On Implant Prosthodontics: One Narrative, Twelve Voices - Introduction.

No abstract available.

Prosthetic treatment time and satisfaction of edentulous patients treated with conventional or implant-stabilized complete mandibular dentures: a case-control study (part 2).

PURPOSE: The aim of this study was to compare, prospectively, treatment with implant-retained mandibular overdentures versus conventional complete dentures. MATERIALS AND METHODS: Part 2 of this paper reports on the outcome after 7 years of denture use, using additional questionnaires. RESULTS: Patients with implant-stabilized overdentures continued to be more satisfied with their mandibular dentures and their diet than those using conventional complete dentures. About 50% of the implant group who completed the questionnaire had had their dentures remade. The other 50% remained satisfied with their original dentures and were still using them at the 7-year review. The average chairside time spent on them was 467 minutes. CONCLUSIONS: Mandibular overdentures with two endosseous implants permit better function than conventional complete dentures.

A 5-year prospective multicenter study on 1-stage smooth-surface Brånemark System implants with early loading in edentulous mandibles.

PURPOSE: The purpose of the current prospective multicenter study was to evaluate the 5-year implant success and peri-implant conditions of smooth-surface Brånemark System implants when using a novel technique including a 1-stage surgical procedure with early loading in edentulous mandibles. MATERIALS AND METHODS: The study protocol included 1-stage surgery as well as placement of the definitive prosthesis within 6 weeks after implant insertion (ie, early loading). Clinical evaluation, as well as evaluation of function and esthetics, was performed at each follow-up visit. Radiographs were obtained at connection of the prostheses and at the 1, 3-, and 5-year check-ups. RESULTS: A total of 40 patients with a mean age of 56 years (range, 30 to 70) were included in the study. In all, 170 implants were placed in between the mental foramina, of which 120 implants in 30 patients were associated with overdenture treatment and 50 implants in 10 patients with fixed complete dentures. Twelve implants failed in 6 patients. The cumulative implant survival rate was 92.9% after both 1 and 5 years of follow-up. Another 3 implants were recorded as mobile but still in function when individually checked at the 5-year visit, which resulted in a cumulative success rate of 91.0%. Mean bone remodeling over the study period was less than 0.1 mm/y after the first year of loading, resulting in a mean marginal bone level of 0.66 mm (SD 0.73, n = 138) apical to the implant collar reference point after 5 years. CONCLUSIONS: One-stage, early loaded smooth-surface Brånemark System implants functioned well for the majority of patients with edentulous mandibles. Stable peri-implant conditions were observed. Bone remodeling resulted in a mean bone level above the first implant thread after 5 years. The somewhat lower success rate of 91.0% compared to a 2-stage procedure may be related to generous inclusion criteria and to a learning curve involving a novel treatment procedure.

Prosthetic treatment time and satisfaction of edentulous patients treated with conventional or implant-supported complete mandibular dentures: a case-control study (part 1).

PURPOSE: The aim of this study was to compare prospective treatment with implant-retained mandibular overdentures (IROs) versus conventional complete dentures (CDs). This paper reports on the study design and 1-year outcomes. Part 2 in this series will report the 7-year outcomes. MATERIALS AND METHODS: Sixty edentulous patients with severely resorbed mandibles, already using a conventional CD, participated. Thirty patients received an IRO and 30 received a conventional CD. The patients were retrospectively matched for age, gender, and social class. The length of each treatment session was recorded. Both groups provided a subjective assessment of their current dentures, and satisfaction with their new dentures was evaluated using questionnaires focusing on denture-related complaints and a general satisfaction scale. RESULTS: Patients with IROs were more satisfied with the performance of their dentures than those using conventional CDs, especially with regard to subjective fit, looseness, and quality of chewing; however, more clinical treatment was required. The mean time taken by the prosthodontist to construct CDs was 268 minutes, compared to 327 minutes for IROs, to the time of the second review appointment after insertion. CONCLUSIONS: Mandibular IROs provided enhanced performance but required more clinical resources.

Midline mandibular deformation during nonmasticatory functional movements in edentulous subjects with dental implants.

PURPOSE: Mandibular deformation during function in patients with implant-supported prostheses is associated with increased strain at the bone-implant interface when dental implants are connected by a relatively rigid superstructure. Whilst there is a body of evidence concerning deformation as measured between the corpora, there are little data on its effects in the midline. This study measured 3 types of midline mandibular deformation during nonmasticatory functional mandibular movements in edentulous subjects with dental implants. MATERIALS AND METHODS: A range of custom displacement transducers was fabricated for 5 edentulous subjects who had been treated with dental implants in the anterior mandible. These transducers were mounted on contralateral implant abutments adjacent to the midline to measure medial convergence, corporal rotation, and anteroposterior shear. Their output was recorded for offline analysis by a personal computer. RESULTS: The values of medial convergence ranged from 15 to 42 microm during opening, from 10 to 21 microm during lateral excursions, and from 18 to 53 microm during protrusion. Corporal rotation varied from 0.05 to 0.11 degrees during opening, from 0.03 to 0.08 degrees during lateral excursions, and from 0.03 to 0.15 degrees during protrusion. Anteroposterior shear varied from 38 to 93 pm during opening, from 28 to 56 microm during lateral excursions, and from 52 to 103 pm during protrusion. DISCUSSION AND CONCLUSIONS: Nonmasticatory physiological mandibular movements cause the jaw to deform about the midline in at least 3 directions. It is important for the clinician to be aware of the phenomenon of mandibular deformation, which should be taken into consideration in the design and monitoring of mandibular prostheses.

Prosthodontics: a past with a future?

As one of the oldest dental specialties, prosthodontics has a long history of innovation and adaptability. This overview of the field presents landmarks in the development of prosthodontics from mediaeval times to the present and speculates on some future trends. It effectively sets the stage for the other articles in this issue, which explore the many facets of prosthodontic evolution.

Preload loss in gold prosthesis-retaining screws as a function of time.

PURPOSE: Screwed joints are widely used in implant dentistry, and their failure is a significant problem that may be related to loss of preload. Preload is the compressive force generated across a joint when a screw is tightened and is responsible for keeping a joint closed. For a given torque, preload is limited by the frictional resistance of the contacting screw threads, flange, and opposing joint surfaces. This study tested the hypothesis that following correct placement, prosthetic gold screws lose preload over time. MATERIALS AND METHODS: The study used standard Nobel Biocare components. Strain gauges mounted on a standard abutment formed a transducer to measure preload. Five sets of new prosthetic gold screws, gold cylinders, and standard abutment screws were assembled in turn on the top of an implant body, using the transducer abutment. The gold screws were tightened with a Nobel Biocare Torque Controller set to 10 Ncm, when it had an output of 12.06 +/- 0.8 Ncm with 95% repeatability. Preload was monitored for 15 hours; then the screws were removed and examined under a scanning electron microscope. RESULTS: Preload ranged from 157.5 to 488.9 N (mean 319.6 N), with a mean reduction over 15 hours of 24.9%, with 40.2% of this occurring within 10 seconds of tightening. DISCUSSION: Torsional relaxation of the screw shaft, embedment relaxation, and localized plastic deformation of the gold alloy and opposing titanium threads were the most likely explanation for this phenomenon. CONCLUSIONS: New prosthetic gold screws suffer significant loss of preload following placement.

Passive tactile sensibility in edentulous subjects treated with dental implants: a pilot study.

STATEMENT OF PROBLEM: Edentulous patients treated with implant-supported prostheses have shown increased passive tactile sensibility compared with those using conventional complete dentures. This is thought to be due to the close mechanical coupling between the implant and bone via the osseointegrated interface, yet the phenomenon has received little attention. PURPOSE: The purpose of this study was to measure passive tactile sensibility in a group of edentulous subjects treated with dental implants, and to relate the measured sensibility to a range of factors thought to be of possible relevance, namely, patient age, gender, time since implant placement, implant length, and implant separation. MATERIAL AND METHODS: Twenty edentulous subjects successfully treated with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. The inclusion criteria were : (1) age of less than 50 years, (2) a period of at least 12 months since implant placement, (3) implant length of at least 10 mm and of standard diameter (excluding narrow and wide platform designs), and (4) implant separation of at least 18 mm. Using a computer-controlled custom-made device, pushing forces (2.1, 2.4, 2.7, and 3.0 N/s) were applied directly and perpendicular to the long axes of the implant abutments until the subjects felt the first sensation of pressure. The magnitude of these forces was measured with an integral transducer. The applied force had a ramped staircase pattern, and force application rates were varied between 2.1 and 3.0 N/s. Multilevel modeling was used to analyze the collected data (alpha=.05). RESULTS: The threshold values of passive tactile sensibility ranged between 3.1 and 15.7 N (mean 10.9; SD 3.9). Analysis failed to show any significant association between passive tactile sensibility and the variables studied. CONCLUSION: Within the limitations of this study, which included a small sample size, no relationship was found between passive tactile sensibility associated with long-standing implants and any of the variables studied (age, gender, time since implant placement, implant length, and implant separation).

3-year prospective multicenter study on one-stage implant surgery and early loading in the edentulous mandible.

BACKGROUND: The long-term success rates achieved in dental implantology suggest that flexibility might well exist within the various implant systems to a degree that an altered protocol (ie, one-stage surgery and immediate or early loading) can be performed under controlled conditions. However, before variations of the protocol can be considered for general use, they must be subjected to critical analysis, particularly with respect to the predictability of osseointegration, alteration of soft tissue barrier, and relative change in bone height around the implants. PURPOSE: The aim of this prospective multicenter study was to evaluate implant survival and periimplant conditions around endosseous implants placed in a one-stage surgical procedure and early loading. MATERIALS AND METHODS: A total of 170 implants were placed in 40 patients with mandibular edentulism and were functionally loaded within 6 weeks with overdentures (n = 30) or fixed prostheses (n = 10). All patients and prosthetic constructions were evaluated according to a standardized protocol during 3 years of follow-up. Cumulative implant survival rates were calculated, and implant loss in relation to implant size and bone quality and quantity were evaluated. Furthermore, the protocol included assessment of clinical (plaque and bleeding scores, prosthesis stability) and radiographic parameters. RESULTS: Over a period of 3 years, the implant survival rate was 93% for both implants and prostheses (fixed or removable). No implants were lost after the first year of loading. The periimplant tissues were in a healthy condition. Mean marginal bone resorption from the time of loading to the 3-year follow-up was 0.41 mm (SD 0.52). CONCLUSIONS: From this study it may be concluded that early loading results in good implant survival and proper periimplant health in edentulous mandibles.

Changes in passive tactile sensibility associated with dental implants following their placement.

PURPOSE: This study investigated the changes that might occur in passive tactile sensibility during a period of 3 months following Implant placement in a group of edentulous subjects treated with dental implants. The effect of changing the velocity of force application on passive tactile sensibility was also investigated. MATERIALS AND METHODS: Five edentulous subjects who had been treated (as a part of an immediate loading study) with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. Pushing forces were applied directly and perpendicular to the long axes of the abutments until the subjects felt the first sensation of pressure, using a computer-controlled, custom-made device. The force was measured with an integral transducer. The applied force had a ramped staircase pattern, which was used at 2 different tip velocities. The measurements were taken on 4 occasions: 1, 2, 4, and 12 weeks after fitting the abutments. RESULTS: Statistical analysis, using multilevel modeling, demonstrated that there was a significant decrease In the tactile threshold over successive weeks following implant placement. It also demonstrated that high velocity exhibited a higher threshold than low velocity. DISCUSSION AND CONCLUSION: It could be concluded that there was a significant increase In passive tactile sensibility during the healing phase following implant placement.

Advances in prosthetic dentistry.

Until recently removable prostheses were the only form of treatment for those who had lost all or most of their natural teeth, while for the partially dentate, dentures were perceived as a poor substitute for a fixed restoration, lacking stability and prone to increasing oral disease. Subsequent studies demonstrated the functional benefits of removable partial dentures (RPDs) and how they could be used with minimal oral harm.

Force transmission in bar-retained implant-stabilised mandibular over-dentures: an in-vitro study.

The effects of attachment clips on force transmission in two implant-stabilised over-dentures with cantilever extensions were investigated, using a previously developed in-vitro model, which simulated functional mandibular deformation. Two retentive configurations were used: an avoid gold bar cranked anteriorly with 13 mm distal cantilevers and the same configuration without attachment clips on the distal cantilevers. The dentures were loaded at individual tooth positions with a strain gauge beam and the forces exerted on the implants were measured using strain gauges mounted on their trans-mucosal abutments. The difference between the two retentive configurations was significant (P < 0.05) as tested by ANOVA. It is concluded that the retentive configuration without clips on the distal cantilevers results in a significant decrease in compressive forces on the implants.