International Journal of Research and Reports in Dentistry

Effect of Ultraviolet Photofunctionalization on Early Osseointegration of Titanium Dental Implants in the Mandibular Region: A Randomized Controlled Trial

2026-06-03T10:03:58+00:00

Background and Objectives: Titanium surface photofunctionalization using ultraviolet (UV) irradiation has emerged as a promising adjunct to conventional implant protocols. This study aimed to evaluate and compare early osseointegration between photofunctionalized and non-photofunctionalized titanium dental implants placed in the mandibular region.

Methods: This randomized double-blinded controlled trial enrolled 24 patients (12 male, 12 female; age 25–40 years) requiring mandibular implant placement. Participants were randomly allocated to receive either UV-treated (n=12) or conventional non-UV (n=12) titanium implants. UV photofunctionalization was performed for 20 seconds using a DIO UV Irradiator prior to implant placement. Implant stability was assessed using resonance frequency analysis (Osstell Mentor; ISQ values) at baseline (immediately after placement), 4 weeks, 8 weeks, and 4 months postoperatively. Marginal bone levels were evaluated on standardized intraoral periapical radiographs at baseline, 8 weeks, and 4 months. Peri-implant soft tissue was assessed at 4 and 8 weeks using the Mombelli modified gingival index (mGI). Statistical analysis was performed using IBM SPSS version 25; intergroup comparisons used unpaired t-tests and chi-square tests.

Results: No significant difference in ISQ values was observed between groups at baseline or 4 weeks (p=0.152 and p=0.174, respectively). At 8 weeks and 4 months, the UV group demonstrated significantly higher ISQ values (p=0.021 and p=0.004, respectively). Both mesial and distal marginal bone loss were significantly lower in the UV group compared to the non-UV group (p=0.041 and p=0.021, respectively). Soft tissue assessment revealed no significant intergroup difference at either 4 weeks (p=1.00) or 8 weeks (p=1.00).

Conclusion: UV photofunctionalization significantly enhances implant stability and reduces peri-implant marginal bone loss from 8 weeks onward, without adversely affecting peri-implant soft tissue health. This technique represents a clinically practical and effective adjunct for improving early osseointegration outcomes, particularly in regions requiring higher predictability.

Histopathological Evaluation of Systemic Immune-Inflammation Index (SII) in Oral Squamous Cell Carcinoma

2026-06-20T09:34:52+00:00

Introduction: Oral squamous cell carcinoma (OSCC) shows considerable biological heterogeneity in clinical behaviour and prognosis. Conventional histopathological grading remains important but may not fully reflect tumour aggressiveness or the systemic immune-inflammatory status of the host. The systemic immune-inflammation index (SII), derived from peripheral blood neutrophil, lymphocyte and platelet counts, may provide an adjunctive indicator of host inflammatory and immune response in OSCC.

Aim: This study evaluated SII in patients with OSCC and correlated SII values with histopathological grades.

Materials and Method: A total of 60 subjects were included, comprising 20 healthy controls and 40 histopathologically confirmed OSCC cases. Before treatment, 2 mL of venous blood was collected under aseptic conditions, and complete blood count analysis was performed using an automated haematology analyser. SII was calculated using the formula: platelet count × neutrophil count / lymphocyte count. Descriptive statistics were expressed as mean ± standard deviation. The independent Student’s t-test was used to compare SII values between healthy controls and OSCC patients, and one-way ANOVA with post hoc analysis was used to assess differences across histopathological grades. A p-value < 0.05 was considered statistically significant.

Results: The mean SII was significantly higher in OSCC patients (2195.98 ± 1165.98) than in healthy controls (429.87 ± 50.20) (p < 0.001). SII values increased progressively from well-differentiated to poorly differentiated OSCC, and this association was statistically significant (p < 0.05).

Conclusion: The findings suggest that SII is elevated in OSCC and shows a positive association with poorer histopathological differentiation. SII may serve as a simple, cost-effective adjunctive inflammatory biomarker for supporting histopathological assessment in OSCC.

Awareness and Perception of Artificial Intelligence Applications in Forensic Odontology: A Questionnaire-Based Cross-Sectional Study

2026-06-24T09:54:48+00:00

Background: Artificial intelligence (AI) is increasingly influencing diagnostic and analytical practices in dentistry and forensic sciences. In forensic odontology, AI has been explored as an adjunctive tool for human identification, age estimation, bite mark analysis and dental record comparison. However, its practical adoption depends on professional awareness, perceived usefulness and recognition of ethical and technical limitations.

Aim: To assess awareness, utilisation and perceptions regarding AI applications in forensic odontology among dental professionals.

Materials and Methods: A questionnaire-based cross-sectional study was conducted over 6 months using a simple random sampling method among 209 dental professionals, including undergraduate students, postgraduate students, teaching faculty, non-teaching faculty and private practitioners. A structured and validated questionnaire assessed awareness of AI, current utilisation, perceived advantages, limitations and attitudes towards its integration into forensic odontology. Data were analysed using SPSS software, and descriptive statistics were used to calculate frequencies and percentages.

Results: Awareness of AI in dentistry was reported by 83.6% of participants, while 62.1% were aware of its applications in forensic odontology. Only 28.8% had used AI-based tools, mainly for bite mark analysis and age estimation. Most participants (96.3%) believed that AI could improve diagnostic accuracy and efficiency. Ethical and data privacy concerns were identified as major challenges by 76.7% of respondents. Overall, 92.6% demonstrated a positive attitude towards AI integration.

Conclusion: The findings indicate high awareness and acceptance of AI in forensic odontology, although practical utilisation remains limited. Structured training, ethical guidance and regulatory frameworks may support responsible implementation.

Oral Health Knowledge and Practices Among Primary School Teachers in Harare, Zimbabwe

2026-05-28T12:18:15+00:00

Background: Primary school teachers play a key role in shaping children’s health behaviours, including oral hygiene practices. Adequate oral health knowledge among teachers can contribute to early prevention of dental diseases and promotion of healthy habits among school-aged children. However, limited awareness may negatively influence both their own oral health practices and the health education they provide to learners.

Aims: The study aims to assess oral health knowledge and practices among primary school teachers in Harare, Zimbabwe.

Study Design: A descriptive mixed-methods study with both qualitative and quantitative data.

Place and Duration of Study: Primary schools in Harare, between July 2020 and April 2021.

Methodology: The study population included all primary schools in Harare, excluding schools located in armed forces’ camps. Participating schools were selected using simple random sampling through the lottery method. A sample size of 33 was calculated using EpiInfo 7, with a 10% non-response rate considered.

Results: The response rate was 93.93% (31 schools). Only 9 (29%) respondents correctly identified the number of deciduous teeth, while 13 (42%) knew the correct number of permanent teeth. About 8 (26%) could correctly describe dental plaque. Only 16% had visited a dentist in the past six months, while 16% had never visited a dentist. Among those who had visited a dentist, 74% sought care due to dental problems rather than routine check-ups.

Conclusion: Oral health knowledge among primary school teachers in Harare was low, and their oral health-seeking behaviour was largely problem-driven. There is a need for targeted oral health education programs to improve teachers’ knowledge and encourage preventive dental care practices.

Oral–Gut Microbial Translocation Axis in Periodontitis: A Critical Review of Mechanisms and Systemic Implications (2015–2025)

2026-05-26T12:51:52+00:00

Periodontitis is a dysbiosis-driven chronic inflammatory disease affecting the tooth-supporting structures that extends its pathological influence well beyond the oral cavity. Over the past decade, the oral–gut microbial translocation axis has emerged as a biologically compelling framework through which periodontal dysbiosis may shape the composition and functional output of the intestinal microbiota, with downstream consequences for systemic health. This review critically examines the mechanistic basis of oral-to-gut bacterial translocation, addressing the survival of swallowed periodontal pathogens through the gastric environment, their disruption of intestinal colonisation resistance, impairment of epithelial tight junction integrity, and induction of systemic immunological cascades involving Th17 cells, regulatory T cells, and inflammasome activation. A comprehensive literature search was conducted across the following electronic databases: PubMed/MEDLINE, Web of Science, Scopus, Embase, and Google Scholar. The roles of keystone periodontal pathogens—principally Porphyromonas gingivalis, Fusobacterium nucleatum, and Klebsiella spp.—are scrutinised in both animal models and clinical studies. The review further evaluates evidence linking the oral–gut axis to inflammatory bowel disease, colorectal cancer, metabolic-associated steatotic liver disease, and cardiovascular disease. The effect of non-surgical periodontal therapy on gut microbial composition is assessed, alongside emerging microbiome-targeted therapeutic strategies including probiotics, prebiotics, and bacteriophage-based approaches. The synthesis of current evidence reveals a bidirectional and mechanistically intricate communication channel between the oral and intestinal ecosystems, yet causal inference from human data remains constrained by methodological heterogeneity, the preponderance of cross-sectional designs, and residual confounding. Future longitudinal and interventional research employing multi-omics platforms is necessary to translate the mechanistic insights reviewed herein into actionable clinical guidance.

Hazards of Mercury Toxicity and Other Heavy Metal Intoxication: A Critical Review

2026-06-03T11:08:19+00:00

Heavy metal contamination poses an enduring and increasingly urgent public health challenge. Mercury, lead, cadmium, arsenic, and several other metals occur widely in terrestrial and aquatic environments as a consequence of both natural geological processes and expanding anthropogenic activity. Chronic, low-level exposure to these substances is now recognised as a major driver of non-communicable disease burden globally, contributing to neurological deterioration, renal dysfunction, cardiovascular disease, skeletal pathology, and multiple forms of cancer. Their toxicity is mediated through interconnected mechanisms that include the generation of reactive oxygen species, disruption of intracellular calcium signalling, enzyme inhibition through binding to sulphydryl groups, and impairment of DNA repair. Particularly vulnerable populations include children, pregnant women, artisanal miners, and communities reliant on contaminated drinking water or subsistence fishing. Despite growing scientific understanding and the emergence of international regulatory instruments such as the Minamata Convention, exposures at toxicologically relevant levels remain widespread. This review critically examines the sources, environmental distribution, mechanistic toxicology, clinical manifestations, diagnostic approaches, treatment strategies, and regulatory context of the principal hazardous heavy metals. Evidence drawn from peer-reviewed literature published predominantly between 2000 and 2026 is synthesised to identify knowledge gaps, highlight persistent challenges in clinical management, and inform priorities for future research and policy action. The findings suggested that heavy metal intoxication, being a major global public health threat, require stronger prevention, monitoring, and treatment strategies to reduce its long-term health and environmental impacts. This study is limited by incomplete geographic representation, undercoverage of certain metals and emerging biomarkers, and reliance on existing literature, indicating the need for future large-scale, globally inclusive epidemiological and mechanistic research on heavy metal toxicity.

Cellular Senescence in Periodontal Ageing: Molecular Mechanisms, Clinical Implications and Emerging Therapeutic Strategies

2026-06-26T12:05:17+00:00

Cellular senescence is increasingly recognised as an important biological process associated with ageing-related tissue dysfunction. In periodontal tissues, senescence may contribute to impaired cellular turnover, reduced regenerative capacity, chronic inflammation, and increased susceptibility to periodontal destruction. Senescent cells are characterised by stable cell-cycle arrest and the production of a senescence-associated secretory phenotype, which includes pro-inflammatory cytokines, chemokines, matrix-degrading enzymes, and growth factors. These mediators may influence the periodontal microenvironment by promoting extracellular matrix degradation, osteoclast activation, altered immune responses, and delayed tissue repair. This review summarises current evidence on the role of cellular senescence in periodontal ageing, with emphasis on molecular mechanisms, tissue-specific effects, clinical implications, and emerging therapeutic strategies. Key mechanisms discussed include telomere attrition, oxidative stress, DNA damage responses, mitochondrial dysfunction, and activation of p53–p21 and p16INK4a–retinoblastoma signalling pathways. The review also considers the contribution of senescent gingival fibroblasts, periodontal ligament cells, osteoblasts, cementoblasts, and mesenchymal stem cells to age-associated periodontal changes. Available evidence suggests that cellular senescence may contribute to a bidirectional relationship between ageing and periodontitis, in which chronic periodontal inflammation promotes senescence while senescent cells further amplify inflammatory tissue damage. Emerging approaches such as senolytics, senomorphics, stem-cell-based therapy, exosome-based therapy, and gene or epigenetic modulation are being investigated as potential strategies to improve periodontal regeneration and reduce senescence-associated dysfunction. However, most evidence remains preclinical, and further well-designed human studies are required before senescence-targeted interventions can be translated into routine periodontal practice.

Digital Workflow-assisted Lithium Disilicate Resin-Bonded Fixed Dental Prosthesis for Missing Maxillary Lateral Incisor: A CARE-Compliant Case Report

2026-05-27T12:34:06+00:00

Background: Resin-bonded fixed dental prostheses (RBFDPs) represent a minimally invasive solution for replacing missing anterior teeth. The evolution of ceramic materials, particularly lithium disilicate, combined with digital CAD-CAM workflows has significantly enhanced the clinical predictability and aesthetic outcomes of these restorations.

Case Presentation: A 33-year-old male patient presented with a missing maxillary left lateral incisor (#12) and multiple missing mandibular anterior teeth following trauma. A lithium disilicate RBFDP was planned and fabricated using intraoral scanning and CAD-CAM technology for the maxillary arch. Abutment preparation was conservative, with supragingival shoulder finish lines created on teeth #11 and #13. The prosthesis was cemented with self-adhesive resin cement following acid etching protocols.

Conclusion: This case demonstrates that lithium disilicate RBFDPs fabricated through a digital workflow provide a reliable, aesthetic, and minimally invasive alternative to conventional fixed partial dentures and implant-supported prostheses for selected patients. Meticulous case selection, surface preparation, and adhesive protocol adherence are pivotal to long-term success.

Nonsurgical Endodontic Management of a Three-Rooted Maxillary First Premolar: A Case Report

2026-06-02T09:48:43+00:00

Successful endodontic treatment relies on accurate diagnosis and thorough management of the entire root canal system, especially in teeth with anatomical variations. Maxillary first premolars are known for their complex root canal morphology, and the presence of three roots and three canals is considered a rare anatomical variation that can present both diagnostic and treatment challenges. Failure to identify such unusual anatomy may result in incomplete debridement and compromised treatment outcomes. This case report describes the nonsurgical endodontic management of a three-rooted maxillary first premolar in a 35-year-old male patient who presented with spontaneous pain in the upper left posterior region. Clinical examination and sensibility tests suggested irreversible pulpitis in tooth #24. During working length determination, an additional root was suspected on radiographic examination and was subsequently confirmed using cone-beam computed tomography (CBCT). Modification of the access cavity to a T-shaped design, combined with 3.5× magnification and careful canal exploration, enabled the identification of three distinct canals—mesiobuccal, distobuccal, and palatal. Cleaning and shaping were carried out using hand and rotary instrumentation with copious irrigation using 3% sodium hypochlorite and 17% EDTA, followed by intracanal calcium hydroxide medication and obturation using BIO C SEALER with gutta-percha. Accurate diagnosis aided by CBCT and careful treatment planning contributed to the successful management of this uncommon anatomical variation.

Application of CBCT and Dental Operating Microscope in the Successful Endodontic Management of a Mandibular First Molar with Three Mesial Canals: A Case Report

2026-06-08T07:32:26+00:00

An additional canal is one of the many anatomical variations that may occur in the root canal system. Comprehensive knowledge of root canal anatomy is a crucial factor in achieving successful endodontic treatment. In mandibular first molars with the possible presence of a fifth canal, careful clinical evaluation, including multiple angulated radiographs, thorough examination of the chamber floor, cone beam computed tomography (CBCT), and other adjunctive aids, can help clinicians prevent endodontic treatment failure. This article describes the endodontic treatment of a mandibular first molar with three canals in the mesial root. The application of CBCT, a dental operating microscope, and several radiographs with different angulations helped effectively identify, prepare, and obturate all five canals, including the middle mesial canal.

Glandular Odontogenic Cyst of the Anterior Maxilla: A Rare Entity in an Unusual Location

2026-06-20T10:03:55+00:00

Glandular odontogenic cyst (GOC) is an uncommon developmental odontogenic cyst characterised by histopathological features that frequently overlap with those of other odontogenic and non-odontogenic lesions, thereby complicating diagnosis. The lesion exhibits morphological similarities to lateral periodontal cysts, botryoid odontogenic cysts, radicular cysts exhibiting mucous metaplasia, and low-grade mucoepidermoid carcinoma, making precise diagnostic differentiation particularly challenging. This study report the case of a 60-year-old female presenting with pain and swelling in the anterior maxilla, an uncommon site for GOC. Radiographic evaluation revealed a well-defined unilocular radiolucency with cortical expansion and root displacement. Histopathological examination confirmed the diagnosis, demonstrating pseudostratified columnar cells with cilia, goblet cells, mucous cells, and intraepithelial microcystic spaces. Complete enucleation of the lesion with extraction of the involved teeth was performed, and no recurrence was observed during the one-year follow-up. This case highlights the importance of correlating clinical, radiographic, and histopathological findings to achieve diagnostic precision. Given the aggressive nature and recurrence potential of GOC, meticulous surgical management and long-term follow-up are essential. Documentation of rare maxillary presentations expands the existing knowledge base, aids in refining diagnostic criteria, and supports evidence-based treatment planning for this challenging entity.

Uncertainty in Internal Matrix Selection During Apexification: A Case-based Critical Appraisal

2026-06-30T07:43:57+00:00

Background: Apexification in immature permanent teeth with open apices requires controlled placement of apical barrier materials to limit overextension and support an apical seal. Internal matrices may assist this procedure; however, their indications and material-selection criteria remain insufficiently defined.

Case Presentation: A 22-year-old female patient presented with intermittent discomfort in tooth #21 and a history of dental trauma. Clinical and radiographic findings, including cone-beam computed tomography, indicated pulpal necrosis with symptomatic apical periodontitis, an immature apex, and a periapical radiolucency. After minimal canal preparation and intracanal calcium hydroxide medication, an amniotic membrane allograft was adapted as an internal matrix. A 4–5 mm mineral trioxide aggregate apical plug was placed, followed by thermoplasticised gutta-percha obturation and definitive coronal restoration.

Discussion: The case is used to critically appraise internal matrix materials, including collagen scaffolds, calcium sulphate, platelet-rich fibrin, and amniotic membrane. Matrix selection appears to be influenced by apical morphology, lesion characteristics, material behaviour, radiographic visibility, operator experience, and practical considerations rather than standardised criteria.

Conclusion: At six months, the tooth remained asymptomatic and showed radiographic and cone-beam computed tomographic evidence of reduced periapical radiolucency. The case illustrates the potential procedural role of an internal matrix in apexification, while highlighting the need for objective clinical criteria and comparative evidence to guide matrix selection.

Chondrolipoma of the Tongue: A Rare Case Report

2026-07-04T13:59:20+00:00

Chondrolipoma is an extremely rare benign mesenchymal tumour characterised by mature adipose tissue with cartilaginous metaplasia. It is uncommon in the oral cavity, and when it occurs intraorally, the tongue is among the most frequently reported sites. This case report describes a 30-year-old female patient who presented with a painless swelling on the left side of the tongue that had been present for 20 years. The lesion involved the dorsal surface, lateral border and ventral surface of the tongue and caused difficulty in mastication because of its size. Clinical examination suggested a benign soft-tissue lesion, and fibroma was considered as the provisional diagnosis. Ultrasonography showed a well-defined hyperechoic lesion with minimal vascularity, while MRI demonstrated a well-defined lesion with peripheral fat intensity and central post-contrast enhancement. Based on radiological findings, lipohaemangioma was considered. Excisional biopsy was performed, and histopathological examination revealed an encapsulated tumour composed of mature adipocytes arranged in lobules with areas of cartilaginous metaplasia and no cellular atypia. These features confirmed the diagnosis of chondrolipoma. The case highlights the diagnostic challenge posed by long-standing tongue swellings and reinforces the need for clinical, radiological and histopathological correlation. Complete surgical excision provided both diagnosis and treatment, with satisfactory postoperative healing.

An Interdisciplinary Periodontal Approach to the Esthetic Rehabilitation of a Complicated Crown-root Fracture: A Case Report

2026-07-04T14:05:45+00:00

Background: Complicated crown–root fractures of anterior teeth present a clinical challenge when the fracture line extends subgingivally because access, isolation, biological width maintenance, and definitive restoration become difficult. A coordinated periodontal, endodontic, and restorative approach may preserve the affected tooth while achieving acceptable function and aesthetics.

Case presentation: A 24-year-old female patient presented with a fractured maxillary anterior tooth following a fall. Clinical and radiographic examination revealed a complicated crown–root fracture involving tooth #12, with the fracture margin extending below the gingival level. The fractured coronal fragment was carefully removed and stored in sterile normal saline. Endodontic treatment was performed, followed by post-space preparation. Because the fracture margin was subgingival, periodontal crown lengthening was planned using a diagnostic cast and an acrylic surgical stent to guide soft-tissue contouring and access to the remaining sound tooth structure. After crown lengthening, a fibre-reinforced composite post was luted, and core build-up was completed using composite resin. The fractured fragment was reshaped and reattached using an adhesive technique to restore tooth form during treatment. Following periodontal healing, definitive rehabilitation was completed with an adhesively cemented lithium disilicate crown. The patient was reviewed at 1 month, 3 months, and at 6-month intervals thereafter, with satisfactory healing and restoration stability.

Conclusion: This case demonstrates that a multidisciplinary approach combining endodontic therapy, periodontal crown lengthening, fibre-post reinforcement, adhesive fragment reattachment, and definitive ceramic restoration can be a conservative treatment option for selected complicated crown–root fractures. Careful case selection, biological width management, adhesive protocol selection, and follow-up are essential for predictable functional and aesthetic outcomes.

Coronal Scaffold Stabilization for Conservative Management of Complicated Crown Fractures

2026-07-09T05:21:01+00:00

Background: Management of complicated crown fractures involving multiple mobile coronal fragments is clinically challenging, particularly when conventional fragment reattachment is not feasible. Removing residual fractured segments may further compromise an already weakened tooth and adversely affect the restorative prognosis. Preservation and adhesive stabilisation of multiple retained mobile coronal fragments may provide a conservative alternative by converting unstable residual tooth structure into a stable coronal scaffold that facilitates subsequent rehabilitation.

Case Presentation: This case series describes the management of two permanent maxillary central incisors with complicated crown fractures using preservation and adhesive stabilisation of residual coronal fragments before definitive treatment. Case 1 involved a mature permanent incisor with a closed apex, in which stabilisation of the retained fragments facilitated conventional root canal treatment followed by full-coverage crown rehabilitation. Case 2 involved an immature permanent incisor with an open apex, in which stabilisation of the residual coronal structure enabled mineral trioxide aggregate (MTA) apexification and subsequent restoration. In both cases, preservation of the remaining tooth structure facilitated endodontic and restorative procedures while maintaining coronal integrity.

Results: Both teeth were rehabilitated successfully with satisfactory aesthetic and functional outcomes. Clinical and radiographic follow-up demonstrated satisfactory functional rehabilitation. Patients were followed up for 6 months, during which no postoperative complications were observed.

Conclusion: Preservation and adhesive stabilisation of residual coronal fragments may represent a tooth-preserving and clinically feasible treatment option for managing complex traumatic crown fractures when conventional fragment reattachment is impractical. This approach may facilitate definitive rehabilitation while minimising further loss of tooth structure.

Minimally Invasive Management of Gingival Recession Using Pouch and Tunnel Technique with T-PRF: A Case Report

2026-07-13T11:43:09+00:00

Gingival recession is a mucogingival deformity characterised by apical migration of the gingival margin, which may result in root exposure, dentinal hypersensitivity and aesthetic concern. Minimally invasive periodontal plastic surgical approaches aim to obtain root coverage while preserving soft-tissue integrity and vascular supply. This case report describes the management of Cairo RT1 gingival recession in the maxillary anterior region of a 32-year-old systemically healthy male patient using the pouch and tunnel technique with titanium-prepared platelet-rich fibrin (T-PRF). Clinical examination revealed recession involving teeth 11, 12 and 13, with no interproximal attachment loss, a thin gingival phenotype and satisfactory plaque control. After initial periodontal therapy and reinforcement of oral hygiene instructions, intrasulcular incisions were made without vertical releasing incisions. A full-thickness mucoperiosteal tunnel was created beyond the mucogingival junction while preserving the interdental papillae. The exposed root surfaces were debrided and planed, and a T-PRF membrane prepared from the patient’s blood was positioned within the tunnel over the recession defects. The gingival margin was coronally advanced and stabilised using sling sutures. Postoperative care included analgesics, chlorhexidine mouth rinse, avoidance of mechanical disturbance and dietary instructions. Healing was uneventful after suture removal, and the treated area showed satisfactory root coverage and improved aesthetic appearance. This case suggests that the combined approach may be suitable for selected Cairo RT1 recession defects, although further controlled studies are required.