Designing Successful Removable Partial DenturesA b stract:In todays busy dental offices, removable partial denture design is often abdicated by dentists, both as a result of a lack of experience and consensus of design and because of educational failure on the part of dental schools. The result is delegation of the clinical design process to the lab technician. The lack of clinical data provided to the dental technician jeopardizes the quality of care. This article will focus on a logical and simple approach to this problem, making removable partial denture design simple and predictably achievable. The clinical evidence related to removable partial denture design will be described, along with a checklist to simplify the process and make it practical and applicable to everyday clinical practice.

CE 3Tony Daher, DDS, MSEd, FACPAssociate Professor Director, Advanced Prosthodontic Program

Dan Hall, DDS, FACD, FICDAssociate Professor Director of International Dental Program

Charles J Goodacre, DDS, MSD, FACPProfessor and Dean Loma Linda University School of Dentistry Loma Linda, California

Ivey of removable prosthodontic laboratories2 showed that 78% of RPDs are designed by dental technicians at the dentists request. Dental education has failed to adequately address this problem. A 2002 study by Hummel and colleagues3 demonstrated that RPD problems are significant, and will continue to impact dentistry in the future. A decrease in the curriculum time allocated to removable prosthodontics may be inappropriate.3 At least a quarter of a million people in the United States under the age of 40 wear RPDs, and of those, at least one third report RPD defects, indicating that there is a great need to improve RPDs.3 Improvements should include new materials that are easy to use, repair, and maintain; simplified designs and fabrication that enable most dentists to provide well-fitting and functioning RPDs with an emphasis on patient education, and need for followup care.3 Many prosthodontists consider RPD fabrication to be a complete mouth rehabilitation, and that it should be taught at the proficiency level, not on a competency level. This has resulted in dental school graduates who are more likely to delegate RPD design to lab technicians and less likely to know the benefits of prosthodontic specialty referral. Thus, the quality of dental care is compromised. This article presents a simplified educational approach to teaching RPD design that leads to predictable results. The lack of a consensus on the design of a conventional RPD is noticeable in the dental literature. Many variations of RPD design have been used for the same clinical situation.4 Several published books concur that RPD design begins by surveying the study cast using a dental surveyor, marking survey lines, and selecting the RPD components.5-9 The most logical approach to determine the design of any RPD is to focus on a clinical approach based on clinical evidence, rather than a laboratory decision-making approach. The following checklist will simplify the process and make it predictable.

n 1969, Atkinson and Elliot 1 showed that over half of all dental school graduates could not design a removable partial denture (RPD) that could be successfully fabricated by a dental technician and worn by a patient. A 1984 sur1. Analyze the total oral environment. 2. Draw the RPD design. 3. Survey the cast and modify the design.

Learning Objecti es: vAfter readingthis article,the reader should be able to: describe the recommended steps for designing a successful removable partial denture. analyze the total oral envi-

ronment necessary before drawing the removable partial denture design. discuss the functions of different removable partial denture components and their importance in fabricating a successful removable partial denture.

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including personal, medical, dental, and prosthetic histories; necessary radiographs; articulat-

CE 3ed dental casts; and a visual and digital extraoral and intraoral clinical exam.5 Many dentists often underestim ate the practical usefulness of articulated dental casts. This results in unforeseen future treatment problems and poor outcomes (Figures 1, 2A through 2D). These preliminary study casts are articulated at the correct therapeutic occlusal vertical dimension in a retruded contact position, on a semiadjustable articulator using an adjusted facebow and often a protrusive record. When the plane of occlusion and/or the vertical dimension of occlusion are not in harmony with the dental arches, placement of denture teeth, restoration of

Figure1Tooth No. 31 dependson the correct vertical dimension. If this occlusalverticaldimensionis the therapeuticdimension, then tooth No. 31 must be sacrificedto create adequate interarchspaceand adequatetissuecoveragefor the prosthesis. Howeve if the occlusalverticaldimensionis to be restored5 r, mm posteriorl then tooth No. 31 is retained. y.

Step1: A nalyze TotalO ralEnvironm ent theDesigning an RPD starts with a complete analysis of the total oral environment. The dentist must determine how to establish an optimum plane of occlusion, occlusal vertical dimension, occlusal scheme, and esthetics for a proper prosthetic restoration. To do so, adequate prosthodontic data must be collected,

A

C

the abutment teeth, and creation of a functional occlusion becomes difficult or impossible to accomplish.6 The dentition in both arches must be analyzed before designing the RPD. The treatment plan should include restoring the plane of occlusion and the vertical dimension, and what type of occlusal scheme is needed for an optimum clinical result.

D

B

Figure2A through 2DMaxilla and mandibularRPD frameworksare compatiblewith populardesign,but when we articulatedthe ry casts (C, D) we were surprisedat the lack of intera distanceto arrangethe prostheticteeth. rch Vol. 27, No. 3 Com pendium

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Figures 3A and Placingat least 1 dental implantin the distal extensionarea will transformthe RPD from a tooth/tissue-borne a 3B to tooth-borne(implant-borne) prosthesis.

The with a poorly fitted RPD. Unfortunately, responsibithough many published research articles study lity for the ultimate success of the RPD is often placed solely on the dentists shoulders. the effects of vertical forces on RPDs, This responsibi lity should be shared by both the a dearth of published research on forces directdentist and ed on RPDs other than vertical forces. It is certhe patient. In tainly helpful to the dentists to understand how reviewan extension base of an RPD will respond to ing many vertical forces,19 but the forces placed on prosperiodontal theses can produce vertical, horizontal, rotationresearch al, or twisting movements, or a combination of studies related to prosthodontics , it can be concluded that RPDs contribute to oral health if above-average oral hygiene is practiced, adequate preprosthetic periodontal therapy is executed, minimal standards for RPD design are upheld, and periodic

there is

10-13 c a r e

A all 4.9 Ultimately the patient wants a stable, minimal standard for

i s m a i n t a i n e d . RPD design well-fitting prosthesis,19 devoid of all movement, should be not just vertical movement. simple and A tooth-borne prosthesis can be considered within the a removable fixed bridge because it is the eascomprehensio iest to design, most accepted by patients, and n of every has a longer survival rate than the tooth/tissuepracticing dentist. The dentist should note whether the patient has an anterior edentulous space in addition to a posterior edentulous space. Anterior edentulous spaces are best treated with fixed 7,20 p because it is easier to achieve borne r prosthesi o s. s t h o d o n t i c s

The tooth/tissue-born e adequate esthetics, and it will decrease the leverage effect of the forces generated during function on the RPD. 7 In a case where soft tissue is lost, anterior edentulous spaces are best replaced with an RPD if surgical correction is contraindicate d. The presence of anterior replacement teeth for RPDs was found to be a significant positive influence on denture wearing.14 Next, the dentist must determin e if the clinical situation is dentoalveolarsupported (tooth-borne), dentoalveolar and mucoosseoussupported (tooth/tissueborne), or mucoosseous-

supported (tissue-borne).8 Each of these possible biomechanical situations will respond differently to occlusal forces.9 Before designing any dental prosthesis, the dentist must understand the types of forces directed on the prosthesis. When the extension base of a tooth/tissue-borne RPD with no guiding plates is subjected to occlusal forces, many fulcrum lines come into play. These fulcrum lines exist only

RPD is not well understood borne prosthesis). Therefore, dentists can turn a by many dentists, tooth/tissue-borne situation into a tooth-borne and its complexity depends situation by the use of a dental implant on the on the span length edentulous side away from the abutment of the edentulous area tooth, 21 (Figures 3A and 3B) or can opt to not and type of arch replace the missing teeth at the extension base involved. with a prosthesis. In addition to this previous Patients have a mechanical advantage, placing an implant tendency to function under the RPD distal extension base has a physand iological advantage. The amount of bone loss of use the areas where the the distal edentulous area is reduced as a result prosthesis is stable (for of its physiological stimulation by the implant.22 example, the tooth-borne side If these choices are not feasible, the dentist of a tooth/tissuecan create multiple opposing guiding surfaces188Com pendiumMarch 2006 / Vol. 27, No. 3

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Figures 4A and RPD design is drawn on the cast in 3 steps: (1) rests and minor connectors,(2) major and denture connectors, 4B (3) direct retainers(claspsor attachments). Note that 3 guidingsurfaces will be established: distal surfaces of teeth Nos. 6 and 12, and the mesialsurface of tooth No. 12 where the minor connectoris placed.15-18

Figures 5A and Tooth No. 32 has a guardedprognosis.The mandibularRPD is designedand fabricatedwithouttaking tooth No. 5B 32 into consideration. Then a stainlesssteel wire occlusalrest is made and connectedto the frameworkthrougha fabricatedloop, with the denturebase acrylic. In case tooth No. 32 is lost, it is easily repairedwithoutremakingthe RPD metal frame.

for the control of these forces and make an altered cast impression procedure for the mandibular RPD. This will limit any possible RPD movements. At least 3 abutments should be selected and set as wide apart as possible (Figure 4A). The biomechanical forces are resisted by a good selection of sound abutment teeth. At least 3 positive rests must be placed on 3 sound abutments. Then, as many guiding surfaces as possible must be established on the abutment teeth. This is an important step in the support, stability, and retention of the future prosthesis. However, using more than 5 abutments compromises the accuracy and fit of the prosthesis.17 If one of the RPD abutments is compromised, it is wise to consider creating a contingency design. A contingency design is defined as an RPD framework design that takes into consideration the presence of a compromised tooth so that, should it be lost, the RPD will

not have to be refabricated.7 Remaking an RPD is costly; repairing or adding teeth is a more reasonable expense (Figures 5A and 5B).

Step 2: D rawthe R PD DesignAfter thoroughly analyzing the oral environment, the optimal design should be drawn on the preliminary cast. The authors believe that it is necessary to draw the optimum RPD design on the cast before it is surveyed (Figures 4A and 4B). The RPD design sequence begins by drawing the most important features of the RPD framework.5 First the rests and

minor connectors are drawn (Figure 4A), followed by the major and denture base connectors, and finally the clasps or attachments (Figure 4B).

The first step is to draw the rests and the minor connectors at the same time. A mini-

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Figures 6A and The path of placementand removalis materializedeither with the fabricationof a preparationguide or with the 6B placementof a line on the cast on a verticalsurface that is parallelto the placementpath. Then align the handpiecebur intraorallywith the establishedguide to executetooth modifications to establishadequateguidingsurfaces. and

mum of 3 positive rests are selected on good abutments as widely apart as possible. A positive rest5 is defined as: one that directs the occlusal forces parallel to the long axis of the teeth one that is strong enough to resist breakage. A strong rest is when it is thick enough, at least 1 mm, for chromecobalt alloy framework. There should be a rounded line angle between the rest and minor connector. The thickness

of the minor connector must be half the width of the rest, and excessive rest inclination must be avoided.23 Positive rests and guiding plates will keep the RPD from moving and exerting excess pressure on the edentulous ridges. Common rests used in modern RPD design are cingulum rests and occlusal rests. Many other forms of positive rests exist, but are rarely used because they are not taught in most dental schools. Minor connectors, or guiding plates, are strong and are rigid parts of an RPD framework, such as proximal, lingual, or buccal-vertical connectors. Their role is to guide the RPD during placement and removal, and to connect other units, such as rests, with the major connector or the denture base connectors. Guiding minor connectors play an important role in modern RPDs. Their functions are to: distribute the occlusal load to both sides of the arch limit the number of paths of placement and removal ensure stability against lateral forces and retention of the prosthesis by their frictional retentive properties against dislodgement forces during function. Thus they

maintain arch integrity by anterior-posterior and lateral bracing action. The buttressing action5 of well-fitted multiple opposing guiding surfaces, in conjunction with positive occlusal rests, provides support, stability, and retention for the prosthesis. An objective in RPD design is to maximize the number of opposing surfaces.24 Any minor connecto r that connects an occlusal rest, to the major con nector is made to contact 2 mini guiding surfaces prepared in the lingual occlusal embrasure of 2 adjacent teeth (Figures 4A and 4B). For this190

reason, the authors prefer to place the rest on the mesial fossa of a RPD distal abutment.

Major and Denture Base ConnectorsCross arch stabilization is provided by a rigid major connector. A main requirement for adequate major connectors is rigidity.25 Also, they must be placed in proper location to minimize the impingement on the oral tissues.8 The difference between maxillary and mandibular major connectors for RPDs is support.8 The horizontal portion of the palate will resist vertical forces and thus play an important role in the support of the tissue/tooth-borne RPD. The vertical portion of the RPD intaglio surface plays a role in the stability of the prosthesis. The maxillary and mandibular major connectors differ in shape but not in function as a result of the different type of oral anatomy. In the authors opinion, the maxillary major connector should not cover the anterior rugae, the playground of the tongue, or the posterior soft palate. The broad central palatal connector or strap is most accepted by patients.26Vol. 27, No. 3

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Single straps are not rigid unless they are wide enough or cover 2 different planes of the hard palate.25 An anterior-posterior (A-P) palatal connector is indicated when a palatal torus is present and its surgical removal is contraindicated. Mechanically speaking, the double strap A-P connector provides maximum rigidity for the least amount of metal bulk present.5 Its major disadvantage is that it has 4 borders that the patient can feel with the tongue inside the mouth. 26 Whenever possible, the border of the anterior strap of the A-P major connector should end in the valleys of the incisal rugae, making it less obtrusive. Complete coverage of the palatal connector is rarely used, and in clinical situations where it is needed, the authors prefer acrylic coverage for practical reasons.

The purpose of the denture base connector is to connect the denture acrylic base to the framework. Large openings supply stronger resin attachments, 28 and they should be located parallel or lingual to the crest of the residual ridge so that they do not interfere with the length of the buccal surfaces of the denture teeth.5 They start and end in a butt joint in the major connector at the internal and external acrylic finish lines. In a narrow edentulous area or in the anterior edentulous area, posts must be placed to retain the anterior teeth. When it is certain that a narrow edentulous area will need to be relined, or in areas of recent extractions, ladder retention must be used. A minimum of 1 thickness of baseplate wax should be used as the relief pad rather than the usual 24- to 28-gauge wax.7 In every other instance, a metal base with appropriate retentive lugs or loops is indicated.5

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Direct Retainers

ental school graduates are more likely to delegate RPD design to lab techniciansand less likely to know the benefitsof prosthodontic specialtyreferral.

Selecting a major connector for the mandibular arch is limited to either a lingual bar or a lingual plate. In the authors opinion, the lingual bar is the better choice because it covers the minimum amount of soft tissues.26 A lingual plate or a sublingual bar are acceptable alternatives to a lingual bar when the vertical lingual space is not available.27 Lingual plates are widely used when the height of the anterior lingual vestibule is minimal as a result of the common presence of lingual gingival recession, high lingual frenum, and/or periodontally treated anterior teeth.5 The presence of diastemas on the mandibular anterior teeth and the lack of adequate height of the lingual vestibule dictate the use of the sublingual bar. Labial or buccal bars are used when the mandibular teeth are severely tilted lingually, or when large tori are present and surgery is contraindicated.Vol. 27, No. 3

Retainers in modern RPDs must be passive in placement and passive at rest.5 Retainers can be either clasps or attachments. Popular clasps used currently are circumferential, I-bar, and wrought wire.29 In the authors experience, I-bar or circumferential clasps are good choices for almost any clinical situation. Wrought wire clasps are technique-sensitive, easily deformed by the patient, and costly. Direct retainers are the least important component of the RPD because their retentive quality is impaired in 6 months because of permanent deformation.30 In the authors clinical experience, clasps used in a situation with multiple opposing guiding surfaces will not easily lose retention. I-bars are considered the best option because they are more retentive than a circumferential clasp for the same undercut, and because they require only minimal tooth coverage. On the other hand, circumferential clasps are preferred over I-bars when there is a lack of vestibular depth, or when undercuts, exostoses, or labially inclined abutments exist.5 Many clasp assemblies are used on the distal abutment of an extension base RPD, such as distal rest and circumferential clasp assemblies, I-bar system,6 Rest-Proximal Plate-I Bar,9 RestProximal plate-Ackers Clasp,18 combination clasps,33 or rigid clasp assemblies with splitC om pendium

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selected RPD design. The optimum RPD path major connectors.34 The efficiency of these of placement approximates the perpendicular various clasp assemblies is described using photoelastic to the plane of occlusion.40 In rare clinical situstudies in ations and during the cast survey, it is necessary the vertical to modify the optimum selected design to minplane. The imize the intraoral preparation. purThe dentist has 2 options in this area. pose of all clasp assemblies is to avoid the tilting and torque of abutment teeth. However, no clinical evidence has been presented that RPDs cause tilting forces on abutment teeth in A retrospective study comEither the dentist locates a surveyor and sur-

D35,36 the long term .

paring the effectivene ss of 2 clasp designs, the distal rest and circumfere ntial clasps system and the Ibar system, found that the success rate of either design is 74%.37 This study emphasize d that a

well-fabricated RPD is an acceptable modality, no matter what type of retainer is used. Tebrock and colleagues35 and Maxfield and colleagues38 attempted to measure abutment mobility in the mouth with different clasp designs and different rest placements. They reported no measurable mobility, regardless of rest position and clasp design, when the altered cast procedure had been used. Good base adaptation, good oral hygiene, and adequate occlusion are the critical factors that minimize the need to design a stress-releasing clasp assembl . y In the past, indirect retention was a vital element in the design of an RPD. Frank and Nicholls39 showed that indirect retainers have little to do with retention of tooth/tissue RPDs; they found that the guiding surfaces create retention and stability in an RPD. In the authors opinion, fabrication of indirect retainers should not be included when teaching RPD design. Placing 1 or 2 additional rests and their

31,32

correspond ing guiding plates as far as possible from the abutment rests will help with force distribution over a wider area, thus improving the support, stability, and retention of the RPD. This will eliminate the need for a socalled indirect retainer. In addition, the additional rest(s) could be considered as points of reference and visual cues during altered cast impression and reline procedures.

the D esignThe purpose of surveying the cast is to check the feasibility of the optimum selected drawn design. Surveying the cast with the RPD design drawn on it will help to identify the intraoral preparation needed to meet the

Step 3: Survey the C ast and M odify

veys the cast, or consults base plate wax, then trim excess wax with with the laboratory the surveyor. Lubricate the selected area technician during the with petroleum jelly, apply a small amount surveying procedure to of autopolymerizing acrylic, and embed a identify areas requiring friction grip bur, using the surveyor (Figure intraoral modification. 6A). Allow the acrylic to set, then finish Once this step is and polish. The bur direction is parallel to completed, the the selected path of insertion of the dentist or designed RPD. The device is placed in the the lab technician tripods mouth and used as a reference to align the the cast for future use handpiece bur to execute the shaping of and makes a preparation the selected guiding surfaces. guide that will be used 2. Select a tooth surface that is parallel to the in the mouth to shape the path of placement, mark it on the cast as a guiding surfaces and reference, and use it in the clinical situation tooth contours, and to to align the bur direction during the intraeliminate undesirable oral preparation procedures (Figure 6B). undercuts on the The second approach will save the practicabutment teeth. The ing dentist time and result in a more successful preparaprosthesis. tion guide is formed in 2 different ways on the C on clus io n cast using the surveyor: This article has focused on a simplified, 1. Select 2 adjacent organized approach to designing modern RPDs. teeth situated equidistant Three steps are enumerated: analyze the total to all guiding environment, draw the RPD design, and check surfaces. Block out the feasibility of the design using the surveyor. cervical This article also describes the different RPD and embrasure tooth components and their function, and relates undercuts with pink some clinical evidence to their use.192Com pendiumMarch 2006 / Vol. 27, No. 3

R eferences1. Atkinson RA, Elliot RW. Removable partial denture designed for laboratory fabrication by recent dental school graduates. J Prosthet Dent. 1969;22:528-543. Taylor TD, Matthews AC, Aquilino SA, et al. Prosthodontic survey. Part 1: Removable prosthodontic laboratory survey. J Prosthet Dent. 1984;52:598-601. Hummel SK, Wilson MA, Marker VA, et al. Quality of removable partial dentures worn by the adult US population. J Prosthet Dent. 2002;38:37-43. Frantz WR. Variations in a removable maxillary partial denture design by dentists. J Prosthet Dent. 1975;34:625-633. Kratochvil FJ. Partial removable prosthodontics. In: Dentistry. Philadelphia: Saunders Core Textbook; 1988: 11,27,67,83-110,132. Stewart KL, Rudd KD, Kuebker WA. Stewarts Clinical Removable Partial Prosthodontics 3rd ed. Quintessence . Publishing Co Inc; 2003:274-282. Brudvik JS. Advanced Removable Partial Dentures. Quintessence Books; 1999:Chapter 2. Krol AJ, Jacobson TE, Finzen FC. RemovablePartial Design. Outline Syllabus. 1999;5th Edition 14,33,48. McGivney GP, Carr AB. Biomechanicsof removable partial dentures. In: McCrackens Removable Partial Prosthodontics. 10th ed. Mosby; Chapter 4. Bergman B, Ericson G. Cross-sectional study of the periodontal status of removable partial denture patients. J Prosthet Dent. 1989;61:208-211. Bergman B, Hugoson A, Olsson CO. Caries, periodontal and prosthetic findings in patients with removable partial dentures: A ten-year longitudinal study. J Prosthet Dent. 1982;48:506-514. Petridis H, Hempton TJ. Periodontal considerations in removable partial denture treatment: a review of the literature. Int J Prosthodont. 2001;14:164-172. Chandler JA, Brudvik JS. Clinical evaluation of patients eight to nine years after placement of removable partial dentures. J Prosthet Dent. 1984;51:736-743. Jepson NJA, Thomason JM, Steele JG. The influence of denture design on patient acceptance of partial dentures. J Prosthet Dent. 1995:178;296-300. Kratochvil FJ, Caputo AA. Photoelastic analysis of pressure on teeth and bone supporting a removable partial dentures. J Prosthet Dent. 1974;32:52-61. Thompson WD, Kratochvil FJ, Caputo AA. Evaluation of photoelastic patterns produced by various designs of bilateral distal-extension removable partial dentures. J Prosthet Dent. 1977;38:261-273. Eliason CM. RPA clasp design for distal-extension removable partial dentures. J Prosthet Dent. 1983;49:25-27. Aviv I, Ben-Ur Z, Cardash HS. An analysis of rotational movement of asymmetrical distal-extension removable partial dentures. J Prosthet Dent. 1989;61:211-214. Frank RP, Brudvik JS, Leroux B, et al. Relationship between the standards of removable partial denture construction, clinical acceptability, and patient satisfaction. J Prosthet Dent. 2000;83:521-527. Vermeulen A, Keltjens H, vant Hof MA, et al. Ten year evaluation of removable partial dentures: Survival rates based on retreatment, not wearing and replacement. J Prosthet Dent. 1996;76:267-272.

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Kuzmanovic DV, Payne AG, Purton DG. Distal implants to modify the Kennedy classification of a removable partial denture: A clinical report. J Prosthet Dent. 2004;92:8-11. Wyatt CC. The effect of prosthodontic treatment on alveolar bone loss: A review of the literature. J Prosthet Dent. 1998;80:362-366. Sato Y, Shindoi N, Koretake K, et al. The effect of occlusal rest size and shape on yield strength. J Prosthet Dent. 2003;89:503-507. Sato Y, Shindoi N, Hosokawa R. Proximal plate in conventional circumferential cast clasp retention. J Prosthet Dent. 2000;83:319-322. Ben-Ur Z, Mijiritsky E, Gorfil C, et al. Stiffness of different designs and cross-sections of maxillary and mandibular major connectors of removable partials dentures. J Prosthet Dent. 1999;81:526-532. Wagner AG, Traweek FC. Comparison of major connectors for removable partial dentures. J Prosthet Dent. 1982; 47:242-245. Hansen CA, Campbell DJ. Clinical comparison of two mandibular major connector designs: The sublingual bar and the lingual plate. J Prosthet Dent. 1985;54:805-809. Dunny JA, King GE. Minor connector designs for anterior acrylic resin bases: A preliminary study. J Prosthet Dent. 1975;34:496-502. Phoenix RD, Cagna DR, DeFreest CF. Clinical Removable Partial Prosthodontics.3rd ed. Quintessence Publishing Co; 2003: Chapter 3. Ghani F, Mahood M. A laboratory examination of the behavior of cast cobalt-chromium clasps. J Oral Rehabil. 1990;17:229-237. Benson D, Spolsky VW. A clinical evaluation of removable partial dentures with I-bar retainers. Part I. J Prosthet Dent. 1979;41:246-254. Stone E. Tripping action of bar clasps. J Am Dent Assoc. 1936;23:596. Brudvik JS, Wormley JH. Construction techniques for wrought wire retentive clasp arms as related to clasp flexibility. J Prosthet Dent. 1973;30:769-774. Reitz PV, Caputo AA. A photoelastic study of stress distribution by a mandibular split major connector. J Prosthet Dent. 1985;54:220-225. Tebrock OC, Rohen RM, Fenster RK, et al. Effects of various clasping systems on mobility of abutment teeth for distal extension removable partial dentures. J Prosthet Dent. 1979;41:511-516. Hosman HJ. The influence of clasp design of distal extension removable partial dentures on the periodontuim of the abutment teeth. Int J Prosthodont. 1990;3:256-265. Kapur KK, Deupree R, Dent RJ, et al. A randomized clinical trial of two basic removable partial denture designs. Part I: Comparisons of five-year success rates and periodontal health. J Prosthet Dent. 1994:72;268-282. Maxfield JB, Nicholls JI, Smith DE. Measurement of forces transmitted to abutment teeth of removable partial dentures. J Prosthet Dent. 1979;41:134-142. Frank RP, Nicholls JI. An investigation of the effectiveness of indirect retainers. J Prosthet Dent. 1977;38:494-506. Bezzon OL, Mattos MG, Ribero RF. Surveying removable partial dentures: the importance of guiding planes and path of insertion for stability. J Prosthet Dent. 1997;78:412-418.

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Quiz31. What percentage of removable partial dentures (RPDs) are designed by dental technicians at the dentists request? a. 28% b. 58% c. 78% d. 88% 2. Designing an RPD starts with: a. b. c. d. drawing the RPD design. surveying the cast with a surveyor. complete analysis of the total oral environment. clasp and rest seat preparation. 5. When drawing the RPD design, 8. The purpose of surveying the first draw: cast is to: a. rests and minor connectors, a. draw the survey line and to then the major and denture select the type of clasp needconnectors, then the clasps ed. or attachments. b. check the feasibility of the b. direct retainers, then the optimum selected drawn major and denture connecdesign. tors, then the rests and guidc. check all the undercuts that ing minor connectors. exist on the dental arch. c. major and denture connecd. place 3 rests as far apart as tors, then the direct retainpossible. ers, then the rests and guid9. The optimum RPD path of ing minor connectors. placement: d. major and denture conneca. approximates the perpendictors, then the rests and guiding minor connectors, then ular to the plane of occlusion. the direct retainers. b. is when at least 2 rest seats can be found. 6. The functions of guiding minor c. is when at least 1 retention connectors are to: clasp can be placed. a. distribute the occlusal load d. is when no tooth preparato both sides of the arch. tion is required. b. limit the number of paths of 10. A preparation guide is used to placement and removal. shape the: c. ensure stability against latera. rest seats. al forces. d. all of the above b. guiding surfaces. c. major connectors. 7. What creates retention and stad. undercuts. bility in an RPD? a. poor base adaptation b. guiding surfaces c. indirect retention d. rest seats

3. Anterior edentulous spaces are best treated with: a. a fixed partial denture prosthesis. b. the same type of RPD, especially when soft tissue is present. c. the same type of RPD, especially when soft tissue surgery is indicated. d. an interim removable prosthesis. 4. The tooth-tissue-borne RPD: a. could be considered a removable fixed bridge. b. is very well understood by many dentists because of its simplicity in design. c. complexity depends on the span length of the edentulous area and type of arch involved. d. does not need multiple opposing guiding surfaces.

Please see tester form on page 195.This article provides 1 hour of CE credit from Ascend Medias Dental Learning Systems, in association with the University of Southern California School of Dentistry and the University of Pennsylvania School of Dental Medicine, representatives of which have reviewed the articles in this issue for acceptance. Record your answers on the enclosed answer sheet or submit them on a separate sheet of paper. You may also phone your answers in to (888) 596-4605 or fax them to (703) 404-1801. Be sure to include your name, address, telephone number, and the last 4 digits of your Social Security number.

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CE ANSWE FORM RCE 11. b d 2. b d 3. b d 4. b d 5. b d 6. b d 7. b d 8. b d 9. b d 10. b d a c a c a c a c a c a c a c a c a c c a

Compendium, March 2006 CE 21. d 2. d 3. d 4. d 5. d 6. d 7. d 8. d 9. d 10. d

CE 3a a a a a a a a a a b b b b b b b b b b c c c c c c c c c c 1. d 2. d 3. d 4. d 5. d 6. d 7. d 8. d 9. d 10. d a a a a a a a a a a b b b b b b b b b b c c c c c c c c c c

n Presently Enrolled in CE Program

Not Enrolledn 1 exam completed = $14.00 n 2 exams completed = $24.00 n 3 exams completed = $38.00

Please enroll me in the The Compendium Continuing Education Program marked below: n Please enroll me in the 12-month CE Program for $234.00 (a 36% saving versus paying for each exam individually). Program includes all 36 exams in The Compendium for 1 year (plus selected supplements). n CHECK (payable to Ascend Medias Dental Learning Systems) n CREDIT CARD Please complete inf ormation and sign below: Card Number n Visa n MasterCard n American Express ______________________________________ ______________

Expiration Date: Mo/Y

(PLEASE PRINT CLEARLY ) Last 4 digits of the SSN

ADA Number AGD Number Month/Date of Birth_________________

The Month and Day (not year) of Birth. Example, Jan 23 is 01/23.

Name ________________________________________________________________________________ Address ______________________________________________________________________________ City _________________________________________________________________________________ State ________ Zip _____________ Daytime Phone_________________________Please mail completed forms with your payment to: ASCEND MEDIAS DENTAL LEARNING SYSTEMS CE Department, 405 Glenn Drive, Suite 4, Sterling, VA 20164-4432 SCORING SERVICES: By Mail Fax: 703-404-1801 Phone-in: 888-596-4605 (9am-5pm ET, Mon.-Fri.) Customer Service Questions? Please Call 888-596-4605

PROGRAM EVALUATION

Please mark your level of agreement with the following statements. (4 = Strongly Agree; 0 = Strongly Disagree)

CE 14

CE 23 2 1 0 4

CE 33 2 1 0

1) Clarity of objectives . . . . . .............. .............. ...... 2) Usefulness of the content . . . . ........... ........... ......... 3) Benefit to your clinical practice . . . . . . . .............. .......... 4) Usefulness of the references .............. .............. .... 5) Quality of the written presentation . . . .............. ........... 6) Quality of the illustrations . ........... ........... ........... . 7) Clarity of review questions .............. .............. ...... 8) Relevance of review questions .............. .............. .. 9) Did this lesson achieve its educational objectives? . . . . . . . . . . . . . . 10) Did this article present new information? . . . . . . . . . . . . . . . . . . . . . 11) How much time did it take you to complete this lesson? . . . . . . . . . . Yes No Yes No ______min Yes No Yes No ______min Yes No Yes No ______min4 3 2 1 0 4 3 2 1 0 4 0 3 2 1 4 3 2 1 0 4 3 2 1 0 4 0 3 2 1

4 0 4 0 4 0

3 3

2 2

1 0 1 0

4 4

3 3

2 2

1 4 1 4 4

3 3 3

2 2 2

1 0 1 0 1 0

3

2

1 0

4

3

2

1

4 0 4 0

3 3

2 2

1 0 1 0

4 4

3 3

2 2

1 4 1 4

3 3

2 2

1 0 1 0

DEADLINE FOR SUBMISSION OF ANSWERS IS 12 MONTHS AFTER THE DATE OF PUBLICATION.