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Introduction: The goal of this pilot study was to evaluate the differences between checking occlusion on implants crowns using 16 or 200 µm thickness of articulating occlusal paper, and to compare the stained occlusal area between the groups after bite forces of 200 and 250 N. Methods: It was included 10 casts of articulated-type IV gypsum, 10 NiCr crowns, articulating occlusal papers (16 µm and 200 µm thick), and a compression test machine. Compressive forces (200 and 250 N.mm) were applied on models, to check the occlusal contact area of fixed and cemented crowns. The contact areas on the crowns were measured through images obtained by the scanning electron microscope. Statistical tests were performed considering the significant level of 5% (p≤0.05). Results: The stains found using 200 µm of articulating paper were higher than those with 16 µm, independent of the force applied. However, the stains obtained in lower teeth with different strengths (200 and 250N) marked with 16 µm articulating paper were not possible to score. The articulating paper variable had significant statistical results (p=0.002), while the variables force (p=0.443) and articulating paper-force interaction (p=0.607) were not significant. The mean area found in staining using the 200 µm and 16 µm papers was, respectively, 8.3380 mm2 and 3.4759 mm2. Conclusion: It was possible to confirm that 200 µm of articulating occlusal paper showed better and significant results to stain the occlusal area, permitting a more accurate adjustment independent of the force applied.
Subject(s)
Bite Force , Dental Implants , Compressive Strength , Crowns , Dental Articulators , Dental Occlusion , MolarABSTRACT
Objective To explore the effect of mucle force on contact force, peak pressure and contact area of foot joint in in vitro biomechanical experiment of foot and ankle, so as to provide references for choosing appropriate loading modes. Methods In neutral position of the ankle joint, fresh calf and foot specimens were simulated with or without mucle force loading. The contact force, peak pressure and contact area of the 1st metatarsophalangeal joint, the 2nd metatarsophalangeal joint, the 1st tarsometatarsal joint, the 2nd tarsometatarsal joint, the medial cuneonavicular joint, the intermediate cuneonavicular joint, the talonavicular joint, the calcicocuboid joint, the subtalar joint ( posterior articular surface) and the tibiotalar joint of normal foot under loading were measured, the results are compared and analyzed. Results Under muscle force loading, the contact force of the 1st metatarsophalangeal joint, the 2nd metatarsophalangeal joint, the 1st tarsometatarsal joint,the 2nd tarsometatarsal joint, the medial cuneonavicular joint, the intermediate cuneonavicular joint, the talonavicular joint and the tibiotalar joint were significantly greater than those without muscle force loading (P<0. 05), and the change percentages were 719. 28% , 311. 37% , 128. 67% , 50. 82% , 54. 89% , 57. 63% ,79. 98% and 50. 34% , respectively. The peak pressures of the 1st metatarsophalangeal joint , the 1st tarsometatarsal joint and the talonavicular joint under muscle force loading were significantly higher than those without muscle force loading ( P < 0. 05), and the change percentages were 176. 14% , 62. 91% and 40. 07% ,respectively. The contact area of the 1st metatarsophalangeal joint, the 1st tarsometatarsal joint, the intermediate cuneonavicular joint and the subtalar joint ( posterior articular surface) under muscle force loading increased significantly (P<0. 05), and the change percentages were 132. 20% , 55. 41% , 30. 97% and 26. 87% , respectively. Conclusions In biomechanical experiment of foot and ankle specimens, muscle force loading has a significant effect on contact force, peak pressure and contact area of each foot joint, especially the forefoot.Therefore, it is necessary to consider the effect of muscle force loading on stress of foot and ankle in the study ofrelated in vitro specimens
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Objective To explore the effects from different contact areas of the instrument causing trauma on biomechanical response parameters of rabbit skull fractures under quasi-static compression conditions. Methods The rabbits were divided into the scalp preservation group and scalp removal group. Each group was subdivided into 3 mm group, 6 mm group, 9 mm group according to contact diameter of the instrument causing trauma. There were 9 rabbits in each group, 54 rabbits in total. All rabbits were put to death by over anesthesia and made into a skull compression model. An electronic universal material testing machine was used to perform quasi-static compression of rabbit skulls to fractures, and biomechanical response parameters such as ultimate load, deformation under ultimate load and compressive strength of rabbit skulls in each group were detected. Results The differences in ultimate load, deformation under ultimate load, and compressive strength of rabbit skulls in scalp preservation group and scalp removal group under different contact areas were statistically significant. The ultimate load was positively correlated with the contact area, and the compressive strength was negatively correlated with the contact area. No correlation was found between deformation under ultimate load and contact area. For scalp preservation group and scalp removal group, the difference in deformation under ultimate load was statistically significant in the 3 mm contact surface diameter group, and there was no statistical significance in the other groups. Conclusions The contact area is positively correlated with the ultimate load of rabbit skull fracture and negatively correlated with compressive strength, while it has no correlation with deformation under ultimate load and is unrelated to whether the scalp is removed.
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Ginger moxibustion has the effect of regulating zang-fu organs and activating qi and blood circulation. When used, ginger paste is required to be close to human skin. Currently, the ginger box used clinically in the hospital can't meet the requirement of large area fitting human skin, and the efficacy of ginger moxibustion is significantly reduced. In this study, a flexible ginger paste box was proposed, which was composed of flexible components polydimethylsiloxane (PDMS), spring and wire netting. The large flexibility of the structure made it fit well with human skin. Finite element method was used to study the fitting degree between ginger paste box and waist soft tissue. Finite element models of flexible ginger paste box and waist soft tissue were established based on Hypermesh and Abaqus software. The equivalent contact area between the flexible ginger paste box and waist was obtained by numerical simulation under different PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness. The four parameters were taken as the influencing factors, and the equivalent contact area was taken as the optimization objective. The typical value analysis and variance analysis of S/N were performed by Taguchi method, and the results showed that among the four influencing factors, the wire netting diameter had the largest influence on equivalent contact area and its contribution rate reached 41.98%. The contribution rates of PDMS unilateral thickness, spring wire diameter and ginger paste layer thickness reached 36.48%, 13.97% and 6.50%, respectively. The optimized PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness were 1.5, 0.4, 0.15, 35 mm, respectively, and the equivalent contact area was 95.60 cm 2. The optimized flexible ginger paste box with great fitting performance can improve the effect of ginger moxibustion.
Subject(s)
Humans , Acupuncture Points , Finite Element Analysis , Ginger/chemistry , Moxibustion/methods , SkinABSTRACT
Objective By developing an automatic procedure for optimization of femoro-tibial contact area for knee prosthesis, to summarize the influence pattern of design parameters on contact area, and discover the relationship between the maximum contact stress and contact area. Methods A parametric finite element (FE) model was developed in the Isight software, which included three components: automatic parameter changes for the geometric model, automatic modeling in the FE software, and automatic FE calculation. The automatic workflow was realized, and then contact areas were statistically analyzed. Results The FE model was validated by using Tekscan pressure distribution system. When the femoral sagittal radius was gradually close to the tibial sagittal radius, the contact area gradually reached to the maximum 295 mm2. The femoral sagittal radius had a positive effect on contact area, while the tibial sagittal radius had a negative effect. The maximum contact stress had a linear relationship with contact area approximately. Conclusions This study analyzed the influence of femoro-tibial sagittal radius on contact stress and contact area, and the research findings would provide references for the design on reducing wear of tibial insert in clinic.
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PURPOSE: Previous studies related with occlusal contact area were limited that interocclusal thickness level or the method of measurement has not been accurate in measuring. The purpose of this study was to investigate the relation between head posture and occlusal contact area using photo occlusion analysis. MATERIALS AND METHODS: 54 subjects with complete dentition (44 men, 10 women / 23 to 33 years of age) were included. To identify the relationship between head posture and occlusal contact area, subjects took interocclusal record in maximal intercuspal position with three different positions(supine position (0°) / inclined position (45°) / upright position (90°)) on the dental unit chair. Occlusal contact area was analyzed using photo occlusion analysis. Statistical analyses were performed with SPSS ver.25.0 at 95% confidence interval. RESULTS: Head posture has no significant effect on the changes of occlusal contact area (P > 0.05). CONCLUSION: When interocclusal relation is stable, head posture does not change a interocclusal record because head posture has no significant effect on occlusal contact area. Analysis of occlusal contact area using photo occlsion analysis device is useful due to its material property and simplicity.
Subject(s)
Female , Humans , Male , Dentition , Head , Methods , PostureABSTRACT
The study compared the proximal contact strength (CS) of different fixed dental prosthesis (FDP) materials. Materials and Methods: Thirty volunteers participated in this study with definitive inclusion and exclusion criteria. Participants were divided into full metal, zirconia, and metal ceramic groups. The CS between the natural teeth and the maxillary posterior quadrant FDP was measured with force gauge. The data were evaluated with one-way analysis of variance test, and Tukey's honest significant difference post hoc was done to compare the mean values. Paired samples t-test was used to compare the mean values between pre- and postoperative CS. Results: The postoperative CS observed in the full metal group in premolar was 0.320 ± 0.1092 N and in second molar was 0.385 ± 0.1130 N. CS obtained with zirconia FDP in both premolar (0.679 ± 0.0927 N) and molar (0.770 ± 0.0960 N) was highest among all groups. The results were statistically significant (P < 0.001). Conclusion: Postoperative CS was greater in zirconia when compared with metal and metal ceramic FDP. Clinical Relevance: FDP materials had acceptable CS. Zirconia is preferable for optimal CS.
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Objective To study the characteristics of mouse-desktop and wrist-desktop contact pressure distributions during different mouse operations, and investigate the influence of desktop on the mouse and wrist during mouse operations, so as to obtain biomechanical references for musculoskeletal disorders of the hand and wrist. Methods The laser scanner and TekScan pressure measurement system were employed to measure contact area and contact pressure of the mouse and wrist during different mouse operations. Results The contact pressure, contact area, and contact force varied with time, and the peak contact pressure of the mouse and wrist with desktop were obtained. The peak contact pressure of the mouse in single clicking of left, right key and scrolling of middle key was 62.87, 33.83, 74.66 kPa, respectively, and for the wrist, the minimum contact pressure appeared in key clicking, being 23.25, 11.02, 16.26 kPa, respectively. Conclusions During mouse operations, the thenar, hypothenar as well as the ulnar and radial sides of the wrist are persistently subjected to the continuous pressure, therefore, repetitive and continuous mouse operation can lead to the development of carpal tunnel syndrome of wrist or other MSDs.
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OBJECTIVE: The objective of this study was to investigate the differences in masticatory efficiency among patients with different Angle's classes of malocclusion and to assess the correlation between masticatory efficiency and the occlusal contact area. METHODS: The mixing ability index (MAI) was calculated for measuring masticatory efficiency of 61 adult patients according to Angle's classifications of malocclusion. The study included 25, 15, and 21 patients with Angle's Class I, II, and III malocclusions, respectively. Silicone interocclusal recording material was used to measure the occlusal contact area. RESULTS: Both the MAI and occlusal contact area showed the highest average values in the Class I malocclusion group, followed by the Class II and Class III malocclusion groups. No significant difference was observed in the MAI values between the Class I and Class II malocclusion groups (p > 0.05), whereas a significant difference was observed between the Class I and Class III malocclusion groups (p < 0.01) and between the Class II and Class III malocclusion groups (p < 0.05). A weak positive correlation was also observed between the MAI and occlusal contact area (p < 0.01, r² = 0.13). CONCLUSIONS: The results of this study indicated that masticatory efficiency was the highest in patients with Angle's Class I malocclusion, followed by those with Angle's Class II and Angle's Class III malocclusions. Moreover, a weak positive correlation was observed between masticatory efficiency and the occlusal contact area.
Subject(s)
Adult , Humans , Classification , Malocclusion , Mastication , Silicon , SiliconesABSTRACT
Objective To study the characteristics of mouse-desktop and wrist-desktop contact pressure distributions during different mouse operations,and investigate the influence of desktop on the mouse and wrist during mouse operations,so as to obtain biomechanical references for musculoskeletal disorders of the hand and wrist.Methods The laser scanner and TekScan pressure measurement system were employed to measure contact area and contact pressure of the mouse and wrist during different mouse operations.Results The contact pressure,contact area,and contact force varied with time,and the peak contact pressure of the mouse and wrist with desktop were obtained.The peak contact pressure of the mouse in single clicking of left,right key and scrolling of middle key was 62.87,33.83,74.66 kPa,respectively,and for the wrist,the minimum contact pressure appeared in key clicking,being 23.25,11.02,16.26 kPa,respectively.Conclusions During mouse operations,the thenar,hypothenar as well as the ulnar and radial sides of the wrist are persistently subjected to the continuous pressure,therefore,repetitive and continuous mouse operation can lead to the development of carpal tunnel syndrome of wrist or other MSDs.
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Tooth preparation design is essential for successful laminate veneer treatment. Preservative tooth preparation limited on enamel, supra-margin advantageous for plaque control, and maintaining contact points known as a standard concept. However, the tooth preparation design has been the controversial issue. In biomechanical considerations, the incisal coverage should be decided on esthetic needs and necessity for the anterior guidance reconstruction. In occasion for sufficient enamel thickness, preparation can prolong to the palatal side but not recommended at palatal concavity. Elongation to contact point is selective option according to the cases. If an old resin restoration located at contact area, laminate veneer should cover over half area of that after surface treatment. The laminate veneer can be also selected at a partially discolored tooth root canal therapy (RCT) and at this occasion, the fiber-reinforced composite (FRC) posts are recommended.
Subject(s)
Dental Enamel , Dental Veneers , Tooth Preparation , Tooth Root , ToothABSTRACT
Aim: Adequate occlusal contacts are believed to be necessary for dentition function. This study aims to evaluate the impact of prosthodontic treatment on intercuspal occlusal contacts in relation to contact number and contact area. Methodology: The pre-treatment and post-treatment models of 13 patients who underwent fixed prosthodontic treatment on several teeth were retrieved. All the models were scanned by a Micro- CT scanner and 3D virtual images were established. To evaluate the occlusion, the models were virtually articulated. Two occlusion variables were evaluated: (1) contact number and (2) contact area. In addition, the impact of the inter-arch location (maxillary vs. mandibular arches) and intraarch location (anterior vs. posterior teeth) was assessed. Results: The prosthodontic treatment had significantly increased the contact number and contact area. The effect of the inter-arch location was insignificant. However, the intra-arch location had significantly affected the contact number and area, where the posterior teeth had a significantly greater contact number and area. The posterior teeth were more influenced by the prosthodontic treatment than the anterior teeth, while the anterior teeth were minimally influenced. Conclusion: The prosthodontic treatment improved the quality of occlusal contacts by increasing the contact number and area. The effect of the prosthodontic treatment was more prominent in the posterior region, while, anteriorly, the occlusal variables were minimally affected.
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OBJECTIVE: This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing. METHODS: Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models. RESULTS: Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078). CONCLUSIONS: In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.
Subject(s)
Bicuspid , Molar , Tooth Movement TechniquesABSTRACT
Objective To study the relationship between comfort and sitting pressure of ejection seat cushion. Methods By measuring sitting pressure distributions on seat cushions with different thickness, indices of sitting pressure such as the contact area, maximum sitting pressure and mean sitting pressure were discussed along with the subjective comfort scores to find the relationship between seat cushion comfort and indices of sitting pressure. Results The contact area, maximum sitting pressure and mean sitting pressure were significantly correlated with the subjective comfort scores. In addition, the comfort score did not increase when thickness of the seat cushion exceeded 4 cm. Conclusions The comfort of seat cushion could be well reflected and evaluated by the contact area, maximum sitting pressure and mean sitting pressure of seat cushion, and thickness of 4 cm is recommended for designing the seat cushion with material used in this paper.
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PURPOSE: Occlusal splints are commonly used to prevent tooth wear caused by bruxism. However, the effects of splints on occlusion are still unclear. Although it is rarely alluded in literature, splints can provoke severe occlusal alterations and other complications. This study was aimed to identify differences in the responses of individuals with bruxism and healthy individuals to a full-arch maxillary stabilization splint in terms of occlusal changes. MATERIALS AND METHODS: Occlusal contacts in 20 (5 male, 15 female) bruxism patients and 20 (5 male, 15 female) controls with normal occlusion were evaluated before and after occlusal splint therapy. T-Scan III, a computerized occlusal analysis system, was used to simultaneously measure occlusion and disclusion times as well as left-right and anterior-posterior contact distributions before splint therapy and 3 months after therapy. Wilcoxon and Mann-Whitney U tests were used for statistical analyses (alpha=.05). RESULTS: No differences were found in the posterior contact of bruxism patients before and after stabilization splint treatment. However, differences in posterior contact were observed between bruxists and normal individuals prior to treatment, and this difference disappeared following treatment. CONCLUSION: The results of this study showed the use of a stabilization splint may not have an effect on occlusion. However, the area of posterior occlusal contact among bruxists was found to be greater than that of normal individuals. According to this study, the clinical use of splints may be harmless.
Subject(s)
Humans , Male , Bruxism , Occlusal Splints , Splints , Tooth WearABSTRACT
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.
Subject(s)
Female , Humans , Male , Bite Force , Malocclusion , Molar , Vertical DimensionABSTRACT
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.
Subject(s)
Aged , Female , Humans , Male , Bicuspid , Bite Force , Bites and Stings , Retention, PsychologyABSTRACT
PURPOSE: This study was performed to compare the contact area between three different correcting angles after the proximal crescentic and Ludloff osteotomies of the first metatarsal. MATERIALS AND METHODS: We used the two sawbone models. Proximal crescentic (PCO) and Ludloff osteotomies (LO) were performed and secured using K-wires under the correcting intermetatarsal angle (IMA) 5degrees, 10degrees, and 15degrees. Then each 6 osteotomized model was scanned five times and measured the contact area using the calculating program. We excluded the highest and lowest values. RESULTS: The mean area of cutting surface was 189 mm2 in PCO, 863 mm2 in LO. The mean contact area (contact ratio; contact area x100/area of cutting surface) of PCO was 149 mm2 (79%) in 5degrees, 139.5 mm2 (74%) in 10degrees, 107 mm2 (57%) in 15degrees IMA. The mean contact area (contact ratio) of LO was 711 mm2 (82%) in 5degrees, 535.5 mm2 (62%) in 10degrees, 330 mm2 (38%) in 15degrees IMA. CONCLUSION: A significant decrease in the contact area and contact ratio according to increase in correcting IMA was noticed in LO. We recommend the PCO rather than LO, when the IMA is needed to correct over 15degrees.
Subject(s)
Hallux Valgus , Metatarsal Bones , OsteotomyABSTRACT
PURPOSE: This study was performed to compare the contact area between three different correcting angles after the proximal crescentic and Ludloff osteotomies of the first metatarsal. MATERIALS AND METHODS: We used the two sawbone models. Proximal crescentic (PCO) and Ludloff osteotomies (LO) were performed and secured using K-wires under the correcting intermetatarsal angle (IMA) 5degrees, 10degrees, and 15degrees. Then each 6 osteotomized model was scanned five times and measured the contact area using the calculating program. We excluded the highest and lowest values. RESULTS: The mean area of cutting surface was 189 mm2 in PCO, 863 mm2 in LO. The mean contact area (contact ratio; contact area x100/area of cutting surface) of PCO was 149 mm2 (79%) in 5degrees, 139.5 mm2 (74%) in 10degrees, 107 mm2 (57%) in 15degrees IMA. The mean contact area (contact ratio) of LO was 711 mm2 (82%) in 5degrees, 535.5 mm2 (62%) in 10degrees, 330 mm2 (38%) in 15degrees IMA. CONCLUSION: A significant decrease in the contact area and contact ratio according to increase in correcting IMA was noticed in LO. We recommend the PCO rather than LO, when the IMA is needed to correct over 15degrees.
Subject(s)
Hallux Valgus , Metatarsal Bones , OsteotomyABSTRACT
PURPOSE: The aim of this study was to evaluate the effect of modified end-to-side neurorrhaphy on functional recovery, by modulating the epineurial window and contact areas with a donor nerve, using a rat median nerve and finger flexors. MATERIALS AND METHODS: Four experimental groups (n=10) were used: a large epineurial window and a spiral circumferential contact with the donor nerve (Group A): a large epineurial window and half a contact with the donor nerve (Group B): a small epineurial window and half a contact with the donor nerve (Group C): and a nontransferred control (Group D). Grasping testing, muscle contractility testing, and a histological study were performed. RESULTS: Twenty weeks after surgery, the grasping strength, tetanic force and nerve fiber count were significantly higher in group A than group C. The modified end-to-side repair can enhance axonal sprouting from an intact nerve, and improve functional recovery. CONCLUSION: Either the epineurial window surface area or the contact configuration with the donor nerve is an important factor in an end-to-side coaptation model.