A COMPREHENSIVE REVIEW OF THE LOCAL RISK-FACTORS ASSOCIATED WITH THE ETIOLOGY OF PERI-IMPLANT DISEASES
compared to non-smokers. In a systematic review and metaanalysis, Sgolastra et al. 57 assessed the role of smoking as a risk factor for peri-implantitis. The implant-based meta-analysis showed a significantly higher risk of peri-implantitis in smokers [ Relative risk: 2.1, 95 % Confidence interval: 1.34-3.29, p = 0.001) than non-smokers. The mechanism behind peri-implant bone loss in smokers is most probably similar to periodontal bone loss. Tsigarida et al. 12 proposed that that smoking shapes the peri-implant microbiomes even in states of clinical health, by supporting a pathogen-rich community. Although the mechanisms by which smoking enhances alveolar bone loss are poorly understood; evidence suggests that smoking enhances bone loss by affecting the host response. Smoking has been reported to impair the function of neutrophils that cause decreased chemotaxis, phagocytosis, and adherence 58, 59. Moreover, it has also been reported that smokers present a decreased oxygen tension in periodontal pockets that could favor anaerobic microbial colonization 60, 61. The same mechanism could be associated with peri-implant diseases, such as peri-implant mucositis and peri-implantitis. It has also been suggested that there is a synergistic effect of tobacco smoking and carriage of interleukin-1 gene polymorphism that results in increased risk of peri-implantitis 62, 63. Moreover, tobacco smoking has also been reported to jeopardize the outcomes of periodontal surgical interventions 64. Galindo-Moreno et al. 65 reported that the rates of marginal bone loss around implants are significantly associated with smoking. Results from a recent systematic review and metaanalysis also reported a significantly higher risk of peri-implantitis in smokers as compared to nonsmokers 66. 3.5. Bruxism There are only a limited number of case-reports that have associated the occurrence of peri-implantitis with bruxism. In a case-report, Merin RL 67 described the case of a 63-year-old female patient with a history of bruxism who reported to the clinic with pain and discomfort around an implant placed in the tooth no. 30 position. Radiographic evaluation showed that this implant had significant periimplant bone loss. The author observed that the peri-implant bone loss was associated with heavy occlusion on the implant restoration 67. The author performed an occlusal adjustment and a radiograph taken five months after occlusal adjustment showed significant repair of the lost alveolar bone 67. Similar results were reported in another case-report by Lin et al. 68 3.6. Cement remnants A conventional approach towards restoration of dental implant using fixed prosthesis is the use of cement-retained restorations. In the absence of occlusal screw access openings, cementretained restorations are useful in enhancing the number of occlusal contacts and simultaneously improving aesthetics 69. However, inadequate removal of excessive cement at the time of implant cementation may lead to a complication, cement-induced peri-implantitis 69. The probability of cement to remain in the peri-implant sulcus is high when margins of the restoration are placed 1.5mm to 3mm subgingivally 70. In a recent systematic review, Pesce et al. 71 appraised the currently available scientific evidence to assess the role played by cement excess and misfitting components on the development of peri-implantitis. The authors reported that there is a correlation between cement excess and the presence of peri-implant disease, particularly among patients with a history of periodontitis 71. The authors also emphasized that removal of excess cement by means of debridement helps resolve most of the symptoms of peri-implantitis 71. Similarly, in a retrospective clinical observational study of fixed implant-supported restorations, cement associated peri-implantitis was assessed 72. In this study, 71 patients with 126 implants were investigated. Cement residues were identified in 59.5 % of the implants. BOP was observed in 80 % of the implants and suppuration at 21.3 % of the implants with excess cement. The results demonstrated that following removal of the excess cement and recementation, a 76.9 % reduction in BOP occurred with no signs of suppuration at follow-up. However, according to Korsch and Walther 73, the frequency of undetected excess cement depends upon the type of cement used. Premier Implant Cement( PIC) tends to leave more undetected excess as compared to Temp Bond( TB) cement. In this regard, implants cemented with PIC tend to have a higher prevalence for periimplant inflammation and cause a more severe peri-implant bone loss as compared to those cemented with TB 73. 3.7. Occlusal overloading Occlusal overloading is a major cause of biomechanical implant complications including fracture and / or loosening of the implant. Occlusal overloading( combined with plaque accumulation) may also disturb the intricate bond between the implant surface and bone thereby leading to periimplantitis and, if left untreated, implant failure 74-76. Prevention of occlusal overloading is associated with performing comprehensive examinations, treatment planning, well-defined surgical and prosthetic treatments and regular maintenance. However, conflicting results have also been reported 77, 78. In a study on dogs, there was no loss of osseointegration and / or peri-implantitis following a period of 8 months of excessive occlusal load on titanium implants 78. 3.8. Interimplant distance Studies have reported that the horizontal distance between two adjacent implants can also influence CBH 79-81. It has been reported that when two implants are placed adjacent to one another, the distance between them influences the degree of lateral bone loss and interproximal bone peak resorption 81. This phenomenon is
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