4. Dental Implantology Flashcards
What are some implant surface modifications?
-Hydroxyapatite (HA): no longer used
-Micro-rough surfaces (0.5-2.0 microns) either by acid etching or spraying implant surface with titanium oxide, hydroxyapatite, aluminum oxide
-Electrowetting: wettability of implants important to improve plasma protein adherence and mesenchymal cell adherence and differentiation (Fluoride and magnesium ions used, some manufacturers package implants in saline).
How does micro surface roughness improve implants?
Increased implant to bone surface area, clot retention, earlier osseointegration, harder and stronger bone around implants by increasing mRNA expression of osteonectin and osteocaclin.
Distance between implants and natural teeth
1.5mm
Normal bone loss in first year and each year after
<1.5mm for first year
0.2mm per year after
Distance between two implants
3mm
Distance between implant and buccal/lingual wall
1mm (2mm in esthetic zone to preserve buccal bone and for emergence profile)
Distance of implant apex to IAN
2mm
Distance of implant apex to nasal floor
1mm
Each 0.25mm increase in diameter yields a x% increase in surface area
10%
Thermal necrosis during drilling occurs above temperatures of x degrees C
47 degrees C
Minimum inter-arch space for cement retained vs. screw retained crowns
5mm cement retained
8mm screw retained
Contact point to crest of bone with preserved papilla
3mm - 100%
4mm - 100%
5mm - 98%
6mm - 56%
7mm - 27%
Define osseointegration
Branemark: direct, structural, and functional connection existing between ordered, living bone and the surface of a functionally loaded implant.
Process of which there is a bone to alloplastic interface without the interposition of non-bone tissue, which is clinically asymptomatic and is maintained in bone during functional load (based on electron micrograph findings)
What is primary stability?
Mechanical stability achieved at the moment of implant placement.
Depends on bone quality (density), shape of implant, and adequacy of surgical technique.
What is secondary stability?
Biological stability achieved after bone healing (osseointegration). Influenced by bone quality, implant surface, overall health of patient, and loading protocols.
Lekholm and Zarb bone classification
Bone classification based on the ratio of cortical and cancellous bone using radiographs:
- Type 1 bone is composed mostly of compact bone
- Type 2 is mostly a compact bone surrounded by a core of trabecular bone
-Type 3 thin layer of cortical bone surrounded mostly by trabecular bone - Type 4 thin layer of cortical bone surrounded by a core of low density trabecular bone
Misch bone density classification
D1: dense cortical bone (mandible)
D2: thick cortical and coarse trabecular (ant. mandible, post mandible, ant maxilla)
D3: Thin cortical compartment with dense trabecular (ant maxilla, post maxilla, post mandible)
D4: fine trabecular, extremely thin cortical (post maxilla)
Insertion torque of an implant should be ___NCm or more. Over torquing ___NCm may impair implant healing.
35 NCm
>80 Ncm
Describe the three loading protocols
- Immediate loading: prosthesis delivered up to 7 days after implant placement
- Early loading: prosthesis is delivered 6-12 weeks after implant placement (some implant surfaces consider 8 weeks as conventional loading).
- Conventional loading: prosthesis is delivered after osseointegration is achieved. 3 months for mandible and 4-6 months for maxilla.
Peri-implantitis is associated with which bacteria?
Gram-negative anaerobes including P. gingivalis, P. intermedia, Aggregatibacter actinomycetemcomitans.
Treatment for peri-implantitis
- local debridement (exposure and cleaning with instrument softer than titanium - consider rubber cup polisher with paste, plastic scalers, abrasive air powder treatment, interdental brushes).
- decontamination (40% citric acid with pH of 1 for 60 seconds, chlorhexidine, tetracycline 50mg/ml saline for 2 minutes, or application of local antibiotics e.g. tetracycline granules), Er:YAG or CO2 laser or 3% H2O2
- surgical - open flap combination of debridement and decontamination with allograft/autograft with membrane
- removal of implant
How does bone grafting heal?
Creeping substitution (osteoclasts resorb bone creating new vascular channels with osteoblastic bone formation resulting in new haversian systems. Laying down new bone and resorption of old bone)
Define osteogenic
Transfer of osteocompetent cells for de novo bone formation (autografts)
Define osteoinduction
Bone formation by stimulation of host mesenchymal cells to differentiate (allograft, BMP)
Define osteoconduction
Provides scaffolding for new bone formation propagated by native bone. Does not contain proteins or cells (xenograft)
Autogenous graft
Tissue from same person
Osteogenic, osteoinductive, and osteoconductive
Gold standard
Disadvantage is second surgical site
Allogeneic graft
Grafts taken from another individual of the same species but different genotype
Osteoinductive and osteoconductive
Strict screening for infections, malignancy, degenerative bone disease, hepatitis B or C, STDs, autoimmune disease, or other diseases that may affect bone quality
-Mineralized freeze-dried bone allograft (FDBA) or demineralized freeze-dried bone allograft (DFDBA). Both provide type 1 collagen which is the exclusive organic component of bone.
-Methods to decrease antigenicity = freeze drying, irradiating, dry heating
Xenograft
Graft taken from another species
- Osteoconductive
No organic component
Treated by sintering at 900 degrees C or high alkaline solution. Risk of prion transmission (bovine spongiform encephalopathy) is theoretical.
Hydroxyapatite crystalline structure allows for ingrowth of vessels and migration of osteogenic cells.
Recombinant Human-Bone Morphogenetic Protein-2 (BMP)
Transforming growth factor beta superfamily
Recombinant DNA technology in chinese ovarian hamster cells allows for transcription and collection of non-contaminated protein
Water soluble, requires collagen type 1 carrier (acellular collagen sponge) for slow release. Requires 15 minutes of absorption.
Concentration of 1.5mg/cc mixed with sterile water (do not substitute with normal saline as too hypertonic.
Chemotactic for pre osteoblasts and stem cells as well induces expression of VEGF by osteoblasts.
Only on label use is for sinus augmentation or alveolar ridge reconstruction.
Extensive edema due to influx of fluid and cells from chemotactic and neovascularization activities of BMP.
Allow 6 months prior to implant placement.
Contraindicated in pregnancy, allergy to rhBMP or type I bovine collagen, active infection at recipient site, active or history of malignancy at site, and skeletal immaturity.
Postoperative steroids and icing of tissue may reduce intensity of swelling.
Platelet-rich plasma (PRP)
Platelet derived growth factors act as mitogen (encourages cell division) and encourage osteoid production and endothelial cell replication.
PRP is a blood clot that is highly consentrated with platelets. Alpha granules in platelets secrete growth factors that bind to transmembrane receptors to induce its effect, initiating a faster initial cellular response.
Collection tube contains citrate dextrose as anticoagulant, which works by binding to calcium
Platelets are spun down either in two spins (separation spin followed with a concentration spin) or some manufacturers offer single spin units.
Activated via addition of CaCl2 and thrombin
Utilized in hard and soft tissue grafting
Platelet-rich fibrin (PRF)
PRF was developed as an improved formulation of previously utilized PRP to serve as a 3D scaffold to biologically enhance healing.
-New approach consists of platelet concentrate without use of anticoagulants. Obtained simply by centrifugation without anticoagulants and is strictly autologous.
-Fibrin matrix contains platelets and leukocytes as well as a variety of growth factors and cytokines including transforming growth factor beta1 (TGF-beta1), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), interleukin (IL)-1beta, IL-4, IL-6.
-These factors act directly on promoting the proliferation and differentiation of osteoblasts, endothelial cells, chondrocytes, and various sources of fibroblasts.
How thick is the schneiderian membrane?
0.13-0.5mm thick, composed of respiratory epithelium
What is the volume of the maxillary sinus
15mL per sinus
2.5cm wide, 3.75 cm tall
Where is the maxillary sinus ostium?
Superior-medial sinus wall (halfway in the AP distance of the sinus just below the orbital floor), 25-35mm above the antral floor. Opens into middle meatus via the infundibulum.
What is the vascular supply to the maxillary sinus?
Branches of the maxillary artery
1. PSA
2. ASA
3. Greater palatine
4. Lesser palatine
5. Lateral and posterior nasal branches of the sphenopalatine
Venous flow from facial vein, sphenopalatine vein, and pterygoid plexus
Implant bar attachment
Use?
Disadvantage?
Vertical restorative space?
Used for retention and support for an implant supported over denture
Need for large prosthetic space
Increased risk of mucositis and hyperplasia due to inadequate hygiene under the bar
Minimum 12-14mm vertical restorative space is required
Locator attachment
Male part consists of implant screw metallic abutment and female part of metallic cap is lined with nylon of different colors depending on their retention capacity, which is anchored to the denture.
Don’t require a large prosthetic space and can correct non-parallel implants up to 40 degrees.
Minimum 8.5mm vertical restorative space and 9mm horizontal space
Pros of screw-retained restorations
Ease of retrievability, low profile retention, limited crown height space, no residual cement, splinting non-parallel implants, screw is weakest link and prevents mechanical overload
Cons of screw-retained restorations
Prosthetic screw loosening or fracture
Device not sealed (bacterial growth)
Passive casting requires more accuracy
Lack of axial occlusal loads
Less esthetic restorations
Angulation problems can lead to undesirable access hole position
Pros of cement-retained restorations
Ease of splinting implants, better passive fit, easier correction of non-passive casting, improved force direction of loads, optimal occlusal contacts, enhanced esthetics,more economical
Cons of cement-retained restorations
Risk of residual cement causing peri-implantitis and implant failure, particularly if implant is placed deep. More difficult to retrieve if abutment becomes loose. Need for more crown height space.
Cantilever extension compared to AP spread
Cantilever extension limited to 1.5x AP spread
When AP spread is 1cm or more, Branemark and colleagues concluded that cantilever could be extended to, but not beyond, 20mm or up to two times the AP spread
Dizzy spell after Summer’s technique sinus lift
Benign paroxysmal positional vertigo (BPPV)
Meclizine (antihistamine)
Refer to ENT
Canalith repositioning procedure (Epley maneuver)
