Immediate Provisionalization on a New Implant Design for Esthetic Restoration and Preserving Crestal Bone

Selection criteria for immediate implant placement and immediate loading for single tooth replacement in the maxillary esthetic zone: A systematic review and meta-analysis

OBJECTIVES

The aim of this study was to review available evidence for Type 1A (immediate implant placement and immediate loading) of single tooth replacement in the maxillary esthetic zone.

MATERIALS AND METHODS

An electronic search was conducted utilizing the databases of MEDLINE, Embase, and Cochrane to identify publications reporting on the outcomes of Type 1A for single tooth replacement in the maxillary esthetic zone. The success and survival rates of the included articles were reported, which were further categorized according to the clinical criteria reported in Type 1A. Mean survival rates were univariately compared between risk groups and additionally between studies published before and since 2012 using bias-corrected and study size-weighed bootstrap tests. A study time-correcting meta-analysis was then performed to obtain an overall effect for the study pool.

RESULTS

A total of 3118 publications were identified in the search, with a total of 68 articles included. A mean number of implants per study were 37.2 and mean follow-up was 2.8 years. All the included studies utilizing Type 1A report highly selective inclusion and exclusion criteria. Univariate risk group comparison determined that studies before 2012 report a significantly lower mean survival rate (difference of -1.9 percentage points [PP], 95% CI: [-0.3, -4.0], p = .02), facial gap dimension had an impact on survival rates (+3.1 PP [0.2, 5.3] for width >2 mm, p = .04), as well as presence of endodontic infection (+2.6 PP [0.9, 5.1], p = .004).

CONCLUSIONS

Type 1A has a high survival rate in studies reporting strict patient and site selection criteria. Further research is required to assess esthetic and functional success with Type 1A treatments.

Platform switching technique and crestal bone loss around the dental implants: A systematic review

Background:

The overall success of dental implants depends on the crestal bone support around the implants. During the initial years of dental implant placement, the bone loss around the implants determines the success rate of treatment. Platform switching (PLS) concept preserves the crestal bone loss, and this approach should be applied clinically for the overall success of dental implants.

Purpose:

The purpose of this study is to discuss the literature dealing with the concept of PLS concept and preservation of marginal bone, the mechanism by which it contributes to maintenance of marginal bone, its clinical applications, advantages, and disadvantages, to assess its survival rates.

Materials and Methods:

PubMed and Google Scholar search was done to find out the studies involving PLS concept from 2005 to 2017. Data were analyzed using SPSS statistical software.

Results:

Literature search revealed studies involving concepts of PLS, comparison of platform-switched and nonplatform-switched implants, case reports on PLS, and studies with histological and finite element analyses regarding PLS.

Conclusion:

PLS helps preserve crestal bone around the implants, and this concept should be followed when clinical situations in implant placement permit.

Bone response after immediate placement of implants in the anterior maxilla: a systematic review

PURPOSE

The objective of this systematic review was to assess the three-dimensional changes in bone tissue after immediate installation of a single implant in a fresh extraction socket in the anterior maxilla.

METHODS

After defining a strategy, an electronic search was carried out using the databases PubMed, Embase, LILACS, Web of Science, Cochrane, and Scopus. In addition, the gray literature was also researched using Google Scholar and ProQuest. Two reviewers independently screened for eligible studies, assessed the methodological quality, and extracted the data. The inclusion criteria were observational studies and experimental studies that assessed bone response after the immediate installation of a single implant in a fresh extraction socket, immediately loaded or not, in the region between the maxillary canines. Studies were included in any language, with no publication date restrictions and with a minimum of 6 months of follow-up after the surgical procedure.

RESULTS

From a total of 3272 articles, only 12 studies met the inclusion criteria and were selected for the review. Bone remodeling after immediate installation of a dental implant was assessed using standardized periapical radiographs and cone beam computed tomography (CBCT).

CONCLUSION

It can be concluded that bone remodeling occurs after tooth extraction and immediate implant installation.

Reconstruction of the Alveolar Buccal Bone Plate in Compromised Fresh Socket after Immediate Implant Placement Followed by Immediate Provisionalization

OBJECTIVE

The aim of this clinical report was to reestablish the buccal bone wall after immediate implant placement. The socket defect was corrected with autogenous bone, and a connective tissue graft was removed from the maxillary tuberosity to increase the thickness, height, and width of the buccal bone and gingival tissue followed by immediate provisionalization of the crown during the same operation.

CLINICAL CONSIDERATIONS

A 66-year-old patient presented with a hopeless maxillary left central incisor with loss of the buccal bone wall. Atraumatic, flapless extraction was performed, and an immediate implant was placed in the extraction socket followed by preparation of an immediate provisional restoration. Subsequently, immediate reconstruction of the buccal bone plate was performed, using the tuberosity as the donor site, to obtain block bone and connective tissue grafts, as well as particulate bone. Finally, immediate provisionalization of the crown followed by simple sutures was performed. Cone-beam computed tomography and periapical radiographs were taken before and after surgery. After 4 months, the final prosthetic crown was made. After a 2-year follow-up, a satisfactory aesthetic result was achieved with lower treatment time and morbidity.

CONCLUSION

This case demonstrates the effective use of immediate reconstruction of the buccal bone wall for the treatment of a hopeless tooth in the maxillary aesthetic area. This procedure efficiently promoted harmonious gingival and bone architecture, recovered lost anatomical structures with sufficient width and thickness, and maintained the stability of the alveolar bone crest in a single procedure.

CLINICAL SIGNIFICANCE

If appropriate clinical conditions exist, immediate dentoalveolar restoration may be the most conservative means of reconstructing the buccal bone wall after immediate implant placement followed by immediate provisionalization with predictable healing and lower treatment time.

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.

Marginal bone and soft tissue behavior following platform switching abutment connection/disconnection--a dog model study

OBJECTIVE

The effect on the marginal peri-implant tissues following repeated platform switching abutment removal and subsequent reconnection was studied.

MATERIAL AND METHODS

Six adult female Beagle dogs were selected, and Pm3 and Pm4 teeth, both left and right sides, were extracted and the sites healed for 3 months. At this time, 24 bone level (BL) (Straumann, Basel, Switzerland) Ø 3.3/8 mm implants were placed, 2 in each side on Pm3 and Pm4 regions. In one side (control group), 12 bone level conical Ø 3.6 mm healing abutments and, on the other side (test group), 12 Narrow CrossFit (NC) multibase abutments (Straumann) , Basel, Switzerland) were connected at time of implant surgery. On test group, all prosthetic procedures were carried out direct to multibase abutment without disconnecting it, where in the control group, the multibase abutment was connected/disconnected five times (at 6/8/10/12/14 weeks) during prosthetic procedures. Twelve fixed metal bridges were delivered 14 weeks after implant placement. A cleaning/control appointment was scheduled 6 months after implant placement. The animals were sacrificed at 9 months of the study. Clinical parameters and peri-apical x-rays were registered in every visit. Histomorphometric analysis was carried out for the 24 implants. The distance from multibase abutment shoulder to the first bone implant contact (S-BIC) was defined as the primary histomorphometric parameter.

RESULTS

Wilcoxon comparison paired test (n = 6) found no statistically significant differences (buccal P = 0.917; Lingual P = 0.463) between test and control groups both lingually and buccally for S-BIC distance. Only Pm3 buccal aBE-BC (distance from the apical end of the barrier epithelium to the first bone implant contact) (P = 0.046) parameter presented statistically significant differences between test and control groups. Control group presented 0.57 mm more recession than test group, being this difference statistically significant between the two groups (P < 0.001).

CONCLUSION

It can be conclude, within the limits of this animal study, that the connection/disconnection of platform switching abutments during prosthetic phase of implant treatment does not induce bone marginal absorption. Furthermore, it may present a negative influence in the buccal connective tissue attachment that becomes shorter anyway preventing marginal hard tissue resorption, especially in thin biotypes.

Clinical and radiographic evaluation of osseotite-expanded platform implants related to crestal bone loss: a 10-year study

OBJECTIVE

The aim of this prospective clinical study was to evaluate the survival rates at 10 years of expanded platform implants placed in the anterior zone of the maxilla and immediately restored with single crowns.

MATERIALS AND METHODS

Implants incorporating the platform-switching concept were placed in fresh extraction sockets in the maxillary arch, with each patient receiving a provisional restoration immediately after implant placement. After 15 days, final screwed restorations were inserted. Mesial and distal bone heights were evaluated using digital radiography on the day following implant placement and at 1, 5, 7, and 10 years. Primary stability was measured with resonance frequency analysis (RFA) using the Osstell Mentor device. Eighty-six implants were placed in 32 men and 32 women ranging in age between 29 and 60 (mean, 39.64 ± 5.16 years).

RESULTS

Marginal bone loss from implant collar to bone crest between baseline and 10 years follow-up was 1.01 mm ± 0.22. Mesial site crestal bone loss ranged from 3.57 mm ± 1.1 at baseline to 3.77 mm ± 0.7 at 10-year. Distal site crestal bone loss ranged from 3.49 mm ± 0.8 at baseline to 3.73 mm ± 0.7 at 10 year.

CONCLUSION

The platform-switched implants remained stable over the course of 10 years and had an overall survival rate of 97.1%.

Esthetic considerations related to bone and soft tissue maintenance and development around dental implants: report of the Committee on Research in Fixed Prosthodontics of the American Academy of Fixed Prosthodontics

In recent years the frequency of and esthetic demand for implant restorations in the esthetic zone has increased. Recent literature has revealed numerous consistent trends which may aid the clinician in achieving predictable esthetics. Maintaining generous facial bone by judicious placement as well as by using implants with diameters of less than 4 mm appears to be beneficial. Avoiding adjacent implants in the esthetic zone while maintaining an implant to tooth distance of between 2 mm and 4 mm seems to aid in bone and soft tissue maintenance. Abutment connections in which the abutment is narrower than the implant offer distinct advantages, most notably increased bone heights. Also, provisional restoration, especially early in treatment provides long-term esthetic benefits.

Digital analysis of anterior dental esthetic parameters in patients with bilateral maxillary lateral incisor agenesis

OBJECTIVE

To analyze anterior dental esthetic parameters-width/height ratio (WHR), gingival zenith (GZ), and apparent contact dimension (ACD)-in patients with maxillary lateral incisor agenesis (MLIA) bilaterally treated with space closure and recontouring of the canines, or with implant-supported prostheses.

METHODS

Fifty-two participants were allocated into three groups as follows: MLIA patients (N = 18) treated with teeth recontouring (RG); MLIA patients (N = 10) treated with implants (IG); and volunteers without agenesis (N = 24), who served as controls (CG). Dental casts of all patients were obtained and electronically scanned. Digital images were analyzed with 3Shape A/S OrthoAnalyser software (Copenhagen, Denmark). Shapiro-Wilk test, Spearman correlation, and Kruskal-Wallis statistical tests (p < 0.05) were used for statistical analysis.

RESULTS

Although IG presented smaller means when compared with RG and CG, no statistical differences were found for WHR among groups (p > 0.05). Concerning GZ, RG presented more discrepancies than IG and CG, with statistically significant differences (p = 0.0165). IG presented statistically significant differences for the ACD in comparison with RG and CG (p < 0.05).

CONCLUSION

Based on the results of this study, patients treated with space closure and teeth recontouring (RG) were shown to be closest to patients without agenesis (CG) in relation to the anterior dental esthetic parameters evaluated.

CLINICAL SIGNIFICANCE

The digital analysis of esthetic principles, such as those investigated in this study involving maxillary incisor agenesis, is paramount to successful esthetic treatment planning. The results of the present study, as well as those found in the literature, indicate that clinicians should use esthetic parameters, such as those investigated herein, when treatment planning extensive oral rehabilitation cases.

Peri-implant esthetics assessment and management

Providing an esthetic restoration in the anterior region of the mouth has been the basis of peri-implant esthetics. To achieve optimal esthetics, in implant supported restorations, various patient and tooth related factors have to be taken into consideration. Peri-implant plastic surgery has been adopted to improve the soft tissue and hard tissue profiles, during and after implant placement. The various factors and the procedures related to enhancement of peri-implant esthetics have been discussed in this review article.

Stress Analysis in Platform-Switching Implants: A 3-Dimensional Finite Element Study

The aim of this study was to evaluate the influence of the platform-switching technique on stress distribution in implant, abutment, and peri-implant tissues, through a 3-dimensional finite element study. Three 3-dimensional mandibular models were fabricated using the SolidWorks 2006 and InVesalius software. Each model was composed of a bone block with one implant 10 mm long and of different diameters (3.75 and 5.00 mm). The UCLA abutments also ranged in diameter from 5.00 mm to 4.1 mm. After obtaining the geometries, the models were transferred to the software FEMAP 10.0 for pre- and postprocessing of finite elements to generate the mesh, loading, and boundary conditions. A total load of 200 N was applied in axial (0°), oblique (45°), and lateral (90°) directions. The models were solved by the software NeiNastran 9.0 and transferred to the software FEMAP 10.0 to obtain the results that were visualized through von Mises and maximum principal stress maps. Model A (implants with 3.75 mm/abutment with 4.1 mm) exhibited the highest area of stress concentration with all loadings (axial, oblique, and lateral) for the implant and the abutment. All models presented the stress areas at the abutment level and at the implant/abutment interface. Models B (implant with 5.0 mm/abutment with 5.0 mm) and C (implant with 5.0 mm/abutment with 4.1 mm) presented minor areas of stress concentration and similar distribution pattern. For the cortical bone, low stress concentration was observed in the peri-implant region for models B and C in comparison to model A. The trabecular bone exhibited low stress that was well distributed in models B and C. Model A presented the highest stress concentration. Model B exhibited better stress distribution. There was no significant difference between the large-diameter implants (models B and C).

Analysis of width/height ratio and gingival zenith in patients with bilateral agenesis of maxillary lateral incisor

OBJECTIVE: The purpose of this study was to evaluate the width/length ratio and the gingival zenith (GZ), by means of dental casts and digital caliper, in patients with missing maxillary lateral incisors after treatment. METHODS: The sample was composed of 52 subjects divided into 3 groups: BRG (n = 18), patients with bilateral agenesis treated with tooth re-contouring; BIG (n = 10) patients with agenesis treated with implants and CG (n = 24), control group. The data were analyzed using Shapiro-Wilk, Spearman correlation, Wilcoxon, Kruskal-Wallis, t test and ANOVA tests (p < 0.05). RESULTS: For the width/length ratio of the lateral incisors, BIG presented the lowest mean values (0.72 right and left), when compared with other groups. However, comparison between groups presented statistically significant differences for the right lateral incisor (BIG x CG) and for the canine (BRG x CG). GZ data evaluation showed the greatest difference for BRG (0.5 right and 0.48 left). BIG (0.95 right and 0.98 left) and CG (0.98 right and 0.8 left) presented more similar values, nevertheless, without statistical difference (p > 0.05). GZ data for the right and left sides of the smile were not considered statistically different. CONCLUSION: Although no statistical difference was found in the comparison between the groups, analysis of the descriptive values showed that group BIG showed the greatest difference in values with regard to width/length ratio. Regarding gingival zenith, BRG showed the greatest difference.

Peri-implant marginal bone level: a systematic review and meta-analysis of studies comparing platform switching versus conventionally restored implants

AIM

To systematically review the literature to compare implant survival (IS) and marginal bone loss (MBL) around platform-switched (PS) versus conventionally restored platform-matching dental implants.

MATERIAL AND METHODS

Randomized, controlled human clinical trials (RCTs) comparing IS and MBL in PS and conventionally restored implants, with 12 months of follow-up and at least 10 implants were identified through electronic and manual search. Review and meta-analysis were performed according to PRISMA statement. Risk ratio (RR) for implant failure and mean difference (MD) for MBL, with 95% confidence interval (CI) were calculated. Sources of heterogeneity among studies were also investigated by subgroup analyses.

RESULTS

Ten RCTs involving 435 subjects and 993 implants contributed to this review. The cumulative estimated implant success rate revealed no statistically significant difference between the two groups. At a patient level, a smaller amount of MBL [MD -0.55 mm, 95%CI (-0.86; -0.24), p = 0.0006] was noted around PS implants. Subgroup analyses performed at implant level suggested less MBL when platform switching showed a larger mismatching.

CONCLUSION

PS technique appeared to be useful in limiting bone resorption. Nevertheless, these data should be interpreted cautiously as significant heterogeneity and possible publication bias were noted. Further research is needed to identify the factors most associated with successful outcomes.

Post-Extractive Implants: Outcome of 40 Cases

In the last two decades, several investigators have reported immediate placement of dental implants into extraction sockets achieving excellent results with a two-stage surgical procedure. Recently immediate loading has become an emerging technique as it has been documented to be a successful and time saving procedure. As regard the possibility of immediate/early loading of implants placed in fresh extraction sockets few reports are available. In addition they are based on limited series with short follow-up. Thus we decided to perform a retrospective study on a series of post-extractive implants. A total of 40 two-piece implants (FMD srl, Rome, Italy) were inserted in post extractive sockets, 22 in females and 18 in males. The median age was 52 ± 11 (min-max 24–69 years). Twenty-one implants were inserted in upper jaw and 19 in mandible. Fixtures replaced 7 incisors, 3 cuspids, 12 premolars and 18 molars. Implant' length was x ≤ 10 mm, 10,30 ≤ x ≤ 12.30, equal to 13 mm and x ≥14 mm in 6,14,9, and 11 cases, respectively. Implant' diameter was narrower than 3.5 mm, equal to 3.8 mm and wider than 4.0 mm in 1,7, and 32 cases, respectively. There were 28, 2 and 10 Elisir, I-fix, and Shiner implant types, respectively. No implant on single tooth rehabilitations, was lost, survival rate = 100%. Then peri-implant bone resorption (i.e. delta IAJ) was used to investigate SCR. Seven fixtures have a crestal bone resorption greater than 1.5 mm (SCR = 82.5%). Statistical analysis demonstrated that there was a difference between surgeons (p= 0.005). In conclusion FMD implants are reliable devices for oral rehabilitation with a very high SCR and SVR.

Crestal bone loss evaluation in osseotite expanded platform implants: a 5-year study

OBJECTIVE

The aim of this prospective clinical study was to evaluate the survival rates at 5 years of expanded platform implants placed in the anterior zone of the maxilla and immediately restored with single crowns.

MATERIALS AND METHODS

Implants incorporating the platform-switching concept were placed in fresh extraction sockets in the maxillary arch, with each patient receiving a provisional restoration immediately after implant placement. After 15 days, final screwed restorations were inserted. Mesial and distal bone heights were evaluated using digital radiography on the day following implant placement and at 1, 3, 6, 9, 12, 24, 36 months and 5 years. Primary stability was measured with resonance frequency analysis (RFA) using the Osstell Mentor device. Sixty-four implants were placed in 32 men and 32 women ranging in age between 29 and 60 (mean: 39.64 ± 5.16 years).

RESULTS

Mean mesial bone loss was 0.08 mm (SD 0.42). Mean distal bone loss was 0.14 mm (SD 0.56). Over the course of the 5 years, the mean RFA value was 72.5 ± 3.1 SD.

CONCLUSION

The platform-switched implants remained stable over the course of 5 years and had an overall survival rate of 97.1%.

The effect of abutment dis/reconnections on peri-implant bone resorption: a radiologic study of platform-switched and non-platform-switched implants placed in animals

OBJECTIVES

The purpose of this animal study was to radiologically measure the influence of abutment disconnection on bone resorption and to compare this influence on platform-switched vs. non-platform-switched implants.

METHODS

The study design included extraction of all mandibular premolars in five canines . After 2 months, six implants were placed in each dog. Four of them were platform-switched (PS) implants and two were non-platform-switched (NPS) implants. Some or all of the abutments connected to the implants were disconnected at pre-ordained post-surgical intervals. Radiographs were taken at the time of implant placement and at every handling. The values for mesial (horizontal and vertical) and distal (horizontal and vertical) bone resorption were taken and compared for each implant at every abutment dis/reconnection.

RESULTS

The average vertical bone resorption around NPS implants after four dis/reconnections was 1.09 mm (SD 0.25 mm), and the average horizontal bone resorption was 0.98 mm (SD 0.27 mm). The average vertical bone resorption around PS implants after four dis/reconnections was 0.24 mm, (SD 0.08 mm) and the average horizontal bone resorption was 0.24 mm (SD 0.13 mm). The difference of the average horizontal and vertical bone resorption around NPS (site D) and PS (site A) implants was statically significant (P < 0.05). The average mesial and distal bone resorption values around PS (site A) implant adjacent to a tooth were compared, and statically significant differences were found (P < 0.05).

CONCLUSIONS

Implants with a PS design show less peri-implant bone resorption during the healing process and as their abutments are disconnected, than do comparably dis/reconnected NPS implants. The location of the PS implant next to a tooth may decrease radiographically visible peri-implant bone resorption significantly.

Morse taper connection implants supporting "planned" maxillary and mandibular bar-retained overdentures: a 5-year prospective multicenter study

OBJECTIVES

In contrast to the excellent long-term outcomes described for implant-supported mandibular overdentures, less favorable long-term survival and success rates have been reported for maxillary implants supporting overdentures. The aim of this study was to evaluate the treatment outcome of "planned" bar-retained maxillary and mandibular overdentures supported by Morse taper connection implants, investigating implant survival, peri-implant tissue health, marginal bone resorption and prosthetic complications.

MATERIAL AND METHODS

Over a 2-year period, 60 patients were enrolled in this study, in four different clinical centers. The overdentures (maxilla 38, mandible 34) were planned with support from four implants anchored on a bar. A total of 288 Morse taper connection implants (Leone Implant System(®)) were inserted (152 maxilla, 136 mandible). Implants were evaluated 5 years after insertion. Success criteria included the absence of pain, suppuration or clinical mobility, the distance between implant shoulder and first crestal bone-implant contact (DIB) <2 mm and no exudate history.

RESULTS

The overall 5-year implant survival rate was 98% (maxilla 97.4%, mandible 98.6%), with 282 implants still in function. Among these surviving implants, 278 (98.6%) were classified in the success group. At the 5-year examination, the mean DIB was 0.7 mm (±0.53). Few prosthetic complications were reported.

CONCLUSIONS

With "planned" bar-retained maxillary and mandibular overdentures supported by Morse taper connection implants, satisfactory survival and success rate can be achieved.

Regular and switching platform: bone stress analysis with varying implant diameter

The aim of this study was to evaluate stress distribution of the peri-implant bone by simulating the biomechanical influence of implants with different diameters of regular or platform switched connections by means of 3-dimensional finite element analysis. Five mathematical models of an implant-supported central incisor were created by varying the diameter (5.5 and 4.5 mm, internal hexagon) and abutment platform (regular and platform switched). For the cortical bone, the highest stress values (σmax and σvm) were observed in situation R1, followed by situations S1, R2, S3, and S2. For the trabecular bone, the highest stress values (σmax) were observed in situation S3, followed by situations R1, S1, R2, and S2. The influence of platform switching was more evident for cortical bone than for trabecular bone and was mainly seen in large platform diameter reduction.

Photoelastic Analysis of the Influence of Platform Switching on Stress Distribution in Implants

The aim of this study was to evaluate the stress distribution of platform switching implants using a photoelastic method. Three models were constructed of the photoelastic resin PL-2, with a single implant and a screw-retained implant-supported prosthesis. These models were Model A, platform 5.0 mm/abutment 4.1 mm; Model B, platform 4.1 mm/abutment 4.1 mm; and Model C, platform 5.00 mm/abutment 5.00 mm. Axial and oblique (45°) loads of 100 N were applied using a Universal Testing Machine (EMIC DL 3000). Images were photographed with a digital camera and visualized with software (AdobePhotoshop) to facilitate the qualitative analysis. The highest stress concentrations were observed at the apical third of the 3 models. With the oblique load, the highest stress concentrations were located at the implant apex, opposite the load application. Stress concentrations decreased in the cervical region of Model A (platform switching), and Models A (platform switching) and C (conventional/wide-diameter) displayed similar stress magnitudes. Finally, Model B (conventional/regular diameter) displayed the highest stress concentrations of the models tested.

Immediate single tooth replacement with subepithelial connective tissue graft using platform switching implants: a case series

This case series evaluated the facial gingival stability following single immediate tooth replacement in conjunction with subepithelial connective tissue graft (SCTG). Implant success rate and peri-implant tissue response were also reported. Ten patients (6 male, 4 female), with a mean age of 52.1 (range = 22.7 to 67.1) years, underwent immediate implant placement and provisionalization with SCTG and were evaluated clinically and radiographically at presurgery (T0), at the time of immediate tooth replacement and SCTG (T1), and 3 months (T2), 6 months (T3), and 12 months (T4) after surgery. Data were analyzed using the Friedman and Wilcoxon signed-ranks tests at the significance level of α = .05. At 1 year, 9 of 10 implants remained osseointegrated with the overall mean marginal bone change of -0.31 mm and a mean facial gingival level change of -0.05 mm. The modified plaque index scores showed that patients were able to maintain a good level of hygiene throughout the study. The papilla index score indicated that at T4, more than 50% of the papilla fill was observed in 89% of all sites. When proper 3-dimensional implant position is achieved and bone graft is placed into the implant-socket gap, favorable success rate and peri-implant tissue response of platform switching implants can be achieved following immediate tooth replacement in conjunction with subepithelial connective tissue graft.

Prospective evaluation of 2,549 Morse taper connection implants: 1- to 6-year data

BACKGROUND

The aim of this study is to evaluate the implant survival, the implant-crown success, and the prosthetic complications of 2,549 Morse taper interference-fit connection implants.

METHODS

A total of 2,549 Morse taper connection implants were inserted in 893 patients from January 2003 until December 2008. At each annual recall, clinical, radiographic, and prosthetic parameters were assessed. The implant-crown success criteria included the absence of pain, suppuration, and clinical mobility; an average distance between the implant shoulder and the first visible bone contact <2 mm from initial surgery; and the absence of prosthetic complications at the implant-abutment interface. Prosthetic restorations were fixed partial prostheses (462 units); fixed full-arch prostheses (60 units); single crowns (531 units); and overdentures (93 units).

RESULTS

The cumulative implant survival rate was 98.23% (97.25% maxilla, 99.05% mandible). The implant-crown success was 92.49%. A few prosthetic complications at implant-abutment interface were reported (0.37%). After 6 years, distance between the implant shoulder and the first visible bone contact was 1.10 mm (± 0.30 mm).

CONCLUSION

The use of Morse taper connection implants represents a successful procedure for the rehabilitation of partially and completely edentulous arches.

Implant platform switching: biomechanical approach using two-dimensional finite element analysis

In implant therapy, a peri-implant bone resorption has been noticed mainly in the first year after prosthesis insertion. This bone remodeling can sometimes jeopardize the outcome of the treatment, especially in areas in which short implants are used and also in aesthetic cases. To avoid this occurrence, the use of platform switching (PS) has been used. This study aimed to evaluate the biomechanical concept of PS with relation to stress distribution using two-dimensional finite element analysis. A regular matching diameter connection of abutment-implant (regular platform group [RPG]) and a PS connection (PS group [PSG]) were simulated by 2 two-dimensional finite element models that reproduced a 2-piece implant system with peri-implant bone tissue. A regular implant (prosthetic platform of 4.1 mm) and a wide implant (prosthetic platform of 5.0 mm) were used to represent the RPG and PSG, respectively, in which a regular prosthetic component of 4.1 mm was connected to represent the crown. A load of 100 N was applied on the models using ANSYS software. The RPG spreads the stress over a wider area in the peri-implant bone tissue (159 MPa) and the implant (1610 MPa), whereas the PSG seems to diminish the stress distribution on bone tissue (34 MPa) and implant (649 MPa). Within the limitation of the study, the PS presented better biomechanical behavior in relation to stress distribution on the implant but especially in the bone tissue (80% less). However, in the crown and retention screw, an increase in stress concentration was observed.

Platform Switching and Bone Platform Switching

Bone platform switching involves an inward bone ring in the coronal part of the implant that is in continuity with the alveolar bone crest. Bone platform switching is obtained by using a dental fixture with a reverse conical neck. A retrospective study was performed to evaluate the effectiveness of conventional vs reverse conical neck implants. In the period between May 2004 and November 2007, 86 patients (55 females and 31 males; median age, 53 years) were operated and 234 implants were inserted: 40 and 194 were conventional vs reverse conical neck implants, respectively. Kaplan-Meier algorithm and Cox regression were used to detect those variables associated with the clinical outcome. No differences in survival and success rates were detected between conventional vs reverse conical neck implants alone or in combination with any of the studied variables. Although bone platform switching leads to several advantages, no statistical difference in alveolar crest resorption is detected in comparison with reverse conical neck implants. We suppose that the proximity of the implant abutment junction to the alveolar crestal bone gives no protection against the microflora contained in the micrograph. Additional studies on larger series and a combination of platform switching and bone platform switching could lead to improved clinical outcomes.

Effect of platform switching on strain developed around implants supporting mandibular overdenture

PURPOSE

The aim of this study was to assess the effect of platform switching, using 3 different abutment sizes on the strain developed around implants supporting mandibular overdenture, using strain gages.

MATERIALS

An implant-supported overdenture was constructed on an acrylic model with 2 implant fixtures placed at canine areas. Abutments of different sizes (5.5 mm, 4.5 mm, and 3.5 mm diameter) were screwed in the implant fixtures (platform switching). Anterior axial, anterior off-axis (lateral), and posterior load were applied on each abutment through a load applicator attached to the upper compartment of a universal testing machine until a load of 100 N, at which instant, the resultant strain on the implants was recorded using 4 strain gages connected to a 4-channel strain indicator. Data were analyzed by 1-way ANOVA at a significance level of 0.05, followed by Tukey-Kramer multiple comparisons test.

RESULTS

Anterior axial load application and decreasing the abutment size lead to a decrease in the strain developed on the loaded abutment and to an increase in the strain developed on the unloaded abutment. Anterior off-axis load application and decreasing the abutment size lead to an increase in the strain developed on the loaded abutment and to a decrease on the unloaded abutment. On the other hand, posterior load application and decreasing the abutment size lead to an increase in the strain developed on the mesial side of the near abutment and a decrease in the strain developed on its distal side, where there was a significant increase in the strain developed on the mesial and distal sides of the far abutment.

CONCLUSION

The distribution of the strain developed because of decreasing the abutment size does not favor the use of platform switching in an implant-supported mandibular overdenture.