Maxillary Changes UnderComplete Dentures Opposing

Mandibular Implant-SupportedFixed Prostheses

Saurahb Gupta, BDS,Sybille K. Lechner, MDS, FRACDS, FPFANorton A. Duckmanton, MDS, FRACDS,

Purpose: The aim of fhis study was to determine whefher a condition similar toCombinafion Syndrome occurs In patients rehabiiifated with a maxillary completedenture opposing a mandibular implant-supported fixed prosthesis. Materials andMethods: Standardized clinical procedures measured fit, occlusal integrity, and bone lossin the anterior maxilla in 1 f edentulous subjects meeting these requiremenfs, from thepatient pool of the Implanf Centre, Unifed Dental Hospital, Sydney, Results: A meanannual loss of 0,17 mm in tine anterior maxillary ridge height was not statisticallysigniticant (P > 0,05). However, Increased pressure in fhe anterior maxillary ridge duringocclusion and loss of posterior occlusal contacts in retruded position were noted on oneor bofh sides in all subjecfs. Conclusior): Loss of posterior occlusion could nof be relafedto anferior maxillary bone loss. However, fo maintain the integrity of ttie prosfheses andtheir supporting structures, it is imporfanf fo schedule periodic recall appointments forreview of the occlusion, Inl Prosthodont 1999,12:492^97.

Osseointegrated implants are widely used inprosthodontic rehabilitation, ranging from a sin-gle-tooth replacement to implant-supported com-plete dentures; these treatments often lead to amarked improvement in chewing efficiency and al-leviation of denture adaptation problems,'""^However, there may also be disadvantages in theform of bone loss in the opposing jaw.^"^

'Graduate Student, Discipline of Removable Prosthodontics,Faculty of Dentistry, University o Sydney, Australia.''Associate Professor and Head, Discipline of RemovableProsthodontics, Faculty of Dentistry, University of Sydney,Australia.'Adiiini:t Associate Professor, Special Prosthodontics, UnitedDental Hospital, Sydney, Australia.

Reprint requesfsi Dr Saurabh Gupta, 17 Civil Lines, NearAllahabad 8ani

Gupta et Cliariges Under Compiete Dentures Opposing Implant Prostheses

cantilever units of the implant prosthesis. As a directconsequence of higher functional forces in such situ-ations, midline fracture of the maxillary denture aswell as increased incidence of relines and remakes arereported in a few studies.^-'^- However, Zarb andSchmitt-^ did not encounter midline fractures or theneed for relining ofthe maxillary denture in 40 patientswith similar prostheses.

A difference of opinion is also evident in 2 studiesinvestigating anterior maxillary bone loss under com-plete dentures opposing implant-supported fixed par-tial dentures, acobs et al^ reported an increased an-nual maxillary bone loss in 12 subjects with theabovementioned prostheses, while Henry et aP' didnot observe increased bone loss and development offlabby ridges in the anterior maxilla in a 10-year fol-low-up study of 12 subjects.

The aim of this study was to determine whether acondition similar to Combination Syndrome occursin patients rehabilitated with a maxillary completedenture opposing a mandibular implant-supportedfixed prostbesis.

Materials and Methods

Eleven edentulous subjects who bad been rehabili-tated witb a mandibular osseointegrated implant-supported fixed prosthesis and a maxillary completeconventional denture were selected from the patientpool ofthe Implant Centre, United Dental Hospital,Sydney, Australia. The sample included 4 men and7 women, their ages ranging from 53 to 74 years(mean 65.6 y). Selection criteria were that they hadbeen wearing these prostheses for at least 21 monthsand their records did not show evidence of any sys-temic factors that might affect bone loss.-""

A subject information statement explaining thepurpose of the study, procedures to be carried out,and duration ofthe appointment was written in plainlanguage and mailed to the prospective subjects fortheir consent.

Each subject was asked if he/she was satisfied withtheir upper denture. They were asked to grade their pre-sent chewing ability from the time of implant treatmentas being the same, better, or poorer. Occurrences ofremakes, relines, and repairs ofthe maxillary denturewere recorded.

Ciinicai Examination

The maxillary denture was checked for stability andretention for each subject using conventional proce-dures for complete dentures,'" and results wererecorded as adequate or poor.

Fig 1 Height o1 Ihe biock ot the Luxatemp cast (DMG| is mea-sured to indicate the discrepancy between tootb surtaces inmaximum occiusal contact and in centric reiatian.

The fit of the maxillary denture was evaluatedusing a pressure-disclosing paste Fit-checker (GC).The amount of material was standardized by havingthe length of the bead of base paste equal to the an-teroposterior length ofthe denture, while the catalystpaste was half this measure. The fit was disclosedtwice in each case:

1. Finger pressure; Index fingers were placed on ei-ther side, midway anteroposteriorly, to seat thedenture, and moderate finger pressure was main-tained until the material was set.

2. Biting pressure: The subject was asked to bitewith moderate force and maintain this pressureuntil the material was set.

Visual differences in thickness between the 2 dis-closing impressions, especially in the anterior part ofthe ridge, were noted.

The discrepancy between maxillary and mandibu-lar teeth in the posterior region was determined bymeasuring the space between posterior tooth surfaceson casts of the prostheses articulated in centric rela-tion, as described by Lechner and Mammen'' (Fig 1 ).

Cephalometric Analysis

Lateral head cephalograms were taken with the den-tures in occlusion. A set of radiographs had been takenduring the implant-supported fixed partial denturetreatment (postoperative cephalogram}. A similar ra-diograph was taken atthe study appointment (follow-up cephalogram). Postoperative lateral cephalograms

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Under Coniplele Denlures Opposing implanl Proslheses

Table 1 Subject Data

Subject123456789

1011

SexFFFMMFMFMF F

Age(Vl7374746168705659606353

Cepti alo metric- .h. , . . ,;rr, "er iod

3 Oi-4-085-01

11-OQ2-053-GO3-013-026-05MA

Duralion ofdenture wear

(y-mo)6-043-114-004-02

10-001-091-092-022-02

15-066-03

"Time elapsed between postoperative and current cephslometric radi-ographs. No postoperaliue radiograph was available tor subject 11

Gupla et a i

Fig 2 Landmariis and points for cephalometric evaluation. ANS- antenor nasai spine; PNS = posterior nasai spine: ANS-PNS= palatai piane; C^most anterior inferior point on maxiiia; dine= iine passing through C perpendicuiar to palatal piane; C - in-tersection ot palatal plane and C iine, F - point 10 mm posteriorto C point aiong the paiatai plane: E line- line passing throughE' point perpendicular to palatal piane: E ^ most inferior maxil-iary point aiong tine E iine: Diine^ line passing through ANS per-pendicuiar to paiatai piane: C-D/ine= line passing through C pointparallel to palatal piane: D= intersection of D iine and C-D line.

had been taken at the time of stage 2 surgery rather thanat the time of issue of the mandibular prosthesis, whichin some cases had been considerably deiayed becauseof a variety of factors. The annual bone changes weretherefore calculated for the interval between the 2 setsof radiographs (observation period), which rangedfrom 2.4 to 11.0 years (mean 5.2 years), and not for theduration of denture wear, although most dentures wereworn for the majority of this period (Table 1 ).

The cephalograms were analyzed using the systemoutlined by Scott et al-'' for vertical and horizontalmeasurements of the edentulous maxilla. Tracings forboth the postoperative radiograph and the follow-upradiograph were made by the same examiner to min-imize tracing errors, and radiographs were traced ran-domly. The relevant landmarks were identified andtraced on tracing paper for both postoperative and fol-low-up radiographs (Fig 2). Cephalometric analysiswas carried out for only 10 subjects, as the postoper-ative cephalogram for one subject was not available.

The vertical and horizontal measurement valuesobtained for the follow-up radiograph were sub-tracted from those of the postoperative radiograph toobtain the effective annual change during the obser-vation period. Means and standard deviations werecalculated fur all measurements. The Student's itest{2-tailed paired means comparison) was used to sta-tistically evaluate bone loss and check tbe signifi-cance (95% confidence level) of the resulting valuesin this group. Simple regression analysis was used todetermine a linear relationship between the annualbone loss and the age of the subject and duration ofwear of the prosthesis.

Results

Subject Assessment of Fit of Maxillary Denture

Eight subjects (73%) found the fit of their maxillarydenture satisfactory, wbiletwo complained of a loosedenture. One subject observed that the denture"seems to be going up in the front and down at theback." The maxillary denture was relined for onesubject once, approximately 1 year before the study,and the denture felt loose again at the follow-up. Anew maxillary denture was made for another subject5 years before the present investigation. The denturehad been remade three times and relined three timesover 6 years for one subject, who reported that thepresent was the "most successful so far."

Retention and Stability of Maxillary Denture

The operator assessed the retention of the maxillarydenture to be adequate in 9 subjects (82%). The sta-bility of the denture was also found to be adequatein 9 subjects (82%). Retention and stability were ob-served to be poor in one subject. One subject hadpoor retention but adequate stability, while anotherexhibited adequate retention but excessive lateralrocking of the denture.

Evaluation of Fit of Maxillary Denture

The thickness of tbe film of Fit-checker in the maxil-lary denture was visually evaluated, revealing a thin-ner film of material in the anterior region under biting

o

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Gupta et I Changes Under Complete Dentures Opposing Implant Prostheses

pressure than with finger pressure (Fig 3). This was ob-served in all 11 subjects.

Posterior Occlusion

A loss of posterior occlusion was observed on one orboth sides of the denture in all subjects, ranging from0 to 2,5 mm on the left and 0 to 2.0 mm on the rightside of the prosthesis. The maximum discrepancy of2.5 mm on the left and 2.0 mm on the right sides wasobserved in one subjecf, while the remainder were1 mm or less. The values were different on the 2 sidesfor 10 subjects (91%).

Cepbalometric Evaluation: Vertical Measurements

C-C. Bone loss ranging from 1 to 4 mm was notedin 4 subjects (40%). No change was observed be-tween postoperative and follow-up values in 3 sub-jects. A 1-mm increase was observed in 3 subjects(30%). The mean annual bone loss was 0.17 mm, butthe difference was not found to be statistically sig-nificant (P> 0-05).

E-E'. Bone loss ranging from 1 to 4 mm was noted in6 subjects (60%), while 4 subjects (40%| showed nochange. The mean annual bone loss was 0.3 mm, andthe difference was found to be statistically significant(P 0.05|.

C-D. The measurements were the same as ANS-C forall subjects.

Fig 3 iulaxillary denture with pressure-aisclosing paste afterseating with biting force. Note heavy anterior contacts.

Discussion

Pressure-disclosing paste revealed a greater amount offorce in the anterior region on biting in all subjects, andlack ofposterior contacts was noted in all subjects. Byallowing shunting of the denture in function, poor oc-clusion often translates into a perceived lack of fit^^^^;the absence of posterior support could therefore wellaccount for the "looseness" of the maxillary denturedescribed by some subjects even though the operatorassessment was that the retention was adequate.

However, the amount of bone loss noted in the an-terior maxilla was equivocal, anda linear relationshipcould notbe established for annual vertical bone losswith respect to the age and sex of the subjects or du-ration of wear of the prosthesis. Loss of posterior oc-clusion could therefore not be attributed to bone lossin the anterior maxillary region as has been suggestedin ridges opposing impiant-supported overdentures.^"''It would havebeen interestingto compare the changesin the subject who showed maximum occlusal loss,but the postoperative cephalogram was not avail-able. The radiographie evaluation indicates that thevertical measurements at the crest of the maxillaryridge (C-C) are nearly even in distribution amongbone loss, no change, and increase in height of theridge. The identification ofthe ANS point was difficultbecause ofthe thin isthmus of bone with a greater su-perimposition of soft tissue and a poor-quality radi-ograph. There seems, however, to be a significant re-duction in the length of the palatal plane (ANS-PNS),as well as in the height of the anterior maxilla (E-E')posterior to the crest of the ridge. The horizontalchange observed was probably a result ofthe poste-rior repositioning of the anterior nasal spine that maybe related to the age of the subject and the pressureexerted by the maxillary denture. The crest of the

Volume 12, Number 5,1999 4 9 5 The Intemational Journal of Prosthodonlics

Under Complete Dftu'es Opposing Implant Prostlieses Gupta ct al

ridge is known to move posteriorly be(-aLi...e ol ihe pat-tern ofresorption,-^ which shifts fhe E'point along thepalatal plane because ofthe posterior repositioning ofthe C line. The paiafal contour narrows from the crestposteriorly in the superoinferior dimension, ' and thissupports the significant reduction in the E-E' dimen-sion. The posterior shift cf both the D line and the Cline possibly accounts for the insignificani changeobserved in the ANS-C dimension. The indecisive na-ture of these measurements may be a result ofthe factthat, compared with a mandibular implant-supportedoverdenture, the implant-supported fixed prosthesiswould show minimal deflection ofthe cantilever seg-ment when opposing a complete denture.

It is more probable that the lost posterior supportis loss of actual tooth structure. Prostheses for allsubjects had been made by one of 2 clinicians and,at the time of issue, all posterior teeth were in con-tact in centric relation. However, all had plastic teelh,which have been shown to be subject to wear,^ '^ - '^The difference in occlusal discrepancy between the2 sides may thus be caused by tbe preferred chew-ing side ofthe subject. Visual comparison of the orig-inal casts to the present prostheses showed wear insome of the cases, although as the study was retro-spective, no attempt could be made to evaluate anydimensional change in the plastic teeth. One subjectdid observe that the denture teeth seemed to be worn.The use of porcelain teeth in implant-supported com-plete dentures could overcome problems associatedwith plastic teeth.

Another explanation for the observed ioss of pos-terior occlusal contact could conceivably be a tissue-directed deflection of the maxillary denture, indicat-ing a loss of posterior maxillary ridge height.However, this possibility was considered marginaland was not investigated.

The scope of this study, being retrospective, waslimited in terms of the records available and theirquality at the time of the study. Errors in this studycoLtId aiso be attributed to the difficulty in identify-ing radiographie landmarks and problems associatedwith radiographie tracing.

Conclusion

In this study, the rehabilitation of the edentulousmandible with an implant-supported fixed prosthe-sis occluding with a maxillary complete denture didnot appear to promote a condition similar toCombination Syndrome, However, loss of posteriorocclusion was observed in every case and must be an-ticipated as a sequela tc such treatment, especiallywitb opposing plastic teeth. Periodic recall appoint-ments to review the occlusion should therefore be

scheduled to maintain occlusal harmony and thehealth cf the supporting tissues,

Euture research could include a larger sample eto provide a clearer picture of bcne loss and a com-parison between tbe effects of porcelain or plasticteeth on occlusal integrity.

References

1. Lindquist LW, Carisson GE, Long-term effects on chewing withmandibular fixed prostfieses on osseo integrated implants. ActaOdontoi Scand 1985;43:39-45.

2. Carlsson GE, Lindquist LW. Ten-year longitudinal study of mas-ticatory function in edentulous patients treated with fised com-plete dentures on osseointegrated implants, Int | Prosthodont]994;7:448-453,

3, Lindquist LW, Carlsson CE, Cfantz P-O, Rehabilitation oftheedentulous mandible with a tissue-integra led fixed prosthesis: Asix-yeai longitudinal study. Quintessence Int 1987;IB:B9-96,

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5, lacobs R, van Steenberghe D, Nys M, Naert I, Maxillary bonersorption in patients with mandibular implant-supported over-dent jres or fixed prostheses. | Prosthet Dent 1993; 70:13 5-140,

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7 Barber HD, Scott RF, Maxson BB, Fonseca R), Evaluation ofanterior maxillary aiveolai ridge rsorption when opposed by thetransmandibular implant, J Oral Maxillofac Surg 1990;48:1,283-1,287,

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12, Tallgren A, Tryde C, Mizutani H, Changes in jaw relations andactivity of masticatory musdes in patients with immediate com-plete upper dentures, J Orai Rehabil 1986;13:311-324,

13, Carlsson CE, Haraldson T, Fundamental aspects of mandibularatrophy. In: VWorthington P, Branemaik P-I (eds). AdvancedOsseointegrationSurgery, Chicago: Quintessence, 1992:109-118.

14, KelsEy CC. Alveolar bone rsorption under complete dentures,I Prosthet Dent 1 971 ;25:152-161,

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Changes Under Complete Dentures Opposing Implant Prostheses

20, Falk H, Laurell L, Lundgren D, Occlusal force patferns in den-filicin5 with mandibular implanl-supporfed fixed cantilever pros-fheses occluded with complefe denfures, Inf ] Oral MaxillofacImplanfs f 989:4:55-62,

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Literature Abstract-

The impact of oral health on stated ability to eat certain foods; Findings fromthe National Diet afid Nutrition Survey of Older People in Great Britain.

Ttiis exfensive study used 2 representative samples of peopie aged 65 years and older: aSffree-living and 275 mstitufionai subjects fiad a denfal exam and were interviewed about ffieirabiiify fo eaf 16 key foods There were more diefary resfiictions reported by fhe institution sam-ple, but in tfie tree-iiving people, many aiso had difticulfies eafing several ot fhe toods f i loreoffhe edentulous subjecfs reported such ditliculfies. If was concluded that the seiection ot foodsin older people is substantially affeofed by ffie number of feeffi, especially posferior occludingpairs of feeth, and the presence of complete dentures. Ttiose clinical parameters in turn affecthow people feel about eafing. This was even more important in institutionalized peopie.Diefifians and caterers should consider caretuily fhe dentai barriers fo eafing essential foods.

Sheifiam A, Steele JG, fHarcenes W, Fincfi S, Walls AWG, GeradoTtotogy 1999:1 S:11-20. References; 26,Reprints: Prof A, Sfieiliarr, Department of Epidemiology and Public hiealth, University College, Londonfuledical School, 1-19 Tomngfon Place, London WCIE6BV, United Kingdom Fax: + 44 (0)20 78f 3 0242,e-mail: A,Sfisiliam(>ucl.ac,uk,flW

Volume 12, Number6, f999 497 The International fojrnal of Proslhodontics