A clinical evaluation of conical crown retained dentures

A clinical

evaluation

Margareta Molin, DDS, Ake Ericson, DDSC

Odont

of conical Dr,a Bo Bergman,

crown DDS,

retained Odont

dentures

Dr,b and

University of Umea,Umea,Sweden In an uncontrolled retrospective recall study of 57 patients treated with conical crown retained dentures, 60 restorations (37 in the maxillae and 23 in the mandible jaw) with a mean wearing time of 30.1 months (range 4 to 76) were evaluated. Of the 248 abutments, eight (3.2%) had been lost. Clinically healthy mucosa was seen in 35 jaws. The marginal Bt of the copings was judged to be good. No caries or new restorations were observed in 44 patients. Thirteen patients had 19 surfaces with new restorations and 20 surfaces with caries lesions. Of these 39 surfaces, 38 were located subgingivally. (J PROSTHET DENT 1993;70:251-6.)

c

onical crown retained dentures (CCRD) have been recommended as a treatment method for patients with advanced caries, periodontal disease, or few remaining teeth, sometimes unfavorably distributed in the arch and with heterogeneous prognoses.1-6 Although the CCRD system has been used for approximately 20 years, there is little scientific clinical documentation on this system. Only a few clinical studies appear to have been published. In a study by Heners and Walther: the extraction rate was examined. The dentures, 500 in the maxillae and 371 in the mandible, had been in place for times that varied from 1 month to 11 years. Of almost 1800 abutments, 71 (3.9 %) had been extracted. No other details about clinical results or patient’s opinions were given. In further studies,sTQthe same authors examined the prognosis for teeth with reduced periodontium. The results showed that periodontally reduced teeth involve a higher risk of extraction and that the survival rate of abutments in severely reduced dentition differs significantly from that in dentition with more than three teeth. In pursuit of more detailed clinical documentation, a study was initiated at the University of Umea, Department of Prosthetic Dentistry, in Umea, Sweden, to reexamine a number of patients provided with dentures retained by conical crowns. lo During 1985 and 1986, 25 patients were treated with conical crown retained dentures, 22 in the maxillary arch and four in the mandible. Fourteen of them replaced teeth on both sides in the molar region, six replaced teeth on one side. The primary indication for the use of this type of therapy was the presence of only a few teeth, mostly in unfavorable positions. Clinical findings after 24 to 43 months were considered promising. Patients

Supported in part by the SwedishDental Society. aAssociateProfessor,Department of Prosthetic Dentistry. bProfessorand Chairman, Department of Prosthetic Dentistry. CAssistantProfessor,Specialist in Private Practice. Copyright @1993 by The Editorial Board of THE JOURNAL OF PROSTHETIC DENTISTRY. 0022-3913/93/$1.00 + .lO 10/l/47314

SEPTEMBER 1993

were generally satisfied and small tissue changes were found. It was considered valuable to examine a number of patients treated outside a University clinic with other clinical and/or economic conditions; thus, this study reports results from three different clinics. MATERIAL

AND

METHODS

Fourteen dentists from three different clinics in northern Sweden were questioned about their production of CCRDs. Eleven dentists who worked in the National Dental Health Service (clinics I and II) and three who were specialists working in a private practice (clinic III) were asked if they would allow their patients who were provided with CCRDs to participate in the study. Our intention was that all CCRD patients should be recalled. The clinics presented a list of 74 patients. Of these, 57 patients, 29 men and 28 women with a mean age of 64.4 years (range 43 to 84), were examined. The reasons for nonattendance (17) were the following: deceased (l), unwillingness to participate or no specific reason given (6), living far away from the clinic (3), therapy changed to osseointegrated prosthesis (l), and unknown reasons (6). The patients examined had been provided with a total of 60 CCRD constructions, 37 in the maxillary jaw and 23 in the mandibular jaw, with a mean wearing time of 30.1 months (range 4 to 76) at the time of the clinical evaluation. Three of the 57 patients had a CCRD in both jaws. Of the remaining 54 patients with a CCRD in one arch, 28 patients had their original teeth and/or a conventional fixed partial denture in the opposing arch, 16 had a complete denture, and 10 patients had their original teeth and a conventional removable partial denture. It was not possible to determine the inclusion criteria from available patient records, but it is our impression that the criteria had varied. However in most cases, there was a combination of few teeth, unfavorable distribution of remaining teeth, and/or heterogeneous prognoses of the teeth. The distribution of the patient’s remaining teeth and the teeth replaced in the CCRD-treated arches is shown in Fig. 251

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BERGMAN,

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Fig. 2. A, CCRD in the maxillae of a 69-year-old woman. The construction had been in place for 60 months. There are copings in gold alloy on the right and left canines and on the left central incisor. The suprastructure has caused indentations beyond the saddles covering the regions distal to the canines. B, Denture in place, occlusal view. The suprastructure is fabricated in gold alloy. The facing material in the anterior segment is composite resin.

Fig. 1. Distribution of the subjects’ remaining teeth replaced by the dentures in the maxillae dibular jaw.

teeth and and man-

1. Initially there were 248 abutments, 164 in the maxillary jaw (mean 4.4) and 84 in the mandibular jaw (mean 3.7) (Table 1). The distribution of treated jaws and abutment teeth related to the three clinics is shown in Table rr.

The alloys used for the abutment copings (as inner crowns) were gold alloys that met the IS0 Standard 1562.” This was also the material of the suprastructure except for two constructions where cobalt-chromium alloys were used. In three constructions, cobalt-chromium alloy appendices were soldered to the gold suprastructure to retain the acrylic resin. The denture base acrylic resin for the constructions made at clinics I and III was SR-Ivoclar 3/60 acrylic resin (Ivoclar AG, Schaan, Liechtenstein). The veneering material for the 20 suprastructures made at clinic I and three of the suprastructures made at clinic III was a chemical-cured composite resin (Isosit, Ivoclar AG), and the veneering material for 15 of the suprastructures made at clinic III was a light-cured composite resin (Dentacolor with t,he Silicoater technique (Kulzer GmbH, Wehrheim, Germany). Corresponding information about the constructions made at clinic II could not be obtained, either from patient records or from direct questioning of the dentists. Thirteen of the suprastructures were designed similar to fixed partial dentures, 13 were designed similar to removable partial dentures with free-end saddles in the

MOLIN,

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Table

I.

AND

Distribution

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of the supporting abutments (initial number 248) in the 60 arches treated No. of abutments 1

2

No. of arches Maxillae

1

Mandible

9 10

Total arches

Table

II.

3

4

5

6

11 3 14

11 6 17

7 3 10

3 3

7

8

9

Total arches

-

4 4

2 2

37 23 60

Treatment data related to clinic Lost No. of

Clinic I II III Total

No. of

dentists

jaws treated

7 4 3 14

20 22 18 60

edentulous area, and the remaining 34 were made with a combination of both designs. Of the 37 maxillary prostheses, one was provided with a transverse major connector and one with a cobalt-chromium palatal base plate. All abutment copings were made with a conical angle of six degrees (taper angle 12 degrees). Of the abutments, 127 (51.2%) were endodontically treated and provided with cast posts and cores of the same alloys as those used for the copings. Factors

analyzed

and criteria

used

The clinical factors were graded according to the following criteria: 1. Occlusion and articulation according to Bergman et a1.12:Occlusion was recorded as satisfactory if intercuspidation was correct without observable gliding on repeated habitual closing of the mouth from a postural rest position, and if firm intermaxillary contact could be demonstrated bilaterally and frontally with the aid of a stiff cement metal spatula. Articulation was considered satisfactory when an examination with a cement metal spatula showed firm bilateral contact in lateral positions after gliding half the width of a premolar, and bilateral contact in protrusion position after forward gliding approximately 3 mm. Otherwise, incorrect articulation was recorded. 2. Retention of the suprastructure when effort was made to remove it manually in an “axial” direction: 0, no retention, quite loose; 1, limited retention; 2, marked retention; 3, extremely marked retention. 3. Condition of the mucosal area covered by the denture according to Bergman et al. 12:0, no reddening or changes (healthy); 1, local reddening, hyperemia, and decubitus (inflamed); 2, edematous, reddened mucosa and/or

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No. of initial abutments 104 71 73 248

abutments

No.

%

5 2 1 8

4.8 2.9 1.4 3.2%

granulamatous surface of entire supportive area (inflamed). 4. Margin index of the copings according to Silness.13 5. Marginal fit of the copings when probed with Maillefer explorer No. 6: 0, good, no discrepancy detectable between coping and tooth; 1, deficit; 2, excess. 6. Bleeding index and plaque index according to Lenox and Kopzcyk. l4 7. Tooth mobility according to Bergman et al.12:0, no mobility; 1, movable up to 1 mm in horizontal plane; 2, movable more than 1.0 mm in horizontal plane; 3, movable in apical direction. 8. Attachment level was measured mesiobuccally, buccally, distobuccally, distolingually, lingually, and mesiolingually. The measurements were made to the nearest millimeter, with the cervical margin of the coping as a reference level. 9. Caries according to Ericson et a1.15:The occurrence of caries was recorded with the help of a dry observation field, mirror, probe, good lighting, and blasts of air. The bite wing radiographs facilitated the diagnosis of interproximal caries. All surfaces were registered. The grading for factors 4 through 6, 8, and 9 was performed by one of the examiners with ~2.5 magnifying loops. The remaining clinical factors analyzed were graded independently by two other examiners after careful calibration. When there was disagreement in the rating, the pair of examiners resolved their disagreements by joint examination. All three examiners were specialists in prosthetic dentistry and had long clinical experience. Intraoral radiographs were produced with the isometric technique. A questionnaire was sent to all of the patients provided with CCRD constructions (Table III) in which they were asked to express their opinions about the treatment results. 253

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Patients’ opinions about the treatment

III.

Y&3 Question

1. Are you satisfied with your restoration? 2. Are you satisfied with the esthetics? 3. Have you become used to the restorat,ion’l 4. Are you using your restoration day and

Questions 11 and

No A

B

A

B

46 48 49

9 10 10

5

45

10

6

48

8

8

2

43

8

3

2

48

8

6 8

3 3

44 36

7 6

19

5

26

5

12

A

B

24 25 1

-

1

3 1 1

night?

5. Do you remove the suprastructure when y+,u clean your teeth? 6. Do you have any speech problems because of it? 7. UC>you suffer any inconvenience while eat.ing? 8. Have you changed your diet? 9. 1s there some food that you can chew now but avoided before? 10. Is lhere some food that you can chew more easily now t,han you could before? 11. How can you chew now compared to previously? Better kinchanged Worse t2. How is your chewing ability? Excellent c: ood 13ad

I?‘. Occlusion and articulation

4 1

2 7

10

38 2

A, Answered yuestiannaires by patients examined (no =

Table

2

61);

-

B, answered questionnaires by patients not examined (no = 10).

among the 57

patients

Table V. Distribution of jaws with healthy and inflamed mucosa with regard to the state of occlusion

No. oPpatients Occlusion

Healthy mucosa

Inflamed mucosa

Total jaws

OCClUSiC~2i

Halanced

46

Unbalanced ‘l’otal

11

57

Articlllation Balanced Cuspid-protected Unbalanced other ‘I’otal

23 27 3 57

RESULTS

4

AND DISCUSSION

The selection of patients in this study was based on the objective to examine all patients treated with CCRD constructions at three clinics. The selection was made by the dentists at each clinic without any influence from the aut.hors, other than the request to recall all patients treated. To the best of our knowledge this request was fulfilled. It

254

Balanced Unbalanced Total

34 1 35

13 12 25

47 13 60

is difficult to draw definite conclusions about any potential influence of nonattendance on the results. However the answers of the nonattendees who replied to the questionnaire (59%) showed the same pattern as that of the attendees. Thus there is reason to believe that the results obtained in this study are representative of the patients treated with CCRD constructions at the three clinics. Fig. 2 illustrates the clinical picture of one patient at the time of examination. Eight abutments distributed among six patients were lost. They had been functioning for a range of 1 to 70 months (median 40.5 months). Seven of these abutments were initially endodontically treated. This corresponds to a loss of 5.8% among the root-filled abutments and 0.8”/,

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Retention of the 60 suprastructures among the 57 patients Upper

Degree of retention

Lower

jaw

NO.

%

No.

%

No.

%

48 26 26

30 15

50 25 25

0

-

1

19

51

11

2

9

3

9

24 24

6 6

0, no retention;

1, limited

Table

Number of abutments with copings in relation to retention of the suprastructure

VII.

retention;

2, marked retention;

Total

jaw

3, extremely

15

marked retention.

No. of abutments Degree of retention

1

1

-

2 3

-

2

3

4

5

6

6 2 2

12

6 5 6

4 4 2

-

1 1

among the vital abutments, and it indicates a greater risk when root-filled teeth are used as abutments in prosthetic constructions. A similar finding was reported by Randow et a1.16for fixed partial dentures. The lost abutments were replaced by pontics included in the existing construction. The intraoral radiographs revealed a perforation in one of the root-filled abutments and signs of apical periodontitis in three out of the 121 endodontically untreated teeth (2.5% ). Unbalanced occlusion was registered in almost 20% of the cases,and unbalanced or otherwise disturbed articulation was found in 53 % (Table IV). A clinically healthy mucosa was seen in 35 of the arches covered by a construction. In two cases,impression in the mucosa was related to pontics, but not in combination with any inflammation. The oral mucosa was inflamed in 25 of the arches and in seven of these cases in combination with granulating tissue. The distribution of healthy and inflamed mucosa with regard to the state of occlusion is shown in Table V. In the three patients provided with CCRDs in both the maxillary and the mandibular jaw, the occlusion was registered as balanced. In three of the arches among these patients, there was no inflammation, but in the remaining three mild inflammations were observed. Inflamed mucosa was proportionally more common in caseswith unbalanced occlusion (12 of 13 jaws) compared with cases with balanced occlusion (13 of 47 jaws). This result is in agreement with previous investigations of removable dentures and reinforces the necessity of establishing and maintaining balanced occlusion. In 50% of the cases, there was a marked or extremely marked retention (Table VI), and in three casesthe suprastructure could be removed only with the help of a percussion-type crown remover. No apparent correlation between the number of abutments with copings and the retention

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2

7 -

1

8

-

9

1

30 15

1

15

-

2 2

Total

was found, although the six constructions with eight and nine abutments had marked or extremely marked retention (Table VII). Regardless of examiner-determined degree of retention, all patients were satisfied. The marginal fit between the copings and the tooth substance was good at all locations. The margins of the copings were subgingivally located in 67 % totally, buccally in 46 % , mesially/distally in 80%) and lingually in 70%. The mean values for the bleeding index and plaque index were 36% and 28%) respectively. The frequency of bleeding was much higher when the margins of the copings were subgingivally located, which confirms numerous previous observations. The mean value of the attachment level was 2.5 mm (range 1 to 9 mm) and no difference in tendency was observed among the sites examined. In 191 (77%) abutment teeth, mobility was graded 0 or 1. Thirty-six of the abutment teeth had a mobility grade of 2; 21 abutments had a mobility grade of 3 distributed among 11 patients. In no case was there any indication for extraction. In 44 patients, no caries or new fillings were observed. In the remaining 13 patients there were 39 new decayed and/or filled (DF) surfaces. All 19 surfaces with new fillings were located at the margins of the copings. Eighteen of the margins were located supragingivally and one subgingivally. The 20 surfaces with carious lesions were located supragingivally at the margins of the copings. Consequently, 38 of the 39 new DF surfaces were located supragingivally. This corresponds to 11.6% DF surfaces of a total of 327 surfaces with supragingivally located margins and 0.16 % of surfaces with subgingival margins. This finding is in agreement with that of Ericson et al.‘O and reinforces the importance of full coverage as a preventive measure against caries. No correlation was found between the number of sur-

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faces with fillings and carious lesions and the functional time of the CCRD construction. Almost 60 % of the new DF surfaces were found in four patients. This indicates that caries is associated with individually dependent factors. In previous studies,*0s I7 no correlation could be found between the occurrence of caries and the number of so-called caries risk factors. Therefore in this study, no analyses of these factors were performed. It may be that some of the present so-called caries risk factors in combination with other, as yet untested, factors will make it easier to predict and explain the occurrence of caries on the individual level. The questionnaire was answered by 89 % of the patients examined and 59% of the patients not examined (Table III): There was no difference of opinions between the examined and the nonexamined patients. Sixteen percent of patients reported they had speech problems related to the treatment. Approximately 45% of the patients reported improvement in their chewing ability and more than 90 % of the patients found their chewing ability to be excellent or good, which resulted in a change of diet among 15% of the patients. Generally patients’ opinions about treatment were positive. CONCLUSIONS The inclusion criteria before the treatment of the CCRD patients examined certainly varied among and within the three clinics. In a few cases the results may have been as good with a conventional fixed partial denture. However, the clinical results and the patients’ opinions in both this with and our previous studylo indicate that treatment CCRD may be suitable for certain patients. Such patients are those with a history of advanced caries and few remaining teeth, sometimes unfavorably distributed in the arch and/or with heterogeneous prognoses. The work and support of participating dentists is gratefully acknowledged.

BERGMAN,

AND

ERICSON

2. KGrber K. Konuskronen-Teleskope. ed 2. Heidelberg, Germany: Dr Alfred Hiithig Verlag, 1971. 3. Kiirber K. Konuskronen, Das rationelle Teleskopsystem Einfiirhrung Klinik und Technik. Heidelberg, Germany: Dr Alfred Hiithig Verlag, 1983. 4. Heners M. Prothetische Behandlung des parodontal erkrankten Gebisses (II). Therapeutische Mittel. Zahntistl. Praxis 1973;24:203-5. 5. Glanz P-O, Attstrom R. Konusteknik. Dentala Proteslaboratoriet AB i MahnG, Sweden, och Tandtekniker Tjlnst AB, Boxholm, Sweden, 1984. 6. Graber G. Partielle Prothetik, in Rateitschak KH. Farbatlanten der Zahnmedisin ~013. Stuttgart, Germany: Georg Thieme Verlag, 1986, pp 12-4, 182-5. 7. Heners M, WaIther W. Klinische Bewlhrung der Konuskrone als erioprosthetischeskonstruktionselement-EineLangzeitstudie.DtschZahnarstl z 1988;43:525-9. 8. Walter W, Heners M. Die Prognose van Pfeilerziihnen mit reducierten Parodont bei herausnehmbaren Zahnersatz. Dtsch Zahnarztl Z 1989; 44:797-800. 9. Heners M, Walther W. Die Prognose van Pfeilersahnen mit r educierten Restzahnbestand. Dtach Zahniintl Z 1990;45:579-81. 10. Ericson A, Nilsson B, Bergman B. Clinical results in patients provided with conical crown retained dentures. Int J Prosthodont 1990;3:513-21. 11. IS0 International Standard 1562: Dental casting gold alloys. ed 2. International Organization of Standardization, 1984. 12. Bergman B, Hugosson A, Olsson C-O. Periodontal and prosthetic conditions in patients treated with removable partial dentures and artificial crowns. A longitudinal two-year study. Acta Odontol Stand 1971; 29621.38. 13. Silness J. Periodontal conditions in patients treated with dental bridges. J Periodont Res 1970;5:60-8. 14. Lenox JA, Kopzcyk RA. A clinical system for scoring a patient’s oral hygiene performance. J Am Dent Assoc 1973;86:849-52. 15. Ericson G, Nilsson H, Bergman B. Cross-sectional study of patients fitted with fixed partial dentures with special reference to the caries situation. Stand J Dent Res 1990;98:8-16. 16. Randow K, Giants P-O, Ziiger B. Technical failures and some related clinical complications in extensive fixed prosthodontics. An epidemiological study of long-term clinical quality. Acta Odontol Stand 1986; 44:241-5. 17. Bergman B, Ericson G. Cross-sectional study of patients treated with removable partial dentures with special reference to the caries situation. Stand J Dent Res 1986;94:436-42.

Reprintrequeststo: DR. MARGARETA MOLIN DEPARTMENT OF PROSTHETIC DENTISTRY UNIVERSITY OF UMEA S-901 87 UMEA SWEDEN

REFERENCES I, Korber K. Konuskronen-Teleskope. fred Hiithig Verlag, 1969.

ed 1. Heidelberg,

Germany:

Dr Al-

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