Christian Stoll

Evaluation of the accuracy of three different computer‐aided surgery systems in dental implantology: optical tracking vs. stereolithographic splint systems

OBJECTIVES In dental implant surgery, computer-aided surgery (CAS) techniques can provide a high medical benefit. Two different techniques are established for transferring a CAS treatment planning to the patient: the use of surgical templates (splints) or intraoperative navigation using optical tracking. The aim of this study was to evaluate the total application accuracy of three different CAS systems (Artma virtual patient, RoboDent LapAccedo, Materialise SurgiGuide): two featuring optical tracking, one featuring stereolithographically manufactured splints. MATERIALS AND METHODS A total of 120 implants were placed into 20 human cadaver mandibles. Preoperative computed tomography (CT) scans imported to the corresponding software were used to plan the implant positions on the computer. Implant placement was performed using either optical tracking or stereolithographic splints. Postoperative CT scans were used to obtain the achieved implant positions. A semi-automatic approach was developed to compare planned and achieved implant positions. Deviations between planned and achieved positions were measured for each implant in position (Delta xy), depth (Delta z) and axis (Delta phi). CONCLUSION Despite the different techniques of transfer, no statistically significant differences were found between all groups. The accuracy achieved corresponded well with the spatial resolution of the CT Scans used.

Quantitative computed tomography bone mineral density measurements in irradiated and non‐irradiated minipig alveolar bone: an experimental study

OBJECTIVE The objective of this study was to analyse the effect of irradiation on bone mineral density (BMD). MATERIALS AND METHODS All maxillary and mandibular pre-molars and molars of six minipigs were extracted. After a 3-month healing period, the maxilla and mandibles of three minipigs received three irradiation exposures at a total dose of 24 Gy. At 3 months after irradiation, quantitative computed tomography (QCT) was performed. As a reference, a calibration bone phantom with pre-determined BMD was attached to the head of the minipigs. The QCT data were imported into a software program to calculate the BMD of the alveolar bone and the calibration bone phantom. In order to compare BMD values of individual minipigs, the so-called bone mineral density quotient (BMDQ) was created, dividing the BMD value of the alveolar bone by the BMD value of the calibration bone phantom. RESULTS Mean BMDQ values appeared to be higher in irradiated than in non-irradiated minipigs. However, the difference was not significant. In both irradiated and non-irradiated minipigs, the average mandibular BMDQ values were statistically significantly higher than the average maxillary BMDQ values (P=0.003). The P-values of the Student t-test, determining the irradiation effect, were 0.11 for maxillary, 0.14 for mandibular, and 0.07 for overall peri-implant BMDQ. P-values of the non-parametric Mann-Whitney test were all 0.05. CONCLUSION It could be concluded that, 3 months after irradiation, the BMD of irradiated alveolar minipig bone was increased, when compared with non-irradiated alveolar minipig bone. However, the increase was not statistically significant.

Analysis of polymorphic TGFB1 codons 10, 25, and 263 in a German patient group with non-syndromic cleft lip, alveolus, and palate compared with healthy adults

BackgroundClefts of the lip, alveolus, and palate (CLPs) rank among the most frequent and significant congenital malformations. Leu10Pro and Arg25Pro polymorphisms in the precursor region and Thr263Ile polymorphism in the prodomain of the transforming growth factor β1 (TGF-β1) gene have proved to be crucial to predisposition of several disorders.MethodsIn this study, polymorphism analysis was performed by real-time polymerase chain reaction (LightCycler) and TGF-β1 levels determined by enzyme-linked immunosorbent assay.ResultsOnly 2/60 Caucasian non-syndromic patients with CLP (3.3%) carried the Arg25Pro and another 2/60 patients (3.3%) the Thr263Ile genotypes, whereas, in a control group of 60 healthy Caucasian blood donors, these heterozygous genotypes were more frequent 16.7% having Arg25Pro (10/60; p < 0.035) and 10,0% having Thr263Ile (6/60), respectively. TGF-β1 levels in platelet-poor plasma of heterozygous Arg25Pro individuals were lower than those of homozygous members (Arg25Arg) in the latter group, but this discrepancy narrowly failed to be significant. Although polymorphisms in codon 10 and 25 were associated with each other, no difference was found between patients and controls concerning the Leu10Pro polymorphism.ConclusionsThe genetic differences in codons 25 and 263 suggest that TGF-β1 could play an important role in occurrence of CLP, however, functional experiments will be required to confirm the mechanisms of disturbed development.

A new adhesive technique for internal fixation in midfacial surgery

BackgroundThe current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market.MethodsThe adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests.ResultsWithout the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa.ConclusionA new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete.

Orthodontic and Surgical Treatment of Patients with Congenital Unilateral and Bilateral Mandibulofacial Dysostosis

Abstract.Aim:Presentation of results following therapy of patients with different forms of mandibulofacial dysostosis.Material and Methods:Case reports of four patients, two with unilateral and two with bilateral mandibulofacial dysostosis, are presented. The symptoms and the problems involved in treatment are described.Results:Protracted treatment resulted in improved facial symmetry, a harmonized profile, and acceptable occlusion.Conclusion:The rehabilitation of patients suffering from congenital facial malformations such as mandibulofacial dysostosis demands an experienced team of orthodontists and maxillofacial surgeons as well as persistence on the part of the patients and their families if good esthetic and functional results are to be achieved.Zusammenfassung.Ziel:Darstellung der Behandlungsergebnisse von Patienten mit verschiedenen Formen der Dysostosis mandibulofacialis.Material und Methoden:In Case-Reports wird der Ablauf der Behandlung von vier Patienten, zwei mit einseitiger, zwei mit doppelseitiger Dysostosis mandibulofacialis, aufgezeigt.Ergebnisse:Nach Darstellung der Symptomatik und der Behandlungsprobleme konnten als Ergebnisse einer langwierigen Behandlung eine bessere Symmetrie des Gesichtes, eine Harmonisierung des Profils und eine akzeptable Okklusion erreicht werden.Schlussfolgerungen:Patienten mit solchen angeborenen Gesichtsfehlbildungen benötigen für ihre Rehabilitation ein erfahrenes Team von Kieferorthopäden und Kieferchirurgen und Geduld ihrerseits und vonseiten der Familie; dann ist ein gutes ästhetisches und funktionelles Ergebnis erreichbar.

The soft-tissue facial profile of patients with unilateral clefts of the lip, alveolus, and palate compared with healthy adults.

AbstractPatients and Methods: In this study the soft-tissue profile of 84 patients aged between 16 and 29 years after complete rehabilitation of a unilateral cleft of the lip, alveolus, and palate was compared on lateral cephalograms with that of 5 adult probands with no cleft formation. Results and Conclusion: In the patient group, the thickness at nasion, the subnasal thickness, the upper alveolabial sulcus thickness, the upper lip prominence, and the mental thickness were less pronounced than in the control group. In contrast, the patients showed significantly higher values in the prominence and thickness of the lower lip. These results indicate a less dominant development of the upper lip and a more voluminous lower lip in comparison to the control group. In contrast, the length of the upper lip did not differ significantly between patients and controls. In both groups the facial integument was thicker in males than in females. The soft-tissue anb-angle, the soft-tissue Holdaway II angle, and the nasolabial angle were significantly smaller in the patients than in the controls. Furthermore, the patients showed a distinctly more concave soft-tissue profile than the controls in measurements of the soft-tissue convexity angle. Thus, it is important for all surgeons involved in the rehabilitation of these patients to pay attention not only to an adequate length of the cleft-sided upper lip, but also to attaining a physiological alignment and reconstruction of the muscles, since the orbicularis oris muscle represents the most important component in the form and function of the lip. In addition, discontinuous muscular slings in the facial area may lead to severe midface growth disturbances.ZusammenfassungPatienten und Methode: In dieser Arbeit wurde das Weichteilprofil von 84 Patienten im Alter zwischen 16 und 29 Jahren nach vollständiger Rehabilitation einer einseitigen Lippen-Kiefer-Gaumen-Spalte mit dem von 58 erwachsenen Probanden ohne Spaltbildungen im Fernröntgenseitenbild verglichen. Ergebnisse und Schlussfolgerung: Die Nasiondicke, die subnasale Dicke, die Oberlippensulkusdicke, die Oberlippenrotprominenz und die mentale Dicke waren in der Gruppe der Spaltpatienten kleiner als in der Kontrollgruppe. Die Messungen der Unterlippenrotprominenz und der Unterlippendicke ergaben dagegen bei den Spaltpatienten signifikant größere Werte. Diese Befunde weisen auf eine weniger füllige Ausbildung der Oberlippe und eine voluminösere Unterlippe im Vergleich zur Kontrollgruppe hin. Die Länge der Oberlippe war bei den Spaltpatienten dagegen nicht signifikant verändert. Die faziale Weichgewebsdecke zeigte sich bei männlichen Vertretern sowohl den Spaltpatienten als auch der Kontrollgrupe dicker ausgeprägt als bei weiblichen. Der Weichgewebs-anb-Winkel, der Holdaway-II-Winkel und der Nasolabialwinkel waren bei den Spaltpatienten signifikant kleiner als in der Kontrollgruppe und bei der Bestimmung des Gesichtsprofils durch den Weichgewebskonvexitätswinkel wiesen die Spaltpatienten ein deutlich konkaveres Weichteilprofil auf als die Probanden der Kontrollgruppe. Es sollte somit für alle an der Rehabilitation der Spaltpatienten beteiligten Behandler ein besonderes Anliegen sein, schon beim Lippenverschluss nicht nur auf eine ausreichende Länge, der spaltseitigen Oberlippe zu achten, sondern auch eine physiologische Ausrichtung und Vereinigung der Muskulatur zu erreichen, da der Musculus orbicularis oris für Form und Funktion im Lippenbereich die wichtigste Grundlage bildet und die unterbrochenen Muskelschlingen im Bereich des Gesichtes zu schwerwiegenden Wachstumsstörungen des Mittelgesichtes führen können.