Changes in the mandibular and dento-alveolar structures by the use of tooth borne mandibular symphyseal distraction devices

Three-dimensional dento-skeletal effects of mandibular midline distraction and surgically assisted rapid maxillary expansion: A retrospective study

It was the aim of the study to provide a three-dimensional evaluation of dento-skeletal effects following bone-borne vs tooth-borne mandibular midline distraction (MMD) and tooth-borne surgically assisted rapid maxillary expansion (SARME). A retrospective observational study was conducted. Cone beam computed tomography (CBCT) records were taken pre-operatively (T1), immediately post-distraction (T2) and 1 year post-operatively (T3). All included 30 patients had undergone MMD (20 bone-borne MMD; 10 tooth-borne MMD). A total of 20 bone-borne MMD and 8 tooth-borne MMD patients had simultaneously undergone tooth-borne SARME. At T1 vs T3, canine (p = 0.007; 26.0 ± 2.09 vs 29.2 ± 2.02) and first premolar (p = 0.005; 33.8 ± 2.70 vs 37.0 ± 2.43) showed significant expansion on the tip level for tooth-borne MMD. This was no significant on the apex level, indicating tipping. Bone-borne MMD showed a parallel distraction gap, whereas tooth-borne MMD showed a V-shape. There was a significant (p = 0.017; 138 ± 17.8 vs 141 ± 18.2) inter-condylar axes increase for bone-borne MMD. In conclusion, bone-borne vs tooth-borne MMD and tooth-borne SARME showed stable dento-skeletal effects at 1 year post-operatively. Bone-borne and tooth-borne MMD seemed not to be superior to each other. The choice of distractor type therefore depends more on anatomical and comfort factors.

Three-dimensional soft tissue evaluation after rapid maxillary expansion and mandibular midline distraction osteogenesis

OBJECTIVES

To evaluate the effects of rapid maxillary expansion (RME) and mandibular midline distraction osteogenesis (MMDO) on facial soft tissues using three-dimensional (3D) images.

MATERIALS AND METHODS

A total of 20 patients (average age 15.86 ± 2.17 years) were treated with RME and MMDO using tooth-borne distractors. Three-dimensional photographs of each patient were taken with a stereophotogrammetry system at baseline (T0), at the end of the distraction period (T1), and at the end of the consolidation period (T2). All data were analyzed using a dependent-samples t-test at a significance level of 5%.

RESULTS

Total and lower face height increased after MMDO (P < .05). Nasal and mouth width increased after RME as compared with baseline (P < .05). The labiomental angle increased at T1 and decreased at T2 (P < .05). After MMDO, the convexity angle increased while the mandibular angle decreased (P < .05). Upper and lower lip angles increased after RME (P < .05). The distance from the lower lip to the E plane increased after MMDO and decreased after RME (P < .05).

CONCLUSIONS

The MMDO and RME procedures provide an efficient nonextraction treatment alternative for transverse maxillomandibular deficiency. MMDO may improve the facial soft tissue profile in the transverse and vertical axis of the mandibular region.

Distraction Osteogenesis: Mandible and Maxilla

Mandibular and maxillary deformities commonly require surgical intervention. Prior to distraction osteogenesis, traditional modalities involving single-staged translocation and rigid fixation were used to correct these craniofacial anomalies. Distraction osteogenesis has evolved as a compelling alternative for treating aesthetic and functional dentofacial defects. The process of distraction osteogenesis involves three phases-latency, activation, and consolidation-which allow for appropriate translation of the affected craniofacial skeleton. This review will cover the role of distraction for managing congenital and acquired deformities of the mandible and maxilla. This novel technique can be performed at numerous anatomical sites along the craniofacial skeleton to treat a variety of anomalies, which serves as a testament to its adaptability and efficacy. Importantly, distraction osteogenesis also has the ability to simultaneously increase bone length and the overlying soft tissue envelope. This advantage results in larger advancements with reduced relapse rates and improved patient satisfaction. While complications remain a concern, it stands to reason that the measurable benefits observed underscore the power and versatility of distraction osteogenesis.

Mandibular Midline Distraction Osteogenesis with a Bone-borne, Tooth-borne or Hybrid Distraction Appliance: a Systematic Review

Objectives

The objective of the present systematic review was to assess the transverse skeletal and dental arch expansion and relapse after mandibular midline distraction osteogenesis with a bone-borne, tooth-borne or hybrid distraction appliance.

Material and Methods

A MEDLINE (PubMed), Embase and Cochrane library search in combination with a hand-search of relevant journals was conducted. Human studies published in English until the 3^rd of July, 2018 were included.

Results

Two comparative and seven non-comparative studies characterized by high risk of bias fulfilled the inclusion criteria. Transverse mandibular widening was achieved with the different types of distraction appliance displaying a horizontal V-shaped opening with larger anterior transverse expansion declining progressively towards the posterior part of the mandible. Bone-borne and hybrid appliance facilitate more skeletal expansion compared with tooth-borne appliance, whereas comparable dental arch expansion was achieved with the different types of distraction appliance. Skeletal and dental arch relapse with the different type of appliance was limited and comparable. However, frequency of complications was higher with bone-borne appliance compared with tooth-borne or hybrid appliance.

Conclusions

Mandibular midline distraction osteogenesis with bone-borne, tooth-borne or hybrid distraction appliance is an effective treatment modality to correct severe transverse mandibular discrepancies, although the skeletal and dental arch expansion pattern was dissimilar with the different types of appliance. However, dissimilar evaluation methods, different outcome measures, various methodological confounding factors posed serious restrictions reviewing the literature in a quantitative systematic manner. Hence, well-designed long-term randomized controlled trials applying three-dimensional technology, patient-related outcome measures and an economic perspective are needed before definite conclusions can be provided.

Three-dimensional evaluation of mandibular midline distraction: A systematic review

OBJECTIVE

To provide a literature overview on mandibular midline distraction (MMD) using three-dimensional (3D) imaging analysis techniques. Regarding different distractor types, the focus was on changes in position and/or morphology of the mandibular condyle and temporomandibular joint (TMJ), skeletal effects, dental effects, soft tissue effects, and biomechanical and masticatory effects, specifically on the mandible and TMJ.

METHODS

Studies up to March 27 2017 were included, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines, using Embase, Medline OvidSP, Web-of-science, Scopus, Cochrane, and Google Scholar.

RESULTS

Thirty-one full-text papers were assessed for eligibility and 15 met the inclusion criteria: prospective (2), retrospective (2), case-report (1) and computational analysis (10). All included studies were graded low (level 4-5) for quality of evidence, using the Oxford Centre for Evidence-Based Medicine criteria.

CONCLUSION

There is a limited number of studies available, with low levels of evidence and small sample sizes. Bone-borne distraction seems preferable when taking skeletal effects into account. Tooth-borne distraction leads to significant dental tipping. Hybrid distractors combined with parasymphyseal step osteotomy seem to be the most stable under functional masticatory loads. The effects of chewing appeared to be marginal during the latency period. No permanent TMJ symptoms were reported, and little is known about soft tissue effects.

SYSTEMATIC REVIEW REGISTRATION

International Prospective Register of Systematic Reviews, PROSPERO CRD42014010010.

Comparison of two preoperative protocols for mandibular symphyseal distraction osteogenesis to reduce the risk of tooth damage

Two techniques to separate the lower incisors prior to mandibular symphyseal distraction osteogenesis (MSDO) were evaluated with respect to avoiding tooth damage.

METHODS

Fifty patients (20.2 ± 7.0 years) requiring MSDO were treated with a tooth-borne appliance by utilizing two preoperative protocols to separate the central incisors: i) brackets and a V-bent wire with an open coil spring (two-step; TS; n = 24) and ii) a wire attached from the appliance to the central incisors with subsequent dento-alveolar expansion prior to surgery (one-step; OS; n = 26). The distance between the lower incisors was measured preoperatively on radiographs and measurements at the cast models were performed. Complications and radiographs were analyzed.

RESULTS

The mean distance (±SD) between the lower central incisors for OS and TS prior to surgery was 3.44 ± 1.05 and 3.18 ± 1.13 mm, respectively. The mean expansion for OS and TS was 4.3 ± 2.9 and 4.3 ± 2.7 mm at the dental level and 3.8 ± 3.2 and 4.0 ± 2.1 mm at the bone level, respectively. Four patients undergoing the TS and one patient undergoing the OS showed transient dental complications.

CONCLUSION

Pre-surgical dento-alveolar expansion by utilizing a one-step technique to separate the lower central incisors reduces the risk of permanent tooth damage and weakens the mandibular bone in the midline.

Effects of a hinged expansion screw for median mandibular distraction treatment on the lower first molars regarding tooth inclination and intermolar transverse distance

OBJECTIVES

The goal of this study was to assess the extent to which median mandibular distraction via a cemented and screw-retained full-coverage splint appliance employing a hinged expansion screw causes inclination changes in the lower first molars and widens the dental arch.

METHODS

Our study included 17 patients (12 females and 5 males; average age 16 years and 3 months) who presented with transverse space deficits and pronounced dental crowding. Baseline and final mandibular casts reflecting the situations before and after 6 weeks of median distraction therapy were created, scanned, and matched via their coordinate systems. Perpendiculars were drawn at the geometric centers between the cusp tips of teeth 36 and 46 and projected against the frontal plane. The intersection angles yielded single-tooth and total inclination values for both molars, and the difference between the intermolar distances measured at the geometric centers of both teeth provided the amount of transverse expansion.

RESULTS

An intraclass correlation coefficient (ICC) of >0.99 was obtained in a series of three measurements. After distraction treatment, the total inclination values between teeth 36 and 46 changed by +2.93 ± 9.14°. The corresponding single-tooth inclinations changed by +0.68 ± 6.32° and -2.25 ± 4.33°, respectively. Both molars underwent similar degrees of buccal or lingual tipping. Compared to a mean expansion of +6.9 ± 1.83 mm at the distraction screw, a distance increase of only +3.77 ± 1.27 mm along the transversal connecting teeth 36 and 46 was recorded. Pearson's correlation coefficient was 0.336 between total tipping and intermolar expansion (p=0.187) and -0.426 between total tipping and patient age (p=0.088).

CONCLUSION

Expansion amounts were approximately twice as long at the expansion screw as between the first molars. This V-shaped expansion pattern was due to the hinged connections between each expansion screw and the full-coverage splints. The buccal and lingual tipping of molars measured may be due to varying heights of the posterior alveolar ridge during mixed dentition or to anatomy-related differences in the expansion-screw position. In all cases we observed a mainly parallel opening of the distraction gap on the vertical plane.

Model to assess duration of distraction compared with degree of incisal crowding in symphyseal distraction osteogenesis

Our aim was to evaluate symphyseal distraction in relation to duration of expansion, and to propose an optimised procedure. Eighteen patients (mean (SD) age 19 (7) years) with transverse mandibular deficiency were treated by symphyseal distraction osteogenesis. The mean (SD) anterior dental crowding measured was 6.8 (4.2) mm. We retrospectively compared the width of expansion between the canines (ICE) and expansion between the first molars (IFME) after symphyseal distraction according to the distraction time. The median (range) duration of expansion was 13.6 (7-21) days. The median (range) ICE distraction width was 5.5 (3.4-8) mm and IFME width 3.3 (1-7.9) mm (p<0.001). There was a significant correlation between expansion width and distraction time (p<0.001). The transverse anterior and posterior expansion widths differed significantly until 14 days after expansion. The expansion ratio (ICE:IFME) decreased as expansion time increased. The results suggest that the duration of activated expansion can be predicted from the degree of incisal crowding using the formula: distraction time (days)=0.84+3.4×[IC (mm)]-0.2×[IC (mm)](2).

Skeletal and dental effects of tooth-borne versus hybrid devices for mandibular symphyseal distraction osteogenesis

OBJECTIVE

To evaluate and compare, retrospectively, the skeletal and dental effects of mandibular symphyseal distraction osteogenesis (MSDO) achieved through the use of tooth-borne versus hybrid distractors.

MATERIALS AND METHODS

Pretreatment (T1), predistraction (T2), postdistraction (T3), and posttreatment (T4) orthodontic records were collected and analyzed for 47 patients (20 tooth-borne, 27 hybrid). At each time point, records included intraoral photographs, study models, postero-anterior cephalometric radiographs, and lateral cephalometric radiographs. Submental vertex radiographs were taken at T2, T3, and T4. Changes in a total of 18 measurements were analyzed to compare patients undergoing tooth-borne versus hybrid distraction.

RESULTS

The cumulative effects of orthodontics and MSDO produced similar gains in measured arch widths, with a decreased irregularity index in both groups (P > .05). However, there were differences in the timing during which the expansion was achieved. The hybrid distractor group gained space during the distraction phase of treatment. The tooth-borne group showed greater gains during pre- and postdistraction orthodontics. Comparisons of intercanine and interbone marker widths demonstrated a more parallel separation of bone during distraction with the hybrid distractor (P < .001). Distraction with the tooth-borne distractor was disproportionate, with greater separation of the canines in alveolar bone than of the bone markers in basal bone. During postdistraction orthodontics, the tooth-borne distractor group showed statistically greater increases in measurements.

CONCLUSION

Both skeletal and dental expansion was achieved with both appliances. Greater skeletal expansion was achieved with a hybrid distractor. Greater dental expansion was achieved with a tooth-borne distractor.

Introduction of the "Rotterdam mandibular distractor" and a biomechanical skull analysis of mandibular midline distraction

The Rotterdam mandibular distractor (RMD) is a slim, rigid, boneborne distractor for use in midline distraction of the mandible. We did a biomechanical study to compare the RMD with the Trans Mandibular Distractor-flex (TMD-flex). This included an anatomical biomechanical study that was conducted on 9 dentate human cadaveric heads using both the RMD and the TMD-flex. In the vertical plane less tipping was measured in the RMD group than in the TMD-flex group. Significantly less skeletal tipping was found in the horizontal plane in the RMD group (P=0.021). There was minimal difference in the intercondylar distance between the groups. As the amount of lateral displacement of the condyle was similar in both groups and there was less rotational movement in the RMD group, the TMD-flex would be expected to increase stress on the temporomandibular joint. As a result of the increased parallel widening in the vertical plane, more basal bone is being created and less relapse is expected using the RMD. The study design involves an in vitro anatomical model and conclusions must be drawn with care. At present clinical studies are under way and results will follow.