Prosthodontic treatment by implant-supported overdentures is effective for edentulous patients. In the past, cantilever length of bar attachments connected to implant bodies was often determined based on clinical experience and have not been well reported based on scientific basis. Hence, the objective of the present study is to establish the guidelines for ideal cantilever length in implant-supported overdentures with magnetic bar attachments using three-dimensional geometric analysis from the view point of biomechanics.
Six patients (12 samples) with implant-supported overdentures which were supported by four implants between the mental foramina on edentulous mandibles participated. Initially, we made silicone models that reproduced denture supporting tissues and bar attachments, and photographed these with certain specifications. Next, we gradually analyzed of occlusal loading for the overdenture, the bar attachment, and the implant in situation of loading at first molar by using them. After that, we examined about the loading force in case of capsizing and parting the bar attachment and overdenture by three-dimensional geometric analysis in simulation of extending the distance from the most distal point of the cantilever by 1 mm.
Consequently, it was suggested to become the more different loading distribution on each implants, the more the occlusal loading increased to the implant. Moreover, it was clearly that the more it extended the cantilever of bar attachment, the more loading distribution on each implants were significant difference. Especially, it was indicated that the vertical load about 2.7 times occlusal force for the most distal implant which supported bar attachment. Furthermore, extending the cantilever of bar attachment was unable to support occlusal force, more than 10 mm, without capsizing overdenture.
Cantilever is very effective in increasing the supporting ability to occlusal force, but it was necessary to require 10 mm at least to support occlusal force on the first molar only by barattachment with implants placed between mental foramens. So it is important that occlusal force at the molar should be supported by not only implants but also denture supporting tissues.

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The aim of this study was to evaluate the effects of pre-treatments, that is, surface treatments and surface modifications on the bonding of an experimental bracket made from Y-TZP ceramics with orthodontic adhesives. The bracket surfaces were treated with three types of surface treatment (GRD, ASB, MDP) and two types of surface modification (TBC, SLP). Then, the bracket was bonded by three types of orthodontic adhesives (MMA, CMPT, and RMGIC) to bovine enamel. Next, the bonding speciment was stored in water at 37ºC for 24 h, or put through thermal cycling 5,000 times. Shear bond tests were performed to measure the bond strengths, and after testing, the area of remnant cement on the fractured surface was measured using image analysis. The shear bond strength of MDP and SLP were statistically significantly higher than that of GRD. The rate of the remnant cement for MDP and SLP for all adhesives indicated high values of 60 percent or over, and were significantly higher than that of GRD and ASB. We concluded that the MDP for surface treatment and SLP for surface modification were suitable pre-treatments to enhance the bonding characteristics of a zirconia ceramics bracket.

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The purpose of this study was to investigate the development of lip function in children with cleft lip and palate and the influence of the labioplastic operation in infancy.
The subjects consisted of 23 unilateral cleft lip and palate children (mean age was 4.5 years old: Cleft group). The normal control group (mean age was 4.9 years old: N group) consisted of 25 children, who did not have any noticeable congenital anomalies or disorders. Their dental stage was primary dentition. Their mean age was 4.9 years old.
Lip closing pressure during eating was measured with a pressure sensor. Lip closing pressure (central and lateral), negative pressure and pressure duration during eating were measured. Differences between the Cleft and N groups were analyzed. Statistical significance was established at either p<0.05 or p<0.01.
The mean of central lip closing pressure in the Cleft group was slightly smaller than that in the N group, and the difference was significant. There were no differences in negative pressure for the cleft side, non-cleft side and N group. The pressure duration times during eating in the Cleft group were significantly longer than in the N group. In both groups, the pressure integral value during eating were the same(the mean workload would also be the same).
In the Cleft group, the central lip closing pressure was small, the pressure duration was long and pressure integral value was the same, in comparison to the N group.
Based on these results, we concluded that the children with cleft lip and palate compensated for less lip pressure with longer pressure duration during eating.

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Casting investments are used by mixing a powder and liquid, and there is a risk of fine powder inhalation causing respiratory disease. Previously, we investigated paste-paste type phosphate-bonded investment with oils. The objective of the present study was to produce paste-paste type phosphate-bonded investments with colloidal silica. Two pastes (PA and PB) were formed before the test. PA was an acidic mixture of cristobalite and magnesium dihydrogenphosphate solution, and PB was an alkaline mixture of MgO in colloidal silica solution. Five experimental investments (PB5, PB10, PB15, PB20, PB25) containing 5, 10, 15, 20, and 25 ml, respectively, of colloidal silica in PB were evaluated. Commercial phosphate-bonded investment was used as a control. PB5 took a long time to set (12 h or more), had no setting expansion, and its compressive strength was very small. Its thermal expansion and XRD analysis results were almost the same as those from the other experimental investments. The setting expansions of PB20 and PB25 were 0.40% and 0.62%, respectively, and they took approximately 16 min to set. These values were close to those of control. Full coverage cast crowns obtained from the experimental investments had a loose fit compared with the control. The gap with the crowns cast from PB20 was smaller than those of other experimental investments, and it showed no significant difference compared to that of the control. These results suggest that it is possible to produce pastepaste type investments using colloidal silica. This limited study suggests that the experimental investment with PB20 is suitable for clinical use.

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The purpose of this study was to investigate the relationship between the TMJ-ID and craniofacial morphology. Eighty-five female patients with bilateral disc displacement were selected as subjects from 163 orthodontic patients with signs and symptoms of TMD who underwent MRI examination before treatment. The subjects were divided into three groups: patients with bilateral disc displacement (DD), patients with unilateral TMJ-OA (UOA), and patients with bilateral TMJ-OA (BOA). The patients without disc displacement and TMJ-OA (N) were control subjects. Craniofacial morphology was analyzed on postero-anterior cephalograms. The Tukey-Kramer method was used for statistical comparisons among the four groups.
The following measurement items showed significant differences between the N group and the other three groups (Y-Me(DD: p<0.05, UOA and BOA: p<0.01), Mo-diff (BOA: p<0.05), ∠Hlf (DD, UOA and BOA: p<0.01), ∠Ocl (UOA: p<0.05). In the UOA, all the patients except one exhibited lateral shift of the Me point that progressed to the intraarticular pathologic side. In the DD and BOA groups, differing from the UOA, the rule did not apply in the direction of the mandibular shift.
These findings show that bilateral TMJ-ID is related to lateral shift of the mandible. Furthermore, craniofacial asymmetry in bilateral TMJ-ID was not a characteristic clinical sign of the UOA, a fact that was clear when looking at the DD and the BOA groups. Therefore, it was suggested that there was relativity between the bilateral TMJ-ID and craniofacial asymmetry.

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The purpose of this study was to investigate the influence of presurgical nasoalveolar molding(NAM)treatment on sucking in children with cleft lip and palate. A questionnaire survey regarding milk sucking before and after NAM treatment and after primary chiloplasty was performed involving 145 parents of children who underwent primary chiloplasty after NAM treatment performed by the Showa University Cleft Lip and Palate Team between April 2004 and January 2008. Responses were obtained from 125 parents (response rate: 86.2%). The results showed that sucking problems gradually deceased from birth, NAM treatment, and chiloplasty. The following is the discussion by cleft-type (UCLA, BCLA, UCLP, and BCLP).
1. More than 50% of children with UCLP and BCLP had sucking problems before NAM appliance placement. In contrast, more than 50% of children with UCLA and BCLA did not present with any sucking problems.
2. Sucking problems decreased in all cleft types except for BCLA after the initiation of NAM treatment.
3. No children with UCLA and BCLA showed sucking problems after chiloplasty. Children with UCLP who experienced sucking problems after chiloplasty compared to during NAM treatment comprised less than 1/3. Children with BCLP did not exhibit any change after chiloplasty.
4. The children with BCLP presented sucking problems before NAM treatment most frequently, and those with UCLP after NAM treatment.
The results showed that NAM treatment is effective for sucking. The tendency was in proportion to the degree of the cleft. Although sucking problems are significantly improved after NAM treatment in BCLP children, it was suggested that such problems often remain after chiloplasty if not improved after NAM treatment.

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Because of promotion of the 8020 campaign and public interest in oral health, the number of existing teeth is presenting an increasing tendency. On the other hand,recently implant overdentures are gain ing the popularity as one of the treatment options for edentulous patients. The purpose of this study is to reveal the mastication level of implant overdentures in edentulous patients relative to dentulous patients and to extract their problems.
Matching the gender and age, subjects in this study were divided by the dentulous group (10 older patients with multiple remaining teeth), IOD group (10 mandibular implant overdenture wearers) and CD group (10 both maxillary and mandibular complete denture wearers). In the above groups, we examined the repetitive saliva swallowing test, physical and social conditions, oral problems, Quality of Life evaluation, occlusal force evaluation using Dental prescale, masticatory efficiency determined by a simplified sieve method and masticatory score (the ratio of acceptable food).
As a result, in the CD group, the mastication score showed their satisfaction although the occlusal force and masticatory efficiency were low. In the IOD group, although the occlusal force and masticatory score were low, the same level of masticatory efficiency with the dentulous group was found. This result suggested that if types and hardness of food are carefully selected, mastication may occur smoothly in the IOD group. In the IOD group, some subjects concerned about esthetic aspects and felt unhappiness regarding their halitosis and other oral problems, suggesting necessity of multidisciplinary approaches in prosthodontic treatment.

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Objectives In the aging society of Japan, geriatric dental care for patients with systemic diseases and changes due to age is needed. The effects of systemic diseases, and the lifestyle and social background of elderly patients on the difficulty level of providing geriatric dental care are unknown.
Methods
We conducted a survey of 167 elderly individuals (65 years old or older) who visited the Department of Geriatric Dentistry, Showa University Dental Hospital, and asked them about the severity of systemic diseases, lifestyle, social background and medications in order to determine items affecting the difficulty level of providing geriatric dental treatment.
Results
Of the 167 subjects, 137 (82%) had multiple systemic diseases. Individuals with hypertension, heart disorder or cerebrovascular disorders accounted for 74%. These individuals were taking antihypertensives, anticoagulants or antiplatelet agents. The incidences of malignant tumors, visual impairment, auditory disorders and osteoporosis were also high.
Discussion
Multiple logistic regression analysis, showed that diabetes, heart disorder, hepatitis, dementia and ambulatory conditions in the severe level of systemic diseases, daily habits and social background of the elderly had strong effects on the evaluation of the difficulty level of providing geriatric dental treatment.

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The patient, a male aged 18 years and 7 months, complained of not being able to bite with his anterior teeth. He was diagnosed as having open bite with osteoarthritis of the temporomandibular joint (TMJ-OA). He did not have closed lock in the TMJ, but had pressure pain. This symptom was improved through use of a stabilization splint, and a stable mandibular position was obtained. Treatment involved use of edgewise orthodontic appliances and extract of the first premolars (upper and lower). It is necessary to consider the progressive mandibular retrusion from the progression of OA in orthodontic treatment of open bite with TMJ-OA.
In this case, good anterior and molar relation, and temporomandibular function were achieved through use of a treatment plan set after checking the mandibular position.

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[in Japanese]

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[in Japanese]

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