Evaluation of design parameters of eight dental implant designs: a two-dimensional finite element analysis.

AIM: Implants could be considered predictable tools for replacing missing teeth or teeth that are irrational to treat. Implant macrodesign includes thread, body shape and thread design. Implant threads should be designed to maximize the delivery of optimal favorable stresses. The aim of this finite element model study was to determine stresses and strains in bone by using various dental implant thread designs. MATERIALS AND METHODS: A two-dimensional finite element model of an implant-bone system is developed by using Ansys. An oblique load of 100 N 45° to the vertical axis of implant as well as a vertical load was considered in the analyses. The study evaluated eight types of different thread designs to evaluate stresses and strains around the implants placed in D1 bone quality. RESULTS: Forty-five-degree oblique von Mises stresses and strains were the highest for the filleted and rounded square thread with an angulation of 30° (216.70 MPa and 0.0165, respectively) and the lowest for the trapezoidal thread (144.39 MPa and 0.0015, respectively). CONCLUSIONS: The findings in this study suggest that the filleted and rounded square thread with an angulation of 30° showed highest stresses and strains at the implant-bone interface. The trapezoidal thread transmitted least amount of stresses and strains to the cortical bone than did other models.

Clinical Evaluation of Increase in the Width of Attached Gingiva using Modified Apically Repositioned Flap: A 9-Month Follow-up Study.

AIM: The purpose of this study is to evaluate the increase in the width of attached gingiva (AG) in single/multiple adjacent teeth using variation of modified apically repositioned flap (MARF). MATERIALS AND METHODS: A total of 20 systemically healthy controls with inadequate width of AG were recruited for the study based on inclusion and exclusion criteria. In all the individuals, variation of MARF technique was performed to increase the width of AG. Outcomes of the surgical techniques were measured in terms of probing pocket depth, clinical attachment level, width of AG, and width of keratinized gingiva (KG). The results were followed up at 3 months and continued till 9 months to confirm the stability of results. RESULTS: Treatment with this procedure resulted in a significant increase in the width of the KG and AG. The increase in KG ranged from baseline (2.0 mm) to 3.85 mm at 3rd month and the results were stable till 9th month (P < 0.001), and the increase in AG ranged from baseline (1.0 mm) to 2.85 mm at 3rd month and the results were stable till 9th month (P < 0.001). CONCLUSION: MARF is an effective technique in increasing the width of the keratinized tissue and AG around teeth and also offers considerable advantages over other mucogingival surgery techniques.

Lip repositioning.

Excessive gingival display is a frequent finding that can occur because of various intraoral or extraoral etiologies. This report describes the use of surgical lip repositioning technique for the management of a gummy smile associated with vertical maxillary excess and hypermobility of the upper lip. The procedure restricts the muscle pull of the elevator lip muscles by shortening the vestibule, thus reducing the gingival display when smiling. Healing was uneventful and follow-up examinations of 10 months revealed reduced gingival display. For patients desiring a less invasive alternative to orthognathic surgery, lip repositioning is a viable alternative.

An in-office, cost effective technique for measuring width of bone using intra-oral periapical radiographs in occlusal projection.

BACKGROUND: The aim of this in vitro study was to determine the dimensions of ridge/width of bone and deviation of center of ridge using Intra Oral Periapical Radiographs (IOPA) in occlusal projection as a preprosthetic diagnostic method. MATERIALS AND METHODS: Mandibles with edentulous space were procured and cold cure acrylic stents were fabricated. Three holes were drilled occlusally, buccally, lingually and filled with gutta percha. Then mandibles were tied to menaquine model which was fitted to a dental chair. IOPA radiographs in occlusal projection were taken. Radiographs were scanned to obtain a digital image which was analyzed using computerized software. Direct measurements were taken and compared. The position of center of ridge was compared in vitro and radiographically using student unpaired t test and width of bone was compared using Karl Pearson's coefficient test. RESULTS: Comparisons of bucco-lingual ridge width using radiographical measurement versus in vitro method showed a mean value of 4.1930 with deviation of 0.5934 and the proposed position of center of ridge for both the methods gave a mean value of 0.2738 with deviation of 0.1164. CONCLUSION: The findings in this study suggested that IOPA radiographs in occlusal projection can be used as a preprosthetic diagnostic method to assess the width of the alveolar bone for future flapless implant placement.

2D FEA of evaluation of micromovements and stresses at bone-implant interface in immediately loaded tapered implants in the posterior maxilla.

AIM: The aim of the study is to evaluate the influence implant length on stress distribution at bone implant interface in single immediately loaded implants when placed in D4 bone quality. MATERIALS AND METHODS: A 2-dimensional finite element models were developed to simulate two types of implant designs, standard 3.75 mm-diameter tapered body implants of 6 and 10 mm lengths. The implants were placed in D4 bone quality with a cortical bone thickness of 0.5 mm. The implant design incorporated microthreads at the crestal part and the rest of the implant body incorporated Acme threads. The Acme thread form has a 29° thread angle with a thread height half of the pitch; the apex and valley are flat. A 100 N of force was applied vertically and in the oblique direction (at an angle of 45°) to the long axis of the implants. The respective material properties were assigned. Micro-movements and stresses at the bone implant interface were evaluated. RESULTS: The results of total deformation (micro-movement) and Von mises stress were found to be lower for tapered long implant (10 mm) than short implant (6 mm) while using both vertical as well as oblique loading. CONCLUSION: Short implants can be successfully placed in poor bone quality under immediate loading protocol. The novel approach of the combination of microthreads at the crestal portion and acme threads for body portion of implant fixture gave promising results.

3D finite element analysis of immediate loading of single wide versus double implants for replacing mandibular molar.

PURPOSE: The purpose of this finite element study was to compare the stresses, strains, and displacements of double versus single implant in immediate loading for replacing mandibular molar. MATERIALS AND METHODS: Two 3D FEM (finite element method) models were made to simulate implant designs. The first model used 5-mm-wide diameter implant to support a single molar crown. The second model used 3.75-3.75 double implant design. Anisotropic properties were assigned to bone model. Each model was analyzed with single force magnitude (100 N) in vertical axis. RESULTS: This FEM study suggested that micromotion can be controlled better for double implants compared to single wide-diameter implants. The Von Mises stress for double implant showed 74.44% stress reduction compared to that of 5-mm implant. The Von Mises elastic strain was reduced by 61% for double implant compared to 5-mm implant. CONCLUSION: Within the limitations of the study, when the mesiodistal space for artificial tooth is more than 12.5 mm, under immediate loading, the double implant support should be considered.

Short implants: A systematic review.

BACKGROUND: Short implants are manufactured for use in atrophic regions of the jaws. Although many studies report on short implants as ≤10 mm length with considerable success, the literature regarding survival rate of ≤7 mm is sparse. PURPOSE: The purpose of this study was to systematically evaluate the publications concerning short dental implants defined as an implant with a length of ≤7 mm placed in the maxilla or in the mandible. MATERIALS AND METHODS: A Medline and manual search was conducted to identify studies concerning short dental implants of length ≤7 mm published between 1991 and 2011. The articles included in this study report data on implant length ≤7 mm, such as demographic variables, implant type, location in jaws, observation time, prostheses and complications. RESULTS: The 28 included studies represent one randomized controlled trial, 12 prospective studies and 10 retrospective studies. The survival rate of short implant was found to be increased from 80% to 90% gradually, with recent articles showing 100%. CONCLUSION: When severe atrophy of jaws was encountered, short and wide implants can be placed successfully.

Evaluation of Micromovements and Stresses around Single Wide-Diameter and Double Implants for Replacing Mandibular Molar: A Three-Dimensional FEA.

Purpose. The purpose of this finite element study was to compare stresses, strains, and displacements of double versus single implant, in immediate loading for replacing mandibular molar. Materials and Methods. Two 3D FEM models were made to simulate implant designs. The first model used 6 mm wide-diameter implant to support a single molar crown. The second model used 3.75-3.75 double implant design. Each model was analyzed with a single force magnitude of 70 N in oblique axis in three locations. Results. This FEM study suggested that micromotion can be well controlled by both double implants and 6 mm single wide-diameter implant. The Von Mises stress for double implant had 31%-43% stress reduction compared to the 6 mm implant. Conclusion. Within the limitations of the paper, when the mesiodistal space for artificial tooth is more than 12.5 mm, under immediate loading, the double implant support should be considered.