Stephen L.-K. Yen

Corticotomy-/Osteotomy-assisted Tooth Movement microCTs Differ

Corticotomy-assisted and osteotomy-assisted tooth movement involves surgical incisions through the alveolar bone. To ascertain whether teeth move by distraction osteogenesis or by regional accelerated phenomenon (RAP), we randomly assigned 30 Sprague-Dawley rats to one of 5 experimental groups: corticotomy alone, corticotomy-assisted tooth movement, osteotomy alone, osteotomy-assisted tooth movement, or tooth movement alone. Each animal was imaged by microtomography immediately after surgery, after 21 days, and after 2 months. After 21 days, regional accelerated phenomenon was observed in the alveolar bone of the corticotomy-treated animals and distraction osteogenesis in the osteotomy-assisted tooth movement animals. Pixel count data were analyzed by nested ANOVA for 5 experimental groups, split-mouth controls, 3 levels along the root, and 5 sites per level. The most demineralized sites after 21 days differed for each of the experimental groups. Our study indicates that osteotomies and corticotomies induce different alveolar bone reactions, which can be exploited for tooth movement.

Tisssue responses in corticotomy- and osteotomy-assisted tooth movements in rats: histology and immunostaining.

INTRODUCTION The purpose of this histologic study was to examine underlying cellular responses to corticotomy- and osteotomy-assisted tooth movements. METHODS Thirty-six rats were divided into 5 groups: corticotomy-assisted tooth movement (CO + TM), sham corticotomy without tooth movement (CO alone), osteotomy-assisted tooth movement (OS + TM), sham osteotomy without tooth movement (OS alone), and unassisted tooth movement (TM alone). Standard orthodontic springs were activated to produce mesial tooth movement. The rats were killed at 3, 21, and 60 days after activation for osteoclast and blood vessel counts, and immunostaining with proliferating cell nuclear antigen (PCNA), transforming growth factor beta 1 (TGF beta 1), vascular endothelial growth factor (VEGF), and osteocalcin were performed. RESULTS The CO + TM group had significantly more osteoclasts at 3 days (P <0.005) compared with the OS + TM group. The alveolar bone surrounding the dental roots was replaced with multicellular tissue at 21 days in the CO + TM group but was intact in the OS + TM group with the exception of a distal distraction site. At day 21, immunostaining with PCNA, TGF beta 1, VEGF, and osteocalcin occurred at the mesial border of bone in the CO + TM group, whereas a diffuse pattern was observed in the distal distraction sites at 21 and 60 days in the OS + TM group. CONCLUSIONS Corticotomy-assisted tooth movement produced transient bone resorption around the dental roots under tension; this was replaced by fibrous tissue after 21 days and by bone after 60 days. Osteotomy-assisted tooth movement resembled distraction osteogenesis and did not pass through a stage of regional bone resorption.

rhBMP-2 with a demineralized bone matrix scaffold versus autologous iliac crest bone graft for alveolar cleft reconstruction.

Background: Secondary alveolar cleft reconstruction using autologous iliac crest bone graft is currently the standard treatment for alveolar clefts. Although effective, harvesting autologous bone may result in considerable donor-site morbidity, most commonly pain and the potential for long-term sensory disturbances. In an effort to decrease patient morbidity, a novel technique using recombinant human bone morphogenetic protein (rhBMP)-2 encased in a demineralized bone matrix scaffold was developed as an alternative to autografting for secondary alveolar cleft reconstruction. Methods: A chart review was conducted for the 55 patients who underwent secondary alveolar cleft reconstruction over a 2-year period with a mean follow-up of 21 months. Of these, 36 patients received rhBMP-2/demineralized bone matrix scaffold (including 10 patients with previously failed repairs using iliac crest bone grafting) and 19 patients underwent iliac crest bone grafting. Postoperatively, bone stock was evaluated using occlusal radiographs rated according to the Bergland and Chelsea scales. Results: Alveolar clefts repaired using rhBMP-2/demineralized bone matrix scaffold were 97.2 percent successful compared with 84.2 percent with iliac crest bone grafting. Radiographically, initial repairs with rhBMP-2/demineralized bone matrix scaffold were superior to iliac crest bone grafting according to both Bergland and Chelsea scales, and significantly more patients in the rhBMP-2/demineralized bone matrix scaffold group had coronal bridging. The postoperative intraoral infection rate following iliac crest bone grafting was significantly greater than for rhBMP-2/demineralized bone matrix scaffold. The cost of rhBMP-2/demineralized bone matrix scaffold products was offset by cost savings associated with a reduction in operative time averaging 102 minutes. Conclusions: rhBMP-2 encased in a demineralized bone matrix scaffold appears to be a viable alternative for secondary alveolar cleft repair. Patients are spared donor-site morbidity and achieve excellent results, decreasing operative time, and increasing operating room use. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Closure of an unusually large palatal fistula in a cleft patient by bony transport and corticotomy-assisted expansion

The management of cleft lip and palate can vary among patients because the size of a cleft defect and its anatomy vary. Although treatments involving orthodontics and surgery have been developed that can help a large number of children with cleft lip and palate, there are always unusual clefts that defy conventional treatments. In such cases, with each gain made during treatment, there also is the possibility of introducing an additional complication. The secondary bone graft performed during the mixed dentition stage of dental development is an example of treatment gains that are balanced against additional complications. Ordinarily, the maxillary segments are expanded to attain a normal archform before the alveolar bone graft. If there is an anterior palatal fistula present before orthodontic expansion, the size of the fistula concomitantly increases as the expanders widen the anterior maxillary segments. There are, however, extreme cases that present with a combination of collapsed maxillary segment, large anterior palatal fistula, and large alveolar clefts. In such cases, orthodontic expansion could make both the alveolar clefts and anterior palatal fistula unmanageable. In the expanded position, there would be insufficient soft tissue to close the fistula or cover the alveolar bone graft. Consequently, dental prosthetics is often needed to cover the palatal fistula to support speech and eating. In this report, we present the case of an 11-year-old girl who had a 20-mm anterior palatal fistula before orthodontic expansion. In the opinion of our surgeons, the fistula was too large to close before the segments were expanded and would prove more difficult to treat after expansion. To make the palatal fistula and cleft sites manageable, the treatment sequence and procedures were modified. Rather than expand the maxillary segments, the segments were compressed to make the cleft space narrower so that the surgeons could graft the alveolar cleft. To provide more bone support and donor soft tissue for a palatal flap, the palatal tooth and surrounding bone were distracted across the anterior palatal opening. A sequence of minor procedures allowed the cleft sites to be grafted, the unusually large palatal fistula to be closed, the lateral segments to be expanded, and the dental alignment to be improved.

Distraction osteogenesis: application to dentofacial orthopedics

Distraction osteogenesis is a surgical-orthopedic method for lengthening bone by separating or distracting a fracture callus. This technique has a long history in limb lengthening and has recently been used to lengthen mandibles and maxillae in human patients. Distraction osteogenesis represents a powerful method of producing unlimited quantities of living bone which can be formed along any plane of space. Because this method uses local host tissue, it offers many advantages over bone grafting. In the authors experience, large (10-22 mm) antero-posterior and vertical corrections of mandibles can be achieved using this technique. The purpose of this article is to review its biological basis and discuss recent clinical applications. This article reviews the history, theory, current management, and limitations of distraction osteogenesis in treating craniofacial anomalies.

Late Maxillary Protraction in Patients With Unilateral Cleft Lip and Palate: A Retrospective Study

Objectives This retrospective study assessed the dentoskeletal effect of late maxillary protraction (LMP; reverse-pull headgear, Class III elastics, and maxillary suturai loosening) in unilateral cleft lip and palate (UCLP) patients versus a control group of untreated UCLP patients. Materials and Methods Cephalograms taken at age 13 to 14 years (T1) and 17 to 18 years (T2) were used for this study. The study group comprised 18 patients (10 male and 8 female, mean age at start of LMP therapy = 13.4 [0.45] years). A control groups of 17 patients (8 male and 9 female, mean age = 13.5 [0.44] years) was used for comparison. Results The repeated-measures analysis of variance showed statistically significant changes across time between groups for the following variables (mean difference [T2–T1] in the study group, 95% confidence interval): SNA (°) (1.95, 0.75 to 3.15), A ┴ Na Perp (mm) (1.82, 0.86 to 2.77), CoA (mm) (2.92, 1.53 to 4.31), ANB (°) (3.13, 2.02 to 4.24), Wits (mm) (7.82, 5.01 to 10.54), Mx-Md Diff (mm) (0.62, −1.58 to 2.83), Occl P-SN (°) (-3.98, −5.99 to −1.98), overjet (mm) (8.82, 5.90 to 11.74), FMIA (°) (4.05, −0.05 to 8.15), and IMPA (°) (-5.77, −9.74 to −1.80). Late maxillary protraction created a slight open bite (0.66 mm). Trends for overeruption of mandibular incisors and an increase in lower face height (P = .07 for both) were noted in the study group. Conclusions Late maxillary protraction produced a combination of skeletal changes (protraction of maxilla, improvement in the maxillo-mandibular skeletal relationship) and dental compensations (counterclockwise rotation of occlusal plane, retroclination of mandibular incisors) in patients with UCLP. Late maxillary protraction was also associated with some unwanted tooth movements (open bite tendency, mandibular incisors overeruption).

Clinical Applications of Orthodontic Microimplant Anchorage in Craniofacial Patients

Microimplant anchors, also known as temporary anchorage devices, mini- and micro-screws, have been used to enhance orthodontic anchorage for difficult tooth movements. Here, the authors describe how microimplants can be used to help treat craniofacial patients by supporting distraction osteogenesis procedures, maxillary protraction procedures, cleft segment expansion and stabilization, and tooth movement into narrow alveolar cleft sites. While most craniofacial patients are treated without microimplants, it would be worthwhile to identify which cases could benefit from microimplant anchorage. As an adjunct to orthodontic treatment, the microimplant offers a potential method for solving troublesome orthodontic and surgical problems such as guiding distraction procedures with orthodontics when primary teeth are exfoliating, addressing residual maxillary cants after vertical distraction osteogenesis of a ramus, stabilizing an edentulous premaxilla, and moving teeth into atrophic alveolar ridges. These cases are presented to open a dialogue on their possible uses in craniofacial patients.

Bilateral maxillary duplication: case report and literature review

Accessory maxillary jaws are extremely rare occurrences. Currently, there is only 1 report of bilateral accessory maxillary jaws in the English-language literature. We present a case of a 7-year-old girl with bilateral bony exostoses extending from the maxillary tuberosities. The patient also had restricted protrusive and lateral excursive movements of the mandible. The histologic report revealed teeth in various developmental stages within the bony exostoses. We concluded that these structures were an isolated form of bilateral accessory maxillary jaws.

A rare case of accessory maxilla and bilateral Tessier no. 7 clefts, a 10-year follow-up

A Tessier no. 7 cleft is a lateral facial cleft which originates from the oral cavity and extends towards the tragus, involving both soft-tissue and skeletal components. A male patient presenting with both maxillary jaw duplication and bilateral Tessier no. 7 clefts, which has been reported only twice in the literature, is described. Bilateral facial clefts, macrostomia and chondro-cutaneous remnants were noted, which were repaired and resected. With further growth, facial asymmetry and asymmetric facial nerve dysfunction became apparent. Radiographic examination showed an accessory maxillary jaw and a flattened and hypoplastic right coronoid process. A maxillary alveolar cleft was also present between the left second bicuspid and the second permanent molar. This case may represent an under-recognized phenotype with an unusual combination of maxillary jaw duplication, macrostomia, Tessier no. 7 clefts, and chondro-cutaneous remnants. A long-term follow-up of these patients is recommended as they often develop craniofacial deformities later in life.

Characterization of Protein Kinases Involved in Dentinogenesis

Protein phosphorylation and dephosphorylation control many different cell functions as well as responses to internal and external signals. It has also been shown that highly phosphorylated acidic proteins have an important role in matrix mediated biomineralization, perhaps functioning as nucleators for crystal formation. Dentine phosphoprotein (DPP) is one of such proteins which is exclusively synthesized by the odontoblast cells and therefore a likely candidate to play a significant role in normal and abnormal dentine biomineralization. These studies are directed at characterizing the protein kinases involved in dentinogenesis and in particular the enzyme(s) responsible for DPP phosphorylation. In this report we present data which indicate that there are several different types of kinases in the odontoblast-enriched dental papilla mesenchyme (DPM), some of which can phosphorylate DPP, such as casein kinase I and II. However, a different DPP-kinase activity was identified. This enzyme(s) appears to be different from other reported kinases, and it is the only kinase that can phosphorylate both phosphorylated DPP and enzymatically dephosphorylated DPP.