Crown Preparation Research Articles

Relative amount of tooth structure removal in different partial- and full-crown preparation designs.

To assess the effect of tooth morphology on the amount of tooth structure removal and the effect of different assessment methods on the detected amount of removed tooth structure. Eight test groups (n = 10) of standardized artificial teeth were prepared for partial and full crowns. All teeth were prepared by the same operator following predefined preparation parameters. Tooth structure removal was measured using three different assessment methods: digital volumetric analysis (DVA), weight analysis (WA), and combined computer-aided manufacture and weight analysis (CAMWA). Nonparametric repeated-measures analysis of variance and post hoc analyses were used to determine the influence of tooth morphology and assessment method on the detected amount of tooth structure removal. For partial crown preparations, only the tooth morphology had a significant impact on the detected amount of tooth structure removal (P < .0001), not the different assessment methods used (P = .08). Tooth structure removal was not significantly different between the canine and incisor groups, but was for the other groupwise comparisons. For full crown preparations, the tooth morphology (P = .047) and different assessment methods (P = .01) had an impact on the detected tooth structure removal. However, only a few groupwise comparisons reached the significance level. The amount of tooth structure removal depended on the tooth morphology and the type of assessment method, which should be taken into account when comparing results across studies. The detected amount of tooth structure removal was below the values described in the literature, independent of the assessment method used.

Micro-CT Evaluation of the Marginal and Internal Fit of Crown and Inlay Restorations Fabricated Via Different Digital Scanners belonging to the Same CAD-CAM System.

To evaluate the marginal and internal adaptation of all-ceramic crowns and inlays fabricated by different scanners of the same CAD/CAM system. All-ceramic crown preparations were performed on typodont maxillary first premolars, and mandibular first molars were prepared for ceramic Class II mesio-occlusal inlays. Two intraoral scanners (CEREC Bluecam and Omnicam, Dentsply Sirona) and one model scanner (CEREC inEos X5, Dentsply Sirona) were used to scan the preparations. All restorations were fabricated by milling single-feldspathic ceramic blocks (CEREC Blocks). The marginal and internal discrepancies of restorations were evaluated via micro-CT analyses. For linear crown measurements, the marginal gaps were 63.75 μm, 88.24 μm, and 90.89 μm for Bluecam, Omnicam, and inEos X5, respectively. For crowns at central groove areas, the maximum values for Bluecam, Omnicam, and inEos X5 were found to be 144.78 μm, 165.19 μm, and 129.49 μm, respectively. For inlays, the highest range at the midpoint of the axiopulpal line angle for Bluecam, Omnicam, and inEos X5 were determined as 138.57 μm, 184.33 μm, and 179.71 μm, respectively. In volumetric measurements, inEos X5 showed lower gap for both crowns (11.47 mm3) and inlays (5.65 mm3) compared to both intraoral scanners. These results are within a clinically acceptable range. When all-ceramic crowns were evaluated, there were generally no significant differences found between scanners for the regional linear measurements, but more gaps occurred in restorations obtained with intraoral scanners for volumetric measurements. On the other hand, when the inlay restorations were evaluated, significant differences were found between groups except for the midpoint of the axio-pulpal line angle and the midpoint of the mesio-gingival margin. However, marginal and internal gaps of both crowns and inlays presented mean values less than 150 μm in many surfaces, which could be considered clinically acceptable.

Analysis of Posterior Zirconia Crowns with Vertical Margin Preparations.

The interest in vertical crown preparation is growing and several variations are presented in the dental literature but limited clinical outcome data exists for teeth prepared for a vertical finish line. To audit clinical outcomes for 73 teeth after vertical preparation for knife-edge zirconia crowns. Seventy-three teeth had knife-edge zirconia crowns placed after vertical finish line preparation. The outcomes for these teeth were analysed from a retrospective audit of clinical records. The mean follow-up time was 21 months (SD: 10 months; range: 6-40). One tooth had to be extracted due to fracture at cervical level. One crown had to be re-made after margin fracture during try-in. No subsequent endodontic treatment was needed for any of the prepared teeth. No change in alveolar bone height was noted on radiographic follow-up. The mean bleeding score for the crowned teeth was higher than the mean bleeding score for a control tooth, but this was not statistically significant. This retrospective evaluation has shown favourable outcomes for 72 teeth after vertical preparation for knife-edge crowns. Longer follow-up is needed but the present results show that the technique is a viable procedure with potential advantages.

Anxiety to dental procedures among adolescents in Nalgonda district, Telangana, India: A cross sectional study

Introduction: Dental anxiety in adolescents is often noticed and is a cause of postponement of appointments, delay in seeking dental care or even avoidance of seeking dental treatment resulting in a poor oral health-related quality of life. Even though dentistry has steer up with much advancement, because of this dental anxiety patients are not stepping in the initial phase of treatment eventually leading to more invasive procedures. This study was undertaken to know which dental procedure will provoke more anxiety in the adolescents. Materials and Methodology: A custom-made questionnaire was prepared related to frequently done dental procedures. A total of 500 adolescents within the age group of 15-19 years were participated in the study. Filled questionnaires were collected; data was tabulated and statistically analyzed. Results: In Group I (male), 76.4% of adolescents were highly anxious to extraction/ surgical procedures followed by root canal treatment (70.8%) and crown preparation with impression procedure (64.4%). In Group II (female) 89.2% of adolescents were highly anxious to extraction/ surgical procedures followed by root canal treatment (84%) and crown preparation with impression procedure (77.2%). Conclusion: Adolescents were highly anxious to surgical and invasive dental procedures. Dentists should reduce their anxiety levels by behavior management techniques before treating them.

Computer-Aided Measurement of Total Occlusal Convergence of Teeth Preparations for All-Ceramic Crowns by Dental Students

Objective: This study was based on the evaluation the degree of total occlusal convergence of teeth preparedfor all-ceramic crowns which is the main factor that retention and resistance form of indirect restorationsdepended on. Teeth preparation done by 3rd year dental students at Al-Esraa university collage, Iraq in 2019.Materials and method: Eighty typodont teeth, maxillary central incisor(n=40) and first premolar teeth(n=40) were prepared for all-ceramic crowns by preclinical dental students under examination condition.The prepared teeth were scanned and digitized using the laser scanner 3Shape D710 (SculptCAD, Texas,USA). The datasets were evaluated using inspection software (shaper 3D zrt. Hungary, 2020) that used forthe assessment of the total occlusal convergence. Each tooth was virtually sectioned by four vertical planes:buccopalatal, mesiodistal, mesiobuccal–distopalatal and distobuccal– mesiopalatal and for each plane thetotal occlusal convergence angle (degree) was measured by drawing lines along the two opposing axialwalls from the finish line extended coronally. The data were analyzed with appropriate statistical tests usinganalysis of variance (ANOVA) and unpaired t-tests. Differences between groups were tested for significanceat 95% confidence interval.Results: The results revealed that the students prepared the central incisor teeth with average TOC valuesof 11.46° ± 6.81°, 9.91° ± 4.92°, 10.54° ± 7.05° and 12.06° ± 6.71° respectively, from the buccopalatal,mesiodistal, mesiobuccal–distopalatal and distobuccal– mesiopalatal planes. Concerning first premolarteeth, students prepared them with average TOC values of 12.03° ± 6.63°,11.57° ± 6.34°, 14.3° ± 6.94° and12.55° ± 6.6° respectively.The findings revealed that the approximated average TOC values for all the measured planes weregreater than the optimal TOC range 4 to 6 ° but stayed within the TOC acceptable range 4 to 14 °.Ordinary one-way ANOVA test showed no significant (P &gt;0.05) differences in the average TOC betweenthe different four planes within each tested group of teeth. The average value of overall total occlusalconvergence (TOCs) in the first premolar teeth= 12.61°± 6.63°was higher than for the central incisor teeth=10.99°±6.4°. Unpaired t-test for the two tested groups revealed significant (p &lt; 0.05) differences.Conclusions: The presented study found that about 85%, 65.83% respectively of upper central incisorand first premolar teeth prepared for all-ceramic crowns by pre-clinical dental students with acceptablerecommended convergence angle range 4-14°.

The Importance of MDP Priming, Silica Blasting or Glazing on the Retention Force of Y-TZP Copings to Varying Geometry Tooth Abutments

To evaluate the influence of the convergence angle of tooth preparations and abutments height and several surface treatments for zirconia copings through the tensile retention test. 120 crown preparations were made in Nema G10 with the maxillary first molar anatomy. In total, 60 abutments of 5 mm height were divided into two groups of 6° and 20° convergence angles of tooth preparations, and 60 abutments with a convergence angle of tooth preparations of 12° were divided into groups of 4 and 6 mm heights. Three surface treatments used were MDP-primer (10-Methacryloyloxydecyl dihydrogen phosphate), glazing or silica blasting. The abutments were scanned to make zirconia copings (3Y-TZP–Yttria-Stabilized Tetragonal Zirconia Polycrystals, Vita In-Ceram YZ). After cementation, the mechanical cycling (2 × 106 cycles, 3 Hz, 100 N) was performed to aging. After cycling, the copings were tested in tensile (1 kN load cell; 0.5 mm/s speed). Both abutments support base and copings were embedded in acrylic resin with the aid of a device that maintained the long axis perpendicular to the horizontal plane. Data were analyzed with the two-way ANOVA and Tukey test (95%). ANOVA revealed that the convergence angle influenced the tensile retention (p = 0.0232), but the abutments height showed no statistically significant difference (p = 0.086). The MDP-primer and silica blasting showed higher retention forces in the specimens with height variations. For bonded zirconia crowns, the retention force provided by high convergence angle preparation is critical and cannot be improved by surface treatments. For short and long crown preparations, MDP-based Primers or Silica blasting are advisable to aid restoration longevity.

Metal Endocrown – Novel Restorative option for Mutilated teeth; A Case Report

Extensively damaged endodontically treated molars pose a constant challenge for the practitioner. Although the classical post and core restoration is widely used in dentistry, its invasiveness has been criticized worldwide. Minimally invasive crown preparation preserving the maximum amount of tooth structure is considered to be the main objective for restoring teeth. Bindl and Mormann described the concept of endocrown in 1999 to limit the use of root anchorages. This case report illustrates this restorative option for functional rehabilitation of a devitalized mandibular molar, presenting with a small amount of remaining coronal tooth structure.

Pilot Study of Tooth Structure Removed in Primary Molar Zirconia Crown Preparations of Typodont Teeth

Prefabricated zirconia crowns (ZRCs) require a passive fit and more reduction than stainless steel crowns (SSC). To determine the mean and maximum reduction depths in the mesial-buccal and occlusal areas for three ZRC brands and one SSC in posterior primary typodont molars and to compare reduction depths to existing literature to determine the preparation’s proximity to pulpal tissue. Four primary maxillary and mandibular typodont teeth (J and S) were prepared according to the manufacturers’ guidelines for three ZRCs and an SSC. The teeth were scanned before and after preparation with an optical scanner, and the mean and maximum depths of reduction for each tooth were calculated in triplicate with custom software and statistically compared among the types of crown. The results were compared to existing data on primary tooth enamel and dentin thickness. Maximum mesial-buccal and occlusal depth respectively of preparation for any ZRC for tooth J was 1.19 mm and 1.58 mm while for tooth S it was 1.06 and 2.07mm Both EZ Crowns and Kinder Krowns required an additional 0.5mm occlusal reduction beyond the manufacturer’s recommendation for tooth S. Ideal preparations of ZRCs require more reduction than SSCs. Both EZ Crowns and Kinder Krowns require more reduction than the manufacturer’s recommendation for a mandibular first primary molar.

Evaluation of gingival displacement methods in terms of periodontal health at crown restorations produced by digital scan: 1-year clinical follow-up.

The purpose of this clinical study was to compare the effects of the gingival displacement techniques of retraction cord, cordless paste system, and Er,Cr:YSGG laser troughing on the periodontal tissues around the crown restoration produced using a digital scan. This was analyzed by recording the probing depth (PD), plaque index, gingival index (GI), mobility, sensitivity, and bleeding on probing (BOP) index. This study included 60 mandibular 1st molars from 52 participants (20 males and 32 females) requiring crown restoration. The margin lines of the crown preparations were placed 1 mm subgingivally. Based on the gingival displacement technique used, the patients were divided into three groups: retraction cord, cordless paste system, and Er,Cr:YSGG laser troughing. A digital scan of the prepared tooth was performed. Follow-up appointments were scheduled at five different times: 1st day, 1st month, 3rd month, 6th month, and 1st year. Six periodontal indices were used to assess the periodontal health. The chi-square test was used to compare categorical variables depending on the groups. There was a significant difference in the PD, GI, and BOP index scores among the three techniques during the 1-year clinical monitoring (p < 0.001). The PD in the three zones of the buccal surface showed a significant increase with time in the retraction cord and cordless paste system groups (p < 0.001). The highest GI scores were observed in the retraction cord group on the 1st day. The Er,Cr:YSGG laser troughing procedure produced lower PD, GI, and BOP index scores as compared to the retraction cord and cordless paste system procedures in the 1-year period.

Aerosol and spatter mitigation in dentistry: Analysis of the effectiveness of 13 setups.

ObjectivesThe current study aims to investigate the aerosol and spatter mitigation quality of 13 dry‐field isolation methods in a simulated setup that replicates real‐life work scenarios encountered in dental practices.MethodsA crown preparation on a manikin was performed on tooth number 30 and repeated five times for each setup to simulate a patient under care. Aerosol, environmental, and operator face shield spatter, and sound intensity was measured. Generalized linear mixed models were used, and posthoc pairwise comparisons were performed to compare least‐squares means when appropriate using a Tukey adjustment.ResultsAll tested setups showed some environmental spatter formation; however, these were able to control most (and in some cases all) spatter on the operator face shield. All methods resulted in excellent aerosol mitigation when a second line of high‐volume evacuation (HVE) was added to the device setup. However, in most setups, total sound levels exceeded 85 dB, posing a concern for prolonged noise exposure.ConclusionsThe Prototype device and four other tested setups with secondary HVE addition completely eliminated aerosol creation as tested. Spatter of the Face Shield was best eliminated using the Prototype device.Clinical SignificanceWithin the limitations of this study, it can be concluded that the dental community has at its disposal equipment that can effectively mitigate aerosol and spatter.

Three-Dimensional Finite Element Analysis of Stress Distribution in a Tooth Restored with Full Coverage Machined Polymer Crown

The effect of a restored machined hybrid dental ceramic crown–tooth complex is not well understood. This study was conducted to determine the effect of the stress state of the machined hybrid dental ceramic crown using three-dimensional finite element analysis. Human premolars were prepared to receive full coverage crowns and restored with machined hybrid dental ceramic crowns using the resin cement. Then, the teeth were digitized using micro-computed tomography and the teeth were scanned with an optical intraoral scanner using an intraoral scanner. Three-dimensional digital models were generated using an interactive image processing software for the restored tooth complex. The generated models were imported into a finite element analysis software with all degrees of freedom concentrated on the outer surface of the root of the crown–tooth complex. To simulate average occlusal load subjected on a premolar a total load of 300 N was applied, 150 N at a buccal incline of the palatal cusp, and palatal incline of the buccal cusp. The von Mises stresses were calculated for the crown–tooth complex under simulated load application was determined. Three-dimensional finite element analysis showed that the stress distribution was more in the dentine and least in the cement. For the cement layer, the stresses were more concentrated on the buccal cusp tip. In dentine, stress was more on the cusp tips and coronal 1/3 of the root surface. The conventional crown preparation is a suitable option for machined polymer crowns with less stress distribution within the crown–tooth complex and can be a good aesthetic replacement in the posterior region. Enamic crowns are a good viable option in the posterior region.

Restoration choices for endodontically treated posterior teeth

There aren't any generally accepted guidelines for the restoration of an endodontically treated tooth. With a questionnaire among dental general practitioners and endodontists, several restorative treatment options for endodontically treated molars and premolars were identified. The questionnaire inventoried the influence of various parameters on treatment preferences. For each case, additional questions were put about material choice, cuspal coverage and the use of root canal posts. Both groups identified the vertical root fracture as the most common reason for extraction. The dentist general practitioner waited longer than the endodontist to make a permanent restoration in the case of apical periodontitis. Treatment preferences were found to be the same for premolars and molars. In the case of premolars, a root canal post was indicated more often and the location of the wall (bearing/non-bearing) influenced the choice of cuspal coverage. Of the dentist general practitioners and endodontists, 51-53% and 75-94%, respectively, preferred a partial over a full crown preparation in the case of single-walled teeth.

Evaluating splatter and settled aerosol during orthodontic debonding: implications for the COVID-19 pandemic.

Introduction Dental procedures produce splatter and aerosol which have potential to spread pathogens such as SARS-CoV-2. Mixed evidence exists on the aerosol-generating potential of orthodontic procedures. The aim of this study was to evaluate splatter and/or settled aerosol contamination during orthodontic debonding.Material and methods Fluorescein dye was introduced into the oral cavity of a mannequin. Orthodontic debonding was undertaken with surrounding samples collected. Composite bonding cement was removed using a speed-increasing handpiece with dental suction. A positive control condition included a water-cooled, high-speed air-turbine crown preparation. Samples were analysed using digital image analysis and spectrofluorometric analysis.Results Contamination across the eight-metre experimental rig was 3% of the positive control on spectrofluorometric analysis and 0% on image analysis. Contamination of the operator, assistant and mannequin was 8%, 25% and 28% of the positive control, respectively.Discussion Splatter and settled aerosol from orthodontic debonding is distributed mainly within the immediate locality of the mannequin. Widespread contamination was not observed.Conclusions Orthodontic debonding is unlikely to produce widespread contamination via splatter and settled aerosol, but localised contamination is likely. This highlights the importance of personal protective equipment for the operator, assistant and patient. Further work is required to examine suspended aerosol.Zusatzmaterial online: Zu diesem Beitrag sind unter 10.1038/s41415-020-2503-9 für autorisierte Leser zusätzliche Dateien abrufbar.

Clinical performance of CAD-CAM crowns provided by predoctoral students at the University of Toronto

Statement of problemThe clinical success of monolithic lithium disilicate glass-ceramic (LDGC) crowns manufactured with computer-aided design and computer-aided manufacturing (CAD-CAM) technology provided by predoctoral students has not been fully investigated. PurposeThe purpose of this retrospective clinical study was to evaluate the performance of laboratory-fabricated monolithic posterior LDGC CAD-CAM crowns provided by predoctoral students at the University of Toronto. Specific patient- and provider-related factors were also investigated. Material and methodsA sample of posterior LDGC CAD-CAM crowns (IPS e.max) provided by predoctoral students was evaluated. Crown preparations were made according to specific criteria, and crowns were milled in an in-house laboratory by using the CEREC Bluecam system. The crowns were cemented with Rely-X Unicem (3M ESPE) and Calibra Universal (Dentsply Sirona) resin cements. Clinical assessments of the crowns and supporting periodontal structures were performed following the modified California Dental Association (CDA) criteria. Intraoral photographs and periapical and bitewing radiographs were obtained for further assessment by 2 evaluators. Descriptive statistics, McNemar, t test, log rank (Mantel-Cox) tests, Pearson chi-squared tests, simple logistic regression, odds ratios, and Kaplan Meier survival analyses were performed (α=.05). ResultsA total of 189 patients receiving 210 crowns (108 premolar and 102 molar) were examined with a follow-up period of up to 6 years. Altogether, 28 complications were observed (12 technical, 11 biological, and 5 esthetic). No significant association was found between patient age, sex, periodontal condition, tooth type, tooth vitality, cement type, and crown longevity. However, significantly lower survival and success rates were found for mandibular crowns than for maxillary crowns (P=.029). The provider’s experience had no significant effect on the clinical performance of LDGC CAD-CAM crowns. The 6-year cumulative survival rate was 93.0%, and the success rate was 86.4%. ConclusionsThe ease of use of the CAD-CAM system and clinical performance of LDGC suggest that this technology should be used in the dental school setting by predoctoral students.

Reabilitação oral com coroa cerâmica fresada em CAD/CAM em dente com ampla destruição coronária – relato de caso

The unitary ceramic crowns are fixed partial dentures cemented on the tooth to be rehabilitated and can be produced from CAD/CAM systems, a device that allows scanning the surface of interest, planning, and making the prosthetic part. The objective of this article is to report dental rehabilitation with the use of ceramic crown manufactured with the CAD/CAM system with the purpose of returning function, aesthetics, and well-being to the patient. Rehabilitation of tooth 26, already endodontically treated, was performed in two consultations, one for the temporary crown and the other for the definitive crown. The preparation for the total crown was done after filling the cavity with composite resin and then it was scanned with a scanner from the CEREC system (Dentsply Sirona). A temporary crown was designed in Cerec SW 4.6 software and then milled from a PMMA Vipiblock (VIPI) resin block. The model of the temporary piece was used to guide the preparation of the definitive crown milled from a leucite-reinforced ceramic block (Empress CAD Multi - Ivoclar) in color B1. After obtaining the crown, it was aesthetic finished to obtain greater naturalness. CAD/CAM system offers advantages in reducing the treatment time, in addition to manufacturing pieces that correctly adapt to the preparation margins and that have occlusal and proximal contact points at the appropriate intensity. It is important that work on methods and materials within dentistry are carried out constantly, keeping professionals updated.

Marginal Integrity of CAD/CAM Ceramic Crowns Using Two Different Finish Line Designs

Objective: Research on evaluation of crowns made by the latest contemporary dental computer-aided design/computer-aided manufacturing (CAD/CAM) systems for their marginal adaptation is scarce. The purpose of this in vitro study was to evaluate the marginal integrity of crowns fabricated by the latest Chairside Economical Restorations of Esthetic Ceramic (CEREC) system using 2 different finish line preparation designs: chamfer and shoulder. Materials and Methods: Typodont teeth were divided equally into 2 groups, A and B. The teeth were prepared for full coverage crowns with a shoulder (group A) and chamfer (group B) finish line design. An experienced prosthodontist prepared all crown preparations. Evaluation of 6 sites per sample was completed by 2 calibrated, experienced prosthodontists using the modified US Public Health Services (USPHS) criteria. The descriptive statistics and Z-test were used to evaluate the results. Results: A total of 180 teeth were included in the study (90 teeth in each group). Only 2 crowns in group A and 1 crown in group B were clinically unacceptable. There was no statistical significance (p = 0.282) between the 2 groups regarding finish line design. Conclusions: The CEREC system provides clinically acceptable crowns and can safely be utilized in dental treatment. Therefore, CAD/CAM restorations could be considered as a safe treatment modality by dental professionals.

Effect of Chairside CAD/CAM Restoration Type on Marginal Fit Accuracy: A Comparison of Crown, Inlay and Onlay Restorations.

Chairside CAD/CAM is a convenient approach for fabricating dental restorations. However, the effect of CAD/CAM restoration type on marginal fit accuracy has not been fully investigated. This study evaluated of the marginal fit accuracy of 3 chairside CAD/ CAM restoration types (crown, inlay and onlay) using CEREC Bluecam (BC) and CEREC Omnicam (OC) scanners. Three artificial maxillary first molars received crown, inlay and onlay preparations. A total of 10 CAD/CAM ceramic restorations were produced for each tooth by each intraoral scanner. The marginal gap was measured along the preparation margin. For the BC, all the restorations had similar marginal gaps (crowns = 113.9 μm; inlays = 120.9 μm; onlays = 132.5 μm) (p = 0.20), while for the OC, the crowns (72.2 μm) and the inlays (74.9 μm) exhibited better marginal fit than the onlays (96.4 μm) (p = 0.003). For every restoration type, the OC provided a superior outcome compared with the BC. Therefore, the restoration type influenced the marginal gap, where the crowns tended to have the least marginal gap while the onlays had the greatest marginal gap. The newer scanner (OC) of the same manufacturer was more accurate than the older scanner (BC).

In vitro evaluation of the application of digital individual tooth tray in the impression making of mandibular full-arch crown abutments

Objective To establish a method for the production of digital individual tooth tray based on three-dimensional (3D) scan, computer-aided design (CAD) and 3D printing, and to evaluate the effect of impression taking of full-arch crown abutments by digital individual tooth tray technique and conventional method through in vitro study. Methods The full crown preparation was performed on all the fourteen resin teeth in a standard model of mandibular dentition. The surface data of prepared abutments was collected by 3D scanning. A new project was created in a dental CAD software including all the fourteen teeth in the mandibular dentition. The design modules of anatomy crown and coping were selected for each tooth. The dentition was divided for three sections: right posterior teeth, anterior teeth, and left posterior teeth areas. The connector design was added between the abutments within the same section. The scanned data of the abutments were imported. The occlusal plane and insertion path were determined. The position of margin line, as well as the shape of anatomy crown and connector as the main body of the individual tooth tray were designed for each abutment. The shape of coping was generated as the space for holding the impression material. The finalized data of the main body was imported into Geomagic software. The retentive attachment was added at the external surface and the tissue stop was formed at the internal surface. The completed individual tooth tray was manufactured by 3D printing with resin material. The data of full-arch crown abutments were modified and printed. The conventional dentition trays A and B, as well as digital individual tooth tray were designed and printed for four copies each. The polyether impressions of the full-arch abutments were made by conventional one-step method using dentition tray A, and by sectional-impression technique using digital individual tooth tray and dentition tray B for four times each. The time spent for each impression taking and the numbers of defects at the shoulder and axial/occlusal surface in each impression were recorded. The impression quality of each abutment was evaluated. The overall quality distribution and the pass rate of abutments between the two methods were analyzed. Results The impressions made by conventional method had more defects at shoulder than those made by digital individual tooth tray technique. No difference of the number of defects at axial/occlusal surface between the two methods was observed. The digital individual tooth tray technique for the full-arch abutment impression exhibited higher pass rate of abutments and better quality of impression, compared with conventional methods. Conclusion A new method for the production of digital individual tooth tray based on digital scanning, CAD and 3D printing was established. Compared with conventional method, using digital individual tooth tray technique for impression taking of full-arch abutments can achieve better effect.

Gondolatok az egybeöntött vagy szóló koronák alkalmazása közötti választásról

A fogpótlások készítése során többször kell eldönteni, hogy egymás melletti fogakra szóló koronák készüljenek, vagya fogakat foglaljuk merev egységbe a koronákkal. Bizonyos szituációkban szükséges a fogak sínezése, azonban ez problémássá teheti az interdentális tér megfelelő tisztítását. Egybeöntött koronák csak alapos megfontolás után készíthetők, betartva a parodontálhigiéniai szempontokat. Ellenkező esetben a betegek nem képesek az interdentális tér tisztítására, aminek gingivitis, későbbiekben parodontitisz lehet a következménye. A fogak csiszolásakor, a lenyomatvételkor,a mintakészítéskor és a koronák mintázása során is figyelembe kell venni az egyéni fogmorfológiát és ezzel biztosítani az interdentális tér anatomikus kialakítását akár szóló korona, akár egybeöntött koronák készülnek. A szerzők összefoglalják a sínezéskor fontos szempontokat.

In Vitro Infrared Thermographic Assessment of Temperature Change in the Pulp Chamber during Provisionalization: Effect of Remaining Dentin Thickness

Interim crowns and partial fixed dental prosthesis materials generate exothermic heat during polymerization. The amount of heat transmitted to the pulp chamber can be a function of several factors, including the thickness and quality of the remaining dentin after crown preparation. The aim of this in vitro study was to measure with infrared thermography the temperature changes on the adjacent surface of the chamber roof of premolar teeth extracted from young and old patients (having different thicknesses of remaining dentin after crown preparation) during fabrication of provisional resinous restorations. Twenty extracted human first and second maxillary premolar teeth (10 from young patients, with a relatively large pulp chamber, and 10 from older patients, with a relatively small pulp chamber) were used. The roots were sectioned to expose the inner side of the chamber roof, and the crowns were provisionalized after preparation for a metal-ceramic crown. Two provisional materials, Turbo Temp 2 and Luxatemp Fluorescence, were used. Temperature changes on the inner side of the chamber roof were measured at 2-second intervals using an infrared thermal imaging camera. After completion of the temperature recordings, the teeth were sectioned and the remaining dentin thickness was determined. The older group (mean thickness: 2.82 mm) and younger group (mean thickness: 1.9 mm) differed significantly in dentin thickness (P < 0.014). The mean greatest temperature increases recorded on the chamber roof of teeth with less remaining dentin were 4.07°C for Turbo Temp 2 and 3.94°C for Luxatemp Fluorescence, while increases in the premolars with greater dentin thickness were 1.69°C for Turbo Temp 2 and 1.64°C for Luxatemp Fluorescence. Significant interactions were found between tooth groups (P < 0.000001for Turbo Temp 2 and for Luxatemp Fluorescence). No significant differences were found between assessed materials regardless of the thickness of the remaining dentin (P > 0.38for the older group and P > 0.29 for the younger group). Dentin had a significant effect in limiting the temperature increase generated during polymerization of provisional materials, indicating good thermal insulating properties of this tissue. A remaining dentin thickness of 1.9 mm or more is sufficient to protect the pulp from any temperature increase during provisionalization using tested materials.