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Papers
1 hour validated CPD
Combination syndrome revisited
Philip W Smith, J Fraser McCord & Nick J A Grey
Abstract Problems of denture instability are aggravated when a complete denture is opposed by an arch containing all or some natural teeth. Two Two scenarios are possible, possible , first of all when whe n the maxillary arch is edentulous and the second is when the mandibular arch is edentulous. The former clinical scenario has been termed the combination syndrome. The aim of this article is to describe treatment options, specifically where “conventional” prosthodontic management is concerned.
Keywords Denture stability, combination syndrome.
Introduction
Philip W Smith BDS MDS PhD FDS DRD MRD RCS(Ed) FDS(Rest) Honorary Consultant Unit of Prosthodontics Prosthodontics J Fraser McCord BDS DDS FDS DRD RCS(Ed) FDS RCS(Eng) Professor and Head of Unit of Prosthodontics Prosthodontics Nick J A Grey BDS MSc PhD DRD MRD RCS(Ed) FDS(Rest) Consultant in Restorative Dentistry Edinburgh Dental Institute Institute Correspondence: Philip W Smith Unit of Prosthodontics Universityy Dental Hospital Universit of Manchester Higher Cambridge Street Manchester M15 6FH Tel: 0161 275 6629 Fax: 0161 275 7822 E-mail
[email protected]
The world-wide success of dental health education and preventive dental strategies means that the number of edentulous individuals is decreasing, and data would suggest that the age at which edentulousn edent ulousness ess occurs is advancing. advan cing. 1 However, in the future there is likely to be a significant number of patients in need of prosthodontic prosthodont ic treatment. It is possible that a number of potential prosthodontic problems may be encountered in an elderly partially dentate population. One such clinical scenario could be the provision of complete dentures in one arch while the opposing arch is either intact, or has some remaining natural teeth, or an implant supported prosthesis. For conventional complete dentures to function acceptably, the clinician should prescribe dentures which exhibit good stability. Denture stability has been defined2 as “that quality of maintaining a constant character or position in the presence of forces that threaten to disturb it”. Where complete dentures are concerned, stability may be considered to be a paradigm of muscle balance and occlusal factors, coupled with good retention and appropriate utilisation of support. The relationship between retention, stability and support, has been comprehensively reviewed by Jacobson and Krol.3 These authors stated that stability was the most significant property in providing for the physiologic comfort of the patient.
The use of accepted prosthodontic techniques directed towards ensuring denture stability, tends to be successful in many cases. In some situations success may be limited by atrophic denture bearing tissues, unfavourable peri-denture musculature and poor/unrealistic patient perceptions. Problems associated with the provision of a complete denture opposed by a natural denture were described classically by Tillman in 19614 and Kelly in 1972.5 Tillman described the complete lower denture opposed by an upper removable partial denture (RPD), while Kelly described the opposite scenario. Conventional wisdom would indicate that the latter condition was most prevalent in clinical practice. This is most likely to be the result of the usual pattern of tooth loss in which maxillary teeth tend to be lost before mandibular teeth.1 Kelly considered that there were five changes which tended tended to occur in the cases which which he studied (Figure 1). These are:
Figure 1. Typical clinical changes in an edentulous maxilla opposed by natural teeth, note in particular the displaceable tissue in the anterior part of the residual ridge.
• Loss of b bone one ffrom rom the anterior anterior part of the maxillary ridge • Overgr Overgrow owth th of the the tubero tuberosit sities ies • Papillary Papillary h hyperplas yperplasia ia in the hard hard palate palate • Extrusion Extrusion of tthe he low lower er anterior anterior teeth • The loss loss of bone bone u under nder an anyy (mandibu (mandibular) lar) partial partial denture bases.
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Kelly based his observations, presumably, on his considerable clinical experience, backed up by serial cephalometric observations of 20 patients. However only six of the latter returned faithfully over a 3 year follow-up period. Whether all five clinical conditions are related as Kelly proposed, the potential for adverse morphological
of a removable onlay appliance or alternatively more extensive fixed restorations. However, for a variety of reasons, many patients, and some clinicians, are wary of embarking on extensive restoration of the opposing teeth in an attempt to increase the chance of improved stability of the opposing complete denture. Therefore, the clinician is
changes to occur in such a situation cannot be disregarded. often faced with the task of fashioning the complete denture Kelly suggested avoidance of this clinical scenario in in such a way that it produces a clinically acceptable result, without recourse recourse to m modifyi odifying ng the opposing opposing natural natural teeth. teeth. the first instance, in what is perhaps the first instance of without At the time that Tillman and Kelly wrote their preventive prosthodontics being advocated. Reference has been made previously to the difficulties respective articles, dental implantology had not advanced to encountered by having to provide a replacement complete the levels of sophistication, and clinically-acceptable denture in one arch while the opposing arch contains a success rates, recently reported for endosseous implants.10,11 natural (or essentially natural) dentition; this challenging There can be no disputing that implant-supported and/or clinical combination was termed the combination retained prostheses would be the treatment of choice in syndrome by Kelly, with reference to the maxillary arch many cases exhibiting ‘combination syndrome’. However, this form of treatment may be ruled out being edentulous. In a development of the theme 6 propounded by Kelly, Saunders et al; stated that six other either because a patient cannot afford implant therapy or changes are commonly associated with this clinical scenario: implant treatment may be contra-indicated for other valid medico-dental reasons. • loss of vertical vertical dimension dimension of o occlu cclusion sion An added factor for general dental practitioners to • oc occlu clusal sal plan planee dis discre crepan pancy cy consider is that many implant–related treatment plans anterior anterior spat spatial ial reposit repositionin ioningg of the the mand mandible ible require surgical and restorative expertise which may poor poor adaptati adaptation on of th thee pro prosth sthese esess require skills above many non-specialist practitioners. epul epulis is fis fissu sura ratu tum m For these reasons, the purpose of this article is to advers adversee period periodont ontal al chan changes ges To these factors a seventh factor might also be added, highlight useful conventional clinical techniques to help in namely the fact that a number of patients may elect not to the provision of complete dentures opposing a partially or dent ate arch. Although Altho ugh not speci speciff ically ical ly the wear a lower prosthesis which was provided with the wholly dentate syndrome detailed by Kelly, we shall describe intention of providing posterior occlusion. This would combination syndrome appear to be especially true of free-end saddle partial two “combination” “scenarios”, one for the edentulous maxillary arch and the second for the edentulous dentures. Saunders et al ; recommended that the essential mandibular arch. objective of treatment planning in these cases was “to provide an occlusal scheme that could best discourage A. Complete maxillary denture opposed by a excessive occlusal pressures in the maxillary anterior dentate/partly dentate mandibular arch In this situation (Figure 2), the t he displacing forces on the region in both centric and eccentric occlusal contacts”. • • • •
They listed the restorative and prosthodontic objectives but did not relate how to achieve this. How the occlusion might be managed to cope with the combination syndrome has been described by Kelly and also reviewed by Lauciello7. Basically, two methods emerge from the literature that may be employed to fashion the occlusion: • a functi functiona onally lly-ge -gener nerate ated d path path • an articulat articulator or which which h has as been been programme programmed d to reproduce the patient’s mandibular movement movements. s. Malposed, tilted or over-erupted teeth in the opposing arch are prone to induce unfavourable occlusal contacts, which whic h in turn may lead to compromis compromised ed denture stability stability.. This may then cause discomfort, trauma (which may result in increased alveolar resorption) and social embarrassment as a result of movement of the prosthesis. Some authors 8, 9 have recommended that the opposing dentition should be modified to give a more favourable occlusal plane and geometry. It is suggested that this might be achieved either by re-shaping the occlusal surfaces by grinding, by provision
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upper denture resulting from mandibular movements movements have to be harnessed, and a variety of ways of maximising the retentive forces and reducing the displacing forces may be utilised.
Figure 2. An upper complete denture, opposed by a partially dentate lower arch which has been restored with a tooth and mucosal borne partial denture.
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The retaining forces are maximised by ensuring that a peripheral seal is present. This is the function of the special tray, which, in conjunction with a suitable border moulding technique, technique, should demonstrate a peripheral seal prior to the recording of the definitive impression. In
• Ensuring Ensuring that the the technic technician ian “mills” “mills” the the occ occlusio lusion n to suit the patient. The latter will inevitably be necessary, necessar y, as (denture tooth) cuspal inclines will be unlikely to equal those of the patient, and this technique technique develops a customised occlusal architecture for the upper
addition there is commonly readily displaceable tissue in the region of the maxillary anterior ridge. This can be accounted for by using an impression technique that aims to use the firmer tissues to support the upper denture. This requires a two-stage impression which uses a close fitting special tray. The first step involves developing peripheral seal, and subsequently a window is made in the tray corresponding to the area of displaceable tissue. The tray is loaded with medium body polyvinylsiloxane (PVS) and an impression made in the usual way, although the excess material escapes through the window. The impression is removed and inspected, and the impression material, which has flowed through the window, is removed. The tray is then carefully re-seated, and the second stage is completed, which involves syringing light
denture. On occasion, however, the clinician may need to refine the laboratory produced occlusal form and use the patient to “mill-in” the occlusion in the chair. A technique sometimes used by the authors of this article is to make a paste of silicon carbide (The Carborundum Company Ltd., Trafford Park, Manchester, England UK) and toothpaste, which is placed on the occlusal surfaces of the complete denture. The patient is then directed to trace out the border movements with the denture stabilised in situ and with the teeth in occlusion. The reader will probably be familiar with the above techniques perhaps with the exception of the gothic arch tracing, and the latter will be described descr ibed in more detail. The gothic arch tracing is produced by a stylus (usually f ixed to
bodied (PVS) through the tray window and over the exposed ridge tissue, to complete the upper impression (Figure 3). Displacing forces are reduced by co-ordinating the maxillary teeth and maxillary plane of occlusion to harmonise with mandibular teeth during mandibular movements. These are achieved via • Using Using a facebow facebow to transf transfer er the pl plane ane of the the upp upper er arch arch to the condylar axis. • Using Using a central-b central-bearing earing sc screw rew to create create aan n arrow arrowhead head (gothic arch) tracing (Figure 4), which is used to determine the retruded jaw position. • Setting Setting the articul articulator ator condy condylar lar an angles gles to aaccor ccord d to the the border tracings on the arrowhead ar rowhead tracing. • Establishi Establishing, ng, car carefull efullyy, at trial insertion insertion,, that RCP RCP is
an acrylic plate retained by the mandibular teeth) which traces out a path on a flat metal plate (fixed horizontally to an upper baseplate) during mandibular excursive movements. The shape produced is rather like an arrowhead, which points posteriorly, posteriorly, the apex of the arrow ar row represents a reproducible retruded jaw position. Although this technique is helpful in determining the retruded jaw relationship, there are limitations to its usefulness: • It requires requires normally normally function functioning ing TMJs TMJs • Th Thee bases bases must must be suffici sufficient ently ly stable stable • There There shoul should d be su sufficient fficient vertic vertical al space space to accommodate accommod ate the apparatus There are other techniques available whereby the desired morphology maxillary occlusal surfaces are generated intra-orally. Perhaps the first author to describe
reproducible.
Figure 3. Upper impression made to take account of displaceable tissue in anterior maxilla.
such a technique was Stansbury in 1951. 12 He
Figure 4. A gothic arch tracing recorded for a patient with an edentulous maxillary arch opposed by natural teeth. Note the apex of the arrowhead represents the retruded jaw relationship.
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recommended the use of a narrow compound maxillary rim which had carding wax placed buccal and palatal to the rim. The wax was subsequently “moulded” by the mandibular teeth in border movements. Vig13, in 1964, updated this when he used an acrylic rim with an acrylic
denture-bearing tissues and the lack of stability of the mandibular denture. Moderately severe residual ridge resorption tends to be the rule in such cases and the difficulties of managing this condition, per se, have been discussed by McCord et al;14. In
fin which engaged the central fossae of the lower teeth. essence, reductions in both quality and quantity of the Soft wax was then added incrementally to form for m the buccal denture-bearing tissues tend to be accompanied by and palatal forms of the maxillary posterior teeth; again the unfavourable peri-denture anatomical forces, i.e. muscle form of the maxillary cusps was generated via the patient attachments encroaching on the residual ridges. As a result, the displacing forces tend to overwhelm retaining making lateral and protrusive mandibular movements. Customised gold occlusal surfaces, created by making features of the mandibular denture and only immense control of the denture will maintain denture a functionally-generated path in the processed dentures, physiological control may also be used, but are potentially expensive, in terms of stability. both material and laboratory time. Another approach, which has been used with some success by the authors of Treatment strategies Two “conventional” strategies are possible here, this article, is to functionally-generate the occlusal anatomy of the maxillary denture teeth using either a namely prosthodontic alone and a combination of prosthodontics tics and pre-prosthetic surgery. light-cured composite resin, or amalgam (Figure 5). When prosthodon using the former we use resin recommended for posterior composite restorations, as it tends to exhibit more Prosthodontic treatment alone appropriate wear properties.
Treatment should be aimed at using an appropriate selective pressure impression technique that satisfies prosthodontic norms whilst allowing the clinician to satisfy him / herself that the denture-bearing tissues can withstand a degree of functional loading.15 Using an appropriately extended special tray with 1mm spacing, an admix of impression compound and tracing compound may be used to make an impression, which may be moulded to effect a peripheral seal and, simultaneously, produce a selective-pressure impression of the denturebearing area (Figure 6).
Figure 5. An upper complete denture illustrating the use of amalgam to form customised occlusal surfaces opposing natural teeth.
As with most complete denture problems, patient cooperation is essential if success is to be achieved. For this reason, patients should be made aware of the potential problems of denture stability at the first clinical visit and be conditioned to their contribution to denture success.
B. Complete mandibular denture opposed by a dentate/partly dentate maxillary arch This extreme of the prosthodontic-problem spectrum has, in the past, been avoided by rendering the maxillary arch edentulous. Most patients, and for that matter many dentists, are disinclined to accept such a treatment plan unless it is absolutely necessary. Clinical experience would certainly suggest that this problem is more difficult to manage than the edentulous maxilla, and although similar techniques are recommended, success tends to be more elusive. Two major problems appear to operate here, namely the impaired support potential of the mandibular
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Figure 6. A lower impression made using an admix of greenstick and red impression compounds to take account of atrophic tissues in a mandible opposed by natural teeth.
At the next clinical stage, the clinician must decide on the occlusal configuration of the denture. This will involvee three related yet distinct procedures. involv • The first first phase, phase, advo advocat cated ed by Till Tillman man4, is to record the relationship of the maxillary occlusal plane to the condylar axis; this requires a facebow transfer.
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Figure 7. Lateral view of a completed ‘gothic arch’ jaw registration for a mandibular complete denture opposed by a natural maxillary dentition, used to articulate casts in RCP.
Figure 8. A lower complete denture opposing a natural upper dentition illustrating customised occlusal surfaces in the lower prosthesis to harmonise with the irregular natural occlusal plane.
• The secon second d phas phasee is to record record appro appropriate priate maxillo maxillo-mandibular relations. One technique useful in these cases is to use a device that allows the production of an arrowhead (gothic arch) tracing (see above), thereby
even occlusal contact in the retruded position. In addition to this, mild chairside customisation may be required, via a carborundum-toothpaste mix ( vide supra).
use of soft soft linings linings has has also also bee been n advocat advocated ed as a ensuring good reproducibility of mandibular • The use 16 possible means of reducing the discomfort beneath a movements when transferred to the articulator. mandibular complete denture opposed by the natural Figure 7 shows articulation of a dentate upper and dentition.17 The use of soft linings has been recently edentulous lower cast, after jaw relations were reviewed18, and despite their shortcomings as regards recorded using a gothic arch tracing to determine a long term clinical performance, it is apparent that their reproducible retruded jaw relationship. The main compliant nature would allow more even distribution limiting factor in using gothic arch tracings in the of occlusally generated forces in this type of adverse lower jaw is lack of stability of the recording base. clinical situation. Clinical experience suggests that a • The third third phase phase relates relates to what what Tillman Tillman termed an an soft lining needs to have a minimum thickness of 3mm “accurately conceived occlusion”. Debate exists to be effective. Therefore, caution needs to be whether anatomical anatomical or or non-anatomical non-anatomical teeth should be be exercised to ensure that the denture base either has selected; in neither case has there been a scientificallysufficient bulk to impart the necessary strength, or based trial to validate the choice of one over the other. alternative methods have been employed to strengthen However, clinical experience would tend to support the prosthesis, for e.g. the incorporation of a cast metal the premise that any “tripping” of the occlusal surface lingual plate. of the lower denture against the maxillary natural teeth &/or RPD, during mandibular movements, will result Prosthodontic/pre-prosthetic surgery in instability of the complete denture. Although a Prosthodontic/pre-prosthetic Undoubtedly, the surgical intervention with the technique was described for creating a functionallygenerated occlusal form for maxillary dentures, such a greatest potential to improve the stability of any prosthesis technique for mandibular dentures may be prone to is the successful placement of osseointegrated implants. In error unless the prosthesis was sufficiently suff iciently stable. Such all such cases, the prosthodontist should have planned the conditions are usually only met when the appliance in prosthesis in consultation with the oral surgeon who question is some form of overdenture. Clearly, any places the fixtures. However, on occasion alternative technique which relies on articulator-based surgical procedures not involving the placement of dental customisation of the occlusal form will require the use implants may be considered appropriate. These may involvee vestibuloplasty to increase the relative height of the of a facebow transfer, and a gothic arch tracing to involv reduce errors in transferring jaw relationships to the anterior mandible, in addition to minor hard or soft tissue articulator. The philosophy here is to eliminate all surgery. The indications for such procedures, particularly t he advent of osseo-integration, are now apparently points of first contact until balancing contacts are with the achieved with the objective of imparting denture less than previously. The details of such procedures are stability (Figure 8). On occasions a ‘check’ occlusal beyond the scope of this article, and the reader is advised record taken after the denture has been processed may to consult standard surgical texts for further information. be helpful to allow the dental technician to produce
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Conclusion The prosthodontic treatment of partially-dentate patients is likely to pose increasingly more difficult clinical problems. Two clinical problems likely to be encountered are the “combination scenarios”, when an edentulous arch is opposed by a partially-dentate or even fully-dentate arch. The identification of such problems is an important component of the treatment planning. Other important areas which deserve earnest consideration are: 1. 2. 3.
4. 5. 6.
7. 8. 9.
References Todd J, Lad Lader er D. Adul Adultt Dental Health, Health, 1 1988. 988. United United Kin Kingdom gdom,, London. London. OPCS. HMSO. Americ American an Acad Academy emy of Pro Prosthod sthodontis ontists. ts. Gloss Glossary ary of Prosthodont Prosthodontic ic Te Terms, rms, 6th ed. J ed. J Prosthet Dent 1994; 41-11 112. 2. Dent 1994; 71: 41Jacob Jacobson son T E, Kr Krol ol A J. A co contemp ntemporary orary revi review ew of the factors factors involv involved ed in complete denture retention, stability and support. J support. J Prosthet Dent 1983; 49: Dent 1983; 5-15. Till Tillman man E J. R Remov emovable able parti partial al upper an and d complete complete lo lower wer den dentures. tures. J. J. 1097-1 -1104. 104. Prosthet Dent 1961; Dent 1961; 11: 1097 Kelly E. Ch Changes anges caused caused by a mand mandibula ibularr remo removable vable p partial artial denture denture opposing a maxillary complete denture. J denture. J Prosthet Dent 1972; 27: 140-15 140-150. 0. Saunders T R, Gillis R E, Desjardins R P. The maxillary complete denture opposing the mandibular bilateral distal-extension partial denture. Treatment considerations. J considerations. J Prosthet Dent 1979 ;41: 124-128. Lauci Lauciello ello F R in Es Essentia sentials ls of Complete Complete Denture Denture Prostho Prosthodonti dontics, cs, 2nd 2nd.. edn. Ed Winkler S. Mosby, St. Louis, 1988: 417-426. Wat Wattt D M, MacGr MacGregor egor A R in Designi Designing ng Complete Complete Dentures Dentures,, Saunders, Saunders, Philadelphia, 1976; p164. MacGr MacGregor egor A R in Clinic Clinical al Den Dental tal Prosthet Prosthetics, ics, 3rd 3rd edn. Wright, Wright, London London 1990:97-307.
• Recordin Recordingg impressio impressions ns that satisf satisfyy the par paramet ameters ers of support, retention and stability. • Conveya Conveyance nce of appr appropriate opriate functio functionall nally-rel y-related ated pati patient ent data, e.g. facebow and inter-maxillary relations. • Creation Creation of appro appropriate priate occlusal occlusal form. • Informing Informing the the patie patient nt of his/her his/her co contribu ntribution tion to denture success.
10. Adell Adell R, Lekh Lekholm olm U U,, Roc Rockler kler B, et al; A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int jaw. Int J Oral 1981;6: 387-416. Oral Sur Surg g 1981; 11 11.. Van Steenberghe D, Qu Quirynen irynen M, Calberson, et al; A prospective evaluation of the fate of 697 consecutive intra-oral fixtures ad modum Branemark in the treatment of edentulism. J edentulism. J Head Neck Pathol 53-58 -58.. Pathol 1987; 6: 53 12. Stansbury Stansbury C B. Single denture denture constru construction ction agai against nst a non-mod non-modified ified natural dentition. J dentition. J Prosthet Dent 1951; Dent 1951; 1: 332-336. 13. Vig R G. A modified ch chew ew in and functional im impression pression technique. J. technique. J. 214-220.. Prosthet Dent 1964; Dent 1964; 14: 214-220 14. McCord J F, Grant A A, Quayle A A. Treatment options for the edentulous mandible. Eur mandible. Eur J Prosthodont Rest Dent 1992; 19-23 -23.. Dent 1992; 1: 19 15. McCord J F, F, Tyson K W. W. A conservative prosthodontic option for the treatment of edentulous patients with atrophic (flat) mandibular ridges. Br 469-472. 72. Dent J 1997; J 1997; 182: 469-4 16. El Gherani-A S, Winstanley R B. T The he value of the Gothic Ar Arch ch tracing in the positioning of denture teeth. J teeth. J Oral Rehab 1988; 15(4): 367-377. 17 17.. Hickey J C, Zarb G A, Bolender C L. Bo Boucher’s ucher’s Prosthodonti Prosthodonticc Treatment for Edentulous Patients, 9th edn. St. Louis: CV Mosby, Mosby, 1985; p560. 18. Braden M, Wright Wright P S, Parker S. Soft lining materials- A review review.. Eur J Prosthodont Rest Dent 1995; 3: 163-174.
MCQ Answers to 2001, Vol 2 No 2 • 1. 2.
3.
4. 5.
• 6.
7.
8.
9. 10.
(K Marshall) Rese Resear arch ch has has sho shown wn ttha hatt in general dental practice: Sma Small ll partic particle le aeros aerosols ols only only rema remain in in the atmosphere for a short time.False The use of rubber rubber dam dam may may rredu educe ce contaminated aerosols by up to 98.5%. True The dental dental tea team, m, other other tthan han the dentist and nurse, are at no increased risk from Hepatitis B. False Saliva Saliva ccont ontain ainss 15 150 0 millio million n mic microb robes es per millilitre. True Pre-op Pre-operat erative ive cchlo hlorhe rhexid xidine ine rinse rinse can assist in reducing contamination. True (T F Walsh & A Rawlinson) Whic Which h of the fo foll llow owin ing g are are correct? Ch Chron ronic ic gi gingi ngivit vitis is may may be pre presen sentt with or without the loss of periodontal attachment having occurred. True Pati Patients ents suffering suffering from necr necrotis otising ing gingivitis have confluent ulcers affecting the tongue and cheeks in addition to gingival tissues. False Adult Adult perio periodon dontit titis is is is usua usually lly recognised in patients between 30 and 40 years of age. True Juv Juveni enile le period periodont ontiti itiss is very very co comm mmon on amongst Caucasian teenagers. False In ra rapidly pidly progressiv progressivee periodontiti periodontitiss there may be acute inflammation and marginal proliferation of the gingival tissues in an active phase. True
(J P J Fearon & C C Youngson) •. The most most signific significant ant causes causes of pulpal trauma during crowning are:
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11. 11. Lack of of adequ adequate ate cool cooling ing of the the bur. True 12. Bacterial Bacterial contam contaminatio ination n of the waterwaterline. False 13 13.. Over-redu Over-reduction ction of the tooth substance. True 14. 14. Irritant cements cements bei being ng used to lute lute the crown. False 15. Crowns Crowns being being cem cemented ented “high “high” ” in occlusion. False
26. Inward Inward pre pressure ssure caused during cementation. False 27. 27. Bacterial Bacterial micro microleakage leakage.. True 28. Dissolution Dissolution of a smear layer subsequent to cementation using conventional cement. True 29. Irritati Irritation on fr from om the cceme ement nt lute. lute. False 30. The material material used to const construct ruct the crown. False
•
•
Duri During ng c cro rown wn fab fabri rica cati tion on beneficial circumstances for the
pulpodentinal complex include: 16. Dentinal Dentinal tubular tubular fluid outflow. outflow. True 17. 17. A decrease decrease in p pulpal ulpal blood blood flow after administration of local. False 18. In the short short term term,, the develo development pment of a smear layer. True 19. Formation Formation o off primary primary dentin dentine. e. False 20. Formation Formation o off tertiary tertiary dentine dentine.. True • 21. 21. 22.
23.
24.
Fact Factor orss th that at w wou ould ld tten end d to compromise the pulpal vitality include: Careful Careful crowning crowning of of a tooth tooth fo forr a young rather than old adult. False A long long time time interval interval between between temporary and definitive crown placement. True Removing Removing the the smear layer layer and and pla placing cing a bonding system on the preparation. False Preparation Preparation well well into into dentine dentine to improve the outward tubular fluid flow. True
25. the Acidsmear etchi etching ng the den dentine tine to rem remove ove layer. False
•
In a defini definitiv tive e cro crown wn whi which ch are the most significant threats to the pulp?
(D A Keetl Keetley) ey) Today some tooth preparation is provided for Resin Retained
Bridges for the following reasons: 31. 31. To allo allow w the me metal tal to be co contained ntained within the contour of the tooth, so as to avoid making changes to the existing occlusion. True 32. To ensure th that at any sstresses tresses created created aare re directed away from the adhesive. True 33. To provi provide de a good area fo forr bonding. bonding. True 34. To give give cle clear ar unamb unambiguou iguouss finishing lines for the technician & to allow positive seating of the appliance on fitting. True 35. Rest seats seats can pr provid ovidee addi additional tional retention. False
39. An ad advantag vantagee of th these ese brid bridges ges is tthat hat they can be cemented by most professionals complementary to dentistry (PCDs). False 40. If th thee bridge fails iitt cann cannot ot be cemented again with the same degree of success. True • Treatment Planning: 41 41.. Is syno synonymo nymous us wit with h the plan plan of treatment. False 42. Is easi easier er wit with h resin retain retained ed bridg bridges es because they are non-invasive. False 43. May in involv volvee a mul multidisc tidisciplina iplinary ry approach. True 44. Requ Requires ires artic articulated ulated study m models odels an and d a surveyor. True 45. Is usua usually lly provid provided ed at th thee patien patients ts first visit. False
• 46. 47. 47. 48.
49.
•
With With rreg egar ard d to cem cement entat atio ion n of Resin Retained Bridges: 36. Hooks from th thee wing ccan an be ext extended ended over the incisal edge to aid location. True 37 37.. Most microfille microfilled d com composites posites will bond to base metal castings.adequately False 38. Glass ionome ionomerr ceme cements nts ar aree now considered to give the best in use longevity. False
50.
The The desi design gn o off a m mod oder ern n re resi sin n retained bridge: Often in involv volves es two wi wings ngs per po pontic. ntic. False May ev even en use two small premolar premolar sized teeth to replace a molar. True Is aid aided ed greatl greatlyy by su surveying rveying tthe he stu study dy models prior to preparation of the tooth. True May in involv volvee keepi keeping ng the m metal etal wi wing ng clear of the incisal edge to improve aesthetics. True Inv Involves olves cconstruc onstruction tion of tthe he wing iin na base metal. This is grit basted with aluminum oxide to aid bonding. True
