The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers

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1 Original article The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers Shelly Singhal 1, Pooran Chand 1, Balendra Pratap Singh 1, Saumyendra Vikram Singh 1, Jitendra Rao 1, Rama Shankar 1 and Santosh Kumar 2 1 Department Prosthodontics, Dental Faculty, CSM Medical University, Lucknow, UP, India; 2 Orthopaedics, Dental Faculty, CSM Medical University, Lucknow, UP, India doi: /j 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 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 dentures 1. 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 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 prosthesis 2. 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 e1059

2 e1060 S. Singhal et al. problems associated with reduced denture stability include pathologic conditions such as dentureinduced hyperplasia and denture-induced stomatitis 3. 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 dentist 4. 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 receptors 5. 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 Braley 6, modified by Kapur and Soman 7. 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 individuals 9. 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 performance 10. 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 risk 11,12. Maxillary and mandibular residual ridges being part of the skeletal system should also be affected 13. 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 bone 14. Wactawski- Wende 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 individuals 4,15. 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

3 Effect of osteoporosis on residual ridge resorption e1061 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 instructions 3,4. 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 contact 16. Similarly, previous studies have shown severely atrophied ridges to have poor masticatory efficiency 17. 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 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 counted 18. 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. 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 BMD 19.AT-score of <)2.5 standard deviations (SD) was considered osteoporotic (group II) while a T- score of more than )1.0 SD was considered normal (group I). Osteopenic subjects were excluded. This was followed by complete denture fabrication for each selected subject. Each denture was assessed on the basis of pre-defined criteria as per which only good-quality dentures (scores of ) were selected for the study. Seven factors were evaluated to assess the quality of dentures, namely anterior teeth arrangement, interocclusal space, stability of mandibular dentures, occlusion, articulation, retention of mandibular dentures and border extension of mandibular dentures. On the basis of the sum of scores, the quality of dentures was rated as good if the sum score was ; average if the sum score was 51 80; and poor if the sum score was Six months following routine delivery and postinsertion procedures, masticatory performance and efficiency of the subject were assessed by the fractional sieving method 7,21. Masticatory performance of the subjects in this study was calculated as the volume percentage after 20 chewing strokes, of that portion of 3 g of peanuts, which was finer than 1700 lm, that is, (F/[F + R]) 100, where

4 e1062 S. Singhal et al. Figure 1 Cephalometric landmarks and reference lines for measuring maxillary sagittal area (SU) = area circumscribed by line following the lower palatal plane from point A to PNS, down along the crest of the alveolar process to Pr and back to point A. F = volume of sedimentation of the filtrate; R = volume sedimentation of residue. After calculating the number of extra chewing strokes required by the test subject to achieve the pre-defined masticatory performance norm (as detailed by Kapur and Soman 7 ), the masticatory efficiency percentage was calculated as (20/number of chewing strokes to achieve the norm 100). This was followed by a repeat lateral cephalogram of all subjects, which was analysed as before. The pre- and post-treatment cephalometric readings were then used to calculate the progression of alveolar bone loss. Intergroup variations were statistically analysed using Statistical Package for Social Sciences (SPSS) version 15.0 (Bangalore, Karnataka, India) for tests such as mean, standard deviation, log values, Z-test and p values (significance value < 0.05). Results In group I, the masticatory performance ranged from 36 to 44.6% (mean, 39.57%; SD, ±3.24), Figure 2 Cephalometric landmarks and reference lines for measuring mandibular sagittal area (SL) = area circumscribed by line following the uppermost contour of the inferior border of the mandible from gnathion to Id- 40, perpendicular to the crest, then forward to the symphysis and back to gnathion. compared with group II where the masticatory performance ranged from 24 to 36% (mean, 31.33%; SD, ±3.67). This difference was significant (Table 2). Masticatory efficiency values were also significantly higher for group I compared with group II (Table 2). The mean pre-treatment maxillary sagittal area in groups I and II showed no significant intergroup difference (Table 3; p = 0.724). On comparing the pre- and post-treatment values in maxillary area, the post-treatment values were significantly lower for both groups. Although the mean post-treatment maxillary bone loss for groups I and II were not significantly different, post-treatment bone loss in group I was 2.26% less as compared to group II. A comparison of the mean pre- and post-treatment mandibular sagittal area for groups I and II (Table 4) showed the same trend as the maxillary sagittal areas. Again, although the mean posttreatment mandibular bone loss for groups I and II was not significantly different, the value for group I was 3.98% less as compared to group II.

5 Effect of osteoporosis on residual ridge resorption e1063 Table 2 Comparison of masticatory performance and efficiency in groups I and II. Group I Group II N Mean SD N Mean SD Z p Masticatory performance (%) Overall <0.001 Men )3.313 <0.001 Women )3.070 <0.001 Masticatory efficiency (%) Overall <0.001 Men )3.313 <0.001 Women )3.070 <0.001 Table 3 Comparison of pre- and post-treatment maxillary sagittal area in groups I and II. Pre-treatment area (mm 2 ) Post-treatment area (mm 2 ) N Mean SD Mean SD Bone loss (%) Z p Group I ) Group II ) Z )0.354 )0.771 p Table 4 Comparison of pre- and post-treatment mandibular sagittal area in groups I and II. Pre-treatment area (mm 2 ) Post-treatment area (mm 2 ) N Mean SD Mean SD Bone loss (%) Z p Group I ) Group II ) Z )0.332 )1.599 p Discussion The study was undertaken to compare masticatory function and RRR in edentulous normal and osteoporotic subjects, rehabilitated with complete dentures. All efforts were made to standardise treatment outcomes and remove confounding factors by selecting subjects with similar attitude towards denture treatment (MM House classification), degree of RRR, ridge relation, previous denture experience and present denture quality. For the same reasons, subjects were selected within an age limit and matched for age, sex and general morphology within the two groups 3,4. To measure maxillary and mandibular alveolar bone loss, lateral cephalograms were used. Lateral cephalograms are more precise compared with panoramic or occlusal radiographs as they include the basal bone of the mandible. The panoramic view has the disadvantage of inherent image distortion, and the occlusal view can only assesses the width of the jaw bone. Computed tomography (CT) scans of the jaw would have been the most accurate option, but we selected the economically viable alternative 22. Masticatory function test was performed 6 months after fabrication of good-quality complete dentures for control and study groups, during which period new muscle memory patterns for mastication would have been established. To date, few studies have attempted to directly correlate the effect of osteoporosis on masticatory function.

6 e1064 S. Singhal et al. Largely, questionnaire-based studies have been conducted for a subjective assessment of masticatory function (masticatory ability) 23. The degree of impairment of mastication can only be measured by objective chewing tests in the form of masticatory performance and efficiency. The fractional sieving method is the most common method for establishing masticatory performance and efficiency 24. The reasons for using this method with peanuts as a test material were simplicity, accuracy and universal availability of material. Hirano et al. 8 investigated the relationship between oral sensorimotor ability and masticatory function (masticatory performance and efficiency) utilising the same method and material. Silicone is also commonly used as a test material for the fractional sieving method 25. Computer-assisted image processing is becoming more common to analyse the size of chewed particles. In spite of its simplicity, speed, accuracy and reproducibility, it is not in common use because of expensive software. Another common method of determining masticatory performance is the colorimetric method 26. The study demonstrated that the osteoporotic group had significantly lower masticatory performance and efficiency after 6 months of denture wearing. A study conducted in dentate elderly patients found that masticatory forces in the high bone mineral density group were significantly greater compared with the low-density group. This was explained on the basis of significantly greater periodontal attachment loss in the low mineral density group 27. Another study concluded that subjective masticatory dysfunction assessment was significantly associated with osteoporosis in elderly men. The investigators, however, concluded that the findings were not easily explainable 28. A study carried out on masticatory muscle electromyographic activity in women diagnosed with osteoporosis stated that facial osteoporosis may interfere with patterns of masticatory muscle activation and maximal bite force 13. A similar study found that edentulous osteoporotics presented with greater electromyographic activity when maintaining mandible postural conditions and consequently lesser activity during clenching or maximal bite force, hence inferring that osteoporosis can interfere with the patterns of masticatory muscle activation 29. Osterberg et al. also found a positive correlation between masticatory performance and osteoporosis. They explained it by stating that RRR may develop rapidly in individuals with osteoporosis, which in turn may result in the deterioration of the stomatognathic system. The mucosa in such a system presents a reduced number of receptors, reducing the number of afferent impulses. This subsequently affects muscle control and activity in addition to the changes associated with the temporomandibular joint, ultimately leading to reduced masticatory performance and efficiency 30. Although the relationship between mandibular alveolar bone loss and osteoporosis is well documented, very little data exist on maxillary involvement in osteoporosis. Moreover, most of the studies have been cross-sectional, studying the relation between osteoporosis and alveolar bone at a particular time period 2,13,22. Therefore, a longitudinal study was conducted to examine the correlation between the rate of RRR under dentures and osteoporosis, both in the maxilla and in the mandible. Significant decrease in maxillary and mandibular sagittal areas was seen in both osteoporotic and normal groups following treatment. This may be explained by RRR being a continuous process, which increases under the load of complete dentures 2. Although the results were statistically not significant, the post-treatment percentage decrease in residual ridge area for the osteoporotic group (maxilla, 10.86%; mandible, 10.38%) was more than the control group (maxilla, 8.6%; mandible, 6.4%). This was probably because osteoporosis resulted in a weakened bone structure caused by rapid loss of minerals that culminated in severe residual ridge atrophy. This compromises the denture-bearing area, making it difficult to produce a denture with qualities of stability, retention, comfort and optimum function 13. Further, the maxillary and mandibular post-treatment residual ridge loss revealed that the maxillary bone loss was 2.26% more in the osteoporotic group and the mandibular bone loss was 3.98% more in the same group. This may be because edentulous patients suffer a greater degree of mandibular resorption than maxillary resorption. Studies have shown that mandibular loss may be four times greater than maxillary loss. These resorption differences are attributed to the support surface for the complete lower dentures being smaller and as such the pressure exercised on them being much greater 31. We came to the conclusion that osteoporosis had a deleterious effect on masticatory performance and efficiency and hastened RRR in edentulous osteoporotic ageing subjects. It is important to remember that such patients already faced inevitable, irreversible and continuous RRR and reduced masticatory function. This may create problems for the dentist in fabricating retentive and stable dentures, and despite his best efforts, the patient may

7 Effect of osteoporosis on residual ridge resorption e1065 be left frustrated with a loose denture that does not help in chewing food. Even if the initial prosthesis has retention and stability, osteoporotics would suffer from post-insertion problems of looseness and ulceration, problems with phonetics and aesthetics, and faulty denture-induced pathologies sooner, as their rate of RRR is higher. Lack of proper comminution of food would lead to physical complications, based on the preferred texture and hardness of consumed food 1 4. A solution to such problems, given the frequency of osteoporosis in ageing adults, would be routine preliminary screening of edentulous patients undergoing prosthetic rehabilitation. Not only would this aid timely management of osteoporosis, but it would also prompt the dentist to modify his treatment protocol and institute regular post-insertion appointments for timely intervention including relines, adjustments or remakes. The patient would also be aware of his condition and therefore more understanding of it 32. Although the study revealed noteworthy findings, it had several limitations, including a small sample size, short follow-up of the patients (6 months) and two-dimensional radiography to measure RRR. Conclusion Within the limitations of this study, the following conclusions were drawn: 1. Post-insertion complaints would be greater in osteoporotic patients as a result of increased RRR and lower masticatory function. 2. Osteoporosis should be routinely screened while planning rehabilitation of edentulous patients. 3. Osteoporotic edentulous patients require more frequent post-denture insertion appointments and denture remakes. References 1. Jacobson TE, Krol AJ. A contemporary review of the factors involved in complete dentures. J Prosthet Dent 1983; 49: Atwood DA. Reduction of residual ridges: a major oral disease entity. J Prosthet Dent 1971; 26: Allen PA, McMillan AS. A review of the functional and psychosocial outcomes of edentulousness treated with complete replacement dentures. J Can Dent Assoc 2003; 69: van Waas MAJ. The influence of psychologic factors on patient satisfaction with complete dentures. JProsthet Dent 1990; 63: Berretin-Felix G, Genaro KF, Trindade IEK, Júnior AST. Masticatory function in temporomandibular dysfunction patients: electromyographic evaluation. J Appl Oral Sci 2005; 13: Manly RS, Braley LC. Masticatory performance and efficiency. J D Res 1950; 29: Kapur KK, Soman S. Masticatory performance and efficiency in denture wearers. J Prosthet Dent 1964; 14: Hirano K, Hirano S, Hayakawa I. The role of oral sensorimotor function in masticatory ability. J Oral Rehabil 2004; 31: Heath MR. The effect of maximum biting force and bone loss upon masticatory function and dietary selection of the elderly. Int Dent J 1982; 32: Morri H, Takaishi Y. Muscular power of masticatory muscles and mandibular osteoporosis. Clin Calcium 2006; 16: Knapp KM, Blake GM, Spector TD, Fogelman I. Can the WHO definition of osteoporosis be applied to multi-site axial transmission quantitative ultrasound? Osteoporos Int 2004; 15: NIH Consensus Development Panel. Osteoporosis prevention, diagnosis, and therapy. J Am Med Assoc 2001; 285: von Wowern, Kollerup G. Systemic osteoporosis a risk factor for residual ridge reduction of the jaws. J Prosthet Dent 1992; 67: Jeffcoat M. The association between osteoporosis and oral bone loss. J Periodontol 2005; 76: Wactawski-Wende J, Grossi SG, Trevisan M et al. The role of osteopenia in oral bone loss and periodontal disease. J Periodontol 1996; 67: Kapur K K, Soman S. The effect of denture factors on masticatory performance. Part II. Influence of the Polished Surface Contour of the Denture Base. J Prosthet Dent 1965; 15: Buschang PH. Masticatory ability and performance: the effects of mutilated and maloccluded dentitions. Semin Orthod 2006; 12: Mercier P, Lafontant R. Residual alveolar ridge atrophy: classification and influence of facial morphology. J Prosthet Dent 1979; 41: St-Onge MP, Wang J, Shen W et al. Dual-energy x-ray absorptiometry measured lean soft tissue mass: differing relation to body cell mass across the adult life span. J Gerontol A Biol Sci Med Sci 2004; 59: Sato Y, Tsuga K, Akagawa Y, Tenma H. A method for quantifying complete denture quality. J Prosthet Dent 1998; 80: Kapur KK, Soman S. Test foods for measuring masticatory performance of denture wearers. J Prosthet Dent 1964; 14: Wical KE, Swoope CC. Studies of residual ridge resorption Part I: use of panoramic radiographs for evaluation and classification of mandibular resorption. J Prosthet Dent 1973; 32: Jacob RF, Zarb GA, Bolender CL. Waxing and processing the dentures, their insertion, and follow-up. In: Zarb GA, Bolender CL eds. Prosthodontic Treatment

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