Primary stability and healing outcomes of apically tapered and straight implants placed into fresh extraction sockets. A pre-clinical in vivo study

Effect of Residual Bone Height and Implant Macro-Design on Primary Stability in Sinus Floor Elevation: An Ex Vivo Study

The objective was to evaluate the influence of residual bone height (RBH) and implant macro-design on the primary stability (PS) of implants using a simultaneous sinus floor elevation (SFE) and implant insertion model. Fresh bovine rib samples that resembled type-IV density that were confirmed by computerized tomography were prepared to represent 4 groups of varying RBHs (3, 6, 9, 15 mm). To simulate simultaneous implant insertion with SFE, 120 implants in different macro-designs (group R: NobelReplace; group P: NobelParallel; group A: NobelActive, Nobel Biocare, Gothenburg, Sweden) were randomly inserted at RBHs of 3, 6, 9, and 15 mm in each rib. The implant stability quotient (ISQ) was measured immediately after implant insertion. RBH and implant macro-design have an impact on ISQ values (P < .001). ISQ values were the highest with RBH of 15 mm, followed by RBHs of 9, 6, and 3 mm. (P < .001). There was no statistically significant difference between different implant macro-designs at RBHs of 3 and 15 mm regarding ISQ values (P = .111, P = .551). ISQ values of group P were higher than those of group R and group A at an RBH of 6 mm (P = .049, P = .029). ISQ values were also higher in group P compared to group A at an RBH of 9 mm (P = .006). A higher PS may be expected in sites with higher RBH, regardless of the macro-design. In addition, cylindric implant design may enhance the PS at RBHs of 6 and 9 mm in simultaneous implant insertion with SFE.

Convergent angles of a tapered implant referred from the root profile of premolars

Background/purpose

Limited studies have discussed the convergent profiles regarding tapered implants based on biological considerations. This study analyzed the convergent angles (CAs) of premolar roots and imitated a tapered implant according to the anatomy of tooth roots.

Materials and methods

A total of 60 single-rooted premolars were explored by micro-computed tomography. Every individual root was divided into 10 segments corono-apically, and the roots' buccolingual (BL) and mesiodistal (MD) CAs were measured by sections. To mimic a dental implant, the irregular shape of examined root cross-sections was transformed into a circular shape with equal areas. A biomimetic dental implant (BDI) was reconstructed and its CAs were compared with those of the natural roots' BL and MD at the examined levels and overall estimation.

Results

In general, the maxillary and mandibular premolars demonstrated comparable CA patterns. However, significantly different CA patterns of BL, MD, and BDI were developed for both the maxillary and mandibular roots at the examined levels. The BL's CAs were greater than those CAs measured from the BDI and MD aspects, particularly for the sections at the middle and apical thirds of the roots. For overall CAs, the BDI's CAs were comparable with the average CAs of the BL and MD for both premolar groups.

Conclusion

Instead of a cylindrical configuration, the BDI prototype demonstrated a tapered model with a continuous slope. The average CA of BDI was 14°-24°, serving as a biological reference for future tapered implant design and research.

Finite Element Analysis of the Stress Distribution Associated With Different Implant Designs for Different Bone Densities

PURPOSE

The main objective of this study was to investigate the influence of implant design, bone type, and abutment angulation on stress distribution around dental implants.

MATERIALS AND METHODS

Two implant designs with different thread designs, but with the same length and brand were used. The three-dimensional geometry of the bone was simulated with four different bone types, for two different abutment angulations. A 30° oblique load of 200 N was applied to the implant abutments. Maximum principal stress and minimum principal stresses were obtained for bone and Von misses stresses were obtained for dental implants.

RESULTS

The distribution of the load was concentrated at the coronal portion of the bone and implants. The stress distributions to the D4 type bone were higher for implant models. Increased bone density and increased cortical bone thickness cause less stress on bone and implants. All implants showed a good distribution of forces for non-axial loads, with higher stresses concentrated at the crestal region of the bone-implant interface. In implant types using straight abutments there was a decrease in stress as the bone density decreased. The change in the abutment angle also caused an increase in stress.

CONCLUSIONS

The use of different implant threads and angled abutments affects the stress on the surrounding bone and implant. In addition, it was observed that a decrease in density in trabecular bone and a decrease in cortical bone thickness increased stress. This article is protected by copyright. All rights reserved.

The primary stability of two dental implant systems in low-density bone

Primary stability in low-density bone is crucial for the long-term success of implants. Tapered implants have shown particularly favourable properties under such conditions. The aim of this study was to compare the primary stability of tapered titanium and novel cylindrical zirconia dental implant systems in low-density bone. Fifty implants (25 tapered, 25 cylindrical) were placed in the anterior maxillary bone of cadavers meeting the criteria of low-density bone. The maximum insertion (ITV) and removal (RTV) torque values were recorded, and the implant stability quotients (ISQ) determined. To establish the isolated influence of cancellous bone on primary stability, the implantation procedure was performed in standardized low-density polyurethane foam bone blocks (cancellous bone model) using the same procedure. The primary stability parameters of both implant types showed significant positive correlations with bone density (Hounsfield units) and cortical thickness. In the cadaver, the cylindrical zirconia implants showed a significantly higher mean ISQ when compared to the tapered titanium implants (50.58 vs 37.26; P < 0.001). Pearson analysis showed significant positive correlations between ITV and ISQ (P = 0.016) and between RTV and ISQ (P = 0.035) for the cylindrical zirconia implants; no such correlations were observed for the tapered titanium implants. Within the limitations of this study, the results indicate that cylindrical zirconia implants represent a comparable viable treatment option to tapered titanium implants in terms of primary implant stability in low-density human bone.

Accuracy and primary stability of tapered or straight implants placed into fresh extraction socket using dynamic navigation: a randomized controlled clinical trial

OBJECTIVES

To compare the accuracy and primary stability of tapered and straight implants undergoing immediate implant placement with dynamic navigation.

MATERIALS AND METHODS

Patients with compromised anterior teeth in maxilla were recruited and allocated randomly into (1) tapered implant group (TI group) and (2) straight implant group (SI group). Implants were inserted into fresh sockets with dynamic navigation. Three-dimensional platform deviation, apex deviation, angular deviation, insertion torque value (ITV) and implant stability quotient (ISQ) were recorded.

RESULTS

Twenty patients with 20 implants were included. The overall platform, apex, and angular deviation were 0.87 ± 0.35 mm, 0.81 ± 0.34 mm, and 2.40 ± 1.31°, respectively. The accuracy was 0.86 ± 0.26 mm, 0.76 ± 0.33 mm, and 2.49 ± 1.54° for TI, and 0.89 ± 0.44 mm, 0.88 ± 0.36 mm, and 2.31 ± 1.01° for SI, with no significant difference (p = 0.85, 0.45, 0.76). Sagittal root position classification (SRP) class I may obtain greater error in numerical values in straight implants (0.97 ± 0.47 mm vs. 0.6 ± 0.16 mm, 0.92 ± 0.36 mm vs. 0.73 ± 0.36 mm, 2.48 ± 1.19° vs. 1.71 ± 0.14°). The overall ISQ was 60.74. ISQ was 60.48 for TI and 60.96 for SI, with no significant difference. Acceptable ITV (> 15 Ncm) was achieved in most of the included patients (SI 7/10, TI 9/10).

CONCLUSIONS

High accuracy and primary stability of immediate implant placement could be achieved both in tapered and straight implants with dynamic navigation systems.

CLINICAL RELEVANCE

Tapered and straight implants did not reach a consensus on which was better in immediate implant regarding to accuracy and primary stability. Our study demonstrated implant macrodesign did not affect accuracy and primary stability in immediate implant using dynamic navigation.

Early implant placement in ridge preserved extraction sockets: A pre-clinical in vivo study

OBJECTIVES

The aim was to analyse the outcomes of early implant placement after 6 and 12 weeks of healing in ridge preserved sites in a canine model.

MATERIALS AND METHODS

Implants were placed in second maxillary incisors sites in 9 dogs 6 weeks after grafting of the sockets with 90% deproteinized bovine bone mineral in 10% collagen matrix (DBBMC) and closure with resorbable type I/III porcine collagen matrix (PCM). The implants were randomly assigned to 6 (T6) and 12 (T12) weeks of healing.

RESULTS

The percentage of bone-to-implant contact (%BIC), old bone, new bone and residual DBBMC was similar between T6 and T12. In relation to the implant shoulder (IS), the original bone crest (IS-ROB) was more apical on the buccal than the palatal side. The regenerated bone crest (IS-C) and IS-ROB were similar between groups. However, the distance from IS to first bone-to implant contact (IS-fBIC) was significantly less in T12 compared with T6 (p = .022; Wilcoxon signed-rank test). The bucco-palatal ridge dimensions between T6 and T12 were similar.

CONCLUSIONS

This study confirms that implants can successfully be placed early in ridge preserved maxillary second incisor sites and are osseointegrated by 6 weeks. There were significantly lower IS-fBIC values at 12 weeks than at 6 weeks on the buccal aspect. The original buccal bone crest underwent greater corono-apical resorption than the palatal crest. The %BIC, relative proportions of mineralized tissues and dimensions of the alveolar ridge demonstrated stability between 6 and 12 weeks of healing.

Relationship between Implant Geometry and Primary Stability in Different Bony Defects and Variant Bone Densities: An In Vitro Study

AIM

This in vitro study aimed to evaluate the effects of implant designs on primary stability in different bone densities and bony defects.

METHODS

Five implant types (tapered-tissue-level, tissue-level, zirconia-tissue-level, bone-level, and BLX implants) were used in this assessment. The implants were inserted into four different artificial bone blocks representing varying bone-density groups: D1, D2, D3, and D4. Aside from the control group, three different types of defects were prepared. Using resonance frequency analysis and torque-in and -out values, the primary stability of each implant was evaluated.

RESULTS

With an increased defect size, all implant types presented reduced implant stability values measured by the implant stability quotient (ISQ) values. Loss of stability was the most pronounced around circular defects. Zirconia and bone-level implants showed the highest ISQ values, whereas tissue level titanium implants presented the lowest stability parameters. The implant insertion without any thread cut led to a small improvement in primary implant stability in all bone densities.

CONCLUSIONS

Compared with implants with no peri-implant defects, the three-wall and one-wall defect usually did not provide significant loss of primary stability. A significant loss of stability should be expected when inserting implants into circular defects. Implants with a more aggressive thread distance could increase primary stability.