Long-term evaluation of 282 implants in maxillary and mandibular molar positions: a prospective study

Do dental implants installed in different types of bone (I, II, III, IV) have different success rates? A systematic review and meta-analysis

Purpose

The objective of this systematic review and meta-analysis was to evaluate the survival rate of implants installed in bone type IV (Lekholm and Zarb, 1995) compared to that of implants installed in bone types I, II, and III.

Material and methods

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA) and was registered in the PROSPERO International Database of Systematic Reviews (CRD42021229775). The PubMed/MEDLINE, Scopus, and Cochrane databases were searched through July 2021. The PICO question was: "Dental implants installed in type IV bone have a lower success rate when compared to implants installed in type I bone, II and III?". The established inclusion criteria were: 1) controlled and randomized clinical trials (RCT), 2) prospective and retrospective studies with at least 10 participants with dental implants, and 3) patients with dental implants installed in bone tissue types I, II, III, and IV (Lekholm and Zarb, 1985). The minimum followup duration was 1 year.

Results

After searching the identified databases, 117 articles were selected for full reading and 68 were excluded. Thus, 49 studies were included for qualitative and quantitative analyses. The total number of participants included was 12,056, with a mean age of 41.56 years and 29,905 implants installed. Bone types I, II, and III exhibit a lower implant failure rate when compared to bone type IV.

Conclusion

Dental implants installed in bone types I, II, and III showed significantly higher survival rates than those installed in type IV. The bone type I success rate was not significantly different than that of type II; however, the success rate of bone type I and II was higher than that of type III.

Clinical performance of short and extrashort dental implants with wide diameter: A systematic review with meta-analysis

STATEMENT OF PROBLEM

Rehabilitation with wide-diameter reduced-length implants has become popular for patients with minimal vertical bone. However, a consensus on the benefits of this approach is lacking.

PURPOSE

The purpose of this systematic review with meta-analysis was to evaluate the influence of wide compared with regular diameter on the clinical performance of short (<10 mm) and extrashort (≤6 mm) dental implants used for rehabilitations with single crowns, fixed partial dentures, or both, in the posterior region.

MATERIAL AND METHODS

A search in 6 databases was conducted to select randomized controlled trials (RCTs) and nonrandomized controlled trials (N-RCTs). Five meta-analyses were performed, where the risk ratio (RR) was evaluated. The certainty of evidence was evaluated, and the risk of bias was determined from the Joanna Briggs Institute checklist.

RESULTS

Fourteen articles were included, 272 wide- and 478 regular-diameter implants. One study presented a low, 3 an unclear, and 11 a high risk of bias. Meta-analyses showed no statistical difference: implant survival, short dental implants in N-RCTs (up to 1 year - RR 1.01 [0.98; 1.03], 1 to 5 years - RR 1.01 [0.94; 1.08], more than 5 years - RR 1.01 [0.97; 1.06]), extrashort dental implants in N-RCTs (RR 1.04 [0.90; 1.20]), RCTs (RR 1.05 [0.88; 1.25]); implant success in N-RCTs (RR 1.01 [0.97; 1.05]); prosthesis success in N-RCTs (RR 1.01 [0.97; 1.05]).

CONCLUSIONS

Short and extrashort dental implants with a wide and regular diameter appear to be clinically appropriate options for implant-supported posterior restorations, with high survival, success, and prosthesis success rates.

The developing patterns of calibrated implant stability quotients of posterior implants

Background/Purpose

Many surgical protocols were modified to improve implant stability. However, the conclusions of applying osteotome condensation technique could enhance implant stability were controversial. The evaluated implant stability quotients (ISQ) were calibrated to differentiate the implant stability improvement that applied by varied surgical techniques and the bone quality at recipient sites. Therefore, this study examine the developing patterns of calibrated ISQ values induced by osteotome bone condensation and conventional drilling technique at the posterior ridges.

Materials and methods

The ISQ values of 4.1/4.8-mm diameter implants were calibrated by 3.3-mm diameter implants (ISQ_b). Osteotome condensation technique was applied on the sites with ISQ_b ≤ 65 while those with ISQ_b > 65 were treated with conventional drilling technique. The implant ISQ values at Week 0, 1, 2, 3, 4, 6, 8, 10, 12 were recorded. The detected and calibrated ISQ values were statistically analyzed.

Results

Maxillary 14 implants and mandibular 16 implants using osteotome technique, maxillary 15 implants and mandibular 16 implants with conventional drilling technique were studied. Both techniques showed a generally similar ISQ developing pattern at both arches. Without calibration, significantly less ISQ values were noted for the osteotome technique of posterior maxilla at initial four weeks; subsequently, both techniques presented a comparable ISQ developing pattern. Osteotome technique demonstrated a greater ISQ increase after calibration on both arches (p < 0.05). All implants reached an ISQ stability plateau between Week 8 and 10.

Conclusion

With calibration, osteotome condensation technique could enhance greater primary and secondary implant stability for both arches.

Retrospective Clinical Study of a Freely Removable Implant-Supported Fixed Dental Prosthesis by a Microlocking System

This retrospective clinical study was conducted to evaluate the clinical usefulness of a freely removable microlocking implant prosthesis (MLP) that was developed to overcome the problems with conventional implant prostheses. A total of 54 patients (male: 31, female: 23) and 100 implant prostheses were included. Patients were divided into three groups such as 6-12 months, 12-18 months, and 18-24 months according to the used period after implant prosthesis delivery, and the patients in each group were recalled for examinations of survival rate, marginal bone resorption, peri-implant soft tissue indices, and complications. The prosthetic complications were analysed by combining the recorded chart data during the periodic checks including the last call for this study. During a 2-year observation period, all the implants showed a 100% survival rate without clinical mobility and functional problems. There was no significant difference in marginal bone resorption, plaque index, and bleeding index over the observation period after implant prosthesis delivery. Probing depth of the 18-24 months group (1.5 ± 0.19 mm) was significantly lower than that of the 6-12 months group (p < 0.05). The main complication was abutment loosening (4%), followed by implant prosthesis fracture (2%) and food impaction (2%) which were recorded. Within the limits of the present study, the implant prostheses with MLP are considered to be an applicable and predictable treatment method.

The impact of the alveolar bone sites on early implant failure: a systematic review with meta-analysis

Dental implants are the first option for replacement of missing teeth. Failure usually involves additional cost and procedures. As a result, the physician should limit the risk factors associated with implant failures. Implant site is one of many factors that can influence the success or failure of dental implants. The association between early implant failure (EIF) and implant site has yet to be documented. This review aims to estimate the impact of insertion site on the percentage of EIFs. An electronic and manual search of studies that reported early failure of dental implants based on collection site. A total of 21 studies were included in the review and examined for the association between EIF and alveolar site. Subgroup analysis, including a comparison between implants inserted in four alveolar ridge regions of both jaws was performed. The early failure rate was higher for maxillary implants (3.14%) compared to mandibular implants (1.96%). Applying a random effect, risk ratio (RR), and confidence interval (CI) of 95% revealed higher failure in the maxilla compared to the mandible (RR 1.41; 95% CI [1.19, 1.67]; P<0.0001; I²=58%). The anterior maxilla is more critical for early implant loss than other alveolar bone sites. Implants in the anterior mandible exhibited the best success rate compared of the sites.

Porous shape memory dental implant by reactive sintering of TiH2-Ni-Urea mixture

We produced bifurcated bone-like shape memory implant (BL-SMI) with desirable tooth-root fixation capability by compact-sintering of TiH₂-Ni-urea mixture. The primary constituents of the porous product were Ni and Ti. We could adjust the pores' shape, size, and interconnectivity for favorite bone ingrowth by using urea as a space holder. Without urea, we obtained an average porosity of 0.30, and a mean void size of 100 μm. With 70 vol % urea, we got 62% interconnected pores of 400 μm average size. Aging allowed us to tune the austenite-martensite transformation temperatures towards the needed body tissue arouse. Differential scanning calorimetry measured the transformation temperatures. Their austenite start, austenite peak, and austenite finish values were A_s = 4, A_p = 22, and A_f = 34 °C, respectively. They retained functional shape recovery and superelastic effect at the body temperature. Mechanical properties, including Young's modulus of the specimens, matched well to maxilla and mandible bone tissue. The measured Young's modulus of the NiTi specimens was as low as 3.5 GPa, which decreased to ∼2.1 GPa with further porosity increase at higher space holder percentages. Superelasticity regime and low Young's modulus of the implant could potentially prevent stress-shielding from the surrounding bone tissues and give rise to secure fixation of the implant into the bone socket. Bending tests showed 0.9 mm recoverable deflection for specimens which assisted immediate self-fixation of the implant into the jaw bone cavity.

7-mm-long dental implants: retrospective clinical outcomes in medically compromised patients

Objectives

Dental implants shorter than 8 mm, called short dental implants (SDIs), have been considered to have a lower success rate than standard length implants. But recent studies have shown that SDIs have a comparable success rate, and implant diameter was more important for implant survival than implant length. Also, SDIs have many advantages, such as no need for sinus lifting or vertical bone grafting, which may limit use in medically compromised patients.

Materials and Methods

In this study, 33 patients with 47 implants 7-mm long were examined over the last four years. All patients had special medical history and were categorized into 3 groups: systemic disorders, such as diabetes mellitus (controlled or uncontrolled), mental disability, and uncontrolled hypertension; oral cancer ablation with reconstruction, with or without radiotherapy; diverse osteomyelitis, such as osteoradionecrosis and bisphosphonate-related osteonecrosis of the jaw. Most of these patients have insufficient residual bone quality due to mandible atrophy or sinus pneumatization.

Results

The implant diameters were 4.0 (n=38), 4.5 (n=8), and 5.0 mm (n=1). Among the 47 implants placed, 2 implants failed before the last follow-up. The survival rate of 7-mm SDIs was 95.74% from stage I surgery to the last follow-up. Survival rates did not differ according to implant diameter. The mean marginal bone loss (MBL) at 3 months, 1 and 2 years was significantly higher than at implant installation, and the MBL at 1 year was also significantly higher than at 3 months. MBL at 1 and 2 years did not differ significantly.

Conclusion

Within the limitations of the present study, the results indicate that SDIs provide a reliable treatment, especially for medically compromised patients, to avoid sinus lifting or vertical bone grafting. Further, long-term follow-up is needed.

Architecture and design of a robotic mastication simulator for interactive load testing of dental implants and the mandible

STATEMENT OF PROBLEM

Determination of interactive loading between a dental prosthesis and the host mandible is essential for implant prosthodontics and to preserve bone.

PURPOSE

The purpose of this study was to develop and evaluate a robotic mastication simulator to replicate the human mastication force cycle to record the required interactive loading using specifically designed force sensors.

MATERIAL AND METHODS

This robotic mastication simulator incorporated a Stewart parallel kinematic mechanism (PKM) controlled in the force-control loop. The hydraulically operated PKM executed the wrench operation, which consisted of the combined effect of forces and moments exhibited by the mastication process. Principal design features of this robotic simulator included PKM kinematic modeling, static force analysis to realize the masticatory wrench characteristics, and the architecture of its hydraulic system. Additionally, the design of a load-sensing element for the mandible and implant interaction was also incorporated. This element facilitated the quantification of the load distribution between implants and the host bone during the masticatory operation produced by the PKM. These loading tests were patient-specific and required separate artificial mandibular models for each patient.

RESULTS

The simulation results demonstrated that the robotic PKM could replicate human mastication. These results validated the hydraulic system modeling for the required range of masticatory movements and effective forces of the PKM end-effector. The overall structural design of the robotic mastication simulator presented the integration of the PKM and its hydraulic system with the premeditated load-recording mechanism.

CONCLUSIONS

The developed system facilitated the teeth-replacement procedure. The PKM accomplished the execution of mastication cycle involving 6 degrees of freedom, enabling any translation and rotation in sagittal, horizontal, and vertical planes. The mechanism can simulate the human mastication cycle and has a force application range of up to 2000 N. The designed load-sensing element can record interactive forces within the range of 200 N to 2000 N with fast response and high sensitivity to produce a robotic mastication simulator with custom-made modules.

Evaluation of the Peri-Implant Bone Level around Platform-Switched Dental Implants: A Retrospective 3-Year Radiographic Study

OBJECTIVE

To describe remodeling of the mesial and distal marginal bone level around platform-switched (PS) and platform-matched (PM) dental implants that were sandblasted with large grit and etched with acid over a three-year period.

MATERIALS AND METHODS

Digital periapical radiographs were obtained at the following time-points: during Stage I of the surgical placement of dental implants, before loading, immediately after loading (baseline), and one, three, six, 12, and 36 months after loading for measuring the horizontal and vertical marginal bone levels.

RESULTS

Sixty implants were successfully osseointegrated during the overall observation period. Vertical marginal bone levels for the PS and PM dental implants were 0.78 ± 0.77 and 0.98 ± 0.81 mm, respectively, whereas the horizontal marginal bone levels for the PS and PM implants were 0.84 ± 0.45 and 0.98 ± 0.68 mm, respectively. During the time leading up to the procedure until 36 months after the procedure, the average vertical marginal bone level resulted in less bone loss for the PS and PM groups-0.96 ± 1.28 and 0.30 ± 1.15 mm, respectively (p < 0.05). The mean levels of the horizontal marginal bone also showed increases of 0.48 ± 1.01 mm in the PS and 0.37 ± 0.77 mm in the PM groups from the time before loading until 36 months after the procedure. However, these increases were not statistically significant (p > 0.05).

CONCLUSION

PS dental implants appeared to be more effective than PM implants for minimizing the mean marginal vertical and horizontal marginal bone loss during the three-year period. Regardless of which abutment connection was used, the dental implant in the present retrospective investigation exhibited minimal marginal bone remodeling, thus indicating long-term stability.

Relationship between cortical bone thickness and implant stability at the time of surgery and secondary stability after osseointegration measured using resonance frequency analysis

Purpose

It has been suggested that resonance frequency analysis (RFA) can measure changes in the stability of dental implants during osseointegration. This retrospective study aimed to evaluate dental implant stability at the time of surgery (primary stability; PS) and secondary stability (SS) after ossseointegration using RFA, and to investigate the relationship between implant stability and cortical bone thickness.

Methods

In total, 113 patients who attended the Tohoku University Hospital Dental Implant Center were included in this study. A total of 229 implants were placed in either the mandibular region (n=118) or the maxilla region (n=111), with bone augmentation procedures used in some cases. RFA was performed in 3 directions, and the lowest value was recorded. The preoperative thickness of cortical bone at the site of implant insertion was measured digitally using computed tomography, excluding cases of bone grafts and immediate implant placements.

Results

The mean implant stability quotient (ISQ) was 69.34±9.43 for PS and 75.99±6.23 for SS. The mandibular group had significantly higher mean ISQ values than the maxillary group for both PS and SS (P<0.01). A significant difference was found in the mean ISQ values for PS between 1-stage and 2-stage surgery (P<0.5). The mean ISQ values in the non-augmentation group were higher than in the augmentation group for both PS and SS (P<0.01). A weak positive correlation was observed between cortical bone thickness and implant stability for both PS and SS in all cases (P<0.01).

Conclusions

Based on the present study, the ISQ may be affected by implant position site, the use of a bone graft, and cortical bone thickness before implant therapy.

Impaired Differentiation of Langerhans Cells in the Murine Oral Epithelium Adjacent to Titanium Dental Implants

Peri-implantitis is a destructive inflammatory process affecting tissues surrounding dental implants and it is considered a new global health concern. Human studies have suggested that the frequencies of Langerhans cells (LCs), the main antigen-presenting cells (APCs) of the oral epithelium, are dysregulated around the implants. Since LCs play a role in regulating oral mucosal homeostasis, we studied the impact of dental titanium implants on LC differentiation using a novel murine model. We demonstrate that whereas the percentage of LC precursors (CD11c⁺MHCII⁺) increased in the peri-implant epithelium, the frequencies of LCs (CD11c⁺MHCII⁺EpCAM⁺langerin⁺) were significantly reduced. Instead, a population of partially developed LCs expressing CD11c⁺MHCII⁺EpCAM⁺ but not langerin evolved in the peri-implant mucosa, which was also accompanied by a considerable leukocyte infiltrate. In line with the increased levels of LC precursors, expression of CCL2 and CCL20, chemokines mediating their translocation to the epithelium, was elevated in the peri-implant epithelium. However, expression of TGF-β1, the major cytokine driving final differentiation of LCs, was reduced in the epithelium. Further analysis revealed that while the expression of the TGF-β1 canonical receptor activing-like kinase (ALK)5 was upregulated, expression of its non-canonical receptor ALK3 was decreased. Since titanium ions releasing from implants were proposed to alter APC function, we next analyzed the impact of such ions on TGF-β1-induced LC differentiation cultures. Concurring with the in vivo studies, the presence of titanium ions resulted in the generation of partially developed LCs that express CD11c⁺MHCII⁺EpCAM⁺ but failed to upregulate langerin expression. Collectively, these findings suggest that titanium dental implants have the capacity to impair the development of oral LCs and might subsequently dysregulate immunity in the peri-implant mucosa.

Comparative evaluation of soft and hard tissue changes following endosseous implant placement using flap and flapless techniques in the posterior edentulous areas of the mandible-a randomized controlled trial

BACKGROUND

Dental implant-supported restorations have long been used as a successful modality for replacing missing teeth. There are two well-established methods of implant placement. The traditional approach to implant surgery involves raising a mucoperiosteal flap and the alternative approach does not involve reflecting a flap, each having its own advantages and disadvantages. The purpose of the present study was to compare and evaluate the soft and hard tissue changes around endosseous implants placed using flap and flapless surgery in mandibular posterior edentulous sites over a period of time.

MATERIALS AND METHODS

A total of 20 systemically healthy patients with a single edentulous site in the posterior mandible were enrolled in this study and 20 endosseous implants were placed (10 in the flap group and 10 in the flapless group). The peri-implant probing depth was assessed. Radiographic assessment was done for changes in the marginal bone levels at the mesial and distal side of the implant with measurements made at baseline, 6 months, and 12 months. Patient-centered outcomes were assessed by using the visual analogue scale (VAS). All these parameters were statistically analyzed using the Wilcoxon signed-rank test, paired Student t test, and two-way ANOVA test and were considered to be significant if the p value was ≤ 0.05.

RESULTS

Twenty patients were enrolled in the present study and endosseous implants were placed. Eighteen subjects were followed up throughout the study period and two patients were excluded from the study. The mean PD in the flapless group was comparatively less than the flap group at 12 months and was found to be statistically significant. During the observation period of 12 months, reduction of crestal bone height around the implants placed by flapless and flap surgery were statistically significant. The flapless group showed less change in the crestal bone height which was statistically significant compared to the flap group. The mean VAS score on day 0 in the flap and flapless group was statistically significant. The flapless group showed significantly less pain when compared to the flap group.

CONCLUSION

Although the flapless technique of endosseous implant placement had statistically significant less PD, bone loss, and pain than the flap technique, the difference was found to have uncertain clinical significance.

Osteocyte morphology and orientation in relation to strain in the jaw bone

Bone mass is important for dental implant success and is regulated by mechanoresponsive osteocytes. We aimed to investigate the relationship between the levels and orientation of tensile strain and morphology and orientation of osteocytes at different dental implant positions in the maxillary bone. Bone biopsies were retrieved from eight patients who underwent maxillary sinus-floor elevation with β-tricalcium phosphate prior to implant placement. Gap versus free-ending locations were compared using 1) a three-dimensional finite-element model of the maxilla to predict the tensile strain magnitude and direction and 2) histology and histomorphometric analyses. The finite-element model predicted larger, differently directed tensile strains in the gap versus free-ending locations. The mean percentage of mineralised residual native-tissue volume, osteocyte number (mean ± standard deviations: 97 ± 40/region-of-interest), and osteocyte shape (~90% elongated, ~10% round) were similar for both locations. However, the osteocyte surface area was 1.5-times larger in the gap than in the free-ending locations, and the elongated osteocytes in these locations were more cranially caudally oriented. In conclusion, significant differences in the osteocyte surface area and orientation seem to exist locally in the maxillary bone, which may be related to the tensile strain magnitude and orientation. This might reflect local differences in the osteocyte mechanosensitivity and bone quality, suggesting differences in dental implant success based on the location in the maxilla.

Dental Implant Surrounding Marginal Bone Level Evaluation: Platform Switching versus Platform Matching-One-Year Retrospective Study

The benefits and feasibility of platform switching have been discussed in several studies, reporting lesser crestal bone loss in platform-switched implants than in platform-matched implants. Objective. The aim of the present study was to observe the changes in vertical and horizontal marginal bone levels in platform-switched and platform-matched dental implants. Materials and Methods. 51 patients received 60 dental implants in the present study over a 1-year period. Measurement was performed between the implant shoulder and the most apical and horizontal marginal defect by periapical radiographs to examine the changes of peri-implant alveolar bone before and 12 months after prosthodontic restoration delivery. Results. These marginal bone measurements showed a bone gain of 0.23 ± 0.58 mm in the vertical gap and 0.22 ± 0.53 mm in the horizontal gap of platform matching, while in platform switching a bone gain of 0.93 ± 1 mm (P < 0.05) in the vertical gap and 0.50 ± 0.56 mm in the horizontal gap was found. The average vertical gap reduction from the baseline until 12 months was 0.92 ± 1.11 mm in platform switching and 0.29 ± 0.85 mm in platform matching (P < 0.05). Conclusions. Within the limitations of the present study, platform switching seemed to be more effective for a better peri-implant alveolar bone vertical and horizontal gap reduction at 1 year.

The influence of crown-to-implant ratio on marginal bone levels around splinted short dental implants: A radiological and clincial short term analysis

BACKGROUND

The amount of marginal bone resorption around dental implants is considered to have a significant impact on implant stability as well as implant survival rates.

PURPOSE

The aim of this prospective study was to investigate the influence of prosthetic as well as patient specific factors on marginal bone loss around short dental implants.

MATERIALS AND METHODS

Seventy-six implants, which supported splinted crowns were included for investigation. All implants were from the same type and had an intraosseous length of 6.5 mm and a diameter of 4.0 mm. Twenty implants were additionally splinted onto longer ones. Measurements of marginal bone loss were performed at a mean of 12.38 months after prosthetic loading and the mean follow-up for clinical evaluation was 20.52 months.

RESULTS

Overall two implant failures were recorded, revealing a survival rate of 97.3%. Marginal bone resorption around 72 short implants measured 0.71 mm (SD: 0.74 mm) and was found to have a strong correlation with calculated Crown-to-Implant ratio (r = .71; P < .001). Age, gender, insertion torque, implant surface area, location, position, bone quality, and insertion torque did not influence peri-implant bone loss after one year of loading.

CONCLUSION

Within the limitations of the study, it is suggested that Crown-to-Implant ratios should not exceed 1.7 to avoid increased early marginal bone loss.

Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant

PURPOSE

The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant.

MATERIALS AND METHODS

Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10⁶ cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05.

RESULTS

Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens.

CONCLUSION

Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

Retrospective clinical study of an implant with a sandblasted, large-grit, acid-etched surface and internal connection: analysis of short-term success rate and marginal bone loss

Background

The purpose of this retrospective study was to evaluate the clinical utility of an implant with a sandblasted, large-grit, acid-etched (SLA) surface and internal connection.

Methods

Six patients who received dental implants in the Department of Oral and Maxillofacial Surgery, Chonnam National University Dental Hospital, were analyzed by factors influencing the success rate and marginal bone loss. Factors included patient’s age, sex, implant installation site, whether bone graft was done, type of bone graft materials, approaching method if sinus lift was done, and the size of the fixture. In addition, the marginal bone loss was analyzed by using a radiograph.

Results

All implants were successful, and the cumulative survival rate was 100 %. Average marginal bone loss of 6 months after the installation was 0.52 mm and 20 months after the functional loading was 1.06 mm. Total marginal bone resorption was 1.58 mm on average. There was no statistically significant difference in mesial and distal marginal bone loss.

Conclusions

The short-term clinical success rate of the implant with an SLA surface and internal connection was satisfactory. Moreover, the marginal bone loss was also consistent with the implant success criteria.

Why guided when freehand is easier, quicker, and less costly?

Computer-assisted implant planning and subsequent production of a surgical template based on this plan has gained attention because it provides restoratively driven esthetics, patient comfort, satisfaction, and the option of flapless surgery and immediate restoration. However, it adds expense and requires more time. Another significant but not so apparent advantage may be improved survival and success over freehand techniques in types III and IV bone. This retrospective analysis was undertaken to examine that possibility. It reports 1-year outcome for 80 implants in 27 consecutively presenting patients treated over a 7-year period using computer-assisted techniques across all bone qualities in commonly encountered treatment indications in private practice. Implants were placed to support single teeth, small bridges, and complete arch restorations in exposed or immediately restored applications, based on primary stability as determined by insertion torque, resonance frequency analysis, and Periotest. For the 80 implants supporting 35 restorations, the median observation period is 2.66 years; 73 implants supporting prostheses in 22 patients had readable radiographs at 1 year. There was a 1-year overall implant survival and a success rate of 100%. Radiographic analysis demonstrated the change in bone level from the platform at 1-year is less than 2 mm. Intra-operative median measurements of primary stability were insertion torque, 40 Ncm; resonance frequency, 76 ISQ; and Periotest, -3. All intra-operative measurements were consistent for acceptable primary stability regardless of bone density. Restoratively driven diagnosis and precision planning and initial fit were possible with computer-assisted techniques resulting in the achievement of high primary stability, even in areas of less dense bone. The ability to plan implant position, drill sequence, and implant design on the basis of predetermined bone density gives the practitioner enhanced pretreatment information which can lead to improved outcome.

Technical and biological complications of single-molar implant restorations

OBJECTIVES

Retrospective evaluation of the biological and technical complications in implant-supported single-tooth molar restorations performed in a private practice after functional periods of ≥4 years.

MATERIAL AND METHODS

Sixty-five patients (34 females, age 51.7 ± 10.6 years) with 112 implants received annual follow-up examinations and participated in a maintenance program. The survival (in situ) and success (complication-free) rates of implants and superstructures were evaluated. Time-dependent peri-implantitis rates were calculated, and the influencing factors were identified using a multiple Cox regression.

RESULTS

The implant survival rate was 100%. Three of 112 crowns required replacement (prosthetic survival rate = 98.1%). Thirty technical complications were observed: loss of retention (16), ceramic fracture (10), and screw loosening (4). The success rate of the superstructures was 79.0% after 7 years. Overall, 9.2% of the patients developed peri-implantitis (probing depth ≥5 mm, BOP, suppuration, bone loss ≥3.5 mm); (smokers: 41.6%, non-smokers: 1.8%). After 7 years, the time-dependent implant success rate (free of peri-implantitis) was 100% for non-smokers and 58.6% for smokers. Multiple analysis showed a significant effect of smoking (hazard ratio, 19.5; P = 0.008) on peri-implantitis.

CONCLUSIONS

Implants with cemented single-tooth restorations in the molar region constitute a reliable treatment in private practice. Smokers have a significantly increased peri-implantitis rate.

Reasons for failures of oral implants

This study reviews the literature regarding the factors contributing to failures of dental implants. An electronic search was undertaken including papers from 2004 onwards. The titles and abstracts from these results were read to identify studies within the selection criteria. All reference lists of the selected studies were then hand-searched, this time without time restrictions. A narrative review discussed some findings from the first two parts where separate data from non-comparative studies may have indicated conclusions different from those possible to draw in the systematic analysis. It may be suggested that the following situations are correlated to increase the implant failure rate: a low insertion torque of implants that are planned to be immediately or early loaded, inexperienced surgeons inserting the implants, implant insertion in the maxilla, implant insertion in the posterior region of the jaws, implants in heavy smokers, implant insertion in bone qualities type III and IV, implant insertion in places with small bone volumes, use of shorter length implants, greater number of implants placed per patient, lack of initial implant stability, use of cylindrical (non-threaded) implants and prosthetic rehabilitation with implant-supported overdentures. Moreover, it may be suggested that the following situations may be correlated with an increase in the implant failure rate: use of the non-submerged technique, immediate loading, implant insertion in fresh extraction sockets, smaller diameter implants. Some recently published studies suggest that modern, moderately rough implants may present with similar results irrespective if placed in maxillas, in smoking patients or using only short implants.

Micro-architecture and mineralization of the human alveolar bone obtained with microCT

OBJECTIVES

The primary dental implant stability depends on the location of the implant in the jaw. This study analysed the architecture and mineralization of the trabecular bone at different jaw locations and thereby identified potential prognostic factors for implant failure. It has checked the hypotheses: (1) the mandible contains more compact and less mineralized trabecular bone than the maxilla and (2) within the mandible the trabecular bone is more compact and less mineralized in the anterior region.

METHODS

Alveolar bone specimens were produced from the cadavers of ten humans (7 males and 3 females; mean age: 73.7±12.5 years) and scanned with a high-resolution microCT system. Volumes of interest were chosen next to the roots of molars and incisors in both the maxilla and mandible. Several morphological parameters as well as the tissue mineral density were determined.

RESULTS

The alveolar bone specimens had a very high bone volume fraction (mean=0.31) with large differences (SD=0.17) between and within subjects. Yet several significant differences were found between the maxilla and the mandible. The bone volume fraction and trabecular thickness were significantly higher in the mandible than in the maxilla (p<0.01). But the tissue mineral density was not significantly different.

CONCLUSIONS

A higher primary implant stability coincides with a higher bone volume fraction and degree of anisotropy Although local differences remain more important for implantology, the results suggest that the micro-structure also affects the implant stability. The tissue mineral density seems to have no predictive value.

Short implants: A systematic review

BACKGROUND

Short implants are manufactured for use in atrophic regions of the jaws. Although many studies report on short implants as ≤10 mm length with considerable success, the literature regarding survival rate of ≤7 mm is sparse.

PURPOSE

The purpose of this study was to systematically evaluate the publications concerning short dental implants defined as an implant with a length of ≤7 mm placed in the maxilla or in the mandible.

MATERIALS AND METHODS

A Medline and manual search was conducted to identify studies concerning short dental implants of length ≤7 mm published between 1991 and 2011. The articles included in this study report data on implant length ≤7 mm, such as demographic variables, implant type, location in jaws, observation time, prostheses and complications.

RESULTS

The 28 included studies represent one randomized controlled trial, 12 prospective studies and 10 retrospective studies. The survival rate of short implant was found to be increased from 80% to 90% gradually, with recent articles showing 100%.

CONCLUSION

When severe atrophy of jaws was encountered, short and wide implants can be placed successfully.

How precise is dental volumetric tomography in the prediction of bone density?

Objectives. The aim of this study was to review the bone density assessment techniques and evaluate the macroscopic structure of bone specimens scored by Hounsfield Units (HUs) and decide if they are always in congruence. Methods. The mandible of a formalin-fixed human cadaver was scanned by dental volumetric tomography (DVT) for planning of the specimen positions and fabrication of a surgical guide and a surgical stent was fabricated afterwards. Bone cylinders of 3.5 mm diameter and 5 mm length, were excised from the mandible using the surgical stent with a slow speed trephine drill. After removal of the cylinders two more scans were performed and the images of the first scan were used for the determination of the HU values. The removed bone cylinder was inspected macroscopically as well by micro-CT scan. Results. The highest HU values were recorded in the interforaminal region, especially in the midline (408–742). Posterior regions showed lower HU values, especially the first molar regions (22–61 for the right; 14–66 for the left first molar regions). Conclusion. Within the limitations of this pilot study, it can be concluded that HU values alone could be a misleading diagnostic tool for the determination of bone density.

Biomechanical rationale for six splinted implants in bilateral canine, premolar, and molar regions in an edentulous maxilla

PURPOSE

To determine the influence of number and location of implants loaded on the stress to the bone in an edentulous maxilla using a three-dimensional finite element model (3D FEM).

MATERIAL AND METHODS

Computed tomographic data with the bone density of a dry skull were used to construct a 3D FEM. Titanium implants were simulated in the configuration as 14 unsplinted implants (US14), 14 splinted implants (S14), 6 splinted implants (canine, premolar, and molar regions, S6), 4 splinted implants (S4), and 6 anterior implants (incisors and canines, A6). Distributed loads of 200 N were applied on the occlusal table of the superstructures.

RESULTS

The S6 model was subjected to a similar amount of stress and deformation to the US14 and the S14. The S4 and A6 models were subjected to approximately three times of stress under the vertical load, and approximately five times of stress under the inclined load, respectively, compared with the S6 model.

CONCLUSIONS

The 3D FEM analyses suggest that the six splinted implants configuration has a similar stress and deformation pattern as compared with naturally positioned splinted 14 implants in the edentulous maxilla.

Assessment of bone density in the posterior maxilla based on Hounsfield units to enhance the initial stability of implants

PURPOSE

The poor bone quality that exists in the posterior maxilla is associated with lower initial stability and higher failure rates in implants. This study examined the bone densities of edentulous posterior maxillae by computed tomography (CT).

MATERIALS AND METHODS

Based on CT images, the voxel values representing implant replacement in the posterior maxillary regions of 30 patients were calculated in the range from 150 to 2,000 Hounsfield units (HU). The bone densities of these regions were categorized according to Misch's classification and compared among individuals and between sexes.

RESULTS

The average of the median individual CT values was 495 HU (95% confidence interval: 442-547 HU) and was significantly higher in males than in females. Most of the bone in the posterior maxillae was classified as D3 (350-850 HU) or D4 (150-350 HU) according to Misch's classification, comprising 50% and 32% of the entire regions, respectively.

CONCLUSIONS

More than 80% of the edentulous posterior maxillae consisted of porous cortical crest or no cortical bone according to CT, although the bone densities varied markedly among individuals. More detailed assessments of bone density may be useful to enhance initial stability of implants in the posterior maxilla.

Ambiguity in bone tissue characteristics as presented in studies on dental implant planning and placement: a systematic review

OBJECTIVES

To survey definitions of bone tissue characteristics and methods of assessing them in studies of dental implant planning and placement.

MATERIAL AND METHODOLOGY

Three databases were searched using specified indexing terms. Three reviewers selected from the titles and retrieved abstracts in accordance with inclusion and exclusion criteria. Descriptions of bone tissue characteristics (bone quality, density and quantity) used before or during dental implant placement were searched for and categorized.

RESULTS

The search yielded 488 titles. One hundred and fort-nine publications were selected and read in full text. One hundred and eight were considered relevant. There were many different definitions and classification systems for bone tissue characteristics and examination protocols. Approximately two-third of the included publications reported the Lekholm & Zarb classification system for bone quality and quantity. However, only four studies implemented the Lekholm & Zarb system as originally proposed. A few publications described bone quality in accordance with the Misch or Trisi and Rao classifications systems. Assessment methods were often described only briefly (or not at all in one-fifth of the publications). Only one study presented the diagnostic accuracy of the assessment method, while only two presented observer performance.

CONCLUSION

The differing definitions and classification systems applied to dental implant planning and placement make it impossible to compare the results of various studies, particularly with respect to whether bone quality or quantity affect treatment outcomes. A consistent classification system for bone tissue characteristics is needed, as well as an appropriate description of bone tissue assessment methods, their diagnostic accuracy and observer performance.

Scanning Electron Microscopy Fractography Analysis of Fractured Hollow Implants

Fracture of the implant is one of the possible complications affecting dental implants; it is a rare event but of great clinical relevance. The aim of the present study was to perform a scanning electron microscopy (SEM) fractography evaluation of 7 International Team for oral Implantology (ITI) hollow implants removed because of fracture. The most common clinical risk factors, such as malocclusion, bruxism, and cantilevers on the prosthesis, were absent. Seven fractured ITI hollow implants were retrieved from 5 patients and were analyzed with the use of SEM. SEM analysis showed typical signs of a cleavage-type fracture. Fractures could be due to an association of multiple factors such as fatigue, inner defects, material electrochemical problems, and tensocorrosion.

Variations in bone density at dental implant sites in different regions of the jawbone

The survival rate of dental implants is markedly influenced by the quality of the bone into which they are placed. The purpose of this study was to determine the trabecular bone density at potential dental implant sites in different regions of the Chinese jawbone using computed tomography (CT) images. One hundred and fifty-four potential implant sites (15 in the anterior mandible, 47 in the anterior maxilla, 55 in the posterior mandible, and 37 in the posterior maxilla) were selected from the jawbones of 62 humans. The data were subjected to statistical analysis to determine any correlation between bone density (in Hounsfield units, HU) and jawbone region using the Kruskal-Wallis test. The bone densities in the four regions decreased in the following order: anterior mandible (530 +/- 161 HU, mean +/- s.d.) approximately equal anterior maxilla (516 +/- 132 HU) > posterior mandible (359 +/- 150 HU) approximately equal posterior maxilla (332 +/- 136 HU). The CT data demonstrate that trabecular bone density varies markedly with potential implant site in the anterior and posterior regions of the maxilla and mandible. These findings may provide the clinician with guidelines for dental implant surgical procedures (i.e., to determine whether a one-stage or a two-stage protocol is required).

Initial Torque Stability of a New Bone Condensing Dental Implant. A Cohort Study of 140 Consecutively Placed Implants

The aim of this paper was to determine the torque resistance of this new implant during placement in different types of bone, immediate placement into sockets, and in grafted bone. The torque at time of placement serves as an indication of initial stability, which is accepted as an important factor for implant osseointegration and immediate loading. Within a 13-month period, 140 NobelActive implants in 84 consecutive patients were placed into types I–IV bone in fresh sockets, and into grafted bone (both in maxillary sinuses and on the facial alveolar surfaces where bone had been lost). The final torque was measured with a manual torque control wrench as manufactured by Nobel Biocare for clinical use with this type of implant. One hundred forty implants with 3.5 to 5 mm diameters and 10 to 15 mm lengths were placed in different types of bone, either as delayed or immediate implants into fresh extraction sockets. These implants demonstrated a mean torque stability value of 50.8 Ncm. The average insertion torque for delayed implants was 49.7 Ncm. For immediate implants the average torque was 52.6 Ncm. Placement into soft bone was also favorable at an average of 47.9 Ncm. Typical straight walled and tapered implants generally exhibit 10 to 35 Ncm insertion torques. The NobelActive implant consistently reaches higher torque levels. This may indicate they are more favorably suited to early provisionalization and loading. Soft bone (type IV) did not seem to decrease significantly the torque of insertion of these implants. Further longer term studies are needed to investigate whether this indeed makes these implants more suited for early provisionalization and loading than traditional root form. Long term studies are also needed to investigate maintenance of bone levels surrounding these implants.

Elastic properties and apparent density of human edentulous maxilla and mandible

The aim of this study was to determine whether elastic properties and apparent density of bone differ in different anatomical regions of the maxilla and mandible. Additional analyses assessed how elastic properties and apparent density were related. Four pairs of edentulous maxilla and mandibles were retrieved from fresh human cadavers. Bone samples from four anatomical regions (maxillary anterior, maxillary posterior, mandibular anterior, mandibular posterior) were obtained. Elastic modulus (EM) and hardness (H) were measured using the nano-indentation technique. Bone samples containing cortical and trabecular bone were used to measure composite apparent density (cAD) using Archimedes' principle. Statistical analyses used repeated measures ANOVA and Pearson correlations. Bone physical properties differed between regions of the maxilla and mandible. Generally, mandible had higher physical property measurements than maxilla. EM and H were higher in posterior than in anterior regions; the reverse was true for cAD. Posterior maxillary cAD was significantly lower than that in the three other regions.

Mandibular Molar Root Resection Versus Implant Therapy: A Retrospective Nonrandomized Study

Success rates for both periodontal and implant therapy are often dependent on site and tooth type. For periodontally involved mandibular molars, the decision to hemisect or to extract and place an implant is often complicated. The purpose of the present study was to evaluate the outcomes of the aforementioned treatment modalities for mandibular molars in a private practice setting. A retrospective chart review was performed. In one group of patients (n = 32), 56 mandibular first or first and second molars were treated by hemisection (Group H). A second group (n = 28) received 36 implants in the mandible to replace periodontally involved first or first and second molars (Group I). All patients had been in maintenance for at least 4 years after treatment. The occurrence and timing of posttreatment complications were evaluated. Data were analyzed by parametric and nonparametric statistics, as indicated. The majority of hemisected teeth (68% of Group H) and implants (89% of Group I) remained free of complications for the entire observation period. Group H had a greater incidence of overall complications (P = .027) and nonsalvageable complications (P = .013) than Group I. For both groups, the percent CAL loss per year was greater for the teeth/implants that experienced complications than in the those that remained complication free (p&lt;0.015). Within the limitations of this study, the results indicated that, in periodontitis patients, hemisected mandibular molars were more prone to complications than implants.