Bite Registration Research Articles

A Novel Technique to Align the Intraoral Scans to the Virtual Articulator and Set the Patient-Specific Sagittal Condylar Inclination.

Customized cast orientations and parameter settings of the virtual articulator according to the patient's condyles are indispensable parts of today's digital workflows in prosthodontics. This article describes a digital technique to align the intraoral scans to a virtual articulator by using a facial scanner to locate the patient's cutaneous landmarks of the arbitrary hinge axis and the reference plane, and to customize the sagittal condylar inclination of the virtual articulator through a digital protrusive interocclusal record and a dental computer-aided design software program. It enables individual cast orientations and virtual articulator parameter settings without conventional facebow transferring and bite registration procedures and can be easily integrated with most virtual articulator systems on the market to allow clinicians and technicians to work in a complete digital workflow and facilitate customized treatment planning and dental prosthesis fabrication.

Alteration of the Occlusal Vertical Dimension for Prosthetic Restoration Using a Target Tracking System

Clinicians and researchers have used various methods to reproduce the maxillomandibular relationship and mandibular movement of individual patients using an articulator, with efforts being made to reduce errors associated with the conventional technique. When a change to a vertical dimension is required during the conventional prosthesis construction process, the maxillary and mandibular casts are mounted on the mechanical articulator using a facebow and bite registration and the elevation of the anterior guide pin of the articulator is used. However, this can inevitably cause errors due to differences between the articulator hinge movement and the actual trajectory of the patient. There has recently been increasing interest in tracking the trajectory of jaw motion of a patient, and this paper presents a new technique for altering the vertical dimension based on the measured trajectory. Target materials for performing tracking are attached to the maxillary and mandibular anterior teeth to record opening and closing movements of the patient’s mouth in real time and align the patient’s scanned intraoral data or cast data. The movements of the targets are replaced with the movement of the patient’s oral scan data. Additionally, then the occlusal vertical dimension is set to a new position based on the obtained trajectory. After determining the optimal vertical dimension with consideration of the space required for restoration, maxillary and mandibular STL files are exported and the designed cast is created using a 3D printer. The printed cast is mounted on an articulator for subsequent procedures. This approach maintains the patient’s actual maxillomandibular relationship at various vertical heights and can also reduce the chair time required when adjusting for errors.

English

BACKGROUND The goal of registering condylar guidance is to program the articulator for simulating the patient’s condylar movements as accurately as possible to save chairside time involved in adjusting the occlusal interferences at the time of fit in. The use of Hanau’s formula (L = H / 8 +12) was advocated by Sir Rudolph Hanau in 1930 which he used to calculate lateral condylar guidance (LCG) for adjusting his articulators. But due to the ease of application, the formula is widely used by dentists till date. Jack Stern, Hanau's longterm partner, confided in 1960 that the 'Formula' was never considered to be precise, after 10 years of study (1920 - 1930). Rather it was a point of approximation. There is a lack of uniformity in the literature regarding average condylar inclinations and its comparison to the Hanau formula, therefore a study was undertaken to evaluate and compare the 2 methods used to determine the lateral condylar guidance. METHODS 24 completely dentulous participants were included in the study. Two methods were used to obtain the lateral condylar guidance, the first method was obtaining the calculated lateral condylar guidance using the hanau’s formula and the second was obtaining the measured lateral condylar guidance using the interocclusal records. Impressions of each participant were made. Protrusive and lateral records were made using interocclusal recording medium (MAARC® Perfect Bite Registration). After completion of facebow transfer, programming of the articulator was done using protrusive record and the horizontal condylar guidance was recorded. The calculated lateral condylar guidance was recorded using the Hanau’s formula & the measured condylar guidance was recorded using right and left lateral records. Both the values obtained were evaluated and compared. RESULTS Mean LCG values obtained using Hanau’s formula was 16 degrees for the left side (SD - 1.404) and for the right side it was 16.17 degrees. (SD - 1.694). Mean LCG values obtained using lateral interocclusal records were 20 degrees for the left side (SD - 6.691) and 20.08 degrees (SD - 4.926) for the right side.There was a statistically significant difference between lateral condylar guidance records obtained using Hanau’s formula and lateral interocclusal records. CONCLUSIONS Application of Hanau formula is helpful to estimate Bennett angle. No doubt the formula is easy to apply and less cumbersome, but when we are working on high precision demanding cases we should try and find better options to record LCG. Making a lateral interocclusal record and then programming the articulator is a more reliable method. KEY WORDS Hanau’s Formula, Bennet Angle, Condylar Guidance, Articulators, Interocclusal Records, Lateral Condylar Guidance

Fabricated bite mark in a case of assault

Identifying a perpetrator by bite mark analysis is generally based on the detection of tooth impressions that correspond to unique and rare odontological traits. A 34-year-old female presented with a history of assault where she also claimed that the assailant bit her during the struggle. There was a well defined bite mark on her left forearm along with blunt force injuries on the head. During forensic odontological examination, the wax bite registration of the victim showed several common dental irregularities which were also represented in the bite mark. The location and orientation of the injury also favoured the possibility of self-infliction and no inconsistencies could be found to exclude this bite mark as a fabricated injury in the setting of an assault. The lack of population specific studies and objective methods of analysis are significant limitations in bite mark analysis. When providing opinion on the identity of the biter, the general recommendation is to use unique features or uncommon irregularities. However, even where only common dental irregularities are seen, a reasonably valid opinion could still be provided using a holistic and deductive approach, if there is sufficient concordance among multiple irregularities with no inconsistencies.

434 Precision Oral Appliance Therapy: The Prime-Time Treatment for OSA

Abstract Introduction CPAP was previously considered the “gold standard” due to its high efficacy in eliminating obstructive events. Despite improvements in technology, the “effectiveness” of CPAP has been compromised by poor real-world compliance. Technological improvements have improved the “effectiveness” of Oral Appliances. This study reports the efficacy of a novel, precision engineered Oral Appliance for the primary treatment of all severities of OSA. Methods Digital scans and digital bite registrations were recorded with a George Gauge utilizing a a 3mm bite fork. Initial protrusion was set at 40–60% and varied according to the degree of overbite and overjet, the severity of OSA, and the presence or absence of TMJ symptoms. All patients were fitted with a ProSomnus (IA) MAD and titrated according to their subjective symptoms. An efficacy study was obtained with a HST after titration and compared to the initial PSG or HST. Results Outcome data on 85 patients (37 female, 48 males, aged 56.7 +/1 10.2 years) was retrospectively reviewed. The patients were consecutively ordered for follow up data, many patients did not return for follow ups. The pre-treatment AHI was 24.5 +/- 19.1 with 36 patients Mild, 26 Moderate and 23 Severe patients. O2 Nadir was 84.1% +/- 5.5%. Post treatment AHI was 5.5 +/- 4.9 with an AHI reduction of 71.6% +/- 20.3%. 59% of the patients scored <5, 31% 10 on the outcome AHI data. O2 Nadir improved to 88.2% overall. 31 patients had RERA’s (RDI-AHI) >10 with an average of 16.7 +/- 7.5, of these patients 27 saw a reduction of RERA’s of 54.4% from 16.9 to 7.1. Conclusion The data shows that a precision oral appliance is capable of successfully treating patients with all levels of severity, with the majority of patients treated to an AHI<5. 23 severe patients with an average AHI of 49.7 were treated to a final average of 8.6, 4 of the patients scored above 10. Additionally, patients successfully saw a reduction in upper airway resistance airflow as evidenced by a reduction of RERA’s of 54.5%, showing that a precision oral appliance can have a significant impact on the upper airway. Support (if any) None

A Full Digital Workflow for the Duplication of an Existing Implant Retained Overdenture Prosthesis: A Novel Approach

The purpose of this clinical case report is to describe a fully digital workflow for the duplication of an existing implant retained overdenture, highlighting the benefits of digitally fabricated dentures. The patient presented with an existing mandibular implant retained overdenture on Locator attachments that needed to be replaced. The existing overdenture was duplicated/scanned with the use of an intraoral scanner and was 3D printed using acrylic resin. This resin duplicate was sectioned in the midline and served as a unilateral record base to digitally record maxillo-mandibular relationship. The occlusal relationship was scanned unilaterally with the record base (sectioned duplicate) in place, and the procedure was repeated for the opposite side. All scans (edentulous, bite registrations and preliminary scan) were superimposed and the software managed to position and stich everything together. A try-in copy denture (ProArtCAD Try in, Ivoclar Vivadent AG, Schaan, Liechtenstein) was milled in order to imitate the conventional wax teeth try-in. A definitive milled overdenture was fabricated and delivered. A reinforcing polyetheretherketone mesh was fabricated, utilizing computer assisted design/computer assisted manufacturing technology and was incorporated into the pre-designed customized space into the polymethylmethacrylate base, using indirect light-polymerized nano-filled composite resin (crea.lign; bredent GmbH & Co. KG). Occlusion was verified and the patient was instructed oral hygiene, home maintenance and was informed for the required recall visits.

Mandibular advancement device as treatment trial for catathrenia (nocturnal groaning).

Catathrenia is a rare disease, classified as isolated symptoms and normal variants under sleep-related breathing disorders in the International Classification of Sleep Disorders, third edition. Because of its rarity, the research on its pathogenesis and treatment is insufficient. This study aimed to evaluate whether the mandibular advancement device (MAD) could be considered an alternative treatment trial and if so, to explore factors predicting its effectiveness. Thirty patients (12 men and 18 women, aged 16-67 years) with catathrenia participated in the study. They underwent standard clinical evaluation, questionnaires, physical examinations, craniofacial evaluations, video polysomnography, and imaging of the upper airway before and after the insertion of the MAD. The groaning index (groaning episodes per hour of sleep) and apnea-hypopnea index were evaluated, and anatomic factors predicting effectiveness were explored. The sleep efficiency of most patients was higher than 80%, and groaning was present throughout all stages of sleep. With the insertion of the MAD, the groaning index decreased significantly from 5.8 (2.7-14.3) to 2.8 (1.3-12.2) events/h (P = .014). Age had a negative effect on efficacy. Mandibular repositioning of the MAD, especially the amount of vertical opening and changes of the cross-sectional area of the hypopharynx, was positively related with efficacy. The MAD could be considered a possible treatment trial for those seeking treatment for groaning. Registry: Chinese Clinical Trial Register; Name: The etiology of catathrenia based on oral and maxillofacial system; URL: http://www.chictr.org.cn/showproj.aspx?proj=22286; Identifier: ChiCTR-COC-17013239. Yu M, Hao Z, Xu L, Wen Y, Han F, Gao X. Mandibular advancement device as treatment trial for catathrenia (nocturnal groaning). J Clin Sleep Med. 2021;17(9):1767-1776.

New Materials for Orthodontic Interceptive Treatment in Primary to Late Mixed Dentition. A Retrospective Study Using Elastodontic Devices.

The aim of this study was to assess the skeletal and dentoalveolar changes obtained after 1 year of treatment with elastodontic appliances (EA) in a retrospective cohort of children reporting early signs of malocclusion. Also, a detailed description of the tested EAs was reported. The study sample included 20 subjects, 8 males and 12 females, with a mean age of 8.4 ± 0.6 years, and a control group consisting of 20 subjects, 9 males and 11 females, with a mean age of 8.1 ± 0.8 years. All subjects in the treated group received the AMCOP second class (SC) (Ortho Protec, Bari, Italy) device. Digital impressions were taken along with a digital bite registration in centric relation before treatment (T0) and after 1 year (T1). Lateral cephalograms were also taken at T0 and T1 and cephalometric analysis was performed to assess the skeletal sagittal changes of the maxilla and the mandible (sella, nasion, A point angle, SNA^; sella, nasion, B point angle, SNB^; and A point–nasion–B point angle, ANB^) as well as the changes of the inter-incisors angle (IIA^). In the treated group, the distribution of subjects according to the presence of crowding and the pattern of malocclusion changed at T1. In the same group, there was an increase of subjects showing no signs of crowding and a class I occlusal relationship, while in the control group, there was a small increase of subjects developing dental crowding and featuring a worse sagittal relationship (class II) compared to pre-treatment condition. A statistically significant reduction of the overjet and overbite was recorded in the treated group between T0 and T1 (p < 0.05); in the control group, a slight increase in the overjet and overbite was detected at T1, being this increment significanct only for the latter parameter. In the tested group, no significant differences were found between SNA^ values detected at T0 and T1 (p > 0.05), instead the SNB^, ANB^, and IIA^ showed a significant increase after 1 year of treatment (p < 0.05). From a clinical perspective, all clinical goals were reached since patients showed remarkable improvements in overjet, overbite, crowding, and the sagittal molar relationship. Within the limitations of the present study, EAs could be effectively used for the interceptive orthodontic in growing patients.

Effect of Impression Technique and Operator Experience on Impression Time and Operator-Reported Outcomes.

To investigate the effect of impression technique (conventional preliminary alginate and digital scan) and operator experience in impression making (experienced in digital and conventional, experienced in conventional and inexperienced in digital, and inexperienced in conventional and digital) on impression time, satisfaction and stress levels, and the preference of the operators. One patient was assigned for each of the 60 operators, who were experienced in impression techniques at different levels (Group 1: experienced in conventional and digital, Group 2: experienced in conventional and inexperienced in digital, Group 3: inexperienced in conventional and digital). They made conventional impressions (irreversible hydrocolloid) and digital scans (Trios 3) from the same patient. The impression times were recorded at each step (patient registration, maxillary arch, mandibular arch, and bite registration) and in total. A visual analog scale (VAS) was used for the operator satisfaction for applicability, comfort, and hygiene; the State-Trait Anxiety Inventory form (STAI-TX1) was used for stress, and a questionnaire was completed to measure the operator's impression preference. The data were analyzed with a 2-way ANOVA and Chi-square test (α = 0.05). A significant interaction was found between the operator experience in impression making and the impression technique on time for maxillary and mandibular arch impressions and total time (p ≤ 0.002). Operator experience and impression technique interaction had a significant effect on comfort and average VAS scores (p ≤ 0.016). Whereas, no significant effect of this interaction was found on stress (p ≥ 0.195). Operator experience in impression making had a significant effect on applicability (p < 0.001), and the impression technique had a significant effect on hygiene VAS scores (p < 0.001). Operators in Group 1 and Group 3 preferred the digital scans, however, operators in Group 2 had no preference (p = 0.022). Operator experience in impression making and impression technique had varying effects on clinician's impression time, comfort, applicability, hygiene, and preference. Operators needed less time for the impressions they were experienced with. Operator stress level was not affected by the operator experience in impression making and the impression technique. Dental students and operators experienced in both techniques were satisfied with the digital scans and they preferred digital scans. Operators experienced with conventional impressions were satisfied with conventional impressions but didn't have a preference for the impression type.

Construction of virtual intercuspal occlusion: Considering tooth displacement.

Common impressions cannot accurately duplicate the dental occlusion under occlusal force due to tooth displacement and mandibular deformation. To establish new methods to construct virtual intercuspal occlusion and assess their construction accuracy. The intraoral occlusal contacts of posterior teeth of 15 subjects were recorded with 8μm and 100μm articulating paper, respectively, and the marked teeth and buccal bite data were scanned with an intraoral scanner. The virtual dental occlusions were separately determined by buccal bite registration (BBR) method, and 3 new methods, namely segmented tooth registration (STR), occlusal contact areas (marked by 8μm articulating paper) registration (OCR) and mixing registration (MR) methods. With the intraoral contact areas marked by 100μm articulating paper set as reference and contact areas of the 4 virtual occlusions as tests, sensitivity, positive predictive value (PPV) and the ratio of overlapping areas were calculated. Kruskal-Wallis test or 1-way ANOVA was used to analyse the difference among groups. The sensitivity ranged from 0.69 to 0.94 and the PPV from 0.67 to 0.90. Sensitivity of OCR group and PPV of STR and OCR groups were different from that of BBR group at overlapping threshold of 50% (P=.028, .028 and .006). There was statistical difference of the ratio of overlapping areas over reference areas, and the values of STR and OCR groups were higher than that of BBR group (P=.045 and .021). The ability of STR and OCR methods to construct virtual intercuspal occlusion was better than BBR method.

Evaluation of the tear strength, compressive resistance, and surface hardness of three commercially available bite registration materials: an in vitro study

Background: For making a successful prosthesis, it is essential to achieve harmony between the maxillomandibular relationship. The precision and occlusal quality of the prosthesis partly depends on interocclusal bite registration material. Interocclusal bite registration material plays an important role in recording and transferring of existing patient’s occlusal records. The procedure used to record and transfer interocclusal relation should be performed with the utmost care and understanding to prevent clinical error. Aim: This study aimed to evaluate the tear strength, compressive resistance and surface hardness of three commercially available bite registration materials. Material and Methods: Three types of commercially available bite registration materials, Bis-acrylate (BA), Polyvinylsiloxane (PVS), and Polyether (PE), were made in Dumbbell and cylindrical shaped samples to evaluate the tear strength and compressive resistance, respectively and were analysed using the universal testing machine. The surface hardness was assessed using a microhardness tester. The obtained data were subjected to statistical analysis using SPSS 16.0 version (Chicago, Inc., USA). ANOVA/Kruskal-Wallis test was used to compare study parameters among the groups. Tukey’s posthoc test was used for inter-group comparisons. Results: Bis-Acrylate exhibited the greatest tear strength, followed by Polyvinylsiloxane and Polyether showed the least tear strength. More compressive resistance was observed in Polyether followed by Bis-Acrylate and lowest in Polyvinylsiloxane. A similar pattern was seen in the surface hardness among the three materials. Conclusion: Bis-acrylate showed greater tear strength and surface hardness, and it can be considered a better bite registration material.

Data on dental bite materials with stability and displacement under load.

It is of interest to document the accuracy, time dependent dimensional stability and displacement to load for 5 types of inter-occlusal recording materials. We used cad bite paste, putty, lab putty, pattern resin and poly tray acrylic material in this study. A total of 25 samples were fabricated to evaluate the accuracy and dimensional stability. The amount of displacement was calculated by applying displacing force on the bite registration materials till they fractured using Instron 3000 UTS machine. Statistical analysis of the data shows that CAD bite paste has the maximum amount of accuracy and dimensional stability whereas pattern resin showed the least amount of displacement to applied force. Thus, we report that CAD bite registration material displayed best results in terms of accuracy and dimensional stability and moderate results in terms of displacement to force.

Accuracy Improvement of Intraoral Scanning and Buccal Bite Registration Using Healing Abutment as Landmarks: An In Vitro Study

This study aimed to determine the influence of the healing abutment (HA), placed at the implant placement site, on the accuracy of intraoral scanning and buccal bite registration in quadrant maxillary and mandibular models when using three types of intraoral scanner (IOS) and elucidate the distribution of arch distortion. Six experimental groups based on whether the HA was connected and the location of missing teeth were digitized using one laboratory scanner (Identica T500) and three IOSs (Trios 3, CS3600, and i500). Three-way ANOVA was used to analyze the effects of the scanner, location and number of missing teeth, and HA using Tukey investigation analyses for multiple comparisons (α = 0.05). Linear distances between hemispheres from the upper and lower arches were analyzed using the Jonckheere–Terpstra trend test to investigate the tendency of distortion from anterior to posterior tooth positions (α = 0.05). The accuracy of IOSs in groups with HAs was found significantly more accurate than groups without HAs. There was a significant trend in distortion from anterior to posterior tooth positions when using the Trios 3 and i500 IOSs. The scanning accuracy was affected by the presence of an HA, and the distortion along with the arch span may vary with the IOS utilized.

Клінічно-лабораторний аналіз результатів реєстрації максимальної інтеркуспідації у пацієнтів із частковими дефектами зубних рядів залежно від використання різних реєстраційних матеріалів

Introduction. In general, it is equally important in dentistry to be able to examine the occlusion and to register it, store and transmit information from oral cavity. The aim of the study. Clinical and laboratory analysis of inter-maxillary relationship formation efficiency in patients with partial defects of dentition in the position of maximum intercuspation of jaws by means of different bite registration materials selected. Materials and methods. Examination of 10 patients (5 women, 5 men) aged 27 to 59 years was conducted. Upon receipt of teeth impressions of both jaws, and fabrication of their cast models, intermaxillary relationship in the position of maximum intercuspation (MIC) of the jaws with the help of selected registration materials (Consiflex (Ukraine), metallized wax (Germany), Futar D (Germany)) was determined. Results. During clinical examination of 10 patients it was found that when using Futar D registration material, biometric deviation of markers (BDM) index in the region of teeth 16-46 was (0.03±0.03) mm, 26-36 - (0.035±0.03) mm (p-value more than 0.75). At the same time, BDM index in the region of teeth 13-44 reached (0.05±0.03) mm, and teeth 23-34 demonstrated values (0.04±0.03) mm (p-value more than 0.5). Studies in the region of teeth 21-31 established BDM value within (0.01±0.03) mm. Application of Consiflex as a registration material demonstrated that BDM index in the region of molars on the right was (0.065±0.04) mm, on the left it reached (0.05±0.05) mm (p-value more than 0.49). According to the results of the study conducted, this index in the region of upper incisors - lower premolars on the right reached (0.08±0.03) mm, being (0.07±0.03) mm (p-value more than 0.53) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.03±0.05) mm. Application of metallized wax as a registration material demonstrated that BDM index in the region of molars on the right was (0.085±0.02) mm, on the left it reached (0.07±0.03) mm (p-value more than 0.28). According to the results of the study conducted, this index in the region of upper incisors - lower premolars on the right reached (0.10±0.03) mm, being (0.08±0.03) mm (p-value more than 0.21) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.04±0.05) mm. During laboratory study of cast models of 10 patients in the MIC position, it was found that when using Futar D registration material, BDM index in the region of teeth 16-46 was (0.03±0.03) mm, teeth 26-36 - (0.35±0.03) mm (p-value more than 0.75). At the same time, this index in the region of teeth 13-44 was (0.055±0.04) mm, teeth 23-34 - (0.045±0.04) mm (p-value more than 0.59), respectively. In the region of teeth 21-31, its value reached (0.01±0.03) mm. Application of Consiflex demonstrated that BDM index on cast models in the region of molars on the right was (0.07±0.05) mm, on the left it reached (0.55±0.055) mm (p-value more than 0.53). According to the results of the studies, this index in the region of upper incisors - lower premolars on the right reached (0.09±0.04) mm, being (0.08±0.04) mm (p-value more than 0.59) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 was determined in the range of (0.03±0.05) mm. Application of metallized wax as a registration material demonstrated that BDM index on cast models in the region of molars on the right was (0.095±0.03) mm, on the left it reached (0.08±0.03) mm (p-value more than 0.23). According to the results of studies, this index in the region of upper incisors - lower premolars on the right reached (0.11±0.03) mm, being (0.09±0.04) mm (p &gt; 0.23) between these pairs of teeth-antagonists on the left side. BDM index in the region of teeth 21-31 reached (0.045±0.05) mm. Conclusions. Application of Futar D demonstrates lower optimum (0.00-0.08 mm) of differences between biometric deviation of markers indices, suggesting better complementarity during maximum intercuspation registration of this material in comparison with Consiflex (0.00-0.11 mm) and metallized wax (0.00-0.13 mm).

EFFECT OF DIFFERENT BITE RECORDING MATERIALS ON MOUNTING ACCURACY OF WORKING CAST

Objective: To assess effect of different bite recording materials on accurate mounting of working casts. Materials and Methods: A 40 maxillary and mandibular stone casts were obtained from dentoform teeth using polyether impression material. Derived stone casts were divided according to bite registration material in to four groups (10 samples each); 1. wax group, 2. polyvinyl siloxane group, 3. polyether group and 4. Bis-crylic resin group. Ten bite records were obtained with poly vinyl siloxane recording material from hand articulated dentoform to serve as control group. The 40 produced mandibular stone casts were mounted on semi adjustable articulators using four bite registrations tested materials. Unilateral Polyvinyl siloxane bite registration were made for 40 mounted stone casts to evaluate bite registration accuracy. Then bite records were placed on a light box and a camera set at a fixed distance 8 inches was used to capture the light transmission that was projected through the bite material. The camera transferred the information to an image analysis program (ImageJ) which measure accuracy of registration materials. Results: Grey scale data showed parametric distribution while measurement error showed non-parametric distribution. The difference between tested groups and control group was compared using ANOVA test. The results revealed that, the different between test groups and control was insignificant (P-value = 0.104). Conclusions: All tested bite registration materials had comparable results, although Luxabite and polyether showed higher errors than polyvinyl siloxane and wax.

Optimizing complex full arch rehabilitation by initial provisional and final CAD/CAM suprastructures

Background: The concepts to treat patients with failing dentition show a high variation. Depending on remaining bone volume the placement of a reduced number of implants without major grafting or the reconstruction of the atrophied jaw by intensive grafting procedures is recommended. All these cases require a reestablishment of the chewing and speech function. Most of the patients are adapted to the compromised situation for many years. After an ideal reconstruction quite often functional disorders appear. Aim/Hypothesis: Various procedures are recommended to reestablish the vertical dimension and to design the lingual appearance of implant borne prosthesis. Can CAD/CAM technologies improve the prosthetic workflow to minimize clinical problems like chipping, screw loosening, framework fractures and speech problems? Materials and Methods: A retrospective analysis of 30 cases which received a removable prosthesis during the healing phase of the implants was performed regarding the possible functional and technical problems of the final superstructure. 12 patients received two stage grafting procedures (TSG) with removable prosthesis TSG. 18 patients were treated with local grafting procedures and simultaneous implant placement (SIP). 15 (5 TSG, 10 SIP) patients received the final fabrication of the suprastructure consequently after implant impression taking within a period of 4.2 ÷ 4.5 week (Group A). The other 15 patients received a CAD/CAM milled provisional superstructure after impression taking within a period of 2.8 ± 3.8 weeks (Group B). These provisional suprastructures were used between 6 and 32 weeks. Results: Patients of group A had to wait longer after second stage surgery to receive a suprastructure with a higher number of consultations to adapt the bite and the vertical. In two cases the framework need to be redone, due to changes between initial bite registration and final try in of the restorations. 5 patients required a remounting after the final delivery with the discomfort of missing the implant borne prosthesis for a least one day. Patients of group A showed a higher occurrence of chipping and relining to improve speech function. Patient of Group B received the necessary adaptation of the provisional suprastructure always chairside without a absende of the restoration. After the adaptation phase the appointments for the final fabrication were reduced, due to the possibility to use the CAD/CAM data of the initial impression taking and matching of the data of the adapted provisional suprastructure. Conclusions and Clinical Implications: The use of a CAD/CAM produced provisional fixed prosthesis improves the digital work flow for the final suprastructure. The patients receive a restoration shortly after second stage surgery. Adaptation are much easier to be performed and corrections on the final restorations are not necessary. Due to the adaptation period significantly less chipping were observed. The use of CAD/CAM technologies allows cost effective prosthetic rehabilitation with a high patient satisfaction. Keywords: full arch rehabilitation, provisional suprastructure, CAD/CAM technologie, Improvement workflow, digital workflow

A comparative evaluation of three dimensional accuracy of different types of interocclusal recording materials - an in vitro study.

IntroductionThe interocclusal registration materials record the occlusal relationship between the natural and /or artificial teeth for planning an occlusal rehabilitation in removable and fixed partial dentures.Aim and objectivesThe aim of this in vitro study was to evaluate and compare the accuracy and the three dimensional stability offered by three different types of interocclusal recording materials at storage time intervals of 1 hour and 24 hours.MethodsThree commercially available interocclusal recording materials were used: Group I-Polyether bite registration paste (Ramitec), Group II-Polyvinylsiloxane bite registration material (Imprint), Group III-Bite registration wax (Maarc). The test was carried out using an epoxy resin model. A total of 30 samples were made with each group consisting of ten samples. Three dimensional measurements were carried out by using 3D-Coordinate measuring machine (CMM) at time intervals of 0–1 hour and 0–24 hours in X, Y and Z-axis.ResultsTwelve readings were obtained for three axes (4 readings for each sample at 1 axis) and the averages of these four values were noted for a particular axis (X/Y/Z). Statistical analysis was performed using analysis of variance (ANOVA) for comparison among the groups and then Tukey’s honestly significant difference (HSD) tests was performed for comparison among groups at the 0.05 level of significance.ConclusionPolyvinylsiloxane was dimensionally the most stable material followed by polyether and finally bite registration wax. Dimensional accuracy and stability is influenced by both “material” and “time” factors.

Accuracy of Vertical Dimension Augmentation Using Different Digital Methods Compared to a Clinical Situation-A Pilot Study.

To test the accuracies of different methods of digital vertical dimension augmentation (VDA) by comparison with a clinical situation. Bite registrations with approximately 5 mm of VDA were made in the incisor regions of 10 subjects (mean VDA 4.5 mm). The conventional maxillary and mandibular stone casts in maximum intercuspation (MICP) and VDA bite registrations were digitized for all subjects using a laboratory scanner (control group). Lateral portraits were taken of all subjects to locate the position of the condylar axis. Four different digital VDA methods were compared to the control group: 100% rotation of the mandible referring to the lateral picture (100RL); 85% rotation and 15% translation referring to the lateral picture (85R15TL); 100% rotation in normal mounting mode of the Trios virtual articulator (100R); and jaw-motion analysis (JMA) equipment. The amount of VDA for each experimental group was compared to the control group. The augmented distances between the central incisors and the second molars were measured using 3D analyzing software. The ratio of the augmented distances between the posterior and anterior regions (P/A ratio) was calculated. One-way analysis of variance and multiple comparisons via least significant difference test were carried out to determine statistical significance. The P/A ratio of each group was as follows: Control = 0.61; 100RL = 0.55; 85R15TL = 0.61; 100R = 0.53; JMA = 0.52. Significant differences were observed for control vs JMA and for 85R15TL vs JMA (P < .05). The addition of translational movement was the primary factor for increasing the accuracy of digital VDA, with the lateral picture being a secondary factor. VDA using a virtual articulator with 100% rotation induces an error when compared to the clinical situation. When a clinician performs digital VDA, the setting of 85% rotation and 15% translation produces results closer to the real clinical condition.

What can a dentist and dental sleep apnea researcher do under COVID-19 lockdown?

Citation:Tanaka Y, Almeida FR. What can a dentist and dental sleep apnea researcher do under COVID-19 lockdown? J Clin Sleep Med. 2020;16(9):1641–1643.

Comparative Evaluation of Compression Resistance Three Different Interocclusal Recording Materials: An In-Vitro Study

Interocclusal recording materials are used to register jaw relationships for mounting dental casts on an articulator. The resistance of these materials to compressive forces is critical, because any deformation during the recording or mounting process would result in, inaccurate articulation of casts and faulty fabrication of restorations. So this in vitro study was conducted to evaluate the deformation with various thicknesses of three different interocclusal recording materials when subjected to a constant compressive load. Method: Three commercially available interocclusal recording materials (Momax 2F zinc oxide eugenol impression paste, Polyvinylsiloxane bite registration material and Ramitec polyether bite registration material) were used for the study. Eight specimens of three different heights (2mm, 5mm and 10mm), a total of 24 specimens were made for each interocclusal recording material. Twelve hours after fabrication, each specimen was subjected to a constant compressive force of 25 N for one minute by means of spring testing machine. The deformation of each specimen was measured after 60 seconds of loading to obtain compression distance values. Results: Significant differences in compression resistance existed between the interocclusal recording materials at each thickness tested. There was a decrease in the compression resistance as the thickness increases among all the interocclusal recording materials. Conclusion: Polyvinylsiloxane bite registration material exhibited the greatest resistance to compression than the other materials at thicknesses of 2, 5 and 10mm. Therefore the interocclusal recording material should be of minimal thickness and an optimal recording material should exhibit minimal distortion during compression.