Impact of placement and restoration timing on single-implant esthetic outcome - a randomized clinical trial.

AIM: The objective of this randomized clinical trial was to investigate the influence of the time of implant placement (immediate vs. early) and the time of restoration (immediate vs. early) on esthetic outcome in maxillary anterior single implants. MATERIAL AND METHODS: Forty-eight patients with a single failing incisor in the maxilla and a natural contralateral site were randomly distributed into four groups. Treatment variations affected the time of implant placement (immediate or early) as well as the time of restoration (immediate or early) - in detail, group 1a with immediate implant placement and immediate temporary restoration, group 1b with immediate implant placement and early restoration, group 2a with early implant placement and immediate temporary restoration, and group 2b with early implant placement and early restoration. All patients received the final prosthetic restoration 10-12 weeks after implant placement. Standardized photographs were taken eight months after tooth extraction. Five competent observers analyzed the esthetic outcome according to the PES after Fürhauser. For statistical analysis, the Kruskal-Wallis test and Dunn's post hoc test were applied. Interobserver reliability was evaluated by Krippendorff's alpha. RESULTS: The overall scores of the four treatment groups revealed PES values of 8.47 (SD 2.08, group 1a), 7.93 (SD 3.21, group 1b), 6.62 (SD 3.24, group 2a), and 8.10 (SD 3.25, group 2b). The differences between groups 2a and 1a and between groups 2a and 2b were statistically significant (P = 0.015 and P = 0.047). The single parameter analysis displayed a certain range of fluctuation and heterogeneity. CONCLUSIONS: Immediate implant placement and restoration appear to be a viable alternative to early implant placement if an experienced surgeon is entrusted with the implantation procedure.

Strain development in 3-unit implant-supported CAD/CAM restorations.

PURPOSE: Passive fit is difficult to achieve in implant-supported restorations with existing superstructure fabrication techniques. The aim of the study presented was to investigate whether computer-generated fixed partial dentures (FPDs) based on optical impressions lead to less strain development than conventionally fabricated FPDs. MATERIALS AND METHODS: A measurement model with 2 implants was set up and strain gauges were attached to the model material mesially and distally adjacent to the implants. Two groups of conventional cementable restorations based on repositioning and pick-up impressions, respectively, and 1 group of CAD/CAM-generated FPDs based on optical impressions were fabricated (n = 10). Strain development during FPD fixation was recorded. In order to compare the different FPD groups with one another, a multivariate analysis of variance (MANOVA) was performed at a level of significance of alpha = .05. RESULTS: The mean strain development at the different strain gauge locations ranged from 80.38 microm/m to 437.11 microm/m. The 2 groups of conventionally fabricated FPDs showed no significant difference in terms of strain development (P = .07). The CAD/CAM-fabricated FPDs revealed a significantly lower strain development than those made from pick-up technique impressions (P = .01). No significant difference could be detected between the FPDs manufactured from repositioning technique impressions and the CAD/CAM-generated restorations (P = .19). CONCLUSION: Within the limitations of the study presented, it can be concluded that restorations fabricated on the basis of optical impressions demonstrate a level of fit which is at least as passive as that of conventional FPDs.

Structural changes in ceramic veneered three-unit implant-supported restorations as a consequence of static and dynamic loading.

OBJECTIVES: Static implant loading caused by non-passive restorations may cause technical complications. As metal-ceramic restorations are most common in implant prosthodontics, the objective of the study was to investigate the effect of static and dynamic loading upon the stability of the ceramic veneer of implant-supported fixed partial dentures (FPDs). METHODS: A total of 10 groups of three-unit implant FPDs with five samples each were investigated in the conditions after fabrication, static loading and dynamic loading (chewing simulator, 20,000 cycles, 100N). The fluorescent penetrant method (FPM) was applied to detect microcracks at the cervical and occlusal aspects of the FPD abutments. Statistical analysis was performed based on the number of microcracks (t-test) and the presence of chipping fractures (Exact Fisher test) with the level of significance set at alpha=0.05. RESULTS: Static and dynamic loading led to an increase both in number of microcracks and frequency of chipping fractures. After static loading, the screw-retained FPDs cast in one piece revealed significantly lower numbers of cervical microcracks than did the cementable restorations fabricated from repositioning technique impressions (p=0.003). The screw-retained FPDs which were fabricated using premachined gold cylinders showed the highest numbers of cracks and chipping fractures both after static and dynamic loading. SIGNIFICANCE: Static loading may damage the ceramic layer of implant-supported restorations. The use of prefabricated components may cause increased numbers of microcracks due to the lack of bonding oxides.

A double-blind study on clonazepam in patients with burning mouth syndrome.

OBJECTIVES/HYPOTHESIS: In the treatment of burning mouth syndrome (BMS), various approaches have been tried with equivocal results. The aim of the present randomized clinical trial was to determine the efficacy of clonazepam, a GABA agonist designed as an antiepileptic drug that exerts the typical effects of benzodiazepines. STUDY DESIGN: Randomized clinical trial. METHODS: Twenty patients with idiopathic BMS were carefully selected. Clonazepam (0.5 mg/day, n = 10) or placebo (lactose, n = 10) were randomly assigned to the patients. RESULTS: Patients on clonazepam significantly improved in pain ratings (P < .001). These changes were less pronounced in the placebo group (P < .11). No significant changes were observed in a mood scale (P = .56) or for depression scores (P = .56). Taste test and salivary flow increased over sessions, but were not different between groups (P = .83 and P = .06, respectively). CONCLUSIONS: Clonazepam appears to have a positive effect on pain in BMS patients.

Interforaminal implant therapy using a split skin graft--treatment outcome after 13 years.

In implant patients who have extended soft tissue deficiencies, split skin grafts have been performed for the prevention of peri-implant inflammation. The aim of this investigation was to assess a patient who received 2 interforaminal implants and a split skin graft 13 years prior. In addition to clinical, mycologic, and radiographic examinations, the condition of the split skin graft was evaluated using histologic analysis of 3 punch biopsies taken from the mucosa, grafted area, and border between both areas. The implants were found to have an overall good clinical condition. Fungal infection was not present. The histologic analysis revealed inflammation-free mucosal and submucosal tissue in all samples. In the area of the skin graft, the mucosa was not keratinized and showed an increased thickness of the submucosal connective tissue. For the patient under examination, an acceptable level of oral rehabilitation was achieved using a split skin graft. The follow-up investigation showed stable conditions for both the implants and the graft.

The effect of load cycling on metal ceramic screw-retained implant restorations with unrestored and restored screw access holes.

STATEMENT OF PROBLEM: It has been shown that under cyclic loading, more chipping fractures of the veneer ceramic occur on the occlusal surface of screw-retained implant-supported fixed partial dentures (FPDs) with unrestored screw access holes (SAHs) than in cemented restorations. This lack of stability may result in esthetic and functional problems. PURPOSE: The purpose of this study was to investigate whether, under dynamic loading, fewer chipping fractures occur on the occlusal surface of screw-retained ceramic veneered implant FPDs with restored SAHs than in those with unrestored SAHs. MATERIAL AND METHODS: Twenty screw-retained ceramic veneered 5-unit FPDs were manufactured for a 3-implant situation and divided into 2 groups of 10 unrestored and 10 SAHs restored with adhesive composite resin restorations (Tetric Evo Ceram). A masticatory simulator was used to load the FPDs occlusal to the implant positions for 20,000 cycles with a force of 100 N applied for 1 second, followed by 1 second of no loading. Three prosthodontists evaluated the FPDs using a light microscope and a dental probe. The number of chipping fractures found were analyzed using a generalized linear model with Poisson response and log link function (alpha =.05). RESULTS: Investigators found significantly more chipping fractures in the group of screw-retained FPDs with unrestored SAHs. The rate ratio of unrestored versus restored prostheses was 3.29 (P=.006). CONCLUSIONS: Adhesive composite resin restorations can significantly reduce the number of chipping fractures occurring around the SAHs of screw-retained implant-supported restorations.

Influence of fixation mode and superstructure span upon strain development of implant fixed partial dentures.

PURPOSE: Implant-borne fixed partial dentures (FPDs) should fit passively in order to avoid complications ranging from screw loosening to loss of osseointegration. The aim of this study was to measure the strain development of three-unit and five-unit screw- and cement-retained implant-supported FPDs. Additionally, the influence of the parameters retention mechanism and FPD span were evaluated. MATERIALS AND METHODS: Three Straumann implants were anchored in a measurement model based on a real-life patient situation and strain gauges (SGs) were fixed mesially and distally adjacent to the implants and on the pontics of the superstructures. During cement setting and screw fixation of 40 implant FPDs (10 samples from each group: three-unit cementable; five-unit cementable; three-unit screw-retained; five-unit screw-retained), strain development was recorded. For statistical analysis, multivariate two-sample tests were performed with the level of significance set at p= 0.1. RESULTS: The mean strain values for the four FPD groups at the different SG sites ranged from 26.0 to 637.6 microm/m. When comparing the four groups, no significant differences in strain magnitude could be detected. Similarly, a comparison of the two FPD spans revealed no significant difference (p= 0.18 for cementable FPDs; p= 0.22 for screw-retained FPDs). A comparison of the two fixation modes also revealed no significant difference (p= 0.67 for three-unit FPDs; p= 0.25 for five-unit FPDs). CONCLUSION: FPD span and retention mechanism appear to have only a minor influence on strain development in implant FPDs. As implant-supported restorations have proven to be successful over time, the question arises as to whether an "absolute" passive fit is a prerequisite for successful implant restorations.

Loading of bone surrounding implants through three-unit fixed partial denture fixation: a finite-element analysis based on in vitro and in vivo strain measurements.

Implant-borne fixed partial dentures (FPDs), whether cementable or screwable superstructures, ought to display a true passive fit. The objective of this in vivo-based finite-element analysis is, therefore, to quantify the degree of stress which occurs in the bone around the implants as a result of the fixation of cemented and screw-retained FPDs. On the basis of a simulated patient situation with two implants, six groups of implant-supported superstructures containing 10 samples each were fabricated. Strain gauges which were mounted on the pontics of the restorations were subsequently used to take in vivo measurements (Ethics Commission Approval No. 2315). Taking the values obtained as a basis, the von Mises equivalent stress was chosen to illustrate bone loading in three-dimensional finite-element models. Superstructure fixation caused residual interface stress as high as 30 MPa. Similar stress magnitudes can be observed for axial implant loading of 200 N. Assuming that the axial loading of a single implant with 200 N is within the bone's physiological range, it can be concluded that the degree of stress resulting from the fixation of superstructures alone does not constitute a risk.

In vivo stress behavior in cemented and screw-retained five-unit implant FPDs.

PURPOSE: When fixing implant-supported fixed partial dentures (FPDs), it is important to achieve passive fit. The objective of the in vivo study presented was to quantify the strain development during the fixation of screw- and cement-retained FPDs. MATERIALS AND METHODS: After informed patient consent had been obtained (Ethics commission Approval No. 2315; FAU Erlangen-Nuremberg, Germany), four groups of five-unit FPDs (five samples per group) were fabricated and investigated in vivo. Group 1: Cementable, repositioning technique impression, burn out plastic coping; Group 2: Screwable, pickup technique impression, burn out plastic coping; Group 3: Screwable, pickup technique impression, cast to gold cylinder; Group 4: Screwable, pickup technique impression, bonded to gold cylinder. Two strain gauges (SG) were attached to the pontics of each bridge (SG-M and SG-D) to measure the strains that occurred during either the cementing or screw-in process. The final values were recorded for analysis. RESULTS: The mean strain values (microm/m) for each SG were: Group 1: SG-M 32 microm/m, SG-D: 89 microm/m; Group 2: SG-M 302 microm/m, SG-D: 197 microm/m; Group 3: SG-M 458 microm/m, SG-D: 268 microm/m; Group 4: SG-M 269 microm/m, SG-D: 52 microm/m. CONCLUSIONS: Although the bridges were clinically acceptable, none of them revealed a truly passive fit with zero microstrain. In contrast to conventional screw-retained bridges, cement retention seems to result in lower strain levels. Bonding bridge pontics to prefabricated implant components seems to allow both the retrievability of a screw-retained bridge and produce moderate strain values.

Mandibular two-implant telescopic overdentures.

To stabilize mandibular overdentures in edentulous patients, various connector types which can be attached to between two and four implants placed in the anterior mandible are possible. Treatment using non-rigid telescopic connectors on two interforaminal implants for overdenture stabilization began in 1989. The objective of this study is to investigate soft- and hard-tissue conditions as well as prosthesis function after a period of 10 years. This also involved an evaluation of correlations between radiographic and clinical parameters. Twenty-three subjects with 46 interforaminal implants (ITI solid screw implants, 12 mm in length, 4.1 mm in diameter; 10.4 years in situ, range, 8-12.8 years) were investigated. Modified plaque index (mPI), sulcus fluid flow rate (SFFR), modified sulcus bleeding index (mBI), probing depth (PD), distance from implant crown margin to the coronal border of the peri-implant mucosa (DIM), attachment level (AL), width of keratinized mucosa (KM), Periotest values (PTVs) and prosthesis function were evaluated. In the radiographic evaluation, the distance between implant shoulder and first crestal bone-implant contact (DIB) in mm and the horizontal bone loss (HBL) in mm were measured. The relatively high mPI scores (mean, 0.82; score, 0 in 44.4%; SD, 0.83) did not result in increased SFFR scores (mean, 12; min, 3, max, 38; SD, 7.43) or higher mBI scores (mean, 0.35; score, 0 in 70.8%; SD, 0.59), which was commensurate with healthy peri-implant mucosa. A mean PD value of 2.15 mm (min, 1 mm; max, 5 mm; SD, 0.96) and a mean DIM value of 0.28 mm (min, 0 mm; max, 2 mm; SD, 0.52) were measured. The implants were stable, showing a mean Periotest value of -1.91 (max, 02, min, -6; SD, 1.76). A mean DIB of 3.19+/-0.95 mm (range, 1.3-5.16 mm) and a mean HBL of 1.6+/-1.52 mm (range, 0.28-8.33 mm) were calculated. A correlation was found between DIB and the parameters SFFR (P=0.060), DIM (P=0.042), AL (P=0.050) and especially PTV (P<0.01), leading to the assumption that these clinical parameters may be useful indicators of peri-implant bone loss. The results of the 10-year follow-up examination show that non-rigid telescopic connectors with two interforaminal implants for overdenture stabilization appear to be an efficient and effective long-term treatment modality in severely resorbed edentulous mandibles. Particularly in geriatric patient treatment this concept may provide advantages in terms of handling, cleaning and long-term satisfaction.

Cement fixation and screw retention: parameters of passive fit. An in vitro study of three-unit implant-supported fixed partial dentures.

It is generally assumed that passively fitting superstructures are a prerequisite for long-lasting implant success. In the study presented, the strain development of three-unit implant fixed partial dentures (FPDs) was evaluated at the bone surrounding the implant and on the superstructure using a strain gauge technique. Six groups of three-unit FPDs representing the commonly used techniques of bridge fabrication were investigated with 10 samples each, in order to quantify the influence of impression technique, mode of fabrication and retention mechanism on superstructure fit. Two ITI implants (Straumann, Waldenburg, Switzerland) were anchored in a measurement model according to a real-life patient situation and strain gauges were fixed mesially and distally adjacent to the implants and on the bridge pontics. The developing strains were recorded during cement setting and screw fixation. For statistical analysis, multivariate two sample tests were performed setting the level of significance at P=0.1. None of the investigated bridges revealed a truly passive fit without strains occurring. About 50% of the measured strains were found to be due to impression taking and model fabrication, whereas the remaining 50% were related to laboratory inaccuracies. The two impression techniques used did not reveal any significant differences in terms of precision. Both modes of fixation--i.e. cement and screw retention--provoked equally high stress levels. In the fabrication of screw-retained FPDs, similar results were obtained from the use of burn-out plastic copings and the technique of casting wax moulds to premachined components. Bonding bridge frames onto gold cylinders directly on the implants significantly reduces strain development.