Three-dimensional finite element analysis of different implant prostheses in maxillary anterior teeth region under different occlusal relationships / 中国组织工程研究

BACKGROUND: In the treatment with dental implant prosthesis, the stress distribution of marginal bone and implant-bone interface Is affected by the factors of restoration and occlusion. The Internal structure and the stress distribution of Implant-bone Interface determine the long-term life of the implant and the stability of the marginal bone. OBJECTIVE: To analyze the effects of zirconia-based all-ceramic crown and Co-Cr alloy porcelain ceramic crown on the stress distribution of implant-bone interface, implant, prosthesis abutment, retention screw, and the inner structure in three occlusal relationships. METHODS: Using Mimics 17.0 software, the implant model of maxillary central incisor was established based on the cone beam CT of a patient undergoing prosthesis implantation Into the maxillary central incisor. Two kinds of three-dimensional finite element models of zirconia-based all-ceramic crown and Co-Cr alloy porcelain ceramic crown were constructed. The edge to edge occlusion, normal occlusion and deep overbite were simulated to analyze the stress distribution of Implant structure and the Implant-bone Interface in the three occlusal relationships. RESULTS AND CONCLUSION: (1) In the Co-Cr alloy porcelain ceramic crown group, when the occlusal relationship changed from the edge-to-edge occlusion to the normal occlusion and deep overbite relationships, the stress at the occlusal point of the prosthesis increased correspondingly, and the stress at the abutment, Implant and the Implant-bone Interface decreased. In the normal occlusal relationship, the stress at the retention screw was more concentrated than that in the other two occlusal relationships, and its peak value of the equivalent stress was higher. (2) In the zirconia-based all-ceramic crown group, when the occlusal relationship changed from edge-to-edge occlusion to the normal and deep overbite relationships, the stress peaks of the abutment, implant and implant-bone interface decreased gradually. In the normal occlusal relationship, the stress peaks of the occlusal point and the retention screw were higher than those in the other two occlusal relationships. (3) In the edge-to-edge occlusion relationship, the peak of equivalent stress at the occlusal point of the implant prosthesis in the Co-Cr alloy porcelain ceramic crown group was slightly higher than that in the zirconia-based all-ceramic crown group. The peaks of equivalent stress of the abutment, retention screw, Implant, and Implant-bone Interface in the Co-Cr alloy porcelain ceramic crown group were slightly lower than those in the zirconia-based all-ceramic crown group. In the normal occlusal relationship, the peak of equivalent stress at the neck of the implant in the Co-Cr alloy porcelain ceramic crown group was slightly higher than that in the zirconia-based all-ceramic crown group. In the deep overbite relationship, the peaks of the equivalent stress at the occlusal site of the implant prosthesis and the neck of the implant in the Co-Cr alloy porcelain ceramic crown group were higher than those in the zirconia-based all-ceramic crown group. The peaks of equivalent stress of the abutment, retention screw, and implant-bone interface In the Co-Cr alloy porcelain ceramic crown group were slightly lower than those in the zirconia-based all-ceramic crown group. (4) These results showed that different occlusal relationships and different upper structures of the implant prosthesis affected the stress distribution in each part of the implant and at the implant-bone interface. This finding may provide a reference for the prediction of long-term complications of implant prosthesis.

Clinical application and complications of short implants (≤6 mm) / 口腔疾病防治

@#Short implants can be used as an alternative in cases of insufficient vertical bone volume after dentition defect or absence of dentition to simplify or avoid bone augmentation procedures. Short implants (≤ 6 mm) are reported to have a mean survival rate of 96% after a period of 1-5 years in function and have been widely used in cases of dentition defects or absence of dentition. Compared with conventional implants (≥ 10 mm) combined with bone augmentation procedures, short implants have fewer surgery-related complications, less marginal bone loss, shortened treatment times and reduced costs, and are preferred by patients. Due to a lack of evidence, a high crown-implant ratio should not be an obstacle for the use of short implants. In addition, most of the current literature has not enough follow-up time, the long-term implant survival data of short implants remain unclear. To improve the clinical outcomes of short implants, attention should be paid to the implant site, bone quality, and occlusal force as well as to the presence of oral health maintenance, periodontal diseases and habits through a careful intraoral and radiographic examination. The choices of wider implant use and splint restoration are recommended, occlusal force should be paid attention during implant maintenance. Inappropriate stress on restorations should be avoided. Future studies should be focused on the long-term clinical outcomes of short implants.

Trauma oclusal: fundamentação teórica e correlações clínicas / Occlusion trauma: theoretical foundation and clinical correlations

Introdução: Na odontologia, a oclusão é a relação dos dentes superiores situados na maxila com os dentes inferiores situados na mandíbula quando se encontram em atividade normal e fisiológica, sem ocasionar desconfortos e dores para o paciente durante a mastigação. De forma contrária, temos uma alteração patológica ou adaptativa que pode lesionar o periodonto devido a forças excessivas, estas podem resultar no trauma oclusal. Objetivos: Sintetizar informações de bases científicas que abordem o trauma oclusal em busca de evidenciar a importância do conhecimento sobre a sua etiologia, diagnóstico e possíveis tratamentos para essa patologia. Métodos: Foi realizada uma revisão de literatura sistematizada nas bases de dados eletrônicas, Pubmed e Medline, limitando-se a busca ao período de 2011 a 2018. Conclusão: Diante das informações apresentadas, o cirurgião-dentista precisa estar apto para obter o diagnóstico correto do trauma dentário. Dessa forma, uma análise criteriosa feita a partir de exames complementares é indispensável para obter êxito no diagnóstico final.

Introduction: In dentistry, occlusion is the relationship of the upper teeth located in the maxilla with the lower teeth located in the mandible when they are in normal and physiological activity, without causing discomforts and pain to the patient during chewing. Conversely, we have a pathological or adaptive alteration that damages the periodontium due to excessive forces resulting in occlusal trauma. Objectives: This paper aims to synthesize scientifically based information that addresses occlusal trauma in order to highlight the importance of knowledge about its etiology, diagnosis and possible treatments for this pathology. Methods: A literature review systematized in the electronic databases, Pubmed and Medline, was limited to the search for the period from 2011 to 2018. Conclusion: Given the information presented, the dental surgeon must be able to obtain the correct diagnosis of dental trauma. Thus, a careful analysis made from complementary tests is indispensable to be successful in the final diagnosis.

Evaluation of pain perception during orthodontic debonding of metallic brackets with four different techniques

Abstract Objective The aim of this study was to evaluate patients' pain levels during four different debonding procedures. The null hypothesis was that the pain perception of the patients undergoing four different debonding applications was not statistically significant different. Material and Methods One hundred and twenty orthodontic patients who underwent orthodontic debonding were included in this study. The patients were randomly divided into 4 groups according to technique used in the patients. Debonding groups were as follows: Group 1) Conventional debonding group, Group 2) Medication group (acetaminophen was given 1 hour before debonding), Group 3) Soft bite wax group, and Group 4) Soft acrylic bite wafer group. The patients' levels of anxiety and fear of pain were evaluated before debonding, and Numerical Rating Scale (NRS) was applied to evaluate their pain perception during debonding. Mann-Whitney U and Kruskal-Wallis tests were used to evaluate non-normally distributed data. Categorical data analysis were carried by chi-square and McNemar tests. The significance level was set at p<0.05. Results Anxiety scores of the patients were not statistically significant between both genders and debonding groups. In the quadrants in which the patients were perceived, the highest pain level was in the left side of the mandible. The teeth in which the highest pain level was perceived were the lower left and upper right lateral incisors. Although there was no statistically significant difference among the pain scores of the patients in each group, quadrant scores of female patients showed significant differences, being the lowest scores in the soft bite wax group. Conclusions Majority of the patients had no fear of pain before debonding. Pain levels of the patients in the conventional debonding group were not significantly different from those of the other groups, except quadrant scores of females in the soft bite wax group. The null hypothesis was accepted.

A study on the occlusal wear patterns in maxillary posterior teeth with palatal side abfractions

PURPOSE: Aims to analyze the occlusal wear patterns in maxillary posterior teeth with palatal side abfractions and study the association between occlusal force and abfractions. MATERIALS AND METHODS: This study was conducted in a total of 308 teeth from 148 patients with palatal side abfractions in maxillary posterior teeth. The occlusal wears in maxillary premolars and molars with palatal side abfractions were classified and recorded. The classification was done by type of teeth, age, and gender, and in order to evaluate the statistical significance between groups, chi-square test was conducted (α = 0.05). RESULTS: Palatal side abfractions in maxillary posterior teeth were observed at the highest frequency in the 1st molars, and in all teeth with palatal side abfractions, more than one occlusal wear was observed. In classification by type of teeth, by age, and by gender, the occlusal wears in teeth with palatal side abfractions were observed at high frequency in cuspal inclined plane, central fossa, and marginal ridge, and there was a statistical significance (P < 0.05). CONCLUSION: Palatal side abfractions were observed at the highest frequency in maxillary 1st molars, and in all maxillary posterior teeth where palatal side abfractions were found, the occlusal wears were observed. And the occlusal wears were observed at high frequency in cuspal inclined plane, central fossa and marginal ridge. Such results show that abfraction is associated with occlusal force.

Time series observation on microstructure development of mandibular bone under different occlusal force in rats / 实用口腔医学杂志

Objective: To study the microstructure development of mandibular bone in rats on timing sequence and under different occlusal force. Methods: 63 male SD rats aged 23 days were randomly divided into three groups (n = 7): Baseline group, soft-diet (SD) group and hard-diet (HD) group. 7 rats were killed at week 0, 2, 4, 6 and 8 respectively after feeding the food with different hardness.Micro-CT was used to reconstruct and analysis microstructure of the region of interest in mandible of the rats. Results: Compared with HD group, bone volume/total volume (BV/TV) and trabecular thickness (Tb. Th) decreased significantly after 4 th week (P ＜ 0. 05), the bone surface/bone volume (BS/BV) and trabecular separation (Tb. Sp) increased significantly during the 4 th to the 6 th week (P ＜0. 05) . Conclusion: In the process of mandibular development in rats, reduction of occlusal force may lead to reduction of bone mass, and the changes of microstructure are closely related to the time of intervention.

Evaluación de la dureza de diversos alimentos / Evaluation of the hardness of various foods

Objetivo: evaluar la dureza de diferentes grupos de alimentos a la masticación. Métodos: se realizó un estudio descriptivo in vitro, en el que se evaluó la dureza de diferentes golosinas, chicharrón y carne bovina. Para ello se utilizó un texturómetro EZ-S Shimadzu. El análisis estadístico de los datos obtenidos fue realizado de manera individual utilizando las pruebas estadísticas Shapiro Wilk, Kruskal-Wallis y la de comparación de Mann Whitney. Resultados: de los grupos de alimentos estudiados, presentó una alta dureza a la masticabilidad la golosina Coffe Deligth® (dulce de café duro) con la mayor fuerza requerida de 268,25 N, seguida de otra golosina Bon Bon Bum® (chupeta) con un valor de 179,5 N y luego las mentas (dulce de menta duro) con 165,25 N. En el caso de la carne bovina y las rosquillas horneadas se encuentraron valores más bajos. Conclusiones: debido a las elevadas fuerzas que hay que aplicar para lograr la fracturabilidad y masticabilidad de los alimentos de alta dureza, el consumo de estos es un eventual factor de riesgo para las restauraciones dentales y para los mismos dientes, con lo que se puede inducir a fracturas en los materiales restauradores o en los propios órganos dentarios(AU)

Objective: evaluate the hardness of various food groups for mastication. Methods: an in vitro descriptive study was conducted to evaluate the hardness of various tidbits, fried pork rinds and beef using the texture meter EZ-S Shimadzu. Statistical analysis of the data obtained was conducted on an individual basis with Shapiro Wilk and Kruskal-Wallis statistical tests, and Mann Whitney comparison test. Results: of the food groups studied, the ones standing out for their hardness were the tidbit Coffee Delight® (hard coffee candy) with 268.25 N, followed by another tidbit, Bon Bon Bum® (lollipop) with 179.5 N and mints (hard mint candy) with 165.25 N. Beef and baked donuts exhibited lower values. Conclusions: due to the intense force that must be applied to fracture and grind very hard food, its consumption constitutes a risk factor for natural teeth and dental restorations alike, since fractures may occur in restorative materials and dental organs(AU)

The effect of occlusal interference on the restoration of the idiopathic cervical lesions / 实用口腔医学杂志

Objective:To evaluate the effect of occlusal adjustment on the restoration of the idiopathic cervical lesions.Methods:295 teeth with dental idiopathic cervical lesions in 83 patients were divided into 2 groups,142 teeth with occlusal interference were included in group 1 and the 153 without occlusal interference in group 2.The deffects of all the teeth were filled with Z350 nano-resin and followed up for 2 years.Then the teeth with treatment failure were divided into the experimental group (A,30 from group 1 and 14 from group 2) and the control group(B,30 from group 1 and 15 from group 2).The idiopathic cervical lesions of all teeth were filled with Z350 nano-resin,the occlusion of the corresponding teeth in group A was adjusted at the same time,that of group B was not treated.The cases were followed up for 1 year.Results:The success rate of group 1 and group 2 was 57.75％ and 81.05％ repectively (P ＜ 0.05).A subsequently treatment and 1 year follow-up showed that the success rate of gorup A and B for the cases with treatment failure of group 1 was 83.33％ and 56.67％ (P ＜ 0.05),for group 2 was 85.72％ and 40％ (P ＜ 0.05) respectively.Conclusion:The occlusal adjustment is benefit to the clinical effect of the treatment outcome of idiopathic cervical lesions.

Changes in occlusal force depending on the movement of the adjacent and opposing teeth after loss of lower first molar: comparative study by using a strain gauge

PURPOSE: The aim of this study was to investigate the changes in occlusal force after loss of the lower first molar depending on the inclination and extrusion of the adjacent and opposing teeth by using a strain gauge. MATERIALS AND METHODS: Anatomic teeth were used to reconstruct the normal dental arch with loss of the lower right first molar. A uniformly thick layer of silicone was applied to the root to mimic the periodontal ligament. Four stages of dies with varying degrees of inclination and extrusion of the adjacent and opposing teeth were constructed and attached to master model interchangeably by using a CAD/CAM fabricated customized die system. The strain gauges were attached to teeth and a universal testing machine was used to determine the changes in occlusal force. An independent t-test and one-way ANOVA were performed (α = .05). RESULTS: While simulating chewing food, the upper first, second premolar and lower second molar showed greater occlusal force than before extraction. When the change of adjacent teeth's occlusal force with their progressive movement after molar loss was evaluated, the difference among four die models was significant and was in the decreasing aspect (P < 0.05). CONCLUSION: When the lower first molar was lost and the adjacent teeth did not move yet, the occlusal force in adjacent teeth was higher than that when the lower first molar still existed. In addition, the occlusal force in the upper premolars and lower second molar decreased significantly with the progressive movement of adjacent teeth.

Assessment of swallowing and masticatory performance in obturator wearers: a clinical study

PURPOSE: To assess function by identifying changes in swallowing and masticatory performance in maxillary obturator prosthesis wearers. MATERIALS AND METHODS: Sixty subjects were recruited for the study, of which 20 were obturator wearers, 20 were completely dentulous and 20 had removable partial/complete dentures with similar Eichner's Index. Swallowing ability was evaluated with and without obturator using the "Water Drinking Test"; Masticatory performance was evaluated with the Sieve test; and maximum occlusal force was recorded with the help of a digital bite sensor. The data was analyzed using the Statistical Package for Social Science version 15.0 with a confidence level at 95%. RESULTS: Profile, behavior of drinking and time taken to drink were significantly improved (P<.001) in subjects after wearing obturator. Masticatory performance was not significantly different (P=.252) in obturator wearer when compared with dentulous or removable partial/complete denture wearer, but significantly (P<.001) high inter group difference in maximum occlusal force existed. Correlation between masticatory performance and maximum occlusal force was not significant (P=.124). CONCLUSION: Swallowing ability was significantly improved after wearing obturator but masticatory performance was not significantly different from those having similar occlusal support zone in their dentition.

Evaluation of the effect of two different occlusal splints on maximum occlusal force in patients with sleep bruxism: a pilot study

PURPOSE: The occlusal splint has been used for many years as an effective treatment of sleep bruxism. Several methods have been used to evaluate efficiency of the occlusal splints. However, the effect of the occlusal splints on occlusal force has not been clarified sufficiently. The purpose of this study was to evaluate the effect of occlusal splints on maximum occlusal force in patients with sleep bruxism and compare two type of splints that are Bruxogard-soft splint and canine protected hard stabilization splint. MATERIALS AND METHODS: Twelve students with sleep bruxism were participated in the present study. All participants used two different occlusal splints during sleep for 6 weeks. Maximum occlusal force was measured with two miniature strain-gage transducers before, 3 and 6 weeks after insertion of occlusal splints. Clinical examination of temporomandibular disorders was performed for all individuals according to the Craniomandibular Index (CMI) before and 6 weeks after the insertion of splints. The changes in mean occlusal force before, 3 and 6 weeks after insertion of both splints were analysed with paired sample t-test. The Wilcoxon test was used for the comparison of the CMI values before and 6 weeks after the insertion of splints. RESULTS: Participants using stabilization splints showed no statistically significant changes in occlusal force before, 3, and 6 weeks after insertion of splint (P>.05) and participants using Bruxogard-soft splint had statistically significant decreased occlusal force 6 weeks after insertion of splint (P<.05). There was statistically significant improvement in the CMI value of the participants in both of the splint groups (P<.05). CONCLUSION: Participants who used Bruxogard-soft splint showed decreases in occlusal force 6 weeks after insertion of splint. The use of both splints led to a significant reduction in the clinical symptoms.

Transient dynamic analysis and optimization of a new customized lingual self-locking appliance during occluding / 医用生物力学

Objective To study the characteristics of stress distributions on a customized lingual self-locking orthodontic appliance under transient occlusal force and optimize its structure. Methods A whole 3D model including denture, appliances and wire was established by CT scanning, reverse engineering method and CAD technology; transient nonlinear dynamic analysis on this model during occluding and its structural optimization were conducted, and the optimized lingual appliance was made based on rapid prototyping technology to verify reliability of the finite element model. Results The equivalent stress on the bracket bottom was larger than that on other parts of the bracket; the maximum equivalent stress on the bracket cover was decreased by 60.9% after installing a reinforcing rib on it, which could effectively prevent stress concentration caused by the contact between the arch wire and bracket cover. The simulation results fundamentally agreed with the loading experiment on the bracket cover. Conclusions For lingual orthodontic treatment in clinic, the relative position between interaction points of the occlusal force and brackets should be concerned so as to avoid impairing the self-locking function; through optimizing the appliance design, the elastic potential energy of arch wire can be transferred more effectively to the teeth and reduce losses of the orthodontic force.

Finite element analysis on the connection types of abutment and fixture / 대한치과보철학회지

PURPOSE: This study was performed to compare the stress distribution pattern of abutment-fixture connection area using 3-dimensional finite element model analysis when 5 different implant systems which have internal connection. MATERIALS AND METHODS: For the analysis, a finite element model of implant was designed to locate at first molar area. Stress distribution was observed when vertical load of 200 N was applied at several points on the occlusal surfaces of the implants, including center, points 1.5 mm, 3.0 mm away from center and oblique load of 200 N was applied 30degrees inclined to the implant axis. The finite element model was analyzed by using of 3G. Author (PlassoTech, California, USA). RESULTS: The DAS tech implant (internal step with no taper) showed more favorable stress distribution than other internally connected implants. AS compare to the situations when the loading was applied within the boundary of implants and an oblique loading was applied, it showed higher equivalent stress and equivalent elastic strain when the loading was applied beyond the boundary of implants. Regardless of loading condition, the abutments showed higher equivalent stress and equivalent elastic strain than the fixtures. CONCLUSION: When the occlusal contact is afforded, the distribution of stress varies depending on the design of connection area and the location of loading. More favorable stress distribution is expected when the contact load was applied within the diameter of fixtures and the DAS tech implant (internal step with no tapering) has more benefits than the other design of internally connected implants.

An investigation into the effect of denture adhesives on incisal bite force of complete denture wearers using pressure transducers: a clinical study

PURPOSE: Study was conducted to determine and assess the effect of different type of denture adhesives on the incisal bite force of complete denture wearers until the dislodgement of upper denture, using pressure transducer. MATERIALS AND METHODS: 30 patients out of 100 were included in the study. Based on the Kapur's method of scoring denture retention and stability, these patients were divided into 3 groups- Group A - Clinically good dentures; Group B - Clinically fair dentures; and Group C - Clinically poor dentures. A custom made occlusal force meter was constructed based on the load cell type of pressure transducers. Different adhesives (powder, paste and adhesive strips) were used in the study. Complete denture wearers were asked to bite on the load cell and the readings of incisal bite force were recorded. The readings of incisal bite force were subjected to statistical analysis using Repeated measures ANOVA followed by post-hoc bonferroni test. RESULTS: The result suggests that denture adhesives improved the incisal bite force of complete denture wearers significantly The incisal bite force (in kg) in Group A without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 2.48 (+/- 0.16), 3.43 (+/- 0.11), 6.01 (+/- 0.11), 3.22 (+/- 0.09) respectively. The incisal bite force (in kg) in Group B without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.87 (+/- 0.18), 3.35 (+/- 0.14), 5.34 (+/- 0.18), 3.21 (+/- 0.12) respectively. The incisal bite force (in kg) in Group C without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.00 (+/- 0.17), 3.07 (+/- 0.14), 4.37 (+/- 0.26), 2.99 (+/- 0.14) respectively. CONCLUSION: Within the limitations of the study, it was concluded that the use of denture adhesive was found to be significantly effective in improving the incisal bite force of complete dentures until the dislodgement of upper denture. Fittydent paste adhesive was found to be more effective than the powder and strips adhesives. The improvement in incisal bite force was found to be higher in Group C in comparison to that of Group A and Group B.

Influence of female hormonal fluctuation on maximum occlusal force

Hormonal fluctuations during the menstrual cycle may influence on muscular tensions and probably alter occlusal force. The aim of this study was to evaluate whether hormonal levels affect maximum occlusal force (MOF) of healthy women throughout the different phases of the menstrual cycle. Sixty complete dentate subjects who were not under use of oral contraceptives were selected to participate in this study. MOF was bilaterally evaluated on the molar region, during 3 complete menstrual cycles, using 5.65 mm-wide sensors. Measurements were carried out during each of the following menstrual cycle phases: menstrual, follicular, periovulatory and luteal, presumed by ovulation test. Data were analyzed by one-way ANOVA and Tukey-Kramer test (p<0.05). Comparisons among menstrual cycle phases showed no differences on MOF (p=0.27). Under the conditions of this study, it may be concluded that hormonal fluctuations during the menstrual cycle do not affect MOF of a sample of healthy women.

As flutuações hormonais durante o ciclo menstrual podem influenciar as tensões musculares e possivelmente alterar a força oclusal. O objetivo deste estudo foi avaliar se os níveis hormonais afetam a força máxima oclusal (FMO) de mulheres saudáveis durante as diferentes fases do ciclo menstrual. Sessenta pacientes completamente dentadas que não usavam contraceptivos orais foram selecionadas para participar neste estudo. FMO foi avaliada bilateralmente na região dos molares, durante 3 ciclos menstruais completos, utilizando sensores de 5,65 mm de espessura. As mensurações foram realizadas durante cada fase do ciclo menstrual: menstrual, folicular e lútea periovulatória, identificadas por teste ovulatório. Os dados foram analisados por ANOVA um critério seguido do teste de Tukey-Kramer (p<0,05). As comparações entre as fases do ciclo menstrual não apresentaram diferenças na FMO (p=0,27). Segundo as condições deste estudo, pode-se concluir que as flutuações hormonais durante o ciclo menstrual não afetaram a FMO de mulheres saudáveis.

Influence of occlusal force on Ni release from Ni-Cr PFM alloys by designing a novel device with dynamic occlusal loads / 医用生物力学

Objective To design a novel device with dynamic occlusal loads so as to investigate the influence of occlusal force on Ni release from Ni-Cr PFM alloys. Methods Based on the average force(45 N) and rate(80 cycles/min) of human mastication, a novel device with dynamic occlusal loads was designed to study the Ni release from three commonly used Ni-Cr PFM alloys (Shangchi, Stellite, BEGO) in the artificial saliva with pH 2.3 and pH 7.4, respectively. Results This novel device with dynamic occlusal loads worked well to simulate the average force and chewing cyclye. In the artificial saliva with pH 2.3, the amount of Ni release in Shangchi, Stellite and BEGO was 6.9(2.07) μg/cm2, 3.7(0.662) μg/cm2 and 5.88(1.57) μg/cm2, respectively; while in the artificial saliva with pH 7.0, the amount of Ni release in Shangchi, Stellite and BEGO was 0.272(0.059) μg/cm2, 0.144(0.014) μg/cm2 and 0.435(0.053) μg/cm2, respectively. For the same Ni-Cr PMF alloys, the amount of Ni release in the artificial saliva with pH 2.3 was much higher than that with pH 7.0 (P<0.01), showing statistical differences. Conclusions The device with dynamic occlusal loads could be used effectively to evaluate the influence of occlusal force on Ni release from Ni-Cr PFM alloys in vitro. The acid environment could obviously accelerate the Ni release from Ni-Cr PFM alloys. This study showed the amount of Ni release in Stellite was relatively lower than that in the other two alloys.

Comparisons of occlusal force according to occlusal relationship, skeletal pattern, age and gender in Koreans / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the occlusal force and contact area and to find its associating factors in Koreans. METHODS: Occlusal force and contact area in maximum intercuspation were measured using the Dental Prescale(R) system in 651 subjects (15 with normal occlusion, 636 with various malocclusions divided into subgroups according to the skeletal pattern, Angle's molar relationship, age and gender). RESULTS: Occlusal force of the normal occlusion group (744.5 +/- 262.6 N) was significantly higher than those of the malocclusion group (439.0 +/- 229.9 N, p < 0.05). Occlusal force was similar regardless of differences in ANB angle or Angle's molar classification, however the increase in vertical dimension significantly reduced occlusal force (p < 0.05). CONCLUSIONS: Occlusal force was significantly lower in the malocclusion group compared to the normal occlusion group, and in females compared to males, but it was not affected by age, antero-posterior skeletal pattern or molar classification. Although a hyperdivergent facial pattern indicated lower occlusal force compared to a hypodivergent facial pattern, the differences in skeletal pattern were not the primary cause of its decrease, but a secondary result induced by the differences in occlusal contact area according to the facial pattern.

Changes in occlusal force and occlusal contact area after orthodontic treatment / 대한치과교정학회지

OBJECTIVE: This study was performed to evaluate functional changes of occlusion after orthodontic treatment by measuring the occlusal force (OcFr) and occlusal contact area (OcAr), and to compare OcFr and OcAr change according to premolar extractions. METHODS: Data were obtained from 74 patients who had finished orthodontic treatment using fixed appliance aged between 18 and 40 years. Subjects were divided into groups who had four premolars extractions or non-extraction (Male extraction-16, Male nonextraction-18, Female extraction-19, Female nonextraction-21). All subjects were asked to bite pressure-sensitive sheets into maximum intercuspation with maximum bite force, and OcFr and OcAr were evaluated by measuring the sheet with a CCD camera. Records were taken right after debonding, 1 week, 1 month, 3 months, 6 months and 1 year after debonding. RESULTS: OcFr and OcAr increased gradually in all groups during the 1 year retention period (p 0.05). CONCLUSIONS: Occlusion was improved functionally throughout the 1 year retention, and premolar extraction did not induce a decline in the functional aspect of occlusion.

Comparison of maximum occlusal forces on osseointegrated implant supported fixed prostheses and natural teeth / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the maximum occlusal force implant prostheses to natural teeth. MATERIAL AND METHOD: Fifty nine patients treated either with Bra.nemark implants and ITI implants during the recent ten years were involved in this study. The maximum occlusal force were measured with unilateral bite force recorder and dental prescale system. RESULTS: 1. The maximum occlusal forces of the implant prostheses and natural teeth were not significantly different where measured with unilateral bite force recorder and dental prescale system. 2. The maximum occlusal forces were not significantly different between Bra.nemark implant and ITI implant prostheses. 3. The maximum occlusal forces of the implant prostheses had lower when compared with natural teeth during 1-6 months functional periods when measured with the unilareral bite force recorder(p<0.05) and 1-12 months functional periods when measured with the dental prescale system(p<0.05). After these periods there was not statistical significant difference between the implant prostheses and natural teeth. 4. The maximum occlusal forces of the wide diameter implant prostheses were higher than the maximum occlusal forces of the regular diameter implant prostheses when measured with dental prescale system(p<0.05), but there was no significant difference between the wide diameter and the regular diameter implant prostheses when measured with unilateral bite force recorder. 5. The maximum occlusal forces of the single implant prostheses were not significantly different with the splinting implants prostheses. 6. The maximum occlusal forces of the implant prostheses were not significantly different by age and sex. 7. There was significantly different between maximum occlusal forces measured with unilateral bite force recorder and dental prescale system(p<0.0001), but there was positive correlation(r=0.52, p<0.05). CONCLUSION: The maximum occlusal forces of the implant prostheses were not significantly different to natural teeth during clenching and unilateral maximum biting.

Occlusal Function Associated with Body Composition in Premenopausal Japanese Women

Objectives: The goal of the present study was to investigate the relationship between occlusal function and body composition in 108 premenopausal healthy Japanese women aged 20−45 years. Methods: Pressure-sensitive sheets were used to measure occlusal function. Whole fat mass and lean mass, fat-free mass, and whole-bone mineral content were measured by dual-energy X-ray absorptiometry (DXA). Results: After being adjusted for age and the square of height, the whole lean mass and grip strength of the large occlusal contact-area group were found to be significantly higher than those of the small occlusal area groups (p<0.05, respectively). In the 1-year follow-up study, changes in weight in the small-occlusal contact-area group and the low-occlusal force group were significantly larger than other occlusal-contact area or occlusal-force groups. The mean occlusal-contact area and occlusal force were both significantly smaller in subjects with partial dentures than in those without (p<0.05). Conclusion: Large occlusal contact-area, high occlusal force, and no dentures may be associated with some good health conditions in premenopausal Japanese women.