A 3-year follow-up study on single implant treatment

The single-tooth implant: a viable alternative for single-tooth replacement

BACKGROUND

The use of dental implants for single-tooth replacement cases introduces a challenge to the performance of these restorations. Clinical data suggest that single-tooth implant restorations do not benefit from lateral support from the surrounding dentition as do bridged implants, and that these restorations are subjected to greater masticatory forces. Therefore, single-tooth implants are exposed to an increased risk of failure. This prospective clinical trial was designed to evaluate the cumulative success rate of dual acid-etched single-tooth replacement implants in two clinical centers.

METHODS

The study protocol included 59 patients between 19 and 73 years. Implants were evaluated for mobility, infection, and crestal bone loss from 30.9 to 60 months.

RESULTS

Seventy-one (71) implants were placed in 59 patients, 20 male and 39 female. Forty-seven (47) were placed in the maxilla and 24 in the mandible. The percentages of anterior and posterior implants were 45.1% and 54.9%, respectively. A total of 13 (18.4%) implants were placed in soft, poor quality (Type IV) bone. Beginning 1 month post-implant placement, cases were followed for 30.9 to 60 months with a mean follow-up of 45.9 months. One implant failed (peri-implant infection) yielding an overall success rate of 98.6%.

CONCLUSIONS

This success rate for single-tooth replacement dual acid-etched implants compares favorably with bridged implants and with success rates of other single-tooth implant studies. Dual acid-etched implants performed well even under conditions of poor quality bone, where concomitant bone augmentation was performed, and when used for immediate replacement of extracted teeth.

A maxillary screw-retained, implant-supported diagnostic wax pattern

This article describes the fabrication of a screw-retained, implant-supported wax pattern that enables the restorative dentist to predict the outcome of the final prosthesis. The wax pattern also affords the patient an opportunity to evaluate and approve the design of the planned prosthesis, thereby enhancing communication between the dentist and patient.

The use of healing abutments for the fabrication of cement-retained, implant-supported provisional prostheses

This article describes the intraoral preparation of healing abutments for use as prefabricated abutments for a cement-retained, implant-supported prosthesis. After the healing abutments are prepared, an impression is made with irreversible hydrocolloid, and the provisional restoration is fabricated indirectly. This technique is an easy and economical alternative for the fabrication of provisional fixed partial dentures or crowns but may be contraindicated for severely misaligned implants.

In vitro effect of transforming growth factor-beta on adhesion molecule expression by human gingival fibroblasts cultured in the presence of a titanium abutment

BACKGROUND

There is little information in the literature on the structural basis mediating gingival cell adhesion to the surface of titanium abutments. We cultured gingival fibroblasts on a titanium abutment creating as closely as possible the in vivo state. We analyzed the constitutive and transforming growth factor (TGF) beta-induced expression of the adhesion molecules CD44, CD49b, CD49c, CD51, CD54, and CD61 and extracellular matrix (ECM) components fibronectin, laminin and collagen IV.

METHODS

Three totally edentulous patients underwent implant treatment to anchor the mandibular denture on 2 implants. Gingival mucosa cell specimens were collected from the mandible during the first surgical stage and the gingival fibroblast cultures were prepared. Cells were cultured for 48 hours with or without isoforms TGF-beta1, TGF-beta2, and TGF-beta3. The expression of adhesion molecules and ECM components was analyzed by immunofluorescence staining and flow cytometry.

RESULTS

The addition of TGF-beta isoforms to the cell culture over the incubation period had little effect on cell growth rate, but significantly influenced cell orientation, which changed from a sun-burst pattern in control conditions to a more elongated organization and perpendicular to abutment surface. In all fibroblast preparations, a marked expression of CD44 and a moderate positivity for anti-CD49b and CD49c were found. By contrast, CD51, CD54, and CD61 expressions were negligible. When fibroblasts were cultured for 48 hours in the presence of TGF-beta, the expression of most of the receptor molecules increased. The cells expressed constitutively moderate levels of laminin and fibronectin and low amounts of collagen IV. By contrast, treatment with any one of the 3 TGF-beta isoforms greatly enhanced the expression levels of fibronectin, laminin, and, especially, collagen IV.

CONCLUSIONS

TGF-beta not only seems to affect the orientation of the cultured gingival fibroblasts, but also to induce a clear-cut modification of their adhesion molecule expression.

Fabricating a provisional restoration for a 2-stage, single-tooth implant with less than optimal angulation

A technique is presented for fabricating a provisional restoration for a buccally angulated implant. This technique describes the fabrication of a provisional restoration for a labially angulated implant. This technique helps the prosthodontists to achieve esthetics and soft-tissue health until the definitive restoration is available.

A meta-analytic, quantitative assessment of osseointegration establishment and evolution of submerged and non-submerged endosseous titanium oral implants

Two implant placement methods are used in oral implantology: submerged (S, two-stage surgical procedure) and non-submerged (NS, one-stage surgery). However, a quantitative assessment of their influence on implant osseointegration, summarising the whole present experience, is not directly possible, owing to the lack of normalisation of the published results. To overcome this difficulty, selection criteria have been applied to the latter in a process of a meta-analysis of specialised literature, in order to authorise a pooled treatment with an adequate statistical method. Survival life tables are established (up to 15 and 10 years respectively for S and NS implants placed in normal situations) for extended samples (13049 S and 5515 NS implants). Early (before loading) failure rates and 95% confidence level ranges of cumulative implant survival rates are shown. For both categories, the quality of the placement stage remains critical to ensure optimal osseointegration behaviour. Both categories match current survival requirements, but with a quite different behaviour over time. NS implants, while osseointegrating better initially, are subject to causes of osseointegration loss, which persist over a longer period of time. Implant design characteristics (including the type of surface) seem to be more relevant than the placement procedure for the implant's behaviour. This is in agreement with recent histological and preliminary clinical results, and should be confirmed by further studies.

Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region

BACKGROUND

The regeneration of gingival papillae after single-implant treatment is an area of current investigation. This study was designed to determine: 1) whether the distance from the base of the contact point to the crest of the bone would correlate with the presence or absence of interproximal papillae adjacent to single-tooth implants, and 2) whether the surgical technique at uncovering influences the outcome.

METHODS

A clinical and radiographic retrospective evaluation of the papilla level around single dental implants and their adjacent teeth was performed in the anterior maxilla in 26 patients restored with 27 implants. Six months after insertion, 17 implants were uncovered with a standard technique, while 10 implants were uncovered with a technique designed to generate papilla-like formation around dental implants. Fifty-two papillae were available for clinical and radiographic evaluation. The presence or absence of papillae was determined, and the effects of the following variables were analyzed: the influence of the 2 surgical techniques; the vertical relation between the papilla height and the crest of bone between the implant and adjacent teeth; the vertical relation between the papilla level and the contact point between the crowns of the teeth and the implant; and the distance from the contact point to the crest of bone.

RESULTS

When the measurement from the contact point to the crest of bone was 5 mm or less, the papilla was present almost 100% of the time. When the distance was > or = 6 mm, the papilla was present 50% of the time or less. The mean distance between the crest of bone and the most coronal papilla level (interproximal soft tissue height) was 3.85 mm (SD = 1.04). When comparing the conventional and modified surgical technique, the relation shifted from 3.77 mm (SD = 1.01) to 4.01 mm (SD = 1.10), respectively.

CONCLUSIONS

These results clearly show the influence of the bone crest on the presence or absence of papillae between implants and adjacent teeth. The data also show a positive influence for the modified surgical technique, aimed at reconstructing papillae at the implant uncovering.

Clinical evaluation and prosthetic complications of single tooth replacements by non-submerged implants

The aim of the present study was to evaluate single tooth replacements by non-submerged implants. In the time period from 1990 to 1998, 72 patients were consecutively admitted for treatment with a total of 109 solid screw ITI-implants supporting single crowns. All crowns were ceramic to metal fused with a ceramic occlusal surface and mounted to the octa-abutment. The mean observation time was 4.3 years, ranging from >1 to 9 years. The implants were monitored regularly by periimplant parameters. Periapical radiographs using the parallel technique were taken after the healing period and in 1999 for comparative measurements. No implant was lost during the healing phase, while 3 failures occurred after a loaded period of 2.5 and >5 years, respectively. The 5-year cumulative survival rate was 99.1%. In the course of the study, only 2 implants exhibited marginal inflammation that required treatment. The radiographically measured distance (DIB) from the implant shoulder to the first implant-bone contact was significantly increased in 1999 and different between the two readings. However, this difference in DIB was not significant between implants with a short (1 year) and long (>5 years) observation period. It was concluded that changes in the crestal bone level occur mostly in the first postsurgical year. Prosthetic complications were rare, mostly encountered in the first year after loading and often limited to re-tightening of the occlusal screw.

Dynamic fatigue properties of the dental implant-abutment interface: joint opening in wide-diameter versus standard-diameter hex-type implants

STATEMENT OF PROBLEM

The clinical long-term success of single-tooth implant restorations depends, in part, on a stable connection between the prosthetic restoration and the implant body.

PURPOSE

The purpose of this experiment was to investigate the fatigue life of UCLA-style abutment screws in wide-diameter versus conventionally sized dental implant restorations.

MATERIAL AND METHODS

Five 3.75 x 15-mm and five 6.0 x 15-mm hexed dental implants were used. Ten frameworks were fabricated, 5 with a single UCLA-style, 3.75-mm hexed gold alloy cylinder, and 5 with a single UCLA-style, 6.0-mm hexed gold alloy cylinder. To simulate a common laboratory procedure, 2 abutment interfaces were relieved with a one-quarter round bur for both diameters. The 3.75-mm implant used a Gold-Tite central abutment screw torqued to 32 Ncm, and the 6.0-mm implant used a titanium central abutment screw torqued to 25 Ncm. Frameworks were dynamically loaded ( approximately 10 Hz) with a 120 +/- 10-N, 4-mm off-axis force. Liquid metal strain gauges were used to measure joint opening. Measurements were made at intervals of 10(3), 10(4), 10(5), and 5x10(5) cycles. Gauge output data were converted to displacement with a conversion factor determined by calibration. Linear regression analysis then was performed.

RESULTS

Two observations were made in this study. Two of three 3.75-mm nonadjusted specimens and all three 6.0-mm nonadjusted specimens maintained joint closure (range of opening 0-20 microm) while measured under dynamic loading. The median joint opening at 5x10(5) cycles for 3.75-mm nonadjusted specimens was 14 +/- 7 microm; for 6.0-mm specimens, it was 11 +/- 10 microm. Both 3.75-mm adjusted specimens and 1 nonadjusted specimen failed to maintain joint closure (excess joint opening >50 microm). One of the 3.75-mm adjusted specimens had abutment screw fracture. One of two 6.0-mm adjusted specimens failed to maintain joint closure because of screw fracture.

CONCLUSION

The dental implant-abutment interface of 3.75-mm and 6.0-mm externally hexed implants experienced similar joint opening after periods of dynamic loading. Laboratory adjustment of the interface significantly decreased the service life of the abutment screw joint.

Immediate loading of single root form implants with the use of a custom acrylic stent

This article describes a technique for fabricating a provisional screw-retained restoration for immediate loading of single implants. Until immediate loading of single implants becomes a well-documented treatment modality, this technique should be used cautiously.

Examination of the implant-abutment interface after fatigue testing

PURPOSE

This study examined potential differences in detorque values of abutment screws after fatigue testing when the dimensions between external implant hexagon and internal abutment hexagon were altered or the implant external hexagonal shape was eliminated.

MATERIAL AND METHODS

Three subsets (N = 10) of NobelBiocare implants were assessed: (1) standard external hexagon (R), (2) modified hexagon (M), and (3) circular (C) platform geometry. Thirty Procera machined abutments with 25-degree angulated loading platforms were manufactured. Abutments were retained with gold Unigrip abutment screws tightened to 32 N/cm with an electronic torque controller. Vertical scribes across the implant-abutment interface allowed longitudinal displacement evaluation. A carousel-type fatigue testing device delivered dynamic loading forces between 20 and 200 N for 5,000,000 cycles, or the approximate equivalent of 5 years in vivo mastication, through a piston to the abutment platform. Macroscopic and radiographic examination of the implant/abutment specimens was performed. The abutment screws were removed and the detorque values recorded. Bearing surfaces were examined microscopically.

RESULTS

No abutment looseness or longitudinal displacements at the implant-abutment interface were noted. Radiographic examination demonstrated no indication of screw bending or displacement. The mean detorque values for R, M, and C were 14.40 +/- 1.84 N/cm, 14.70 +/- 1.89 N/cm, and 16.40 +/- 2.17 N/cm, respectively. The analysis of variance demonstrated significant differences between only designs R and C (P=.031).

CONCLUSION

Increasing the vertical height, or degree of fit tolerance, between the implant external hexagon and the abutment internal hexagon or completely eliminating the implant external hexagon did not produce a significant effect on the detorque values of the abutment screws after 5,000,000 cycles in fatigue testing, or the equivalent of 5 years' of mastication for the implant/abutment specimens evaluated.

Micromotion and dynamic fatigue properties of the dental implant-abutment interface

STATEMENT OF PROBLEM

Clinical loading may result in micromotion and metal fatigue in apparently stable implant screw joints. This micromotion may contribute to tissue inflammation and prosthesis failure.

PURPOSE

This study investigated dental implant screw joint micromotion and dynamic fatigue as a function of varied preload torque applied to abutment screws when tested under simulated clinical loading.

MATERIAL AND METHODS

Fifteen noble alloy single-tooth implant restorations, each containing a hexed UCLA-style gold cylinder, were randomly assigned to 3 preload groups (16, 32, and 48 N.cm). Each group consisted of 5 implants (each 3.75 x 15 mm) and 5 square gold alloy abutment screws. A mechanical testing machine applied a compressive cyclic sine wave load between 20 and 130 N at 6 Hz to a contact point on each implant crown. A liquid metal strain gauge recorded the micromotion of the screw joint interface after 100, 500, 1,000, 5,000, 10,000, 50,000, and 100,000 cycles. Baseline data at 0 N.cm were collected before the application of the specified preload torque.

RESULTS

The 16 N.cm group exhibited greater micromotion (P<.001) than both the 32 and 48 N.cm groups at all cycle intervals (2-way ANOVA, Tukey HSD). Micromotion of the implant-abutment interface remained constant (P=.99) for each of the preload groups through 105 cycles.

CONCLUSION

Under the loading parameters of this study, no measurable fatigue of the implant-abutment interface occurred. However, dental implant screw joints tightened to lower preload values exhibited significantly greater micromotion at the implant-abutment interface.

Variables affecting survival of single-tooth hydroxyapatite-coated implants in anterior maxillae at 3 years

BACKGROUND

The development and expanded use of endosseous dental implants over the last two decades have been remarkably rapid. It is, therefore, imperative that the dental profession closely monitor the performance of root-form implants used in a variety of applications. The Dental Implant Clinical Research Group (DICRG) was established in 1990 by the Department of Veterans Affairs as a forum for conducting prospective, multidisciplinary, multicentered studies in the field of implant dentistry. The DICRG comprised 30 VA medical centers and 2 dental schools at the time of this study. This paper reports on the survival of hydroxyapatite (HA)-coated grooved implants used to replace single missing teeth in anterior maxillae at 3 years post-implant placement.

METHODS

During a 4-year accrual period, a total of 247 single-tooth implant restorations were placed in anterior maxillae. This paper focuses on the survival of 222 implants (149 patients) for which 3-year data were recorded for the period from placement. Survival was examined with respect to patient demographics and health status, implant location, surgical variables, and 2-week post-placement use of chlorhexidine digluconate (0.12%) rinses. Implant stability was recorded using a hand-held probe. Periodontal-type measures were recorded and evaluated, and all complications related to osseointegration were noted. Failure was defined as removal of the implant for any reason.

RESULTS

Establishment and maintenance of osseointegration at 3 years post-placement was 97.3%. During this 3 year period, 6 implants were removed due to either failure to osseointegrate or loss of osseointegration. Implant length correlated positively with 3-year survival (P = 0.003, exact test). The use of preoperative antibiotics was nearly significant to implant survival (P = 0.051. Pearson chi-square). Mean stability values (PTVs) increased incrementally from -4.5 at uncovering to +1.1 at 36 months, indicating a decrease in stability of the bone-implant-prosthesis complex. The most common complication was related to inadequate available bone to fully house implants.

CONCLUSIONS

Three-year post-placement survival data suggest that the use of HA-coated, grooved, endosseous implants to support maxillary anterior single-tooth replacements is a predictable and reliable procedure that can offer significant benefits. Longer implants demonstrated higher survival than shorter implants. The use of preoperative antibiotics was nearly significant to implant survival, and there was an increase in mean PTVs observed over the duration of the study. Further research is needed to assess stability of the hydroxyapatite-bone interface over time.

Effect of repeated closures on opening torque values in seven abutment-implant systems

STATEMENT OF PROBLEM

Implant abutment screw joints tend to loosen under clinical conditions. During impression and prosthesis fabrication, repeated clinical closing and opening of abutment screws may cause component wear and decrease frictional fit of the mating parts, resulting in altered resistance to opening and potential for loss of preload in function.

PURPOSE

This study recorded changes in opening torque values due to multiple consecutive closures at a constant torque within and between different abutment/implant (A/I) systems.

MATERIAL AND METHODS

Repeated opening-closing cycles were used to simulate in vitro embedment relaxation and component wear of 7 A/I systems from 5 manufacturers. Screw opening torque values were recorded up to 200 consecutive closures at 20 N/cm.

RESULTS

A progressive decrease in opening torque values was measured in all implant systems. Significant differences were found between A/I systems. Systems with morse tapered and spline connections consistently maintained a higher resistance to opening force. Percentage torque loss ranged from 3% to 20% on immediate opening, and from 4.5% to 36% for average of first 30 opening/closing cycles.

CONCLUSION

Repeated opening and closing of implant abutment screws caused progressive loss of torque retention with variations between systems. This was probably due to a decrease in the coefficient of friction between the mating components.

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.

A systematic review of single-tooth restorations supported by implants

OBJECTIVES

To make an inventory of clinical studies on single-tooth restorations supported by implants using a systematic review procedure and to aggregate overall survival results.

DATA SOURCES

Papers referring to single-tooth implants were located by a MEDLINE search 1990 to April 1998. Three hundred and twenty references were found, and they were subjected to a systematic review procedure.

STUDY SELECTION

A three-step inclusion/exclusion procedure was applied to identify papers that represented: good scientific practice (GSP), reported results of all patients, implants and crowns for more than 2years, and had sufficient data to generate life-table analyses. The outcomes were 'implant failure' and 'crown completion'. Nine studies survived. These data showed an overall mean GSP of 0.37 with a predicted 4year implant survival of 97% (n=459), and an uncomplicated crown maintenance of 83% (n=240).

CONCLUSION

Single-tooth implants show an acceptable short-term survival of 4years, but crown complications are common.

Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns

STATEMENT OF PROBLEM

The assumption that increasing the diameter of the abutment/crown components will provide greater resistance to crown loosening forces than standard-sized components has not been reported either with clinical trials or in the laboratory.

PURPOSE

This study attempted to determine what effect abutment dimension and type of luting agent have on the retention of the prosthetic crown.

METHODS AND MATERIAL

Test specimens consisted of standard, wide, and "experimental" CeraOne titanium abutments and matching CeraOne gold cylinders cemented with a zinc phosphate permanent or a zinc oxide eugenol provisional cement. The mean uniaxial force (Newtons) and the load (MPa) required to dislodge the cylinder from the abutment was determined. Statistical analysis of the sample data was performed using a 2-way analysis of variance test (alpha=.05).

RESULTS

Mean uniaxial resistance force (Newtons) was significantly greater for zinc phosphate cement than for zinc oxide cement (P <. 001). Abutment size was a significant factor when permanent luting cement is used (P <.001). Retention strength per unit area (MPa) of the wide abutments was lower than the standard size and "experimental" abutments.

CONCLUSION

Permanent luting cement produced uniaxial retention forces approximately 3 times greater than provisional cement. The increase in surface area provided by a wide abutment did not result in an improvement in retention strength over the standard abutment.

On Cutting Torque Measurements during Implant Placement: A 3-Year Clinical Prospective Study

BACKGROUND

Evaluation of jaw bone quality at implant placement is mainly based on preoperative radiographic assessments and subjective hand registrations during implant site preparation. An objective technique with cutting torque measurements has been introduced, presenting an objective bone quality or bone hardness value of individual implant sites.

PURPOSE

The purpose of this study was to evaluate cutting torque measurements during implant placement and to compare these values in different regions in mandibles and maxillae. The objective was to identify implants at risk for failing at implant placement.

MATERIAL AND METHODS

Cutting torque measurements were performed during placement of Mk II self-tapping implants (Brånemark System) in 105 patients, comprising 72 edentulous (40 maxillae) and 34 partially edentulous (22 maxillae) jaws. A total of 523 implants were inserted, of which 420 were of the Mk II design and of which 412 were subjected to cutting torque measurements. Statistical analyses were performed by comparing cutting torque values of maxillae and mandibles and of different jaw regions. Cutting torque values were also correlated with radiographically and clinically assessed bone quality scores. Patients were followed clinically for a minimum of 3 years.

RESULTS

A statistically significant difference in cutting torque values of maxillae and mandibles was seen, although not when comparing anterior and posterior regions within the same jaws or of different jaws. Significant correlations were found between values of cutting torque and bone quality. The majority of failures were seen in bone of medium to high density, whereas implants inserted in bone of poor density presented a better outcome, perhaps due to an adapted surgical protocol and an extended healing period. The overall implant survival rate at 3 years was 95%, and when analyzing different jaw categories, survival rates of 92.0% and 99.4% were seen for edentulous maxillae and mandibles, respectively. The corresponding figures for partially edentulous jaws were 95.4% and 97.6%.

CONCLUSION

It was not possible to identify sites at risk for future implant losses or to determine a lower limit value of cutting torque in order to achieve successful implant integration.

A 3 to 4 year study of single tooth hydroxylapatite coated endosseous dental implants

OBJECTIVE

To evaluate the clinical effectiveness, common complications and maintenance associated with hydroxylapatite (HA) coated cylindrical implants when used to support single crowns.

DESIGN

A prospective medium term clinical study of the Calcitek HA-coated implant.

SETTING

Implant placement, crown fabrication and follow-up procedures were carried out at the Leeds Dental Institute, between 1990 and 1998.

SUBJECTS AND METHOD

26 patients (33 implants) participated in the trial. They were referred from general dental practitioners because of their suitability for single tooth implant placement.

MAIN OUTCOME MEASURES

The implants were assessed using recognised clinical review procedures e.g. radiographs and soft tissue assessments.

RESULTS

At exposure there was 100% implant integration. The cumulative survival rate over 4 years was 100%. In five implants there was cervical bone loss of more than 4 mm and these were classified as failing. This gave an overall cumulative success rate of 58% by year 4.

CONCLUSION

The Calcitek HA-coated single tooth implant shows exceptionally high initial integration however, the longer term results suggest that the cervical bone level adjacent to the implant failed to establish a steady state. Doubts remain regarding the long-term prognosis of these cylindrical HA-coated implants.

Manual closing torque in five implant abutment systems: an in vitro comparative study

STATEMENT OF PURPOSE

A significant percentage of abutment/implant (A/I) assemblies tend to unscrew on functional loading.

PURPOSE

This in vitro study evaluated the maximum closing torque generated manually for comparison with recommended closing torque values in 5 implant systems.

METHODS

Closing torque generated by 9 operators with 5 manual torque drivers was measured and compared by using a mannequin and torque gauge assembly.

RESULTS

Closing torque values were found to be significantly different between operators and between implant systems (P <.0001). Mean closing torque values of 9 operators performing 5 closures for 5 systems ranged from 7 to 14.6 N/cm for habitual closures and from 9.4 to 19.9 N/cm for maximum closures.

CONCLUSIONS

The results demonstrated that maximum manual closure did not approach recommended closing torque in any of the system measured. Significant interoperator and intraoperator variability was found in the closing torque with manual drivers, and the driver diameter and grip were probably an important feature in the generation of high closing torque.

Clinical complications of osseointegrated implants

STATEMENT OF PROBLEM

There is no comprehensive review of the literature that identifies the complications reported in clinical dental implant studies.

PURPOSE

This article attempted to determine the types of complications that have been reported and to provide data regarding their frequency.

METHODS

All available clinical studies from 1981 to 1997, published in English or with English abstract, that presented success/failure data regarding implant treatment were evaluated to determine the types of reported complications and to quantify implant loss as it relates to type of prosthesis, arch, time, implant length, and bone quality.

RESULTS

Greater implant loss occurred with overdentures than with other types of prostheses. There was greater loss in the maxilla than mandible with fixed complete dentures and overdentures, whereas little arch difference was noted with fixed partial dentures. Implant loss increased with short implants and poor bone quality. The time of implant loss (preprosthetic vs postprosthetic) varied with type of prosthesis. Surgical complications included neurosensory disturbance, hematoma, mandibular fracture, hemorrhage, and tooth devitalization. Initial and long-term marginal bone changes were identified. Peri-implant soft tissue complications included dehiscence, fistulas, and gingival inflammation/proliferation. Mechanical complications were screw loosening/fracture, implant fractures, framework, resin base and veneering material fractures, opposing prosthesis fractures, and overdenture mechanical retention problems. Some studies also presented phonetic and esthetic complications.

CONCLUSIONS

Although the literature presents considerable information on implant complications, variations in study design and reporting procedures limited the available data and therefore precluded proper analysis of certain complications.

The effect of prosthodontic treatment on alveolar bone loss: a review of the literature

STATEMENT OF PROBLEM

Complete, fixed partial, removable partial, and implant-supported dentures have been used to comfortably and esthetically replace missing teeth. However, it is not certain what effect these prostheses have on the residual ridge.

PURPOSE

This article compares various prosthetic treatments to restore completely and partially edentulous mouths for their ability to preserve residual alveolar bone.

MATERIAL AND METHODS

A review of the literature was performed to discuss the effects of tooth replacement on residual alveolar bone.

RESULTS

The literature seems to indicate that the presence of a dental prosthesis affects the size and form of the residual alveolar ridge and bone.

CONCLUSION

An implant-supported fixed prosthesis to restore missing teeth in partially or completely edentulous jaws seems to be the best means of preserving residual alveolar bone.

The fit of cast and premachined implant abutments

STATEMENT OF PROBLEM

There is insufficient information regarding the adaptation of abutments to implants.

PURPOSE

This study assessed the adaptation of premachined, cast, and laboratory modified premachined abutments to implants at two sites: abutment/implant interface and screw to screw seat.

MATERIAL AND METHODS

Six combinations of abutments and implants were studied: CeraOne abutments joined to Nobel Biocare implants; STR (Implant Innovations Inc.) abutments joined to 31 implants; Cast UCLA (31) abutments subjected to porcelain firing cycles and joined to 31 implants; Cast UCLA abutments subjected to porcelain firing cycles and joined to Nobel Biocare implants; UCLA premachined abutments cast with gold palladium alloy and subjected to porcelain firing cycles (later joined to 31 implants); and UCLA premachined abutments joined to 31 implants. Each group contained five assemblies.

RESULTS

The adaptation of abutments to implants was closer and the amounts of contact larger for assemblies with premachined and laboratory modified premachined abutments than for those with cast abutments.

CONCLUSION

The finishing of custom-made abutments requires further refinement.

Use of titanium dental implants as an integrated part of a CLP protocol

The problem of edentulousness in the cleft area of patients with cleft lip and palate was formerly resolved with a conventional fixed bridge construction, but this approach did not always prove optimal. Nowadays, in these patients the bridge can be substituted by a crown on an osseointegrated titanium implant fixture. The concept of dental rehabilitation using titanium implants has gradually merged into our routine treatment for patients with cleft lip and palate. In this report we describe our surgical technique using osseointegrated titanium implants and evaluate our result in patients with cleft lip and palate. Sixteen patients with cleft lip and palate, 11 men and five women, were divided into two groups: group 1 consisted of six patients who did not need bone grafting prior to the fixture installation, and group 2 comprised 10 patients who had additional bone grafting three months before the fixture installation. Abutments were applied six months after fixture installation. Dental crowns and fixed bridges were then constructed. All patients were seen on regular follow-up visits. Routine roentgenograms were obtained preoperatively and when the abutments were applied. Photographs were taken at these occasions and also after the prosthodontic work was completed. Of a total of 31 fixtures, all except two were osseointegrated at the time of the abutment connection, and the remaining 29 have all been functional during the observation period, giving a success rate of 93%. In group 1 all fixtures (100%) were osseointegrated. The non-integrated fixtures were found in group 2 giving a success rate of 91% in this group. The mean follow-up time after fixture installation was six years and three months, and the mean observation time with loaded fixtures was five years and six months.

A retrospective multicenter evaluation of single tooth implant experience at three centers in the United Kingdom

STATEMENT OF PROBLEM

Implant treatment in the United Kingdom has been provided mainly in specialist, regional dental hospitals. However, increasingly, general dentists are providing implant-supported prostheses in a private office setting.

PURPOSE

This study investigated the nature, timing, and frequency of complications associated with single tooth implant therapy in a dental hospital and two dental offices.

METHODS

The dental records of 58 patients provided with 76 implants during the period of 1989-95 were reviewed retrospectively. Fifty-three single tooth crowns on implants were placed by general dentists and 23 by specialists in the dental hospital.

RESULTS

Implant survival rate was 96%. Twenty-eight guided bone regeneration procedures were required, including 13 unplanned ones. Prosthodontic complications included the need for recontouring of three crowns and the recementation of three crowns. Only two abutment screws required retightening. Peri-implant soft tissue inflammation occurred around six crowns and recession around two.

CONCLUSION

The single tooth implant-supported crown appears to be an effective and durable restorative treatment with a relatively low prevalence of postoperative complications.

Implant reconstruction in the posterior mandible: a long-term retrospective study

STATEMENT OF PROBLEM

Because there is a lack of long-term data, it is unclear whether the determinants of implant and prosthesis survival include the location, angle, design, or number of implants and use of prosthesis cantilevers.

PURPOSE

This retrospective study evaluated the long-term outcome, determinants of outcome, and the type and prevalence of prosthetic complications in a series of patients treated consecutively with Brånemark implants in the partially edentulous posterior mandible.

MATERIAL AND METHODS

A total of 392 consecutively placed Brånemark implants were inserted in 152 partially edentulous patients and restored with 56 single-tooth and 168 fixed partial dentures restorations.

RESULTS

The cumulative success rates of implants and prostheses were 89.0% +/- 0.03% and 81.9% +/- 0.03%, respectively, at 6 years, with no further decrease in success noted during the remainder of the 10-year study. Significantly fewer major complications were found in prostheses supported by one or more implants, located exclusively in premolar sites, versus prostheses supported by either molar implant(s) or both premolar and molar implants. In single-tooth restorations, fewer major complications were seen in the cemented restorations, compared with the screw retained.

CONCLUSION

The results were strongly influenced by the phase of experience.

Cement-retained versus screw-retained implant restorations: achieving optimal occlusion and esthetics in implant dentistry

STATEMENT OF PROBLEM

Optimal occlusion and esthetics are goals in prosthetic treatment. Implant dentistry is no exception.

PURPOSE OF ARTICLE

The purpose of this article is to discuss how the choice to use screw-retained or cement-retained implants dramatically influences the occlusion and esthetics.

Hypodontia of the permanent dentition. Case reports

Hypodontia has been observed as one of the most common human dental developmental anomalies. It may be defined as agenesis of one or more teeth. The prevalence in the permanent lower central and lateral incisor region is low, ranging from 0.23 percent to 0.08 percent, respectively. This is compared with an overall incidence of hypodontia of 3.49 percent. However, significant racial variation occurs. Treatment options generally available are: no treatment, closure of spaces orthodontically, or prosthetic replacement. Aetiology, associated anomalies, and factors involved in treatment choice are discussed. A report of four cases of hypodontia of the permanent lower anterior teeth and their orthodontic management is presented.

Effects of infection control procedures on the accuracy of a new mechanical torque wrench system for implant restorations

Loosening of screw components for implant restorations has been attributed to insufficient tightening. The degree of tightening may be increased and more closely controlled by use of calibrated mechanical torque wrenches. The DynaTorq wrench system has been introduced to the market and consists of three individual wrenches with torque values of 10, 20, and 30 newton-centimeters (Ncm). This study evaluated the accuracy of the DynaTorq wrench system before and after steam autoclave and Chemiclave sterilization treatment. Before sterilization treatments, the wrenches demonstrated high accuracy and precision. Autoclaving resulted in increases in torque values for the 10 Ncm torque wrench compared with baseline measurements. Except for the effect of autoclaving on the 10 Ncm torque wrench, sterilization procedures did not adversely affect the accuracy of the DynaTorq torque wrench system.

Comparison of screw loosening, rotation, and deflection among three implant designs

A common problem associated with single tooth implant restorations is abutment screw loosening. Manufacturers of implants have attempted to overcome this problem by incorporating antirotational design characteristics into their systems. Micromovement and torque levels required to loosen abutment screws for straight and angled antirotational screw-retained abutment/implant combinations from three different manufacturers were examined in this in vitro investigation. A custom-built machine was used and each sample was subjected to compressive horizontal reciprocal movements over a 25-degree incline for a simulated 1-month period. Data were generated that showed movements of the crown/abutment complex during force application. The amount of torque necessary to loosen the abutment screws before and after testing was also recorded and compared for each system. The results indicated no significant differences (p < 0.05) among all the straight and angled abutments for the variables studied.

Surgical and prosthodontic training of general practitioners for single tooth implants: a study of treatments performed at four general practitioners' offices and at a specialist clinic after 2 years

Both the surgical and the prosthodontic procedures will be performed by one and the same general practitioner (GP) for many implant patients, as access to specialists is limited or non-existent in a large number of places. However, treatment by GPs has not been documented to the same extent as treatment performed by specialists. This lack of knowledge was the reason for the present study, in which four GPs performed both the surgery and the prosthodontics on patients requiring single tooth implant replacements. The treatments were performed after an initial training of the GP and his/her dental assistant for 8 days. The treatments by the GPs exhibited clinical results corresponding to those achieved at a specialist clinic. The outcome indicates that complete single tooth implant treatments might be performed by GPs who have passed an initial training and demonstrated an interest in a close co-operation with specialists in oral surgery/periodontics and prosthodontics. Such a co-operation should be based on the distribution of complicated cases to the specialists and of non-complicated cases to the GPs.