Tilted implants as an alternative to maxillary sinus grafting: a clinical, radiologic, and periotest study.

BACKGROUND: Owing to mechanical and anatomic difficulties, implant treatment in the atrophic maxilla represents a challenge. The maxillary sinus floor augmentation procedure is still not universally accepted because of its complexity and its unpredictability. PURPOSE: In this study, a combination of tilted and axial implants was used in patients with severely resorbed posterior maxillae as an alternative to sinus grafting. MATERIALS AND METHODS: Twenty-five patients were rehabilitated with 29 fixed partial prostheses supported by 101 Brånemark System implants. Fifty-nine implants were installed in an axial and 42 in a tilted direction. The average follow-up period was 37 months (range: 21-87 mo post loading). RESULTS: After 5 years, the implant cumulative success rate was 95.2% (survival: rate 100%) for the tilted implants and 91.3% (survival rate: 96.5%) for the axial implants, and the prosthesis survival rate was 100%. At the fifth year, the average marginal bone loss was 1.21 mm for the tilted implants and 0.92 mm for the axial ones. The mean Periotest values (PTV) at loading time were -2.62 and -3.57, and after 5 years the PTVs were -4.73 and -5.00 for the tilted and the axial implants, respectively. During the follow-up, all prostheses but two were mechanically stable, retightening of 18 abutment screws and of 5 gold screws in 14 prostheses was done, and fracture of two abutment screws and two occlusal surfaces was experienced. CONCLUSIONS: Results indicate that the use of tilted implants is an effective and safe alternative to maxillary sinus floor augmentation procedures.

Marginal bone resorption at different treatment concepts using Brånemark dental implants in anterior mandibles.

BACKGROUND: Different implant treatment modalities, one- and two-step surgery, and one-step surgery combined with early functional loading have successfully been used in the anterior mandible for rehabilitation of edentulism. However, the marginal bone remodeling has not been compared among the three different techniques. PURPOSE: The purpose was to compare the marginal bone level in a short- and long-term perspective study using Brånemark dental implants placed according to either a one- or a two-step surgical procedure or a one-step surgical procedure combined with early functional loading. MATERIALS AND METHODS: Seven patients were treated with a split-mouth technique with a one-step surgical technique on one side and a two-step technique on the other side. In this latter group, the fixtures were submerged during a 3- to 4-month healing period before abutment connection and loading. In 13 patients, following one-step surgery, the permanent prosthetic suprastructure was connected within 20 days from implant surgery. All patients were operated on by the same surgeon. The level of the marginal bone was radiographically measured relative to the fixture-abutment junction and was followed up to 5 years from fixture installation. RESULTS: After connection of the supraconstruction, the marginal bone resorption was significantly lower in the early functional loading group compared to the one- and two-step surgical technique groups. However, after 18 months and after 5 years, the marginal bone was located approximately 1 mm apical to the fixture-abutment level in all three groups. CONCLUSION: There was no difference in marginal bone resorption in a long-term perspective between one- and two-step surgical procedures and a one-step surgical procedure with early functional loading of Brånemark dental implants.

Tilting of posterior mandibular and maxillary implants for improved prosthesis support.

Rehabilitation of atrophied edentulous arches with endosseous implants in the posterior regions is often associated with anatomic problems such as jaw shape and location of the mental loop, mandibular canal, and maxillary sinuses. The purpose of this investigation was to modify the method for implant placement in the posterior part of the jaws to extend fixed implant-connected prostheses further distally, and to reduce the length of cantilevers in complete-arch prostheses without transpositioning the mandibular nerve or performing bone grafting in the maxilla. Forty-seven consecutive patients were treated with implants (25 patients/36 mandibular implants, 22 patients/30 maxillary implants) placed in tilted positions. They were followed a mean of 40 months (mandibles) and 53 months (maxillae). In the mandible, implants close to the mental foramina were tilted posteriorly approximately 25 to 35 degrees. In the maxilla, the posterior implants were placed close to and parallel with the sinus walls and were titled anteriorly/posteriorly approximately 30 to 35 degrees. Patients gained a mean distance of 6.5 mm of prosthesis support in the mandible and 9.3 mm in the maxilla, as a result of implant tilting. There were no implant failures in mandibles. The cumulative success rates in the maxilla at 5 years were 98% for tilted implants and 93% for non-tilted implants. Paresthesias of the mental nerve were observed on 4 sides during the first 2 to 3 weeks after implant placement. Analysis of the load distribution in one mandibular case showed no significant difference between tilted and the non-tilted implants, and the improved prosthesis support was confirmed. Satisfactory medium-term results concerning osseointegration and significant extension of prosthesis support show that the method can be recommended. This technique may allow for longer implants to be placed with improved bone anchorage.

Immediate function of Brånemark implants in the esthetic zone: a retrospective clinical study with 6 months to 4 years of follow-up.

BACKGROUND: Immediate implant function is a psychological benefit for the patient and makes a substantial reduction in treatment cost possible. Currently, immediate function using Brånemark implants has become an accepted alternative for complete-arch fixed restorations in mandibles and for overdenture support for some other screw-shaped implants. Clinical documentation is lacking for other applications. PURPOSE: The purpose of this study was to investigate a concept for immediate function of Brånemark implants supporting fixed prosthesis in the esthetic regions of the jaws. MATERIALS AND METHODS: This retrospective clinical study included 49 consecutively treated patients with 94 implants supporting 54 fixed prostheses, all in esthetically critical regions: 23 of the prostheses were bridges, 14 in maxillae and 9 in mandibles; 31 of the prostheses were crowns, 22 in maxillae and 9 in mandibles. At surgery, the implant platform was positioned above the surrounding bone level and bicortical anchorage was the goal whenever possible. The minimum insertion torque for accepting the implant for immediate function was 32 Ncm. Provisional implant-supported prostheses without occlusal contacts were delivered at time of surgery, and final prostheses with normal occlusion were delivered 5 months later. RESULTS: Eighty-five of the implants (90%) have passed the 1-year and 40 (43%) the 2-year follow-ups, respectively. Two implants failed in one patient before the 6-month follow-up, and another two implants between the 6-month and the 1-year follow-up, in two other patients, giving a cumulative survival rate of 96%. The average bone resorption was 0.8 mm after the first year as evaluated from 35 patients with readable radiographs. The failed implants were replaced after 3 to 4 months with immediate function; these were successful in all cases (not included in this study). The number of complications was small and did not differ in character from those normally encountered at implant treatment using a conventional protocol. CONCLUSIONS: The cumulative survival rate of 96% at 1 and 2 years indicates that immediate function of Brånemark implants used in the esthetic zone in both jaws can be a viable concept. All failures occurred in fresh extraction sites, and extra care is recommended to avoid situations with ongoing inflammation in these situations.

Osseointegrated implant for single-tooth replacement: a retrospective multicenter study on routine use in private practice.

BACKGROUND: Implant restorations first started with total edentulism. Later, the scientific community gave its approval for restorations in partial edentulism, and only recently some studies confirmed the validity of the treatment for single-tooth replacement. PURPOSE: The purpose of the study was to evaluate implant survival and prosthesis stability of Brånemark implants (titanium screws) when used routinely for single-tooth replacement in all regions. MATERIALS AND METHODS: Two hundred and fourteen patients received 252 implants for single-tooth replacement over a period of 8 years at five private clinics in Italy. The patients were treated in accordance with the protocol for Brånemark implants, and the data gathered have been analyzed according to established evaluation methods. RESULTS: During the observation period, 10 failures were recorded and 229 restorations were carried out. After the first year of loading, the total cumulative survival rate (CSR) was 96%, which then remained stable over the study time. The most frequent complication was loosening of the abutment screws (n = 22), amounting to 35% of all of the complications. This problem was related mainly to earlier types of abutments, whereas the more recent design, CeraOne abutment, showed a low frequency of screw loosening. CONCLUSIONS: The high survival rate, which is similar to that presented for prospective multicenter studies for single-tooth restorations with Brånemark implants, led to the conclusion that the use of this treatment modality is a reliable treatment for routine use in all oral regions.

Brånemark System Wide Platform implants for single molar replacement: clinical evaluation of prospective and retrospective materials.

BACKGROUND: The use of oral implants for single tooth replacement has become a predictable treatment modality. As single tooth loss is most common in posterior areas of the jaws, the use of the protocol is of specific interest in those regions. New implant designs aimed at this purpose have also been introduced. PURPOSE: The aim of the study was to present the outcomes for wide diameter implant treatment when being used in posterior areas of the jaws. MATERIALS AND METHODS: This paper presents the 3-year results of a prospective multicenter study (three clinics; n = 38 implants) and the 1-year results from a retrospective multicenter study (two clinics; n = 20 implants) on wide diameter implants for single molar replacement. Based on the hypothesis that dense bone in posterior mandibles would benefit from careful surgery and longer remodeling time, the influences of surgical technique and healing time on implant success and bone resorption were particularly addressed. RESULTS: The outcome demonstrated a good predictability for Brånemark System Wide Platform implants, at least short term, when used as single molar support (prospective group cumulative success rate [CSR] = 92% after 3 years; retrospective group CSR = 95% after 1 year). The increased mechanical strength of the wide platform implant/abutment complex also turned out to be important for mechanical stability. CONCLUSIONS: The study indicated that it was important to carefully perform surgery in posterior mandibles in order to preserve and optimally use the existing dense bone. It was suggested that from bone healing and remodeling aspects, posterior mandibles may be more demanding to handle than corresponding areas of maxillae.

Long-term study of quality and safety of osseointegration for the retention of auricular prostheses.

The aim of this article is to describe the safety and quality of the osseointegrated implant technique for the retention of craniofacial prostheses, to present a protocol for collection of clinical data, and to discuss the impact of the procedure on the patient quality of life. A protocol was designed and used to study patients who had received auricular prostheses consecutively since 1979 at our department. The patients were asked to answer a questionnaire designed to describe symptoms and problems specific for someone wearing an auricular prosthesis. In total, 99 patients received 107 prosthetic ears (8 patients had bilateral defects) retained on 309 implants (2 to 4 implants/ear). Patients of all ages were represented, and only 9 discontinuities were reported. Most patients (95%) wear their prosthesis every day, in most cases more than 10 hours/day. The follow-up period ranged from 1 to 12 years, giving a total of 2624 postoperative observations of implants, with a 3% incidence of significant skin reaction. We conclude that the surgical technique for auricular prostheses retained on osseointegrated implants is simple and associated with a low rate of peroperative and long-term complications. It offers a high degree of stability and aesthetic satisfaction.

Functional loads on freestanding and connected implants in three-unit mandibular prostheses opposing complete dentures: an in vivo study.

In vivo measurements of vertical forces and bending moments during biting and chewing were carried out on 10 three-unit prostheses in the posterior mandibles of five patients. Each patient had two prostheses, one supported by two implants and the other supported by one implant and one tooth. The results demonstrated no major difference in functional load magnitudes related to the support type. The distribution of load between the abutments was influenced more by the prosthesis geometry and implant placement than by the difference in load characteristics of tooth and implant. This conclusion, however, is limited to one implant connected to a tooth, because multiple implants form a considerably stiffer unit than do teeth. An increase in vertical load resulting from cantilever extensions on the prostheses was documented, both at bite fork measurements and during chewing. No substantial lateral bending was registered, probably because the flat occlusal surfaces and the presence of the opposing complete denture reduced lateral forces.

Load factor control for implants in the posterior partially edentulous segment.

There are inherent biomechanical differences in the implant treatment of completely edentulous arches and posterior partially edentulous segments. The partial prosthesis does not benefit from cross-arch stabilization and is, therefore, more susceptible to bending loads. Because of the difference in mobility between teeth and implants, implants may carry a major share of load when mixed with teeth in the same quadrant. However, the frequency of implant overload in posterior partial restorations is low, and, with appropriate treatment planning, overload in these situations is almost always preventable. A checklist procedure is proposed to help the clinician enumerate and evaluate deleterious load factors. By screening patients for such factors in advance, the clinician may identify and avoid potential overload situations when conceiving and fabricating implant-supported posterior partial prostheses. A second checklist, for use at follow-up appointments, lists alarm factors that serve as an early warning of overload once the prosthesis is in place.

Influence of implant diameters on the integration of screw implants. An experimental study in rabbits.

The influence of diameter on the integration of titanium screw-shaped implants was studied in the rabbit tibia by means of removal torque measurements and histomorphometry. Implants 3.0, 3.75, 5.0, and 6.0 mm in diameter and 6.0 mm long were inserted through one cortical layer in the tibial metaphyses of nine rabbits and allowed to heal for 12 weeks. The implants were then unscrewed with a torque gauge, and the peak torque required to shear off the implants was recorded. The histologic analysis in undemineralized ground sections comprised (1) a gross description of the implant sites and assessments of (2) the total implant length in bone and (3) in the cortical passage, as well as (4) the thickness of the cortical bone adjacent to the implants. From the removal torque values obtained and morphometric measurements, a mean shear stress value was calculated for each implant type. The biomechanical tests showed a statistically significant increase of removal torque with increasing implant diameter. The resistance to shear seemed to be determined by the implant surface in supportive cortical bone, whereas the newly formed bone at the periosteal and endosteal surfaces did not seem to have any supportive properties after 12 weeks. It is suggested that wide diameter implants may be used clinically to increase implant stability.

Design, maintenance and biomechanical considerations in implant placement.

Successful treatment using implants involves careful consideration of fixture placement and prosthesis design if the biomechanical conditions are to be optimized. These parameters may be related to the implant/tissue interface at the individual fixture level, and thence to the relationship between the components of a prosthesis. The influence of the nature and magnitude of occlusal forces can also be significant and should be carefully assessed before placement.

A comparative study of one implant versus two replacing a single molar.

A comparative study between one and two Brånemark implants replacing a single molar was conducted. Forty-seven individuals comprised two groups of 22 patients treated with one implant and 25 with two implants. A total of 72 implants were placed, 66 (92%) in the mandible and six (8%) in the maxilla. After the first year of function, the success rate was 99%, with only one implant lost. Between the second- and third-year follow-ups, 100% of the implants continued to function in the remaining 46 patients, giving a 3-year cumulative success rate of 99%. The marginal bone loss between 1 and 3 years of function was 0.10 mm (SD 0.20) for the group with one implant and 0.24 mm (SD 0.20) for the group with two implants. No changes were observed in the Sulcus Bleeding Index during the 3-year follow-up. Prosthesis mobility or screw loosening was the most frequent complication and was predominant in the group using one implant (48%), but was substantially reduced in the group using two implants (8%). These mechanical problems, using one implant only, seem to be preventable using a stronger screw joint (CeraOne abutment). Precise centric occlusal contact was established and maintained over the study period, which was thought to contribute to the very high success rate for the single-implant-supported molars, despite their high degree of mechanical problems. This study suggests that implant-supported molars can be effective therapy, and the results confirm the biomechanical analysis that two implants provide more advantageous support than does one.

On the influence of superstructure connection on implant preload: a methodological and clinical study.

In a combined in vitro and in vivo study strain gauges were used to register the deformation in two terminal implant abutment cylinders, when connecting three different prosthetic appliances. The prosthetic constructions were placed on the abutments and fastened in vitro and in vivo by using different torque sequences. Furthermore, in the in vitro situation the three medial abutments were replaced by abutments which were 100 microns shorter. The results show that even if the prosthetic constructions were judged to have a good clinical fit, relatively large External Preloads were registered both in vitro and in vivo. No significant differences in axial force or in bending movement were found between the torque sequences in vivo. There were, however, significant differences in axial force as well as in bending moment in the in vitro experiment. When the shorter medial abutments were used in vitro, a change in the axial force of approximately 200 N was registered. The results confirm that the methodological approach used in this study is valid when evaluating preloads.

Stabilization of the nipple base with titanium rings when reoperating patients with continent urostomies for nipple dysfunction.

Nipple dysfunction in Kock reservoirs used for continent urinary diversion is usually caused by a flattening out of the intestinal nipple due to a lateral tore at the base of the nipple when the reservoir expands. This study describes a new method to repair dysfunctioning nipples based on the use of titanium rings applied outside the reservoir around the base of the nipple. Experiments on dogs and rats have shown that rings and plates of titanium rapidly attach to the serosal surface of ileum exposed to urine with only minor signs of inflammation. Ten patients with Kock reservoirs for urinary diversion have been reoperated for nipple dysfunction due to nipple sliding with elongation of the nipple and fixation of the nipple base with titanium rings. The functional result is excellent in 9 out of the 10 patients. No signs of erosion of the rings into the reservoirs have been noted. With this new method for nipple repair the need for using more intestine to construct a new nipple is eliminated.

Mechanical evaluation of craniofacial osseointegration retention systems.

This study evaluates mechanical behavior of retention systems that have been used in craniofacial osseointegration. A loading/measuring apparatus was custom designed and constructed. Test bases that represented a typical auricular situation were constructed. These bases allowed for three points of retention. Jigs that could be reproducibly positioned carried the reciprocal portion of the retentive components. The test apparatus provided vertical and horizontal loads in five locations. The system was used to test two ball-and-socket attachments (Dalla Bona; Nobelpharma), cast and preformed bar and clips (Nobelpharma), and three magnet systems (Dynamag; Neomag; Technovent). The loading/measuring apparatus was also used to evaluate the performance of two facial prosthetic adhesives. Retention systems employed in craniofacial osseointegration offer more predictable retention than the facial prosthetic adhesives. The mechanical retention systems are best suited to situations where tensile and shear forces will operate. Magnet systems are best used where only tensile forces are anticipated or where horizontal forces on the implants are to be avoided.

Bending overload and implant fracture: a retrospective clinical analysis.

Thirty-nine patients with implant fractures treated by three of the authors have been analyzed as to probable causes. Thirty-five (90%) of the fractures occurred in the posterior region. Thirty (77%) of the prostheses were supported by one or two implants, which were exposed to a combination of cantilever load magnification and bruxism or heavy occlusal forces. It was concluded that prostheses supported by one or two implants and replacing missing posterior teeth are subjected to an increased risk of bending overload. The literature review indicates that the fracture frequency is low in these situations and this study demonstrates that with appropriate treatment planning, such overload situations can essentially be prevented.

Vertical load distribution on a three-unit prosthesis supported by a natural tooth and a single Brånemark implant. An in vivo study.

In vivo bite forces, implant axial forces and bending moments were measured on 5 patients with fixed posterior prostheses supported by a natural tooth and a single Brånemark implant. The results demonstrate that the vertical loads applied to the prostheses are shared between the tooth and the implant. The maximum bending moment transferred to the implant (10-15 N.cm) was well below the acceptable load limits for the mechanical components (50-60 N.cm), even at bite forces exceeding 100 N. The main reason for this load sharing seems to be the inherent bending flexibility of the implant screw joint, which matches the axial flexibility of the periodontal ligament of the tooth.

Biomechanics of the Brånemark system.

A dental implant restoration defines a biomechanical structure comprising both biological tissue, the bone, and mechanical components, the implant and the suprastructure. The relation between the applied load from the prosthesis and the supporting capacity of implant and bone will effect the long term outcome of treatment. Therefore, the biomechanical aspect is an essential element of the treatment planning. Related principles have been evolved through theoretical models, laboratory investigations, animal studies and in vivo measurements. Recently a number of clinical studies referring to implant treatment in partially edentulous jaws have been presented, revealing new aspects. In this article, results from these studies are discussed and related to fundamental biomechanical principles for treatment planning.

On clinical loading of osseointegrated implants. A methodological and clinical study.

Strain gauges were used to record in vivo and in vitro functional deformations in a fixed prosthetic appliance supported and retained by osseointegrated titanium implants. Four linear gauges were attached to each of totally 5 implant abutment cylinders and gauge signals were transferred into a computer via a digital converter. A computer program (ASYST) was used for collection, calibration and analysis of data obtained. Based on the results of a series of explorative in vitro tests, in vivo experiments were performed at maximum biting as well as during chewing on certain normally available food items. The results show fundamental differences between in vitro and in vivo testing conditions. Unexpectedly high bending of the implants was recorded in many of the in vivo loading situations.

Mechanical and biomechanical guidelines for the use of Brånemark System--general principles.

The understanding of biomechanical principles increases in importance as the number of potential indications for implant treatment increases. Recognising these principles as they relate to specific treatment indications helps to prevent conditions leading to overload. One consequence of recent findings shows that prosthetic loading conditions could significantly differ in the partially edentulous or single tooth cases as opposed to full arch bridges. It is reasonable to imagine that if you can make a full arch bridge on 4 to 6 fixtures, then two fixtures would be more than enough support for the traditional three-unit bridge. However, full arch restorations are based on multiple fixtures spread in an arch form which allows the masticatory forces to load the implants generally in an axial direction. Axial forces, whether compressive or tensile in nature, provide favourable loading throughout the entire cross-sectional area of the implants, and the forces are distributed through a maximum bone/implant interface. On the other hand, in partial restorations, the implants are placed more along a straight line. Any straight line arrangement increases the possibility for bending forces on the implants around an axis of rotation. Bending has much poorer stress distribution patterns on both the components and the supporting bone than axial load.