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Journal of Morphology Jan 2019Molars are highly integrated biological structures that have been used for inferring evolutionary relationships among taxa. However, parallel and convergent...
Molars are highly integrated biological structures that have been used for inferring evolutionary relationships among taxa. However, parallel and convergent morphological traits can be affected by developmental and functional constraints. Here, we analyze molar shapes of platyrrhines in order to explore if platyrrhine molar diversity reflects homogeneous patterns of molar variation and covariation. We digitized 30 landmarks on mandibular first and second molars of 418 extant and 11 fossil platyrrhine specimens to determine the degree of integration of both molars when treated as a single module. We combined morphological and phylogenetic data to investigate the phylogenetic signal and to visualize the history of molar shape changes. All platyrrhine taxa show a common shape pattern suggesting that a relatively low degree of phenotypic variation is caused by convergent evolution, although molar shape carries significant phylogenetic signal. Atelidae and Pitheciidae show high levels of integration with low variation between the two molars, whereas the Cebinae/Saimiriinae, and especially Callitrichinae, show greater variation between molars and trend toward a modular organization. We hypothesize that biomechanical constraints of the masticatory apparatus, and the dietary profile of each taxon are the main factors that determine high covariation in molars. In contrast, low molar shape covariation may result from the fact that each molar exhibits a distinct ecological signal, as molars can be exposed to distinct occlusal loadings during food processing, suggesting that different selective pressures on molars can reduce overall molar integration.
Topics: Anatomic Landmarks; Animals; Body Size; Fossils; Mandible; Molar; Phylogeny; Primates; Principal Component Analysis
PubMed: 30556948
DOI: 10.1002/jmor.20907 -
Pediatric Dentistry Jan 2018To explore cost-effective options for pulpotomy, chamber fillings, and crowns in primary molars using bioactive cements. (Comparative Study)
Comparative Study Randomized Controlled Trial
PURPOSE
To explore cost-effective options for pulpotomy, chamber fillings, and crowns in primary molars using bioactive cements.
METHODS
Thirty extracted primary molars were divided into five groups, each having two sets of three teeth (one first molar and two second molars). Pulpotomy and restorative options were randomly assigned: Biodentine plus Ketac Molar; NuSmile NeoMTA plus Tempit LC; NeoMTA Plus plus Fuji IX; MTA Angelus plus IRM capsule; MTA Flow plus IRM powder and liquid. After mixing one dose, pulp chambers of the first molar and one second molar were filled with a two-millimeter layer of bioactive cement and filling material (protocol A). The other second molar's chamber was solo filled by a single mixed dose of bioactive cement (protocol B). The cost for each material was calculated independently, regardless of the group to which they belonged. A market assessment for primary molar crowns was performed, and a comparison table was produced.
RESULTS
For protocol A, the lowest mean cost per tooth (LMC) was obtained for NeoMTA cements and IRM powder and liquid; for solo bioactive cement pulp chamber filling, protocol (B), LMC was obtained for NeoMTA cements. Zirconia crowns were the costliest.
CONCLUSIONS
NeoMTA-type cements were the most cost-effective option for single-tooth pulpotomy. Zirconia crowns had the highest cost per tooth.
Topics: Cost-Benefit Analysis; Crowns; Dental Cements; Dental Restoration, Permanent; Humans; Molar; Pulpotomy; Tooth, Deciduous
PubMed: 29482683
DOI: No ID Found -
Journal of Dentistry Jun 2020Recent software advancements have facilitated quantification of erosive tooth wear progression using intraoral scans. This paper investigated if wear on commonly...
OBJECTIVES
Recent software advancements have facilitated quantification of erosive tooth wear progression using intraoral scans. This paper investigated if wear on commonly affected surfaces (central incisors and first molars) was representative of wear on the full arch.
METHODS
Bimaxillary digital intraoral scans (True Definition, 3 M, USA) of patients (n = 30) from the monitoring arm of the Radboud Tooth Wear Project, were taken at baseline and at 3 years (+/-10months). The occlusal/incisal surface of each tooth (excluding 3rd molars) was analysed for volume change and volume change per mm of analysed surface area in WearCompare (www.leedsdigitaldentistry.com/Wearcompare) following previously published protocols. Data were normal, descriptives and multi-level linear regression analysis was performed in Stata v15.1 taking patient level and surface type data into account.
RESULTS
Data from 556 surfaces in 29 patients were included in analysis. Per patient, mean volume loss (95 % CI) was -0.91mm(-1.28,-0.53) on all surfaces, -1.85mm(-2.83,-0.86) on index surfaces, -2.53mm(-3.91,-1.15) on molar surfaces and -0.83 mm(-1.34,-0.31) on upper central incisal surfaces. Statistical differences were observed between analysing all surfaces and index teeth(p = 0.002) in addition to molar surfaces(p < 0.0001). Mean volume loss per mm of surface analysed was -0.024 mm (-0.031,-0.017), -0.028mm (-0.041,-0.014), -0.030mm (-0.046,-0.013) and -0.025mm (-0.041,-0.010) for all surfaces, index surfaces, first molar surfaces and central incisor surfaces respectively with no statistical differences between groups.
CONCLUSIONS
Wear on upper central incisors was not statistically different to full arch wear analysis. If the surface area is standardised, wear on both index surfaces are statistically similar to wear on the full arch.
CLINICAL SIGNIFICANCE
These results suggest that analysing rates of wear on index teeth can be a resource-saving substitute for analysing rates of wear on the entire dentition, provided the surface area is standardised. If whole surfaces are analysed, the molar surfaces will show greater rates of wear.
Topics: Dentition; Humans; Incisor; Molar; Tooth Attrition; Tooth Erosion; Tooth Wear
PubMed: 32360512
DOI: 10.1016/j.jdent.2020.103342 -
BMC Oral Health Jul 2022The mandibular second molars demonstrate variations on root and canal morphology. The aim of this study was to investigate all the root canal morphology of mandibular...
BACKGROUND
The mandibular second molars demonstrate variations on root and canal morphology. The aim of this study was to investigate all the root canal morphology of mandibular second molars and analyze the morphological variations in patients by gender and age in a Chinese population use CBCT imaging.
METHODS
Cone-beam computed tomographic images of 1200 bilateral mandibular second molars were obtained from 600 patients (300 females and 300 males) who required a preoperative assessment for implant surgery, surgical removal of impacted teeth, orthodontic treatment, surgery of maxillofacial tumour and cysts or LeFort I osteotomy. CBCT images were divided into 5 groups according to age: "15-24 years", "25-34 years", "35-44 years", "45-54 years" and "≥ 55 years"; and 2 groups by gender: "females" and "males". The following information were recorded: the number of roots and canals and their morphology, the frequency and configuration of C-shaped canals by gender, age and position (left and right). The chi-square test was used to analyse differences between groups. P value of < 0.05 was considered statistically significant.
RESULTS
Of the 1200 teeth, 61% had two separate roots located mesiodistally, 35.6% had one C-shaped root. The 45.3% teeth had three canals in two-rooted mandibular second molars. The mesial root showed a Vertucci type II configuration in 28.9% cases followed by type IV(24.4%). While the distal root showed a significant higher prevalence of type I configuration in 95.6%. In the examined 1200 teeth, 430 teeth (35.8%) had C-shaped root canals. The prevalence of C-shaped root canal systems was significantly higher in females (42.5%) than in males (29.1%) (P = 0.000), and did not differ with age (P = 0.126). The 80.4% C-shaped canals were bilateral (P = 0.000) and did not differ with side (left and right) (P = 0.758).
CONCLUSIONS
The most commonly observed root morphology for the mandibular second molars was 2 separate roots with three canals.The prevalence of C-shaped root canal is 35.8% and is more higher in females than in males.
Topics: Adolescent; Adult; China; Cone-Beam Computed Tomography; Dental Pulp Cavity; Female; Humans; Male; Mandible; Molar; Young Adult
PubMed: 35790917
DOI: 10.1186/s12903-022-02299-8 -
The Journal of International Medical... Jun 2020This study aimed to assess the positional relationships between the maxillary sinus and the first and second molars in a western Chinese population by using cone-beam...
OBJECTIVE
This study aimed to assess the positional relationships between the maxillary sinus and the first and second molars in a western Chinese population by using cone-beam computed tomography.
METHODS
This study included 212 patients (652 maxillary molars and 1956 roots). Patient demographics (sex and age) and cone-beam computed tomography data regarding the relationship between molar roots and the maxillary sinus were obtained. This relationship was stratified into four types for statistical analysis.
RESULTS
Sex and side did not significantly influence the distance between maxillary molar roots and the maxillary sinus. However, the distance between maxillary molar roots and the maxillary sinus increased with age. The mesiobuccal root of the second molar was nearest to the maxillary sinus. The most common relationship type involved absence of root contact with the sinus border and presence of a maxillary sinus cross-section above the root apex.
CONCLUSIONS
Compared with other teeth, the maxillary posterior teeth have a complex anatomical structure and are closely related to the sinus. These findings may serve as reference information for root canal treatment, tooth extraction, dental implant, and other dental clinical procedures among patients in western China.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; China; Cone-Beam Computed Tomography; Female; Humans; Male; Maxillary Sinus; Middle Aged; Molar; Postoperative Complications; Retrospective Studies; Tooth Extraction; Tooth Root; Young Adult
PubMed: 32489120
DOI: 10.1177/0300060520926896 -
L' Orthodontie Francaise Dec 2022Despite a high prevalence of agenesis, third molars should frequently be considered in our orthodontic treatment plans.
INTRODUCTION
Despite a high prevalence of agenesis, third molars should frequently be considered in our orthodontic treatment plans.
MATERIAL AND METHOD
The aim of this study was to describe, according to the literature, the therapeutic possibilities of third molar management.
RESULTS
The avulsion isn't systematic. The French National Authority for Health has updated its guidance about it. Indeed, surgical procedures can present with potentially irreversible risks (nerve damage, bone necrosis). It is necessary to assess the benefit/risk balance and to inform the patient accordingly. Whether symptomatic or not, pathological third molars are among the most obvious indication for avulsion as well as third molars that may lead to resorption or carious lesion of the adjacent molar. On the other hand, it is not recommended to avulse third molars to prevent the appearance of anterior crowding or in case of a favorable evolution. Some of our orthodontic therapies can lead to the avulsion of the third molars: the orthognathic surgery (especially mandibular surgery) or the distalization. They can be placed by transplantation, by mesialization, sometimes with the help of bone anchors, or by straightening the axis for a prosthetic or implant-prosthetic restoration.
DISCUSSION
In the adolescent, the germs of the third molars would not limit the amount of distalization; these molars would continue to grow despite the distalization of the more anterior molars.
CONCLUSION
Wisdom teeth should be considered as third molars in their own right and can thus be used in edentulous situations.
Topics: Adolescent; Humans; Molar, Third; Molar; Tooth Extraction; Dental Care; Malocclusion; Tooth Movement Techniques
PubMed: 36718757
DOI: 10.1684/orthodfr.2022.105 -
Homo : Internationale Zeitschrift Fur... May 2018Crenulated molars have been used extensively in biological anthropology. However, the trait has not been formally defined, nor have population frequencies been...
Crenulated molars have been used extensively in biological anthropology. However, the trait has not been formally defined, nor have population frequencies been thoroughly outlined. This study provides a formal definition of molar crenulations and data on their presence in a large sample. Data were collected on maxillary and mandibular molars of modern dental material from various populations: South African, Hispanic, Japanese, American White, and American Black (n = 750). Molar crenulations were defined and a rank-scale created. Statistical analyses include chi-squared, correspondence analysis, and trait correlations. Significant statistical differences were found between populations in all molars. Minimal sexual dimorphism was noted, and is most pronounced among the American Black sample. Generally, American White and Japanese samples showed lower frequencies of molar crenulations, the highest frequencies were seen in the American Black and South African samples, and the Hispanic sample was intermediate. Correspondence analysis showed that American Black samples tended towards grade 2, and South African samples were more often a grade 1. American White and Japanese samples were most often grade 0, and Hispanic samples were intermediate. Correlations were noted across the molars. Population differences exist in the presence of molar crenulations, which were likely shaped by evolution. Based on these results molar crenulations can be added to the suite of traits currently used to study population differences.
Topics: Asian People; Biological Evolution; Black People; Female; Hispanic or Latino; Humans; Male; Mandible; Maxilla; Molar; Sex Characteristics; White People
PubMed: 30007496
DOI: 10.1016/j.jchb.2018.06.001 -
Clinical Oral Investigations Dec 2023This study assessed the outcome of shaping the mesial roots of mandibular first molars containing band-shaped isthmuses with an isthmus floor located at the apical third...
OBJECTIVE
This study assessed the outcome of shaping the mesial roots of mandibular first molars containing band-shaped isthmuses with an isthmus floor located at the apical third with Reciproc Blue and Rotate instruments in terms of canal transportation, canal aberrations and unprepared apical canals.
MATERIALS AND METHODS
Pair-matched mesial roots of mandibular first molars according to their isthmus location (distance from apical foramina) and size were constructed based on quantitative measurements (length, major and minor diameter at isthmus roof and floor) on preoperative micro-CT scanning (n = 10). The pair-matched specimens were prepared either using Reciproc Blue R25 (25.08v) or Rotate (15.04, 20.05, 25.06) instruments and then subjected to a second micro-CT scanning. Micro-CT scans were analysed to evaluate the canal transportation at the apical foramen and isthmus floor levels and the frequency of procedural errors (separated instruments, artificial canal preparation, cross shaping and unprepared apical canals). Canal transportation values were compared using Mann-Whitney U, and the distribution of procedural errors was compared with chi-square tests with a 5% significance threshold.
RESULTS
Greater transportation values were detected in the apical foramen level compared to the isthmus floor in both groups. No significant difference was detected between Rotate and Reciproc Blue groups in terms of absolute transportation values and the incidence of procedural errors (p > .05).
CONCLUSION
Preparation of mesial root canals containing a band-shaped isthmus at the apical portion with Reciproc Blue and Rotate instruments caused transportation of the original canal position at the isthmus floor and the apical foramen levels and resulted in procedural errors.
CLINICAL RELEVANCE
This ex vivo micro-CT study using controlled pair-matched specimens showed that presence of a band-shaped isthmus complicates canal preparation procedure irrespective of the preparation systems.
Topics: X-Ray Microtomography; Root Canal Preparation; Dental Pulp Cavity; Tooth Apex; Molar; Equipment Design
PubMed: 37861748
DOI: 10.1007/s00784-023-05324-4 -
Homo : Internationale Zeitschrift Fur... Mar 2021Crenulated occlusal surfaces have previously been described on maxillary and mandibular molars; however, the occurrence of crenulations on premolars is only anecdotally...
Crenulated occlusal surfaces have previously been described on maxillary and mandibular molars; however, the occurrence of crenulations on premolars is only anecdotally supported. This study applies a modified version of a recordation scale developed for molar crenulations to record the frequency of crenulated premolars on the maxillary and mandibular premolars of modern individuals from a variety of populations: African, African American, Asian, Australian, European American, Latino, and Malay ( = 1238). Crenulations on the molars of the same individuals were also recorded to assess the relationship between occurrences on premolars and molars. Observations were compiled into frequency tables and analyzed using chi-square tests and correspondence analysis; relationships among teeth were quantified with polychoric correlation coefficients. Although crenulated premolars are observed rarely overall, the frequency of occurrence is significantly associated with group membership. Crenulated premolars occur most frequently in African, African American, and Australian samples and are observed least often among European American and Malay samples. Additionally, there is a strong relationship between third and fourth premolars, particularly within a jaw, and between fourth premolars and the molars in the same jaw. Interestingly, crenulations in premolars are most strongly associated with Grade 2 crenulations on molars. The observed differences between populations, and the associations between crenulated premolars and molars are evaluated with respect to function, tooth size, and dental development. Based on the results presented here, we recommend the addition of premolar crenulations to existing dental morphological traits used to study human population variation.
Topics: Australia; Bicuspid; Humans; Maxilla; Molar; White People
PubMed: 33585856
DOI: 10.1127/homo/2021/1228 -
Oral and Maxillofacial Surgery Sep 2022A correlation between impacted maxillary third molars on the eruption potential of the maxillary second molar has been identified. There is little published evidence...
BACKGROUND
A correlation between impacted maxillary third molars on the eruption potential of the maxillary second molar has been identified. There is little published evidence available in the literature regarding a treatment modality for this presentation. AIMS : The aim of this case series is to propose a joint surgical and orthodontic approach for the management of such cases. METHOD : A retrospective search of all patients treated for impacted second and third maxillary molars from 2014 to 2020 revealed 24 cases. Surgical planning was facilitated with the use of a CBCT to help orientate the teeth in 3-D and assess any associated pathology to nearby structures. Twenty-three cases were treated via surgical removal of the impacted third molar and subsequently monitored for spontaneous maxillary second molar eruption.
CONCLUSION
All treated cases showed complete or partial spontaneous eruption followed by orthodontic repositioning if required.
Topics: Humans; Maxilla; Molar; Molar, Third; Retrospective Studies; Tooth, Impacted
PubMed: 34625858
DOI: 10.1007/s10006-021-01011-4