Naoumova Julia
Swed Dent J Suppl. 2014(234):7-118.
In 2% of the Swedish population the canine fails to erupt and in 85% of the cases the canine is palatally displaced. The most common interceptive treatment of palatally displaced canines (PDCs) is extraction of the deciduous canine at the age of 10-13 years and follow-up of the canine for 12 months to monitor whether its eruption path will normalize. In case the canine does not erupt spontaneously, a surgical exposure and orthodontic treatment is commonly considered. However, an early and easy interceptive treatment is preferable both from a health economic perspective as well as to reduce the risk of root resorption of the adjacent teeth and to avoid later comprehensive treatments.
The aims of this thesis were: to develop a reliable and valid method to measure the position of PDCs on 3D images (Cone Beam Computed Tomography, CBCT) (paper I). To evaluate children's subjective experience before, during and after extraction of the deciduous canine (paper II). To compare whether extraction of the deciduous canine more often results in spontaneous eruption of the permanent canine compared to non extraction (paper III) and to find out which clinical cases benefit from interceptive extraction (paper IV).
In total 89 PDCs in 67 children (10-13 years of age) were randomly assigned to either have their deciduous canine extracted (extraction group, EG) or not extracted (control group, CG). Clinical and radiographic examinations were carried out at baseline (TO), after 6 (T1) and 12 months (T2) in both groups. 3D images of 20 patients out of 67 were randomly chosen and measured by two dentists at different occasions. The validity of the method to measure the displaced canines was assessed by comparing measurements on the 3D images with measurements on a dry skull. Children who had extraction of the deciduous canine were asked to answer a questionnaire before, the same day as and one week after the extraction.
The radiographic method to measure and assess the position of the PDCs on 3D images was reliable and had a high validity (paper I). The reported pain and discomfort were in overall low. The injection was experienced as more painful compared to the extraction, and analgesics were taken the first evening by 42% of the children (paper II). Extraction of the deciduous canine resulted in eruption of the PDCs in 69% of the cases compared to 39% in the CG. Significantly more positional changes and a shorter mean eruption time were seen in the EG (paper III). PDCs with a mesioangular angle of 103 degrees, distance of the canine cusp tip-dental arch plane of 2.5 mm and distance of the canine cusp tip-midline of 11 mm in patients < 11 years will likely erupt without interceptive extraction. However, PDCs with a less favourable position, i.e. a mesioangular angle of 116 degrees, canine cusp tip-dental arch plane of 5mm and canine cusp tip-midline of 6 mm, in patients > 11-12 years old, will not erupt spontaneously in spite of interceptive extraction of the deciduous canine (paper IV).
The radiographic method to measure and assess the position of the PDCs was reliable and valid and can be used in future studies. Adequate analgesics and dose should be given to children before and after extracting the deciduous canine. Interceptive extraction of the deciduous canine at 10-13 years of age was effective and will result in significantly more spontaneous eruptions of the permanent canine compared to a control group. The cutoff points may be a helpful tool for the clinician to chose whether the patient benefit from interceptive extraction of the deciduous canine or whether immediate surgical exposure should be performed.
在瑞典2%的人口中，尖牙未能萌出，其中85%的病例中尖牙腭向移位。腭向移位尖牙（PDC）最常见的阻断性治疗方法是在10 - 13岁时拔除乳尖牙，并对尖牙进行12个月的随访，以监测其萌出路径是否会恢复正常。如果尖牙没有自发萌出，通常会考虑进行外科暴露和正畸治疗。然而，从健康经济学角度以及降低相邻牙齿牙根吸收风险和避免后期综合治疗来看，早期且简便的阻断性治疗更为可取。
本论文的目的是：开发一种可靠且有效的方法来测量三维图像（锥形束计算机断层扫描，CBCT）上PDC的位置（论文I）。评估儿童在拔除乳尖牙之前、期间及之后的主观感受（论文II）。比较拔除乳尖牙与不拔除相比，是否更常导致恒尖牙自发萌出（论文III），并找出哪些临床病例从阻断性拔除中获益（论文IV）。
将67名10 - 13岁儿童的89颗PDC随机分为拔除乳尖牙组（拔除组，EG）和不拔除组（对照组，CG）。两组均在基线（T0）、6个月后（T1）和12个月后（T2）进行临床和影像学检查。从67名患者中随机选取20名患者的三维图像，由两名牙医在不同时间进行测量。通过将三维图像上的测量结果与干燥颅骨上的测量结果进行比较，评估测量移位尖牙方法的有效性。拔除乳尖牙的儿童在拔牙前、拔牙当天及拔牙后一周被要求回答一份问卷。
在三维图像上测量和评估PDC位置的影像学方法可靠且有效性高（论文I）。报告的疼痛和不适总体较低。与拔牙相比，注射被认为更痛，42%的儿童在拔牙后的第一个晚上服用了镇痛药（论文II）。拔除乳尖牙后，69%的病例中PDC萌出，而对照组为39%。拔除组出现明显更多的位置变化，平均萌出时间更短（论文III）。11岁以下患者中，近中角为103度、尖牙尖至牙弓平面距离为2.5毫米、尖牙尖至中线距离为11毫米的PDC可能无需阻断性拔除即可萌出。然而，11 - 12岁以上患者中，位置不太有利，即近中角为116度、尖牙尖至牙弓平面距离为5毫米、尖牙尖至中线距离为6毫米的PDC，即使拔除乳尖牙也不会自发萌出（论文IV）。
测量和评估PDC位置的影像学方法可靠且有效，可用于未来的研究。在拔除乳尖牙前后，应给儿童使用足够的镇痛药和剂量。10 - 13岁时对乳尖牙进行阻断性拔除是有效的，与对照组相比，将显著增加恒尖牙的自发萌出。这些截断点可能是临床医生选择患者是否从乳尖牙阻断性拔除中获益或是否应立即进行外科暴露的有用工具。
