Intraoral hydrolysis of monofluorophosphate

The intraoral hydrolysis of monofluorophosphate (MFP) was compared in nine subjects with natural teeth and in nine edentulous subjects after a 1-min mouthrinse with a 100 ppm MFP solution. Analyses of total F and F- in whole saliva samples collected up to 15 min after the rinse suggested that apatite catalyzed breakdown of MFP mediated by dental enamel contributes significantly to the intraoral hydrolysis of MFP.     

The effect of pH,temperature and plaque thickness on the hydrolysis of monofluorophosphate in experimental dental plaque

Monofluorophosphate (MFP), an anti-caries agent commonly used in toothpaste, is known to be degraded to fluoride and orthophosphate by bacterial phosphatases in dental plaque. We have examined the effect of pH, temperature, plaque thickness and some ions on this process. Both natural plaque and artificial microcosm plaque incubated with purified MFP at pH 4-10 showed an optimum pH of approximately 8 for hydrolysis. Diffusion and concomitant hydrolysis were examined in an apparatus in which artificial plaque was held between rigid membranes separating two chambers. When MFP diffused through a plaque of 0.51-mm thickness over 4 h it was almost completely hydrolysed at pH 8, but hydrolysis on diffusion decreased as the pH deviated from 8. MFP in toothpaste extract showed a similar pH susceptibility to hydrolysis, according to the inherent pH of the toothpaste. Hydrolysis of MFP in the toothpaste was reduced by no more than 10% when compared with a matched-pH control, suggesting that other toothpaste ingredients had no major influence on hydrolysis. Transport was slower and hydrolysis at pH 6 more complete the thicker the plaque, but hydrolysis was not significantly slower at 23 degrees C than at 37 degrees C. The addition of various potential activating or inhibiting ions at 0.1 and 1.0 mmol/l had small and non-significant effects on hydrolysis. The results suggest that MFP toothpaste should be formulated and used to maximise enzymic hydrolysis of this complex anion, and that plaque pH control is probably the most important factor.     

Parenteral monofluorophosphate (MFP) is a more potent inducer of enamel fluorotic defects in neonatal hamster molars than sodium fluoride

Supra-optimal intake of sodium fluoride (NaF) during early childhood results in formation of irreversible enamel defects. Monofluorophosphate (MFP) was considered as less toxic than NaF but equally cariostatic. We compared the potency of MFP and NaF to induce pre-eruptive sub-ameloblastic cysts and post-eruptive white spots and pits in developing hamster enamel. Hamster pups were injected subcutaneously with either NaF or MFP in equimolar doses of either 9 mg or 18 mg F/kg body weight. At 9 mg F/kg, MFP induced more but smaller sub-ameloblastic cysts with a collective cyst volume twice as large as that induced by NaF. Eight days after F injection, all F-injected groups had formed 4–6 white spots per molar, with an additional 2 pits per molar in the low MFP group. Twenty-eight days after injection, most white spots had turned into pits (5–6 per molar) and only the high MFP group still contained 2 white spots per molar. We conclude that parenterally applied MFP is more potent in inducing enamel defects than NaF. Most white spots formed turn into pits by functional use of the dentition. The higher potency of parenteral MFP may be associated with sustained elevated F levels in the enamel organ by enzymatic hydrolysis of MFP by alkaline phosphatase activity.     

Fluoride retention in clean and plaque-covered demineralized enamel in vivo after application of monofluorophosphate

The retention of fluoride in clean and plaquc-covcred demineralized enamel in vivo was measured 1 wk after a single application of a MFP solution with low or high content of free fluoride. Demineralization of the enamel was induced in vivo during a 4-wk period prior to application of fluoride by applying orthodontic bands on a pair of premolars scheduled for extraction of orthodontic reasons. The band from one tooth of each pair was then removed and the tooth cleaned (clean enamel lesion). The band on the contralateral tooth (plaque-covered enamel lesion) was left in place. The MFP solutions were applied and the teeth extracted after one more week. The chemical form of fluorine in the lesions was analyzed by conventional acid etching of the enamel combined with KOH dissolution and by a nondestructive surface analysis using ESCA to detect intact monofluorophosphate ions. The ESCA measurements showed that MFP was only present in the clean enamel lesions, indicating complete hydrolysis by dental plaque. Alkali soluble fluoride could be extracted from both plaque-covered and clean enamel lesions. Conflicting results regarding the amount of fluoride uptake in the lesions were obtained with the acid etching and the ESCA technique. It was thus not clearly established whether plaque enhanced fluoride uptake in carious lesions after MFP application.     

Fluoride retention in clean and plaque-covered demineralized enamel in vivo after application of monofluorophosphate

The retention of fluoride in clean and plaque-covered demineralized enamel in vivo was measured 1 wk after a single application of a MFP solution with low or high content of free fluoride. Demineralization of the enamel was induced in vivo during a 4-wk period prior to application of fluoride by applying orthodontic bands on a pair of premolars scheduled for extraction of orthodontic reasons. The band from one tooth of each pair was then removed and the tooth cleaned (clean enamel lesion). The band on the contralateral tooth (plaque-covered enamel lesion) was left in place. The MFP solutions were applied and the teeth extracted after one more week. The chemical form of fluorine in the lesions was analyzed by conventional acid etching of the enamel combined with KOH dissolution and by a nondestructive surface analysis using ESCA to detect intact monofluorophosphate ions. The ESCA measurements showed that MFP was only present in the clean enamel lesions, indicating complete hydrolysis by dental plaque. Alkali soluble fluoride could be extracted from both plaque-covered and clean enamel lesions. Conflicting results regarding the amount of fluoride uptake in the lesions were obtained with the acid etching and the ESCA technique. It was thus not clearly established whether plaque enhanced fluoride uptake in carious lesions after MFP application.     

The decomposition of monofluorophosphate by enzymes in whole human saliva.

The hydrolysis of monofluorophosphate (MFP) in freshly-secreted whole saliva was studied over the pH range 4–10. Depending on the sample tested, two or three peaks of activity were found, but the point of maximum activity always fell between pH 7.2–8.6. Saliva controls heated at 100 °C showed no activity at any pH tested. There was a significant correlation between the ability of individual whole saliva samples to hydrolyse MFP and the ability to hydrolyse an ester phosphate, p-nitrophenyl phosphate; this supported the hypothesis that non-specific salivary phosphatases were responsible for the hydrolysis of MFP.     

Psychometric profiles and facial pain

The myofacial pain-dysfunction syndrome and atypical facial pain are the most prevalent chronic pain disorders of the facial region. Previously, the myofacial pain-dysfunction syndrome included all TMJ/masticatory muscle pain, jaw dysfunction, and joint clicking. We have segregated two major subgroups subsumed within this diagnostic classification and have assigned them to a myogenic facial pain (MFP) group and a TMJ internal derangement (TMJID) group. Significant age and personality differences were uncovered when these subpopulations were compared to subjects with atypical facial pain (AFP). Both MFP and TMJID groups are relatively homologous, involving younger persons than AFP subjects. Alternatively, when MFP, TMJID, and AFP subjects were compared for differences in MMPI psychometric scales, MFP and AFP subjects exhibited significantly higher scores, particularly for hypochondriasis, depression, and hysteria, than did TMJID subjects. It is concluded that subcategorization of myofascial pain-dysfunction patients into a myogenic pain group and a TMJ internal derangement group is justified on the basis of psychometric differences. Furthermore, psychopathologic factors are more significant among MFP and AFP subjects than among TMJID patients.     

In vitro hydrolysis of monofluorophosphate by dental plaque microorganisms

Enzymic hydrolysis of sodium monofluorophosphate by suspensions of dental microorganisms has been demonstrated at pH 5.1, pH 7.0, and pH 8.4, using a fluoride-selective electrode. The extracellular medium from viable Streptococcus mutans K1R cells contained low MFPase and paranitrophenyl phosphatase activity. It is hypothesized that the enzymes responsible for MFP hydrolysis by S. mutans K1R are intracellular, and that cell disruption is necessary for hydrolysis to be manifested; this question requires further study. In vitro MFPase activity was of a magnitude consistent with the hypothesis that it may significantly raise the fluoride ion concentration of plaque within the several minutes MFP would be in the mouth during toothbrushing.     

The inhibition of acid production in human saliva by monofluorophosphate.

Sodium monofluorophosphate (MFP) and NaF were compared for their ability to inhibit acid production in human saliva-glucose mixtures. Whole stimulated saliva was incubated at 37 °C with 2.5 per cent glucose in the presence of NaF (1.05 mmol/l) or MFP (initially 1.05 mmol/1 or neither (controls). Because MFP was gradually decomposed, releasing fluoride, further incubations were included in which increments of NaF were added to reproduce this increasing fluoride concentration. Acid production in the MFP incubations was less than in the controls and greater than in those containing equimolar NaF, but almost the same as in those in which added fluoride reproduced the release from MFP. This showed that the inhibition of acid production in the MFP incubations was due to the fluoride released and that the PO₃F^2? ion itself had little or no effect. The hydrolysis of MFP by salivary enzymes was greater at pH 7 than at pH 4. A direct effect on plaque microorganisms by MFP is an unlikely explanation for the cariostatic properties of MFP toothpastes.     

Prosthetic reconstruction after oncological surgery in the head and neck region

The aim of maxillofacial prosthetics is the treatment of patients with head and neck disease in a multidisciplinary way. Intraoral and facial defects are preferably reconstructed by surgical transplantation methods. Patient factors and oncologic factors determine the indication of prosthetic reconstructions. The treatment of patients with an intraoral or facial defect should be based on a close cooperation between maxillofacial prosthetist and MFP technician. The rehabilitation process and the specific role of each are described.     

Intra-oral air mercury released from dental amalgam

Intra-oral air was analyzed for mercury (Hg) vapor concentration in 46 subjects, 35 of whom had dental amalgam restorations. Measurements were made with a Jerome Hg detector both before and ten min after chewing stimulation. Subjects with dental amalgams had unstimulated Hg vapor concentrations that were nine times greater than basal levels in control subjects with no amalgams. Chewing stimulation in subjects with amalgams increased their Hg concentration six-fold over unstimulated Hg levels, or a 54-fold increase over levels observed in control subjects. Concentrations of Hg measured in intra-oral air larger than those reported in expired air were attributed to the rate and direction of air passage across amalgam surfaces. There were significant correlations between Hg vapor released into intra-oral air after chewing stimulation and the numbers and types of amalgam restorations. It is concluded that intraoral air is a reliable physiological indicator of Hg released from dental amalgam that may reflect a major source of chronic Hg exposure.     

Association between rhythmic masticatory muscle activity during sleep and masticatory myofascial pain: a polysomnographic study

AIMS: To test for an association between rhythmic masticatory muscle activity during sleep, as assessed according to polysomnographic criteria for sleep bruxism (RMMA-SB), and myofascial pain (MFP), as well as the chance of occurrence of MFP in patients with RMMA-SB. METHODS: Thirty MFP patients (diagnosed according to the Research Diagnostic Criteria for Temporomandibular Disorders) and 30 age- and gender-matched asymptomatic controls underwent a polysomnographic examination. Also, any self-reporting of daytime clenching (DC) was registered in 58 of these subjects. RESULTS: Most MFP patients reported mild or moderate pain (46.67% and 43.33%, respectively), and only 3 (10%) reported severe pain. Pain duration ranged from 2 to 120 months (mean 34.67 +/- 36.96 months). Significant associations were observed between RMMA-SB and MFP as well as between DC and MFP. CONCLUSIONS: (1) RMMA-SB is significantly associated with MFP; (2) although RMMA-SB represents a risk factor for MFP, this risk is low; and (3) DC probably constitutes a stronger risk factor for MFP than RMMA-SB.     

Fluoride in plaque fluid and saliva after NaF or MFP rinses

A micro-analytic method, capable of measuring the fluoride concentration in 5 nl of plaque fluid, was used to follow changes in fluoride concentration in saliva and plaque fluid at 6 single tooth-sites in 6 subjects for 180 min after a 0.048 M fluoride rinse as a NaF or MFP (sodium monoftuorophosphate) solution. The maximum fluoride concentrations in saliva after NaF was 13 × higher than with MFP. About 5% of the total amount of fluoride following the 20 ml NaF rinse was retained in the oral cavity. The corresponding figure following MFP was < 1%. The saliva/plaque fluid fluoride ratios for upper molars and lower incisors were significantly higher than for the upper incisors and lower molars. There was a tendency for a decline in the ratios with respect to time for all sites. To characterize the plaque fluid fluoride intra-oral single-site distribution and clearance, fluoride concentration versus time (AUC) was calculated from 10 to 60 min after a rinse. The NaF AUC followed the order: upper incisor, lower molar, upper molar and lower incisors reflecting a different exposure and clearance pattern due to the different access of the plaque to saliva. The MFP AUC values varied more, but were all significantly lower than the NaF AUC values. Analysis of plaque fluid fluoride curves at various sites revealed an exponential decline in most cases. With NaF, the baseline plaque fluid fluoride levels were not reached within 3 h. It is concluded that NaF solutions result in a significantly higher intra-oral fluoride exposure than MFP solutions. The fluoride distribution and clearance of fluoride from different sites in the oral cavity are linked to salivary access to these sites. These site-specific differences may have clinical consequences with regard to the dynamics of fluoride in the de- and remineralization processes.     

Myofascial face pain. Clinical characteristics of those with regional vs. widespread pain

BACKGROUND: The authors conducted a study to determine whether there are differences in salient clinical characteristics between patients who have both myofascial face pain, or MFP, and comorbid fibromyalgia, or FM, and patients who have MFP but not FM. METHODS: The authors enrolled in the study 162 female subjects who had histories of MFP. In physical examinations at the time of initial consultation, they recorded facial pain signs and symptoms. At the research interview follow-up (seven years post-consultation), participants were screened for a lifetime history of FM and other health problems. In addition, psychiatric interviewers conducted the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised, to assess each patient's history of depression and other psychiatric disorders. RESULTS: Of the 162 participants, 38 (23.5 percent) reported a history of FM. At the time of treatment for MFP, both the FM and non-FM groups had similar signs and symptoms of MFP. At the time of the research interview follow-up, participants with FM histories were significantly less likely than those without FM histories to report that they were free of MFP. On recall, those with FM histories reported experiencing more symptoms of MFP. Those with FM histories also were more likely to have had major depression and to report somatization symptoms. Finally, those who had FM more commonly had a history of facial pain's interference with social and occupational functioning and had more severe pain than did those without FM. CONCLUSIONS: Patients who have MFP and a history of widespread pain suggestive of FM are likely to have more persistent and debilitating MFP and to have higher rates of depression and somatization symptoms than those who have no history of widespread pain.     

The influence of plaque on reaction mechanism of MFP and NaF in vivo

A modified Intra-oral Cariogenicity Test was used to study the influence of plaque on the reaction mechanism of sodium monofluorophosphate (MFP) or sodium fluoride (NaF) in either sound or demineralized enamel in vivo. Volunteer students, wearing mouth appliances holding enamel blocks, rinsed their mouths with MFP or NaF solution (1,000 ppm F-) three times a day. The amount of loosely-bound and acquired fluoride was determined after an experimental period of five days in plaque-covered, demineralized (PCD); clean, demineralized (CD); plaque-covered, sound (PCS); and clean sound enamel (CS). While no measurable loosely-bound fluoride could be found after MFP treatment, NaF caused deposition of a significant amount of alkali-soluble fluoride in all experimental groups. After MFP rinses, fluoride concentration in the enamel was increased in the following order: CS, PCS, CD, and PCD. After NaF treatment, demineralized enamel exhibited a higher fluoride acquisition when compared with sound enamel. Plaque had a minor effect on F- acquisition. It is concluded that demineralization of enamel enhances F- uptake from both NaF and MFP solutions. In the presence of plaque, F- acquisition was additionally increased only after MFP rinses in vivo.     

Occupation as a potential contributing factor for temporomandibular disorders,bruxism, and cervical muscle pain: a controlled comparative study

The aim of the study was to compare the prevalence of cervical muscle pain (CMP) and myogenic temporomandibular disorders (MFP) among female dentists, high‐tech workers, and a group of subjects employed in other occupations; to investigate the associations among CMP, MFP, and bruxism in those groups; and to evaluate the influence of work‐related stress on MFP and CMP. Evaluation was based on clinical examinations of MFP and CMP and self‐reported questionnaires concerning pain and stress. The diagnosis of sleep bruxism was adapted using the validated diagnostic criteria of the American Academy of Sleep Medicine (International Classification of Sleep Disorders (ICSD‐2), 2005, Westchester, IL), whilst the diagnosis of awake bruxism was made on the basis of a questionnaire. The odds of a subject with MFP experiencing concurrent CMP or bruxism (sleep and/or awake) ranged from 2.603 to 3.077. These results suggest that high‐tech workers and dentists are at greater risk for developing temporomandibular disorders (TMDs) and CMP when compared with general occupation workers, as defined in this study. Furthermore, the associations shown here between TMDs and CMP highlight the importance of palpating neck musculature as part of any routine examination of TMD.     

Fluoride in plaque fluid, plaque, and saliva measured for 2 hours after a sodium fluoride monofluorophosphate rinse

Sodium monofluorophosphate (NaMFP) and sodium fluoride (NaF) are the two most common sources of fluoride used in currently marketed fluoride dentifrices. The purpose of this study was to investigate the effect of mouth rinses containing NaF or NaMFP on the concentrations of fluoride, or the MFP ion, in saliva, whole plaque, and plaque fluid. Twelve subjects abstained from tooth brushing for 48 h, fasted overnight, and then rinsed 1 min with 12 mmol/l (228 ppm [microg/g] F) NaF or NaMFP in the morning. Before the rinse and at 30, 60 and 120 min afterwards, upper and lower molar and premolar plaque samples and whole saliva samples were collected. Aliquots of plaque fluid and centrifuged saliva were obtained from these samples, and the whole plaque residue acid extracted. The F and MFP concentrations were then measured in these samples using ultramicro methods. For both rinses, a higher concentration of plaque fluid fluoride was found at lower molar sites while the reverse was true for the whole plaque fluoride. Furthermore, for both rinses, plaque fluid, whole plaque, but not salivary, fluoride concentrations were above baseline at 120 min. Following the NaMFP rinse, a substantial amount of unhydrolyzed MFP was found in plaque fluid and saliva. Although there was a very large range in these measurements, fluoride in plaque fluid (excluding fluoride in unhydrolyzed MFP) and whole plaque were significantly (p<0.05) greater after the NaF rinse at all time periods. In saliva, the NaF rinse produced a statistically significant greater salivary fluoride (excluding fluoride in unhydrolyzed MFP) only at 60 min. The lack of a clear correlation between these measurements and clinical studies suggest a novel mechanism may enhance the effectiveness of NaMFP dentifrices.     

A change of occlusal conditions after splint therapy for bruxers with and without pain in the masticatory muscles

Bruxism has been suggested as an initiating or perpetuating factor in a certain subgroup of temporomandibular disorders (TMD), however, the exact association between bruxism and TMD remains unclear. This study aimed to demonstrate the difference in responses between bruxism and a subgroup of TMD to a full-arch maxillary stabilization splint from the standpoint of an occlusal condition. This study was conducted to verify the null hypothesis that there were no differences between bruxer groups with and without myofascial pain (MFP) with respect to the changes in occlusal conditions after the use of a splint. Thirty bruxers with MFP and 30 without MFP participated. Occlusal conditions were examined before and after splint therapy, and occlusal changes following the use of a splint were compared between the two groups. The frequency of occlusal changes after splint therapy was significantly higher in the MFP bruxer group than the non-MFP bruxer group (p < 0.05) for the occlusal conditions investigated in the present study. However, no statistical differences were found with regard to each occlusal condition. This result may show the variety of splint effects and may demonstrate a heterogeneous aspect to bruxism and myofascial pain.     

Toothbrush abrasion of erosively altered enamel after intraoral exposure to saliva: an in situ study.

The aim of this in situ study was to test the effect of toothbrush abrasion on enamel previously exposed to a standardized artificial erosive agent. To generate moderate erosive lesions, slabs of the buccal surface of human premolars were immersed in a solution of citric acid for 3 min. Then they were attached to intraoral appliances and each one was exposed for 0 min (= toothbrushing immediately after intraoral exposure), 30 or 60 min to the oral milieu of 1 of 7 female subjects with a mean age of 22 years. Immediately thereafter the volunteers brushed the slabs for 30 s with toothpaste using their preferred brushing technique. For each test person the secretion rate of resting and paraffin-stimulated saliva, buffering capacity and pH were measured. The following mean losses of substance at the surface were registered: 0.258+/-0.141 microm (toothbrushing immediately after intraoral exposure), 0. 224+/-0.087 microm (toothbrushing after intraoral exposure of 30 min) and 0.195+/-0.075 microm (toothbrushing after intraoral exposure of 60 min). Toothbrush abrasion in situ was significantly lower after 60-min exposure to the oral environment than after 0-min (p<0.001). Also, the 30- and 60-min values were significantly different from each other (p<0.001). Multiple linear regression analyses revealed that in this model toothbrush abrasion was associated with the intraoral exposure to saliva (p = 0.026), the severity of the erosive attack (p<0.001) and the secretion rate of resting saliva (p = 0.029). If no other preventive measures are taken we suggest that individuals at risk for erosive tooth wear wait at least 1 h before brushing their teeth after consuming erosive foodstuffs or beverages.     

Speech adaptation: an aerodynamic study of adults with a childhood history of articulation defects

Three groups of subjects were studied; former lispers, persons with a history of /l/ or /r/ distortion, and normal subjects with no history of speech defects. All were normal-sounding adult speakers of English at the time of participation. Subjects were asked to wear an experimental removable dental prosthesis that provided 4 mm of thickness in the alveolar region. Measurements of oral air flow and intraoral pressure during the reading of sentence material were made, with the focus on the consonants /s/ and /t/. The sibilant /s/ was experienced as the greatest problem for speech adaptation, regardless of the type of former articulation defect. Both groups of subjects with a history of articulation defects showed evidence of slower adaptation and use of compensatory strategies for /s/. They tended as a group to have the same minimum airflow values for /s/ after 2 weeks of practice speaking with the prosthesis as after 1 day of practice. Aerodynamic calculation of the size of the constriction for /s/ also showed little or no change for most of the former speech-defective subjects. Evidence based on intraoral pressure indicated that particular effort was expended for /s/ even after 2 weeks of practice in speaking with the prosthesis.