Investigating the impact of diameters and thread designs on the Biomechanics of short implants placed in D4 bone: a 3D finite element analysis.

BACKGROUND: Dental implants emerge as a dependable and efficacious alternative for patients experiencing partial or complete tooth loss. The stability of these implants is influenced by surface topography and macro-level design. In cases where the height of the maxillary posterior region is diminished, employing short implants can prove advantageous. With the aim of examining the distribution of von Mises stress, strain, and micromovement in D4 bone quality surrounding platform-switched short implants, measuring 6 mm in length and featuring diameters ranging from 4 to 6 mm, as well as different thread designs, an in-depth finite element analysis was conducted under immediate loading conditions. METHODOLOGY: A 3D finite element model was constructed to simulate maxillary molar crowns, incorporating an implant with a length of 6 mm and varying diameters and thread designs. The diameters utilized were 4/3.6 mm, 5/4 mm, and 6/4.8 mm, while the thread designs included buttress, square, and triangle patterns. Each model underwent analysis with a 100 N force applied in two directions: vertical and oblique, relative to the long axis of the implant. Stress, strain, and micromovement in the peri-implant region were recorded, employing the Ansys Workbench R v.18.1 software for modelling and analysis. RESULTS: When comparing all three diameters, the wide diameter (6 mm threads) exhibited the lowest values of peri-implant von Mises stresses (3.3 MPa and 35.1 MPa), strains (194 Ɛ and 484 Ɛ), and micromovements (0.7 µm and 1.3 Ɛ) subjected to axial and non-axial loading of a 100 N force. Notably, square microthreads yielded the most favorable stress parameters among the different thread shapes, manifesting the minimum values of stress, strains, and micromovements in their vicinity. CONCLUSION: For the treatment of atrophic ridges or in scenarios necessitating extensive surgical preparation of the implant site, a combination of short implants, wide diameters, and platform switching can be employed. In situations with reduced bone height and the requirement for an implant-supported prosthesis to replace a missing permanent maxillary molar, the utilization of wide-diameter platform-switched short implants measuring 6 mm in length, featuring a square thread design, should be taken into consideration.

Three-Dimensional FEA Analysis of the Stress Distribution on Titanium and Graphene Frameworks Supported by 3 or 6-Implant Models.

Titanium is the main component of dental implants. It is also routinely used as a framework material for implant-supported full-arch prostheses due to its low density, biocompatibility, and other mechanical properties. Remarkable mechanical properties such as lesser mass density and higher young's modulus of graphene have gained popularity among scientists, improving the properties of biomedical implants. Thus, our study aimed to compare the outcome through the von Mises stresses generated on All-on-6 and All-on-3 implant models, as well as on the framework, and evaluate the effect of stress patterns on the crestal bone around implants in the mandible. FEA (Finite Element Analysis) study was carried out using edentulous mandible models. Four 3D FEA models with 3 and 6 implants were used (Model 1: Titanium bar-supported 6 straight implants; Model 2: Graphene bar-supported 6 straight implants; Model 3: Titanium bar-supported 3 implants with 30 degrees-tilted; Model 4: Graphene bar-supported 3 implants with 30 degrees-tilted) in order to simulate endosseous implant designs. The implant measuring 4.2 mm in diameter and 11.5 mm in length were used. The most distal implants in the 3-implant models were placed with angulation of 30 degrees; in 6 implants, they were vertically placed. All the models were analyzed for vertical and oblique axis with a single force magnitude of 100 N. In all four implant models and under loading conditions, the peak stress points were always on the neck of the most distal implant. von Mises stresses were within the normal stress range. In a conventional six-straight implant model supported by a titanium framework, the cortical stress in the region of implants was 25.27 MPa, whereas, in the graphene framework, it was 12.18 MPa. Under vertical load, there was a significant difference in the cortical stress around the tilted implants (30 degrees) in the 3-implant system of titanium and graphene frameworks, respectively, 70.31 MPa and 21.27 MPa. The graphene framework demonstrated better results than the titanium framework for the conventional six-implant system under vertical load, achieving stress of 30.09 MPa and 76.60 MPa, respectively. In the case of the 3-implant system, a significant difference in the bar stress was observed between graphene and titanium, respectively, 256.32 MPa and 180.1 MPa of bar stress. Within the limitation of this study, the peri-implant stresses were decreased using graphene framework models. Hence, it was possible to conclude that the best load-bearing capacity results were found in the graphene framework group compared to the titanium framework for All-on-6 and All-on-3 implant models, even though both materials are reliable options used as framework materials in implant-supported full-arch prostheses.

Influence of implant design and length on stress distribution in immediately loaded implants in posterior maxilla - A two-dimensional finite element analysis.

Aim: The aim of this two dimensional (2D) finite element analysis study was to evaluate the influence of implant design (step and tapered) and length on stress distribution at bone implant interface, when placed in maxillary posterior bone under immediate loading protocol. Materials and Methods: 2D finite element models were developed to simulate the two types of implant designs, i.e., Tapered and step implants of 3.75-mm - Diameter and 6 and 10 mm lengths, respectively. Maxillary posterior bone quality (D4 bone) was simulated with a very thin cortical bone (0.5 mm) for the placement of implants. The respective material properties were assigned. The implant designs incorporated microthreads at the crestal part and rest of the implant body incorporated Acme threads. Forces of 100 Newtons were applied vertically and in oblique direction (at an angle of 45°) to long axis of the implants. Total deformation (micromovements), stresses and strains were evaluated at the bone implant interface. Results: The results of micromovements, stresses and strains were found to be lower for long implants as compared to short implants. Also, all the values were found to be higher for oblique loads as compared to vertical loads. The von mises stress values were highest for 6 mm step implants and lowest for 10 mm step implants. Conclusion: In the presence of low bone density with optimal bone height, standard diameter long step implants can be used. Incorporation of microthreads at the crestal portion and acme threads for body portion of the implant presents a good option to be used under immediate loading protocol.

Analysis of micromovements and peri-implant stresses and strains around ultra-short implants - A three-dimensional finite-element method study.

BACKGROUND: Success of an implant depends on its placement in the bone and how well the stress and strain are distributed to the surrounding structures when occlusal force is applied to it. The size and shape of the implant plays an important role is the formation and distribution of stress and strains in the periodontium. Von Mises stresses and micromovements need to be evaluated while placing implants in D4 bone quality regions for a higher success rate. AIM: To evaluate the peri-implant Von Mises stresses, strains, and micromovements distribution in D4 bone quality around ultra-short implants of 5 mm length with varying diameters of 4 mm, 5 mm, and 6 mm. MATERIALS AND METHODS: The finite element method was employed to make models replacing maxillary molars in D4 type bone that was missing. Implants that could be classified as ultrashort (5 mm) were used. These implants were of varying diameters of 4, 5, and 6 mm. In each model, the implant was subjected to a force of 100 N and analyzed. The force was applied in an oblique (45 degrees) and vertical direction (90°) to the long axis of the tooth. The models were made such that they simulated cortical and cancellous anisotropic properties of the bone. The models were then analyzed using the program ANSYS workbench version 12.1. RESULTS: When all the three diameters were compared wide diameter, i.e., 6 mm threads had the least values of peri-implant von Mises stresses, strains, and micro-movements around them. When thread shapes were taken into consideration square micro thread created the most favorable stress parameters around them with minimum values of stress, strains, and micromovements. CONCLUSION: Ultrashort implants combined with a wide diameter and platform switched can be used in atrophic ridges or when there is a need for extensive surgery to prepare the implant site.

Changes in cellular and molecular components of peripheral blood in patients with generalized aggressive periodontitis.

AIM: The association between periodontitis and systemic health is evident; however, until recently, there has been a lack of scientific evidence to define the relationship between aggressive periodontitis and systemic conditions. The aim of the present study was to evaluate the changes in the white blood cell count and levels of serum proteins in patients with generalized aggressive periodontitis (GAP) and to compare it with periodontally-healthy controls. METHODS: Patients with GAP (n = 60) and periodontally-healthy controls (n = 60) were recruited. Clinical parameters, including probing depth and clinical attachment level, were examined. Blood cell variables, including leukocyte, neutrophil, and lymphocyte counts, and serum protein parameters, including total protein, albumin (ALB), globulin (GLB), ALB/GLB (A/G) ratio, and C-reactive protein levels, were analyzed. RESULTS: The results showed a statistically-significant increase in neutrophil numbers and serum GLB and C-reactive protein levels in patients with GAP compared to the controls (P < 0.001), whereas the ALB level and A/G ratio were significantly lower compared to the control group. CONCLUSION: The results showed possible changes in the cellular and molecular components of peripheral blood in patients with GAP compared to periodontally-healthy controls. These changes might represent the contribution of periodontal infections to systemic inflammation in relatively young individuals.

Determination of clinical biologic width in chronic generalized periodontitis and healthy periodontium: A clinico-radiographical study.

BACKGROUND: The dimensions of dentogingival junction have been evaluated from autopsy jaw specimens. Previous studies demonstrated variability in histologic biologic width (BW) in periodontal health and mild periodontitis. Few studies have been done on the measurement of clinical BW in periodontitis. BW variation provides implications for selection of surgical or nonsurgical approaches. The purpose of this study was to determine clinical BW in periodontal health and chronic generalized periodontitis and to compare it with histologic dimensions of BW. MATERIALS AND METHODS: A total of 20 subjects with chronic generalized periodontitis and 20 subjects with healthy periodontium were included in the present study. Plaque index and community periodontal index of treatment needs were scored; moreover, probing depth (PD) and clinical attachment level were measured. Full mouth intraoral periapical radiographs were taken, and digitalized images were obtained to measure the crestal bone level using computerized software. RESULTS: Clinical BW was significantly greater in both healthy and periodontitis groups than previously reported histologic BW of 2.04 mm (P < 0.001). The mean clinical BW was 3.98 mm. CONCLUSION: Mean clinical BW in both groups was significantly greater than histologic BW and sites with shallow PDs demonstrated greatest BW, suggesting that these sites may be at increased risk for losing significant attachment during surgical procedures.

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.

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.

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.

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.