The Influence of Thickness on Light Transmission for Pre- and Fully Crystallized Chairside CAD/CAM Lithium Disilicate Ceramics.

AIM: This in vitro study aimed to compare the light-transmission properties of two chairside CAD/CAM lithium disilicate (LD) ceramics (a novel fully crystallized and a traditional pre-crystallized) across varying thicknesses. MATERIALS AND METHODS: One hundred flat specimens were obtained from precrystallized (e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein) and fully crystallized (LiSi GC Block; GC, Tokyo, Japan) LD at five different thicknesses (0.5, 0.75, 1.0, 1.50 and 2.0 mm). All specimens were polished with a polishing system for lithium disilicate restorations following recommendations from the manufacturer. Light transmission was evaluated with a radiometer. The statistical analysis between e.max CAD and LiSi GC Block was performed using a Mann-Whitney test for each thickness at a significance level of 0.05 (p < 0.05), followed by a Kruskal-Wallis test to compare the light transmission between the thicknesses of e.max CAD and LiSi GC Block. RESULTS: Light transmittance was significantly affected by ceramic thickness. The 0.5 mm thick specimens exhibited the highest transmittance values compared to all other groups, while a light transmittance of 0.00 was observed in the 2.0 mm thick specimens for both e.max CAD and LiSi GC Block. In the comparison between e.max CAD and LiSi GC Block according to thickness, there was a statistically significant difference exclusively between groups with a thickness of 1.50 mm (p = 0.002). CONCLUSIONS: Light transmission for pre- and fully crystallized CAD/CAM lithium disilicate ceramics only showed a statistical difference at the thickness of 1.50 mm (p = 0.002). E.max CAD demonstrated acceptable light transmission up to a thickness of 1.5 mm. CLINICAL SIGNIFICANCE: A thickness of 2 mm for chairside CAD/CAM lithium disilicate ceramics, whether pre-crystallized or fully crystallized, necessitates the use of dual-cure resin luting cement due to reduced light transmission.

Fracture resistance of chairside CAD-CAM lithium disilicate occlusal veneer with various designs after mechanical aging.

PURPOSE: This study evaluated the fracture resistance of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate crown, onlay, and non-anatomical occlusal veneer (A-OV) with and without margin fabricated. MATERIALS AND METHODS: Sixty-four CAD-CAM lithium disilicate restorations were designed as (1) complete coverage crown (CCC); (2) A-OV with margin; (3) non-A-OV with margin (NA-OV-M); and (4) non-A-OV without margin (NA-OV-NM), 16 of each. Restorations were crystallized and adhesively luted to resin dies using resin cement. Specimens were then subjected to 400,000 cycles of chewing in a mastication simulator. A universal testing machine was used to apply a compressive load at a crosshead speed of 1 mm/min to the long axis of the tooth with a stainless-steel sphere until fracture occurred. One-way ANOVA followed by post hoc tests were used to assess the impact of preparation design on the fracture load of CAD-CAM lithium disilicate restorations. RESULTS: The highest fracture load was recorded for CAD-CAM lithium disilicate indirect restorations for non-A-OVs preparation with margin (2549 ± 428 N) and onlay (2549 ± 293 N) and the lowest fracture load was recorded for CCCs (2389 ± 428 N); however, there was no significant (p = 0.640) between groups. CONCLUSIONS: CAD-CAM lithium disilicate restorations fabricated for anatomical and non-A-OV preparation display a fracture resistance similar to CCCs. Conservative partial coverage restorations may be considered an acceptable approach for posterior teeth.

The Effect of Die Material on the Crown Fracture Strength of Zirconia Crowns.

BACKGROUND: Determination of the eligibility of several tooth analog materials for use in crown fracture testing. METHODS: A standardized premolar crown preparation was replicated into three types of resin dies (C&B, low modulus 3D printed resin; OnX, high modulus 3D printed resin composite; and highest modulus milled resin composite). 0.8 mm zirconia crowns were bonded to the dies and the maximum fracture load of the crowns was tested. Twelve extracted human premolars were prepared to a standardized crown preparation, and duplicate dies of the prepared teeth were 3D printed out of C&B. Zirconia crowns were bonded to both the dies and natural teeth, and their fracture load was tested. RESULTS: There was no statistical difference between the fracture load of zirconia crowns bonded to standardized dies of C&B (1084.5 ± 134.2 N), OnX (1112.7 ± 109.8 N) or Lava Ultimate (1137.5 ± 88.7 N) (p = 0.580). There was no statistical difference between the fracture load of crowns bonded to dentin dies (1313 ± 240 N) and a 3D-printed resin die (C&B, 1156 ± 163 N) (p = 0.618). CONCLUSIONS: There was no difference in the static fracture load of zirconia crowns bonded to standardized resin dies with different moduli or between a low modulus resin die and natural dentin die.

Expediting the Rehabilitation of Severely Resorbed Ridges Using a Combination of CAD-CAM and Analog Techniques: A Case Report.

With the life expectancy increasing, there is a growing need for prosthetic dental treatments to restore the oral health, function, and quality of life of edentulous patients. Presently, only a few articles are available describing the oral rehabilitation of patients with severely resorbed ridges with milled complete dentures. This clinical case report provides a straightforward protocol consisting of a combination of analog and digital techniques for the rehabilitation of edentulous patients with severely resorbed ridges with milled fixed and removable complete dentures. This technique permits the minimization of the number of appointments, improves patient comfort, allows for the digital archiving of important clinical data, and permits the manufacture of prostheses with improved mechanical properties. These favorable outcomes were achieved by using the patient's existing PMMA complete denture as a custom tray for a final impression with light-bodied Polyvinylsiloxane. Subsequently, the resulting models were digitized, and a digital complete denture was designed and manufactured in an expedited manner using CAD-CAM techniques. Therefore, this case report highlights the potential of CAD/CAM technology to predictably restabilize oral functions and improve patients' quality of life.

The Effect of Restoration Thickness on the Fracture Resistance of 5 mol% Yttria-Containing Zirconia Crowns.

BACKGROUND: To determine what thickness of 5 mol% yttria zirconia (5Y-Z) translucent crowns cemented with different cements and surface treatments would have equivalent fracture resistance as 3 mol% yttria (3Y-Z) crowns. METHODS: The study included 0.8 mm, 1.0 mm, and 1.2 mm thickness 5Y-Z (Katana UTML) crowns and 0.5 and 1.0 mm thickness 3Y-Z (Katana HT) crowns as controls. The 5Y-Z crowns were divided among three treatment subgroups (n = 10/subgroup): (1) cemented using RMGIC (Rely X Luting Cement), (2) alumina particle-abraded then luted with the same cement, (3) alumina particle-abraded and cemented using a resin cement (Panavia SA Cement Universal). The 3Y-Z controls were alumina particle-abraded then cemented with RMGIC. The specimens were then loaded in compression at 30° until failure. RESULTS: All 5Y-Z crowns (regardless of thickness or surface treatment) had a similar to or higher fracture force than the 0.5 mm 3Y-Z crowns. Only the 1.2 mm 5Y-Z crowns with resin cement showed significantly similar fracture force to the 1 mm 3Y-Z crowns. CONCLUSION: In order to achieve a similar fracture resistance to 0.5 mm 3Y-Z crowns cemented with RMGIC, 5Y-Z crowns may be as thin as 0.8 mm. To achieve a similar fracture resistance to 1.0 mm 3Y-Z crowns cemented with RMGIC, 5Y-Z crowns must be 1.2 mm and bonded with resin cement.

Evaluation of Candida albicans Adherence to CAD-CAM Milled, 3D-Printed, and Heat-Cured PMMA Resin and Efficacy of Different Disinfection Techniques: An In Vitro Study.

PURPOSE: Candida albicans has been regarded as the most predominant oral fungal pathogen and the main cause of denture stomatitis. This study aimed to investigate C. albicans adherence to three types of denture base polymers: heat-cured polymethylmethacrylate (PMMA), CAD-CAM milled and 3D-printed. The efficacy of four common disinfection techniques, glutaraldehyde, brushing, microwave irradiation, and Polident overnight tablets, were also examined. MATERIAL AND METHODS: Sixty blocks of pink acrylic specimens were fabricated from each polymer group. To investigate the C. albicans adherence, as well as the efficacy of different disinfection techniques on removing the yeast from the different materials, specimens were cultured within the fungal culture overnight followed by disinfection. The adhered C. albicans on the materials were then obtained by vortexing in phosphate buffered saline (PBS), and the numbers of the yeast in the suspensions were evaluated by measuring the optical density and/or colony-forming units on agar plates. Data were expressed as mean ± SEM (standard error of the mean). Statistical differences were evaluated by one-way analysis of variance (ANOVA) followed by the post hoc Tukey HSD tests. RESULTS: Significant differences in C. albicans adherence to the three polymers were noted. CAD-CAM milled and heat-cured PMMA showed significantly less C. albicans adherence compared with 3D printed PMMA. No significant difference was noted between milled and heat-cured PMMA. In the disinfection test, microwave irradiation, mechanical brushing, and Polident tablets were found to be effective in removing fungal attachment on the different denture materials, while glutaraldehyde was found to be the least effective. CONCLUSION: C. albicans adherence to the polymers varies greatly based on the types of PMMA. 3D-printed had the highest fungal biofilm attachment. Microwave irradiation, mechanical brushing, and Polident overnight tablets had comparable results in removing C. albicans from all types of PMMA, while glutaraldehyde was not as effective.

Soft Tissue Management on Pontic and Implant Sites Before Implants Insertion.

Complex implant therapy can include methods requiring several phases of treatment, and they are usually referred to as one-stage and two-stage approaches. The reasons for the staged approach include the extraction of non-restorable teeth. Such a treatment approach may offer a fixed provisional prosthesis during implant osseointegration that enables the patient to avoid removable prostheses. However, this case aims to demonstrate how to manage the soft tissue in the pontic region prior to immediate implant placement. A 45- years old female patient presented with non-restorable teeth from the maxillary right lateral incisor to the left lateral incisor were removed, followed by socket preservation and fixed provisional restoration from right maxillary canine to left canine. Soft tissue was contoured to achieve ovate shape by first with a tooth-supported provisional restoration from the maxillary left canine to the right canine and then by re-shaping with carbide and diamond burs; after the tissue obtained the desired architecture, implants were inserted on sites of the maxillary right lateral incisor and left central lateral incisor without immediate loading, but the same provisional fixed restoration maintained the previously contour tissue. Once implant osseointegration was achieved, screw-retained provisional restoration was placed, followed by the definitive fixed implant restoration. Because the soft tissue was previously contoured, the screw-retained implant provisional restorations maintained the tissue architecture. These initial contouring procedures provided a more predictable outcome for the final tissue contour after implants were inserted. The final re-shaping with the implant screw-retained provisional restorations was minimum, and prostheses followed the previously provided tissue architecture. Before the endosteal implants are inserted, soft-tissue contouring prior to implant placement may provide a more predictable outcome of the final tissue architecture for pontic and implant areas. The patient and clinician can evaluate the success and limitations of tissue contouring prior to implant placement. It may also shorten the time required for tissue contouring with provisional implant restorations.

A Multidisciplinary Approach to Congenitally Missing Central Incisors: A Case Report.

Hypodontia is one of the most common developmental problems of human dentition. The treatment of missing maxillary central incisors is always a challenging task, often requiring a multidisciplinary approach. This case report describes such a multidisciplinary approach for a female patient with congenitally missing maxillary central incisors and class II division 1 occlusion. Significant horizontal overlap was present with class II division 1 occlusion in a patient with a history of cleft palate. Implant therapy was thereby not an option. Orthodontic treatment was provided to decrease the horizontal overlap and reposition the teeth. Esthetic crown lengthening was performed and monolithic lithium disilicate crowns were placed. Critical analysis of the treatment plan through cooperation among specialists is required to obtain the ideal result. Orthodontic treatment may be necessary to close or gain more space, followed by implant placement (if acceptable), and restorative treatment. It is important to create the treatment plan through a multidisciplinary approach involving orthodontists, surgeons, and restorative specialists before initiating treatment.

Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) Complete Dentures for Atrophic Alveolar Ridges: Workflow Combining Conventional and Novel Techniques.

Extreme residual ridge resorption is a challenging clinical situation for the fabrication of complete dental prostheses. Computer-aided design and computer-aided manufacturing (CAD/CAM) complete dentures have been shown to have superior fit and material strength to conventionally fabricated dentures, but no clinical protocols have been described for cases of extreme residual ridge resorption. This report describes a workflow combining conventional and novel techniques for CAD/CAM complete dentures fabrication for atrophic alveolar ridges and demonstrates that a CAD/CAM workflow is an effective tool for solving this complex situation.

Esthetic outcome for implant therapy of a maxillary lateral incisor using prefabricated titanium and customized zirconia abutments: 4-year clinical reports.

The reported clinical scenarios presented two patients, one managed with a prefabricated abutment and the other with a customized abutment, and both patients were pleased with the outcome. However, from a professional viewpoint, the esthetic outcome using the custom zirconia abutment was superior to that using the prefabricated titanium abutment.

Two-year clinical trial of a universal adhesive in total-etch and self-etch mode in non-carious cervical lesions.

OBJECTIVES: To compare the clinical performance of Scotchbond™ Universal Adhesive used in self- and total-etch modes and two-bottle Scotchbond™ Multi-purpose Adhesive in total-etch mode for Class 5 non-carious cervical lesions (NCCLs). METHODS: 37 adults were recruited with 3 or 6 NCCLs (>1.5mm deep). Teeth were isolated, and a short cervical bevel was prepared. Teeth were restored randomly with Scotchbond Universal total-etch, Scotchbond Universal self-etch or Scotchbond Multi-purpose followed with a composite resin. Restorations were evaluated at baseline, 6, 12 and 24 months for marginal adaptation, marginal discoloration, secondary caries, and sensitivity to cold using modified USPHS Criteria. Patients and evaluators were blinded. Logistic and linear regression models using a generalized estimating equation were applied to evaluate the effects of time and adhesive material on clinical assessment outcomes over the 24 month follow-up period. Kaplan-Meier method was used to compare the retention between adhesive materials. RESULTS: Clinical performance of all adhesive materials deteriorated over time for marginal adaptation, and discoloration (p<0.0001). Both Scotchbond Universal self-etch and Scotchbond Multi-purpose materials were more than three times as likely to contribute to less satisfying performance in marginal discoloration over time than Scotchbond Universal total-etch. The retention rates up to 24 months were 87.6%, 94.9% and 100% for Scotchbond Multi-purpose and Scotchbond Universal self-etch and total-etch, respectively. CONCLUSIONS: Scotchbond Universal in self- and total- etch modes performed similar to or better than Scotchbond Multipurpose, respectively. CLINICAL SIGNIFICANCE: 24 month evaluation of a universal adhesive indicates acceptable clinical performance, particularly in a total-etch mode.

A comparison of retention characteristics in prefabricated and custom-cast dental attachments.

PURPOSE: The aim of this in vitro study was to investigate the retention characteristics of attachments fabricated by machine milling or by custom casting. In addition, the retention of reduced dimension attachments was also evaluated. MATERIALS AND METHODS: Three types of ERA matrices, one prefabricated and two cast, were used. Ten specimens were made for each type, and white nylon patrices were transferred to denture bases. Tests were performed at a crosshead speed of 0.2 in/min with an Instron machine. The dislodging force at baseline, 100, 200, 300, 400, 500, and subsequently after every 500 pulls up to 2500 pulls were measured. ANOVA and Student's t-test were used to analyze the measurements. RESULTS: All three groups showed no difference at the baseline, but the cast groups showed greater variation within group. The prefabricated group showed higher retention after 200 pulls. Decreased-dimension attachments have no significant difference when compared to the cast regular dimension group after 400 pulls. CONCLUSION: The prefabricated attachments had superior retention than the cast groups over time. Reduced dimension did not reduce the retention when compared to the cast group.