Stress distribution of various designs of prostheses on short implants or standard implants in posterior maxilla: a three dimensional finite element analysis.

INTRODUCTION: Although many previous studies have reported on the high success rate of short dental implants, prosthetic design still plays an important role in the long-term implant treatment results. This study aims to evaluate stress distribution characteristics involved with various prosthetic designs on standard implants or short implants in the posterior maxilla. MATERIALS AND METHODS: Six finite element models were simulated representing the missing first and second maxillary molars. A standard implant (PW+ implant: 5.0×10 mm) and a short implant (PW+ implant: 5.0×6.0 mm) were applied under the various prosthetic conditions. The peri-implant maximum bone stress (V on mises stress) was evaluated when 200 N 30° oblique load was applied. A type III bone was approximated and complete osseous integration was assumed. RESULTS: Maximum Von mises stress was numerically located at the cortical bone around the implant neck in all models. In every standard implant model shows better stress distribution. Stress values and concentration area decreased in the cortical and cancellous bone when implants were splinted in both the standard and short implant models. With regard to the non-replacing second molar models found that the area of stress at the cortical bone around the first molar implant to be more intensive. Moreover, in the non-replacing second molar models, the stress also spread to the second pre-molar in both the standard and short implant models. CONCLUSIONS: The length of the implant and prosthetics designs both affect the stress value and distribution of stress to the cortical and cancellous bones around the implant.

Immunoprofile of the adenomatoid odontogenic tumor.

This study was focused on the immunohistochemical profile of the adenomatoid odontogenic tumor. A Pub/Medline search revealed a number of immunohistochemical studies including cytokeratin profiles, extracellular matrix proteins, Integrins, ameloblast-associated proteins resorption regulators (RANK, RANKL), p53, PCNA, MDM2 protein, cyclin D1, Ki-67, Bcl-2 metallothionein, metalloproteinases, D56 hepatocyte growth factor, c-met, DNA methyltransferase, podoplanin, TGF-ßI, Smad-2/3, Smad-I-5/-8, Smad 4, beta- catenin, calretinin, and clonality. Careful interpretation of the findings indicates that the adenomatoid odontogenic tumor may be more of a hamartomatous than neoplastic nature.

Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study.

Finite Element Analysis (FEA) has been used for prediction of stress and strain between dental implant components and bone in the implant design process. PURPOSE: Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. MATERIALS AND METHODS: Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. RESULTS: There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. CONCLUSIONS: Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. CLINICAL IMPLICATIONS: Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant should exhibit the same behavior to chewing force.

Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading.

PURPOSE: The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. METHODS: The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer's recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. RESULTS: Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, P<.05). After cyclic loading, removal torque in all groups decreased significantly (P<.05). Group C revealed significantly less removal torque than groups A and B (P<.005). Tensile force in all groups significantly increased after cyclic loading (P<.05), group A had significantly less tensile force than groups B and C (P<.005). CONCLUSIONS: Removal torque reduced significantly after cyclic loading. Before cyclic loading, tapered screws maintained more preload than did flat head screws. After cyclic loading, tapered and flat head screws maintained even amounts of preload. The tensile force that dislodged abutment from implant fixture increased immensely after cyclic loading.

Dental implants in patients with oral mucosal diseases - a systematic review.

To reveal dental implants survival rates in patients with oral mucosal diseases: oral lichen planus (OLP), Sjögren's syndrome (SjS), epidermolysis bullosa (EB) and systemic sclerosis (SSc). A systematic literature search using PubMed/Medline and Embase databases, utilising MeSH and search term combinations identified publications on clinical use implant-prosthetic rehabilitation in patients with OLP, SjS, EB, SSc reporting on study design, number, gender and age of patients, follow-up period exceeding 12 months, implant survival rate, published in English between 1980 and May 2015. After a mean observation period (mOP) of 53·9 months (standard deviation [SD] ±18·3), 191 implants in 57 patients with OLP showed a survival rate (SR) of 95·3% (SD ±21·2). For 17 patients with SjS (121 implants, mOP 48·6 ± 28·7 months), 28 patients with EB (165 implants, mOP 38·3 ± 16·9 months) and five patients with SSc (38 implants, mOP 38·3 ± 16·9 months), the respective SR was 91·7 ± 5·97% (SjS), 98·5 ± 2·7% (EB) and 97·4 ± 4·8% (SSc). Heterogeneity of data structure and quality of reporting outcomes did not allow for further comparative data analysis. For implant-prosthetic rehabilitation of patients suffering from OLP, SjS, EB and SSc, no evidence-based treatment guidelines are presently available. However, no strict contraindication for the placement of implants seems to be justified in patients with OLP, SjS, EB nor SSc. Implant survival rates are comparable to those of patients without oral mucosal diseases. Treatment guidelines as for dental implantation in patients with healthy oral mucosa should be followed.

Oral Candida species and betel quid-associated oral lesions in Padaung women of Northern Thailand.

Purpose of the present investigation was to study the association between the betel quid chewing (BQC) habits, the oral yeast flora and oral lesions in female Padaung of northern Thailand. Oral swabs were taken from the tongue and palate of 50 Padaung women with and 50 control individuals without BQC habit. The spectrum of oral Candida species in both groups was determined microbiologically. In addition, oral mucosal lesions were registered in both groups. Mean age of BQ chewers was 35.4 years, of non-chewers was 19.2 years. Candida parapsilosis was the most common Candida spp. isolated both in BQ chewers (46%) and non-chewers (44%). Candida albicans was revealed in 24% of BQ chewers and 18% of non-chewers. There was no significant difference in carriage of Candida spp. isolated between both groups. Forty-four per cent of BQ chewers revealed betel chewers mucosa, 10% showed leukoedema. Isolated populations such as the Padaung may reveal different patterns of candidal flora, in this case a predominance of Candida parapsilosis.

Oral manifestations in HIV-infected individuals from Thailand and Cambodia.

Oral manifestations were studied in 87 HIV-positive Thai adults (study 1), 45 HIV-positive children (study 2) and 101 HIV-positive (study 3). In study 1, 48% of patients had oral lesions; 23% had one and 13.8% two oral manifestations. Oral pseudomembranous candidiasis was found in 10.3%, erythematous candidiasis in 6.9%, and hairy leukoplakia (HL) in 11.5% of the patients. In study 2, 24.4% of children revealed one, 17.8% two and 6.6% three oral lesions; erythematous candidiasis was seen in 17.8%, and HL in 6.7% of the children. Fifteen patients (33.3%) received antiretroviral therapy. In study 3, pseudomembranous candidiasis was found in 52.5%, HL in 35.6% and necrotizing gingivo-periodontitis in 27.7%. Only 10% of patients were without oral lesions. The present three studies among HIV-infected Thai and Cambodians indicated a high prevalence of oral lesions, particularly variants of oral candidiasis such as pseudomembranous and erythematous candidiasis. Also, oral HL was a common finding, more so in patients with AIDS-associated diseases as represented by patients of study 3. Oral candidiasis and oral HL also seem to be quite prevalent in pediatric HIV-infected patients. In the absence of parameters indicating the degree of immunosuppression (CD4(+) cell counts and viral load) these oral lesions may be considered strong indicators of HIV-associated immunodeficiency.

Decline of oropharyngeal cancer in Chiangmai province, Thailand, between 1988 and 1999.

A decline of oropharyngeal cancer has already been predicted for Thailand since the early 1960s. To substantiate these predictions it was the purpose of this study to examine trends in the incidence of oropharyngeal cancer in the province of Chiangmai, (1988-1999). Data on cancer incidence were extracted from the annual reports of the Cancer Registry, Cancer Unit, Faculty of Medicine, Chiangmai University, Thailand (1992-1999) and an IARC report on cancer in Thailand (1988-1991). The age-standardized annual incidence per 100000 of oral cancer in males dropped from 3.6 (1988-1991) to 1.2 in 1999 (P for trend 0.0002) and in females from 2.6 (1988-1991) to 1.1 in 1999 (P for trend 0.007). Similar trends in males and females for cancer of the tongue, oropharynx and hypopharynx were seen. The age-standardized annual incidence for cancer of the lip, salivary gland and nasopharyngeal carcinoma remained unchanged. Changes of traditional oral habits such as betel quid chewing and smoking of traditional cigars seem to have resulted in a marked decrease of oral cancer in both men and women in the recent past.

Aspergillosis of the maxillary sinus as a complication of overfilling root canal material into the sinus: report of two cases.

Aspergillosis of the maxillary sinus is a relatively rare disease in nonimmunocompromised patients. In recent years a number of cases of aspergillosis of the maxillary sinus have been reported in association with overextension of root canals fillings with certain root canal cements. It has been suggested that zinc oxide-based root canal cements might promote the infection with the Aspergillus species. In particular Aspergillus fumigatus has been found to be associated with the maxillary sinus infection. Radiographically the unique appearance of a dense opacity foreign body reaction in the maxillary sinus was considered a characteristic finding in maxillary sinus aspergillosis. Because this association of overfilling of root canal cements and aspergillosis of the maxillary sinus is not too well known we report two cases of young healthy female patients with the characteristic findings, both radiographically and clinically. In both patients the first maxillary molar was involved. Patients were symptomless and the diagnosis was made accidently. However at surgical inspection both patients revealed aspergillomas, including the overextended root canal cement. The surgical procedure is described as are the microscopic findings in both cases showing the characteristic branching hyphae and conidophores typical of Aspergillus. Overextension into the maxillary sinus with root canal cements has to be avoided; material has to be removed from the sinus because otherwise aspergillosis infection may ensue.

Thai dental students' knowledge of the betel quid chewing habit in Thailand.

385 questionnaires submitted by volunteer Thai dental students on the betel quid chewing habit in Thailand were evaluated. Questions related to the composition of the betel quid, general and oral effects as well as sociological aspects. Only 62.6% considered the habit as typical for Thailand. Knowledge about the composition of the betel quid showed that 30% of the students were poorly informed. Only 58.4% thought slaked lime to be part of the quid. Similar results were obtained for some of the questions relating to physiological and oral effects and the percentage of "do not know" answers was about 30%. It was widely accepted that betel quid chewing is more common in the provinces (83.6%) and that it is a habit of older people (92.2%); particularly women (70.7%). 71.2% of the students did not know where to buy a betel quid. The decline of the habit was monitored by the fact that 96.1% of the students' parents did not indulge in chewing the betel quid compared to 38.7% of grandparents who did. 70% of the students were convinced that the habit will totally disappear. The knowledge of the betel quid chewing habit of Thai dental students indicated a number of deficits showing that these do not come in close contact with this habit anymore in their families or societies. Since elderly people still indulge in chewing betel quid, dental education still has to focus on oral and general effects and side-effects such as oral precancer, oral cancer and oral submucous fibrosis.