OBJECTIVE: To measure and analyze the occlusal force and contact in children with mixed dentition, and to preliminarily provide baseline data on the occlusion of individual normal occlusion children with mixed dentition. METHODS: A cross-sectional study was conducted, including 20 children with mixed dentition and individual normal occlusion, consisting of 12 boys and 8 girls, aged 6.5-9.8 years. The Dental Prescale Ⅱ occlusal analysis system was used to measure the occlusal force and contact at the intercuspal position, including the maximum occlusal force (N) and the occlusal contact area (mm²) of the entire dentition, and the left and right sides, average occlusal pressure (MPa), maximum occlusal pressure (MPa), and to determine the position of the center of occlusal force. The gender differences in maximum occlusal force, average occlusal pressure, and occlusal contact area were analyzed, the bilateral symmetry of occlusion in children with mixed dentition and individual normal occlusion was compared, and the correlation between occlusal data and age, height, weight, and body mass index (BMI) was analyzed. RESULTS: (1) The average maximum occlusal force of the entire dentition in the 20 children with mixed dentition at the intercuspal position was (869.18±106.64) N, the average occlusal contact area was (25.19±2.89) mm², the average occlusal pressure was (34.37±5.98) MPa, and the maximum occlusal pressure M(P₂₅, P₇₅) was 120 (120, 120) MPa; (2) There was no statistically significant difference in the maximum occlusal force, average occlusal pressure, maximum occlusal pressure, and occlusal contact area between the left and right sides (P>0.05); (3) At the intercuspal position, the average occlusal contact area for 12 boys and 8 girls was (26.71±3.91) mm² and (21.62±3.08) mm² respectively, and the average maximum occlusal force was (911.92±145.05) N and (769.47±116.45) N respectively, with statistically significant differences (P < 0.05), while there was no statistically significant difference in the average occlusal pressure between boys and girls (P>0.05); (4) The maximum occlusal force at the intercuspal position was weakly correlated with age (r=0.219, P=0.046), and strongly positively correlated with the occlusal contact area (r=0.949, P < 0.001), while the average occlusal pressure, maximum occlusal pressure, and occlusal contact area were not correlated with age, height, weight, or BMI; (5) The center of occlusal force in the 20 children with mixed dentition and individual normal occlusion was located in the molar region, with 7 children having the maximum occlusal pressure point only in the first permanent molar region, 10 children having it in both the deciduous molar region and the first permanent molar region, and 3 children having it only in the deciduous molar region. CONCLUSION In children with mixed dentition and individual normal occlusion, the maximum occlusal force, occlusal contact area, average occlusal pressure, and maximum occlusal pressure at the intercuspal position show good bilateral symmetry; there are gender differences in the maximum occlusal force and occlusal contact area, with boys having greater values than girls; the maximum occlusal force is positively correlated with the occlusal contact area.
Humans ; Child ; Male ; Bite Force ; Female ; Dentition, Mixed ; Cross-Sectional Studies ; Dental Occlusion

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.
Male ; Female ; Humans ; Bite Force ; Tooth ; Mandible ; Molar ; Occlusal Adjustment

As a representative part of the oral system and masticatory robot system, the modeling method of the dental model is an important factor influencing the accuracy of the multi-body dynamic model. Taking the right first molars of the masticatory robot as the research object, an equivalent model, point-contact higher kinematic pair composed of v-shaped surface and sphere surface, was proposed. Firstly, the finite element method was used to analyze the occlusal dynamics of the original model in three static contact cases (intrusive contact, centric occlusion, and extrusive contact) and one dynamic chewing case, and the expected bite force was obtained. Secondly, the Hertz contact model was adopted to establish the analytical expression of the bite force of the equivalent model in three static contact cases. The normal vectors and contact stiffness in the expression were designed according to the expected bite force. Finally, the bite force performance of the equivalent model in three static contact cases and one dynamic chewing case was evaluated. The results showed that the equivalent model could achieve the equivalent bite force of 8 expected items in the static contact cases. Meanwhile, the bite force in the early and late stages of the dynamic chewing case coincides well with the original model. In the middle stage, a certain degree of impact is introduced, but it can be weakened by subsequent trajectory planning. The equivalent modeling scheme of the dental model proposed in this paper further improves the accuracy of the dynamic model of the multi-body system. It provides a new idea for the dynamic modeling of other complex human contacts.
Biomechanical Phenomena ; Bite Force ; Humans ; Mastication ; Molar

Stress distribution of denture is an important criterion to evaluate the reasonableness of technological parameters, and the bite force derived from the antagonist is the critical load condition for the calculation of stress distribution. In order to improve the accuracy of stress distribution as much as possible, all-ceramic crown of the mandibular first molar with centric occlusion was taken as the research object, and a bite force loading method reflecting the actual occlusal situation was adopted. Firstly, raster scanning and three dimensional reconstruction of the occlusal surface of molars in the standard dental model were carried out. Meanwhile, the surface modeling of the bonding surface was carried out according to the preparation process. Secondly, the parametric occlusal analysis program was developed with the help of OFA function library, and the genetic algorithm was used to optimize the mandibular centric position. Finally, both the optimized case of the mesh model based on the results of occlusal optimization and the referenced case according to the cusp-fossa contact characteristics were designed. The stress distribution was analyzed and compared by using Abaqus software. The results showed that the genetic algorithm was suitable for solving the occlusal optimization problem. Compared with the reference case, the optimized case had smaller maximum stress and more uniform stress distribution characteristics. The proposed method further improves the stress accuracy of the prosthesis in the finite element model. Also, it provides a new idea for stress analysis of other joints in human body.
Bite Force ; Ceramics ; Crowns ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Molar ; Prostheses and Implants ; Stress, Mechanical

OBJECTIVE: This study aims to investigate the occlusal and myoelectric characteristics of implant-supported fixed denture in the mandibular region and provide reference for the design of fixed restoration. METHODS: Sixty edentulous patients with implant-supported fixed denture were selected and divided into three groups: group A, 20 cases with implant-supported fixed restoration in the maxillary region; group B, 20 cases with natural dentition, and group C, 20 cases with removable partial denture. The T-scan 8.0 digital occlusion analysis system was used to evaluate the occlusal characteristics of patients in the three groups at intercuspal, protrusion, and left and right lateral positions. Electromyography was used to analyze the myoelectric amplitude and bilateral asymmetry index of the anterior temporalis and masseter of the three groups in different states such as resting and clenching. The relationship between occlusion and myoelectricity was also investigated. RESULTS: In the occlusion analysis by T-scan, the occlusion time, the balance of left and right bite force, the left and right asymmetry of the occlusion center, the trajectory of central occlusion force, and the disclusion time were higher in group C than in groups A and B (P<0.05). No significant differences were observed in the anterior and posterior asymmetry of the occlusion center and percentage of bite force at anterior region among the three groups. In the analysis of myoelectricity, the myoelectric amplitude at resting state and the asymmetry index of masticatory muscles in group C were higher than those in groups A and B (P<0.05). The myoelectric amplitude during clenching in groups A and B groups was higher than that in group C (P<0.05). CONCLUSIONS In implant-supported fixed restoration at edentulous mandibular, when maxillary includes the removable partial denture, degree of occlusal instability and left and right asymmetry of occlusion center are greater than those with the natural dentition and implant-supported fixed denture at maxillary. The myoelectricity is closely related to occlusion. The removable partial denture can increase the myoelectric activity and reduce the potential of the masticatory muscle. The asymmetry of bilateral myoelectricity is related to the occlusion imbalance.
Bite Force ; Dental Implants ; Dental Prosthesis, Implant-Supported ; Humans ; Mandible ; Masticatory Muscles

In the case of edentulous patients, the total amount of occlusal force is dispersed by the keratinized gingiva during mastication, in result, causing lower masticatory and chewing efficiency. In particular, the mandibular area has more side effects such as pain than the maxilla has. It gets worse when the patient has more absorption of alveolar bone, but the implant treatment is often interrupted due to the existence of the inferior alveolar nerve. In this case, a patient treated with the all-on-4 method by placing the implant in the anterior part of mandible and with the conventional complete denture for the maxilla has maintained without complications and was satisfied with the restoration both functionally and esthetically.
Absorption ; Bite Force ; Denture, Complete ; Gingiva ; Humans ; Mandible ; Mandibular Nerve ; Mastication ; Maxilla ; Methods

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.
Bicuspid ; Bite Force ; Classification ; Humans ; Molar ; Tooth Attrition ; Tooth Fractures ; Tooth

OBJECTIVE: To evaluate the efficacy of occlusal improvement in the labial fixed orthodontic treatment in aggressive periodontitis patients and to explore the relationship between occlusal improvement and inflammation control. METHODS: Twenty-two aggressive periodontitis patients who underwent combined periodontal-orthodontic treatment were included in this study. The patient's photos were matched to the dental models and digital three dimentional models were acquired using 3Shape R700 laser scanner. The occlusal force distribution maps were generated in the OrthoAnalyzer software. The newly established occlusal force distribution score (OFDS) and proximal contact score (PCS) were used to evaluate the occlusal distribution changes before and after labial fixed orthodontic treatment for assessing the effectiveness of orthodontic treatment. The multi-level linear regression analysis was used to explore the relationship between the probing depth changes and OFDS or PCS changes to screen out the favorable orthodontic strategy for inflammation control, which would provide clinical strategy for combined periodontal-orthodontic treatment in aggressive periodontitis patients. RESULTS: At the patient level, OFDS was improved significantly after orthodontic treatment compared with the score before orthodontic treatment (84.5±20.9 vs.105.3±22.6, P <0.001) and PCS was improved significantly after orthodontic treatment compared with the score before orthodontic treatment (68.9±9.1 vs. 83.7±6.3, P <0.001).At the tooth level, the OFDS was significantly increased in the maxillary anterior teeth (P <0.001) while the PCS of the anterior teeth in both maxillary and mandible arches were significantly increased significantly (P <0.01). No significant changes were found in other tooth positions. The multilevel linear regression model showed that no significant correlation was found between age and gender and probing depth decrease (P >0.05). The baseline probing depth,OFDS improvements and PCS improvements (P <0.001) were positively correlated with probing depth decrease. CONCLUSION This study showed that the distribution of occlusal force was more reasonable and the proximal contacts were more ideal in aggressive periodontitis patients. Orthodontic treatment was effective in improving occlusal force distribution by the above two ways. Especially, the OFDS and PCS improvements were both positively correlated with probing depth decrease, indicating that in the combined periodontal-orthodontic treatment for aggressive periodontitis patients, occlusal force distribution and proximal contact should be improved in order to facilitate periodontal improvement.
Aggressive Periodontitis ; Bite Force ; Dental Care ; Humans ; Regression Analysis

OBJECTIVE: To analyze changes in occlusal force distribution and occlusal contact in posterior partial fixed implant-supported prostheses over time, and to provide reference for the precise occlusion design, adjustment and maintenance of implant prostheses. METHODS: According to certain inclusion and exclusion criteria, patients were recruited from partially edentulous patients who had received implant-supported single crown or fixed bridge in the posterior region. The patients were collected since the implant prostheses settling and scheduled for the routine examination of implant prostheses and the occlusal examinations of complete dentition after 2 weeks, 3, 6, and 12 months. Occlusal examinations were taken with the articulating papers and T-Scan III (Tekscan, South Boston, USA), which could check and measure the occlusal contact condition of complete dentition. The occlusion time and relative occlusal forces of implant prostheses, mesial adjacent teeth and control teeth were recorded at the same time. RESULTS: Thirty-seven posterior partial fixed implant prostheses in 33 patients (17 women and 16 men, aged 24-70 years) were followed up for 3-12 months (average 8.3 months). At baseline, the relative occlusal forces of implant prostheses were significantly lower than those of the corresponding control teeth (P<0.001). However, after 3 months, the relative occlusal forces of implant prostheses had significantly increased (P<0.05), while control teeth decreased significantly (P<0.05), resulting in no statistical significance between them. The implant prostheses occlusion time ratio also increased significantly from 2 weeks to 3 months (P<0.05). There was no significant difference from the third month to the sixth month, or from the sixth month to the twelfth month (P>0.05). CONCLUSION Light contact and time-delayed occlusion of posterior implant prostheses changes significantly in the first three months after settling implant prostheses. These changes mainly include the advance of the time point of the implant prosthesis to start the occlusion contact, and the increase of the occlusal force of the implant prosthesis. The occlusion of posterior implant prostheses should be carefully monitored at end of the third month follow-up clinically.
Adult ; Aged ; Bite Force ; Crowns ; Dental Prosthesis, Implant-Supported ; Denture, Partial, Fixed ; Female ; Humans ; Male ; Middle Aged ; Mouth, Edentulous ; Young Adult

PURPOSE: Zirconia materials have been used for implant-retained restorations, but the stress distribution of zirconia is not entirely clear. The aim of this study is to evaluate the stress distribution and risky areas caused by the different design of zirconia restorations on the atrophic bone of the posterior maxilla. MATERIALS AND METHODS: An edentulous D4-type bone model was prepared from radiography of an atrophic posterior maxilla. Monolithic zirconia and zirconia-fused porcelain implant-retained restorations were designed as splinted or non-splinted. 300-N occlusal forces were applied obliquely. Stress analyses were performed using a 3D FEA program. RESULTS: According to stress analysis, the bone between the 1) molar implant and the 2) premolar in the non-splinted monolithic zirconia restoration model was stated as the riskiest area. Similarly, the maximum von Mises stress value was detected on the bone of the non-splinted monolithic zirconia models. CONCLUSION: Splinting of implant-retained restorations can be more critical for monolithic zirconia than zirconia fused to porcelain for the longevity of the bone.
Bicuspid ; Bite Force ; Dental Implants ; Dental Porcelain ; Finite Element Analysis ; Longevity ; Maxilla ; Molar ; Radiography ; Splints