Occlusal Contact Points Research Articles

Zirconia endocrown with intracanal extension and zirconia posts on maxillary molars: in silicio study.

The study aims to evaluate the stress distribution on tooth and restoration of zirconia endocrowns with pulp chamber or intracanal extension and zirconia post performed maxillary first molar using finite element analysis. Three three-dimensional endodontically treated maxillary molars were modeled. Cortical bone and cementum were modeled 2 mm and 200 μm in thickness. Periodontal ligament at 250 μm thickness was constructed. Zirconia endocrown with pulp chamber extension of 2 mm (Model E+PCE), zirconia endocrown with intracanal extension of 4 mm (Model E+ICE), and zirconia post of 4 mm and crown (ZP) were modeled using software. All restoration models were placed on the maxillary molars. Models were subjected to 400 N loading from the three occlusal contact points. Von Mises stress was recorded. Expectingly, points where the stress was applied showed high stress compared to other regions of the models. The stress did not occur at the trifurcation in any of the models. For the stresses occurring in the restoration material, there were 14.67 MPa, 57.79 MPa, and 155.56 MPa, in Models E+PCE, E+ICE, and ZP, respectively. At the remaining dentin, these values were 47.04 MPa, 32.85 MPa, and 33.42 MPa in Models E+PCE, E+ICE, and ZP, respectively. Within the limitation of the study, zirconia endocrowns with intracanal extension exhibit more favorable stress distribution in both restoration material and dentin compared to zirconia posts and pulpal extension endocrowns. These findings suggest that endocrown with intracanal extension may be a better restorative option for reducing stress.

Analyzing The Correlation Between The Conventional Complete Denture Occlusal Contact Points And Patient’s Satisfaction

Background: Conventional complete dentures continue to be a vital and essential method for restoring oral function in edentulous adults. However the quality of complete dentures influences the satisfaction level, thereby improves the psychological wellbeing of dentulous adults. Aim: A prospective in vivo study aims to analyse the presence of conventional complete denture occlusal contact points significantly influence patients' satisfaction levels. Materials and methods: Thirty patients who had received complete dentures were evaluated for their occlusal contact points one the day of insertion and 2 weeks later. Patient satisfaction questionnaire, which included subjective parameters such as initial adaptability, post insertion problems, aesthetics, masticatory ability, speech, retention was conducted at day 1 (day of insertion) and 2 weeks later. Results: Number of contact points almost were same on day 1 and 2 weeks later. The overall satisfaction of the patient has improved during the time interval. But correlation of the occlusal contact points to the patient satisfaction has no statistically significant value. Conclusion: Therefore, the overall satisfaction of the patient increased while using the complete denture from 1st day of denture insertion and after 14 days irrespective of number of contact points in the conventional complete denture with same occlusal scheme

3D-printed short-span hybrid composite implant-supported restorations fabricated through tilting stereolithography: A retrospective clinical study on 85 patients with 1 year of follow-up

PurposeTo report the clinical results obtained with fixed short-span (single crowns [SCs] and fixed partial prostheses [FPPs]) implant-supported hybrid composite restorations fabricated through tilting stereolithography (TSLA). MethodsThis retrospective clinical study included 85 patients who had been restored with 95 fixed short-span implant-supported hybrid composite (Irix Max®, DWS Systems) restorations (70 SCs and 25 FPPs up to three units) fabricated with TSLA. The full-digital model-free workflow was based on intraoral implant scanning, computer-assisted design (CAD) and 3D printing using TSLA (Dfab®, DWS Systems). The primary outcomes were the marginal adaptation, the quality of the occlusal and interproximal contact points, and the chromatic integration of the restorations, assessed independently by two experienced operators (a prosthodontist and a periodontist). A score from 1 to 5 (with 5 as the highest value, 4 for satisfactory quality, 3 for acceptable quality, and 2 and 1 as the lowest values, expressing unsatisfactory quality) was assigned by each operator to each restoration at delivery. The secondary outcomes were the survival and success of the restorations at the 1-year follow-up. The restoration was defined as successful in the absence of any complications throughout the follow-up period. A statistical analysis was conducted. ResultsFor the quality of the marginal closure and occlusal and interproximal contact points, the 3D-printed hybrid composite restorations scored highly; the aesthetic integration was satisfactory. One year after placement, all restorations survived, with a low incidence (4.2 % overall, 5.7 % SCs) of complications (two abutment screw loosenings, two decementation of the restorations, and one upper portion of the hybrid abutment decemented from the titanium base), for a success rate of 95.8 %. ConclusionsWithin the limits of this study (retrospective design, follow-up limited to 1 year from the delivery, and only cemented restorations included) fixed short-span implant-supported hybrid composite crowns and bridges fabricated through TSLA were clinically precise, presenting a low incidence of complications at 1 year. Statement of clinical relevanceThe use of TSLA printing technology can open new perspectives for the treatment of small edentulous gaps with definitive implant-supported prosthetic restorations.

Evaluation of stress distributions of calcium silicate-based root canal sealer in bulk or with main core material: A finite element analysis study.

This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used.

Accuracy of Occlusal Contacts of All-Ceramic Single Crowns Designed by Virtual Articulators from a CAD/CAM System: A Preliminary Evaluation.

To compare the static and dynamic occlusion of all-ceramic single crowns designed by mechanical and virtual articulators, by evalua6ng the accuracy of occlusal contacts of prostheses designed by virtual articulators and the feasibility of clinical application of CAD/CAM virtual articulators. Nine subjects with an average age of 27 years who needed crown repair were recruited. After preparation of the all-ceramic crowns, two zirconia crowns were designed and fabricated through digital procedures and traditional methods. The intraoral scanner, Geomagic software, and T-Scan analyzer were used to analyze the occlusal contact points, areas, and the occlusal force percentage peak before the treatment and after the two crowns were temporarily fixed. There was a significant difference in the number of occlusal contact points and areas between the mechanical group and control group (preoperation group), but there was no obvious difference between the virtual group and control group. The occlusal contact overlapping areas of the virtual-control group were significantly larger than those of the mechanical-control group. The occlusal force percentage peak of the tested teeth was slightly larger in the mechanical group than in the virtual group. The posterior single crown designed by a virtual articulator restored the intercuspal occlusal better than one designed by a mechanical articulator, and it produced less dynamic occlusal interference. This finding suggests that virtual articulators can provide guidance for the design and adjustment of the occlusal surface of posterior single crown prostheses.

Tooth morphology, internal fit, occlusion and proximal contacts of dental crowns designed by deep learning-based dental software: A comparative study

ObjectivesThis study compared the tooth morphology, internal fit, occlusion, and proximal contacts of dental crowns automatically generated via two deep learning (DL)-based dental software systems with those manually designed by an experienced dental technician using conventional software. MethodsThirty partial arch scans of prepared posterior teeth were used. The crowns were designed using two DL-based methods (AA and AD) and a technician-based method (NC). The crown design outcomes were three-dimensionally compared, focusing on tooth morphology, internal fit, occlusion, and proximal contacts, by calculating the geometric relationship. Statistical analysis utilized the independent t-test, Mann–Whitney test, one-way ANOVA, and Kruskal–Wallis test with post hoc pairwise comparisons (α = 0.05). ResultsThe AA and AD groups, with the NC group as a reference, exhibited no significant tooth morphology discrepancies across entire external or occlusal surfaces. The AD group exhibited higher root mean square and positive average values on the axial surface (P < .05). The AD and NC groups exhibited a better internal fit than the AA group (P < .001). The cusp angles were similar across all groups (P = .065). The NC group yielded more occlusal contact points than the AD group (P = .006). Occlusal and proximal contact intensities varied among the groups (both P < .001). ConclusionsCrowns designed by using both DL-based software programs exhibited similar morphologies on the occlusal and axial surfaces; however, they differed in internal fit, occlusion, and proximal contacts. Their overall performance was clinically comparable to that of the technician-based method in terms of the internal fit and number of occlusal contact points. Clinical significanceDL-based dental software for crown design can streamline the digital workflow in restorative dentistry, ensuring clinically-acceptable outcomes on tooth morphology, internal fit, occlusion, and proximal contacts. It can minimize the necessity of additional design optimization by dental technician.

Trueness, precision, time-efficiency and cost analysis of chairside additive and subtractive versus lab-based workflows for manufacturing single crowns: An in vitro study

PurposeTo evaluate the trueness, precision, time efficiency, and cost of three different workflows for manufacturing single crowns (SCs). MethodsA plaster model with a prepared tooth (#15) was scanned with an industrial scanner, and an SC was designed in computer-assisted-design (CAD) software. Ten SCs were printed with a hybrid composite (additive chairside) and a stereolithographic (SLA) printer (Dfab®), 10 SCs were milled in lithium disilicate (subtractive chairside) using a chairside milling unit (inLab MC XL®), and 10 SCs were milled in zirconia (lab-based) using a five-axis laboratory machine (DWX-52D®). All SCs were scanned with the same scanner after polymerization/sinterization. Each scan was superimposed to the marginal area of the original CAD file to evaluate trueness: absolute average (ABS AVG), root mean square (RMS), and (90˚–10˚)/2 percentile were calculated for each group. Marginal adaptation and quality of the occlusal and interproximal contact points were also investigated by two prosthodontists on 3D printed and plaster models. Finally, the three workflows’ time efficiency and costs were evaluated. ResultsAdditive chairside and subtractive lab-based SCs had significantly better marginal trueness than subtractive chairside SCs in all three parameters (ABS AVG, p < 0.01; RMS, p < 0.01; [90˚–10˚]/2, p < 0.01). However, the two prosthodontists found no significant differences between the three manufacturing procedures in the quality of the marginal closure (p = 0.186), interproximal (p = 0.319), and occlusal contacts (p = 0.218). Both time efficiency and cost show a trend favoring the chairside additive workflow. ConclusionsChairside additive technology seems to represent a valid alternative for manufacturing definitive SCs, given the high marginal trueness, precision, workflow efficiency and low costs. Statement of clinical relevanceAdditive chairside manufacturing of definitive hybrid composite SCs is now possible and shows high accuracy, time efficiency, and competitive cost.

Accuracy and reproducibility of real and virtual occlusal contact points in implant-supported fixed prostheses.

To evaluate the accuracy and reproducibility of real and virtual occlusal contact points in implant-supported, fixed complete dentures. The study included 19 participants using mandibular interim complete-arch fixed prosthesis supported by 3 or 4 implants as opposed to conventional removable complete dentures. At installation, an examiner installed the prostheses and verified the occlusal contact points through 2 methods: recording the real contact points with carbon paper (RC) followed by occlusal photography and intraoral scanning (VC) to record the virtual contact points to obtain a screen print of the software. Then, the two images were randomized to determine the order to be inserted into Microsoft PowerPoint for blind and paired evaluation. The independent variables consisted of the distribution of occlusal contacts points (qualification through pre-defined scores based on the position of the contact points on the surfaces of the teeth) and the reproducibility of the methods by verifying the number of occlusal points. For this, a descriptive analysis was used to evaluate the distribution of occlusal contacts points and the Wilcoxon test for the reproducibility of the occlusal contact points between the methods (p<0.05). The methods had 100% and 73.6% real and virtual occlusal contact points, respectively, which is considered clinically excellent. There was no significant difference regarding the reproducibility of the methods by the number of occlusal contact points (RC: x̅13.32; VC: x̅13.68; p=0.715). The use of the tested intraoral scanner can be an easy and fast tool for studying and mapping the occlusion, and storing data for future treatment, with the conventional method being the preferred method for performing the occlusal adjustment.

Finite Element Analysis of Occlusal Interferences in Dental Prosthetics Caused by Occlusal Adjustment.

To investigate the influence of occlusal interference using finite element analysis (FEA). The FEA model designed for this study centered on an all-ceramic, bilayered, fixed partial denture (FPD) retained on the maxillary first premolar and first molar, with the second premolar replaced by a pontic. The surrounding structures-such as the neighboring teeth, antagonists, and periodontium-were modeled. Four different loading cases were designed at occlusal interferences of 0, 8, 12, and 24 μm and were loaded by a simulated bite force of 300 N. Principal and von Mises stresses, as well as strain, were evaluated for all included structures. For interferences of 12 and 24 μm, failure-relevant tensile stresses in the veneering layer were observed at the occlusal surfaces. Stress found in the zirconia FPD did not reach fatigue or flexural strength for any test load. Peak tensile stress was observed in close proximity to occlusal contact points, increasing with increasing occlusal interference. The FEA results suggest that the majority of occlusal stress is absorbed by the deformation of the periodontal ligament. Framework failure caused by the simulated interferences was not expected. Surface defects may ultimately lead to failure due to fracture or chipping, especially in cases of weaker ceramics or veneering.

Distribution patterns of occlusal contact areas on natural posterior teeth – Evaluations of a cross-sectional population-based study with the Greifswald Digital Analyzing System (GEDAS)

AimThe aim of our investigations is to optimize the anatomical basis for the design of a sufficient occlusal relationship, especially in view of the innovative technologies by analyzing the occlusal contact point patterns at cusp structures according to A-, B-, C- localization tooth by tooth on the individual occlusal surfaces in the posterior region in static habitual occlusal position. Materials and methodsIn 3300 subjects of the population-based Study of Health in Pomerania (SHIP 1) the interocclusal registration in habitual intercuspation using silicone registration was used and analyzed by using the special evaluation software Greifswald Digital Analyzing System (GEDAS II).Chi square test was used to investigate whether the distribution of contact areas differed in the group of premolars or molars - each considered separately for maxilla and mandible - on the basis of the probability of error p < 0.05. ResultsIn 709 subjects (446 male with a mean age of 48.9 ± 13.04 years; 283 female with a mean age of 52.4 ± 14.23 years) the antagonistic situation was specifically considered on natural posterior teeth without conservative or restorative-prosthetic interventions, i.e. without caries, fillings, crowns or other restorations. On the basis of these subjects, the silicone registrations were analyzed using GEDAS II. For the first and second upper molars, the ABC contact distribution was the most frequent: 20.4 % for the first and 15.3 % for the second molar. The second most frequent contact area for maxillary molars was area 0. The upper molars had contact areas only at the maxillary palatal cusp (B-/C-contacts). This contact relationship was most frequent in the maxillary premolar (18.1–18.6 %). In mandibular premolars, with the buccal cusps areas A and B were frequently involved (15.4–16.7 %). Mandibular molars showed a frequent contact pattern involving all A-, B-, C- and 0- contact areas (13.3–24.2 %). To capture the possible influence of the antagonistic dentition situation, the antagonistic situation was specifically considered and except for the mandibular premolars (p < 0.05) the contact distribution did not differ for molars and maxillary premolars regarding the dental status of the antagonistic teeth.Natural posterior teeth without occlusal contacts were observed from 20.0 % in the second lower molars to 9.7 % in the first upper molars. ConclusionOur results suggest a clinically relevant due to the fact, that this study is the first population-based epidemiological study to analyze the occlusal contact point patterns at cusp structures according to A-, B-, C- localization tooth by tooth on the individual occlusal surfaces in the posterior region in static habitual occlusal position in order to optimize the anatomical basis for the design of a sufficient occlusal relationship.

A comprehensive study on the mechanical effects of implant-supported prostheses under multi-directional loading and different occlusal contact points

AimsTo evaluate screw loosening and fracture load and angular deviation of a single implant-supported prosthesis under multi-directional loading condition at three different occlusal contact points.MethodsA total of 40 metal crowns were cemented to external connection implants and were embedded vertically and obliquely. The occlusal surface of the crown was designed with three flat surfaces, contact a, b, and c, representing outer and inner 20-degree inclination for buccal and lingual cusps. The angular deviations of implant crown under static 50N of loading were measured. And screw removal torque was evaluated before and after 57,600 load cycles. Then, fracture load was measured for each specimen. Data analysis was performed using one-way analysis of variance test of significance followed by Tukey honest significant difference (HSD) test(p < 0.05).ResultsAngular deviation results showed statistical significance between all contact points in vertically embedded group compared to obliquely embedded group, which showed similar results between contact A and B compared to C. In the other hand, screw loosening evaluation did not show statistical significance among the tested groups. And for the fracture load evaluation the maximum values reached twice the yield values in all contact areas.ConclusionsMechanical effects were different regarding to diverse loading direction and contact points. The results of this study suggest that the stress concentration might increase in unfavorable vector direction.

Effect of different occlusal forces on the accuracy of interocclusal records of loose teeth.

This study aimed to investigate the effect of loose teeth on the accuracy of occlusal records by comparing the differences in the number of occlusal contact points, occlusal contact area, and the center of the occlusal contact region under different occlusal forces in patients with periodontitis. The effects of different occlusal forces on the occlusal contact point (OCP), occlusal contact area (OCA) and the center of occlusal contact region (OCC) of loose teeth. Occlusal training was performed on the thirty patients who completed periodontal serial treatment. One doctor took the occlusal records with silicone rubber and the T-scan system; the patients were digitally scanned intraorally by a technician. The data of the healthy teeth were recorded as the control group, and the data of the loose teeth were recorded as the experimental group. Then we used Image J to measure the numbers of OCP and OCA and Auto CAD to calculate the coordinates of OCC. A paired t-test was used to analyze whether the differences in OCP, OCA, and OCC were statistically significant when the occlusal forces were different. The OCA of all three experimental methods increased under heavy occlusal force (p<.01), and the silicone rubber OCA increased the most. The OCC of all three experimental methods was shifted in the buccal and mesial (p<.01). And the occlusal records obtained by the T-scan system showed a low correlation between the differences of OCA and OCC. Whether the teeth were loose or not, the OCA increased under heavy occlusal forces. For patients with loose teeth, the OCC was shifted toward the buccal under heavy occlusal force.

Morphology and mechanical performance of dental crown designed by 3D-DCGAN.

This study utilised an Artificial Intelligence (AI) method, namely 3D-Deep Convolutional Generative Adversarial Network (3D-DCGAN), which is one of the true 3D machine learning methods, as an automatic algorithm to design a dental crown. Six hundred sets of digital casts containing mandibular second premolars and their adjacent and antagonist teeth obtained from healthy personnel were machine-learned using 3D-DCGAN. Additional 12 sets of data were used as the test dataset, whereas the natural second premolars in the test dataset were compared with the designs in (1) 3D-DCGAN, (2) CEREC Biogeneric, and (3) CAD for morphological parameters of 3D similarity, cusp angle, occlusal contact point number and area, and in silico fatigue simulations with finite element (FE) using lithium disilicate material. The 3D-DCGAN design and natural teeth had the lowest discrepancy in morphology compared with the other groups (root mean square value = 0.3611). The Biogeneric design showed a significantly (p<0.05) higher cusp angle (67.11°) than that of the 3D-DCGAN design (49.43°) and natural tooth (54.05°). No significant difference was observed in the number and area of occlusal contact points among the four groups. FE analysis showed that the 3D-DCGAN design had the best match to the natural tooth regarding the stress distribution in the crown. The 3D-DCGAN design was subjected to 26.73MPa and the natural tooth was subjected to 23.97MPa stress at the central fossa area under physiological occlusal force (300N); the two groups showed similar fatigue lifetimes (F-N curve) under simulated cyclic loading of 100-400N. Designs with Biogeneric or technician would yield respectively higher or lower fatigue lifetime than natural teeth. This study demonstrated that 3D-DCGAN could be utilised to design personalised dental crowns with high accuracy that can mimic both the morphology and biomechanics of natural teeth.

Fatigue performance analysis of strength-graded zirconia polycrystals for monolithic three-unit implant-supported prostheses

The aim of this study was to evaluate the fatigue behavior of strength-graded zirconia polycrystals used as monolithic three-unit implant-supported prosthesis; complementarily, crystalline phase and micromorphology were also assessed. Fixed prostheses with 3 elements supported by 2 implants were confectioned, as follows: Group 3Y/5Y – monolithic structures of a graded 3Y-TZP/5Y-TZP zirconia (IPS e.max® ZirCAD PRIME); Group 4Y/5Y - monolithic structures of a graded 4Y-TZP/5Y-TZP zirconia (IPS e.max® ZirCAD MT Multi); Group Bilayer – framework of a 3Y-TZP zirconia (Zenostar T) veneered with porcelain (IPS e.max Ceram). The samples were tested for fatigue performance with step-stress analysis. The fatigue failure load (FFL), the number of cycles required until failure (CFF), and the survival rates in each cycle were recorded. The Weibull module was calculated and the fractography analyzed. The crystalline structural content via Micro-Raman spectroscopy and the crystalline grain size via Scanning Electron microscopy were also assessed for graded structures. Group 3Y/5Y showed the highest FFL, CFF, probability of survival, and reliability (based on Weibull modulus). Group 4Y/5Y showed significantly superior FFL and probability of survival than group bilayer. Fractographic analysis revealed catastrophic flaws in the monolithic structure and cohesive fracture of porcelain in bilayer prostheses, all originating from the occlusal contact point. The graded zirconia presented small grain size (≤0.61 μm), with the smallest values at the cervical region. The main composition of graded zirconia was of grains at tetragonal phase. The strength-graded monolithic zirconia, especially the 3Y-TZP/5Y-TZP, showed to be promising for use as monolithic three-unit implant-supported prosthesis.

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.

Optimal occlusal force field of masticatory system under clenching by simplex method and principal component analysis

In the present paper, a method to evaluate the occlusal state and occlusal morphology that can integrate an optimal occlusal force field under clenching is proposed using simplex optimization and principal component analysis (PCA). The objective function of the optimization is taken as a sum of the weighted occlusal forces and reaction on temporomandibular joint (TMJ) to maximize the former and to minimize the latter. The optimized solutions in the region defined by the combination among three kinds of muscle forces were obtained by two-step simplex method, and the subregion with no reaction of TMJ was summarized as a ratio to the whole region, newly defined here as a good balance ratio. As a result of PCA of total 528 samples of the good balance ratios for 13 different muscle force combinations, two principal components (PCs) are enough to represent the optimized masticatory system. The first PC suggests the ideal state of occlusion and the second one implies the characterization of combination among muscles. From the consideration of PCA, with the wider equalizer angle, the easier it is to support the force of the temporalis muscle in an ideal occlusal position, and the more the occlusal contact point is shifted backward, the harder it is to support the force of the temporalis muscle. Comprehensively, the proposed good balance ratio becomes the effective quantity to evaluate the ideal masticatory system with the optimized occlusal force field for the statistically reduced indexes showing the combination of muscles.

Clinical application of digitalization of occlusal contacts with dental scanner

This study aimed to evaluate the number, intensity and position of occlusal contact points in a case of mesiocclusion, hyperdivergence, with open bite. An occlusal record was taken from a patient with anterior and lateral open bite mesiocclusion, using the Planmeca Esmerald S intraoral scanner in maximum intercuspation. The intensity of the occlusal contact was analyzed with the software 3shape Ortho Analyzer Orthodontics, using the Occlusion Map module, through the 3D Color Map tool, with a 0.5 mm virtual articular paper. These results were compared to the occlusal support points defined by Planas [10]. The interpretation of the data obtained was made by assessing the interocclusal intensity of the contact points, number of contacts and position during three different moments (1S, 2S, 3S) in the record taking process. The chromatic scale of the Color Map is: red, orange, yellow, green and blue. To identify the occlusal contact points in digital, they are shown in red points when full contact occurs, while minimum contact is shown in blue. We evaluated the number of teeth with interocclusal contacts. It was determined that having the appropriate number of contacts does not imply that they are in the correct position. In addition, the method suggests reliability in the filing and record keeping of occlusal contacts. By identifying intensity, number and position of the occlusal support point we can objectively record interocclusal alterations.

Occlusal Analysis in Natural Dentition: Systematic Review.

This study aimed to evaluate the effectiveness of conventional occlusal analysis in contrast with digital occlusal analysis in natural dentition. Occlusal analysis allows the identification of normal and abnormal occlusal contact points that alter the craniomandibular cervical system. We searched for articles with keywords [[dental occlusion]], [[natural dentition]], [[occlusal adjustment]], [[Immediate Complete Anterior Guidance Development]] [[mastication]], [[bite force]], [[premature contact]], [[occlusal balance]] [[articulating paper]]], [[spray]], [[Occlusal contacts]], and [[bite strength]]. They were considered observational , odds ratio and case control studies. We found 189 items. After evaluating the abstracts and full texts of the articles, 10 papers met the inclusion criteria. It was found that occlusal analysis allows the identification of the relationship between poor occlusion and the sensitivity of the teeth due to occlusal trauma, which is also related to temporomandibular joint pain in dynamic occlusion. The contacts of greater strength were observed in nonfunctional cusps, 48%, without ruling out the functional cusps, 24%. Despite being the universal method of occlusal control to date, the use of joint paper, remains subjective compared to the digital occlusal control device. Posture is considered directly related to occlusal trauma and temporomandibular disorders; without proper occlusal analysis, a clear diagnosis of the patient's joint condition cannot be obtained. Digital occlusal analysis is more objective than traditional occlusal analysis.

Accuracy and reproducibility of the visualization of occlusal contact points using analog articulating foil or digital intraoral scanners in vitro.

The accuracy and reproducibility of occlusal contact points visualized by articulating foil (AF) were investigated and then compared with those calculated by three different intraoral scanners (IOSs). Occlusal contact points were visualized on a standardized resin dental tooth model using AF 50 times in maximum intercuspation and with a constant biting force. The occlusal contact points were photographed from a vertical position above the model and superimposed on a screen to test the reproducibility of the model. This was followed by 50-fold repetition by scans and computation of the occlusal contact points by three different IOSs: CS 3600 (CS ScanFlow v.1, 4th version), Trios 3 (Basic 2019), and Cerec Omnicam (software version 5.1). The results of the computation were captured with screenshots and were then overlaid with the photographs of the AF. The image overlays were classified into five categories: 1 = total overlapping of contact points, 2 = partial overlapping of contact points, 3 = adjacent contact points without overlapping, 4 = contact points identified only by AF, 5 = contact points identified only by IOS. All data were statistically evaluated (95% confidence interval). In total, the visualization of the occlusal contact points by the IOSs were significantly less accurate and less reproducible compared with the AF (P < 0.05). When sensitivity and accuracy were combined, the Trios 3 (3Shape) showed significantly better results than the other IOSs tested (P < 0.05). In vitro, AF displayed a significantly more accurate visualization of the occlusal contact points than the IOSs.