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Assessment of Microbial Growth and Salivary pH in Patients Wearing Fixed Partial Denture.

The normal microbial flora of oral cavity is complex and consists of large number of species of bacteria including mycoplasma, fungi and protozoa. This is because of fact that mouth has many distinct habitats including saliva and crevicular fluids, surface of soft tissues such as lips, palate, cheek, tongue, gums and hard surfaces of teeth (1) The moist condition is mainly due to the presence of saliva .Any increase or decrease in this salivary flow rate will result in the alternation of the microbes present in the oral cavity. Fixed prosthesis is a restoration of one or more missing teeth that cannot be readily removed by the patient. It is permanently attached to natural teeth or roots that furnish the primary support to the appliance. It provide a protected habitat, especially beneath the fitting surface, which results in colonization and growth by a range of bacteria . This paves for many other complications of oral cavity (2). Lesions of the oral mucosa associated with the wearing of dentures may represent acute or chronic reactions to microbial denture plaque, a reaction to constituents of the denture base material, or a mechanical denture injury. They include denture stomatitis, angular cheilitis, traumatic ulcers; denture irritation hyperplasia, flabby ridges, and oral carcinomas (3). It has been observed that the majority of denture wearers do not pay necessary attention to the cleanliness. This may be due to decreasing manual abilities due to an advanced age, the nature of design, lack of awareness, improper storage, and failure to maintain asepsis of dental prosthesis that leads to the growth of microbial agents and formation of biofilms, which are reservoirs of infection (4) Previous studies suggested that proper replacement of dentures will increase the salivary flow rate along with improved occlusal force at the same time it enhances the accumulation of dental plaque and bacteria on the surface of the denture (5-6) The bacteria which depend on hard surfaces for attachment and growth will in part recolonize the mouth if a denture is worn .Investigations and researches revealed that a number of pathogenic microorganisms which were present in the mouth when the patient was dentate, they were harboured in the oral cavity even when they are in the edentulous state (7). The study was conducted to assess the salivary ph and microbial growth in patients wearing fixed partial denture before and after cementation.


The study was carried out in Saveetha Dental College and hospitals, Saveetha University. The study consisted of 20 partially edentulous patients desiring replacement with fixed partial denture were enrolled in the study after obtaining informed consent. The sample collected was saliva. The swab was used to collect the microbial sample in the cervical margin of gingiva before FPD cementation and were cultured for different bacteria and salivary PH was estimated using PH indicator strip. Patients were given FPD and oral hygiene instruction. The microbial samples were obtained after 2 weeks of denture wearing and same salivary PH and microbial parameters were estimated and compared. The swabs were suspended in saline solution. The sample obtained from the patients were cultured in three different culture media namely lactobacillus, Mitis salivarius agar base and MHA medium. Lactobacillus medium: 67.15 g of lactobacillus powder was suspended in 1000 ml of distilled water. The media is then heated to dissolve the powder completely in water. The media is then autoclaved at 15 lbs pressure for 15 minutes. Once the process of autoclave is done, the suspension is mixed well and poured into sterile petri plates. Mitis salivarius agar base: 3 scoops of agar is heated for 15 minutes . The heated agar is then transferred to the plates after cooling it. The plates are then kept in autoclave for 4 hours. It is then kept in hot air oven for 20 minutes. Muller-Hinton agar: Suspend 38 gm of the medium in one litre of distilled water. Heat with frequent agitation and boil for one minute to completely dissolve the medium. Autoclaving is then done at 121[degrees]C for 15 minutes. Cool to room temperature. Pour cooled Mueller Hinton Agar into sterile petri dishes on a level, horizontal surface to give uniform depth. Allow to cool to room temperature and store the plates (Fig. 1).


The microbial growth was expressed in colony forming units. A paired sample t test was used to estimate statistically significant difference at 5% significance level ([+ or -] =0.05). Results inferred there is statistically significant difference between klebsiella species (p=0.02,<0.05) before and after cementation were 1.50 x [10.sup.6]cfu and 1.70 x [10.sup.6]cfu, spirochete (p=0.015,<0.05) were 1.50 x 106cfu and 1.64 x [10.sup.6]cfu, lactobacillus (p=0.04,<0.05) were 1.47 x [10.sup.6]cfu and 1.73 x [10.sup.6]cfu, streptococcus (p= 0.013,<0.05) were 1.36 x [10.sup.6]cfu and 1.52 x [10.sup.6]cfu. There is a marked significant difference in salivary ph in oral cavity. They were represented in Table 1 and Fig.2.


It has become very essential to know the oral micro flora so as to prevent and treat other systemic diseases caused by it. Previous studies suggested that with loss of teeth, bacteria associated with hard subjects, strict anaerobes generally found in periodontal pockets and very fastidious organisms tend to disappear from the oral cavity. Bacteria that depend on hard surfaces for attachment and growth will in part recognize the mouth if the denture is worn (8,9,10). The normal range of salivary PH is 5.6-7 with an average of 6.7. Saliva buffers maintain the PH and offer protection in the mouth by preventing colonisation of potentially pathological microorganism, by denying them optimisation of environmental conditions. Saliva buffers also neutralise the acids produced by acidigenic microorganism and prevent enamel demineralisation (11,12)Strep. mutans is a predominant microorganism isolated from mucosa and saliva of denture wearing subjects, it is common inhabitant to all oral sites(2). Staphylococcus is found to be present in elderly individuals. Lactobacillus in edentulous mouth is very low. Lactobacillus is found to contribute to 1% of the total microbial flora and Neisseria to be a commensal in the oral cavity (13,14)- In earlier studies, Klebsella and E.coli were described as transient commensal of the oral cavity (15,16)- In the present study a statistical significant difference were observed for streptococcus, lactobacillus, klebsiella and spirochete before and after denture fpd cementation. The rise in streptococcus after fpd cementation proved that it is found in close association with the tooth structure as discussed above. There is also marked significance difference in salivary ph in oral cavity showing that there is difference in salivary ph before and after fpd cementation.


This study observed increased microbial colonisation following denture cementation. This could be attributed to compromised oral hygiene practices and surface characteristics of denture material used. Hence, meticulous oral hygiene measure and denture hygiene measures needs to be practised to minimise microbial colonisation and thus could promote improved oral health.


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S. Swetha [1] and Ashish R. Jain [2]

[1] Department of Prosthodontics, Saveetha Dental College and Hospital Saveetha University,Chennai, India.

[2] Reasearch Scholar, Reader, Department of Prosthodontics, Saveetha Dental College and Hospitals, Saveetha University, Chennai, India.

(Received: 20 September 2017; accepted: 09 November 2017)

* To whom all correspondence should be addressed.

Tel.: +91-9884233423; E-mail:

Caption: Fig. 1. Bacterial Culture
Table 1. Paired Sample T Test

                                Mean     N

Pair 1     Klebsiella before        1.5    20
           Klebsiella after         1.7    20
Pair 2       Ecoli before          1.68    20
              Ecoli after          1.52    20
Pair 3     Spirochete before       1.52    20
           Spirochete after        1.63    20
Pair 4      Candida before         1.42    20
             Candida after         1.42    20
Pair 5   Staphylococcus before     1.52    20
         Staphylococcus after      1.57    20
Pair 6   Lactobacillus before      1.47    20
          Lactobacillus after      1.73    20
Pair 7   Streptococcus before      1.36    20
          Streptococcus after      1.52    20
Pair 8         Ph before           7.21    20
               Ph after            7.31    20

                                Std. deviation    Std. error mean

Pair 1     Klebsiella before             0.512       0.114
           Klebsiella after               0.47       0.105
Pair 2       Ecoli before                0.512       0.117
              Ecoli after                0.477       0.109
Pair 3     Spirochete before             0.499       0.113
           Spirochete after              0.512       0.117
Pair 4      Candida before               0.507       0.116
             Candida after               0.507       0.116
Pair 5   Staphylococcus before           0.507       0.116
         Staphylococcus after            0.512       0.117
Pair 6   Lactobacillus before            0.452       0.103
          Lactobacillus after            0.512       0.117
Pair 7   Streptococcus before            0.495       0.113
          Streptococcus after            0.512       0.117
Pair 8         Ph before                  0.63       0.144
               Ph after                  0.749       0.171

                                    95% confidence
                                   interval of the

                                  Lower      Upper

Pair 1     Klebsiella before
           Klebsiella after      -0.088      0.488
Pair 2       Ecoli before
              Ecoli after        -0.448      0.132
Pair 3     Spirochete before
           Spirochete after      -0.211      0.422
Pair 4      Candida before
             Candida after       -0.359      0.359
Pair 5   Staphylococcus before
         Staphylococcus after    -0.287      0.392
Pair 6   Lactobacillus before
          Lactobacillus after    -0.007      0.534
Pair 7   Streptococcus before
          Streptococcus after    -0.244      0.559
Pair 8         Ph before
               Ph after           -0.4        0.61

                                  t      df     Sig. 2 (tailed)

Pair 1     Klebsiella before
           Klebsiella after     1.453     19        0.02
Pair 2       Ecoli before
              Ecoli after       -1.143    18        0.268
Pair 3     Spirochete before
           Spirochete after     0.697     18        0.015
Pair 4      Candida before
             Candida after        0       18          1
Pair 5   Staphylococcus before
         Staphylococcus after   0.325     18        0.749
Pair 6   Lactobacillus before
          Lactobacillus after   2.041     18        0.04
Pair 7   Streptococcus before
          Streptococcus after   0.825     18        0.013
Pair 8         Ph before
               Ph after         0.428     18        0.667

Fig. 2. Mean Of Salivary Ph And Microbes Before And After Fpd


                  Before   After

Klebsiella        1.5      1.73
Ecoli             1.6      1.5
Spirochete        1.52     1.63
Candida           1.42     1.42
Staphylococcus    1.52     1.57
Lactobacillus     1.47     1.73
Streptococcus     1.36     1.52
Ph                1.21     1.31

Note: Table made of bar graph.
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Article Details
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Author:Swetha, S.; Jain, Ashish R.
Publication:Journal of Pure and Applied Microbiology
Article Type:Report
Date:Dec 1, 2017
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