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Hua Xi Kou Qiang Yi Xue Za Zhi = Huaxi... Jun 2023This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using... (Comparative Study)
Comparative Study
OBJECTIVES
This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using the mandibular movement track and the movement parameters of a virtual articulator.
METHODS
Twenty-two participants were recruited. Digital casts of the maxillary and mandibular arches were obtained using an intraoral scanner, and the jaw registration system was used to record the data of the mandibular movement track and the movement parameters of the articulator. Four kinds of restorations with 0.3 mm occlusal interferences were designed with dental design software. In particular, single crowns were designed for teeth 44 and 46, whereas three-unit bridges were designed for teeth 44-46 and 45-47, and the corresponding natural teeth were virtually extracted. Virtual adjustment of the restorations was performed using two dynamic occlusal recordings, namely, the mandibular movement track and the movement parameters of the virtual articulator. A reverse-engineering software was used to measure the root-mean-square of the three-dimensional deviation of the occlusal surfaces between natural teeth and the adjusted restorations. The differences between the two methods of virtual-occlusion adjustment were compared and analyzed.
RESULTS
For the same group of restorations, the three-dimensional deviation of the mandibular movement track group were lower than those of the virtual articulator group, and the differences were statistically significant (<0.05). For the four groups of restorations adjusted by the same method, the three-dimensional deviation of the 46-tooth single crown was the largest and the smallest three-dimensional deviation was that of the 44-tooth single crown. Statistical differences existed between the 44-tooth single crown and the other groups (<0.05).
CONCLUSIONS
For the occlusal design of posterior single crown and three-unit bridge, the mandibular movement track could be a more effective approach to virtual occlusal adjustment than the movement parameters of the virtual articulator.
Topics: Humans; Mouth, Edentulous; Occlusal Adjustment; Jaw Relation Record; Dental Articulators; Software
PubMed: 37277790
DOI: 10.7518/hxkq.2023.2022452 -
The Journal of Prosthetic Dentistry May 2023Some contemporary articulator systems claim to be highly precise in their interchangeability, with tolerances below 10 μm in vertical error; however, the claims have...
STATEMENT OF PROBLEM
Some contemporary articulator systems claim to be highly precise in their interchangeability, with tolerances below 10 μm in vertical error; however, the claims have not been independently verified.
PURPOSE
The purpose of this study was to investigate the interchangeability of calibrated semiadjustable articulators in service over time.
MATERIAL AND METHODS
A calibrated mounting articulator served as the master articulator, while the test groups were used articulators with a minimum of 1-year use by predoctoral dental students (n=10); used articulators with a minimum of 1-year use by prosthodontic residents (n=10); and new articulators (n=10). One set of mounted maxillary and mandibular master models was positioned in the master and test articulators. High-precision reference markers on the master models were used to determine interarch 3D distance distortions (dR, dR, and dR), interocclusal 3D distance distortion (dR), interocclusal 2D distance distortions (dx, dy, and dz), and interocclusal angular distortion (dθ) relative to the master articulator. All measurements were conducted three times using a coordinate measuring machine and then averaged to derive the final data set.
RESULTS
For interarch 3D distance distortion, the mean dR ranged from 4.6 ±21.6 μm for new articulators to 56.3 ±47.6 μm for articulators used by prosthodontic residents; mean dR ranged from 65 ±48.6 μm for new articulators to 119.0 ±58.8 μm for articulators used by prosthodontic residents; and mean dR ranged from 12.7 ±39.7 μm for articulators used by prosthodontic residents to 62.8 ±75.2 μm for new articulators. For interocclusal 3D distance distortion, the mean dR ranged from 21.5 ±49.8 μm for new articulators to 68.6 ±64.9 μm for articulators used by predoctoral dental students. For the 2D distance distortions, the mean dx ranged from -17.9 ±43.4 μm for articulators used by predoctoral dental students to -61.9 ±48.3 μm for articulators used by prosthodontic residents; mean dy ranged from 18.1 ±59.4 μm for new articulators to 69.3 ±115.1 μm for articulators used by prosthodontic residents; and mean dz ranged from 29.5 ±20.2 μm for new articulators to 70.1 ±37.8 μm for articulators used by prosthodontic residents. Mean dθ ranged from -0.018 ±0.289 degree for new articulators to 0.141 ±0.267 degree for articulators used by prosthodontic residents. One-way ANOVA by articulator type revealed statistically significant differences among the test groups for dR (P=.007) and dz (P=.011) only, where articulators used by prosthodontic residents fared significantly poorer than the other test groups.
CONCLUSIONS
The new and used articulators tested did not fulfill the manufacturer's claim of accuracy of up to 10 μm in the vertical dimension. Up to 1 year of time in service, none of the investigated test groups fulfilled the criterion for articulator interchangeability, even if the more lenient threshold of 166 μm were accepted.
PubMed: 37244795
DOI: 10.1016/j.prosdent.2023.04.009 -
The Journal of Prosthetic Dentistry Jun 2023Digital occlusal analyzers allow the recording of dental contact forces. Some authors assume a unique location for the center of contact forces at the position of...
STATEMENT OF PROBLEM
Digital occlusal analyzers allow the recording of dental contact forces. Some authors assume a unique location for the center of contact forces at the position of maximum intercuspation, while others indicate variations in dental contact forces when recorded at different times of the day. Which approach is more appropriate is unclear.
PURPOSE
The purpose of this in vitro study was to analyze whether a change in the balance of masticatory forces influences the location of the center of contact forces and its magnitude.
MATERIAL AND METHODS
Three different dental casts, selected under dental criteria, were mounted in maximum intercuspation on a semiadjustable articulator equipped with a pattern indicating 9 different force application points (intersection point between 3 longitudinal rows and 3 transverse columns). A force of constant magnitude (169 N) was applied 10 times at each of the application points, and occlusal forces were recorded with a digital occlusal analyzer. Then, two variables were studied: the location of the center of contact forces and its magnitude. Each force application position (9 positions × 3 dental casts=27 in total) was repeated 10 times, and measured data were statistically analyzed with 2-way repeated measures ANOVA (α=.05) test.
RESULTS
The repeatability of the method indicated that the coefficient of variation mean was 0.37% in the location of the center of contact forces and that its magnitude was 3.70%. The 2-way repeated measures ANOVA test revealed statistically significant variations in the location of the center of contact forces and its magnitude, revealing that longitudinal changes of the application point of masticatory forces affected the magnitude of contact forces and that longitudinal and transverse changes of the application point of masticatory forces affected the location of the center of contact forces.
CONCLUSIONS
The location of the center of contact force and its magnitude provided by a digital occlusal analyzer at the position of maximum intercuspation are not necessarily unique to each articulated dental cast. Even if the intensity of the masticatory force remains unchanged, changes in its lateral or longitudinal balance also influence the result of the occlusion forces.
Topics: Bite Force; Dental Occlusion; Dental Articulators
PubMed: 37003941
DOI: 10.1016/j.prosdent.2023.03.007 -
BMC Oral Health Mar 2023Precise occlusal design of implant-supported fixed prostheses is difficult to achieve by the conventional wax-up method, often requiring chairside adjustments. The...
BACKGROUND
Precise occlusal design of implant-supported fixed prostheses is difficult to achieve by the conventional wax-up method, often requiring chairside adjustments. The computer-aided design (CAD) method is promising. This study aims to compare the occlusal contacts and clearance of posterior implant-supported single crowns designed by the CAD and conventional methods.
METHODS
Sample size calculation indicated fourteen samples per group. Two sets of type-IV plaster casts with a single implant analog inserted in the posterior teeth region were mounted as master casts in a mechanical articulator in maximal intercuspal position (MIP). Seven working cast sets were obtained from each master cast by a closed tray technique, and mounted in MIP. Two implant-supported single crowns were designed with an occlusal clearance to achieve light occlusal contact in each working cast set by CAD and conventional method, separately. For the CAD group, the crown was designed in digital models obtained by scanning the working casts. For the conventional group, wax-up of the crown was prepared on the working casts and scanned to generate a STL file. In the working and master casts, mean and minimum occlusal clearances in the designed occlusal contact area of the both finished prostheses were calculated using the occlusal clearance (OC) and occlusal record (OR) method. The prostheses' occlusion was evaluated in master casts.
RESULTS
For the evaluation in the working casts, both design methods had similar mean occlusal clearances by the OC method (195.4 ± 43.8 vs. 179.8 ± 41.8 μm; P = 0.300), while CAD group resulted in a significantly larger minimum occlusal clearance in the designed occlusal contact area (139.5 ± 52.3 vs. 99.8 ± 43.8 μm; P = 0.043). Both design methods had similar mean and minimum occlusal clearances by the OR method (P > 0.05). For the evaluation in the master casts, both design techniques had similar mean and minimum occlusal clearances, number and distribution of occlusal contacts, and lateral interference ratios (P > 0.05).
CONCLUSION
Occlusal contact and clearance of posterior implant-supported single crowns designed by the CAD method can be at least as good as those designed by the conventional wax-up method.
Topics: Humans; Crowns; Computer-Aided Design; Dental Occlusion; Research Design; Dental Impression Technique; Dental Prosthesis Design
PubMed: 36918877
DOI: 10.1186/s12903-023-02847-w -
The Journal of Advanced Prosthodontics Feb 2023To compare the sagittal condylar inclination (SCI) in dentate individuals measured by the different methods with mechanical articulator (MA), virtual articulator (VA),...
PURPOSE
To compare the sagittal condylar inclination (SCI) in dentate individuals measured by the different methods with mechanical articulator (MA), virtual articulator (VA), and a jaw tracking device (JTD) system.
MATERIALS AND METHODS
A total of 22 healthy dentate participants were enrolled in this study. For MA workflow, the SCI was obtained by a semi-adjustable articulator with protrusive interocclusal records. The SCI was also set on a VA by aligning intraoral scan (IOS) with cone beam computed tomography (CBCT) and facial scan (FS), respectively. These virtual workflows were conducted in a dental design software, namely VA and VA. Meanwhile, a JTD system was also utilized to perform the measurement. Intraclass correlation was used to assess the repeatability within workflows. The bilateral SCI values were compared by Wilcoxon matched-pairs signed rank test for each workflow, and Kruskal-Wallis test and post hoc p-value Bonferroni correction were used to compare the differences among four workflows. The agreement of VA, VA, and JTD compared with MA was evaluated by Bland-Altman analysis.
RESULTS
Intraclass correlation of the SCI revealed a high degree of repeatability for each workflow. There were no significant differences between the left and right sides ( > .05), except for VA ( = .028). Significant differences were not found between MA and VA ( > .05). Bland-Altman plots indicated VA, VA, and JTD were considered to substitute MA with high 95% limits of agreement.
CONCLUSION
The workflow of VA provided an alternative approach to measure the SCI compared with MA.
PubMed: 36908753
DOI: 10.4047/jap.2023.15.1.11 -
Life (Basel, Switzerland) Jan 2023A complex prosthodontic treatment is believed to be more successful when the condylar path is replicated using the articulator. However, there is an ongoing major...
Complicated Relationships between Anterior and Condylar Guidance and Their Clinical Implications-Comparison by Cone Beam Computed Tomography and Electronic Axiography-An Observational Cohort Cross-Sectional Study.
A complex prosthodontic treatment is believed to be more successful when the condylar path is replicated using the articulator. However, there is an ongoing major disagreement between the researchers as the exact relationship between the posterior and anterior determinants has not been clear. The purpose of this study was to investigate whether the protrusive movement of the mandible does correlate with the temporomandibular joint (TMJ) anatomy or with incised features. Subjects (15 males and 15 females) were qualified for this study based on an initial interview including the following criteria: age 21-23 (+/-1), no history of trauma, orthodontic treatment, or temporomandibular disorders (TMD). For each patient, the angle of the condylar path, incisal guidance angle (IGA), interincisal angle, as well as overbite and overjet were measured on cone beam computed tomography (CBCT). This was followed by the examination with the Modjaw electronic axiograph recording and calculating the functional sagittal condylar guidance angle (SCGA) for the right and left TMJ during the protrusion. The results show that the mean functional axiographic measurement of SCGA in protrusion significantly correlates with the TMJ anatomy presented on CBCT. Moreover, a significant correlation was found between the values of SCGA in the functional and anatomical measurements in all its variants. It turned out that, statistically, the AB measurement was the most accurate. Finally, results showed that incisal relationships of permanent teeth such as overbite, overjet, incisal guidance angle and interincisal angle do not correlate with TMJ anatomy, and therefore, regarding an analyzed study group, do not affect the TMJ formation in young adults.
PubMed: 36836692
DOI: 10.3390/life13020335 -
The Journal of Advanced Prosthodontics Dec 2022The purpose of this study was to assess whether scanning strategies of virtual interocclusal record (VIR) affect the accuracy of VIR during intraoral scanning.
PURPOSE
The purpose of this study was to assess whether scanning strategies of virtual interocclusal record (VIR) affect the accuracy of VIR during intraoral scanning.
MATERIALS AND METHODS
Five pairs of reference cubes were added to the digital upper and lower dentitions of a volunteer, which were printed into resin casts. Subsequently, the resin casts were articulated in the maximal intercuspal position in a mechanical articulator and scanned with an industrial computed tomography system, of which the VIR was served as a reference VIR. The investigated VIR of the upper and lower jaws of the resin master cast were recorded with an intraoral scanner according to 9 designed scanning strategies. Then, the deviation between the investigated VIRs and reference VIR were analyzed, which were measured by the deviation of the distances of six selected reference points on the upper reference cubes in each digital cast to the XY-plane between the investigated VIRs and reference VIR.
RESULTS
For the deviation in the right posterior dentitions, RP group (only scanning of right posterior dentitions) showed the smallest deviation. Besides, BP group (scanning of bilateral posterior dentitions) showed the smallest deviation in the left posterior dentitions. Moreover, LP group (scanning of left posterior dentitions) showed the smallest deviation in the anterior dentitions. For the deviation of full dental arches, BP group showed the smallest deviation.
CONCLUSION
Different scanning strategies of VIR can influence the accuracy of alignment of virtual dental casts. Appropriate scanning strategies of VIR should be selected for different regions of interest and edentulous situations.
PubMed: 36685791
DOI: 10.4047/jap.2022.14.6.369 -
Journal of Clinical Medicine Jan 2023Available knowledge about malocclusion and cephalometric variables and their connection with an increased risk of condylar displacement (CD) is scarce. This article aims... (Review)
Review
The Role of Maxillofacial Structure and Malocclusion on Condylar Displacement in Maximum Intercuspation and Centric Relation in Patients Seeking Orthodontic Treatment-A Scoping Review.
BACKGROUND
Available knowledge about malocclusion and cephalometric variables and their connection with an increased risk of condylar displacement (CD) is scarce. This article aims to present current information on the relationship between centric relation-maximum intercuspal position discrepancies and maxillofacial morphology and malocclusion in patients seeking orthodontic treatment as well as to identify those who require expanded diagnostic evaluation for this disorder.
METHODS
This review analyzed the PubMed, Cochrane Library, Web of Science, and Scopus electronic databases up to February 2022. Keywords and additional manual searches were performed. Literature selection was based the PRISMA-ScR checklist. The JBI Critical Appraisal Tool assessed the methodological quality of included studies.
RESULTS
The databases search provided 2321 studies. A total of 10 studies were included in this review after eligibility criteria and JBI assessment. This review was separated into five parts that evaluated CD correlations depending on the following: maxillofacial structure in different vertical and sagittal skeletal patterns, vertical, horizontal, and transverse malocclusions.
CONCLUSIONS
A hyperdivergent facial skeletal structure is a risk factor for increased CD, particularly in the vertical dimension. The condylar processes are usually displaced in a posteroinferior direction. Further studies are warranted to elucidate the relationship among remaining skeletal and dental malocclusions and the occurrence of CD.
PubMed: 36675620
DOI: 10.3390/jcm12020689 -
Cureus Dec 2022Introduction The importance of disocclusion in maintaining the health of the stomatognathic system is well established. However, the quantification of the same is...
Introduction The importance of disocclusion in maintaining the health of the stomatognathic system is well established. However, the quantification of the same is limited. This study aimed to determine the amount of posterior teeth disocclusion in protrusive and laterotrusive movements to establish the desired disocclusion in occlusal treatments. Materials and methods Twenty dentate subjects with Angles Class I occlusion, 18-30 years, were included in the study. Direct and indirect techniques measured disocclusion at the mesiobuccal cusp tip of the mandibular first molar. In the direct technique, the protrusive and working and nonworking records were made intraorally at the edge-to-edge position of maxillary and mandibular central incisors and canines, respectively. For the indirect technique, putty indices were made on a semi-adjustable articulator at 2 millimeters (mm) eccentric movements and the disocclusion records were then made intraorally using indices at the predetermined excursions. The records were trimmed, and the disocclusion was measured using an optical microscope (ZEISS Axio Imager 2; Carl Zeiss Microscopy Deutschland GmbH, Oberkochen, Germany). The comparison of disocclusion by both techniques was done by paired t-test. The Pearson correlation coefficient was used to analyze the statistical correlation between the disocclusion obtained during different excursive movements. Results The mean disocclusion obtained by direct technique was 1.72 ± .49 mm in protrusion, 1.19 ± .50 mm for the working side, and 2.54 ± .70 mm for the nonworking side. For the indirect technique, the disocclusion obtained was 1.22 ± .37 mm in protrusion, 8.57 ± .33 mm for the working side, and 1.71 ± .61 mm for the nonworking side. On comparison, there was a statistically significant difference (<0.05) seen for the values between the groups for direct and indirect subgroups except for the left working subgroup (>0.05) with higher values in the direct group. Conclusions The disocclusion obtained by the direct technique was higher than that obtained by the indirect technique. For both techniques, as the working side disocclusion increased, the nonworking side disocclusion also increased.
PubMed: 36627993
DOI: 10.7759/cureus.32306 -
Journal of Indian Prosthodontic Society 2023The fabrication of an accurate prosthesis depends mainly on precise recording of the maxillo-mandibular relationship of the patient and transferring it to the...
Evaluation of dimensional stability, compressive resistance, and detail reproduction of thermoplastic resin (IMPRESS), elastomeric and composite bite registration material: An study.
AIM
The fabrication of an accurate prosthesis depends mainly on precise recording of the maxillo-mandibular relationship of the patient and transferring it to the articulator. BDIMPRESS is a new thermoplastic material that has been proposed as a potential material to be used as an inter-occlusal registration, but there has been no literature evidence regarding its application as a bite registration. The main purpose of this study is to evaluate and compare the dimensional stability, detail reproduction, and compressive resistance of new interocclusal recording material with other two commonly used materials.
SETTINGS AND DESIGN
In Vitro Comparative study.
MATERIALS AND METHODS
The study was conducted according to ADA Specification standards of testing for dimensional stability, detail reproduction and compressive resistance. Specimens were prepared for three different materials (Thermoplastic resin, Polyvinyl siloxane, and Bis- acrylic) with 12 samples each.
STATISTICAL ANALYSIS USED
One way ANOVA was done for statistical analysis.
RESULTS
Polyvinyl siloxane material was dimensionally stable (mean at 1 hr: 24.928 mm; 24 hrs: 24.919 mm & 48 hrs: 24.912 mm) followed by Bis- acrylic material (mean at 1 hr: 24.851 mm; 24 hrs: 24.825 mm & 48 hrs: 24.815 mm). On one way ANOVA, strong significance was observed between groups (P = 0.00). Thermoplastic resin showed higher amount of detail reproduction with 10 (out of 12 samples) samples showing satisfactory results. While bis- acrylic material showed the least compressive resistance (Strain %: 0.484%; Displacement- 0.0990mm). One-way ANOVA showed presence of significance between the groups (P = 0.024).
CONCLUSION
Polyvinyl siloxane showed superior dimensional stability, thermoplastic resin showed better detail reproduction and bis- acrylic showed high resistance to compression over other materials.
Topics: Humans; Siloxanes; Jaw Relation Record; Polyvinyls; Resins, Plant; Polymethyl Methacrylate
PubMed: 36588377
DOI: 10.4103/jips.jips_146_22