Stress Distribution in Bone and Implants in Mandibular 6-Implant-Supported Cantilevered Fixed Prosthesis: A 3D Finite Element Study.

PURPOSE: The purpose of the study was to evaluate by a 3-dimensional finite element analysis the load transmission to periimplant bone by a framework supported by 6 implants placed in an edentulous mandible and to compare the stress distribution for varying cantilever lengths. METHODOLOGY: A computerized model of the anterior segment of a mandible with a 6-implant-supported bridge was created in software. The length of the cantilever segment was considered as 10, 15, and 20 mm. A 150 N load was applied to the terminal point of the cantilever segment, and Von Mises stresses were analyzed along implants, framework, and bone. RESULTS: When the cantilever length was increased from 10 to 20 mm, the stress increased 79.66% in the framework, 68.16% in implants, and 59.96% and 52.81% in cortical and cancellous bones, respectively. CONCLUSION: The greatest amount of stress was seen around the distal-most region of the distal-most implant. The framework absorbed the maximum amount of stresses followed by the implants, cortical bone, and cancellous bone. Extension of the cantilever beyond 15 mm could lead to greater stress in the lingual cortical plate, which could compromise the integrity of the implants.

A Clinical Study Evaluating Changes in the Microbial Flora Around Dental Implants During Various Stages of Implant Restoration.

PURPOSE: This study evaluated the microbial colonization of dental implants in healthy patients before placing the implants and during the various stages of implant treatment. MATERIALS AND METHODS: Saliva (in completely edentulous patients) and gingival crevicular fluid samples (in partially edentulous patients) were collected from patients and analyzed to estimate the growth of microorganisms after culture. Samples were collected during 10 phases of implant placement and prosthesis insertion. Sixty dental implants, 18 of NobelReplace Select (Nobel Biocare) and 42 of GSIII/TSIII (Osstem), were evaluated. The microbial titer was estimated in colony-forming units (CFU) per milliliter. The percentage distribution of the organisms during the various phases was noted and the average was compared. RESULTS: Most prevalent microorganism found was gram-positive Streptococci (3.59 × 10 CFU/mL). The titer of Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, and Pseudomonas being 0.42 × 10 CFU/ml, 0.15 × 10 CFU/mL, 0.09 × 10 CFU/mL, and 0.03 × 10 CFU/mL, respectively. The titer of these organisms noted during the experimental phase was low. A similarity was observed in the maximum colony-forming unit per milliliter between baseline and completion of implant therapy indicating establishment of equilibrium. CONCLUSION: Regular microbial evaluation along with clinical and radiographic monitoring could help in recognizing the potential for periimplantitis and in prevention of the same.

Influence of platform switching on periimplant bone loss: a systematic review and meta-analysis.

PURPOSE: This meta-analysis aims to systematically review and draw a comparison between conventional implant designs and "platform-switched" implants in terms of crestal bone loss. MATERIALS AND METHODS: Electronic (PubMed) and hand searches were conducted. Literature, clinical studies, and case reports pertaining to reduction of crestal bone loss and obtaining better esthetic outcome by platform switching were reviewed till October 2011. Controlled trials comparing marginal bone-level changes around platform-switched and platform-matched implants were selected. For the assessment of accuracy, meta-analysis was performed. RESULTS: The marginal bone loss around platform-switched implants was significantly lesser than platform-matched implants (mean difference [MD]: -0.34; 95% confidence interval [CI]: -0.37 to -0.30; P < 0.00001). CONCLUSIONS: According to this review and meta-analysis, platform switching seems to preserve periimplant bone and soft tissue levels. However, long-term clinical studies on the proper diameter of abutment without deformation and the effective degree of platform switching in terms of the bone resorption are still awaited.

A correlation between bone (B), insertion torque (IT), and implant stability (S): BITS score.

STATEMENT OF PROBLEM: Although criteria for assessing bone quality have been reported, an overall score that correlates bone quality with the primary stability and secondary stability of implants is not yet available. PURPOSE: The purpose of this article was to propose a scoring index that will establish a correlation among the bone density values from computed tomography, maximum insertion torque values, and resonance frequency analysis in different phases of implant treatment. MATERIAL AND METHODS: In this study, 60 implant sites were evaluated to assess bone density (Hounsfield units), insertion torque values (Ncm), and primary stability and secondary stability (implant stability quotient values obtained by using resonance frequency analysis). On the basis of computed tomography data, the bone was classified as D1 to D4. The insertion torque was noted and classified into 2 groups, A and B. The implant stability quotient values obtained from resonance frequency analysis depicting primary stability and secondary stability were classified into 5 groups. The primary score noted was a result of the values obtained for the 3 parameters at the time of implant placement. The secondary score was obtained by considering the values of the bone density and resonance frequency analysis recorded at different time intervals. RESULTS: Bone densities of D2, D3, and D4 were noted, dividing the bone type into 3 groups. The maximum torque noted in the study was 40 Ncm. The difference between various insertion torque values and bone types was found to be statistically nonsignificant. Higher mean implant stability quotient values were obtained for primary and secondary stability for the D2 bone than for D3 and D4 bone. When analyzed according to the time of insertion, the mean values increased at second stage surgery in all bone types. The difference in mean values among all bone types was found to be statistically significant (P<.001). A comparison of primary and secondary implant stability quotient values in all bone types did not find any statistical significance (P=.780). A score was recorded at the time of implant placement and at the time of second stage surgery, and the prosthetic treatment was planned accordingly. CONCLUSIONS: The score highlights the importance of considering the association of bone quality, insertion torque values, and stability as denoted by implant stability quotient throughout treatment. Based on the variation in the score noted at recall visits, alterations in the treatment plan can be made with respect to the healing period and prosthetic design.

Efficacy of antibacterial sealing gel and O-ring to prevent microleakage at the implant abutment interface: an in vitro study.

Gaps and hollow spaces at the implant abutment interface will act as a bacterial reservoir that may cause peri-implantitis. Hence, the sealing ability of O-ring (in addition to polysiloxane) and GapSeal (an antibacterial sealing gel) was evaluated. A total of 45 identical implant systems (ADIN Dental Implant Systems) were divided into 3 groups of 15 implants each: an unsealed group, a group sealed with O-rings, and a group sealed with GapSeal gel. The implant and abutment were gamma sterilized after assembly. Two implants from each group were randomly incubated in sterile brain heart infusion (BHI) broth tubes and checked for sterility. The remaining 13 implants were incubated in BHI broth inoculated with Enterococcus and incubated for 5 days. They were then removed from the tubes, dried aseptically, placed in 2% sodium hypochlorite solution for 30 minutes, and washed with sterile saline for 5 minutes. Next, the assembly was dried aseptically and put in sterile BHI broth tubes and incubated for 24 hours to check surface sterility. Keeping 2 implants as controls from each group, the remaining 11 implants were dismantled group-wise and placed in liquid BHI broth; the test tubes were then shaken thoroughly so that the broth would come in contact with all implant surfaces. The solution from this tube was poured on pre-prepared sterile agar plates and incubated for 24 hours. The colonies formed on the agar plate were then counted using a digital colony counter. The data thus obtained were subjected to statistical analysis by Kruskal-Wallis analysis of variance and Mann-Whitney U test. It was concluded that though microbial growth is seen in all the 3 groups, the least growth was seen in the GapSeal group followed by the O-ring group.

Restricted mouth opening and its definitive management: A literature review.

PURPOSE: This review was intended to discuss the various possible modifications suggested in the literature for prosthetic steps and surgical corrective procedures in nonresponding or complicated cases during rehabilitation of patients with restricted mouth opening. MATERIAL AND METHODS:: Medline, PubMed, and Google were searched electronically for articles using keywords: microstomia and treatment options for restricted mouth opening. The various articles on prosthodontic rehabilitation in microstomia were segregated. From these, various modifications in the prosthetic steps were reviewed. RESULTS:: Oral hygiene maintenance is difficult for patient either due to limited access or due to associated lack of manual dexterity, so dental decay and periodontal problems are more extensive in such patients; hence, tooth loss is a common finding. All prosthetic procedures require wide mouth opening to carry out various steps, starting from tray placement during impression making to the final prosthesis insertion, especially removable prosthesis. Various prosthetic modifications given by authors are included in this review for each step in prosthodontic management. A total of eight stock tray designs, 12 custom tray designs, and 17 removable prosthesis designs are discussed along with fixed (either tooth-supported or implant-supported) and maxillofacial prosthesis. However, some patients require surgical intervention also for the correction of microstomia either for function or for esthetic purpose before prosthetic rehabilitation and are also enumerated here. CONCLUSION: Among all prosthetic restorative options, removable prosthesis is most difficult for dentist to fabricate as conventional methods are either very difficult or impossible to apply. To get a more accurate final prosthesis, we need to modify these steps according to the existing case. Several modifications available are discussed here which can help while managing these patients.

Assessment of chair side techniques for composite resin restoration--a survey.

The purpose of this survey was to assess the awareness of dental practitioners relating to chair side techniques in restoring teeth with light cure composite. The survey package consisted of a consent form, a leaflet stating the rationale and purpose of the survey and the questionnaire. Randomised sample of dental surgeons in practice was selected. The collected data was then analysed. A 52% response was obtained. Gross deficiencies in practice technique were observed, especially related to parameters like isolation, etching, bond and composite application and finishing of the restoration. Significantly individual assessment of problems by dental practitioners was found to be different from objective rationale. It is suggested that adequate and periodic re-evaluation of techniques must be made by the general dental practitioners, through continuing dental education or workshops so as to achiEve optimum quality.

Repair of fractured abutment teeth under pre-existing crowns: an alternative approach.

This article describes a technique for repair of abutment tooth which fractured during removal of a provisional restoration before bisque trial. The technique uses plastic templates to fabricate new composite core foundation for the existing crowns. This technique helps the dentist to rebuild the core in a single appointment.

A survey on variability in shade selection by practicing dentists.

PURPOSE: To evaluate the variability in shade selection for general practitioners (GPs) and postgraduate (MDS) practitioners and to assess if a shade selection bias exists. MATERIALS AND METHODS: 2070 samples of the chosen shade(s) by 31 GPs and 18 MDS practitioners in the form of work authorization forms and slips were collected from dental laboratories. The mouth was divided into four quadrants: maxillary anteriors and posteriors, and mandibular anteriors and posteriors. The data was grouped and analyzed. RESULTS: The same shade or combination was repeated by the GPs and the MDS practitioners 38% and 35% of the time, respectively. The GP group prescribed a single shade in 84% of cases and a combination of two shades per tooth in 14% of cases, in contrast to the MDS practitioners, who prescribed a single shade in 51% of cases and two shades in 47% of cases. CONCLUSION: A shade selection bias exists among both general and MDS practitioners, as a particular shade or combination was repeated a significant number of times. However, MDS practitioners use a combination of two shades more frequently than general practitioners, who rely mostly on a single shade for a tooth.

Corrective primary impression technique.

The article describes a simple, quick and corrective technique for making the preliminary impression. It records the extensions better as compared to the impressions made using only impression compound. This technique is accurate and gives properly extended custom tray. Any deficiencies seen in the compound primary impression are corrected using this technique hence, this technique is called as a "corrective primary impression technique".

Custom sectional impression trays with interlocking type handle for microstomia patients.

Making impressions in microstomia patients is often cumbersome. A modification of standard impression procedure is often necessary while treating such patients. This article describes the fabrication of a custom sectional impression tray with interlocking type of a handle for definitive impression procedures in a microstomia patient.

Factors determining post selection: a literature review.

Most endodontically treated teeth require a post-and-core build-up for restoring the teeth to optimum health and function. Selection of an appropriate post-and-core system from the wide variety of those available may be a clinical dilemma. Therefore, the purpose of this article is to review the literature to identify the various factors that influence the selection of the post-and-core assembly. English-language peer-reviewed articles between 1961 and 2002 were identified using MEDLINE, as well as a hand search. The following key words were used: post, design, retention, fracture resistance, survivability, and esthetics. Selection of a post and core system should satisfy many interrelated biologic, mechanical, and esthetic factors to optimally restore the endodontically treated tooth to adequate form and function. This review may serve as a guide to aid the clinician in the selection of a post-and-core system.