THE EDENTULOUS AND : FIXED VERSUS REMOVABLE TREATMENT PLANNING Increasing Demand for Dental Implants

(1) patients living longer (2) age-related tooth loss (3) patients are more socially active and esthetic conscious (4) conventional prosthesis complications (5) the inherent advantages of implant-supported restoration Anatomic Consequences Of Edentulism ■ Bone requires stimulation to maintain its form and density ■ Teeth transmit compressive and tensile forces to the surrounding bone. ■ When a tooth is lost, the lack of stimulation to the residual bone causes a decrease in trabeculae and bone density in the area, with loss in external width, then height, of the bone volume ■ There is a 25% decrease in the width of bone during the first year after tooth loss and an overall 4 mm decrease in height during the first year after extractions for an immediate denture Advantages of Implant-Supported Prostheses

■ Maintenance of Bone ■ Occlusion Stability ■ Occlusal Awareness ■ Masticatory Efficiency ■ General Health ■ Higher Success in Comparison To Other Treatments ■ Increased Biting Force ■ Nutrition ■ Psychological Health Mandibular Treatment Planning Principles Anteroposterior Spread

■ The distance from the center of the most anterior implant to a line joining the distal aspect of the two most distal implants on each side

■ the greater the A-P spread, the farther the distal cantilever may be extended to replace the missing posterior teeth ■ when five to six anterior implants are placed in the anterior mandible between the foramina to support a fixed prosthesis, the cantilever should not exceed two times the A- P spread, with all other stress factors being low ■ The A-P distance is affected by the arch form. The types of arch forms may be separated into 1. Square 0 to 6 mm

2. Ovoid 7 to 9 mm

3. Tapering greater than 9 mm

 Hence whereas a tapering arch form may support a 20-mm cantilever, a square arch form requires the cantilever to be reduced to 12 mm or less, however is directly dependent upon force factors. ■ The position of the mental foramen can affect the A-P spread  The farther forward the foramen, the shorter the cantilever length because the A-P spread is reduced ■ If the stress factors are high (e.g., parafunction, height, masticatory musculature dynamics, opposing arch), the cantilever length of a prosthesis should be reduced and may even be contraindicated. ■ The density of bone is also an important criterion. The softest bone types (D3 and D4) should not have as great of a cantilever than the denser types (D1 and D2( Mandibular Flexure

■ Many reports have addressed the dimensional changes of the mandible during jaw activity as a result of masticatory muscle action. ■ Medial convergence is the one most commonly addressed ■ The mandible between the mental foramina is stable relative to flexure and torsion. However, distal to the foramina, the mandible exhibits considerable movement toward the midline on opening. ■ This movement is caused primarily by the attachment of internal pterygoid muscles on the medial ramus of the mandible  The distortion of the mandible occurs early in the opening cycle, and the maximum changes may occur with as little as 28% opening (or about 12 mm). This flexure has also been observed during protrusive jaw movements Torsion

■ the mandible twisted on the working side and bent in the parasagittal plane on the balancing side during the power stroke of mastication and unilateral biting ■ The torsion during parafunction is caused primarily by forceful contraction of the masseter muscle attachments ■ Therefore parafunctional bruxism and clenching may cause torsion-related problems in the implant support system and prosthesis when the mandibular teeth are splinted from the molar-to-molar regions Mandibular Overdenture Treatment Planning (RP-4 and RP-5) Anatomy of the Mandible

■ In treatment planning the mandible for a fixed or removable prosthesis, the mandible is divided into three regions: (1) anterior mandible (2) posterior right (3) posterior left ■ The available bone in the anterior mandible is divided into five equal columns of bone serving as potential implant sites, labeled A, B, C, D, and E, starting from the patient’s right side Overdenture Option 1

■ The first treatment option for mandibular overdentures (OD-1) is indicated primarily when cost is the most significant patient factor and minimal retention is required ■ Bone volume should be abundant (Division A or B) in the anterior, and the posterior ridge form should be an inverted U shape, with high parallel walls for good-to-excellent anatomic conditions for conventional denture, support, and stability

 The buccal shelf (primary stress bearing area) should be prominent to withstand the forces  Under these conditions, two implants may be inserted in the B and D positions. The implants usually remain independent of each other and are not connected with a superstructure ■ Positioning of the implants in the B and D positions is a much better prosthetic option in OD-1 than positioning in the A and E regions ■ Independent implants in the A and E positions allow a greater amplitude of rocking of the prosthesis compared with implants in the B and D regions

■ When using B and D implants, the anterior movement of the prosthesis is reduced, and the prosthesis even may act as a splint for the two implants during anterior biting forces, thereby decreasing the stress to each implant ■ Hygiene procedures also are facilitated with independent attachments.

■ The disadvantages of the OD-1 relate to its relatively poor implant support and stability, compared with the other options, because of the independent nature of the two implants. The other disadvantages of OD-1 relate to an increase in prosthetic maintenance appointments. ■ For the prosthesis to be inserted and function ideally, the two implants should be parallel to each other, perpendicular to the occlusal plane, at the same horizontal height (parallel to the occlusal plane), and equal distance off the midline

 If one implant is not parallel to the other, the prosthesis will wear one attachment faster because of the greater displacement during insertion and removal than the other.

 is severe, the prosthesis at all. ■ The two independent implants should be positioned at the same occlusal height, parallel to the occlusal plane. If one implant is higher than the other, the prosthesis will disengage from the lower implant during function and rotate primarily on the higher implant. ■ This situation will accelerate the wear of the attachment on the lower implant. In addition, because the higher implant receives the majority of the occlusal load, an increased risk for complications may occur, including abutment screw loosening, crestal bone loss, and implant failure ■ The implants should be equal distance off the midline. If one implant is more distal (farther from the midline) , it will serve as the primary rotation point or fulcrum when the patient occludes in the posterior segments. As such, the more medial implant attachment will wear faster, and the more distal implant will receive a greater occlusal load

Overdenture Option 2

■ Three root form implants are placed in the A, C, and E positions for the second overdenture treatment option ■ The additional implant provides a six fold reduction in superstructure flexure (i.e. if splinted bar is used) and limits the consequences previously discussed.  screw loosening occurs less frequently  The greater surface area of implant to bone allows better distribution of forces. ■ The risk for abutment or coping screw loosening is reduced further because force factors are decreased. ■ distribute stresses more efficiently and minimize crestal bone loss

■ Ideally, the implants in the A, C, and E positions should not form a straight line ■ The C implant is anterior to the more distal A and E implants and directly under the cingulum position of the denture teeth  The greater the A-P spread of the A, C, and E implants, the greater the biomechanical advantage to reduce stress on the implant and the better the lateral stability of the implant bar and overdenture system  Rotation of the prosthesis may also be more limited compared with OD-1 ■ This is usually the first treatment option for a patient with minimal complaints who is concerned primarily with retention and anterior stability when cost is a moderate factor. ■ If the anterior and posterior ridge form is favorable (Divisions A or B), the implants are placed in the A, C, and E areas, and a wide range of attachments is available ■ If the posterior ridge form is poor (Division C−h), the lack of lateral stability places additional forces on the anterior implants. Implants then are best placed in the B-C-D position to allow greater freedom of movement of the prosthesis

■ The prosthesis movement for three implants with C−h posterior bone should be greater to minimize forces on the implants and bar or individual attachment system. Overdenture Option 3

■ In the third mandibular overdenture option (OD-3), four implants are placed in the A, B, D, and E positions ■ These implants usually provide sufficient support to include a distal cantilever up to 10 mm on each side if the stress factors are low ■ The patient’s indications for this OD-3 include moderate-to-poor posterior anatomy that causes a lack of retention and stability, soft tissue abrasions, and difficulty with speech ■ The edentulous posterior mandible resorbs four times faster than the anterior mandible. ■ In the C−h posterior mandible the external oblique and mylohyoid ridges are high and often correspond to the crest of the residual ridge. The muscle attachments therefore are at the crest of the ridge.  The OD-3 prosthesis is indicated to obtain greater stability and a more limited range of prosthesis motion. The overdenture attachments often are placed in the distal cantilevers. The prosthesis is still RP-5, but with the least soft tissue support of all RP-5 designs Overdenture Option 4

■ The fourth mandibular overdenture option (OD-4) is designed for three types of patients: 1) This is a minimum treatment option for patients with moderate-to-severe problems related to a traditional restoration. The needs and desires of the patient are often most demanding and may include limiting the bulk or amount of the prosthesis, major concerns regarding function or stability, posterior sore spots, and the inability to wear a mandibular denture 2) for the treatment of continued bone loss in the posterior mandible 3) patient who suffers from severe soft tissue sore spots or a history of xerostomia. ■ Because of the completely supported nature of this implant treatment plan, no resultant force will be applied to the soft tissue. ■ Therefore even when no posterior implants are inserted, the attachments, cantilevered bar, and overdenture avoid load to the residual ridge and often halt its resorption process Division C−h Anterior

■ The increase in crown/implant ratio and decrease in implant surface area mandate modification of these initial options ■ In the C−h anterior bone volume patient, one more implant is added to each option and OD-1 is eliminated completely. Fixed Prosthesis

Fixed Prosthesis Advantages: 1) Psychological 2) Improved Speech 3) Decreased Soft Tissue Irritation 4) Increased Biting Force 5) Less Bone Resorption 6) Less Soft Tissue Extension 7) Less Long-Term Expenses 8) Less Interocclusal Space Requirement 9) Patients with Limited Dexterity 10) Increased Chewing Efficiency Mandibular Fixed Prosthesis Treatment Option 1: The Brånemark Approach

■ This classical treatment plan involves four to six implants between the mental foramina, and bilateral distal cantilevers replace the mandibular posterior teeth, usually to the first molar region ■ The mandible does not flex or exhibit significant torsion between the mental foramina. Therefore anterior implants may be splinted together without risk or compromise ■ Treatment option 1 depends greatly on patient force factors; arch form; and implant number, size, and design. ■ As a result, this option should be reserved for patients with low force factors, opposing a removable prosthesis, lower biting force, favorable bone density, and available bone for ideal implant dimensions Treatment Option 2: Modified Brånemark Technique ■ A slight variation of the ad modum Brånemark protocol is to place additional implants above the mental foramina because the mandible flexes distal to the foramen. ■ An implant above one or both foramina presents several advantages: 1) the number of implants may be increased to as many as seven, which increases the implant surface area. 2) the A-P spread for implant placement is greatly increased. The more distal implant positions will reduce the class 1 lever forces generated from the distal cantilever prosthesis 3) The length of the cantilever is reduced dramatically because the distal most implants are positioned at least one tooth more posterior ■ A prerequisite for treatment option 2 is the presence of available bone in height and width over one or both foramina. ■ When available bone is present, the foramen often requires implants of reduced height compared with the anterior implants.  The most distal implant bears the greatest load when loads are placed on the cantilever (acts as fulcrum); therefore the greatest forces are generated on the shortest implants.  A minimum recommended implant height of 8 mm and a greater diameter or an enhanced surface area design are recommended to compensate for the reduced implant length ■ The key implant positions in treatment option 2 are the second positions, the canine positions, and the central or midline position. The two optional implant sites are the first premolar sites and are more often indicated when the patient force factors are greater than usual Treatment Option 3: Anterior Implants and Unilateral Posterior Implant

■ The third fixed treatment option is used when inadequate bone is present over the foramina and support is required more posteriorly ■ an improved treatment plan option to support a fixed mandibular prosthesis consists of additional implants in the first molar or second premolar position (or both) connected to four or five implants between the mental foramina. Hence five to seven implants usually are placed in this treatment option ■ The key implant positions for treatment option 3 are the first molar (on one side only), the bilateral first premolar positions, and the bilateral canine sites. The secondary implant positions include the second premolar position on the same side as the molar implant and the central incisor (midline) position. ■ Although mandibular movement during function occurs, it has not been observed to cause complications, because the side opposite to the molar implant has no splinted implant(s) ■ This approach is superior to treatment option 1 or 2 with bilateral cantilevers because: (1) the A-P spread is dramatically increased (1.5 to 2) (2) more implants may be used if desired (3) only one side has a cantilever. However, this option requires available bone in at least one posterior region of the mandible Treatment Option 4: Anterior Implants and Bilateral Posterior Implants

■ Treatment plan options for fixed full-arch prostheses also may include bilateral posterior implants as long as they are not splinted together in one prosthesis. ■ This option is selected when force factors are great or the bone density is poor. Poor bone quality most often is observed in the posterior maxilla, but on occasion it is also found in the mandible ■ In treatment option 4, implants are placed in all three segments of the mandible. Key implant positions for this treatment option include the two first molars, two first , and two canine sites. Secondary implants may be added in the second premolars or the incisor (midline) position (or both) ■ Prosthetically, all implants in the anterior and one posterior side may be splinted together for a fixed prosthesis. ■ The other posterior segment is restored independently with an independent three-unit, fixed prosthesis supported by implants in the first premolar and first molar region. ■ At least six implants typically are used in this option, but seven are more often used, so the smaller segment has three implants ■ The primary advantage of this treatment option is the elimination of cantilevers. As a result, risks for occlusal overload are reduced.  Another advantage is that the prosthesis has two segments rather than one. The larger segment (molar to contralateral canine) has an improved advantage because it has implants in three to four different horizontal planes.  Because no cantilever is present, less damaging forces are applied to the prosthesis.  If the prosthesis requires repair, the affected segment may be removed more easily because only the segment requiring repair needs to be removed. ■ Disadvantages for treatment option 4 include the need for abundant bone in both mandibular posterior regions and the additional costs incurred for one to four additional implants. ■ Another modification for the completely edentulous mandible is to fabricate three independent prostheses rather than two. ■ The anterior region of the mandible may have four to five implants. The key implants are in the two first molar sites, the two first premolar sites, and two canine regions. Secondary positions are the two second premolar and central incisor (midline) sites. With this protocol, the posterior restorations extend from first molar to first premolar, and an anterior restoration replaces the six anterior teeth. ■ The advantages of this option are smaller segments for individual restorations in case one should fracture or become uncemented. ■ In addition, if greater mandibular body movement is expected because of parafunction or a decrease in size of the body of the mandible, the independent restorations allow the most flexibility and torsion of the mandible Treatment Option 5: All-on-Four Protocol

■ The treatment option 5 includes the “all-on-four” concept, which was developed to avoid regenerative procedures that potentially increase the treatment costs and patient morbidity. ■ This protocol, developed by Malo, uses four implants in the anterior part of a completely edentulous jaw to support a provisional, fixed, and immediately loaded prosthesis. ■ Most commonly, the two most anterior implants are placed axially, whereas the two posterior implants are placed at an angle (i.e., usually at an approximately 45-degree angle) to increase A-P spread along with decreasing the cantilever length ■ Tilted implants have been shown to generate favorable biomechanical outcomes and in a meta analysis, there was no significant difference in either failure rate compared with axially placed implants or marginal bone loss. ■ The tilted implants offer several advantages, which include the use of longer implants (i.e., greater surface area and primary stability), reduced or eliminated cantilever length, and avoidance of vital structures such as the inferior alveolar canal. ■ Because of the increased skill level required, clinicians early on their learning curve should exercise caution in these cases The Edentulous Maxilla: Fixed versus Removable Treatment Planning Treatment Planning Factors

■ Smile Line ■ Lip Support ■ Ridge Position ■ Crown Height Space (Interocclusal Space) Fixed Maxillary Treatment Plans

■ All reports concur with the finding that maxillary bone tends to be of poorer quality and volume, and presents several biomechanical disadvantages. ■ To compensate for the poor local conditions, a greater number of implants should be planned, along with a greater anteroposterior (A-P) distance. ■ Therefore a number of core principles are used when treatment planning an edentulous maxillary arch for a fixed prosthesis; following these principles increases the success rate. 1. The number of implants is related to the dental arch form. 2. The arch form is dictated by the final dentition or prosthesis, not the edentulous ridge arch form. 3. Key implant positions exist: anterior, canine, premolar, and molar. 4. An RP-4 (totally implant supported removable prosthesis) prosthesis is treatment planned the same as a fixed prosthesis ■ Three common dental arch forms for the maxilla exist: 1) Square 2) Ovoid 3) Tapering  As a consequence of bone resorption the edentulous ridge arch form usually will differ from the dentate arch form. The dental arch form of the patient is determined by the final teeth position in the premaxilla and not the arch shape of the residual ridge.  The number and position of implants are related to the arch form of the final dentition (prosthesis), not the existing edentulous arch form ■ The dental arch form in the anterior maxilla is determined by the distance from two horizontal lines. ■ The first line is drawn from one canine (i.e., in a diagnostic wax-up or existing prosthesis if no teeth are present) incisal edge tip to the other. This line most often bisects the incisive papilla. ■ The second line is drawn parallel to the first line, along the facial position of the anterior teeth

Maxillary Fixed Prosthesis Treatment Option 1

■ In a dental square arch form, lateral and central are minimally cantilevered facially from the canine position, resulting in a lesser requirement of an implant in the central or lateral position. ■ When maxillary fixed prosthesis treatment option 1 is used, mandibular excursions and occlusal forces exert less stress on the canine implants. ■ As a result, implants in the canine position to replace the six anterior teeth may suffice when the force factors are low and if they are splinted to additional posterior implants

Maxillary Fixed Prosthesis Treatment Option 2

■ If the final teeth position is an ovoid arch form, at least three implants should be inserted into the premaxilla: one in each canine and preferably one in a central incisor position ■ The central incisor position increases the A-P distance from the canine to central and provides improved biomechanical support to the prosthesis ■ In long-term edentulous maxillae with significant atrophy, treatment option 2 will most likely require bone augmentation before implant insertion  When patient force factors are low to moderate, the anterior implant may be positioned in a lateral incisor site if the central site in nonideal. ■ bilateral second premolar sites, and the bilateral distal half of the maxillary first molar sites. ■ The seven implants should be splinted together to function as an arch. These implant positions create sufficient space between each implant to allow for greater implant diameters (i.e., when required for force or bone density factors) Maxillary Fixed Prosthesis Treatment Option 3

■ The prosthesis treatment planned in a tapered dental arch form places the greatest forces on the anterior implants. ■ As such, four implants should be considered to replace the six anterior teeth ■ The bilateral canine and central incisor positions represent the best option. These positions are preferred when other force factors are greater, such as crown height, parafunction, and masticatory muscular dynamics  The worst-case scenario is a patient who requires restoration of a dental tapered arch form with a square residual ridge form. Not only are four implants then ideally required to compensate for the cantilevered tooth position, but these implants should be connected to additional posterior implants, which can extend to the second molar sites ■ Therefore in treatment plan 3, when force factors are moderate or the dental arch form is tapered, the minimum implant number should increase to eight implants ■ When force factors are greater than usual or bone density is poorer, additional implants may be used in any of the arch forms. In the square and ovoid arch form, at least one additional implant is positioned in the premaxilla. ■ For patients with higher force factors or poor bone density, two additional implants are planned in the distal half of the second molar position to improve the arch form. This will result in an increased A-P distance compared with the first molar site, which will compensate for the increased force factors or poor bone density Maxillary Fixed Treatment Option 4: All-on-Four

■ In general the all-on four technique includes placing four implants in the maxillary arch, with two axially placed implants in the anterior and two posterior implants positioned angulated at 30 to 45 degrees. ■ Even though the placement of four implants is far less than what has been accepted for years (i.e., usually six to eight implants required for a fixed prosthesis in the maxilla) in implant dentistry, high success rates of 93% to 98% have been shown ■ Zampelis et al. concluded in a finite element analysis model that the tilted posterior implants have a biomechanical advantage in comparison with cantilevering axial placed implants. The all-on-four technique is most commonly used for immediate load situations ■ Because of the pneumatization of the maxillary sinuses and the requirement of bone grafting in many cases, the all-on-four technique allows for the avoidance of the sinus anatomy by tilting the implants, which ultimately increases the A-P spread Removable Maxillary Treatment Plans

■ The primary advantage of a maxillary Implant Overdenture (IOD) compared with a fixed prosthesis is the ability to provide a flange for maxillary lip support and the reduced fee compared with a fixed restoration. ■ Maxillary IOD complications, such as attachment wear and prosthesis or component fracture, are more frequent than with a fixed restoration and primarily occur as a result of inadequate bulk of acrylic and minimal strength of the framework, compared with a fixed restoration Maxillary Removable Implant Overdenture Treatment Options

■ Only two treatment options are available for maxillary IODs, whereas five treatment options are available for the mandibular IOD. The difference is due primarily to the biomechanical disadvantages of the maxilla compared with the mandible. ■ As such, the two treatment options are limited to an RP-5 with four to six implants with soft tissue support, or an RP-4 restoration with six to eight implants (which is completely supported, retained, and stabilized by implants). Option 1: Removable Maxillary RP-4 Implant Overdenture

■ The first option for a maxillary IOD is an RP-4 prosthesis with six to eight implants, which is rigid during function (i.e., primary support is by implants, no soft tissue support). ■ This option is the preferred IOD design because it maintains greater bone volume and provides improved retention and confidence to the patient compared with a denture or RP-5 prosthesis. ■ Because the palate is removed from this prosthesis (i.e., horseshoe-shaped), soft tissue support is lost, thereby requiring increased number of implants. The cost of treatment is similar to a fixed prosthesis because of the increased number of implants required ■ Treatment planning for RP-4 maxillary overdentures is similar to a fixed prosthesis, because the IOD is fixed during function.  Two of the key implant positions for the RP-4 maxillary IOD are in the bilateral canines and distal half of the first molar positions. These implant positions usually require sinus augmentation in the molar position.  Additional posterior implants are located bilaterally in the premolar position, preferably the second premolar site.  In addition, at least one anterior implant between the canines often is required. Six implants is the minimum number for an RP-4 treatment option. ■ When force factors are greater, the next most important sites are the second molar positions (bilaterally) to increase the A-P spread and improve the biomechanics of the system.

Option 2: Removable Maxillary RP-5 Implant Overdenture

■ A maxillary conventional complete denture usually has good retention, support, and stability. Although an RP-5 maxillary IOD is superior to a complete denture, many patients do not see much of a difference. ■ The major advantages of an RP-5 maxillary IOD are the maintenance of the anterior bone and it being a less expensive treatment option in comparison with an RP-4 or fixed prosthesis. ■ The treatment is far less expensive because bilateral sinus grafts are not required and molar implants are not indicated. ■ Therefore this treatment plan is often used as a transition to an RP-4 or FP-3 prosthesis when financial considerations of the patient require a staged treatment over several years. ■ The first treatment option for a completely edentulous maxilla uses four to six implants supporting an RP-5 prosthesis, of which at least three are positioned in the premaxilla

■ The key implants are positioned in the bilateral canine regions and at least one central or lateral incisor position.

 In some cases, implant placement in the central incisor region may reduce the amount of available space for the prosthesis. Additional secondary implants may be placed in the first or second premolar region.  The maxillary RP-5 IOD is designed exactly as a complete denture with fully extended palate and flanges

THANK YOU