The "Chesterfield stent": an aid to the placement of midpalatal implants.

A palatal endosseous implant is a valuable adjunct to orthodontic treatment. Its insertion is considerably simplified by the use of a stent that was designed in our department and that we describe here.

Orthodontic palatal implants: clinical technique.

The aim of this paper is to familiarize the readers with some of the clinical considerations necessary to ensure successful use of mid-palatal implants. Both surgical and technical aspects will be discussed along with a description of impression techniques used.

Fluoridated elastomers: in vivo versus in vitro fluoride release.

OBJECTIVES: To compare (i) the in vivo release of fluoride from fluoridated elastomers to the in vitro release, and (ii) the residual fluoride content of the elastomers after 1 week in the mouth with and without fluoride toothpaste and mouthrinse. DESIGN: A prospective, longitudinal, cross-over study. SUBJECTS AND METHOD: Six subjects were recruited by poster to take part in the study. Each subject had one premolar in each quadrant to which a bracket could be fixed and exemplary oral hygiene. Elastomers were then placed on these brackets. INTERVENTION: The study was divided into two parts: (i) subjects used oral hygiene products with fluoride and (ii) oral hygiene products with fluoride were excluded. Both groups of elastomers were left in the mouth for 1 week. After collection the elastomers were stored in distilled water. MAIN OUTCOME MEASURES: The amount of residual fluoride in the ligatures after they have been placed in the mouth for 1 week was compared with the cumulative fluoride release in vitro over 1 week and 6 months. RESULTS: Only 13 per cent of the total amount of fluoride in fluoridated elastomers was released during the first week in vitro, compared with 90 per cent in vivo. There was a significantly greater amount (P = 0.001) of residual fluoride when the elastomers were in the mouth for 1 week in the presence of fluoride toothpaste and mouthrinse, than when fluoride supplements were excluded. CONCLUSIONS: (1) Higher levels of fluoride are lost from the fluoride elastomers in vivo than in vitro during the first week. (2) A significantly greater amount of residual fluoride was released from the elastomers placed in the mouth when fluoride toothpaste and mouthrinse were used.

Implant complications and failures: the fixed prosthesis.

The implant-retained fixed prosthesis has been advocated as an effective restoration offering significant benefits over conventional prosthetics. The success of treatment depends on careful pre-surgical planning and prosthesis design. This paper outlines some common complications encountered during the planning, fabrication and maintenance of both large and small fixed prostheses and suggests how these complications can be minimized.

Case report: the transmandibular implant system.

This series of case reports outlines the use of the transmandibular implant system to rehabilitate 10 patients with severely resorbed mandibles. The implants were placed according to manufacturers' guidelines with the patient under a general anaesthetic and reviewed bi-annually thereafter. Three patients experienced problems: in two of these this involved the loss of integration of the distal posts, in the other patient the transmandibular implant was removed in its entirety. Distal locking screws became loose shortly after placement in three patients. Prosthetic complications included difficulty in obtaining passive fit of the superstructure in 7 patients and a high long-term maintenance commitment.

Implant complications and failures: the complete overdenture.

The implant-retained overdenture has been advocated as an effective method of restoring the edentulous patient with an appliance that offers significant benefits over conventional prosthetics. However, the success and survival of such appliances have been shown to vary considerably, depending on which jaw is treated: implants supporting overdentures in the maxilla have a significantly higher failure rate. The restoration also requires considerable maintenance, which is both time consuming and costly. The purpose of this paper is to look at common restorative complications and maintenance problems following the placement of dental implants to support an overdenture. A number of implant systems have been reviewed and the results of the authors' clinical experiences with referred and their own cases are reported.

A comparison of hydroxylapatite coated implant retained fixed and removable mandibular prostheses over 4 to 6 years.

In a 6-year prospective clinical study, 181 hydroxylapatite coated endosseous dental implants were placed into the anterior mandible of 48 patients. Twenty-one patients were treated with fixed prostheses and 27 patients with an overdenture. When the implants were exposed all 181 had integrated. To date, there is 100% survival of all implants and they all retain a functioning prostheses. The initial results were very promising, in both groups the interval success was over 95% in the first 4 years of the study. However, by year 6, the interval success rates had fallen to 83% for both the fixed and removable groups. This study also compares the construction and maintenance complications for the two types of restorations. The clinical time taken, after implant exposure, to construct the prostheses was similar whether the fixed (mean of 8 visits) or removable option (mean of 7 visits) was chosen. However, the removable restoration cost less than half the price of the fixed when both technical time and implant component costs were evaluated. Maintenance for both groups was higher than expected, but patients required more appointments in the removable group both in the first year and beyond. Regarding the prostheses itself, the incidence of remakes, relines and general adjustments was higher in the removable group. This study has shown that the overdenture offers an effective and initially a more economical alternative to the fixed prostheses, in the treatment of the edentulous mandible. However, long-term maintenance of such a prosthesis can be significant.

Implant complications and failures: the single-tooth restoration.

The single-tooth implant restoration appears to be an ideal method of replacing missing natural teeth in a healthy dentition. Most follow-up studies report a high success rate. The restoration is seen by many clinicians as a relatively straightforward technique easily adapted to general dental practice and popular with patients, although it is not without complications. The purpose of this paper is to look at common problems following the placement of root-formed endosseous dental implants. A number of implant systems are reviewed and the results of the authors' clinical experiences reported.

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.

A survey of U.K. centres on implant failures.

This study investigated the experience of endossoseus implants in the U.K. - how success rates compare with other countries; the common causes of failure; early detection, definition and treatment of the failing implant. Information was gathered by means of a questionnaire sent to 120 centres in the U.K. Thirty-nine centres responded to the survey, reporting on a total of 5328 implants which had been placed over an average time period of 6.5 years. A mean failure rate of 4.3% was reported in the mandible with 16% in the maxilla. The survey showed that 11 different implant systems were in use and that implants were used to support an overdenture in 56% of cases, and bridgework in 26%. The definition of the failing implant and the causes of failure were unclear, with a wide range of opinions given. A combination of methods were used to treat the failing implant including surgical techniques and chemotherapeutic agents, but the long-term success of these treatments was uncertain. Failure rates especially in the maxilla at some of the centres appear higher than have been previously suggested in the U.K. or abroad. Universal agreement on the criteria for 'success' and 'failure' of fixtures is needed along with agreed treatment protocols for the failing implant.

A 3- to 6-year study of overdentures supported by hydroxyapatite-coated endosseous dental implants.

PURPOSE: The purpose of this study was to evaluate the clinical effectiveness of hydroxyapatite-coated cylindrical implants to support overdentures. These implants were placed between 1990 and 1994 and have been followed up over a period of 3 to 6 years. MATERIALS AND METHODS: One hundred thirty-nine Calcitek dental implants were placed in 43 patients to support 14 maxillary and 30 mandibular overdentures. Standardized clinical review procedures were used. RESULTS: At exposure all the implants were found to be osseointegrated. To date only 7 implants (5%) have completely failed and two associated overdentures (5%) have been lost. The cumulative survival rate of all implants over 6 years was 92%. However, if failure is defined by the loss of more than 4 mm of cervical bone, 33 implants could be classified as being in the process of failing. Using these figures, interval success rates as low as 82% were found by year 6, and the cumulative success rate would fall to 39%. Maxillary survival and success rates were significantly lower than mandibular rates, at 38% and 10%, respectively, by year 5. CONCLUSION: Failure rates were higher in the maxillary arch, in poor quality bone, in smokers, and where implants were opposed by a natural dentition or an implant-supported prosthesis. The results suggest that the cervical bone level adjacent to the Calcitek cylindrical hydroxyapatite-coated implant failed to establish a steady state, particularly in the maxillary arch. Doubts remain regarding the long-term prognosis of these cylindrical implants.

The permeability of dental gloves following exposure to certain dental materials.

OBJECTIVES: This investigation sought to study the permeability of three commonly used clinical gloves when exposed to chemical agents. METHODS: A total of 35 gloves of each type were selected at random and were assigned to one of seven equally sized treatment groups. The effective barrier properties were investigated following treatment for 15 min with one of: acid etchant, Trim, cavity varnish, Hibiscrub, Hydrex and Vitremer using a dye permeability test. Following the chemical insult a 0.02% solution of erythrosine dye was introduced into each glove and the outer glove surface was washed with 10 ml of distilled water at intervals of 30, 60, 90 and 120 min. The percentage absorption of the collected washings, at 530 nm, was determined using a spectrophotometer. The results were compared with those values obtained from untreated gloves. RESULTS: Acid etchant and Hydrex had little effect on any of the gloves. Trim caused an increase in permeability of the vinyl gloves but had little or no effect upon those made of latex. Cavity varnish increased the permeability of both Biogel D and Tru-Touch but had no effect on Featherlite. The integrity of the latex gloves was diminished by Hibiscrub but little effect was observed in the case of the vinyl based glove. The permeability of all three gloves was increased by exposure to Vitremer liquid. CONCLUSIONS: Manufacturers should provide details of potential glove chemical interactions to assist dentists in glove selection.

Extraction procedures for atomic absorption spectrometric analysis of toxic metals in urban dust.

A comparison has been made of eight acid extraction systems prior to the atomic absorption analysis of lead, nickel, copper, cadmium, cobalt, chromium, zinc, arsenic and mercury in street dust samples. Statistical treatment of the results enabled a valid comparison to be made in terms of overall extraction efficiency. For the purposes of carrying out large scale environmental surveys it was found that extraction with dilute nitric acid was the most suitable method. Analysis of the extracts by atomic absorption spectroscopy was shown to permit the accumulation of reliable data with the minimum requirement of apparatus and time.

Use of a liquid ion-exchanger in the solvent extraction and atomic-absorption determination of trace copper in waters.

Copper in the 10-100 ppM range has been determined by a solvent extraction and atomic-absorption procedure involving the use of the liquid ion-exchanger Amberlite LA 2 in thiocyanate form. The procedure is rapid and gives results of good precision, and uses stable reagents and standard instrumentation.