ABSTRACT
Objective@# To investigate the effect of a metal occlusal surface and stress interruption design on minimally invasive prosthodontics for patients with distal extension absence and insufficient occlusal gingival distance.@*Methods @# We retrospectively studied the case of minimally invasive prosthodontic (Vitallium 2000) combined with a metal occlusal surface for distal extension absence in a patient with insufficient occlusal gingival distance; the stress breaking design and pressure impression technology are examined, and relevant articles are reviewd. @*Results@#The design effectively solves the problems of insufficient occlusal gingival distance, large occlusal force and easy denture fracture. Reviewing the relevant literature, stress interruption design can effectively protect abutment teeth, but the behavior of stress interruption design and stress conduction phenomena in the mouths of patients has not been reported. The T-scan test results of this study showed that before and after wearing the denture, the occlusal force distribution ratio of the patient changed from 77.5% on the left and 22.5% on the right to 61.3% on the left and 38.7% on the right. The occlusal force distribution ratio of the right dentition to the total occlusal force increased by 16.2%, and the occlusal force became better distributed. Further analysis showed that the occlusal forces on the left and right sides were nearly the same in the initial occlusion stage. As the occlusal force was further increased, the proportion of the occlusal force on the right side decreased in the middle of the occlusion stage and further decreased in the final occlusion stage until it reached a dynamic balance. The above T-scan test and literature review results suggest that this dynamic balance phenomenon of bite force is related to the stress interruption design and the stress conduction effect of the split framework.@* Conclusion @#The composite of stress interruption design and metal occlusal surface allows for minimally invasive prosthodontics for the treatment of distal extension absence in patients with insufficient occlusal gingival distance.
ABSTRACT
SUMMARY: Descriptive observational cross-sectional study to determine the AOP of the second molars (55, 65, 75, 85) and the first permanent molars (16, 26, 36 and 46) in 459 study models corresponding to six ethnic groups in Colombia, Embera indigenous of Alto Baudó (Chocó), Caucasoid mestizos of Cali (Valle del Cauca), African descent of Cali (Valle del Cauca), Misak indigenous of Silvia (Cauca), Nasa indigenous of Morales (Cauca), and indigenous of Leticia (Amazonas). There were no significant differences of AOP among the six ethnic groups except when compared to the Amazon Indians with African descent of Cali, Embera indigenous and Nasa indigenous. There was no sexual dimorphism except tooth 65 for all ethnic groups. There was bilateral symmetry except between teeth 16 and 26. The distance matrix showed that Caucasoid mestizos of Cali were grouped with microdont populations, Amazon indigenous, Embera indigenous, Misak indigenous and Nasa indigenous, and African descendants of Cali were grouped with mesodont populations. The Embera and Amazon indigenous had the highest values of OAP associated with the relative isolation and less mestizaje. Overall, there was no sexual dimorphism or bilateral asymmetry. This study coincides with the different theories about reducing the size of the teeth as evolutionary characteristic of hominids.
RESUMEN: Estudio observacional descriptivo de corte transversal en el que se determinó el APO de los segundos molars deciduos (55, 65, 75, 85) y de los primeros molares permanentes (16, 26, 36, 46) en 459 modelos de estudio correspondientes a seis grupos étnicos de Colombia: Indígenas embera del Alto Baudó (Chocó), mestizos caucasoides de Cali (Valle del Cauca), afrodescendientes de Cali (Valle del Cauca), indígenas misak de Silvia (Cauca), indígenas nasa de Morales (Cauca) e indígenas de Leticia (Amazonas). No se encontraron diferencias significativas en el APO de los seis grupos étnicos, excepto entre indígenas del Amazonas y de afrodescendientes de Cali, e indígenas embera e indígenas nasa. No se evidenció dimorfismo exual en ninguno de los seis grupos. Hubo simetría bilateral, excepto entre los dientes 16 y 26. La matriz de distancias demostró que los mestizos caucasoides de Cali se agrupan con poblaciones microdontes, indígenas del amazonas, indígenas embera, indígenas misak e indígenas nasa; mientras que los afrodescendientes de Cali se agrupan con poblaciones mesodentes. Los indígenas embera y del Amazonas presentaron altos valores del APO, asociado a su aislamiento relativo y bajo mestizaje. En términos generales, no hubo dimorfismo sexual ni asimetría bilateral. Los resultados de este estudio concuerdan con diferentes teorías sobre la reducción del tamaño dental como una característica evolutiva de los himínidos.
Subject(s)
Humans , Male , Female , Dental Occlusion , Racial Groups , Molar/anatomy & histology , Ethnicity , Cross-Sectional Studies , Sex Characteristics , Colombia , Forensic DentistryABSTRACT
Background@#The development of caries is dependent on the interaction of four primary factors. These are a host (tooth surface), a substrate (food), the presence of oral bacteria, and time. Caries will not develop if any of these four primary factors are not present. Although the primary molars are naturally replaced by the age of 10–12 years, caries, pulpitis, periapical periodontitis, primary molar defects, even loss of primary molars can have adverse effects on the permanent teeth. The bite force is created by the dynamic action of the muscles during the physiologic act of mastication. Determination of individual bite force level has been widely used in dentistry, mainly to understand the mechanics of mastication for evaluation of the therapeutic effects of prosthetic devices and to provide reference values for studies on the biomechanics of prosthetic devices.@*Methods@#The 4-5 year olds who were treated at the National University of Medical Sciences, School of Dentistry, Dental Hospital were admitted to this study. The magnitude of the bite force in Newtons (N) was measured (Occlusal Force Meter GM10) bilaterally corresponding with the 1st and 2nd primary molars using a specifically designed single tooth bite force gauge.@*Results@#Fifty three children were included in the study. The prevalence of dental caries was found to be 66.04% respective. No significant differences were found between the male and the female in bite force and p values of the study. Analysis of variance evaluated difference among the three groups. The means of maximum bite force were 258.83, 216.43 and 189.15 N for the groups. Significant differences between first molar and second molar’s occlusal surface area were detected. The analysis of correlation showed that the caries and bite force presented weak inverse (r=-0.36) correlation.@*Conclusion@#The bite force of 4-5 years old children was independent of gender, body weight, body height and side of mastication. The bite force on teeth with caries were 189.15 N. The caries was in weak inverse correlation with the bite force quantity. The amount of bite force measured was dependent on tooth occlusal surface area.
ABSTRACT
Objective:To evaluate the effect of the occlusal surface height of a mandibular posterior implant-supported single crown on stress in bone tissues.Methods:Three-dimensional finite element models of the implant-supported single crown replacing the missing right lower second premolar,mesial and distal natural teeth,periodontal membrane,alveolar bone,loaded rigid body and analog food of almond were established.Using the Federation Dentaire International (FDI)system,the first premolar, the second premolar and the first molar were represented with 44,45,46.Three occlusal surface heights of the crown were studied:(1 )normal height;(2)1 5 μm reduction in height;(3)30 μm reduction in height.The models were loaded by independent loading with maximal occlusal force(44 by 280 N,45 by 360 N,and 46 by 480 N)and average occlusal force(44 by 1 40 N,45 by 1 80 N,and 46 by 240 N)on the single crown;combined loading (maximal occlusal force transformed into uniform load of 3 .7 MPa on top of rigid body,in contact with points on the occlusal surface),and analog almond-like food loading (average occlusal force transformed into uniform load of 1 .67 MPa in simulated food chewing,in contact with points on the occlusal surface).Results:For maximal biting force under independent loading,Von Mises stress peak values in bone tissues around 44,45,and 46 were 82.57 MPa,45.26 MPa and 27.79 MPa;For average biting force,peak values were 41 .28 MPa,22.63 MPa and 1 3.89 MPa.Under com-bined loading,compared with the normal occlusal surface height group,Von Mises stress peak values de-creased 4.6 MPa,by 0.84%;increased 7.52 MPa,by 20.04%,and decreased 1 .8 MPa,by 5.84%, for 45,46,and 44 in the 30 μm infra-occlusion group,respectively.Under food loading,Von Mises stress peak values decreased 0.34 MPa,by 1 .62%;increased 1 .1 1 MPa,by 2.66%;and increased 0.06 MPa,by 0.54%,and for 45,46,and 44 in the 30 μm infra-occlusion group,respectively.Con-clusion:Within the limitation of this study,within 30 μm reduction of the occlusal surface height of im-plant-supported single crown,no significant difference of the peak values was observed.
ABSTRACT
Presence of accessory cusp on the occlusal surface of a tooth may occasionally pose problems to dentists’. Although its presents may not be a cause for alarm in most instances, nevertheless it can lead to serious consequences if it is damaged. This report describes a rare finding of bilateral central accessory cusp seen on the occlusal surface of both the 2nd maxillary deciduous molars and the need for continuous dental surveillance and preventive measures have been highlighted.