advantages: this is the least expensive option for the replacement of teeth. the least invasive, no surgery needed (usually). disadvantages: quite often rely solely on the mucosa for support, do not tend to be as stable as the other options. very difficult to keep clean and can exacerbate any oral hygiene issues. they are difficult to learn to use. quite often require complex muscular control to hold them in place. not as efficient as other options. foods such as apples and nuts will often have to be avoided. dental implants: to replace a single tooth, a screw (the implant) is placed into the jaw bone, which a false tooth is screwed onto. implants can also be used to support bridges or dentures. advantages: they are much more realistic than the other options. they have similar efficiency and aesthetics to an actual tooth. they do not require the destruction of the adjacent teeth like bridges. they last 5-8 times longer than both bridges and dentures. despite the initial higher cost, it pays off in the long term. much easier to maintain, with oral hygiene procedures being rather similar to an actual tooth. disadvantages: cost: they are very expensive. a single implant will cost between £2000-3000 on average. surgery: their placement requires quite invasive surgery. with surgery comes risks (e.g. infection, swelling, bleeding). replacement: the actual implant itself rarely requires replacement, but the actual abutment, or tooth sitting on top of the implant will. this needs replacing on average every 10–15 years. time: once an implant has been placed, the tooth replacement does not occur immediately. implants take time for bone integration. the majority require 3 to 6 months before the final restoration is placed. clinical classification a classification system has been developed by the american college of prosthodontists. the classification are based on diagnostic findings, which is used to help practitioners determine appropriate treatments for patients. the diagnostic criteria used to classify edentulism are: location and extent of the edentulous areas condition of abutment teeth occlusal scheme residual ridge there are four categories which are class i, ii, iii and iv. class i: minimally compromised this class is most likely to be successfully treated with complete dentures. the characteristics include: residual bone height of 21mm or more measured at the lowest vertical height of the mandible shown on a panoramic radiograph. residual ridge morphology resists horizontal and vertical movement of the denture base location of muscle attachments that arc conducive to denture base stability and retention class i maxillomandibular relationship. class ii: moderately compromised this class is distinguished by the continued degradation of the denture‐supporting anatomy. it is also characterised by specific patient management and lifestyle considerations as well as systemic disease interactions. characteristics include: residual bone height of 16 to 20mrn measured at the lowest vertical height of the mandible on a panoramic radiograph. residual ridge morphology that does not show horizontal and vertical movement of the denture base. location of muscle attachments with limited influence on denture base stability and retention. class i maxillomandibular relationship. minor modifiers, psychosocial considerations, mild systemic disease with oral manifestation. class iii: substantially compromised this classification level is where surgical revision of supporting structures is needed to allow for adequate prosthodontic function. residual alveolar bone height of 11 to 15mm measured at the least vertical height of the mandible on a panoramic radiograph. residual ridge morphology has minimum influence to resist horizontal or vertical movement of the denture base. location of muscle attachments with moderate influence on denture base stability and retention. class i, ii or iii maxillomandibular relationship. the conditions that need preprosthetic surgery include: minor soft tissue procedures minor hard tissue procedures including alveoloplasty simple implant placement, no augmentation required multiple extractions leading to complete edentulism for immediate denture placement. class iv: severely compromised this classification level depicts the most debilitated edentulous condition. surgical reconstruction is almost always indicated but cannot always be accomplished because of the patient's health, preferences, dental history, and financial considerations. when surgical revision is not an option, prosthodontic techniques of a specialized nature must be used to achieve an adequate treatment outcome. residual vertical bone height of 10mm or less measured at the least vertical height of the mandible on a panoramic radiograph. residual ridge offers no resistance to horizontal or vertical movement. muscle attachment location that can be expected to have significant influence on denture base stability and retention. class i, ii, or iii maxillomandibular relationships. history of paresthesia or dysesthesia. major conditions requiring preprosthetic surgery complex implant placement, augmentation required surgical correction of dentofacial deformities hard tissue augmentation required major soft tissue revision required, i.e., vestibular extensions with or without soft tissue grafting. epidemiology disability-adjusted life year for edentulism per 100,000 inhabitants in 2004. no data less than 30 30–35 35–40 40–45 45–50 50–60 60–65 65–70 70–75 75–80 80–85 more than 85 edentulism affects approximately 158 million people globally as of 2010 (2.3% of the population). it is more common in women at 2.7% compared to the male rate of 1.9%. a cross-sectional analysis of data from the survey of health, ageing and retirement in europe (share) from 14 european countries (austria, belgium, czech republic, denmark, estonia, france, germany, italy, luxembourg, the netherlands, slovenia, spain, sweden, and switzerland) and israel showed substantial variation in the age-standardized mean numbers of natural teeth amongst people aged 50 years and older, ranging from 14.3 teeth (estonia) to 24.5 teeth (sweden). the oral health goal of retaining at least 20 teeth at age 80 years was achieved by 25% of the population or less in most countries. a target concerning edentulism (≤15% in population aged 65–74 years) was reached in sweden, switzerland, denmark, france, and germany. tooth replacement practices varied especially for a number of up to five missing teeth which were more likely to be replaced in austria, germany, luxembourg, and switzerland than in israel, denmark, estonia, spain, and sweden. the prevalence of kennedy class iii partial denture was predominant among younger population of 21-30 year and 31–40 years, whereas in group iii between 41 and 50 years class i was predominant. it can be stated that the need for prosthodontics care is expected to increase with age, and hence, more efforts should be made for improving dental education and motivation among patients. edentulism occurs more often in people from the lower end of the socioeconomic scale. society and culture it is estimated that tooth loss results in worldwide productivity losses in the size of about us$63 billion yearly.