Implant Prosthodontics Basics
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Direct answer
Osseointegration — Brånemark's term for the direct structural and functional connection between vital bone and a titanium implant surface — is the biological foundation of implant prosthodontics. A titanium fixture (commercially pure titanium grades or Ti-6Al-4V alloy, with roughened surfaces such as SLA or anodised coatings to accelerate healing) is allowed to integrate for roughly three months in the mandible and up to six in the maxilla under classic protocols, then restored with single crowns, fixed bridges, full-arch fixed prostheses or overdentures; the two-implant mandibular overdenture was declared the first-choice standard for the edentulous mandible at the 2002 McGill consensus. Success is judged by Albrektsson's criteria, including less than 1 mm of marginal bone loss after the first year in function.
What you must remember
- Osseointegration: direct bone-to-implant contact at the light microscopic level, without intervening fibrous tissue; first achieved reliably with commercially pure titanium by Brånemark's group.
- Implant materials: commercially pure titanium (grades I-IV) and Ti-6Al-4V alloy; surface roughening — titanium plasma spray, hydroxyapatite coating, sandblasted and acid-etched (SLA), anodised — enlarges bone contact and shortens healing.
- Classic two-stage healing: about three months unloaded in the mandible, four to six in the maxilla; one-stage systems and immediate loading hinge on primary stability (insertion torque thresholds around 35 Ncm are commonly quoted).
- Components: fixture (implant body), abutment, abutment screw, cover screw and healing abutment, impression copings (open and closed tray) and analogues; connections are external hex, internal hex or morse-taper (conical).
- Platform switching — a narrower abutment on the implant platform — aims to preserve marginal bone by moving the inflammatory connective tissue zone inward.
- Prosthetic options: single crowns, implant-supported fixed partial dentures, full-arch fixed (including tilted-posterior four-implant designs), and overdentures retained by bars, studs or locators.
- Albrektsson's success criteria (1986): individual unattached implant immobile, no radiolucent perimplant zone, bone loss under 1 mm in the first year and under 0.2 mm annually thereafter, no pain or infection — commonly quoted with long-term survival expectations above 85-90 percent.
- Contraindications and risks: uncontrolled diabetes, heavy smoking, previous head and neck radiotherapy, antiresorptive (bisphosphonate-related) osteonecrosis risk and untreated periodontitis; peri-implant mucositis versus peri-implantitis distinguishes reversible inflammation from progressive bone loss.
Planning an edentulous mandible, step by step
A 65-year-old with a loose lower denture and a resorbed ridge asks what implants can do. Work through the decision rather than the catalogue. History first — controlled type 2 diabetes is acceptable with good glycaemic control; smoking halves success odds and is discussed honestly; any history of bisphosphonate therapy is searched for specifically. Examination and imaging (OPG and cross-sectional imaging for bone height and width, and to map the inferior alveolar canal) determine feasibility: for an interforaminal mandible, two implants in the canine region with locator retention transforms a lower denture at moderate cost — the McGill consensus position — while four to six implants enable a fixed full-arch prosthesis for patients who demand stability and can maintain hygiene. Surgical planning sets spacing, depth and prosthetically driven positioning (the surgical guide communicates the planned tooth position, not the reverse). After placement, either unloaded healing per protocol or immediate loading if primary stability is high; then prosthetics: torque-verified abutments, verification of passive fit for a bar or framework, and occlusion designed to limit lateral forces (consider night guards for bruxists). Maintenance intervals tighten: professional cleaning around the peri-implant sulcus and radiographs track bone against Albrektsson's thresholds. This whole chain — biology, hardware, prosthesis, maintenance — is the exam structure of implant prosthodontics.
Success criteria and slips
Two answers reveal shallow preparation. Asked "what makes an implant successful?", candidates describe placement surgery; the examiner expects Albrektsson's measurable criteria, particularly the under-1 mm first-year bone loss figure. Asked about complications, they recite failures of integration alone and forget peri-implant diseases — mucositis (reversible soft tissue inflammation) versus peri-implantitis (progressive bone loss requiring surgical management) — the distinction examiners now probe in every implant viva.
Frequently asked questions
What is osseointegration?
The direct structural and functional connection between living bone and the titanium implant surface, without intervening fibrous tissue — the biological basis of implant support, established by Brånemark.
How long is the classical healing period before loading?
About three months in the mandible and four to six months in the maxilla under classic two-stage protocols; immediate loading is reserved for implants with high primary stability.
What did the McGill consensus conclude?
That the two-implant retained mandibular overdenture should be the first-choice standard of care for the edentulous mandible, offering superior function and quality of life over a conventional lower denture.
What are Albrektsson's success criteria?
Clinical immobility, absence of perimplant radiolucency, marginal bone loss under 1 mm in the first year and under 0.2 mm annually thereafter, and freedom from pain, infection or neuropathy.
Which conditions contraindicate implant placement?
Uncontrolled diabetes, active periodontitis, heavy smoking, recent head and neck irradiation and antiresorptive (bisphosphonate) therapy carrying osteonecrosis risk — each is weighed as relative or absolute per current guidance.