurements from the vestibular and occlusal surfaces were performed using a 2D image analysis method and cusps, including the Carabelli trait, were counted. Two-way analysis of variance was performed. ResultsThe dimensions of the mild hypodontia group had smaller values than the controls, with many measurements being significantly different (significance values varied from p=0.049 to p=0.001). The most affected regions were the upper and lower anterior region in both sexes. Mesio-distal, bucco-lingual and occlusal area and perimeter dimensions were affected. Females from the hypodontia group had significantly less tricuspidated lower premolars when compared with the control group. Carabelli cusps were present in the hypodontia group less frequently, the difference being highly significant (p=0.0002) in women. ConclusionsThe hypodontia patients presented with reduced crown dimensions and shape compared with controls. This is the first published study to demonstrate smaller cusp numbers in patients with hypodontia than in controls. The findings are compatible with a model of dental development as a Complex Adaptive System incorporating associations between tooth number, size and shape.

Taurodontism, variations in tooth number, and misshapened crowns in Wnt10a null mice and human kindreds.

WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated with tooth agenesis. We characterized Wnt10a null mice generated by the knockout mouse project (KOMP) and six families with WNT10A mutations, including a novel p.Arg104Cys defect, in the absence of EDA,EDAR, or EDARADD variations. Wnt10a null mice exhibited supernumerary mandibular fourth molars, and smaller molars with abnormal cusp patterning and root taurodontism. Wnt10a−/− incisors showed distinctive apical–lingual wedge-shaped defects. These findings spurred us to closely examine the dental phenotypes of our WNT10A families. WNT10A heterozygotes exhibited molar root taurodontism and mild tooth agenesis (with incomplete penetrance) in their permanent dentitions. Individuals with two defective WNT10A alleles showed severe tooth agenesis and had fewer cusps on their molars. The misshapened molar crowns and roots were consistent with the Wnt10a null phenotype and were not previously associated with WNT10A defects. The missing teeth contrasted with the presence of supplemental teeth in the Wnt10a null mice and demonstrated mammalian species differences in the roles of Wnt signaling in early tooth development. We conclude that molar crown and root dysmorphologies are caused by WNT10A defects and that the severity of the tooth agenesis correlates with the number of defective WNT10A alleles.

Using a Hollow Braiding Technique to Prepare 316L Stainless Steel Braids as Coronary Stents

This study proposes a novel manufacturing method, a hollow braiding technique, to make reticular tubes. Coronary stents for coronary arteries have to have a size equal to the size of the arteries, and as a result, material and diameter of stents are both critical designed parameters. By using a hollow braiding technique and a braiding machine, 316L stainless steel fibers are made into coronary stents with an internal diameter of 3 mm, which meets the requirement of coronary arteries. The experiment results show that the hollow braiding technique can effectively braid reticular tubes with an internal diameter of 3 mm. In addition, variation in tooth number on the take-up gear can influence the braiding angle but does not influence the stability of the braiding structure and metal cover rate. In this study, the hollow braiding technique successfully produces coronary stents in the form of reticular tubes with a size equal to coronary arteries.

Toward a reduction in tooth number: the case of P1 in roe deer from Slovenia

The permanent dentition of roe deer (Capreolus capreolus L.) comprises 30–32 teeth with the following dental formula: I 0/3, C 0/(1), P 3/3, M 3/3. Variations in tooth number and shape are rather uncommon in this species and factors determining roe deer dentition are considered to be quite stable. In both upper and lower jaws the first premolar is normally missing, but can be occasionally observed. To discover the frequency of P1 in the whole population, its occurrence was studied in the left hemi-mandibles of the total one-year (2007) roe deer mortality in Slovenia, representing a large sample set of 41,895 individuals. The first premolar was detected in only 27 individuals (13 males, 12 females, 2 without data), indicating that its occurrence is very low and sporadic (0.6‰). Furthermore, the results of previous archaeozoological and embryological studies were analyzed. On the basis of observed facts, we conclude that the first mandibular premolars of roe deer belong to a category of tooth that has been suppressed in the evolution of the Cervidae.

Places in the dental arch that show a greater variability in tooth number, shape and position—A prevalence study

ObjectiveThe aim of this study was to assess the frequency of variations in tooth number, shape and position in the dental arch to determine if there are parts of the dental arch that show a higher prevalence of tooth variability. Design198 randomly selected Caucasian subjects (93 females, 105 males) aged between 10.0 and 24.5 years (mean age 14.15, SD 2.34 years) were included. A total of 5544 teeth were examined and dental anomalies of tooth number, shape and position (oral teeth positions and teeth rotations greater than 45°) were recorded. Results18.68 per cent of the subjects had one or more unerupted teeth. Aplasia as the cause of uneruption was found in 12.12 per cent of the subjects, statistically significantly more frequently in females than males (Fisher test, p<0.05). Tooth shape anomalies were found in 6.57 per cent of the sample, more frequently in males than females (Fisher test, p<0.05). Oral position of one or more teeth was found in 47.98 per cent of the sample, whilst rotations greater than 45° were found in 15.66 per cent, with no statistically significant differences between females and males. One or more of the observed dental anomalies were found in several tooth types, however all the observed dental anomalies were found only in second premolars and in upper lateral incisor. ConclusionsAccording to the results of this study, it seems that some places in the dental arch show a greater variability in terms of tooth number, shape and position. This could be a result of genetic and environmental influences during odontogenesis or a result of evolutionary trends.

The Orthodontic-Restorative Interface: 2. Compensating for Variations in Tooth Number and Shape

The aim of this second article in this series of two is to outline a variety of methods which may be used to compensate for variations in tooth shape and number using a combination of orthodontic and restorative approaches. It will also provide an overview of other areas of patient care which necessitate a multi-disciplinary orthodontic/restorative approach. The article will highlight the importance of combined planning from the outset and the close relationship between the different specialties, which must be maintained throughout treatment. The methods of compensating for variations in tooth number and shape will often require contributions from both orthodontist and restorative dentist. It is important that both disciplines are involved in the assessment and treatment planning process so that they know what will be expected of them during the patient's care. Treatment planning in isolation may lead to care being delivered which is below the optimum standard which can be achieved. The orthodontist and restorative dentist are likely to liaise with the patient's general dental practitioner so that he/she can provide the restorative treatment in some cases. Great improvements in aesthetics and function may be obtained using an interdisciplinary approach for patients who have variations in tooth number and shape.

The Orthodontic-Restorative Interface: 1. Patient Assessment

The first article in this series of two aims to outline the assessment of patients for whom a combined orthodontic-restorative approach would be beneficial. In particular, it will concentrate on the assessment of patients who have hypodontia and tooth size discrepancies. The importance of the aesthetic assessment for these cases will be highlighted. Variations in tooth number and tooth size discrepancy often require a combined treatment planning approach from the orthodontist and restorative dentist. The referring general dental practitioner has a key role in recognizing that this approach may be required and highlighting this in the initial patient referral. It is likely in the more straightforward cases that the GDP will be providing the restorative treatment and so an increased understanding of these cases would be beneficial. In the second paper, treatment options will be presented. For patients who require a combined orthodontic/restorative approach, it is important that orthodontic and restorative disciplines liaise closely in the assessment and treatment planning process so that optimal care may be planned.

Number of teeth, body mass index, and dental anxiety in middle-aged Swedish women

Risk factors for poor dental health include obesity, low socio-economic status, poor dietary habits, and dental anxiety. The aim of this study was to explore the complex relation between body mass index (BMI) and number of teeth in middle-aged women taking education, dietary intake patterns, dental care utilization, and dental anxiety into account. Three groups of women (37-60 years): reference women (group I, BMI 23.8 - 3.1 kg/m2), obese women (group II, BMI 35.0 - 2.6 kg/m2), and severely obese women (group III, BMI 41.0 - 3.4 kg/m2) were included. Questionnaires were used to assess education, smoking, number of teeth, dental care utilization, dental anxiety, dietary intake, and meal patterns. Age, education, and smoking habits did not differ significantly between groups. However, there were significant global differences in number of teeth (27.2 - 3.4, 23.0 - 9.2, 24.7 - 5.9) and reported daily energy intake (9756 - 3363 kJ, 10344 - 3850 kJ, 11970 - 3786 kJ in groups I, II, and III, respectively). In a multiple regression model, a lower number of teeth was independently associated with higher age, higher BMI, lower education, irregular dental care, high dental anxiety, higher energy intake, and lower iron intake. These variables explained 25% of the variation in number of teeth. In conclusion, BMI is an independent predictor of number of teeth in middle-aged women when socio-economic, dietary, and psychological factors are taken into account.

Molecular strategies in the evolution of mammalian dental patterning

The acquisition of masticatory capability by mammals allowed a better processing of food and a consequent increase in the efficiency of nutrients intake by the digestive system. The development of tooth classes and variations in tooth number can be considered intrinsic characteristics of mammalian dentition. These features allowed species to develop specialized dentitions, creating new adaptive zones. Comparative developmental data from knockout mutant mice and human tooth agenesis present new insights on the molecular strategies that permitted rapid phenotypic differentiation, adaptation and speciation of mammalian dentition.

Distribution patterns of primary and permanent dentition in children with unilateral complete cleft lip and palate.

To investigate the distribution patterns of primary and permanent teeth in the cleft area and the numerical variation in teeth in unilateral complete cleft lip and palate (UCLP) patients. A survey of the dentition in UCLP patients. Craniofacial Center, Chang Gung Memorial Hospital, Taipei, Taiwan. 137 UCLP patients who met the following criteria: (1) have had at least one panoramic film taken, (2) the first panoramic film illustrates either primary or early mixed dentition. Evaluation of both permanent and primary dentition was available in 91 cases. Two evaluators performed independent evaluations of number and distribution of teeth in UCLP patients. The hypothesis that there are two odontogenic origins for maxillary lateral incisors was proposed to explain the occurrence of distribution patterns of dentition in the cleft area and to explain differences between primary and permanent dentition in UCLP patients. Four distribution patterns in the cleft area were identified in both the primary and the permanent dentition. In the primary dentition, placement of the lateral incisor distal to the alveolar cleft was the predominant pattern (pattern y, 82.4%), followed by absence of the cleft side maxillary lateral incisor (pattern ab, 9.9%), presence of one tooth on each side of the alveolar cleft (pattern xy, 5.5%), and placement of the lateral incisor mesial to the alveolar cleft (pattern x, 2.2%). In the permanent dentition, the most common pattern was the absence of the maxillary lateral incisor on the cleft side (pattern AB, 51.8%), followed by lateral incisor placement distal to the alveolar cleft (pattern Y, 46%), lateral incisor placement mesial to the alveolar cleft (pattern X, 1.5%) and the presence of one tooth on each side of the alveolar cleft (pattern XY, 0.7%). The discrepancy between the distribution patterns of primary dentition and permanent dentition successors is 57.1%. Variations in tooth number in both primary and permanent dentition of UCLP patients occurred most often in the cleft area. Abnormalities in the number of teeth (hypodontia or hyperdontia) outside the cleft area were more common in the permanent dentition than in the primary dentition (24.1% versus 4.4%). Four distribution patterns in the cleft area were identified in both sets of dentition. Our findings of distribution patterns in UCLP patients support the hypothesis that there may be two odontogenic origins for maxillary lateral incisors. Clinicians involved in managing the dentition of UCLP patients should consider the high frequency of numerical variation both in and outside the cleft area before starting dental treatment.

Supernumerary Teeth in Moose and Variations in Tooth Number in North American Cervidae

Journal Article Supernumerary Teeth in Moose and Variations in Tooth Number in North American Cervidae Get access D. Gentry Steele, D. Gentry Steele Department of Anthropology, University of Alberta, Edmonton, Alberta, Canada T6G 2H4 Search for other works by this author on: Oxford Academic Google Scholar W. David Parama W. David Parama Department of Anthropology, University of Alberta, Edmonton, Alberta, Canada T6G 2H4 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 60, Issue 4, 20 November 1979, Pages 852–854, https://doi.org/10.2307/1380210 Published: 20 November 1979 Article history Received: 26 February 1979 Accepted: 14 May 1979 Published: 20 November 1979

Unusual Dentition in Mule Deer

Cowan (Canad. Jour. Res., D , 24: 71–103) states that “variations in numbers of teeth in the genus Odocoileus are rare.” He further reports but one instance of supernumerary incisors in Odocoileus hemionus and quotes two cases of canines encountered by Nordquist (Calif. Fish and Game, 27(1): 39–40). Because of this apparent rarity of variations in number of teeth the writer is reporting on four cases of fewer teeth than normal and four cases of more than normal which he has encountered among Rocky Mountain mule deer, O. h. hemionus , of Utah and eastern Nevada. Fewer than normal deciduous or permanent teeth .—Case 1 involved a 28-month-old doe with all permanent premolars functional except the first one (P2) of the left mandible, where a tiny milk tooth 2 mm. in height and in diameter was still retained. Removal of the underlying bone revealed no corresponding permanent tooth. …