doi: 10.1111/j.1741-2358.2011.00610.x. The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers. Aim: To ...
Original article
The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers Shelly Singhal1, Pooran Chand1, Balendra Pratap Singh1, Saumyendra Vikram Singh1, Jitendra Rao1, Rama Shankar1 and Santosh Kumar2 1
Department Prosthodontics, Dental Faculty, CSM Medical University, Lucknow, UP, India; 2Orthopaedics, Dental Faculty, CSM Medical University, Lucknow, UP, India
Gerodontology 2012; doi: 10.1111/j.1741-2358.2011.00610.x The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers Aim: To compare masticatory performance, masticatory efficiency and residual ridge resorption (RRR) in osteoporotic and non-osteoporotic edentulous subjects after rehabilitation with complete dentures. Method: Thirty subjects fulfilling the inclusion criteria were enrolled from the patients visiting the Department of Prosthodontics for complete denture fabrication. Two groups consisting of control subjects (group I; N = 15) and osteoporotic subjects (group II; N = 15) were formed. Complete dentures satisfying certain criteria were fabricated for both groups. Masticatory performance and efficiency were measured 6 months after denture insertion. Areal measurements were taken on lateral cephalograms before and 6 months after denture fabrication. The data were then computed to analyse differences between groups I and II using SPSS statistical software version 15.0. Results: Six months after denture fabrication, the masticatory performance and efficiency were significantly higher (p < 0.001) for group I, with a significant decrease in maxillary and mandibular sagittal area seen in both groups. The rate of bone loss was more in group II compared with group I. Conclusion: Greater masticatory function was demonstrated by the non-osteoporotic group, and the rate of RRR was more in the osteoporotic group compared with the normal group. In this pilot study, osteoporosis leads to greater RRR, decreased masticatory performance and efficiency in edentulous subjects 6 months after denture insertion. Screening for osteoporosis is suggested as a routine procedure for all edentulous subjects undergoing rehabilitation. Recall check-ups for osteoporotic patients should be more frequent, and these patients may require more frequent denture remakes. Keywords: osteoporosis, bone mineral density, masticatory performance, residual ridge resorption. Accepted 4 September 2011
Introduction Successful rehabilitation of an edentulous patient depends largely on the relation of the dentures to the supporting and limiting anatomical structures. The underlying bone plays a pivotal role in providing support to the dentures1. The health of the residual ridge depends upon various local and systemic conditions, which may compromise bone quality and the prognosis of prosthodontic treatment in turn. Residual ridge resorption (RRR) is a progressive, inevitable, multifactorial and biomechanical disease that results from a combination of anatomical, functional, metabolic and prosthetic 2012 The Gerodontology Society and John Wiley & Sons A/S
determinants. As a result of RRR, even the bestmade dentures become loose over a period of time, leading to the reline or remake of the prosthesis2. RRR leads to a decrease in the size of the denturebearing area with problems in denture retention and stability. Alveolar bone may occasionally be replaced by fibrous tissue, which can cause the dentures to become displaced during function. As bone loss progresses, anatomical structures such as the mylohyoid ridge and genial tubercles may become prominent. Mucosa overlying these areas is thin, friable and often incapable of withstanding functional stress. Pain and ulceration arising from these areas may also be a complication. Some other 1
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problems associated with reduced denture stability include pathologic conditions such as dentureinduced hyperplasia and denture-induced stomatitis3. Thus, patients with a resorbed residual ridge may receive a prosthesis with compromised retention and support, causing denture failure despite the best efforts of the dentist4. Masticatory function includes the relationship between morphological and functional aspects of the temporomandibular joint, teeth and neuromuscular system. It may be influenced by the consistency and nature of foods. The basic masticatory cycles perform rhythmic and coordinated movements for breathing and swallowing, which originate from a central pattern generator, coordinating jaw elevators, depressors and associated muscles, in synergistic and antagonistic actions. Such cyclical sequences are modulated by sensory information from a variety of receptors, mainly muscle spindles and periodontal receptors5. Mastication in complete denture wearers is a random process where the degree of pulverisation of food is greatly diminished. Dentures provide poor functional replacements for a natural dentition. The simplest and most commonly used definitions of masticatory performance and efficiency for complete denture wearers were given by Manly and Braley6, modified by Kapur and Soman7. Masticatory performance is defined as the particle size distribution of food when chewed for a given number of strokes as a percentage. This ratio provides a measurement of performance of a dentition, but fails to disclose the degree of impairment. This was assessed using masticatory efficiency, which was defined in terms of the number of extra chewing strokes required by the concerned denture wearer to achieve the same degree of food pulverisation as the pre-defined norm. The norm they selected (with peanuts as the test food) was the 95th percentile of the average masticatory performance of the subjects, that is, a performance of 43%7,8. There is a consensus that masticatory performance of individuals wearing complete dentures is significantly less than dentate individuals. Complete denture wearers experience more difficulty in chewing hard foods than dentate subjects. Heath found that masticatory performance of edentulous individuals was one-sixth of that achieved by dentate individuals9. Morii and Takaishi found a relationship between bone mineral density (BMD) and strength of masticatory muscles. They stated that this may be because the most powerful stimulus for bone formation is stretching of muscles. Therefore, the decrease in BMD of alveolar bone could be partly due to decrease in the power of
masticatory muscles, which would manifest as decreased masticatory performance10. Osteoporosis is a common metabolic disorder characterised by low bone mass and microarchitectural deterioration of bone tissue, leading to higher bone fragility and increased fracture risk11,12. Maxillary and mandibular residual ridges being part of the skeletal system should also be affected13. Jeffcoat showed that loss of oral bone may be related to systemic osteoporosis. There was also evidence that therapies designed to influence systemic bone mineral density such as hormone replacement and bisphosphonates were associated with slower loss of alveolar bone14. WactawskiWende et al. suggested that severity of osteoporosis was related to loss of alveolar crestal height and tooth loss in post-menopausal women. This relationship was particularly evident in edentulous individuals4,15. Our study was carried out to compare the masticatory performance and efficiency in osteoporotic and non-osteoporotic complete denture wearers and to evaluate the effect of osteoporosis on RRR. Studies have been conducted in the past as described in the preceding paragraphs, which implicate osteoporosis in RRR and decreased masticatory function. However, these studies have been cross-sectional in nature and have not evaluated the effect of prosthetic loads on osteoporotic denture-bearing alveolar bone. The aim of this study was therefore to evaluate the effect of osteoporosis on RRR and masticatory performance in rehabilitated edentulous subjects aged between 45 and 60. The rehabilitation consisted of complete dentures, fabricated in the Department of Prosthodontics. The null hypothesis of this study was that there would be no difference in masticatory performance, masticatory efficiency and RRR in osteoporotic and control subjects.
Methods This study was carried out in the Department of Prosthodontics, Dental Faculty, CSM Medical University, Lucknow, UP, India, after obtaining approval from the ethics committee. The study sample consisted of 30 edentulous subjects aged between 45 and 60 who desired prosthetic rehabilitation. The patients in the osteoporotic group (group II; N = 15) had to fulfil the following inclusion criteria and participate in the informed consent process before becoming part of the study: (i) class I edentulous subject with moderate alveolar ridge atrophy, (ii) osteoporosis confirmed at the time of study without any other systemic 2012 The Gerodontology Society and John Wiley & Sons A/S
Effect of osteoporosis on residual ridge resorption
disease based on history and examination, (iii) no denture-wearing history and (iv) philosophic attitude. Subjects with a philosophical mindset (MM House classification) were selected as such patients recognise their responsibility of being an active partner in the treatment. They would probably be more compliant with recall appointments and denture-wearing instructions3,4. Exclusion criteria included (i) history of undergoing treatment for bone, systemic or endocrine disease, or history of smoking/alcohol intake and (ii) mild or severely resorbed alveolar ridges, or ridges having a class II/III ridge relation. Patients with diseases affecting the physiology of bone formation and resorption (other than osteoporosis) were excluded to avoid errors in studying the association of bone mineral density with masticatory function and bone resorption. Subjects with class II and III ridge relations were excluded as these occlusions cause masticatory impairment because of decreased interocclusal contact16. Similarly, previous studies have shown severely atrophied ridges to have poor masticatory efficiency17. Previous denture wearers may be able to chew better because of trained muscular function, as compared to those having no denture experience, and were therefore excluded. All criteria aimed to minimise variation in masticatory performance, efficiency and alveolar bone loss because of factors other than bone mineral density. Edentulous subjects satisfying all the above criteria, except that they were non-osteoporotic, were selected for the control group (N = 15; group I). It was ascertained that groups I and II were matched for age, sex and morphology. The study duration was from June 2009 to September 2010. First, a lateral cephalogram of the subject (Rotograph Plus; Villa Sistemi Medicali SpA, Buccinasco, Italy) was taken using a standard technique by the same operator (to reduce interoperator bias). While shooting the cephalogram, patients were required to pronounce the letter ‘M’ before closing their lips in order to standardise the maxillo-mandibular relation. Cephalograms were traced on acetate graph tracing sheets, and landmarks and reference lines drawn to calculate areal measurements as per Table 1 and Figs 1 and 2. Area was calculated in millimetre square by counting the number of circumscribed squares. If less than half of a square was involved, it was not counted18. Three investigators made the measurements separately and if any variation was noted, a consensus was reached. The measured sagittal area served to calculate the degree of resorption of the residual ridges. 2012 The Gerodontology Society and John Wiley & Sons A/S
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Table 1 Cephalometric landmarks and reference lines used. Gonion (Go) Pogonion (Po) Gnathion (Gn) Anterior nasal spine (ANS) Posterior nasal spine (PNS) Point (O) Prosthion (Pr)
Point A Id-40 Mandibular plane
Most postero-inferior point at the angle of mandible Most anterior point in the contour of chin Most antero-inferior point in contour of chin Tip of the anterior nasal spine seen in X-ray film from norma lateralis Tip of the posterior spine of palatine bone in hard palate The projection of the pogonion on the mandibular plane The most prominent point of the alveolar process of the anterior aspect of the maxillae Deepest point on the line joining ANS and Pr A point on the mandibular plane 40 mm from the point O Plane joining Go and Gn
Then the bone mineral density of the subject was tested using a DXA machine (Analysis version: 11.40; GE Healthcare, Chalfont St Giles, UK). The dual-energy X-ray absorptiometry test (DEXA) is considered as the gold standard for measuring BMD19. A T-score of
