Application of palatal plate for nonextraction treatment in an adolescent boy with severe overjet

A modified C-palatal plate (MCPP) is introduced as a treatment option for adolescent patients with Class I malocclusion and severe overjet. A boy, 10 years 11 months old, was successfully treated without extractions in 22 months. Indications for clinical application of the MCPP as well as procedures and biomechanical analysis of the treatment effects are described in detail. The MCPP was used to distalize the maxillary dentition. The results were stable 1 year after retention. Clinicians should consider the application of MCPP as a nonextraction treatment option for adolescents with Class I malocclusion and severe overjet when the patient or parent refuses extractions.

Highlights

  • Modified C-palatal plate distalized the maxillary dentition in a 10-year-old boy.

  • MCPP treatment corrected the severe overjet without extractions.

  • Indications, procedures, and biomechanics of treatment with MCPP are discussed.

  • MCPP is a valid treatment option for Class I malocclusion and severe overjet.

With life expectancy increasing, patients and parents are shying away from treatments that require tooth extractions. They want to preserve what they have and are increasingly looking for nonextraction treatment options.

Distalization of the maxillary dentition is necessary for nonextraction Class II treatment, but it is challenging to achieve bodily movement without extrusion of the molars. In such cases, the palatal approach might be a key element in obtaining these results. Palatal bone thickness and density, and soft tissue thickness can usually support temporary skeletal anchorage devices in adults and adolescents. Studies have identified the most appropriate regions in the palate for their placement.

Recently, Kook et al reported on the treatment effects of palatal plates in the distalization of maxillary dentitions in adults and adolescents. The modified C-palatal plate (MCPP) can be an important tool for correction of maxillary protrusion in patients who decline extraction treatment. However, the clinical procedures and the biomechanics of this appliance have not been fully reported.

We introduce the use of palatal plates in nonextraction treatment of growing patients with Class I malocclusion and severe overjet. Indications, procedures, biomechanics, and stability of treatment with MCPPs are discussed.

The indications for MCPPs are (1) Class I malocclusion with bimaxillary protrusion or severe overjet, (2) maxillary total distalization in patients with Class II dental relationship, (3) additional correction of severe lip protrusion after premolar extraction, (4) anterior open-bite tendency in dental Class II patients, and (5) distalization of the maxillary molars in Class III patients combined with mandibular setback to avoid extraction of the maxillary premolars.

MCPPs come with 2 extended lever arms that have 3 notches on each of them. The notches are designed to provide a more secure engagement during intrusion mechanics. The arms are connected through a body containing 3 miniscrew tubes (2.5 mm long) that accept 8-mm long, 2-mm diameter screws, 2 posterior and 1 anterior, located in the paramedian region to avoid the midpalatal suture. This should be considered especially important when treating adolescent patients. The 2 extended lever arms curve distally to increase the range of action of the distalizing springs or elastics and to avoid contact with the palatal archwire.

MCPPs should be placed as posteriorly as possible to increase the range of action; however, bone thickness of the far posterior palate might not be sufficient to support the appliances. Therefore, it is recommended to install the miniscrews for the MCPP in the region between the second premolar and first molar.

A tight adaptation between the tube and miniscrew reduces the potential for plate tipping. However, soft-tissue impingement can result when force is applied. Therefore, a silicone jig is placed on the maxillary posterior teeth to hold the palatal plate and to ensure the accuracy of the placement of the plate in its predetermined site where the arms are at a consistent distance from the palatal tissues. The plate is adapted to the selected placement site using the patient’s dental casts, and the arms are adjusted to be 2 mm away from palatal soft tissues. This jig is made by applying a 3-mm thickness of silicone material on the palatal surface of the dental cast and extending it over the occlusal surfaces of the premolars (or deciduous molars) and molars. Then, the plate is pressed gently into position, and the jig-plate assembly is heat-cured. After removing the assembly from the cast, the silicone should be removed from the screw tubes, and diagonal cuts should be made through the silicone to facilitate its removal after delivery of the plate. The assembly should be sterilized in ethylene oxide gas for 24 hours before placement ( Fig 1 , A ).

Fig 1
A, Silicon jig-MCPP complex; B, placement procedures of MCPP: a , the palate after local anesthesia; b , the jig-MCPP complex placed in mouth; c , miniscrews installed in the screw tubes with a contra-angle motor while the jig-MCPP complex is held in position; d , removal of the jig using a plier; e , the MCPP placed in the palate; f , the palatal bar placed on the maxillary first molars, and power chains connected between its hooks and the MCPP hooks.

After administration of local anesthesia, the jig-plate assembly is placed in position. Self-drilling miniscrews are installed in the tubes using a rotary screwdriver at 30 rpm with 30 Ncm of force. The tubes are inserted into the palatal soft tissue, contacting or almost contacting the palatal bone. Then the jig is removed by pulling gently and firmly from each side with utility pliers, and the miniscrews are tightened manually, if necessary. The palatal bar is then placed. Distalization can be started immediately after placement by connecting the MCPP to the palatal bar with elastomeric chains or nickel-titanium closed-coil springs ( Fig 1 , B ). An analgesic might be prescribed to alleviate the postoperative pain. See Supplemental Materials for a short video presentation about this study.

Diagnosis and etiology

A boy, aged 10 years 11 months, visited the Department of Orthodontics, Seoul St. Mary’s Hospital in Korea, with chief complaints of protrusion and deepbite. He had no significant medical and dental history. He had both protrusive upper and lower lips with a convex profile. Due to his severe overjet and short upper lip, he showed severe lip incompetency (7-mm interlabial gap). There were no signs or symptoms of temporomandibular joint dysfunction.

Intraorally, the patient had a 7-mm overjet and a 50% overbite. He had Class I molar relationships and end-on Class II canine relationships on both sides. There was mild crowding in his maxillary arch and moderate crowding in his mandibular arch with a moderate curve of Spee. His dental midlines were coincident with his facial midline ( Figs 2 and 3 ).

Fig 2
Pretreatment intraoral and facial photographs.

Fig 3
Pretreatment study models.

His maxillary second molars had not erupted yet. A lateral cephalometric analysis indicated skeletal Class I (ANB, 3.5°; Wits appraisal, –1.5 mm) with a hypodivergent growth pattern (FMA, 23.0°). The maxillary and mandibular incisors were proclined (U1-FH, 121.0°; IMPA, 96.0°) ( Fig 4 , Table ).

Fig 4
Pretreatment: A, panoramic radiograph; B, lateral cephalogram; and C, tracing.

Table
Cephalometric measurements
Norm Pretreatment Posttreatment
Cephalometric analysis
SNA (°) 82.0 85.5 86.0
SNB (°) 80.0 81.5 82.0
ANB (°) 2.0 3.5 3.0
A-point–N Perp (mm) 1.1 3.0 3.5
Pog-N Perp (mm) −0.3 −2.0 0.0
Wits (mm) −2.2 −1.5 1.5
Harvold (mm) 35.8 27.5 33.0
Vertical skeletal pattern
Facial height ratio (P/A) (%) 66.4 66.5 70.0
FMA (°) 24.0 23.0 22.0
ODI (°) 73.3 72.0 71.5
Dental analysis
U1 to FH (°) 116.5 121.0 107.0
IMPA (°) 90.0 96.0 96.0
Interincisal angle 124.0 123.0 132.0
FH to occlusal plane (°) 10.5 5.0 7.0
Soft tissue analysis
TVL to UL (mm) 5.0 8.0 6.5
TVL to LL (mm) 2.5 5.0 4.0
TVL to Pog’ (mm) −3.0 −5.0 −5.0
Nasolabial angle (°) 85.0 86.0 101.5
Interlabial gap (mm) 2.0 7.0 3.0
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Dec 12, 2018 | Posted by in Orthodontics | Comments Off on Application of palatal plate for nonextraction treatment in an adolescent boy with severe overjet
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