Subjective and objective assessments of short-term adverse effects induced by oral appliance therapy in obstructive sleep apnea: a preliminary study.

UNLABELLED: Abnormal occlusal sensation induced by wearing oral appliance (OA) was assessed in this study. MATERIALS AND METHODS: Twelve non-apneic healthy subjects with normal dental occlusion were used in this study. The 12 subjects slept wearing OAs at night. Occlusal sensation, biting force, occlusal contact area and muscle fatigue were evaluated every 15 minutes during 4 hours after removals of worn OAs when they waked up on the following morning. Same procedures were repeated on the same subjects after the sleep without OAs on the other day. RESULT: The differences of occlusal sensation was statistically significant up to 75 minutes after removal of OAs (p < 0.05). The difference of biting force was statistically significant immediately after removal of OAs (p < 0.05). There were statistically significant correlations (p < 0.05) between occlusal sensation and biting force in 9 of 12 subjects. Two of 12 subjects showed significant correlations (p < 0.05) between occlusal sensation and muscle fatigue. Only one of 12 subjects showed significant correlation (p < 0.05) between biting force and muscle fatigue. CONCLUSION: Abnormal occlusal sensation is probably elicited by non-physiological displacement of TMJs, nonphysiological extension of the chewing muscles and/or continuous compression toward the periodontal membranes by using OAs for hours at night.

Properties of human dentin surface after ArF excimer laser irradiation.

Recently, improvement of the properties of dentin surface using dental lasers to increase bonding strength has been anticipated in the field of adhesive dentistry. The objective of this study was to investigate changes in the surface properties of human dentin after ArF excimer laser irradiation at different irradiation times, pulse repetition rates and energy densities. The SEM images of the irradiated surfaces were observed, and the contact angle and the roughness of the irradiated surface were measured. As a result, SEM demonstrated that the dentin surface became irregular following ArF excimer laser irradiation. When the energy density increased, the irregularity became more minute and dentinal tubules were more easily identified. By contrast, such changes were not observed when the irradiation time and pulse repetition rate were changed. Moreover, as energy densities increased, the contact angle tended to decrease and the surface roughness tended to increase. These results suggested that the area of the irradiated surface and wettability increased after irradiation with the ArF excimer laser. Consequently, irradiation with ArF excimer lasers could improve the surface properties and be potentially useful for adhesive dentistry.

Tensile strength of dentin after bleaching treatment.

The mechanical properties of dentin are changed after bleaching, although the effects of the bleaching conditions on the tensile strength of dentin have not been determined. In the current study, a tensile test of bovine dentin was conducted after bleaching and the effects of the bleaching conditions were investigated, including the number of bleaching times, the location where the bleaching agent was applied, and the kind of illumination. The weight of organic content in dentin before and after application of the agent was also measured. The results showed that the tensile strengths did not change after three times office bleaching procedure, and the location where the bleaching agent was applied, the kind of bleaching agent and the kind of illumination did not have influence on the tensile strength. On the other hand, organic component in dentin significantly decreased after application of the agent (p<0.05). Since the bleaching agent would potentially affect tensile strength with deterioration of collagen matrix, the frequency of bleaching treatment should be minimized in clinical use.

Overweight patients with severe sleep apnea experience deeper oxygen desaturation at apneic events.

We investigated differences in the depth of hypoxia produced by apneic events of the same duration (30 seconds) amongst patients with different degrees of OSAS according to their AIs (apnea indices). The relationship between apnea duration (seconds) and fall in oxygen saturation (%) was evaluated by means of a linear regression analysis. The fall induced by a 30-second apnea event was designated as the "oxygen desaturation value 30" (ODV30). We analyzed the polysomnographic recordings of 122 OSAS patients who showed significant correlations (p<0.01) between apnea duration and subsequent fall in oxygen saturation and calculated their respective ODV30. We evaluated the influence of AI and BMI on ODV30 by multi-comparison and found out that standardized partial regression coefficients of BMI and AI were 0.578 and 0.148, respectively (multi-regression analysis, SPSS). BMI was proved to be more influential on ODV30 than AI was. On the other hand, the ODV30 of mild, moderate and severe OSAS patients was 8.84 +/- 2.62% (Mean +/- S.D.), 8.25 +/- 2.45% and 10.59 +/- 3.32%, respectively. Our study shows that fall in oxygen saturation is particularly extensive in severe OSAS patients and that fall in oxygen saturation is deepened as obesity increases. We think ODV30 is a useful variable for evaluating OSAS.

Effect of polymorphism of SiO2 addition on mechanical properties of Feldspathic porcelains.

The present study aimed to investigate the effects of SiO2 polymorphism on the mechanical properties of feldspathic porcelains. Seven kinds of experimental feldspathic porcelains were prepared using chemical reagents; three types of low-fusing feldspathic glasses and four types of two-phase porcelains by adding 10 or 20 mass% of fused silica (T-F) or cristobalite (T-C). Flexural strength and fracture toughness of these porcelains were evaluated. Flexural strengths of two-phase porcelains did not show any significant increase when compared with those of single-phase glasses. On the other hand, fracture toughnesses of porcelains with cristobalite showed a significant increase when compared with those of single-phase glasses. Circumferential cracks were observed in the porcelains with cristobalite. These results suggested that cristobalite could strengthen fracture toughness of feldspathic porcelains, but not flexural strength.

Effects of a small electric current on sterilization of a dental unit water line.

In the present study, water was circulated in a simulated dental unit water line with electrifying a small current. The morphology of the biofilm developed on inner surface of the water line and the number of heterotrophic bacteria were investigated to elucidate the effect of a low level electric current on the biofilms formation associated with bacteria reproduction. Destruction and malconformation of biofilms by electrification was observed using SEM, in addition to deformation and hypertrophy of the bacteria. By naked eye observation, small pieces, which were possibly exfoliated biofilms, were detected in electrified water. While an adherent, yellow gel was demonstrated on the inner surface of the water line without electrification. With electrification, the number of bacteria decreased during the first week, however the bacteria increased gradually after that. The number of bacteria without electrification was consistently greater than that with electrification and the difference was statistically significant (P<0.05). The predominant bacteria were identified as Sphingomonas paucimobilis. The excess chlorine levels decreased to a minimum value within one week. The small current appeared to have effects on biofilm formation of heterotrophic bacteria that resulted in enhanced chlorine sterilization of dental unit water. Thus, electrification has considerable potential for the extermination of bacterial biofilms in dental unit water lines.

Effects of exposure to 4-META/MMA-TBB resin on pulp cell viability.

Adhesive restorative systems have expanded the range of possibilities for direct pulp-capping technique, with evidences of clinical success in vital pulp therapy. However, quite few studies have described the direct responses of pulp cells following the application of resinous materials to pulp exposure. To address this issue, effects of exposure to an adhesive resin, 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane (4-META/MMA-TBB) resin on cellular activity were investigated in an established rat dental pulp cell line (RPC-C2A). RPC-C2A cells were cultured on normal plastic plates or the disks prepared from 4-META/MMA-TBB resin (Super Bond C&B) in a-MEM containing 10% FBS. After 3, 7 and 14 days, DNA content and alkaline phosphatase (ALP) activity were measured. Total RNA in each group was extracted and RT-PCR analysis was performed. Moreover, the live cell ratio was also evaluated by cytotoxicity assay after treatment with various concentrations of 4-META/MMA-TBB. At day 3, 7 and 14, amount of DNA and ALP activity of the cells on normal plastic plates and the one on the 4-META/MMA-TBB were comparable. Cells of both groups expressed mRNA of type I collagen (Coll), ALP, osteopontin (OPN), osteocalcin (OC), and bone morphogenetic protein (BMP-2). Furthermore, 4-META/MMA-TBB (10(-1)% or less) did not influence dead cell ratio in the confluent state. According to the results of these in vitro studies, exposure to this resinous material would not induce cytotoxic response in the pulp cells.

Comparison of tongue volume/oral cavity volume ratio between obstructive sleep apnea syndrome patients and normal adults using magnetic resonance imaging.

Obstructive sleep apnea syndrome (OSAS) is a group of disorders in which breathing stops intermittently and repeatedly for 10 seconds or more during sleep. The causal site of the disorders is thought to be in the upper airway above the glottis. In order to understand the three-dimensional features of the oral and peripharyngeal structures involved in the disorders, we calculated the tongue volume/oral cavity volume ratio (TV/OCV ratio) in the oral cavity using magnetic resonance imaging (MRI) for both OSAS patients and normal controls. The study subjects comprised 20 male patients with OSAS (apnea-hypopnea index [AHI] > or = 5.0, with a diagnosis of OSAS) and 20 normal male adults (AHI<5.0, with no history of OSAS) as the controls. We performed MRI to acquire T1- and T2-weighted images. We estimated tongue volumes on the basis of the cross-sectional area of each image, then using the tongue volume data, we calculated TV/OCV ratios. In the normal control group, mean (+/- SD) body mass index (BMI) was 21.68 +/- 1.73 and the mean TV/OCV ratio was 86.98 +/- 3.16%, whereas these values were 25.0 +/- 15.94 and 90.56 +/- 2.15%, respectively, in the OSAS patient group. The TV/OCV ratio of the OSAS patient group was significantly higher than that of the normal control group (p<0.01).

Effects of laser irradiation on tensile strength of bovine dentin.

OBJECTIVE: The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties. BACKGROUND DATA: Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues. MATERIALS AND METHODS: Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy. RESULTS: The tensile strengths of the lased dentin and the control group for the Er:YAG, CO2, and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation. CONCLUSION: Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.

Study of finite element modeling from CT images.

The use of finite element analysis is becoming more widespread with rapid advancements in computer technology. However, the field of dentistry is not enjoying the spillover benefits of the expanded use of this design simulation and analysis tool. Finite element modeling requires measurement of the object. However, as the living body is morphologically very complex, this requires a great deal of both time and skill using CAD applications, thus preventing its widespread adoption in the dental field. Although there have been reports of finite element modeling from CT images, these methods require skilled programmers for software development--which is another factor that prevents its widespread adoption in dentistry. Therefore, establishing a finite element modeling method that is both accurate and practical will be of great benefit in clinical dentistry. In the present study, a method using computer tomography and existing software was examined for finite element model construction based on computer tomography images. The results suggested that the method developed here is feasible and practical for clinical use.

[Educative effect of feedback after medical interview in objective structured clinical examination].

OBJECTIVE: Objective Structured Clinical Examination (OSCE) is widely used to assess the core competency of dental residents. However, the educative effect of feedback in OSCE has not been fully examined. Therefore, we investigated the educative effect of formative feedback in a medical interview station. METHODS: The subjects were 51 residents in the clinical training course of our dental hospital. After completing the medical interview station, residents were individually given formative feedback by evaluators and standardized patients. Two months later, residents were asked to fill in a questionnaire about the contents of feedback and self-rating mental strain level during OSCE. Videotaped performance and feedback were reviewed by investigators to check the answers to the questionnaire. RESULTS: Evaluators provided an average of 3.1 feedback items, and standardized patients provided an average of 1.6 feedback items for each resident. However, each resident remembered an average of 1.3 feedback items from evaluators and 0.9 from standardized patients. The lower the score of residents in the medical interview station, the more feedback items were given to residents. A significant negative correlation was found between the score of evaluators and self-rating mental strain level (Spearman rho = -0.326, p = 0.019). CONCLUSION: For effective feedback, evaluators or standardized patients should focus on 2 to 3 items of essential points in OSCE. Repetition of feedback using videotaped performance may be useful to improve communication skills for medical interview.

Interfacial gaps following ceramic inlay cementation vs direct composites.

This study compared the interfacial integrity of Class II ceramic inlay restorations and direct resin composite restorations. The influence of a flowable resin composite liner was also evaluated. Class II DO cavities were prepared in 40 recently extracted mandibular molars and assigned to four treatment groups. Group A: direct composite restoration; Group B: Cerec inlays fabricated and cemented with a resin cement; Group C: adhesive lining with a flowable resin composite used prior to resin composite restoration; Group D: lining with a flowable resin composite prior to cementation of Cerec inlays. After finishing, polishing and thermocycling (4 degrees C and 60 degrees C x 500), the samples were cross-sectioned in a mesio-distal direction along the center of the fillings or inlays. The cross-sectioned surface was polished, and the adhesive interfaces between resin and enamel or dentin were observed under a scanning laser measurement microscope. Ceramic inlay restorations showed no interfacial gaps in enamel, but direct resin composite restorations showed a significantly higher incidence of gaps at the interface or cracks in the interfacial enamel (p=0.0002). No differences were found in the resin-dentin interfaces for both the inlay and direct resin composite restorations. The use of a flowable resin composite as an adhesive liner produced a significantly greater gap-free resin-dentin interface in Cerec inlay and direct resin composite restorations (p=0.0233 & 0.0009), but it did not reduce gap formation at the resin-enamel interface.

Cephalometric evaluation of craniofacial and upper airway structures in Japanese patients with obstructive sleep apnea.

In order to investigate the morphological characteristics of Japanese patients with obstructive sleep apnea (OSA) and basis for selection of an oral appliance (OA) therapy, the craniofacial skeleton, soft tissue and upper airway were analyzed on lateral cephalograms from 103 patients with OSA and 98 control subjects. At first, the 103 OSA patients were divided into two groups according to their body mass index (BMI). The results were the following: Micrognathia was a major risk factor of Japanese OSA patients instead of obesity; the narrowing in the hypopharynx was observed due to the inferior-located hyoid bone, especially in the obese group, an enlarged tongue and sticking of fatty-tissue to upper airway wall were observed in addition. Secondly, the 103 OSA patients were treated by OA, and were classified according to the reduction ratio of AHI (rAHI) again. The results suggested that the patients group which showed rAHI > or = 50% had a balanced relationship between the maxilla and mandible. These findings proved that the morphological characteristics specific to Japanese patients with OSA and patients who were allowed to accept the OA therapy were exist.

Effects of chloramines and sodium hypochlorite on carious dentin.

In chemo-mechanical caries removal procedures, chloramines are typically used for chemical softening of carious dentin. However, the specific effect of chloramines to be compared to sodium hypochlorite has not been sufficiently clarified. In present study, the effect of chloramines used in the Carisolv-system on carious dentin mechanical properties and morphology were investigated, using Vickers hardness test and scanning electron microscopy (SEM). Sections of permanent teeth with dentin caries were treated with chloramines, prepared by mixing amino acids (glutamic acid, lysine, and leucine) with sodium hypochlorite or with sodium hypochlorite alone or with purified water. There was a tendency that the application of the sodium hypochlorite solution softened the sound dentin and/or inner layer of carious dentin more than the application of the chloramines solution did. In SEM observations, the application of chloramines resulted in opening dentinal tubules in the outer layer of carious dentin: Occluded dentinal tubules were seen after sodium hypochlorite application. There is a possibility that the amino acids in the Carisolv-system decrease the aggressive effect of sodium hypochlorite on sound dentin and/or inner layer of carious dentin and also would enhance the disrupting effect on degenerated collagen in carious dentin outer layer.

Evaluation of an articulated measuring apparatus for use in the oral cavity.

The aim of this study was to evaluate the trial Teaching Robot for the development of a contact-type measuring apparatus for using directly in the oral cavity. A standard model was used to mimic the dentition by placing an arrangement of three bearing balls. The diameters of the balls were measured. A practical dentition model was used. The coordinates were measured on the top of the buccal cusp of the right and left first premolars and the distal contact points of the right and left first molars and the mesial contact point of the right incisor. The arch width and length were calculated. The diameters of the bearing balls and the widths and lengths of the dental arches were not significantly different from the results of the XYZAX G-800D. Therefore, we suggest that the trial Teaching Robot has superior efficiency for measurements in oral cavity.

[A study of oral status of adults who received regular checkups and professional care].

The purpose of this study was to investigate the effect of regular professional care on oral health status. We examined the oral health status of 255 adults (76 males, 179 females; 61.8 +/- 7.8 yrs) who received professional dental care at the Dental Hospital of Tokyo Medical and Dental University at least once a year. The oral health care included checkups and prevention (oral health education, scaling, polishing, topical application of fluoride). We compared the oral health status of adults who received regular professional care with the status of subjects of similar age reported in national and Tokyo surveys of dental diseases in 1999. The following results were obtained. 1. The number of teeth present among adults who received regular oral health care was greater than that reported in the national and Tokyo surveys of dental diseases in 1999. 2. The number of untreated decayed teeth among adults who received regular oral health care was smaller than that reported in the national and Tokyo surveys of dental diseases in 1999. The results show that the oral health status of adults who received regular oral health care was better than the oral health condition of those reported in the national and Tokyo surveys of dental diseases in 1999. Therefore, it is suggested that regular professional care by a dentist or dental hygienist will assist in achieving the objective of the 8020 movement (20 healthy teeth at age 80).

[Home care workers' oral health awareness and practice for disabled elderly].

The purpose of this study was to investigate the level of oral health awareness, and to explore the needs for home care workers to provide oral health care for disabled elderly. We conducted a questionnaire survey at two home-help service centers and a social welfare council. Subjects for this investigation were 63 home care workers. The results were as follows: 1. Ninety-six percent of home care workers thought it was necessary to provide oral health care for disabled elderly, but only 11 percent of them put oral care into practice on a daily basis. 2. From the results of a cause and effect diagram, necessities of oral care were summarized as six major causes: 1) Disabled elderly are often unable to brush their teeth, 2) The oral hygiene level may affect physical condition, 3) Disabled elderly should be protected from oral diseases, 4) Disabled elderly should have their mouths kept clean, 5) Eating and swallowing may become increasingly difficult, 6) Disabled elderly should take in adequate nutrition. 3. Sixty-eight percent of home care workers took part in a training course of nursing care including oral care. 4. Home care workers, dentists, dental hygienists, and nurses taught oral health care to home care workers. 5. From the results of a cause and effect diagram, there were three major items that home care workers want to know: 1) denture management, 2) the routine of oral care, 3) infection control. 6. Home care workers recognized that oral care should be provided by family members of disabled elderly or home care workers.