Three‐Dimensional Image Correlation Analyses for Strains Generated by Cement and Screw‐Retained Implant Prostheses

Purpose: This study aimed to measure and compare strains generated by splinted implant crowns retained by cement or screws for two implants with applied load. Materials and Methods: A stereolithic resin model was printed using computed tomography data from a patient missing all mandibular molar teeth. Two 4 × 6 mm implants were consecutively placed in the left side. One set of splinted cement and screw‐retained crowns were made to fit the two implants. Image correlation technique was used for full‐field measurement of strains using an image correlation software and two synchronized high‐resolution digital cameras. A random dot pattern was applied to the model surface. Cameras recorded changes in random dot patterns as prostheses were loaded up to 400 N in vertical and oblique directions using a universal testing machine. Testing was repeated three times for cement and screw‐retained prostheses. An image correlation algorithm used the dot pattern to define correlation areas or virtual strain gauge boxes. Three‐dimensional coordinates of gauge box centers were determined for each recorded photograph and used to calculate strains. Strain distribution data were compared for major, minor, and von Mises strains for each loading condition, as well as peak and average strains for the field of view using an analysis of variance (α = 0.05). Results: Patterns and magnitudes of strain for cement‐ and screw‐retained splinted crowns were similar under vertical loading. Neither peak nor mean strains were significantly different for the two retention methods. For oblique loading, peak strains were lower for the screw‐retained crowns; however, there were no statistically significant differences between the two groups when strains were averaged throughout the entire field of view. Conclusions: Cement retention did not improve the magnitude of transferred strains for splinted implant crowns using either loading condition.     

Human ex vivo bone tissue strains around natural teeth vs. immediate oral implants

Purpose: To compare ex vivo bone tissue strains around natural teeth with immediate implants supporting unsplinted and splinted fixed prostheses. Material and methods: Six linear strain gauges were bonded on the labial marginal bone of bilateral maxillary anterior teeth in two fresh‐frozen human cadavers. The natural teeth were loaded in centric occlusion via an occlusal splint with integrated miniature load cells. Strain measurements were performed at a sample rate of 10 kHz and under a maximum load of 100 N, simultaneously monitored from a computer connected to data acquisition system. Upon extraction of the anterior teeth, Ø 4.1 mm and Ø 4.8 mm ITI^® dental implants were placed into sockets of incisors and canines, respectively. Installation torque value (ITV) of each implant was measured by a custom‐made torque wrench and resonance frequency analyses (RFA) were also undertaken. Strain measurements were performed for (1) single‐tooth implant restorations, (2) unilateral splinted anterior implants, and (3) bilateral splinted anterior implants. Finally, an autopolymerizing acrylic resin was injected into the implant sockets for simulation of osseointegration and strain measurements were performed. Results: Microstrains of all groups were statistically comparable (P>0.05), although lower strains were elicited for implants in sockets of incisors in comparison with natural teeth. Microstrains around canine implants were comparable or higher than those induced around natural canines. For all groups, microstrains around canines were higher than those around lateral (P<0.05) and central incisors (P<0.01), which had similar strain levels (P>0.05). The RFA values of implants were comparable. The ITVs of implants in sockets of lateral incisors and canines were similar and were higher than those of implants in central incisor regions. Conclusion: The labial marginal bone having no contact with immediate implants may experience strain gradients within physiologic levels due to deformation of bone under load. Although one prosthetic design does not seem to have clear advantages over another, splinting of implants may be considered as a safety measure for immediately loaded immediate implants, if possible.     

Photoelastic stress analysis of different designs of cement-retained fixed partial dentures on Morse taper oral implants

There is no consensus in literature regarding the best plan for prosthetic rehabilitation with partial multiple adjacent implants to minimize stress generated in the bone-implant interface. The aim of this study was to evaluate the biomechanical behavior of cemented fixed partial dentures, splinted and nonsplinted, on Morse taper implants and with different types of coating material (ceramic and resin), using photoelastic stress analysis. A photoelastic model of an interposed edentulous space, missing a second premolar and a first molar, and rehabilitated with 4 different types of cemented crowns and supported by 2 adjacent implants was used. Groups were as follows: UC, splinted ceramic crowns; IC, nonsplinted ceramic crowns; UR, splinted resin crowns; and IR, nonsplinted resin crowns. Different vertical static loading conditions were performed: balanced occlusal load, 10 kgf; simultaneous punctiform load on the implanted premolar and molar, 10 kgf; and alternate punctiform load on the implanted premolar and molar, 5 kgf. Changes in stress distribution were analyzed in a polariscope, and digital photographs were taken of each condition to allow comparison of stress pattern distribution around the implants. Cementation of the fixed partial dentures generated stresses between implants. Splinted restorations distributed the stresses more evenly between the implants than nonsplinted when force was applied. Ceramic restorations presented better distribution of stresses than resin restorations. Based on the results obtained, it was concluded that splinted ceramic restorations promote better stress distribution around osseointegrated implants when compared with nonsplinted crowns; metal-ceramic restorations present less stress concentration and magnitude than metal-plastic restorations.     

Biomechanical rationale for short implants in splinted restorations: an in vitro study

Seven implants provided with strain gauges were placed in an acrylic block to evaluate the biomechanical performance of short implants in splinted restorations. Two 7-mm-long implants with the same diameter (3.8, 4.4, or 5.0 mm) were splinted together (short-short implant splinted restoration [SS]) or individually with a 4.4 ? 12.0-mm implant (short-long implant splinted restoration [SL]), and a 50-N oblique load was applied to both restorations. The strain decreased significantly with an increase in implant diameter in both the SS and SL restorations, and the observed strain was identical between splinted implants of the same diameter and those splinted with the long implant, suggesting that splinting of two short implants has the same biomechanical effectiveness as splinting with a single long implant.     

Straight and Offset Implant Placement under Axial and Nonaxial Loads in Implant‐Supported Prostheses: Strain Gauge Analysis

Purpose: The aim of this in vitro study was to quantify strain development during axial and nonaxial loading using strain gauge analysis for three‐element implant‐supported FPDs, varying the arrangement of implants: straight line (L) and offset (O). Materials and Methods: Three Morse taper implants arranged in a straight line and three implants arranged in an offset configuration were inserted into two polyurethane blocks. Microunit abutments were screwed onto the implants, applying a 20 Ncm torque. Plastic copings were screwed onto the abutments, which received standard wax patterns cast in Co‐Cr alloy (n = 10). Four strain gauges were bonded onto the surface of each block tangential to the implants. The occlusal screws of the superstructure were tightened onto microunit abutments using 10 Ncm and then axial and nonaxial loading of 30 Kg was applied for 10 seconds on the center of each implant and at 1 and 2 mm from the implants, totaling nine load application points. The microdeformations determined at the nine points were recorded by four strain gauges, and the same procedure was performed for all of the frameworks. Three loadings were made per load application point. The magnitude of microstrain on each strain gauge was recorded in units of microstrain (μ?). The data were analyzed statistically by two‐way ANOVA and Tukey's test (p < 0.05). Results: The configuration factor was statistically significant (p= 0.0004), but the load factor (p= 0.2420) and the interaction between the two factors were not significant (p= 0.5494). Tukey's test revealed differences between axial offset (μ?) (183.2 ± 93.64) and axial straight line (285.3 ± 61.04) and differences between nonaxial 1 mm offset (201.0 ± 50.24) and nonaxial 1 mm straight line (315.8 ± 59.28). Conclusion: There was evidence that offset placement is capable of reducing the strain around an implant. In addition, the type of loading, axial force or nonaxial, did not have an influence until 2 mm.     

In vitro strain gauge analysis of axial and off-axial loading on implant supported fixed partial dentures

The purpose of this study was to compare the in vitro strains on dental implants supporting cement-retained fixed partial dentures under axial and off-axial loading conditions. Ten implants incorporating strain gauges were placed in a certain configuration to simulate different clinical situations and were embedded in an experimental model. Two implant supported three-unit fixed partial dentures were fabricated on four groups of implants, and each group consisted of seven restorations. The prostheses were cemented with a temporary cement. Fifty N vertical load was applied on predetermined axial and off-axial loading locations on the prostheses. Strain indicator readings were recorded at a standardized time following each loading sequence. The point of load transfer affected strains on implants. For all prosthetic designs, off-axial loading generated more strain than axial loading on implants (P < 0.05). In comparison with axial loading, off-axial loading causes bending of the implants that may affect bone loss around the implant collar. Axial loading of implants should be provided by using wide diameter implants, narrow occlusal tables, and proper occlusal contacts on implant restorations.     

Effect of splinting and interproximal contact tightness on load transfer by implant restorations

STATEMENT OF PROBLEM: To circumvent the difficulty of achieving a passive framework fit, some authors have suggested that multiple adjacent implants be restored individually. This protocol requires that each unit be able to withstand mastication forces. Non-splinted restorations have numerous interproximal contacts that require adjustments prior to placement, with an unknown outcome relative to load transfer. PURPOSE: This in vitro simulation study examined the effect of splinting and interproximal contact tightness on passivity of fit and the load transfer characteristics of implant restorations. MATERIAL AND METHODS: A photoelastic model of a human partially edentulous left mandible with 3 screw-type implants (3.75 x 10 mm) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 custom-milled titanium abutments. After the units were cemented, 5 levels of interproximal contact tightness were evaluated: open, ideal (8 microm shim stock drags without tearing), light (ideal +10 microm), medium (ideal + 50 microm), and heavy (ideal + 90 microm). For splinted restorations, five 3-unit fixed partial dentures were fabricated, internally adjusted with silicone disclosing material, and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions (6.8 kg) were analyzed with a polariscope. RESULTS: In the simulated alveolar structures, non-splinted restorations with heavier interproximal contacts were associated with increased tensile stresses between implants; occlusal loads tended to concentrate around the specific loaded implant. Splinted restorations shared the occlusal loads and distributed the stresses more evenly between the implants when force was applied. The load-sharing effect was most evident on the center implant but also was seen on the terminal abutments of the splinted restorations. CONCLUSION: The results of this in vitro study suggest that excessive contact tightness between individual crowns can lead to a non-passive situation. In this experiment, splinted restorations exhibited better load sharing than non-splinted restorations.     

Effects of splinted prosthesis supported a wide implant or two implants: a three-dimensional finite element analysis

OBJECTIVES: Three-dimensional finite element (FE) models of splinted prosthetic crowns were studied and stress analyses were evaluated with different types of implant support, including standard, wide or two implant(s) for partial, posterior edentulous restorations. MATERIAL AND METHODS: The FE models were constructed based on a cadaver mandible containing the 2nd premolar and the 1st molar. The crowns of these two teeth were modeled as connected and disconnected to mimic the splinted and non-splinted designs, respectively. One standard implant was placed at the premolar region, while three types of implant support, one at a time (the standard implant, wide implant and two implants), were used to support the molar crown. A 100 N oblique load was applied to the buccal cusp on each crown. The FE simulation was validated experimentally via strain gauge measurement. RESULTS: The experimental data were well correlated with the FE predictions (r(2)=0.97). When compared with the standard implant used in the molar area, the wide implant and two implants reduced the peak stress in crestal bone by 29-37% for both splinted and non-splinted cases. Inserting the standard implant into both the premolar and molar area, the bone stresses were identical for splinted and non-splinted designs. However, splinting the adjacent crowns has shown to decrease the bone stresses at the premolar region by 25%, while the wide implant or two implants were placed at the molar region. CONCLUSION: The biomechanical advantages of using the wide implant or two implants are almost identical. The benefit of load sharing by the splinted crowns is notable only when the implants on the premolar and molar regions have different supporting ability.     

Splinted and unsplinted overdenture attachment systems: A systematic review and meta‐analysis

Splinted and unsplinted overdenture attachment systems have unique advantages and disadvantages. The aim of the present systematic review was to determine the influence of splinted and unsplinted overdenture attachment systems on the marginal bone loss, prosthetic complications and implant survival rate. PubMed/MEDLINE , Scopus and Cochrane databases were searched for articles published up to October 2017, using the following search terms: “overdenture AND attachment OR overdenture AND bar OR overdenture splinted.” The PICO question “Do splinted overdenture attachment systems promote better clinical results in comparison to unsplinted systems?” was evaluated. Eligible studies included randomized controlled clinical trials, prospective studies with at least 10 participants and a minimum follow‐up of 6 months, and studies published in English that compared splinted and unsplinted attachment systems within the same study. The 95% confidence interval (CI ) was considered for all outcomes analysed. After completion of the different steps in the article selection process, nine articles were included in the qualitative and quantitative analyses. A total of 984 implants were placed in 380 patients (mean age: 62.8 years). The meta‐analysis demonstrated no statistically significant differences between splinted and unsplinted attachment systems with regard to marginal bone loss (P  = .39; MD : ?0.11; 95% CI : ?0.37 to 0.14), complications (P  = .31; RR : 1.26; CI : 0.80‐1.99) and implant survival rate (P  = .14; RR : 0.37% CI : 0.10‐1.36). In addition, splinted and unsplinted overdenture attachment systems achieved similar results with regard to marginal bone loss, prosthetic complications and implant survival rate.     

Cemented CeraOne and porcelain fused to TiAdapt abutment single-implant crown restorations: a 10-year comparative follow-up study

Background: Long‐term data comparing cemented and noncemented single‐implant restorations has not been reported. Aim: To compare clinical and radiographic performance of single‐implant crown restorations made by either directly baked porcelain to custom‐made TiAdapt? titanium abutments (Nobel Biocare AB, Göteborg, Sweden) (test) or cement crowns onto CeraOne® (Nobel Biocare AB) abutments (control) after 10 years in function. Materials and Methods: Altogether, 35 consecutive patients were provided with 41 turned single Brånemark System® implants (Nobel Biocare AB) in the partially edentulous upper jaw. By random, 15 and 20 patients were provided with 18 test and 23 control implant crowns, respectively. Thereafter, clinical and radiographic data were collected and compared between the two groups. Results: None of the implants were found loose during the follow‐up period (100%). Few clinical problems were observed, and the overall average marginal bone loss was 0.26 mm (SD 0.64) during 10 years in function. After the final tightening of the crowns, no significant differences were observed between the test and control groups (p > .05). The head of the implants was placed on an average 6.3 mm (SD 2.24) below the cement/enamel junction of the adjacent teeth (range 2.5–10.0 mm). Implants with reported mechanical and/or mucosal problems or placed more apically in relation to the adjacent teeth did not present more bone loss as compared with implants with no problems or placed more coronally, respectively (p > .05). Conclusions: There seems to be no obvious clinical or radiographic differences between the test and control single‐implant restorations during 10 years of follow‐up. Occasionally, some restorations presented loose abutment screws and/or fistulas during follow‐up. This implies a certain need for maintenance where a one‐piece single‐implant protocol (test) allows both for a simple clinical procedure at placement without cementation problems, as well as for an easy and simple maintenance of installed single implant crowns in long‐term function.     

The water content in human gingival tissue

Abstract

Objective. The aim of this study was to investigate the various events occurring in unsplinted implant restoration in posterior jaws during a period of 4 years. Materials and methods. From August 2008 to April 2009, eight volunteers (three men and five women) who had two or more consecutively missing teeth received 20 implants in posterior maxillae and mandibles. Unsplinted single crowns were delivered to each implant. For the 4-year follow-up periods, patients were enrolled in a maintenance schedule at 1, 3, 6, 12, 24, 36 and 48 months. The data, including a questionnaire, radiography, mobility and probing were recorded on regular check-ups. Results. A total of 20 implants in eight patients were followed up for 48 months, showing a 100% survival rate. Mean marginal bone loss around implants was 0.26 mm. Statistical analysis revealed insignificant correlation between metal-ceramic and zirconia-ceramic crowns and among implant lengths (8.5 mm, 10 mm and 11.5 mm). Mean probing depths were similar or insignificantly different, regardless of the materials used or length of implants. The most frequent complications, in decreasing order, were food impaction (65%) and porcelain chipping (45%), sensitivity (25%), pain (20%) and loose contact (15%). Compared with metal-ceramic crowns, zirconia-ceramic crowns showed more unfavorable cases of porcelain chipping (p = 0.017), pain (p = 0.007) and loose contact with an adjacent crown (p = 0.031). Conclusions. Within the limits of the sample size, this study showed that unsplinted implant-supported single restorations to replace consecutive posterior missing teeth may function well.     

Long‐Term Follow‐Up of CeraOne™ Single‐Implant Restorations: An 18‐Year Follow‐Up Study Based on a Prospective Patient Cohort

Background: Knowledge on long‐term clinical performance of more than 5 years on the single‐implant CeraOne? (Nobel Biocare AB, Gothenburg, Sweden) concept is limited. Purpose: The aim of this study is to report the long‐term clinical performance of the first CeraOne single‐implant restorations, installed 17 to 19 years ago. Materials and Methods: The group comprised 57 patients provided with 65 CeraOne single‐tooth restorations. Sixty‐two all‐ceramic and three metal‐ceramic crowns were cemented between 1989 and 1991. Patients were followed up clinically and with intraoral radiographs at placement, after 1, 5, and between 17 and 19 years after placement. Results: Data were available for altogether 48 patients, followed up on an average time of 18 years. Excluding deceased patients (n = 2) and failed implant patients (n = 2), only five patients were lost to follow‐up (8.8%). Two implants failed, resulting in an 18‐year implant cumulative success rate (CSR) of 96.8%, and altogether eight original single‐crown restorations were replaced (CSR 83.8%). The most common reason for crown replacement was infra‐position of the implant crown (n = 3). Many of the remaining original crowns showed various signs of implant crown infraposition at the termination of the study. In general, the soft tissue at the restorations was assessed to be healthy and comparable with the gingiva at the adjacent natural teeth. Bone levels were on an average stable with only few patients exhibiting bone loss of more than 2 mm during 18 years in function. Conclusion: This long‐term follow‐up study of single‐implant restorations shows encouraging results with few implant failures and minimal bone loss over an 18‐year period. Original single‐crown restorations were replaced more frequently, because of, for example, implant crown infraposition and veneer fractures. The CeraOne concept proved to be a highly predictable and safe prosthodontic treatment.     

Analysis of fractured dental implant body from five different implant systems: a long-term retrospective study

The aim of this study was to perform an analysis of the incidence of implant body fracture and to identify possible risk factors. A long-term follow-up retrospective evaluation of 3477 patients who received 8588 implants from five implant systems was performed. Overall, 2810 patients who received 7502 implants, with an average follow-up of 6.9 years, were included in the analysis. The overall body fracture rate was 0.49% (37/7502), among which 32.4% (12/37) were implants with a reduced diameter. The estimated cumulative fracture rate was 1.24%. Fractures were observed in two patients with three Brånemark implants, 13 patients with 15 Nobel Replace implants, eight patients with eight Camlog implants, eight patients with 11 Ankylos implants, and none of the patients with Thommen implants. Most fractures occurred in the molar region (29/37) and in single implant-supported restorations (30/37). The results showed significant differences between splinted and unsplinted restorations (P = 0.005) and between regular and narrow diameter implants (P = 0.009). Within the limitations of this retrospective analysis, a narrow implant diameter is a potential risk factor for implant body fracture in the posterior region. Furthermore, unsplinted restorations appear to be associated with a higher rate of implant fracture.     

Stability and marginal bone level measurements of unsplinted implants used for mandibular overdentures: a 1-year randomized prospective clinical study comparing early and conventional loading protocols

Objectives: The aim of this study was to compare the performance of two non‐splinted implants used as retention for a mandibular overdenture when applying conventional or early loading protocols. Material and methods: Twenty edentulous patients were treated with two unsplinted and non‐submerged implants (15 mm long, TiUnite RP, Brånemark System) in the anterior mandible. The patients were randomly allotted into two groups: (i) test group (Group A), in which the overdenture was connected 1 week after surgery, and (ii) control group (Group B), in which the overdenture was connected after 12 weeks of healing. Resonance frequency analyses (RFA) for implant stability measurements were performed at implant surgery and after 1, 3, 6, 9 and 12 months. Marginal bone levels were evaluated at implant surgery and after 6 and 12 months. Results: No implant from either group was lost and all implants showed less than 1 mm of marginal bone resorption during the first year. The mean implant stability quotient (ISQ) values at implant surgery were 76.2±2.8 for Group A and 75.6±4.5 for Group B. The 12‐month measurements showed 76.4±2.5 ISQ and 76.4±2.8 ISQ for Groups A and B, respectively. There were no statistically significant changes between or within the groups with time. There were no differences in marginal bone loss, which was on average 0.3 mm for both groups after 1 year. Conclusion: Although a limited number of patients were followed for 1 year only, the results of the present study indicate that early loading of two unsplinted 15 mm long implants with an overdenture does not negatively affect implant stability or marginal bone conditions when compared with implants subjected to 12 weeks of healing before loading.     

Immediate and delayed loading of fixed dental prostheses supported by single or two splinted implants: A histomorphometric study in dogs

To evaluate presumptive differences in osseointegration at implants supporting crowns that are physiologically loaded either immediately or 3 months after installation. All premolars and first molars were extracted bilaterally in six dogs. After 3 months of healing, three implants were installed on the premolar region and two in the molar region in one side of the mandible. Likewise, after another 3 months, five implants were installed in the contralateral side, and impressions were taken bilaterally. Within 48 hours, two single crowns were screwed bilaterally onto two implants in the premolar region, and two splinted crowns reproducing the shape of the first molar were screwed bilaterally onto the implants in the molar region. The mesial implants were used as no‐loaded controls. Sacrifices were performed after 3 months, and histological analyses were performed. At the premolar sites, mineralised bone‐to‐implant contact (MBIC%) was 78.0 ± 4.0% and 70.9 ± 7.9% at the delayed and immediately loaded sites, respectively. This difference was statistically significant. At the control implants, MBIC% was 61.4 ± 14.7% and 63.1 ± 13.1% at the delayed and the immediately loaded sites, respectively. At the molar sites, MBIC% was 79.2 ± 10.9% and 61.1 ± 10.3% at the delayed and immediately loaded sites, respectively. Applying a delayed loading to fixed dental prostheses supported by single or two splinted implants yielded higher proportions of bone‐to‐implant contact (osseointegration) compared to immediately loaded implants. Moreover, both types of loading protocols yielded a higher rate of osseointegration compared to unloaded implant sites after 3 months following implant installation.     

A 3‐year prospective radiographic evaluation of marginal bone level around different implant systems

Summary The aim of this study was to evaluate the change of marginal bone level radiographically around three different implant systems after 3 years in function. Fifty‐four patients were included and randomly assigned to three treatment groups of rough‐surface implants (TiUnite, n = 37), hybrid of smooth and rough‐surface implants (Restore, n = 38) and rough surface with microthread implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline), 1 and 3 years after loading. A three‐level mixed‐effect analysis of covariance (ancova ) was used to test the significance of the mean marginal bone change of the three implant groups. A total 120 of 135 implants completed the study. None of the implants failed to integrate. Significant differences were noted in the marginal bone loss recorded for the three groups (P < 0·0001). At 3 years, the rough surface with microthread implants had a mean crestal bone loss of 0·59 ± 0·30 mm; the rough‐surface implants, 0·95 ± 0·27 mm; and the hybrid surface implants, 1·05 ± 0·34 mm. Within the limitations of this study, rough‐surface implants with microthread at the coronal part might have a long‐term positive effect in maintaining the marginal bone level against functional loading in comparison with implants without these two features.     

One-Year Prospective Evaluation of the Early Loading of Unsplinted Conical Brånemark Fixtures with Mandibular Overdentures Immediately following Surgery

Background: Prospective evaluation of the early loading of unsplinted Branemark implants with mandibular over‐dentures opposing conventional dentures is not evident in the implant‐related literature. Purpose: To clinically evaluate progressive and early loading of 20 unsplinted conical Brånemark implants in edentulous mandibles with overdentures. Materials and Methods: Ten edentulous patients all had two conical Brånemark implants placed in the anterior mandible with mandatory primary stability with bicortical anchorage. Ball abutment connection was performed simultaneously. Previously constructed conventional mandibular dentures were temporarily relined with tissue conditioner postoperatively and worn with moderation for the first 2 weeks to allow progressive loading. Early loading of the implants followed after 2 weeks, with inclusion of the respective matrices in the mandibular dentures, using a definitive reline procedure. Results: All patients successfully functioned with their mandibular implant overdentures from 2 to 52 weeks postoperatively. Mean marginal bone loss was within established criteria for success:0.22 mm (SD = 0.48 mm) mesially and 0.30 mm (SD = 0.39 mm) distally on the conical implants. Mobility tests using the Periotest instrument became more negative, although not at statistically significant levels. Difficulties in the management of the peri‐implant mucosa between surgery and loading at 2 weeks were observed in 40% of the patients. Conclusions: These preliminary 1‐year results show that successful early loading of unsplinted conical Brånemark implants with mandibular overdentures is possible.     

A Retrospective Evaluation of the Survival Rates of Splinted and Non‐Splinted Short Dental Implants in Posterior Partially Edentulous Jaws

Background: The aim of the present study is to evaluate the survival rate and bone loss around short implants (≤10 mm) supporting splinted or non‐splinted posterior prostheses during a follow‐up period of 3 to 16 years. Methods: A total of 453 implants from 198 patients was divided into splinted or non‐splinted groups. Implant survival rate was calculated for each group, and potential risk was represented as odds ratio (OR). The final linear distance from implant platform level to the first bone‐to‐implant contact was compared to this same reference just after loading by digital periapical radiographs to determine the marginal bone loss (BL). Results: The splinted group comprised 219 implants in 86 patients, whereas the non‐splinted group included 234 implants from 112 patients. The mean follow‐up period was 9.7 ± 3.7 years. Although different success rates were found for splinted (97.7%) and non‐splinted (93.2%) groups, they exhibited similar BL (1.22 ± 0.95 mm and 1.27 ± 1.15 mm, respectively). The success of splinted implants was associated with no other variable, whereas non‐splinted implants exhibited higher risk of failure when placed in men (OR = 3.2) and when implants shorter than 10 mm were used (OR = 3.6 and 4.1 for 8.5 mm and 7 mm, respectively). Regardless of group, 71.4% of the unsuccessful implants failed before the end of the first year after loading. Conclusion: Non‐splinted posterior short implants had a somewhat lower success rate than splinted short implants, and the failure rate in non‐splinted short implants appeared to be greater in males as well as in implants ≤10 mm.     

Does crown/implant ratio influence the survival and marginal bone level of short single implants in the mandibular molar? A preliminary investigation consisting of 12 patients

Crown/implant (C/I) ratio has been proven to not affect the survival of the implants; however, it is also a fact that no evidence exists with regard to the use of single short implants in the mandibular molar. The aim of this study was to determine whether the crown/implant ratios of single implant‐supported fixed restorations on implants of 6–8 mm in the mandibular molar have an impact on the implant survival and marginal bone maintenance. Twelve short dental implants (6–8 mm) were installed and restored with single crowns, loaded after 3 months of healing. The restorations were divided according to crown‐to‐implant ratio into two groups: Group 1: C/I < 2·0 and Group 2: C/I ≧ 2·0. Alveolar bone loss was measured using CBCT scan, taken at the implant placement and after 12 months follow‐up from loading. Reduced implant/crown ratio shown no statistic significant differences on implant survival and the alveolar bone level compared with recommended implant/crown ratio. Within the limitation of this study, it can be concluded that reduced C/I ratio could be used as a substitute for recommended C/I ratio in severely mandibular atrophic residual alveolar ridges.     

Splinting effect on posterior implants under various loading modes: a 3D finite element analysis

This three-dimensional finite element study compared stresses, intensities and displacements of three mandibular posterior implants restored with cemented crowns (two molars and a premolar in straight line), splinted versus non-splinted. Hundred newton occlusal loads were vertically or horizontally applied, either on one single crown or on all of them. Maximal stresses and implants displacements were higher under horizontal loading. Splinting major effects appeared under single horizontal load with a decrease in stresses (34-49%) and displacements (16-19%) of the loaded crown. Splinting seems more appropriate for implant-supported restorations submitted to frequent single horizontal or oblique loads than vertical ones.