MALAYSIAN DENTAL JOURNAL. The Status Of The Abutment Teeth In Distal Extension Removable Partial Dentures

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1 MALAYSIAN DENTAL JOURNAL Malaysian Dental Journal (2009) 30(1) The Malaysian Dental Association The Status Of The Abutment Teeth In Distal Extension Removable Partial Dentures Mahmood WA, BDS, MDSc; 1 Salim SA 2, Saharudin S 2, 1 Associate Professor, Dept of Prosthetic Dentistry, Faculty of Dentistry, University of Malaya , Kuala Lumpur. Malaysia 2 Faculty of Dentistry, University of Malaya , Kuala Lumpur. Malaysia ABSTRACT The status of the abutment teeth were reviewed following insertion of a new set or replacement distal extension removable partial dentures. Periodontal condition, caries and loss of teeth with regard to different denture base materials and the duration of denture wearing were noted. All of the prostheses were constructed by undergraduate students in the Prosthetic Department, Dental Faculty, University of Malaya. Sixty-one patients with 201 abutment teeth were involved. Comparisons were made between two sets of examination and diagnosis forms which were the earlier charting of status of the abutment teeth after receiving the earlier set of removable partial denture. The second set was the updated abutment status before making the replacement set of dentures. No clinical examination was conducted. The results showed 40.8% of abutment teeth were still present, from which 22.9% were sound and 17.9% abutment had to be restored. There were 29.9% of the abutment teeth with periodontal complications; 16.9% abutments became carious and 12.4% were extracted. The deterioration of the abutment teeth was found to be associated with acrylic resin denture bases. The negative outcomes were between the third to ninth years of denture wearing. Good oral hygiene instructions, motivation and periodic reviews of removable partial denture patients should be reinforced and this will increase the life span of the abutment teeth. Sound knowledge of principles in denture design plays an important role in the success of removable partial dentures. Correct indications for removable partial denture base materials do affect the abutment teeth and surrounding mucosa. Denture designs with preventive consideration should be emphasized. Key Words Removable partial dentures (RPD), distal extension prostheses, abutment teeth, denture design. Introduction Various surveys and longitudinal studies on removable partial dentures (RPDs) and the effect on oral health especially the supporting structures and the remaining teeth 1-3 have been carried out. RPDs have been associated with gingivitis, periodontitis and tooth mobility. Apart from RPD design, the choice for denture base materials is also an important aspect in the success of prosthesis. Distal extension RPDs are considered to be one of the most difficult situations for successful clinical treatment outcome. Problems arise with differential loading between the supporting denture base and the abutment teeth. The abutment teeth act as fulcrum for the partial dentures and are subjected to torque forces. For these reasons, it is important to consider the status and prognosis of the selected abutment teeth. A properly executed treatment plan with appropriate design of the RPDs will contribute to the preservation of the remaining natural teeth, osseous structure and gingival tissues in the long term. The objectives of this retrospective study were to assess the status of the abutment teeth in relation to periodontal health (mobility, recession and pocket depth), caries, restorations and loss of teeth following insertion of distal extension removable partial denture prostheses. The status of the abutment teeth in relation 13

2 The Status Of The Abutment Teeth In Distal Extension Removable Partial Dentures to different denture base materials was also evaluated. The findings will also relate the abutment teeth status to duration of denture wearing. MATERIALS AND METHODS Sixty-one patients who had received prosthetic treatment in the Dental Faculty, University of Malaya were recruited for this study. These patients requested either for new dentures or replacement dentures. All the treatments were completed by undergraduate dental students under the clinical supervision by academic staff from the Department of Prosthetic Dentistry. Prior to the prosthetic treatments, all the required preprosthetic treatments such as periodontal and restorative treatment were carried out. All the patients were given oral hygiene instructions and motivations prior to commencement of treatment. The inclusion criteria were: (1) Distal extension removable partial dentures in resin acrylic and cobalt - chromium alloy (Kennedy Classification I and II without modification). (2) Patient has worn denture for at least two years or more. Comparisons between two sets of examination and diagnosis (E&D) forms were made. First set (the baseline) The earlier E&D forms would represent charting of the abutment teeth at insertion of the earlier set of RPD. Second set (current status) The present status of the abutment with the same set of denture, but require a replacement denture. This is before commencement of the new set of RPD. Any changes in the abutment status were noted. The aspects observed were the periodontal status of abutment teeth such as tooth mobility, gingival recession and pocket depth. Caries and loss of abutment teeth were noted. The periodontal charting (from the record) was done by the dental students earlier based on clinical examination. Tooth mobility was assessed as mobile or non-mobile clinically. Gingival recession and periodontal pocket depth were measured using a periodontal probe and all the readings were recorded. Measurements were made with the probes inserted into the pockets and held parallel to the long axis of the tooth. Four sites were examined; mesial, distal, buccal or labial and lingual or palatal. All tooth surfaces were examined for caries using a probe and the numbers of decayed teeth were recorded. Loss of abutment teeth was noted. All the data were collected and subsequently compared. RESULTS Subjects in this study The mean age of the subjects in this study is 62.5 years. The distribution of RPD in the maxilla and mandible according to type and design is shown in Table 1. Table 1 Distribution of RPD in the maxilla and mandible with different denture base material and design Maxilla Mandible (n = 34) (n = 50) Type of RPD Cobalt-chromium Acrylic resin Design of RPD Unilateral Distal extension Bilateral Distal extension Cobalt-Chromium = 42 Acrylic resin = 42 Total = 84 Mean age of subjects = 62.5 years Mean age of denture wearing = 4.8 years Abutment teeth There were 201 abutment teeth. In the mandible, the bicuspids are the common abutment teeth (Table 2). Some of the abutments may present with more than one condition for eg: an abutment may have caries with mobility grade 1. Table 2 Distribution of abutment teeth in the upper and lower jaw TEETH UPPER LOWER DENTURE DENTURE Central incisors 0 5 Lateral incisors 6 9 Canine First premolar Second premolars Molars 8 7 TOTAL n = 72 n = 129 Total number of abutment teeth, N = 201 The status of the abutment teeth at insertion of the earlier RPD (baseline) is shown in Table 3. The status of abutment teeth was updated before commencement of a new set or replacement denture shown in Table 4. 14

3 Mahmood / Salim / Saharudin Table 3 Abutment status with the earlier set of RPD (baseline) CONDITION No % Mobility 12 (6) Recession 28 (13.9) Pocketing 9 (4.5) Restored 30 (14.9) Extracted 0 Sound 122 (60.7) Table 4 Present status of the abutment with the new set/ replacement RPD CONDITION No % Sound 46 (22.9) Restored 36 (17.9) Periodontal problems 60 (29.9) Caries 34 (16.9) Extracted 25 (12.4) Periodontal status of the abutment teeth Periodontal problems were subdivided into mobility, recession and pocket depth. Mobility, recession and pocketing status of abutment teeth according to grades and depths were shown in Table 5. The earlier charting from the previous set of denture is the baseline. The present data is the updated charting when patient had a new set or replacement RPD. Table 5 Periodontal status of the abutment teeth (A) Recession (mm) Baseline At Present > TOTAL (B) Mobility(Grade) Baseline At Present I 8 9 II 3 5 III 1 0 TOTAL (C) Pocket Depth (mm) Baseline At Present Caries incidence on abutment teeth Table 6 showed the incidence of new caries and secondary caries. Table 6 Present status of the caries incidence Caries n = 34 (16.9%) New 14 Secondary 20 Extracted abutment teeth Most of the abutment teeth were extracted due to more than one condition i.e. they were carious with periodontal complication (40%). There were more abutment teeth extracted due to periodontal condition (36%) in comparison to extracted carious abutments (24%) (Table 7). Table 7 Reason for extraction of abutment teeth Extracted n = 25 (12.4%) Periodontal problems 9 Caries 6 Periodontal and caries 10 Table 8 Mean duration of denture wearing (DW) and mean age of subjects for mobility, pocket depth, recession and caries status in the abutments Mean duration of DW RECESSION (mm) > MOBILITY (grade) I II POCKET DEPTH (mm) CARIES New Secondary Mean age of subjects TOTAL

4 The Status Of The Abutment Teeth In Distal Extension Removable Partial Dentures Figure 1: Comparisons made of the status of the abutment at baseline and at present with the new set / replacement RPD Figure 2: Abutment status in relation to duration of denture wearing Figure 3: Abutment status with different denture base material DISCUSSION This study looked into records of 61 patients. A total of 201 abutments were involved. The mean age of the patients were 63 years with the age range from 34 to 93 years old. The majority of the patients were in the 50 s to 60 s years of age. All the patients have used the denture for at least 2 years. The maximum duration of denture wearing in the present study was 18 years. In this study, the number of RPD in Kennedy Class I and II constructed in acrylic and cobaltchromium were of equal distribution. Although the costs of fabricating metal denture were higher, in order to encourage more patients to participate, the cost of the metal framework was subsidized. This explained the equal distribution between the two types of dentures. Bilateral distal extension situation There were 59 bilateral distal extension (DE) in this present study with more than half (36) presented in the lower arch. The higher figure of distal extension in RPD has been reported earlier 7,8. A major concern with the DE situation in RPD is the control of excessive torque forces that may act on the abutment teeth. However, some clinical studies suggested that there is a tendency for reduction of torque exerted on abutment teeth as the denture wearing period increased. This settling period lasts about 1 to 1.5 months from the time of insertion 9,10. In the upper bilateral DE, the RPD is generally solely mucosal support. This was found to be less damaging because it is possible to gain support for the denture from the hard palate. Unilateral distal extension situation There were 25 unilateral DE, with 11 in the upper arch and 14 in the lower arch respectively. A unilateral distal extension RPD is an extreme situation where the axis of rotation is at an angle to the long axis of the residual ridge instead of parallel to it. Management of the potential biomechanical stresses is especially important in the distal extension base design. The status of the present remaining abutments from the data compiled was compared and analyzed. Comparisons were made to the earlier charting when the RPD was first provided. Mandibular bicuspids were the most common abutments involved for distal extension RPD. While in the upper arch, canines and the first premolar were the common abutments respectively. With increased duration of denture wearing, less sound teeth remained. To date, 40.8% of the abutments were still present. There were 22.9% sound abutments and 17.9% abutments restored. 29.9% with periodontal disease, 16.9% were carious and 12.4% had to be extracted. The causes of extraction were caries and periodontal disease. 40% of Abutment teeth were extracted due to a combination of caries and periodontal disease. Periodontal problems were found to be the common factors affecting the abutments (29.9%). 16

5 Mahmood / Salim / Saharudin Periodontal conditions were analysed based on the condition for recession, mobility and pocketing of the abutments. Recession Loss of attachment is presented clinically as gingival recession. Among the three periodontal conditions, gingival recession was found in 50% of the abutments. This was also observed in other studies However, most recession (73.3%) occurred 5mm. There are several factors leading to recession. Abutments that were not in contact with the opposing teeth or opposing unrestored edentulous space, could present clinically in the form of post eruption. The exposed root appeared as recession of the gingival margin. This study also showed that all recession occurred in the lower denture abutment in patients above 50 years of age. These may be degenerative changes due to age factor and loss of support because of periodontal condition 13. It was also observed that recession was not related to the duration of wearing. In fact generally the recession were found through out the duration of wearing between 2 to 10 years. The other possibility for recession in the present study would be from the position and placement of some denture components i.e the retainers. Lower denture design lacking of support was generally known as gum strippers and this would cause gum recession to the abutment and all the teeth in contact with denture. Periodontal pockets Previous cross sectional studies reported increased pocket depths around the remaining teeth including the abutments Although this study indicated some increment in pocket depth, there were only a small amount of abutment teeth (16) being affected. Most (87.5%) of the pocket were between 3 to 5mm in depth with the mean duration of denture wearing of 3.6 years. Previous workers 16,118 suggested that periodontal sites with a probing depth of less than 4mm were not regarded as having a pathological pocket. Pocket depth increased with duration of wearing denture. An increment between 6 to 8mm were observed in only 12.5% with the denture worn at average of 6 years Mobility Tooth mobility is an indication for increased stress to the periodontal tissues. Mobility of the abutment teeth in this study was minimal at 6.97% of the abutments having mobility between grades I to II. This study recorded that mobility of the abutment teeth increased with the duration of denture wearing. The mobility increased in the first 2 years of denture use. Although it was suggested by earlier workers 19,20, such an increased in tooth mobility may be a physiological adaptation to increased functional demands and this symptom is not necessarily indicative of a pathological state. The wearing of a new RPD is followed by a settling period that lasts about 1 to 1.5 months and leads to a reduction of the initial torque exerted on the abutment teeth. However, it was felt that the cause of mobility in this study is periodontal breakdown. An increase rate of periodontal breakdown has been observed in the elderly population 20, in this study, however there was no relation between patient s age and mobility of the abutment. Most mobility was observed in acrylic resin denture wearers. Some researches have shown that traumatic occlusion may cause an increase in tooth mobility1, In the present study, there was one single case of abutment mobility in a unilateral lower bilateral distal extension case opposing natural teeth involving a young patient aged 34. The abutment was found to be subjected to traumatic occlusion. Caries Caries activity has been reported to be high in patients with RPD 2. Prior to the provision of RPD, there were 60.7% sound abutment teeth with components such as rests and retainers. All the carious abutments were restored. Within 2 years after using RPD, the incidences of secondary caries were more compared to new caries. 16.9% abutments developed caries and of this figure, 17.9% were secondary caries from restored abutments. Caries was observed to be active in the third year of denture wearing. However, the incidence of caries declined after 10 years of denture wearing. As the patient became older, with longer duration of denture wearing, caries activities also decreased. Good oral hygiene can reduce the progression of caries in denture wearer over a period of time 21,22. Patients need to be motivated and routine recall from time to time at least to curb the progress of caries to a minimum. Denture base material Denture design will vary with the choice of denture base material. Very few longitudinal studies focused on metal dentures. This study indicated that more than half of the sound abutment teeth were still present in cobalt-chromium RPDs. Less mobility and pocket depth were observed. According to longitudinal studies 1,3,24, the halflife of conventional RPD with cast cobalt-chromium framework is about 10 years. In this study, cobaltchromium RPD provided to patient s were found to be still in service after 2 years and some still in service even up to 10 years. Unlike metal dentures, the designs for acrylic dentures are more conservative. Tissue coverage and maximum extension are required in acrylic resin dentures. This study showed there was more incidence of tooth mobility, less sound abutment present and 79% abutment teeth were extracted with acrylic dentures. Although it was found that acrylic dentures were related 17

6 The Status Of The Abutment Teeth In Distal Extension Removable Partial Dentures to more mobility, pocket depth, less sound teeth and more extracted abutments, there were no clear relations if the design contributed to the cause. Although the choice in the denture base material is largely based on the clinical indication especially the condition of the abutments, however patients preference and cost factor may affect the decision. Cobalt-chromium RPDs can be made smaller and simpler because of its rigid property. This allows the concepts of minimal tooth and gingival coverage put to use in an attempt to minimise plaque accumulations under clasps and other components and hence reduce the risk to develop caries. The sample size in this study was determined by the availability of DE situation and reliability of the record. It is a non-clinical study based on the records in the patient s file. Since this is a non-clinical survey, parameters in oral hygiene assessment such as plaque score, quality and quantity of plaque were unavailable. However, this preliminary work yield some useful information despite the fact that patients were not on regular recall. Although periodontal disease were very closely related to RPD wearing, in this study the loss of attachment such as pocketing and mobility were relatively low. Despite progress with the use of implants to restore posterior regions in DE situation, RPDs are still viable treatment option for some patients. It is a conservative and simplified approach in replacing many missing teeth at a lower cost. CONCLUSION The findings from this study showed that status of the abutment teeth in distal extension situation were affected by removable partial denture (RPD) wearing. There were 40.8% abutments which were still present with 22.9% sound abutments and 17.9% restored abutments. Almost 30% of the abutments progressed to periodontal disease, 16.9% developed caries and 12.4% had to be extracted. However, the findings also showed that loss of attachment such as pocketing and mobility were relatively low amongst the abutment teeth. More tooth mobility, less sound abutment and 80% of the total extracted abutment teeth were related to patients wearing acrylic resin dentures. Caries incidence was found to be the same in acrylic and cobalt-chromium dentures. Caries activity and extraction of the abutments were observed more in the third to ninth years of denture wearing. REFERENCES 1. 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;42: Carlsson GE, Hedegard B, Koivumaa KK: Studies in partial denture prosthesis Iv. Final results of a 4-year longitudinal investigation of dentogingivally supported partial dentures. 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7 Mahmood / Salim / Saharudin 21. Bergman B, Hugoson A, Olsson CO: Periodontal and prosthetic conditions in patients treated with removable partial dentures and artificial crowns. A longitudinal two-year study. Acta Odontol Scand 1971; 29: Bergman B, Hugoson A, Olsson CO.: A 25 year longitudinal study of patients treated with removable partial dentures. J Oral Rehabil 1995; 22: Germundsson B, Hellman M, Odman P: Effect of rehabilitation with conventional removable partial denture oral health- a cross-sectional study. Swedish Dental Journal 1984: 171. Address for correspondence: Associate Professor Dr. Wan Adida Azina Bt Mahmood Dept of Prosthetic Dentistry, Faculty of Dentistry, University of Malaya, 50603, Kuala Lumpur, Malaysia wanadida@um.edu.my 19