CHAPTER 11: HOST MODULATION & IMPLANT THERAPY

ppt + discussion

host modulation therapy (HMT)

used in addition to SRP and surgery

modifies or reduces destructive aspects and regulates protective aspects of the host response

adjunctive approach to conventional periodontal therapy targeting the patient’s immune-inflammatory response, which drives tissue breakdown

purpose of host modulation therapy (HMT)

periodontal stability

enhance wound healing

aims to reduce excessive inflammation

risk factors of host modulation therapy (HMT)

addresses the host side of the host-bacterial interaction

produces excessive inflammatory processes to enhance wound healing and periodontal stability

addresses factors that adversely affect host response (ex: smoking, diabetes, genetic susceptibility)

drug classes that evaluated as HMTs:

BMPs

NSAIDs

growth factors

tetracyclines

bisphosphonates

enamel matrix proteins

comprehensive management of host modulation therapy

patient education

bacterial reduction (SP)

site-specific antibacterial treatment

risk factor modification

surgery if needed

host modulation therapy (HMT) agents

NSAIDs

bisphosphonates

sub-antimicrobial-dose doxycycline (SDD)

NSAIDs

systemic use can significantly slow alveolar bone loss

inhibit prostaglandin (PGE2), which regulates bone resorption

stopping it may cause a “rebound effect” with accelerated bone loss

not indicated as adjunctive HMT due to serious side effects and the need for long-term daily use

risk of NSAIDs

GI problems

hemorrhage

higher fragility of bone

—due to daily use for up to 3 years showed benefits however these can be an effect:

bisphosphonates

inhibits osteoclast activity, shown to enhance alveolar bone status in studies.

bone-seeking agents that inhibit bone resorption by disrupting osteoclast activity

not approved for periodontal disease; discouraged due to risk primarily with intravenous use

risk of bisphosphonates

osteonecrosis of the jaws (ONJ)

sub-antimicrobial-dose doxycycline (SDD)

must not be used as monotherapy

can be combined with local antimicrobial delivery systems

only FDA-approved systemically administered HMT adjunct to SRP for chronic periodontitis

acts via:

• enzyme, cytokine reduction

• MMP (MMP-8 and MMP-9) inhibition

• osteoblast stimulation—not an antibiotic effect

MMP → matrix metalloproteinases (ex: Periostat)

indications of sub-antimicrobial-dose doxycycline (SDD)

chronic and aggressive periodontitis as adjunct to SRP

in refractory cases and high-risk patients (smokers, diabetics, osteoporotic, genetically susceptible)

contraindications of sub-antimicrobial-dose doxycycline (SDD)

children <12 years

allergy to tetracycline

pregnancy / lactation

disadvantage: may reduce efficacy of oral contraceptives

benefits of sub-antimicrobial-dose doxycycline (SDD)

gains in attachment

reduced probing depth

stimulates osteoblasts

no resistance risk at 20mg dose

effective even in high-risk patients (e.g., smokers)

dosage of sub-antimicrobial-dose doxycycline (SDD)

20mg BID for 3–9 months → first round of SRP

SDD + local delivery (atridox) + SRP

demonstrated >2mm improvement in attachment gains and probing depth reductions vs SRP alone (p<0.0001) in a 6-month, 180 patient trial

locally administered HMTs

used as adjuncts to surgical procedures to stimulate regeneration

topical NSAIDs have not been approved

examples of FDA-approved locally administered HMTs

enamel matrix proteins (Emdogain)

bone morphogenetic proteins (rhBMP-2 / INFUSE)

recombinant human platelet-derived growth factor-BB (GEM 215)

discovery of osseointegration

in the 1950s, Per-Ingvar Bränemark discovered an intimate bone-to-titanium apposition while studying blood circulation in bone (a serendipitous breakthrough)

his implants anchored prosthetic teeth in edentulous jaws; the first patient was treated in 1965

subsequent studies confirmed 15-year success with CP titanium implants using a strict unloaded healing protocol.

the standard early implant designs

screw-shaped threaded cylindric implant

osseointegration

clinically defined as asymptomatic rigid fixation

historically defined as direct structural and functional connection between living bone and implant surface without soft tissue

initial healing of osseointegration

mirrors bone fracture repair

immobility: movement >150 μm prevents osteoblast differentiation → fibrous scar tissue → nonintegration

temperature: bone necrosis occurs if overheating during drilling exceeds 47°C for 1min

bone maturation

steady remodeling state reached after 18 months

progresses from fast-growing, poorly mineralized woven bone to slow-growing, dense lamellar bone

primary stability (placement) of osseointegration

depends on implant geometry and bone quantity/quality

secondary stability (over time) of osseointegration

depends on implant surface and percentage of bone contact

peri-implant soft tissues

includes:

• oral epithelium, sulcular epithelium

• a sulcus, long junctional epithelial attachment

• underlying connective tissue — similar to teeth

implant

bone is in direct contact with the implant

lacks PDL, cementum, and Sharpey’s fibers

long junctional epithelium

attaches to titanium via basal lamina and hemidesmosomes

peri-implant “biologic width”

3-4mm or 4-4.5mm

combined height of epithelial attachment and supracrestal connective tissue

connective tissue fibers

cannot insert into the implant surface

run mostly parallel or in a cuff-like circular orientation, forming a soft tissue “seal”

laser-microgrooved surfaces can stop epithelial down-growth and establish perpendicular connective tissue insertion

keratinized tissue

not required for long-term success

may cause pain or discomfort during oral hygiene due to mobility of nonkeratinized mucosa

not a strict prerequisite for success, but its absence Increases susceptibility to peri-implant problems and patient discomfort during oral hygiene.

soft tissue grafting can augment it

vascular supply

scarcer than around teeth; no contribution from PDL

peri-implant tissues respond to plaque with inflammation similar to periodontal tissues

probe stops in healthy tissue

1.5mm coronal to alveolar crest (above the bone)

clinical consequences (teeth vs. implants)

• lack of resiliency:

  • implants lacks PDL, so they are rigidly attached and cannot move to compensate for occlusal disharmony

  • overload can cause microfractures and bone loss

• growth:

  • implants placed before growth completion will not migrate or erupt with natural teeth

  • can lead to occlusal problems; therefore, contraindicated in growing patients

• maintenance:

  • long-term success requires meticulous plaque control

  • frequent maintenance visits are recommended every 3-4 months

comprehensive periodontal management

patient education & oral hygiene

high-quality SRP + local delivery

host modulation (SDD)

risk factor modification

surgery + HMT if indicated

implant geometry: macrodesigns

blade implants

pins & disks implants

subperiosteal implants

transmandibular staple implants

blade implants

<50% success at 5 years

thin, flat metal plates inserted into the jawbone

removal required sacrificing significant surrounding bone

designed for narrow ridges where standard implants won’t fit

popular in the past, but now rarely used due to lower long-term success (attributed to biotolerance, not osseointegration)

relied on fibroosseous integration → fibrous scar tissue at the bone-implant interface → mistakenly thought to mimic the pdl

high-speed drilling can cause:

necrosis

marsupialization

epithelial downgrowth

transmandibular implants

used for severely resorbed mandibles

now largely obsolete due to safer alternatives

requires major surgery under general anesthesia

a metal plate placed through the entire lower jaw (mandible)

stable implant: 93% survival at 5 years but 10-15% complication rate

pins & disks implants

fibrous encapsulation and infection led to implant loss

pins:

• small metal pins inserted into bone

• used to stabilize dentures or other implants

• limited use today

disk implants:

• flat, circular implants placed laterally into bone

• designed for thin jawbones

• also mostly outdated

subperiosteal implant

used when there is insufficient bone height

placed on top of the bone but under the gum

<50% survival at 5-10 years; rarely used today

custom metal framework supports prosthetic teeth

fibrous encapsulation and rapid bone resorption led to abandonment

root form implants

ITI hollow cylinder

IMZ solid cylinder

screw-shaped

ITI hollow cylinder

developed by Straumann (formerly ITI)

hollow cylindrical design placed into bone

early version of modern implant systems

allows bone ingrowth to grow into the hollow space

disappointing survival rates → withdrawn from use

IMZ solid cylinder

developed in Germany (IMZ system)

aimed to mimic natural tooth movement

eventually fell out of favor due to mechanical complications

solid cylindrical implant with an internal shock-absorbing element

89.9% at 60 months, but only 38% at 10 years

screw-shaped

parallel or tapered geometry

most widely used implant today

high success rate and long-term stability

root-form design that mimics natural tooth roots

threaded design disperses axial forces in multiple directions

surgically inserted into bone and integrates via → osseointegration

implant surface: microdesign

additive processes

subtractive processes

surface free energy

additive processes

you add material onto the implant

like coating or layering something on top

makes the surface more friendly for bone to attach

ex:

• plasma spraying

• hydroxyapatite coating

• calcium phosphates → increase surface roughness and accelerate initial bone cell adaptation

subtractive processes

you remove material from the implant

like scratching or roughening the surface

helps the bone grip the implant better

rough surfaces → speed bone apposition but may increase ion leakage and macrophage adherence

ex:

• machining, acid etching

• blasting-promote favorable cellular responses

• increased bone formation at the microscopic level

surface free energy

related idea → wettability (how easily liquid spreads)

how well the implant surface attracts liquids (like blood)

• if not → healing is slower

• if it attracts liquid well → bone cells stick better

bone-to-implant interface rigidity

the predominant biomechanical factor for load-bearing success

soft tissue interface quality

critical for stable marginal bone levels long-term

treatment sequence for peri-implant infection