Prosthetic Options in Dentistry Hakimeh Siadat, DDS, MSc Associate Professor Dental Research Center, Department of Prosthodontics & Dental s Faculty of Dentistry, Tehran University of Medical Sciences (TUMS) www.drsiadat.com Fixed prosthesis Removable prosthesis FP-1 FP-2 FP-3 RP-4 RP-5 FP-1 FP-2 FP-3 FP-1 Fixed prosthesis; replaces only the crown; looks like a natural tooth. FP-2 Fixed prosthesis; replaces the crown and a portion of the root; crown contour appears normal in the occlusal half but is elongated or hypercontoured in the gingival half. FP-3 Fixed prosthesis; replaces missing crowns and gingival color and portion of the edentulous site; prosthesis most often uses denture teeth and acrylic gingiva but may be porcelain to metal. RP-4 RP-4 Removable prosthesis; overdenture supported completely by implant. FP-1 Fixed prosthesis FP-2 Fixed prosthesis The difference between FP-2 and FP-3 most often is related to the maxillary high lip position during smiling or the mandibular lip position during sibilant sounds of speech. FP-3 Fixed prosthesis Porcelain gingiva FP-3 Fixed prosthesis acrylic gingiva RP-5 RP-5 Removable prosthesis; overdenture supported by soft tissue and implant. 1
RP-4 Removable prosthesis RP-4 Removable prosthesis RP-4 prostheses have complete implant support anterior and posterior. In the mandible the superstructure bar often is cantilevered from implants positioned between the foramens. The maxillary RP-4 prosthesis usually has more implants and little to no cantilever. RP-5 Removable prosthesis RP-5 Removable prosthesis An RP-5 restoration has primarily anterior implant support and posterior soft tissue support in the maxilla or mandible. Often fewer implants are required and bone grafting is less indicated. Location of Dr Hakimeh Siadat, DDS, MSc Department of Prosthodontics & Faculty of Dentistry, Tehran University of Medical Sciences (TUMS) hsiadat@sina.tums.ac.ir The biological complications Caries Endodontic problems The biomechanical complications loss of retention Fracture of the porcelain J Dent Res. 1990;69:1126-1130 J Prosthet Dent. 2003;90:31-41 Eur J Oral Sci. 1998;106:527-551 The biological complications the bone-implant interface (successful 95% ) The biomechanical complications the magnitude of force Biomechanical treatment plane sequence Key implant position Patient force factors Available bone Prosthesis design design Misch CE. Contemporary Dentistry. Mosby; 1993:3-256. Misch CE. Part I: Diagnosis and treatment planning. Mosby; 1999:3-204. Misch CE. Stress factors: influence on treatment planning. In: Mosby; 2005:71-90. Bone density size number the overall treatment plan should: (1) assess the largest forces on the system (2) establish mechanisms to protect the total implant-bone-restoration system. Patient Fixture location and angulation should NOT dictate prosthesis type and design 2
Alveolar Ridge Evaluation Anatomic Limitations Selection Alveolar Ridge Evaluation Mesiodistal Bacolingual Occlusogingival Anatomic Limitations (Maxilla) Maxillary Sinus Nasal floor Incisive foramen Position of Gingival Margin Evaluation of Bone & Tissue Graft The most ideal posterior tooth to replace with an implant is the first premolar Anatomic Limitations (Mandible) Lingual perforation Submandibular space Inferior Alveolar Nerve Mental foramen The most ideal posterior tooth to replace with an implant is the first premolar Selection (diameter) Mesiodistal Dimension Buccolingual Dimension Emergence Profile Abutment Screw loosening Ideal implant size 1.5 mm from bucco-oral dimension 1.5 to 2 mm from an adjacent tooth At least 0.5 mm of bone on the lateral aspects of the implant body 3 mm from an adjacent implant J Periodontol 2000; 71:546-69. J Prosthodont 2001; 10:154-9. Int J Oral Maxillofac s 2006; 21:45-51. Int J Oral Maxillofac s 2004; 19:43-61.. Ideal implant size 0.5 mm of bone on the lateral aspects of the implant body 1.5 mm 3 mm Ideal implant size When the facial bone (bacco-oral) thickness is inferior to 1.4 mm Bone loss may result 1.5 to 2 mm from an adjacent tooth 1.5 mm or Increased probing depths Increased risk of soft tissue shrinkage 1.5 mm from bacco-oral bone or May affected bacterial flora Cervical esthetics This may be why gingival recession around wide-diameter implants has been greater than with a standard diameter 3
Measurement Device Selection Mesiodistal Distance Converging Adjacent Dentition A missing first premolar in either arch is often indicated as an implant prosthesis. A FPD with a canine abutment is more at risk Vertical column of bone is usually in front of the anatomic limitations The natural premolar tooth root is 4.2 mm in diameter on average at a distance of 2 mm below the CEJ. The most common implant diameter is about 4 mm at the crest module. The mesiodistal space is 7 mm or greater. The maxillary canine root is often angled 11 degrees distally A maxillary first premolar implant may need to be parallel to the canine. The mandibular canine also may have a distal inclination. When the mesiodistal dimension is only 6.5 mm, a 3.5 mm implant is suggested The first premolar implant may need to be placed parallel to the canine root & may need a shorter-than-ideal implant. Gingival sulcus measures 4mm inter-proximally, 2mm facially When the intratooth space is 8 to 12 mm When the intratooth space is 12-14 mm When the intratooth space is 14 mm When the intratooth space is 14-20 mm The natural molar tooth root is 8 to 12mm in mesiodistal dimension. When a 4 mm diameter implant is placed!!!! Biomecanical Complications 4-5 mm cantilever on the marginal ridges. The magnified occlusal forces may cause abutment screw loosening Exaggerated emergence profile on the crown Maxilla/ Mandible/ Mesio Distal CEJ Mesio Distal CEJ 1st Molar 7.9 9.2 Bone loss body fracture 4
When the intratooth space is 8 to 12 mm with a buccolingual width greater than 7 mm, a 5 to 6 mm diameter implant body is suggested. When the interatooth space is 14 mm, the ideal implant size is: 14mm - 6mm /2 = 4mm (for each implant) Some studies found implant screw loosening was a common complication.(48%) This problem was reduced to 8% when two splinted implants replaced the first molar Other studies found the wide diameter implant had greater screw loosening than two splinted implants J Oral Implanol 2001;27:63-72. J Periodontal Dent 2004;92:434-440 When possible, a larger diameter implant or two splinted traditional size implants should be inserted to enhance the mechanical properties of the implant. When the intratooth space is 14 to 20 mm, two implants are used to restore the space. The implants are positioned 1.5 to 2.0 mm from each tooth. The two implant crowns are splinted together and usually made the size of premolars. A 5 mm diameter implant may result in cantilevers up to 5 mm on each side. Two implants present a greater surgical, prosthetic, and hygiene risk. The first option is to slightly reduce the standard implant diameter to 3.5 mm, rather than 3.75 or 4.0 mm. Enameloplastyof the adjacent teeth. Orthodontics to upright a tilted second molar or increase the intratooth space. The implants may be offset to increase space between the implants. (0.5 to 1 mm) In the Mandible distal implant placed more buccal and the mesial implant more lingual. To facilitate access of a floss threaded 5
Single Molar replacement options The implants may be offset to increase space between the implants. (0.5 to 1 mm) In the Maxilla distal implant placed more lingual and the mesial implant more buccal. Improve Esthetic Mesiodistal Dimension Diameter (mm) 7 4 mm 8 to 12 5 mm 12 to 14 Gain additional space, Place 2 4 mm 14 For 14 mm, 2 4 mm For 15 mm, 1 5 mm, 1 4 mm For 16 mm, 2 5 mm Occluso Gingival Height Height between bone crest and opposing tooth. (cemented VS screw retained implants) Disadvantages of Replacing a Mandibular Second Molar Not in esthetic zone Less than 5% of total chewing efficiency A 10% higher bite force Bone loss risk Porcelain fracture risk Abutment screw loosening Disadvantages of Replacing a Mandibular Second Molar Less predictable location of mandibular canal Less dense bone Submendibular fossa depth greater Limited to unfavorable crown height space For cement retention For Screw retention Disadvantages of Replacing a Mandibular Second Molar Limited access for correct implant boby placement Crossbite position implant placed more buccal than maxillary tooth Hygiene access more difficult Cheek biting more common Increased risk of uncementation Limited access for occlusal screw placement supported Fixed Partial Dentures Biomechanical treatment plane sequence supported Fixed Partial Denture Key implant position Patient force factors Prosthesis design Bone density number Available bone design size Misch CE. Contemporary Dentistry. Mosby; 1993:3-256. Misch CE. Part I: Diagnosis and treatment planning. Mosby; 1999:3-204. Misch CE. Stress factors: influence on treatment planning. In: Mosby; 2005:71-90. 6
Guidelines for key implant positions The canine and first molar sites are key abutment positions. Cantilevers on the prosthesis should be preferably eliminated. An arch may be divide into several segments Three adjacent pontics should not be designed in the prosthesis, especially in the posterior regions of the mouth. Bidez MW, Misch CE. Clinical biomechanics in implant dentistry. Mosby; 1999:303-316. Misch CE. Mandibular full-arch implant fixed prosthetic options. Mosby; 2005:252-264. Misch CE. Maxillary partial and complete edentulous implant treatment plansmosby; 2005:281-308. Cantilevers on the prosthesis should be preferably eliminated. screw loosening, crestal bone loss, and fracture Dent Today. 2006 May;25(5):80, 82, 84-5; quiz 85. Biomechanical complication All pontic spans No three adjacent pontics Misch CE, ed. Contemporary Dentistry. 2nd ed. St. Louis, Mo: Mosby; 1999:303-316. Metal flexure 27 times more than a one-pontic Un-cemented prostheses Screw loosening Shear & tensile load on the abutments Porcelain fracture The canine sites are key abutment positions To help disclude the posterior teeth in mandibular excursions. Dent Today. 2006 May;25(5):80, 82, 84-5; quiz 85. The first molar sites are key abutment positions bite force doubles in the molar position missing first molar is 10 to 12 mm, compared to a 7-mm span for a premolar first molar has twice the surface area of a premolar tooth natural dentition uses 3 roots splinted together Key arch positions An arch may be divide into several segments. When more than one segment of an arch is being replaced, a key implant position is at least one implant in each segment. The tripod effect is greater & as a benefit is created. Key arch positions in Maxilla Key arch positions Key arch positions in Mandible The right canine The two central & two lateral incisors The left canine The right canine The right premolars & molars The two central & two lateral incisors The left canine The left premolars & molars From a biomechanical perspective, an edentulous mandible may be divided into 3 sections: canine to canine The right premolars & molars The left premolars & molars Bidez MW, Misch CE. Clinical biomechanics in implant dentistry. Mosby; 1999:303-316. Misch CE. Mandibular full-arch implant fixed prosthetic options. Mosby; 2005:252-264. Misch CE. Maxillary partial and complete edentulous implant treatment plansmosby; 2005:281-308. The right premolars & molars The left premolars & molars 7
Key implant position Attention besides the key positions When the first premolar, second premolar, first molar and second molar are missing: the key implant position are the first premolar, first molar and second molar. The key implant position are for ideal clinical position ( force, crown height, bone density, ). Therefore additional implants are added to the treatment plan. Additional implants (besides the key positions) are also usually needed, with the total number of implants determined by patient force factors and bone density www.oralhealthjournal.com/issues/isarticle.as Dent. 1992;1:289-294 Key implant position The key implant positions are the first premolar, first molar and second molar. Since the patient has higher force factors than average (parafunction and younger male) an additional implant is inserted into the second premolar region Key implant position Key arch positions One or two additional implants are required in most clinical situations depending on: Patient force factors Bone density Attention When four implants support a 12-unit fixed prosthesis, the position of the implants cannot follow the four key implant position rules. number The additional implants Reduce the cantilever length Reduce the number of pontics Increased the retention of the restoration Reduced risk of screw loosening Reduced risk of uncemented prosthesis Less localized stress to crestal bone Risk factors in implant dentistry;1999,quintessence. J Prosthet Dent 2000; 83;332-42. Dent. 1992;1:289-294 AND number Placing one implant for each lost tooth is usually not necessary for multiple missing teeth AND A young male who bruxes severely Patients with moderate force factors and poor bone density (D4) Require one implant for each missing root 8
For a full edentulous arch For a full edentulous arch number More than 10 implants are rarely required. Fewer than 5 implants are rarely suggested. As a general rule for a fixed prosthesis In Maxilla Range 7 to 10 In Mandible Range 5 to 9 The ideal seven-implant position for a maxillary edentulous arch. In case of heavy stress factors, an additional anterior implant and bilateral second molar positions may be of benefit. Dent Today. 2006 May;25(5):80, 82, 84-5; quiz 85. Key arch positions Selection Selection Usually the second molar is not replaced in the edentulous mandible The implant diameter should be within 1mm of the diameter of the restoration (at the CEJ). Wöhrle Maxilla MesioDistal FacioPalatal Ideal CEJ CEJ Diameter Central 6.4 6.4 5.0 6.0 Lateral 4.7 5.8 3.5 4.3 Cuspid 5.6 7.6 4.3 5.0 1st Bicuspid 4.8 8.2 4.3 5.0 2nd Bicuspid 4.7 8.1 4.3 5.0 1st Molar 7.9 10.7 6.0 2nd Molar 7.6 10.3 6.0 Hebel/ Gajjar Misch Selection MesioDistal MesioDistal Ideal Mandible CEJ CEJ - 2mm Diameter Central 3.5 3.5 3.5 Lateral 3.8 3.5 3.5 Cuspid 5.2 4.1 4.3 5.0 1st Bicuspid 4.8 4.5 4.3 5.0 2nd Bicuspid 5.0 4.7 4.3 5.0 1st Molar 9.2 9.0 6.0 2nd Molar 9.2 8.5 6.0 Hebel/ Gajjar Misch Selection Level or Abutment Level? External fixture or Internal Fixture Which Platform? (Narrow, Regular, Wide) Screw retained or Cement retained 9