4. Dental Implantology

Question 1

What are some implant surface modifications?

Answer 1

-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).

Question 2

How does micro surface roughness improve implants?

Answer 2

Increased implant to bone surface area, clot retention, earlier osseointegration, harder and stronger bone around implants by increasing mRNA expression of osteonectin and osteocaclin.

Question 3

Distance between implants and natural teeth

Answer 3

1.5mm

Question 4

Normal bone loss in first year and each year after

Answer 4

<1.5mm for first year
0.2mm per year after

Question 5

Distance between two implants

Answer 5

3mm

Question 6

Distance between implant and buccal/lingual wall

Answer 6

1mm (2mm in esthetic zone to preserve buccal bone and for emergence profile)

Question 7

Distance of implant apex to IAN

Answer 7

2mm

Question 8

Distance of implant apex to nasal floor

Answer 8

1mm

Question 9

Each 0.25mm increase in diameter yields a x% increase in surface area

Answer 9

10%

Question 10

Thermal necrosis during drilling occurs above temperatures of x degrees C

Answer 10

47 degrees C

Question 11

Minimum inter-arch space for cement retained vs. screw retained crowns

Answer 11

5mm cement retained
8mm screw retained

Question 12

Contact point to crest of bone with preserved papilla

Answer 12

3mm - 100%
4mm - 100%
5mm - 98%
6mm - 56%
7mm - 27%

Question 13

Define osseointegration

Answer 13

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)

Question 14

What is primary stability?

Answer 14

Mechanical stability achieved at the moment of implant placement.

Depends on bone quality (density), shape of implant, and adequacy of surgical technique.

Question 15

What is secondary stability?

Answer 15

Biological stability achieved after bone healing (osseointegration). Influenced by bone quality, implant surface, overall health of patient, and loading protocols.

Question 16

Lekholm and Zarb bone classification

Answer 16

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

Question 17

Misch bone density classification

Answer 17

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)

Question 18

Insertion torque of an implant should be ___NCm or more. Over torquing ___NCm may impair implant healing.

Answer 18

35 NCm
>80 Ncm

Question 19

Describe the three loading protocols

Answer 19

1. Immediate loading: prosthesis delivered up to 7 days after implant placement
2. Early loading: prosthesis is delivered 6-12 weeks after implant placement (some implant surfaces consider 8 weeks as conventional loading).
3. Conventional loading: prosthesis is delivered after osseointegration is achieved. 3 months for mandible and 4-6 months for maxilla.

Question 20

Peri-implantitis is associated with which bacteria?

Answer 20

Gram-negative anaerobes including P. gingivalis, P. intermedia, Aggregatibacter actinomycetemcomitans.

Question 21

Treatment for peri-implantitis

Answer 21

1. local debridement (exposure and cleaning with instrument softer than titanium - consider rubber cup polisher with paste, plastic scalers, abrasive air powder treatment, interdental brushes).
2. 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
3. surgical - open flap combination of debridement and decontamination with allograft/autograft with membrane
4. removal of implant

Question 22

How does bone grafting heal?

Answer 22

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)

Question 23

Define osteogenic

Answer 23

Transfer of osteocompetent cells for de novo bone formation (autografts)

Question 24

Define osteoinduction

Answer 24

Bone formation by stimulation of host mesenchymal cells to differentiate (allograft, BMP)

Question 25

Define osteoconduction

Answer 25

Provides scaffolding for new bone formation propagated by native bone. Does not contain proteins or cells (xenograft)

Question 26

Autogenous graft

Answer 26

Tissue from same person Osteogenic, osteoinductive, and osteoconductive Gold standard Disadvantage is second surgical site

Question 27

Allogeneic graft

Answer 27

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

Question 28

Xenograft

Answer 28

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.

Question 29

Recombinant Human-Bone Morphogenetic Protein-2 (BMP)

Answer 29

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.

Question 30

Platelet-rich plasma (PRP)

Answer 30

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

Question 31

Platelet-rich fibrin (PRF)

Answer 31

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.

Question 32

How thick is the schneiderian membrane?

Answer 32

0.13-0.5mm thick, composed of respiratory epithelium

Question 33

What is the volume of the maxillary sinus

Answer 33

15mL per sinus 2.5cm wide, 3.75 cm tall

Question 34

Where is the maxillary sinus ostium?

Answer 34

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.

Question 35

What is the vascular supply to the maxillary sinus?

Answer 35

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

Question 36

Implant bar attachment Use? Disadvantage? Vertical restorative space?

Answer 36

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

Question 37

Locator attachment

Answer 37

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

Question 38

Pros of screw-retained restorations

Answer 38

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

Question 39

Cons of screw-retained restorations

Answer 39

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

Question 40

Pros of cement-retained restorations

Answer 40

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

Question 41

Cons of cement-retained restorations

Answer 41

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.

Question 42

Cantilever extension compared to AP spread

Answer 42

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

Question 43

Dizzy spell after Summer's technique sinus lift

Answer 43

Benign paroxysmal positional vertigo (BPPV) Meclizine (antihistamine) Refer to ENT Canalith repositioning procedure (Epley maneuver)