# Restorative Longevity Evidence > Restorative longevity evidence for NEET-MDS Conservative Dentistry: annual failure rates, secondary caries overdiagnosis, patient factors and repair philosophy. - Canonical URL: https://prepelephant.com/topics/neet-mds/conservative-dentistry/restorative-longevity-evidence-mds - Exam / course: NEET-MDS · Subject: Conservative Dentistry - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Restorative Longevity Evidence", PrepElephant, https://prepelephant.com/topics/neet-mds/conservative-dentistry/restorative-longevity-evidence-mds ## Direct answer Median figures hide the message: practice-based data put the average composite at six to seven years, yet trials show annual failure rates of just 1-3 per cent — Opdam's review of posterior composites — because longevity is decided less by material than by patient risk, operator skill and cavity size. Amalgam reviews report roughly 1.6 per cent annual failure against composite's 2.9 per cent — a modest difference dwarfed by caries risk and bruxism — while secondary caries tops failure-reason lists yet is dentistry's most overdiagnosed finding: many restorations replaced for "recurrent caries" show no pathology. Hence the modern philosophy: monitor rather than replace, repair rather than re-restore, and read every number with its population attached. ## What you must remember - **Headline numbers:** posterior composite annual failure rate 1-3 per cent in reviews (Opdam 2014); practice-based average composite lifespan around six to seven years; amalgam about 1.6 per cent annual failure versus composite's 2.9 per cent in a common comparison. - **Failure reasons ranked:** secondary (recurrent) caries first in most series, then bulk and marginal fracture, wear, and endodontic complications — with material-specific patterns (composites to fracture and secondary caries, amalgams to fracture and marginal breakdown). - **The overdiagnosis finding:** a substantial share of restorations replaced for secondary caries are sound on re-examination — "replacement dentistry" — the evidence base for monitoring. - **Patient factors dominate:** caries risk, bruxism, oral hygiene and socioeconomic status move survival more than material class; operator factors (isolation, matrix discipline) sit just behind. - **Cavity size penalty:** failure risk rises steeply with number of surfaces — an MOD composite fails at multiples of the rate of a single-surface one; large defects belong to indirect restorations. - **Repair philosophy:** repair of a localised defect (refinishing, marginal repair) extends restoration life and preserves tooth structure, and is endorsed in contemporary consensus statements over wholesale replacement. - **Evidence hierarchy:** systematic reviews of practice-based networks out-predict manufacturer claims; ask who was restored, by whom, and for how long. - **Amalgam's exit:** with the Minamata parties deciding in 2025 to end amalgam use by 2034, longevity comparisons increasingly answer a question about a material being retired — the contemporary framing examiners have begun to test. ## Reading an annual failure rate like an examiner A review quotes 3 per cent annual failure for posterior composites in a practice network: 97 per cent survive each year, compounding to about 74 per cent at ten years (0.97 to the power of ten) — respectable, and better than the "composites last five years" folklore. Vary the population as the exam does: high-caries-risk patients multiply the rate; single-surface restorations in low-risk adults fall toward 1 per cent (about 90 per cent at ten years). Compare materials fairly: the amalgam-composite gap (1.6 versus 2.9 per cent) is real but small beside risk-factor swings, and shrinks further with rigorous isolation — the reason reviews still endorse composite in most posterior situations. Apply the policy lens: with amalgam exiting by 2034, the question becomes "how do I make composites last" — rubber dam, matrix discipline, incremental placement, cuspal coverage for the big ones. Longevity literacy is a number, a population, a time horizon, and a decision. ## Where students slip Quoting a single survival percentage without its population is the first error — trial-condition numbers transferred to high-risk practice overpromise by years. The second is treating secondary caries as an objective finding: the diagnosis is notoriously operator-dependent, and a candidate who says "stain at a margin is not caries until it is" shows the critical reading examiners reward. The third is missing the repair option in scenario stems: a localized marginal defect on an otherwise serviceable restoration is repaired or refinished, not replaced — replacement loses tooth structure the tooth never recovers. Fourth, the arithmetic: converting an annual failure rate into a ten-year survival in one line separates candidates who understand the evidence from those who memorise it. ## Frequently asked questions ### What annual failure rates do posterior composites show? About 1-3 per cent per year in systematic reviews of posterior composites, with practice-based average lifespans around six to seven years. ### What is the commonest recorded reason for restoration replacement? Secondary caries, followed by fracture — though a substantial proportion of such diagnoses are overcalls, supporting monitoring and repair. ### How do amalgam and composite compare in longevity reviews? Amalgam shows lower annual failure (about 1.6 versus 2.9 per cent for composite in a commonly cited comparison), a gap smaller than the effect of patient risk factors. ### Why do practice-based and trial longevity figures differ? Trial populations and maintenance are idealised; practice-based networks include real-world risk factors and technique variation, producing shorter survival. ### What is the repair-over-replacement philosophy? Localised defects are repaired or refinished while the sound remainder is retained, preserving tooth structure and extending restoration life — now preferred to wholesale replacement.