Dental Articulator Research Articles

Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study.

To compare the effect of different ultraviolet-C (UV-C) light exposure times on the dimensional stability of addition silicone dental impressions. The dimensional stability of the addition silicone dental impressions was assessed by measuring specific dimensions on dental casts that were recovered from an upper acrylic resin model of dental implants. The impressions were reproduced using a customized tray adapted in a three-point simplex dental articulator permitting only opening and closing movements. Addition silicone dental impressions were divided into five groups (N = 12) according to the UV-C light exposure time. Group A was untreated; group B received 10 minutes; group C, 20 minutes; group D, 30 minutes; and group E, 40 minutes. All the impressions were poured with type IV dental stone and the internal edges of the upper silicone retainers of impression copings were used as five reference points (E, D, C, B, and A) to determine six linear measurements between ED, CB, EA, AD, EB, and CD points using a traveling microscope of 0.001 mm accuracy. One-way analysis of variance (ANOVA) was used for the statistical analysis (p < 0.05). Expansion and contraction were noted among ED, CB, EA, and EB measurements, whereas only expansion was noted among AD and CD measurements. The ANOVA analysis showed there was no significant difference in the arithmetic means for the measurements between and within group A and the other groups (p > 0.05). The UV-C light exposure time of 10, 20, 30, and 40 minutes did not have any negative effect on the dimensional stability of the addition silicone dental impressions evaluated. In the daily routine dental practice, dental impressions need to be washed and disinfected immediately after making to prevent cross-infections. The UV-C light has been proposed as a promising method for disinfection, but only a few studies have been published about its effect on the dimensional stability of dental silicones. How to cite this article: Bravo-Cueto AG, Tinedo-López PL, Malpartida-Carrillo V. Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study. J Contemp Dent Pract 2024;25(6):507-513.

A Proof of Concept: Optimized Jawbone-Reduction Model for Mandibular Fracture Surgery.

Previous research on computer-assisted jawbone reduction for mandibular fracture surgery has only focused on the relationship between fractured sections disregarding proper dental occlusion with the maxilla. To overcome malocclusion caused by overlooking dental articulation, this study aims to provide a model for jawbone reduction based on dental occlusion. After dental landmarks and fracture sectional features are extracted, the maxilla and two mandible segments are aligned first using the extracted dental landmarks. A swarm-based optimization is subsequently performed by simultaneously observing the fracture section fitting and the dental occlusion condition. The proposed method was evaluated using jawbone data of 12 subjects with simulated and real mandibular fractures. Results showed that the optimized model achieved both accurate jawbone reduction and desired dental occlusion, which may not be possible by existing methods.

Children mandibular fractures: Epidemiological and anatomo-clinical aspects

IntroductionMaxillofacial trauma in children is uncommon, accounting for between 1 % and 14 % of all facial trauma in the general population. ObjectiveTo describe the epidemiological and anatomical-clinical aspects of mandibular fractures in children. Material and methodThis was a retrospective descriptive cross-sectional study with non-probabilistic accidental sampling. It took place in the maxillofacial surgery and stomatology department of Cocody University Hospital in the Republic of Côte d'Ivoire, over a 20-year period (2000–2019). The study population consisted of patients aged 0–16 years admitted to our department for a mandibular fracture. At the end of this study, we identified 58 patients. Data was entered using Excel 2016. Tables and graphs were processed using Excel version 2016. Resultswe have identified 58 patients. The mean age of patients was 9.35 ± 2.1 years, with extremes of 1 and 16 years, and a sex ratio of 2,22 in favouring men. The 6–12 age group was the most affected (n: 34 cases or 60.35 %). Soft tissue wounds were present in all our patients, followed by peri-mandibular swelling (n: 37 cases or 63.79 %) and disorders of the dental articulation (n: 28 cases or 48.2 %). Condylar fractures were the most frequent (46.87 %).Mandibular fracture lines were uni-focal in 75 % of cases. These fractures were associated with other facial lesions in 48.28 % of cases and with extra-facial lesions in 34.48 % of cases. ConclusionMandibular fractures are common in maxillofacial trauma in children. Condylar fractures are the most common, almost always associated with chin injuries. Hence the importance of a systematic examination of the mandibular condyles.

Virtual Dental Articulation Using Computed Tomography Data and Motion Tracking.

Dental articulation holds crucial and fundamental importance in the design of dental restorations and analysis of prosthetic or orthodontic occlusions. However, common traditional and digital articulators are difficult and cumbersome in use to effectively translate the dental cast model to the articulator workspace when using traditional facebows. In this study, we have developed a personalized virtual dental articulator that directly utilizes computed tomography (CT) data to mathematically model the complex jaw movement, providing a more efficient and accurate way of analyzing and designing dental restorations. By utilizing CT data, Frankfurt's horizontal plane was established for the mathematical modeling of virtual articulation, eliminating tedious facebow transfers. After capturing the patients' CT images and tracking their jaw movements prior to dental treatment, the jaw-tracking information was incorporated into the articulation mathematical model. The validation and analysis of the personalized articulation approach were conducted by comparing the jaw movement between simulation data (virtual articulator) and real measurement data. As a result, the proposed virtual articulator achieves two important functions. Firstly, it replaces the traditional facebow transfer process by transferring the digital dental model to the virtual articulator through the anatomical relationship derived from the cranial CT data. Secondly, the jaw movement trajectory provided by optical tracking was incorporated into the mathematical articulation model to create a personalized virtual articulation with a small Fréchet distance of 1.7 mm. This virtual articulator provides a valuable tool that enables dentists to obtain diagnostic information about the temporomandibular joint (TMJ) and configure personalized settings of occlusal analysis for patients.

Articulators in Prosthodontics and Dentofacial Orthopedics

The advanced dental technology has enabled prosthodontists and general dental practitioners to provide accurate prosthodontic treatments to patients. The dental articulator is an indispensable tool to enhance the quality of delivered work and increase patient satisfaction (1). The aim of this review paper is to provide an overview of articulators in dentistry, particularly in fixed and removable prosthodontics, their different types or classifications, indications, advantages, and limitations

Zur Sonderentwicklung des Ayin neben Het

“On the special development of Ayin near Het” The consonant represented by ‹o› (so-called oAyin, but originally a voiced dental stop or spirant) shows graphic peculiarities after the Old Kingdom if the same root contains a ‹H› (Oet). This paper presents all words hitherto known to display this feature and attempts to provide a phonetic interpretation. It is argued that the regular shift of the sound represented by ‹o› towards a pharyngeal spirant was suppressed under the said condition. Instead, the consonant either preserved its original dental articulation throughout the Middle Kingdom (at the end of a syllable, as well as immediately following ‹H›), or else it was lost altogether (at the beginning of a syllable unless immediately following ‹H›). Building upon these conclusions, some additional proposals concerning the historical phonology of Egyptian are advanced.

Noise-based acoustic features of Polish retroflex fricatives in children with normal pronunciation and speech disorder

This study addresses Polish retroflex sibilants /ʂ, ʐ/ produced by preschool children. The aims of our research were (1) to explore acoustic characteristics of normal and distorted (dental and interdental) articulation patterns of retroflex fricatives and (2) to define and verify new acoustic features of frication noise. We extracted and analyzed a set of 80 acoustic features, including full-spectrum-based metrics (linear cepstral coefficients, mel-frequency cepstral coefficients, spectral moments) and noise-based metrics (noise energies, fricative formants, and original features: noise cepstral coefficients and fricative formant relations). The analysis involved linear mixed-effects models and Spearman’s rank correlation over speech samples from 42 Polish children (21 with normal and 21 with distorted pronunciation). Normal articulation of Polish retroflex sibilants proved to be acoustically distinguishable from non-normative interdental and dental articulation. Significant acoustic differences between the classes considered were found both in the full-spectrum-based and noise-based features, including our proposed measures (p<0.05). Thirty-six of 80 analyzed features proved significantly correlated (Spearman’s |ρ|>0.5,p<0.05) with tongue position and front-cavity size. More evident cues for articulation pathologies were found in the voiceless sibilant /ʂ/ than in /ʐ/. Our study confirms that metrics describing the structure of frication noise bring information distinctive in particular articulatory oppositions for a more comprehensive acoustic description of sibilants.

Clinical feasibility evaluation of digital dental articulation for three-piece maxillary orthognathic surgery: a proof-of-concept study

Digital dental articulation for three-piece maxillary orthognathic surgery is challenging. The purpose of this proof-of-concept study was to evaluate the clinical feasibility of a newly developed mathematical algorithm to digitally establish the final occlusion for three-piece maxillary surgery. Five patients with jaw deformities who had undergone a three-piece double-jaw surgery that was planned virtually were randomly selected for this study. The final occlusion had been hand-articulated using stone casts, scanned into the computer and used in the surgery. These hand-articulated occlusions served as the control group. To form the experimental group, the three-piece maxillary dental arch was articulated again automatically from the patient’s original occlusion using the mathematical algorithm. The hand- and algorithm-articulated occlusions were then evaluated qualitatively by two experienced orthodontists. A quantitative evaluation was also performed. The results of the qualitative evaluation showed that all of the three-piece occlusions, hand- and algorithm-articulated, were clinically acceptable based on the American Board of Orthodontics grading system. When compared, two of the algorithm-articulated occlusions were clearly better (40%), one was the same (20%), and two were slightly worse (40%) than the hand-articulated occlusions. All of the quantitative measurements were comparable between the two articulation methods. In conclusion, the results of this study demonstrate that it is clinically feasible to digitally articulate the three-piece maxillary arch to the intact mandibular dental arch.

A severe skeletal Class III malocclusion treated with Le Fort I combined with sagittal split ramus osteotomy, mandibular body ostectomy and tongue reduction surgery. A case report

This case report describes the orthodontic-orthognathic management of a 17-year-old male patient with extremely severe skeletal Class III malocclusion due to a marked mandibular protrusion with a small and narrowed upper jaw which increased the remarkable concave facial profile. Dental articulation was entirely lacking, resulting in great difficulty in masticating food. A two-jaw surgery combined with mandibular body ostectomy was performed to correct mandibular asymmetry and the severe sagittal skeletal discrepancy (Wits appraisal –36.5 mm and ANB angle –14.3°). Bi-maxillary surgery was performed in two-stages; the first surgery consisted of maxillary advancement with Le Fort I osteotomy followed by a second surgery where a combination of sagittal split ramus osteotomy (SSRO) and mandibular body ostectomy was performed to correct the severe mandibular prognathism. A partial glossectomy was also carried out to address macroglossia. After a total treatment time of 32 months, a Class I occlusion with a favorable facial profile and lip competence were obtained. The occlusion was made approximately ideal, and mastication improved remarkably. Three years after retention, the occlusion was stable and no relapse was observed. The patient’s complaints and orthodontic problems were completely resolved. Therefore, a combination of two-jaw surgeries with Le Fort I maxillary osteotomy, mandibular SSRO, mandibular ostectomy, and glossectomy may be a viable option in the correction of extremely severe anteroposterior skeletal discrepancy.

Hot water–assisted separation of mounted casts and retrieval of articulator mounting plates

Dental casts are commonly attached to dental articulators with removable mounting plates by using mounting gypsum materials such as plaster or stone.1 Some processes require that the cast be separated from their supporting media for a remount procedure.2-5 On occasion, the interocclusal relationship of the casts6,7 may have to be revised. At the completion of patient treatment, the definitive casts may be discarded, but the operator may wish to reuse the mounting plates.

Update on the parameters influencing the adjustment of the sagittal and transversal condylar inclination of dental articulators.

The literature review aimed to compile and summarize the results of research relating to the recordings of condylar displacements obtained with extraoral devices, to guide clinicians to set dental (virtual) articulator parameters. The meta-analysis was undertaken to assess the sagittal condylar inclination (SCI) and transversal condylar inclination (TCI, also known as Bennett angle) values according to horizontal reference planes, movement studied, and patient characteristics: dental status, interocclusal relationship, skeletal pattern, and signs and symptoms of temporomandibular disorders (TMD). A bibliographic search was conducted in the three following electronic databases: MEDLINE, EMBASE, and Cochrane Library and Best Evidence. The review was restricted to trials involving participants meeting the following criteria: (1) adult, (2) no previous surgery in the temporomandibular region, and (3) no serious comorbidity conditions. Descriptive statistics were calculated for all study groups and were compared by applying a one-way ANOVA. All 20 articles selected corresponded to a total of 933 subjects evaluated. The recording devices and horizontal reference planes had a significant impact on the SCI values. Age, dental status, and the presence of symptoms and signs of TMD in subjects had no influence on SCI values, unlike Angle class II, division 2, the class II sagittal pattern, or the increased vertical skeletal pattern SCI parameters (P < .05). The mean TCI value was 8 degrees and was independent of individual patient characteristics and the extraoral recording device used. For accurate kinematic simulation, the patient's personal plane of reference must be transferred to the system.

Surgical treatment of a mandibular condyle fracture

The condylar region is the most frequent anatomical site for mandibular fractures in children. Most surgeons opt for functional treatment which is not satisfactory in the long term because of the appearance of facial asymmetry and TMJ dysfunction, hence the interest in surgical management of displaced condylar fractures. In this article, we will describe the case of a 7-year-old child who fell from a height and sustained a subcondylar fracture with anteromedial dislocation. The clinical examination revealed a disorder of the dental articulation with laterodeviation. A panoramic radiograph was done which confirmed the fracture and then we performed a CT scan with 3D reconstruction which informed us about the degree of displacement of the fracture. The treatment was surgical with a mini TCP plate which allowed the correction of all these clinical manifestations. We believe that surgical treatment of displaced mandibular condyle fractures in children is still essential to avoid long-term complications.

The patient-specific anatomical articulator

Currently available dental articulators have limitations for reproducing human mandibular movements. The present article describes an innovative device that is a true patient-specific anatomical articulator that accurately simulates patient anatomy and eliminates all technique-sensitive mounting procedures, thus substantially diminishing potential errors in mounting and articulator settings. By using three-dimensional (3D) printing technology, patient cone beam computed tomography (CBCT) data are used to print 3D replicas of the condylar fossae, as well as the actual condyles, at the correct intercondylar distance. The maxilla (maxillary teeth and edentulous ridge) is printed with the correct spatial relationship to the condylar complexes and the Frankfort horizontal plane (FHP). Those printed structures are then premounted onto a modified articulator frame to render it “anatomic.” This new custom anatomical articulator, which accurately mimics patient anatomical movements rather than relying on average values, represents the first truly fully adjustable articulator that is more precise than can be generated by a pantographic tracing. It saves money, time, and effort by eliminating earbow transfers and mounting errors in complex prosthodontic treatment.

Clinical evaluation of the precision of interocclusal registration by using digital and conventional techniques

Statement of problemAlthough studies have evaluated the accuracy of data obtained by intraoral scanners (IOSs), studies on the precision of interocclusal registrations made with IOSs are lacking. PurposeThe purpose of this clinical study was to compare the precision of IOS interocclusal registration with that of conventional methods with a silicone impression material and a gypsum cast. Material and methodsEight participants with complete natural dentitions were enrolled. Images of their maxillary and mandibular quadrant arches and their interocclusal relationship were scanned with 2 IOSs: the 3M True Definition Scanner and the TRIOS Scanner 3. In the conventional method, impressions of complete-arch dentition and quadrant-arch dentition were made with a silicone impression material, and gypsum casts were fabricated, mounted on a dental articulator related with a silicone interocclusal record, and scanned with a 3D laboratory scanner. These procedures were repeated 4 times, and 4 sets of interocclusal registration data in standard tessellation language (STL) format were generated for each condition. Interocclusal registration precision was evaluated by determining the discrepancy of the STL data between repeated measurements by using the best-fit-algorithm method. ResultsThe average discrepancies for all participants were 25 ±12 μm for the True Definition, 31 ±7 μm for the TRIOS 3, 154 ±59 μm for the complete arch, and 128 ±33 μm for the quadrant arch. The Kruskal-Wallis test revealed that the effect of the impression methods on the discrepancy was statistically significant (P<.001). The Steel-Dwass test showed that both digital scan methods exhibited significantly smaller discrepancies than the 2 conventional methods (P=.005). ConclusionsThese results suggest that the intermaxillary relationship captured by the digital scan method by using IOSs had better precision than that obtained by the conventional method.

Technique to Maintain the Correct Spatial Orientation of the Maxillary Diagnostic Cast to that of the Master Cast in a Full-Mouth Rehabilitation Case.

A common challenge in full-mouth rehabilitation is preserving the correct spatial orientation of the maxillary diagnostic, diagnostic wax-up and master casts within the dental articulator. Any malposition of the maxillary master cast will immediately invalidate the articulator settings that were programmed from the pantographic or axiographic tracing. This will subsequently affect the occlusal morphology of the restorations. The technique presented in this article helps to precisely relocate the maxillary master cast to the same spatial orientation as both the initial diagnostic, and diagnostic wax-up casts.

Modeling of digital dental articulator and its accuracy verification using optical measurement

Background and ObjectivesTemporomandibular joint has been considered one of the most complex joints in human body. Dental articulation hinged upon temporomandibular joint is essential and fundamentally important for dental restoration design and prosthetic/orthodontic occlusion analysis. As digital dentistry rapidly grows, a complete digital work flow requires the use of a digital articulator for occlusion analysis. However, commercial CAD/CAM systems do not provide any method to verify the modeling accuracy of a digital articulator. There is also a lack of detail and generalized mathematical modeling of the digital articulator for simulating the jaw movement. MethodsThis paper presents the development of a digital articulator by mathematically modeling a general dental articulator which simulates the relative jaw motion between the maxilla and mandible. As the digital articulator moves, the digital upper teeth move relatively to the digital lower teeth, thus simulating the occlusal path with teeth collision detection function. To verify the accuracy of our modeled digital articulator, an improved optical tracking method is proposed to measure the pose of a mechanical articulator with 6 degrees of freedom and compare that with the digital articulator. ResultsThe digital articulator system proposed in this paper achieves the following functions: 1. Digitalize the dental articulator with verified precision. Combined with dental design software, restorations can be designed with more efficiency and accuracy. 2. Provide an improved optical tracking method which can compare the movement error between the mechanical articulator and digital articulator. Thus the accuracy of the digital articulation can be verified. The result shows the error of our system is controlled under sub-millimeter which provides sufficient accuracy for the design of restoration under static and dynamic occlusion conditions. ConclusionsWe develop a general digital articulator which can simulate jaw movement between opposing teeth and an improved optical tracking method to verify the accuracy of the digital articulator. The modeling and accuracy verification of the digital articulator shows that there is a systematic and reliable way to replace traditional mechanical articulator and can close the gap for digital restoration fabrication.

Computer Program for Digital Data Analysis of Facebow Records – Part І

Abstract The purpose of the study is to create computer program for the achievement of precise digital data processing of records performed with the “Facebow Mini-Maxi” and the facilitation of information transfer to the articulator. Material and method: A conceptual project was developed in order to create a new software product and requirements were defined towards its capacities, which are to provide guidance for its creation. With the assistance of computer programmer, the project was implemented. Results: The computer program “Facebow Mini-Maxi Analyzer” for digital data processing of registrants performed with the auricular type facebow was created. The program provides automatic recognition, reading, calibration and measurement of data obtained by “Facebow Mini-Maxi”. The main module gives us opportunities for measuring the values of: the sagittal condylar pathway; the arrow point angle and the length of the hinge axis. After finalizing the calculations, the software automatically generates a scheme with visualization of the parameters that significantly supports the dental technician when it comes to defining the accurate position of the models in dental articulator with individual parameters. Conclusion: The computer program provides accurate analysis of facebow records and assists in determining individual patient movement parameters of the lower jaw. The obtained results from the analysis improve the precision of casts mounting in articulator. The program cuts down the risk of subjective error when analysing the data via manual measurement of the recorded parameters on paper carrier.

Setting the sagittal condylar inclination on a virtual articulator by using a facial and intraoral scan of the protrusive interocclusal position: A dental technique

Setting the condylar inclination of a dental articulator enables the delivery of prostheses without occlusal interferences. This technique article describes obtaining the sagittal condylar inclination (SCI) by using a facial and an intraoral scan of the protrusive interocclusal position. The SCI can be used on a virtual articulator in dental computer-aided design (CAD) software programs, which can facilitate the fabrication of functional prostheses without occlusal interferences.

An automatic approach to establish clinically desired final dental occlusion for one-piece maxillary orthognathic surgery.

One critical step in routine orthognathic surgery is to reestablish a desired final dental occlusion. Traditionally, the final occlusion is established by hand articulating stone dental models. To date, there are still no effective solutions to establish the final occlusion in computer-aided surgical simulation. In this study, we consider the most common one-piece maxillary orthognathic surgery and propose a three-stage approach to digitally and automatically establish the desired final dental occlusion. The process includes three stages: (1) extraction of points of interest and teeth landmarks from a pair of upper and lower dental models; (2) establishment of Midline-Canine-Molar (M-C-M) relationship following the clinical criteria on these three regions; and (3) fine alignment of upper and lower teeth with maximum contacts without breaking the established M-C-M relationship. Our method has been quantitatively and qualitatively validated using 18 pairs of dental models. Qualitatively, experienced orthodontists assess the algorithm-articulated and hand-articulated occlusions while being blind to the methods used. They agreed that occlusion results of the two methods are equally good. Quantitatively, we measure and compare the distances between selected landmarks on upper and lower teeth for both algorithm-articulated and hand-articulated occlusions. The results showed that there was no statistically significant difference between the algorithm-articulated and hand-articulated occlusions. The proposed three-stage automatic dental articulation method is able to articulate the digital dental model to the clinically desired final occlusion accurately and efficiently. It allows doctors to completely eliminate the use of stone dental models in the future.

Accuracy of intercuspal occlusion in 3D reconstruction with the dental articulator position method

To evaluate the three-dimensional (3D) reconstruction accuracy of the intercuspal occlusion (ICO) of the dental casts, by the dental articulator position method, and provide a reference for clinical application. The standard dental casts in ICO were mounted on average values articulator, and five pairs of milling resin cylinders were respectively attached to the base of both the casts. 100 μm articulating paper and occlusal record silicone rubber were used to detect the occlusal contact number between the posterior teeth of casts mounted on articulator in ICO. The occlusal contact numbers NA detected by the two methods were calculated simultaneously, as the reference. After the upper and lower casts were scanned separately, and the buccal data of casts in ICO were scanned with the aid of the dental articulator position, registration was carried out utilizing the registration software. Then the digital casts mounted in ICO as well as the buccal occlusal data were saved in standard tessellation language (STL) format. Geomagic Studio 2013 software was used to analyze the contact number NS between digital upper and lower casts by the "deviation analysis" function. The differences were compared between NS and NA, to evaluate the sensitivity and positive predict value (PPV) of the model scanner to reproduce the occlusal contact with the aid of dental articulator position. The distance DR between the centers of the circles at the top surface of the upper and lower corresponding cylinders was obtained by the three-coordinate measuring system Faro Edge, as the reference value. The Geomagic Studio 2013 software was used to construct the cylinders of digital casts and the distance DM between the centers of the circles at the top surface of the corresponding cylinders were measured, as the test value. The one-sample T test was used to analyze the variable differences between DM and DR. The PPV of reproducing the occlusal contact point was 0.76 and sensitivity was 0.81. The distance error of the opposite cylinder was (0.232±0.089) mm. There was no statistical difference between the feature points 5-5', while there were statistical differences between the other feature points. By the dental articulator position method, the model scanner reproduces the occlusal contact point with high sensitivity and PPV, and that meets clinical needs. Meanwhile, the distance between the feature points is greater than the reference value, which will lead to occlusal disturbance, and require clinical grinding.