The Employment of CBCT in Assessing Bone Loss around Dental Implants in Patients Receiving Mandibular Implant Supported over dentures

The aim of this study is to evaluate bone loss around implants after delivery of implant supported over dentures using CBCT.This study was performed to evaluate Postoperative bone level around mandibular dental implants using cone beamcomputed tomography (CBCT). The study was conducted on 10 completely edentulous patients that were rehabilitated bycomplete overdentures Patients retained mandibular overdentures by two implants installed in the canine region andretained locator attachments. Standard clinical and laboratory techniques were followed for implant insertion and dentureconstruction for all patients. The implants were divided in two groups. Implants bearing locator attachment with blue nyloninsert (Group I) and implants bearing locator attachment with transparent nylon insert (Group II). The twenty insertedimplants were left undisturbed for three months to achieve osseointegration. The mesial, distal, buccal and lingual bonelevel around the dental implants was evaluated, using the CBCT i-CAT scan with Blue sky Plan® software. Bone level wasobtained at six and twelve months after loading. The CBCT measurements of bone level revealed that there was bone lossaround all aspects of the inserted twenty dental implants

A two-short-implant-supported molar restoration in atrophic posterior maxilla: A finite element analysis

PURPOSE: The aim of this study was to investigate the stress distribution of 2-short implants (2SIs) installed in a severely atrophic maxillary molar site. MATERIALS AND METHODS: Three different diameters of internal connection implants were modeled: narrow platform (NP), regular platform (RP), and wide platform (WP). The maxillary first molars were restored with one implant or two short implants. Three 2SI models (NP-oblique, NP-vertical, and NP-horizontal) and four single implant models (RP and WP in a centered or cantilevered position) were used. Axial and oblique loadings were applied on the occlusal surface of the crown. The von Mises stress values were measured at the bone-implant, peri-implant bone, and implant/abutment complex. RESULTS: The highest stress distribution at the bone-implant interface and the peri-implant bone was noticed in the RP group, and the lowest stress distribution was observed in the 2SI groups. Cantilevered position showed unfavorable stress distribution with axial loading. 2SI types did not affect the stress distribution in oblique loading. The number and installation positions of the implant, rather than the bone level, influenced the stress distribution of 2SIs. The implant/abutment complex of WP presented the highest stress concentration while that of 2SIs showed the lowest stress concentration. CONCLUSION: 2SIs may be useful for achieving stable stress distribution on the surrounding bone and implant-abutment complex in the atrophic posterior maxilla.

Efeito do artefato de "beam hardening" na capacidade de identificação das alterações periodontais e peri-implantares / "Beam Hardening" artefact effect in identifying capacity of periodontal and peri-implant changes

O diagnóstico por imagem é um exame complementar importante para o diagnóstico e acompanhamento da doença periodontal e peri-implantar e atualmente a tomografia computadorizada de feixe cônico (TCFC) substitui o uso das tomografias convencionais odontológicas e da tomografia computadorizada médica. No entanto, artefatos ocorrem principalmente, próximos de estruturas de alta densidade como o metal, sendo que essa alteração pode interferir na interpretação das imagens e no diagnóstico. Sendo assim, o presente estudo tem como objetivo realizar uma revisão de literatura relacionada ao efeito do artefato de "beam hardening" na capacidade de identificação das alterações periodontais e peri-implantares. Conclui-se que a TCFC promove uma avaliação tridimensional de doença periodontal e da peri-implantite, mas na presença de artefatos metálicos pode haver uma limitação da qualidade da imagem do nível ósseo ao redor dos dentes e implantes.(AU)

Diagnostic imaging is an important complementary method for the diagnosis and follow up of periodontal disease and peri-implant and nowadays cone-beam computed tomography (CBCT) replaces the use of conventional dental CT scans and medical CT scan. However, artifacts occur mainly near high-density structures such as metal, and this change may interfere interpretation of the images and diagnosis. Therefore, this study aims to conduct a literature review on the effect of "beam hardening" artifact in identifying capacity of periodontal and peri-implant changes. We conclude that CBCT promote three-dimensional evaluation of periodontal disease and peri-implantitis, but presence of metal artifacts could be a limitation of the image quality of bone level around the teeth and implants.(AU)

Implant-supported overdentures with different bar designs: A retrospective evaluation after 5-19 years of clinical function

PURPOSE: This retrospective study evaluated the outcome of implant-retained overdentures (IODs) after 5-19 years of clinical function. MATERIALS AND METHODS: A retrospective analysis of patient files was performed referring to 27 patients who received 36 IODs with 3 different bar designs (group A=prefabricated round bars, n=7; group B=one-piece anterior milled bars, n=20; and group C=two bilaterally placed milled bars, n=9) in the mandible (n=24) and/or in the maxilla (n=12). The analysis focused on the survival and success rates (according to Kaplan-Meier) of the implants and prostheses. Technical complication rates for each type of restoration were analyzed and compared via one-way ANOVA and the Chi-squared test. The prevalence of peri-implantitis (radiographic bone loss > or =3.5 mm) was evaluated by digital analysis of panoramic radiographs taken post-operative (baseline) and after 5-19 years of clinical function (follow-up). RESULTS: The mean observational time was 7.3 years. The survival rates of the prostheses and implants were 100% and 97.7%, respectively. Technical complications occurred more frequently in group A (mean: 3.5 during observational time) than in the other two groups (B: 0.8; C: 1.0). However, this difference was not statistically significant (P=0.58). Peri-implantitis was diagnosed for 12.4% of the implants in 37% of the patients. CONCLUSION: Bar-retained IODs are an adequate treatment option for edentulous jaws. These restorations may exhibit high implant/prosthesis survival rates (>97%), and a limited incidence of technical complications after a mean observational period of >7 years. Nevertheless, peri-implantitis was identified as a frequent and serious biological complication for this type of reconstruction.

Effect of prosthetic designs and alveolar bone conditions on stress distribution in fixed partial dentures with pier abutments / 대한치과보철학회지

STATEMENT OF PROBLEM: Pier abutments act as a Class I fulcrum lever system when the teeth are incorporated in a fixed partial denture with rigid connectors. Therefore non-rigid connector incorporated into the fixed partial denture might reduce the stresses created by the leverage. PURPOSE: The purpose of this study was to evaluate, by means of finite element method, the effects of non-rigid connectors and supporting alveolar bone level on stress distribution for fixed partial dentures with pier abutments. MATERIAL AND METHODS: A 2-dimensional finite element model simulating a 5-unit metal ceramic fixed partial denture with a pier abutment with rigid or non-rigid designs, the connector was located at the distal region of the second premolar, was developed. In the model, the lower canine, second premolar, and second molar served as abutments. Four types of alveolar bone condition were employed. One was normal bone condition and others were supporting bone reduced 20% height at one abutment. Two different loading conditions, each 150 N on 1st premolar and 1st molar and 300N on 1st molar, were used. RESULTS: Two types of FPD were displaced apically. The amount of displacement decreased in an almost linear slope away from the loaded point. Non-rigid design tended to cause the higher stresses in supporting bone of premolar and molar abutments and the lower stresses in that of canine than rigid design. Alveolar bone loss increased the stresses in supporting bone of corresponding abutment. CONCLUSION: Careful evaluation of the retentive capacity of retainers and the periodontal condition of abutments may be required for the prosthetic design of fixed partial denture with a pier abutment.

Radiographic evaluation of marginal bone resorption around two types of external hex implants: preliminary study / 대한치과보철학회지

STATEMENT OF PROBLEM: Changes of the marginal bone around dental implants have significance not only for the functional maintenance but also for the esthetic success of the implant. It was proposed that bone-retention elements such as microthreads at the coronal part of implant might help maintain the marginal bone level. PURPOSE: This study was designed to evaluate the effect of microthread configuration within the marginal coronal portion of the implant fixture at the marginal bone changes after loading around two different external hex implants. MATERIAL AND METHODS: Twenty-four patients were included and randomly assigned to treatment with Branemark system implants (Group 1, rough-surfaced implants, n=20) and Oneplant system implants (Group 2, rough-surfaced neck with microthreads, n=20). Clinical and radiographic examinations were conducted at baseline (implant loading) and 1 year postloading. Data analysis was performed by the SAS statistical package version 9.1.3 (SAS Institute, Cary, NC, USA) and the final model was calculated by the MIXED procedure (three-level ANCOVA) for marginal bone change of each test group at baseline and 1 year follow-up. RESULTS: Comparing to baseline, significant differences were noted in marginal bone level changes for the 2 groups at 1 year follow-up (P<0.05). Group 1 had a mean crestal bone level changes of 0.83+/-0.31mm; Group 2 had a mean crestal bone level changes of 0.44+/-0.36mm. Rough-surfaced with microthreads implants showed significantly less marginal bone loss than rough surfaced neck without microthread implants. CONCLUSION: A rough surface with microthreads at the implant was beneficial design to maintain the marginal bone level against functional loading.

Marginal tissue response to different Implant neck design / 대한치과보철학회지

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers' protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.

Stability changes of immediately loaded and delayed loaded implants in edentulous mandible / 대한치과보철학회지

STATEMENT OF PROBLEM: It was reported high success rate of implant-supported fixed prostheses using with 5.6 implants on anterior mandible. Recently, immediate loading protocol was focused to overcome disadvantages of classic 2-stage delayed loading protocol. PURPOSE: This clinical study was to evaluate stability changes with time of immediately loaded and delayed loaded implants in edentulous mandible and to compare stability changes with time according to implantation sites. MATERIALS AND METHODS: Five or six implants were placed on anterior mandible depending on the arch shape. The immediately loading group was consisted of 8 patients received their prostheses within 24.48 hours after implantation. The delayed loading group was consisted of 8 patients received their definitive prostheses following classical prosthetic procedures after a healing period of 3 months. All patients were recalled every 6 months for check-up. The evaluations of radiographic examination, ISQ value measurement and recording of complication were done. To evaluate marginal bone level, intraoral periapical radiographs were taken with long cone paralleling technique. At every evaluation recall, all prostheses were removed and ISQ values were measured with Osstell(TM) on individual implants. RESULTS: 1. None of implants was failed. All implants showed stable marginal bone levels and ISQ values. 2. Marginal bone level changes with time showed statistically significant difference between immediately loading group and delayed loading group (P<0.001). 3. ISQ value changes with time did not show statistically significant difference between immediately loading group and delayed loading group (P=0.079). ISQ value decreased with time in both groups, however, all implants showed stable ISQ value at 30 months-recall evaluation. 4. Marginal bone level changes with time did not show statistically significant differences among implantation sites (P=0.604). 5. ISQ value changes with time showed statistically significant differences among implantation sites (P=0.047). ISQ values of most posterior implants decreased with time comparing to other implants. CONCLUSION: Although the marginal bone level of the terminal abutment didn't different with the other implants, ISQ value of the terminal abutment was lower than that of the other implants. Therefore, further clinical evaluation would be needed in this point of view.

An 1 year prospective comparative study evaluating the effect of microthread on the maintenance of marginal bone level / 대한치주과학회지

The success of dental implant therapy relies mainly upon the presence and maintenance of bone adjacent to implant. An 1-year prospective study was performed, upon the patients who were diagnosed as having chronic adult periodontitis, and had been treated with dental implant. The purpose of this study was to measure the radiographic bone level changes proximal to Astra Tech Single Tooth Implants (ATST, Astra Tech AB, MOlndal, Sweden) with microthread and Astra Tech TiOblast Implant (ATTB) without microthread supporting fixed partial prosthesis. Measurements were used to determine mean marginal bone loss during the first year of loading. 17 subjects with its partial prosthesis supported by 37 implants were followed up for an 1-year period. The marginal bone loss of implants was positively correlated with the retention factor, microthread (Microthread(TM)) in crestal area of ATST. The results were as follows. 1. The mean marginal bone loss of ATST was 0.226+/-0.395mm, while ATTB was 0.440+/-0.360mm. There was a statistically significant difference between ATST and ATTB (p0.05). 3. The mean bone loss of ATST was lower than that of ATTB at all sites according to bone quality. There was a statistically significant difference between ATST and ATTB at bone quality type III (p<0.05). In conclusion, the mean bone loss of ATST was smaller than that of ATTB. Therefore, the retention factor of crestal area, microthread (Microthread(TM)) was effective to maintenance of marginal bone level around fixture.