The fusion of permanent teeth is a development anomaly of dental hard tissue. It may require a hard multidisciplinary approach with orthodontics, endodontics, surgery and prosthetics to solve aesthetic and functional problems.

Root canal disinfection remains challenging due to anatomical complexity and the limitations of mechanical instrumentation. Evidence on irrigation is often fragmented and focused on isolated outcomes, limiting clinically integrated protocols. This narrative review provides a clinically oriented interpretation of contemporary irrigation and activation strategies, introducing a substrate-centered perspective emphasizing dentin modification and material interaction. A structured narrative search was conducted in PubMed, Scopus, and Web of Science up to February 2026 using keywords related to irrigants, irrigation protocols, activation techniques, and dentin–material interactions. Studies were selected based on clinical relevance, including complex anatomy, mature biofilms, and realistic irrigation sequences. Irrigation effectiveness is determined by the interplay between irrigant chemistry, fluid dynamics, and activation-mediated distribution within the root canal system, as well as by irrigation-induced dentin modifications influencing the dentin–material interface. Sodium hypochlorite and chelating agents remain central, although their performance depends on delivery and activation. Activation enhances irrigant exchange, biofilm disruption, and penetration into complex regions. Irrigation also induces physicochemical changes in dentin, affecting sealer penetration and interfacial stability. It should not only be considered a disinfection step but also a substrate-conditioning phase linking cleaning to obturation, with implications for treatment predictability and long-term outcomes.

Background/Objectives: The management of edentulism and severe alveolar bone loss in older adults remains a significant challenge in implant dentistry. Given the potential biological and therapeutic burden associated with extensive regenerative procedures, increasing interest has been directed toward treatment strategies that utilize available anatomy and reduce surgical complexity. This narrative review examined contemporary augmentation-avoidance approaches for implant rehabilitation in geriatric patients. Methods: A structured narrative literature search was performed in PubMed/MEDLINE, Scopus, and Web of Science, including studies published up to 30 May 2026. Clinical studies, systematic, umbrella and narrative reviews, meta-analyses that evaluate augmentation-avoidance approaches in implant dentistry were considered. The review examined evidence relevant to older adults, including clinical, prosthetic, functional, and patient-centered outcomes. Results: The available literature describes multiple strategies for managing reduced bone availability, including short and ultra-short implants, narrow-diameter implants, tilted implant concepts, pterygoid and trans-sinus implants, zygomatic implants, immediate loading protocols, flapless and computer-guided surgery, and implant-retained overdentures. These approaches have broadened the range of treatment options available for patients with reduced bone availability and may reduce the need for extensive regenerative procedures in selected clinical situations. In addition to implant and prosthetic outcomes, increasing attention has been directed toward oral health-related quality of life, masticatory function, treatment satisfaction, and maintenance requirements. However, evidence specifically focused on geriatric populations remains limited. Conclusions: Contemporary implant dentistry offers several alternatives to extensive bone regeneration in carefully selected geriatric patients, although current evidence is largely extrapolated from mixed adult populations. Treatment planning should integrate anatomical conditions with systemic health, functional status, frailty-related factors, and long-term maintenance considerations. Further geriatric-focused research is needed to support patient-centered decision-making and optimize long-term rehabilitation outcomes in aging populations.