Masking capacity of minimally invasive lithium disilicate restorations on discolored teeth-The impact of ceramic thickness, the material's translucency, and the cement color.

OBJECTIVES: To evaluate minimally invasive restorations' capacity to mask discolored teeth and explore the impact of ceramic thickness, translucency, and cement color. MATERIALS AND METHODS: Twenty-four assessment pairs of naturally colored and discolored bovine dentin samples were formed, using lithium disilicate specimens in six different thicknesses (0.3-0.8 mm), two different translucencies (high, low), and two cements (transparent, tooth-colored). Evaluators assessed the color differences in each assessment pair, and the threshold for detecting a color difference was determined using sequential testing and the Bonferroni-Holm method. RESULTS: A thickness of 0.6 mm effectively masked color differences using high translucent ceramic with transparent cement, detectable differences were still observed at 0.7/0.8 mm. A threshold thickness of 0.4 mm was seen using high translucent ceramic and tooth-colored cement, with color differences still discernible at 0.5 and 0.8 mm. A threshold thickness of 0.4 mm was detected using low translucent ceramic and transparent cement, while detectable differences persisted at 0.5, 0.7, and 0.8 mm. A 0.5 mm threshold thickness was observed when using low translucent ceramic and tooth-colored cement, and no detectable color differences were detected beyond this thickness. CONCLUSIONS: Masking can be achieved with a thickness of 0.4-0.5 mm using a low translucent material and tooth-colored cement. CLINICAL SIGNIFICANCE: Understanding the impact of ceramic thickness, translucency, and cement color can aid clinicians in making informed decisions for achieving the best esthetic outcomes while preserving tooth structure. Effective masking can be accomplished with ceramic thicknesses starting at 0.4 mm, especially when employing a low translucent material and tooth-colored cement. However, clinicians should be aware that discolorations may still be detectable in certain scenarios when using minimally invasive lithium disilicate restorations.

Additively and subtractively manufactured implant-supported fixed dental prostheses: A systematic review.

AIM: To compare and report on the performance of implant-supported fixed dental prostheses (iFDPs) fabricated using additive (AM) or subtractive (SM) manufacturing. METHODS: An electronic search was conducted (Medline, Embase, Cochrane Central, Epistemonikos, clinical trials registries) with a focused PICO question: In partially edentulous patients with missing single (or multiple) teeth undergoing dental implant therapy (P), do AM iFDPs (I) compared to SM iFDPs (C) result in improved clinical performance (O)? Included were studies comparing AM to SM iFDPs (randomized clinical trials, prospective/retrospective clinical studies, case series, in vitro studies). RESULTS: Of 2'184 citations, no clinical study met the inclusion criteria, whereas six in vitro studies proved to be eligible. Due to the lack of clinical studies and considerable heterogeneity across the studies, no meta-analysis could be performed. AM iFDPs were made of zirconia and polymers. For SM iFDPs, zirconia, lithium disilicate, resin-modified ceramics and different types of polymer-based materials were used. Performance was evaluated by assessing marginal and internal discrepancies and mechanical properties (fracture loads, bending moments). Three of the included studies examined the marginal and internal discrepancies of interim or definitive iFDPs, while four examined mechanical properties. Based on marginal and internal discrepancies as well as the mechanical properties of AM and SM iFDPs, the studies revealed inconclusive results. CONCLUSION: Despite the development of AM and the comprehensive search, there is very limited data available on the performance of AM iFDPs and their comparison to SM techniques. Therefore, the clinical performance of iFDPs by AM remains to be elucidated.

Solving Challenges in Static Computer-Assisted Guided Surgery for Posterior Open-End Situations.

This technical note serves as a practical guide for clinicians aiming to provide solutions to optimize the precision of static computer-assisted implant surgery (sCAIS) and the success of implant placement in free-end situations. Five methods are introduced for enhancing surgical guide stabilization and improving the accuracy of implant placements in situations lacking stabilizing adjacent teeth. Techniques include the use of keratinized soft tissues, implant-borne stabilizers, lateral fixation pins, transitional implants, and digital bone segmentation for guide support. Each method is evaluated for its potential to address the specific challenges faced in sCAIS, aiming to contribute to the field through practical solutions for clinicians.

Computer-Assisted Implant Planning: A Review of Data Registration Techniques.

Computer-assisted implant planning allows for a comprehensive treatment plan by combining radiographic data provided by a Cone Beam Computed Tomography (CBCT) with surface optical scan (IOs) data that includes patient intraoral situation and the intended restorative planning. Integrating a tailored restorative design with the patient's anatomical conditions through virtual implant planning allows for an ideal bio-restorative treatment planning to maximize biological, functional, and esthetic outcomes. This article discusses dataset registration techniques that combine radiographic CBCT data with restorative information as the main path to create a virtual patient. The described techniques include the use of removable radiographic templates with radiopaque markers, dual scan technique, and direct digital file registration of intra-oral scans using anatomical references. Depending on the individual clinical situation, different factors must be considered to appropriately select methods that achieve an optimal registration of diverse datasets. An inherent challenge lies in the presence of scattering artifacts in CBCT scans. Two approaches are proposed for these situations - the use of chairside-fabricated composite resin markers or adhesive spot-markers fabricated for the use with CBCT scans. Both techniques exhibit limitations that need to be taken into consideration. Further approaches should be developed for situations involving scattering in CBCT.

The Capacity to Change the Lightness of Discolored Tooth Substrates by Means of Minimally Invasive Restorations: Perception by Dentists, Dental Technicians, and Laypersons

PURPOSE: To evaluate the minimal ceramic thickness needed to increase the lightness by one value by means of glass-ceramic restorations perceived by dental technicians, dentists, and laypersons. MATERIAL AND METHODS: A total of 15 assessment pairs (reference and test samples) were formed using glass-ceramic blocks in four different colors. Each assessment pair was comprised of two underground blocks differing in one value of lightness. On top of the underground blocks, glass-ceramic platelets were cemented in five different thicknesses (0.1 to 0.5 mm) and in the same color as the reference. Dental technicians, dentists, and laypersons (n = 41/group) were asked to determine the presence of a color difference between the two samples under standardized lighting conditions. The threshold ceramic thickness was defined as the thickness at which ≥ 50% of the evaluators were not able to perceive a difference within an assessment pair. The thresholds were analyzed, and groups were compared by applying chi-square test (P < .05). RESULTS: The majority of dentists and dental technicians (> 50%) detected a lightness difference between the test and reference samples up to a ceramic thickness of 0.5 mm. The majority of laypersons (≥ 50%) did not perceive a lightness difference with ceramic thickness of 0.5 mm. If separated by the different color changes, the threshold ceramic thickness started at 0.4 mm and varied within the groups of evaluators and by the lightness of the assessed color. CONCLUSION: A considerable number of evaluators perceived a lightness difference when minimally invasive ceramic restorations of 0.5-mm thickness were applied. The threshold ceramic thickness, however, was reduced when the lightness of the substrate was lower.