Lost-wax or laser sintering? Findings on marginal and internal adaptation of metallic copings

Marginal and internal adaptation are parameters of crucial importance to the success of prosthetic crowns. Automatized process creates an expectative of superior or equivalent results compared to restorations manufactured ​​by conventional lost-wax technique. The purpose of this study was to evaluate the marginal adaptation and internal adaptation (cement space) of metal-ceramic crown copings produced by lost-wax (LW) and direct metal laser sintering (DMLS) techniques. An artificial lower first molar was prepared for a full crown, duplicated in plaster and scanned. Twenty metal-ceramic crown copings were fabricated in cobalt-chromium by the two techniques (n=10). The copings were filled with low viscosity silicone and seated on the prepared tooth, resulting in a replica of the internal space. The pellicle formed was embedded in heavy body silicone, sectioned and captured by means of a stereomicroscope at 50x magnification, according to replica technique (RT). Shapiro-Wilk test followed by Holm-Sidak test were used for statistical analysis (α=.05). Marginal adaptation presented no difference between LW (101.5 ± 41.6) and DMLS (86.3 ± 39.9) groups (p=0.24). Conventional LW technique showed significantly lower occlusal (p<0.008) and axial spaces (p<0.03). Measurements of all regions showed numerically larger adaptation values than that defined during design​​ for DMLS group. Both the LW technique and the DMLS technique are within the clinically acceptable.

Use of fiberglass CAD-CAM post-and-core for rapid orthodontic extrusion of anterior tooth – Case Report

This report describes the restoration of an anterior fractured tooth with a fiberglass CAD-CAM post-and-core followed by rapid orthodontic extrusion. The post space was prepared, the post-and-core was luted and a interim crown was luted to allow the tooth extrusion through the use of orthodontic buttons and elastic rubber bands. A lithium disilicate glass-ceramic crown was luted and the case was followed up after 6 and 12 months.

Endodontically Treated Maxillary Premolars Restored with Glass Fiber Post under All Ceramic Crown

Glass fiber posts and core are increasingly used in order to restore severely damaged endodontically treated teeth and particularly maxillary premolars that are prone to fracture. Their low modulus of elasticity which is similar to that of dentin allows the post to absorb stress and prevent root fracture. In addition, the glass fiber posts provide a natural hue by integrally bonding to the composite, thereby improving the aesthetics without compromising much on the strength. Various factors are involved in the longevity of such treatment option, remaining tooth structure seems to be the most important. Key words: glass fiber posts, premolars, endodontically treated teeth, composite resin, fracture resistance, crown, ferrule, failure .

Aesthetic Rehabilitation of Anterior Incisor: Post and core treatment –A Case Report

This case report describes the post and core treatment of a maxillary central incisor. An 18-year-old female patient reported to the Department of Conservative Dentistry and Endodontics with the chief complaint of pain in upper front tooth region. On clinical examination, there was Ellis class III fracture resulting in loss of significant tooth structure necessitating post and core treatment. Treatment was initiated with removal of carious region, canal was located, working length was established followed by chemo mechanical preparation and obturation. Post space preparation was done in the canal followed by post cementation and core build up. Keywords: Post, core, ceramic, crown lengthening.

In Vitro Investigations in a Biomimetic Approach to Restore One-Piece Zirconia Implants

The objective of this study was to evaluate the fracture load and retention force of different bonding systems while restoring one-piece zirconia implants with a novel cementation approach using a mesostructure. Polymer-infiltrated ceramic mesostructures (n = 112) were therefore designed as caps on the implant abutment, and a molar feldspathic ceramic crown was constructed on top of it as a suprastructure. For cementation, different bonding systems were used. Fracture load and retention force were measured immediately after storage in water at 37 °C for 24 h (n = 8) as well as after artificial aging in a chewing simulator and subsequent thermal cycling (n = 8). Combined restorations showed higher fracture load compared to monolithic restorations of polymer-infiltrated ceramic (n = 8) or feldspathic ceramic (n = 8) identical in shape. However, the fracture load of the combined restorations was significantly affected by aging, independent of the primers and cements used. Restorations cemented with primers containing methyl methacrylate and 10-methacryloyloxydecyl dihydrogen phosphate exhibited the highest retention force values. Aging did not affect the retention force significantly. Similar fracture load values can be expected from combination restorations when compared with monolithic crowns.

Microdontia treatment with orthodontics and indirect restoration: clinical case

Objective: This case report aims to present the microdontia treatment of tooth 35 through pre-prosthetic orthodontics, followed by re-anatomization with an indirect restoration. Case report: A 21-year-old female patient presented with microdontia in tooth 35, with a distalized and vestibularized crown. In addition, tooth 34 was gyroverted with mesial diastema. Orthodontic mechanics with segmented arch were used to centralize tooth 35 in the alveolar ridge, close the diastema in the mesial of tooth 34, and correct its gyroversion. For lingualization of tooth 35, a first-order fold (in set) was performed, and for mesialization, an open-coil spring was used between teeth 35 and 36. A closed-coil spring was used to delimit the movement of tooth 35 to mesial. The force applied by the open spring for mesialization of tooth 35 was transmitted to tooth 34, through the closed spring, resulting in its mesialization; this, closed the diastema between teeth 33 and 34 and corrected the gyroversion. Subsequently, the coronary preparation was performed with diamond tips 1014 and 3146, and confection of the temporary crown in acrylic resin. For the ceramic system, IPS™ e.max Press was used. The ceramic crown was luting using the adhesive technique, followed by light curing for 40 seconds on each face of the tooth. Conclusion: It can be concluded that the re-anatomization of a small tooth should be the first treatment option. However, pre-prosthetic orthodontic treatment may be necessary.

Comparative Stress Evaluation between Bilayer, Monolithic and Cutback All-Ceramic Crown Designs: 3D Finite Element Study

Different all-ceramic crown designs are available to perform indirect restoration; however, the mechanical response of each model should still be elucidated. The study aims to evaluate the stress distribution in three different zirconia crown designs using finite element analysis. Different three-dimensional molar crowns were simulated: conventional bilayer zirconia covered with porcelain, a monolithic full-contour zirconia crown, and the cutback modified zirconia crown with porcelain veneered buccal face. The models were imported to the computer-aided engineering (CAE) software. Tetrahedral elements were used to form the mesh and the mechanical properties were assumed as isotropic, linear and homogeneous materials. The contacts were considered ideal. For the static structural mechanical analysis, 100 N occlusal load was applied and the bone tissue was fixed. Maximum principal stress showed that the stress pattern was different for the three crown designs, and the traditional bilayer model showed higher stress magnitude comparing to the other models. However, grayscale stress maps showed homogeneous stress distribution for all models. The all-ceramic crown designs affect the stress distribution, and the cutback porcelain-veneered zirconia crown can be a viable alternative to adequate function and esthetic when the monolithic zirconia crown cannot be indicated.

Effect of proximal box elevation on fracture resistance and microleakage of premolars restored with ceramic endocrowns

Background Restoration of endodontically treated premolar is in high risk for biomechanical failure, and often presents with subgingival margins. Proximal box elevation (PBE) has been used to relocate subgingival cavity outlines. Objective To evaluate the influence of PBE on fracture resistance and gingival microleakage of premolars with endodontic access cavities following ceramic endocrown. Methods Eighty sound maxillary premolars with standardized Class II cavities on mesial surfaces were randomly assigned to four groups (n = 20 in each group). Groups E1, E2 and E3, with proximal margins located in dentin/cementum, 2 mm below the cemento-enamel junction (CEJ), simulated subgingival location. Group E4 (supragingival group), with proximal margins located in enamel, 1 mm above the CEJ, was used as the positive control. For margin elevation of the proximal cavities, bulk-fill Smart Dentin Replacement (SDR), a visible light cured resin composite, was applied in group E1, and conventional resin composite (3M Z350 XT, a light-activated composite) was placed in group E2. Group E3 was only treated with a ceramic crown and served as the negative control. In all groups, computer-aided design (CAD) ceramic endocrowns were adhesively inserted, and fracture resistance, failure mode and microleakage were evaluated. Results A higher fracture resistance value was observed in PBE groups E1 and E2, regardless of the materials used (P = 0.038, and 0.010, respectively, vs E3), and fracture resistance in group E1 was higher than that in group E2. In teeth without PBE, the percentage of catastrophic failures reached 70%. Compared to group E3, a lower frequency distribution of microleakage was detected in supragingival group E4 (P = 0.031). No increased percentage of microleakage was observed in groups treated with PBE. Conclusion For endodontically treated maxillary premolars restored with ceramic endocrowns, PBE increases fracture resistance but not microleakage.