Background/Objectives: Multilayer zirconia restorations can feature a shade gradient or a strength gradient, with layers differing in color or phase composition within the same material. The aim of this in vitro study was to evaluate the color stability in all layers of multilayer zirconia after exposure to staining solutions and artificial aging. Methods: Square-shaped specimens (N = 120) of color A2 were fabricated from 4Y-PSZ and 3Y/4Y-PSZ multilayer zirconia—Katana STML, DD Cube One ML, and Katana YML—and their baseline color values (T0) were measured with a clinical spectrophotometer (VITA Easyshade V). The specimens were randomly divided into four groups (n = 10/gp) and immersed in physiologic solution, 0.2% chlorhexidine gluconate (CHX) mouth rinse, and staining coffee solution. Then, they were measured continuously for 7 (T1), 14 (T2), and 21 days (T3). The last group of specimens underwent accelerated aging in a steam autoclave at 134 °C and 2 bar pressure and measured after 1 (T1), 3 (T2), and 5 h (T3). After the immersion process and artificial aging, discoloration values (ΔE) were calculated using the formula ΔE = [(ΔL*)² + (Δa*)² + (Δb*)²]^1/2 and analyzed with the SPSS v 23.0 software with a p value < 0.05. Results: All specimens showed significant color differences in the T3 measurements after exposure to coffee and CHX, with the highest ΔE values in the enamel layers. Katana YML showed the most significant differences in ΔE in the cervical layers after exposure to artificial aging. Conclusions: Multilayer zirconia exhibited dependent optical changes, with the enamel layers being the most affected after exposure to staining solutions. Gradient pigmentation and differences in phase composition caused differences in color to the multilayer zirconia layers after exposure to staining solutions and artificial aging.

Background White spot lesions (WSLs) are the earliest clinical sign of enamel demineralisation and a frequent adverse outcome of fixed orthodontic therapy. Their development is multifactorial, reflecting an interaction between appliance, biofilm, and patient factors. Objective This mini review summarises and critically evaluates the evidence published since 2018 on the contribution of fixed orthodontic appliances to the development of WSLs, with attention to pathogenesis, risk factors, and clinical implications. Materials and methods A structured narrative review was conducted using PubMed/MEDLINE, Scopus, and Web of Science. Articles published between January 1, 2018 and September 30, 2025, were screened. Selected pre-2018 studies were retained for background on enamel demineralisation, biofilm behaviour, and orthodontic bonding. Search terms combined controlled vocabulary (MeSH) and free text keywords linked by Boolean operators, including "white spot lesions", "enamel demineralization", "fixed orthodontic appliances", "orthodontic brackets", "biofilm", and "oral hygiene". The initial search was not restricted by language, but only English-language full texts were retained during eligibility screening. Results WSLs may develop at any stage of fixed orthodontic therapy, but the majority appear within the first three to six months after appliance placement. Lesions are observed most often on the labial and cervical enamel adjacent to brackets. Reported drivers include plaque retention around appliance components, an acidogenic and aciduric biofilm shift (dysbiosis), iatrogenic enamel changes from acid etching, and patient-level factors such as oral hygiene, diet, and treatment duration. Discussion The change in the oral environment created by fixed appliances is necessary but not sufficient for WSL development. Patient-related factors, particularly oral hygiene and dietary behaviour, modulate the appliance-related risk. The first three to six months after bonding is the period of greatest enamel vulnerability and the optimal window for individualised preventive intensification. Conclusions WSLs are common but largely preventable. Risk-based, individualised preventive programmes initiated at the start of treatment, combined with sound bonding technique and careful biofilm control, are essential for protecting enamel and safeguarding the aesthetic outcome of fixed orthodontic therapy.

Background/Objectives: Diabetes mellitus is associated with significant health complications, including challenges in periodontal health. Gingival inflammation is especially common among diabetic patients and can significantly impact overall diabetes management. This study aims to investigate the correlation between glycosylated hemoglobin (HbA1c) levels, an established marker of glycemic control, and gingival inflammation using the Quantitative Gingival Bleeding Index (QGBI) among hospitalized diabetic patients, thereby placing the question within a broader clinical context. Methods: The study enrolled 671 hospitalized patients with diabetes complications at “Mother Theresa University Hospital” in Tirana, AL, USA. Glycemic control was assessed through glycosylated hemoglobin (HbA1c) levels, and gingival health was evaluated using the Quantitative Gingival Bleeding Index (QGBI). Behavioral variables were also documented, including smoking habits and routine oral care practices. Spearman’s correlation coefficient (r_s) was applied to determine the relationship between HbA1c levels and QGBI scores. Results: Our findings revealed a strong positive correlation between glycemic control (HbA1c) and gingival inflammation (QGBI) among the participants (Spearman’s coefficient r_s = 0.868, p < 0.001). Additionally, significant positive associations were observed between behavioral factors, such as smoking habits and regular oral care practices, further underscoring their role in periodontal health in diabetic patients. Conclusions: The study highlights a significant positive relationship between poor glycemic control and increased gingival inflammation, emphasizing the importance of periodontal health in the comprehensive management of diabetes mellitus. Our results support integrating periodontal evaluation and management into standard diabetes care, which could improve patient outcomes and overall well-being.