Composite Resin Crowns Research Articles

Evaluation of stress distributions in endodontically treated anterior incisors under occlusal and trauma-induced forces following various restoration treatments: A finite element analysis.

The aim of this study was to calculate the stress distribution of fiberglass post associated with resin composite crown restoration and fiberglass posts with zirconia restorations in mature and immature endodontically treated central maxillary incisor under various loading conditions. The study created six different study models in a virtual environment: healthy mature maxillary central teeth, intact immature maxillary central teeth, mature maxillary central teeth with fiberglass post associated with resin composite crown restoration, immature maxillary central teeth with fiberglass post associated with resin composite crown restoration, mature maxillary central teeth with fiberglass posts and zirconia restoration, and immature maxillary central teeth with fiberglass posts and zirconia restoration. Loading conditions simulating mastication, trauma, and bruxism were applied to each of the models at different angles and amounts. The von Mises and the maximum and minimum principal stress values in tooth structures (dentin) and support structures (bone, PDL) and materials were observed using finite element stress analysis. The highest stress values in the tissue and the restoration structure were observed for masticating force and crowns rehabilitated with zirconia restorations. None of the compared loading conditions and restorations showed destructive stress values on periodontal ligament or bone. The mature and immature endodontically treated central maxillary incisors can be better rehabilitated using fiberglass post associated with resin composite crown restoration and may be preferred to zirconia restorations in order to reduce the stresses on the surrounding tissues and teeth. However, further clinical studies are needed to fully explore this topic.

Bone Regeneration on Chronic Apical Abscess After Root Canal Treatment

Chronic Apical Abscess is explained as an inflammatory reaction to pulp infection and necrosis. It is characterized by intermittent discharge of pus through an intraoral sinus tract and usually associated with little or no discomfort. On radiograph examination showed radiolucency as signs of periapical bone destruction. Root canal treatment can elimination bacteria as source of the infection in root canal system. Purpose: these two case report aims to present the management of chronic apical abscess with bone destruction in periapical area. Case report: (1) A 21-years-old female came to complained of a lack of self-confidence due to her upper-front tooth was broken about 8 years ago. Clinical examination showed no discomfort on percussion test, negative on palpation and vitality test. Periapical radiography showed a radiolucent with clear but indistinct boundaries, oval in shape with a diameter of approximately 4 mm. (2) A 20-years-old male complained that his front teeth were broken and discoloured. This complaint had been felt for a long time about 7 years ago. The patient had felt spontaneous pain in the tooth that was hit during the accident for a week. Currently, the tooth is no longer painful. There is no swelling in the gum area where the tooth has changed colour. Radiological examination showed bone damage with a periapical radiolucent appearance with diffuse oval borders with a diameter of 5-6 mm. The diagnosis of these two cases were pulp necrosis with chronic apical abscess. Root canal treatment were performed to elimination bacteria of source infection. First case was restoration using composite resin crown with fiber post intracanal restoration and the second case was restoration using direct restoration. Conclusion: proper root canal treatment resulting bone regeneration and periapical lesions healing in chronic apical abscess cases.

Stresses in Premolars Restored Using Different Post-and-Core and Crown Materials: An FEA Study.

The aim of the present study was to investigate the influence of three post-and-core systems and two crown materials on stresses in restored premolars using Finite Element Analysis (FEA). A maxillary second premolar 3D model was created in SolidWorks 2014 (Dassault Systémés). Severe loss of tooth structure was simulated with six restorative options: 1) glass-fiber-reinforced composite post and composite core (GFRC)+CAD/CAM leucite-reinforced glass-ceramic crown (LRC); 2) carbon-fiberreinforced composite post and composite core (CFRC)+LRC; 3) metal cast post-and-core (MPC)+LRC 4) GFRC+CAD/CAM composite resin crown (CC); 5) CFRC+CC; 6) MPC+CC. Three-point occlusal loading (150N) was simulated and von Misses and maximum principal stresses calculated. Although maximum von Mises stresses in the crown and dentin were similar across groups (137.9-139.2MPa crown; 17.2-19.6 dentin), there were important differences in stress distribution in dentin. Only in MPC+CC group the maximum stresses were on the bottom of the post preparation cavity. Stress values within the posts were: CFRC(4.8MPa)>GFRC(6.7MPa)>MPC(10.3MPa). CC-restored models presented higher von Mises stresses within the post-and-core compared to the LRC groups. Maximum principal stresses were lower compared to von Mises stresses, following the same trend, and were distributed similarly in all the groups. Both GFRC and CFRC showed favourable stresses distribution in the dentin and restorative materials, while MPC increased stresses in core, post and post cement. The more rigid crown material seems to transmit less stresses to the underlying core and crown cement compared to CC.

Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials.

This study aimed to assess the marginal and internal adaptation of provisional crowns fabricated from polymethyl methacrylate (PMMA) blocks by the computer-aided design/computer-aided manufacturing (CAD/CAM) system, autopolymerizing PMMA, and acrylic base composite resin. In this in vitro experimental study, a brass die was obtained, and provisional crowns were fabricated in three groups using Teliocad PMMA blocks by the CAD/CAM system, Tempron GC auto-polymerizing PMMA, and Bisico acrylic base composite resin (n = 7 in each group). The provisional crowns were coded and randomly placed on the die. Their marginal adaptation was evaluated under a stereomicroscope at 40× magnification, while their internal adaptation was assessed by the replica technique. Data were analyzed by one-way analysis of variance (ANOVA) (α = 0.05). The mean marginal gap was the highest in autopolymerizing PMMA and the lowest in the CAD/CAM PMMA group (p < 0.05). The mean marginal gap in the autopolymerizing PMMA group was significantly higher than that in the resin material (p = 0.014) and CAD/CAM PMMA (p = 0.000) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.13). The mean internal gap was the highest in autopolymerizing PMMA group and the lowest in CAD/CAM PMMA group (p < 0.05). The mean internal gap in autopolymerizing PMMA group was significantly higher than that in composite resin (p = 0.002) and CAD/CAM PMMA (p = 0.00) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.322). Computer-aided design/Computer-aided manufacturing PMMA provisional crowns showed the highest marginal and internal adaptation followed by acrylic base resin material crowns. Computer-aided design/computer-aided manufacturing PMMA crowns demonstrate superior marginal and internal adaptation compared with autopolymerizing PMMA and acrylic base composite resin crowns, suggesting CAD/CAM technology's potential for enhancing clinical outcomes. How to cite this article: Jalalian E, Younesi F, Golalipour S, et al. Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials. J Contemp Dent Pract 2023;24(11):853-858.

Mechanical Behavior of Repaired Monolithic Crowns: A 3D Finite Element Analysis.

This study evaluated the mechanical behavior and risk of failure of three CAD-CAM crowns repaired with different resin composites through a three-dimensional (3D) finite element analysis. Three-dimensional models of different cusp-repaired (conventional nanohybrid, bulk-fill, and flowable resin composites) crowns made of zirconia, lithium disilicate, and CAD-CAM resin composite were designed, fixed at the cervical level, and loaded in 100 N at the working cusps, including the repaired one. The models were analyzed to determine the Maximum Principal and Maximum Shear stresses (MPa). Complementary, an in vitro shear bond strength test (n = 10) was performed to calculate the risk of failure for each experimental group. The stress distribution among the models was similar when considering the same restorative material. The crown material affected the stress concentration, which was higher for the ceramic models (±9 MPa for shear stress; ±3 MPa for tensile stress) than for the CAD-CAM composite (±7 MPa for shear stress; ±2 MPa for tensile stress). The shear bond strength was higher for the repaired CAD-CAM resin composite (±17 MPa) when compared to the ceramics (below 12 MPa for all groups), while the repair materials showed similar behavior for each substrate. The stress distribution is more homogenous for repaired resin composite crowns, and a flowable direct resin composite seems suitable to repair ceramic crowns with less risk of failure.

Effect of different post and core on composite resin crowns .An vitro study

Effect of different post and core on composite resin crowns .An vitro study

In vitro analysis of durability of S-PRG filler-containing composite crowns for primary molar restoration.

To evaluate the reliability, maximum principal stress, shear stress, and crack initiation of a computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite (RC) incorporating surface pre-reacted glass (S-PRG) filler for primary molar teeth. Mandibular primary molar crowns fabricated by experimental (EB) or commercially available CAD/CAM RCs (HC) were prepared and cemented to a resinous abutment tooth using an adhesive resin cement (Cem) or a conventional glass-ionomer cement (CX). These specimens were subjected to a single compressive test (n=5/each) and the step-stress accelerated life testing (SSALT) (n=12/each). Data was evaluated using Weibull analyses and reliability was calculated. Afterwards, the maximum principal stress and crack initiation point of each crown was analyzed by finite element analysis. To evaluate bonding of EB and HC to dentin, microtensile bond strength (μTBS) testing was conducted using primary molar teeth (n=10/each). There was no significant difference between the fracture loads of EB and HC for either cement (p>0.05). The fracture loads of EB-CX and HC-CX were significantly lower than EB-Cem and HC-Cem (p<0.05). The reliability at 600N for EB-Cem was greater than that for EB-CX, HC-Cem, and HC-CX. The maximum principal stress concentrated on EB was lower than that on HC. The shear stress concentrated in the cement layer for EB-CX was higher than that for HC-CX. There was no significant difference among the μTBSs of EB-Cem, EB-CX, HC-Cem, and HC-CX (p>0.05). The crowns fabricated with the experimental CAD/CAM RC incorporating S-PRG filler yielded greater fracture loads and reliability than the crowns manufactured with commercially available CAD/CAM RC regardless of the luting materials. These findings suggest that the experimental CAD/CAM RC crown may be clinically useful for the restoration of primary molars.

Multidisciplinary Approach for Autotransplantation and Restoration of a Maxillary Premolar into an Area of an Avulsed Anterior Tooth: A Case Report with a 6-Year Follow-up

The loss of an anterior tooth because of avulsion has been reported in up to 3% of dental injuries. Management alternatives, such as implant-supported restorations and a fixed partial denture, are contraindicated in growing patients because of the continuous growth of the alveolar process. At the same time, orthodontic treatment for gap closure will result in asymmetry and will require adjustment of the adjacent healthy teeth. Therefore, restoring a missing tooth imposes a treatment challenge, especially in children and young adults. Tooth autotransplantation is a treatment modality with high reported survival and success rates that overcome these mentioned limitations. It might also help to preserve the alveolar bone and the soft tissues. This case report describes a multidisciplinary approach for managing a 13-year-old boy who lost his right maxillary central incisor because of a fall. Management included autotransplantation of the left maxillary second premolar to the site of the lost right maxillary central incisor, management of external inflammatory resorption with an endodontic treatment, orthodontic treatment, and aesthetic restoration of the area with composite resin crowns that can be adapted to the expected changes of the jaws during the craniofacial growing period. At the 6-year follow-up, the teeth demonstrated a positive outcome.

Influence of thermo-mechanical aging on fracture resistance and wear of digitally standardized chairside computer-aided-designed/computer-assisted-manufactured restorations

ObjectivesTo investigate the influence of thermal cycling and mechanical loading (TCML) aging on fracture resistance and wear behavior of various chairside computer-aided-designed/computer-assisted-manufactured (CAD/CAM) premolar crowns cemented on standardized tooth abutments. MethodsEighty chairside CAD/CAM crowns were prepared using lithium disilicate (IPS e.max CAD; EM), zirconia-infiltrated lithium silicate (Celtra Duo; CD), polymer-infiltrated ceramic network (Vita Enamic; VE), and resin nanoceramics (Cerasmart; CS) (n = 20). The specimens were divided into two groups (n = 10). In one group, they were subjected to TCML: thermocycling (6000 cycles in distilled water at 5–55 °C) and mechanical loading (50 N for 1.2 × 106 cycles), while in control group they were stored in distilled water (37 °C for 24 h). The fracture load, height loss, and volume wear of the crowns were measured after TCML. Fractography was performed on fractured specimens. Data were analyzed using analysis of variance and multiple comparison tests (α=0.05). ResultsThe mean fracture loads of EM and CD were significantly higher than those of EC and CS (p<0.05). There was no significant change in the fracture load of any CAD/CAM crowns after TCML (p>0.05). CS exhibited a significantly higher volume wear than the other materials investigated. The wear tracts of all TCML crowns acted as failure origins during the fracture test. ConclusionsThe fracture resistance of glass-ceramic CAD/CAM crowns was significantly higher than that of resin composite crowns. A 5-year TCML aging did not affect the fracture resistance of CAD/CAM crowns investigated. However, TCML treatment produces a larger wear track in CS than in other materials. Clinical SignificanceAppropriate chairside CAD/CAM restorative material should be selected for successful clinical practice after considering the fracture and wear resistance of the crowns.

Comparison of the accuracy of resin-composite crowns fabricated by three-dimensional printing and milling methods.

This study aimed to compare the dimensional accuracies of three-dimensional (3D)-printed and milled resin-composite crowns, and to determine acceptable abutment-tooth shapes for printing. Four first-molar abutment models were prepared: the master model form and three models with sharp occluso-axial line angles. Crowns were designed on each abutment using computer-aided design software. The drill-offset value was set at 0.0 or 0.5 mm to evaluate the effect on the dimensional accuracy of milling. A digital light processing-based 3D printer was used to fabricate 3D-printed crowns. Milled crowns were fabricated by wet-milling. The trueness was evaluated by superimposing the design data. Regardless of the abutment form, 3D-printed crowns showed higher accuracy with fewer marginal discrepancies than milled crowns. Milled crowns showed significant dimensional deviations, especially at cusps. Moreover, offset correction resulted in grooves on the internal surface of milled crowns with negative deviations, which were especially evident in crowns for the sharp models.

Impact of the occlusal contact pattern and occlusal adjustment on the wear and stability of crowns

ObjectivesTo investigate the impact of the occlusal contact situation and occlusal adjustment on wear, roughness, and fracture force of molar crowns. Materials and methodsCAD/CAM crowns (lower right first molar, n = 64; 4 groups à 8, 3Y-TZP zirconia and resin composite) and corresponding antagonists (upper right first molar; 3Y-TZP zirconia) were manufactured. Crowns were constructed according to two principles of occlusion (group “T”: Peter K. Thomas’ “point-centric” cusp-to-fossa tripodization concept, with 15 contact points; group ”RA” Sigurd P. Ramfjord and Major M. Ash, “freedom in centric” concept with four contacts). On one half of the crowns, occlusal adjustment was performed (groups “T adjusted” and “RA adjusted”). All crowns underwent combined thermal cycling (TC) and mechanical loading (ML) (ML: 1.2 × 106 cycles, 50 N, 2 Hz, mouth opening 1 mm; TC: 2 × 3000 cycles, 5/55°C). Wear area and depth of each contact point on the occlusal surfaces of crowns and antagonists were determined using a digital microscope. Surface roughness (Ra, Rz) was measured in and besides (reference) the worn area (3D laser-scanning microscope). Fracture force of the crowns was determined (statistics: Levene-test, one-way-ANOVA; Bonferroni-post-hoc-test; between-subjects effects, Pearson correlation, α=0.05). ResultsThe resin composite crowns yielded significantly higher mean values for wear area and depth (p < 0.001) and lower fracture forces (p < 0.001). Resin composite surfaces showed increased roughness after TCML while zirconia exhibited smoothened surfaces. The occlusal design significantly impacted wear depth (p = 0.012) and fracture force (p < 0.001). Resin composite crowns with fewer contact points (group RA) showed more wear and lower fracture force. Adjusted resin composite crowns showed increased wear areas and depths (p = 0.009-0.013). For zirconia crowns, the adjustment impacted wear area (p = 0.013), wear depth (p = 0.008), and fracture force (p = 0.006), with adjusted zirconia crowns exhibiting more wear and lower maximum forces until fracture. Zirconia wear depth was also impacted by the occlusal design (p = 0.012). Antagonistic wear was influenced by the restorative material, the occlusal contact pattern, and the adjustment. ConclusionsThe investigated materials show strongly varying performances with zirconia being significantly influenced by the adjustment, while for resin composites, contact design and adjustment had a major impact. Clinical relevanceThe results show the necessity of adapting occlusal design and adjustment in order to improve roughness, wear, and stability of zirconia and resin composite crowns.

Thickness and internal adjustment of monolithic resin composite milled crowns: Effect on the load-bearing capacity under fatigue

ObjectivesTo evaluate the fatigue failure load (FFL), cycles for fatigue failure (CFF) and survival rates of different occlusal thicknesses of resin composite simplified crowns with internal adjustments (IA) or without as control (C). Methods30 monolithic simplified crowns of CAD/CAM resin composite (Tetric CAD, Ivoclar) were milled in three different occlusal thicknesses (0.5 mm, 1.0 mm, and 1.5 mm). Half of the crowns were submitted to restricted adjustment with diamond burs on the crown's inner surface and half remained milled without internal adjustment. The samples were treated and adhesively luted onto a prosthetic preparation made of epoxy resin reinforced by glass-fiber substrate. The sets were subjected to a fatigue test (cyclic fatigue: initial load of 200 N; step-size of 50 N; 10,000 cycles/step; 20 Hz; maximum load: 2800 N).Microscopic analysis of tested representative samples was performed. The fatigue data were statistically analyzed (α= 0.05) and the micrograpic images were qualitatively evaluated. ResultsAll specimens from groups 1.0C and 1.5C survived the cyclic loads, while all 0.5C samples failed during the test. The 1.0IA and 1.5IA crowns showed no statistical difference for FFL (2530 N= 2670 N) and CFF (471,000 cycles= 499,000 cycles) between them, and they were both statistically superior to the 0.5IA (FFL= 1812.50 N; CFF= 327,500 cycles). The 1.0 mm and 1.5 mm crowns presented superior fatigue behavior (2530 N–2800 N) compared to the 0.5 mm crowns (1812 N–2140 N), whether internal adjustment was performed or not. A statistically significant difference was found for FFL and CFF of 0.5 mm crowns with and without internal adjustment, with a deleterious impact of the adjustment for both parameters (FFL and CFF: 0.5C > 0.5IA). SignificanceResin composite milled crowns can bear high cyclic fatigue loads despite thickness, although thicker crowns had better mechanical behavior; however, the internal adjustment in the composite resin crown leads to a detrimental effect on its fatigue behavior, which presents a risk of mechanical failure due to premature fatigue.

Accelerated Fatigue Resistance of Bonded Composite Resin and Lithium Disilicate Screw-Retained Incisor Crowns with Long and Short Titanium Bases.

This study evaluates the fatigue resistance and failure mode of CAD/CAM composite resin and lithium disilicate-bonded screw-retained incisor crowns with long and short titanium bases. Sixty CAD/CAM implant restorations were fabricated using lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) and composite resin (Block HC, Shofu). The central incisor crowns were bonded to a prefabricated titanium base 6 mm tall (groups: Emax6 and Shofu6; n = 15 each) or a modified abutment 4 mm tall (groups: Emax4 and Shofu4; n = 15 each). The intaglio surface of the restorations was conditioned according to the material and bonded to the titanium abutments/bases using dual-cure cement. All assembled crowns were torqued onto implants and subjected to cyclic isometric loading at the incisal edge along the implant axis. Samples were loaded until fracture. Groups were compared using Kaplan-Meier survival analysis (log rank test at P = .05). The number of mean survived cycles differed significantly, with Emax6 and Emax4 at 48,448 and 43,727 cycles, respectively, and Shofu6 and Shofu4 at 44,124 and 37,620 cycles, respectively. Post hoc tests showed similar fatigue resistance for Emax6, Emax4, and Shofu6. Shofu4 was less resistant than all other groups (P < .03). All restorations survived significantly above physiologic load limits. Lithium disilicate screw-retained incisor crowns can be used with long and short titanium bases, while it is recommended to keep a long titanium base for screw-retained composite resin crowns. The composite resin material required the full height of the abutment for optimal strength but may offer enhanced shock absorption and wear-friendliness when considering function and antagonistic wear.

In Silico Finite Element Analysis of Implant-Supported CAD-CAM Resin Composite Crowns.

The aim of this study was to evaluate the mechanical behavior of an implant-supported crown made using computer-aided design and computer-aided manufacturing (CAD-CAM) resin composite (RC) blocks in the posterior region. Four commercially available CAD-CAM RC blocks were used in this study: Cerasmart 300 (CS300; GC, Tokyo, Japan), Katana Avencia P Block (KAP; Kuraray Noritake Dental, Niigata, Japan); KZR HR3 Gamma Theta (HR3; Yamakin, Osaka, Japan), and Estelite P block (ESP; Tokuyama Dental, Tokyo, Japan). Katana Zirconia STML (ST; Kuraray Noritake Dental) was used as the control group. The elastic moduli of each material were determined by a three-point bending test. After the CAD models were designed, two different loading scenarios (oblique, vertical) were created. 3D finite element analysis was conducted with the prepared models. The elastic modulus of the material utilized for the implant restorations did not cause any change in the stresses transmitted to the implant or peripheral bone. An important difference was detected in the abutment-crown junction area. The minimum von Mises value at the abutment-crown interface was obtained in ST, which has the closest elastic modulus to the titanium abutment. The 3D finite element model designed in this study was used to demonstrate that implant-supported crowns fabricated with four different CAD-CAM RCs showed no critical stress concentrations in the bone or implant under all loading conditions. These results suggest that CAD-CAM RC blocks could be used as an alternative material for implant-supported restorations in the posterior region in terms of stress distribution.

Strip Crowns Technique for Aesthetic Rehabilitation of Primary Anterior Teeth: Case Report

Abstract: Early childhood caries is a condition that affects millions of children worldwide. This issue must be treated in early childhood. The current study describes a case of aesthetic-functional rehabilitation using laboratory-made strip crows and composite in a 3-year-old child with lesions of early childhood caries. Composite resin restorations were placed on all upper anterior teeth to restore aesthetics and function, providing the kid and her family with a higher quality of life. The use of strip crowns in the manufacture of composite resin crowns resulted in a faster clinical time, a superior cosmetic outcome, and the rehabilitation of the patient's smile and personality. Keywords: Strip Crown, Rehabilitation, Early Childhood Caries.

Potential complications of CAD/CAM-produced resin composite crowns on molars: A retrospective cohort study over four years.

PurposeEvaluation of the clinical performance of computer-aided design/computer-aided manufacturing-produced resin composite crowns (CAD/CAM composite crowns) on molars with a particular focus on placement location.MethodsA retrospective cohort study was performed based on the clinical records of patients with CAD/CAM composite crowns on molars (June 2016 to March 2021). The hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated based the Cox proportional hazard model to evaluate the effect of tooth location on complication type and occurrence. Covariates included crown location (maxilla/mandible, distalmost tooth/not distalmost tooth, and first molar/second or third molar) and endodontically treated (nonvital) or untreated (vital) tooth.ResultsOverall, 362 crowns were evaluated (mean follow-up: 378 days, median: 286 days), and 106 crowns (29.3%) showed complications, most frequently crown debonding. The cumulative success and survival rates were 70.9% and 93.7%, respectively, after 1 year and 49.5% and 86.5%, respectively, after 3 years. There was no significant difference in the HRs and log-rank tests in the Kaplan–Meier curves based on crown location parameters (P > 0.05). However, placement on vital teeth was associated with higher risks than on nonvital teeth (HR, 1.55; 95% CI, 1.03–2.23). In addition, the cement as a covariate yielded a high HR.ConclusionsThe location of CAD/CAM composite molar crowns is unlikely a risk factor for complications; therefore, these crowns can be clinically applied to all molars. However, the application of such molar crowns to vital teeth and the use of a cement other than adhesive resin cement present risks.

Four-year clinical evaluation of CAD/CAM indirect resin composite premolar crowns using 3D digital data: Discovering the causes of debonding.

To analyze the causes of debonding of computer-aided design/computer-aided manufacturing (CAD/CAM) indirect resin composite premolar crowns with a focus on the morphological factors of the crown and abutment teeth. The clinical courses of 109 CAD/CAM indirect resin composite crowns were observed, and the patients' background characteristics, crown locations, luting methods, types of abutments, distal-most/non-distal-most molars, and types of resin blocks were confirmed. To investigate the influence of the morphology of the crown and abutment teeth, the 1) vertical dimension of the abutment teeth, 2) taper, and 3) thickness of the crown occlusal surface during events were measured from the three-dimensional digital data. The Kaplan-Meier method and multivariable Cox proportional hazard model were used for the statistical analyses. The nonlinearity of the effect of each comparison factor was included in the model. Complications included 21 debonding cases, two crown fractures, five root fractures, and two core debondings. The cumulative no-debonding and no-crown-fracture rate over 1423 days (3 years and 11 months) was 77.4%. The multivariable Cox regression analysis revealed that the abutment teeth type of tooth (first or second premolar) (P = 0.02) and luting materials (P < 0.01) significantly influenced the debonding frequency. All morphological factors (1-3) significantly influenced the debonding. The hazard ratios and nonlinear graph indicated that the crown thickness was less effective than the vertical dimension and taper. The combination analysis of clinical outcomes and 3D digital data revealed that preparation of the abutment is important for avoiding crown debonding.

Clinical and basic research of CAD / CAM indirect resin composite crown：Establishment of Japanese original metal-free treatment

Clinical and basic research of CAD / CAM indirect resin composite crown：Establishment of Japanese original metal-free treatment

Effect of Printing Layer Thickness on the Trueness and Margin Quality of 3D-Printed Interim Dental Crowns

The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with milled crowns. The crowns were printed in 3 different layer thicknesses (20, 50, and 100 μm) by using a hybrid resin based on acrylic esters with inorganic microfillers or milled from polymethylmethacrylate (PMMA) discs and digitized with an intraoral scanner (test scans). The compare tool of the 3D analysis software was used to superimpose the test scans and the computer-aided design file by using the manual alignment tool and to virtually separate the surfaces. Deviations at different surfaces on crowns were calculated by using root mean square (RMS). Margin quality of crowns was examined under a stereomicroscope and graded. The data were evaluated with one-way ANOVA and Tukey HSD tests. The layer thickness affected the trueness and margin quality of 3D-printed interim crowns. Milled crowns had higher trueness on intaglio and intaglio occlusal surfaces than 100 μm-layer thickness crowns. Milled crowns had the highest margin quality, while 20 μm and 100 μm layer thickness printed crowns had the lowest. The quality varied depending on the location of the margin.

Trends, Characteristics, and Success Rates of Treatment for Severe Early Childhood Caries Under General Anesthesia: A Retrospective Study in Northwest China.

To retrospectively analyze the characteristics, tendencies, and success rates of dental treatments for severe early childhood caries (SECC) under general anesthesia (GA) in in northwest China. Children diagnosed with SECC were included in this retrospective study. From January 2015 to December 2018, they received dental treatment under GA at Affiliated Stomatology Hospital of Xi'an Jiaotong University. Demographic information, caries status and treatment characteristics were collected from electronic medical record system. Success rates of different treatments at 6-month and 12-month follow up were also analyzed. A total of 846 children (477 male, 369 female) received dental treatment under GA. The case number was increased from 148 in 2015 to 278 in 2018. There were 81.2% and 70.8% of the children participated the 6-month and 12-month follow up. SSC and pulpotomy was the most successful restorations and pulp therapy, with the success rate of 97.09% and 93.98% in 12-month follow up, respectively. The use of crown restorations (including composite resin crown and stainless steel crown) and pulp reservation therapies (including indirect pulp therapy and pulpotomy) were significantly increased while composite resin filling and pulpectomy decreased during 2015 to 2018. There has been an increasing demand for dental treatment under GA for children with SECC in northwest China, with a trend toward younger ages. With better clinical outcomes, crown restorations and pulp reservation therapies were the fastest-growing treatments under GA.