Palatal implants: The Straumann Orthosystem

Impression material accuracy for palatal orthodontic miniscrews

Purpose

This study investigates the accuracy of abutment transfer with current impression materials and provides a concise overview, including other relevant factors, in order to enable clinicians to make an informed decision about the optimal impression for this treatment procedure.

Methods

In all, 96 impressions of a cadaver head with two orthodontic miniscrews in place were taken with four common impression materials by two observers and using two methods of application. After pouring with a standard type IV stone and abutment transfer, all models and the upper jaw (which had been separated from the head) were scanned in a standard model scanner (Zirkonzahn® [Zirkohnzahn GmbH, Gais, Italy] S600 ARTI) and evaluated using a computer-aided design (CAD) program (GOM-Inspect [Gesellschaft für optische Messtechnik m.b.H., Braunschweig, Germany]). The deviations were measured at six points per screw and statistically evaluated with SPSS® (IBM, Chicago, IL, USA).

Results

Optimal values were obtained with biphasic polyvinylsiloxane, while monophasic polyvinylsiloxane, alginate and polyether also resulted in acceptable accuracy. Observer experience showed no effect and the method of application had only a minor effect on accuracy.

Conclusions

Within the limitations of this study, it seems that all impression materials are suitable for miniscrew abutment transfer, provided that methods of intraoral adaptation of the orthodontic appliance can be employed. If higher accuracy is needed or for clinicians with less experienced, a biphasic polyvinylsiloxane impression with the putty-wash technique should be used as this combination reduces setting time. The most cost-effective version, alginate, can be used if the consequences of greater deviations can be handled. Caution is advised with polyether if undercuts are present.

Effects of the zygoma anchorage system on canine retraction

The aim of this study was to compare the effects of the Gjessing (PG) retraction spring used with and without the zygoma anchorage system (ZAS) on canine retraction. Thirty patients, with an Angle Class I or Class II malocclusion, whose upper first premolars were scheduled for extraction, were divided into two equal groups. Group 1 comprised maximum anchorage cases (nine females and six males with a mean age of 16 years 8 months) in which the ZAS was used to improve posterior anchorage and the PG retraction springs for canine retraction. Moderate anchorage cases (10 females and 5 males with a mean age of 15 years 5 month) were included in group 2 and canine retraction was achieved using only PG retraction springs. Study models and lateral cephalometric radiographs obtained at the initial and final stages of canine retraction were used for comparison of the groups to determine the effects of zygoma anchorage on canine retraction. All measurements were evaluated statistically using a Student's t-test, 2 × 2 repeated measures analysis of variance, Bonferroni-adjusted t-test, and Mann-Whitney U and Wilcoxon tests according to the normality of the distribution of the variables. Mesial crown movement of the molars was 0.63 mm (P < 0.05) in group 1 and 1.50 mm (P < 0.001) in group 2. There was a statistically significant difference (P < 0.05) between the groups. No significant difference was observed between the groups for the rate of canine retraction or sagittal and vertical movement of the canines. The ZAS is a reliable and successful anchorage reinforcement method for canine retraction in extraction cases.

Mini-implants in orthodontics: a systematic review of the literature

INTRODUCTION

In this article, we systematically reviewed the literature to quantify success and complications encountered with the use of mini-implants for orthodontic anchorage, and to analyze factors associated with success or failure.

METHODS

Computerized and manual searches were conducted up to March 31, 2008, for clinical studies that addressed these objectives. The selection criteria required that these studies (1) reported the success rates of mini-implants on samples sizes of 10 implants or more, (2) gave a definition of success, (3) used implants with a diameter smaller than 2.5 mm, and (4) applied forces for a minimum duration of 3 months. Factors associated with implant success were accepted only if potentially influencing variables were controlled. The Cochrane Handbook for Systematic Reviews of Interventions was used as the guideline for this article.

RESULTS

Nineteen reports met the inclusion criteria, but definitions of success, duration of force application, and quality of the methodology of these studies varied widely. Rates of primary outcomes ranged from 0% to 100%, but most articles reported success rates greater than 80% if mobile and displaced implants were included as successful. Adverse effects of miniscrews included biologic damage, inflammation, and pain and discomfort. Only a few articles reported negative outcomes. All proposed correlations between clinical success and specific variables such as implant, patient, location, surgery, orthodontic, and implant-maintenance factors were rejected because they did not meet the selection criteria for controlling those variables.

CONCLUSIONS

Mini-implants can be used as temporary anchorage devices, but research in this field is still in its infancy. Interpretation of findings was conditioned by lack of clarity and poor methodology of most studies. Questions concerning patient acceptability, rate and severity of adverse effects of miniscrews, and variables that influenced success remain unanswered. This article includes a guideline for future studies of these issues, based on specific definitions of primary and secondary outcomes correlated with specific operational variables.

Sagittal and vertical load-deflection and permanent deformation of transpalatal arches connected with palatal implants: an in-vitro study

INTRODUCTION

The purposes of this laboratory investigation were to (1) measure the sagittal and vertical deflection of loaded transpalatal arches (TPAs) connected to a palatal implant, (2) measure the extent of permanent deformation of the connecting TPA in the sagittal and vertical directions, (3) test various wire dimensions in terms of deflection behavior, and (4) evaluate soldering vs laser welding vs adhesive bonding of TPAs in terms of load deflection behavior.

METHODS

Stainless steel wires of 6 dimensions were tested: 0.8 x 0.8, 0.9, 1, 1.1, 1.2, and 1.2 x 1.2 mm. For each dimension, 10 specimens were soldered to the palatal implant abutment, 10 were laser welded, and 10 were adhesively bonded to the implant abutment (total, 180 specimens). The measuring device applied increments of force of 50 cN, from 0 to 500 cN. Then the specimens were unloaded. The values were statistically described and analyzed with ANOVA and Wilcoxon rank sum tests.

RESULTS AND CONCLUSIONS

Absolute orthodontic anchorage without deformation of TPAs was not observed with the wire dimensions tested. To prevent loss of anchorage greater than 370 mum (sagittal deflection of 1.2 x 1.2 mm adhesively bonded TPA at 500 cN force level), wires thicker than 1.2 x 1.2 mm or cast anchorage elements must be considered for clinical practice. However, larger cross sections might cause more patient discomfort, and laboratory procedures increase costs.

Temporary Anchorage Devices for Tooth Movement: A Review and Case Reports

BACKGROUND

Temporary anchorage devices (TADs) are immediately loaded miniscrews and osseointegrated palatal implants that are placed to control tooth movement during orthodontic treatment and removed when the treatment is completed. They are a relatively new addition to the dental armamentarium and can be used in some cases to replace traditional orthodontic extraoral appliances. Because placement requires a surgical procedure, orthodontists often refer patients to periodontists for this stage of the overall treatment plan.

METHODS

The purpose of this article is to introduce TADs to the periodontal community by reviewing their purpose, various systems that are available, indications for use, site selection, and surgical technique. Case reports are included to illustrate this new treatment approach.

RESULTS

Placement of osseointegrated implants for restorative purposes is an established procedure in most periodontal offices. Although placement of TADs is a modification of these familiar techniques, most of these devices serve a very different purpose, involving new loading protocols with no expectation of osseointegration in patients usually not receiving concomitant periodontal therapy.

CONCLUSIONS

Periodontists' knowledge of soft and hard tissue anatomy and their ability to manage soft tissue position them well to collaborate with orthodontists in this multidisciplinary treatment. However, as with every new modality, clinicians need to understand the specific uses and limitations of TADs and work closely with their referring orthodontists in identifying patients for whom miniscrew implants are a viable option. Periodontal practices are based primarily on referrals from dental colleagues, and the concept of periodontists working cooperatively with orthodontists is not new. Including TAD placement among the services periodontists offer provides another opportunity to further this relationship and to establish periodontists as appropriate resources for this segment of orthodontic treatment.

Ninety percent success in palatal implants loaded 1 week after placement: a clinical evaluation by resonance frequency analysis

To investigate the behaviour of early loaded palatal implants when observed with resonance frequency analysis (RFA). Twenty patients (seven males and 13 females, mean age 26.4 years) received one palatal implant each (length: 4 mm, diameter: 3.3 mm; Orthosystem) for maximum orthodontic anchorage. The implants' stability was observed by RFA. Measurements were carried out at the time of surgery, after first orthodontic loading and subsequently once a week over a period of 12 weeks. Two palatal implants were lost. The other 18 remained stable. The average period from insertion to first loading was 6.7+/-0.8 days. The mean orthodontic force applied was 272.2+/-73.2 cN. The implant stability quotient (ISQ) value at the time of surgery averaged 69.4+/-3.9. The mean ISQ value 6.7 days after insertion was 69.8+/-3.6. Twelve weeks post-surgery the mean ISQ value was 69.8+/-3.5. A statistically significant decrease in stability was observed after 2 and 3 weeks post-surgery (P=0.005 and 0.04). The behaviour of early loaded palatal implants showed an initial decrease of the ISQ values. From 6 weeks post-surgery onward the ISQ values increased. Within the limitations of this study, the results suggest that the healing time of palatal implants reported in the literature (12 weeks) should be discussed. An orthodontic loading of palatal implants 6 weeks post-surgery with a force up to 400 cN seems to be justified. Yet further investigations are necessary to evaluate the behaviour of early loaded palatal implants considering observation periods of over 12 weeks.