A diagnostically and digitally driven tooth preparation protocol by using a patient monitoring tool with an intraoral scanner.

Finding the right balance between the preservation of tooth structure and providing adequate space for the restorative material is a major challenge in prosthetic dentistry. A technique is presented using the patient monitoring tool available in standard software programs of an intraoral scanner to constantly monitor preparation dimensions in relation to the optimal definitive restoration.

A digital protocol for the fabrication of anatomic-contour implant zirconia crowns directly screwed on external hexagonal implant connections without the interposition of a Ti-base component.

A straightforward and effective restorative option is proposed for implant-supported fixed prostheses with external connections by using monolithic zirconia without the interposition of a Ti-base component. The technique is based on a modification of the Brånemark connection used to link metal-ceramic or metal-composite resin restorations directly to the implant.

Survival analysis up to 7 years of 621 zirconia monolithic single crowns with feather-edge margins fabricated with a cast-free workflow starting from intraoral scans: A multicentric retrospective study.

STATEMENT OF PROBLEM: Clinical studies on the fabrication of monolithic zirconia restorations with a feather-edge tooth preparation from digital scans and a cast-free fully digital workflow are lacking. PURPOSE: The purpose of this retrospective multicentric study in private practices was to evaluate the outcomes of monolithic zirconia crowns fabricated with feather-edge margins and a cast-free approach. MATERIAL AND METHODS: A total of 621 teeth were prepared with feather-edge margins and restored with monolithic zirconia crowns fabricated with a fully digital cast-free workflow. Data were analyzed by using the Kaplan-Meier test and descriptive statistics. The clinical evaluation adopted the California Dental Association-modified criteria after recalling all patients between April and July 2021. RESULTS: The clinical survival of 619 of 621 crowns, including recemented crowns placed in 427 patients (217 men, 220 women) over 5 years (2014 to 2019 with crowns in service between 12 and 85 months), was analyzed. The 2 excluded crowns were delivered to patients who dropped out of the study. Of the 619 crowns, 5 failed during the follow-up period: 4 teeth were extracted because of fracture and 1 restoration fractured. No other technical or biological failures were observed. The mean overall survival time was 84.4 months (standard error, 0.255; 95% confidence interval for the mean, 83.92 to 84.92). The overall survival probability was 99.1% up to 85 months. CONCLUSIONS: The clinical outcomes of the monolithic zirconia crowns with feather-edge margins evaluated were comparable with outcomes reported using other margin designs and materials.

Durability and Weibull Characteristics of Lithium Disilicate Crowns Bonded on Abutments with Knife-Edge and Large Chamfer Finish Lines after Cyclic Loading.

PURPOSE: The aim of this study was to evaluate the durability of lithium disilicate crowns bonded on abutments prepared with two types of finish lines after long-term cyclic loading. MATERIALS AND METHODS: Pressed lithium disilicate all-ceramic molar crowns were bonded (Variolink II) to epoxy abutments (height: 5.5 mm, Ø: 7.5 mm, conicity: 6°) (N = 20) with either knife-edge (KE) or large chamfer (LC) finish lines. Each assembly was submitted to cyclic loading (1,200,000×; 200 N; 1 Hz) in water and then tested until fracture in a universal testing machine (1 mm/min). Failure types were classified and further evaluated under stereomicroscope and SEM. The data (N) were analyzed using one-way ANOVA. Weibull distribution values including the Weibull modulus (m), characteristic strength (0), probability of failure at 5% (0.05), 1% (0.01), and correlation coefficient were calculated. RESULTS: Type of finish line did not significantly influence the mean fracture strength of pressed ceramic crowns (KE: 1655 ± 353 N; LC: 1618 ± 263 N) (p = 0.7898). Weibull distribution presented lower shape value (m) of KE (m = 5.48; CI: 3.5 to 8.6) compared to LC (m = 7.68; CI: 5.2 to 11.3). Characteristic strengths (0) (KE: 1784.9 N; LC: 1712.1 N) were higher than probability of failure at 5% (0.05) (KE: 1038.1 N; LC: 1163.4 N) followed by 1% (0.01) (KE: 771 N; LC: 941.1 N), with a correlation coefficient of 0.966 for KE and 0.924 for LC. Type V failures (severe fracture of the crown and/or tooth) were more common in both groups. SEM findings showed that fractures occurred mainly from the cement/ceramic interface at the occlusal side of the crowns. CONCLUSION: Lithium disilicate ceramic crowns bonded onto abutment teeth with KE preparation resulted in similar fracture strength to those bonded on abutments with LC finish line. CLINICAL SIGNIFICANCE: Pressed lithium disilicate ceramic crowns may not require invasive finish line preparations since finish line type did not impair the strength after aging conditions.

Survival Analysis up to 8 Years of 304 Anatomic-Contour Implant Zirconia Crowns Fabricated with a Fully Digital Cast-Free Workflow and Directly Screwed on External Hexagonal Implant Connections without the Interposition of a Ti-Base: A Multicentric Retrospective Study.

STATEMENT OF PROBLEM: Data on the clinical performance of monolithic Zirconia screw-retained crowns on external hexagon implants fabricated from digital scans through a cast-free, fully digital workflow is lacking and needs to be included. PURPOSE: This retrospective multicentric study aimed to evaluate the real-life clinical results of monolithic Zirconia screw-retained crowns without the interposition of a Ti-base on external hexagon implants fabricated from intraoral scans and a cast-free approach in private practices. MATERIALS AND METHODS: Single external hex implant fixtures were restored with monolithic zirconia crowns without the interposition of a Tibase. The crowns were directly screwed on external hexagonal implant connections with a castfree, fully digital workflow. Data were analyzed using descriptive statistics and the Kaplan- Meier test. Between September 2022 and March 2023, the California Dental Association modified criteria were adopted for clinical evaluation after recalling all patients. RESULTS: A total of 304 single tooth restorations in the maxillary and mandibular posterior regions fabricated between July 2014 and July 2022 in 252 patients (120 males and 132 females, mean age 53.6 years, SD 23.3). Seven crowns were excluded because of patient dropout. The most common minor technical complications were screw loosening (3 crowns) and loss of the screw-access hole filling (3 crowns). Four failures included two implant failures with mobility and two fractured crowns. No screw or implant fractures were recorded. The overall cumulative survival rate was 98.6% and the average success rate (crowns experiencing no failures or complications) was 96.0%. The mean overall survival time was 101.3 months (standard error, 0.847; 95% confidence interval for the mean, 99.67-102.99). The overall survival probability was 87.9% up to 97 months. CONCLUSIONS: With careful case selection and comprehensive periodontal maintenance program, single crowns directly screwed onto an external hexagon platform have shown to have excellent survival and success (complication-free) rates, comparable to available data regarding single crowns with a metal implant- prosthetic interface.

A modified scan technique for multiple abutment teeth using the trim and lock function.

OBJECTIVES: To describe a new protocol for digital scanning of multiple abutment teeth using the trim and lock software tools. METHODS: A reverse workflow technique was used. Scanning was performed with the interim restoration in position. The abutment teeth were then trimmed from the scan. The retraction cord or interim restoration from either the first mesial or distal abutment tooth was removed and only that tooth was scanned, allowing the dentist to easily manage gingival displacement and keep the tooth dry from crevicular fluid and saliva. Consequently, the preparation margin remained visible and uncontaminated during the scan. The adjacent abutment teeth detected in the scan were deleted from it, and the scan was then locked using a tool of the scanning software. Next, the retraction cord or interim restoration of the next abutment tooth was removed, and only that tooth was scanned. The procedure was repeated until all prepared teeth were individually scanned. RESULTS: The technique presented here facilitated the scanning of multiple abutment teeth in a simple and predictable way by utilizing the trim and lock surface tools of the scanning software and helped in avoiding closure of the gingival crevice. CONCLUSIONS: Splitting the scan for a complex case with multiple abutment teeth allows reliable 3D acquisition of the finish line of each abutment tooth. Therefore, this technique simplifies the full-arch intraoral scanning process and can improve treatment efficiency. CLINICAL SIGNIFICANCE: The trim and lock tool allows scanning of each prepared abutment tooth separately, transforming a full-arch impression into multiple single scans. This technique helps to easily manage gingival displacement and maintain an uncontaminated and dry preparation margin during the scan.

Bonding lithium disilicate ceramic to feather-edge tooth preparations: a minimally invasive treatment concept.

PURPOSE: To report the short-term clinical outcome of a new minimally invasive prosthetic approach utilizing monolithic lithium-disilicate full crowns bonded to feather-edge tooth preparations. MATERIALS AND METHODS: 235 teeth, 136 anterior and 99 posterior, requiring a full crown were prepared with a feather-edge finish line providing a minimum space on the vertical walls of 0.3 mm at the margin, 0.5 mm along the axial walls, and an occlusal space of 1 to 1.5 mm to ensure sufficient resistance of the restoration. The dental technician manufactured the monolithic restorations using either CAD-CAM or pressed technology. The restorations were individualized with a staining technique to obtain the necessary esthetic characterization and bonded to the natural abutments using an adhesive cementation procedure. RESULTS: Out of 235 treated elements, only one monolithic restoration in a molar position fractured after 3 years of service. No biological or technical complications were observed. The final esthetic result was optimal. CONCLUSION: This procedure can be considered a further option for the conservative restorative treatment of single elements where a full crown is required.

Minimally invasive vertical preparation design for ceramic veneers: a multicenter retrospective follow-up clinical study of 265 lithium disilicate veneers.

The esthetic treatment of the anterior teeth has always presented a challenge in clinical practice. With the improvement of dental materials, many restorative options such as resin composites, all-ceramic crowns, and ceramic veneers have become available. The current challenge in reconstructive dentistry is how to obtain excellent esthetic results while preserving the biological structures involved as much as possible. Thanks to the introduction of high-strength etchable dental ceramics, clinicians and technicians now have materials and procedures at their disposal that allow for the restoration of esthetics and function through a minimally invasive approach. New-generation, all-ceramic restorations and adhesive systems allow greater preservation of residual hard tooth structures, especially with regard to single elements. PURPOSE: To evaluate the clinical performance of lithium disilicate (LiDiSi) veneers with a feather-edge finish line margin. MATERIALS AND METHODS: A total of 265 LiDiSi veneers were cemented with resin cement after fluoridric acid and silane surface treatment and observed by different clinicians. These veneers were placed in 53 (32 female, 21 male) patients between October 2009 and April 2015, with a mean observation period of 54.4 months. Of these, 211 veneers were placed in the maxilla (77 central incisors, 65 lateral incisors, 49 canines, 12 first bicuspids, 5 second bicuspids, 2 first molars, 1 second molar), and 54 in the mandible (16 central incisors, 14 lateral incisors, 13 canines, 6 first bicuspids, 1 second bicuspid, 2 first molars, 2 second molars). The clinical evaluation used the modified California Dental Association (CDA) and Ryge criteria after recalling all patients between January and March 2017. The clinical parameters evaluated were color matching, quality of the ceramic surface, the presence of marginal discoloration, and marginal integrity. The data were analyzed through descriptive statistical analysis. RESULTS: The clinical survival of the 265 veneers over the follow-up period was 99.63%. One restoration showed adhesive failure due to a traumatic event after 3 years of clinical service. The color matching parameter was classified as Alfa in 93.9% (248/265) and Bravo in 6.4% (17/265) of the restorations, with no Charlie or Delta ratings recorded. The ceramic surface was rated as Alfa in 97.7% (259/265) and Bravo in 2.2% (6/265), marginal discoloration as Alfa in 97.3% (257/265) and Bravo in 3% (8/265), and marginal integrity as Alfa in 96.9% (256/265) and Bravo in 3.4% (9/265) of the restorations. CONCLUSION: In this retrospective analysis, LiDiSi veneers with a vertical finish line showed good clinical performance in terms of color matching, ceramic surface, marginal discoloration, and marginal integrity. Despite the present results, further clinical studies are needed in order to investigate the long-term performance of this type of restoration.

Monolithic lithium disilicate complete single crowns with feather-edge preparation design in the posterior region: A multicentric retrospective study up to 12 years.

OBJECTIVE: This retrospective study evaluated the clinical success and survival of monolithic lithium disilicate single crowns in the posterior region fabricated with feather-edge margins and cemented with resin-based self-etching cement. METHOD AND MATERIALS: In total, 627 pressed monolithic lithium disilicate restorations on posterior teeth (110 first premolars, 151 second premolars, 240 first molars, 121 second molars, 5 third molars) were placed in 335 patients. All teeth were prepared with feather-edge margins and restored with single crowns. The modified California Dental Association criteria were used to clinically evaluate subjects during regular maintenance recalls. RESULTS: The mean follow-up time was 48.17 months (SD, 27.7; range, 6 to 144). Nine crowns were replaced during the follow-up period due to bulk fracture of the material (overall 97.93% survival rate), and four teeth were extracted. No other technical or biologic failure was observed. CONCLUSION: In this retrospective evaluation, monolithic lithium disilicate crowns with feather-edge margins yielded clinical outcomes similar to those reported with other margin designs and materials. Following the same clinical protocol, crowns on second molars showed lower survival rates when compared to restorations on other teeth in the posterior region. Careful evaluation is mandatory in high-risk patients and terminal teeth. Alternative restorative materials, such as full-contour zirconia crowns, should be considered for the restoration of second molars.

Minimally invasive vertical preparation design for ceramic veneers.

The esthetic treatment of anterior teeth has always presented a challenge in clinical practice. With the improvement of dental materials, many restorative options such as composite resins, all-ceramic crowns, and ceramic veneers have become available. The current challenge in reconstructive dentistry is to obtain excellent esthetic results while preserving the biological structures involved as much as possible. Thanks to the introduction of high-strength etchable dental ceramics, clinicians and technicians have materials and procedures at their disposal that allow them to restore esthetics and function through a minimally invasive approach. New-generation all-ceramic restorations and adhesive systems allow a greater preservation of residual hard tooth structures, especially with regard to single elements. This article describes a vertical preparation technique for ceramic veneers.

Rehabilitation of severely eroded dentition utilizing all-ceramic restorations.

Tooth wear is becoming an increasing concern, particularly in younger patients. Clinicians will increasingly encounter such problems as more natural teeth are retained into older age and patients' aesthetic demands and expectations rise. The use of all-ceramic restorations has increased due to the materials' natural appearance and strength. This, together with the new generation of resin cements, allows the provision of predictable single-unit restorations. This article reviews the etiology of erosion, which currently appears to be a primary contributor to tooth wear. Aesthetic treatment of a patient is also presented using all-ceramic restorations.

Clinical flexibility of the metal free approach.

The present possibility of defining a plan for reconstructive treatment taking into consideration metal-free materials and related clinical procedures offers wider therapeutic options for the clinician and the dental technician, establishing function, esthetics and longevity in prosthetic rehabilitation. The metal-free approach may be regarded as a new philosophy of treatment that extends beyond the solution of esthetic and cosmetic shortcomings in the anterior regions and involves a greater variety of complex clinical cases such as periodontal breakdown conditions and edentulous sites requiring implant therapies with varying degrees of difficulty. Nevertheless, as the use of new metal-free materials is such a recent introduction, there is insufficient long-term evaluation and scientific support available for these to be accepted as an established treatment option. This article presents two complex prosthetic rehabilitations showing the applicability of the metal-free approach to different clinical conditions including, as well as healthy sites, various patterns of periodontal disease and edentulism.

The metal-free approach to restorative treatment planning.

Considerable developments in the area of metal-free restorations--in response to increasing esthetic demands from patients--are offering the clinician and dental technician new therapeutic paths to follow when performing restorative treatments. Effective and reliable high-strength ceramic systems, suitable for anterior and posterior sites, may allow the achievement of predictable esthetics and function. Along with the evident indications for the treatment of anterior compromised elements, these types of restorations may be used in a wider variety of clinical cases, including complex prosthetic rehabilitations. Appropriate usage of different materials according to the specific clinical situation is mandatory for long-lasting, functional, and esthetic results. Therefore, a thorough application of metal-free restorations may be considered a "metal-free approach", which includes a specific formulation of treatment planning. In this article, the different materials, selection criteria, clinical indications, and benefits are evaluated, with a particular regard for treatment planning.