Implant survival to 36 months as related to length and diameter

Evaluation of stress distributions in peri-implant and periodontal bone tissues in 3- and 5-unit tooth and implant-supported fixed zirconia restorations by finite elements analysis

OBJECTIVE

In this study, it is aimed to compare the distribution of stress on periodontal and peri-implant bone tissues in 3- and 5-unit-dental and implant-supported zirconia restorations using finite element analysis.

MATERIALS AND METHODS

Stress distribution formed in periodontal and peri-implant bone tissues as a result of chewing forces was analyzed in dental and implant-supported three-dimensional (3D) finite element models of zirconia restoration with 5-unit placed on the numbers of 43, 44, 45, 46, and 47 and with 3-unit placed on the number of 45, 46, and 47. Four different loading conditions were used. 200 N force was applied in 30° from the buccal inclination of number 43, 45, and 47 restorations separately and totally 850 N force was applied in 30° from the buccal inclination of whole restoration. The study was performed through static nonlinear analysis with the 3D finite element analysis method.

RESULTS

Stress accumulation in bone tissues in the tooth-supported model was found less than in implant-supported models. Stress accumulation was observed in the cervical portion of the implant in implant-supported models, and stress accumulation was observed surrounding bone of roots in tooth-supported models. The highest stress values were occurred in 5 unit implant-supported model in all loadings.

CONCLUSION

In posterior restorations increased in the number of supported teeth and implant can reduce the destructive forces on periodontal and peri-implant bone tissues and may allow longer period retention of the restorations in the mouth.

Effect of implant design on primary stability using torque-time curves in artificial bone

Background

Primary stability following implant placement is essential for osseointegration and is affected by both implant design and bone density. The aim of this study was to compare the relationships between torque-time curves and implant designs in a poor bone quality model.

Methods

Nine implant designs, with five implants in each category, were compared. A total of 90 implants (Straumann: Standard RN, Bone Level RC, Tapered Effect RN; Nobel Biocare: Brånemark MKIII, MKIV) were placed in type IV artificial bone. Torque-time curves of insertion and removal were recorded at the rate of 1000 samples/s by a torque analyzer.

Results

The torque-time curves were divided into initial, parallel, tapered, and platform areas. The mean torque rise rate of the parallel area was smallest at 0.36 N · cm/s, with a significant difference from those of the other areas (p < 0.05). Values of 2.14, 2.33, and 2.65 N · cm/s were obtained for the initial, tapered, and platform areas, respectively. The removal torque for six of the implant designs (Bone Level RC 8, 10, and 12 mm; Tapered Effect RN 10 mm; Brånemark MKIII 10 mm, MKIV 10 mm) was significantly smaller than the corresponding insertion torque (p < 0.05). However, the removal torque for ST6, 8, and 10 was almost the same as or slightly greater than the corresponding insertion torque.

Conclusions

The insertion torque-time curves and design features of the implants were accurately transferred. Increasing implant taper angle appeared to increase the torque rate. Torque was mainly generated from the superior surface to the valley of the thread and the inferior and axial surfaces of the platform, while the inferior and axial surfaces of the thread did not significantly affect torque generation.

Transcrestal guided sinus lift without grafting materials: a 36 months clinical prospective study

PURPOSE

This study describes the ability to perform a technique for bone regeneration in maxillary posterior deficit (TGSL) without the use of bone grafting materials using a highly minimally invasive protocol.

MATERIALS AND METHODS

Sixty six implants have been inserted in the sinus floor of a total of 39 patients through the transcrestal guided sinus lift technique (TGSL). All patients have been followed for at least three years in function. The drilling protocol was adapted on the basis of bone density of each implant site to achieve a torque between 45 and 55 Ncm. Healing titanium abutments tightened to 35 Ncm have been used. A CAD/CAM metal ceramics final prosthetic restoration has been generated a six months after the tissues healing and the provisional functionalization of the occlusion. Survival rate of implants and prostheses, biological and biomechanical complications, changes in marginal bone levels, and total height of alveolar crest bone before and after surgery have been evaluate and measured by the results obtained in this prospective study. It was also measured the periodontal parameters as well as levels of perception of pain by the patient during the entire recovery period.

RESULTS

The result of the data of follow-up was 41.96 (24 to 36) months. Cumulative implant survival was 98.53% at 3 years. There were no biological and mechanical complications and there were no prosthetic failures during the whole period of follow-up. The Marginal Bone Loss (MBL) average during the first year of operation was from 0.33 to 0.36 mm, while the 3-year follow-up, the MBL average was 0.51 to 0.29 mm. The average of residual bone height of alveolar ridge before treatment was 6.7 to 1.6 mm (range 5.1 to 9.2 mm), while the average bone height was gained 6,4 - 1.6 mm (range 3.2 to 8.1 mm). All patients reported lower pain levels and found to have normal periodontal parameters.

CONCLUSIONS

This study suggests that the use of guided surgery to perform transcrestal maxillary sinus lift to increase the sub-antral crestal height is a minimally invasive technique of success for the short and medium-term of follow-up, thus avoiding the extended treatment time and reducing the morbidity associated with the lifting of the floor of the maxillary sinus with traditional technique using bone grafting materials. Furthermore, this protocol without the use of graft materials does not vary the final outcome that have demonstrated the presence of newly formed bone around implants offering always predictable results, and giving a further reduction in the costs of the procedure rehabilitation.

Analysis of implant-failure predictors in the posterior maxilla: a retrospective study of 1395 implants

The aim of this study was to analyze predictors for dental implant failure in the posterior maxilla. A database was created to include patients being treated with dental implants posterior to the maxillary cuspids. Independent variables thought to be predictive of potential implant failure included (1) sinus elevation, (2) implant length, (3) implant diameter, (4) indication, (5) implant region, (6) timepoint of implant placement, (7) one-vs. two-stage augmentation, and (8) healing mode. Cox regression analysis was used to evaluate the influence of predictors 1-3 on implant failure as dependent variable. The predictors 4-9 were analyzed strictly descriptively. The final database included 592 patients with 1395 implants. The overall 1- and 5-year implant survival rates were 94.8% and 88.6%, respectively. The survival rates for sinus elevation vs. placement into native bone were 94.4% and 95.4%, respectively (p = 0.33). The survival rates for the short (<10 mm), the middle (10-13 mm) and the long implants (>13 mm) were 100%, 89% and 76.8%, respectively (middle-vs. long implants p = 0.62). The implant survival rates for the small- (<3.6 mm), the middle- (3.6-4.5 mm) and the wide diameter implants (>4.5 mm) were 92.5%, 87.9% and 89.6%, respectively (p = 0.0425). None of the parameters evaluated were identified as predictor of implant failure in the posterior maxilla.

Key local and surgical factors related to implant failure

The concept of osseointegration has revolutionized the treatment options for the replacement of missing teeth in both partially and completely edentulous patients. Dental implants are widely used because clinical practice and studies have documented its successful outcomes. However, implants can occasionally fail, and such failures can be classified as early or late. Measures that can aid in the early recognition of failing osseointegrated implants are needed, as are measures that can facilitate appropriate treatment methods aimed at saving failing implants by determining the probable etiologic factors. This article summarizes our current understanding of the local factors that can be linked to implant failure.

Photoelastic analysis of fixed partial prosthesis crown height and implant length on distribution of stress in two dental implant systems

The aim of this study was to evaluate by photoelastic analysis stress distribution on short and long implants of two dental implant systems with 2-unit implant-supported fixed partial prostheses of 8 mm and 13 mm heights. Sixteen photoelastic models were divided into 4 groups: I: long implant (5 × 11 mm) (Neodent), II: long implant (5 × 11 mm) (Bicon), III: short implant (5 × 6 mm) (Neodent), and IV: short implants (5 × 6 mm) (Bicon). The models were positioned in a circular polariscope associated with a cell load and static axial (0.5 Kgf) and nonaxial load (15°, 0.5 Kgf) were applied to each group for both prosthetic crown heights. Three-way ANOVA was used to compare the factors implant length, crown height, and implant system (α = 0.05). The results showed that implant length was a statistically significant factor for both axial and nonaxial loading. The 13 mm prosthetic crown did not result in statistically significant differences in stress distribution between the implant systems and implant lengths studied, regardless of load type (P > 0.05). It can be concluded that short implants showed higher stress levels than long implants. Implant system and length was not relevant factors when prosthetic crown height were increased.

Small-diameter titanium Grade IV and titanium-zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial

OBJECTIVE

The aim of this study was to compare crestal bone-level changes, soft tissue parameters and implant success and survival between small-diameter implants made of titanium/zirconium (TiZr) alloy or of Grade IV titanium (Ti) in edentulous mandibles restored with removable overdentures.

MATERIALS AND METHODS

This was a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann bone-level implants (diameter 3.3 mm), one of Ti Grade IV (control) and one of TiZr (test), in the interforaminal region. Implants were loaded after 6-8 weeks and removable Locator-retained overdentures were placed within 2 weeks of loading. Modified plaque and sulcus bleeding indices, radiographic bone level, and implant survival and success were evaluated up to 36 months.

RESULTS

Of 91 treated patients, 75 completed the three-year follow-up. Three implants were lost (two control and one test implant). The survival rates were 98.7% and 97.3%, and the mean marginal bone level change was -0.78 ± 0.75 and -0.60 ± 0.71 mm for TiZr and Ti Grade IV implants. Most patients had a plaque score of 0 or 1 (54% for test and 51.7% for control), and a sulcus bleeding score of 0 (46.1% for test and 44.9% for control). No significant differences were found between the two implant types for bone-level change, soft tissue parameters, survival and success.

CONCLUSIONS

After 36 months, similar outcomes were found between Ti Grade IV and TiZr implants. The results confirm that the results seen at 12 months continue over time.

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.

Long-term retrospective evaluation of short implants in the posterior areas: clinical results after 10-12 years

AIM

To evaluate the long-term clinical results of short implants in the posterior areas and analyse the possible influence of different variables on implant success rate and marginal bone loss (MBL).

METHODS

A retrospective study design was used. Patients were included if they had received one or more short implants (≤8.5 mm long) in the posterior jaws at least 10 years earlier. All implants were embedded in plasma rich in growth factors (PRGF). The cumulative success rate was the primary outcome. MBL and the influence of different variables as secondary outcomes were assessed.

RESULTS

A total of 111 short implants (7.0, 7.5 and 8.5 mm in length) placed in 75 patients met the inclusion criteria. Of which, 94 were splinted to longer ones. The mean follow-up was 123.3 months (SD = 10.4 months). The mean crown-implant ratio was 1.4 (SD = 0.3). The mean MBL was 1.0 mm at mesial (SD = 0.7) and 0.9 mm (SD = 0.6) at distal aspect. One short implant failed. Success rate was 98.9% and 98.2% for the implant and patient-based analysis respectively. No relationship was observed between the studied variables and the MBL.

CONCLUSIONS

These clinical results support the use of short implants as an effective and safe long-term treatment option.

2D FEA of evaluation of micromovements and stresses at bone-implant interface in immediately loaded tapered implants in the posterior maxilla

AIM

The aim of the study is to evaluate the influence implant length on stress distribution at bone implant interface in single immediately loaded implants when placed in D4 bone quality.

MATERIALS AND METHODS

A 2-dimensional finite element models were developed to simulate two types of implant designs, standard 3.75 mm-diameter tapered body implants of 6 and 10 mm lengths. The implants were placed in D4 bone quality with a cortical bone thickness of 0.5 mm. The implant design incorporated microthreads at the crestal part and the rest of the implant body incorporated Acme threads. The Acme thread form has a 29° thread angle with a thread height half of the pitch; the apex and valley are flat. A 100 N of force was applied vertically and in the oblique direction (at an angle of 45°) to the long axis of the implants. The respective material properties were assigned. Micro-movements and stresses at the bone implant interface were evaluated.

RESULTS

The results of total deformation (micro-movement) and Von mises stress were found to be lower for tapered long implant (10 mm) than short implant (6 mm) while using both vertical as well as oblique loading.

CONCLUSION

Short implants can be successfully placed in poor bone quality under immediate loading protocol. The novel approach of the combination of microthreads at the crestal portion and acme threads for body portion of implant fixture gave promising results.

A retrospective study of implant-abutment connections on crestal bone level

This study compared the effects of external hex, internal octagon, and internal Morse taper implant-abutment connections on the peri-implant bone level before and after the occlusal loading of dental implants. Periapical radiographs of 103 implants (63 patients) placed between 2002 and 2010 were collected, digitized, standardized, and classified into groups based on the type of implant-abutment connection. These radiographs were then analyzed with image-processing software to measure the peri-implant crestal bone change during the healing phase (4 months after implant placement) and at loading phases 1 and 2 (3 and 6 months after occlusal loading, respectively). A generalized estimating equation method was employed for statistical analysis. The amount of peri-implant crestal bone change differed significantly among all time-phase pairs for all 3 types of implant-abutment connection, being greater in the healing phase than in loading phase 1 or 2. However, the peri-implant crestal bone change did not differ significantly among the 3 types of implant-abutment connections during the healing phase, loading phase 1, or loading phase 2. This retrospective clinical study reveals that the design of the implant-abutment connection appears to have no significant impact on short-term peri-implant crestal bone change.

Maxillary Sinus Augmentation with Autologous and Heterologous Bone Graft: A Clinical and Radiographic Report of Immediate and Delayed Implant Placement

PURPOSE

The aim of this study was to evaluate cumulative survival rate of implants placed on augmented maxillary sinus using a mixture of autologous bone harvested from the maxillary tuberosity and bovine-derived HA and to assess the height of the grafted material through radiographic evaluation.

METHODS

Thirty-five patients were treated with maxillary sinus augmentation and 93 implant fixtures were installed. The height of the augmented sinus and the gain of bone volume were measured by Cone Beam CT Scan and intraoral radiographs immediately after augmentation and up to 48 months subsequently. Changes in the height of the sinus graft material were calculated radiographically.

RESULTS

The cumulative survival rate was 98.92 % in all 93 implants. Additionally, normal healing process without any complication was observed in all patients. The original sinus height was a mean of 4.52 mm (range 2.0-6.4 mm) and the augmented sinus height was a mean of 14.1 mm (range 12.0-16.5 mm) after the surgery. The bone volume gain was a mean 9.613 mm (range 7-13 mm).

CONCLUSIONS

Within the limitations of this study, it would appear from the clinical and radiographic results that the sinus lift procedure with autologous bone graft harvested from the maxillary tuberosity combined with deproteinized bovine bone allows for a predictable outcome regarding the amount of bone formation in sinus floor augmentation and the immediate placement of implants, when possible, is recommended.

The influence of implant diameter on its survival: a meta-analysis based on prospective clinical trials

BACKGROUND

The use of narrow-diameter implants has been proposed to restore small edentulous spans, thus avoiding extensive bone augmentation procedures and reducing the surgical complexity of implant rehabilitations. Although success rates of narrow-diameter implants have already been analyzed in the literature, to the best of the authors' knowledge, no meta-analysis based on prospective and randomized controlled trials has been performed. The aim of this study is to analyze the survival rates of narrow-diameter implants compared with standard or wide-diameter implants.

METHODS

An electronic search from three databases and a hand search in implant-related journals of studies published in English before September 1, 2012 were performed. Prospective human clinical studies with at least 10 implants and a follow-up period of 1 year were included in the meta-analysis. Implants were divided into two groups based on their diameters.

RESULTS

The initial search yielded 484 articles, of which 49 were evaluated in full text for eligibility. Finally, 16 studies were chosen and separated into two groups: 1) implants of diameter <3.3 mm (group 1) and 2) implants of diameter ≥3.3 mm (group 2). A meta-analysis performed for groups 1 and 2 showed survival rates of 75% and 87%, respectively.

CONCLUSIONS

This meta-analysis showed that narrower implants (<3.3 mm) had significantly lower survival rates compared with wider implants (≥3.3 mm). Other variables, such as type of prosthesis, implant surface, and timing of prosthetic loading, were found to have influenced the implant survival rates.

Biomechanics and load resistance of short dental implants: a review of the literature

This paper was aimed to review the studies published about short dental implants. In the focus were the works that investigated the effect of biting forces of the rate of marginal bone resorption around short implants and their survival rates. Bone deformation defined by strain was obviously higher around short implants than the conventional ones. The clinical outcomes of 6 mm short implants after 2 years showed a survival rate of 94% to 95% and lower survival rate (<80%) for 7 mm short implants after 3 to 6 years for single crown restorations. The short implants used for supporting fixed partial prostheses had a survival rate of 98.9%. Short implants can be considered as a good alternative implant therapy to support single crown or partial fixed restorations.

Short implants in maxillary and mandibular rehabilitations: interim results (6 to 42 months) of a prospective study

The aim of this single-cohort study was to evaluate clinical survival and success of partial rehabilitation supported by reduced-length implants in maxilla and mandible. Data from 53 short implants placed in 41 patients are presented. Before surgery mean residual bone height was 6.21 ± 1.05 mm in the upper jaw and 10.73 ± 1.63 mm in the mandible. None of the implants failed, and the cumulative survival rate was 100% at 1 year after prosthetic loading. Mean peri-implant bone loss was 0.69 ± 0.24 mm for maxillary implants and 0.73 ± 0.23 mm for mandibular implants, and there was no significant difference between the 2 jaws. No complications were recorded. Despite the limitations of this study concerning study design and sample size, short implants may be considered effective in supporting partial rehabilitation in both maxilla and mandible. More well-designed studies with a larger sample size and longer follow-up are needed to validate the use of short implants.

Minimally invasive transcrestal guided sinus lift (TGSL): a clinical prospective proof-of-concept cohort study up to 52 months

PURPOSE

This study describes a new procedure for sinus elevation using computer-guided planning and guided surgical approach through the use of computer-aided design (CAD)/computer-aided manufacturing (CAM)-generated surgical template in combination with expander-condensing osteotomes thus providing a minimally invasive surgical technique.

MATERIALS AND METHODS

Sixty-six consecutive patients were treated with 136 implants placed by transcrestal-guided sinus floor elevation technique and the patients were followed for at least 3 years in function. The drilling protocol is customized based on the bone density of each implant site to achieve an insertion torque ranging between 45 and 55 Ncm. Titanium temporary abutments were connected to the implants with prosthetic screws tightened to 35 Ncm and an acrylic resin provisional restoration was adapted and delivered immediately. Six months after initial loading, a definitive CAD/CAM-generated restoration was delivered. Outcome measurements assessed were implant and prosthesis survival rate, biological or biomechanical complications, marginal bone level changes, total alveolar ridge bone height before and after procedure, periodontal parameters measured as well as patient's perception of pain levels during recovery period.

RESULTS

Mean follow-up was 43.96 (range from 36 to 52) months. Cumulative implant survival rate was 98.53% at 3 years. No biological or mechanical complications were encountered and no prosthetic failures occurred during the entire follow-up period. Mean marginal bone loss (MBL) during the first year of function was 0.33 ± 0.36 mm, while at the 3-year follow-up, the mean MBL was 0.51 ± 0.29 mm. The mean residual bone height of the alveolar crest prior to grafting was of 6.7 ± 1.6 mm (range 5.1-9.2 mm), while, the mean bone height gained was 6.4 ± 1.6 mm (range 3.2-8.1 mm). All patients reported low levels of pain and found to have normal periodontal parameters.

CONCLUSION

This proof-of-concept study suggests that the use of guided surgery to perform transcrestal maxillary sinus floor elevation for alveolar ridge height augmentation is a successful minimally invasive technique for the short- to medium-term follow-up, thus avoiding the extended treatment time and morbidities associated with maxillary sinus floor augmentation.

Are short dental implants (<10 mm) effective? a meta-analysis on prospective clinical trials

BACKGROUND

This study aims to compare the survival rate of short (<10 mm) and standard (≥10 mm) rough-surface dental implants under functional loading.

METHODS

An electronic literature search using PubMed and Medline databases was conducted. Prospective clinical human trials, published in English from January 1997 to July 2011, that examined dental implants of <10 mm with a 12-month follow-up were included in this meta-analysis. The following data were retrieved from the included articles: the number of implants, implant dimensions, implant locations, types of prostheses, follow-up periods, and implant survival rates. Kaplan-Meier survival estimates and the hazard rates were analyzed and compared between short and standard implants.

RESULTS

Thirteen studies were selected, examining 1,955 dental implants, of which 914 were short implants. Short dental implants had an estimated survival rate of 88.1% at 168 months, when standard dental implants had a similar estimated survival rate of 86.7% (P = 0.254). The peak failure rate of short dental implants was found to occur between 4 and 6 years of function. This occurred at an earlier time point compared with standard dental implants, where the peak failure rate occurred between 6 and 8 years of function.

CONCLUSIONS

This study shows that in the long term, implants of <10 mm are as predictable as longer implants. However, they fail at an earlier stage compared with standard implants.

Two versus three narrow-diameter implants with locator attachments supporting mandibular overdentures: a two-year prospective study

Purpose. To compare treatment outcome (survival rate, condition of hard and soft peri-implant tissues) and prosthodontic maintenance requirements of two versus three narrow-diameter bone level implants with Locator attachments supporting mandibular overdentures. Materials and Methods. Twenty completely edentulous patients with atrophic mandibles were treated. Ten patients (Group A) were treated with overdentures supported by two narrow (3.3-mm diameter) implants (Straumann AG, Basel, Switzerland) and ten patients (Group B) were treated with overdentures supported by three narrow implants. Locator (Zest Anchors, USA) attachments were used for prosthetic anchorage. Standardized clinical and radiographic parameters (survival rate, plaque index, calculus index, gingival index, bleeding index, probing depth and marginal bone loss) were evaluated at the time of the completion of the prosthetic treatment (baseline) and after 6, 12 and 24 months of functional loading. Prosthodontic maintenance requirements were also scored. Results. Only one implant was lost (Group B) during the healing period. There were no significant differences with regards to any of the studied clinical and radiographic parameters between the two groups (P > 0.05). Few prosthetic complications were recorded. Conclusions. No need to insert more than two narrow-diameter bone level implants with Locator attachments in cases of atrophic mandible to support an overdenture, however, long-term prospective studies are required to support this notion.

Crestal sinus lift with sequential drills and simultaneous implant placement in sites with <5 mm of native bone: a multicenter retrospective study

PURPOSE

The aim of this multicenter retrospective clinical study was to evaluate the survival rate of implants placed in the posterior maxilla with a residual bone height of <5 mm.

MATERIALS AND METHODS

One hundred seventeen patients, recruited from 6 different centers, had 134 implants placed below the maxillary sinus. The patient population consisted of 52 men and 65 women ranging in age from 39 to 78 years (mean age, 53.2 years). Sinus lift procedures were performed following a crestal approach using a specific sequence of drills (Cosci's technique). All implants were submerged. Periapical radiographs were obtained with a paralleling technique and were digitized. The pattern of bone remodeling was subsequently evaluated.

RESULTS

The average (±SD) follow-up time was 48.2 months (±29.30 months; range, 24 to 120 months). Of the original 134 implants placed, 5 implants (3.7%) failed. The implant survival rate was 96.3%. The average residual bone height was 3.46 mm (±0.91 mm) at baseline. The average height of the alveolar crest in the treated implant sites was 9.94 ± 2.29 mm. The radiographic bone gain was 6.48 ± 2.38 mm.

CONCLUSION

The investigation suggests that this crestal drill approach can be a successful sinus lifting procedure in a severe atrophic maxilla with <5 mm of crestal bone height.

Analysis of the biomechanical feasibility of a wide implant in moderately atrophic maxillary sinus region with finite element method

OBJECTIVE

The aim of this study was to evaluate the biomechanical feasibility of a short wide implant in a moderately atrophic posterior maxilla.

STUDY DESIGN

A normal maxillary posterior section with a standard screwed implant (model 1) and a moderately atrophic maxillary posterior section with a short wide screwed implant (model 2) were created. The maximum von Mises stresses in maxilla and the maximum displacements in the implant-abutment complex were evaluated.

RESULTS

When the implant diameter exceeded 5.0 mm, the most stable and minimal value of stress in maxilla and displacement in the implant-abutment complex could be achieved in model 2, which were almost all lower than those in model 1.

CONCLUSIONS

The effect of a short wide implant in the moderately atrophic maxillary sinus region is favorable and similar to that of the standard implant in the normal sinus region. From the biomechanical point of view, implant diameter exceeding 5.0 mm is a relatively optimal selection in a moderately atrophic maxilla.

Zygomatic implants: a critical review of the surgical techniques

PURPOSE

The purpose of the present study is to identify and describe the different surgical techniques for placement of zygomatic implants reported in the literature and discuss the differences between them.

METHODS

An electronic search was undertaken in July 2011. The titles and abstracts from these results (n = 130) were read for identifying studies, which reported different surgical techniques for placement of zygomatic implants, which resulted in 41 articles.

RESULTS

Five different surgical approaches were identified: (1) the classical approach, (2) the sinus slot technique, (3) the exteriorized approach, (4) the minimally invasive approach by the use of custom-made drill guides, and (5) the computer-aided surgical navigation system approach. When the maxilla is severely resorbed, the concavity formed by the ridge crest is small, and the original classical technique should be used. When maxillary resorption generates a large concavity, it would be better to exteriorize the zygomatic implant. The externalized technique has fewer surgical steps than the classical and sinus slot methods, is less invasive, and reduces surgical time. It is recommended that utilization of the sinus slot technique together with the CT-based drilling guide would enhance the final results. Although the technique that uses the computer-aided surgical navigation system approach may produce an improved precision in the clinical procedure, its use is expensive, prolongs the operation time, and is limited to centers that have the necessary equipment for the surgery.

CONCLUSIONS

Preference for one technique over the other should take into consideration the concavity formed by the ridge crest, maxillary sinus, and region of implant insertion in the zygomatic bone.

Marginal Bone Loss Around Implants Supporting Fixed Restorations

A key criterion of success following dental implants is the marginal bone level. Long-term clinical and radiographic evaluation is necessary to test the results of in vitro studies investigating how cantilevering of restorations or implant size affect bone level changes around implants. There is no consensus on the effect of several variables such as age, gender, implant size, and cantilever prostheses on marginal bone levels around fixed dentures supported by dental implants. Patients who received cemented, fixed restorations supported by implants and who were examined in routine recall sessions 6, 12, 24, and 36 months after loading were included in the study group. Comparative bone level measurements were obtained from images of radiographs at ×20 magnification using the CorelDraw 11.0 software program. Statistical analysis was performed using the Student t test and 1-way analysis of variance. In the 36-month observation period, there were no incidences of implant failure, excessive bone loss around implants, or peri-implant inflammation. One hundred twenty-six implants in 36 patients were evaluated, and the effect of several factors on marginal bone loss (MBL) during the 36 months after loading was analyzed statistically. There was no significant relationship between MBL and implant length or diameter, whereas age, gender, and cantilevers affected bone loss rates. MBL was elevated in older and female patients as well as in patients who received cantilevers. In cases of limiting anatomic conditions, short and/or narrow implants should be preferred over cantilever extensions.

Retrospective analysis of survival rates and marginal bone loss on short implants in the mandible

OBJECTIVES

Short implants have become an interesting alternative to bone augmentation in dental implantology. Design of shorter implants and longer surveillance times are a current research issue. The goal of this study was to show the survival rates of short implants below 9 mm in the partly edentulous mandibular premolar and molar regions with fixed prosthetics. Marginal vertical and 2D bone loss was evaluated additionally. Different implant designs are orientationally evaluated.

MATERIAL AND METHODS

A total of 247 dental implants with fixed prosthetics (crowns and bridges) in the premolar and molar region of the mandible were evaluated; 47 implants were 9 mm or shorter. Patient data were evaluated to acquire implant survival rates, implant diameter, gender and age. Panoramic X-rays were analysed for marginal bone loss.

RESULTS

Average surveillance time was 1327 days. Cumulative survival rate (CSR) of short implants was 98% (1 implants lost) compared to 94% in the longer implants group without significance. Thirty-five of the short implants were Astratech (0 losses) and 12 were Camlog Screw Line Promote Plus (1 loss). Early vertical and two-dimensional marginal bone loss was not significantly different in short and regular length implant group with an average of 0.6 mm and 0.7 mm(2) in short implants over the observation period.

CONCLUSIONS

Within the limitations of this study, we conclude that short implants with a length of 9 mm or less have equal survival rates compared with longer implants over the observation period of 1-3 years.

Implants (3.3 mm diameter) for the rehabilitation of edentulous posterior regions: a retrospective clinical study with up to 11 years of follow-up

BACKGROUND

There is limited evidence for the use of narrow-diameter implants for rehabilitation of the posterior regions of the jaws using different surgical techniques.

PURPOSE

The purpose of this study was to report the clinical results of implant-supported prosthetic rehabilitations in the posterior regions of both jaws, using narrow-diameter implants.

MATERIALS AND METHODS

The study included 147 patients (115 males and 32 females), with an age range of 26 to 77 years (mean = 47.5 years), with a total of 247 implants inserted and followed between 1 and 11 years, with a median follow-up time of 5 years. The patients were in need of fixed prosthetic implant-supported rehabilitations in the posterior region of the jaw, presenting a reduced interradicular bone or a thin alveolar crest. The implant survival estimate was computed using the Kaplan-Meier product limit estimator.

RESULTS

The survival rate for narrow diameter implants was 95.1% at 11 years (Kaplan-Meier), with a distribution of 91.4% at 11 years, 95.9% at 10 years, and 95.5% at 9 years for the two-stage, one-stage, and immediate function techniques, respectively. The mean marginal bone resorption recorded at 1, 5, and 10 years were 1.16, 1.53, and 1.74 mm, respectively. Backward conditional logistic regression identified "type of implant" as a strong protective factor against implant failure (MkIII and NobelSpeedy implants compared to the MkII implant; OR = 0.14), and "type of rehabilitation" as a strong risk factor for implant failure (partial rehabilitations compared to single teeth rehabilitations; OR = 4.75).

CONCLUSIONS

The results indicate that within the limitations of this study, the use of narrow-diameter implants for the prosthetic rehabilitation of posterior regions of the jaws is viable, with good outcomes in the long-term, irrespective of the surgical technique implemented.

The use of root form implants in overdenture treatment for the atrophic mandible: a clinical report

Four short root form implants were inserted in an atrophic mandible and the case restored with a lower connecting bar and an overdenture, opposing a complete maxillary denture. Root form implants were selected, as opposed to a subperiosteal implant in this case. The patient had a favorable medical history, appeared healthy, did not smoke, drink, or do illicit drugs, and had good bone quality.

Wired/Classic and Wireless/Periotest "M" instruments: an in vitro assessment of repeatability of stability measurements

This in vitro study evaluated agreement among 10 trained evaluators when assessing implant stability with the Wired/Classic and Wireless/Periotest "M." A difference of 1 Periotest value (PTV) between the wired (-7) and wireless (-8) instruments was observed for the pretest calibration ring. No significant differences were found between the instruments and for all evaluators for all tests (analysis of variance, P < .05). Each instrument can provide meaningful and reproducible recordings of stability measurements.

The comparison of marginal bone loss around mandibular overdenture-supporting implants with two different attachment types in a loading period of 36 months

OBJECTIVE

The aim of this study was to assess the influence of attachment types on the marginal bone loss (MBL) around dental implants supporting mandibular overdentures (OVD).

BACKGROUND

There are a number of in vitro studies evaluating the influence of several factors on MBL around implants.

MATERIAL AND METHODS

Mandibular OVD patients appearing at routine recall sessions consecutively 6, 12, 24 and 36 months after loading were included in the study group. All patients received mandibular OVD with either ball or bar attachments. Measurements were obtained from images of successive radiographs, which were scanned and digitised before, and analysed at ×20 magnification. Statistical analyses were utilised in this study to assess the mean marginal bone level changes as well as to explore the potential effect of several parameters such as the cantilever or the attachment type on bone loss.

RESULTS

One hundred and twenty-six implants in 51 patients with a mean age of 59.39 ± 9.99 years were evaluated. There was no statistical significant difference between the distal and mesial bone loss rates of single or splinted attachment types, whereas bone loss rates were statistically higher in cantilever situations.

CONCLUSION

Within the limitations of this study, gender, age and diameter of the implants do not play a role in MBL. Length of the implant is an important factor in marginal bone level maintenance. The attachment type for OVD support seems not to influence MBL, but cantilevering of the bars increases bone loss significantly.

Histological evaluation of healing after transalveolar maxillary sinus augmentation with bioglass and autogenous bone

OBJECTIVES

The aim was to evaluate histologically the outcome of a bioglass and autogenous bone (at 1 : 1 ratio) composite implantation for transalveolar sinus augmentation.

METHODS

In 31 patients, during implant installation ca. 4 months after sinus augmentation, biopsies were harvested through the transalveolar osteotomy by means of a trephine bur and non-decalcified sections through the long axis of the cylinder were produced. After a strict selection process, taking into account the presurgical residual bone height and biopsy length, 8 and 15 biopsies representing the new tissues formed inside the sinus and the transalveolar osteotomy, respectively, qualified for analysis. The tissue fractions occupied by newly formed bone (mineralized tissue+bone marrow), soft connective tissue, residual biomaterial+empty spaces, and debris inside the sinus cavity or the transalveolar osteotomy were estimated.

RESULTS

Bone and connective tissue fraction in the newly formed tissues inside the sinus cavity averaged 23.4 ± 13.2% and 54.1 ± 23.5%, respectively. Residual biomaterial, empty spaces, and debris averaged 1.9 ± 3.5%, 10.5 ± 6.3%, and 8.4 ± 14.5%, respectively. In the transalveolar osteotomy, bone and connective tissue fraction averaged 41.6 ± 14.3% and 46.1 ± 13%, respectively, while the amount of residual biomaterial, empty spaces, and debris was 2.8 ± 5%, 4.7 ± 1.9%, and 3.2 ± 2.6%, respectively. Statistically significant differences between the sinus cavity and the transalveolar osteotomy were found only for bone and empty spaces' values (P=0.02 and 0.04, respectively).

CONCLUSION

Sinus augmentation with a bioglass and autogenous bone composite is compatible with bone formation that, in a short distance from the floor of the sinus, shows similar density as that reported previously for other commonly used bone substitutes. New bone fraction inside the transalveolar osteotomy was almost twice as much as in the sinus cavity, while the amount of residual biomaterial was much less than that inside the sinus.

A wide-body implant as an alternative for sinus lift or bone grafting

PURPOSE

The aim was to evaluate the outcome of a short wide-body implant in the atrophic posterior jaw without a grafting procedure.

MATERIALS AND METHODS

Patients treated with a tapered wide-body implant measuring 8 to 9 mm in width and 7 to 9 mm in length (Max implant; Southern Implants, Irene, South Africa) were recalled to scrutinize implant survival. Preoperative cone beam computed tomography images were analyzed to measure bone height in reference to the mandibular canal and sinus floor.

RESULTS

There were 57 implants inserted in 18 men and 24 women after a 2-stage procedure and delayed loading. The mean follow-up was 15 months (SD, 10; range, 1-32 months), with 63.2% of the implants having at least 1 year of follow-up and 26.3% having at least 2 years' follow-up. Forty-six implants were inserted in the posterior maxilla and eleven in the mandible. Fifteen were placed in an extraction socket and forty-two in healed bone. Thirteen implants were supporting a single crown. Two implants failed, resulting in a survival rate of 96.5%, with rates of 90.9% and 97.8% for mandible and maxilla, respectively. This was not affected by gender, jaw, immediate or delayed placement, implant diameter and length, or the use of a bone substitute. The mean preoperative bone height was 7.21 mm in maxilla and 8.76 mm in mandible. In 41 cases implant length surpassed available bone height.

CONCLUSIONS

Despite the compromised bone condition and height, the survival rate of 96.5% is comparable to normal implants and, therefore, placing a wide-body implant may be an alternative to avoid grafting procedures. This is probably related to the enlarged implant surface area and the good primary stability.