Occlusal Contact Area Research Articles

Evaluation of the accuracy of T-scan system and Cerec Omnicam system used in occlusal contact assessment

PurposeThe objective of the present study was to determine the accuracy of T-scan system and Cerec Omnicam system with respect to the evaluation of occlusal contact by quantitatively comparing the occlusal contact areas and the overlapping ratios of occlusal contact areas obtained from these systems. Material and methodsThe occlusal contact of 20 adolescents with normal occlusion was measured with the T-scan system and the Cerec Omnicam system, respectively. The occlusal contact areas in the intercuspal position were then quantified with Adobe Photoshop CS6 Software. The same procedure was repeated for each subject using with 8 μm articulating paper as the control group. The overlapping ratio of T-scan system and Cerec Omnicam system was calculated respectively, which is defined as the ratio of overlapping areas comparing with those obtained from articulating paper. To examine the accuracy of T-scan system and Cerec Omnicam system, the Paired t-test was applied. The reproducibility of T-scan system was evaluated with Wilcoxon matched-pairs signed-ranks test by comparing the occlusal contact areas between two repeated measurements. In all statistical analysis, the level of significance was set to α = 0.05. ResultsResults demonstrated measured occlusal contact areas were significantly different between those obtained between T-scan system and Cerec Omnicam system (P < 0.05). The tooth position of two-dimensional virtual dental arch established by T-scan system based on the width of the central incisor was in disagreement with the actual tooth position. The overlapping ratios obtained from Cerec Omnicam system were higher than those obtained from the T-Scan system (P < 0.05). The sensitivity of T-Scan system in anterior teeth area decreased when sensors are used more than once (P < 0.05). ConclusionsIn the intercuspal position, the accuracy of Cerec Omnicam system for occlusal contact assessment is higher than that of T-scan system. The T-scan system demonstrates good reproducibility in the premolar region and the molar region, but poor reproducibility in the anterior teeth region. Clinical implicationsIn the intercuspal position, Cerec Omnicam system is more accurate than T-scan system, which can quantitatively analyze occlusal relationship in terms of number, position, size and distribution of occlusal contact points. When evaluating occlusal contacts, the accuracy of T-scan system in anterior teeth region is significantly lower than that of premolar and molar regions.

Comparison of Virtual Intersection and Occlusal Contacts between Intraoral and Laboratory Scans: An In-Vivo Study.

The inaccurate maxillomandibular relationship of virtual casts following alignment by the vestibular scan may result in intersection (intermesh penetration) between opposing dental arch surfaces. Intersection occurs at short interocclusal distances in the occlusal contact area (OCA) and may result in infra-occluded definitive restorations. The purpose of this clinical study was to compare initial (by the proprietary scanner software) and new alignments (by a standalone 3D software) of virtual casts regarding OCA and intersection failure. New alignments aimed to rectify intersections by refinement of occlusal contacts. The virtual casts of 30 patients following digital and conventional impression-taking were analyzed, which were acquired for single implant restoration in the posterior site. Digital impressions were performed by both IOS 1 (3M True Definition) and IOS 2 (TRIOS 3), either as complete- or partial-arch scans, respectively. Mounted gypsum casts were digitized as complete-arch by a laboratory scanner (LS) in enabled and disabled mode to avoid intersection [LS (+)/LS (-)]. All virtual casts were newly aligned by a 3D software. The difference of the OCA and the area of intersection were calculated for initial and new alignments, using interocclusal distance ranges of 0-100 μm, 0-10 μm or <0 μm (=intersection). The difference of the OCA was compared using a linear mixed model. The distribution of occlusal contact points per modality and alignment was assessed independently by three observers and estimated by inter- and intraclass correlation (ICC) coefficients. Virtual casts following initial alignment demonstrated intersections irrespective of the modality. The mean area of the intersection was most for IOS 2 (79.23 mm2), followed by IOS 1 (48.28 mm2), LS (-) (2.77 mm2), and LS (+) (2.01 mm2) in partial-arch scans. Complete-arch scans demonstrated an area of intersection of 70.63 mm2 for IOS 1 followed by 65.52 mm2 (IOS 2), 6.13 mm2 [LS (-)] and 2.76 mm2 [LS (+)]. Newly aligned scans showed no intersections. The overall distribution of occlusal contact points demonstrated moderate reliability (ICC 0.63). Good reliability could be observed (ICC 0.9) for LS (-) scans. Intersections in the area of occlusal contact points are a phenomenon restricted to virtual casts, which should be considered in CAD/CAM. Initial alignments of LS are less affected by this virtual phenomenon, and contact points may be more distinct according to their anatomic region compared to IOS. Furthermore, intersections can be rectified in a 3D software by adjustment of the maxillomandibular relationship.

Occlusal function and electromyographic activity of masticatory muscles in skeletal Class III patients with different patterns of mandibular asymmetry.

Although jaw asymmetry is commonly seen in skeletal Class III patients, its correlation with occlusal function and masticatory muscle activity has not been fully elucidated. The purpose of this study was to investigate the occlusal function and masticatory muscle activity in skeletal Class III patients with various patterns of mandibular asymmetry. Forty-two patients and 10 normal participants were examined. The patients were categorised into three groups. Groups 1 and 2 exhibited menton and ramus deviation to the same side. Menton deviation was larger than ramus deviation in Group 1, whereas Group 2 showed the inverse relation. Group 3 patients showed menton and ramus deviation in opposite directions. Occlusal contact area (OCA), relative bite force (RBF), and temporalis anterior (TA) and masseter muscle (MM) activity at maximum clenching were measured using T-Scan Novus system and Bio-EMG-III. Statistical analysis was performed using the t-test, one-way analysis of variance with Bonferroni correction and Spearman correlation (α=.05). Compared with normal participants, the patients had smaller OCA and greater asymmetry in the distribution of masticatory muscle activity. Greater ramus deviation was associated with smaller OCA in Group 1 but with larger OCA in Group 3. In Group 1, greater menton deviation was related to stronger TA activity on the non-deviation side. In Group 2, greater ramus deviation was related to stronger MM activity on the deviation side. Deviation of the menton and ramus was individually related to OCA and masticatory muscle activity, and this relationship varied according to the pattern of mandibular asymmetry.

Relationship between the number of teeth, occlusal force, occlusal contact area, and dietary hardness in older Japanese adults: The SONIC study.

Individuals with impaired masticatory function tend to prefer soft foods, which results in decreased masticatory muscle activity. This study examined the association between the oral condition (number of teeth, occlusal force, and occlusal contact area) and dietary hardness using a daily dietary questionnaire. This cross-sectional study evaluated 1841 participants aged 69-71 and 79-81 years. Registered dentists examined the number of teeth, occlusal force, and occlusal contact area. Dietary hardness was defined as the estimated masticatory muscle activity required for a habitual diet. Habitual diet during the preceding month was assessed using a brief self-administered diet history questionnaire. Confounding factors, such as age, sex, socioeconomic status, smoking habits, history of chronic diseases (hypertension, hyperlipidemia, and diabetes), and cognitive function were also evaluated. Multivariate linear regression analyses were performed to assess the association between dietary hardness and each oral condition. Occlusal force (standardized regression coefficients [β]=0.08, P < 0.01) and occlusal contact area (β=0.06, P < 0.01) were significantly associated with dietary hardness after adjusting for the confounding factors. Number of teeth was not significantly associated with dietary hardness. In addition, the associations between dietary hardness, sex, and a history of diabetes were stronger than those between dietary hardness and oral factors. Occlusal force and contact area were significantly associated with dietary hardness as estimated from the masticatory muscle activity using a daily diet questionnaire.

Influence of Occlusion on Flight Time in Trampoline Competition

Purpose: The aim of this study was to clarify the effect of occlusion on flight time in trampoline competition. Materials and methods: Participants were 10 male trampoline gymnasts (18.9 ± 0.8 years). Dental Prescale was used to measure the occlusal contact state, and the lateral difference in the occlusal contact area was calculated. An all-in-one measurement system (HDTS EU-7100) was used to measure the flight time during consisted of 10 consecutive straight jumps. The correlation between the lateral difference in occlusal contact area and flight time was analyzed using Pearson’s product-moment correlation coefficient. A custom mouthguard was fabricated using a 2.0-mm-thick thermoplastic sheet and was adjusted so that all teeth were in even contact with light clenching. Differences in flight times with and without a mouthguard were compared using a paired t-test. Spearman’s rank correlation coefficient was used to analyze the relationship between the lateral difference in occlusal contact area and the rate of flight-time prolongation due to wearing a mouthguard. Results: A negative correlation was observed between the lateral difference in occlusal contact area and flight time (P&lt;0.05, R=−0.697). As a result of comparing the flight time with and without a mouthguard, flight time was significantly longer with a mouthguard (P&lt;0.05). A significant positive correlation was observed between the lateral difference in occlusal contact area and the extension rate of flight time due to wearing a mouthguard (P&lt;0.05, R=0.657). Conclusion: This study revealed a relationship between occlusion and flight time during straight jumps in the trampoline competition and found that the smaller the left-right difference in the occlusal contact area, the longer the flight time. In addition, it was clarified that achieving uniform occlusal contact by wearing a mouthguard contributed to the extension of flight time, and this effect was more pronounced in athletes with uneven occlusal contact.

Accuracy of optical interocclusal registration using an intraoral scanner.

This study aimed to clarify the effect of occlusal force on appropriate optical interocclusal registration in clinical practice, considering periodontal ligament and jawbone deformation. Forty participants with natural, healthy dentition were enrolled (19 men and 21 women; mean age, 27.7 ± 2.0 years). A TRIOS3 intraoral scanner was used to scan the right lateral first premolar to the second molar areas of the upper and lower jaws. During scanning for interocclusal registration, participants were instructed to "bite normally," "bite lightly," and "bite strongly" to obtain data for the three occlusal patterns. The standard triangulated language (STL) data for each occlusion condition were superimposed using the appropriate software, following which the tooth displacement was calculated. The conventional method was also used to record the occlusal contact area for a silicone model using a dental contact analyzer. Tooth displacement was significantly lower for the strong-bite condition than for the weak-bite condition (0.018 mm vs. 0.028 mm, P<0.05). As the occlusal force increased, the occlusal contact area also increased, and significant differences were observed among the different occlusal conditions (P<0.05). Occlusal contact area changed depending on the bite force when using the silicone impression or optical intraoral scanning methods. Moreover, using optical impression methods in "strong bite force" may reduce the deviation and allow for stable interocclusal registration.

Comparison Between Interocclusal Registration Using Silicone Bite Registration Material and Intraoral Scanner on Clenching Strength.

To clarify the influence of clenching strength on interocclusal registration using an intraoral scanner (IOS). The study includes eight volunteers as subjects, and the two experimental conditions were light clenching (LC) and 40% maximum voluntary clenching (MVC). Conventional silicone bite registration and an IOS were used for comparison. Occlusal contact areas (OCAs) for different clenching strengths were compared, along with variation of measured values (VMVs) between recording methods. Significant differences were observed between conditions on OCA and between methods on VMV. Clenching strength influenced interocclusal registration using IOS.

Marginal bone loss associated with unilateral free end mandibular implant supporting superstructures constructed with different occlusal schemes

AimsThis study was designed to evaluate the amount of bone resorption related to implant in free end saddle in response to different occlusal designs.Patients and methodsTwenty patients with unilateral free end saddle in the lower arch till the second premolar were selected and received delayed single dental implants replacing the first molar tooth. They were divided into two main groups according to the implant superstructure deign (n = 10). Group 1: implant-supported fixed dental prosthesis which follow the principals of implant protected occlusion, and with the occlusal contact area of the crown smaller than the occlusal contact area of adjacent tooth. Group 2: implant-supported fixed dental prosthesis which follow the principals of implant protected occlusion, and with the occlusal contact area of the crown larger than the occlusal contact area of adjacent tooth. Patients were evaluated for the amount of marginal bone level at the time of crown insertion, after 3 and 6 months of function.ResultsThere was a statistically significant change by time in marginal bone loss in both groups especially during the first 3 months. However, there was no statistically significant difference between marginal bone loss regarding the two groups.ConclusionIt was concluded that increasing the occlusal contact area of the implant superstructure has no effect on marginal bone loss.

Changes in masticatory performance during the retention period following 4-premolar extraction and non-extraction orthodontic treatment.

To evaluate changes in masticatory performance (MP) during the retention period after extraction and non-extraction treatment and compare it with MP in individuals with normal occlusion. Adult patients who had completed orthodontic fixed appliance treatment comprised the extraction and non-extraction treatment groups, and those with normal occlusion comprised the control group. Their mixing ability (MA), maximum bite force (MBF), and occlusal contact area (OCA) were recorded immediately after the fixed appliance was removed and at 1month, 6months, and 1year post-treatment. The MA was measured via the two-color chewing gum MA test using ViewGum software, and the MBF and OCA were measured using Dental Prescale II system. MA immediately after orthodontic treatment was lower than that in the normal group but showed a time-dependent gradual increase during a 1-year retention period (P < 0.01). The MA at 1month post-treatment was not significantly different between the three groups (P > 0.05). The MA revealed a significant correlation with the MBF and OCA (P < 0.01). The MP immediately after orthodontic treatment was lower than that in the normal group but increased gradually, with levels comparable to those of the normal occlusion group at 1month post-treatment. Further, extraction did not affect the recovery of the MP after orthodontic treatment. No other study has evaluated the changes in MP during the retention period after orthodontic treatment. The findings show that compared with MBF and OCA, the patients' MP improved faster to levels found in normal occlusion.

Oral function of implant-assisted removable partial dentures with magnetic attachments using short implants: A prospective study.

This prospective study aimed to compare the oral functions of removable partial dentures (RPDs) with those of implant-assisted removable partial dentures (IARPDs) with short implants and magnetic attachments in patients with mandibular Kennedy class I and II. Thirty participants with mandibular Kennedy class I or II and at least three distal missing teeth were recruited. Oral functions, including mixing ability, comminuting ability, maximum bite force, and occlusal contact area, were assessed for RPDs (stage 0), IARPDs with healing caps (stage 1), and IARPDs with magnetic attachments (stage 2). The implants were loaded with occlusal force in stages 1 and 2. Finally, the data of the 27 participants who completed the evaluation at stage 2 were analyzed. The Wilcoxon signed-rank test with Bonferroni correction was used to assess the differences in the oral functions among the different stages. The implant survival rate was 93.8%. There were significant differences in the comminuting ability and occlusal contact area between stages 0 and 2 (p< .001 and p= .036, respectively) and stages 1 and 2 (p= .003 and p= .015, respectively). Regarding the maximum bite force, there was a significant difference between stages 1 and 2 (p= .018). However, there was no significant difference in the mixing ability between the three stages. Within the limitations of this study, it was concluded that IARPDs in the mandible with short implants and magnetic attachments may improve oral functions.

In vivo evaluation of the reliability and validity of three digital occlusion analysis methods

ObjectivesThe reliability and validity of three digital occlusion analysis methods was evaluated in vivo. MethodsThe three method evalueated were:scanning of articulating paper marks (SA), dental prescale occlusal analysis system (DP) and a virtual occlusion constructed method (VO). A conventional silicone transmission method (ST) was used as the standard for comparison. Each of the 20 enroled human subjects was tested with the four methods. Retest of each method was performed at 2-week intervals. Occlusal contact area (OCA) and occlusal contact numbers (OCN) were calculated for analyses. For reliability evaluation, intraclass correlation coefficients (ICC) of the OCA and OCN values obtained from each method were compared. For validity evaluation, Pearson correlations coefficients, paired t-tests, regression analysis and Bland-Altman analysis were examined. ResultsThe ICC values of OCA and OCN were in the order: ST>SA>DP>VO. The highest OCA and OCN values were found ST while the lowest values were obtained from DP. Paired t-test identified a significant difference when OCA values obtained from the three digital methods were compared with ST, and between the OCN values of DP and ST. Pearson correlation showed high coefficients between ST and three digital methods (0.583–0.885 for OCA; 0.779–0.836 for OCN). A significant linear correlation was found between the results from ST and those from SA or VO. Bland-Altman analysis showed good agreement between OCN values of SA and ST, and between those of VO and ST. ConclusionsThe three digital occlusal analysis methods showed good reliability and validity for in vivo clinical application. Clinical significanceThe three digital occlusion analysis systems examined demonstrate good potential in in vivo quantitative analysis, with good reliability and validity. The use of these analytical methods should facilitate digital workflow in clinical practice.

Factors affecting masticatory performance during the mixed dentition period.

During the mixed dentition period, masticatory performance may temporarily decline as deciduous teeth are replaced by permanent teeth. This may lead to an insufficient intake of chewy foods. This study aimed to clarify the characteristics of factors that affect masticatory performance during the dentition exchange period. The participants were 229 students in grades 4-6 who were in the lateral dentition exchange period. Shearing performance (SP) was evaluated using gummy jelly, and mixing performance (MP) was evaluated using colour-changing gum. The chewing rate, occlusal force and area, number of teeth, Hellman's tooth age, Rohrer index, grip strength and walking speed were also evaluated. The χ2 test, Mann-Whitney test, Spearman's rank correlation coefficient and a generalised linear model were used for statistical analysis. SP/MP showed a significant positive correlation with occlusal force, occlusal contact area and chewing rate for gummy jelly and gum but there was a difference in the strength of the correlation between boys and girls. Chewing rate for gummy jelly and gum showed a significant relationship with both SP and MP, suggesting that masticatory performance is higher with slower chewing. Maximum occlusal force was selected as a significant independent variable for SP, and Rohrer index was selected as a significant independent variable for MP. When the occlusal force was higher and the Rohrer index was lower, the masticatory performance tended to be higher. Our results suggest that masticatory performance during the dentition exchange period is higher with slower chewing and a stronger occlusal force, which may be related to obesity.

CLINICAL AND INSTRUMENTAL STUDY RESULTS OF COMPARING DIGITAL OCCLUSION INDICES AT REGISTRATION OF INTERCUSPAL POSITION IN PATIENTS WITH EDENTULOUS SPACES BEFORE AND AFTER PROSTHETIC REHABILITATION

Aim. The research aims at carrying out a comparative clinical and instrumental analysis related to registering occlusal relations of intercuspal contact position in patients with edentulous spaces before and after prosthetic rehabilitation using various registration materials.&#x0D; Material and Methods. Examination of 5 patients of both genders aged 28 to 51 years was performed at clinical bases of the department of surgical and prosthetic dentistry of the Faculty of Postgraduate Education at Danylo Halytskyi Lviv National Medical University. Clinically, all patients were provided with a standard diagnostic dental examination including the control of a temporomandibular joint condition, examination of masticatory muscles, as well as the static and dynamic occlusion with the help of articulating wax and paper according to the two-stage Bausch method. The examination also involved impressions of dental arches of both jaws. Their cast models were produced for laboratory study. The received register, involving the use of materials, namely Futar D, metalized wax, and Consiflex, were reexamined for compliance with the intercuspal contact position in all patients. Location of the occlusal contact areas of antagonistic teeth was determined using Bausch Progress 100® 0.1 mm thick articulating paper (Bausch, Germany). Simultaneously, instrumental registration of digital occlusion indices was performed using the T-scan III device (Boston, USA).&#x0D; Results and Discussion. While comparing mean values of the percentage distribution between the left and right halves, the greatest asymmetry was recorded with the use of Futar D material in the D mode both before and after treatment. According to the results of performed instrumental study concerning occlusal relations with the help of the T-Scan III device, it was found that in case of applying Futar D registration material in patients before prosthetic rehabilitation, mean values of occlusal forces at MAX on the left were (50.72 ± 13.86)%, on the right they were (49.28±13.86)%, after prosthetic rehabilitation they made up (50.12±8.75)% on the left, and (49.88±8.75)% on the right. In case of Consiflex registration material application in patients before prosthetic rehabilitation, it was found that COF mean values at MAX on the left accounted (41.28±16.97) %, while on the right they accounted (58,72±16,97) %. After prosthetic rehabilitation - (54.72±13.39) % on the left, and (45.28±13.39) % on the right, respectively. The conducted instrumental studies demonstrate challenging opportunities for revealing personalized features of static and dynamic occlusal balance at clinical registration of intermaxillary position of intercuspation by various registration materials and methods.&#x0D; Conclusions. &#x0D; 1. A uniform contact of dental arches with synchronous contact of all tooth groups is an important feature of physiologically coordinate dentofacial system functioning.&#x0D; &#x0D; Frequent sliding contacts are observed in ending intercuspal contact position at static and dynamic occlusion. Area of the contact surfaces of the teeth expands with the increase of occlusal pressure in the direction of the maximum intercuspal contact position (maximum intercuspation). At the same time, occlusal pressure occurs in this area, causing the redistribution of functional load of the patients' dentofacial system components.&#x0D; Occlusal space in the intercuspal contact position and the maximum intercuspation or the D index, which can be established using the "Tekscan III" digital technology, manifests the spatiotemporal indices of inter-maxillary relations redistribution. The values of these indices in patients with partial anodontia provoke a special interest.&#x0D; The use of Futar D registration material at performing clinical and instrumental analysis of digital indices of the transition from intercuspal contact position to maximum intercuspation, allowed establishing the extension of occlusal joining of teeth duration after dental prosthetics by 1.02 times, reduction of the length of joining trajectory by 1.37 times. The use of Consiflex resulted in the identical length of joining trajectory and extension of the duration of occlusal joining of teeth after dental prosthetics by 1.04 times. The application of metalized wax was characterized by the identical length of joining trajectory and prolonged occlusion time after dental prosthetics by 1.61 times.&#x0D;

Comparison of the bite force and occlusal contact area of the deviated and non-deviated sides after intraoral vertical ramus osteotomy in skeletal Class III patients with mandibular asymmetry: Two-year follow-up.

The objectives of this study were to compare the time-dependent changes in occlusal contact area (OCA) and bite force (BF) of the deviated and non-deviated sides in mandibular prognathic patients with mandibular asymmetry before and after orthognathic surgery and investigate the factors associated with the changes in OCA and BF on each side. The sample consisted of 67 patients (33 men and 34 women; age range 15-36 years) with facial asymmetry who underwent 2-jaw orthognathic surgery. OCA and BF were taken before presurgical orthodontic treatment, within 1 month before surgery, and 1 month, 3 months, 6 months, 1 year, and 2 years after surgery. OCA and BF were measured using the Dental Prescale System. The OCA and BF decreased gradually before surgery and increased after surgery on both sides. The OCA and BF were significantly greater on the deviated side than on the non-deviated side before surgery, and there was no difference after surgery. According to the linear mixed-effect model, only the changes in the mandibular plane angle had a significant effect on BF (p < 0.05). There was a difference in the amount of the OCA and BF between the deviated and non-deviated sides before surgery. The change in mandibular plane angle affects the change, especially on the non-deviated side, during the observation period.

Assessment of occlusion and temporomandibular joint after placing preformed metal crowns on all primary molars in children.

Placing preformed metal crowns (PMCs) on all eight primary molars at one single clinical visit may disrupt a child's occlusion; the literature regarding the effects on occlusion and temporomandibular joint (TMJ) is scarce. This study aimed to quantify the changes in occlusion using T-Scan III and to investigate whether there was TMJ dysfunction after placing eight PMCs at the same time. In this study, we enrolled children with severe early childhood caries (S-ECC) and dental phobia, who needed eight PMCs to be placed under general anesthesia. The participants underwent occlusal examinations with a computed occlusal analysis system. The vertical dimension of occlusion (VDO) was measured using a dental vertical dimension gauge, TMJ dysfunction signs were recorded by the clinical dysfunction index (Di), and TMJ dysfunction symptoms were recorded using a questionnaire. The data were collected before treatment (T0 ), 1 week after treatment (T1 ), and 1 month (T2 ) and 3 months (T3 ) after treatment during follow-up visits. Repeated-measures analysis of variance and Friedman's test were used for occlusal data analysis. In addition, the Di and symptoms were compared over time using McNemar's test. Forty patients (mean age=4.25 ± 0.63 years, age range=3-5 years, 21 boys and 19 girls) were followed up for 3 months. The occlusal contact area 3 months after treatment did not return to the pretreatment status (p=.03). The total of force at the 3-month follow-up visit increased significantly (p=.009) compared with that at the pretreatment. The asymmetric ratio of occlusal force at the 1-month follow-up visit was restored to pretreatment. Concerning the occlusion time, no significant changes were observed for any time intervals (p=.069). The VDO was recovered at the 1-month follow-up visit. The statistical analysis of TMJ dysfunction showed no significant differences in the Di and TMJ dysfunction symptoms before and after treatment (p > .05). After undergoing eight PMC restorations under general anesthesia, occlusal re-equilibration was attained approximately after 1 month. There were no significant signs and symptoms of TMJ dysfunction after treatment.

Comparison of the bite force and occlusal contact area of the deviated and non-deviated sides after intraoral vertical ramus osteotomy in skeletal Class III patients with mandibular asymmetry: Two-year follow-up

ObjectiveThe objectives of this study were to compare the time-dependent changes in occlusal contact area (OCA) and bite force (BF) of the deviated and non-deviated sides in mandibular prognathic patients with mandibular asymmetry before and after orthognathic surgery and investigate the factors associated with the changes in OCA and BF on each side.MethodsThe sample consisted of 67 patients (33 men and 34 women; age range 15–36 years) with facial asymmetry who underwent 2-jaw orthognathic surgery. OCA and BF were taken before presurgical orthodontic treatment, within 1 month before surgery, and 1 month, 3 months, 6 months, 1 year, and 2 years after surgery. OCA and BF were measured using the Dental Prescale System.ResultsThe OCA and BF decreased gradually before surgery and increased after surgery on both sides. The OCA and BF were significantly greater on the deviated side than on the non-deviated side before surgery, and there was no difference after surgery. According to the linear mixed-effect model, only the changes in the mandibular plane angle had a significant effect on BF (p < 0.05).ConclusionsThere was a difference in the amount of the OCA and BF between the deviated and non-deviated sides before surgery. The change in mandibular plane angle affects the change, especially on the non-deviated side, during the observation period.

Editorial: Dental Ceramics: From Science and Technology to Clinical Application

Editorial: Dental Ceramics: From Science and Technology to Clinical Application

Does postoperative masticatory training for prognathism contribute to functional improvement?

ObjectiveIntroduction of postoperative oral rehabilitation has been expected to improve the oral function after orthognathic surgery for mandibular prognathism, but remains uncertain on its efficacy. This study was to clarify what kind of improvement in oral function is associated with postoperative oral rehabilitation. Methods51 patients of mandibular prognathism underwent orthognathic surgery. Gum chewing exercise was introduced in all patients from the third month after surgery. At the fourth month only 12 patients (EG) performed training perfectly and continued till the sixth month, however another group of 12 patients (NEG) quitted training then. The occlusal contact area(OCA), the maximum bite force(MBF), and the chewing ability(CA) were measured at the day before surgery, the first, the third, and the sixth month compared with a control group comprised of 20 normal subjects. The chewing pathway area of EG and NEG were measured using a mandibular movement measurement device. Each measured value was compared by Shapiro-Wilk normality test. Analysis of variance was performed by ANOVA, and multiple comparison test (p Value＜0.05). ResultsOCA and MBF were low significantly at the sixth month after surgery compared to the control group. There was no difference in OCA and MBF at the third month between in EG and in NEG, but CA was improved and the chewing pathway area was higher at the sixth month in EG. ConclusionGum chewing exercise as postoperative oral rehabilitation may restore chewing ability even in a short period of months after orthognathic surgery for mandibular prognathism.

Reliability and validity of two computerised occlusion analysis systems

ObjectivesThe present in vitro study evaluated the reliability and validity of two computerised occlusion analysis systems. MethodsThree occlusion analysis methods were evaluated. The methods included one traditional method (scanning of articulating paper marks (SAP)) and two computerised systems: (dental prescale occlusion analysis system (DPO) and a modified virtual occlusion construction method (VOC)). For reliability evaluation, the occlusion of an articulator-mounted anatomical dentoform was analysed ten times with each of the three methods. Occlusal contact areas and contact number values were obtained and the coefficient of variation (CoV) of each method was compared. For validity evaluation, resin casts of the dentition of 10 human subjects were used for analysis. Paired t-tests, regression analysis and Bland-Altman analysis were used to evaluate the difference and agreement amongst the three methods. ResultsThe CoV values of occlusal contact areas from the entire dentition were in the order: SAP (5.7%) < DPO (12.7%) < VOC (15.6%). Higher values was found in the anterior teeth (19.8–40.8%). Significant differences were identified in the occlusal contact areas of the entire dentition and posterior teeth obtained from SAP and DPO; a significant correlation was detected between the two methods (P < 0.01). Bland-Altman agreement analysis indicated good agreement between SAP and VOC. ConclusionsBoth DPO and VOC have good reliability and validity. They are potential alternatives for analysis of occlusal contacts. Clinical significanceThe dental prescale occlusion analysis system and the modified virtual occlusion constructed method combine convenience with the objectivity of digital technology. These computerised occlusion analysis systems may be used for quantitative analysis of occlusal contacts in clinical practice, with good reliability and validity.

Association of Gonial Angle with Hand Grip Strength in Vertical, Horizontal and Average Growers: A Cross-sectional Study

Introduction: The orthodontic treatment focuses on improving facial esthetics and functional occlusion by improving the masticatory function, including masticatory chewing pattern, masticatory muscle activity, maximum occlusal force, and occlusal contact area. In orthodontics, every decision is based on the patient’s growth pattern and muscle strength. Aim: To evaluate the gonial angle, hand grip strength and association of the gonial angle with Hand Grip Strength(HGS) in vertical, horizontal and average growers. Materials and Methods: This cross-sectional study was conducted from 24th June 2021 to 24th July 2022 in the Orthodontics Department at Sharad Pawar Dental College and Hospital in Sawangi, Wardha District, Maharashtra, India on a total of 196 patients. Data were categorized according to the growth pattern. For the vertical growth pattern, 49 patients were selected, 49 for the horizontal growth pattern, and 98 for the average growth pattern. A Jamar hand dynamometer was used to measure HGS and gonial angle using a lateral cephalogram. Study compared the results using inferential and descriptive statistics with a Analysis of Variance (ANOVA) (one-way) and multiple comparisons with the Tukey test. Also, p&lt;0.05 was considered as a level of significance. Results: The data of total of 49 patients in vertical growth pattern, 49 for the horizontal growth pattern, and 98 for the average growth pattern was collected and analysed. Grip strength and Gonial angle were compared between horizontal, average, and vertical growers. The gonial angle ranged from 101°to 124° in the average growth pattern, 81° to 99° in the horizontal growth pattern and 121° to 156° in the vertical growth pattern. The HGS in the horizontal growth pattern patients ranged from 27.2 Kg to 57.5 Kg. The HGS in the vertical growth pattern ranged from 14.7 Kg to 37.7 Kg. In the vertical growth pattern, the HGS was decreased compared to the Horizontal growth pattern group. To determine the factor of HGS, Gonial angle is the most prominent one. The assessment of growth patterns is vital in diagnosis and treatment planning. Conclusion: The study concluded that due to weak muscle strength, vertical group cases should be treated more carefully