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Favoring Trauma as an Etiological Factor in Denture Stomatitis
1 Department of Restoration and Correspondence: * corresponding author, jocelyne. feine{at}mcgill.ca
The etiology of denture stomatitis remains controversial. Trauma due to unstable dentures has been suggested as an etiological factor. Therefore, we tested the hypothesis that the prevalence of denture stomatitis is reduced when mandibular dentures are stabilized by implants. Data were collected at a one-year follow-up from 173 edentulous elders who had randomly received mandibular implant overdentures or conventional dentures. The diagnosis of denture stomatitis was determined according to the Newton classification. Elders wearing conventional dentures were almost 5 times more likely to have denture stomatitis than those wearing mandibular two-implant overdentures (P < 0.0001, Fisher’s exact test). Adjusted odds ratios showed that only the type of the prosthesis (AOR = 4.54, 95% CI 2.20 to 9.40) and nocturnal wear (AOR = 3.03, 95% CI 1.24 to 7.40) predict the frequency of denture stomatitis. Thus, implant overdentures may reduce oral mucosal trauma and control denture stomatitis.
Key Words: implant overdentures • dental prostheses • denture stomatitis • randomized cross-sectional study • oral health
There is growing interest in identification of the pathological determinants of conditions affecting the oral health of elders, since the size of this population is increasing worldwide (Jainkittivong et al., 2002). Denture stomatitis is a prevalent and longstanding problem in elders wearing removable dentures (Cunha-Cruz, 2006). Poor oral hygiene, nocturnal wear of the prosthesis, trauma, smoking, systemic conditions, allergic reactions to denture base materials, and bacterial and fungal infections, particularly Candida albicans, have all been proposed as causal or associated factors in denture stomatitis (Budtz-Jorgensen and Bertram, 1970; Shulman et al., 2005; Zissis et al., 2006). Given that no studies showing a cause-and-effect relationship have yet been carried out, there is presently no consensus on the etiologic factors of denture stomatitis (Barbeau et al., 2003; Emami et al., 2007). Mechanical forces are recognized for their important role in tissue changes (Mori et al., 1997). It is believed that denture trauma due to unstable dentures is one of the etiological factors of denture stomatitis. Denture stomatitis is an inflammatory reaction, and the inflammatory process varies, depending on the type of tissue involved, as well as on the intensity and concentration of the transmitted forces. It has been demonstrated (Nakashima et al., 1994) that covering the palatal mucosa with a denture base, without mechanical pressure, reduces physiological stimulation, with no histopathological changes. The histopathological changes in denture-supporting tissue seem to be dependent on the strength and distribution of occlusal pressure (Mori et al., 1997). Immunohistochemical analysis of the mucosal tissue involved in denture stomatitis has demonstrated a possible role of trauma in the variation of expression of the basement membrane antigens (Le Bars et al., 2001). Furthermore, it has been shown that dentures attached to implants lead to more uniform distribution of loads to the mucosa (Preti et al., 1996). Therefore, more stable dentures, such as those with implant retention, may offer more consistent biting force vectors, thereby reducing trauma to the denture-bearing mucosa. This study is the first that aims to determine the frequency of denture stomatitis in elderly edentulous populations wearing maxillary full dentures and mandibular two-implant overdentures or conventional dentures. The frequency of denture stomatitis and the influence of classic risk factors were also investigated. Our hypothesis was that the frequency of denture stomatitis is less in elders wearing mandibular implant-retained overdentures than in those wearing conventional dentures.
Trial Characteristics One hundred seventy-five edentulous individuals who had previously participated in a randomized clinical trial agreed to participate in this study. The McGill University Institutional Review Board approved the protocol, and informed written consent was obtained from each person. By means of a computer-generated permuted block scheme, the participants were randomly assigned to receive either mandibular overdentures retained by ball attachments on 2 implants (ITI, Straumann, Waldenburg, Switzerland) (IOD) or conventional dentures (CD), both opposed by new conventional maxillary dentures, according to a balanced occlusal scheme. Details of the randomized controlled trial have been previously described (Esfandiari et al., 2006; Perri et al., 2006). Participants who had worn their new prostheses on a regular basis in the previous 12 months were eligible for inclusion in this study. Those who had not worn their prostheses, or if the attachment system had been changed, were excluded (n = 2), leaving a total sample of n = 173 (80 men and 93 women; mean age, 72.13 ± 4.39 yrs; IOD n = 97 and CD n = 76; Fig. 1  , Appendix Table).
The outcome of this study was "denture stomatitis frequency" on the palatal mucosa. Based upon previous estimates of the prevalence of denture stomatitis in individuals wearing conventional dentures (approximately 40%) (Cumming et al., 1990), we calculated the sample size (n = 164) necessary to detect a 20% difference in prevalence between groups (Conventional, 40%; Implant, 20%), with a power of 0.80 and an alpha of 0.05 (two-tailed), using Systat II and a test of equality of two proportions for an unequal group size ratio of 1.28. Such a difference is clinically relevant. Before treatment intervention, all participants were evaluated for the presence of any mucosal disease and were treated if necessary. Two independent, calibrated examiners performed oral examinations and diagnoses of denture stomatitis, according to the Newton classification (Newton, 1962): Newton Type I, localized simple inflammation, usually found around the small palatal salivary glands; Newton Type II, a generalized inflammation of the denture-bearing area; and Newton Type III, a hyperplasic palatal surface. The diagnosis of denture stomatitis was assessed on the bearing mucosa of maxillary prostheses, because denture stomatitis is rarely seen beneath mandibular dentures (Wilson, 1998). Furthermore, since the dynamic contact of the denture teeth transmits forces to denture-bearing tissues, the stability or instability of the mandibular denture can have an impact on the opposing denture-bearing mucosa. A research assistant, blinded to treatment assignment, entered data into a computer database.
The association between denture stomatitis frequency and sociodemographic and classic risk factors was investigated. The demographic variables (age, sex, education), hygienic habits (nocturnal wear, denture-cleaning frequency, palatal brushing, mouthwash use, denture cleanliness), and smoking habits were gathered from questionnaires and clinical examinations, then categorized and summarized as dichotomous variables (Table 1
To determine whether denture stability was associated with occurrence of denture stomatitis, we measured perceived denture stability, which could be a proxy measure for trauma during chewing. Satisfaction with perceived stability of the prosthesis was rated by participants using the item "How satisfied are you with the stability of your mandibular prosthesis?" on 100-millimeter visual analogue scales (VAS), with anchor words of "not at all satisfied" and "completely satisfied" (Awad et al., 2003). Mycological investigations to determine the frequency of Candida-associated denture stomatitis were performed on a convenience sample of 48 participants. Cost issues restricted the testing of all 173 individuals. Collection of denture plaque was made by a sonication technique (Webb et al., 2005; Al-Fattani and Douglas, 2006). The recovered plaque was inoculated on Sabouraud-Dextrose 4% Agar (SD, Difco, Detroit, MI, USA) and Trypticase Yeast Extract Agar. All cultures were incubated in a humidified incubator at 37°C, 2.5% CO2 for 48 hrs. Candida species were identified by the germ test tube identification system induction essay, API 20 CAUX (bioMérieux, l’Etoile, France) and growth on selective culture medium (CHROMagar Candida, Paris, France).
Statistical Analyses We used Pearson Chi-square and Fisher’s exact test (two-tailed) to analyze the association between frequency of denture stomatitis and dichotomized perceived stability (low satisfaction vs. high satisfaction). Differences were considered statistically significant at P < 0.05. All analyses were carried out with SPSS version 15 (SPSS Inc., Chicago, IL, USA).
The frequency of denture stomatitis was 63.6% in the entire population. About one-third of those in the sample had no denture stomatitis (Healthy, n = 63), and the other two-thirds fell equally into Newton Type I (n = 55) and Newton Type II (n = 51) groups. Only four persons were diagnosed as Newton Type III. Gender, age, and level of education, as well as frequency of denture cleaning, palatal brushing, the use of mouthwash, maxillary denture cleanliness, and smoking, were not significantly associated with denture stomatitis (Chi-square, Fisher’s Exact Test P > 0.05; Table 1  ). Inter-observer agreement on diagnosis of denture stomatitis was high (kappa 0.87). In a sample of 48 participants, a microbiological analysis revealed that 22 were Candida yeast carriers. Three species of Candida were identified: C. krusei, C. tropicalis, and C. albicans. No statistical difference was found between healthy persons and those with stomatitis in Candida yeast carriage (P = 0.60, Pearson Chi-square).
The risk of denture stomatitis was 4.5 times greater in individuals wearing conventional dentures than in those who wore mandibular two-implant overdentures (P < 0.0001, OR = 4.52, CI 2.24 to 9.14; Fig. 2
There were no differences between the two groups in denture cleanliness (P = 0.11) or frequency of denture cleaning (P = 0.07).
The logistic regression model showed that only 2 independent variables, type of prosthesis and nocturnal wear of the prosthesis, were associated with the frequency of denture stomatitis (Table 2
We carried out this study to determine the effect of implant overdenture treatment on the occurrence of denture stomatitis in elderly edentulous individuals. We found that the type of and continuous wearing of the prosthesis predict the presence of denture stomatitis. This supports our hypothesis that the etiology of denture stomatitis is trauma. Denture stomatitis is the most important outcome variable in the clinical measurement of oral health in complete-denture wearers (Frenkel et al., 2001), and the literature contains an impressive amount of information on the cause and treatments (Budtz-Jorgensen et al., 2000; Dorko et al., 2001; Cross et al., 2004; Golecka et al., 2006). However, a cause-and-effect relationship has never been shown, since most of the previous studies were observational. Many previous studies have shown a high prevalence of denture stomatitis among complete-denture wearers (Budtz-Jorgensen et al., 1996; Barbeau et al., 2003), findings that were supported in this study. Also in agreement with results from our previous studies (Barbeau et al., 2003; Emami et al., 2007), we found no significant relationship between denture stomatitis and classic risk factors such as sex, age, hygienic habits, denture cleanliness, and the presence of Candida sp. Our finding that continuous and nocturnal wear of prostheses increases the frequency of denture stomatitis is also consistent with the literature (Wilson, 1998). This finding is generally explained by the fact that nocturnal wear of the prosthesis can reduce the protective effect of saliva, cleaning action of the tongue, and good oxygenation of the mucosa, which are key factors in the resistance of mucosal tissue to mechanical and microbiological aggression (Shulman et al., 2005; Emami et al., 2007). The impact of mandibular implant overdentures on the frequency of denture stomatits supports the concept that denture stomatitis may be more strongly related to denture trauma than to other risk factors, such as microbiological factors. It has been shown that the extent of inflammation determines the presence of yeast infections (Barbeau et al., 2003). Therefore, inflammation could be a precursor to bacterial and fungal colonization. Previous studies were unable to detect a relationship between the isolation of yeast and the clinical appearance of denture-bearing mucosa (Wright et al., 1985). Furthermore, many investigations have demonstrated that inflammatory changes in the mucosal tissue were not produced when the palatal mucosa was covered with a denture that had no masticatory contact (Hara et al., 1996; Mori et al., 1997). It has been suggested that incorrect vertical dimension of occlusion is a contributing factor in the occurrence of denture stomatitis (Nyquist, 1952; Budtz-Jorgensen and Bertram, 1970; Zissis et al., 2006). Since the accuracy of the vertical dimension of the participants was confirmed during follow-up prosthodontic examination, we hypothesized that vertical dimension is not itself a causative factor. However, its deficiency could lead to uneven distribution of loads and traumatogenic contacts. The results of this research suggest that continuous traumatogenic occlusal contact could increase the frequency of denture stomatitis. Our explanation of these results would be that an inflammatory reaction is the result of denture trauma. Consequently, inflammation due to trauma may create an environment favorable to micro-organisms found in denture stomatitis. The technique of combining the different types of Newton classifications together into one group has been used previously in several studies on this topic (Barbeau et al., 2003; Shulman et al., 2005; Zissis et al., 2006; Emami et al., 2007). The grouping technique does not appear to invalidate study results. In this study, there were more cases of denture stomatitis in the conventional denture group than in the implant overdenture group, for each individual Newton type. Our finding concerning the association between denture stomatitis and perceived stability of the prosthesis shows that the proxy measure—the individual’s satisfaction with the stability of the prosthesis—was not sufficiently sensitive to measure the amount of stability required to reduce trauma during chewing. Although all of the participants were given the same clinical instructions on methods of cleaning their dentures and their mouths, those who received the implant overdentures appeared to have a tendency to pay more attention to their oral hygiene. This information should be considered by oral health planners as an important response to new technology in oral health promotion for the elderly. Further experimental studies are needed to gauge the generalizability of these findings and the potential sources of bias caused by cross-sectional analysis. It should also be noted that this population consists only of elders. Thus, the results may not be extrapolated to other age groups. In summary, this study suggests that, in edentulous elders, better maxillary oral mucosal health may result when mandibular dentures are supported by a minimum of 2 implants. Implant overdentures could be effective in controlling denture stomatitis by preventing trauma to the oral mucosa.
The authors gratefully acknowledge the generous contributions of Dr. Kimoto, Jean-François Ross, Stephanie Wollin, and Nicolas Drolet to this study. This research was funded by a CIHR Industry Grant with Straumann Canada Limited. Dr. Emami is supported by a stipend from the CIHR Strategic Training Program in Applied Oral Health Research. A preliminary report was presented at the IADR 85th General Session & Exhibition, New Orleans, LA, USA, 2007.
A supplemental appendix to this article is published electronically only at http://jdr.iadrjournals.org/cgi/content/full/87/5/440/DC1. JDR Associate Editor Feine was not involved in the review of this manuscript. Received for publication October 22, 2007. Revision received January 22, 2008. Accepted for publication March 3, 2008.
Journal of Dental Research, Vol. 87, No. 5,
440-444 (2008)
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ABSTRACT
INTRODUCTION
E, Tkáciková L (2001). Candida-associated denture stomatitis. Folia Microbiol (Praha) 46:443–446.
ska-Nastalska E, Adamczyk-Sosi