Orthodontic palatal implants: clinical technique

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.

Predictive values of resonance frequency analysis as a diagnostic tool in palatal implant loss

OBJECTIVES

To determine the diagnostic value of resonance frequency analysis (RFA) in predicting palatal implant (PI) loss.

MATERIALS AND METHODS

RFA values of 32 patients (study center at Mainz and Dresden) were evaluated in a prospective randomized controlled trial addressing clinical performance of two loading concepts on PI (Orthosystem, Straumann, Basel, Switzerland). Group 1: conventional loading after a 12-week healing period vs group 2: immediate loading within one week after insertion. Stability was assessed by RFA after surgical insertion (T1), one week (T2), and 12 weeks (T3) later.

RESULTS

All 32 PI were clinically stable after surgical insertion; 14 PI were loaded conventionally and 18 immediately. One implant in group 1 was lost 6 weeks after insertion. One drop-out was registered in group 2. One false positive and three false negative implant stability quotients (ISQ) were observed. ISQ values of clinically stable PI in group 1 were 67.2 (SD ± 9.5) at T1, 62.3 (SD ± 11.7) at T2, and 68.2 (SD ± 5.5) at T3. Group 2 showed 67.1 (SD ± 11.7) at T1, 65.4 (SD ± 10.4) at T2, and 72.3 (SD ± 5.6) at T3. Differences between groups were not statistically significant for starting time (P = .88) and change from T1 to T2: 0.08 but were significant from T1 to T3: P = .04; (regression analysis).

CONCLUSIONS

RFA had no sensitivity for prediction of stability. General decrease after primary stability and increase with secondary stability gives support for specificity. Within the limits of the study, only the diagnostic value of RFA identifying stable palatal implants could be confirmed.

Combined cephalometric and stent planning for palatal implants

Several aspects of palatal implant usage are technique sensitive. In particular, problems during the insertion stage may compromise implant osseo-integration, or its subsequent ease of handling and effectiveness. This paper describes a systematic approach to combined cephalometric and model planning, and subsequent stent fabrication for Orthosystem palatal implants. The authors recommend this protocol in order to optimize three-dimensional control of implant positioning, and to both simplify and standardize the insertion stage.

Midpalatal miniscrews and high-pull headgear for anteroposterior and vertical anchorage control: cephalometric comparisons of treatment changes

INTRODUCTION

Our aim was to evaluate which anchorage system is better suited for both anteroposterior and vertical anchorage control of maxillary posterior teeth.

METHODS

Fifty-one subjects requiring maximum anchorage were divided into 2 groups according to maxillary posterior anchorage reinforcement: high-pull headgear, conventional transpalatal arch, and interarch elastics (n = 28); or modified transpalatal arch supported by 2 midpalatal miniscrews (n = 23). Bilateral maxillary first premolars were extracted in all patients. Pretreatment and posttreatment lateral cephalometric radiographs were superimposed to compare skeletal and dental changes between the groups.

RESULTS

(1) The miniscrew group had less mesial movement of the maxillary first molars (0.85 vs 3.63 mm) and greater maxillary incisor retraction (6.87 vs 4.50 mm) than did the headgear group with the same treatment duration. (2) The maxillary molars were significantly intruded in the miniscrew group (1.30 mm), whereas they were extruded in the headgear group (0.71 mm). In the miniscrew group, intrusion of the maxillary molars resulted in a statistically significant decrease in the mandibular plane angle (0.80°). Patients using high-pull headgear showed no significant decrease in these measurements.

CONCLUSIONS

In both the anteroposterior and vertical directions, a modified transpalatal arch supported by 2 midpalatal miniscrews provided more stable anchorage.

Does thread design influence relative bone-to-implant contact rate of palatal implants?

AIM

To determine histologically whether (a) changing the thread design between first- and second-generation palatal implants (Straumann, Basel, Switzerland) influences the bone-to-implant contact (BIC) rate of palatal implants subjected to conventional loading, and (b) whether histological evidence of peri-implantitis appears in this setting.

PATIENTS AND METHODS

Patients who had received an orthodontic palatal implant for skeletal anchorage between January 1998 and December 2007 were examined. First-generation palatal implants (Straumann, Basel, Switzerland) 3.3 mm in diameter and 6 mm or 4 mm long were used, as were second-generation implants 4.1 mm in diameter and 4.2 mm long. After completion of active orthodontic treatment, the implants were removed and prepared for histological investigation. This study was designed as a comparative analysis of a series of two cases: 28 explanted first-generation (n = 14) and second-generation (n = 14) palatal implants were analyzed.

RESULTS

Bone healing was achieved with all implants. Both types of implants revealed a mean bone-to-implant contact (BIC) rate that was nearly equal: 80.7% (SD 10.7%) for the first-generation and 81% (SD 13.1%) for the second-generation implants. Bone resorption was only observed in 5 palatal implants (3/14 of the first, and 2/14 of the second generation).

CONCLUSION

Despite differing thread designs, second-generation palatal implants revealed similar bone-to-implant contact rates as did those of the first generation. Few patients presented bone resorption in the peri-implant bone.

Clinical study of temporary anchorage devices for orthodontic treatment--stability of micro/mini-screws and mini-plates: experience with 455 cases

The aim of this retrospective study was to determine factors that might cause complications in use of temporary anchorage devices (TADs) for orthodontic anchorage. We investigated 904 TADs in 455 patients. Clinical diagnoses requiring orthodontic treatment were malocclusion, jaw deformity, various syndromes, cleft lip and palate and impacted teeth. All patients underwent surgery at Tokyo Dental College Chiba Hospital between November 2000 and June 2009. Three kinds of titanium screw of different diameter and length were used: self-drilling mini-screws (Dual Top Autoscrew® and OSAS®), pre-drilling micro-screws (K1 system®) and palatal screws (PIAS®). Mini-plates fixed with 2 or 3 screws (SAS system®) were also used for skeletal anchorage. Patients were aged between 8 and 68 years (25.7±9.8 years). A total of 460 screw-type and 444 plate-type TADs were used. These comprised the following: mini-plates, 444; self-drilling mini-screws, 225; pre-drilling micro-screws, 83; and palatal screws, 152. Each type of implant had a high success rate of over about 90%. Failure rates were as follows: micro-screws, 7%; mini-screws, 6%; palatal implants, 11%; and mini-plates, 6%. Inflammation rate occurring in soft tissue surrounding TADs was follows: plate-type, 7.6%; mini-screws, 1.3%; micro-screws, 0%; and palatal implants, 2.5%. Inflammation frequencies depended on degree of mucosal penetration. Granulation rate in soft tissue surrounding TADs occurred as follows: micro-screws, 5.7%; self-drilling mini-screws, 0%; palatal screws, 0.6%; plate-type, 0.9%. Both plate- and screwtype orthodontic implants showed excellent clinical performance.

Vertical palatal bone dimensions on lateral cephalometry and cone-beam computed tomography: implications for palatal implant placement

OBJECTIVES

To evaluate the necessity of three-dimensional imaging (computed tomography [CT]/cone-beam computed tomography [CBCT]) for paramedian insertion of palatal implants.

MATERIAL AND METHODS

Lateral radiographs and CBCT scans were performed from 18 human skulls. For lateral cephalometry, the nasal floor (right/left) and the oral hard palate of all skulls were lined with a tin foil for contrast enhancement. The quantity of vertical bone as measured on lateral radiographs was compared with CBCT measurements obtained in median and parasagittal planes and at minimum bone height. Spearman's rank correlation coefficients were determined for bivariate correlation analysis.

RESULTS

The median palatal bone height on CBCT (mean 8.98 mm; standard deviation [SD] 3.4) was markedly higher than the vertical height seen on lateral radiographs (mean 6.6 mm; SD 3.2). Comparing lateral cephalometry with CBCT, the strongest association was observed at the minimum palatal bone height (r=0.926; P<0.001; Spearman's rank correlation coefficient).

CONCLUSIONS

Lateral radiographs allow accurate and adequate assessment of vertical bone before paramedian insertion of palatal implants. The vertical bone dimension as displayed on lateral cephalometry reflects the minimum bone height rather than maximum bone in the median plane. Therefore, a preoperative CT or CBCT is only indicated when the lateral cephalometry reveals a marginal quantity of bone.

Success Rate of Second-Generation Palatal Implants

Objective: To analyze the clinical outcome of a prospective two-center study of second-generation palatal implants 6 months after functional loading.

Material and Methods: From 2005 to 2006, 30 patients aged 12 to 41 years were included in the study. In all patients, orthodontic treatment required stationary anchorage. The palatal implants (Straumann, Basel, Switzerland) were placed in the median region of the anterior palate.

Results: All implants were initially stable at the time of placement. However, two (6.7%) were lost during the unloaded healing period. The remaining 28 (93.3%) were subjected to functional loading after a mean healing period of 12 weeks. Typical signs of slight superficial inflammation were observed in the peri-implant mucosa (n = 28). During the orthodontic loading phase, the implants were equipped with either a modified pendulum appliance for distalization or a transpalatal arch for stationary anchorage to the posterior teeth. No implant loosening or loss was registered during the active treatment period.

Conclusions: The failure rate of palatal implants of the second generation was low (6.7%). Slight inflammatory reactions of peri-implant tissue caused neither implant loss nor pain.

Reinforcement of anchorage during orthodontic brace treatment with implants or other surgical methods

BACKGROUND

The term anchorage in orthodontic treatment refers to the control of unwanted tooth movement. This is conventionally provided either by anchor sites within the mouth, such as the teeth and the palate or from outside the mouth (headgear). Orthodontic implants which are surgically inserted to bone in the mouth are increasingly being used as an alternative form of anchorage reinforcement in orthodontics.

OBJECTIVES

The primary objective of this review was to evaluate the effectiveness of surgical methods for preventing unwanted tooth movement compared with conventional anchorage reinforcement techniques. The secondary objectives were to examine patient acceptance, discomfort and failure rates associated with these techniques.

SEARCH STRATEGY

The Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE and EMBASE were searched. No language restrictions were applied. Authors were identified and contacted to identify unpublished trials. The most recent search was conducted in February 2006.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials involving the use of surgically assisted means of anchorage reinforcement on orthodontic patients. Inclusion and exclusion criteria were applied when considering the studies to be included in this review.

DATA COLLECTION AND ANALYSIS

Data extraction was performed by two review authors working independently using a previously piloted data collection form. Data were entered into RevMan with planned analysis of mean differences (MD) and 95% confidence intervals (CI) for continuous outcomes and risk ratios (RR) and 95% CI for dichotomous outcomes. Pooling of data and meta-analysis were not performed due to an insufficient number of similar studies.

MAIN RESULTS

At present few trials have been carried out in this field and there are little data of adequate quality in the literature to meet the objectives of the review. The review authors were only able to find one study assessing the use of surgical anchorage reinforcement systems. This trial examined 51 patients with 'absolute anchorage' requirements treated in two centres. Patients were randomly allocated to receive either headgear or a mid-palatal osseointegrated implant. Anchorage loss was measured cephalometrically by mesial movement of dental and skeletal reference points between T1 (treatment start) and T2 (end of anchorage reinforcement). All skeletal and dental points moved mesially more in the headgear group than the implant group. Results showed significant differences for mesial movement of the maxillary molar in both groups. The mean change in the implant group was 1.5 mm (standard deviation (SD) 2.6; 95% CI 0.4 to 2.7) and for the headgear group 3.0 mm (SD 3.4; 95% CI 1.6 to 4.5). The trial was designed to test a clinically significant difference of 2 mm, so the result was not statistically significant, but the authors conclude that mid-palatal implants do effectively reinforce anchorage and are an acceptable alternative to headgear in absolute anchorage cases.

AUTHORS' CONCLUSIONS

There is limited evidence that osseointegrated palatal implants are an acceptable means of reinforcing anchorage. The review authors were unable to identify trials addressing the secondary objectives of the review relating to patient acceptance, discomfort and failure rates. In view of the fact that this is a dynamic area of orthodontic practice we feel there is a need for high quality, randomised controlled trials. There are financial restrictions in running trials of this nature. However it would be in the interest of implant manufacturers to fund high quality, independently conducted, trials of their products.

Current products and practice: bone anchorage devices in orthodontics

Bone anchorage is a promising new field in orthodontics and already a wide variety of bone anchorage devices (BADs) are available commercially. This review aims to assist clinicians by outlining the principles of bone anchorage and the salient features of the available systems, especially those that may influence the choice of a specific BAD for anchorage reinforcement.