The completely edentulous mandible: Treatment plans for fixed restoration

1. The completely edentulous mandible:Treatment plans for fixed restoration Presented by: Dr. GlarehEblaghian Supervised by: Dr. MansourRismanchian and Dr. saiedNosouhian Dental of Implantology Dental Implants Research Center Isfahan university of medical science

2. The completely edentulous mandible: Treatment plans for fixed restoration

3. Over the last 15 years, many of completely edentulusmandibular arches have been treated with implant overdentures • Many of these patients choose to have a removable prosthesis because of financial consideretions • Advantages of maxillary supported removable prosthesis is: • upper lip support for aesthetic and daily maintanance • Labial flange of mandibularoverdenture rarely is requred for aesthetic • For hybrid fix restoration and fully implant supported overdenture (RP4): • labratoary and component cost is simillar • Chair time required is similar But because dentures and partial dentures typically cost several times less than fixed restorations, the doctor often chareges half the fee for an implant denture

4. Comparing fixed versus removable implant prostheses: 2. Removable implant overdentures require greater maintenance and exhibit more complications than fixed restorations Problem of IODs in review of litrature by Goodacare: Retention and adjestement problem(30%) Clip or attachment fracture(17%) Fracture of prosthesis (12%) Reline(19%) 3. Mandibularoverdenture often traps food below its flanges the daily care for bar implant overdenture is similar to that for fixed mandibular restoration ( because ridge lap pontics are not required) 1. Feeling and acting simillar to natural teeth 4.Important role for the presence of complete implant supported restoration is the maintenance and regeneration of posterior bone in mandible

5. Force factors: • the amount of force transmitted to an implant fixed prosthesis is similar to RP4 (then the number of implants to support either prosthesis should be simillar) • For nocturalparafunctional overload, patient is willing to remove the maxillary denture at night • For patient with natural teeth or implants in the maxillary, more implants usually are indicated for mandibular fix prosthesis • Force factores: parafunction, crown height, masticatory dynamics, bone density of implant region

6. Force factors: increased force factores contribute to Uncemented restorations, screw loosening, component fracture, crestal bone loss Fixed prosthesis may required an improved biomechanical position

7. Mandibular dynamicsmedial movement: • five different movement have been postulated (medial convergence is most common): • Mandible between mental foraminae is stable • Distal to the foraminae , mandible exhibits movement toward the midline on opening ( because of attachment of internal ptrygoid) • distortion of the mandible occurs early in the opening cycle • maximum changes occure with as little as 28% opening (12mm) • Flexture also occure during protrusive movement • Amount of movement depends on density and volume of bone and location of the site

8. Mandibular dynamicsmedial movement: Mandibular body flexture to midline: • 1500 micron in ramus to ramus • 800 micron in first molar to first molar

9. Torsion: • In animal study: mandible twisted on working side and bent on balancing side in the parasagital plan during power stroke • in human study Using strain gauges on screws attached to cortical bone Using implant supported prosthesis • the torsion during parafunction is caused by contraction of masseter muscle attachments • Posterior bone gain in edentulous patients restored with cantilevered prosthesis may be consequence of mandibularflexture and torsion • Because bite force may increase 300% with an implant prosthesis compared with denture stimulate posterior mandibular body to increase size

10. Torsion: • most common position of mental foramen is between the first and second premolar mandibular dynamic should be consider in splinting teeth distal to the bilateral premolar The more distal the rigid splint from one side to other , the greater the risk thetmandiblular dynamics may influence the prognosis The body of mandible flexes more when the size of bone decreases (C-h or D ≥ A)

11. Difference in movement between an implant and tooth: • natural tooth 28 micron movement apically • 56-108 micron movement laterally • rigid implant 5 micron movement apically • 10-80 micron movement lateraly • Mandibularflexture and torsion may be more than 10-20 times Flexture and torsion of mandibular body are more critical • In the past , 4 implant in the mandible is thwarted by the prosthesis but this introduces lateral stress to the implants

12. Molar implants, screws and bone have increase risk because of mandibularflexture and torsion Consequence of cross arch connection of posterior mandibular implants loss of implant fixation material fracture (implant or prosthesis) unretained restorations discomfort upon opening JustImplants placed in front of foraminaeand splinted together, or implants in one posterior quadrant joined to antrior implants have not shown these complication

13. Therfore all edentulous mandibular patients should be given the option of having fixed prosthesis There are five treatment option used to restore a complete edentulous mandible with fixed prosthesis or RP4 overdenture

14. The mandible does not flex or exhibit significant torsion between mental foraminae, soanterior implants may be splinted together • Branemark approach: placement of 4 or 6 anterior root form implant between the mental foraminae and distal cantilever offeach side to replace the posterior teeth Treatment option 1:the Branemark approach Result: 80% to 90% implant survival for 5 to 12 years after first year 84% success rate for 18 to 23 years • The anterior arch form + foraminae position , affects the position of the distal most implants • The anterior arch form (square, oval, tapered) is related to the anterior most implant position

15. The greater the A-P spread, the further the distal cantilever may be extended • The most common number of implants used today in the Branemark option is five • This number allows as great an A-P spred as six implants with greater interimplant distance • If bone loss occurs on one implant, the loss whould not automatically affect the adjacent implant sites Genaral rule: for five anterior implants in the anterior mandible between the foraminae the cantilever should not exceed 2.5 times the A-P spread

16. If the stress factors are high ( parafunction , crown height, masticatory musculature dynamics, opposing arch) , cantilevering may be contraindicated • →Length of the posterior cantilever depends on the specific force factors of the patients • The area over which the forces are applied from the prosthesis to the implant can be modified through the number, size, and design of the implants • A cantilever rarely is indicated on three implants, even with a simillar A-P spread as five implants • Narrow implants are not designed to support cantilevers

17. treatment option 1 depends greatly on patient force factors, archform, number, size and design of implants • The safest action: reserve this option for patients with low force factors such as older female, wearing upper denture, abundant anterior bone, crown height to 15mm , tapered or ovoid mandibular arches

18. Treatment option 2: A slight variation of the Branemark protocol to place additional implants above the mental foraminae

19. A slight variation of the Branemark protocol is to place additional implants above the mental foraminae Bone strain model of flexture and torsion in university of Alabama Advantages : 1. number of implants may be increased to as many as seven 2. A-P spread for implant placement is greatly increased, even when the total implant number is 5 3.The length of the cantilever is reduced dramatically because the distalmost implant is placed one tooth more distal

20. A prerequisite available bone in height and width over the foraminae (because foraminae usually is located 12mm above the inferior border of the mandible) • themost distal implant bears the greatest load when loads are placed on the cantilever • A minimum recommended implant height of 9mm and a greater diammeter of an enhanced surface area recommended • Key implant positions: second premolars, canines, centeral incisor or midline position

22. Treatment option 3: One posterior segment connected to anterior segment

23. Misch has evaluated full-arch fixed prostheses on implants with one posterior segment connected to the anterior region over the last decade • another treatment option to support a fixed mandibularprosthese consist of additional implants in the first molar or second premolar, connected to 4 or 5 implant between the mental foraminae

24. The key implant position are: first molar (on one side), bilateral premolar, bilateral canine • The secondary impalnt position are: second premolar on the same side as the molar implant, central incisor (midline) • One pice casting can be fabricated and one cantilever to the opposite side of the molar implant would replace those posterior teeth • When one or two implants are placed distal to the foraminae on one side and joined to anterior implants, a considrable biomechanical advantage is gained

25. option 3 is a better option than anterior implants with bilateral cantilevers • The A-P spread is 1.5 to 2 times greater , because on one side the distal aspect of the last implant now corresponds to the distal aspect of the first molar • When force factors are greater , 6 or 7 implant may be used • five implant between foraminae and one or two implant distal on one side • this option requires available bone in at least one posterior region

27. Treatment option 4: Bilateral implant that they are not splinted together

28. This option is selected : When force factors are great or the bone density is poor When the body of mandible is division C-h and subperiosteal or disc like implants are used for posterior • Key implant positions: first molars, first premolars, canines • Secondary implant positions: second premolars and/or incisor

29. al l implants in the anterior and one posterior side are splinted together for a 9-unitfixed prostheses • The other posterior segment is restored independently • Most often three implant are used for smaller segment to compensate for force factoresand the alignment of the implants almost in a straight line advantages: Elimination of cantilever risk of uncementedrestorations and occlusal overload are reduced prostheses has two segments rather than one

30. 4. Weaker cements can be used 5. If the prostheses requires repair , the affected segment may be removed easily Disadvantages need for abundant bone in both posterior region additional cost The restoration should exhibit posterior disclusion in excursions to limit lateral loads, especially to the prostheses supported by fewer implants

31. Treatment option 5: Three independent prostheses

32. Key implant positions: 1. Two first molars, two first premolars, two canines posterior restoration extend from first molar to first premolar and anterior restoration replaces the six anterior Treatment option 4 is better 2. Two first molars , second premolars, first premolars, and both canines Treatment option 5 is better

33. posterior restorations are two independent implant prostheses unit and anterior prosthesis extend from first premolar to first premolar • Advantages : • Smaller segments for individual restorations • Most flexibility and torsion of the mandible in greater body movement (in parafunction and decrease in size of the body) • choice option when force factors are sever • Disadvantages: • Greater number of implants required • Available bone needs are greatest in this option • Most common scenario for option 5 is when the posterior mandible is C-H bone volume and a circumferential subperiosteal or disc-design Implant is used as the second premolar and first molar