Limited utility of salivary mineral content in prediction of fragility fractures among postmenopausal women.

BACKGROUND: Osteoporosis is a metabolic disease characterized by increased bone fragility. As it is characterized as a general skeletal disease, changes can also be seen in the stomatognathic system (edentulism, wrong fitting of dentures, etc.). The question is whether early changes in the salivary mineral content and acid-base balance may reflect skeletal status and risk of bone fracture. OBJECTIVES: The objective of the study was to evaluate whether minerals in the saliva were associated with skeletal fractures in a population of postmenopausal women. MATERIAL AND METHODS: In this observational study, dental examinations along with the collection of saliva were conducted in 117 randomly recruited women (mean age 64.6 ±5.9 years). The study group included 23 study participants with fractures, of which 10 had a history of osteoporotic fractures. Saliva samples for mineral content including copper (Cu), zinc (Zn), calcium (Ca), and phosphorus (P), as well as salivary pH were collected and analyzed to determine associations between salivary mineral content and fracture risk. RESULTS: As a result, the median pH value was 6.8, and the median levels for Cu (0.35 µmol/L), Zn (0.61 µmol/L), Ca (0.7 mmol/L), and P (6.64 mmol/L) were observed. No differences were noted in salivary mineral content and acid-basic balance between the fractured and non-fractured participants. CONCLUSIONS: The results of our study suggest that salivary mineral content has limited usability in predicting skeletal fragility in postmenopausal women when used alone.

Relationship between emotional state and masticatory system function in a group of healthy volunteers aged 18-21.

OBJECTIVE: To determine the role of emotional state in the masticatory system function in a group of young adults. METHODS: Ninety-six generally healthy randomly selected students aged 18-21 were examined. They were subjected to a questionnaire survey determining their emotional state, clinical examination, and instrumental diagnostics (EMG, Cadiax Compact, JVA). RESULTS: The stress symptoms group revealed a greater intensity of neck and shoulder muscles pain (p < 0.05) and an increase of electrical potential of the masseter muscles in maximal voluntary clench (p < 0.05). They reported more often headache (p < 0.001), tension/contracture of the head, neck and nape (p < 0.05), and pain while opening the mouth wide (p < 0.05). The values of parameters obtained in the instrumental diagnostics did not reveal differences between the groups. CONCLUSION: Stressful situations increase muscular tension but do not have a direct impact on the temporomandibular joints function.

Can devices for the instrumental analysis of temporomandibular joints be used interchangeably?

Objective: To compare the results obtained in instrumental analysis of temporomandibular joints function using joint vibration analysis and computerized axiography in healthy young adults.Methods: The study involved 187 people aged 18-21 years old. All the participants were subjected to a clinical examination and instrumental diagnostics that included joint vibration analysis and computerized axiography.Results: Significant differences in the maximum range of condylar movement (p = 0.0001) were reported between the group of people with healthy joints (p = 0.001) and the remaining groups. There were significant statistical differences (p = 0.02) between the group of people with loose articular ligaments and subluxation of the joint in terms of the parameter describing the symmetry of the sagittal position of the condyle on the distance of 5 mm.Discussion: Electrovibratography and computerized axiography did not reveal the same abnormalities in the functioning of the masticatory system.

Salivary Content Might be Associated With Skeletal Status in Postmenopausal Women: SilesiaOsteoActive Study Results.

AIM: The aim of the study was to investigate whether salivary mineral content may be associated with bone status in women after menopause. MATERIAL AND METHODS: The study group consisted of 125 postmenopausal women aged 64.3 ± 6.9 yr, derived from the epidemiological SilesiaOsteoActive Study. All participants underwent hip and spine bone densitometry using dual energy X-ray absorptiometry, dental examination, and saliva content analysis. Data for salivary pH, copper, calcium, phosphorus, and zinc concentrations were evaluated. RESULTS: Mean femoral neck bone mineral density (BMD) was 0.739 ± 0.118 g/cm2, total hip BMD 0.891 ± 0.14 g/cm2, and spine BMD 0.868 ± 0.14 g/cm2. Salivary pH was significantly lower in women with spinal osteoporosis defined as T-score below -2.5, compared to individuals with normal BMD (pH: 6.65 ± 0.67 vs 6.96 ± 0.58, p < 0.05). There was a significant though weak inverse correlation between Ca concentration in saliva and femoral neck BMD (r = -0.23, p < 0.05). CONCLUSIONS: High salivary calcium content and low salivary pH may be indicative of low hip and decreased spine BMD, respectively. These associations may reflect demineralization process (calcium redistribution) influencing bone, and a negative effect of acidity on mineral tissues, although causal pathway remains not clear.

Bacteria Residing at Root Canals Can Induce Cell Proliferation and Alter the Mechanical Properties of Gingival and Cancer Cells.

Understanding the importance of oral microbiota in human health and disease also leads to an expansion of the knowledge on functional, metabolic, and molecular alterations directly contributing to oral and systemic pathologies. To date, a compelling number of studies have documented the crucial role of some oral cavity-occurring microbes in the initiation and progression of cancers. Although this effect was noted primarily for Fusobacterium spp., the potential impact of other oral microbes is also worthy of investigation. In this study, we aimed to assess the effect of Enterococcus faecalis, Actinomyces odontolyticus, and Propionibacterium acnes on the proliferation capability and mechanical features of gingival cells and cell lines derived from lung, breast, and ovarian cancers. For this purpose, we incubated selected cell lines with heat-inactivated bacteria and supernatants collected from biofilms, cultured in both anaerobic and aerobic conditions, in the presence of surgically removed teeth and human saliva. The effect of oral bacteria on cell population growth is variable, with the highest growth-promoting abilities observed for E. faecalis in relation to human primary gingival fibroblasts (HGF) and lung cancer A549 cells, and P. acnes in relation to breast cancer MCF-7 and ovarian cancer SKOV-3 cells. Notably, this effect seems to depend on a delicate balance between the pro-stimulatory and toxic effects of bacterial-derived products. Regardless of the diverse effect of bacterial products on cellular proliferation capability, we observed significant alterations in stiffness of gingival and lung cancer cells stimulated with E. faecalis bacteria and corresponding biofilm supernatants, suggesting a novel molecular mechanism involved in the pathogenesis of diseases in oral cavities and tooth tissues. Accordingly, it is proposed that analysis of cancerogenic features of oral cavity bacteria should be multivariable and should include investigation of potential alterations in cell mechanical properties. These findings corroborate the important role of oral hygiene and root canal treatment to assure the healthy stage of oral microbiota.

Smoking Prevalence, Attitudes and Behavior among Dental Students in Poland and Italy.

The aim of the study was to perform preliminary research to compare the smoking prevalence, attitudes and behavior between dentistry students in two universities in Europe using the standardized Global Health Professions Student Survey (GHPSS) questionnaire. This was cross-sectional carried out among dentistry students from the Medical University in Bialystok, Poland and Sapienza University of Rome, Italy. There were 582 participants; 282 were Italians, 202 were smokers and 42% were Italians. The response rate was 79.9% of Italian students and 79.6% of Polish students. The prevalence of smoking was significantly higher among Italian students (42% vs. 28.0%). Attitudes and behaviour of smokers and non-smokers differed statistically. Polish and Italian dental students presented statistically different behavior regarding the time to smoke the first cigarette, the willingness to stop smoking and trying to stop smoking in the last year. The multiple logistic regression analysis revealed that two independent variables, exposure to second-hand smoke (SHS) both at home and in public places (OR = 3.26 and OR = 5.9, respectively), showed a significantly higher occurrence of smoking. There is a high use of tobacco among dental students, which is particularly high in Italian dental students. Students realizes the positive perception of their own tobacco counsellor role in a dental setting. Dental students should be role models to their peers and patients.

Two unrelated families with variable expression of Fraser syndrome due to the same pathogenic variant in the FRAS1 gene.

We report on two unrelated families of Polish origin with variable expression of Fraser syndrome (FS; MIM#219000) due to homozygosity for the same pathogenic variant, c.6963_6964dup, of FRAS1. In one family, the disorder presented with perinatal and prenatal lethality. One affected female from family 2 who was followed-up for 32 years, represented a relatively favorable long-term outcome. She displayed the typical craniofacial dysmorphism, including right cryptophthalmos, cutaneous syndactyly, abnormalities of the stomathognatic system, bilateral atresia of the external ear canals resulting in conductive hearing loss, and malformations of the larynx, spleen, kidney, and genitourinary tract. Her intellectual capacities were normal. Our observations illustrate that expression and severity of FS, even when caused by the same pathogenic variant, may be quite different ranging from a lethal disorder to a condition with multiple physical malformations but normal psychomotor development. In addition, we propose that the FRAS1 c.6963_6964dup variant may be a founder mutation in the Polish population. Therefore, it would be reasonable to test specifically for this variant first in any FS1 patient of Polish ancestry.

Evaluation of Orofacial and General Pain Location in Patients With Temporomandibular Joint Disorder-Myofascial Pain With Referral.

Introduction: Pain is an emotional experience. As a subjective feeling, it is associated with pathophysiological processes occurring in the central nervous system, which in turn may negatively affect the psychophysical function, cognitive abilities, level of functioning and quality of life. The Aim: The aim of the study was to assess orofacial and general pain location in patients with temporomandibular joint disorder-myofascial pain with referral. Materials and Methods: The study group consisted of 50 randomly selected, generally healthy people with complete natural dentition (37 women and 13 men) at the age of 23.36 ± 2.14 years, referred to the Department of Prosthodontics of the Medical University. All patients underwent clinical examination according to the Diagnostic Criteria for Temporomandibular Disorders (Axes I and II). The subjects were classified as people with myofascial pain with referral. The evaluation of severity of temporomandibular disorders was based on the Temporomandibular Disorder Pain Screener and the Graded Chronic Pain Scale. In order to assess orofacial and general pain location, a bodychart drawing of pain was used. Results: The study group indicated 40 different areas of the body affected by pain. 2-3 isolated pain locations were declared by a total of six subjects. One person identified 17 affected areas. Forty four people reported pain in at least four regions of the body. 70% of patients suffered from pain within the right masseter muscle. Pain of the left masseter muscle was noted in 68% of cases. Cervical ailments were reported by 56% of people. Pain of the left temporomandibular joint was observed in 68% of patients, and of the right one in 54%. Conclusion: The patients with myofascial pain with referral suffer from general ailments in different regions of the body. Only the frequency of pain in the right masseter muscle and right temporomandibular joint differed with respect to gender. The suggestion that the prevalence of pain in other areas of the body varies between men and women has not been confirmed. Due to a small sample size, such differences cannot be excluded. Further studies in this area are needed.

The evaluation of zinc and copper content in tooth enamel without any pathological changes - an in vitro study.

OBJECTIVES: The objectives of the study were to evaluate the content of copper and zinc in individual layers of tooth enamel and to analyze the relationships between the study minerals in individual layers of tooth enamel. PATIENTS AND METHODS: Fifteen human permanent teeth were cut off every 150 µm alongside the labial surface. Acid biopsy of each layer was performed. The zinc content was determined using the air-acetylene flame method. The copper content was determined using the electrothermal technique with argon. RESULTS: The mean zinc concentrations increased significantly starting from the outer enamel surface, with the maximum concentration in the 150-300 µm layer. The mean copper concentrations increased substantially from the outer enamel surface to a depth of 150 µm, and then a slight downward trend of this mineral levels was seen, down to a depth of 450 µm. Strong positive correlation was found between the zinc and copper concentrations at depths of 150-300, 450-600 and 600-750 µm. CONCLUSION: The levels of zinc and copper in the outer enamel layers may have an effect on the increased content of unipolar minerals at deeper enamel layers. The content of the study elements determined may reflect the process of mineralization and maturation of enamel in the pre-eruption period.

Evaluation of calcium and magnesium contents in tooth enamel without any pathological changes: in vitro preliminary study.

Enamel is the structure that covers the entire clinical crown of a tooth. It enables to chew and crush food, and gives a final shape to the crowns of teeth. To evaluate calcium and magnesium contents in tooth enamel and analyse relationships between the study minerals extracted human permanent teeth were cut at every 150 microns and subjected into acid biopsy. The amounts of calcium and magnesium were assessed in the laboratory using atomic absorption spectroscopy with an air/acetylene flame. The lowest calcium and magnesium contents were found on the enamel surface of the teeth. Statistically significant correlation between the calcium and magnesium concentrations was found at a depth between 150 and 900 µm. Calcium and magnesium contents increased with increasing enamel depth. Calcium and magnesium deposits appeared to be stable through all the enamel layers studied. It would be suggested that mineralization/demineralization affect only external layer of the enamel, whereas deeper layers are not affected by these processes.

Assessment of the Temporomandibular Joint Function in Young Adults without Complaints from the Masticatory System.

Objective of the study was to evaluate the clinical status of the masticatory system in young adults with full permanent dentition and no stomatognathic system complaints. The study involved 186 randomly selected people with full dental arches with normal occlusal conditions corresponding to Angle's Class I aged 18 - 21 years with an average age of 19 years. Subjects were clinically examined and temporomandibular joint (TMJ) vibrations were recorded during open-wide and close movements using BioJVA. Then, patients were categorized into groups according to Piper's classification system. The TMJs of the subjects were categorized according to the values of the vibration energy and the Piper protocol. This detected 33.4% of the joints with loosened ligaments, subluxation in 8.28%, initial signs of disc dysfunction in 5.08% and disc displacement without locking in 1.6 %. Median frequency differed significantly (p < 0.05) between the group of subjects with initial signs of TMJ dysfunction and other groups. Peak Frequency differed significantly (p < 0.05) between the healthy joints and those with TMJ subluxation. In this group of young healthy people, the majority of study joints generated small vibrations. However, a subset of people manifested higher vibrations that may indicate an early stage of TMJ dysfunction. Median Frequency was an important parameter for detecting initial symptoms of TMJ dysfunction. Peak Frequency was an important characteristic parameter for detecting TMJ subluxation.

Relationship between depression and masticatory muscles function in a group of adolescents.

OBJECTIVE: The aim of the study is to determine association between depressive symptoms and the electrical activity of muscles in maximum voluntary clench in a group of young adults. METHODS: A total of 186 volunteers (Females = 98, Males = 88), with a mean age of 19 years, were recruited to the study. All participants took a questionnaire survey stating the level of depression (Beck's scale), clinical examination, and instrumental diagnostics (EMG). RESULTS: Symptoms of mild or medium depression were found in 35 of the subjects (18.82%). Average electric potentials of the masticatory muscles in maximal voluntary clench were significantly higher among the subjects with depression symptoms in comparison with subjects without those symptoms (85.96 ± 10.25 vs 78.97 ± 15.32, p < . 0.05). DISCUSSION: An increase in the electrical potentials of masseter muscles in maximal voluntary clench was found in the group with depression symptoms. The study should be continued to confirm this finding.

Alveolar ridge atrophy related to facial morphology in edentulous patients.

OBJECTIVES: The morphology of the alveolar process determines the retention and stability of prosthetic restorations, thereby determining the result of the therapy. Considering that the edentulous jaws may be affected by the atrophy process, it was hypothesized that the morphology of the alveolar process of the maxilla may be dependent on the anterior facial height and anatomy of the mandible. SUBJECTS AND METHODS: Twenty-five healthy edentulous Caucasian individuals were randomly chosen. Each subject underwent a lateral cephalogram before and after prosthetic rehabilitation. During exposition, newly made prostheses were placed in the patient's mouth. Teeth remained in maximal intercuspidation. Morphological parameters were evaluated according to the Ricketts, McNamara, and Tallgren's method. RESULTS: An inversely proportional association was observed between patient age and the distal part of the maxilla. A statistically significant connection was noted between the vertical dimension of alveolar ridge and anterior total and lower facial height conditioned by prosthetic rehabilitation. CONCLUSION: The height of the lateral part of the alveolar ridge of the maxilla remains in connection with the anterior total and lower facial height obtained in the course of prosthetic rehabilitation. The vertical dimension of the alveolar ridge of the maxilla seems to be in close relationship with the morphology of the lower jaw.

Salivary protective factors in patients suffering from decompensated type 2 diabetes.

PURPOSE: Defining the level of protective factors in saliva of patients suffering from decompensated type 2 diabetes. MATERIAL AND METHODS: 50 Patients with diagnosis of decompensated type 2 diabetes, including 32 women and 18 men at the age of 57.9±9.2 years. The control group consisted of 50 people among whom there were 38 women and 12 men whose average age was estimated at 51.2±9.9 years. RESULTS: It was stated the increased concentration of total protein by 60% and decreased concentration of IgA by 70%, of lysozyme by 27% and of lactoferrin by 40% in resting saliva of patients with type 2 diabetes if compared to the control group. These outcomes were really statistically meaningful. The evaluation of dependences between the analyzed protective factors and the indicator of oral cavity condition proved the positive correlation between the concentration of total protein and the number of DMFT (i.e. the rate of caries intensity). The remaining coefficients of correlation being evaluated proved to be negative and statistically meaningless. CONCLUSION: The obtained outcomes prove a high influence of proteins included in saliva on the prevalence and development of caries at patients with decompensated type 2 diabetes.

The influence of occlusal morphology on occlusion time.

OBJECTIVES: The aim of the study was to assess how the morphology of the occlusal surfaces of premolars and molars influenced the occlusion time in a mixed gender group of young adults with full natural dentition. METHODS: Fifty healthy volunteers with Angle's Class I occlusion were included in the study. After clinical examination, the alginate impressions of both arches were taken, and plaster casts were prepared. To assess the morphology of lateral teeth, the digital models were measured. Occlusal analysis was performed with the T-Scan® III to assess occlusion time. RESULTS: A direct correlation was found between the cusp distance for the first upper premolar and occlusion time (r = -0.29, p<0.05) and the distance between distal buccal and distal lingual cusps of the first lower premolar and occlusion time (r = 0.33, p<0.05). The parameters that had their impact on occlusion time were the opening angle of lingual cusps for the lower molars and the furrow angle of aperture between cusps for first upper premolar. DISCUSSION: Occlusal surface morphologies of premolars may have direct impact on occlusion time. However, anterior guidance parameters and morphologies of molars could also influence the time teeth are in contact coming to maximal intercuspation.

Assessment of masticatory muscle activity and occlusion time in patients with advanced tooth wear.

OBJECTIVE: Tooth wear is a basic physiological adjustment mechanism in the masticatory system. Unfortunately, it is not clear what the relationship is between the activity of the masticatory muscles and the tooth hard tissue loss (mainly enamel) in patients with advanced tooth wear. The aims of this study were (1) to compare the occlusion times and (2) to compare the EMG activity in maximal voluntary clench of the masseter and anterior temporalis muscles of patients with advanced tooth wear to the same activity of healthy volunteers. DESIGN: 50 (16F, 34M) patients and 30 (12F, 18M) age matched controls were clinically examined to assess the degree of wear (TWI). Each subject underwent electromyographic analysis (bilateral anterior temporalis, superficial masseter, anterior digastric and sternocleidomastoid muscles) and digital occlusal analysis. RESULTS: Mean values of the electrical potentials of the mandible elevating muscles during clench were higher in the study group compared to the controls. A negative correlation was found between the temporalis and masseter muscle activities during clench and the mean value of TWI (r=-0.383, p=0.009; r=-0.447, p=0.002). Occlusion time was longer in the study group compared to controls (p<0.05). CONCLUSIONS: Mandibular adductors demonstrated lower muscular activities during clenching in the tooth wear patients; however, the cause of this finding is not certain. Prolongation of occlusion time may exacerbate occlusal surfaces wear or excessive wear may prolong occlusion time.

Effect of the dental arches morphology on the masticatory muscles activities in normal occlusion young adults.

OBJECTIVES: The aim of this study was to assess the relationship between the morphology of dental arches and the activity of the masticatory muscles activities in healthy volunteers with full natural dentition. METHODS: Two-hundred youthful Class I volunteers (113 females, 87 males) were clinically investigated. Alginate impressions of dental arches were taken, and plaster casts were prepared and measured. EMG data from eight masticatory muscles was recorded to assess their activities in central occlusion, lateral and protrusive movements. RESULTS: Clinical measurements and plaster casts analyses confirmed normal values of parameters investigated. Most of the arch measurements were significantly larger in the males than in the females. Weak positive correlations were found between overbite and masseter activity in centric occlusion (the right Mm R = 0.151, P ≤ 0.05; the left Mm R = 0.191, P ≤ 0.05). Also, the range of protrusive movement positively correlated with masseter activities in central occlusion (the right Mm R = 0.194, P ≤ 0.05; the left R = 0.201, P ≤ 0.05). CONCLUSIONS: The null hypothesis that morphology of dental arches does not affect the masticatory muscles' activities was rejected. The findings of this investigation indicate that systemic, longitudinal analyses of morphology of occlusion and muscular response, even in normal subjects, are needed.

The relationship between facial morphology and the structure of the alveolar part of the mandible in edentulous complete denture wearers. A preliminary study.

OBJECTIVE: Although the effect of involutional processes that occurs in the maxilla and mandible of edentulous subjects is obvious, the problem of factors definitely determining the direction of changes still remains unsolved. This study was aimed at determining the relationship between facial morphology and the structure of the alveolar part and the body of the mandible in edentulous complete denture wearers. MATERIALS AND METHODS: Twenty-five healthy edentulous Caucasian patients in the 70.5 ± 9 years of age group were examined. All patients underwent tele-X-ray examination with the presence of currently used dentures in the oral cavity. To assess morphological parameters of the facial skeleton, cephalograms were analyzed according to Ricketts and Mc Namara method. To assess the mandible morphology, the films were measured using the method of Tallgren. RESULTS: The period of edentulism was found to be negatively correlated with the anterior segment of the body of the mandible within its symphysis. The parameter corresponding to the location of the first lower molar showed a directly proportional correlation with G'-Sn', G'-Me', Sn'-Me', N-Ans, N-Me, Ans-Me, Co-Gn and Co-Go. Positive correlations were found between the parameters describing contour of the alveolar part of the body of the mandible and mandibular symphysis and G'-Me', Sn'-Me', N-Me, Ans-Me describing the height of the occlusal vertical dimension. CONCLUSION: The study showed a directly proportional correlation between the vertical occlusal dimension of the lower face conditioned by prosthetic rehabilitation and the height of the alveolar part in the lateral regions of the mandible.

Enamel mineral content in patients with severe tooth wear.

PURPOSE: The amounts of calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu) in enamel may be crucial for maintaining its integrity and to attenuate potential environmental effects on teeth. The aim of this study was to examine whether the mineral composition of enamel could influence tooth wear. MATERIALS AND METHODS: A total of 50 patients with severe tooth wear were compared with 20 healthy volunteers. Tooth wear was assessed using clinical examination according to the protocol of Smith and Knight. Subsequently, the maxillary central incisors of each subject were subjected to acid biopsies to assess the mineral composition in the enamel. Atomic absorption spectroscopy with an air/acetylene flame was used to analyze for Ca, Zn, and Mg. Graphite furnace atomic absorption spectroscopy was used to analyze for Cu. RESULTS: The concentrations of Ca and Mg in tooth enamel were comparable in the study and control groups. Zn enamel content was higher in patients with tooth wear, and Cu enamel content was lower in these patients compared with the control group. CONCLUSION: The differing Zn and Cu contents in tooth enamel might offer a reason for excessive tooth wear in these patients. However, the results require further, more detailed study.

Morphological and Functional Parameters in Patients with Tooth Wear before and after Treatment.

UNLABELLED: Advanced tooth wear often results in lost vertical dimension and impacts facial aesthetics. Complex restorative treatment can replace the lost tooth structure and improve functional occlusal and facial skeleton parameters. PURPOSE: The aim of the study is to assess changes in the morphological and functional occlusal parameters of the facial skeleton after prosthetic rehabilitation that increased lost occlusal vertical dimension. MATERIAL AND METHODOLOGY: 50 patients with advanced tooth wear were clinically examined, to assess the degree of wear. Each subject underwent cephalometric analysis, digital occlusal analysis, and electromyographic analysis, of the anterior temporalis, superficial masetter, anterior digastric, and the sternocleidomastoid muscles. Prosthodontic treatment was performed to restore the occlusal vertical dimension of each subject's occlusion, which was followed by repeating the pretreatment analyses. Pre and post treatment parameters were statistically compared. RESULTS: Pre-treatment cephalometric analysis showed that lost vertical dimension reduced anterior facial height and resulted in small angular skeletal parameters. Post treatment anterior facial height increased from the increased occlusal vertical dimension. The mean value of functional electrical activity during clenching post treatment, increased compared to pretreatment. CONCLUSION: Increasing the vertical dimension of occlusion improved facial aesthetics by positively affecting facial skeletal angles. The restored occlusal surface morphology changed the pre treatment flat broad occlusal contacts into more point contacts. The increased vertical dimension of occlusion after treatment also increased muscle activity levels over the pretreatment levels after three months period of adaptation.