Multiple dental implant failures: A retrospective analysis of implant retention time and risk factors.

BACKGROUND: The present retrospective study investigates implant retention time in patients who had experienced multiple implant failures and explores possible risk factors. MATERIALS AND METHODS: Patients who underwent placement of at least two implants and experienced failure of two or more implants between 2004 and 2022 were included in the study population. Both patient- and implant-related risk factors, including age, sex, medical history, medication intake, smoking, alcohol consumption, implant properties and anatomical and surgical factors, were evaluated. Descriptive analysis and univariate and multivariate statistical analysis were performed to assess implant retention time and failure risk, with the level of statistical significance set at 0.05. RESULTS: A total of 371 patients (178 men and 193 women, median age 63 years) with 3,141 implants were included in the analysis (3.14% of all patients treated since 2004). Out of these implants, 1,090 failures were observed (59.01% of all failed implants at the Academy of Oral Implantology, Vienna, Austria), with a median retention time of 108.11 months. Patients who lost teeth due to periodontitis did not show a tendency towards early implant failure (P > 0.001). Nicotine consumption (P < 0.001), age < 50 years and > 70 years (P < 0.001), maxillary location (P = 0.05), transgingival healing (P < 0.001), no provisional restoration (P = 0.035) and short implant length (P < 0.001) were associated with statistically significantly shorter implant retention times. CONCLUSIONS: Patients with multiple implant failures displayed cluster behaviour and had a median implant retention time of 9 years. Smoking, short implant length, single-stage surgery and immediate loading were all associated with a higher risk of failure, whereas age between 50 and 70 years and tooth loss due to periodontitis were associated with a longer implant retention time.

Single tooth implants in the esthetic zone following a two-stage all flapless approach: A retrospective analysis.

BACKGROUND: Due to chronic inflammation or trauma facial bone is frequently missing after tooth loss in the esthetic zone. As a consequence, procedures to augment or at least to preserve bone are frequently necessary prior to implant placement. PURPOSE: The aim of this retrospective case series is to demonstrate the applicability of a staged all-flapless concept to establish satisfactory implant restorations following situations of partial missing facial bone in the esthetic zone. MATERIALS AND METHODS: Radiological/clinical data of 25 patients were analyzed and an esthetic evaluation of 24 patients was performed. The staged concept included ridge preservation at time of tooth extraction and delayed guided implant placement. Marginal bone loss was measured radiologically and esthetic evaluation was performed based on standardized photographs using the Pink Esthetic Score as well as the Papilla Index. RESULTS: Implant success rate revealed 100%. The mean radiological peri-implant marginal bone loss measured 1.16 mm (SD: 0.16). Regarding the esthetic outcome 71% of patients were evaluated with a Pink Esthetic Score higher or equal to 10 constituting satisfactory esthetics (median pink esthetic score: 10). The mean follow-up time for clinical and radiographic analysis was 1.3 years (SD: 0.6 years) and 1.2 years (SD: 0.6) for esthetic evaluation. CONCLUSION: Although marginal bone loss cannot be avoided, the staged concept of flapless ridge preservation and subsequent delayed flapless guided implant placement carries the potential to improve esthetics of single-tooth implants in the anterior maxilla.

Extra-short (< 7 mm) and extra-narrow diameter (< 3.5 mm) implants: a meta-analytic literature review.

AIM: To review available evidence in scientific literature on oral implants of severely reduced length or diameter. MATERIALS AND METHODS: Electronic and hand searches up to May 2017 were performed in order to identify clinical investigations providing implant survival and/or marginal bone resorption data for extra-short implants < 7.0 mm in length and extra-narrow implants < 3.5 mm in diameter (excluding one-piece mini-implants). RESULTS: A total of 2929 extra-short implants and 3048 extra-narrow diameter implants were investigated in 53 and 29 clinical studies, respectively. Shorter implants between 4.0 mm and 5.4 mm in length showed comparable results to implant lengths of 5.5 mm to 6.5 mm (95.1% vs. 96.4%, P = 0.121) and no difference regarding marginal bone resorption (0.7 mm vs 0.5 mm, P = 0.086). Implant lengths of 5.5 mm to 6.5 mm, however, performed significantly better in the mandible compared with the maxilla (P = 0.010). Smaller diameters between 3.0 mm and 3.25 mm yielded a significantly lower survival rate of 94.3% than wider implants of 3.3 mm to 3.4 mm diameter (97.7%, P < 0.001), while marginal bone resorption did not differ (0.4 mm vs 0.5 mm, P = 0.447). CONCLUSIONS: The results of the present literature review suggest that extra-short and extra-narrow-diameter implants show satisfactory survival rates of around 95% and little marginal bone resorption of around 0.5 mm after a mean follow-up of 3 years. However, implant lengths < 7 mm in the maxilla and < 5.5 mm in the mandible as well as diameters < 3.3 mm may increase early failure rates.

A description of the sequence of long-term behavior of autogenous boneblock in maxillary sinus augmentation in sheep: Additional morphologic and histomorphometric evidence.

OBJECTIVE: To document the behavior of autogenous bone block in sinus lift and surgical consequences. STUDY DESIGN: Twelve sinus lifts with autogenous hip bone blocks and simultaneous insertion of two implants in 6 adult female sheep. Polychrome sequential labelling and histologic and histomorphometric evaluation after 6, 16, and 26 weeks. RESULTS: Augmentation material in the apical third was almost fully resorbed after 26 weeks (P = .00388). Percentage of bone tissue increased 0.5-1.0 mm from the implant in crestal region (15.3 ± 7.5% to 16.2 ± 10.1%), whereas it vanished in the apical region from 16 to 26 weeks (4.2 ± 10.4% to 0%) (P = .363). CONCLUSIONS: Autogenous bone block leaves an apical thin but functionally crucial layer covering implants in a form follows function way. Denial of animal-originated biomaterials and prion diseases remain a rarely discussed issue. The use of an implant length-adapted autogenous transplant with osseoinductive advantages should be taken into consideration.

Alveolar Ridge Augmentation Using Dystopic Autogenous Tooth: 2-Year Results of an Open Prospective Study.

PURPOSE: To evaluate the use of chemically unchanged tooth material in lateral alveolar ridge augmentation or for the filling of jaw defects. MATERIALS AND METHODS: A total of 20 patients underwent either lateral augmentation of the alveolar process (11 patients) or filling of jaw defects (6 patients) with autogenous unaltered tooth material in a longitudinal 2-year study. In three patients, the jaw defect was so marked that a bone block graft had to be used for augmentation in addition to particulate dental material. In four patients, an autogenous tooth block was exclusively used; in seven, crushed tooth material was exclusively used; and in the remaining six, dystopic teeth that had been extracted were removed, crushed, and reinserted into the defect in particulate form. Fully impacted teeth served as autogenous donor teeth. RESULTS: After a healing time of 3 to 6 months, 28 implants could be placed (10 immediate implants, 18 delayed implants). At 6, 12, and 24 months postrestoration, peri-implant bone loss as assessed by x-ray was 0 mm, 0.4 mm, and 0.6 mm, respectively. Peri-implant probing depth was 1 mm after 1 year and 2 mm after 2 years. Bleeding on probing was not seen in any of the implants after 2 years. CONCLUSION: Autogenous tooth material appears to be suitable for the restoration of lateral and intraosseous defects of the alveolar ridge with both complete blocks and in particulate form. However, additional long-term studies with higher case numbers will be required for substantiating these results.

Immediate Restoration of Immediate Implants in the Esthetic Zone of the Maxilla Via the Copy-Abutment Technique: 5-Year Follow-Up of Pink Esthetic Scores.

BACKGROUND: Implant esthetics may benefit from individualized zirconia abutments copying the emergence profile of the natural tooth and delivered within days after immediate implant insertion. PURPOSE: To investigate the esthetic outcome of the Copy-Abutment technique using the Pink Esthetic Score (PES). MATERIALS AND METHODS: A total of 77 patients with single-tooth implants in the anterior maxilla restored at the day of immediate implant placement using Copy-Abutments and provisional crowns were followed-up after 1 week, 1 month, 4 months, 6 months, 1, 2, 3, 4, and 5 years to assess implant esthetics. RESULTS: PES ranged between 7 and 14 (median: 13) and improved significantly between the 6 month and 1 year follow-up (p < .001), then remained stable up to the fifth year. Significant improvement was seen for the variables PES-6 soft tissue color (p = .002) and PES-7 soft tissue texture (p < .001) up to the 1 year follow-up, while PES-5 alveolar process deficiency deteriorated (p = .016). Mean mucosal recession was 0.26 ± 0.86 mm (range: 0-1.6) after 5 years and not related to gingival biotype. CONCLUSION: Copy-Abutments for immediate restoration of implants in the esthetic zone show satisfactory long-term esthetic outcomes.

Graftless Full-Arch Implant Rehabilitation with Interantral Implants and Immediate or Delayed Loading-Part II: Transition from the Failing Maxillary Dentition.

PURPOSE: To compare long-term survival and marginal bone loss of immediate interantral implants in the nonaugmented maxilla subjected to immediate vs delayed loading. MATERIALS AND METHODS: Graftless maxillary cross-arch rehabilitation was performed in a total of 362 patients in the years 2004 to 2013 (1,797 implants). Of the 240 patients with immediate implants replacing their failing maxillary dentition, 81% were subjected to immediate loading and 19% to delayed loading of their 4 to 6 interantral implants (980 and 235 implants, respectively). Kaplan-Meier survival estimates were computed and marginal bone loss was evaluated in a stratified random sample of 20 patients per group. RESULTS: Thirty-one of 1,215 implants failed within the mean observation period of 3.9 years, and no difference in 8-year survival estimates could be seen between immediate (97.6% [95% CI: 96.7 to 98.6]) and delayed (96.6% [95% CI: 94.3 to 98.9]) loading protocols (P = .359). Mean marginal bone resorption following implant insertion did not differ significantly between the groups (1.5 ± 1.7 mm vs 0.7 ± 1.1 mm, P = .379); however, it was significantly associated with a reduced number of implants (P = .017) and patient history of periodontal disease (P < .001). CONCLUSION: Immediate loading of interantral implants yields satisfactory results in the transition of patients from a failing maxillary dentition to full-arch implant rehabilitation and thus may be favored over delayed loading concepts.

Trends in techniques to avoid bone augmentation surgery: Application of short implants, narrow-diameter implants and guided surgery.

INTRODUCTION: Minimally invasive implantology using reduced implant dimensions as well as virtual treatment planning and CAD/CAM stereolithographic templates has gained popularity in recent years. The aim of the present investigation was to analyze prevailing trends in clinical utilization of these graftless therapeutic options. MATERIAL AND METHODS: A total of 12.865 dental implants were placed in 5.365 patients at the Academy for Oral Implantology in Vienna, of which 5.5% were short (length < 10 mm), 19.5% narrow (diameter < 3.75 mm) and 10.6% template-guided. Application trends were analyzed using linear regression and compared between jaw location and dentition subgroups. RESULTS: Use of short implants and guided surgery increased significantly in all subgroups. Narrow-diameter implants were most frequent in single-tooth gaps (24.1%), however, upward trends could only be observed in partially and completely edentulous patients. Short implants were predominantly used in the mandible (9.9% vs. 2.5%, P < 0.001) while guided surgery was favored in the maxilla (14.2% vs. 5.4%, P < 0.001). CONCLUSION: Short implants (most frequent in partial edentulism) and guided implant surgery (most frequent in complete edentulism) represent uprising and promising surgical approaches to avoid patient morbidity associated with bone graft surgery.

Periimplantitis Treatment: Long-Term Comparison of Laser Decontamination and Implantoplasty Surgery.

PURPOSE: Periimplantitis is the most frequent cause of late implant failure; however, little is known about the long-term success of periimplantitis treatment and the effectiveness of various therapeutic interventions. MATERIALS AND METHODS: A total of 142 patients were referred to the Academy for Oral Implantology in Vienna for the treatment of recurrent periimplantitis around single-tooth implants. Of them, 72 patients (51%) were treated by laser decontamination, 47 patients (33%) by implantoplasty surgery, and 23 patients (16%) by a combination of both approaches. RESULTS: Overall success of periimplantitis therapy was 89% after 9 years of follow-up, and it did not differ significantly between female and male patients (P = 0.426). The number of implant failures that could not be prevented by periimplantitis treatment was 6 after laser decontamination (8%), 6 after implantoplasty surgery (13%), and 4 after a combination of both therapies (17%). Implant loss occurred after 4.9 ± 1.9 years of therapy, on average. No significant difference between the 3 treatment groups could be observed (P = 0.393). CONCLUSION: The present results suggest that success rates of periimplantitis therapy with either laser decontamination or surgical implantoplasty are high. These success rates do not appear to be associated with patient gender or treatment strategy.

Graftless Full-Arch Implant Rehabilitation with Interantral Implants and Immediate or Delayed Loading-Part I: Reconstruction of the Edentulous Maxilla.

PURPOSE: To compare long-term survival and marginal bone loss of late interantral implants in the nonaugmented edentulous maxilla subjected to immediate vs delayed loading. MATERIALS AND METHODS: One hundred twenty-two edentulous patients with implants in native, healed jawbone were subjected to either immediate loading (179 implants) or delayed loading (403 implants) of their four to six interantral implants (part I of 362 graftless maxillary cross-arch rehabilitations performed in the years 2004 to 2013). Kaplan-Meier survival estimates were computed, and marginal bone loss was evaluated in a stratified random sample of 20 patients per group. RESULTS: Fifteen of 582 implants failed within the mean observation period of 4.7 years, and no difference in 8-year survival estimates could be seen between immediate (98.3% [95% CI: 96.4-100.0]) and delayed (96.7% [95% CI: 94.7-98.6]) loading protocols (P = .370). Mean marginal bone resorption following implant insertion did not differ significantly between the groups (1.1 ± 1.3 mm vs 1.4 ± 1.3 mm, P = .490). CONCLUSION: Immediate loading of interantral implants in the nonaugmented edentulous maxilla yields favorable results comparable to delayed loading and may be considered to shorten periods of removable provisional prostheses in maxillary edentulism.

Patient-Perceived Morbidity and Subjective Functional Impairment Following Immediate Transition from a Failing Dentition to Fixed Implant Rehabilitation.

PURPOSE: Failing residual dentition gives rise to patient concerns about the surgical and prosthodontic management of immediate implant rehabilitation. The purpose of this study was to assess subjective patient experiences of full-arch immediate implant loading. MATERIALS AND METHODS: Patients made a transition from poor dentition in the maxilla (25 patients) or mandible (25 patients) to full-arch rehabilitation on the day of extraction using four interantral or interforaminal implants. Provisional restoration was performed, and postoperative pain, swelling, and patient-perceived impairment in the first week was recorded. RESULTS: Absence of pain was reported by 40%, 52%, and 66% of patients, on the day of surgery, on the first day after surgery, and on the second day after surgery, respectively; pain levels decreased significantly (from 1.8 to 0.9, P < .001) and patient-reported swelling decreased from 1.5 to 1.3 (P = .058) on a 10-point scale. Postoperative impairment of everyday life and work (mean score = 1.1) was significantly less pronounced than impairment of food intake (mean score = 2.2; P = .004) or speech (mean score = 1.9; P = .002). Of these patients, 88% would again undergo the procedure without doubt. CONCLUSION: Although patient-perceived morbidity after immediate full-arch implant rehabilitation is low in general, minor masticatory and phonetic impairment should be taken into account.

Denture-Related Biomechanical Factors for Fixed Partial Dentures Retained on Short Dental Implants.

Prosthodontically driven biomechanical considerations are essential for longterm successful outcomes in dental implant therapy. Correct protocols seek to preclude potential consequences associated with functional and parafunctional occlusal overload such as screw loosening, component fracture, compromised marginal bone maintenance, and the integrity of the induced osseointegration response. Other concerns also need to be addressed, more especially when other implants are selected, for example: bridge insertion torque (BIT) in cases of immediate loading, cantilever length-anteroposterior spread ratio (CL-AP), overall crown-to-implant ratio (oCIR), total bone-to-implant surface area (tBICA), and the status of the opposing dentition. In spite of promising clinical results, evidence-based clinical protocols demand that such biomechanical limits still need to be determined.

Esthetics of Flapless Single-Tooth Implants in the Anterior Maxilla Using Guided Surgery: Association of Three-Dimensional Accuracy and Pink Esthetic Score.

BACKGROUND: Flapless implant placement using surgical templates may guarantee predictable and esthetic results provided that preplanned implant positions are transfered precisely into surgical reality. PURPOSE: The study aims to investigate the effect of three-dimensional accuracy in guided implant surgery on the esthetic outcome of single-tooth implants in the anterior maxilla. MATERIALS AND METHODS: Single-tooth implants for delayed replacement of upper incisors were inserted in 27 patients using stereolithographic templates. Superimposition of postoperative cone beam computed tomography (CBCT) scans allowed assessment of positional inaccuracy at the implant shoulder and apex, as well as angular deviation. Objective evaluation of implant esthetics was performed after a mean follow-up of 2.3 years using the Pink Esthetic Score (PES). RESULTS: Mean deviation between planned and actual implant position was 0.84 mm at the implant shoulder and significantly correlated to average PES of 12 (p = .031). Inaccuracy toward the buccal side was most frequent (70%). Deviations ≥ 0.8 mm resulted in significantly worse implant esthetics (median PES: 9.5, interquartile range [IQR]: 8-11) compared with more accurate implant positions (median PES: 13, IQR: 12-13, p = .039). CONCLUSION: Positional inaccuracy is low in guided implant surgery, but may however significantly compromise implant esthetics in the anterior maxilla.

Patients' preferences towards minimally invasive treatment alternatives for implant rehabilitation of edentulous jaws.

PURPOSE: To evaluate patient satisfaction, oral health-related quality of life, and patients' preferences towards minimally invasive treatment options for graftless rehabilitation of complete edentulism by means of dental implants. MATERIAL AND METHODS: A MEDLINE search of literature in the English language up to the year 2013 was performed to summarise current evidence from the patient's perspective. The final selection included 37 studies reporting on minimally invasive implant treatment of 648 edentulous maxillae and 791 edentulous mandibles in 1328 patients, via a total of 5766 implants. RESULTS: Patient satisfaction averaged 91% with flapless implant placement (range: 77 to 100%), 89% with short implants, 87% with narrow-diameter implants (range: 80 to 93%), 90% with a reduced number of implants (range: 77 to 100%), 94% with tilted implant placement (range: 58 to 100%), and 83% with zygomatic fixtures (range: 50 to 97%). Indirect comparison yielded patient preference towards tilted implant placement compared to a reduced number of implants (P = 0.036), as well as to zygomatic implants (P = 0.001). CONCLUSIONS: While little evidence on patients' preferences towards minimally invasive treatment alternatives vs. bone augmentation surgery could be identified from within-study comparison, it may be concluded that patient satisfaction with graftless solutions for implant rehabilitation of completely edentulous jaws is generally high. Comparative effectiveness research is needed to substantiate their positive appeal to potential implant patients and possible reduction of the indication span for invasive bone graft surgery.

Peri-implant bone loss as a function of tooth-implant distance.

PURPOSE: In a retrospective study, the radiographs of 39 patients with Applegate-Kennedy Class I or II in the posterior mandible who had been treated with screw-anchored fixed partial dentures supported by IMZ implants and natural teeth were examined for the presence of radiologically detectable peri-implant bone loss. Furthermore, the results were correlated with a mathematical model. MATERIALS AND METHODS: The radiographs of the implants were digitized, and the areas of bone atrophy mesial and distal to the implants were determined semi-automatically. The data obtained were correlated with the distance between the implant and the abutment tooth. The connection between the tooth-supported crown and the implant-supported denture was made with a vertical screw-lock precision attachment. In a mathematical analysis it was assumed that the fixed partial prosthesis was a rigid beam with 3 elastically embedded supports. RESULTS: The mean distance between the tooth and the first implant was 11.02 mm (SD: 4.24), and between the tooth and the second implant was 20.25 mm (SD: 5.16). Peri-implant bone loss significantly followed a rational function (mesial implant: P = .03, distal implant: P = .02), meaning that, as the tooth-implant distance increased, the area of atrophy became rapidly larger and then diminished gradually. Distances of 8 to 14 mm between the tooth and the first implant and of 17 to 21 mm between the tooth and the second implant were associated with a more pronounced bone loss. These results were also confirmed mathematically. CONCLUSION: A tooth-implant distance of 8 to 14 mm for the first implant and 17 to 21 mm for the second implant should be avoided for implant placement if prosthetic rehabilitation is planned using a fixed partial denture supported by a premolar and 2 IMZ implants in the mandible. Although this investigation was done on IMZ implants only, the results were confirmed by a mathematical model, which indicated that the observed bone loss may be the same in other types of implants placed in the same positions.

Porous hydroxyapatite for grafting the maxillary sinus in sheep: comparative pullout study of dental implants.

PURPOSE: In this experimental study, dental implants placed after maxillary sinus grafting with either porous hydroxyapatite (HA) (Interpore 200) or autogenous bone were examined for their mechanical stress tolerance. MATERIALS AND METHODS: A total of 54 titanium plasma flame-sprayed cylindric implants were placed in the lateral sinus wall bilaterally of 27 mountain sheep. The bony sinuses were opened through an extraoral approach. Eighteen sinuses were grafted with porous HA, and another 18 were grafted with cancellous bone from the iliac crest. Eighteen non-grafted sinuses were used as controls. In the same operation, 2 cylindric implants were placed in each of the sinuses. One implant of each sinus was tested for mechanical strength of the bone-implant interface at 12, 16, and 26 weeks using pullout force. RESULTS: The mean pullout force was 259.3 N in the control group, 356.7 N in the autogenous bone group, and 376 N in the HA group. Pooled data for the grafted sites showed the pullout force to be significantly higher than in the empty control sites (P = .02). The pullout force increased significantly with ongoing healing time (P = .02), but there was considerable variation within the groups. While the force remained more or less constant throughout the follow-up time in the controls (248 N at week 12 to 276 N at week 26), it increased dramatically in the group augmented with autogenous bone (223.8 N at week 12 to 523.16 N at week 26). The pullout force was initially highest in the HA group (302.3 N at week 12) and increased to 423.5 N at 26 weeks, but it did not reach the levels recorded in the autografted group. DISCUSSION AND CONCLUSION: Mechanical tests of bone-to-implant contact in a sheep model showed that HA for 1-stage sinus floor elevation significantly increased the pullout force versus ungrafted sinuses, although it was less than that found with autogenous bone after 26 weeks.

[Objective assessment and therapeutic efficacy of an improved mandibular advancement device for snoring and sleep apnea syndromes with polysomnography]. / Objektivierung der Therapieeffizienz eines neuartigen mandibulären Protrusionsbehelfs für Schnarchen und schlafbezogene Atmungsstörungen mittels Polysomnographie.

In the treatment of snoring (SN) and sleep-related breathing disorders (SRBD), mandibular advancement devices (MAD) are of increasing importance. Their mode of action is based on the advancement of the mandible, thereby increasing various upper airway dimensions and thus airway patency and airflow during sleep. The aim of the present study was to investigate efficacy and tolerability of an individually fitted MAD on 11 patients (10 males, 1 female), mean age 57 years, using sleep laboratory methods in 3 subsequent nights (adaptation-, baseline-, treatment night). The MAD consists of 2 separate parts that attach to both dental arches. On occlusion the upper maxillary part with a protruding cone meets an inclined plane of the lower mandibulary part, thereby forcing the mandible to advance. 10 patients (6 with obstructive sleep apnea, 3 with obstructive hypopnea and 1 primary snorer) tolerated the MAD well; one patient (primary snorer) removed the MAD after 1 hour. Regarding the target variable, the snoring index (SI), confirmatory statistics demonstrated a significant improvement from 108 to 53/h sleep, though normalisation could not be achieved. Descriptive data analysis showed significant improvement of the apnea-hypopnea index (AHI) from 15 to 5.5/h and of the oxygen desaturation index (O2-DI) from 21 to 13/h sleep. Arousal variables and periodic leg movement index (PLMI) improved as well. Objective sleep efficiency and subjective sleep- and awakening quality remained unchanged. Thus, besides the good therapeutic efficacy (the medians of improvement of the SI, AI, AHI, O2-DI and PLMI were 37, 48, 53, 51 and 29%, respectively), acute acceptance of the MAD was also satisfactory. Last but not least our present study showed once more the necessity of an adaptation night, as from the first to the second sleep laboratory night respiratory indices deteriorated significantly.

A long-term follow-up of 76 Bränemark single-tooth implants.

In a previous study (Haas et al. 1995), we reported on preliminary results of 76 Brånemark implants placed in 71 patients with single-tooth gaps. The present study examines the results of the same group over a longer period of time: 55 implants were followed for more than 5 years, 12 for a period between 4 and 5 years and 1 implant for 46 months. One patient died 3 years after implant placement. Five patients lost their implant within 24 months after insertion. The drop-out rate was 2 implants in 2 patients. The recall rate was thus 97%. Of the 5 implant failures, 2 were located in the maxilla and 3 in the mandible. The Kaplan-Meier survival probability was 93% after 120 months. 74% of the sites showed healthy peri-implant soft tissue conditions. At 15 implants (22%) a bone resorption of more than 2 mm was observed on intraoral radiographs. The mean bone resorption was 1.8 mm in the maxilla and 1.3 mm in the mandible and did not increase with time (Pearson correlation coefficient: r = -0.06, P = 0.59). Abutment loosening occurred in 7 implants (10%), however all abutments that were fixed with a defined torque subsequently remained stable. Thus the favourable preliminary results could be maintained over an average 66 months, indicating that if implant loss happens it seems to occur during the first 2 years after insertion.

Effect of low-power laser irradiation on bony implant sites.

This study was designed to examine the effects of low-energy laser irradiation on osteocytes and bone resorption at bony implant sites. Five male baboons with a mean age of 6.5 years were used in the study. Four holes for accommodating implants were drilled in each iliac crest. Sites on the left side were irradiated with a 100 mW low-energy laser (690 nm) for 1 min (6 Joule) immediately after drilling and insertion of four sandblasted and etched (Frialit-2 Synchro) implants. Five days later, the bone was removed en bloc and was evaluated histomorphometrically. The mean osteocyte count per unit area was 109.8 cells in the irradiated group vs. 94.8 cells in the control group. As intra-individual cell counts varied substantially, osteocyte viability was used for evaluation. In the irradiated group, viable osteocytes were found in 41.7% of the lacuna vs. 34.4% in the non-irradiated group. This difference was statistically significant at P < 0.027. The total resorption area, eroded surface, was found to be 24.9% in the control group vs. 24.6% in the irradiated group. This difference was not statistically significant. This study showed that osteocyte viability was significantly higher in the samples that were subjected to laser irradiation immediately after implant site drilling and implant insertion, in comparison to control sites. This may have positive effects on the integration of implants. The bone resorption rate, in contrast, was not affected by laser irradiation.