Creating an anatomical wax-up in partially edentulous patients by means of a statistical shape model.

PURPOSE: Creating wax-ups of missing teeth for backward planning in implant surgery is a complex and time-consuming process. To facilitate implant-planning procedures, the automatic generation of a virtual wax-up would be useful. In the present study, the reconstruction of missing teeth in partially edentulous patients was performed automatically using newly developed software. The accuracy was investigated in order to test its clinical applicability. MATERIALS AND METHODS: This study presents a new method for creating an automatic virtual wax-up, which could serve as a basic tool in modern implant-planning procedures. First, a statistical shape model (SSM) based on 76 maxillary and mandibular arch scans from dentally healthy individuals was generated. Then, artificially generated tooth gaps were reconstructed. The accuracy of the workflow was evaluated on a separate testing sample of 10 individuals with artificially created tooth gaps given as a median deviation, in millimeters. Scans of three clinical cases with partial edentulism were equally reconstructed using the SSM and compared with the final prosthodontic work. RESULTS: The reconstruction of the artificial tooth gaps could be performed with the following median reconstruction accuracy: gap 21 with 0.15 mm; gap 27 with 0.20 mm; gap 34 with 0.22 mm: gap 36 with 0.22 mm; gaps 12 to 22 with 0.22 mm; gaps 34 to 36 with 0.22 mm. A scenario for an almost edentulous mandible with all teeth missing except teeth 33 and 43 could be reconstructed with a median reconstruction accuracy of 0.37 mm. The median tooth gap deviation of the SSM-based reconstruction in clinical cases differed from the final inserted prosthodontic teeth by 0.49 to 0.86 mm in median. CONCLUSION: A first feasibility of creating virtual wax-ups using an SSM could be shown. Artificially generated tooth gaps could be reconstructed close to the original with the proposed workflow. In the clinical cases, the SSM proposes an anatomical reconstruction, which does not yet consider prosthodontic aspects. To obtain clinical use, contact with antagonist teeth must be considered and more training data must be implemented. However, the presented method offers a fast and viable way for the approximate placement of missing crowns. This could be used in a digital planning workflow when implant position must be determined. (Int J Comput Dent 2022;25(4):349-0; doi: 10.3290/j.ijcd.b2599407).

Biomechanical strain-induced modulation of proliferation coincides with an ERK1/2-independent nuclear YAP localization.

Biomechanical strain induces activation of the transcriptional co-activator yes-associated protein (YAP) by nuclear re-distribution. Recent findings indicate that the mechanically responsive mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK) 1/2 is involved in the amount of nuclear YAP, reflecting its activation. In this context, we conducted experiments to detect how biomechanical strain acts on the subcellular localization of YAP in periodontal cells. To this end, cells were subjected to 2.5% static equiaxial strain for different time periods. Western blot and fluorescence imaging-based analyses revealed a clear modulation of nuclear YAP localization. This modulation fairly coincided with the altered course of the KI-67 protein amount in conjunction with the percentage of KI-67-positive and thus proliferating cells. The inhibition of the ERK1/2 activity via U0126 yielded an unchanged strain-related modulation of nuclear YAP localization, while YAP amount in whole cell extracts of strained cells was decreased. Administration of the YAP-inhibiting drug Verteporfin evoked a clear reduction of KI-67-positive and thus proliferating cells by approximately 65%, irrespective of strain. Our data reveal YAP as a regulator of strain-modulated proliferation which occurs in a MAPK-independent fashion.

What is the best position for palatal implants? A CBCT study on bone volume in the growing maxilla.

OBJECTIVE: The objectives of the present study are the following: (a) to investigate limitations (bone height, proximity to nasopalatine nerve and roots) in juvenile patients, (b) to review the recommended site for surgical insertion (level of the maxillary first premolars), and (c) to reassess the rationale behind the manufacturer's age limitation (12 years). PATIENTS AND METHODS: Cone beam CT images of 100 patients aged 10 to 20 years were analyzed. Vertical bone heights were measured in the median plane as well as 3- and 6-mm paramedian along the prospective axis of insertion, at the level of the first premolars (level 0), 3 mm anterior (level 1) and 3 mm posterior (level 2). The Mann-Whitney U test was used to compare bone heights between gender groups. RESULTS: The risk of damage to the nasopalatine nerve is highest in the median region on level 1 (46 %). The risk was lowest in the midsagittal region on level 0 (recommended insertion site; 3 %) and level 2 (0 %), as well as paramedian on levels 0 and 2. The risk of damaging roots was irrelevant for median insertion at all levels; the only critical region was 6-mm paramedian on level 1. CONCLUSIONS: The recommendation of surgical insertion at the level of the maxillary first premolars is still justified, but a slightly more posterior implant position might improve safety. We found no relevant growth-related changes in the vertical bone heights in the median palatal area. Thus, our data do not support the strict 12-year age restriction for palatal implants.

Orthodontic strain affects the Hippo-pathway effector YAP concomitant with proliferation in human periodontal ligament fibroblasts.

Objectives: During orthodontic tooth movement (OTM), human periodontal ligament fibroblasts (hPDLFs) sense, and respond to mechanical forces. Since the molecular constituents involved in these processes are not fully elucidated, the objective of the present study was to identify further key molecules of the cellular strain response. Materials and Methods: Primary hPDLFs were strained with a static equiaxial strain of 2.5 per cent for 15 minutes, 1 hour, 6 hours, and 24 hours. Western blot (WB) and indirect immunofluorescence (IIF) analyses were performed to investigate the quantity and activation state of proteins involved in mechanotransduction, namely extracellular signal-regulated kinase (ERK) 1/2 and yes-associated protein (YAP). On the cell behavioural level, proliferation was assessed by the marker of proliferation KI-67. Results: In response to the applied strain, an early decline of phosphorylated and thus activated ERK1/2 was observed, followed by a mild recovery. Furthermore, both WB and IIF analyses revealed a modulation of nuclear YAP localisation. Concomitant with the modulation of YAP, the applied strain evoked an early increase in nuclear KI-67 amount, followed by a continuous decrease. Limitations: Consecutive studies will focus on scrutinising the suggested relationship between YAP and proliferation in response to static strain. Conclusions: Our findings provide evidence of ERK1/2 and YAP being biomechanically responsive molecular players in the context of OTM, among which YAP rather than ERK1/2 seems to be mechanistically interrelated with proliferation. Furthermore, the molecular and cell behavioural strain-induced early modulations may point to an involvement of the investigated molecules in the initial and the following lag phase of OTM.

Intermediate rehabilitation with (non)-prep all-ceramic onlays in an adolescent patient with oligodontia--4-year follow-up.

BACKGROUND: Initial rehabilitation in juvenile patients with oligodontia is a major challenge for the dentist. Conventional permanent prosthetic and/or implantological treatment options alongside permanent natural teeth are contraindicated in growing patients, because their skeletal development is still in progress. CASE REPORT: A non-invasive temporary-fixed treatment option for an adolescent patient is presented by the use of adhesively cemented (non-prep) all-ceramic onlays of primary teeth. The outcome of treatment was monitored over a period of 4 years. CONCLUSION: Long-term preservation of persistent primary teeth may be a meaningful alternative to removable dentures in growing patients with oligodontia. Intermediate rehabilitation should cause no more than mild psychological stress for the patient and improve quality of life, especially when extensive orthodontic and/or implantological treatment is planned at the end of the patient's skeletal growth.

Forces and moments generated by removable thermoplastic aligners: incisor torque, premolar derotation, and molar distalization.

INTRODUCTION: The exact force systems as well as their progressions generated by removable thermoplastic appliances have not been investigated. Thus, the purposes of this experimental study were to quantify the forces and moments delivered by a single aligner and a series of aligners (Invisalign; Align Technology, Santa Clara, Calif) and to investigate the influence of attachments and power ridges on the force transfer. METHODS: We studied 970 aligners of the Invisalign system (60 series of aligners). The aligners came from 30 consecutive patients, of which 3 tooth movements (incisor torque, premolar derotation, molar distalization) with 20 movements each were analyzed. The 3 movement groups were subdivided so that 10 movements were supported with an attachment and 10 were not. The patients' ClinCheck (Align Technology, Santa Clara, Calif) was planned so that the movements to be investigated were performed in isolation in the respective quadrant. Resin replicas of the patients' intraoral situation before the start of the investigated movement were taken and mounted in a biomechanical measurement system. An aligner was put on the model, the force systems were measured, and the calculated movements were experimentally performed until no further forces or moments were generated. Subsequently, the next aligners were installed, and the measurements were repeated. RESULTS: The initial mean moments were about 7.3 N·mm for maxillary incisor torque and about 1.0 N for distalization. Significant differences in the generated moments were measured in the premolar derotation group, whether they were supported with an attachment (8.8 N·mm) or not (1.2 N·mm). All measurements showed an exponential force change. CONCLUSIONS: Apart from a few maximal initial force systems, the forces and moments generated by aligners of the Invisalign system are within the range of orthodontic forces. The force change is exponential while a patient is wearing removable thermoplastic appliances.

Treatment outcome and efficacy of an aligner technique--regarding incisor torque, premolar derotation and molar distalization.

BACKGROUND: The aim of this study was to investigate the efficacy of orthodontic treatment using the Invisalign® system. Particularly, we analyzed the influence of auxiliaries (Attachment/Power Ridge) as well as the staging (movement per aligner) on treatment efficacy. METHODS: We reviewed the tooth movements of 30 consecutive patients who required orthodontic treatment with Invisalign®. In all patients, one of the following tooth movements was performed: (1) Incisor Torque >10°, (2) Premolar derotation >10° (3) Molar distalization >1.5 mm. The groups (1)-(3) were subdivided: in the first subgroup (a) the movements were supported with the use of an attachment, while in the subgroup (b) no auxiliaries were used (except incisor torque, in which Power Ridges were used). All tooth movements were performed in a split-mouth design. To analyze the clinical efficacy, pre-treatment and final plaster cast models were laser-scanned and the achieved tooth movement was determined by way of a surface/surface matching algorithm. The results were compared with the amount of tooth movement predicted by ClinCheck®. RESULTS: The overall mean efficacy was 59% (SD = 0.2). The mean accuracy for upper incisor torque was 42% (SD = 0.2). Premolar derotation showed the lowest accuracy with approximately 40% (SD = 0.3). Distalization of an upper molar was the most effective movement, with efficacy approximately 87% (SD = 0.2). CONCLUSION: Incisor torque, premolar derotation and molar distalization can be performed using Invisalign® aligners. The staging (movement/aligner) and the total amount of planned movement have an significant impact on treatment efficacy.

Prognostic parameters contributing to palatal implant failures: a long-term survival analysis of 239 patients.

OBJECTIVE: To evaluate the demographic, radiological and therapeutic parameters that influence the overall clinical performance of palatal implants subjected to orthodontic loading. PATIENTS AND METHODS: The data of all patients who had received an orthodontic palatal implant for skeletal anchorage between January 1998 and December 2007 were reviewed retrospectively. The primary endpoint was the implant loss. The following parameters were assessed by univariate (log-rank test) and multivariate (Cox's regression) analysis: (a) age and gender, (b) vertical bone height along the prospective implant axis, (c) surgeon's experience and (d) implant type. RESULTS: Two-hundred and thirty-nine palatal implants were inserted in patients aged between 10 and 65 years. In all, 11/239 (4.6%) implants were lost: nine during the healing phase and two under functional loading. On univariate analysis, "surgeon's experience" was associated with a better implant survival and vice versa (P=0.0005; log-rank test). The significance of "surgeon's experience" was confirmed by Cox's regression analysis (P=0.001; Wald test). All other parameters had no impact on implant loss. CONCLUSIONS: The survival probability of palatal implants is not related to demographic and radiological parameters. Implant losses mainly occurred early in the healing phase of the palatal implant. According to our data, "surgeon's experience" is the cornerstone of palatal implant success.

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.

Immediate versus conventional loading of palatal implants in humans: a first report of a multicenter RCT.

This study aims to analyze the clinical performance of two loading concepts on second-generation palatal implants (Orthosystem, Straumann, Basel, Switzerland) in a prospective multicenter randomized controlled clinical trial. At the time of this interim analysis, 41 patients have been randomized on a 1:1 basis to one of two treatment groups. Group 1 underwent conventional loading of palatal implants after a healing period of 12 weeks (gold standard) while group 2 underwent immediate implant loading within 1 week after implant insertion. We report initial results at 6 months after functional loading. The primary outcome parameter was implant success (no implant mobility, no implant loss). The implants in both groups were initially stable at the time of insertion, and all were eligible for randomization. Twenty-two patients (group 1) were subjected to conventional implant loading after 12 weeks while 19 patients (group 2) received immediate functional loading within the first week after insertion. Direct (e.g. distal jet appliances) as well as indirect forms of anchorage (conventional or modified transpalatal arch) were used. The magnitude of orthodontic forces ranged between 1 and 4 N for the immediate loading group and between 1 and 5 N for the conventional loading group. One implant in group 1 was lost during the healing phase. One dropout was registered in group 2. Thirty-nine implants were functionally loaded for over 6 months now. These preliminary data provide first evidence of the fact that immediate loading of palatal implants yields equivalent success rates as conventional loading to 4 N after 6 months.

Immediate vs. conventional loading of palatal implants in humans.

OBJECTIVES: To analyze the clinical performance and bone-to-implant contact (BIC) rate of two loading concepts on successfully healed and explanted palatal implants in humans. METHODS: From 2000 to 2006, two independent groups of patients, requiring maximum anchorage, were treated. Group 1 (n=36) was subjected to immediate functional loading within the first 24 h after insertion while group 2 (n=40) received conventional implant loading after 12 weeks. The magnitude of orthodontic forces ranged between 1 and 3 N. After orthodontic treatment, the implants were removed with a trephine drill. Histological workup by the cutting and grinding technique was performed for nearly the last third of palatal implants. Outcome variables were clinical implant survival and histological BIC rates. RESULTS: The implants in both groups were initially stable at the time of insertion. However, 3/36 in group 1 and 1/40 in group 2 were lost. The remaining implants were clinically stable and no mobility was recognized. The median BIC rates were 76% (SD, 25) in group 1 (n=10) and 84% (SD, 13) in group 2 (n=12) (P=0.262; Mann-Whitney U-test, not significant). CONCLUSIONS: The data support the concept of immediate indirect loading on palatal implants with forces of up to 3 N. On histological evaluation, immediate loading yielded similar BIC rates as conventional loading.

New method of temporary rehabilitation after traumatic tooth loss in a juvenile patient: a case report.

We report a 12-year-old female patient who had experienced traumatic loss of one of her permanent central incisors. In the course of interdisciplinary treatment, the gap in the front teeth was filled with a prosthetic plastic tooth fastened to an orthodontic palatal implant by means of a wire extension (stainless steel 1.2 mm; laser-welded). A palatal implant is a temporary orthodontic anchorage device which, in contrast to a conventional single tooth implant, is not inserted in the toothless alveolar bone but in the palatal region to permit unhindered maxillary growth. The advantages of this treatment compared with traditional treatment options are that it permits secure fixation, adjustment to vertical growth and good hygiene. Besides, it is an economical treatment modality, can be used as anchorage in conjunction with orthodontic treatment and provides good comfort, esthetics and phonetics.

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.

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.

Primary loading of palatal implants for orthodontic anchorage--a pilot animal study.

OBJECTIVES: This study aimed at evaluating the clinical performance and osseointegration of short orthodontic implants immediately loaded with orthodontic forces. MATERIAL AND METHODS: The investigation was designed as an experimental animal study. Eight palatal implants of the Ortho-system were immediately loaded with 100 cN after palatal insertion in 4 female German shepherd dogs. Xylene orange and calcein green were used for polychrome sequential labelling. Histological preparation utilized the cutting and grinding technique. Outcome variables were clinical implant success, histological osseointegration and bone-to-implant contact rates. RESULTS: All (8/8) implants were clinically successful and stable when the animals were sacrificed. One implant showed fibrous encapsulation and was histologically classified as "failed" for "osseointegration". Upon morphometrical analysis, bone to implant contact rates for newly formed or remodelled bone were 19% at 4 weeks and 26% at 6 months. The fluorochrome labelling indicated substantial mineral apposition on the surface of the implants at the end of the first and the second postoperative months. CONCLUSION: This study revealed borderline reliability of osseointegration for immediately loaded palatal implants but reasonable bone formation at the 4th postoperative week. Thus, two clinical concepts are both supported: early orthodontic loading after 4 weeks as well as improvement of primary stability to provide a biomechanical basis for immediate orthodontic loading.

Bone-to-implant contact of orthodontic implants in humans--a histomorphometric investigation.

The purpose of the present study was to evaluate the percentage of direct bone-to-implant contact (BIC) of orthodontic anchorage implants (Orthosystem) after active orthodontic treatment. Twenty orthodontic implants (diameter, 3.3 mm; length, 4 or 6 mm) were inserted for orthodontic anchorage in different anatomical regions of 18 adult patients (nine males, nine females) aged 18-63 years. Fifteen implants (one per patient) were placed in the mid-palatal area, one implant (one patient) in the retromolar area of the mandible, one in the retromolar area and the mid-palatal area (one patient), and two (bilaterally, one patient) in the zygomatic area. The duration of the unloaded healing period was 3 months while that of the loading period ranged from 9 to 22 months. Subsequently, the implants were removed with a bone drill and prepared for histological and histomorphometric evaluation. Histological analysis was performed using the ground thin-section technology. Outcome variables were clinical implant survival and BIC rates. Statistical evaluation included analysis of the measured values, minimum, maximum, means, and standard deviations of the means. The mean percentage of direct BIC at the endosseous implant body was 68.22 per cent for the palatal implants [n = 16, standard deviation (SD): 14.35], 64.85 per cent (SD: 2.89) for the retromolar implants (n = 2), and 60.45 per cent (SD: 0.49) for the zygomatic implants (n = 2). A relatively high BIC was registered at the surfaces of the loaded implants. This finding might favour the maintenance of osseointegration during orthodontic loading of length-reduced implants.

An interdisciplinary noninvasive all-ceramic treatment concept for nonsyndromic oligodontia in adolescence.

Oligodontia has a substantial oral functional and psychosocial impact on the quality of life of children. The treatment of oligodontia in adolescence is an interdisciplinary approach which can include extraction of the primary teeth with orthodontic space closure, or prosthodontic rehabilitation. This case report describes a conservative approach for the rehabilitation of a 12-year-old patient with 19 ageneses (excluding third molars) of permanent teeth, infraocclusion of the persisting primary teeth, deep overbite, and reduced mesiodistal dimension of the maxillary incisors with a central diastema. The treatment plan to restore esthetics and function included an initial noninvasive prosthetic rehabilitation for deep bite correction with additive leucite-reinforced glass-ceramic onlays/veneers until definitive orthodontic and implant therapy are reevaluated and determined in adulthood. Esthetics, functional occlusion, and crown-to-root ratio remained stable over a follow-up period of 3 years. No signs of fractures within the all-ceramic restorations or symptoms of a temporomandibular disorder were evident.

Immediate nonfunctional loading of NobelPerfect implants in the anterior dental arch in private practice--5-year data.

BACKGROUND: The concept of scalloped implants to maintain the natural contour of the alveolar ridge has been a source of controversy for many years. PURPOSE: This study examined the long-term clinical performance of the scalloped NobelPerfect implant in a one-stage procedure (immediate loading in the esthetic zone). MATERIALS AND METHODS: In 20 patients, immediate prosthetic restorations were placed on 31 NobelPerfect implants in a private practice and followed for up to 78 months. Twenty-one implants were placed immediately after extraction, seven implants were placed after osseous consolidation of the extraction sockets, and three implants were placed secondary to extended alveolar ridge augmentation procedures. All implants were provisionalized on the day of implant placement and adjusted to clear all contacts in centric occlusion and during eccentric movements. Outcome variables were success rates, marginal bone levels, and pink esthetic score (PES) assessed per implant. RESULTS: One implant failed after 1.4 months. Five patients with six implants in total were scored in the 5-year follow-up as dropouts. Mean follow-up period of remaining 24 implants was 65 months (range, 55-78 months). Cumulative success rates according to the criteria specified by Smith and Zarb were 96.8%. Marginal bone levels averaged 1.1 mm above the first thread. Mean PES ratings were 10.5 (range, 3-13). CONCLUSIONS: Survival rates, marginal bone levels, and esthetic results suggest proof of principle for the preservation of the interproximal bony lamella with a scalloped implant design in long-term data.